How to center the elements in ConstraintLayout

just add

android:gravity="center"

and done :)

Job for mysqld.service failed See "systemctl status mysqld.service"

remove any command of "secure_file_priv" in /etc/mysql/my.cnf and restart mysql. If you want to use a file in mysql, copy those files to the main folder. The main folder is obtained this way : SHOW VARIABLES LIKE "secure_file_priv";

Importing a csv into mysql via command line

Most answers missing an important point like if you have created csv file exported from Microsoft Excel on windows and importing the same in linux environment, you will get unexpected result.

the correct syntax would be

load data local infile 'file.csv' into table table fields terminated by ',' enclosed by '"' lines terminated by '\r\n'

here the difference is '\r\n' as against simply '\n

How can I position my div at the bottom of its container?

Don't wanna use "position:absolute" for sticky footer at bottom. Then you can do this way:

_x000D_

 html,_x000D_
        body {_x000D_
            height: 100%;_x000D_
            margin: 0;_x000D_
        }_x000D_
        .wrapper {_x000D_
            min-height: 100%;_x000D_
            /* Equal to height of footer */_x000D_
            /* But also accounting for potential margin-bottom of last child */_x000D_
            margin-bottom: -50px;_x000D_
        }_x000D_
        .footer{_x000D_
            background: #000;_x000D_
            text-align: center;_x000D_
            color: #fff;_x000D_
        }_x000D_
        .footer,_x000D_
        .push {_x000D_
            height: 50px;_x000D_
        }

_x000D_

<html>_x000D_
<body>_x000D_
    <!--HTML Code-->_x000D_
    <div class="wrapper">_x000D_
        <div class="content">content</div>_x000D_
        <div class="push"></div>_x000D_
    </div>_x000D_
    <footer class="footer">test</footer>_x000D_
</body>_x000D_
</html>

_x000D_

import dat file into R

The dat file has some lines of extra information before the actual data. Skip them with the skip argument:

read.table("http://www.nilu.no/projects/ccc/onlinedata/ozone/CZ03_2009.dat", 
           header=TRUE, skip=3)

An easy way to check this if you are unfamiliar with the dataset is to first use readLines to check a few lines, as below:

readLines("http://www.nilu.no/projects/ccc/onlinedata/ozone/CZ03_2009.dat", 
          n=10)
# [1] "Ozone data from CZ03 2009"   "Local time: GMT + 0"        
# [3] ""                            "Date        Hour      Value"
# [5] "01.01.2009 00:00       34.3" "01.01.2009 01:00       31.9"
# [7] "01.01.2009 02:00       29.9" "01.01.2009 03:00       28.5"
# [9] "01.01.2009 04:00       32.9" "01.01.2009 05:00       20.5"

Here, we can see that the actual data starts at [4], so we know to skip the first three lines.

Update

If you really only wanted the Value column, you could do that by:

as.vector(
    read.table("http://www.nilu.no/projects/ccc/onlinedata/ozone/CZ03_2009.dat",
               header=TRUE, skip=3)$Value)

Again, readLines is useful for helping us figure out the actual name of the columns we will be importing.

But I don't see much advantage to doing that over reading the whole dataset in and extracting later.

Make selected block of text uppercase

I think you can use Step 1: Select text Step 2: Ctrl + Shift + P Step 3: Enter Uppercae

Laravel 5.2 - pluck() method returns array

laravel pluck returns an array

if your query is:

 $name = DB::table('users')->where('name', 'John')->pluck('name');

then the array is like this (key is the index of the item. auto incremented value):

[
    1 => "name1",
    2 => "name2",
    .
    .
    .
    100 => "name100"
]

but if you do like this:

$name = DB::table('users')->where('name', 'John')->pluck('name','id');

then the key is actual index in the database.

key||value
[
    1 => "name1",
    2 => "name2",
    .
    .
    .
    100 => "name100"
]

you can set any value as key.

Time calculation in php (add 10 hours)?

You can simply make use of the `DateTime` class , OOP Style.

<?php
$date = new DateTime('1:00:00');
$date->add(new DateInterval('PT10H'));
echo $date->format('H:i:s a'); //"prints" 11:00:00 a.m

convert base64 to image in javascript/jquery

Have to add this based on @Joseph's answer. If someone want to create image object:

var image = new Image();
image.onload = function(){
   console.log(image.width); // image is loaded and we have image width 
}
image.src = 'data:image/png;base64,iVBORw0K...';
document.body.appendChild(image);

How do I make the return type of a method generic?

 private static T[] prepareArray<T>(T[] arrayToCopy, T value)
    {
        Array.Copy(arrayToCopy, 1, arrayToCopy, 0, arrayToCopy.Length - 1);
        arrayToCopy[arrayToCopy.Length - 1] = value;
        return (T[])arrayToCopy;
    }

I was performing this throughout my code and wanted a way to put it into a method. I wanted to share this here because I didn't have to use the Convert.ChangeType for my return value. This may not be a best practice but it worked for me. This method takes in an array of generic type and a value to add to the end of the array. The array is then copied with the first value stripped and the value taken into the method is added to the end of the array. The last thing is that I return the generic array.

When should I use "this" in a class?

With respect to William Brendel's posts and dbconfessions question, regarding case 2. Here is an example:

public class Window {

  private Window parent;

  public Window (Window parent) {
    this.parent = parent;
  }

  public void addSubWindow() {
    Window child = new Window(this);
    list.add(child);
  }

  public void printInfo() {
    if (parent == null) {
      System.out.println("root");
    } else {
      System.out.println("child");
    }
  }

}

I've seen this used, when building parent-child relation's with objects. However, please note that it is simplified for the sake of brevity.

Which is the default location for keystore/truststore of Java applications?

Like bruno said, you're better configuring it yourself. Here's how I do it. Start by creating a properties file (/etc/myapp/config.properties).

javax.net.ssl.keyStore = /etc/myapp/keyStore
javax.net.ssl.keyStorePassword = 123456

Then load the properties to your environment from your code. This makes your application configurable.

FileInputStream propFile = new FileInputStream("/etc/myapp/config.properties");
Properties p = new Properties(System.getProperties());
p.load(propFile);
System.setProperties(p);

Insert value into a string at a certain position?

var sb = new StringBuilder();
sb.Append(beforeText);
sb.Insert(2, insertText);
afterText = sb.ToString();

SQL use CASE statement in WHERE IN clause

No you can't use case and in like this. But you can do

SELECT * FROM Product P    
WHERE @Status='published' and P.Status IN (1,3)
or @Status='standby' and P.Status IN  (2,5,9,6)
or @Status='deleted' and P.Status IN (4,5,8,10)
or P.Status IN (1,3)

BTW you can reduce that to

SELECT * FROM Product P    
WHERE @Status='standby' and P.Status IN (2,5,9,6)
or @Status='deleted' and P.Status IN (4,5,8,10)
or P.Status IN (1,3)

since or P.Status IN (1,3) gives you also all records of @Status='published' and P.Status IN (1,3)

How to dynamically update labels captions in VBA form?

Use Controls object

For i = 1 To X
    Controls("Label" & i).Caption =  MySheet.Cells(i + 1, i).Value
Next

How do I change the database name using MySQL?

Try:

RENAME database1 TO database2;

Using Jasmine to spy on a function without an object

If you are defining your function:

function test() {};

Then, this is equivalent to:

window.test = function() {}  /* (in the browser) */

So spyOn(window, 'test') should work.

If that is not, you should also be able to:

test = jasmine.createSpy();

If none of those are working, something else is going on with your setup.

I don't think your fakeElement technique works because of what is going on behind the scenes. The original globalMethod still points to the same code. What spying does is proxy it, but only in the context of an object. If you can get your test code to call through the fakeElement it would work, but then you'd be able to give up global fns.

Java way to check if a string is palindrome

Here is a simple one"

public class Palindrome {

    public static void main(String [] args){
        Palindrome pn = new Palindrome();

        if(pn.isPalindrome("ABBA")){
            System.out.println("Palindrome");
        } else {
            System.out.println("Not Palindrome");
        }   
    }

    public boolean isPalindrome(String original){
        int i = original.length()-1;
        int j=0;
        while(i > j) {
            if(original.charAt(i) != original.charAt(j)) {
                return false;
            }
            i--;
            j++;
        }
        return true;
    }
}

Comparing two columns, and returning a specific adjacent cell in Excel

In cell D2 and copied down:

=IF(COUNTIF($A$2:$A$5,C2)=0,"",VLOOKUP(C2,$A$2:$B$5,2,FALSE))

Are static methods inherited in Java?

Many have voiced out their answer in words. This is an extended explanation in codes:

public class A {
    public static void test() {
        System.out.println("A");
    }
    public static void test2() {
        System.out.println("Test");
    }
}

public class B extends A {
    public static void test() {
        System.out.println("B");
    }
}

// Called statically
A.test();
B.test();
System.out.println();

// Called statically, testing static inheritance
A.test2();
B.test2();
System.out.println();

// Called via instance object
A a = new A();
B b = new B();
a.test();
b.test();
System.out.println();

// Testing inheritance via instance call
a.test2();
b.test2();
System.out.println();

// Testing whether calling static method via instance object is dependent on compile or runtime type
((A) b).hi();
System.out.println();

// Testing whether null instance works
A nullObj = null;
nullObj.hi();

Results:

A
B

Test
Test

A
B

Test
Test

A

A

Therefore, this is the conclusion:

When we call the static in a static manner via ., it will look for the static defined in that class, or the class nearest to that in the inheritance chain. This proves that static methods are inherited.
When static method is called from an instance, it calls the static method defined in the compile-time type.
Static method can be called from a null instance. My guess is that the compiler will use the variable type to find the class during compilation, and translate that to the appropriate static method call.

how to set length of an column in hibernate with maximum length

You can use Length annotation for a column. By using it you can maximize or minimize column length. Length annotation only be used for Strings.

@Column(name = "NAME", nullable = false, length = 50)  
@Length(max = 50)
public String getName() {
    return this.name;
}

Time complexity of Euclid's Algorithm

Here's intuitive understanding of runtime complexity of Euclid's algorithm. The formal proofs are covered in various texts such as Introduction to Algorithms and TAOCP Vol 2.

First think about what if we tried to take gcd of two Fibonacci numbers F(k+1) and F(k). You might quickly observe that Euclid's algorithm iterates on to F(k) and F(k-1). That is, with each iteration we move down one number in Fibonacci series. As Fibonacci numbers are O(Phi ^ k) where Phi is golden ratio, we can see that runtime of GCD was O(log n) where n=max(a, b) and log has base of Phi. Next, we can prove that this would be the worst case by observing that Fibonacci numbers consistently produces pairs where the remainders remains large enough in each iteration and never become zero until you have arrived at the start of the series.

We can make O(log n) where n=max(a, b) bound even more tighter. Assume that b >= a so we can write bound at O(log b). First, observe that GCD(ka, kb) = GCD(a, b). As biggest values of k is gcd(a,c), we can replace b with b/gcd(a,b) in our runtime leading to more tighter bound of O(log b/gcd(a,b)).

Can I style an image's ALT text with CSS?

In Firefox and Chrome (and possibly more) we can insert the string ‘( .... )’ into the alt text of an image that hasn’t loaded.

_x000D_

img {_x000D_
  font-style: italic;_x000D_
  color: #c00;_x000D_
}_x000D_
_x000D_
img:after {_x000D_
  content: " (Image - Right click to reload if not loaded)";_x000D_
}_x000D_
_x000D_
img::after {_x000D_
  content: " (Image - Right click to reload if not loaded)";_x000D_
}

_x000D_

<img alt="Alt text - " />

_x000D_

css background image in a different folder from css

Since you are providing a relative pathway to the image, the image location is looked for from the location in which you have the css file. So if you have the image in a different location to the css file you could either try giving the absolute URL(pathway starting from the root folder) or give the relative file location path. In your case since img and css are in the folder assets to move from location of css file to the img file, you can use '..' operator to refer that the browser has to move 1 folder back and then follow the pathway you have after the '..' operator. This is basically how relative pathway works and you can use it to access resoures in different folders. Hope it helps.

How to use LDFLAGS in makefile

In more complicated build scenarios, it is common to break compilation into stages, with compilation and assembly happening first (output to object files), and linking object files into a final executable or library afterward--this prevents having to recompile all object files when their source files haven't changed. That's why including the linking flag -lm isn't working when you put it in CFLAGS (CFLAGS is used in the compilation stage).

The convention for libraries to be linked is to place them in either LOADLIBES or LDLIBS (GNU make includes both, but your mileage may vary):

LDLIBS=-lm

This should allow you to continue using the built-in rules rather than having to write your own linking rule. For other makes, there should be a flag to output built-in rules (for GNU make, this is -p). If your version of make does not have a built-in rule for linking (or if it does not have a placeholder for -l directives), you'll need to write your own:

client.o: client.c
    $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -o $@ $<

client: client.o
    $(CC) $(LDFLAGS) $(TARGET_ARCH) $^ $(LOADLIBES) $(LDLIBS) -o $@

How to list npm user-installed packages?

Use npm list and filter by contains using grep

Example:

npm list -g | grep name-of-package

Android - SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length

In my case, the EditText fields with inputType as text / textCapCharacters were casing this error. I noticed this in my logcat whenever I used backspace to completely remove the text typed in any of these fields.

The solution which worked for me was to change the inputType of those fields to textNoSuggestions as this was the most suited type and didn't give me any unwanted errors anymore.

How to embed a YouTube channel into a webpage

Seems like the accepted answer does not work anymore. I found the correct method from another post: https://stackoverflow.com/a/46811403/6368026

Now you should use:

http://www.youtube.com/embed/videoseries?list=USERID And the USERID is your youtube user id with 'UU' appended.

For example, if your user id is TlQ5niAIDsLdEHpQKQsupg then you should put UUTlQ5niAIDsLdEHpQKQsupg. If you only have the channel id (which you can find in your channel URL) then just replace the first two characters (UC) with UU.

So in the end you would have an URL like this:

http://www.youtube.com/embed/videoseries?list=UUTlQ5niAIDsLdEHpQKQsupg

Oracle PL/SQL - How to create a simple array variable?

Another solution is to use an Oracle Collection as a Hashmap:

declare 
-- create a type for your "Array" - it can be of any kind, record might be useful
  type hash_map is table of varchar2(1000) index by varchar2(30);
  my_hmap hash_map ;
-- i will be your iterator: it must be of the index's type
  i varchar2(30);
begin
  my_hmap('a') := 'apple';
  my_hmap('b') := 'box';
  my_hmap('c') := 'crow';
-- then how you use it:

  dbms_output.put_line (my_hmap('c')) ;

-- or to loop on every element - it's a "collection"
  i := my_hmap.FIRST;

  while (i is not null)  loop     
    dbms_output.put_line(my_hmap(i));      
    i := my_hmap.NEXT(i);
  end loop;

end;

Python base64 data decode

Python 3 (and 2)

import base64
a = 'eW91ciB0ZXh0'
base64.b64decode(a)

Python 2

A quick way to decode it without importing anything:

'eW91ciB0ZXh0'.decode('base64')

or more descriptive

>>> a = 'eW91ciB0ZXh0'
>>> a.decode('base64')
'your text'

How do I get ASP.NET Web API to return JSON instead of XML using Chrome?

In the Global.asax I am using the code below. My URI to get JSON is http://www.digantakumar.com/api/values?json=true

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();

    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);

    GlobalConfiguration.Configuration.Formatters.JsonFormatter.MediaTypeMappings.Add(new  QueryStringMapping("json", "true", "application/json"));
}

Setting size for icon in CSS

you can change the size of an icon using the font size rather than setting the height and width of an icon. Here is how you do it:

<i class="fa fa-minus-square-o" style="font-size: 0.73em;"></i>

There are 4 ways to specify the dimensions of the icon.

px : give fixed pixels to your icon

em : dimensions with respect to your current font. Say ur current font is 12px then 1.5em will be 18px (12px + 6px).

pt : stands for points. Mostly used in print media

% : percentage. Refers to the size of the icon based on its original size.

SQL Server command line backup statement

You can use sqlcmd to run a backup, or any other T-SQL script. You can find the detailed instructions and examples on various useful sqlcmd switches in this article: Working with the SQL Server command line (sqlcmd)

How to create an Array with AngularJS's ng-model

First thing is first. You need to define $scope.telephone as an array in your controller before you can start using it in your view.

$scope.telephone = [];

To address the issue of ng-model not being recognised when you append a new input - for that to work you have to use the $compile Angular service.

From the Angular.js API reference on $compile:

Compiles an HTML string or DOM into a template and produces a template function, which can then be used to link scope and the template together.

// I'm using Angular syntax. Using jQuery will have the same effect
// Create input element
var input = angular.element('<div><input type="text" ng-model="telephone[' + $scope.inputCounter + ']"></div>');
// Compile the HTML and assign to scope
var compile = $compile(input)($scope);

Have a look on JSFiddle

JS. How to replace html element with another element/text, represented in string?

As the Jquery replaceWith() code was too bulky, tricky and complicated, here's my own solution. =)

The best way is to use outerHTML property, but it is not crossbrowsered yet, so I did some trick, weird enough, but simple.

Here is the code

var str = '<a href="http://www.com">item to replace</a>'; //it can be anything
var Obj = document.getElementById('TargetObject'); //any element to be fully replaced
if(Obj.outerHTML) { //if outerHTML is supported
    Obj.outerHTML=str; ///it's simple replacement of whole element with contents of str var
}
else { //if outerHTML is not supported, there is a weird but crossbrowsered trick
    var tmpObj=document.createElement("div");
    tmpObj.innerHTML='<!--THIS DATA SHOULD BE REPLACED-->';
    ObjParent=Obj.parentNode; //Okey, element should be parented
    ObjParent.replaceChild(tmpObj,Obj); //here we placing our temporary data instead of our target, so we can find it then and replace it into whatever we want to replace to
    ObjParent.innerHTML=ObjParent.innerHTML.replace('<div><!--THIS DATA SHOULD BE REPLACED--></div>',str);
}

That's all

What is the difference between visibility:hidden and display:none?

visibility:hidden will keep the element in the page and occupies that space but does not show to the user.

display:none will not be available in the page and does not occupy any space.

How to get the current date/time in Java

I'll go ahead and throw this answer in because it is all I needed when I had the same question:

Date currentDate = new Date(System.currentTimeMillis());

currentDate is now your current date in a Java Date object.

How to allow http content within an iframe on a https site

Note: While this solution may have worked in some browsers when it was written in 2014, it no longer works. Navigating or redirecting to an HTTP URL in an iframe embedded in an HTTPS page is not permitted by modern browsers, even if the frame started out with an HTTPS URL.

The best solution I created is to simply use google as the ssl proxy...

https://www.google.com/search?q=%http://yourhttpsite.com&btnI=Im+Feeling+Lucky

Tested and works in firefox.

Other Methods:

Use a Third party such as embed.ly (but it it really only good for well known http APIs).
Create your own redirect script on an https page you control (a simple javascript redirect on a relative linked page should do the trick. Something like: (you can use any langauge/method)

https://example.com That has a iframe linking to...

https://example.com/utilities/redirect.html Which has a simple js redirect script like...

document.location.href ="http://thenonsslsite.com";
Alternatively, you could add an RSS feed or write some reader/parser to read the http site and display it within your https site.
You could/should also recommend to the http site owner that they create an ssl connection. If for no other reason than it increases seo.

Unless you can get the http site owner to create an ssl certificate, the most secure and permanent solution would be to create an RSS feed grabing the content you need (presumably you are not actually 'doing' anything on the http site -that is to say not logging in to any system).

The real issue is that having http elements inside a https site represents a security issue. There are no completely kosher ways around this security risk so the above are just current work arounds.

Note, that you can disable this security measure in most browsers (yourself, not for others). Also note that these 'hacks' may become obsolete over time.

How to convert char* to wchar_t*?

You're returning the address of a local variable allocated on the stack. When your function returns, the storage for all local variables (such as wc) is deallocated and is subject to being immediately overwritten by something else.

To fix this, you can pass the size of the buffer to GetWC, but then you've got pretty much the same interface as mbstowcs itself. Or, you could allocate a new buffer inside GetWC and return a pointer to that, leaving it up to the caller to deallocate the buffer.

Including external jar-files in a new jar-file build with Ant

You can use a bit of functionality that is already built in to the ant jar task.

If you go to The documentation for the ant jar task and scroll down to the "merging archives" section there's a snippet for including the all the *.class files from all the jars in you "lib/main" directory:

<jar destfile="build/main/checksites.jar">
    <fileset dir="build/main/classes"/>
    <restrict>
        <name name="**/*.class"/>
        <archives>
            <zips>
                <fileset dir="lib/main" includes="**/*.jar"/>
            </zips>
        </archives>
    </restrict>
    <manifest>
      <attribute name="Main-Class" value="com.acme.checksites.Main"/>
    </manifest>
</jar>

This Creates an executable jar file with a main class "com.acme.checksites.Main", and embeds all the classes from all the jars in lib/main.

It won't do anything clever in case of namespace conflicts, duplicates and things like that. Also, it will include all class files, also the ones that you don't use, so the combined jar file will be full size.

If you need more advanced things like that, take a look at like one-jar and jar jar links

How to spawn a process and capture its STDOUT in .NET?

Here's code that I've verified to work. I use it for spawning MSBuild and listening to its output:

process.StartInfo.UseShellExecute = false;
process.StartInfo.RedirectStandardOutput = true;
process.OutputDataReceived += (sender, args) => Console.WriteLine("received output: {0}", args.Data);
process.Start();
process.BeginOutputReadLine();

Serialize an object to XML

public string ObjectToXML(object input)
{
    try
    {
        var stringwriter = new System.IO.StringWriter();
        var serializer = new XmlSerializer(input.GetType());
        serializer.Serialize(stringwriter, input);
        return stringwriter.ToString();
    }
    catch (Exception ex)
    {
        if (ex.InnerException != null)
            ex = ex.InnerException;

        return "Could not convert: " + ex.Message;
    }
}

//Usage
var res = ObjectToXML(obj)

You need to use following classes:

using System.IO;
using System.Xml;
using System.Xml.Serialization;

Data truncation: Data too long for column 'logo' at row 1

Use data type LONGBLOB instead of BLOB in your database table.

Understanding ibeacon distancing

The iBeacon output power is measured (calibrated) at a distance of 1 meter. Let's suppose that this is -59 dBm (just an example). The iBeacon will include this number as part of its LE advertisment.

The listening device (iPhone, etc), will measure the RSSI of the device. Let's suppose, for example, that this is, say, -72 dBm.

Since these numbers are in dBm, the ratio of the power is actually the difference in dB. So:

ratio_dB = txCalibratedPower - RSSI

To convert that into a linear ratio, we use the standard formula for dB:

ratio_linear = 10 ^ (ratio_dB / 10)

If we assume conservation of energy, then the signal strength must fall off as 1/r^2. So:

power = power_at_1_meter / r^2. Solving for r, we get:

r = sqrt(ratio_linear)

In Javascript, the code would look like this:

function getRange(txCalibratedPower, rssi) {
    var ratio_db = txCalibratedPower - rssi;
    var ratio_linear = Math.pow(10, ratio_db / 10);

    var r = Math.sqrt(ratio_linear);
    return r;
}

Note, that, if you're inside a steel building, then perhaps there will be internal reflections that make the signal decay slower than 1/r^2. If the signal passes through a human body (water) then the signal will be attenuated. It's very likely that the antenna doesn't have equal gain in all directions. Metal objects in the room may create strange interference patterns. Etc, etc... YMMV.

What does operator "dot" (.) mean?

The dot itself is not an operator, .^ is.

The .^ is a pointwise¹ (i.e. element-wise) power, as .* is the pointwise product.

.^ Array power. A.^B is the matrix with elements A(i,j) to the B(i,j) power. The sizes of A and B must be the same or be compatible.

C.f.

"Array vs. Matrix Operations": https://mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html
"Pointwise": http://en.wikipedia.org/wiki/Pointwise
"Element-Wise Operations": http://www.glue.umd.edu/afs/glue.umd.edu/system/info/olh/Numerical/Matlab_Matrix_Manipulation_Software/Matrix_Vector_Operations/elementwise

¹) Hence the dot.

System.BadImageFormatException: Could not load file or assembly

It seems that you are using the 64-bit version of the tool to install a 32-bit/x86 architecture application. Look for the 32-bit version of the tool here:

C:\Windows\Microsoft.NET\Framework\v4.0.30319

and it should install your 32-bit application just fine.

How do I export (and then import) a Subversion repository?

Assuming you have the necessary privileges to run svnadmin, you need to use the dump and load commands.

OS X: equivalent of Linux's wget

You could use curl instead. It is installed by default into /usr/bin.

How can I clone an SQL Server database on the same server in SQL Server 2008 Express?

This is the script I use. A bit tricky but it works. Tested on SQL Server 2012.

DECLARE @backupPath nvarchar(400);
DECLARE @sourceDb nvarchar(50);
DECLARE @sourceDb_log nvarchar(50);
DECLARE @destDb nvarchar(50);
DECLARE @destMdf nvarchar(100);
DECLARE @destLdf nvarchar(100);
DECLARE @sqlServerDbFolder nvarchar(100);

SET @sourceDb = 'db1'
SET @sourceDb_log = @sourceDb + '_log'
SET @backupPath = 'E:\tmp\' + sourceDb + '.bak' --ATTENTION: file must already exist and SQL Server must have access to it
SET @sqlServerDbFolder = 'E:\DB SQL\MSSQL11.MSSQLSERVER\MSSQL\DATA\'
SET @destDb = 'db2'
SET @destMdf = @sqlServerDbFolder + @destDb + '.mdf'
SET @destLdf = @sqlServerDbFolder + @destDb + '_log' + '.ldf'

BACKUP DATABASE @sourceDb TO DISK = @backupPath

RESTORE DATABASE @destDb FROM DISK = @backupPath
WITH REPLACE,
   MOVE @sourceDb     TO @destMdf,
   MOVE @sourceDb_log TO @destLdf

How do I call a dynamically-named method in Javascript?

Here is a working and simple solution for checking existence of a function and triaging that function dynamically by another function;

Trigger function

function runDynmicFunction(functionname){ 

    if (typeof window[functionname] == "function"  ) { //check availability

        window[functionname]("this is from the function it "); //run function and pass a parameter to it
    }
}

and you can now generate the function dynamically maybe using php like this

function runThis_func(my_Parameter){

    alert(my_Parameter +" triggerd");
}

now you can call the function using dynamically generated event

<?php

$name_frm_somware ="runThis_func";

echo "<input type='button' value='Button' onclick='runDynmicFunction(\"".$name_frm_somware."\");'>";

?>

the exact HTML code you need is

<input type="button" value="Button" onclick="runDynmicFunction('runThis_func');">

What is the most appropriate way to store user settings in Android application

shared preferences is easiest way to store our application data. but it is possible that anyone can clear our shared preferences data through application manager.so i don't think it is completely safe for our application.

How to split a comma-separated value to columns

Try this:

declare @csv varchar(100) ='aaa,bb,csda,daass';
set @csv = @csv+',';

with cte as
(
    select SUBSTRING(@csv,1,charindex(',',@csv,1)-1) as val, SUBSTRING(@csv,charindex(',',@csv,1)+1,len(@csv)) as rem 
    UNION ALL
    select SUBSTRING(a.rem,1,charindex(',',a.rem,1)-1)as val, SUBSTRING(a.rem,charindex(',',a.rem,1)+1,len(A.rem)) 
    from cte a where LEN(a.rem)>=1
    ) select val from cte

What is difference between cacerts and keystore?

Check your JAVA_HOME path. As systems looks for a java.policy file which is located in JAVA_HOME/jre/lib/security. Your JAVA_HOME should always be ../JAVA/JDK.

Multiple WHERE Clauses with LINQ extension methods

If you working with in-memory data (read "collections of POCO") you may also stack your expressions together using PredicateBuilder like so:

// initial "false" condition just to start "OR" clause with
var predicate = PredicateBuilder.False<YourDataClass>();

if (condition1)
{
    predicate = predicate.Or(d => d.SomeStringProperty == "Tom");
}

if (condition2)
{
    predicate = predicate.Or(d => d.SomeStringProperty == "Alex");
}

if (condition3)
{
    predicate = predicate.And(d => d.SomeIntProperty >= 4);
}

return originalCollection.Where<YourDataClass>(predicate.Compile());

The full source of mentioned PredicateBuilder is bellow (but you could also check the original page with a few more examples):

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;

public static class PredicateBuilder
{
  public static Expression<Func<T, bool>> True<T> ()  { return f => true;  }
  public static Expression<Func<T, bool>> False<T> () { return f => false; }

  public static Expression<Func<T, bool>> Or<T> (this Expression<Func<T, bool>> expr1,
                                                      Expression<Func<T, bool>> expr2)
  {
    var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
    return Expression.Lambda<Func<T, bool>>
          (Expression.OrElse (expr1.Body, invokedExpr), expr1.Parameters);
  }

  public static Expression<Func<T, bool>> And<T> (this Expression<Func<T, bool>> expr1,
                                                       Expression<Func<T, bool>> expr2)
  {
    var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
    return Expression.Lambda<Func<T, bool>>
          (Expression.AndAlso (expr1.Body, invokedExpr), expr1.Parameters);
  }
}

Note: I've tested this approach with Portable Class Library project and have to use .Compile() to make it work:

Where(predicate .Compile() );

How can I reorder my divs using only CSS?

Little late to the party, but you can also do this:

<div style="height: 500px; width: 500px;">

<div class="bottom" style="height: 250px; width: 500px; background: red; margin-top: 250px;"></div>

<div class="top" style="height: 250px; width: 500px; background: blue; margin-top: -500px;"></div>

Java Hashmap: How to get key from value?

import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;

public class ValueKeysMap<K, V> extends HashMap <K,V>{
    HashMap<V, Set<K>> ValueKeysMap = new HashMap<V, Set<K>>();

    @Override
    public boolean containsValue(Object value) {
        return ValueKeysMap.containsKey(value);
    }

    @Override
    public V put(K key, V value) {
        if (containsValue(value)) {
            Set<K> keys = ValueKeysMap.get(value);
            keys.add(key);
        } else {
            Set<K> keys = new HashSet<K>();
            keys.add(key);
            ValueKeysMap.put(value, keys);
        }
        return super.put(key, value);
    }

    @Override
    public V remove(Object key) {
        V value = super.remove(key);
        Set<K> keys = ValueKeysMap.get(value);
        keys.remove(key);
        if(keys.size() == 0) {
           ValueKeysMap.remove(value);
        }
        return value;
    }

    public Set<K> getKeys4ThisValue(V value){
        Set<K> keys = ValueKeysMap.get(value);
        return keys;
    }

    public boolean valueContainsThisKey(K key, V value){
        if (containsValue(value)) {
            Set<K> keys = ValueKeysMap.get(value);
            return keys.contains(key);
        }
        return false;
    }

    /*
     * Take care of argument constructor and other api's like putAll
     */
}

How can I make a float top with CSS?

This works for me:

margin-bottom: auto;

"Cross origin requests are only supported for HTTP." error when loading a local file

In an Android app — for example, to allow JavaScript to have access to assets via file:///android_asset/ — use setAllowFileAccessFromFileURLs(true) on the WebSettings that you get from calling getSettings() on the WebView.

How to get full REST request body using Jersey?

Turns out you don't have to do much at all.

See below - the parameter x will contain the full HTTP body (which is XML in our case).

@POST
public Response go(String x) throws IOException {
    ...
}

File upload along with other object in Jersey restful web service

I used file upload example from,

http://www.mkyong.com/webservices/jax-rs/file-upload-example-in-jersey/

in my resource class i have below method

@POST
    @Path("/upload")
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    public Response  attachupload(@FormDataParam("file") byte[] is,
@FormDataParam("file") FormDataContentDisposition fileDetail,
@FormDataParam("fileName") String flename){
attachService.saveAttachment(flename,is);
}

in my attachService.java i have below method

 public void saveAttachment(String flename,  byte[] is) {
            // TODO Auto-generated method stub
         attachmentDao.saveAttachment(flename,is);

        }

in Dao i have

attach.setData(is);
attach.setFileName(flename);

in my HBM mapping is like

<property name="data" type="binary" >
            <column name="data" />
</property>

This working for all type of files like .PDF,.TXT, .PNG etc.,

Online Internet Explorer Simulators

You could try Firebug Lite

It's a pure JavaScript-implementation of Firebug that runs directly in any browser (at least in all major ones: IE6+, Firefox, Opera, Safari and Chrome)

You'll still need the VM to actually run IE, but at least you'll get a quicker testing cycle.

Sorting std::map using value

In the following sample code, I wrote an simple way to output top words in an word_map map where key is string (word) and value is unsigned int (word occurrence).

The idea is simple, find the current top word and delete it from the map. It's not optimized, but it works well when the map is not large and we only need to output the top N words, instead of sorting the whole map.

const int NUMBER_OF_TOP_WORDS = 300;
for (int i = 1; i <= NUMBER_OF_TOP_WORDS; i++) {
  if (word_map.empty())
    break;
  // Go through the map and find the max item.
  int max_value = 0;
  string max_word = "";
  for (const auto& kv : word_map) {
    if (kv.second > max_value) {
      max_value = kv.second;
      max_word = kv.first;
    }
  }
  // Erase this entry and print.
  word_map.erase(max_word);
  cout << "Top:" << i << " Count:" << max_value << " Word:<" << max_word << ">" <<     endl;
}

How can I switch my git repository to a particular commit

To create a new branch (locally):

With the commit hash (or part of it)
```
git checkout -b new_branch 6e559cb
```
or to go back 4 commits from HEAD
```
git checkout -b new_branch HEAD~4
```

Once your new branch is created (locally), you might want to replicate this change on a remote of the same name: How can I push my changes to a remote branch

For discarding the last three commits, see Lunaryorn's answer below.

For moving your current branch HEAD to the specified commit without creating a new branch, see Arpiagar's answer below.

How do you use script variables in psql?

I really miss that feature. Only way to achieve something similar is to use functions.

I have used it in two ways:

perl functions that use $_SHARED variable
store your variables in table

Perl version:

   CREATE FUNCTION var(name text, val text) RETURNS void AS $$
        $_SHARED{$_[0]} = $_[1];
   $$ LANGUAGE plperl;
   CREATE FUNCTION var(name text) RETURNS text AS $$
        return $_SHARED{$_[0]};
   $$ LANGUAGE plperl;

Table version:

CREATE TABLE var (
  sess bigint NOT NULL,
  key varchar NOT NULL,
  val varchar,
  CONSTRAINT var_pkey PRIMARY KEY (sess, key)
);
CREATE FUNCTION var(key varchar, val anyelement) RETURNS void AS $$
  DELETE FROM var WHERE sess = pg_backend_pid() AND key = $1;
  INSERT INTO var (sess, key, val) VALUES (sessid(), $1, $2::varchar);
$$ LANGUAGE 'sql';

CREATE FUNCTION var(varname varchar) RETURNS varchar AS $$
  SELECT val FROM var WHERE sess = pg_backend_pid() AND key = $1;
$$ LANGUAGE 'sql';

Notes:

plperlu is faster than perl
pg_backend_pid is not best session identification, consider using pid combined with backend_start from pg_stat_activity
this table version is also bad because you have to clear this is up occasionally (and not delete currently working session variables)

Integer division with remainder in JavaScript?

You can use the function parseInt to get a truncated result.

parseInt(a/b)

To get a remainder, use mod operator:

a%b

parseInt have some pitfalls with strings, to avoid use radix parameter with base 10

parseInt("09", 10)

In some cases the string representation of the number can be a scientific notation, in this case, parseInt will produce a wrong result.

parseInt(100000000000000000000000000000000, 10) // 1e+32

This call will produce 1 as result.

Renaming columns in Pandas

Renaming columns in Pandas is an easy task.

df.rename(columns={'$a': 'a', '$b': 'b', '$c': 'c', '$d': 'd', '$e': 'e'}, inplace=True)

Open URL in Java to get the content

It may be more useful to use a http client library like such as this

There are more things like access denied , document moved etc to handle when dealing with http.

(though, it is unlikely in this case)

List all column except for one in R

You can index and use a negative sign to drop the 3rd column:

data[,-3]

Or you can list only the first 2 columns:

data[,c("c1", "c2")]
data[,1:2]

Don't forget the comma and referencing data frames works like this: data[row,column]

Lightbox to show videos from Youtube and Vimeo?

videobox-lb.sourceforge.net

Run jar file with command line arguments

For the question

How can i run a jar file in command prompt but with arguments

To pass arguments to the jar file at the time of execution

java -jar myjar.jar arg1 arg2

In the main() method of "Main-Class" [mentioned in the manifest.mft file]of your JAR file. you can retrieve them like this:

String arg1 = args[0];
String arg2 = args[1];

How do I get the browser scroll position in jQuery?

Since it appears you are using jQuery, here is a jQuery solution.

$(function() {
    $('#Eframe').on("mousewheel", function() {
        alert($(document).scrollTop());
    });
});

Not much to explain here. If you want, here is the jQuery documentation.

How to check if an object implements an interface?

If you want a method like public void doSomething([Object implements Serializable]) you can just type it like this public void doSomething(Serializable serializableObject). You can now pass it any object that implements Serializable but using the serializableObject you only have access to the methods implemented in the object from the Serializable interface.

How can I concatenate a string and a number in Python?

Since Python is a strongly typed language, concatenating a string and an integer as you may do in Perl makes no sense, because there's no defined way to "add" strings and numbers to each other.

Explicit is better than implicit.

...says "The Zen of Python", so you have to concatenate two string objects. You can do this by creating a string from the integer using the built-in str() function:

>>> "abc" + str(9)
'abc9'

Alternatively use Python's string formatting operations:

>>> 'abc%d' % 9
'abc9'

Perhaps better still, use str.format():

>>> 'abc{0}'.format(9)
'abc9'

The Zen also says:

There should be one-- and preferably only one --obvious way to do it.

Which is why I've given three options. It goes on to say...

Although that way may not be obvious at first unless you're Dutch.

How to toggle a boolean?

bool = bool != true;

One of the cases.

Carriage return in C?

Program prints ab, goes back one character and prints si overwriting the b resulting asi. Carriage return returns the caret to the first column of the current line. That means the ha will be printed over as and the result is hai

How do I create a folder in a GitHub repository?

Click on new file in github repo online. Then write file name as myfolder/myfilename then give file contents and commit. Then file will be created within that new folder.

How do I use a delimiter with Scanner.useDelimiter in Java?

With Scanner the default delimiters are the whitespace characters.

But Scanner can define where a token starts and ends based on a set of delimiter, wich could be specified in two ways:

Using the Scanner method: useDelimiter(String pattern)
Using the Scanner method : useDelimiter(Pattern pattern) where Pattern is a regular expression that specifies the delimiter set.

So useDelimiter() methods are used to tokenize the Scanner input, and behave like StringTokenizer class, take a look at these tutorials for further information:

And here is an Example:

public static void main(String[] args) {

    // Initialize Scanner object
    Scanner scan = new Scanner("Anna Mills/Female/18");
    // initialize the string delimiter
    scan.useDelimiter("/");
    // Printing the tokenized Strings
    while(scan.hasNext()){
        System.out.println(scan.next());
    }
    // closing the scanner stream
    scan.close();
}

Prints this output:

Anna Mills
Female
18

What is a stack trace, and how can I use it to debug my application errors?

In simple terms, a stack trace is a list of the method calls that the application was in the middle of when an Exception was thrown.

Simple Example

With the example given in the question, we can determine exactly where the exception was thrown in the application. Let's have a look at the stack trace:

Exception in thread "main" java.lang.NullPointerException
        at com.example.myproject.Book.getTitle(Book.java:16)
        at com.example.myproject.Author.getBookTitles(Author.java:25)
        at com.example.myproject.Bootstrap.main(Bootstrap.java:14)

This is a very simple stack trace. If we start at the beginning of the list of "at ...", we can tell where our error happened. What we're looking for is the topmost method call that is part of our application. In this case, it's:

at com.example.myproject.Book.getTitle(Book.java:16)

To debug this, we can open up Book.java and look at line 16, which is:

15   public String getTitle() {
16      System.out.println(title.toString());
17      return title;
18   }

This would indicate that something (probably title) is null in the above code.

Example with a chain of exceptions

Sometimes applications will catch an Exception and re-throw it as the cause of another Exception. This typically looks like:

34   public void getBookIds(int id) {
35      try {
36         book.getId(id);    // this method it throws a NullPointerException on line 22
37      } catch (NullPointerException e) {
38         throw new IllegalStateException("A book has a null property", e)
39      }
40   }

This might give you a stack trace that looks like:

Exception in thread "main" java.lang.IllegalStateException: A book has a null property
        at com.example.myproject.Author.getBookIds(Author.java:38)
        at com.example.myproject.Bootstrap.main(Bootstrap.java:14)
Caused by: java.lang.NullPointerException
        at com.example.myproject.Book.getId(Book.java:22)
        at com.example.myproject.Author.getBookIds(Author.java:36)
        ... 1 more

What's different about this one is the "Caused by". Sometimes exceptions will have multiple "Caused by" sections. For these, you typically want to find the "root cause", which will be one of the lowest "Caused by" sections in the stack trace. In our case, it's:

Caused by: java.lang.NullPointerException <-- root cause
        at com.example.myproject.Book.getId(Book.java:22) <-- important line

Again, with this exception we'd want to look at line 22 of Book.java to see what might cause the NullPointerException here.

More daunting example with library code

Usually stack traces are much more complex than the two examples above. Here's an example (it's a long one, but demonstrates several levels of chained exceptions):

javax.servlet.ServletException: Something bad happened
    at com.example.myproject.OpenSessionInViewFilter.doFilter(OpenSessionInViewFilter.java:60)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.example.myproject.ExceptionHandlerFilter.doFilter(ExceptionHandlerFilter.java:28)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.example.myproject.OutputBufferFilter.doFilter(OutputBufferFilter.java:33)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:943)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.jetty.bio.SocketConnector$Connection.run(SocketConnector.java:228)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: com.example.myproject.MyProjectServletException
    at com.example.myproject.MyServlet.doPost(MyServlet.java:169)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.example.myproject.OpenSessionInViewFilter.doFilter(OpenSessionInViewFilter.java:30)
    ... 27 more
Caused by: org.hibernate.exception.ConstraintViolationException: could not insert: [com.example.myproject.MyEntity]
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelectingDelegate.java:64)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2329)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2822)
    at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268)
    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)
    at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
    at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
    at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:705)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:693)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:689)
    at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344)
    at $Proxy19.save(Unknown Source)
    at com.example.myproject.MyEntityService.save(MyEntityService.java:59) <-- relevant call (see notes below)
    at com.example.myproject.MyServlet.doPost(MyServlet.java:164)
    ... 32 more
Caused by: java.sql.SQLException: Violation of unique constraint MY_ENTITY_UK_1: duplicate value(s) for column(s) MY_COLUMN in statement [...]
    at org.hsqldb.jdbc.Util.throwError(Unknown Source)
    at org.hsqldb.jdbc.jdbcPreparedStatement.executeUpdate(Unknown Source)
    at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeUpdate(NewProxyPreparedStatement.java:105)
    at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelectingDelegate.java:57)
    ... 54 more

In this example, there's a lot more. What we're mostly concerned about is looking for methods that are from our code, which would be anything in the com.example.myproject package. From the second example (above), we'd first want to look down for the root cause, which is:

Caused by: java.sql.SQLException

However, all the method calls under that are library code. So we'll move up to the "Caused by" above it, and look for the first method call originating from our code, which is:

at com.example.myproject.MyEntityService.save(MyEntityService.java:59)

Like in previous examples, we should look at MyEntityService.java on line 59, because that's where this error originated (this one's a bit obvious what went wrong, since the SQLException states the error, but the debugging procedure is what we're after).

My eclipse won't open, i download the bundle pack it keeps saying error log

Make sure you have the prerequisite, a JVM (http://wiki.eclipse.org/Eclipse/Installation#Install_a_JVM) installed.

This will be a JRE and JDK package.

There are a number of sources which includes: http://www.oracle.com/technetwork/java/javase/downloads/index.html.

How to get a user's time zone?

NSTimeZone *timeZone = [NSTimeZone localTimeZone];
NSString *tzName = [timeZone name];

The name will be something like "Australia/Sydney", or "Europe/Lisbon".

Since it sounds like you might only care about the continent, that might be all you need.

Why do you need ./ (dot-slash) before executable or script name to run it in bash?

All has great answer on the question, and yes this is only applicable when running it on the current directory not unless you include the absolute path. See my samples below.

Also, the (dot-slash) made sense to me when I've the command on the child folder tmp2 (/tmp/tmp2) and it uses (double dot-slash).

SAMPLE:

[fifiip-172-31-17-12 tmp]$ ./StackO.sh

Hello Stack Overflow

[fifi@ip-172-31-17-12 tmp]$ /tmp/StackO.sh

Hello Stack Overflow

[fifi@ip-172-31-17-12 tmp]$ mkdir tmp2

[fifi@ip-172-31-17-12 tmp]$ cd tmp2/

[fifi@ip-172-31-17-12 tmp2]$ ../StackO.sh

Hello Stack Overflow

C++ convert from 1 char to string?

I honestly thought that the casting method would work fine. Since it doesn't you can try stringstream. An example is below:

#include <sstream>
#include <string>
std::stringstream ss;
std::string target;
char mychar = 'a';
ss << mychar;
ss >> target;

String comparison technique used by Python

Strings are compared lexicographically using the numeric equivalents (the result of the built-in function ord()) of their characters. Unicode and 8-bit strings are fully interoperable in this behavior.

Play audio as microphone input

Just as there are printer drivers that do not connect to a printer at all but rather write to a PDF file, analogously there are virtual audio drivers available that do not connect to a physical microphone at all but can pipe input from other sources such as files or other programs.

I hope I'm not breaking any rules by recommending free/donation software, but VB-Audio Virtual Cable should let you create a pair of virtual input and output audio devices. Then you could play an MP3 into the virtual output device and then set the virtual input device as your "microphone". In theory I think that should work.

If all else fails, you could always roll your own virtual audio driver. Microsoft provides some sample code but unfortunately it is not applicable to the older Windows XP audio model. There is probably sample code available for XP too.

Remove HTML tags from a String

Alternatively, one can use HtmlCleaner:

private CharSequence removeHtmlFrom(String html) {
    return new HtmlCleaner().clean(html).getText();
}

Is it a bad practice to use break in a for loop?

It's perfectly valid to use break - as others have pointed out, it's nowhere in the same league as goto.

Although you might want to use the vFound variable when you want to check outside the loop whether the value was found in the array. Also from a maintainability point of view, having a common flag signalling the exit criteria might be useful.

Does Android keep the .apk files? if so where?

if you are using eclipse goto DDMS and then file explorer there you will see System/Apps folder and the apks are there

R numbers from 1 to 100

If you need the construct for a quick example to play with, use the : operator.

But if you are creating a vector/range of numbers dynamically, then use seq() instead.

Let's say you are creating the vector/range of numbers from a to b with a:b, and you expect it to be an increasing series. Then, if b is evaluated to be less than a, you will get a decreasing sequence but you will never be notified about it, and your program will continue to execute with the wrong kind of input.

In this case, if you use seq(), you can set the sign of the by argument to match the direction of your sequence, and an error will be raised if they do not match. For example,

seq(a, b, -1)

will raise an error for a=2, b=6, because the coder expected a decreasing sequence.

AngularJS : When to use service instead of factory

Services

Syntax: module.service( 'serviceName', function ); Result: When declaring serviceName as an injectable argument you will be provided the actual function reference passed to module.service.

Usage: Could be useful for sharing utility functions that are useful to invoke by simply appending () to the injected function reference. Could also be run with injectedArg.call( this ) or similar.

Factories

Syntax: module.factory( 'factoryName', function );

Result: When declaring factoryName as an injectable argument you will be provided the value that is returned by invoking the function reference passed to module.factory.

Usage: Could be useful for returning a 'class' function that can then be new'ed to create instances.

Providers

Syntax: module.provider( 'providerName', function );

Result: When declaring providerName as an injectable argument you will be provided the value that is returned by invoking the $get method of the function reference passed to module.provider.

Usage: Could be useful for returning a 'class' function that can then be new'ed to create instances but that requires some sort of configuration before being injected. Perhaps useful for classes that are reusable across projects? Still kind of hazy on this one.

java.security.cert.CertificateException: Certificates does not conform to algorithm constraints

Eclipse failed to connect to SVN https repositories (should also apply to any app using SSL/TLS).

svn: E175002: Connection has been shutdown: javax.net.ssl.SSLHandshakeException: java.security.cert.CertificateException: Certificates does not conform to algorithm constraints

The issue was caused by latest Java 8 OpenJDK update that disabled MD5 related algorithms. As a workaround until new certificates are issued (if ever), change the following keys at java.security file

WARNING
Keep in mind that this could have security implications as disabled algorithms are considered weak. As an alternative, the workaround can be applied on a JVM basis by a command line option to use an external java.security file with this changes, e.g.:
java -Djava.security.properties=/etc/sysconfig/noMD5.java.security
For Eclipse, add a line on eclipse.ini below -vmargs
-Djava.security.properties=/etc/sysconfig/noMD5.java.security

original keys

jdk.certpath.disabledAlgorithms=MD2, MD5, RSA keySize < 1024
jdk.tls.disabledAlgorithms=SSLv3, RC4, MD5withRSA, DH keySize < 768

change to

jdk.certpath.disabledAlgorithms=MD2, RSA keySize < 1024
jdk.tls.disabledAlgorithms=SSLv3, RC4, DH keySize < 768

java.security file is located in linux 64 at /usr/lib64/jvm/java/jre/lib/security/java.security

how to set font size based on container size?

You may be able to do this with CSS3 using calculations, however it would most likely be safer to use JavaScript.

Here is an example: http://jsfiddle.net/8TrTU/

Using JS you can change the height of the text, then simply bind this same calculation to a resize event, during resize so it scales while the user is making adjustments, or however you are allowing resizing of your elements.

How to build a 2 Column (Fixed - Fluid) Layout with Twitter Bootstrap?

- Another Update -

Since Twitter Bootstrap version 2.0 - which saw the removal of the .container-fluid class - it has not been possible to implement a two column fixed-fluid layout using just the bootstrap classes - however I have updated my answer to include some small CSS changes that can be made in your own CSS code that will make this possible

It is possible to implement a fixed-fluid structure using the CSS found below and slightly modified HTML code taken from the Twitter Bootstrap Scaffolding : layouts documentation page:

HTML

<div class="container-fluid fill">
    <div class="row-fluid">
        <div class="fixed">  <!-- we want this div to be fixed width -->
            ...
        </div>
        <div class="hero-unit filler">  <!-- we have removed spanX class -->
            ...
        </div>
    </div>
</div>

CSS

/* CSS for fixed-fluid layout */

.fixed {
    width: 150px;  /* the fixed width required */
    float: left;
}

.fixed + div {
     margin-left: 150px;  /* must match the fixed width in the .fixed class */
     overflow: hidden;
}


/* CSS to ensure sidebar and content are same height (optional) */

html, body {
    height: 100%;
}

.fill { 
    min-height: 100%;
    position: relative;
}

.filler:after{
    background-color:inherit;
    bottom: 0;
    content: "";
    height: auto;
    min-height: 100%;
    left: 0;
    margin:inherit;
    right: 0;
    position: absolute;
    top: 0;
    width: inherit;
    z-index: -1;  
}

I have kept the answer below - even though the edit to support 2.0 made it a fluid-fluid solution - as it explains the concepts behind making the sidebar and content the same height (a significant part of the askers question as identified in the comments)

Important

Answer below is fluid-fluid

Update As pointed out by @JasonCapriotti in the comments, the original answer to this question (created for v1.0) did not work in Bootstrap 2.0. For this reason, I have updated the answer to support Bootstrap 2.0

To ensure that the main content fills at least 100% of the screen height, we need to set the height of the html and body to 100% and create a new css class called .fill which has a minimum-height of 100%:

html, body {
    height: 100%;
}

.fill { 
    min-height: 100%;
}

We can then add the .fill class to any element that we need to take up 100% of the sceen height. In this case we add it to the first div:

<div class="container-fluid fill">
    ...
</div>

To ensure that the Sidebar and the Content columns have the same height is very difficult and unnecessary. Instead we can use the ::after pseudo selector to add a filler element that will give the illusion that the two columns have the same height:

.filler::after {
    background-color: inherit;
    bottom: 0;
    content: "";
    right: 0;
    position: absolute;
    top: 0;
    width: inherit;
    z-index: -1;  
}

To make sure that the .filler element is positioned relatively to the .fill element we need to add position: relative to .fill:

.fill { 
    min-height: 100%;
    position: relative;
}

And finally add the .filler style to the HTML:

HTML

<div class="container-fluid fill">
    <div class="row-fluid">
        <div class="span3">
            ...
        </div>
        <div class="span9 hero-unit filler">
            ...
        </div>
    </div>
</div>

Notes

If you need the element on the left of the page to be the filler then you need to change right: 0 to left: 0.

How to embed PDF file with responsive width

<html>
<head>
<style type="text/css">
#wrapper{ width:100%; float:left; height:auto; border:1px solid #5694cf;}
</style>
</head>
<div id="wrapper">
<object data="http://partners.adobe.com/public/developer/en/acrobat/PDFOpenParameters.pdf" width="100%" height="100%">
<p>Your web browser doesn't have a PDF Plugin. Instead you can <a href="http://partners.adobe.com/public/developer/en/acrobat/PDFOpenParameters.pdf"> Click
here to download the PDF</a></p>
</object>
</div>
</html>

When is each sorting algorithm used?

First, a definition, since it's pretty important: A stable sort is one that's guaranteed not to reorder elements with identical keys.

Recommendations:

Quick sort: When you don't need a stable sort and average case performance matters more than worst case performance. A quick sort is O(N log N) on average, O(N^2) in the worst case. A good implementation uses O(log N) auxiliary storage in the form of stack space for recursion.

Merge sort: When you need a stable, O(N log N) sort, this is about your only option. The only downsides to it are that it uses O(N) auxiliary space and has a slightly larger constant than a quick sort. There are some in-place merge sorts, but AFAIK they are all either not stable or worse than O(N log N). Even the O(N log N) in place sorts have so much larger a constant than the plain old merge sort that they're more theoretical curiosities than useful algorithms.

Heap sort: When you don't need a stable sort and you care more about worst case performance than average case performance. It's guaranteed to be O(N log N), and uses O(1) auxiliary space, meaning that you won't unexpectedly run out of heap or stack space on very large inputs.

Introsort: This is a quick sort that switches to a heap sort after a certain recursion depth to get around quick sort's O(N^2) worst case. It's almost always better than a plain old quick sort, since you get the average case of a quick sort, with guaranteed O(N log N) performance. Probably the only reason to use a heap sort instead of this is in severely memory constrained systems where O(log N) stack space is practically significant.

Insertion sort: When N is guaranteed to be small, including as the base case of a quick sort or merge sort. While this is O(N^2), it has a very small constant and is a stable sort.

Bubble sort, selection sort: When you're doing something quick and dirty and for some reason you can't just use the standard library's sorting algorithm. The only advantage these have over insertion sort is being slightly easier to implement.

Non-comparison sorts: Under some fairly limited conditions it's possible to break the O(N log N) barrier and sort in O(N). Here are some cases where that's worth a try:

Counting sort: When you are sorting integers with a limited range.

Radix sort: When log(N) is significantly larger than K, where K is the number of radix digits.

Bucket sort: When you can guarantee that your input is approximately uniformly distributed.

Stop form from submitting , Using Jquery

A different approach could be

    <script type="text/javascript">
    function CheckData() {
    //you may want to check something here and based on that wanna return true and false from the         function.
    if(MyStuffIsokay)
     return true;//will cause form to postback to server.
    else
      return false;//will cause form Not to postback to server
    }
    </script>
    @using (Html.BeginForm("SaveEmployee", "Employees", FormMethod.Post, new { id = "EmployeeDetailsForm" }))
    {
    .........
    .........
    .........
    .........
    <input type="submit" value= "Save Employee" onclick="return CheckData();"/>
    }

convert a list of objects from one type to another using lambda expression

I believe something like this should work:

origList.Select(a => new TargetType() { SomeValue = a.SomeValue});

How to provide shadow to Button

Use this approach to get your desired look.
button_selector.xml :

<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item>
    <layer-list>
        <item android:right="5dp" android:top="5dp">
            <shape>
                <corners android:radius="3dp" />
                <solid android:color="#D6D6D6" />
            </shape>
        </item>
        <item android:bottom="2dp" android:left="2dp">
            <shape>
                <gradient android:angle="270" 
                    android:endColor="#E2E2E2" android:startColor="#BABABA" />
                <stroke android:width="1dp" android:color="#BABABA" />
                <corners android:radius="4dp" />
                <padding android:bottom="10dp" android:left="10dp" 
                    android:right="10dp" android:top="10dp" />
            </shape>
        </item>
    </layer-list>
</item>

</selector>

And in your xml layout:

<Button
   android:background="@drawable/button_selector"
   ...
   ..
/>

what is the use of annotations @Id and @GeneratedValue(strategy = GenerationType.IDENTITY)? Why the generationtype is identity?

Simply, @Id: This annotation specifies the primary key of the entity. 

@GeneratedValue: This annotation is used to specify the primary key generation strategy to use. i.e Instructs database to generate a value for this field automatically. If the strategy is not specified by default AUTO will be used. 

GenerationType enum defines four strategies: 
1. Generation Type . TABLE, 
2. Generation Type. SEQUENCE,
3. Generation Type. IDENTITY   
4. Generation Type. AUTO

GenerationType.SEQUENCE

With this strategy, underlying persistence provider must use a database sequence to get the next unique primary key for the entities. 

GenerationType.TABLE

With this strategy, underlying persistence provider must use a database table to generate/keep the next unique primary key for the entities. 

GenerationType.IDENTITY
This GenerationType indicates that the persistence provider must assign primary keys for the entity using a database identity column. IDENTITY column is typically used in SQL Server. This special type column is populated internally by the table itself without using a separate sequence. If underlying database doesn't support IDENTITY column or some similar variant then the persistence provider can choose an alternative appropriate strategy. In this examples we are using H2 database which doesn't support IDENTITY column.

GenerationType.AUTO
This GenerationType indicates that the persistence provider should automatically pick an appropriate strategy for the particular database. This is the default GenerationType, i.e. if we just use @GeneratedValue annotation then this value of GenerationType will be used.

Reference:- https://www.logicbig.com/tutorials/java-ee-tutorial/jpa/jpa-primary-key.html

jquery getting post action url

$('#signup').on("submit", function(event) {
    $form = $(this); //wrap this in jQuery

    alert('the action is: ' + $form.attr('action'));
});

Insert data into hive table

Although there is an accepted answer I would want to add that as of Hive 0.14, record level operations are allowed. The correct syntax and query would be:

INSERT INTO TABLE tweet_table VALUES ('data');

Send a ping to each IP on a subnet

Not all machines have nmap available, but it's a wonderful tool for any network discovery, and certainly better than iterating through independent ping commands.

$ nmap -n -sP 10.0.0.0/24

Starting Nmap 4.20 ( http://insecure.org ) at 2009-02-02 07:41 CST
Host 10.0.0.1 appears to be up.
Host 10.0.0.10 appears to be up.
Host 10.0.0.104 appears to be up.
Host 10.0.0.124 appears to be up.
Host 10.0.0.125 appears to be up.
Host 10.0.0.129 appears to be up.
Nmap finished: 256 IP addresses (6 hosts up) scanned in 2.365 seconds

Grouping into interval of 5 minutes within a time range

You should rather use GROUP BY UNIX_TIMESTAMP(time_stamp) DIV 300 instead of round(../300) because of the rounding I found that some records are counted into two grouped result sets.

sql query to return differences between two tables

You can use except , for example something like this :

-- DB1..Tb1 have values than DB2..Tb1 not have
Select Col1,Col2,Col3 From DB1..Tb1
except
Select Col1,Col2,Col3 From DB2..Tb1
-- Now we change order
-- DB2..Tb1 have values than DB1..Tb1 not have
Select Col1,Col2,Col3 From DB2..Tb1
except
Select Col1,Col2,Col3 From DB1..Tb1

C free(): invalid pointer

You can't call free on the pointers returned from strsep. Those are not individually allocated strings, but just pointers into the string s that you've already allocated. When you're done with s altogether, you should free it, but you do not have to do that with the return values of strsep.

How to get all key in JSON object (javascript)

I use Object.keys which is built into JavaScript Object, it will return an array of keys from given object MDN Reference

var obj = {name: "Jeeva", age: "22", gender: "Male"}
console.log(Object.keys(obj))

Where can I find the Java SDK in Linux after installing it?

On Linux Fedora30 several versions of the full java JDK are available, specifically package names:

java-1.8.0-openjdk-devel.x86_64 
java-11-openjdk-devel.x86_64

Once installed, they are found in: /usr/lib/jvm

To select the location/directory of a full development JDK (which is different from the simpler runtime only JRE) look for entries:

ls -ld java*openjdk*

Here are two good choices, which are links to specific versions, where you will have to select the version:

/usr/lib/jvm/java-1.8.0-openjdk
/usr/lib/jvm/java-11-openjdk

Delete with Join in MySQL

One solution is to use subquery

DELETE FROM posts WHERE post_id in (SELECT post_id FROM posts p
INNER JOIN projects prj ON p.project_id = prj.project_id 
INNER JOIN clients c on prj.client_id = c.client_id WHERE c.client_id = :client_id 
);

The subquery returns the ID that need to be deleted; all three tables are connected using joins and only those records are deleted that meets the filter condition (in yours case i.e. client_id in the where clause).

How to set width to 100% in WPF

You could use HorizontalContentAlignment="Stretch" as follows:

<ListBox HorizontalContentAlignment="Stretch"/>

How can you flush a write using a file descriptor?

If you want to go the other way round (associate FILE* with existing file descriptor), use fdopen() :

                                                          FDOPEN(P)

NAME

       fdopen - associate a stream with a file descriptor

SYNOPSIS

       #include <stdio.h>

       FILE *fdopen(int fildes, const char *mode);

Catch an exception thrown by an async void method

The reason the exception is not caught is because the Foo() method has a void return type and so when await is called, it simply returns. As DoFoo() is not awaiting the completion of Foo, the exception handler cannot be used.

This opens up a simpler solution if you can change the method signatures - alter Foo() so that it returns type Task and then DoFoo() can await Foo(), as in this code:

public async Task Foo() {
    var x = await DoSomethingThatThrows();
}

public async void DoFoo() {
    try {
        await Foo();
    } catch (ProtocolException ex) {
        // This will catch exceptions from DoSomethingThatThrows
    }
}

How to remove square brackets in string using regex?

str.replace(/[[\]]/g,'')

Move_uploaded_file() function is not working

Easiest Way to Uplaod a file

$FileName = $file_name;
$path = 'Users/Desktop/uploads/images'; 
$location = $path . $data['name']; 
move_uploaded_file($data['temp_name'],$location);

Count rows with not empty value

=counta(range)

counta: "Returns a count of the number of values in a dataset"

Note: CountA considers "" to be a value. Only cells that are blank (press delete in a cell to blank it) are not counted.

Google support: https://support.google.com/docs/answer/3093991
countblank: "Returns the number of empty cells in a given range"

Note: CountBlank considers both blank cells (press delete to blank a cell) and cells that have a formula that returns "" to be empty cells.

Google Support: https://support.google.com/docs/answer/3093403

If you have a range that includes formulae that result in "", then you can modify your formula from

=counta(range)

to:

=Counta(range) - Countblank(range)

EDIT: the function is countblank, not countblanks, the latter will give an error.

Open PDF in new browser full window

<a href="#" onclick="window.open('MyPDF.pdf', '_blank', 'fullscreen=yes'); return false;">MyPDF</a>

The above link will open the PDF in full screen mode, that's the best you can achieve.

How Can I Remove “public/index.php” in the URL Generated Laravel?

I just installed Laravel 5 for a project and there is a file in the root called server.php.

Change it to index.php and it works or type in terminal:

$cp server.php index.php

SFTP in Python? (platform independent)

Twisted can help you with what you are doing, check out their documentation, there are plenty of examples. Also it is a mature product with a big developer/user community behind it.

Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set()

If you are running your application just on localhost and it is not yet live, I believe it is very difficult to send mail using this.

Once you put your application online, I believe that this problem should be automatically solved. By the way,ini_set() helps you to change the values in php.ini during run time.

This is the same question as Failed to connect to mailserver at "localhost" port 25

also check this php mail function not working

Python: finding an element in a list

assuming you want to find a value in a numpy array, I guess something like this might work:

Numpy.where(arr=="value")[0]

Git's famous "ERROR: Permission to .git denied to user"

Its due to a conflict.

Clear all keys from ssh-agent

ssh-add -d ~/.ssh/id_rsa
ssh-add -d ~/.ssh/github

Add the github ssh key

ssh-add   ~/.ssh/github

It should work now.

How to search a Git repository by commit message?

Though a bit late, there is :/ which is the dedicated notation to specify a commit (or revision) based on the commit message, just prefix the search string with :/, e.g.:

git show :/keyword(s)

Here <keywords> can be a single word, or a complex regex pattern consisting of whitespaces, so please make sure to quote/escape when necessary, e.g.:

git log -1 -p ":/a few words"

Alternatively, a start point can be specified, to find the closest commit reachable from a specific point, e.g.:

git show 'HEAD^{/fix nasty bug}'

See: git revisions manual.

What is MATLAB good for? Why is it so used by universities? When is it better than Python?

Seems to be pure inertia. Where it is in use, everyone is too busy to learn IDL or numpy in sufficient detail to switch, and don't want to rewrite good working programs. Luckily that's not strictly true, but true enough in enough places that Matlab will be around a long time. Like Fortran (in active use where i work!)

Cloning an array in Javascript/Typescript

Cloning Arrays and Objects in javascript have a different syntax. Sooner or later everyone learns the difference the hard way and end up here.

In Typescript and ES6 you can use the spread operator for array and object:

const myClonedArray  = [...myArray];  // This is ok for [1,2,'test','bla']
                                      // But wont work for [{a:1}, {b:2}]. 
                                      // A bug will occur when you 
                                      // modify the clone and you expect the 
                                      // original not to be modified.
                                      // The solution is to do a deep copy
                                      // when you are cloning an array of objects.

To do a deep copy of an object you need an external library:

import {cloneDeep} from 'lodash';
const myClonedArray = cloneDeep(myArray);     // This works for [{a:1}, {b:2}]

The spread operator works on object as well but it will only do a shallow copy (first layer of children)

const myShallowClonedObject = {...myObject};   // Will do a shallow copy
                                               // and cause you an un expected bug.

To do a deep copy of an object you need an external library:

 import {cloneDeep} from 'lodash';
 const deeplyClonedObject = cloneDeep(myObject);   // This works for [{a:{b:2}}]

Rank function in MySQL

@Sam, your point is excellent in concept but I think you misunderstood what the MySQL docs are saying on the referenced page -- or I misunderstand :-) -- and I just wanted to add this so that if someone feels uncomfortable with the @Daniel's answer they'll be more reassured or at least dig a little deeper.

You see the "@curRank := @curRank + 1 AS rank" inside the SELECT is not "one statement", it's one "atomic" part of the statement so it should be safe.

The document you reference goes on to show examples where the same user-defined variable in 2 (atomic) parts of the statement, for example, "SELECT @curRank, @curRank := @curRank + 1 AS rank".

One might argue that @curRank is used twice in @Daniel's answer: (1) the "@curRank := @curRank + 1 AS rank" and (2) the "(SELECT @curRank := 0) r" but since the second usage is part of the FROM clause, I'm pretty sure it is guaranteed to be evaluated first; essentially making it a second, and preceding, statement.

In fact, on that same MySQL docs page you referenced, you'll see the same solution in the comments -- it could be where @Daniel got it from; yeah, I know that it's the comments but it is comments on the official docs page and that does carry some weight.

Parsing GET request parameters in a URL that contains another URL

$get_url = "http://google.com/?var=234&key=234";
$my_url = "http://localhost/test.php?id=" . urlencode($get_url);

$my_url outputs:

http://localhost/test.php?id=http%3A%2F%2Fgoogle.com%2F%3Fvar%3D234%26key%3D234

So now you can get this value using $_GET['id'] or $_REQUEST['id'] (decoded).

echo urldecode($_GET["id"]);

Output

http://google.com/?var=234&key=234

To get every GET parameter:

foreach ($_GET as $key=>$value) {
  echo "$key = " . urldecode($value) . "<br />\n";
  }

$key is GET key and $value is GET value for $key.

Or you can use alternative solution to get array of GET params

$get_parameters = array();
if (isset($_SERVER['QUERY_STRING'])) {
  $pairs = explode('&', $_SERVER['QUERY_STRING']);
  foreach($pairs as $pair) {
    $part = explode('=', $pair);
    $get_parameters[$part[0]] = sizeof($part)>1 ? urldecode($part[1]) : "";
    }
  }

$get_parameters is same as url decoded $_GET.

Unique constraint violation during insert: why? (Oracle)

Your error looks like you are duplicating an already existing Primary Key in your DB. You should modify your sql code to implement its own primary key by using something like the IDENTITY keyword.

CREATE TABLE [DB] (
    [DBId] bigint NOT NULL IDENTITY,
    ...

    CONSTRAINT [DB_PK] PRIMARY KEY ([DB] ASC),

);

Display image at 50% of its "native" size

Maybe one of the easiest solutions would be to use the x descriptor of the srcset attribute as such:

_x000D_

<!-- Original image -->
<img src="https://fr.wikipedia.org/static/images/mobile/copyright/wikipedia.png" />

<!-- With a 80% size reduction (1/0.8=1.25) -->
<img srcset="https://fr.wikipedia.org/static/images/mobile/copyright/wikipedia.png 1.25x" />

<!-- With a 50% size reduction (1/0.5=2) -->
<img srcset="https://fr.wikipedia.org/static/images/mobile/copyright/wikipedia.png 2x" />

_x000D_

Currently supported by all browsers except IE. (caniuse)

MDN documentation

Displaying files (e.g. images) stored in Google Drive on a website

Con can disable javascript in your browser open the image file and in the view page source or right click on the image, you will see the image link. ( check share preference before )

Best Way to Refresh Adapter/ListView on Android

If nothing works, just create the adapter instance again with the new set of results or the updated set of results. Then you can see the new view.

XYZAdapter adbXzy = new XYZAdapter(context, 0, listData);
xyzListView.setAdapter(adbXzy);

adbXzy.notifyDataSetChanged();

How do I send email with JavaScript without opening the mail client?

Well, PHP can do this easily.

It can be done with the PHP mail() function. Here's what a simple function would look like:

<?php     
$to_email = '[email protected]';
$subject = 'Testing PHP Mail';
$message = 'This mail is sent using the PHP mail function';
$headers = 'From: [email protected]';
mail($to_email,$subject,$message,$headers);
?>

This will send a background e-mail to the recipient specified in the $to_email.

The above example uses hard coded values in the source code for the email address and other details for simplicity.

Let’s assume you have to create a contact us form for users fill in the details and then submit.

Users can accidently or intentional inject code in the headers which can result in sending spam mail
To protect your system from such attacks, you can create a custom function that sanitizes and validates the values before the mail is sent.

Let’s create a custom function that validates and sanitizes the email address using the filter_var() built in function.

Here's an example code:

<?php 
function sanitize_my_email($field) {
    $field = filter_var($field, FILTER_SANITIZE_EMAIL);
    if (filter_var($field, FILTER_VALIDATE_EMAIL)) {
        return true;
    } else {
        return false;
    }
}
$to_email = '[email protected]';
$subject = 'Testing PHP Mail';
$message = 'This mail is sent using the PHP mail ';
$headers = 'From: [email protected]';
//check if the email address is invalid $secure_check
$secure_check = sanitize_my_email($to_email);
if ($secure_check == false) {
    echo "Invalid input";
} else { //send email 
    mail($to_email, $subject, $message, $headers);
    echo "This email is sent using PHP Mail";
}
?>

We will now let this be a separate PHP file, for example sendmail.php.

Then, will use this file on form submission, using the action attribute of the form, like:

<form action="sendmail.php" method="post">
   <input type="text" value="Your Name: ">
   <input type="password" value="Set Up A Passworrd">
   <input type="submit" value="Signup">
   <input type="reset" value="Reset Form">
</form>

Hope I could help

Subtract two variables in Bash

Use Python:

#!/bin/bash
# home/victoria/test.sh

START=$(date +"%s")                                     ## seconds since Epoch
for i in $(seq 1 10)
do
  sleep 1.5
  END=$(date +"%s")                                     ## integer
  TIME=$((END - START))                                 ## integer
  AVG_TIME=$(python -c "print(float($TIME/$i))")        ## int to float
  printf 'i: %i | elapsed time: %0.1f sec | avg. time: %0.3f\n' $i $TIME $AVG_TIME
  ((i++))                                               ## increment $i
done

Output

$ ./test.sh 
i: 1 | elapsed time: 1.0 sec | avg. time: 1.000
i: 2 | elapsed time: 3.0 sec | avg. time: 1.500
i: 3 | elapsed time: 5.0 sec | avg. time: 1.667
i: 4 | elapsed time: 6.0 sec | avg. time: 1.500
i: 5 | elapsed time: 8.0 sec | avg. time: 1.600
i: 6 | elapsed time: 9.0 sec | avg. time: 1.500
i: 7 | elapsed time: 11.0 sec | avg. time: 1.571
i: 8 | elapsed time: 12.0 sec | avg. time: 1.500
i: 9 | elapsed time: 14.0 sec | avg. time: 1.556
i: 10 | elapsed time: 15.0 sec | avg. time: 1.500
$

Get current time in seconds since the Epoch on Linux, Bash

Create component to specific module with Angular-CLI

If you have multiple apps declared in .angular-cli.json ( e.g. in case working on feature module)

"apps": [{
    "name": "app-name",
    "root": "lib",
    "appRoot": ""
}, {...} ]

You can :

ng g c my-comp -a app-name

-a stands for --app (name)

DateTime.TryParse issue with dates of yyyy-dd-MM format

This should work based on your example "2011-29-01 12:00 am"

DateTime dt;
DateTime.TryParseExact(dateTime, 
                       "yyyy-dd-MM hh:mm tt", 
                       CultureInfo.InvariantCulture, 
                       DateTimeStyles.None, 
                       out dt);

What is the ultimate postal code and zip regex?

As noted elsewhere the variation around the world is huge. And even if something that matches the pattern does not mean it exists.

Then, of course, there are many places where postcodes are not used (e.g. much or Ireland).

How to prevent form from being submitted?

You can add eventListner to the form, that preventDefault() and convert form data to JSON as below:

_x000D_

const formToJSON = elements => [].reduce.call(elements, (data, element) => {_x000D_
  data[element.name] = element.value;_x000D_
  return data;_x000D_
_x000D_
}, {});_x000D_
_x000D_
const handleFormSubmit = event => {_x000D_
    event.preventDefault();_x000D_
    const data = formToJSON(form.elements);_x000D_
    console.log(data);_x000D_
  //  const odata = JSON.stringify(data, null, "  ");_x000D_
  const jdata = JSON.stringify(data);_x000D_
    console.log(jdata);_x000D_
_x000D_
    (async () => {_x000D_
      const rawResponse = await fetch('/', {_x000D_
        method: 'POST',_x000D_
        headers: {_x000D_
          'Accept': 'application/json',_x000D_
          'Content-Type': 'application/json'_x000D_
        },_x000D_
        body: jdata_x000D_
      });_x000D_
      const content = await rawResponse.json();_x000D_
_x000D_
      console.log(content);_x000D_
    })();_x000D_
};_x000D_
_x000D_
const form = document.forms['myForm']; _x000D_
form.addEventListener('submit', handleFormSubmit);

_x000D_

<form id="myForm" action="/" method="post" accept-charset="utf-8">_x000D_
    <label>Checkbox:_x000D_
        <input type="checkbox" name="checkbox" value="on">_x000D_
    </label><br /><br />_x000D_
_x000D_
    <label>Number:_x000D_
        <input name="number" type="number" value="123" />_x000D_
    </label><br /><br />_x000D_
_x000D_
    <label>Password:_x000D_
        <input name="password" type="password" />_x000D_
    </label>_x000D_
    <br /><br />_x000D_
_x000D_
    <label for="radio">Type:_x000D_
        <label for="a">A_x000D_
            <input type="radio" name="radio" id="a" value="a" />_x000D_
        </label>_x000D_
        <label for="b">B_x000D_
            <input type="radio" name="radio" id="b" value="b" checked />_x000D_
        </label>_x000D_
        <label for="c">C_x000D_
            <input type="radio" name="radio" id="c" value="c" />_x000D_
        </label>_x000D_
    </label>_x000D_
    <br /><br />_x000D_
_x000D_
    <label>Textarea:_x000D_
        <textarea name="text_area" rows="10" cols="50">Write something here.</textarea>_x000D_
    </label>_x000D_
    <br /><br />_x000D_
_x000D_
    <label>Select:_x000D_
        <select name="select">_x000D_
            <option value="a">Value A</option>_x000D_
            <option value="b" selected>Value B</option>_x000D_
            <option value="c">Value C</option>_x000D_
        </select>_x000D_
    </label>_x000D_
    <br /><br />_x000D_
_x000D_
    <label>Submit:_x000D_
        <input type="submit" value="Login">_x000D_
    </label>_x000D_
    <br /><br />_x000D_
_x000D_
_x000D_
</form>

_x000D_

Is it safe to store a JWT in localStorage with ReactJS?

Localstorage is designed to be accessible by javascript, so it doesn't provide any XSS protection. As mentioned in other answers, there is a bunch of possible ways to do an XSS attack, from which localstorage is not protected by default.

However, cookies have security flags which protect from XSS and CSRF attacks. HttpOnly flag prevents client side javascript from accessing the cookie, Secure flag only allows the browser to transfer the cookie through ssl, and SameSite flag ensures that the cookie is sent only to the origin. Although I just checked and SameSite is currently supported only in Opera and Chrome, so to protect from CSRF it's better to use other strategies. For example, sending an encrypted token in another cookie with some public user data.

So cookies are a more secure choice for storing authentication data.

How to convert a string variable containing time to time_t type in c++?

This should work:

int hh, mm, ss;
struct tm when = {0};

sscanf_s(date, "%d:%d:%d", &hh, &mm, &ss);


when.tm_hour = hh;
when.tm_min = mm;
when.tm_sec = ss;

time_t converted;
converted = mktime(&when);

Modify as needed.

installing vmware tools: location of GCC binary?

sudo apt-get install build-essential is enough to get it working.

How to search a string in a single column (A) in excel using VBA

Below are two methods that are superior to looping. Both handle a "no-find" case.

The VBA equivalent of a normal function VLOOKUP with error-handling if the variable doesn't exist (INDEX/MATCH may be a better route than VLOOKUP, ie if your two columns A and B were in reverse order, or were far apart)

VBAs FIND method (matching a whole string in column A given I use the xlWhole argument)

Sub Method1()
Dim strSearch As String
Dim strOut As String
Dim bFailed As Boolean

strSearch = "trees"

On Error Resume Next
strOut = Application.WorksheetFunction.VLookup(strSearch, Range("A:B"), 2, False)
If Err.Number <> 0 Then bFailed = True
On Error GoTo 0

If Not bFailed Then
MsgBox "corresponding value is " & vbNewLine & strOut
Else
MsgBox strSearch & " not found"
End If
End Sub

Sub Method2()
    Dim rng1 As Range
    Dim strSearch As String
    strSearch = "trees"
    Set rng1 = Range("A:A").Find(strSearch, , xlValues, xlWhole)
    If Not rng1 Is Nothing Then
        MsgBox "Find has matched " & strSearch & vbNewLine & "corresponding cell is " & rng1.Offset(0, 1)
    Else
        MsgBox strSearch & " not found"
    End If
End Sub

Drop rows containing empty cells from a pandas DataFrame

Pythonic + Pandorable: `df[df['col'].astype(bool)]`

Empty strings are falsy, which means you can filter on bool values like this:

df = pd.DataFrame({
    'A': range(5),
    'B': ['foo', '', 'bar', '', 'xyz']
})
df
   A    B
0  0  foo
1  1     
2  2  bar
3  3     
4  4  xyz

df['B'].astype(bool)                                                                                                                      
0     True
1    False
2     True
3    False
4     True
Name: B, dtype: bool

df[df['B'].astype(bool)]                                                                                                                  
   A    B
0  0  foo
2  2  bar
4  4  xyz

If your goal is to remove not only empty strings, but also strings only containing whitespace, use str.strip beforehand:

df[df['B'].str.strip().astype(bool)]
   A    B
0  0  foo
2  2  bar
4  4  xyz

Faster than you Think

.astype is a vectorised operation, this is faster than every option presented thus far. At least, from my tests. YMMV.

Here is a timing comparison, I've thrown in some other methods I could think of.

Benchmarking code, for reference:

import pandas as pd
import perfplot

df1 = pd.DataFrame({
    'A': range(5),
    'B': ['foo', '', 'bar', '', 'xyz']
})

perfplot.show(
    setup=lambda n: pd.concat([df1] * n, ignore_index=True),
    kernels=[
        lambda df: df[df['B'].astype(bool)],
        lambda df: df[df['B'] != ''],
        lambda df: df[df['B'].replace('', np.nan).notna()],  # optimized 1-col
        lambda df: df.replace({'B': {'': np.nan}}).dropna(subset=['B']),  
    ],
    labels=['astype', "!= ''", "replace + notna", "replace + dropna", ],
    n_range=[2**k for k in range(1, 15)],
    xlabel='N',
    logx=True,
    logy=True,
    equality_check=pd.DataFrame.equals)

update one table with data from another

Oracle 11g R2:

create table table1 (
  id number,
  name varchar2(10),
  desc_ varchar2(10)
);

create table table2 (
  id number,
  name varchar2(10),
  desc_ varchar2(10)
);

insert into table1 values(1, 'a', 'abc');
insert into table1 values(2, 'b', 'def');
insert into table1 values(3, 'c', 'ghi');

insert into table2 values(1, 'x', '123');
insert into table2 values(2, 'y', '456');

merge into table1 t1
using (select * from table2) t2
on (t1.id = t2.id)
when matched then update set t1.name = t2.name, t1.desc_ = t2.desc_;

select * from table1;

        ID NAME       DESC_
---------- ---------- ----------
         1 x          123
         2 y          456
         3 c          ghi

How do I do pagination in ASP.NET MVC?

I wanted to cover a simple way of doing this with the front end too:

Controller:

public ActionResult Index(int page = 0)
{
    const int PageSize = 3; // you can always do something more elegant to set this

    var count = this.dataSource.Count();

    var data = this.dataSource.Skip(page * PageSize).Take(PageSize).ToList();

    this.ViewBag.MaxPage = (count / PageSize) - (count % PageSize == 0 ? 1 : 0);

    this.ViewBag.Page = page;

    return this.View(data);
}

View:

@* rest of file with view *@

@if (ViewBag.Page > 0)
{
    <a href="@Url.Action("Index", new { page = ViewBag.Page - 1 })" 
       class="btn btn-default">
        &laquo; Prev
    </a>
}
@if (ViewBag.Page < ViewBag.MaxPage)
{
    <a href="@Url.Action("Index", new { page = ViewBag.Page + 1 })" 
       class="btn btn-default">
        Next &raquo;
    </a>
}

Select default option value from typescript angular 6

Correct Way would be :

<select id="select-type-basic" [(ngModel)]="status">
    <option *ngFor="let status_item of status_values">
    {{status_item}}
    </option>
</select>

Value Should be avoided inside option if the value is to be dynamic,since that will set the default value of the 'Select field'. Default Selection should be binded with [(ngModel)] and Options should be declared likewise.

status : any = "47";
status_values: any = ["45", "46", "47"];

Checking if a SQL Server login already exists

This works on SQL Server 2000.

use master
select count(*) From sysxlogins WHERE NAME = 'myUsername'

on SQL 2005, change the 2nd line to

select count(*) From syslogins WHERE NAME = 'myUsername'

I'm not sure about SQL 2008, but I'm guessing that it will be the same as SQL 2005 and if not, this should give you an idea of where t start looking.

Checking if an input field is required using jQuery

A little bit of a more complete answer, inspired by the accepted answer:

$( '#form_id' ).submit( function( event ) {
        event.preventDefault();

        //validate fields
        var fail = false;
        var fail_log = '';
        var name;
        $( '#form_id' ).find( 'select, textarea, input' ).each(function(){
            if( ! $( this ).prop( 'required' )){

            } else {
                if ( ! $( this ).val() ) {
                    fail = true;
                    name = $( this ).attr( 'name' );
                    fail_log += name + " is required \n";
                }

            }
        });

        //submit if fail never got set to true
        if ( ! fail ) {
            //process form here.
        } else {
            alert( fail_log );
        }

});

In this case we loop all types of inputs and if they are required, we check if they have a value, and if not, a notice that they are required is added to the alert that will run.

Note that this, example assumes the form will be proceed inside the positive conditional via AJAX or similar. If you are submitting via traditional methods, move the second line, event.preventDefault(); to inside the negative conditional.

Is there any difference between "!=" and "<>" in Oracle Sql?

At university we were taught 'best practice' was to use != when working for employers, though all the operators above have the same functionality.

IntelliJ can't recognize JavaFX 11 with OpenJDK 11

Quick summary, you can do either:

Include the JavaFX modules via --module-path and --add-modules like in José's answer.

OR
Once you have JavaFX libraries added to your project (either manually or via maven/gradle import), add the module-info.java file similar to the one specified in this answer. (Note that this solution makes your app modular, so if you use other libraries, you will also need to add statements to require their modules inside the module-info.java file).

This answer is a supplement to Jose's answer.

The situation is this:

You are using a recent Java version, e.g. 13.
You have a JavaFX application as a Maven project.
In your Maven project you have the JavaFX plugin configured and JavaFX dependencies setup as per Jose's answer.
You go to the source code of your main class which extends Application, you right-click on it and try to run it.
You get an IllegalAccessError involving an "unnamed module" when trying to launch the app.

Excerpt for a stack trace generating an IllegalAccessError when trying to run a JavaFX app from Intellij Idea:

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:464)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:363)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1051)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:900)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:195)
    at java.base/java.lang.Thread.run(Thread.java:830)
Caused by: java.lang.IllegalAccessError: class com.sun.javafx.fxml.FXMLLoaderHelper (in unnamed module @0x45069d0e) cannot access class com.sun.javafx.util.Utils (in module javafx.graphics) because module javafx.graphics does not export com.sun.javafx.util to unnamed module @0x45069d0e
    at com.sun.javafx.fxml.FXMLLoaderHelper.<clinit>(FXMLLoaderHelper.java:38)
    at javafx.fxml.FXMLLoader.<clinit>(FXMLLoader.java:2056)
    at org.jewelsea.demo.javafx.springboot.Main.start(Main.java:13)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:846)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:455)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
Exception running application org.jewelsea.demo.javafx.springboot.Main

OK, now you are kind of stuck and have no clue what is going on.

What has actually happened is this:

Maven has successfully downloaded the JavaFX dependencies for your application, so you don't need to separately download the dependencies or install a JavaFX SDK or module distribution or anything like that.
Idea has successfully imported the modules as dependencies to your project, so everything compiles OK and all of the code completion and everything works fine.

So it seems everything should be OK. BUT, when you run your application, the code in the JavaFX modules is failing when trying to use reflection to instantiate instances of your application class (when you invoke launch) and your FXML controller classes (when you load FXML). Without some help, this use of reflection can fail in some cases, generating the obscure IllegalAccessError. This is due to a Java module system security feature which does not allow code from other modules to use reflection on your classes unless you explicitly allow it (and the JavaFX application launcher and FXMLLoader both require reflection in their current implementation in order for them to function correctly).

This is where some of the other answers to this question, which reference module-info.java, come into the picture.

So let's take a crash course in Java modules:

https://www.baeldung.com/java-9-modularity

The key part is this:

4.9. Opens

If we need to allow reflection of private types, but we don't want all of our code exposed, we can use the opens directive to expose specific packages.

But remember, this will open the package up to the entire world, so make sure that is what you want:
module my.module { opens com.my.package; }

So, perhaps you don't want to open your package to the entire world, then you can do:

4.10. Opens … To

Okay, so reflection is great sometimes, but we still want as much security as we can get from encapsulation. We can selectively open our packages to a pre-approved list of modules, in this case, using the opens…to directive:

module my.module { opens com.my.package to moduleOne, moduleTwo, etc.; }

So, you end up creating a src/main/java/module-info.java class which looks like this:

module org.jewelsea.demo.javafx.springboot {
    requires javafx.fxml;
    requires javafx.controls;
    requires javafx.graphics;
    opens org.jewelsea.demo.javafx.springboot to javafx.graphics,javafx.fxml;
}

Where, org.jewelsea.demo.javafx.springboot is the name of the package which contains the JavaFX Application class and JavaFX Controller classes (replace this with the appropriate package name for your application). This tells the Java runtime that it is OK for classes in the javafx.graphics and javafx.fxml to invoke reflection on the classes in your org.jewelsea.demo.javafx.springboot package. Once this is done, and the application is compiled and re-run things will work fine and the IllegalAccessError generated by JavaFX's use of reflection will no longer occur.

But what if you don't want to create a module-info.java file

If instead of using the the Run button in the top toolbar of IDE to run your application class directly, you instead:

Went to the Maven window in the side of the IDE.
Chose the javafx maven plugin target javafx.run.
Right-clicked on that and chose either Run Maven Build or Debug....

Then the app will run without the module-info.java file. I guess this is because the maven plugin is smart enough to dynamically include some kind of settings which allows the app to be reflected on by the JavaFX classes even without a module-info.java file, though I don't know how this is accomplished.

To get that setting transferred to the Run button in the top toolbar, right-click on the javafx.run Maven target and choose the option to Create Run/Debug Configuration for the target. Then you can just choose Run from the top toolbar to execute the Maven target.

Vertically centering Bootstrap modal window

The best solution to centralize your modal with width and height is, in css add and in modal add this 'centralize' as a class..

.centralize{
   position:absolute;
   left:50%;
   top:50%;

   background-color:#fff;
   transform: translate(-50%, -50%);
   width: 40%; //specify watever u want
   height: 50%;
   }

String field value length in mongoDB

This query will give both field value and length:

db.usercollection.aggregate([
{
    $project: {
        "name": 1,
        "length": { $strLenCP: "$name" }
    }} ])

How to index an element of a list object in R

Indexing a list is done using double bracket, i.e. hypo_list[[1]] (e.g. have a look here: http://www.r-tutor.com/r-introduction/list). BTW: read.table does not return a table but a dataframe (see value section in ?read.table). So you will have a list of dataframes, rather than a list of table objects. The principal mechanism is identical for tables and dataframes though.

Note: In R, the index for the first entry is a 1 (not 0 like in some other languages).

Dataframes

l <- list(anscombe, iris)   # put dfs in list
l[[1]]             # returns anscombe dataframe

anscombe[1:2, 2]   # access first two rows and second column of dataset
[1] 10  8

l[[1]][1:2, 2]     # the same but selecting the dataframe from the list first
[1] 10  8

Table objects

tbl1 <- table(sample(1:5, 50, rep=T))
tbl2 <- table(sample(1:5, 50, rep=T))
l <- list(tbl1, tbl2)  # put tables in a list

tbl1[1:2]              # access first two elements of table 1

Now with the list

l[[1]]                 # access first table from the list

1  2  3  4  5 
9 11 12  9  9 

l[[1]][1:2]            # access first two elements in first table

1  2 
9 11

How to use Python to execute a cURL command?

Some background: I went looking for exactly this question because I had to do something to retrieve content, but all I had available was an old version of python with inadequate SSL support. If you're on an older MacBook, you know what I'm talking about. In any case, curl runs fine from a shell (I suspect it has modern SSL support linked in) so sometimes you want to do this without using requests or urllib2.

You can use the subprocess module to execute curl and get at the retrieved content:

import subprocess

// 'response' contains a []byte with the retrieved content.
// use '-s' to keep curl quiet while it does its job, but
// it's useful to omit that while you're still writing code
// so you know if curl is working
response = subprocess.check_output(['curl', '-s', baseURL % page_num])

Python 3's subprocess module also contains .run() with a number of useful options. I'll leave it to someone who is actually running python 3 to provide that answer.

Hibernate openSession() vs getCurrentSession()

If we talk about SessionFactory.openSession()

It always creates a new Session object.
You need to explicitly flush and close session objects.
In single threaded environment it is slower than getCurrentSession().
You do not need to configure any property to call this method.

And If we talk about SessionFactory.getCurrentSession()

It creates a new Session if not exists, else uses same session which is in current hibernate context.
You do not need to flush and close session objects, it will be automatically taken care by Hibernate internally.
In single threaded environment it is faster than openSession().
You need to configure additional property. "hibernate.current_session_context_class" to call getCurrentSession() method, otherwise it will throw an exception.

if condition in sql server update query

Since you're using SQL 2008:

UPDATE
    table_Name

SET
    column_A  
     = CASE
        WHEN @flag = '1' THEN @new_value
        ELSE 0
    END + column_A,

    column_B  
     = CASE
        WHEN @flag = '0' THEN @new_value
        ELSE 0
    END + column_B 
WHERE
    ID = @ID

If you were using SQL 2012:

UPDATE
    table_Name
SET
    column_A  = column_A + IIF(@flag = '1', @new_value, 0),
    column_B  = column_B + IIF(@flag = '0', @new_value, 0)
WHERE
    ID = @ID

Set selected item in Android BottomNavigationView

Just adding another way to perform a selection programatically - this is probably what was the intention in the first place or maybe this was added later on.

Menu bottomNavigationMenu = myBottomNavigationMenu.getMenu();
bottomNavigationMenu.performIdentifierAction(selected_menu_item_id, 0);

The performIdentifierAction takes a Menu item id and a flag.

See the documentation for more info.

Reading Space separated input in python

If you have it in a string, you can use .split() to separate them.

>>> for string in ('Mike 18', 'Kevin 35', 'Angel 56'):
...   l = string.split()
...   print repr(l[0]), repr(int(l[1]))
...
'Mike' 18
'Kevin' 35
'Angel' 56
>>>

Difference between add(), replace(), and addToBackStack()

When We Add First Fragment --> Second Fragment using add() method

 btn_one.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(),"Click First 
Fragment",Toast.LENGTH_LONG).show();

                Fragment fragment = new SecondFragment();
                getActivity().getSupportFragmentManager().beginTransaction()
                        .add(R.id.fragment_frame, fragment, fragment.getClass().getSimpleName()).addToBackStack(null).commit();
//                        .replace(R.id.fragment_frame, fragment, fragment.getClass().getSimpleName()).addToBackStack(null).commit();

            }
        });

When we use add() in fragment

E/Keshav SecondFragment: onAttach
E/Keshav SecondFragment: onCreate
E/Keshav SecondFragment: onCreateView
E/Keshav SecondFragment: onActivityCreated
E/Keshav SecondFragment: onStart
E/Keshav SecondFragment: onResume

When we use replace() in fragment

going to first fragment to second fragment in First -->Second using replace() method

 btn_one.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(),"Click First Fragment",Toast.LENGTH_LONG).show();

                Fragment fragment = new SecondFragment();
                getActivity().getSupportFragmentManager().beginTransaction()
//                        .add(R.id.fragment_frame, fragment, fragment.getClass().getSimpleName()).addToBackStack(null).commit();
                        .replace(R.id.fragment_frame, fragment, fragment.getClass().getSimpleName()).addToBackStack(null).commit();

            }
        });

E/Keshav SecondFragment: onAttach
E/Keshav SecondFragment: onCreate

E/Keshav FirstFragment: onPause -------------------------- FirstFragment
E/Keshav FirstFragment: onStop --------------------------- FirstFragment
E/Keshav FirstFragment: onDestroyView -------------------- FirstFragment

E/Keshav SecondFragment: onCreateView
E/Keshav SecondFragment: onActivityCreated
E/Keshav SecondFragment: onStart
E/Keshav SecondFragment: onResume

In case of Replace First Fragment these method is extra called ( onPause,onStop,onDestroyView is extra called )

E/Keshav FirstFragment: onPause

E/Keshav FirstFragment: onStop

E/Keshav FirstFragment: onDestroyView

How to find index of STRING array in Java from a given value?

Refactoring the above methods and showing with the use:

private String[] languages = {"pt", "en", "es"};
private Integer indexOf(String[] arr, String str){
   for (int i = 0; i < arr.length; i++)
      if(arr[i].equals(str)) return i;
   return -1;
}
indexOf(languages, "en")

Get Mouse Position

PointerInfo a = MouseInfo.getPointerInfo();
Point b = a.getLocation();
int x = (int) b.getX();
int y = (int) b.getY();
System.out.print(y + "jjjjjjjjj");
System.out.print(x);
Robot r = new Robot();
r.mouseMove(x, y - 50);

C# Foreach statement does not contain public definition for GetEnumerator

You don't show us the declaration of carBootSaleList. However from the exception message I can see that it is of type CarBootSaleList. This type doesn't implement the IEnumerable interface and therefore cannot be used in a foreach.

Your CarBootSaleList class should implement IEnumerable<CarBootSale>:

public class CarBootSaleList : IEnumerable<CarBootSale>
{
    private List<CarBootSale> carbootsales;

    ...

    public IEnumerator<CarBootSale> GetEnumerator()
    {
        return carbootsales.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return carbootsales.GetEnumerator();
    }
}

How to restore the dump into your running mongodb

For mongoDB database restore use this command here . First go to your mongodb database location such as For Example : cd Downloads/blank_db/v34000 After that Enter mongorestore -d v34000 ./

Printing integer variable and string on same line in SQL

Double check if you have set and initial value for int and decimal values to be printed.

This sample is printing an empty line

declare @Number INT
print 'The number is : ' + CONVERT(VARCHAR, @Number)

And this sample is printing -> The number is : 1

declare @Number INT = 1
print 'The number is : ' + CONVERT(VARCHAR, @Number)

DataGridView AutoFit and Fill

Try this :

  DGV.AutoResizeColumns();
  DGV.AutoSizeColumnsMode=DataGridViewAutoSizeColumnsMode.AllCells;

How do you convert a C++ string to an int?

Perhaps I am misunderstanding the question, by why exactly would you not want to use atoi? I see no point in reinventing the wheel.

Am I just missing the point here?

Remove white space above and below large text in an inline-block element

The browser is not adding any padding. Instead, letters (even uppercase letters) are generally considerably smaller in the vertical direction than the height of the font, not to mention the line height, which is typically by default about 1.2 times the font height (font size).

There is no general solution to this because fonts are different. Even for fixed font size, the height of a letter varies by font. And uppercase letters need not have the same height in a font.

Practical solutions can be found by experimentation, but they are unavoidably font-dependent. You will need to set the line height essentially smaller than the font size. The following seems to yield the desired result in different browsers on Windows, for the Arial font:

_x000D_

span.foo_x000D_
{_x000D_
  display: inline-block;_x000D_
  font-size: 50px;_x000D_
  background-color: green;_x000D_
  line-height: 0.75em;_x000D_
  font-family: Arial;_x000D_
}_x000D_
_x000D_
span.bar_x000D_
{_x000D_
  position: relative;_x000D_
  bottom: -0.02em;_x000D_
}

_x000D_

<span class=foo><span class=bar>BIG TEXT</span></span>

_x000D_

The nested span elements are used to displace the text vertically. Otherwise, the text sits on the baseline, and under the baseline, there is room reserved for descenders (as in letters j and y).

If you look closely (with zooming), you will notice that there is very small space above and below most letters here. I have set things so that the letter “G” fits in. It extends vertically a bit farther than other uppercase letters because that way the letters look similar in height. There are similar issues with other letters, like “O”. And you need to tune the settings if you’ll need the letter “Q” since it has a descender that extends a bit below the baseline (in Arial). And of course, if you’ll ever need “É”, or almost any diacritic mark, you’re in trouble.

Difference between JSON.stringify and JSON.parse

JSON.stringify(obj [, replacer [, space]]) - Takes any serializable object and returns the JSON representation as a string.

JSON.parse(string) - Takes a well formed JSON string and returns the corresponding JavaScript object.

Verify a method call using Moq

You're checking the wrong method. Moq requires that you Setup (and then optionally Verify) the method in the dependency class.

You should be doing something more like this:

class MyClassTest
{
    [TestMethod]
    public void MyMethodTest()
    {
        string action = "test";
        Mock<SomeClass> mockSomeClass = new Mock<SomeClass>();

        mockSomeClass.Setup(mock => mock.DoSomething());

        MyClass myClass = new MyClass(mockSomeClass.Object);
        myClass.MyMethod(action);

        // Explicitly verify each expectation...
        mockSomeClass.Verify(mock => mock.DoSomething(), Times.Once());

        // ...or verify everything.
        // mockSomeClass.VerifyAll();
    }
}

In other words, you are verifying that calling MyClass#MyMethod, your class will definitely call SomeClass#DoSomething once in that process. Note that you don't need the Times argument; I was just demonstrating its value.

Ant: How to execute a command for each file in directory?

Short Answer

Use <foreach> with a nested <FileSet>

Foreach requires ant-contrib.

Updated Example for recent ant-contrib:

<target name="foo">
  <foreach target="bar" param="theFile">
    <fileset dir="${server.src}" casesensitive="yes">
      <include name="**/*.java"/>
      <exclude name="**/*Test*"/>
    </fileset>
  </foreach>
</target>

<target name="bar">
  <echo message="${theFile}"/>
</target>

This will antcall the target "bar" with the ${theFile} resulting in the current file.

Matplotlib connect scatterplot points with line - Python

In addition to what provided in the other answers, the keyword "zorder" allows one to decide the order in which different objects are plotted vertically. E.g.:

plt.plot(x,y,zorder=1) 
plt.scatter(x,y,zorder=2)

plots the scatter symbols on top of the line, while

plt.plot(x,y,zorder=2)
plt.scatter(x,y,zorder=1)

plots the line over the scatter symbols.

See, e.g., the zorder demo

What causes the Broken Pipe Error?

Maybe the 40 bytes fits into the pipe buffer, and the 40000 bytes doesn't?

Edit:

The sending process is sent a SIGPIPE signal when you try to write to a closed pipe. I don't know exactly when the signal is sent, or what effect the pipe buffer has on this. You may be able to recover by trapping the signal with the sigaction call.

To check if string contains particular word

.contains() is perfectly valid and a good way to check.

(http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/String.html#contains(java.lang.CharSequence))

Since you didn't post the error, I guess d is either null or you are getting the "Cannot refer to a non-final variable inside an inner class defined in a different method" error.

To make sure it's not null, first check for null in the if statement. If it's the other error, make sure d is declared as final or is a member variable of your class. Ditto for c.

How do you copy the contents of an array to a std::vector in C++ without looping?

Assuming you know how big the item in the vector are:

std::vector<int> myArray;
myArray.resize (item_count, 0);
memcpy (&myArray.front(), source, item_count * sizeof(int));

http://www.cppreference.com/wiki/stl/vector/start

How do I specify the JDK for a GlassFish domain?

Here you can find how to set path to JDK for Glassfish: http://www.devdaily.com/blog/post/java/fixing-glassfish-jdk-path-problem-solved

Check

glassfish\config\asenv.bat

where java path is configured

REM set AS_JAVA=C:\Program Files\Java\jdk1.6.0_04\jre/..
set AS_JAVA=C:\Program Files\Java\jdk1.5.0_16

Registry key Error: Java version has value '1.8', but '1.7' is required

My short contribution, for sharing the same problem with Talend Open Studio 64 bit version.

Launch ..\TOS_DI-Win32-20150702_1326-V6.0.0\TOS_DI-win-x86_64.exe manually (not link an startup Windows menu)
and this registry error message appears

To resolve this, remove all java.exe, javaw.exe and javaws.exe files on c:\ProgramData\Oracle\Java\javapath\

and TOS start with 64 bits version correctly !

Where to get this Java.exe file for a SQL Developer installation

you should browse to where java installed, then go to bin directory which contains the java.exe file.

example - C:\Program Files\Java\jdk1.6.0_03\bin\java.exe

but you should run your SQL Developer as Administrator

Java String array: is there a size of method?

The answer is "All of them". A java array is allocated with a fixed number of element slots. The "length" attribute will tell you how many. That number is immutable for the life of the array. For a resizable equivalent, you need one of the java.util.List classes - where you can use the size() method to find out how many elements are in use.

However, there's "In use" and then there's In Use. In an class object array, you can have element slots whose elements are null objects, so even though they count in the length attribute, but most people's definitions, they're not in use (YMMV, depending on the application). There's no builtin function for returning the null/non-null counts.

List objects have yet another definition of "In Use". To avoid excessive creation/destruction of the underlying storage structures, there's typically some padding in these classes. It's used internally, but isn't counted in the returned size() method. And if you attempt to access those items without expanding the List (via the add methods), you'll get an illegal index exception.

So for Lists, you can have "In Use" for non-null, committed elements, All committed elements (including null elements), or All elements, including the expansion space presently allocated.

Cannot deserialize the current JSON array (e.g. [1,2,3])

This could be You

Before trying to consume your json object with another object just check that the api is returning raw json via the browser api/rootobject, for my case i found out that the underlying data provider mssqlserver was not running and throw an unhanded exception !

as simple as that :)

How to pass an array to a function in VBA?

This seems unnecessary, but VBA is a strange place. If you declare an array variable, then set it using Array() then pass the variable into your function, VBA will be happy.

Sub test()
    Dim fString As String
    Dim arr() As Variant
    arr = Array("foo", "bar")
    fString = processArr(arr)
End Sub

Also your function processArr() could be written as:

Function processArr(arr() As Variant) As String
    processArr = Replace(Join(arr()), " ", "")
End Function

If you are into the whole brevity thing.

React.js: How to append a component on click?

As @Alex McMillan mentioned, use state to dictate what should be rendered in the dom.

In the example below I have an input field and I want to add a second one when the user clicks the button, the onClick event handler calls handleAddSecondInput( ) which changes inputLinkClicked to true. I am using a ternary operator to check for the truthy state, which renders the second input field

class HealthConditions extends React.Component {
  constructor(props) {
    super(props);


    this.state = {
      inputLinkClicked: false
    }
  }

  handleAddSecondInput() {
    this.setState({
      inputLinkClicked: true
    })
  }


  render() {
    return(
      <main id="wrapper" className="" data-reset-cookie-tab>
        <div id="content" role="main">
          <div className="inner-block">

            <H1Heading title="Tell us about any disabilities, illnesses or ongoing conditions"/>

            <InputField label="Name of condition"
              InputType="text"
              InputId="id-condition"
              InputName="condition"
            />

            {
              this.state.inputLinkClicked?

              <InputField label=""
                InputType="text"
                InputId="id-condition2"
                InputName="condition2"
              />

              :

              <div></div>
            }

            <button
              type="button"
              className="make-button-link"
              data-add-button=""
              href="#"
              onClick={this.handleAddSecondInput}
            >
              Add a condition
            </button>

            <FormButton buttonLabel="Next"
              handleSubmit={this.handleSubmit}
              linkto={
                this.state.illnessOrDisability === 'true' ?
                "/404"
                :
                "/add-your-details"
              }
            />

            <BackLink backLink="/add-your-details" />

          </div>
         </div>
      </main>
    );
  }
}

SonarQube Exclude a directory

Easiest way is to go to the server URL after starting the server(localhost:8080) then login as admin,Go to settings>Exclusions> Source File Exclusions- Add your packages here. Restart the server.

Install python 2.6 in CentOS

You could also use the EPEL-repository, and then do sudo yum install python26 to install python 2.6

How can I initialize a String array with length 0 in Java?

You can use ArrayUtils.EMPTY_STRING_ARRAY from org.apache.commons.lang3

import org.apache.commons.lang3.ArrayUtils;

    class Scratch {
        public static void main(String[] args) {
            String[] strings = ArrayUtils.EMPTY_STRING_ARRAY;
        }
    }

Sort hash by key, return hash in Ruby

Note: Ruby >= 1.9.2 has an order-preserving hash: the order keys are inserted will be the order they are enumerated. The below applies to older versions or to backward-compatible code.

There is no concept of a sorted hash. So no, what you're doing isn't right.

If you want it sorted for display, return a string:

"{" + h.sort.map{|k,v| "#{k.inspect}=>#{v.inspect}"}.join(", ") + "}"

or, if you want the keys in order:

h.keys.sort

or, if you want to access the elements in order:

h.sort.map do |key,value|
  # keys will arrive in order to this block, with their associated value.
end

but in summary, it makes no sense to talk about a sorted hash. From the docs, "The order in which you traverse a hash by either key or value may seem arbitrary, and will generally not be in the insertion order." So inserting keys in a specific order into the hash won't help.

Error: Cannot find module 'webpack'

I solved the same problem by reinstalling, execute these commands

rm -Rf node_modules
rm -f package-lock.json
npm install

rmis always a dangerous command, especially with -f, please notice that before executing it!!!!!

Determine number of pages in a PDF file

One Line:

int pdfPageCount = System.IO.File.ReadAllText("example.pdf").Split(new string[] { "/Type /Page" }, StringSplitOptions.None).Count()-2;

Recommended: ITEXTSHARP

How to copy a dictionary and only edit the copy

Python never implicitly copies objects. When you set dict2 = dict1, you are making them refer to the same exact dict object, so when you mutate it, all references to it keep referring to the object in its current state.

If you want to copy the dict (which is rare), you have to do so explicitly with

dict2 = dict(dict1)

dict2 = dict1.copy()

How do I prevent Eclipse from hanging on startup?

In my case similar symptoms were caused by some rogue git repository with a ton of junk system files.

Universal remedy, as mentioned above, is to use Process Monitor to discover offending files. It's useful to set the following 2-line filter:

Process Name is eclipse.exe
Process Name is javaw.exe

Javascript: How to pass a function with string parameters as a parameter to another function

Me, I'd do it something like this:

HTML:

onclick="myfunction({path:'/myController/myAction', ok:myfunctionOnOk, okArgs:['/myController2/myAction2','myParameter2'], cancel:myfunctionOnCancel, cancelArgs:['/myController3/myAction3','myParameter3']);"

JS:

function myfunction(params)
{
  var path = params.path;

  /* do stuff */

  // on ok condition 
  params.ok(params.okArgs);

  // on cancel condition
  params.cancel(params.cancelArgs);  
}

But then I'd also probable be binding a closure to a custom subscribed event. You need to add some detail to the question really, but being first-class functions are easily passable and getting params to them can be done any number of ways. I would avoid passing them as string labels though, the indirection is error prone.

HTML: How to center align a form

Just move align="center" to de form tag

<form align="center" action="advsearcher.php" method="get">
    Search this website:<input type="text" name="search" />
    <input type="submit" value="Search"/>
</form>

What is the best way to connect and use a sqlite database from C#

There's also now this option: http://code.google.com/p/csharp-sqlite/ - a complete port of SQLite to C#.

Change WPF window background image in C# code

The problem is the way you are using it in code. Just try the below code

public partial class MainView : Window
{
    public MainView()
    {
        InitializeComponent();

        ImageBrush myBrush = new ImageBrush();
        myBrush.ImageSource =
            new BitmapImage(new Uri("pack://application:,,,/icon.jpg", UriKind.Absolute));
        this.Background = myBrush;
    }
}

You can find more details regarding this in
http://msdn.microsoft.com/en-us/library/aa970069.aspx

How to cancel a local git commit

Use --soft instead of --hard flag:

git reset --soft HEAD^

How to create a testflight invitation code?

after you add the user for testing. the user should get an email. open that email by your iOS device, then click "Start testing" it will bring you to testFlight to download the app directly. If you open that email via computer, and then click "Start testing" it will show you another page which have the instruction of how to install the app. and that invitation code is on the last line. those All upper case letters is the code.

How to delete an SVN project from SVN repository

"Obliberating" contents from a svn repository, i.e. wiping this contents from the disc, can be done as described in this article http://www.limilabs.com/blog/how-to-permanently-remove-svn-folder

It requires access to the server side svn repository, thus you must have some admin privileges.

It works by (a) dumping the repository content into a file, (b) excluding some contents and (c) wiping and re-creating the plain repository again and eventually by (d) loading the filtered repository contents:

svnadmin dump "path/to/svnrepo" > svnrepo.txt                    // (a)
svndumpfilter exclude "my/folder" < svnrepo.txt > filtered.txt   // (b)
rm -rf "path/to/svnrepo" && svnadmin create "path/to/svnrepo"    // (c)
svnadmin load "path/to/svnrepo" < filtered.txt                   // (d)

The repository counter is unchanged by this operations. However, your repository is now "missing" all those revision numbers used to create that contents you removed in step (b).

Subversion 1.7.5 appears to handle this "missing" revisions pretty well. Using "svn ls -r $missing" for example, reports the very same as "svn ls -r $(( missing - 1))".

Contrary to this, my (pretty old) VIEWVC reports "no contents" when querying a "missing" revision.

Setting JDK in Eclipse

JDK 1.8 have some more enrich feature which doesn't support to many eclipse .

If you didn't find java compliance level as 1.8 in java compiler ,then go ahead and install the below eclipse 32bit or 64 bit depending on your system supports.

Install jdk 1.8 and then set the JAVA_HOME and CLASSPATH in environment variable.
Download eclipse-jee-neon-3-win32 and unzip : supports to java 1.8
Or download Oracle Enterprise Pack for Eclipse (12.2.1.5) and unzip :Supports java 1.8 with 64 bit OS
Right click your project > properties
Select “Java Compiler” on left and set java compliance level to 1.8 [select from the dropdown 1.8]

Try running one java program supports to java 8 like lambda expression as below and if no compilation error ,means your eclipse supports to java 1.8, something like this:

interface testI{
    void show();
}

/*class A implements testI{
    public void show(){
        System.out.println("Hello");
    }
}*/

public class LambdaDemo1 {
    public static void main(String[] args) {
        testI test ;
        /*test= new A();
        test.show();*/
        test = () ->System.out.println("Hello,how are you?"); //lambda 
        test.show();
    }        
}

How to set background color of HTML element using css properties in JavaScript

You can use:

  <script type="text/javascript">
     Window.body.style.backgroundColor = "#5a5a5a";
  </script>

Switching the order of block elements with CSS

Possible in CSS3: http://www.w3.org/TR/css3-writing-modes/#writing-mode

Why not change the orders of the tags? Your HTML page isn't made out of stone, are they?

What do 3 dots next to a parameter type mean in Java?

Also to shed some light, it is important to know that var-arg parameters are limited to one and you can't have several var-art params. For example this is illigal:

public void myMethod(String... strings, int ... ints){
// method body
}

Difference between frontend, backend, and middleware in web development

There are in fact 3 questions in your question :

Define frontend, middle and back end
How and when do they overlap ?
Their associated usual bottlenecks.

What JB King has described is correct, but it is a particular, simple version, where in fact he mapped front, middle and bacn to an MVC layer. He mapped M to the back, V to the front, and C to the middle.

For many people, it is just fine, since they come from the ugly world where even MVC was not applied, and you could have direct DB calls in a view.

However in real, complex web applications, you indeed have two or three different layers, called front, middle and back. Each of them may have an associated database and a controller.

The front-end will be visible by the end-user. It should not be confused with the front-office, which is the UI for parameters and administration of the front. The front-end will usually be some kind of CMS or e-commerce Platform (Magento, etc.)

The middle-end is not compulsory and is where the business logics is. It will be based on a PIM, a MDM tool, or some kind of custom database where you enrich your produts or your articles (for CMS). It'll also be the place where you code business functions that need to be shared between differents frontends (for instance between the PC frontend and the API-based mobile application). Sometimes, an ESB or tool like ActiveMQ will be your middle-end

The back-end will be a 3rd layer, surrouding your source database or your ERP. It may be jsut the API wrting to and reading from your ERP. It may be your supplier DB, if you are doing e-commerce. In fact, it really depends on web projects, but it is always a central repository. It'll be accessed either through a DB call, through an API, or an Hibernate layer, or a full-featured back-end application

This description means that answering the other 2 questions is not possible in this thread, as bottlenecks really depend on what your 3 ends contain : what JB King wrote remains true for simple MVC architectures

at the time the question was asked (5 years ago), maybe the MVC pattern was not yet so widely adopted. Now, there is absolutely no reason why the MVC pattern would not be followed and a view would be tied to DB calls. If you read the question "Are there cases where they MUST overlap, and frontend/backend cannot be separated?" in a broader sense, with 3 different components, then there times when the 3 layers architecture is useless of course. Think of a simple personal blog, you'll not need to pull external data or poll RabbitMQ queues.

Scroll to the top of the page after render in react.js

Nothing worked for me but:

componentDidMount(){

    $( document ).ready(function() {
        window.scrollTo(0,0);
    });
}

Why do we assign a parent reference to the child object in Java?

This situation happens when you have several implementations. Let me explain. Supppose you have several sorting algorithm and you want to choose at runtime the one to implement, or you want to give to someone else the capability to add his implementation. To solve this problem you usually create an abstract class (Parent) and have different implementation (Child). If you write:

Child c = new Child();

you bind your implementation to Child class and you can't change it anymore. Otherwise if you use:

Parent p = new Child();

as long as Child extends Parent you can change it in the future without modifying the code.

The same thing can be done using interfaces: Parent isn't anymore a class but a java Interface.

In general you can use this approch in DAO pattern where you want to have several DB dependent implementations. You can give a look at FactoryPatter or AbstractFactory Pattern. Hope this can help you.

How to check if image exists with given url?

From here:

// when the DOM is ready
$(function () {
  var img = new Image();
  // wrap our new image in jQuery, then:
  $(img)
    // once the image has loaded, execute this code
    .load(function () {
      // set the image hidden by default    
      $(this).hide();
      // with the holding div #loader, apply:
      $('#loader')
        // remove the loading class (so no background spinner), 
        .removeClass('loading')
        // then insert our image
        .append(this);
      // fade our image in to create a nice effect
      $(this).fadeIn();
    })
    // if there was an error loading the image, react accordingly
    .error(function () {
      // notify the user that the image could not be loaded
    })
    // *finally*, set the src attribute of the new image to our image
    .attr('src', 'images/headshot.jpg');
});

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