Programs & Examples On #Java

Java (not to be confused with JavaScript or JScript or JS) is a general-purpose object-oriented programming language designed to be used in conjunction with the Java Virtual Machine (JVM). "Java platform" is the name for a computing system that has installed tools for developing and running Java programs. Use this tag for questions referring to the Java programming language or Java platform tools.

What exactly is an instance in Java?

When you use the keyword new for example JFrame j = new JFrame(); you are creating an instance of the class JFrame.

The new operator instantiates a class by allocating memory for a new object and returning a reference to that memory.
Note: The phrase "instantiating a class" means the same thing as "creating an object." When you create an object, you are creating an "instance" of a class, therefore "instantiating" a class.

Take a look here
Creating Objects


The types of the Java programming language are divided into two categories: primitive types and reference types.
The reference types are class types, interface types, and array types.
There is also a special null type.
An object is a dynamically created instance of a class type or a dynamically created array.
The values of a reference type are references to objects.

Refer Types, Values, and Variables for more information

Boolean checking in the 'if' condition

It really also depends on how you name your variable.

When people are asking "which is better practice" - this implicitly implies that both are correct, so it's just a matter of which is easier to read and maintain.

If you name your variable "status" (which is the case in your example code), I would much prefer to see

if(status == false) // if status is false

On the other hand, if you had named your variable isXXX (e.g. isReadableCode), then the former is more readable. consider:

if(!isReadable) { // if not readable
  System.out.println("I'm having a headache reading your code");
}

Hibernate Criteria Query to get specific columns

You can use multiselect function for this.

   CriteriaBuilder cb=session.getCriteriaBuilder();
            CriteriaQuery<Object[]> cquery=cb.createQuery(Object[].class);
            Root<Car> root=cquery.from(User.class);
            cquery.multiselect(root.get("id"),root.get("Name"));
            Query<Object[]> q=session.createQuery(cquery);
            List<Object[]> list=q.getResultList();
            System.out.println("id        Name");
            for (Object[] objects : list) {
                System.out.println(objects[0]+"        "+objects[1]);
             }
            

This is supported by hibernate 5. createCriteria is deprecated in further version of hibernate. So you can use criteria builder instead.

Java variable number or arguments for a method

That's correct. You can find more about it in the Oracle guide on varargs.

Here's an example:

void foo(String... args) {
    for (String arg : args) {
        System.out.println(arg);
    }
}

which can be called as

foo("foo"); // Single arg.
foo("foo", "bar"); // Multiple args.
foo("foo", "bar", "lol"); // Don't matter how many!
foo(new String[] { "foo", "bar" }); // Arrays are also accepted.
foo(); // And even no args.

Counting Line Numbers in Eclipse

You could use a batch file with the following script:

@echo off
SET count=1
FOR /f "tokens=*" %%G IN ('dir "%CD%\src\*.java" /b /s') DO (type "%%G") >> lines.txt
SET count=1
FOR /f "tokens=*" %%G IN ('type lines.txt') DO (set /a lines+=1)
echo Your Project has currently totaled %lines% lines of code. 
del lines.txt
PAUSE

How do I install Java on Mac OSX allowing version switching?

With Homebrew and jenv:

Assumption: Mac machine and you already have installed homebrew.

Install cask:

$ brew tap caskroom/cask
$ brew tap caskroom/versions

To install latest java:

$ brew cask install java

To install java 8:

$ brew cask install java8

To install java 9:

$ brew cask install java9

If you want to install/manage multiple version then you can use 'jenv':

Install and configure jenv:

$ brew install jenv
$ echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.bash_profile
$ echo 'eval "$(jenv init -)"' >> ~/.bash_profile
$ source ~/.bash_profile

Add the installed java to jenv:

$ jenv add /Library/Java/JavaVirtualMachines/jdk1.8.0_202.jdk/Contents/Home
$ jenv add /Library/Java/JavaVirtualMachines/jdk1.11.0_2.jdk/Contents/Home

To see all the installed java:

$ jenv versions

Above command will give the list of installed java:

* system (set by /Users/lyncean/.jenv/version)
1.8
1.8.0.202-ea
oracle64-1.8.0.202-ea

Configure the java version which you want to use:

$ jenv global oracle64-1.6.0.39

Fastest way to check a string is alphanumeric in Java

Use String.matches(), like:

String myString = "qwerty123456";
System.out.println(myString.matches("[A-Za-z0-9]+"));

That may not be the absolute "fastest" possible approach. But in general there's not much point in trying to compete with the people who write the language's "standard library" in terms of performance.

Exception thrown in catch and finally clause

A method can't throw two exceptions at the same time. It will always throw the last thrown exception, which in this case it will be always the one from the finally block.

When the first exception from method q() is thrown, it will catch'ed and then swallowed by the finally block thrown exception.

q() -> thrown new Exception -> main catch Exception -> throw new Exception -> finally throw a new exception (and the one from the catch is "lost")

Regular expression include and exclude special characters

[a-zA-Z0-9~@#\^\$&\*\(\)-_\+=\[\]\{\}\|\\,\.\?\s]*

This would do the matching, if you only want to allow that just wrap it in ^$ or any other delimiters that you see appropriate, if you do this no specific disallow logic is needed.

Error: Registry key 'Software\JavaSoft\Java Runtime Environment'\CurrentVersion'?

Adjust the sequence of your environment variable %path% to make sure jre 1.7 is the default one.

Format LocalDateTime with Timezone in Java8

The prefix "Local" in JSR-310 (aka java.time-package in Java-8) does not indicate that there is a timezone information in internal state of that class (here: LocalDateTime). Despite the often misleading name such classes like LocalDateTime or LocalTime have NO timezone information or offset.

You tried to format such a temporal type (which does not contain any offset) with offset information (indicated by pattern symbol Z). So the formatter tries to access an unavailable information and has to throw the exception you observed.

Solution:

Use a type which has such an offset or timezone information. In JSR-310 this is either OffsetDateTime (which contains an offset but not a timezone including DST-rules) or ZonedDateTime. You can watch out all supported fields of such a type by look-up on the method isSupported(TemporalField).. The field OffsetSeconds is supported in OffsetDateTime and ZonedDateTime, but not in LocalDateTime.

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd HH:mm:ss.SSSSSS Z");
String s = ZonedDateTime.now().format(formatter);

What exactly is a Context in Java?

Simply saying, Java context means Java native methods all together.

In next Java code two lines of code needs context: // (1) and // (2)

import java.io.*;

public class Runner{
    public static void main(String[] args) throws IOException { // (1)           
        File file = new File("D:/text.txt");
        String text = "";
        BufferedReader reader = new BufferedReader(new FileReader(file));
        String line;
        while ((line = reader.readLine()) != null){ // (2)
            text += line;
        }
        System.out.println(text);
    }
}

(1) needs context because is invoked by Java native method private native void java.lang.Thread.start0();

(2) reader.readLine() needs context because invokes Java native method public static native void java.lang.System.arraycopy(Object src, int srcPos, Object dest, int destPos, int length);

PS.

That is what BalusC is sayed about pattern Facade more strictly.

Java null check why use == instead of .equals()

You code breaks Demeter's law. That's why it's better to refactor the design itself. As a workaround, you can use Optional

   obj = Optional.ofNullable(object1)
    .map(o -> o.getIdObject11())
    .map(o -> o.getIdObject111())
    .map(o -> o.getDescription())
    .orElse("")

above is to check to hierarchy of a object so simply use

Optional.ofNullable(object1) 

if you have only one object to check

Hope this helps !!!!

Mapping a JDBC ResultSet to an object

Let's assume you want to use core Java, w/o any strategic frameworks. If you can guarantee, that field name of an entity will be equal to the column in database, you can use Reflection API (otherwise create annotation and define mapping name there)

By FieldName

/**

Class<T> clazz - a list of object types you want to be fetched
ResultSet resultSet - pointer to your retrieved results 

*/

    List<Field> fields = Arrays.asList(clazz.getDeclaredFields());
    for(Field field: fields) {
        field.setAccessible(true);
    }

    List<T> list = new ArrayList<>(); 
    while(resultSet.next()) {

        T dto = clazz.getConstructor().newInstance();

        for(Field field: fields) {
            String name = field.getName();

            try{
                String value = resultSet.getString(name);
                field.set(dto, field.getType().getConstructor(String.class).newInstance(value));
            } catch (Exception e) {
                e.printStackTrace();
            }

        }

        list.add(dto);

    }

By annotation

@Retention(RetentionPolicy.RUNTIME)
public @interface Col {

    String name();
}

DTO:

class SomeClass {

   @Col(name = "column_in_db_name")
   private String columnInDbName;

   public SomeClass() {}

   // ..

}

Same, but

    while(resultSet.next()) {

        T dto = clazz.getConstructor().newInstance();

        for(Field field: fields) {
            Col col = field.getAnnotation(Col.class);
            if(col!=null) {
                String name = col.name();
                try{
                    String value = resultSet.getString(name);
                    field.set(dto, field.getType().getConstructor(String.class).newInstance(value));
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        list.add(dto);

    }

Thoughts

In fact, iterating over all Fields might seem ineffective, so I would store mapping somewhere, rather than iterating each time. However, if our T is a DTO with only purpose of transferring data and won't contain loads of unnecessary fields, that's ok. In the end it's much better than using boilerplate methods all the way.

Hope this helps someone.

Rounding a double to turn it into an int (java)

public static int round(double d) {
    if (d > 0) {
        return (int) (d + 0.5);
    } else {
        return (int) (d - 0.5);
    }
}

Getting java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory exception

Two options (at least):

  1. Add the commons-logging jar to your file by copying it into a local folder.

Note: linking the jar can lead to problems with the server and maybe the reason why it's added to the build path but not solving the server startup problem.

So don't point the jar to an external folder.

OR...

  1. If you really don't want to add it locally because you're sharing the jar between projects, then...

If you're using a tc server instance, then you need to add the jar as an external jar to the server instance run configurations.

go to run as, run configurations..., {your tc server instance}, and then the Class Path tab.

Then add the commons-logging jar.

Android : How to read file in bytes?

here it's a simple:

File file = new File(path);
int size = (int) file.length();
byte[] bytes = new byte[size];
try {
    BufferedInputStream buf = new BufferedInputStream(new FileInputStream(file));
    buf.read(bytes, 0, bytes.length);
    buf.close();
} catch (FileNotFoundException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

Add permission in manifest.xml:

 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

How to install JDK 11 under Ubuntu?

In Ubuntu, you can simply install Open JDK by following commands.

sudo apt-get update    
sudo apt-get install default-jdk

You can check the java version by following the command.

java -version

If you want to install Oracle JDK 8 follow the below commands.

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer

If you want to switch java versions you can try below methods.

vi ~/.bashrc and add the following line export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_221 (path/jdk folder)

or

sudo vi /etc/profile and add the following lines

#JAVA_HOME=/usr/lib/jvm/jdk1.8.0_221
JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
export PATH=$JAVA_HOME/bin:$PATH
export JAVA_HOME
export JRE_HOME
export PATH

You can comment on the other version. This needs to sign out and sign back in to use. If you want to try it on the go you can type the below command in the same terminal. It'll only update the java version for a particular terminal.

source /etc/profile

You can always check the java version by java -version command.

java.net.SocketTimeoutException: Read timed out under Tomcat

I had the same problem while trying to read the data from the request body. In my case which occurs randomly only to the mobile-based client devices. So I have increased the connectionUploadTimeout to 1min as suggested by this link

What is System, out, println in System.out.println() in Java

System is a final class from the java.lang package.

out is a class variable of type PrintStream declared in the System class.

println is a method of the PrintStream class.

Spring JPA and persistence.xml

I'm confused. You're injecting a PU into the service layer and not the persistence layer? I don't get that.

I inject the persistence layer into the service layer. The service layer contains business logic and demarcates transaction boundaries. It can include more than one DAO in a transaction.

I don't get the magic in your save() method either. How is the data saved?

In production I configure spring like this:

<jee:jndi-lookup id="entityManagerFactory" jndi-name="persistence/ThePUname" />

along with the reference in web.xml

For unit testing I do this:

<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
    p:dataSource-ref="dataSource" p:persistence-xml-location="classpath*:META-INF/test-persistence.xml"
    p:persistence-unit-name="RealPUName" p:jpaDialect-ref="jpaDialect"
    p:jpaVendorAdapter-ref="jpaVendorAdapter" p:loadTimeWeaver-ref="weaver">
</bean>

How can I print to the same line?

Format your string like so:

[#                    ] 1%\r

Note the \r character. It is the so-called carriage return that will move the cursor back to the beginning of the line.

Finally, make sure you use

System.out.print()

and not

System.out.println()

IntelliJ - Convert a Java project/module into a Maven project/module

  1. Open 'Maven projects' (tab on the right side).
  2. Use 'Add Maven Projects'
  3. Find your pom.xml

How to send HTTP request in java?

Apache HttpComponents. The examples for the two modules - HttpCore and HttpClient will get you started right away.

Not that HttpUrlConnection is a bad choice, HttpComponents will abstract a lot of the tedious coding away. I would recommend this, if you really want to support a lot of HTTP servers/clients with minimum code. By the way, HttpCore could be used for applications (clients or servers) with minimum functionality, whereas HttpClient is to be used for clients that require support for multiple authentication schemes, cookie support etc.

Convert string to float?

Try this:

String numberStr = "3.5";
Float number = null;
try {
   number = Float.parseFloat(numberStr);
} catch (NumberFormatException e) {
    System.out.println("numberStr is not a number");
}

Maven won't run my Project : Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:exec

Had the same problem, I worked around it by changing ${java.home}/../bin/javafxpackager to ${java.home}/bin/javafxpackager

ArrayList insertion and retrieval order

Yes, it will always be the same. From the documentation

Appends the specified element to the end of this list. Parameters: e element to be appended to this list Returns: true (as specified by Collection.add(java.lang.Object))

ArrayList add() implementation

public boolean More ...add(E e) {
    ensureCapacity(size + 1);  // Increments modCount!!
    elementData[size++] = e;
    return true;
}

getting the difference between date in days in java

Calendar start = Calendar.getInstance();
Calendar end = Calendar.getInstance();
start.set(2010, 7, 23);
end.set(2010, 8, 26);
Date startDate = start.getTime();
Date endDate = end.getTime();
long startTime = startDate.getTime();
long endTime = endDate.getTime();
long diffTime = endTime - startTime;
long diffDays = diffTime / (1000 * 60 * 60 * 24);
DateFormat dateFormat = DateFormat.getDateInstance();
System.out.println("The difference between "+
  dateFormat.format(startDate)+" and "+
  dateFormat.format(endDate)+" is "+
  diffDays+" days.");

This will not work when crossing daylight savings time (or leap seconds) as orange80 pointed out and might as well not give the expected results when using different times of day. Using JodaTime might be easier for correct results, as the only correct way with plain Java before 8 I know is to use Calendar's add and before/after methods to check and adjust the calculation:

start.add(Calendar.DAY_OF_MONTH, (int)diffDays);
while (start.before(end)) {
    start.add(Calendar.DAY_OF_MONTH, 1);
    diffDays++;
}
while (start.after(end)) {
    start.add(Calendar.DAY_OF_MONTH, -1);
    diffDays--;
}

What is the difference between persist() and merge() in JPA and Hibernate?

This is coming from JPA. In a very simple way:

  • persist(entity) should be used with totally new entities, to add them to DB (if entity already exists in DB there will be EntityExistsException throw).

  • merge(entity) should be used, to put entity back to persistence context if the entity was detached and was changed.

Static Vs. Dynamic Binding in Java

The compiler only knows that the type of "a" is Animal; this happens at compile time, because of which it is called static binding (Method overloading). But if it is dynamic binding then it would call the Dog class method. Here is an example of dynamic binding.

public class DynamicBindingTest {

    public static void main(String args[]) {
        Animal a= new Dog(); //here Type is Animal but object will be Dog
        a.eat();       //Dog's eat called because eat() is overridden method
    }
}

class Animal {

    public void eat() {
        System.out.println("Inside eat method of Animal");
    }
}

class Dog extends Animal {

    @Override
    public void eat() {
        System.out.println("Inside eat method of Dog");
    }
}

Output: Inside eat method of Dog

how to convert image to byte array in java?

Here is a complete version of code for doing this. I have tested it. The BufferedImage and Base64 class do the trick mainly. Also some parameter needs to be set correctly.

public class SimpleConvertImage {
    public static void main(String[] args) throws IOException{
        String dirName="C:\\";
        ByteArrayOutputStream baos=new ByteArrayOutputStream(1000);
        BufferedImage img=ImageIO.read(new File(dirName,"rose.jpg"));
        ImageIO.write(img, "jpg", baos);
        baos.flush();

        String base64String=Base64.encode(baos.toByteArray());
        baos.close();

        byte[] bytearray = Base64.decode(base64String);

        BufferedImage imag=ImageIO.read(new ByteArrayInputStream(bytearray));
        ImageIO.write(imag, "jpg", new File(dirName,"snap.jpg"));
    }
}

Reference link

IO Error: The Network Adapter could not establish the connection

In my case, I needed to specify a viahost and viauser. Worth trying if you're in a complex system. :)

How to redirect in a servlet filter?

In Filter the response is of ServletResponse rather than HttpServletResponse. Hence do the cast to HttpServletResponse.

HttpServletResponse httpResponse = (HttpServletResponse) response;
httpResponse.sendRedirect("/login.jsp");

If using a context path:

httpResponse.sendRedirect(req.getContextPath() + "/login.jsp");

Also don't forget to call return; at the end.

This compilation unit is not on the build path of a Java project

Go to Project-> right Click-> Select Properties -> project Facets -> modify the java version for your JDK version you are using.

Exact difference between CharSequence and String in java

CharSequence is a contract (interface), and String is an implementation of this contract.

public final class String extends Object 
    implements Serializable, Comparable<String>, CharSequence

The documentation for CharSequence is:

A CharSequence is a readable sequence of char values. This interface provides uniform, read-only access to many different kinds of char sequences. A char value represents a character in the Basic Multilingual Plane (BMP) or a surrogate. Refer to Unicode Character Representation for details.

How to read an external properties file in Maven

This answer to a similar question describes how to extend the properties plugin so it can use a remote descriptor for the properties file. The descriptor is basically a jar artifact containing a properties file (the properties file is included under src/main/resources).

The descriptor is added as a dependency to the extended properties plugin so it is on the plugin's classpath. The plugin will search the classpath for the properties file, read the file''s contents into a Properties instance, and apply those properties to the project's configuration so they can be used elsewhere.

How to blur background images in Android

you can use Glide for load and transform into blur image, 1) for only one view,

val requestOptions = RequestOptions()
                requestOptions.transform(BlurTransformation(50)) // 0-100
Glide.with(applicationContext).setDefaultRequestOptions(requestOptions)
                        .load(imageUrl).into(view)

2) if you are using the adapter to load an image in the item, you should write your code in the if-else block, otherwise, it will make all your images blurry.

 if(isBlure){
  val requestOptions = RequestOptions()
                requestOptions.transform(BlurTransformation(50))
                Glide.with(applicationContext).setDefaultRequestOptions(requestOptions)
                        .load(imageUrl).into(view )
}else{
 val requestOptions = RequestOptions()
            Glide.with(applicationContext).setDefaultRequestOptions(requestOptions).load(imageUrl).into(view)
}

Parse JSON file using GSON

One thing that to be remembered while solving such problems is that in JSON file, a { indicates a JSONObject and a [ indicates JSONArray. If one could manage them properly, it would be very easy to accomplish the task of parsing the JSON file. The above code was really very helpful for me and I hope this content adds some meaning to the above code.

The Gson JsonReader documentation explains how to handle parsing of JsonObjects and JsonArrays:

  • Within array handling methods, first call beginArray() to consume the array's opening bracket. Then create a while loop that accumulates values, terminating when hasNext() is false. Finally, read the array's closing bracket by calling endArray().
  • Within object handling methods, first call beginObject() to consume the object's opening brace. Then create a while loop that assigns values to local variables based on their name. This loop should terminate when hasNext() is false. Finally, read the object's closing brace by calling endObject().

Java ArrayList how to add elements at the beginning

import java.util.*:
public class Logic {
  List<String> list = new ArrayList<String>();
  public static void main(String...args) {
  Scanner input = new Scanner(System.in);
    Logic obj = new Logic();
      for (int i=0;i<=20;i++) {
        String string = input.nextLine();
        obj.myLogic(string);
        obj.printList();
      }
 }
 public void myLogic(String strObj) {
   if (this.list.size()>=10) {
      this.list.remove(this.list.size()-1);
   } else {
     list.add(strObj); 
   }
 }
 public void printList() {
 System.out.print(this.list);
 }
}

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.testing.models.Account

Solve problem with two method parse common

  1. Whith type is an object
public <T> T jsonToObject(String json, Class<T> type) {
        T target = null;
        try {
            target = objectMapper.readValue(json, type);
        } catch (Jsenter code hereonProcessingException e) {
            e.printStackTrace();
        }
    
        return target;
    }
  1. With type is collection wrap object
public <T> T jsonToObject(String json, TypeReference<T> type) {
    T target = null;
    try {
        target = objectMapper.readValue(json, type);
    } catch (JsonProcessingException e) {
        e.printStackTrace();
    }
    return target;
}

What is PECS (Producer Extends Consumer Super)?

In a nutshell, three easy rules to remember PECS:

  1. Use the <? extends T> wildcard if you need to retrieve object of type T from a collection.
  2. Use the <? super T> wildcard if you need to put objects of type T in a collection.
  3. If you need to satisfy both things, well, don’t use any wildcard. As simple as that.

Make the console wait for a user input to close

The problem with Java console input is that it's buffered input, and requires an enter key to continue.

There are these two discussions: Detecting and acting on keyboard direction keys in Java and Java keyboard input parsing in a console app

The latter of which used JLine to get his problem solved.

I personally haven't used it.

What is the main difference between Collection and Collections in Java?

collection is an interface and it is a root interface for all classes and interfaces like set,list and map.........and all the interfaces can implement collection interface.

Collections is a class that can also implements collection interface.......

Method has the same erasure as another method in type

The problem is that Set<Integer> and Set<String> are actually treated as a Set from the JVM. Selecting a type for the Set (String or Integer in your case) is only syntactic sugar used by the compiler. The JVM can't distinguish between Set<String> and Set<Integer>.

Select an Option from the Right-Click Menu in Selenium Webdriver - Java

Better and easy way.

Actions action = new Actions(driver);
action.moveToElement(driver.findElement(By.cssSelector("a[href^='https://www.amazon.in/ap/signin']"))).contextClick().build().perform();

You can use any selector at the place of cssSelector.

Removing whitespace from strings in Java

When using st.replaceAll("\\s+","") in Kotlin, make sure you wrap "\\s+" with Regex:

"myString".replace(Regex("\\s+"), "")

How do I convert the date from one format to another date object in another format without using any deprecated classes?

  private String formatDate(String date, String inputFormat, String outputFormat) {

    String newDate;
    DateFormat inputDateFormat = new SimpleDateFormat(inputFormat);
    inputDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
    DateFormat outputDateFormat = new SimpleDateFormat(outputFormat);
    try {
        newDate = outputDateFormat.format((inputDateFormat.parse(date)));
    } catch (Exception e) {
        newDate = "";
    }
    return newDate;

}

Ignore self-signed ssl cert using Jersey Client

This code will only ever be run against test servers so I don't want to go to the hassle of adding new trusted certs each time we set up a new test server.

This is the kind of code that will eventually find its way in production (if not from you, someone else who's reading this question will copy and paste the insecure trust managers that have been suggested into their applications). It's just so easy to forget to remove this sort of code when you have a deadline, since it doesn't show up as a problem.

If you're worried about having to add new certificates every time you have a test server, create your own little CA, issue all the certificates for the test servers using that CA and import this CA certificate into your client trust store. (Even if you don't deal with things like online certificate revocation in a local environment, this is certainly better than using a trust manager that lets anything through.)

There are tools to help you do this, for example TinyCA or XCA.

Check if int is between two numbers

One problem is that a ternary relational construct would introduce serious parser problems:

<expr> ::= <expr> <rel-op> <expr> |
           ... |
           <expr> <rel-op> <expr> <rel-op> <expr>

When you try to express a grammar with those productions using a typical PGS, you'll find that there is a shift-reduce conflict at the point of the first <rel-op>. The parse needs to lookahead an arbitrary number of symbols to see if there is a second <rel-op> before it can decide whether the binary or ternary form has been used. In this case, you could not simply ignore the conflict because that would result in incorrect parses.

I'm not saying that this grammar is fatally ambiguous. But I think you'd need a backtracking parser to deal with it correctly. And that is a serious problem for a programming language where fast compilation is a major selling point.

Maven version with a property

If you have a parent project you can set the version in the parent pom and in the children you can reference sibling libs with the ${project.version} or ${version} properties.

If you want to avoid to repeat the version of the parent in each children: you can do this:

<modelVersion>4.0.0</modelVersion>
<groupId>company</groupId>
<artifactId>build.parent</artifactId>
<version>${my.version}</version>
<packaging>pom</packaging>

<properties>
<my.version>1.1.2-SNAPSHOT</my.version>
</properties>

And then in your children pom you have to do:

    <parent>
      <artifactId>build.parent</artifactId>
      <groupId>company</groupId>
      <relativePath>../build.parent/pom.xml</relativePath>
      <version>${my.version}</version>
    </parent>

    <modelVersion>4.0.0</modelVersion>
    <groupId>company</groupId>
    <artifactId>artifact</artifactId>
    <packaging>eclipse-plugin</packaging>

    <dependencies>
        <dependency> 
           <groupId>company</groupId>
           <artifactId>otherartifact</artifactId>   
           <version>${my.version}</version>
or
           <version>${project.version}</version>
        </dependency>
    </dependencies>

hth

How to create a HashMap with two keys (Key-Pair, Value)?

Use a Pair as keys for the HashMap. JDK has no Pair, but you can either use a 3rd party libraray such as http://commons.apache.org/lang or write a Pair taype of your own.

Reading Data From Database and storing in Array List object

Create CustomerDTO Object every time inside while loop

Check the below code

    while (rs.next()) {

    Customer customer = new Customer();

    customer.setId(rs.getInt("id"));
    customer.setName(rs.getString("name"));
    customer.setAddress(rs.getString("address"));
    customer.setPhone(rs.getString("phone"));
    customer.setEmail(rs.getString("email"));
    customer.setBountPoints(rs.getInt("bonuspoint"));
    customer.setTotalsale(rs.getInt("totalsale"));

    customers.add(customer);
}

ArrayList of int array in java

Integer is wrapper class and int is primitive data type.Always prefer using Integer in ArrayList.

Java 11 package javax.xml.bind does not exist

According to the release-notes, Java 11 removed the Java EE modules:

java.xml.bind (JAXB) - REMOVED
  • Java 8 - OK
  • Java 9 - DEPRECATED
  • Java 10 - DEPRECATED
  • Java 11 - REMOVED

See JEP 320 for more info.

You can fix the issue by using alternate versions of the Java EE technologies. Simply add Maven dependencies that contain the classes you need:

<dependency>
  <groupId>javax.xml.bind</groupId>
  <artifactId>jaxb-api</artifactId>
  <version>2.3.0</version>
</dependency>
<dependency>
  <groupId>com.sun.xml.bind</groupId>
  <artifactId>jaxb-core</artifactId>
  <version>2.3.0</version>
</dependency>
<dependency>
  <groupId>com.sun.xml.bind</groupId>
  <artifactId>jaxb-impl</artifactId>
  <version>2.3.0</version>
</dependency>

Jakarta EE 8 update (Mar 2020)

Instead of using old JAXB modules you can fix the issue by using Jakarta XML Binding from Jakarta EE 8:

<dependency>
  <groupId>jakarta.xml.bind</groupId>
  <artifactId>jakarta.xml.bind-api</artifactId>
  <version>2.3.3</version>
</dependency>
<dependency>
  <groupId>com.sun.xml.bind</groupId>
  <artifactId>jaxb-impl</artifactId>
  <version>2.3.3</version>
  <scope>runtime</scope>
</dependency>

Jakarta EE 9 update (Nov 2020)

Use latest release of Eclipse Implementation of JAXB 3.0.0:

<dependency>
  <groupId>jakarta.xml.bind</groupId>
  <artifactId>jakarta.xml.bind-api</artifactId>
  <version>3.0.0</version>
</dependency>
<dependency>
  <groupId>com.sun.xml.bind</groupId>
  <artifactId>jaxb-impl</artifactId>
  <version>3.0.0</version>
  <scope>runtime</scope>
</dependency>

Note: Jakarta EE 9 adopts new API package namespace jakarta.xml.bind.*, so update import statements:

javax.xml.bind -> jakarta.xml.bind

Get unicode value of a character

You can do it for any Java char using the one liner here:

System.out.println( "\\u" + Integer.toHexString('÷' | 0x10000).substring(1) );

But it's only going to work for the Unicode characters up to Unicode 3.0, which is why I precised you could do it for any Java char.

Because Java was designed way before Unicode 3.1 came and hence Java's char primitive is inadequate to represent Unicode 3.1 and up: there's not a "one Unicode character to one Java char" mapping anymore (instead a monstrous hack is used).

So you really have to check your requirements here: do you need to support Java char or any possible Unicode character?

How do I discover memory usage of my application in Android?

This is a work in progress, but this is what I don't understand:

ActivityManager activityManager = (ActivityManager) context.getSystemService(ACTIVITY_SERVICE);
MemoryInfo memoryInfo = new ActivityManager.MemoryInfo();
activityManager.getMemoryInfo(memoryInfo);

Log.i(TAG, " memoryInfo.availMem " + memoryInfo.availMem + "\n" );
Log.i(TAG, " memoryInfo.lowMemory " + memoryInfo.lowMemory + "\n" );
Log.i(TAG, " memoryInfo.threshold " + memoryInfo.threshold + "\n" );

List<RunningAppProcessInfo> runningAppProcesses = activityManager.getRunningAppProcesses();

Map<Integer, String> pidMap = new TreeMap<Integer, String>();
for (RunningAppProcessInfo runningAppProcessInfo : runningAppProcesses)
{
    pidMap.put(runningAppProcessInfo.pid, runningAppProcessInfo.processName);
}

Collection<Integer> keys = pidMap.keySet();

for(int key : keys)
{
    int pids[] = new int[1];
    pids[0] = key;
    android.os.Debug.MemoryInfo[] memoryInfoArray = activityManager.getProcessMemoryInfo(pids);
    for(android.os.Debug.MemoryInfo pidMemoryInfo: memoryInfoArray)
    {
        Log.i(TAG, String.format("** MEMINFO in pid %d [%s] **\n",pids[0],pidMap.get(pids[0])));
        Log.i(TAG, " pidMemoryInfo.getTotalPrivateDirty(): " + pidMemoryInfo.getTotalPrivateDirty() + "\n");
        Log.i(TAG, " pidMemoryInfo.getTotalPss(): " + pidMemoryInfo.getTotalPss() + "\n");
        Log.i(TAG, " pidMemoryInfo.getTotalSharedDirty(): " + pidMemoryInfo.getTotalSharedDirty() + "\n");
    }
}

Why isn't the PID mapped to the result in activityManager.getProcessMemoryInfo()? Clearly you want to make the resulting data meaningful, so why has Google made it so difficult to correlate the results? The current system doesn't even work well if I want to process the entire memory usage since the returned result is an array of android.os.Debug.MemoryInfo objects, but none of those objects actually tell you what pids they are associated with. If you simply pass in an array of all pids, you will have no way to understand the results. As I understand it's use, it makes it meaningless to pass in more than one pid at a time, and then if that's the case, why make it so that activityManager.getProcessMemoryInfo() only takes an int array?

How to escape comma and double quote at same time for CSV file?

You could also look at how Python writes Excel-compatible csv files.

I believe the default for Excel is to double-up for literal quote characters - that is, literal quotes " are written as "".

How to find the maximum value in an array?

If you can change the order of the elements:

 int[] myArray = new int[]{1, 3, 8, 5, 7, };
 Arrays.sort(myArray);
 int max = myArray[myArray.length - 1];

If you can't change the order of the elements:

int[] myArray = new int[]{1, 3, 8, 5, 7, };
int max = Integer.MIN_VALUE;
for(int i = 0; i < myArray.length; i++) {
      if(myArray[i] > max) {
         max = myArray[i];
      }
}

Array Length in Java

It will contain the actual size of the array as that is what you initialized the array to be when you declared it. Java has no concept of the "logical" size of an array, as far as it is concerned the default value of 0 is just as logical as the values you have manually set.

Java time-based map/cache with expiring keys

Typically, a cache should keep objects around some time and shall expose of them some time later. What is a good time to hold an object depends on the use case. I wanted this thing to be simple, no threads or schedulers. This approach works for me. Unlike SoftReferences, objects are guaranteed to be available some minimum amount of time. However, the do not stay around in memory until the sun turns into a red giant.

As useage example think of a slowly responding system that shall be able to check if a request has been done quite recently, and in that case not to perform the requested action twice, even if a hectic user hits the button several times. But, if the same action is requested some time later, it shall be performed again.

class Cache<T> {
    long avg, count, created, max, min;
    Map<T, Long> map = new HashMap<T, Long>();

    /**
     * @param min   minimal time [ns] to hold an object
     * @param max   maximal time [ns] to hold an object
     */
    Cache(long min, long max) {
        created = System.nanoTime();
        this.min = min;
        this.max = max;
        avg = (min + max) / 2;
    }

    boolean add(T e) {
        boolean result = map.put(e, Long.valueOf(System.nanoTime())) != null;
        onAccess();
        return result;
    }

    boolean contains(Object o) {
        boolean result = map.containsKey(o);
        onAccess();
        return result;
    }

    private void onAccess() {
        count++;
        long now = System.nanoTime();
        for (Iterator<Entry<T, Long>> it = map.entrySet().iterator(); it.hasNext();) {
            long t = it.next().getValue();
            if (now > t + min && (now > t + max || now + (now - created) / count > t + avg)) {
                it.remove();
            }
        }
    }
}

How to cast ArrayList<> from List<>

You can cast List<> to ArrayList<> if you understand what you doing. Java compiler won't block it.

But:

  1. It's bad practice to casting parent type to child type (or interface to implementation type) without checking. This way better:

if (list instanceof ArrayList<Task>) { ArrayList<Task> arraylist = (ArrayList<Task>) list; }

  1. Maybe you don't need implementation type as reference. Look SonarQube warning https://sbforge.org/sonar/rules/show/squid:S1319. You can avoid this casting in the most cases.
  2. You can use Guava method: ArrayList<Task> arraylist = Lists.newArrayList(list);

Java 8 Lambda filter by Lists

Look this:

List<Client> result = clients
    .stream()
    .filter(c -> 
        (users.stream().map(User::getName).collect(Collectors.toList())).contains(c.getName()))
        .collect(Collectors.toList());

How do I find out my MySQL URL, host, port and username?

mysql> SHOW VARIABLES WHERE Variable_name = 'hostname';
+---------------+-----------+
| Variable_name | Value     |
+---------------+-----------+
| hostname      | karola-pc |
+---------------+-----------+
1 row in set (0.00 sec)

For Example in my case : karola-pc is the host name of the box where my mysql is running. And it my local PC host name.

If it is romote box than you can ping that host directly if, If you are in network with that box you should be able to ping that host.

If it UNIX or Linux you can run "hostname" command in terminal to check the host name. if it is windows you can see same value in MyComputer-> right click -> properties ->Computer Name you can see ( i.e System Properties)

Hope it will answer your Q.

getting JRE system library unbound error in build path

I too faced the same issue. I followed the following steps to resolve my issue -

  • Right click on your project -> Properties
  • Select Java Build Path in the left menu
  • Select Libraries tab
  • Under the module path, select the troublesome JRE entry
  • Click on Edit button
  • Select Workspace default JRE.
  • Click on Finish button

If the above steps don't work for you, instead of Workspace default JRE, you can choose an Alternate JRE and give the path to the JRE that you want to point.

How to resize JLabel ImageIcon?

And what about it?:

ImageIcon imageIcon = new ImageIcon(new ImageIcon("icon.png").getImage().getScaledInstance(20, 20, Image.SCALE_DEFAULT));
label.setIcon(imageIcon);

From: Resize a picture to fit a JLabel

JSONObject - How to get a value?

String loudScreaming = json.getJSONObject("LabelData").getString("slogan");

Scanner doesn't read whole sentence - difference between next() and nextLine() of scanner class

I had the same question. This should work for you:

s.nextLine();

Android - how to replace part of a string by another string?

rekaszeru

I noticed that you commented in 2011 but i thought i should post this answer anyway, in case anyone needs to "replace the original string" and runs into this answer ..

Im using a EditText as an example


// GIVE TARGET TEXT BOX A NAME

 EditText textbox = (EditText) findViewById(R.id.your_textboxID);

// STRING TO REPLACE

 String oldText = "hello"
 String newText = "Hi";      
 String textBoxText = textbox.getText().toString();

// REPLACE STRINGS WITH RETURNED STRINGS

String returnedString = textBoxText.replace( oldText, newText );

// USE RETURNED STRINGS TO REPLACE NEW STRING INSIDE TEXTBOX

textbox.setText(returnedString);

This is untested, but it's just an example of using the returned string to replace the original layouts string with setText() !

Obviously this example requires that you have a EditText with the ID set to your_textboxID

How can I calculate the difference between two ArrayLists?

Although this is a very old question in Java 8 you could do something like

 List<String> a1 = Arrays.asList("2009-05-18", "2009-05-19", "2009-05-21");
 List<String> a2 = Arrays.asList("2009-05-18", "2009-05-18", "2009-05-19", "2009-05-19", "2009-05-20", "2009-05-21","2009-05-21", "2009-05-22");

 List<String> result = a2.stream().filter(elem -> !a1.contains(elem)).collect(Collectors.toList());

What is a daemon thread in Java?

Traditionally daemon processes in UNIX were those that were constantly running in background, much like services in Windows.

A daemon thread in Java is one that doesn't prevent the JVM from exiting. Specifically the JVM will exit when only daemon threads remain. You create one by calling the setDaemon() method on Thread.

Have a read of Daemon threads.

Rest-assured. Is it possible to extract value from request json?

To serialize the response into a class, define the target class

public class Result {
    public Long user_id;
}

And map response to it:

Response response = given().body(requestBody).when().post("/admin");
Result result = response.as(Result.class);

You must have Jackson or Gson in the classpath as the documentation states: http://rest-assured.googlecode.com/svn/tags/2.3.1/apidocs/com/jayway/restassured/response/ResponseBodyExtractionOptions.html#as(java.lang.Class)

Eclipse JUnit - possible causes of seeing "initializationError" in Eclipse window

I received this error when the class was annotated with @Ignore and I tried to run a specific test via right clicking on it. Removing the @Ignore fixed the problem.

how to run a command at terminal from java program?

I know this question is quite old, but here's a library that encapsulates the ProcessBuilder api.

What is the difference between JSF, Servlet and JSP?

JSP (JavaServer Pages)

JSP is a Java view technology running on the server machine which allows you to write template text in client side languages (like HTML, CSS, JavaScript, ect.). JSP supports taglibs, which are backed by pieces of Java code that let you control the page flow or output dynamically. A well-known taglib is JSTL. JSP also supports Expression Language, which can be used to access backend data (via attributes available in the page, request, session and application scopes), mostly in combination with taglibs.

When a JSP is requested for the first time or when the web app starts up, the servlet container will compile it into a class extending HttpServlet and use it during the web app's lifetime. You can find the generated source code in the server's work directory. In for example Tomcat, it's the /work directory. On a JSP request, the servlet container will execute the compiled JSP class and send the generated output (usually just HTML/CSS/JS) through the web server over a network to the client side, which in turn displays it in the web browser.

Servlets

Servlet is a Java application programming interface (API) running on the server machine, which intercepts requests made by the client and generates/sends a response. A well-known example is the HttpServlet which provides methods to hook on HTTP requests using the popular HTTP methods such as GET and POST. You can configure HttpServlets to listen to a certain HTTP URL pattern, which is configurable in web.xml, or more recently with Java EE 6, with @WebServlet annotation.

When a Servlet is first requested or during web app startup, the servlet container will create an instance of it and keep it in memory during the web app's lifetime. The same instance will be reused for every incoming request whose URL matches the servlet's URL pattern. You can access the request data by HttpServletRequest and handle the response by HttpServletResponse. Both objects are available as method arguments inside any of the overridden methods of HttpServlet, such as doGet() and doPost().

JSF (JavaServer Faces)

JSF is a component based MVC framework which is built on top of the Servlet API and provides components via taglibs which can be used in JSP or any other Java based view technology such as Facelets. Facelets is much more suited to JSF than JSP. It namely provides great templating capabilities such as composite components, while JSP basically only offers the <jsp:include> for templating in JSF, so that you're forced to create custom components with raw Java code (which is a bit opaque and a lot of tedious work) when you want to replace a repeated group of components with a single component. Since JSF 2.0, JSP has been deprecated as view technology in favor of Facelets.

Note: JSP itself is NOT deprecated, just the combination of JSF with JSP is deprecated.

Note: JSP has great templating abilities by means of Taglibs, especially the (Tag File) variant. JSP templating in combination with JSF is what is lacking.

As being a MVC (Model-View-Controller) framework, JSF provides the FacesServlet as the sole request-response Controller. It takes all the standard and tedious HTTP request/response work from your hands, such as gathering user input, validating/converting them, putting them in model objects, invoking actions and rendering the response. This way you end up with basically a JSP or Facelets (XHTML) page for View and a JavaBean class as Model. The JSF components are used to bind the view with the model (such as your ASP.NET web control does) and the FacesServlet uses the JSF component tree to do all the work.

Related questions

Where to get "UTF-8" string literal in Java?

Constant definitions for the standard. These charsets are guaranteed to be available on every implementation of the Java platform. since 1.7

 package java.nio.charset;
 Charset utf8 = StandardCharsets.UTF_8;

How do I add one month to current date in Java?

Java 8

LocalDate futureDate = LocalDate.now().plusMonths(1);

Preferred Java way to ping an HTTP URL for availability

Is this any good at all (will it do what I want?)

You can do so. Another feasible way is using java.net.Socket.

public static boolean pingHost(String host, int port, int timeout) {
    try (Socket socket = new Socket()) {
        socket.connect(new InetSocketAddress(host, port), timeout);
        return true;
    } catch (IOException e) {
        return false; // Either timeout or unreachable or failed DNS lookup.
    }
}

There's also the InetAddress#isReachable():

boolean reachable = InetAddress.getByName(hostname).isReachable();

This however doesn't explicitly test port 80. You risk to get false negatives due to a Firewall blocking other ports.


Do I have to somehow close the connection?

No, you don't explicitly need. It's handled and pooled under the hoods.


I suppose this is a GET request. Is there a way to send HEAD instead?

You can cast the obtained URLConnection to HttpURLConnection and then use setRequestMethod() to set the request method. However, you need to take into account that some poor webapps or homegrown servers may return HTTP 405 error for a HEAD (i.e. not available, not implemented, not allowed) while a GET works perfectly fine. Using GET is more reliable in case you intend to verify links/resources not domains/hosts.


Testing the server for availability is not enough in my case, I need to test the URL (the webapp may not be deployed)

Indeed, connecting a host only informs if the host is available, not if the content is available. It can as good happen that a webserver has started without problems, but the webapp failed to deploy during server's start. This will however usually not cause the entire server to go down. You can determine that by checking if the HTTP response code is 200.

HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
connection.setRequestMethod("HEAD");
int responseCode = connection.getResponseCode();
if (responseCode != 200) {
    // Not OK.
}

// < 100 is undetermined.
// 1nn is informal (shouldn't happen on a GET/HEAD)
// 2nn is success
// 3nn is redirect
// 4nn is client error
// 5nn is server error

For more detail about response status codes see RFC 2616 section 10. Calling connect() is by the way not needed if you're determining the response data. It will implicitly connect.

For future reference, here's a complete example in flavor of an utility method, also taking account with timeouts:

/**
 * Pings a HTTP URL. This effectively sends a HEAD request and returns <code>true</code> if the response code is in 
 * the 200-399 range.
 * @param url The HTTP URL to be pinged.
 * @param timeout The timeout in millis for both the connection timeout and the response read timeout. Note that
 * the total timeout is effectively two times the given timeout.
 * @return <code>true</code> if the given HTTP URL has returned response code 200-399 on a HEAD request within the
 * given timeout, otherwise <code>false</code>.
 */
public static boolean pingURL(String url, int timeout) {
    url = url.replaceFirst("^https", "http"); // Otherwise an exception may be thrown on invalid SSL certificates.

    try {
        HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
        connection.setConnectTimeout(timeout);
        connection.setReadTimeout(timeout);
        connection.setRequestMethod("HEAD");
        int responseCode = connection.getResponseCode();
        return (200 <= responseCode && responseCode <= 399);
    } catch (IOException exception) {
        return false;
    }
}

RestTemplate: How to send URL and query parameters together

One-liner using TestRestTemplate.exchange function with parameters map.

restTemplate.exchange("/someUrl?id={id}", HttpMethod.GET, reqEntity, respType, ["id": id])

The params map initialized like this is a groovy initializer*

Using JAXB to unmarshal/marshal a List<String>

I would've saved time if I found Resteasy Jackson Provider sooner.

Just add the Resteasy Jackson Provider JAR. No entity wrappers. No XML annotations. No custom message body writers.

How does the enhanced for statement work for arrays, and how to get an iterator for an array?

I'm a recent student but I BELIEVE the original example with int[] is iterating over the primitives array, but not by using an Iterator object. It merely has the same (similar) syntax with different contents,

for (primitive_type : array) { }

for (object_type : iterableObject) { }

Arrays.asList() APPARENTLY just applies List methods to an object array that it's given - but for any other kind of object, including a primitive array, iterator().next() APPARENTLY just hands you the reference to the original object, treating it as a list with one element. Can we see source code for this? Wouldn't you prefer an exception? Never mind. I guess (that's GUESS) that it's like (or it IS) a singleton Collection. So here asList() is irrelevant to the case with a primitives array, but confusing. I don't KNOW I'm right, but I wrote a program that says that I am.

Thus this example (where basically asList() doesn't do what you thought it would, and therefore is not something that you'd actually use this way) - I hope the code works better than my marking-as-code, and, hey, look at that last line:

// Java(TM) SE Runtime Environment (build 1.6.0_19-b04)

import java.util.*;

public class Page0434Ex00Ver07 {
public static void main(String[] args) {
    int[] ii = new int[4];
    ii[0] = 2;
    ii[1] = 3;
    ii[2] = 5;
    ii[3] = 7;

    Arrays.asList(ii);

    Iterator ai = Arrays.asList(ii).iterator();

    int[] i2 = (int[]) ai.next();

    for (int i : i2) {
        System.out.println(i);
    }

    System.out.println(Arrays.asList(12345678).iterator().next());
}
}

How print out the contents of a HashMap<String, String> in ascending order based on its values?

 SmartPhone[] sp=new SmartPhone[4];
 sp[0]=new SmartPhone(1,"HTC","desire","black",20000,10,true,true);
 sp[1]=new SmartPhone(2,"samsung","grand","black",5000,10,false,true);
 sp[2]=new SmartPhone(14,"google nexus","desire","black",2000,30,true,false);
 sp[3]=new SmartPhone(13,"HTC","desire","white",50000,40,false,false);

Java: splitting the filename into a base and extension

What's wrong with your code? Wrapped in a neat utility method it's fine.

What's more important is what to use as separator — the first or last dot. The first is bad for file names like "setup-2.5.1.exe", the last is bad for file names with multiple extensions like "mybundle.tar.gz".

What's the difference between getPath(), getAbsolutePath(), and getCanonicalPath() in Java?

I find I rarely have need to use getCanonicalPath() but, if given a File with a filename that is in DOS 8.3 format on Windows, such as the java.io.tmpdir System property returns, then this method will return the "full" filename.

Which comes first in a 2D array, rows or columns?

While Matt B's may be true in one sense, it may help to think of Java multidimensional array without thinking about geometeric matrices at all. Java multi-dim arrays are simply arrays of arrays, and each element of the first-"dimension" can be of different size from the other elements, or in fact can actually store a null "sub"-array. See comments under this question

Is the buildSessionFactory() Configuration method deprecated in Hibernate

Yes it is deprecated. Replace your SessionFactory with the following:

In Hibernate 4.0, 4.1, 4.2

private static SessionFactory sessionFactory;
private static ServiceRegistry serviceRegistry;

public static SessionFactory createSessionFactory() {
    Configuration configuration = new Configuration();
    configuration.configure();
    ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(
            configuration.getProperties()). buildServiceRegistry();
    sessionFactory = configuration.buildSessionFactory(serviceRegistry);
    return sessionFactory;
}

UPDATE:

In Hibernate 4.3 ServiceRegistryBuilder is deprecated. Use the following instead.

serviceRegistry = new StandardServiceRegistryBuilder().applySettings(
            configuration.getProperties()).build();

Installing Java on OS X 10.9 (Mavericks)

This error happens because the plist file of IntelliJ IDEA requires Java version 1.6*. To solve this problem, replace the 1.6* with 1.8*.

<key>JVMOptions</key>
<dict>
    <key>ClassPath</key>
      ...

    <key>JVMVersion</key>
    <string>1.8*</string>

    <key>MainClass</key>
    <string>com.intellij.idea.Main</string>
    <key>Properties</key>
<dict>

java.io.FileNotFoundException: /storage/emulated/0/New file.txt: open failed: EACCES (Permission denied)

If you are running in Android 29 then you have to use scoped storage or for now, you can bypass this issue by using:

android:requestLegacyExternalStorage="true"

in manifest in the application tag.

JUnit: how to avoid "no runnable methods" in test utils classes

To prevent JUnit from instantiating your test base class just make it

public abstract class MyTestBaseClass { ... whatever... }

(@Ignore reports it as ignored which I reserve for temporarily ignored tests.)

Encode String to UTF-8

String value = new String(myString.getBytes("UTF-8"));

and, if you want to read from text file with "ISO-8859-1" encoded:

String line;
String f = "C:\\MyPath\\MyFile.txt";
try {
    BufferedReader br = Files.newBufferedReader(Paths.get(f), Charset.forName("ISO-8859-1"));
    while ((line = br.readLine()) != null) {
        System.out.println(new String(line.getBytes("UTF-8")));
    }
} catch (IOException ex) {
    //...
}

Cleanest way to build an SQL string in Java

One technology you should consider is SQLJ - a way to embed SQL statements directly in Java. As a simple example, you might have the following in a file called TestQueries.sqlj:

public class TestQueries
{
    public String getUsername(int id)
    {
        String username;
        #sql
        {
            select username into :username
            from users
            where pkey = :id
        };
        return username;
    }
}

There is an additional precompile step which takes your .sqlj files and translates them into pure Java - in short, it looks for the special blocks delimited with

#sql
{
    ...
}

and turns them into JDBC calls. There are several key benefits to using SQLJ:

  • completely abstracts away the JDBC layer - programmers only need to think about Java and SQL
  • the translator can be made to check your queries for syntax etc. against the database at compile time
  • ability to directly bind Java variables in queries using the ":" prefix

There are implementations of the translator around for most of the major database vendors, so you should be able to find everything you need easily.

How to change the JDK for a Jenkins job?

Be careful with jobs

1 - if you have a job based in maven, Jenkins takes your default java configuration and you decide the compilation level in your POM.XML.

2 - if you have a free style job, in the the configuration option of the job you can select the JDK that you want to use.

Hope this help.

How to add 10 minutes to my (String) time?

You have a plenty of easy approaches within above answers. This is just another idea. You can convert it to millisecond and add the TimeZoneOffset and add / deduct the mins/hours/days etc by milliseconds.

String myTime = "14:10";
int minsToAdd = 10;
Date date = new Date();
date.setTime((((Integer.parseInt(myTime.split(":")[0]))*60 + (Integer.parseInt(myTime.split(":")[1])))+ date1.getTimezoneOffset())*60000);
System.out.println(date.getHours() + ":"+date.getMinutes());
date.setTime(date.getTime()+ minsToAdd *60000);
System.out.println(date.getHours() + ":"+date.getMinutes());

Output :

14:10
14:20

Error: unmappable character for encoding UTF8 during maven compilation

I came across this problem just now and ended up resolving it like so: I opened up the offending .java file in Notepad++ and from the Encoding menu I selected "Convert to UTF-8 without BOM". Saved. Re-ran maven, all went through ok.

If the offending resource was not encoded in UTF-8 - as you have configured for your maven compiler plugin - you would see in the Encoding menu of Np++ a bullet mark next to the file's current encoding (in my case I saw it was set to "Encode in ANSI").

So your maven compiler plugin invoked the Java compiler with the -encoding option set to UTF-8, but the compiler encountered a ANSI-encoded source file and reported this as an error. This used to be a warning previously in Java 5 but is treated as an error in Java 6+

RecyclerView onClick

Check out a similar question @CommonsWare's comment links to this, which implements the OnClickListener interface in the viewHolder.

Here's a simple example of the ViewHolder:

    TextView textView;//declare global with in adapter class

public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

      private ViewHolder(View itemView) {
            super(itemView);
            itemView.setOnClickListener(this);
            textView = (TextView)view.findViewById(android.R.id.text1);

      }

      @Override
      public void onClick(View view) {
            Toast.makeText(view.getContext(), "position = " + getLayoutPosition(), Toast.LENGTH_SHORT).show();

         //go through each item if you have few items within recycler view
        if(getLayoutPosition()==0){
           //Do whatever you want here

        }else if(getLayoutPosition()==1){ 
           //Do whatever you want here         

        }else if(getLayoutPosition()==2){

        }else if(getLayoutPosition()==3){

        }else if(getLayoutPosition()==4){

        }else if(getLayoutPosition()==5){

        }

        //or you can use For loop if you have long list of items. Use its length or size of the list as 
        for(int i = 0; i<exampleList.size(); i++){

        }


      }
  }

The Adapter then looks like this:

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view =LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1, parent, false);

        return new ViewHolder(view);
    }

How to stop the task scheduled in java.util.Timer class

Keep a reference to the timer somewhere, and use:

timer.cancel();
timer.purge();

to stop whatever it's doing. You could put this code inside the task you're performing with a static int to count the number of times you've gone around, e.g.

private static int count = 0;
public static void run() {
     count++;
     if (count >= 6) {
         timer.cancel();
         timer.purge();
         return;
     }

     ... perform task here ....

}

Is it possible to use Java 8 for Android development?

Yes, you can use Java 8 Language features in Android Studio but the version must be 3.0 or higher. Read this article for how to use java 8 features in the android studio.

https://bijay-budhathoki.blogspot.com/2020/01/use-java-8-language-features-in-android-studio.html

SQLException: No suitable Driver Found for jdbc:oracle:thin:@//localhost:1521/orcl

i have changed my old path: jdbc:odbc:thin:@localhost:1521:orcl

to new : jdbc:oracle:thin:@//localhost:1521/orcl

and it worked for me.....hurrah!! image

SAP Crystal Reports runtime for .Net 4.0 (64-bit)

I have found a variety of runtimes including Visual Studio(VS) versions are available at http://scn.sap.com/docs/DOC-7824

How do Python's any and all functions work?

The concept is simple:

M =[(1, 1), (5, 6), (0, 0)]

1) print([any(x) for x in M])
[True, True, False] #only the last tuple does not have any true element

2) print([all(x) for x in M])
[True, True, False] #all elements of the last tuple are not true

3) print([not all(x) for x in M])
[False, False, True] #NOT operator applied to 2)

4) print([any(x)  and not all(x) for x in M])
[False, False, False] #AND operator applied to 1) and 3)
# if we had M =[(1, 1), (5, 6), (1, 0)], we could get [False, False, True]  in 4)
# because the last tuple satisfies both conditions: any of its elements is TRUE 
#and not all elements are TRUE 

HashMap - getting First Key value

Java 8 way of doing,

String firstKey = map.keySet().stream().findFirst().get();

How to solve error "Missing `secret_key_base` for 'production' environment" (Rails 4.1)

What I did : On my production server, I create a config file (confthin.yml) for Thin (I'm using it) and add the following information :

environment: production
user: www-data
group: www-data
SECRET_KEY_BASE: mysecretkeyproduction

I then launch the app with

thin start -C /whereeveristhefieonprod/configthin.yml

Work like a charm and then no need to have the secret key on version control

Hope it could help, but I'm sure the same thing could be done with Unicorn and others.

How can I undo a `git commit` locally and on a remote after `git push`

Try using

git reset --hard <commit id> 

Please Note : Here commit id will the id of the commit you want to go to but not the id you want to reset. this was the only point where i also got stucked.

then push

git push -f <remote> <branch>

Display progress bar while doing some work in C#?

For me the easiest way is definitely to use a BackgroundWorker, which is specifically designed for this kind of task. The ProgressChanged event is perfectly fitted to update a progress bar, without worrying about cross-thread calls

How to install pandas from pip on windows cmd?

pip install pandas make sure, this is 'pandas' not 'panda'

If you are not able to access pip, then got to C:\Python37\Scripts and run pip.exe install pandas.

Alternatively, you can add C:\Python37\Scripts in the env variables for windows machines. Hope this helps.

Sum a list of numbers in Python

Generators are an easy way to write this:

from __future__ import division
# ^- so that 3/2 is 1.5 not 1

def averages( lst ):
    it = iter(lst) # Get a iterator over the list
    first = next(it)
    for item in it:
        yield (first+item)/2
        first = item

print list(averages(range(1,11)))
# [1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5]

change the date format in laravel view page

In Laravel 8 you can use the Date Casting: https://laravel.com/docs/8.x/eloquent-mutators#date-casting

In your Model just set:

protected $casts = [
    'my_custom_datetime_field' => 'datetime'
];

And then in your blade template you can use the format() method:

{{ $my_custom_datetime_field->format('d. m. Y') }}

multiple classes on single element html

Short Answer

Yes.


Explanation

It is a good practice since an element can be a part of different groups, and you may want specific elements to be a part of more than one group. The element can hold an infinite number of classes in HTML5, while in HTML4 you are limited by a specific length.

The following example will show you the use of multiple classes.

The first class makes the text color red.

The second class makes the background-color blue.

See how the DOM Element with multiple classes will behave, it will wear both CSS statements at the same time.

Result: multiple CSS statements in different classes will stack up.

You can read more about CSS Specificity.


CSS

.class1 {
    color:red;
}

.class2 {
    background-color:blue;
}

HTML

<div class="class1">text 1</div>
<div class="class2">text 2</div>
<div class="class1 class2">text 3</div>

Live demo

spring autowiring with unique beans: Spring expected single matching bean but found 2

If you have 2 beans of the same class autowired to one class you shoud use @Qualifier (Spring Autowiring @Qualifier example).

But it seems like your problem comes from incorrect Java Syntax.

Your object should start with lower case letter

SuggestionService suggestion;

Your setter should start with lower case as well and object name should be with Upper case

public void setSuggestion(final Suggestion suggestion) {
    this.suggestion = suggestion;
}

Copy or rsync command

For a local copy, the only advantage of rsync is that it will avoid copying if the file already exists in the destination directory. The definition of "already exists" is (a) same file name (b) same size (c) same timestamp. (Maybe same owner/group; I am not sure...)

The "rsync algorithm" is great for incremental updates of a file over a slow network link, but it will not buy you much for a local copy, as it needs to read the existing (partial) file to run it's "diff" computation.

So if you are running this sort of command frequently, and the set of changed files is small relative to the total number of files, you should find that rsync is faster than cp. (Also rsync has a --delete option that you might find useful.)

How to make the background DIV only transparent using CSS

Just do not include a background color for that div and it will be transparent.

How do I query for all dates greater than a certain date in SQL Server?

To sum it all up, the correct answer is :

select * from db where Date >= '20100401'  (Format of date yyyymmdd)

This will avoid any problem with other language systems and will use the index.

How to have multiple colors in a Windows batch file?

Several methods are covered in
"51} How can I echo lines in different colors in NT scripts?"
http://www.netikka.net/tsneti/info/tscmd051.htm

One of the alternatives: If you can get hold of QBASIC, using colors is relatively easy:

  @echo off & setlocal enableextensions
  for /f "tokens=*" %%f in ("%temp%") do set temp_=%%~sf
  set skip=
  findstr "'%skip%QB" "%~f0" > %temp_%\tmp$$$.bas
  qbasic /run %temp_%\tmp$$$.bas
  for %%f in (%temp_%\tmp$$$.bas) do if exist %%f del %%f
  endlocal & goto :EOF
  ::
  CLS 'QB
  COLOR 14,0 'QB
  PRINT "A simple "; 'QB
  COLOR 13,0 'QB
  PRINT "color "; 'QB
  COLOR 14,0 'QB
  PRINT "demonstration" 'QB
  PRINT "By Prof. (emer.) Timo Salmi" 'QB
  PRINT 'QB
  FOR j = 0 TO 7 'QB
    FOR i = 0 TO 15 'QB
      COLOR i, j 'QB
      PRINT LTRIM$(STR$(i)); " "; LTRIM$(STR$(j)); 'QB
      COLOR 1, 0 'QB
      PRINT " "; 'QB
    NEXT i 'QB
    PRINT 'QB
  NEXT j 'QB
  SYSTEM 'QB

Clicking a button within a form causes page refresh

You should declare the attribute ng-submit={expression} in your <form> tag.

From the ngSubmit docs http://docs.angularjs.org/api/ng.directive:ngSubmit

Enables binding angular expressions to onsubmit events.

Additionally it prevents the default action (which for form means sending the request to the server and reloading the current page).

Passing multiple values for a single parameter in Reporting Services

I'm new to the site, and couldn't figure how to comment on a previous answer, which is what I feel this should be. I also couldn't up vote Jeff's post, which I believe gave me my answer. Anyways...

While I can see how some of the great posts, and subsequent tweaks, work, I only have read access to the database, so no UDF, SP or view-based solutions work for me. So Ed Harper's solution looked good, except for VenkateswarluAvula's comment that you can not pass a comma-separated string as a parameter into an WHERE IN clause and expect it to work as you need. But Jeff's solution to the ORACLE 10g fills that gap. I put those together with Russell Christopher's blog post at http://blogs.msdn.com/b/bimusings/archive/2007/05/07/how-do-you-set-select-all-as-the-default-for-multi-value-parameters-in-reporting-services.aspx and I have my solution:

Create your multi-select parameter MYPARAMETER using whatever source of available values (probably a dataset). In my case, the multi-select was from a bunch of TEXT entries, but I'm sure with some tweaking it would work with other types. If you want Select All to be the default position, set the same source as the default. This gives you your user interface, but the parameter created is not the parameter passed to my SQL.

Skipping ahead to the SQL, and Jeff's solution to the WHERE IN (@MYPARAMETER) problem, I have a problem all my own, in that 1 of the values ('Charge') appears in one of the other values ('Non Charge'), meaning the CHARINDEX might find a false-positive. I needed to search the parameter for the delimited value both before and after. This means I need to make sure the comma-separated list has a leading and trailling comma as well. And this is my SQL snippet:

where ...
and CHARINDEX(',' + pitran.LINEPROPERTYID + ',', @MYPARAMETER_LIST) > 0

The bit in the middle is to create another parameter (hidden in production, but not while developing) with:

  • A name of MYPARAMETER_LIST
  • A type of Text
  • A single available value of ="," + join(Parameters!MYPARAMETER.Value,",") + "," and a label that
    doesn't really matter (since it will not be displayed).
  • A default value exactly the same
  • Just to be sure, I set Always Refresh in both parameters' Advanced properties

It is this parameter which gets passed to SQL, which just happens to be a searchable string but which SQL handles like any piece of text.

I hope putting these fragments of answers together helps somebody find what they're looking for.

Link and execute external JavaScript file hosted on GitHub

rawgithub.com redirects to rawgit.com So the above example would now be

http://rawgit.com/user/package/master/link.min.js

Parsing JSON using C

cJSON has a decent API and is small (2 files, ~700 lines). Many of the other JSON parsers I looked at first were huge... I just want to parse some JSON.

Edit: We've made some improvements to cJSON over the years.

What is the difference between "expose" and "publish" in Docker?

Most people use docker compose with networks. The documentation states:

The Docker network feature supports creating networks without the need to expose ports within the network, for detailed information see the overview of this feature).

Which means that if you use networks for communication between containers you don't need to worry about exposing ports.

How can I see the request headers made by curl when sending a request to the server?

dump the headers in one file and the payload of the response in a different file

curl -k -v -u user:pass  "url" --trace-ascii headers.txt >> response.txt

Specified cast is not valid.. how to resolve this

If you are expecting double, decimal, float, integer why not use the one which accomodates all namely decimal (128 bits are enough for most numbers you are looking at).

instead of (double)value use decimal.Parse(value.ToString()) or Convert.ToDecimal(value)

How do I insert non breaking space character &nbsp; in a JSF page?

You can also use primefaces <p:spacer width="10" height="10" />

How do I run Visual Studio as an administrator by default?

Windows 10

  1. Right click "Visual Studio" and select "Open file location Right click "Visual Studio" and select "Open file location"
  2. Right click "Visual Studio" and select "Properties" Right click "Visual Studio" and select "Properties"
  3. Click "Advanced" and check "Run as administrator" Click "Advanced" and check "Run as administrator"

How to find index of all occurrences of element in array?

I just want to update with another easy method.

You can also use forEach method.

var Cars = ["Nano", "Volvo", "BMW", "Nano", "VW", "Nano"];

var result = [];

Cars.forEach((car, index) => car === 'Nano' ? result.push(index) : null)

Doctrine 2 ArrayCollection filter method

Your use case would be :

    $ArrayCollectionOfActiveUsers = $customer->users->filter(function($user) {
                        return $user->getActive() === TRUE;
                    });

if you add ->first() you'll get only the first entry returned, which is not what you want.

@ Sjwdavies You need to put () around the variable you pass to USE. You can also shorten as in_array return's a boolean already:

    $member->getComments()->filter( function($entry) use ($idsToFilter) {
        return in_array($entry->getId(), $idsToFilter);
    });

How do I determine the size of my array in C?

I would advise to never use sizeof (even if it can be used) to get any of the two different sizes of an array, either in number of elements or in bytes, which are the last two cases I show here. For each of the two sizes, the macros shown below can be used to make it safer. The reason is to make obvious the intention of the code to maintainers, and difference sizeof(ptr) from sizeof(arr) at first glance (which written this way isn't obvious), so that bugs are then obvious for everyone reading the code.


TL;DR:

#define ARRAY_SIZE(arr)     (sizeof(arr) / sizeof((arr)[0]) + must_be_array(arr))

#define ARRAY_SSIZE(arr)    ((ptrdiff_t)ARRAY_SIZE(arr))

#define ARRAY_BYTES(arr)    (sizeof(arr) + must_be_array(arr))

#define ARRAY_SBYTES(arr)   ((ssize_t)ARRAY_BYTES(arr))

must_be_array(arr) (defined below) IS needed as -Wsizeof-pointer-div is buggy (as of april/2020):

#define is_same_type(a, b)  __builtin_types_compatible_p(typeof(a), typeof(b))
#define is_array(arr)       (!is_same_type((arr), &(arr)[0]))
#define must_be(e, ...)     (                               \
        0 * (int)sizeof(                                                \
                struct {                                                \
                        _Static_assert((e)  __VA_OPT__(,)  __VA_ARGS__);\
                        char ISO_C_forbids_a_struct_with_no_members__;  \
                }                                                       \
        )                                                               \
)
#define must_be_array(arr)  must_be(is_array(arr), "Not a `[]` !")

There have been important bugs regarding this topic: https://lkml.org/lkml/2015/9/3/428

I disagree with the solution that Linus provides, which is to never use array notation for parameters of functions.

I like array notation as documentation that a pointer is being used as an array. But that means that a fool-proof solution needs to be applied so that it is impossible to write buggy code.

From an array we have three sizes which we might want to know:

  • The size of the elements of the array
  • The number of elements in the array
  • The size in bytes that the array uses in memory

The size of the elements of the array

The first one is very simple, and it doesn't matter if we are dealing with an array or a pointer, because it's done the same way.

Example of usage:

void foo(ptrdiff_t nmemb, int arr[static nmemb])
{
        qsort(arr, nmemb, sizeof(arr[0]), cmp);
}

qsort() needs this value as its third argument.


For the other two sizes, which are the topic of the question, we want to make sure that we're dealing with an array, and break the compilation if not, because if we're dealing with a pointer, we will get wrong values. When the compilation is broken, we will be able to easily see that we weren't dealing with an array, but with a pointer instead, and we will just have to write the code with a variable or a macro that stores the size of the array behind the pointer.


The number of elements in the array

This one is the most common, and many answers have provided you with the typical macro ARRAY_SIZE:

#define ARRAY_SIZE(arr)     (sizeof(arr) / sizeof((arr)[0]))

Given that the result of ARRAY_SIZE is commonly used with signed variables of type ptrdiff_t, it is good to define a signed variant of this macro:

#define ARRAY_SSIZE(arr)    ((ptrdiff_t)ARRAY_SIZE(arr))

Arrays with more than PTRDIFF_MAX members are going to give invalid values for this signed version of the macro, but from reading C17::6.5.6.9, arrays like that are already playing with fire. Only ARRAY_SIZE and size_t should be used in those cases.

Recent versions of compilers, such as GCC 8, will warn you when you apply this macro to a pointer, so it is safe (there are other methods to make it safe with older compilers).

It works by dividing the size in bytes of the whole array by the size of each element.

Examples of usage:

void foo(ptrdiff_t nmemb)
{
        char buf[nmemb];

        fgets(buf, ARRAY_SIZE(buf), stdin);
}

void bar(ptrdiff_t nmemb)
{
        int arr[nmemb];

        for (ptrdiff_t i = 0; i < ARRAY_SSIZE(arr); i++)
                arr[i] = i;
}

If these functions didn't use arrays, but got them as parameters instead, the former code would not compile, so it would be impossible to have a bug (given that a recent compiler version is used, or that some other trick is used), and we need to replace the macro call by the value:

void foo(ptrdiff_t nmemb, char buf[nmemb])
{

        fgets(buf, nmemb, stdin);
}

void bar(ptrdiff_t nmemb, int arr[nmemb])
{

        for (ptrdiff_t i = 0; i < nmemb; i++)
                arr[i] = i;
}

The size in bytes that the array uses in memory

ARRAY_SIZE is commonly used as a solution to the previous case, but this case is rarely written safely, maybe because it's less common.

The common way to get this value is to use sizeof(arr). The problem: the same as with the previous one; if you have a pointer instead of an array, your program will go nuts.

The solution to the problem involves using the same macro as before, which we know to be safe (it breaks compilation if it is applied to a pointer):

#define ARRAY_BYTES(arr)        (sizeof((arr)[0]) * ARRAY_SIZE(arr))

Given that the result of ARRAY_BYTES is sometimes compared to the output of functions that return ssize_t, it is good to define a signed variant of this macro:

#define ARRAY_SBYTES(arr)   ((ssize_t)ARRAY_BYTES(arr))

How it works is very simple: it undoes the division that ARRAY_SIZE does, so after mathematical cancellations you end up with just one sizeof(arr), but with the added safety of the ARRAY_SIZE construction.

Example of usage:

void foo(ptrdiff_t nmemb)
{
        int arr[nmemb];

        memset(arr, 0, ARRAY_BYTES(arr));
}

memset() needs this value as its third argument.

As before, if the array is received as a parameter (a pointer), it won't compile, and we will have to replace the macro call by the value:

void foo(ptrdiff_t nmemb, int arr[nmemb])
{

        memset(arr, 0, sizeof(arr[0]) * nmemb);
}

Update (23/apr/2020): -Wsizeof-pointer-div is buggy:

Today I found out that the new warning in GCC only works if the macro is defined in a header that is not a system header. If you define the macro in a header that is installed in your system (usually /usr/local/include/ or /usr/include/) (#include <foo.h>), the compiler will NOT emit a warning (I tried GCC 9.3.0).

So we have #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0])) and want to make it safe. We will need C11 _Static_assert() and some GCC extensions: Statements and Declarations in Expressions, __builtin_types_compatible_p:

#define is_same_type(a, b)      __builtin_types_compatible_p(typeof(a), typeof(b))
#define is_array(arr)           (!is_same_type((arr), &(arr)[0]))
#define Static_assert_array(arr) _Static_assert(is_array(arr), "Not a `[]` !")

#define ARRAY_SIZE(arr)         (                                       \
{                                                                       \
        Static_assert_array(arr);                                       \
        sizeof(arr) / sizeof((arr)[0]);                                \
}                                                                       \
)

Now ARRAY_SIZE() is completely safe, and therefore all its derivatives will be safe.


Update: libbsd provides __arraycount():

Libbsd provides the macro __arraycount() in <sys/cdefs.h>, which is unsafe because it lacks a pair of parentheses, but we can add those parentheses ourselves, and therefore we don't even need to write the division in our header (why would we duplicate code that already exists?). That macro is defined in a system header, so if we use it we are forced to use the macros above.

#include <stddef.h>
#include <sys/cdefs.h>
#include <sys/types.h>


#define is_same_type(a, b)      __builtin_types_compatible_p(typeof(a), typeof(b))
#define is_array(arr)           (!is_same_type((arr), &(arr)[0]))
#define Static_assert_array(arr) _Static_assert(is_array(arr), "Not a `[]` !")

#define ARRAY_SIZE(arr)         (                                       \
{                                                                       \
        Static_assert_array(arr);                                       \
        __arraycount((arr));                                            \
}                                                                       \
)

#define ARRAY_SSIZE(arr)        ((ptrdiff_t)ARRAY_SIZE(arr))
#define ARRAY_BYTES(arr)        (sizeof((arr)[0]) * ARRAY_SIZE(arr))
#define ARRAY_SBYTES(arr)       ((ssize_t)ARRAY_BYTES(arr))

Some systems provide nitems() in <sys/param.h> instead, and some systems provide both. You should check your system, and use the one you have, and maybe use some preprocessor conditionals for portability and support both.


Update: Allow the macro to be used at file scope:

Unfortunately, the ({}) gcc extension cannot be used at file scope. To be able to use the macro at file scope, the static assertion must be inside sizeof(struct {}). Then, multiply it by 0 to not affect the result. A cast to (int) might be good to simulate a function that returns (int)0 (in this case it is not necessary, but then it is reusable for other things).

Additionally, the definition of ARRAY_BYTES() can be simplified a bit.

#include <stddef.h>
#include <sys/cdefs.h>
#include <sys/types.h>


#define is_same_type(a, b)     __builtin_types_compatible_p(typeof(a), typeof(b))
#define is_array(arr)          (!is_same_type((arr), &(arr)[0]))
#define must_be(e, ...)        (                                        \
        0 * (int)sizeof(                                                \
                struct {                                                \
                        _Static_assert((e)  __VA_OPT__(,)  __VA_ARGS__);\
                        char ISO_C_forbids_a_struct_with_no_members__;  \
                }                                                       \
        )                                                               \
)
#define must_be_array(arr)      must_be(is_array(arr), "Not a `[]` !")

#define ARRAY_SIZE(arr)         (__arraycount((arr)) + must_be_array(arr))
#define ARRAY_SSIZE(arr)        ((ptrdiff_t)ARRAY_SIZE(arr))
#define ARRAY_BYTES(arr)        (sizeof(arr) + must_be_array(arr))
#define ARRAY_SBYTES(arr)       ((ssize_t)ARRAY_BYTES(arr))

Notes:

This code makes use of the following extensions, which are completely necessary, and their presence is absolutely necessary to achieve safety. If your compiler doesn't have them, or some similar ones, then you can't achieve this level of safety.

I also make use of the following C11 feature. However, its absence by using an older standard can be overcome using some dirty tricks (see for example: What is “:-!!” in C code?).

I also use the following extension, but there's a standard C way of doing the same thing.

CSS override rules and specificity

The important needs to be inside the ;

td.rule2 div {     background-color: #ffff00 !important; } 

in fact i believe this should override it

td.rule2 { background-color: #ffff00 !important; } 

Differences between C++ string == and compare()?

std::string::compare() returns an int:

  • equal to zero if s and t are equal,
  • less than zero if s is less than t,
  • greater than zero if s is greater than t.

If you want your first code snippet to be equivalent to the second one, it should actually read:

if (!s.compare(t)) {
    // 's' and 't' are equal.
}

The equality operator only tests for equality (hence its name) and returns a bool.

To elaborate on the use cases, compare() can be useful if you're interested in how the two strings relate to one another (less or greater) when they happen to be different. PlasmaHH rightfully mentions trees, and it could also be, say, a string insertion algorithm that aims to keep the container sorted, a dichotomic search algorithm for the aforementioned container, and so on.

EDIT: As Steve Jessop points out in the comments, compare() is most useful for quick sort and binary search algorithms. Natural sorts and dichotomic searches can be implemented with only std::less.

REST API Token-based Authentication

In the web a stateful protocol is based on having a temporary token that is exchanged between a browser and a server (via cookie header or URI rewriting) on every request. That token is usually created on the server end, and it is a piece of opaque data that has a certain time-to-live, and it has the sole purpose of identifying a specific web user agent. That is, the token is temporary, and becomes a STATE that the web server has to maintain on behalf of a client user agent during the duration of that conversation. Therefore, the communication using a token in this way is STATEFUL. And if the conversation between client and server is STATEFUL it is not RESTful.

The username/password (sent on the Authorization header) is usually persisted on the database with the intent of identifying a user. Sometimes the user could mean another application; however, the username/password is NEVER intended to identify a specific web client user agent. The conversation between a web agent and server based on using the username/password in the Authorization header (following the HTTP Basic Authorization) is STATELESS because the web server front-end is not creating or maintaining any STATE information whatsoever on behalf of a specific web client user agent. And based on my understanding of REST, the protocol states clearly that the conversation between clients and server should be STATELESS. Therefore, if we want to have a true RESTful service we should use username/password (Refer to RFC mentioned in my previous post) in the Authorization header for every single call, NOT a sension kind of token (e.g. Session tokens created in web servers, OAuth tokens created in authorization servers, and so on).

I understand that several called REST providers are using tokens like OAuth1 or OAuth2 accept-tokens to be be passed as "Authorization: Bearer " in HTTP headers. However, it appears to me that using those tokens for RESTful services would violate the true STATELESS meaning that REST embraces; because those tokens are temporary piece of data created/maintained on the server side to identify a specific web client user agent for the valid duration of a that web client/server conversation. Therefore, any service that is using those OAuth1/2 tokens should not be called REST if we want to stick to the TRUE meaning of a STATELESS protocol.

Rubens

How to Identify port number of SQL server

You can also use this query

USE MASTER GO xp_readerrorlog 0, 1, N'Server is listening on' GO

Source : sqlauthority blog

Set type for function parameters?

It can easilly be done with ArgueJS:

function myFunction ()
{
  arguments = __({myDate: Date, myString: String});
  // do stuff
};

How to use Selenium with Python?

You just need to get selenium package imported, that you can do from command prompt using the command

pip install selenium

When you have to use it in any IDE just import this package, no other documentation required to be imported

For Eg :

import selenium 
print(selenium.__filepath__)

This is just a general command you may use in starting to check the filepath of selenium

Testing the type of a DOM element in JavaScript

Although the previous answers work perfectly, I will just add another way where the elements can also be classified using the interface they have implemented.

Refer W3 Org for available interfaces

_x000D_
_x000D_
console.log(document.querySelector("#anchorelem") instanceof HTMLAnchorElement);_x000D_
console.log(document.querySelector("#divelem") instanceof HTMLDivElement);_x000D_
console.log(document.querySelector("#buttonelem") instanceof HTMLButtonElement);_x000D_
console.log(document.querySelector("#inputelem") instanceof HTMLInputElement);
_x000D_
<a id="anchorelem" href="">Anchor element</a>_x000D_
<div id="divelem">Div Element</div>_x000D_
<button id="buttonelem">Button Element</button>_x000D_
<br><input id="inputelem">
_x000D_
_x000D_
_x000D_

The interface check can be made in 2 ways as elem instanceof HTMLAnchorElement or elem.constructor.name == "HTMLAnchorElement", both returns true

How to get current user, and how to use User class in MVC5?

Try something like:

var store = new UserStore<ApplicationUser>(new ApplicationDbContext());
var userManager = new UserManager<ApplicationUser>(store);
ApplicationUser user = userManager.FindByNameAsync(User.Identity.Name).Result;

Works with RTM.

Error : ORA-01704: string literal too long

Try to split the characters into multiple chunks like the query below and try:

Insert into table (clob_column) values ( to_clob( 'chunk 1' ) || to_clob( 'chunk 2' ) );

It worked for me.

Round a floating-point number down to the nearest integer?

If you working with numpy, you can use the following solution which also works with negative numbers (it's also working on arrays)

import numpy as np
def round_down(num):
    if num < 0:
        return -np.ceil(abs(num))
    else:
        return np.int32(num)
round_down = np.vectorize(round_down)

round_down([-1.1, -1.5, -1.6, 0, 1.1, 1.5, 1.6])
> array([-2., -2., -2.,  0.,  1.,  1.,  1.])

I think it will also work if you just use the math module instead of numpy module.

jQuery: Clearing Form Inputs

I'd recomment using good old javascript:

document.getElementById("addRunner").reset();

@UniqueConstraint annotation in Java

Unique annotation should be placed right above the attribute declaration. UniqueContraints go into the @Table annotation above the data class declaration. See below:

@Entity
@Table(uniqueConstraints= arrayOf(UniqueConstraint(columnNames = arrayOf("col_1", "col_2"))))
data class Action(
        @Id @GeneratedValue @Column(unique = true)
        val id: Long?,
        val col_1: Long?,
        val col_2: Long?,
)

How to use the "required" attribute with a "radio" input field

You can use this code snippet ...

<html>
  <body>
     <form>
          <input type="radio" name="color" value="black" required />
          <input type="radio" name="color" value="white" />
          <input type="submit" value="Submit" />
    </form>
  </body>
</html>

Specify "required" keyword in one of the select statements. If you want to change the default way of its appearance. You can follow these steps. This is just for extra info if you have any intention to modify the default behavior.

Add the following into you .css file.

/* style all elements with a required attribute */
:required {
  background: red;
}

For more information you can refer following URL.

https://css-tricks.com/almanac/selectors/r/required/

getFilesDir() vs Environment.getDataDirectory()

Try this

getExternalFilesDir(Environment.getDataDirectory().getAbsolutePath()).getAbsolutePath()

How to access the elements of a function's return array?

Your function is:

function data(){

$a = "abc";
$b = "def";
$c = "ghi";

return array($a, $b, $c);
}

It returns an array where position 0 is $a, position 1 is $b and position 2 is $c. You can therefore access $a by doing just this:

data()[0]

If you do $myvar = data()[0] and print $myvar, you will get "abc", which was the value assigned to $a inside the function.

Understanding repr( ) function in Python

1) The result of repr('foo') is the string 'foo'. In your Python shell, the result of the expression is expressed as a representation too, so you're essentially seeing repr(repr('foo')).

2) eval calculates the result of an expression. The result is always a value (such as a number, a string, or an object). Multiple variables can refer to the same value, as in:

x = 'foo'
y = x

x and y now refer to the same value.

3) I have no idea what you meant here. Can you post an example, and what you'd like to see?

TSQL PIVOT MULTIPLE COLUMNS

Since you want to pivot multiple columns of data, I would first suggest unpivoting the result, score and grade columns so you don't have multiple columns but you will have multiple rows.

Depending on your version of SQL Server you can use the UNPIVOT function or CROSS APPLY. The syntax to unpivot the data will be similar to:

select ratio, col, value
from GRAND_TOTALS
cross apply
(
  select 'result', cast(result as varchar(10)) union all
  select 'score', cast(score as varchar(10)) union all
  select 'grade', grade
) c(col, value)

See SQL Fiddle with Demo. Once the data has been unpivoted, then you can apply the PIVOT function:

select ratio = col,
  [current ratio], [gearing ratio], [performance ratio], total
from
(
  select ratio, col, value
  from GRAND_TOTALS
  cross apply
  (
    select 'result', cast(result as varchar(10)) union all
    select 'score', cast(score as varchar(10)) union all
    select 'grade', grade
  ) c(col, value)
) d
pivot
(
  max(value)
  for ratio in ([current ratio], [gearing ratio], [performance ratio], total)
) piv;

See SQL Fiddle with Demo. This will give you the result:

|  RATIO | CURRENT RATIO | GEARING RATIO | PERFORMANCE RATIO |     TOTAL |
|--------|---------------|---------------|-------------------|-----------|
|  grade |          Good |          Good |      Satisfactory |      Good |
| result |       1.29400 |       0.33840 |           0.04270 |    (null) |
|  score |      60.00000 |      70.00000 |          50.00000 | 180.00000 |

How to get the next auto-increment id in mysql

use "mysql_insert_id()". mysql_insert_id() acts on the last performed query, be sure to call mysql_insert_id() immediately after the query that generates the value.

Below are the example of use:

<?php
    $link = mysql_connect('localhost', 'username', 'password');
if (!$link) {
    die('Could not connect: ' . mysql_error());
}
mysql_select_db('mydb');

mysql_query("INSERT INTO mytable  VALUES('','value')");
printf("Last inserted record has id %d\n", mysql_insert_id());
    ?>

I hope above example is useful.

How to reload the datatable(jquery) data?

None of these solutions worked for me, but I did do something similar to Masood's answer. Here it is for posterity. This assumes you have <table id="mytable"></table> in your page somewhere:

function generate_support_user_table() {
        $('#mytable').hide();
        $('#mytable').dataTable({
            ...
            "bDestroy": true,
            "fnInitComplete": function () { $('#support_user_table').show(); },
            ...
        });
}

The important parts are:

  1. bDestroy, which wipes out the current table before loading.
  2. The hide() call and fnInitComplete, which ensures that the table only appears after everything is loaded. Otherwise it resizes and looks weird while loading.

Just add the function call to $(document).ready() and you should be all set. It will load the table initially, as well as reload later on a button click or whatever.

Python copy files to a new directory and rename if file name already exists

For me shutil.copy is the best:

import shutil

#make a copy of the invoice to work with
src="invoice.pdf"
dst="copied_invoice.pdf"
shutil.copy(src,dst)

You can change the path of the files as you want.

how to add button click event in android studio

in Activity java class you would need a method first to find the view of the button as :

btnSum =(Button)findViewById(R.id.button);

after this set on click listener

btnSum.setOnClickListener(new View.OnClickListener() {

and override onClick method for your functionality .I have found a fully working example here : http://javainhouse.blogspot.in/2016/01/button-example-android-studio.html

Java compiler level does not match the version of the installed Java project facet

I resolved this problem by setting the java version in Project Facet property of the project properties, Right click the project root folder -> Properties, search for Project Facets, and select compatible java version.

For reference -

enter image description here

How do I run a program with a different working directory from current, from Linux shell?

why not keep it simple

cd SOME_PATH && run_some_command && cd -

the last 'cd' command will take you back to the last pwd directory. This should work on all *nix systems.

Printing the correct number of decimal points with cout

I had an issue for integers while wanting consistent formatting.

A rewrite for completeness:

#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
    //    floating point formatting example
    cout << fixed << setprecision(2) << 122.345 << endl;
    //    Output:  122.34

    //    integer formatting example
    cout << fixed << setprecision(2) << double(122) << endl;
    //    Output:  122.00
}

Find and replace specific text characters across a document with JS

ECMAScript 2015+ approach

Pitfalls when solving this task

This seems like an easy task, but you have to take care of several things:

  • Simply replacing the entire HTML kills all DOM functionality, like event listeners
  • Replacing the HTML may also replace <script> or <style> contents, or HTML tags or attributes, which is not always desired
  • Changing the HTML may result in an attack
  • You may want to replace attributes like title and alt (in a controlled manner) as well

Guarding against attacks generally can’t be solved by using the approaches below. E.g. if a fetch call reads a URL from somewhere on the page, then sends a request to that URL, the functions below won’t stop that, since this scenario is inherently unsafe.

Replacing the text contents of all elements

This basically selects all elements that contain normal text, goes through their child nodes — among those are also text nodes —, seeks those text nodes out and replaces their contents.

You can optionally specify a different root target, e.g. replaceOnDocument(/€/g, "$", { target: someElement });; by default, the <body> is chosen.

const replaceOnDocument = (pattern, string, {target = document.body} = {}) => {
  // Handle `string` — see the last section
  [
    target,
    ...target.querySelectorAll("*:not(script):not(noscript):not(style)")
  ].forEach(({childNodes: [...nodes]}) => nodes
    .filter(({nodeType}) => nodeType === document.TEXT_NODE)
    .forEach((textNode) => textNode.textContent = textNode.textContent.replace(pattern, string)));
};

replaceOnDocument(/€/g, "$");

Replacing text nodes, element attributes and properties

Now, this is a little more complex: you need to check three cases: whether a node is a text node, whether it’s an element and its attribute should be replaced, or whether it’s an element and its property should be replaced. A replacer object provides methods for text nodes and for elements.

Before replacing attributes and properties, the replacer needs to check whether the element has a matching attribute; otherwise new attributes get created, undesirably. It also needs to check whether the targeted property is a string, since only strings can be replaced, or whether the matching property to the targeted attribute is not a function, since this may lead to an attack.

In the example below, you can see how to use the extended features: in the optional third argument, you may add an attrs property and a props property, which is an iterable (e.g. an array) each, for the attributes to be replaced and the properties to be replaced, respectively.

You’ll also notice that this snippet uses flatMap. If that’s not supported, use a polyfill or replace it by the reduceconcat, or mapreduceconcat construct, as seen in the linked documentation.

const replaceOnDocument = (() => {
    const replacer = {
      [document.TEXT_NODE](node, pattern, string){
        node.textContent = node.textContent.replace(pattern, string);
      },
      [document.ELEMENT_NODE](node, pattern, string, {attrs, props} = {}){
        attrs.forEach((attr) => {
          if(typeof node[attr] !== "function" && node.hasAttribute(attr)){
            node.setAttribute(attr, node.getAttribute(attr).replace(pattern, string));
          }
        });
        props.forEach((prop) => {
          if(typeof node[prop] === "string" && node.hasAttribute(prop)){
            node[prop] = node[prop].replace(pattern, string);
          }
        });
      }
    };

    return (pattern, string, {target = document.body, attrs: [...attrs] = [], props: [...props] = []} = {}) => {
      // Handle `string` — see the last section
      [
        target,
        ...[
          target,
          ...target.querySelectorAll("*:not(script):not(noscript):not(style)")
        ].flatMap(({childNodes: [...nodes]}) => nodes)
      ].filter(({nodeType}) => replacer.hasOwnProperty(nodeType))
        .forEach((node) => replacer[node.nodeType](node, pattern, string, {
          attrs,
          props
        }));
    };
})();

replaceOnDocument(/€/g, "$", {
  attrs: [
    "title",
    "alt",
    "onerror" // This will be ignored
  ],
  props: [
    "value" // Changing an `<input>`’s `value` attribute won’t change its current value, so the property needs to be accessed here
  ]
});

Replacing with HTML entities

If you need to make it work with HTML entities like &shy;, the above approaches will just literally produce the string &shy;, since that’s an HTML entity and will only work when assigning .innerHTML or using related methods.

So let’s solve it by passing the input string to something that accepts an HTML string: a new, temporary HTMLDocument. This is created by the DOMParser’s parseFromString method; in the end we read its documentElement’s textContent:

string = new DOMParser().parseFromString(string, "text/html").documentElement.textContent;

If you want to use this, choose one of the approaches above, depending on whether or not you want to replace HTML attributes and DOM properties in addition to text; then simply replace the comment // Handle `string` — see the last section by the above line.

Now you can use replaceOnDocument(/Güterzug/g, "G&uuml;ter&shy;zug");.

NB: If you don’t use the string handling code, you may also remove the { } around the arrow function body.

Note that this parses HTML entities but still disallows inserting actual HTML tags, since we’re reading only the textContent. This is also safe against most cases of : since we’re using parseFromString and the page’s document isn’t affected, no <script> gets downloaded and no onerror handler gets executed.

You should also consider using \xAD instead of &shy; directly in your JavaScript string, if it turns out to be simpler.

Access mysql remote database from command line

If you want to not use ssh tunnel, in my.cnf or mysqld.cnf you must change 127.0.0.1 with your local ip address (192.168.1.100) in order to have access over the Lan. example bellow:

sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf

Search for bind-address in my.cnf or mysqld.cnf

bind-address            =  127.0.0.1

and change 127.0.0.1 to 192.168.1.100 ( local ip address )

bind-address            =  192.168.1.100

To apply the change you made, must restart mysql server using next command.

sudo /etc/init.d/mysql restart

Modify user root for lan acces ( run the query's bellow in remote server that you want to have access )

[email protected]:~$ mysql -u root -p

..

CREATE USER 'root'@'%' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION;
FLUSH PRIVILEGES;

If you want to have access only from specific ip address , change 'root'@'%' to 'root'@'( ip address or hostname)'

CREATE USER 'root'@'192.168.1.100' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON *.* TO 'root'@'192.168.1.100' WITH GRANT OPTION;
FLUSH PRIVILEGES;

Then you can connect:

nobus@xray:~$ mysql -h 192.168.1.100 -u root -p

tested on ubuntu 18.04 server

PHP, How to get current date in certain format

date("Y-m-d H:i:s"); // This should do it.

Remove trailing comma from comma-separated string

For more than one commas

            String names = "Hello,World,,,";
    System.out.println(names.replaceAll("(,)*$", ""));

Output: Hello,World

SQLAlchemy: how to filter date field?

In fact, your query is right except for the typo: your filter is excluding all records: you should change the <= for >= and vice versa:

qry = DBSession.query(User).filter(
        and_(User.birthday <= '1988-01-17', User.birthday >= '1985-01-17'))
# or same:
qry = DBSession.query(User).filter(User.birthday <= '1988-01-17').\
        filter(User.birthday >= '1985-01-17')

Also you can use between:

qry = DBSession.query(User).filter(User.birthday.between('1985-01-17', '1988-01-17'))

How to automatically select all text on focus in WPF TextBox?

In App.xaml file:

<Application.Resources>
    <Style TargetType="TextBox">
        <EventSetter Event="GotKeyboardFocus" Handler="TextBox_GotKeyboardFocus"/>
    </Style>
</Application.Resources>

In App.xaml.cs file:

private void TextBox_GotKeyboardFocus(Object sender, KeyboardFocusChangedEventArgs e)
{
    ((TextBox)sender).SelectAll();
}

With this code you reach all TextBox in your application.

how to delete a specific row in codeigniter?

It will come in the url so you can get it by two ways. Fist one

<td><?php echo anchor('textarea/delete_row', 'DELETE', 'id="$row->id"'); ?></td>
$id = $this->input->get('id');

2nd one.

$id = $this->uri->segment(3);

But in the second method you have to count the no. of segments in the url that on which no. your id come. 2,3,4 etc. then you have to pass. then in the ();

How can I convert a timestamp from yyyy-MM-ddThh:mm:ss:SSSZ format to MM/dd/yyyy hh:mm:ss.SSS format? From ISO8601 to UTC

Hope this Helps:

public String getSystemTimeInBelowFormat() {
    String timestamp = new SimpleDateFormat("yyyy-mm-dd 'T' HH:MM:SS.mmm-HH:SS").format(new Date());
    return timestamp;
}

CSS How to set div height 100% minus nPx

div {
    height: 100%;
    height: -webkit-calc(100% - 60px);
    height: -moz-calc(100% - 60px);
    height: calc(100% - 60px);
}

Make sure while using less

height: ~calc(100% - 60px);

Otherwise less is no going to compile it correctly

Return sql rows where field contains ONLY non-alphanumeric characters

If you have short strings you should be able to create a few LIKE patterns ('[^a-zA-Z0-9]', '[^a-zA-Z0-9][^a-zA-Z0-9]', ...) to match strings of different length. Otherwise you should use CLR user defined function and a proper regular expression - Regular Expressions Make Pattern Matching And Data Extraction Easier.

Build Maven Project Without Running Unit Tests

With Intellij Toggle Skip Test Mode can be used from Maven Projects tab:

Log4j: How to configure simplest possible file logging?

I have one generic log4j.xml file for you:

<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd" >
<log4j:configuration debug="false">

    <appender name="default.console" class="org.apache.log4j.ConsoleAppender">
        <param name="target" value="System.out" />
        <param name="threshold" value="debug" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{ISO8601} %-5p [%c{1}] - %m%n" />
        </layout>
    </appender>

    <appender name="default.file" class="org.apache.log4j.FileAppender">
        <param name="file" value="/log/mylogfile.log" />
        <param name="append" value="false" />
        <param name="threshold" value="debug" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{ISO8601} %-5p [%c{1}] - %m%n" />
        </layout>
    </appender>

    <appender name="another.file" class="org.apache.log4j.FileAppender">
        <param name="file" value="/log/anotherlogfile.log" />
        <param name="append" value="false" />
        <param name="threshold" value="debug" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{ISO8601} %-5p [%c{1}] - %m%n" />
        </layout>
    </appender>

    <logger name="com.yourcompany.SomeClass" additivity="false">
        <level value="debug" />
        <appender-ref ref="another.file" />
    </logger>

    <root>
        <priority value="info" />
        <appender-ref ref="default.console" />
        <appender-ref ref="default.file" />
    </root>
</log4j:configuration>

with one console, two file appender and one logger poiting to the second file appender instead of the first.

EDIT

In one of the older projects I have found a simple log4j.properties file:

# For the general syntax of property based configuration files see
# the documentation of org.apache.log4j.PropertyConfigurator.

# The root category uses two appenders: default.out and default.file.
# The first one gathers all log output, the latter only starting with 
# the priority INFO.
# The root priority is DEBUG, so that all classes can be logged unless 
# defined otherwise in more specific properties.
log4j.rootLogger=DEBUG, default.out, default.file

# System.out.println appender for all classes
log4j.appender.default.out=org.apache.log4j.ConsoleAppender
log4j.appender.default.out.threshold=DEBUG
log4j.appender.default.out.layout=org.apache.log4j.PatternLayout
log4j.appender.default.out.layout.ConversionPattern=%-5p %c: %m%n

log4j.appender.default.file=org.apache.log4j.FileAppender
log4j.appender.default.file.append=true
log4j.appender.default.file.file=/log/mylogfile.log
log4j.appender.default.file.threshold=INFO
log4j.appender.default.file.layout=org.apache.log4j.PatternLayout
log4j.appender.default.file.layout.ConversionPattern=%-5p %c: %m%n

For the description of all the layout arguments look here: log4j PatternLayout arguments

Equivalent of *Nix 'which' command in PowerShell?

I have this which advanced function in my PowerShell profile:

    function which {
    <#
    .SYNOPSIS
    Identifies the source of a PowerShell command.
    .DESCRIPTION
    Identifies the source of a PowerShell command. External commands (Applications) are identified by the path to the executable
    (which must be in the system PATH); cmdlets and functions are identified as such and the name of the module they are defined in
    provided; aliases are expanded and the source of the alias definition is returned.
    .INPUTS
    No inputs; you cannot pipe data to this function.
    .OUTPUTS
    .PARAMETER Name
    The name of the command to be identified.
    .EXAMPLE
    PS C:\Users\Smith\Documents> which Get-Command
    
    Get-Command: Cmdlet in module Microsoft.PowerShell.Core
    
    (Identifies type and source of command)
    .EXAMPLE
    PS C:\Users\Smith\Documents> which notepad
    
    C:\WINDOWS\SYSTEM32\notepad.exe
    
    (Indicates the full path of the executable)
    #>
        param(
        [String]$name
        )
    
        $cmd = Get-Command $name
        $redirect = $null
        switch ($cmd.CommandType) {
            "Alias"          { "{0}: Alias for ({1})" -f $cmd.Name, (. { which $cmd.Definition } ) }
            "Application"    { $cmd.Source }
            "Cmdlet"         { "{0}: {1} {2}" -f $cmd.Name, $cmd.CommandType, (. { if ($cmd.Source.Length) { "in module {0}" -f $cmd.Source} else { "from unspecified source" } } ) }
            "Function"       { "{0}: {1} {2}" -f $cmd.Name, $cmd.CommandType, (. { if ($cmd.Source.Length) { "in module {0}" -f $cmd.Source} else { "from unspecified source" } } ) }
            "Workflow"       { "{0}: {1} {2}" -f $cmd.Name, $cmd.CommandType, (. { if ($cmd.Source.Length) { "in module {0}" -f $cmd.Source} else { "from unspecified source" } } ) }
            "ExternalScript" { $cmd.Source }
            default          { $cmd }
        }
    }

How to add items to array in nodejs

Here is example which can give you some hints to iterate through existing array and add items to new array. I use UnderscoreJS Module to use as my utility file.

You can download from (https://npmjs.org/package/underscore)

$ npm install underscore

Here is small snippet to demonstrate how you can do it.

var _ = require("underscore");
var calendars = [1, "String", {}, 1.1, true],
    newArray = [];

_.each(calendars, function (item, index) {
    newArray.push(item);
});

console.log(newArray);

How to draw a filled circle in Java?

public void paintComponent(Graphics g) {
   super.paintComponent(g);
   Graphics2D g2d = (Graphics2D)g;
   // Assume x, y, and diameter are instance variables.
   Ellipse2D.Double circle = new Ellipse2D.Double(x, y, diameter, diameter);
   g2d.fill(circle);
   ...
}

Here are some docs about paintComponent (link).

You should override that method in your JPanel and do something similar to the code snippet above.

In your ActionListener you should specify x, y, diameter and call repaint().

About catching ANY exception

I've just found out this little trick for testing if exception names in Python 2.7 . Sometimes i have handled specific exceptions in the code, so i needed a test to see if that name is within a list of handled exceptions.

try:
    raise IndexError #as test error
except Exception as e:
    excepName = type(e).__name__ # returns the name of the exception

How to Calculate Jump Target Address and Branch Target Address?

For small functions like this you could just count by hand how many hops it is to the target, from the instruction under the branch instruction. If it branches backwards make that hop number negative. if that number doesn't require all 16 bits, then for every number to the left of the most significant of your hop number, make them 1's, if the hop number is positive make them all 0's Since most branches are close to they're targets, this saves you a lot of extra arithmetic for most cases.

  • chris

Python matplotlib multiple bars

I know that this is about matplotlib, but using pandas and seaborn can save you a lot of time:

df = pd.DataFrame(zip(x*3, ["y"]*3+["z"]*3+["k"]*3, y+z+k), columns=["time", "kind", "data"])
plt.figure(figsize=(10, 6))
sns.barplot(x="time", hue="kind", y="data", data=df)
plt.show()

enter image description here

Create JSON object dynamically via JavaScript (Without concate strings)

This topic, especially the answer of Xotic750 was very helpful to me. I wanted to generate a json variable to pass it to a php script using ajax. My values were stored into two arrays, and i wanted them in json format. This is a generic example:

valArray1 = [121, 324, 42, 31];
valArray2 = [232, 131, 443];
myJson = {objArray1: {}, objArray2: {}};
for (var k = 1; k < valArray1.length; k++) {
    var objName = 'obj' + k;
    var objValue = valArray1[k];
    myJson.objArray1[objName] = objValue;
}
for (var k = 1; k < valArray2.length; k++) {
    var objName = 'obj' + k;
    var objValue = valArray2[k];
    myJson.objArray2[objName] = objValue;
}
console.log(JSON.stringify(myJson));

The result in the console Log should be something like this:

{
   "objArray1": {
        "obj1": 121,
        "obj2": 324,
        "obj3": 42,
        "obj4": 31
   },
   "objArray2": {
        "obj1": 232,
        "obj2": 131,
        "obj3": 443
  }
}

How do I truly reset every setting in Visual Studio 2012?

Executing the command: Devenv.exe /ResetSettings like :

C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE>devenv.exe /ResetSettings , resolved my issue :D

For more: https://msdn.microsoft.com/en-us/library/ms241273.aspx

Pushing an existing Git repository to SVN

Using git rebase directly will lose the first commit. Git treats it different and can't rebase it.

There is a procedure that will preserve full history: http://kerneltrap.org/mailarchive/git/2008/10/26/3815034

I will transcribe the solution here, but credits are for Björn.

Initialize git-svn:

git svn init -s --prefix=svn/ https://svn/svn/SANDBOX/warren/test2

The --prefix gives you remote tracking branches like "svn/trunk" which is nice because you don't get ambiguous names if you call your local branch just "trunk" then. And -s is a shortcut for the standard trunk/tags/branches layout.

Fetch the initial stuff from SVN:

git svn fetch

Now look up the hash of your root commit (should show a single commit):

git rev-list --parents master | grep '^.\{40\}$'

Then get the hash of the empty trunk commit:

git rev-parse svn/trunk

Create the graft:

git replace --graft <root-commit-hash> <svn-trunk-commit-hash>

Now, "gitk" should show svn/trunk as the first commit on which your master branch is based.

Make the graft permanent:

git filter-branch -- ^svn/trunk --all

Drop the graft:

git replace -d <root-commit-hash>

gitk should still show svn/trunk in the ancestry of master.

Linearize your history on top of trunk:

git svn rebase

And now "git svn dcommit -n" should tell you that it is going to commit to trunk.

git svn dcommit

PHP check whether property exists in object or class

Solution

echo $person->middleName ?? 'Person does not have a middle name';

To show how this would look in an if statement for more clarity on how this is working.

if($person->middleName ?? false) {
    echo $person->middleName;
} else {
    echo 'Person does not have a middle name';
}

Explanation

The traditional PHP way to check for something's existence is to do:

if(isset($person->middleName)) {
    echo $person->middleName;
} else {
    echo 'Person does not have a middle name';
}

OR for a more class specific way:

if(property_exists($person, 'middleName')) {
    echo $person->middleName;
} else {
    echo 'Person does not have a middle name';
}

These are both fine in long form statements but in ternary statements they become unnecessarily cumbersome like so:

isset($person->middleName) ? echo $person->middleName : echo 'Person does not have a middle name';

You can also achieve this with just the ternary operator like so:

echo $person->middleName ?: 'Person does not have a middle name';

But... if the value does not exist (is not set) it will raise an E_NOTICE and is not best practise. If the value is null it will not raise the exception.

Therefore ternary operator to the rescue making this a neat little answer:

echo $person->middleName ?? 'Person does not have a middle name';

Search for highest key/index in an array

I had a situation where I needed to obtain the next available key in an array, which is the highest+1.

For example, if the array is $data=['1'=>'something,'34'=>'something else'] then I needed to calculate 35 to add a new element to the array that had a key higher than any of the others. In the case of an empty array I needed 1 as next available key.

This is the solution that worked:

    $highest = 0;
    foreach($data as $idx=>$dummy)
    {
        if($idx > $highest)$highest=$idx;
    }
    $highest++;

It will work in all cases, empty array or not. If you only need to find the highest key rather than highest key + 1, delete the last line. You will then get a value of 0 if the array is empty.

How to sort an array of objects in Java?

You can implement the "Comparable" interface on a class whose objects you want to compare.

And also implement the "compareTo" method in that.

Add the instances of the class in an ArrayList

Then the "java.utils.Collections.sort()" method will do the necessary magic.

Here's--->(https://deva-codes.herokuapp.com/CompareOnTwoKeys) a working example where objects are sorted based on two keys first by the id and then by name.

What is PECS (Producer Extends Consumer Super)?

let’s try visualizing this concept.

<? super SomeType> is an “undefined(yet)” type, but that undefined type should be a superclass of the ‘SomeType’ class.

The same goes for <? extends SomeType>. It’s a type that should extend the ‘SomeType’ class (it should be a child class of the ‘SomeType’ class).

If we consider the concept of 'class inheritance' in a Venn diagram, an example would be like this:

enter image description here

Mammal class extends Animal class (Animal class is a superclass of Mammal class).

Cat/Dog class extends Mammal class (Mammal class is a superclass of Cat/Dog class).

Then, let’s think about the ‘circles’ in the above diagram as a ‘box’ that has a physical volume.

enter image description here

You CAN’T put a bigger box into a smaller one.

You can ONLY put a smaller box into a bigger one.

When you say <? super SomeType>, you wanna describe a ‘box’ that is the same size or bigger than the ‘SomeType’ box.

If you say <? extends SomeType>, then you wanna describe a ‘box’ that is the same size or smaller than the ‘SomeType’ box.

so what is PECS anyway?

An example of a ‘Producer’ is a List which we only read from.

An example of a ‘Consumer’ is a List which we only write into.

Just keep in mind this:

  • We ‘read’ from a ‘producer’, and take that stuff into our own box.

  • And we ‘write’ our own box into a ‘consumer’.

So, we need to read(take) something from a ‘producer’ and put that into our ‘box’. This means that any boxes taken from the producer should NOT be bigger than our ‘box’. That’s why “Producer Extends.”

“Extends” means a smaller box(smaller circle in the Venn diagram above). The boxes of a producer should be smaller than our own box, because we are gonna take those boxes from the producer and put them into our own box. We can’t put anything bigger than our box!

Also, we need to write(put) our own ‘box’ into a ‘consumer’. This means that the boxes of the consumer should NOT be smaller than our own box. That’s why “Consumer Super.”

“Super” means a bigger box(bigger circle in the Venn diagram above). If we want to put our own boxes into a consumer, the boxes of the consumer should be bigger than our box!

Now we can easily understand this example:

public class Collections { 
  public static <T> void copy(List<? super T> dest, List<? extends T> src) {
      for (int i = 0; i < src.size(); i++) 
        dest.set(i, src.get(i)); 
  } 
}

In the above example, we want to read(take) something from src and write(put) them into dest. So the src is a “Producer” and its “boxes” should be smaller(more specific) than some type T.

Vice versa, the dest is a “Consumer” and its “boxes” should be bigger(more general) than some type T.

If the “boxes” of the src were bigger than that of the dest, we couldn’t put those big boxes into the smaller boxes the dest has.

If anyone reads this, I hope it helps you better understand “Producer Extends, Consumer Super.”

Happy coding! :)

Align Div at bottom on main Div

I guess you'll need absolute position

.vertical_banner {position:relative;}
#bottom_link{position:absolute; bottom:0;}

Converting map to struct

Hashicorp's https://github.com/mitchellh/mapstructure library does this out of the box:

import "github.com/mitchellh/mapstructure"

mapstructure.Decode(myData, &result)

The second result parameter has to be an address of the struct.

Enable binary mode while restoring a Database from an SQL dump

Have you tried opening in notepad++ (or another editor) and converting/saving us to UTF-8?

See: notepad++ converting ansi encoded file to utf-8

Another option may be to use textwrangle to open and save the file as UTF-8: http://www.barebones.com/products/textwrangler/

How does tuple comparison work in Python?

Tuples are compared position by position: the first item of the first tuple is compared to the first item of the second tuple; if they are not equal (i.e. the first is greater or smaller than the second) then that's the result of the comparison, else the second item is considered, then the third and so on.

See Common Sequence Operations:

Sequences of the same type also support comparisons. In particular, tuples and lists are compared lexicographically by comparing corresponding elements. This means that to compare equal, every element must compare equal and the two sequences must be of the same type and have the same length.

Also Value Comparisons for further details:

Lexicographical comparison between built-in collections works as follows:

  • For two collections to compare equal, they must be of the same type, have the same length, and each pair of corresponding elements must compare equal (for example, [1,2] == (1,2) is false because the type is not the same).
  • Collections that support order comparison are ordered the same as their first unequal elements (for example, [1,2,x] <= [1,2,y] has the same value as x <= y). If a corresponding element does not exist, the shorter collection is ordered first (for example, [1,2] < [1,2,3] is true).

If not equal, the sequences are ordered the same as their first differing elements. For example, cmp([1,2,x], [1,2,y]) returns the same as cmp(x,y). If the corresponding element does not exist, the shorter sequence is considered smaller (for example, [1,2] < [1,2,3] returns True).

Note 1: < and > do not mean "smaller than" and "greater than" but "is before" and "is after": so (0, 1) "is before" (1, 0).

Note 2: tuples must not be considered as vectors in a n-dimensional space, compared according to their length.

Note 3: referring to question https://stackoverflow.com/questions/36911617/python-2-tuple-comparison: do not think that a tuple is "greater" than another only if any element of the first is greater than the corresponding one in the second.

Rails formatting date

Try this:

created_at.strftime('%FT%T')

It's a time formatting function which provides you a way to present the string representation of the date. (http://ruby-doc.org/core-2.2.1/Time.html#method-i-strftime).

From APIdock:

%Y%m%d           => 20071119                  Calendar date (basic)
%F               => 2007-11-19                Calendar date (extended)
%Y-%m            => 2007-11                   Calendar date, reduced accuracy, specific month
%Y               => 2007                      Calendar date, reduced accuracy, specific year
%C               => 20                        Calendar date, reduced accuracy, specific century
%Y%j             => 2007323                   Ordinal date (basic)
%Y-%j            => 2007-323                  Ordinal date (extended)
%GW%V%u          => 2007W471                  Week date (basic)
%G-W%V-%u        => 2007-W47-1                Week date (extended)
%GW%V            => 2007W47                   Week date, reduced accuracy, specific week (basic)
%G-W%V           => 2007-W47                  Week date, reduced accuracy, specific week (extended)
%H%M%S           => 083748                    Local time (basic)
%T               => 08:37:48                  Local time (extended)
%H%M             => 0837                      Local time, reduced accuracy, specific minute (basic)
%H:%M            => 08:37                     Local time, reduced accuracy, specific minute (extended)
%H               => 08                        Local time, reduced accuracy, specific hour
%H%M%S,%L        => 083748,000                Local time with decimal fraction, comma as decimal sign (basic)
%T,%L            => 08:37:48,000              Local time with decimal fraction, comma as decimal sign (extended)
%H%M%S.%L        => 083748.000                Local time with decimal fraction, full stop as decimal sign (basic)
%T.%L            => 08:37:48.000              Local time with decimal fraction, full stop as decimal sign (extended)
%H%M%S%z         => 083748-0600               Local time and the difference from UTC (basic)
%T%:z            => 08:37:48-06:00            Local time and the difference from UTC (extended)
%Y%m%dT%H%M%S%z  => 20071119T083748-0600      Date and time of day for calendar date (basic)
%FT%T%:z         => 2007-11-19T08:37:48-06:00 Date and time of day for calendar date (extended)
%Y%jT%H%M%S%z    => 2007323T083748-0600       Date and time of day for ordinal date (basic)
%Y-%jT%T%:z      => 2007-323T08:37:48-06:00   Date and time of day for ordinal date (extended)
%GW%V%uT%H%M%S%z => 2007W471T083748-0600      Date and time of day for week date (basic)
%G-W%V-%uT%T%:z  => 2007-W47-1T08:37:48-06:00 Date and time of day for week date (extended)
%Y%m%dT%H%M      => 20071119T0837             Calendar date and local time (basic)
%FT%R            => 2007-11-19T08:37          Calendar date and local time (extended)
%Y%jT%H%MZ       => 2007323T0837Z             Ordinal date and UTC of day (basic)
%Y-%jT%RZ        => 2007-323T08:37Z           Ordinal date and UTC of day (extended)
%GW%V%uT%H%M%z   => 2007W471T0837-0600        Week date and local time and difference from UTC (basic)
%G-W%V-%uT%R%:z  => 2007-W47-1T08:37-06:00    Week date and local time and difference from UTC (extended)

How to run JUnit test cases from the command line

If your project is Maven-based you can run all test-methods from test-class CustomTest which belongs to module 'my-module' using next command:

mvn clean test -pl :my-module -Dtest=CustomTest

Or run only 1 test-method myMethod from test-class CustomTest using next command:

mvn clean test -pl :my-module -Dtest=CustomTest#myMethod

For this ability you need Maven Surefire Plugin v.2.7.3+ and Junit 4. More details is here: http://maven.apache.org/surefire/maven-surefire-plugin/examples/single-test.html

Sending Windows key using SendKeys

OK turns out what you really want is this: http://inputsimulator.codeplex.com/

Which has done all the hard work of exposing the Win32 SendInput methods to C#. This allows you to directly send the windows key. This is tested and works:

InputSimulator.SimulateModifiedKeyStroke(VirtualKeyCode.LWIN, VirtualKeyCode.VK_E);

Note however that in some cases you want to specifically send the key to the application (such as ALT+F4), in which case use the Form library method. In others, you want to send it to the OS in general, use the above.


Old

Keeping this here for reference, it will not work in all operating systems, and will not always behave how you want. Note that you're trying to send these key strokes to the app, and the OS usually intercepts them early. In the case of Windows 7 and Vista, too early (before the E is sent).

SendWait("^({ESC}E)") or Send("^({ESC}E)")

Note from here: http://msdn.microsoft.com/en-us/library/system.windows.forms.sendkeys.aspx

To specify that any combination of SHIFT, CTRL, and ALT should be held down while several other keys are pressed, enclose the code for those keys in parentheses. For example, to specify to hold down SHIFT while E and C are pressed, use "+(EC)". To specify to hold down SHIFT while E is pressed, followed by C without SHIFT, use "+EC".

Note that since you want ESC and (say) E pressed at the same time, you need to enclose them in brackets.

Unzip files (7-zip) via cmd command

make sure that your path is pointing to .exe file in C:\Program Files\7-Zip (may in bin directory)

How to retry after exception?

I prefer to limit the number of retries, so that if there's a problem with that specific item you will eventually continue onto the next one, thus:

for i in range(100):
  for attempt in range(10):
    try:
      # do thing
    except:
      # perhaps reconnect, etc.
    else:
      break
  else:
    # we failed all the attempts - deal with the consequences.

Go to beginning of line without opening new line in VI

Type "^". And get a good "Vi" tutorial :)

"NOT IN" clause in LINQ to Entities

If you are using an in-memory collection as your filter, it's probably best to use the negation of Contains(). Note that this can fail if the list is too long, in which case you will need to choose another strategy (see below for using a strategy for a fully DB-oriented query).

   var exceptionList = new List<string> { "exception1", "exception2" };

   var query = myEntities.MyEntity
                         .Select(e => e.Name)
                         .Where(e => !exceptionList.Contains(e.Name));

If you're excluding based on another database query using Except might be a better choice. (Here is a link to the supported Set extensions in LINQ to Entities)

   var exceptionList = myEntities.MyOtherEntity
                                 .Select(e => e.Name);

   var query = myEntities.MyEntity
                         .Select(e => e.Name)
                         .Except(exceptionList);

This assumes a complex entity in which you are excluding certain ones depending some property of another table and want the names of the entities that are not excluded. If you wanted the entire entity, then you'd need to construct the exceptions as instances of the entity class such that they would satisfy the default equality operator (see docs).

Extract directory path and filename

You can simply do:

base=$(basename "$fspec")

How can I suppress the newline after a print statement?

print didn't transition from statement to function until Python 3.0. If you're using older Python then you can suppress the newline with a trailing comma like so:

print "Foo %10s bar" % baz,

MySQL > Table doesn't exist. But it does (or it should)

I had the same issue in windows. In addition to copying the ib* files and the mysql directory under thd data directory, I also had to match the my.ini file.

The my.ini file from my previous installation did not have the following line:

innodb-page-size=65536

But my new installation did. Possibly because I did not have that option in the older installer. I removed this and restarted the service and the tables worked as expected. In short, make sure that the new my.ini file is a replica of the old one, with the only exception being the datadir, the plugin-dir and the port#, depending upon your new installation.

I need a Nodejs scheduler that allows for tasks at different intervals

I've used node-cron and agenda.

node-cron is a very simple library, which provide very basic and easy to understand api like crontab. It doesn't need any config and just works.

var cronJob = require('cron').CronJob;
var myJob = new cronJob('00 30 11 * * 1-5', function(){...});
myJob.start();

agenda is very powerful and fit for much more complex services. Think about ifttt, you have to run millions of tasks. agenda would be the best choice.

Note: You need Mongodb to use Agenda

var Agenda = require("Agenda");
var agenda = new Agenda({db: { address: 'localhost:27017/agenda-example'}});
agenda.every('*/3 * * * *', 'delete old users');
agenda.start();

Callback functions in C++

There is also the C way of doing callbacks: function pointers

//Define a type for the callback signature,
//it is not necessary, but makes life easier

//Function pointer called CallbackType that takes a float
//and returns an int
typedef int (*CallbackType)(float);  


void DoWork(CallbackType callback)
{
  float variable = 0.0f;

  //Do calculations

  //Call the callback with the variable, and retrieve the
  //result
  int result = callback(variable);

  //Do something with the result
}

int SomeCallback(float variable)
{
  int result;

  //Interpret variable

  return result;
}

int main(int argc, char ** argv)
{
  //Pass in SomeCallback to the DoWork
  DoWork(&SomeCallback);
}

Now if you want to pass in class methods as callbacks, the declarations to those function pointers have more complex declarations, example:

//Declaration:
typedef int (ClassName::*CallbackType)(float);

//This method performs work using an object instance
void DoWorkObject(CallbackType callback)
{
  //Class instance to invoke it through
  ClassName objectInstance;

  //Invocation
  int result = (objectInstance.*callback)(1.0f);
}

//This method performs work using an object pointer
void DoWorkPointer(CallbackType callback)
{
  //Class pointer to invoke it through
  ClassName * pointerInstance;

  //Invocation
  int result = (pointerInstance->*callback)(1.0f);
}

int main(int argc, char ** argv)
{
  //Pass in SomeCallback to the DoWork
  DoWorkObject(&ClassName::Method);
  DoWorkPointer(&ClassName::Method);
}

Twitter bootstrap scrollable modal

/* Important part */
.modal-dialog{
    overflow-y: initial !important
}
.modal-body{
    max-height: calc(100vh - 200px);
    overflow-y: auto;
}

This works for Bootstrap 3 without JS code and is responsive.

Source

jQuery issue - #<an Object> has no method

This usually has to do with a selector not being used properly. Check and make sure that you are using the jQuery selectors like intended. For example I had this problem when creating a click method:

$("[editButton]").click(function () {
    this.css("color", "red");
});

Because I was not using the correct selector method $(this) for jQuery it gave me the same error.

So simply enough, check your selectors!

Automatically open Chrome developer tools when new tab/new window is opened

On a Mac: Quit Chrome, then run the following command in a terminal window:

open -a "Google Chrome" --args --auto-open-devtools-for-tabs

How to embed matplotlib in pyqt - for Dummies

For those looking for a dynamic solution to embed Matplotlib in PyQt5 (even plot data using drag and drop). In PyQt5 you need to use super on the main window class to accept the drops. The dropevent function can be used to get the filename and rest is simple:

def dropEvent(self,e):
        """
        This function will enable the drop file directly on to the 
        main window. The file location will be stored in the self.filename
        """
        if e.mimeData().hasUrls:
            e.setDropAction(QtCore.Qt.CopyAction)
            e.accept()
            for url in e.mimeData().urls():
                if op_sys == 'Darwin':
                    fname = str(NSURL.URLWithString_(str(url.toString())).filePathURL().path())
                else:
                    fname = str(url.toLocalFile())
            self.filename = fname
            print("GOT ADDRESS:",self.filename)
            self.readData()
        else:
            e.ignore() # just like above functions  

For starters the reference complete code gives this output: enter image description here

Search in lists of lists by given index

>>> the_list =[ ['a','b'], ['a','c'], ['b''d'] ]
>>> any('c' == x[1] for x in the_list)
True

link with target="_blank" does not open in new tab in Chrome

Replace 

<a href="http://www.foracure.org.au" target="_blank"></a>    

with 

<a href="#" onclick='window.open("http://www.foracure.org.au");return false;'></a>

in your code and will work in Chrome and other browsers.

Thanks Anurag

How can I find out if an .EXE has Command-Line Options?

This is what I get from console on Windows 10:

C:\>find /?
Searches for a text string in a file or files.

FIND [/V] [/C] [/N] [/I] [/OFF[LINE]] "string" [[drive:][path]filename[ ...]]

  /V         Displays all lines NOT containing the specified string.
  /C         Displays only the count of lines containing the string.
  /N         Displays line numbers with the displayed lines.
  /I         Ignores the case of characters when searching for the string.
  /OFF[LINE] Do not skip files with offline attribute set.
  "string"   Specifies the text string to find.
  [drive:][path]filename
             Specifies a file or files to search.

If a path is not specified, FIND searches the text typed at the prompt
or piped from another command.

How to persist a property of type List<String> in JPA?

When using the Hibernate implementation of JPA , I've found that simply declaring the type as an ArrayList instead of List allows hibernate to store the list of data.

Clearly this has a number of disadvantages compared to creating a list of Entity objects. No lazy loading, no ability to reference the entities in the list from other objects, perhaps more difficulty in constructing database queries. However when you are dealing with lists of fairly primitive types that you will always want to eagerly fetch along with the entity, then this approach seems fine to me.

@Entity
public class Command implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    Long id;

    ArrayList<String> arguments = new ArrayList<String>();


}

Convert month int to month name

CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(
    Convert.ToInt32(e.Row.Cells[7].Text.Substring(3,2))).Substring(0,3) 
    + "-" 
    + Convert.ToDateTime(e.Row.Cells[7].Text).ToString("yyyy");

The type initializer for 'System.Data.Entity.Internal.AppConfig' threw an exception

I Found that removing the references to Entity Framework and installing the latest version of Entity Framework from NuGet fixed the issue. It recreates all the required entries for you during install.

Python dictionary: are keys() and values() always the same order?

According to http://docs.python.org/dev/py3k/library/stdtypes.html#dictionary-view-objects , the keys(), values() and items() methods of a dict will return corresponding iterators whose orders correspond. However, I am unable to find a reference to the official documentation for python 2.x for the same thing.

So as far as I can tell, the answer is yes, but only in python 3.0+

Cannot install Aptana Studio 3.6 on Windows

I have some issue, the fix is:

  1. Uninstall any nodejs version.
  2. Install https://nodejs.org/dist/v0.10.36/x64/node-v0.10.36-x64.msi.
  3. Install Aptana.
  4. Code...

greetings!

Turning Sonar off for certain code

This is a FAQ. You can put //NOSONAR on the line triggering the warning. I prefer using the FindBugs mechanism though, which consists in adding the @SuppressFBWarnings annotation:

@edu.umd.cs.findbugs.annotations.SuppressFBWarnings(
    value = "NAME_OF_THE_FINDBUGS_RULE_TO_IGNORE",
    justification = "Why you choose to ignore it")

is there a css hack for safari only NOT chrome?

Replace your class in (.myClass)

/* Safari only */ .myClass:not(:root:root) { enter code here }

How to select date without time in SQL

Use is simple:

convert(date, Btch_Time)

Example below:

Table:

Efft_d       Loan_I  Loan_Purp_Type_C   Orig_LTV    Curr_LTV    Schd_LTV    Un_drwn_Bal_a      Btch_Time            Strm_I  Btch_Ins_I
2014-05-31  200312500   HL03             NULL         1.0000    1.0000         1.0000      2014-06-17 11:10:57.330  1005    24851e0a-53983699-14b4-69109


Select * from helios.dbo.CBA_SRD_Loan where Loan_I in ('200312500') and convert(date, Btch_Time) = '2014-06-17'

SQL: How to properly check if a record exists

It's better to use either of the following:

-- Method 1.
SELECT 1
FROM table_name
WHERE unique_key = value;

-- Method 2.
SELECT COUNT(1)
FROM table_name
WHERE unique_key = value;

The first alternative should give you no result or one result, the second count should be zero or one.

How old is the documentation you're using? Although you've read good advice, most query optimizers in recent RDBMS's optimize SELECT COUNT(*) anyway, so while there is a difference in theory (and older databases), you shouldn't notice any difference in practice.

How do you use math.random to generate random ints?

int abc= (Math.random()*100);//  wrong 

you wil get below error message

Exception in thread "main" java.lang.Error: Unresolved compilation problem: Type mismatch: cannot convert from double to int

int abc= (int) (Math.random()*100);// add "(int)" data type

,known as type casting

if the true result is

int abc= (int) (Math.random()*1)=0.027475

Then you will get output as "0" because it is a integer data type.

int abc= (int) (Math.random()*100)=0.02745

output:2 because (100*0.02745=2.7456...etc)

How to convert string representation of list to a list?

There is a quick solution:

x = eval('[ "A","B","C" , " D"]')

Unwanted whitespaces in the list elements may be removed in this way:

x = [x.strip() for x in eval('[ "A","B","C" , " D"]')]

Angular ng-click with call to a controller function not working

Use alias when defining Controller in your angular configuration. For example: NOTE: I'm using TypeScript here

Just take note of the Controller, it has an alias of homeCtrl.

module MongoAngular {
    var app = angular.module('mongoAngular', ['ngResource', 'ngRoute','restangular']);

    app.config([
        '$routeProvider', ($routeProvider: ng.route.IRouteProvider) => {
            $routeProvider
                .when('/Home', {
                    templateUrl: '/PartialViews/Home/home.html',
                    controller: 'HomeController as homeCtrl'
                })
                .otherwise({ redirectTo: '/Home' });
        }])
        .config(['RestangularProvider', (restangularProvider: restangular.IProvider) => {
        restangularProvider.setBaseUrl('/api');
    }]);
} 

And here's the way to use it...

ng-click="homeCtrl.addCustomer(customer)"

Try it.. It might work for you as it worked for me... ;)

How do I handle newlines in JSON?

According to the specification, http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf:

A string is a sequence of Unicode code points wrapped with quotation marks (U+0022). All characters may be placed within the quotation marks except for the characters that must be escaped: quotation mark (U+0022), reverse solidus (U+005C), and the control characters U+0000 to U+001F. There are two-character escape sequence representations of some characters.

So you can't pass 0x0A or 0x0C codes directly. It is forbidden! The specification suggests to use escape sequences for some well-defined codes from U+0000 to U+001F:

  • \f represents the form feed character (U+000C).
  • \n represents the line feed character (U+000A).

As most of programming languages uses \ for quoting, you should escape the escape syntax (double-escape - once for language/platform, once for JSON itself):

jsonStr = "{ \"name\": \"Multi\\nline.\" }";

add new row in gridview after binding C#, ASP.net

you can try the following code

protected void Button1_Click(object sender, EventArgs e)
   {
       DataTable dt = new DataTable();

       if (dt.Columns.Count == 0)
       {
           dt.Columns.Add("PayScale", typeof(string));
           dt.Columns.Add("IncrementAmt", typeof(string));
           dt.Columns.Add("Period", typeof(string));
       }

       DataRow NewRow = dt.NewRow();
       NewRow[0] = TextBox1.Text;
       NewRow[1] = TextBox2.Text;
       dt.Rows.Add(NewRow); 
       GridView1.DataSource = dt;
       GridViewl.DataBind();
   }

here payscale,incrementamt and period are database field name.

Check if a JavaScript string is a URL

The question asks a validation method for an url such as stackoverflow, without the protocol or any dot in the hostname. So, it's not a matter of validating url sintax, but checking if it's a valid url, by actually calling it.

I tried several methods for knowing if the url true exists and is callable from within the browser, but did not find any way to test with javascript the response header of the call:

  • adding an anchor element is fine for firing the click() method.
  • making ajax call to the challenging url with 'GET' is fine, but has it's various limitations due to CORS policies and it is not the case of using ajax, for as the url maybe any outside my server's domain.
  • using the fetch API has a workaround similar to ajax.
  • other problem is that I have my server under https protocol and throws an exception when calling non secure urls.

So, the best solution I can think of is getting some tool to perform CURL using javascript trying something like curl -I <url>. Unfortunately I did not find any and in appereance it's not possible. I will appreciate any comments on this.

But, in the end, I have a server running PHP and as I use Ajax for almost all my requests, I wrote a function on the server side to perform the curl request there and return to the browser.

Regarding the single word url on the question 'stackoverflow' it will lead me to https://daniserver.com.ar/stackoverflow, where daniserver.com.ar is my own domain.

Why does python use 'else' after for and while loops?

Great answers are:

  • this which explain the history, and
  • this gives the right citation to ease yours translation/understanding.

My note here comes from what Donald Knuth once said (sorry can't find reference) that there is a construct where while-else is indistinguishable from if-else, namely (in Python):

x = 2
while x > 3:
    print("foo")
    break
else:
    print("boo")

has the same flow (excluding low level differences) as:

x = 2
if x > 3:
    print("foo")
else:
    print("boo")

The point is that if-else can be considered as syntactic sugar for while-else which has implicit break at the end of its if block. The opposite implication, that while loop is extension to if, is more common (it's just repeated/looped conditional check), because if is often taught before while. However that isn't true because that would mean else block in while-else would be executed each time when condition is false.

To ease your understanding think of it that way:

Without break, return, etc., loop ends only when condition is no longer true and in such case else block will also execute once. In case of Python for you must consider C-style for loops (with conditions) or translate them to while.

Another note:

Premature break, return, etc. inside loop makes impossible for condition to become false because execution jumped out of the loop while condition was true and it would never come back to check it again.

Finding even or odd ID values

For finding the even number we should use

select num from table where ( num % 2 ) = 0

Typescript: Type X is missing the following properties from type Y length, pop, push, concat, and 26 more. [2740]

You are returning Observable<Product> and expecting it to be Product[] inside subscribe callback.

The Type returned from http.get() and getProducts() should be Observable<Product[]>

public getProducts(): Observable<Product[]> {
    return this.http.get<Product[]>(`api/products/v1/`);
}

Interface vs Abstract Class (general OO)

Interface Types vs. Abstract Base Classes

Adapted from the Pro C# 5.0 and the .NET 4.5 Framework book.

The interface type might seem very similar to an abstract base class. Recall that when a class is marked as abstract, it may define any number of abstract members to provide a polymorphic interface to all derived types. However, even when a class does define a set of abstract members, it is also free to define any number of constructors, field data, nonabstract members (with implementation), and so on. Interfaces, on the other hand, contain only abstract member definitions. The polymorphic interface established by an abstract parent class suffers from one major limitation in that only derived types support the members defined by the abstract parent. However, in larger software systems, it is very common to develop multiple class hierarchies that have no common parent beyond System.Object. Given that abstract members in an abstract base class apply only to derived types, we have no way to configure types in different hierarchies to support the same polymorphic interface. By way of example, assume you have defined the following abstract class:

public abstract class CloneableType
{
// Only derived types can support this
// "polymorphic interface." Classes in other
// hierarchies have no access to this abstract
// member.
   public abstract object Clone();
}

Given this definition, only members that extend CloneableType are able to support the Clone() method. If you create a new set of classes that do not extend this base class, you can’t gain this polymorphic interface. Also, you might recall that C# does not support multiple inheritance for classes. Therefore, if you wanted to create a MiniVan that is-a Car and is-a CloneableType, you are unable to do so:

// Nope! Multiple inheritance is not possible in C#
// for classes.
public class MiniVan : Car, CloneableType
{
}

As you would guess, interface types come to the rescue. After an interface has been defined, it can be implemented by any class or structure, in any hierarchy, within any namespace or any assembly (written in any .NET programming language). As you can see, interfaces are highly polymorphic. Consider the standard .NET interface named ICloneable, defined in the System namespace. This interface defines a single method named Clone():

public interface ICloneable
{
object Clone();
}

IE 8: background-size fix

Also i have found another useful link. It is a background hack used like this

.selector { background-size: cover; -ms-behavior: url(/backgroundsize.min.htc); }

https://github.com/louisremi/background-size-polyfill

Formatting floats in a numpy array

[ round(x,2) for x in [2.15295647e+01, 8.12531501e+00, 3.97113829e+00, 1.00777250e+01]]

Generating Unique Random Numbers in Java

Check this

public class RandomNumbers {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int n = 5;
        int A[] = uniqueRandomArray(n);
        for(int i = 0; i<n; i++){
            System.out.println(A[i]);
        }
    }
    public static int[] uniqueRandomArray(int n){
        int [] A = new int[n];
        for(int i = 0; i< A.length; ){
            if(i == A.length){
                break;
            }
            int b = (int)(Math.random() *n) + 1;
            if(f(A,b) == false){
                A[i++] = b;
            } 
        }
        return A;
    }
    public static boolean f(int[] A, int n){
        for(int i=0; i<A.length; i++){
            if(A[i] == n){
                return true;
            }
        }
        return false;
    }
}

What is the difference between "JPG" / "JPEG" / "PNG" / "BMP" / "GIF" / "TIFF" Image?

Since others have covered the differences, I'll hit the uses.

TIFF is usually used by scanners. It makes huge files and is not really used in applications.

BMP is uncompressed and also makes huge files. It is also not really used in applications.

GIF used to be all over the web but has fallen out of favor since it only supports a limited number of colors and is patented.

JPG/JPEG is mainly used for anything that is photo quality, though not for text. The lossy compression used tends to mar sharp lines.

PNG isn't as small as JPEG but is lossless so it's good for images with sharp lines. It's in common use on the web now.

Personally, I usually use PNG everywhere I can. It's a good compromise between JPG and GIF.

Clear the entire history stack and start a new activity on Android

Immediately after you start a new activity, using startActivity, make sure you call finish() so that the current activity is not stacked behind the new one.

What does it mean "No Launcher activity found!"

Manifest is case sensitive, so please compare this lines for any case mismatch especially the word MAIN in:

<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />

Best method to download image from url in Android

Try to use this:

public Bitmap getBitmapFromURL(String src) {
    try {
        java.net.URL url = new java.net.URL(src);
        HttpURLConnection connection = (HttpURLConnection) url
                .openConnection();
        connection.setDoInput(true);
        connection.connect();
        InputStream input = connection.getInputStream();
        Bitmap myBitmap = BitmapFactory.decodeStream(input);
        return myBitmap;
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
}

And for OutOfMemory issue:

 public Bitmap getResizedBitmap(Bitmap bm, int newHeight, int newWidth) {
    int width = bm.getWidth();
    int height = bm.getHeight();
    float scaleWidth = ((float) newWidth) / width;
    float scaleHeight = ((float) newHeight) / height;
    // CREATE A MATRIX FOR THE MANIPULATION
    Matrix matrix = new Matrix();
    // RESIZE THE BIT MAP
    matrix.postScale(scaleWidth, scaleHeight);

    // "RECREATE" THE NEW BITMAP
    Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height,
            matrix, false);

    return resizedBitmap;
}

How to add key,value pair to dictionary?

I am not sure what you mean by "dynamic". If you mean adding items to a dictionary at runtime, it is as easy as dictionary[key] = value.

If you wish to create a dictionary with key,value to start with (at compile time) then use (surprise!)

dictionary[key] = value

SSH to AWS Instance without key pairs

Answer to Question 1

Here's what I did on a Ubuntu EC2:

A) Login as root using the keypairs

B) Setup the necessary users and their passwords with

# sudo adduser USERNAME
# sudo passwd USERNAME

C) Edit /etc/ssh/sshd_config setting

For a valid user to login with no key

PasswordAuthentication yes

Also want root to login also with no key

PermitRootLogin yes

D) Restart the ssh daemon with

# sudo service ssh restart

just change ssh to sshd if you are using centOS

Now you can login into your ec2 instance without key pairs.

How to get the current user in ASP.NET MVC

In Asp.net Mvc Identity 2,You can get the current user name by:

var username = System.Web.HttpContext.Current.User.Identity.Name;

AngularJS: No "Access-Control-Allow-Origin" header is present on the requested resource

This is a server side issue. You don't need to add any headers in angular for cors. You need to add header on the server side:

Access-Control-Allow-Headers: Content-Type
Access-Control-Allow-Methods: GET, POST, OPTIONS
Access-Control-Allow-Origin: *

First two answers here: How to enable CORS in AngularJs

How do I shrink my SQL Server Database?

Not sure how practical this would be, and depending on the size of the database, number of tables and other complexities, but I:

  1. defrag the physical drive
  2. create a new database according to my requirements, space, percentage growth, etc
  3. use the simple ssms task to import all tables from the old db to the new db
  4. script out the indexes for all tables on the old database, and then recreate the indexes on the new database. expand as needed for foreign keys etc.
  5. rename databases as needed, confirm successful, delete old

Determine path of the executing script

If rather than the script, foo.R, knowing its path location, if you can change your code to always reference all source'd paths from a common root then these may be a great help:

Given

  • /app/deeply/nested/foo.R
  • /app/other.R

This will work

#!/usr/bin/env Rscript
library(here)
source(here("other.R"))

See https://rprojroot.r-lib.org/ for how to define project roots.

How to hide soft keyboard on android after clicking outside EditText?

I got this working with a slight variant on Fernando Camarago's solution. In my onCreate method I attach a single onTouchListener to the root view but send the view rather than activity as an argument.

        findViewById(android.R.id.content).setOnTouchListener(new OnTouchListener() {           
        public boolean onTouch(View v, MotionEvent event) {
            Utils.hideSoftKeyboard(v);
            return false;
        }
    });

In a separate Utils class is...

    public static void hideSoftKeyboard(View v) {
    InputMethodManager imm = (InputMethodManager) v.getContext().getSystemService(Context.INPUT_METHOD_SERVICE); 
    imm.hideSoftInputFromWindow(v.getWindowToken(), 0);
}

how to destroy an object in java?

Short Answer - E

Answer isE given that the rest are plainly wrong, but ..

Long Answer - It isn't that simple; it depends ...

Simple fact is, the garbage collector may never decide to garbage collection every single object that is a viable candidate for collection, not unless memory pressure is extremely high. And then there is the fact that Java is just as susceptible to memory leaks as any other language, they are just harder to cause, and thus harder to find when you do cause them!

The following article has many good details on how memory management works and doesn't work and what gets take up by what. How generational Garbage Collectors work and Thanks for the Memory ( Understanding How the JVM uses Native Memory on Windows and Linux )

If you read the links, I think you will get the idea that memory management in Java isn't as simple as a multiple choice question.

Linq select object from list depending on objects attribute

Answers = Answers.GroupBy(a => a.id).Select(x => x.First());

This will select each unique object by email

Difference between static STATIC_URL and STATIC_ROOT on Django

STATICFILES_DIRS: You can keep the static files for your project here e.g. the ones used by your templates.

STATIC_ROOT: leave this empty, when you do manage.py collectstatic, it will search for all the static files on your system and move them here. Your static file server is supposed to be mapped to this folder wherever it is located. Check it after running collectstatic and you'll find the directory structure django has built.

--------Edit----------------

As pointed out by @DarkCygnus, STATIC_ROOT should point at a directory on your filesystem, the folder should be empty since it will be populated by Django.

STATIC_ROOT = os.path.join(BASE_DIR, 'staticfiles')

or

STATIC_ROOT = '/opt/web/project/static_files'

--------End Edit -----------------

STATIC_URL: '/static/' is usually fine, it's just a prefix for static files.

Produce a random number in a range using C#

Use:

Random r = new Random();
 int x= r.Next(10);//Max range

JUnit: how to avoid "no runnable methods" in test utils classes

Assuming you're in control of the pattern used to find test classes, I'd suggest changing it to match *Test rather than *Test*. That way TestHelper won't get matched, but FooTest will.

Addition for BigDecimal

//you can do in this way...as BigDecimal is immutable so cant set values except in constructor

BigDecimal test = BigDecimal.ZERO;
BigDecimal result = test.add(new BigDecimal(30));
System.out.println(result);

result would be 30

DataTrigger where value is NOT null?

My solution is in the DataContext instance (or ViewModel if using MVVM). I add a property that returns true if the Not Null condition I want is met.

    Public ReadOnly Property IsSomeFieldNull() As Boolean
        Get
            Return If(SomeField is Null, True, False)
        End Get
    End Property

and bind the DataTrigger to the above property. Note: In VB.NET be sure to use the operator If and NOT the IIf function, which doesn't work with Null objects. Then the XAML is:

    <DataTrigger Binding="{Binding IsSomeFieldNull}" Value="False">
      <Setter Property="TextBlock.Text" Value="It's NOT NULL Baby!" />
    </DataTrigger>

Return a value of '1' a referenced cell is empty

Beware: There are also cells which are seemingly blank, but are not truly empty but containg "" or something that is called NULL in other languages. As an example, when a formula results in "" or such result is copied to a cell, the formula

ISBLANK(A1) 

returns FALSE. That means the cell is not truly empty.

The way to go there is to use enter code here

COUNTBLANK(A1)

Which finds both truly empty cells and those containing "". See also this very good answer here

What is the simplest way to swap each pair of adjoining chars in a string with Python?

''.join(s[i+1]+s[i] for i in range(0, len(s), 2)) # 10.6 usec per loop

or

''.join(x+y for x, y in zip(s[1::2], s[::2])) # 10.3 usec per loop

or if the string can have an odd length:

''.join(x+y for x, y in itertools.izip_longest(s[1::2], s[::2], fillvalue=''))

Note that this won't work with old versions of Python (if I'm not mistaking older than 2.5).

The benchmark was run on python-2.7-8.fc14.1.x86_64 and a Core 2 Duo 6400 CPU with s='0123456789'*4.

How to read XML response from a URL in java?

do it with the following code:

DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();

    try {
        DocumentBuilder builder = builderFactory.newDocumentBuilder();
        Document doc = builder.parse("/home/codefelix/IdeaProjects/Gradle/src/main/resources/static/Employees.xml");
        NodeList namelist = (NodeList) doc.getElementById("1");

        for (int i = 0; i < namelist.getLength(); i++) {
            Node p = namelist.item(i);

            if (p.getNodeType() == Node.ELEMENT_NODE) {
                Element person = (Element) p;
                NodeList id = (NodeList) person.getElementsByTagName("Employee");
                NodeList nodeList = person.getChildNodes();
                List<EmployeeDto> employeeDtoList=new ArrayList();

                for (int j = 0; j < nodeList.getLength(); j++) {
                    Node n = nodeList.item(j);

                    if (n.getNodeType() == Node.ELEMENT_NODE) {
                        Element naame = (Element) n;
                        System.out.println("Employee" + id + ":" + naame.getTagName() + "=" +naame.getTextContent());
                    }
                }
            }
        }
    } catch (ParserConfigurationException e) {
        e.printStackTrace();
    } catch (SAXException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

Map over object preserving keys

const mapObject = (obj = {}, mapper) =>
  Object.entries(obj).reduce(
    (acc, [key, val]) => ({ ...acc, [key]: mapper(val) }),
    {},
  );

HTML not loading CSS file

HTML was not loading my css because i had placed the style.css in template folder rather it should be in static folder . After replacing my file to static folder it worked for me

'DataFrame' object has no attribute 'sort'

Pandas Sorting 101

sort has been replaced in v0.20 by DataFrame.sort_values and DataFrame.sort_index. Aside from this, we also have argsort.

Here are some common use cases in sorting, and how to solve them using the sorting functions in the current API. First, the setup.

# Setup
np.random.seed(0)
df = pd.DataFrame({'A': list('accab'), 'B': np.random.choice(10, 5)})    
df                                                                                                                                        
   A  B
0  a  7
1  c  9
2  c  3
3  a  5
4  b  2

Sort by Single Column

For example, to sort df by column "A", use sort_values with a single column name:

df.sort_values(by='A')

   A  B
0  a  7
3  a  5
4  b  2
1  c  9
2  c  3

If you need a fresh RangeIndex, use DataFrame.reset_index.

Sort by Multiple Columns

For example, to sort by both col "A" and "B" in df, you can pass a list to sort_values:

df.sort_values(by=['A', 'B'])

   A  B
3  a  5
0  a  7
4  b  2
2  c  3
1  c  9

Sort By DataFrame Index

df2 = df.sample(frac=1)
df2

   A  B
1  c  9
0  a  7
2  c  3
3  a  5
4  b  2

You can do this using sort_index:

df2.sort_index()

   A  B
0  a  7
1  c  9
2  c  3
3  a  5
4  b  2

df.equals(df2)                                                                                                                            
# False
df.equals(df2.sort_index())                                                                                                               
# True

Here are some comparable methods with their performance:

%timeit df2.sort_index()                                                                                                                  
%timeit df2.iloc[df2.index.argsort()]                                                                                                     
%timeit df2.reindex(np.sort(df2.index))                                                                                                   

605 µs ± 13.6 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
610 µs ± 24.2 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
581 µs ± 7.63 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

Sort by List of Indices

For example,

idx = df2.index.argsort()
idx
# array([0, 7, 2, 3, 9, 4, 5, 6, 8, 1])

This "sorting" problem is actually a simple indexing problem. Just passing integer labels to iloc will do.

df.iloc[idx]

   A  B
1  c  9
0  a  7
2  c  3
3  a  5
4  b  2

Select first occurring element after another element

Simplyfing for the begginers:

If you want to select an element immediatly after another element you use the + selector.

For example:

div + p The "+" element selects all <p> elements that are placed immediately after <div> elements


If you want to learn more about selectors use this table

Download file from an ASP.NET Web API method using AngularJS

We also had to develop a solution which would even work with APIs requiring authentication (see this article)

Using AngularJS in a nutshell here is how we did it:

Step 1: Create a dedicated directive

// jQuery needed, uses Bootstrap classes, adjust the path of templateUrl
app.directive('pdfDownload', function() {
return {
    restrict: 'E',
    templateUrl: '/path/to/pdfDownload.tpl.html',
    scope: true,
    link: function(scope, element, attr) {
        var anchor = element.children()[0];

        // When the download starts, disable the link
        scope.$on('download-start', function() {
            $(anchor).attr('disabled', 'disabled');
        });

        // When the download finishes, attach the data to the link. Enable the link and change its appearance.
        scope.$on('downloaded', function(event, data) {
            $(anchor).attr({
                href: 'data:application/pdf;base64,' + data,
                download: attr.filename
            })
                .removeAttr('disabled')
                .text('Save')
                .removeClass('btn-primary')
                .addClass('btn-success');

            // Also overwrite the download pdf function to do nothing.
            scope.downloadPdf = function() {
            };
        });
    },
    controller: ['$scope', '$attrs', '$http', function($scope, $attrs, $http) {
        $scope.downloadPdf = function() {
            $scope.$emit('download-start');
            $http.get($attrs.url).then(function(response) {
                $scope.$emit('downloaded', response.data);
            });
        };
    }] 
});

Step 2: Create a template

<a href="" class="btn btn-primary" ng-click="downloadPdf()">Download</a>

Step 3: Use it

<pdf-download url="/some/path/to/a.pdf" filename="my-awesome-pdf"></pdf-download>

This will render a blue button. When clicked, a PDF will be downloaded (Caution: the backend has to deliver the PDF in Base64 encoding!) and put into the href. The button turns green and switches the text to Save. The user can click again and will be presented with a standard download file dialog for the file my-awesome.pdf.

getting the difference between date in days in java

Calendar start = Calendar.getInstance();
Calendar end = Calendar.getInstance();
start.set(2010, 7, 23);
end.set(2010, 8, 26);
Date startDate = start.getTime();
Date endDate = end.getTime();
long startTime = startDate.getTime();
long endTime = endDate.getTime();
long diffTime = endTime - startTime;
long diffDays = diffTime / (1000 * 60 * 60 * 24);
DateFormat dateFormat = DateFormat.getDateInstance();
System.out.println("The difference between "+
  dateFormat.format(startDate)+" and "+
  dateFormat.format(endDate)+" is "+
  diffDays+" days.");

This will not work when crossing daylight savings time (or leap seconds) as orange80 pointed out and might as well not give the expected results when using different times of day. Using JodaTime might be easier for correct results, as the only correct way with plain Java before 8 I know is to use Calendar's add and before/after methods to check and adjust the calculation:

start.add(Calendar.DAY_OF_MONTH, (int)diffDays);
while (start.before(end)) {
    start.add(Calendar.DAY_OF_MONTH, 1);
    diffDays++;
}
while (start.after(end)) {
    start.add(Calendar.DAY_OF_MONTH, -1);
    diffDays--;
}

What's sizeof(size_t) on 32-bit vs the various 64-bit data models?

size_t is 64 bit normally on 64 bit machine

How to make <input type="file"/> accept only these types?

for powerpoint and pdf files:

<html>
<input type="file" placeholder="Do you have a .ppt?" name="pptfile" id="pptfile" accept="application/pdf,application/vnd.ms-powerpoint,application/vnd.openxmlformats-officedocument.presentationml.slideshow,application/vnd.openxmlformats-officedocument.presentationml.presentation"/>
</html>

Set height of chart in Chart.js

The easiest way is to create a container for the canvas and set its height:

<div style="height: 300px">
  <canvas id="chart"></canvas>
</div>

and set

options: {  
    responsive: true,
    maintainAspectRatio: false
}

Error: unexpected symbol/input/string constant/numeric constant/SPECIAL in my code

These errors mean that the R code you are trying to run or source is not syntactically correct. That is, you have a typo.

To fix the problem, read the error message carefully. The code provided in the error message shows where R thinks that the problem is. Find that line in your original code, and look for the typo.


Prophylactic measures to prevent you getting the error again

The best way to avoid syntactic errors is to write stylish code. That way, when you mistype things, the problem will be easier to spot. There are many R style guides linked from the SO R tag info page. You can also use the formatR package to automatically format your code into something more readable. In RStudio, the keyboard shortcut CTRL + SHIFT + A will reformat your code.

Consider using an IDE or text editor that highlights matching parentheses and braces, and shows strings and numbers in different colours.


Common syntactic mistakes that generate these errors

Mismatched parentheses, braces or brackets

If you have nested parentheses, braces or brackets it is very easy to close them one too many or too few times.

{}}
## Error: unexpected '}' in "{}}"
{{}} # OK

Missing * when doing multiplication

This is a common mistake by mathematicians.

5x
Error: unexpected symbol in "5x"
5*x # OK

Not wrapping if, for, or return values in parentheses

This is a common mistake by MATLAB users. In R, if, for, return, etc., are functions, so you need to wrap their contents in parentheses.

if x > 0 {}
## Error: unexpected symbol in "if x"
if(x > 0) {} # OK

Not using multiple lines for code

Trying to write multiple expressions on a single line, without separating them by semicolons causes R to fail, as well as making your code harder to read.

x + 2 y * 3
## Error: unexpected symbol in "x + 2 y"
x + 2; y * 3 # OK

else starting on a new line

In an if-else statement, the keyword else must appear on the same line as the end of the if block.

if(TRUE) 1
else 2
## Error: unexpected 'else' in "else"    
if(TRUE) 1 else 2 # OK
if(TRUE) 
{
  1
} else            # also OK
{
  2
}

= instead of ==

= is used for assignment and giving values to function arguments. == tests two values for equality.

if(x = 0) {}
## Error: unexpected '=' in "if(x ="    
if(x == 0) {} # OK

Missing commas between arguments

When calling a function, each argument must be separated by a comma.

c(1 2)
## Error: unexpected numeric constant in "c(1 2"
c(1, 2) # OK

Not quoting file paths

File paths are just strings. They need to be wrapped in double or single quotes.

path.expand(~)
## Error: unexpected ')' in "path.expand(~)"
path.expand("~") # OK

Quotes inside strings

This is a common problem when trying to pass quoted values to the shell via system, or creating quoted xPath or sql queries.

Double quotes inside a double quoted string need to be escaped. Likewise, single quotes inside a single quoted string need to be escaped. Alternatively, you can use single quotes inside a double quoted string without escaping, and vice versa.

"x"y"
## Error: unexpected symbol in ""x"y"   
"x\"y" # OK
'x"y'  # OK  

Using curly quotes

So-called "smart" quotes are not so smart for R programming.

path.expand(“~”)
## Error: unexpected input in "path.expand(“"    
path.expand("~") # OK

Using non-standard variable names without backquotes

?make.names describes what constitutes a valid variable name. If you create a non-valid variable name (using assign, perhaps), then you need to access it with backquotes,

assign("x y", 0)
x y
## Error: unexpected symbol in "x y"
`x y` # OK

This also applies to column names in data frames created with check.names = FALSE.

dfr <- data.frame("x y" = 1:5, check.names = FALSE)
dfr$x y
## Error: unexpected symbol in "dfr$x y"
dfr[,"x y"] # OK
dfr$`x y`   # also OK

It also applies when passing operators and other special values to functions. For example, looking up help on %in%.

?%in%
## Error: unexpected SPECIAL in "?%in%"
?`%in%` # OK

Sourcing non-R code

The source function runs R code from a file. It will break if you try to use it to read in your data. Probably you want read.table.

source(textConnection("x y"))
## Error in source(textConnection("x y")) : 
##   textConnection("x y"):1:3: unexpected symbol
## 1: x y
##       ^

Corrupted RStudio desktop file

RStudio users have reported erroneous source errors due to a corrupted .rstudio-desktop file. These reports only occurred around March 2014, so it is possibly an issue with a specific version of the IDE. RStudio can be reset using the instructions on the support page.


Using expression without paste in mathematical plot annotations

When trying to create mathematical labels or titles in plots, the expression created must be a syntactically valid mathematical expression as described on the ?plotmath page. Otherwise the contents should be contained inside a call to paste.

plot(rnorm(10), ylab = expression(alpha ^ *)))
## Error: unexpected '*' in "plot(rnorm(10), ylab = expression(alpha ^ *"
plot(rnorm(10), ylab = expression(paste(alpha ^ phantom(0), "*"))) # OK

Removing duplicate characters from a string

d = {}
s="YOUR_DESIRED_STRING"
res=[]
for c in s:
    if c not in d:
      res.append(c)
      d[c]=1
print ("".join(res))

redirect to current page in ASP.Net

http://en.wikipedia.org/wiki/Post/Redirect/Get

The most common way to implement this pattern in ASP.Net is to use Response.Redirect(Request.RawUrl)

Consider the differences between Redirect and Transfer. Transfer really isn't telling the browser to forward to a clear form, it's simply returning a cleared form. That may or may not be what you want.

Response.Redirect() does not a waste round trip. If you post to a script that clears the form by Server.Transfer() and reload you will be asked to repost by most browsers since the last action was a HTTP POST. This may cause your users to unintentionally repeat some action, eg. place a second order which will have to be voided later.

How do I remove duplicate items from an array in Perl?

Method 1: Use a hash

Logic: A hash can have only unique keys, so iterate over array, assign any value to each element of array, keeping element as key of that hash. Return keys of the hash, its your unique array.

my @unique = keys {map {$_ => 1} @array};

Method 2: Extension of method 1 for reusability

Better to make a subroutine if we are supposed to use this functionality multiple times in our code.

sub get_unique {
    my %seen;
    grep !$seen{$_}++, @_;
}
my @unique = get_unique(@array);

Method 3: Use module List::MoreUtils

use List::MoreUtils qw(uniq);
my @unique = uniq(@array);

How to clear input buffer in C?

The lines:

int ch;
while ((ch = getchar()) != '\n' && ch != EOF)
    ;

doesn't read only the characters before the linefeed ('\n'). It reads all the characters in the stream (and discards them) up to and including the next linefeed (or EOF is encountered). For the test to be true, it has to read the linefeed first; so when the loop stops, the linefeed was the last character read, but it has been read.

As for why it reads a linefeed instead of a carriage return, that's because the system has translated the return to a linefeed. When enter is pressed, that signals the end of the line... but the stream contains a line feed instead since that's the normal end-of-line marker for the system. That might be platform dependent.

Also, using fflush() on an input stream doesn't work on all platforms; for example it doesn't generally work on Linux.

Is it possible to start activity through adb shell?

Launch adb shell and enter the command as follows

am start -n yourpackagename/.activityname

Is it possible to use an input value attribute as a CSS selector?

As mentioned before, you need more than a css selector because it doesn't access the stored value of the node, so javascript is definitely needed. Heres another possible solution:

<style>
input:not([value=""]){
border:2px solid red;
}
</style>

<input type="text" onkeyup="this.setAttribute('value', this.value);"/>

I want to vertical-align text in select box

So far this is working fine for me:

line-height: 100%;

Post values from a multiple select

You need to add a name attribute.

Since this is a multiple select, at the HTTP level, the client just sends multiple name/value pairs with the same name, you can observe this yourself if you use a form with method="GET": someurl?something=1&something=2&something=3.

In the case of PHP, Ruby, and some other library/frameworks out there, you would need to add square braces ([]) at the end of the name. The frameworks will parse that string and wil present it in some easy to use format, like an array.

Apart from manually parsing the request there's no language/framework/library-agnostic way of accessing multiple values, because they all have different APIs

For PHP you can use:

<select name="something[]" id="inscompSelected" multiple="multiple" class="lstSelected">

recursion versus iteration

Question :

And if recursion is usually slower what is the technical reason for ever using it over for loop iteration?

Answer :

Because in some algorithms are hard to solve it iteratively. Try to solve depth-first search in both recursively and iteratively. You will get the idea that it is plain hard to solve DFS with iteration.

Another good thing to try out : Try to write Merge sort iteratively. It will take you quite some time.

Question :

Is it correct to say that everywhere recursion is used a for loop could be used?

Answer :

Yes. This thread has a very good answer for this.

Question :

And if it is always possible to convert an recursion into a for loop is there a rule of thumb way to do it?

Answer :

Trust me. Try to write your own version to solve depth-first search iteratively. You will notice that some problems are easier to solve it recursively.

Hint : Recursion is good when you are solving a problem that can be solved by divide and conquer technique.

Fastest way to remove first char in a String

You could profile it, if you really cared. Write a loop of many iterations and see what happens. Chances are, however, that this is not the bottleneck in your application, and TrimStart seems the most semantically correct. Strive to write code readably before optimizing.

How can I change CSS display none or block property using jQuery?

you can do it by button

<button onclick"document.getElementById('elementid').style.display = 'none or block';">

How to obtain a Thread id in Python?

I saw examples of thread IDs like this:

class myThread(threading.Thread):
    def __init__(self, threadID, name, counter):
        self.threadID = threadID
        ...

The threading module docs lists name attribute as well:

...

A thread has a name. 
The name can be passed to the constructor, 
and read or changed through the name attribute.

...

Thread.name

A string used for identification purposes only. 
It has no semantics. Multiple threads may
be given the same name. The initial name is set by the constructor.

No resource found that matches the given name: attr 'android:keyboardNavigationCluster'. when updating to Support Library 26.0.0

I had to change compileSdkVersion = 26 and buildToolsVersion = '26.0.1' in all my dependencies build.gradle files

Efficient way to remove keys with empty strings from a dict

BrenBarn's solution is ideal (and pythonic, I might add). Here is another (fp) solution, however:

from operator import itemgetter
dict(filter(itemgetter(1), metadata.items()))

Get all files and directories in specific path fast

This method is much faster. You can only tel when placing a lot of files in a directory. My A:\ external hard drive contains almost 1 terabit so it makes a big difference when dealing with a lot of files.

static void Main(string[] args)
{
    DirectoryInfo di = new DirectoryInfo("A:\\");
    FullDirList(di, "*");
    Console.WriteLine("Done");
    Console.Read();
}

static List<FileInfo> files = new List<FileInfo>();  // List that will hold the files and subfiles in path
static List<DirectoryInfo> folders = new List<DirectoryInfo>(); // List that hold direcotries that cannot be accessed
static void FullDirList(DirectoryInfo dir, string searchPattern)
{
    // Console.WriteLine("Directory {0}", dir.FullName);
    // list the files
    try
    {
        foreach (FileInfo f in dir.GetFiles(searchPattern))
        {
            //Console.WriteLine("File {0}", f.FullName);
            files.Add(f);                    
        }
    }
    catch
    {
        Console.WriteLine("Directory {0}  \n could not be accessed!!!!", dir.FullName);                
        return;  // We alredy got an error trying to access dir so dont try to access it again
    }

    // process each directory
    // If I have been able to see the files in the directory I should also be able 
    // to look at its directories so I dont think I should place this in a try catch block
    foreach (DirectoryInfo d in dir.GetDirectories())
    {
        folders.Add(d);
        FullDirList(d, searchPattern);                    
    }

}

By the way I got this thanks to your comment Jim Mischel

how to set ASPNETCORE_ENVIRONMENT to be considered for publishing an asp.net core application?

  1. Create your appsettings.*.json files. (Examples: appsettings.Development.json, appsettings.Staging.json, appsettings.Production.json)

  2. Add your variables to those files.

  3. Create a separate publish profile for each environment, like you normally would.

  4. Open PublishProfiles/Development.pubxml (naming will be based on what you named the Publish Profile).

  5. Simply add a tag to the PublishProfile to set the EnvironmentName variable, the appsettings.*.json file naming convention does the rest.

    <PropertyGroup>
      <EnvironmentName>Development</EnvironmentName>
    </PropertyGroup>

Reference: https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/visual-studio-publish-profiles?view=aspnetcore-3.1

Refer to the “Set the Environment” section.

Correlation heatmap

The code below will produce this plot:

enter image description here

import pandas as pd
import seaborn as sns
import matplotlib.pyplot as plt
import numpy as np

# A list with your data slightly edited
l = [1.0,0.00279981,0.95173379,0.02486161,-0.00324926,-0.00432099,
0.00279981,1.0,0.17728303,0.64425774,0.30735071,0.37379443,
0.95173379,0.17728303,1.0,0.27072266,0.02549031,0.03324756,
0.02486161,0.64425774,0.27072266,1.0,0.18336236,0.18913512,
-0.00324926,0.30735071,0.02549031,0.18336236,1.0,0.77678274,
-0.00432099,0.37379443,0.03324756,0.18913512,0.77678274,1.00]

# Split list
n = 6
data = [l[i:i + n] for i in range(0, len(l), n)]

# A dataframe
df = pd.DataFrame(data)

def CorrMtx(df, dropDuplicates = True):

    # Your dataset is already a correlation matrix.
    # If you have a dateset where you need to include the calculation
    # of a correlation matrix, just uncomment the line below:
    # df = df.corr()

    # Exclude duplicate correlations by masking uper right values
    if dropDuplicates:    
        mask = np.zeros_like(df, dtype=np.bool)
        mask[np.triu_indices_from(mask)] = True

    # Set background color / chart style
    sns.set_style(style = 'white')

    # Set up  matplotlib figure
    f, ax = plt.subplots(figsize=(11, 9))

    # Add diverging colormap from red to blue
    cmap = sns.diverging_palette(250, 10, as_cmap=True)

    # Draw correlation plot with or without duplicates
    if dropDuplicates:
        sns.heatmap(df, mask=mask, cmap=cmap, 
                square=True,
                linewidth=.5, cbar_kws={"shrink": .5}, ax=ax)
    else:
        sns.heatmap(df, cmap=cmap, 
                square=True,
                linewidth=.5, cbar_kws={"shrink": .5}, ax=ax)


CorrMtx(df, dropDuplicates = False)

I put this together after it was announced that the outstanding seaborn corrplot was to be deprecated. The snippet above makes a resembling correlation plot based on seaborn heatmap. You can also specify the color range and select whether or not to drop duplicate correlations. Notice that I've used the same numbers as you, but that I've put them in a pandas dataframe. Regarding the choice of colors you can have a look at the documents for sns.diverging_palette. You asked for blue, but that falls out of this particular range of the color scale with your sample data. For both observations of 0.95173379, try changing to -0.95173379 and you'll get this:

enter image description here

javax.net.ssl.SSLHandshakeException: java.security.cert.CertPathValidatorException: Trust anchor for certification path not found

This can happen for several reasons, including:

  1. The CA that issued the server certificate was unknown
  2. The server certificate wasn't signed by a CA, but was self signed
  3. The server configuration is missing an intermediate CA

please check out this link for solution: https://developer.android.com/training/articles/security-ssl.html#CommonProblems

How to force a component's re-rendering in Angular 2?

Rendering happens after change detection. To force change detection, so that component property values that have changed get propagated to the DOM (and then the browser will render those changes in the view), here are some options:

  • ApplicationRef.tick() - similar to Angular 1's $rootScope.$digest() -- i.e., check the full component tree
  • NgZone.run(callback) - similar to $rootScope.$apply(callback) -- i.e., evaluate the callback function inside the Angular 2 zone. I think, but I'm not sure, that this ends up checking the full component tree after executing the callback function.
  • ChangeDetectorRef.detectChanges() - similar to $scope.$digest() -- i.e., check only this component and its children

You will need to import and then inject ApplicationRef, NgZone, or ChangeDetectorRef into your component.

For your particular scenario, I would recommend the last option if only a single component has changed.

Fetch frame count with ffmpeg

In Unix, this works like a charm:

ffmpeg -i 00000.avi -vcodec copy -acodec copy -f null /dev/null 2>&1 \
                                          | grep 'frame=' | cut -f 2 -d ' '

How to use Tomcat 8 in Eclipse?

To add the Tomcat 9.0 (Tomcat build from the trunk) as a server in Eclipse.

Update the ServerInfo.properties file properties as below.

server.info=Apache Tomcat/@VERSION@
server.number=@VERSION_NUMBER@
server.built=@VERSION_BUILT@


server.info=Apache Tomcat/7.0.57
server.number=7.0.57.0
server.built=Nov 3 2014 08:39:16 UTC

Build the tomcat server from trunk and add the server as tomcat7 instance in Eclipse.

ServerInfo.properties file location : \tomcat\java\org\apache\catalina\util\ServerInfo.properties

Post Build exited with code 1

Get process monitor from SysInternals set it up to watch for the Lunaverse.DbVerse (on the Path field) look at the operation result. It should be obvious from there what went wrong

What is the best way to get all the divisors of a number?

My solution via generator function is:

def divisor(num):
    for x in range(1, num + 1):
        if num % x == 0:
            yield x
    while True:
        yield None

Android, How to create option Menu

import android.app.Activity;
import android.os.Bundle;
import android.view.*;
import android.widget.*;

public class AndroidWalkthroughApp2 extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // show menu when menu button is pressed
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.options_menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // display a message when a button was pressed
        String message = "";
        if (item.getItemId() == R.id.option1) {
            message = "You selected option 1!";
        }
        else if (item.getItemId() == R.id.option2) {
            message = "You selected option 2!";
        }
        else {
            message = "Why would you select that!?";
        }

        // show message via toast
        Toast toast = Toast.makeText(this, message, Toast.LENGTH_LONG);
        toast.show();

        return true;
    }
}

Iterating through struct fieldnames in MATLAB

You have to use curly braces ({}) to access fields, since the fieldnames function returns a cell array of strings:

for i = 1:numel(fields)
  teststruct.(fields{i})
end

Using parentheses to access data in your cell array will just return another cell array, which is displayed differently from a character array:

>> fields(1)  % Get the first cell of the cell array

ans = 

    'a'       % This is how the 1-element cell array is displayed

>> fields{1}  % Get the contents of the first cell of the cell array

ans =

a             % This is how the single character is displayed

C#: List All Classes in Assembly

I'd just like to add to Jon's example. To get a reference to your own assembly, you can use:

Assembly myAssembly = Assembly.GetExecutingAssembly();

System.Reflection namespace.

If you want to examine an assembly that you have no reference to, you can use either of these:

Assembly assembly = Assembly.ReflectionOnlyLoad(fullAssemblyName);
Assembly assembly = Assembly.ReflectionOnlyLoadFrom(fileName);

If you intend to instantiate your type once you've found it:

Assembly assembly = Assembly.Load(fullAssemblyName);
Assembly assembly = Assembly.LoadFrom(fileName);

See the Assembly class documentation for more information.

Once you have the reference to the Assembly object, you can use assembly.GetTypes() like Jon already demonstrated.

Get full query string in C# ASP.NET

Request.QueryString returns you a collection of Key/Value pairs representing the Query String. Not a String. Don't think that would cause a Object Reference error though. The reason your getting that is because as Mauro pointed out in the comments. It's QueryString and not Querystring.

Try:

Request.QueryString.ToString();

or

<%                                 
    string URL = Request.Url.AbsoluteUri 
    System.Net.WebClient wc = new System.Net.WebClient();
    string data = wc.DownloadString(URL);
    Response.Output.Write(data);
%>

Same as your code but Request.Url.AbsoluteUri will return the full path, including the query string.

Storing Form Data as a Session Variable

To use session variables, it's necessary to start the session by using the session_start function, this will allow you to store your data in the global variable $_SESSION in a productive way.

so your code will finally look like this :

<strong>Test Form</strong>
<form action="" method"post">
<input type="text" name="picturenum"/>
<input type="submit" name="Submit" value="Submit!" />
</form>

<?php 
 
 // starting the session
 session_start();


 if (isset($_POST['Submit'])) { 
 $_SESSION['picturenum'] = $_POST['picturenum'];
 } 
?> 

<strong><?php echo $_SESSION['picturenum'];?></strong>

to make it easy to use and to avoid forgetting it again, you can create a session_file.php which you will want to be included in all your codes and will start the session for you:

session_start.php

 <?php
   session_start();
 ?> 

and then include it wherever you like :

<strong>Test Form</strong>
<form action="" method"post">
<input type="text" name="picturenum"/>
<input type="submit" name="Submit" value="Submit!" />
</form>

<?php 
 
 // including the session file
 require_once("session_start.php");


 if (isset($_POST['Submit'])) { 
 $_SESSION['picturenum'] = $_POST['picturenum'];
 } 
?> 

that way it is more portable and easy to maintain in the future.

other remarks

  • if you are using Apache version 2 or newer, be careful. instead of
    <?
    to open php's tags, use <?php, otherwise your code will not be interpreted

  • variables names in php are case-sensitive, instead of write $_session, write $_SESSION in capital letters

good work!

Best way to convert string to bytes in Python 3?

It's easier than it is thought:

my_str = "hello world"
my_str_as_bytes = str.encode(my_str)
type(my_str_as_bytes) # ensure it is byte representation
my_decoded_str = my_str_as_bytes.decode()
type(my_decoded_str) # ensure it is string representation

How do I free my port 80 on localhost Windows?

That agony has been solved for me. I found out that what was taking over port 80 is http api service. I wrote in cmd:

net stop http

Asked me "The following services will be stopped, do you want to continue?" Pressed y

It stopped a number of services actually.

Then wrote localhost and wallah, Apache is up and running on port 80.
Hope this helps

Important: Skype uses port 80 by default, you can change this in skype options > advanced > connection - and uncheck "use port 80"

How to exit when back button is pressed?

finish your current_activity using method finish() onBack method of your current_activity

and then add below lines in onDestroy of the current_activity for Removing Force close

@Override
public void onDestroy()
{
    android.os.Process.killProcess(android.os.Process.myPid());
    super.onDestroy();
}

How do I generate a SALT in Java for Salted-Hash?

Inspired from this post and that post, I use this code to generate and verify hashed salted passwords. It only uses JDK provided classes, no external dependency.

The process is:

  • you create a salt with getNextSalt
  • you ask the user his password and use the hash method to generate a salted and hashed password. The method returns a byte[] which you can save as is in a database with the salt
  • to authenticate a user, you ask his password, retrieve the salt and hashed password from the database and use the isExpectedPassword method to check that the details match
/**
 * A utility class to hash passwords and check passwords vs hashed values. It uses a combination of hashing and unique
 * salt. The algorithm used is PBKDF2WithHmacSHA1 which, although not the best for hashing password (vs. bcrypt) is
 * still considered robust and <a href="https://security.stackexchange.com/a/6415/12614"> recommended by NIST </a>.
 * The hashed value has 256 bits.
 */
public class Passwords {

  private static final Random RANDOM = new SecureRandom();
  private static final int ITERATIONS = 10000;
  private static final int KEY_LENGTH = 256;

  /**
   * static utility class
   */
  private Passwords() { }

  /**
   * Returns a random salt to be used to hash a password.
   *
   * @return a 16 bytes random salt
   */
  public static byte[] getNextSalt() {
    byte[] salt = new byte[16];
    RANDOM.nextBytes(salt);
    return salt;
  }

  /**
   * Returns a salted and hashed password using the provided hash.<br>
   * Note - side effect: the password is destroyed (the char[] is filled with zeros)
   *
   * @param password the password to be hashed
   * @param salt     a 16 bytes salt, ideally obtained with the getNextSalt method
   *
   * @return the hashed password with a pinch of salt
   */
  public static byte[] hash(char[] password, byte[] salt) {
    PBEKeySpec spec = new PBEKeySpec(password, salt, ITERATIONS, KEY_LENGTH);
    Arrays.fill(password, Character.MIN_VALUE);
    try {
      SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
      return skf.generateSecret(spec).getEncoded();
    } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
      throw new AssertionError("Error while hashing a password: " + e.getMessage(), e);
    } finally {
      spec.clearPassword();
    }
  }

  /**
   * Returns true if the given password and salt match the hashed value, false otherwise.<br>
   * Note - side effect: the password is destroyed (the char[] is filled with zeros)
   *
   * @param password     the password to check
   * @param salt         the salt used to hash the password
   * @param expectedHash the expected hashed value of the password
   *
   * @return true if the given password and salt match the hashed value, false otherwise
   */
  public static boolean isExpectedPassword(char[] password, byte[] salt, byte[] expectedHash) {
    byte[] pwdHash = hash(password, salt);
    Arrays.fill(password, Character.MIN_VALUE);
    if (pwdHash.length != expectedHash.length) return false;
    for (int i = 0; i < pwdHash.length; i++) {
      if (pwdHash[i] != expectedHash[i]) return false;
    }
    return true;
  }

  /**
   * Generates a random password of a given length, using letters and digits.
   *
   * @param length the length of the password
   *
   * @return a random password
   */
  public static String generateRandomPassword(int length) {
    StringBuilder sb = new StringBuilder(length);
    for (int i = 0; i < length; i++) {
      int c = RANDOM.nextInt(62);
      if (c <= 9) {
        sb.append(String.valueOf(c));
      } else if (c < 36) {
        sb.append((char) ('a' + c - 10));
      } else {
        sb.append((char) ('A' + c - 36));
      }
    }
    return sb.toString();
  }
}

Disable Copy or Paste action for text box?

UPDATE : The accepted answer provides the solution, but .on() is the method that should be use from now on.

"As of jQuery 3.0, .bind() has been deprecated. It was superseded by the .on() method for attaching event handlers to a document since jQuery 1.7, so its use was already discouraged."

http://api.jquery.com/bind/

SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443

Hi everyone I found the solution regarding this github issue and it works for me no longer able to use private ssh key

Try following theses steps:

1 - Use HTTPS if possible. That will avoid SSH keys entirely.
2 - Manually add the SSH key to the running SSH agent. See manually generate ssh key
3 - If the two others doesn't work, delete all your ssh keys and generate some new one thats what I did after weeks of issues.

Hope it will help you..

Efficient SQL test query or validation query that will work across all (or most) databases

Assuming the OP wants a Java answer:

As of JDBC3 / Java 6 there's the isValid() method which should be used rather than inventing one's own method.

The implementer of the driver is required to execute some sort of query against the database when this method id called. You - as a mere JDBC user - do not have to know or understand what this query is. All you have to do is to trust that the creator of the JDBC driver has done his/her work properly.

NoClassDefFoundError on Maven dependency

This is due to Morphia jar not being part of your output war/jar. Eclipse or local build includes them as part of classpath, but remote builds or auto/scheduled build don't consider them part of classpath.

You can include dependent jars using plugin.

Add below snippet into your pom's plugins section

    <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>3.0.0</version>
        <configuration>
            <descriptorRefs>
                <descriptorRef>jar-with-dependencies</descriptorRef>
            </descriptorRefs>
        </configuration>
    </plugin>

How can I find script's directory?

Try sys.path[0].

To quote from the Python docs:

As initialized upon program startup, the first item of this list, path[0], is the directory containing the script that was used to invoke the Python interpreter. If the script directory is not available (e.g. if the interpreter is invoked interactively or if the script is read from standard input), path[0] is the empty string, which directs Python to search modules in the current directory first. Notice that the script directory is inserted before the entries inserted as a result of PYTHONPATH.

Source: https://docs.python.org/library/sys.html#sys.path

import android packages cannot be resolved

try this in eclipse: Window - Preferences - Android - SDK Location and setup SDK path

Smooth scroll without the use of jQuery

edit: this answer has been written in 2013. Please check Cristian Traìna's comment below about requestAnimationFrame

I made it. The code below doesn't depend on any framework.

Limitation : The anchor active is not written in the url.

Version of the code : 1.0 | Github : https://github.com/Yappli/smooth-scroll

(function() // Code in a function to create an isolate scope
{
var speed = 500;
var moving_frequency = 15; // Affects performance !
var links = document.getElementsByTagName('a');
var href;
for(var i=0; i<links.length; i++)
{   
    href = (links[i].attributes.href === undefined) ? null : links[i].attributes.href.nodeValue.toString();
    if(href !== null && href.length > 1 && href.substr(0, 1) == '#')
    {
        links[i].onclick = function()
        {
            var element;
            var href = this.attributes.href.nodeValue.toString();
            if(element = document.getElementById(href.substr(1)))
            {
                var hop_count = speed/moving_frequency
                var getScrollTopDocumentAtBegin = getScrollTopDocument();
                var gap = (getScrollTopElement(element) - getScrollTopDocumentAtBegin) / hop_count;

                for(var i = 1; i <= hop_count; i++)
                {
                    (function()
                    {
                        var hop_top_position = gap*i;
                        setTimeout(function(){  window.scrollTo(0, hop_top_position + getScrollTopDocumentAtBegin); }, moving_frequency*i);
                    })();
                }
            }

            return false;
        };
    }
}

var getScrollTopElement =  function (e)
{
    var top = 0;

    while (e.offsetParent != undefined && e.offsetParent != null)
    {
        top += e.offsetTop + (e.clientTop != null ? e.clientTop : 0);
        e = e.offsetParent;
    }

    return top;
};

var getScrollTopDocument = function()
{
    return document.documentElement.scrollTop + document.body.scrollTop;
};
})();

Permission denied (publickey) when deploying heroku code. fatal: The remote end hung up unexpectedly

At first make sure hidden files are visible in your Mac. If not do:

  • Open terminal and type in defaults write com.apple.Finder AppleShowAllFiles TRUE
  • killall Finder

Next steps:

  • Going to Users/user_name/.ssh/ removed all the files.
  • Opening terminal type in ssh-keygen -t dsa
  • Then heroku keys:add ~/.ssh/id_dsa.pub

N.B. I did it in Mac OSX 10.7.2 Lion. Though the procedure should be same in others too.

Add back button to action bar

You'll need to check menuItem.getItemId() against android.R.id.home in the onOptionsItemSelected method

Duplicate of Android Sherlock ActionBar Up button

Check whether a value is a number in JavaScript or jQuery

there is a function called isNaN it return true if it's (Not-a-number) , so u can check for a number this way

if(!isNaN(miscCharge))
{
   //do some thing if it's a number
}else{
   //do some thing if it's NOT a number
}

hope it works

ERROR: Cannot open source file " "

This was the top result when googling "cannot open source file" so I figured I would share what my issue was since I had already included the correct path.

I'm not sure about other IDEs or compilers, but least for Visual Studio, make sure there isn't a space in your list of include directories. I had put a space between the ; of the last entry and the beginning of my new entry which then caused Visual Studio to disregard my inclusion.

Check if instance is of a type

Try the following

if (c is TForm) { 
 ...
}

jQuery select2 get value of select tag?

To get Select element you can use $('#first').val();

To get the text of selected value - $('#first :selected').text();

Can you please post your select2() function code

How to specify multiple return types using type-hints

The statement def foo(client_id: str) -> list or bool: when evaluated is equivalent to def foo(client_id: str) -> list: and will therefore not do what you want.

The native way to describe a "either A or B" type hint is Union (thanks to Bhargav Rao):

def foo(client_id: str) -> Union[list, bool]:

I do not want to be the "Why do you want to do this anyway" guy, but maybe having 2 return types isn't what you want:

If you want to return a bool to indicate some type of special error-case, consider using Exceptions instead. If you want to return a bool as some special value, maybe an empty list would be a good representation. You can also indicate that None could be returned with Optional[list]