Programs & Examples On #Raii

Resource Acquisition Is Initialization (RAII) is a common idiom used in C++ to manage the lifetime of resources, including memory allocations, file handles or database connections. In brief, every resource should be wrapped in an owning class, whose lifetime controls the lifetime of the resource.

throwing exceptions out of a destructor

As an addition to the main answers, which are good, comprehensive and accurate, I would like to comment about the article you reference - the one that says "throwing exceptions in destructors is not so bad".

The article takes the line "what are the alternatives to throwing exceptions", and lists some problems with each of the alternatives. Having done so it concludes that because we can't find a problem-free alternative we should keep throwing exceptions.

The trouble is is that none of the problems it lists with the alternatives are anywhere near as bad as the exception behaviour, which, let's remember, is "undefined behaviour of your program". Some of the author's objections include "aesthetically ugly" and "encourage bad style". Now which would you rather have? A program with bad style, or one which exhibited undefined behaviour?

Does C++ support 'finally' blocks? (And what's this 'RAII' I keep hearing about?)

Not really, but you can emulate them to some extend, for example:

int * array = new int[10000000];
try {
  // Some code that can throw exceptions
  // ...
  throw std::exception();
  // ...
} catch (...) {
  // The finally-block (if an exception is thrown)
  delete[] array;
  // re-throw the exception.
  throw; 
}
// The finally-block (if no exception was thrown)
delete[] array;

Note that the finally-block might itself throw an exception before the original exception is re-thrown, thereby discarding the original exception. This is the exact same behavior as in a Java finally-block. Also, you cannot use return inside the try&catch blocks.

General guidelines to avoid memory leaks in C++

If you can, use boost shared_ptr and standard C++ auto_ptr. Those convey ownership semantics.

When you return an auto_ptr, you are telling the caller that you are giving them ownership of the memory.

When you return a shared_ptr, you are telling the caller that you have a reference to it and they take part of the ownership, but it isn't solely their responsibility.

These semantics also apply to parameters. If the caller passes you an auto_ptr, they are giving you ownership.

How can I show a message box with two buttons?

Cannot be done. MsgBox buttons can only have specific values.
You'll have to roll your own form for this.

To create a MsgBox with two options (Yes/No):

MsgBox("Some Text", vbYesNo)

Android - border for button

If your button does not require a transparent background, then you can create an illusion of a border using a Frame Layout. Just adjust the FrameLayout's "padding" attribute to change the thickness of the border.

<FrameLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="1sp"
        android:background="#000000">
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Your text goes here"
            android:background="@color/white"
            android:textColor="@color/black"
            android:padding="10sp"
            />
</FrameLayout>

I'm not sure if the shape xml files have dynamically-editable border colors. But I do know that with this solution, you can dynamically change the color of the border by setting the FrameLayout background.

Sql Server equivalent of a COUNTIF aggregate function

Why not like this?

SELECT count(1)
FROM AD_CurrentView
WHERE myColumn=1

VBA Public Array : how to?

Declare array as global across subs in a application:

Public GlobalArray(10) as String
GlobalArray = Array('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L')

Sub DisplayArray()
    Dim i As Integer

    For i = 0 to UBound(GlobalArray, 1)
        MsgBox GlobalArray(i)

    Next i
End Sub

Method 2: Pass an array to sub. Use ParamArray.

Sub DisplayArray(Name As String, ParamArray Arr() As Variant)
    Dim i As Integer

    For i = 0 To UBound(Arr())
        MsgBox Name & ": " & Arr(i)
    Next i
End Sub

ParamArray must be the last parameter.

Run cURL commands from Windows console

I have also found that if I put the cygwin bin on my windows path I can run curl from a windows command line. It also will give you access to things like ls and grep

What is the purpose of a self executing function in javascript?

(function(){
    var foo = {
        name: 'bob'
    };
    console.log(foo.name); // bob
})();
console.log(foo.name); // Reference error

Actually, the above function will be treated as function expression without a name.

The main purpose of wrapping a function with close and open parenthesis is to avoid polluting the global space.

The variables and functions inside the function expression became private (i.e) they will not be available outside of the function.

Tried to Load Angular More Than Once

In my case I was getting this error while using jquery as well as angular js on the page.

<script src="http://code.jquery.com/jquery-2.1.3.min.js" type="text/javascript"></script>
<script src="js/angular.js" type="text/javascript"></script>
<script src="js/angular-route.js" type="text/javascript"></script>

I removed :

<script src="http://code.jquery.com/jquery-2.1.3.min.js" type="text/javascript"></script>

And the warning disappeared.

Serializing with Jackson (JSON) - getting "No serializer found"?

Here are the three options:

  1. Data/class that's been accessed needs to be public
  2. If not public, add getters & setters
  3. Or add @JsonIgnore("context")

Delete newline in Vim

set backspace=indent,eol,start

in your .vimrc will allow you to use backspace and delete on \n (newline) in insert mode.

set whichwrap+=<,>,h,l,[,]

will allow you to delete the previous LF in normal mode with X (when in col 1).

Create JSON object dynamically via JavaScript (Without concate strings)

This is what you need!

function onGeneratedRow(columnsResult)
{
    var jsonData = {};
    columnsResult.forEach(function(column) 
    {
        var columnName = column.metadata.colName;
        jsonData[columnName] = column.value;
    });
    viewData.employees.push(jsonData);
 }

MySQL: How to reset or change the MySQL root password?

I am sharing the step by step final solution to reset a MySQL password in Linux Ubuntu.

Reference taken from blog (dbrnd.com)

Step 1: Stop MySQL Service.

sudo stop mysql

Step 2: Kill all running mysqld.

sudo killall -9 mysqld

Step 3: Starting mysqld in Safe mode.

sudo mysqld_safe --skip-grant-tables --skip-networking &

Step 4: Start mysql client

mysql -u root

Step 5: After successful login, please execute this command to change any password.

FLUSH PRIVILEGES;

Step 6: You can update mysql root password .

UPDATE mysql.user SET Password=PASSWORD('newpwd') WHERE User='root';

Note: On MySQL 5.7, column Password is called authentication_string.

Step 7: Please execute this command.

FLUSH PRIVILEGES;

How to let an ASMX file output JSON

This is probably old news by now, but the magic seems to be:

  • [ScriptService] attribute on web service class
  • [ScriptMethod(UseHttpGet = true, ResponseFormat = ResponseFormat.Json)] on method
  • Content-type: application/json in request

With those pieces in place, a GET request is successful.

For a HTTP POST

  • [ScriptMethod(UseHttpGet = false, ResponseFormat = ResponseFormat.Json)] on method

and on the client side (assuming your webmethod is called MethodName, and it takes a single parameter called searchString):

        $.ajax({
            url: "MyWebService.asmx/MethodName",
            type: "POST",
            contentType: "application/json",
            data: JSON.stringify({ searchString: q }),
            success: function (response) {                  
            },
            error: function (jqXHR, textStatus, errorThrown) {
                alert(textStatus + ": " + jqXHR.responseText);
            }
        });

What's the difference between subprocess Popen and call (how can I use them)?

There are two ways to do the redirect. Both apply to either subprocess.Popen or subprocess.call.

  1. Set the keyword argument shell = True or executable = /path/to/the/shell and specify the command just as you have it there.

  2. Since you're just redirecting the output to a file, set the keyword argument

    stdout = an_open_writeable_file_object
    

    where the object points to the output file.

subprocess.Popen is more general than subprocess.call.

Popen doesn't block, allowing you to interact with the process while it's running, or continue with other things in your Python program. The call to Popen returns a Popen object.

call does block. While it supports all the same arguments as the Popen constructor, so you can still set the process' output, environmental variables, etc., your script waits for the program to complete, and call returns a code representing the process' exit status.

returncode = call(*args, **kwargs) 

is basically the same as calling

returncode = Popen(*args, **kwargs).wait()

call is just a convenience function. It's implementation in CPython is in subprocess.py:

def call(*popenargs, timeout=None, **kwargs):
    """Run command with arguments.  Wait for command to complete or
    timeout, then return the returncode attribute.

    The arguments are the same as for the Popen constructor.  Example:

    retcode = call(["ls", "-l"])
    """
    with Popen(*popenargs, **kwargs) as p:
        try:
            return p.wait(timeout=timeout)
        except:
            p.kill()
            p.wait()
            raise

As you can see, it's a thin wrapper around Popen.

Java - Check if input is a positive integer, negative integer, natural number and so on.

Use like below code.

if(number >=0 ) {
            System.out.println("Number is natural and positive.");
}

inline if statement java, why is not working

Syntax is Shown below:

"your condition"? "step if true":"step if condition fails"

How to delete rows in tables that contain foreign keys to other tables

Need to set the foreign key option as on delete cascade... in tables which contains foreign key columns.... It need to set at the time of table creation or add later using ALTER table

How can I create a correlation matrix in R?

An example,

 d <- data.frame(x1=rnorm(10),
                 x2=rnorm(10),
                 x3=rnorm(10))
cor(d) # get correlations (returns matrix)

Does VBA contain a comment block syntax?

prefix the comment with a single-quote. there is no need for an "end" tag.

'this is a comment

Extend to multiple lines using the line-continuation character, _:

'this is a multi-line _
   comment

This is an option in the toolbar to select a line(s) of code and comment/uncomment:

enter image description here

How to send and retrieve parameters using $state.go toParams and $stateParams?

None of these examples on this page worked for me. This is what I used and it worked well. Some solutions said you cannot combine url with $state.go() but this is not true. The awkward thing is you must define the params for the url and also list the params. Both must be present. Tested on Angular 1.4.8 and UI Router 0.2.15.

In the state add your params to end of state and define the params:

url: 'view?index&anotherKey',
params: {'index': null, 'anotherKey': null}

In your controller your go statement will look like this:

$state.go('view', { 'index': 123, 'anotherKey': 'This is a test' });

Then to pull the params out and use them in your new state's controller (don't forget to pass in $stateParams to your controller function):

var index = $stateParams.index;
var anotherKey = $stateParams.anotherKey;
console.log(anotherKey); //it works!

SQL SERVER DATETIME FORMAT

This is my favorite use of 112 and 114

select (convert(varchar, getdate(), 112)+ replace(convert(varchar, getdate(), 114),':','')) as 'Getdate() 

112 + 114 or YYYYMMDDHHMMSSMSS'

Result:

Getdate() 112 + 114 or YYYYMMDDHHMMSSMSS

20171016083349100

How to sort an ArrayList?

For your example, this will do the magic in Java 8

List<Double> testList = new ArrayList();
testList.sort(Comparator.naturalOrder());

But if you want to sort by some of the fields of the object you are sorting, you can do it easily by:

testList.sort(Comparator.comparing(ClassName::getFieldName));

or

 testList.sort(Comparator.comparing(ClassName::getFieldName).reversed());

or

 testList.stream().sorted(Comparator.comparing(ClassName::getFieldName).reversed()).collect(Collectors.toList());

Sources: https://docs.oracle.com/javase/8/docs/api/java/util/Comparator.html

Two's Complement in Python

in case someone needs the inverse direction too:

def num_to_bin(num, wordsize):
    if num < 0:
        num = 2**wordsize+num
    base = bin(num)[2:]
    padding_size = wordsize - len(base)
    return '0' * padding_size + base

for i in range(7, -9, -1):
    print num_to_bin(i, 4)

should output this: 0111 0110 0101 0100 0011 0010 0001 0000 1111 1110 1101 1100 1011 1010 1001 1000

Multi-Column Join in Hibernate/JPA Annotations

If this doesn't work I'm out of ideas. This way you get the 4 columns in both tables (as Bar owns them and Foo uses them to reference Bar) and the generated IDs in both entities. The set of 4 columns has to be unique in Bar so the many-to-one relation doesn't become a many-to-many.

@Embeddable
public class AnEmbeddedObject
{
    @Column(name = "column_1")
    private Long column1;
    @Column(name = "column_2")
    private Long column2;
    @Column(name = "column_3")
    private Long column3;
    @Column(name = "column_4")
    private Long column4;
}

@Entity
public class Foo
{
    @Id
    @Column(name = "id")
    @GeneratedValue(generator = "seqGen")
    @SequenceGenerator(name = "seqGen", sequenceName = "FOO_ID_SEQ", allocationSize = 1)
    private Long id;
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumns({
        @JoinColumn(name = "column_1", referencedColumnName = "column_1"),
        @JoinColumn(name = "column_2", referencedColumnName = "column_2"),
        @JoinColumn(name = "column_3", referencedColumnName = "column_3"),
        @JoinColumn(name = "column_4", referencedColumnName = "column_4")
    })
    private Bar bar;
}

@Entity
@Table(uniqueConstraints = @UniqueConstraint(columnNames = {
    "column_1",
    "column_2",
    "column_3",
    "column_4"
}))
public class Bar
{
    @Id
    @Column(name = "id")
    @GeneratedValue(generator = "seqGen")
    @SequenceGenerator(name = "seqGen", sequenceName = "BAR_ID_SEQ", allocationSize = 1)
    private Long id;
    @Embedded
    private AnEmbeddedObject anEmbeddedObject;
}

How can I update npm on Windows?

1. Installing latest npm version

npm install –g npm@latest 

(You can type "npm –version" to check that)


2. Installing Node

a. Install node new version via following URL: https://nodejs.org/en/download/current/ Follow the default choices
b. Remove C:\Users\\AppData\Roaming\NPM
c. Remove C:\Users\\AppData\Roaming\npm-cache


Optionally:

d. (Delete node_modules folder in your current project folder)
e. npm cache verify
f. npm install

Node.js heap out of memory

I've faced this same problem recently and came across to this thread but my problem was with React App. Below changes in the node start command solved my issues.

Syntax

node --max-old-space-size=<size> path-to/fileName.js

Example

node --max-old-space-size=16000 scripts/build.js

Why size is 16000 in max-old-space-size?

Basically, it varies depends on the allocated memory to that thread and your node settings.

How to verify and give right size?

This is basically stay in our engine v8. below code helps you to understand the Heap Size of your local node v8 engine.

const v8 = require('v8');
const totalHeapSize = v8.getHeapStatistics().total_available_size;
const totalHeapSizeGb = (totalHeapSize / 1024 / 1024 / 1024).toFixed(2);
console.log('totalHeapSizeGb: ', totalHeapSizeGb);

How do I get a specific range of numbers from rand()?

if you care about the quality of your random numbers don't use rand()

use some other prng like http://en.wikipedia.org/wiki/Mersenne_twister or one of the other high quality prng's out there

then just go with the modulus.

Can we convert a byte array into an InputStream in Java?

Use ByteArrayInputStream:

InputStream is = new ByteArrayInputStream(decodedBytes);

Integrating MySQL with Python in Windows

You can try to use myPySQL. It's really easy to use; no compilation for windows, and even if you need to compile it for any reason, you only need Python and Visual C installed (not mysql).

http://code.google.com/p/mypysql/

Good luck

How to display list of repositories from subversion server

Sometimes you may wish to check on the timestamp for when the repo was updated, for getting this handy info you can use the svn -v (verbose) option as in

svn list -v svn://123.123.123.123/svn/repo/path

Python slice first and last element in list

Another python3 solution uses tuple unpacking with the "*" character:

first, *_, last = range(1, 10)

How to PUT a json object with an array using curl

It should be mentioned that the Accept header tells the server something about what we are accepting back, whereas the relevant header in this context is Content-Type

It's often advisable to specify Content-Type as application/json when sending JSON. For curl the syntax is:

-H 'Content-Type: application/json'

So the complete curl command will be:

curl -H 'Content-Type: application/json' -H 'Accept: application/json' -X PUT -d '{"tags":["tag1","tag2"],"question":"Which band?","answers":[{"id":"a0","answer":"Answer1"},{"id":"a1","answer":"answer2"}]}' http://example.com/service`

How do I remedy "The breakpoint will not currently be hit. No symbols have been loaded for this document." warning?

Using Dependency Injection, Autofac in my case, to automatically resolve by scanning assemblies. One of the referenced assemblies was not getting resolved.

My fix was to directly reference a class from the assembly to force Visual Studio to load the assembly. Just having the assembly as a reference will not load the assembly when the application runs.

Is JavaScript a pass-by-reference or pass-by-value language?

Mostly simplest way

// Copy JS object without reference
var first = {"a":"value1","b":"value2"};
var clone = JSON.parse( JSON.stringify( first ) ); 

var second = ["a","b","c"];
var clone = JSON.parse( JSON.stringify( second ) ); 

Run local python script on remote server

It is possible using ssh. Python accepts hyphen(-) as argument to execute the standard input,

cat hello.py | ssh [email protected] python -

Run python --help for more info.

Convert a RGB Color Value to a Hexadecimal String

A one liner but without String.format for all RGB colors:

Color your_color = new Color(128,128,128);

String hex = "#"+Integer.toHexString(your_color.getRGB()).substring(2);

You can add a .toUpperCase()if you want to switch to capital letters. Note, that this is valid (as asked in the question) for all RGB colors.

When you have ARGB colors you can use:

Color your_color = new Color(128,128,128,128);

String buf = Integer.toHexString(your_color.getRGB());
String hex = "#"+buf.substring(buf.length()-6);

A one liner is theoretically also possible but would require to call toHexString twice. I benchmarked the ARGB solution and compared it with String.format():

enter image description here

Argument Exception "Item with Same Key has already been added"

To illustrate the problem you are having, let's look at some code...

Dictionary<string, string> test = new Dictionary<string, string>();

test.Add("Key1", "Value1");  // Works fine
test.Add("Key2", "Value2");  // Works fine
test.Add("Key1", "Value3");  // Fails because of duplicate key

The reason that a dictionary has a key/value pair is a feature so you can do this...

var myString = test["Key2"];  // myString is now Value2.

If Dictionary had 2 Key2's, it wouldn't know which one to return, so it limits you to a unique key.

Is it possible to use std::string in a constexpr?

C++20 will add constexpr strings and vectors

The following proposal has been accepted apparently: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0980r0.pdf and it adds constructors such as:

// 20.3.2.2, construct/copy/destroy
constexpr
basic_string() noexcept(noexcept(Allocator())) : basic_string(Allocator()) { }
constexpr
explicit basic_string(const Allocator& a) noexcept;
constexpr
basic_string(const basic_string& str);
constexpr
basic_string(basic_string&& str) noexcept;

in addition to constexpr versions of all / most methods.

There is no support as of GCC 9.1.0, the following fails to compile:

#include <string>

int main() {
    constexpr std::string s("abc");
}

with:

g++-9 -std=c++2a main.cpp

with error:

error: the type ‘const string’ {aka ‘const std::__cxx11::basic_string<char>’} of ‘constexpr’ variable ‘s’ is not literal

std::vector discussed at: Cannot create constexpr std::vector

Tested in Ubuntu 19.04.

Select first and last row from grouped data

Another approach with lapply and a dplyr statement. We can apply an arbitrary number of whatever summary functions to the same statement:

lapply(c(first, last), 
       function(x) df %>% group_by(id) %>% summarize_all(funs(x))) %>% 
bind_rows()

You could for example be interested in rows with the max stopSequence value as well and do:

lapply(c(first, last, max("stopSequence")), 
       function(x) df %>% group_by(id) %>% summarize_all(funs(x))) %>%
bind_rows()

How to enable cross-origin resource sharing (CORS) in the express.js framework on node.js

app.use(function(req, res, next) {
var allowedOrigins = [
  "http://localhost:4200"
];
var origin = req.headers.origin;
console.log(origin)
console.log(allowedOrigins.indexOf(origin) > -1)
// Website you wish to allow to
if (allowedOrigins.indexOf(origin) > -1) {
  res.setHeader("Access-Control-Allow-Origin", origin);
}

// res.setHeader("Access-Control-Allow-Origin", "http://localhost:4200");

// Request methods you wish to allow
res.setHeader(
  "Access-Control-Allow-Methods",
  "GET, POST, OPTIONS, PUT, PATCH, DELETE"
);

// Request headers you wish to allow
res.setHeader(
  "Access-Control-Allow-Headers",
  "X-Requested-With,content-type,Authorization"
);

// Set to true if you need the website to include cookies in the requests sent
// to the API (e.g. in case you use sessions)
res.setHeader("Access-Control-Allow-Credentials", true);

// Pass to next layer of middleware
next();

});

Add this code in your index.js or server.js file and change the allowed origin array according to your requirement.

Rails how to run rake task

Rake::Task['reklamer:orville'].invoke

or

Rake::Task['reklamer:orville'].invoke(args)

Android "hello world" pushnotification example

Overview of gcm: You send a request to google server from your android phone. You receive a registration id as a response. You will then have to send this registration id to the server from where you wish to send notifications to the mobile. Using this registration id you can then send notification to the device.

Answer:

  1. To send a notification you send the data(message) with the registration id of the device to https://android.googleapis.com/gcm/send. (use curl in php).
  2. To receive notification and registration etc, thats all you will be requiring.
  3. You will have to store the registration id on the device as well as on server. If you use GCM.jar the registration id is stored in preferences. If you wish you can save it in your local database as well.

Can't connect to local MySQL server through socket '/var/mysql/mysql.sock' (38)

Try running following command:

sudo /etc/init.d/mysql start

How to set password for Redis?

i couldnt find though what i should add exactly to the configuration file to set up the password.

Configuration file should be located at /etc/redis/redis.conf and password can be set up in SECURITY section which should be located between REPLICATION and LIMITS section. Password setup is done using the requirepass directive. For more information try to look at AUTH command description.

How to make a simple modal pop up form using jquery and html?

I have placed here complete bins for above query. you can check demo link too.

Demo: http://codebins.com/bin/4ldqp78/2/How%20to%20make%20a%20simple%20modal%20pop

HTML

<div id="panel">
  <input type="button" class="button" value="1" id="btn1">
  <input type="button" class="button" value="2" id="btn2">
  <input type="button" class="button" value="3" id="btn3">
  <br>
  <input type="text" id="valueFromMyModal">
  <!-- Dialog Box-->
  <div class="dialog" id="myform">
    <form>
      <label id="valueFromMyButton">
      </label>
      <input type="text" id="name">
      <div align="center">
        <input type="button" value="Ok" id="btnOK">
      </div>
    </form>
  </div>
</div>

JQuery

$(function() {
    $(".button").click(function() {
        $("#myform #valueFromMyButton").text($(this).val().trim());
        $("#myform input[type=text]").val('');
        $("#myform").show(500);
    });
    $("#btnOK").click(function() {
        $("#valueFromMyModal").val($("#myform input[type=text]").val().trim());
        $("#myform").hide(400);
    });
});

CSS

.button{
  border:1px solid #333;
  background:#6479fd;
}
.button:hover{
  background:#a4a9fd;
}
.dialog{
  border:5px solid #666;
  padding:10px;
  background:#3A3A3A;
  position:absolute;
  display:none;
}
.dialog label{
  display:inline-block;
  color:#cecece;
}
input[type=text]{
  border:1px solid #333;
  display:inline-block;
  margin:5px;
}
#btnOK{
  border:1px solid #000;
  background:#ff9999;
  margin:5px;
}

#btnOK:hover{
  border:1px solid #000;
  background:#ffacac;
}

Demo: http://codebins.com/bin/4ldqp78/2/How%20to%20make%20a%20simple%20modal%20pop

What does the [Flags] Enum Attribute mean in C#?

@Nidonocu

To add another flag to an existing set of values, use the OR assignment operator.

Mode = Mode.Read;
//Add Mode.Write
Mode |= Mode.Write;
Assert.True(((Mode & Mode.Write) == Mode.Write)
  && ((Mode & Mode.Read) == Mode.Read)));

How to modify a specified commit?

Based on Documentation

Amending the message of older or multiple commit messages

git rebase -i HEAD~3 

The above displays a list of the last 3 commits on the current branch, change 3 to something else if you want more. The list will look similar to the following:

pick e499d89 Delete CNAME
pick 0c39034 Better README
pick f7fde4a Change the commit message but push the same commit.

Replace pick with reword before each commit message you want to change. Let say you change the second commit in the list, your file will look like the following:

pick e499d89 Delete CNAME
reword 0c39034 Better README
pick f7fde4a Change the commit message but push the same commit.

Save and close the commit list file, this will pop up a new editer for you to change your commit message, change the commit message and save.

Finaly Force-push the amended commits.

git push --force

Unable to install packages in latest version of RStudio and R Version.3.1.1

My solution that worked was to open R studio options and select global miror (the field was empty before) and the error went away.

Facebook API error 191

UPDATE:
To answer the API Error Code: 191
The redirect_uri should be equal (or relative) to the Site URL.
enter image description here

Tip: Use base URLs instead of full URLs pointing to specific pages.

NOT RECOMMENDED: For example, if you use www.mydomain.com/fb/test.html as your Site URL and having www.mydomain.com/fb/secondPage.html as redirect_uri this will give you the 191 error.

RECOMMENDED: So instead have your Site URL set to a base URL like: www.mydomain.com/ OR www.mydomain.com/fb/.


I went through the Facebook Python sample application today, and I was shocked it was stating clearly that you can use http://localhost:8080/ as Site URL if you are developing locally:

Configure the Site URL, and point it to your Web Server. If you're developing locally, you can use http://localhost:8080/

While I was sure you can't do that, based on my own experience (very old test though) it seems that you actually CAN test your Facebook application locally!

So I picked up an old application of mine and edited its name, Site URL and Canvas URL: Site URL: http://localhost:80/fblocal/

I downloaded the latest Facebook PHP-SDK and threw it in my xampp/htdocs/fblocal/ folder.

But I got the same error as yours! I noticed that XAMPP is doing an automatic redirection to http://localhost/fblocal/ so I changed the setting to simply http://localhost/fblocal/ and the error was gone BUT I had to remove the application (from privacy settings) and re-install my application and here are the results:
alt text

After that, asked for the publish_stream permission, and I was able to publish to my profile (using the PHP-SDK):

$user = $facebook->getUser();
if ($user) {
    try {
        $post = $facebook->api('/me/feed', 'post', array('message'=>'Hello World, from localhost!'));
    } catch (FacebookApiException $e) {
        error_log($e);
        $user = null;
    }
}

Results: alt text

App can't be opened because it is from an unidentified developer

Control Click the application in the Applications folder, not lauchpad. Choose open and then you get an options to actually open it.

Setting an environment variable before a command in Bash is not working for the second command in a pipe

Use a shell script:

#!/bin/bash
# myscript
FOO=bar
somecommand someargs | somecommand2

> ./myscript

Is there a command to undo git init?

Git keeps all of its files in the .git directory. Just remove that one and init again.

This post well show you how to find the hide .git file on Windows, Mac OSX, Ubuntu

How to update two tables in one statement in SQL Server 2005?

You should place two update statements inside a transaction

The intel x86 emulator accelerator (HAXM installer) revision 6.0.5 is showing not compatible with windows

You likely have Hyper-V enabled. The manual installer provides this detailed notice when it refuses to install on a Windows with it on.

This computer does not support Intel Virtualization Technology (VT-x) or it is being exclusively used by Hyper-V. HAXM cannot be installed. Please ensure Hyper-V is disabled in Windows Features, or refer to the Intel HAXM documentation for more information.

.prop('checked',false) or .removeAttr('checked')?

I recommend to use both, prop and attr because I had problems with Chrome and I solved it using both functions.

if ($(':checkbox').is(':checked')){
    $(':checkbox').prop('checked', true).attr('checked', 'checked');
}
else {
    $(':checkbox').prop('checked', false).removeAttr('checked');
}

How to save a PNG image server-side, from a base64 data string

Try this:

file_put_contents('img.png', base64_decode($base64string));

file_put_contents docs

Google Maps API v3: How to remove all markers?

You need to set map null to that marker.

var markersList = [];    

function removeMarkers(markersList) {
   for(var i = 0; i < markersList.length; i++) {
      markersList[i].setMap(null);
   }
}

function addMarkers() {
   var marker = new google.maps.Marker({
        position : {
            lat : 12.374,
            lng : -11.55
        },
        map : map
       });
      markersList.push(marker);
   }

What does the keyword "transient" mean in Java?

Transient variables in Java are never serialized.

problem with php mail 'From' header

The web host is not really playing foul. It's not strictly according to the rules - but compared with some some of the amazing inventions intended to prevent spam, its not a particularly bad one.

If you really do want to send mail from '@gmail.com' why not just use the gmail SMTP service? If you can't reconfigure the server where PHP is running, then there are lots of email wrapper tools out there which allow you to specify a custom SMTP relay phpmailer springs to mind.

C.

How to add a footer to the UITableView?

I had the same problem but I replaced the following line in my header:

@interface MyController : UIViewTableViewController <UITableViewDelegate, UITableViewDataSource>

with this line and it works as expected:

@interface RequestViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>

Notice the UIViewController. Good luck :)

LabelEncoder: TypeError: '>' not supported between instances of 'float' and 'str'

As string data types have variable length, it is by default stored as object type. I faced this problem after treating missing values too. Converting all those columns to type 'category' before label encoding worked in my case.

df[cat]=df[cat].astype('category')

And then check df.dtypes and perform label encoding.

Error: Configuration with name 'default' not found in Android Studio

Removing few react-native dependencies solved the problem

Deleting these lines the problem is resolved. This line is created by rnpm link but is a bug.

compile project(':react-native-gps')
compile project(':react-native-maps')

Increase max_execution_time in PHP?

Add this to an htaccess file (and see edit notes added below):

<IfModule mod_php5.c>
   php_value post_max_size 200M
   php_value upload_max_filesize 200M
   php_value memory_limit 300M
   php_value max_execution_time 259200
   php_value max_input_time 259200
   php_value session.gc_maxlifetime 1200
</IfModule>

Additional resources and information:


2021 EDIT:

As PHP and Apache evolve and grow, I think it is important for me to take a moment to mention a few things to consider and possible "gotchas" to consider:

  • PHP can be run as a module or as CGI. It is not recommended to run as CGI as it creates a lot of opportunities for attack vectors [Read More]. Running as a module (the safer option) will trigger the settings to be used if the specific module from <IfModule is loaded.
  • The answer indicates to write mod_php5.c in the first line. If you are using PHP 7, you would replace that with mod_php7.c.
  • Sometimes after you make changes to your .htaccess file, restarting Apache or NGINX will not work. The most common reason for this is you are running PHP-FPM, which runs as a separate process. You need to restart that as well.
  • Remember these are settings that are normally defined in your php.ini config file(s). This method is usually only useful in the event your hosting provider does not give you access to change those files. In circumstances where you can edit the PHP configuration, it is recommended that you apply these settings there.
  • Finally, it's important to note that not all php.ini settings can be configured via an .htaccess file. A file list of php.ini directives can be found here, and the only ones you can change are the ones in the changeable column with the modes PHP_INI_ALL or PHP_INI_PERDIR.

How do I empty an array in JavaScript?

I'm surprised no one has suggested this yet:

let xs = [1,2,3,4];
for (let i in xs)
    delete xs[i];

This yields an array in quite a different state from the other solutions. In a sense, the array has been 'emptied':

xs
=> Array [ <4 empty slots> ]

[...xs]
=> Array [ undefined, undefined, undefined, undefined ]

xs.length
=> 4

xs[0]
=> ReferenceError: reference to undefined property xs[0]

You can produce an equivalent array with [,,,,] or Array(4)

What is the difference between ports 465 and 587?

I use port 465 all the time.

The answer by danorton is outdated. As he and Wikipedia say, port 465 was initially planned for the SMTPS encryption and quickly deprecated 15 years ago. But a lot of ISPs are still using port 465, especially to be in compliance with the current recommendations of RFC 8314, which encourages the use of implicit TLS instead of the use of the STARTTLS command with port 587. (See section 3.3). Using port 465 is the only way to begin an implicitly secure session with an SMTP server that is acting as a mail submission agent (MSA).

Basically, what RFC 8314 recommends is that cleartext email exchanges be abandoned and that all three common IETF mail protocols be used only in implicit TLS sessions for consistency when possible. The recommended secure ports, then, are 465, 993, and 995 for SMTPS, IMAP4S, and POP3S, respectively.

Although RFC 8314 certainly allows the continued use of explicit TLS with port 587 and the STARTTLS command, doing so opens up the mail user agent (MUA, the mail client) to a downgrade attack where a man-in-the-middle intercepts the STARTTLS request to upgrade to TLS security but denies it, thus forcing the session to remain in cleartext.

Python None comparison: should I use "is" or ==?

is is generally preferred when comparing arbitrary objects to singletons like None because it is faster and more predictable. is always compares by object identity, whereas what == will do depends on the exact type of the operands and even on their ordering.

This recommendation is supported by PEP 8, which explicitly states that "comparisons to singletons like None should always be done with is or is not, never the equality operators."

registerForRemoteNotificationTypes: is not supported in iOS 8.0 and later

Swift 2.0

// Checking if app is running iOS 8
    if application.respondsToSelector("isRegisteredForRemoteNotifications") {

        print("registerApplicationForPushNotifications - iOS 8")

        application.registerUserNotificationSettings(UIUserNotificationSettings(forTypes: [.Alert, .Badge, .Sound], categories: nil));
        application.registerForRemoteNotifications()

    } else {
        // Register for Push Notifications before iOS 8
        print("registerApplicationForPushNotifications - <iOS 8")
        application.registerForRemoteNotificationTypes([UIRemoteNotificationType.Alert, UIRemoteNotificationType.Badge, UIRemoteNotificationType.Sound])

    }

How do you put an image file in a json object?

I can think of doing it in two ways:

1.

Storing the file in file system in any directory (say dir1) and renaming it which ensures that the name is unique for every file (may be a timestamp) (say xyz123.jpg), and then storing this name in some DataBase. Then while generating the JSON you pull this filename and generate a complete URL (which will be http://example.com/dir1/xyz123.png )and insert it in the JSON.

2.

Base 64 Encoding, It's basically a way of encoding arbitrary binary data in ASCII text. It takes 4 characters per 3 bytes of data, plus potentially a bit of padding at the end. Essentially each 6 bits of the input is encoded in a 64-character alphabet. The "standard" alphabet uses A-Z, a-z, 0-9 and + and /, with = as a padding character. There are URL-safe variants. So this approach will allow you to put your image directly in the MongoDB, while storing it Encode the image and decode while fetching it, it has some of its own drawbacks:

  • base64 encoding makes file sizes roughly 33% larger than their original binary representations, which means more data down the wire (this might be exceptionally painful on mobile networks)
  • data URIs aren’t supported on IE6 or IE7.
  • base64 encoded data may possibly take longer to process than binary data.

Source

Converting Image to DATA URI

A.) Canvas

Load the image into an Image-Object, paint it to a canvas and convert the canvas back to a dataURL.

function convertToDataURLviaCanvas(url, callback, outputFormat){
    var img = new Image();
    img.crossOrigin = 'Anonymous';
    img.onload = function(){
        var canvas = document.createElement('CANVAS');
        var ctx = canvas.getContext('2d');
        var dataURL;
        canvas.height = this.height;
        canvas.width = this.width;
        ctx.drawImage(this, 0, 0);
        dataURL = canvas.toDataURL(outputFormat);
        callback(dataURL);
        canvas = null; 
    };
    img.src = url;
}

Usage

convertToDataURLviaCanvas('http://bit.ly/18g0VNp', function(base64Img){
    // Base64DataURL
});

Supported input formats image/png, image/jpeg, image/jpg, image/gif, image/bmp, image/tiff, image/x-icon, image/svg+xml, image/webp, image/xxx

B.) FileReader

Load the image as blob via XMLHttpRequest and use the FileReader API to convert it to a data URL.

function convertFileToBase64viaFileReader(url, callback){
    var xhr = new XMLHttpRequest();
    xhr.responseType = 'blob';
    xhr.onload = function() {
      var reader  = new FileReader();
      reader.onloadend = function () {
          callback(reader.result);
      }
      reader.readAsDataURL(xhr.response);
    };
    xhr.open('GET', url);
    xhr.send();
}

This approach

  • lacks in browser support
  • has better compression
  • works for other file types as well.

Usage

convertFileToBase64viaFileReader('http://bit.ly/18g0VNp', function(base64Img){
    // Base64DataURL
});

Source

private constructor

One common use is in the singleton pattern where you want only one instance of the class to exist. In that case, you can provide a static method which does the instantiation of the object. This way the number of objects instantiated of a particular class can be controlled.

Write-back vs Write-Through caching?

The benefit of write-through to main memory is that it simplifies the design of the computer system. With write-through, the main memory always has an up-to-date copy of the line. So when a read is done, main memory can always reply with the requested data.

If write-back is used, sometimes the up-to-date data is in a processor cache, and sometimes it is in main memory. If the data is in a processor cache, then that processor must stop main memory from replying to the read request, because the main memory might have a stale copy of the data. This is more complicated than write-through.

Also, write-through can simplify the cache coherency protocol because it doesn't need the Modify state. The Modify state records that the cache must write back the cache line before it invalidates or evicts the line. In write-through a cache line can always be invalidated without writing back since memory already has an up-to-date copy of the line.

One more thing - on a write-back architecture software that writes to memory-mapped I/O registers must take extra steps to make sure that writes are immediately sent out of the cache. Otherwise writes are not visible outside the core until the line is read by another processor or the line is evicted.

How to sum a variable by group

Another solution that returns sums by groups in a matrix or a data frame and is short and fast:

rowsum(x$Frequency, x$Category)

Can I do a max(count(*)) in SQL?

This question is old, but was referenced in a new question on dba.SE. I feel the best solutions haven't been provided, yet, so I am adding another one.

First off, assuming referential integrity (typically enforced with foreign key constraints) you do not need to join to the table movie at all. That's dead freight in your query. All answers so far fail to point that out.


Can I do a max(count(*)) in SQL?

To answer the question in the title: Yes, in Postgres 8.4 (released 2009-07-01, before this question was asked) or later you can achieve that by nesting an aggregate function in a window function:

SELECT c.yr, count(*) AS ct, max(count(*)) OVER () AS max_ct
FROM   actor   a
JOIN   casting c ON c.actorid = a.id
WHERE  a.name = 'John Travolta'
GROUP  BY c.yr;

Consider the sequence of events in a SELECT query:

The (possible) downside: window functions do not aggregate rows. You get all rows left after the aggregate step. Useful in some queries, but not ideal for this one.


To get one row with the highest count, you can use ORDER BY ct LIMIT 1 like @wolph hinted:

SELECT c.yr, count(*) AS ct
FROM   actor   a
JOIN   casting c ON c.actorid = a.id
WHERE  a.name = 'John Travolta'
GROUP  BY c.yr
ORDER  BY ct DESC
LIMIT  1;

Using only basic SQL features available in any halfway decent RDBMS - the LIMIT implementation varies:

Or you can get one row per group with the highest count with DISTINCT ON (only Postgres):


Answer

But you asked for:

... rows for which count(*) is max.

Possibly more than one. The most elegant solution is with the window function rank() in a subquery. Ryan provided a query but it can be simpler (details in my answer above):

SELECT yr, ct
FROM  (
   SELECT c.yr, count(*) AS ct, rank() OVER (ORDER BY count(*) DESC) AS rnk
   FROM   actor   a
   JOIN   casting c ON c.actorid = a.id
   WHERE  a.name = 'John Travolta'
   GROUP  BY c.yr
   ) sub
WHERE  rnk = 1;

All major RDBMS support window functions nowadays. Except MySQL and forks (MariaDB seems to have implemented them at last in version 10.2).

Return a 2d array from a function

returning an array of pointers pointing to starting elements of all rows is the only decent way of returning 2d array.

Why should hash functions use a prime number modulus?

Primes are used because you have good chances of obtaining a unique value for a typical hash-function which uses polynomials modulo P. Say, you use such hash-function for strings of length <= N, and you have a collision. That means that 2 different polynomials produce the same value modulo P. The difference of those polynomials is again a polynomial of the same degree N (or less). It has no more than N roots (this is here the nature of math shows itself, since this claim is only true for a polynomial over a field => prime number). So if N is much less than P, you are likely not to have a collision. After that, experiment can probably show that 37 is big enough to avoid collisions for a hash-table of strings which have length 5-10, and is small enough to use for calculations.

How to convert a pandas DataFrame subset of columns AND rows into a numpy array?

Use its value directly:

In [79]: df[df.c > 0.5][['b', 'e']].values
Out[79]: 
array([[ 0.98836259,  0.82403141],
       [ 0.337358  ,  0.02054435],
       [ 0.29271728,  0.37813099],
       [ 0.70033513,  0.69919695]])

How to format font style and color in echo

foreach($months as $key => $month){
  if(strpos($filename,$month)!==false){
        echo "<div style ='font:11px/21px Arial,tahoma,sans-serif;color:#ff0000'> Movie List for $key 2013</div>";
    }
}

javax.xml.bind.JAXBException: Class *** nor any of its super class is known to this context

JAX-RS implementations automatically support marshalling/unmarshalling of classes based on discoverable JAXB annotations, but because your payload is declared as Object, I think the created JAXBContext misses the Department class and when it's time to marshall it it doesn't know how.

A quick and dirty fix would be to add a XmlSeeAlso annotation to your response class:

@XmlRootElement
@XmlSeeAlso({Department.class})
public class Response implements Serializable {
  ....

or something a little more complicated would be "to enrich" the JAXB context for the Response class by using a ContextResolver:

import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.ext.ContextResolver;
import javax.ws.rs.ext.Provider;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;

@Provider
@Produces({ MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML })
public class ResponseResolver implements ContextResolver<JAXBContext> {
    private JAXBContext ctx;

    public ResponseResolver() {
        try {
            this.ctx = JAXBContext.newInstance(

                        Response.class, 
                        Department.class

                    );
        } catch (JAXBException ex) {
            throw new RuntimeException(ex);
        }
    }

    public JAXBContext getContext(Class<?> type) {
        return (type.equals(Response.class) ? ctx : null);
    }
}

Get error message if ModelState.IsValid fails?

If Modal State is not Valid & the error cannot be seen on screen because your control is in collapsed accordion, then you can return the HttpStatusCode so that the actual error message is shown if you do F12. Also you can log this error to ELMAH error log. Below is the code

if (!ModelState.IsValid)
{
              var message = string.Join(" | ", ModelState.Values
                                            .SelectMany(v => v.Errors)
                                            .Select(e => e.ErrorMessage));

                //Log This exception to ELMAH:
                Exception exception = new Exception(message.ToString());
                Elmah.ErrorSignal.FromCurrentContext().Raise(exception);

                //Return Status Code:
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest, message);
}

But please note that this code will log all validation errors. So this should be used only when such situation arises where you cannot see the errors on screen.

How to change the size of the font of a JLabel to take the maximum size

JLabel label = new JLabel("Hello World");
label.setFont(new Font("Calibri", Font.BOLD, 20));

JUnit assertEquals(double expected, double actual, double epsilon)

Epsilon is your "fuzz factor," since doubles may not be exactly equal. Epsilon lets you describe how close they have to be.

If you were expecting 3.14159 but would take anywhere from 3.14059 to 3.14259 (that is, within 0.001), then you should write something like

double myPi = 22.0d / 7.0d; //Don't use this in real life!
assertEquals(3.14159, myPi, 0.001);

(By the way, 22/7 comes out to 3.1428+, and would fail the assertion. This is a good thing.)

How to move git repository with all branches from bitbucket to github?

In case you couldn't find "Import code" button on github, you can:

  1. directly open Github Importer and enter the url. It will look like: Screenshot of github importer
  2. give it a name (or it will import the name automatically)
  3. select Public or Private repo
  4. Click Begin Import

UPDATE: Recently, Github announced the ability to "Import repositories with large files"

How to programmatically set SelectedValue of Dropdownlist when it is bound to XmlDataSource

DropDownList1.Items.FindByValue(stringValue).Selected = true; 

should work.

Extracting Ajax return data in jQuery

You can use .filter on a jQuery object that was created from the response:

success: function(data){
    //Create jQuery object from the response HTML.
    var $response=$(data);

    //Query the jQuery object for the values
    var oneval = $response.filter('#one').text();
    var subval = $response.filter('#sub').text();
}

What does "Git push non-fast-forward updates were rejected" mean?

You need to merge and resolve the conflicts locally before you push your changes to remote repo/fork.

1) pull (fetch and merge)

$ git pull remote branch 

2) Push the changes

$ git push remote branch 

Still you have a quick choice to push forcibly by using --force option but should be avoided as it may result in changes loss or affect badly on other contributors.

Capture Signature using HTML5 and iPad

The options already listed are very good, however here a few more on this topic that I've researched and came across.

1) http://perfectionkills.com/exploring-canvas-drawing-techniques/
2) http://mcc.id.au/2010/signature.html
3) https://zipso.net/a-simple-touchscreen-sketchpad-using-javascript-and-html5/

And as always you may want to save the canvas to image:
http://www.html5canvastutorials.com/advanced/html5-canvas-save-drawing-as-an-image/

good luck and happy signing

Can't access RabbitMQ web management interface after fresh install

If on Windows and installed using chocolatey make sure firewall is allowing the default ports for it:

netsh advfirewall firewall add rule name="RabbitMQ Management" dir=in action=allow protocol=TCP localport=15672
netsh advfirewall firewall add rule name="RabbitMQ" dir=in action=allow protocol=TCP localport=5672

for the remote access.

NSDate get year/month/day

Swift 2.x

extension NSDate {
    func currentDateInDayMonthYear() -> String {
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "d LLLL yyyy"
        return dateFormatter.stringFromDate(self)
    }
}

You can use it as

NSDate().currentDateInDayMonthYear()

Output

6 March 2016

ssl.SSLError: tlsv1 alert protocol version

The only thing you have to do is to install requests[security] in your virtualenv. You should not have to use Python 3 (it should work in Python 2.7). Moreover, if you are using a recent version of macOS, you don't have to use homebrew to separately install OpenSSL either.

$ virtualenv --python=/usr/bin/python tempenv  # uses system python
$ . tempenv/bin/activate
$ pip install requests
$ python
>>> import ssl
>>> ssl.OPENSSL_VERSION
'OpenSSL 0.9.8zh 14 Jan 2016'  # this is the built-in openssl
>>> import requests
>>> requests.get('https://api.github.com/users/octocat/orgs')
requests.exceptions.SSLError: HTTPSConnectionPool(host='api.github.com', port=443): Max retries exceeded with url: /users/octocat/orgs (Caused by SSLError(SSLError(1, u'[SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:590)'),))
$ pip install 'requests[security]'
$ python  # install requests[security] and try again
>>> import requests
>>> requests.get('https://api.github.com/users/octocat/orgs')
<Response [200]>

requests[security] allows requests to use the latest version of TLS when negotiating the connection. The built-in openssl on macOS supports TLS v1.2.

Before you install your own version of OpenSSL, ask this question: how is Google Chrome loading https://github.com?

What is the default font of Sublime Text?

Yes. You can use Console of Sublime with (Linux):

Ctrl + `

And type:

view.settings().get('font_face')

Get any setting the same way.

ADB Driver and Windows 8.1

Use the awesome "Universal ADB (Android Debug Bridge) Driver for Windows": https://plus.google.com/103583939320326217147/posts/BQ5iYJEaaEH https://github.com/koush/UniversalAdbDriver

  • Windows 8 compatible
  • comes signed, so does not require you to turn off windows driver signature checks

Tested under Win8.1.1 x64.

How to concatenate string and int in C?

Look at snprintf or, if GNU extensions are OK, asprintf (which will allocate memory for you).

gnuplot : plotting data from multiple input files in a single graph

You may find that gnuplot's for loops are useful in this case, if you adjust your filenames or graph titles appropriately.

e.g.

filenames = "first second third fourth fifth"
plot for [file in filenames] file."dat" using 1:2 with lines

and

filename(n) = sprintf("file_%d", n)
plot for [i=1:10] filename(i) using 1:2 with lines

Cannot redeclare function php

Remove the function and check the output of:

var_dump(function_exists('parseDate'));

In which case, change the name of the function.

If you get false, you're including the file with that function twice, replace :

include

by

include_once

And replace :

require

by

require_once

EDIT : I'm just a little too late, post before beat me to it !

Move cursor to end of file in vim

If you want to paste some clipboard content at the end of the file type:

:$ put +

$ ............ last line
put .......... paste 
+ ............ clipboard

How can I URL encode a string in Excel VBA?

Version of the above supporting UTF8:

Private Const CP_UTF8 = 65001

#If VBA7 Then
  Private Declare PtrSafe Function WideCharToMultiByte Lib "kernel32" ( _
    ByVal CodePage As Long, _
    ByVal dwFlags As Long, _
    ByVal lpWideCharStr As LongPtr, _
    ByVal cchWideChar As Long, _
    ByVal lpMultiByteStr As LongPtr, _
    ByVal cbMultiByte As Long, _
    ByVal lpDefaultChar As Long, _
    ByVal lpUsedDefaultChar As Long _
    ) As Long
#Else
  Private Declare Function WideCharToMultiByte Lib "kernel32" ( _
    ByVal CodePage As Long, _
    ByVal dwFlags As Long, _
    ByVal lpWideCharStr As Long, _
    ByVal cchWideChar As Long, _
    ByVal lpMultiByteStr As Long, _
    ByVal cbMultiByte As Long, _
    ByVal lpDefaultChar As Long, _
    ByVal lpUsedDefaultChar As Long _
    ) As Long
#End If

Public Function UTF16To8(ByVal UTF16 As String) As String
Dim sBuffer As String
Dim lLength As Long
If UTF16 <> "" Then
    #If VBA7 Then
        lLength = WideCharToMultiByte(CP_UTF8, 0, CLngPtr(StrPtr(UTF16)), -1, 0, 0, 0, 0)
    #Else
        lLength = WideCharToMultiByte(CP_UTF8, 0, StrPtr(UTF16), -1, 0, 0, 0, 0)
    #End If
    sBuffer = Space$(lLength)
    #If VBA7 Then
        lLength = WideCharToMultiByte(CP_UTF8, 0, CLngPtr(StrPtr(UTF16)), -1, CLngPtr(StrPtr(sBuffer)), LenB(sBuffer), 0, 0)
    #Else
        lLength = WideCharToMultiByte(CP_UTF8, 0, StrPtr(UTF16), -1, StrPtr(sBuffer), LenB(sBuffer), 0, 0)
    #End If
    sBuffer = StrConv(sBuffer, vbUnicode)
    UTF16To8 = Left$(sBuffer, lLength - 1)
Else
    UTF16To8 = ""
End If
End Function

Public Function URLEncode( _
   StringVal As String, _
   Optional SpaceAsPlus As Boolean = False, _
   Optional UTF8Encode As Boolean = True _
) As String

Dim StringValCopy As String: StringValCopy = IIf(UTF8Encode, UTF16To8(StringVal), StringVal)
Dim StringLen As Long: StringLen = Len(StringValCopy)

If StringLen > 0 Then
    ReDim Result(StringLen) As String
    Dim I As Long, CharCode As Integer
    Dim Char As String, Space As String

  If SpaceAsPlus Then Space = "+" Else Space = "%20"

  For I = 1 To StringLen
    Char = Mid$(StringValCopy, I, 1)
    CharCode = Asc(Char)
    Select Case CharCode
      Case 97 To 122, 65 To 90, 48 To 57, 45, 46, 95, 126
        Result(I) = Char
      Case 32
        Result(I) = Space
      Case 0 To 15
        Result(I) = "%0" & Hex(CharCode)
      Case Else
        Result(I) = "%" & Hex(CharCode)
    End Select
  Next I
  URLEncode = Join(Result, "")

End If
End Function

Enjoy!

Correct way to initialize empty slice

Empty slice and nil slice are initialized differently in Go:

var nilSlice []int 
emptySlice1 := make([]int, 0)
emptySlice2 := []int{}

fmt.Println(nilSlice == nil)    // true
fmt.Println(emptySlice1 == nil) // false
fmt.Println(emptySlice2 == nil) // false

As for all three slices, len and cap are 0.

How to import Swagger APIs into Postman?

  • Click on the orange button ("choose files")
  • Browse to the Swagger doc (swagger.yaml)
  • After selecting the file, a new collection gets created in POSTMAN. It will contain folders based on your endpoints.

You can also get some sample swagger files online to verify this(if you have errors in your swagger doc).

How to toggle boolean state of react component?

Since nobody posted this, I am posting the correct answer. If your new state update depends on the previous state, always use the functional form of setState which accepts as argument a function that returns a new state.

In your case:

this.setState(prevState => ({
  check: !prevState.check
}));

See docs


Since this answer is becoming popular, adding the approach that should be used for React Hooks (v16.8+):

If you are using the useState hook, then use the following code (in case your new state depends on the previous state):

const [check, setCheck] = useState(false);
// ...
setCheck(prevCheck => !prevCheck);

String to char array Java

A string to char array is as simple as

String str = "someString"; 
char[] charArray = str.toCharArray();

Can you explain a little more on what you are trying to do?

* Update *

if I am understanding your new comment, you can use a byte array and example is provided.

byte[] bytes = ByteBuffer.allocate(4).putInt(1695609641).array();

for (byte b : bytes) {
   System.out.format("0x%x ", b);
}

With the following output

0x65 0x10 0xf3 0x29

How do you concatenate Lists in C#?

I know this is old but I came upon this post quickly thinking Concat would be my answer. Union worked great for me. Note, it returns only unique values but knowing that I was getting unique values anyway this solution worked for me.

namespace TestProject
{
    public partial class Form1 :Form
    {
        public Form1()
        {
            InitializeComponent();

            List<string> FirstList = new List<string>();
            FirstList.Add("1234");
            FirstList.Add("4567");

            // In my code, I know I would not have this here but I put it in as a demonstration that it will not be in the secondList twice
            FirstList.Add("Three");  

            List<string> secondList = GetList(FirstList);            
            foreach (string item in secondList)
                Console.WriteLine(item);
        }

        private List<String> GetList(List<string> SortBy)
        {
            List<string> list = new List<string>();
            list.Add("One");
            list.Add("Two");
            list.Add("Three");

            list = list.Union(SortBy).ToList();

            return list;
        }
    }
}

The output is:

One
Two
Three
1234
4567

How to remove element from ArrayList by checking its value?

You would need to use an Iterator like so:

Iterator<String> iterator = a.iterator();
while(iterator.hasNext())
{
    String value = iterator.next();
    if ("abcd".equals(value))
    {
        iterator.remove();
        break;
    }
}

That being said, you can use the remove(int index) or remove(Object obj) which are provided by the ArrayList class. Note however, that calling these methods while you are iterating over the loop, will cause a ConcurrentModificationException, so this will not work:

for(String str : a)
{
    if (str.equals("acbd")
    {
        a.remove("abcd");
        break;
    }
}

But this will (since you are not iterating over the contents of the loop):

a.remove("acbd");

If you have more complex objects you would need to override the equals method.

jQuery AJAX submit form

JavaScript

(function ($) {
    var form= $('#add-form'),
      input = $('#exampleFormControlTextarea1');


   form.submit(function(event) {

       event.preventDefault(); 

       var req = $.ajax({
           url: form.attr('action'),
           type: 'POST',
           data: form.serialize()
       });
    req.done(function(data) {
       if (data === 'success') {
           var li = $('<li class="list-group-item">'+ input.val() +'</li>');
            li.hide()
                .appendTo('.list-group')
                .fadeIn();
            $('input[type="text"],textarea').val('');
        }
   });
});


}(jQuery));

HTML

    <ul class="list-group col-sm-6 float-left">
            <?php
            foreach ($data as $item) {
                echo '<li class="list-group-item">'.$item.'</li>';
            }
            ?>
        </ul>

        <form id="add-form" class="col-sm-6 float-right" action="_inc/add-new.php" method="post">
            <p class="form-group">
                <textarea class="form-control" name="message" id="exampleFormControlTextarea1" rows="3" placeholder="Is there something new?"></textarea>
            </p>
            <button type="submit" class="btn btn-danger">Add new item</button>
        </form>

Scheduling recurring task in Android

Timer

As mentioned on the javadocs you are better off using a ScheduledThreadPoolExecutor.

ScheduledThreadPoolExecutor

Use this class when your use case requires multiple worker threads and the sleep interval is small. How small ? Well, I'd say about 15 minutes. The AlarmManager starts schedule intervals at this time and it seems to suggest that for smaller sleep intervals this class can be used. I do not have data to back the last statement. It is a hunch.

Service

Your service can be closed any time by the VM. Do not use services for recurring tasks. A recurring task can start a service, which is another matter entirely.

BroadcastReciever with AlarmManager

For longer sleep intervals (>15 minutes), this is the way to go. AlarmManager already has constants ( AlarmManager.INTERVAL_DAY ) suggesting that it can trigger tasks several days after it has initially been scheduled. It can also wake up the CPU to run your code.

You should use one of those solutions based on your timing and worker thread needs.

Best way to restrict a text field to numbers only?

You can do like this to accept only Numbers in text Box,

 function onChange(event){
   var ckeckChars = /[^0-9]/gi;
   if(checkChars.test(event.target.value)) {
        event.target.value = event.target.value.replace(ckeckChars,"");
  }

Defining a percentage width for a LinearLayout?

Google introduced new API called PercentRelativeLayout

Add compile dependency like

compile 'com.android.support:percent:22.2.0'

in that PercentRelativeLayout is what we can do percentagewise layout

How to get the number of columns from a JDBC ResultSet?

This will print the data in columns and comes to new line once last column is reached.

ResultSetMetaData resultSetMetaData = res.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
for(int i =1; i<=columnCount; i++){
                if(!(i==columnCount)){

                    System.out.print(res.getString(i)+"\t");
                }
                else{
                    System.out.println(res.getString(i));
                }

            }

babel-loader jsx SyntaxError: Unexpected token

This works perfect for me

{
    test: /\.(js|jsx)$/,
    loader: 'babel-loader',
    exclude: /node_modules/,
    query: {
        presets: ['es2015','react']
    }
},

Python DNS module import error

Very possible the version of pip you're using isn't installing to the version of python you're using. I have a box where this is the case...

try:

which python

python --version

pip -V

If it looks like pip doesn't match your python, then you probably have something like the multiple versions of python and pip I found on my box...

[root@sdpipeline student]# locate bin/pip

/home/student/class/bin/pip

/home/student/class/bin/pip-2.7

/usr/bin/pip

/usr/bin/pip-python

As long as I use /home/student/class/bin/pip (2.7 that matches my python version on that box), then my imports work fine.

You can also try installing pip from source: http://www.pip-installer.org/en/latest/installing.html

There's probably a better way to do this, I'm still learning my way around too, but that's how I solved it -- hope it helps!

XML serialization in Java?

XStream is pretty good at serializing object to XML without much configuration and money! (it's under BSD license).

We used it in one of our project to replace the plain old java-serialization and it worked almost out of the box.

Which .NET Dependency Injection frameworks are worth looking into?

Ninject is great. It seems really fast, but I haven't done any comparisons. I know Nate, the author, did some comparisons between Ninject and other DI frameworks and is looking for more ways to improve the speed of Ninject.

I've heard lots of people I respect say good things about StructureMap and CastleWindsor. Those, in my mind, are the big three to look at right now.

Read a Csv file with powershell and capture corresponding data

What you should be looking at is Import-Csv

Once you import the CSV you can use the column header as the variable.

Example CSV:

Name  | Phone Number | Email
Elvis | 867.5309     | [email protected]
Sammy | 555.1234     | [email protected]

Now we will import the CSV, and loop through the list to add to an array. We can then compare the value input to the array:

$Name = @()
$Phone = @()

Import-Csv H:\Programs\scripts\SomeText.csv |`
    ForEach-Object {
        $Name += $_.Name
        $Phone += $_."Phone Number"
    }

$inputNumber = Read-Host -Prompt "Phone Number"

if ($Phone -contains $inputNumber)
    {
    Write-Host "Customer Exists!"
    $Where = [array]::IndexOf($Phone, $inputNumber)
    Write-Host "Customer Name: " $Name[$Where]
    }

And here is the output:

I Found Sammy

How do I find out what is hammering my SQL Server?

You can find some useful query here:

Investigating the Cause of SQL Server High CPU

For me this helped a lot:

SELECT s.session_id,
    r.status,
    r.blocking_session_id 'Blk by',
    r.wait_type,
    wait_resource,
    r.wait_time / (1000 * 60) 'Wait M',
    r.cpu_time,
    r.logical_reads,
    r.reads,
    r.writes,
    r.total_elapsed_time / (1000 * 60) 'Elaps M',
    Substring(st.TEXT,(r.statement_start_offset / 2) + 1,
    ((CASE r.statement_end_offset
WHEN -1
THEN Datalength(st.TEXT)
ELSE r.statement_end_offset
END - r.statement_start_offset) / 2) + 1) AS statement_text,
    Coalesce(Quotename(Db_name(st.dbid)) + N'.' + Quotename(Object_schema_name(st.objectid, st.dbid)) + N'.' +
    Quotename(Object_name(st.objectid, st.dbid)), '') AS command_text,
    r.command,
    s.login_name,
    s.host_name,
    s.program_name,
    s.last_request_end_time,
    s.login_time,
    r.open_transaction_count
FROM sys.dm_exec_sessions AS s
    JOIN sys.dm_exec_requests AS r
ON r.session_id = s.session_id
    CROSS APPLY sys.Dm_exec_sql_text(r.sql_handle) AS st
WHERE r.session_id != @@SPID
ORDER BY r.cpu_time desc

In the fields of status, wait_type and cpu_time you can find the most cpu consuming task that is running right now.

Java URLConnection Timeout

I have used similar code for downloading logs from servers. I debug my code and discovered that implementation of URLConnection which is returned is sun.net.www.protocol.http.HttpURLConnection.

Abstract class java.net.URLConnection have two attributes connectTimeout and readTimeout and setters are in abstract class. Believe or not implementation sun.net.www.protocol.http.HttpURLConnection have same attributes connectTimeout and readTimeout without setters and attributes from implementation class are used in getInputStream method. So there is no use of setting connectTimeout and readTimeout because they are never used in getInputStream method. In my opinion this is bug in sun.net.www.protocol.http.HttpURLConnection implementation.

My solution for this was to use HttpClient and Get request.

How to remove unique key from mysql table

All keys are named, you should use something like this -

ALTER TABLE tbl_quiz_attempt_master
  DROP INDEX index_name;

To drop primary key use this one -

ALTER TABLE tbl_quiz_attempt_master
  DROP INDEX `PRIMARY`;

ALTER TABLE Syntax.

WAMP server, localhost is not working

The best solution is:

  1. Right click on Computer -> Properties -> Device manager.
  2. View -> Show hidden devices.
  3. Choose Non-plug and plug drivers -> HTTP -> Disable.
  4. Restart your computer.

Best Java obfuscator?

I don't know for sure if the solution is safe, but about the ClassGuard solution, it's interesting to read the article and the comment at: http://www.javaworld.com/community/?q=node/1604#comment-12296

Display html text in uitextview

For Swift3

    let theString = "<h1>H1 title</h1><b>Logo</b><img src='http://www.aver.com/Images/Shared/logo-color.png'><br>~end~"

    let theAttributedString = try! NSAttributedString(data: theString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!,
        options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
        documentAttributes: nil)

    UITextView_Message.attributedText = theAttributedString

ffmpeg - Converting MOV files to MP4

The command to just stream it to a new container (mp4) needed by some applications like Adobe Premiere Pro without encoding (fast) is:

ffmpeg -i input.mov -qscale 0 output.mp4

Alternative as mentioned in the comments, which re-encodes with best quaility (-qscale 0):

ffmpeg -i input.mov -q:v 0 output.mp4

"Expected BEGIN_OBJECT but was STRING at line 1 column 1"

Invalid JSON from the server should always be an expected use case. A million things can go wrong during transmission. Gson is a bit tricky, because its error output will give you one problem, and the actual exception you catch will be of a different type.

With all that in mind, the proper fix on the client side is

try
{
  gson.fromJSON(ad, Ad.class);
  //...
}
catch (IllegalStateException | JsonSyntaxException exception)
{
  //...

If you want to know why the JSON you received from the server is wrong, you can look inside your catch block at the exception. But even if it is your problem, it's not the client's responsibility to fix JSON it is receiving from the internet.

Either way, it is the client's responsibility to decide what to do when it gets bad JSON. Two possibilities are rejecting the JSON and doing nothing, and trying again.

If you are going to try again, I highly recommend setting a flag inside the try / catch block and then responding to that flag outside the try / catch block. Nested try / catch is likely how Gson got us into this mess with our stack trace and exceptions not matching up.

In other words, even though I'll admit it doesn't look very elegant, I would recommend

boolean failed = false;

try
{
  gson.fromJSON(ad, Ad.class);
  //...
}
catch (IllegalStateException | JsonSyntaxException exception)
{
  failed = true;
  //...
}

if (failed)
{
  //...

How to round an image with Glide library?

Check this post, glide vs picasso...
Edit: the linked post doesn't call out an important difference in the libraries. Glide does the recycling automatically. See TWiStErRob's comment for more.

Glide.with(this).load(URL).transform(new CircleTransform(context)).into(imageView);

public static class CircleTransform extends BitmapTransformation {
    public CircleTransform(Context context) {
        super(context);
    }

    @Override protected Bitmap transform(BitmapPool pool, Bitmap toTransform, int outWidth, int outHeight) {
        return circleCrop(pool, toTransform);
    }

    private static Bitmap circleCrop(BitmapPool pool, Bitmap source) {
        if (source == null) return null;

        int size = Math.min(source.getWidth(), source.getHeight());
        int x = (source.getWidth() - size) / 2;
        int y = (source.getHeight() - size) / 2;

        // TODO this could be acquired from the pool too
        Bitmap squared = Bitmap.createBitmap(source, x, y, size, size);

        Bitmap result = pool.get(size, size, Bitmap.Config.ARGB_8888);
        if (result == null) {
            result = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888);
        }

        Canvas canvas = new Canvas(result);
        Paint paint = new Paint();
        paint.setShader(new BitmapShader(squared, BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP));
        paint.setAntiAlias(true);
        float r = size / 2f;
        canvas.drawCircle(r, r, r, paint);
        return result;
    }

    @Override public String getId() {
        return getClass().getName();
    }
} 

Check if a value is within a range of numbers

I like Pointy's between function so I wrote a similar one that worked well for my scenario.

/**
 * Checks if an integer is within ±x another integer.
 * @param {int} op - The integer in question
 * @param {int} target - The integer to compare to
 * @param {int} range - the range ±
 */
function nearInt(op, target, range) {
    return op < target + range && op > target - range;
}

so if you wanted to see if x was within ±10 of y:

var x = 100;
var y = 115;
nearInt(x,y,10) = false

I'm using it for detecting a long-press on mobile:

//make sure they haven't moved too much during long press.
if (!nearInt(Last.x,Start.x,5) || !nearInt(Last.y, Start.y,5)) clearTimeout(t);

Deploying my application at the root in Tomcat

The fastest way.

  1. Make sure you don't have ROOT app deployed, undeploy if you have one

  2. Rename your war to ROOT.war, deploy, thats all, no configuration changes needed

What is the difference between SAX and DOM?

Here in simpler words:

DOM

  • Tree model parser (Object based) (Tree of nodes).

  • DOM loads the file into the memory and then parse- the file.

  • Has memory constraints since it loads the whole XML file before parsing.

  • DOM is read and write (can insert or delete nodes).

  • If the XML content is small, then prefer DOM parser.

  • Backward and forward search is possible for searching the tags and evaluation of the information inside the tags. So this gives the ease of navigation.

  • Slower at run time.

SAX

  • Event based parser (Sequence of events).

  • SAX parses the file as it reads it, i.e. parses node by node.

  • No memory constraints as it does not store the XML content in the memory.

  • SAX is read only i.e. can’t insert or delete the node.

  • Use SAX parser when memory content is large.

  • SAX reads the XML file from top to bottom and backward navigation is not possible.

  • Faster at run time.

How can I scale an image in a CSS sprite

You could use background-size, as its supported by most browsers (but not all http://caniuse.com/#search=background-size)

background-size : 150% 150%;

Or

You can use a combo of zoom for webkit/ie and transform:scale for Firefox(-moz-) and Opera(-o-) for cross-browser desktop & mobile

[class^="icon-"]{
    display: inline-block;
    background: url('../img/icons/icons.png') no-repeat;
    width: 64px;
    height: 51px;
    overflow: hidden;
    zoom:0.5;
    -moz-transform:scale(0.5);
    -moz-transform-origin: 0 0;
}

.icon-huge{
    zoom:1;
    -moz-transform:scale(1);
    -moz-transform-origin: 0 0;
}

.icon-big{
    zoom:0.60;
    -moz-transform:scale(0.60);
    -moz-transform-origin: 0 0;
}

.icon-small{
    zoom:0.29;
    -moz-transform:scale(0.29);
    -moz-transform-origin: 0 0;
}

Java - How to find the redirected url of a url?

Have a look at the HttpURLConnection class API documentation, especially setInstanceFollowRedirects().

How to semantically add heading to a list

As Felipe Alsacreations has already said, the first option is fine.

If you want to ensure that nothing below the list is interpreted as belonging to the heading, that's exactly what the HTML5 sectioning content elements are for. So, for instance you could do

<h2>About Fruits</h2>
<section>
  <h3>Fruits I Like:</h3>
  <ul>
    <li>Apples</li>
    <li>Bananas</li>
    <li>Oranges</li>
  </ul>
</section>
<!-- anything here is part of the "About Fruits" section but does not 
     belong to the "Fruits I Like" section. -->

Fastest way to download a GitHub project

Downloading with Git using Windows CMD from a GitHub project

You can get download the link from GitHub <b>HTTPS clone URL</b>

Download with Window Command Prompt cmd for above picture HTTPS clone URL

  1. Copy the HTTPS clone URL shown in picture 1

  2. Open CMD

  3. git clone //paste the URL show in picture 2

What is the bit size of long on 64-bit Windows?

In the Unix world, there were a few possible arrangements for the sizes of integers and pointers for 64-bit platforms. The two mostly widely used were ILP64 (actually, only a very few examples of this; Cray was one such) and LP64 (for almost everything else). The acronynms come from 'int, long, pointers are 64-bit' and 'long, pointers are 64-bit'.

Type           ILP64   LP64   LLP64
char              8      8       8
short            16     16      16
int              64     32      32
long             64     64      32
long long        64     64      64
pointer          64     64      64

The ILP64 system was abandoned in favour of LP64 (that is, almost all later entrants used LP64, based on the recommendations of the Aspen group; only systems with a long heritage of 64-bit operation use a different scheme). All modern 64-bit Unix systems use LP64. MacOS X and Linux are both modern 64-bit systems.

Microsoft uses a different scheme for transitioning to 64-bit: LLP64 ('long long, pointers are 64-bit'). This has the merit of meaning that 32-bit software can be recompiled without change. It has the demerit of being different from what everyone else does, and also requires code to be revised to exploit 64-bit capacities. There always was revision necessary; it was just a different set of revisions from the ones needed on Unix platforms.

If you design your software around platform-neutral integer type names, probably using the C99 <inttypes.h> header, which, when the types are available on the platform, provides, in signed (listed) and unsigned (not listed; prefix with 'u'):

  • int8_t - 8-bit integers
  • int16_t - 16-bit integers
  • int32_t - 32-bit integers
  • int64_t - 64-bit integers
  • uintptr_t - unsigned integers big enough to hold pointers
  • intmax_t - biggest size of integer on the platform (might be larger than int64_t)

You can then code your application using these types where it matters, and being very careful with system types (which might be different). There is an intptr_t type - a signed integer type for holding pointers; you should plan on not using it, or only using it as the result of a subtraction of two uintptr_t values (ptrdiff_t).

But, as the question points out (in disbelief), there are different systems for the sizes of the integer data types on 64-bit machines. Get used to it; the world isn't going to change.

How to add a where clause in a MySQL Insert statement?

INSERT INTO users (id,username, password) 
VALUES ('1','Jack','123')
ON DUPLICATE KEY UPDATE username='Jack',password='123'

This will work only if the id field is unique/pk (not composite PK though) Also, this will insert if no id of value 1 is found and update otherwise the record with id 1 if it does exists.

How do I read configuration settings from Symfony2 config.yml?

Rather than defining contact_email within app.config, define it in a parameters entry:

parameters:
    contact_email: [email protected]

You should find the call you are making within your controller now works.

Eclipse: How to build an executable jar with external jar?

You can do this by writing a manifest for your jar. Have a look at the Class-Path header. Eclipse has an option for choosing your own manifest on export.

The alternative is to add the dependency to the classpath at the time you invoke the application:

win32: java.exe -cp app.jar;dependency.jar foo.MyMainClass
*nix:  java -cp app.jar:dependency.jar foo.MyMainClass

How can I reorder a list?

One more thing which can be considered is the other interpretation as pointed out by darkless

Code in Python 2.7

Mainly:

  1. Reorder by value - Already solved by AJ above
  2. Reorder by index

    mylist = ['a', 'b', 'c', 'd', 'e']
    myorder = [3, 2, 0, 1, 4]
    
    mylist = sorted(zip(mylist, myorder), key=lambda x: x[1])
    print [item[0] for item in mylist]
    

This will print ['c', 'd', 'b', 'a', 'e']

Comparing strings in Java

did the same here needed to show "success" twice response is data from PHP

 String res=response.toString().trim;

                            Toast.makeText(sign_in.this,res,Toast.LENGTH_SHORT).show();
    if ( res.compareTo("success")==0){
    Toast.makeText(this,res,Toast.LENGTH_SHORT).show();
    }

How to ALTER multiple columns at once in SQL Server

select 'ALTER TABLE ' + OBJECT_NAME(o.object_id) + 
    ' ALTER COLUMN ' + c.name + ' DATETIME2 ' + 
    CASE WHEN c.is_nullable = 0 THEN 'NOT NULL' ELSE 'NULL' END
from sys.objects o
inner join sys.columns c on o.object_id = c.object_id
inner join sys.types t on c.system_type_id = t.system_type_id
where o.type='U'
and c.name = 'Timestamp'
and t.name = 'datetime'
order by OBJECT_NAME(o.object_id)

courtesy of devio

Passing a string array as a parameter to a function java

How about:

public class test {
    public static void someFunction(String[] strArray) { 
        // do something 
    }

    public static void main(String[] args) {
        String[] strArray = new String[]{"Foo","Bar","Baz"};
        someFunction(strArray);
    }
}

SQL Server equivalent to MySQL enum data type?

It doesn't. There's a vague equivalent:

mycol VARCHAR(10) NOT NULL CHECK (mycol IN('Useful', 'Useless', 'Unknown'))

What is the difference between ManualResetEvent and AutoResetEvent in .NET?

Taken from C# 3.0 Nutshell book, by Joseph Albahari

Threading in C# - Free E-Book

A ManualResetEvent is a variation on AutoResetEvent. It differs in that it doesn't automatically reset after a thread is let through on a WaitOne call, and so functions like a gate: calling Set opens the gate, allowing any number of threads that WaitOne at the gate through; calling Reset closes the gate, causing, potentially, a queue of waiters to accumulate until its next opened.

One could simulate this functionality with a boolean "gateOpen" field (declared with the volatile keyword) in combination with "spin-sleeping" – repeatedly checking the flag, and then sleeping for a short period of time.

ManualResetEvents are sometimes used to signal that a particular operation is complete, or that a thread's completed initialization and is ready to perform work.

Open a folder using Process.Start

You're escaping the backslash when the at sign does that for you.

System.Diagnostics.Process.Start("explorer.exe",@"c:\teste");

What is the functionality of setSoTimeout and how it works?

The JavaDoc explains it very well:

With this option set to a non-zero timeout, a read() call on the InputStream associated with this Socket will block for only this amount of time. If the timeout expires, a java.net.SocketTimeoutException is raised, though the Socket is still valid. The option must be enabled prior to entering the blocking operation to have effect. The timeout must be > 0. A timeout of zero is interpreted as an infinite timeout.

SO_TIMEOUT is the timeout that a read() call will block. If the timeout is reached, a java.net.SocketTimeoutException will be thrown. If you want to block forever put this option to zero (the default value), then the read() call will block until at least 1 byte could be read.

What is the difference between Bower and npm?

2017-Oct update

Bower has finally been deprecated. End of story.

Older answer

From Mattias Petter Johansson, JavaScript developer at Spotify:

In almost all cases, it's more appropriate to use Browserify and npm over Bower. It is simply a better packaging solution for front-end apps than Bower is. At Spotify, we use npm to package entire web modules (html, css, js) and it works very well.

Bower brands itself as the package manager for the web. It would be awesome if this was true - a package manager that made my life better as a front-end developer would be awesome. The problem is that Bower offers no specialized tooling for the purpose. It offers NO tooling that I know of that npm doesn't, and especially none that is specifically useful for front-end developers. There is simply no benefit for a front-end developer to use Bower over npm.

We should stop using bower and consolidate around npm. Thankfully, that is what is happening:

Module counts - bower vs. npm

With browserify or webpack, it becomes super-easy to concatenate all your modules into big minified files, which is awesome for performance, especially for mobile devices. Not so with Bower, which will require significantly more labor to get the same effect.

npm also offers you the ability to use multiple versions of modules simultaneously. If you have not done much application development, this might initially strike you as a bad thing, but once you've gone through a few bouts of Dependency hell you will realize that having the ability to have multiple versions of one module is a pretty darn great feature. Note that npm includes a very handy dedupe tool that automatically makes sure that you only use two versions of a module if you actually have to - if two modules both can use the same version of one module, they will. But if they can't, you have a very handy out.

(Note that Webpack and rollup are widely regarded to be better than Browserify as of Aug 2016.)

UIButton Image + Text IOS

It's really simple,just add image to background of you button and give text to titlelabel of button for uicontrolstatenormal. That's it.

[btn setBackgroundImage:[UIImage imageNamed:@"img.png"] forState:UIControlStateNormal];
[btn setContentVerticalAlignment:UIControlContentVerticalAlignmentBottom];
[btn setTitle:@"Click Me" forState:UIControlStateNormal];

BadValue Invalid or no user locale set. Please ensure LANG and/or LC_* environment variables are set correctly

Generating locales

Missing locales are generated with locale-gen:

locale-gen en_US.UTF-8

Alternatively a locale file can be created manually with localedef:[1]

localedef -i en_US -f UTF-8 en_US.UTF-8

Setting Locale Settings

The locale settings can be set (to en_US.UTF-8 in the example) as follows:

export LANGUAGE=en_US.UTF-8
export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8
locale-gen en_US.UTF-8
dpkg-reconfigure locales

The dpkg-reconfigure locales command will open a dialog under Debian for selecting the desired locale. This dialog will not appear under Ubuntu. The Configure Locales in Ubuntu article shows how to find the information regarding Ubuntu.

Favicon not showing up in Google Chrome

I also experienced the same thing. I found out that my favicon.ico had not been processed as a legitimate shortcut icon. I understand that favicons must be scaled to 16x16 and follow the Microsoft Icon format.

What is the best way to merge mp3 files?

Personally I would use something like mplayer with the audio pass though option eg -oac copy

How to list all Git tags?

You can list all existing tags git tag or you could filter the list with git tag -l 'v1.1.*', where * acts as a wildcard. It will return a list of tags marked with v1.1.

You will notice that when you call git tag you do not get to see the contents of your annotations. To preview them you must add -n to your command: git tag -n2.

$ git tag -l -n2

v1.0 Release version 1.0

v1.1 Release version 1.1

The command lists all existing tags with maximum 3 lines of their tag message. By default -n only shows the first line. For more info be sure to check this tag related article as well.

How do I make XAML DataGridColumns fill the entire DataGrid?

Another spin on the same theme:

protected void OnWindowSizeChanged(object sender, SizeChangedEventArgs e)
{
    dataGrid.Width = e.NewSize.Width - (e.NewSize.Width * .1);

    foreach (var column in dataGrid.Columns)
    {
       column.Width = dataGrid.Width / dataGrid.Columns.Count;
    }
 }

Bold & Non-Bold Text In A Single UILabel?

No need for NSRange with the following code I just implemented in my project (in Swift):

//Code sets label (yourLabel)'s text to "Tap and hold(BOLD) button to start recording."
let boldAttribute = [
  //You can add as many attributes as you want here.
  NSFontAttributeName: UIFont(name: "HelveticaNeue-Bold", size: 18.0)!
]
        
let regularAttribute = [NSFontAttributeName: UIFont(name: "HelveticaNeue-Light", size: 18.0)!]
        
let beginningAttributedString = NSAttributedString(string: "Tap and ", attributes: regularAttribute )
let boldAttributedString = NSAttributedString(string: "hold ", attributes: boldAttribute)
let endAttributedString = NSAttributedString(string: "button to start recording.", attributes: regularAttribute )
let fullString =  NSMutableAttributedString()
        
fullString.appendAttributedString(beginningAttributedString)
fullString.appendAttributedString(boldAttributedString)
fullString.appendAttributedString(endAttributedString)

yourLabel.attributedText = fullString

How can I set the default value for an HTML <select> element?

If you are using select with angular 1, then you need to use ng-init, otherwise, second option will not be selected since, ng-model overrides the defaul selected value

<select ng-model="sortVar" ng-init='sortVar="stargazers_count"'>
  <option value="name">Name</option>
  <option selected="selected" value="stargazers_count">Stars</option>
  <option value="language">Language</option>
</select>

JavaScript + Unicode regexes

September 2018 (updated February 2019)

It seems that regexp /\p{L}/u for match letters (as unicode categories)

  • works on Chrome 68.0.3440.106 and Safari 11.1.2 (13605.3.8)
  • NOT working on Firefox 65.0 :(

Here is a working example

_x000D_
_x000D_
In below field you should be able to to type letters but not numbers<br>_x000D_
<input type="text" name="field" onkeydown="return /\p{L}/u.test(event.key)" >
_x000D_
_x000D_
_x000D_

I report this bug here.

Update

After over 2 years according to: 1500035 > 1361876 > 1634135 finally this bug is fixed and will be available in Firefox v.78+

Query to list number of records in each table in a database

Shnugo's answer is the ONLY one that works in Azure with Externa Tables. (1) Azure SQL doesn't support sp_MSforeachtable at all and (2) rows in sys.partitions for an External table is always 0.

pandas how to check dtype for all columns in a dataframe?

To go one step further, I assume you want to do something with these dtypes. df.dtypes.to_dict() comes in handy.

my_type = 'float64' #<---

dtypes = dataframe.dtypes.to_dict()

for col_nam, typ in dtypes.items():
    if (typ != my_type): #<---
        raise ValueError(f"Yikes - `dataframe['{col_name}'].dtype == {typ}` not {my_type}")

You'll find that Pandas did a really good job comparing NumPy classes and user-provided strings. For example: even things like 'double' == dataframe['col_name'].dtype will succeed when .dtype==np.float64.

What is causing ERROR: there is no unique constraint matching given keys for referenced table?

It's because the name column on the bar table does not have the UNIQUE constraint.

So imagine you have 2 rows on the bar table that contain the name 'ams' and you insert a row on baz with 'ams' on bar_fk, which row on bar would it be referring since there are two rows matching?

Cannot construct instance of - Jackson

Your @JsonSubTypes declaration does not make sense: it needs to list implementation (sub-) classes, NOT the class itself (which would be pointless). So you need to modify that entry to list sub-class(es) there are; or use some other mechanism to register sub-classes (SimpleModule has something like addAbstractTypeMapping).

Creating dummy variables in pandas for python

When I think of dummy variables I think of using them in the context of OLS regression, and I would do something like this:

import numpy as np
import pandas as pd
import statsmodels.api as sm

my_data = np.array([[5, 'a', 1],
                    [3, 'b', 3],
                    [1, 'b', 2],
                    [3, 'a', 1],
                    [4, 'b', 2],
                    [7, 'c', 1],
                    [7, 'c', 1]])                


df = pd.DataFrame(data=my_data, columns=['y', 'dummy', 'x'])
just_dummies = pd.get_dummies(df['dummy'])

step_1 = pd.concat([df, just_dummies], axis=1)      
step_1.drop(['dummy', 'c'], inplace=True, axis=1)
# to run the regression we want to get rid of the strings 'a', 'b', 'c' (obviously)
# and we want to get rid of one dummy variable to avoid the dummy variable trap
# arbitrarily chose "c", coefficients on "a" an "b" would show effect of "a" and "b"
# relative to "c"
step_1 = step_1.applymap(np.int) 

result = sm.OLS(step_1['y'], sm.add_constant(step_1[['x', 'a', 'b']])).fit()
print result.summary()

How to remove empty lines with or without whitespace in Python

Try list comprehension and string.strip():

>>> mystr = "L1\nL2\n\nL3\nL4\n  \n\nL5"
>>> mystr.split('\n')
['L1', 'L2', '', 'L3', 'L4', '  ', '', 'L5']
>>> [line for line in mystr.split('\n') if line.strip() != '']
['L1', 'L2', 'L3', 'L4', 'L5']

Retrieving subfolders names in S3 bucket from boto3

Why not use the s3path package which makes it as convenient as working with pathlib? If you must however use boto3:

Using boto3.resource

This builds upon the answer by itz-azhar to apply an optional limit. It is obviously substantially simpler to use than the boto3.client version.

import logging
from typing import List, Optional

import boto3
from boto3_type_annotations.s3 import ObjectSummary  # pip install boto3_type_annotations

log = logging.getLogger(__name__)
_S3_RESOURCE = boto3.resource("s3")

def s3_list(bucket_name: str, prefix: str, *, limit: Optional[int] = None) -> List[ObjectSummary]:
    """Return a list of S3 object summaries."""
    # Ref: https://stackoverflow.com/a/57718002/
    return list(_S3_RESOURCE.Bucket(bucket_name).objects.limit(count=limit).filter(Prefix=prefix))


if __name__ == "__main__":
    s3_list("noaa-gefs-pds", "gefs.20190828/12/pgrb2a", limit=10_000)

Using boto3.client

This uses list_objects_v2 and builds upon the answer by CpILL to allow retrieving more than 1000 objects.

import logging
from typing import cast, List

import boto3

log = logging.getLogger(__name__)
_S3_CLIENT = boto3.client("s3")

def s3_list(bucket_name: str, prefix: str, *, limit: int = cast(int, float("inf"))) -> List[dict]:
    """Return a list of S3 object summaries."""
    # Ref: https://stackoverflow.com/a/57718002/
    contents: List[dict] = []
    continuation_token = None
    if limit <= 0:
        return contents
    while True:
        max_keys = min(1000, limit - len(contents))
        request_kwargs = {"Bucket": bucket_name, "Prefix": prefix, "MaxKeys": max_keys}
        if continuation_token:
            log.info(  # type: ignore
                "Listing %s objects in s3://%s/%s using continuation token ending with %s with %s objects listed thus far.",
                max_keys, bucket_name, prefix, continuation_token[-6:], len(contents))  # pylint: disable=unsubscriptable-object
            response = _S3_CLIENT.list_objects_v2(**request_kwargs, ContinuationToken=continuation_token)
        else:
            log.info("Listing %s objects in s3://%s/%s with %s objects listed thus far.", max_keys, bucket_name, prefix, len(contents))
            response = _S3_CLIENT.list_objects_v2(**request_kwargs)
        assert response["ResponseMetadata"]["HTTPStatusCode"] == 200
        contents.extend(response["Contents"])
        is_truncated = response["IsTruncated"]
        if (not is_truncated) or (len(contents) >= limit):
            break
        continuation_token = response["NextContinuationToken"]
    assert len(contents) <= limit
    log.info("Returning %s objects from s3://%s/%s.", len(contents), bucket_name, prefix)
    return contents


if __name__ == "__main__":
    s3_list("noaa-gefs-pds", "gefs.20190828/12/pgrb2a", limit=10_000)

Use multiple css stylesheets in the same html page

You can't control which you're referencing, given the same level of specificity in the rule (e.g. both are simply .banner) the stylesheet included last will win.

It's per-property, so if there's a combination going on (for example one has background, the other has color) then you'll get the combination...if a property is defined in both, whatever it is the last time it appears in stylesheet order wins.

How can you remove all documents from a collection with Mongoose?

DateTime.remove({}, callback) The empty object will match all of them.

How to call a function after a div is ready?

inside your <div></div> element you can call the $(document).ready(function(){}); execute a command, something like

<div id="div1">
    <script>
        $(document).ready(function(){
         //do something
        });
    </script>
</div>

and you can do the same to other divs that you have. this was suitable if you loading your div via partial view

Is there a JavaScript strcmp()?

localeCompare() is slow, so if you don't care about the "correct" ordering of non-English-character strings, try your original method or the cleaner-looking:

str1 < str2 ? -1 : +(str1 > str2)

This is an order of magnitude faster than localeCompare() on my machine.

The + ensures that the answer is always numeric rather than boolean.

How to inject a Map using the @Value Spring Annotation?

I believe Spring Boot supports loading properties maps out of the box with @ConfigurationProperties annotation.

According that docs you can load properties:

my.servers[0]=dev.bar.com
my.servers[1]=foo.bar.com

into bean like this:

@ConfigurationProperties(prefix="my")
public class Config {

    private List<String> servers = new ArrayList<String>();

    public List<String> getServers() {
        return this.servers;
    }
}

I used @ConfigurationProperties feature before, but without loading into map. You need to use @EnableConfigurationProperties annotation to enable this feature.

Cool stuff about this feature is that you can validate your properties.

How do I keep jQuery UI Accordion collapsed by default?

Add the active: false option (documentation)..

$("#accordion").accordion({ header: "h3", collapsible: true, active: false });

Maven: how to override the dependency added by a library

Simply specify the version in your current pom. The version specified here will override other.

Forcing a version
A version will always be honoured if it is declared in the current POM with a particular version - however, it should be noted that this will also affect other poms downstream if it is itself depended on using transitive dependencies.


Resources :

Javascript variable access in HTML

Here you go: http://codepen.io/anon/pen/cKflA

Although, I must say that what you are asking to do is not a good way to do it. A good way is this: http://codepen.io/anon/pen/jlkvJ

How set maximum date in datepicker dialog in android?

Get today's date (& time) and apply them as maximum date.

Calendar c = Calendar.getInstance();
c.set(2017, 0, 1);//Year,Mounth -1,Day
your_date_picker.setMaxDate(c.getTimeInMillis());

ALSO WE MAY DO THIS (check this Stackoverflow answer for System.currentTimeMillis() vs Calendar method)

long now = System.currentTimeMillis() - 1000;
dp_time.setMinDate(now);
dp_time.setMaxDate(now+(1000*60*60*24*7)); //After 7 Days from Now

What is “the inverse side of the association” in a bidirectional JPA OneToMany/ManyToOne association?

Simple rules of bidirectional relationships:

1.For many-to-one bidirectional relationships, the many side is always the owning side of the relationship. Example: 1 Room has many Person (a Person belongs one Room only) -> owning side is Person

2.For one-to-one bidirectional relationships, the owning side corresponds to the side that contains the corresponding foreign key.

3.For many-to-many bidirectional relationships, either side may be the owning side.

Hope can help you.

Adding click event listener to elements with the same class

(ES5) I use forEach to iterate on the collection returned by querySelectorAll and it works well :

document.querySelectorAll('your_selector').forEach(item => { /* do the job with item element */ });

Longer object length is not a multiple of shorter object length?

Yes, this is something that you should worry about. Check the length of your objects with nrow(). R can auto-replicate objects so that they're the same length if they differ, which means you might be performing operations on mismatched data.

In this case you have an obvious flaw in that your subtracting aggregated data from raw data. These will definitely be of different lengths. I suggest that you merge them as time series (using the dates), then locf(), then do your subtraction. Otherwise merge them by truncating the original dates to the same interval as the aggregated series. Just be very careful that you don't drop observations.

Lastly, as some general advice as you get started: look at the result of your computations to see if they make sense. You might even pull them into a spreadsheet and replicate the results.

How to map to multiple elements with Java 8 streams?

To do this, I had to come up with an intermediate data structure:

class KeyDataPoint {
    String key;
    DateTime timestamp;
    Number data;
    // obvious constructor and getters
}

With this in place, the approach is to "flatten" each MultiDataPoint into a list of (timestamp, key, data) triples and stream together all such triples from the list of MultiDataPoint.

Then, we apply a groupingBy operation on the string key in order to gather the data for each key together. Note that a simple groupingBy would result in a map from each string key to a list of the corresponding KeyDataPoint triples. We don't want the triples; we want DataPoint instances, which are (timestamp, data) pairs. To do this we apply a "downstream" collector of the groupingBy which is a mapping operation that constructs a new DataPoint by getting the right values from the KeyDataPoint triple. The downstream collector of the mapping operation is simply toList which collects the DataPoint objects of the same group into a list.

Now we have a Map<String, List<DataPoint>> and we want to convert it to a collection of DataSet objects. We simply stream out the map entries and construct DataSet objects, collect them into a list, and return it.

The code ends up looking like this:

Collection<DataSet> convertMultiDataPointToDataSet(List<MultiDataPoint> multiDataPoints) {
    return multiDataPoints.stream()
        .flatMap(mdp -> mdp.getData().entrySet().stream()
                           .map(e -> new KeyDataPoint(e.getKey(), mdp.getTimestamp(), e.getValue())))
        .collect(groupingBy(KeyDataPoint::getKey,
                    mapping(kdp -> new DataPoint(kdp.getTimestamp(), kdp.getData()), toList())))
        .entrySet().stream()
        .map(e -> new DataSet(e.getKey(), e.getValue()))
        .collect(toList());
}

I took some liberties with constructors and getters, but I think they should be obvious.

how does int main() and void main() work

If you really want to understand ANSI C 89, I need to correct you in one thing; In ANSI C 89 the difference between the following functions:

int main()
int main(void)
int main(int argc, char* argv[])

is:

int main()

  • a function that expects unknown number of arguments of unknown types. Returns an integer representing the application software status.

int main(void)

  • a function that expects no arguments. Returns an integer representing the application software status.

int main(int argc, char * argv[])

  • a function that expects argc number of arguments and argv[] arguments. Returns an integer representing the application software status.

About when using each of the functions

int main(void)

  • you need to use this function when your program needs no initial parameters to run/ load (parameters received from the OS - out of the program it self).

int main(int argc, char * argv[])

  • you need to use this function when your program needs initial parameters to load (parameters received from the OS - out of the program it self).

About void main()

In ANSI C 89, when using void main and compiling the project AS -ansi -pedantic (in Ubuntu, e.g) you will receive a warning indicating that your main function is of type void and not of type int, but you will be able to run the project. Most C developers tend to use int main() on all of its variants, though void main() will also compile.

How to write :hover using inline style?

Not gonna happen with CSS only

Inline javascript

<a href='index.html' 
    onmouseover='this.style.textDecoration="none"' 
    onmouseout='this.style.textDecoration="underline"'>
    Click Me
</a>

In a working draft of the CSS2 spec it was declared that you could use pseudo-classes inline like this:

<a href="http://www.w3.org/Style/CSS"
   style="{color: blue; background: white}  /* a+=0 b+=0 c+=0 */
      :visited {color: green}           /* a+=0 b+=1 c+=0 */
      :hover {background: yellow}       /* a+=0 b+=1 c+=0 */
      :visited:hover {color: purple}    /* a+=0 b+=2 c+=0 */
     ">
</a>

but it was never implemented in the release of the spec as far as I know.

http://www.w3.org/TR/2002/WD-css-style-attr-20020515#pseudo-rules

Where are shared preferences stored?

I just tried to get path of shared preferences below like this.This is work for me.

File f = getDatabasePath("MyPrefsFile.xml");

if (f != null)
    Log.i("TAG", f.getAbsolutePath());

How to copy a dictionary and only edit the copy

i ran into a peculiar behavior when trying to deep copy dictionary property of class w/o assigning it to variable

new = copy.deepcopy(my_class.a) doesn't work i.e. modifying new modifies my_class.a

but if you do old = my_class.a and then new = copy.deepcopy(old) it works perfectly i.e. modifying new does not affect my_class.a

I am not sure why this happens, but hope it helps save some hours! :)

System.Security.SecurityException when writing to Event Log

This exception was occurring for me from a .NET console app running as a scheduled task, and I was trying to do basically the same thing - create a new Event Source and write to the event log.

In the end, setting full permissions for the user under which the task was running on the following keys did the trick for me:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\eventlog\Application
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\eventlog\Security
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\eventlog

Find largest and smallest number in an array

You can initialize after filling the array or you can write:

 small =~ unsigned(0)/2; // Using the bit-wise complement to flip 0's bits and dividing by 2 because unsigned can hold twice the +ve value an

integer can hold.

 big =- 1*(small) - 1;

instead of:

big = small = values[0]

because when you write this line before filling the array, big and small values will equal to a random leftover value (as integer is a POD) from the memory and if those numbers are either bigger or smaller than any other value in you array, you will get them as an output.

What is the garbage collector in Java?

The basic principles of garbage collection are to find data objects in a program that cannot be accessed in the future, and to reclaim the resources used by those objects. https://en.wikipedia.org/wiki/Garbage_collection_%28computer_science%29

Advantages

1) Saves from bugs, which occur when a piece of memory is freed while there are still pointers to it, and one of those pointers is dereferenced. https://en.wikipedia.org/wiki/Dangling_pointer

2) Double free bugs, which occur when the program tries to free a region of memory that has already been freed, and perhaps already been allocated again.

3) Prevents from certain kinds of memory leaks, in which a program fails to free memory occupied by objects that have become unreachable, which can lead to memory exhaustion.

Disadvantages

1) Consuming additional resources, performance impacts, possible stalls in program execution, and incompatibility with manual resource management. Garbage collection consumes computing resources in deciding which memory to free, even though the programmer may have already known this information.

2) The moment when the garbage is actually collected can be unpredictable, resulting in stalls (pauses to shift/free memory) scattered throughout a session. Unpredictable stalls can be unacceptable in real-time environments, in transaction processing, or in interactive programs.


Oracle tutorial http://www.oracle.com/webfolder/technetwork/tutorials/obe/java/gc01/index.html

Garbage collection is the process identifying which objects are in use and which are not, and deleting the unused objects.

In a programming languages like C, C++, allocating and freeing memory is a manual process.

int * array = new int[size];
processArray(array); //do some work.
delete array; //Free memory

The first step in the process is called marking. This is where the garbage collector identifies which pieces of memory are in use and which are not.

Step 2a. Normal deletion removes unreferenced objects leaving referenced objects and pointers to free space.

To improve performance, we want to delete unreferenced objects and also compact the remaining referenced objects. We want to keep referenced objects together, so it will be faster to allocate new memory.

As stated earlier, having to mark and compact all the objects in a JVM is inefficient. As more and more objects are allocated, the list of objects grows and grows leading to longer and longer garbage collection time.

Continue reading this tutorial, and you will know how GC takes this challenge.

In short, there are three regions of the heap, YoungGeneration for short life objects, OldGeneration for long period objects, and PermanentGeneration for objects that live during the application life, for example, classes, libraries.

Running a script inside a docker container using shell script

You could also mount a local directory into your docker image and source the script in your .bashrc. Don't forget the script has to consist of functions unless you want it to execute on every new shell. (This is outdated see the update notice.)

I'm using this solution to be able to update the script outside of the docker instance. This way I don't have to rerun the image if changes occur, I just open a new shell. (Got rid of reopening a shell - see the update notice)

Here is how you bind your current directory:

docker run -it -v $PWD:/scripts $my_docker_build /bin/bash

Now your current directory is bound to /scripts of your docker instance.

(Outdated) To save your .bashrc changes commit your working image with this command:

docker commit $container_id $my_docker_build

Update

To solve the issue to open up a new shell for every change I now do the following:

In the dockerfile itself I add RUN echo "/scripts/bashrc" > /root/.bashrc". Inside zshrc I export the scripts directory to the path. The scripts directory now contains multiple files instead of one. Now I can directly call all scripts without having open a sub shell on every change.

BTW you can define the history file outside of your container too. This way it's not necessary to commit on a bash change anymore.

How to generate a create table script for an existing table in phpmyadmin?

Query information_schema.columns directly:

select * from information_schema.columns 
where table_name = 'your_table' and table_schema = 'your_database'

How to check if a string contains only numbers?

You may just remove all spaces and leverage LINQ All:

Determines whether all elements of a sequence satisfy a condition.

Use it as shown below:

Dim number As String = "077 234 211"
If number.Replace(" ", "").All(AddressOf Char.IsDigit) Then
    Console.WriteLine("The string is all numeric (spaces ignored)!")
Else
    Console.WriteLine("The string contains a char that is not numeric and space!")
End If

To only check if a string consists of only digits use:

If number.All(AddressOf Char.IsDigit) Then

How to pause javascript code execution for 2 seconds

You can use setTimeout to do this

function myFunction() {
    // your code to run after the timeout
}

// stop for sometime if needed
setTimeout(myFunction, 5000);

Select objects based on value of variable in object using jq

I had a similar related question: What if you wanted the original object format back (with key names, e.g. FOO, BAR)?

Jq provides to_entries and from_entries to convert between objects and key-value pair arrays. That along with map around the select

These functions convert between an object and an array of key-value pairs. If to_entries is passed an object, then for each k: v entry in the input, the output array includes {"key": k, "value": v}.

from_entries does the opposite conversion, and with_entries(foo) is a shorthand for to_entries | map(foo) | from_entries, useful for doing some operation to all keys and values of an object. from_entries accepts key, Key, name, Name, value and Value as keys.

jq15 < json 'to_entries | map(select(.value.location=="Stockholm")) | from_entries'

{
  "FOO": {
    "name": "Donald",
    "location": "Stockholm"
  },
  "BAR": {
    "name": "Walt",
    "location": "Stockholm"
  }
}

Using the with_entries shorthand, this becomes:

jq15 < json 'with_entries(select(.value.location=="Stockholm"))'
{
  "FOO": {
    "name": "Donald",
    "location": "Stockholm"
  },
  "BAR": {
    "name": "Walt",
    "location": "Stockholm"
  }
}

EF Code First "Invalid column name 'Discriminator'" but no inheritance

Here is the Fluent API syntax.

http://blogs.msdn.com/b/adonet/archive/2010/12/06/ef-feature-ctp5-fluent-api-samples.aspx

class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string FullName { 
        get {
            return this.FirstName + " " + this.LastName;
        }
    }
}

class PersonViewModel : Person
{
    public bool UpdateProfile { get; set; }
}


protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    // ignore a type that is not mapped to a database table
    modelBuilder.Ignore<PersonViewModel>();

    // ignore a property that is not mapped to a database column
    modelBuilder.Entity<Person>()
        .Ignore(p => p.FullName);

}

SQL Server : How to test if a string has only digit characters

DECLARE @x int=1
declare @exit bit=1
WHILE @x<=len('123c') AND @exit=1
BEGIN
IF ascii(SUBSTRING('123c',@x,1)) BETWEEN 48 AND 57
BEGIN
set @x=@x+1
END
ELSE
BEGIN
SET @exit=0
PRINT 'string is not all numeric  -:('
END
END

sql server invalid object name - but tables are listed in SSMS tables list

Same problem with me when I used this syntax problem solved.

Syntax:

Use [YourDatabaseName]
Your Query Here

Why did a network-related or instance-specific error occur while establishing a connection to SQL Server?

I had the same error, and it turned out .NET created a database on localhost which I wasn't aware of. When I tried to get the site live it didn't create the database, so the code was pointing to a database that was non existent.

Hopefully this might help some other people out trying to troubleshoot.

CSS background image URL failing to load

I know this is really old, but I'm posting my solution anyways since google finds this thread.

background-image: url('./imagefolder/image.jpg');

That is what I do. Two dots means drill back one directory closer to root ".." while one "." should mean start where you are at as if it were root. I was having similar issues but adding that fixed it for me. You can even leave the "." in it when uploading to your host because it should work fine so long as your directory setup is exactly the same.

What's the difference between %s and %d in Python string formatting?

%d and %s are placeholders, they work as a replaceable variable. For example, if you create 2 variables

variable_one = "Stackoverflow"
variable_two = 45

you can assign those variables to a sentence in a string using a tuple of the variables.

variable_3 = "I was searching for an answer in %s and found more than %d answers to my question"

Note that %s works for String and %d work for numerical or decimal variables.

if you print variable_3 it would look like this

print(variable_3 % (variable_one, variable_two))

I was searching for an answer in StackOverflow and found more than 45 answers to my question.

How to get current date & time in MySQL?

Yes, you can use the CURRENT_TIMESTAMP() command.

See here: Date and Time Functions

UL has margin on the left

The <ul> element has browser inherent padding & margin by default. In your case, Use

#footer ul {
    margin: 0; /* To remove default bottom margin */ 
    padding: 0; /* To remove default left padding */
}

or a CSS browser reset ( https://cssreset.com/ ) to deal with this.

Collection was modified; enumeration operation may not execute

InvalidOperationException- An InvalidOperationException has occurred. It reports a "collection was modified" in a foreach-loop

Use break statement, Once the object is removed.

ex:

ArrayList list = new ArrayList(); 

foreach (var item in list)
{
    if(condition)
    {
        list.remove(item);
        break;
    }
}

How to create a jQuery function (a new jQuery method or plugin)?

Simplest example to making any function in jQuery is

jQuery.fn.extend({
    exists: function() { return this.length }
});

if($(selector).exists()){/*do something here*/}

Adding hours to JavaScript Date object?

There is an add in the Datejs library.

And here are the JavaScript date methods. kennebec wisely mentioned getHours() and setHours();

Can you display HTML5 <video> as a full screen background?

I might be a bit late to answer this but this will be useful for new people looking for this answer.

The answers above are good, but to have a perfect video background you have to check at the aspect ratio as the video might cut or the canvas around get deformed when resizing the screen or using it on different screen sizes.

I got into this issue not long ago and I found the solution using media queries.

Here is a tutorial that I wrote on how to create a Fullscreen Video Background with only CSS

I will add the code here as well:

HTML:

<div class="videoBgWrapper">
    <video loop muted autoplay poster="img/videoframe.jpg" class="videoBg">
        <source src="videosfolder/video.webm" type="video/webm">
        <source src="videosfolder/video.mp4" type="video/mp4">
        <source src="videosfolder/video.ogv" type="video/ogg">
    </video>
</div>

CSS:

.videoBgWrapper {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    overflow: hidden;
    z-index: -100;
}
.videoBg{
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

@media (min-aspect-ratio: 16/9) {
  .videoBg{
    width: 100%;
    height: auto;
  }
}
@media (max-aspect-ratio: 16/9) {
  .videoBg {
    width: auto;
    height: 100%;
  }
}

I hope you find it useful.

Android - java.lang.SecurityException: Permission Denial: starting Intent

Similar to Olayinka's answer about the configuration file for ADT: I just had the same issue on IntelliJ's IdeaU v14.

I'm working through a tutorial that had me change the starting activity from MyActivity to MyListActivity (Which is a list of MyActivity). I started getting Permissions Denial.

After much trial, toil and pain: In .idea\workspace.xml:

...
<configuration default="false" name="MyApp" type="AndroidRunConfigurationType" factoryName="Android Application">
    <module name="MyApp" />
    <option name="ACTIVITY_CLASS" value="com.domain.MyApp.MyActivity" />
    ...
</configuration>
...

I changed the MyActivity to MyListActivity, reloaded the project and I'm off to a rolling start again.

Not sure which IDE you are using, but maybe your IDE is overriding or forcing a specific starting activity?

Slick Carousel Uncaught TypeError: $(...).slick is not a function

It's hard to tell without looking at the full code but this type of error

Uncaught TypeError: $(...).slick is not a function

Usually means that you either forgot to include slick.js in the page or you included it before jquery.

Make sure jquery is the first js file and you included the slick.js library after it.

Package doesn't exist error in intelliJ

I had the same problem and it was fixed for me by changing the "Maven home directory" in Settings from "Bundled" to my locally installed maven. Perhaps this triggered some kind of refresh somewhere since I had not changed this setting for months without any issue.