Programs & Examples On #Eventqueue

Maven build Compilation error : Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project Maven

You should add the code into pom.xml like:


How to fix Error: this class is not key value coding-compliant for the key tableView.'

You have your storyboard set up to expect an outlet called tableView but the actual outlet name is myTableView.

If you delete the connection in the storyboard and reconnect to the right variable name, it should fix the problem.

libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

In my case, it was XCode getting tired and failing to start app with this message, due to an assertion failing (that was set by our code).

Running on another device showed the assertion failure, which we were able to fix, and everything went back to normal.

Spring Boot Remove Whitelabel Error Page

In Spring Boot 1.4.1 using Mustache templates, placing error.html under templates folder will be enough:

<!DOCTYPE html>
<html lang="en">

  <meta charset="utf-8">

  <h1>Error {{ status }}</h1>
  <p>{{ error }}</p>
  <p>{{ message }}</p>
  <p>{{ path }}</p>


Additional variables can be passed by creating an interceptor for /error

java IO Exception: Stream Closed

You call writer.close(); in writeToFile so the writer has been closed the second time you call writeToFile.

Why don't you merge FileStatus into writeToFile?

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException Error

NullPointerExceptions are among the easier exceptions to diagnose, frequently. Whenever you get an exception in Java and you see the stack trace ( that's what your second quote-block is called, by the way ), you read from top to bottom. Often, you will see exceptions that start in Java library code or in native implementations methods, for diagnosis you can just skip past those until you see a code file that you wrote.

Then you like at the line indicated and look at each of the objects ( instantiated classes ) on that line -- one of them was not created and you tried to use it. You can start by looking up in your code to see if you called the constructor on that object. If you didn't, then that's your problem, you need to instantiate that object by calling new Classname( arguments ). Another frequent cause of NullPointerExceptions is accidentally declaring an object with local scope when there is an instance variable with the same name.

In your case, the exception occurred in your constructor for Workshop on line 75. <init> means the constructor for a class. If you look on that line in your code, you'll see the line


There are fairly clearly two objects on this line: denimjeansButton and this. this is synonymous with the class instance you are currently in and you're in the constructor, so it can't be this. denimjeansButton is your culprit. You never instantiated that object. Either remove the reference to the instance variable denimjeansButton or instantiate it.

fix Read timed out

Here are few pointers/suggestions for investigation

  1. I see that every time you vote, you call vote method which creates a fresh HTTP connection.
  2. This might be a problem. I would suggest to use a single HttpClient instance to post to the server. This way it wont create too many connections from the client side.
  3. At the end of everything, HttpClient needs to be shut and hence call httpclient.getConnectionManager().shutdown(); to release the resources used by the connections.

Displaying Image in Java

import java.awt.FlowLayout;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;

 * To change this template, choose Tools | Templates
 * and open the template in the editor.

public class DisplayImage {

    public static void main(String avg[]) throws IOException
        DisplayImage abc=new DisplayImage();

    public DisplayImage() throws IOException
        BufferedImage File("f://images.jpg"));
        ImageIcon icon=new ImageIcon(img);
        JFrame frame=new JFrame();
        frame.setLayout(new FlowLayout());
        JLabel lbl=new JLabel();

Why does writeObject throw and how do I fix it? can occur when you serialize an inner class instance because:

serializing such an inner class instance will result in serialization of its associated outer class instance as well

Serialization of inner classes (i.e., nested classes that are not static member classes), including local and anonymous classes, is strongly discouraged

Ref: The Serializable Interface

Jetty: HTTP ERROR: 503/ Service Unavailable

2012-04-20 11:14:32.617:WARN:oejx.XmlParser:FATAL@file:/C:/Users/***/workspace/Test/WEB-INF/web.xml line:1 col:7 : org.xml.sax.SAXParseException: The processing instruction target matching "[xX][mM][lL]" is not allowed.

You Log says, that you web.xml is malformed. Line 1, colum 7. It may be a UTF-8 Byte-Order-Marker

Try to verify, that your xml is wellformed and does not have a BOM. Java doesn't use BOMs.

Programmatically select a row in JTable

It is an old post, but I came across this recently

Selecting a specific interval

As @aleroot already mentioned, by using

table.setRowSelectionInterval(index0, index1);

You can specify an interval, which should be selected.

Adding an interval to the existing selection

You can also keep the current selection, and simply add additional rows by using this here

table.getSelectionModel().addSelectionInterval(index0, index1);

This line of code additionally selects the specified interval. It doesn't matter if that interval already is selected, of parts of it are selected.

How to draw in JPanel? (Swing/graphics Java)

When working with graphical user interfaces, you need to remember that drawing on a pane is done in the Java AWT/Swing event queue. You can't just use the Graphics object outside the paint()/paintComponent()/etc. methods.

However, you can use a technique called "Frame buffering". Basically, you need to have a BufferedImage and draw directly on it (see it's createGraphics() method; that graphics context you can keep and reuse for multiple operations on a same BufferedImage instance, no need to recreate it all the time, only when creating a new instance). Then, in your JPanel's paintComponent(), you simply need to draw the BufferedImage instance unto the JPanel. Using this technique, you can perform zoom, translation and rotation operations quite easily through affine transformations.

How to send a stacktrace to log4j?

You can also get stack trace as string via ExceptionUtils.getStackTrace.


I use it only for log.debug, to keep log.error simple.

How to convert object array to string array in Java

Another alternative to System.arraycopy:

String[] stringArray = Arrays.copyOf(objectArray, objectArray.length, String[].class);

How to destroy a JavaScript object?

While the existing answers have given solutions to solve the issue and the second half of the question, they do not provide an answer to the self discovery aspect of the first half of the question that is in bold:

"How can I see which variable causes memory overhead...?"

It may not have been as robust 3 years ago, but the Chrome Developer Tools "Profiles" section is now quite powerful and feature rich. The Chrome team has an insightful article on using it and thus also how garbage collection (GC) works in javascript, which is at the core of this question.

Since delete is basically the root of the currently accepted answer by Yochai Akoka, it's important to remember what delete does. It's irrelevant if not combined with the concepts of how GC works in the next two answers: if there's an existing reference to an object it's not cleaned up. The answers are more correct, but probably not as appreciated because they require more thought than just writing 'delete'. Yes, one possible solution may be to use delete, but it won't matter if there's another reference to the memory leak.

Another answer appropriately mentions circular references and the Chrome team documentation can provide much more clarity as well as the tools to verify the cause.

Since delete was mentioned here, it also may be useful to provide the resource Understanding Delete. Although it does not get into any of the actual solution which is really related to javascript's garbage collector.

How to create an Observable from static data similar to http one in Angular?

This is how you can create a simple observable for static data.

let observable = Observable.create(observer => {
  setTimeout(() => {
    let users = [
      {username:"test",city:"mumbai"}]; // This method same as resolve() method from Angular 1
    console.log("am done");
    observer.complete();//to show we are done with our processing
    // observer.error(new Error("error message"));
  }, 2000);


to subscribe to it is very easy

  console.log(data); // users array display

I hope this answer is helpful. We can use HTTP call instead static data.

How to grant "grant create session" privilege?

You would use the WITH ADMIN OPTION option in the GRANT statement


How to check if the docker engine and a docker container are running?

Run this command in the terminal:

docker ps

If docker is not running, you wil get this message:

Error response from daemon: dial unix docker.raw.sock: connect: connection refused

CSS Display an Image Resized and Cropped

.imgContainer {
  overflow: hidden;
  width: 200px;
  height: 100px;
.imgContainer img {
  width: 200px;
  height: 120px;
<div class="imgContainer">
  <img src="imageSrc" />

The containing div with essentially crop the image by hiding the overflow.

PHP array printing using a loop

Another advanced method is called an ArrayIterator. It’s part of a wider class that exposes many accessible variables and functions. You are more likely to see this as part of PHP classes and heavily object-oriented projects.

$fnames = ["Muhammed", "Ali", "Fatimah", "Hasan", "Hussein"];

$arrObject = new ArrayObject($fnames);
$arrayIterator = $arrObject->getIterator();

while( $arrayIterator->valid() ){
echo $arrayIterator->current() . "<br />";

htons() function in socket programing

the htons() function converts values between host and network byte orders. There is a difference between big-endian and little-endian and network byte order depending on your machine and network protocol in use.

Difference between string and StringBuilder in C#

A string instance is immutable. You cannot change it after it was created. Any operation that appears to change the string instead returns a new instance:

string foo = "Foo";
// returns a new string instance instead of changing the old one
string bar = foo.Replace('o', 'a');
string baz = foo + "bar"; // ditto here

Immutable objects have some nice properties, such as they can be used across threads without fearing synchronization problems or that you can simply hand out your private backing fields directly without fearing that someone changes objects they shouldn't be changing (see arrays or mutable lists, which often need to be copied before returning them if that's not desired). But when used carelessly they may create severe performance problems (as nearly anything – if you need an example from a language that prides itself on speed of execution then look at C's string manipulation functions).

When you need a mutable string, such as one you're contructing piece-wise or where you change lots of things, then you'll need a StringBuilder which is a buffer of characters that can be changed. This has, for the most part, performance implications. If you want a mutable string and instead do it with a normal string instance, then you'll end up with creating and destroying lots of objects unnecessarily, whereas a StringBuilder instance itself will change, negating the need for many new objects.

Simple example: The following will make many programmers cringe with pain:

string s = string.Empty;
for (i = 0; i < 1000; i++) {
  s += i.ToString() + " ";

You'll end up creating 2001 strings here, 2000 of which are thrown away. The same example using StringBuilder:

StringBuilder sb = new StringBuilder();
for (i = 0; i < 1000; i++) {
  sb.Append(' ');

This should place much less stress on the memory allocator :-)

It should be noted however, that the C# compiler is reasonably smart when it comes to strings. For example, the following line

string foo = "abc" + "def" + "efg" + "hij";

will be joined by the compiler, leaving only a single string at runtime. Similarly, lines such as

string foo = a + b + c + d + e + f;

will be rewritten to

string foo = string.Concat(a, b, c, d, e, f);

so you don't have to pay for five nonsensical concatenations which would be the naïve way of handling that. This won't save you in loops as above (unless the compiler unrolls the loop but I think only the JIT may actually do so and better don't bet on that).

How to empty (clear) the logcat buffer in Android

The following command will clear only non-rooted buffers (main, system ..etc).

adb logcat -c

If you want to clear all the buffers (like radio, kernel..etc), Please use the following commands

adb root
adb logcat -b all -c


adb root
adb shell logcat -b all -c 

Use the following commands to know the list of buffers that device supports

adb logcat -g
adb logcat -b all -g
adb shell logcat -b all -g

Find what 2 numbers add to something and multiply to something

That's basically a set of 2 simultaneous equations:

x*y = a
X+y = b

(using the mathematical convention of x and y for the variables to solve and a and b for arbitrary constants).

But the solution involves a quadratic equation (because of the x*y), so depending on the actual values of a and b, there may not be a solution, or there may be multiple solutions.

How to round up value C# to the nearest integer?

Math.Round(0.5) returns zero due to floating point rounding errors, so you'll need to add a rounding error amount to the original value to ensure it doesn't round down, eg.

Console.WriteLine(Math.Round(0.5, 0).ToString()); // outputs 0 (!!)
Console.WriteLine(Math.Round(1.5, 0).ToString()); // outputs 2
Console.WriteLine(Math.Round(0.5 + 0.00000001, 0).ToString()); // outputs 1
Console.WriteLine(Math.Round(1.5 + 0.00000001, 0).ToString()); // outputs 2

How to convert IPython notebooks to PDF and HTML?

You can use this simple online service. It supports both HTML and PDF.

Adding a default value in dropdownlist after binding with database

After data-binding, do this:

ddlColor.Items.Insert(0, new ListItem("Select","NA")); //updated code

Or follow Brian's second suggestion if you want to do it in markup.

You should probably add a RequiredFieldValidator control and set its InitialValue to "NA".

<asp:RequiredFieldValidator .. ControlToValidate="ddlColor" InitialValue="NA" />

How do I select an element with its name attribute in jQuery?

You can use:

jQuery('[name="' + nameAttributeValue + '"]');

this will be an inefficient way to select elements though, so it would be best to also use the tag name or restrict the search to a specific element:

jQuery('div[name="' + nameAttributeValue + '"]'); // with tag name
jQuery('div[name="' + nameAttributeValue + '"]',
     document.getElementById('searcharea'));      // with a search base

QR Code encoding and decoding using zxing

I tried using ISO-8859-1 as said in the first answer. All went ok on encoding, but when I tried to get the byte[] using result string on decoding, all negative bytes became the character 63 (question mark). The following code does not work:

// Encoding works great
byte[] contents = new byte[]{-1};
QRCodeWriter codeWriter = new QRCodeWriter();
BitMatrix bitMatrix = codeWriter.encode(new String(contents, Charset.forName("ISO-8859-1")), BarcodeFormat.QR_CODE, w, h);

// Decodes like this fails
LuminanceSource ls = new BufferedImageLuminanceSource(encodedBufferedImage);
Result result = new QRCodeReader().decode(new BinaryBitmap( new HybridBinarizer(ls)));
byte[] resultBytes = result.getText().getBytes(Charset.forName("ISO-8859-1")); // a byte[] with byte 63 is given
return resultBytes;

It looks so strange because the API in a very old version (don't know exactly) had a method thar works well:

Vector byteSegments = result.getByteSegments();

So I tried to search why this method was removed and realized that there is a way to get ByteSegments, through metadata. So my decode method looks like:

// Decodes like this works perfectly
LuminanceSource ls = new BufferedImageLuminanceSource(encodedBufferedImage);
Result result = new QRCodeReader().decode(new BinaryBitmap( new HybridBinarizer(ls)));
Vector byteSegments = (Vector) result.getResultMetadata().get(ResultMetadataType.BYTE_SEGMENTS);  
int i = 0;
int tam = 0;
for (Object o : byteSegments) {
    byte[] bs = (byte[])o;
    tam += bs.length;
byte[] resultBytes = new byte[tam];
i = 0;
for (Object o : byteSegments) {
    byte[] bs = (byte[])o;
    for (byte b : bs) {
        resultBytes[i++] = b;
return resultBytes;

Transport security has blocked a cleartext HTTP

NOTE: The exception domain in your plist should be in LOWER-CASE.

Example: you have named your machine "MyAwesomeMacbook" under Settings->Sharing; your server (for test purposes) is running on MyAwesomeMacbook.local:3000, and your app needs to send a request to http://MyAwesomeMacbook.local:3000/files..., your plist you will need to specify "myawesomemacbook.local" as the exception domain.


Your info.plist would contain...

      <!--Include to allow subdomains-->
      <!--Include to allow HTTP requests-->

Entity Framework rollback and remove bad migration

As of .NET Core 2.2, TargetMigration seems to be gone:

get-help Update-Database


    Updates the database to a specified migration.

    Update-Database [[-Migration] <String>] [-Context <String>] [-Project <String>] [-StartupProject <String>] [<CommonParameters>]

    Updates the database to a specified migration.


    To see the examples, type: "get-help Update-Database -examples".
    For more information, type: "get-help Update-Database -detailed".
    For technical information, type: "get-help Update-Database -full".
    For online help, type: "get-help Update-Database -online"

So this works for me now:

Update-Database -Migration 20180906131107_xxxx_xxxx

As well as (no -Migration switch):

Update-Database 20180906131107_xxxx_xxxx

On an added note, you can no longer cleanly delete migration folders without putting your Model Snapshot out of sync. So if you learn this the hard way and wind up with an empty migration where you know there should be changes, you can run (no switches needed for the last migration):


It will clean up the mess and put you back where you need to be, even though the last migration folder was deleted manually.

AssertNull should be used or AssertNotNull

assertNotNull asserts that the object is not null. If it is null the test fails, so you want that.

What is the function __construct used for?

I believe that function __construct () {...} is a piece of code that can be reused again and again in substitution for TheActualFunctionName () {...}. If you change the CLASS Name you do not have to change within the code because the generic __construct refers always to the actual class name...whatever it is. You code less...or?

What is the string concatenation operator in Oracle?

There's also concat, but it doesn't get used much

select concat('a','b') from dual;

Hiding the address bar of a browser (popup)

In the Edge browser as of build 20.10240.16384.0 you can hide the address bar by setting location=no in the features.

How do I set the value property in AngularJS' ng-options?

Here is how I solve this problem in a legacy application:


ng-options=" for kitType in vm.kitTypes track by" ng-model="vm.itemTypeId"

In JavaScript:

vm.kitTypes = [
    {"id": "1", "name": "Virtual"},
    {"id": "2", "name": "Physical"},
    {"id": "3", "name": "Hybrid"}


vm.itemTypeId = vm.kitTypes.filter(function(value, index, array){
    return === (vm.itemTypeId || 1);

My HTML displays the option value properly.

Skipping every other element after the first

items = range(10)
print items
>>> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
print items[1::2] # every other item after the second; slight variation
>>> [1, 3, 5, 7, 9]

How to iterate over the keys and values with ng-repeat in AngularJS?

Here's a working example:

<div class="item item-text-wrap" ng-repeat="(key,value) in form_list">
  <b>{{key}}</b> : {{value}}


Add/delete row from a table

Hi I would do something like this:

var id = 4; // inital number of rows plus one
function addRow(){
   // add a new tr with id 
   // increment id;

function deleteRow(id){
   $("#" + id).remove();

and i would have a table like this:

<table id = 'dsTable' >
      <tr id=1>
         <td> Relationship Type </td>
         <td> Date of Birth </td>
         <td> Gender </td>
      <tr id=2>
         <td> Spouse </td>
         <td> 1980-22-03 </td>
         <td> female </td>
         <td> <input type="button" id ="addDep" value="Add" onclick = "add()" </td>
         <td> <input type="button" id ="deleteDep" value="Delete" onclick = "deleteRow(2)"  </td>
       <tr id=3>
         <td> Child </td>
         <td> 2008-23-06 </td>
         <td> female </td>
         <td> <input type="button" id ="addDep" value="Add" onclick = "add()"</td>
         <td>  <input type="button" id ="deleteDep" value="Delete" onclick = "deleteRow(3)" </td>

Also if you want you can make a loop to build up the table. So it will be easy to build the table. The same you can do with edit:)

How to add a Java Properties file to my Java Project in Eclipse

If you are working with core java, create your file(.properties) by right clicking your project. If the file is present inside your package or src folder it will throw an file not found error

How to query nested objects?

db.messages.find( { headers : { From: "[email protected]" } } )

This queries for documents where headers equals { From: ... }, i.e. contains no other fields.

db.messages.find( { 'headers.From': "[email protected]" } )

This only looks at the headers.From field, not affected by other fields contained in, or missing from, headers.

Dot-notation docs

Limit the height of a responsive image with css

You can use inline styling to limit the height:

<img src="" class="img-responsive" alt="" style="max-height: 400px;">

Javascript variable access in HTML

It is also possible to use span tag instead of a tag:

   var simpleText = "hello_world";
   var finalSplitText = simpleText.split("_");
   var splitText = finalSplitText[0];

   document.getElementById('someId').InnerHTML = splitText;

  <span id="someId"></span>


It worked well for me

Gradle Sync failed could not find constraint-layout:1.0.0-alpha2

I used with classpath '', it worked like charm.

How can I change the user on Git Bash?

For any OS

This helped me so I'll put it here, just in case. Once you are done with adding the rsa keys for both the accounts, add a config file in your .ssh directory for both the accounts (.ssh/config)

# First account
   User git
   IdentityFile ~/.ssh/id_rsa_user1
# Second account
   User git
   IdentityFile ~/.ssh/id_rsa_user2

Make sure you use the correct usernames and RSA files. Next, you can open the terminal/git bash on the repository root and check which account you would be pushing from

git config

Suppose this returns the first user email and you want to push from the second user. Change the local and :

git config "SECOND_USER"
git config "[email protected]"

(This won't change the global config and you can have the first user set up as the global user). Once done, you can confirm with git config and it should return the email of the second user. You're all set to push to GitHub with the second user. The rest is all the same old git add , git commit and git push. To push from the first user, change the local again and follow the same steps. Hope it helps :)

If the above steps are still not working for you, check to see if you have uploaded the RSA keys within GitHub portal. Refer to GitHub documentation:

Then, clear your ssh cached keys Reference

ssh-add -D

Then add you 2 ssh keys

ssh-add ~/.ssh/id_rsa_user1
ssh-add ~/.ssh/id_rsa_user2

Then type in your terminal:

ssh -T [email protected]<SECOND_ACCOUNT_USERNAME_HERE>

You should see the following output:

Hi <SECOND_USERNAME>! You've successfully authenticated, but GitHub does not provide shell access.

Then, assign the correct remote to your local repository. Make sure you put the same username as the one you gave in your .ssh/config file next to Host. In the following case [email protected]<SECOND_ACCOUNT_USERNAME_HERE>.

git remote rm origin
git remote add origin [email protected]<SECOND_ACCOUNT_USERNAME_HERE>:/your_username/your_repository.git

Pass request headers in a jQuery AJAX GET call

            url: URL,_x000D_
            type: 'GET',_x000D_
            dataType: 'json',_x000D_
            headers: {_x000D_
                'header1': 'value1',_x000D_
                'header2': 'value2'_x000D_
            contentType: 'application/json; charset=utf-8',_x000D_
            success: function (result) {_x000D_
               // CallBack(result);_x000D_
            error: function (error) {_x000D_

Difference between return and exit in Bash functions

First of all, return is a keyword and exit is a function.

That said, here's a simplest of explanations.


It returns a value from a function.


It exits out of or abandons the current shell.

Animate visibility modes, GONE and VISIBLE

Well there is a very easy way, but just setting android:animateLayoutChanges="true" will not work. You need to enableTransitionType in you activity. Check this link for more info:

Select statement to find duplicates on certain fields

If you're using SQL Server 2005 or later (and the tags for your question indicate SQL Server 2008), you can use ranking functions to return the duplicate records after the first one if using joins is less desirable or impractical for some reason. The following example shows this in action, where it also works with null values in the columns examined.

create table Table1 (
 Field1 int,
 Field2 int,
 Field3 int,
 Field4 int 

insert  Table1 
values    (1,1,1,1)
        , (1,1,1,2)
        , (1,1,1,3)
        , (2,2,2,1)
        , (3,3,3,1)
        , (3,3,3,2)
        , (null, null, 2, 1)
        , (null, null, 2, 3)

select    *
from     (select      Field1
                    , Field2
                    , Field3
                    , Field4
                    , row_number() over (partition by   Field1
                                                      , Field2
                                                      , Field3
                                         order by       Field4) as occurrence
          from      Table1) x
where     occurrence > 1

Notice after running this example that the first record out of every "group" is excluded, and that records with null values are handled properly.

If you don't have a column available to order the records within a group, you can use the partition-by columns as the order-by columns.

Difference between TCP and UDP?

Reasons UDP is used for DNS and DHCP:

DNS - TCP requires more resources from the server (which listens for connections) than it does from the client. In particular, when the TCP connection is closed, the server is required to remember the connection's details (holding them in memory) for two minutes, during a state known as TIME_WAIT_2. This is a feature which defends against erroneously repeated packets from a preceding connection being interpreted as part of a current connection. Maintaining TIME_WAIT_2 uses up kernel memory on the server. DNS requests are small and arrive frequently from many different clients. This usage pattern exacerbates the load on the server compared with the clients. It was believed that using UDP, which has no connections and no state to maintain on either client or server, would ameliorate this problem.

DHCP - DHCP is an extension of BOOTP. BOOTP is a protocol which client computers use to get configuration information from a server, while the client is booting. In order to locate the server, a broadcast is sent asking for BOOTP (or DHCP) servers. Broadcasts can only be sent via a connectionless protocol, such as UDP. Therefore, BOOTP required at least one UDP packet, for the server-locating broadcast. Furthermore, because BOOTP is running while the client... boots, and this is a time period when the client may not have its entire TCP/IP stack loaded and running, UDP may be the only protocol the client is ready to handle at that time. Finally, some DHCP/BOOTP clients have only UDP on board. For example, some IP thermostats only implement UDP. The reason is that they are built with such tiny processors and little memory that the are unable to perform TCP -- yet they still need to get an IP address when they boot.

As others have mentioned, UDP is also useful for streaming media, especially audio. Conversations sound better under network lag if you simply drop the delayed packets. You can do that with UDP, but with TCP all you get during lag is a pause, followed by audio that will always be delayed by as much as it has already paused. For two-way phone-style conversations, this is unacceptable.

Compare every item to every other item in ArrayList

for (int i = 0; i < list.size(); i++) {
  for (int j = i+1; j < list.size(); j++) {
    // compare list.get(i) and list.get(j)

'printf' with leading zeros in C

Your format specifier is incorrect. From the printf() man page on my machine:

0 A zero '0' character indicating that zero-padding should be used rather than blank-padding. A '-' overrides a '0' if both are used;

Field Width: An optional digit string specifying a field width; if the output string has fewer characters than the field width it will be blank-padded on the left (or right, if the left-adjustment indicator has been given) to make up the field width (note that a leading zero is a flag, but an embedded zero is part of a field width);

Precision: An optional period, '.', followed by an optional digit string giving a precision which specifies the number of digits to appear after the decimal point, for e and f formats, or the maximum number of characters to be printed from a string; if the digit string is missing, the precision is treated as zero;

For your case, your format would be %09.3f:

#include <stdio.h>

int main(int argc, char **argv)
  printf("%09.3f\n", 4917.24);
  return 0;


$ make testapp
cc     testapp.c   -o testapp
$ ./testapp 

Note that this answer is conditional on your embedded system having a printf() implementation that is standard-compliant for these details - many embedded environments do not have such an implementation.

How to convert variable (object) name into String

You can use deparse and substitute to get the name of a function argument:

myfunc <- function(v1) {

[1] "foo"

How to get a path to the desktop for current user in C#?

// Environment.GetFolderPath
Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData); // Current User's Application Data
Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData); // All User's Application Data
Environment.GetFolderPath(Environment.SpecialFolder.CommonProgramFiles); // Program Files
Environment.GetFolderPath(Environment.SpecialFolder.Cookies); // Internet Cookie
Environment.GetFolderPath(Environment.SpecialFolder.Desktop); // Logical Desktop
Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory); // Physical Desktop
Environment.GetFolderPath(Environment.SpecialFolder.Favorites); // Favorites
Environment.GetFolderPath(Environment.SpecialFolder.History); // Internet History
Environment.GetFolderPath(Environment.SpecialFolder.InternetCache); // Internet Cache
Environment.GetFolderPath(Environment.SpecialFolder.MyComputer); // "My Computer" Folder
Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments); // "My Documents" Folder
Environment.GetFolderPath(Environment.SpecialFolder.MyMusic); // "My Music" Folder
Environment.GetFolderPath(Environment.SpecialFolder.MyPictures); // "My Pictures" Folder
Environment.GetFolderPath(Environment.SpecialFolder.Personal); // "My Document" Folder
Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles); // Program files Folder
Environment.GetFolderPath(Environment.SpecialFolder.Programs); // Programs Folder
Environment.GetFolderPath(Environment.SpecialFolder.Recent); // Recent Folder
Environment.GetFolderPath(Environment.SpecialFolder.SendTo); // "Sent to" Folder
Environment.GetFolderPath(Environment.SpecialFolder.StartMenu); // Start Menu
Environment.GetFolderPath(Environment.SpecialFolder.Startup); // Startup
Environment.GetFolderPath(Environment.SpecialFolder.System); // System Folder
Environment.GetFolderPath(Environment.SpecialFolder.Templates); // Document Templates

Check if a specific tab page is selected (active)

I think that using the event tabPage1.Enter is more convenient.

tabPage1.Enter += new System.EventHandler(tabPage1_Enter);

private void tabPage1_Enter(object sender, EventArgs e)
    MessageBox.Show("you entered tabPage1");

This is better than having nested if-else statement when you have different logic for different tabs. And more suitable in case new tabs may be added in the future.

Note that this event fires if the form loads and tabPage1 is opened by default.

Clearing state es6 React

class x extends Components {
constructor() {
 this.state = {

  name: 'mark',
  age: 32,
  isAdmin: true,
  hits: 0,

  // since this.state is an object
  // simply add a method..

  resetSelectively() {
         //i don't want to reset both name and age
    // THIS IS FOR TRANSPARENCY. You don't need to code for name and age
    // it will assume the values in default..
    // =;   //which means the current state.
    // this.age = this.age;

    // do reset isAdmin and hits(suppose this.state.hits is 100 now)

    isAdmin = false;
    hits = 0;
  }// resetSelectively..


/* now from any function i can just call */
myfunction() {
   * this function code..

}// myfunction..

resetValues() {

//finally you can reset the values in constructor selectively at any point of the class..


update one table with data from another

UPDATE table1
`ID` = (SELECT FROM table2 WHERE table1.`name`=table2.`name`)

How does String.Index work in Swift

func change(string: inout String) {

    var character: Character = .normal

    enum Character {
        case space
        case newLine
        case normal

    for i in stride(from: string.count - 1, through: 0, by: -1) {
        // first get index
        let index: String.Index?
        if i != 0 {
            index = string.index(after: string.index(string.startIndex, offsetBy: i - 1))
        } else {
            index = string.startIndex

        if string[index!] == "\n" {

            if character != .normal {

                if character == .newLine {
                    string.remove(at: index!)
                } else if character == .space {
                    let number = string.index(after: string.index(string.startIndex, offsetBy: i))
                    if string[number] == " " {
                        string.remove(at: number)
                    character = .newLine

            } else {
                character = .newLine

        } else if string[index!] == " " {

            if character != .normal {

                string.remove(at: index!)

            } else {
                character = .space

        } else {

            character = .normal



    // startIndex
    guard string.count > 0 else { return }
    if string[string.startIndex] == "\n" || string[string.startIndex] == " " {
        string.remove(at: string.startIndex)

    // endIndex - here is a little more complicated!
    guard string.count > 0 else { return }
    let index = string.index(before: string.endIndex)
    if string[index] == "\n" || string[index] == " " {
        string.remove(at: index)


how to run or install a *.jar file in windows?

To run usually click and it should run, that is if you have java installed. If not get java from here Sorry thought it was more general open a command prompt and type java -jar jbpm-installer-3.2.7.jar

How do I clone a subdirectory only of a Git repository?

Git 1.7.0 has “sparse checkouts”. See “core.sparseCheckout” in the git config manpage, “Sparse checkout” in the git read-tree manpage, and “Skip-worktree bit” in the git update-index manpage.

The interface is not as convenient as SVN’s (e.g. there is no way to make a sparse checkout at the time of an initial clone), but the base functionality upon which simpler interfaces could be built is now available.

OSError [Errno 22] invalid argument when use open() in Python

I had the same problem It happens because files can't contain special characters like ":", "?", ">" and etc. You should replace these files by using replace() function:

filename = filename.replace("special character to replace", "-")

How to filter array in subdocument with MongoDB

Above solution works best if multiple matching sub documents are required. $elemMatch also comes in very use if single matching sub document is required as output

db.test.find({list: {$elemMatch: {a: 1}}}, {'list.$': 1})


  "_id": ObjectId("..."),
  "list": [{a: 1}]

Sending email from Azure

I know this is an old post but I've just signed up for Azure and I get 25,000 emails a month for free via SendGrid. These instructions are excellent, I was up and running in minutes:

How to Send Email Using SendGrid with Azure

Azure customers can unlock 25,000 free emails each month.

How do I include a JavaScript script file in Angular and call a function from that script?

You can either

import * as abc from './abc';;


import { xyz } from './abc';

Removing address bar from browser (to view on Android)

I found that if you add the command to unload, he keeps down the page, ie the page that move! Hope it works with you too!

window.addEventListener("load", function() { window.scrollTo(0, 1); });
window.addEventListener("unload", function() { window.scrollTo(0, 1); });

Using a 7-inch tablet with android, visit my website and check how it behaves page, I use this command in my portal.

How to change TextField's height and width?

To increase the height of TextField Widget just make use of the maxLines: properties that comes with the widget. For Example: TextField( maxLines: 5 ) // it will increase the height and width of the Textfield.

CSS/Javascript to force html table row on a single line

If you hide the overflow and there is a long word, you risk loosing that word, so you could go one step further and use the "word-wrap" css attribute.

Copying Code from Inspect Element in Google Chrome

Click on the line or element you want to copy. Copy to clipboard. Paste.

The only tricky thing is if you click on a line, you get everything that line includes if it was folded. For example if you click on a div, and copy, you get everything that the div includes.

You can also get only what you want by Right Clicking, and select 'Edit as HTML'. This will make that section essentially text, with none of the folding activated. You can then select, copy and paste the relevant bits.

Java : Convert formatted xml file to one line string

//filename is filepath string
BufferedReader br = new BufferedReader(new FileReader(new File(filename)));
String line;
StringBuilder sb = new StringBuilder();

while((line=br.readLine())!= null){

using StringBuilder is more efficient then concat

arranging div one below the other

If you want the two divs to be displayed one above the other, the simplest answer is to remove the float: left;from the css declaration, as this causes them to collapse to the size of their contents (or the css defined size), and, well float up against each other.

Alternatively, you could simply add clear:both; to the divs, which will force the floated content to clear previous floats.

How to remove specific elements in a numpy array

Remove specific index(i removed 16 and 21 from matrix)

import numpy as np
mat = np.arange(12,26)
a = [4,9]
del_map = np.delete(mat, a)


array([[12, 13, 14, 15],
      [17, 18, 19, 20],
      [22, 23, 24, 25]])

What range of values can integer types store in C++

In C++, now int and other data is stored using 2's compliment method. That means the range is:

-2147483648 to 2147483647

or -2^31 to 2^31-1

1 bit is reserved for 0 so positive value is one less than 2^(31)

null check in jsf expression language

Use empty (it checks both nullness and emptiness) and group the nested ternary expression by parentheses (EL is in certain implementations/versions namely somewhat problematic with nested ternary expressions). Thus, so:

styleClass="#{empty obj.validationErrorMap ? ' ' :  
 (obj.validationErrorMap.contains('key') ? 'highlight_field' : 'highlight_row')}"

If still in vain (I would then check JBoss EL configs), use the "normal" EL approach:

styleClass="#{empty obj.validationErrorMap ? ' ' :  
 (obj.validationErrorMap['key'] ne null ? 'highlight_field' : 'highlight_row')}"

Update: as per the comments, the Map turns out to actually be a List (please work on your naming conventions). To check if a List contains an item the "normal" EL way, use JSTL fn:contains (although not explicitly documented, it works for List as well).

styleClass="#{empty obj.validationErrorMap ? ' ' :  
 (fn:contains(obj.validationErrorMap, 'key') ? 'highlight_field' : 'highlight_row')}"

How to use global variables in React Native?

The global scope in React Native is variable global. Such as = foo, then you can use anywhere.

But do not abuse it! In my opinion, global scope may used to store the global config or something like that. Share variables between different views, as your description, you can choose many other solutions(use redux,flux or store them in a higher component), global scope is not a good choice.

A good practice to define global variable is to use a js file. For example global.js = foo; = bar;

Then, to make sure it is executed when project initialized. For example, import the file in index.js:

import './global.js'
// other code

Now, you can use the global variable anywhere, and don't need to import global.js in each file. Try not to modify them!

Valid characters of a hostname?

If you're registering a domain and the termination (ex .com) it is not IDN, as Aaron Hathaway said: Hostnames are composed of series of labels concatenated with dots, as are all domain names. For example, is a hostname. Each label must be between 1 and 63 characters long, and the entire hostname (including the delimiting dots but not a trailing dot) has a maximum of 253 ASCII characters.

The Internet standards (Requests for Comments) for protocols mandate that component hostname labels may contain only the ASCII letters a through z (in a case-insensitive manner), the digits 0 through 9, and the hyphen -. The original specification of hostnames in RFC 952, mandated that labels could not start with a digit or with a hyphen, and must not end with a hyphen. However, a subsequent specification (RFC 1123) permitted hostname labels to start with digits. No other symbols, punctuation characters, or white space are permitted.

Later, Spain with it's .es,,, .nom,es, and introduced IDN tlds, if your tld is one of .es or any other that supports it, any character can be used, but you can't combine alphabets like Latin, Greek or Cyril in one hostname, and that it respects the things that can't go at the start or at the end.

If you're using non-registered tlds, just for local networking, like with local DNS or with hosts files, you can treat them all as IDN.

Keep in mind some programs could not work well, especially old, outdated and unpopular ones.

How to get value from form field in django framework?

You can do this after you validate your data.

if myform.is_valid():
  data = myform.cleaned_data
  field = data['field']

Also, read the django docs. They are perfect.

Oracle PL/SQL string compare issue

Only change the line str1:=''; to str1:=' ';

What are projection and selection?

Projections and Selections are two unary operations in Relational Algebra and has practical applications in RDBMS (relational database management systems).

In practical sense, yes Projection means selecting specific columns (attributes) from a table and Selection means filtering rows (tuples). Also, for a conventional table, Projection and Selection can be termed as vertical and horizontal slicing or filtering.

Wikipedia provides more formal definitions of these with examples and they can be good for further reading on relational algebra:

Executing set of SQL queries using batch file?

Different ways:

  1. Using SQL Server Agent (If local instance)
    schedule a job in sql server agent with a new step having type as "T-SQL" then run the job.

  2. Using SQLCMD
    To use SQLCMD refer

  3. Using SQLPS
    To use SQLPS refer

Count table rows

Just do a


You can specify conditions with a Where after that

SELECT COUNT(*) FROM table WHERE eye_color='brown';

How to read connection string in .NET Core?

ASP.NET Core (in my case 3.1) provides us with Constructor injections into Controllers, so you may simply add following constructor:

public class TestController : ControllerBase
    private readonly IConfiguration m_config;

    public TestController(IConfiguration config)
        m_config = config;

    public string Get()
        //you can get connection string as follows
        string connectionString = m_config.GetConnectionString("Default")

Here what appsettings.json may look like:

    "ConnectionStrings": {
        "Default": "YOUR_CONNECTION_STRING"

"Sources directory is already netbeans project" error when opening a project from existing sources

The advice here about removing the nbproject directory is not quite the whole story.

What Netbeans seems to do (and we are guessing at reverse engineering here) is to look for an xml file which has opening and closing project tags in it. This it concludes is evidence of an already existing project. Now if your files have an nbproject directory there, that will contain a project.xml file which contains the said tags. So removing that will do what you want.

But, my files don't have a nbproject directory but still NetBeans tells me there is an existing project maybe in memory. The reason is: my files include a file called pom.xml and that contains the said project tags in the xml (it was created by an entirely different system). Once that xml file is removed, then NetBeans will create an html project for me importing my code.

In sum: look through any xml files in you existing code, and be wary of project tags.

Setting a Sheet and cell as variable

Yes, set the cell as a RANGE object one time and then use that RANGE object in your code:

Sub RangeExample()
Dim MyRNG As Range

Set MyRNG = Sheets("Sheet1").Cells(23, 4)

Debug.Print MyRNG.Value

End Sub

Alternately you can simply store the value of that cell in memory and reference the actual value, if that's all you really need. That variable can be Long or Double or Single if numeric, or String:

Sub ValueExample()
Dim MyVal As String

MyVal = Sheets("Sheet1").Cells(23, 4).Value

Debug.Print MyVal

End Sub

Spring boot: Unable to start embedded Tomcat servlet container

This could happen due to the change in java version of the project.Say for example if the project is build in java 8 and if we change the java version to 11 then there can be such issue. In intellij idea go to the File->Project Structure then change the Project SDK Version.

PHP DateTime __construct() Failed to parse time string (xxxxxxxx) at position x

Use the createFromFormat method:

$start_date = DateTime::createFromFormat("U", $dbResult->db_timestamp);


I now recommend the use of Carbon

Favicon: .ico or .png / correct tags?

See here: Cross Browser favicon

Thats the way to go:

<link rel="icon" type="image/png" href=""><!-- Major Browsers -->
<!--[if IE]><link rel="SHORTCUT ICON" href=""/><![endif]--><!-- Internet Explorer-->

Postgres ERROR: could not open file for reading: Permission denied

for macbook first i opened terminal then type

open /tmp

or in finder directory you directly enter command+shift+g then type /tmp in go to the folder.

it opens temp folder in finder. then i paste copied csv file into this folder.then again i go to postgres terminal and typed below command and then it is copied my csv data into db table

\copy recharge_operator FROM '/private/tmp/operator.csv' DELIMITER ',' CSV;

UnicodeDecodeError: 'utf8' codec can't decode byte 0x9c

Just in case of someone has the same problem. I'am using vim with YouCompleteMe, failed to start ycmd with this error message, what I did is: export LC_CTYPE="en_US.UTF-8", the problem is gone.

Query comparing dates in SQL

Instead of '2013-04-12' whose meaning depends on the local culture, use '20130412' which is recognized as the culture invariant format.

If you want to compare with December 4th, you should write '20131204'. If you want to compare with April 12th, you should write '20130412'.

The article Write International Transact-SQL Statements from SQL Server's documentation explains how to write statements that are culture invariant:

Applications that use other APIs, or Transact-SQL scripts, stored procedures, and triggers, should use the unseparated numeric strings. For example, yyyymmdd as 19980924.


Since you are using ADO, the best option is to parameterize the query and pass the date value as a date parameter. This way you avoid the format issue entirely and gain the performance benefits of parameterized queries as well.


To use the the the ISO 8601 format in a literal, all elements must be specified. To quote from the ISO 8601 section of datetime's documentation

To use the ISO 8601 format, you must specify each element in the format. This also includes the T, the colons (:), and the period (.) that are shown in the format.

... the fraction of second component is optional. The time component is specified in the 24-hour format.

How do I get a plist as a Dictionary in Swift?

Swift 3.0

if let path = Bundle.main.path(forResource: "config", ofType: "plist") {
    let dict = NSDictionary(contentsOfFile: path)

    // use dictionary

The easiest way to do this in my opinion.

Display Animated GIF


Use glide:

dependencies {
  implementation 'com.github.bumptech.glide:glide:4.0.0'


Glide.with(context).load(GIF_URI).into(new GlideDrawableImageViewTarget(IMAGE_VIEW));

see docs

Jquery in React is not defined

Try add jQuery to your project, like

npm i jquery --save

or if you use bower

bower i jquery --save


import $ from 'jquery'; 

How can I get the console logs from the iOS Simulator?

Download the safari technology review. With the simulator running, select develop > simulator > localhost

WebAPI to Return XML

Here's another way to be compatible with an IHttpActionResult return type. In this case I am asking it to use the XML Serializer(optional) instead of Data Contract serializer, I'm using return ResponseMessage( so that I get a return compatible with IHttpActionResult:

return ResponseMessage(new HttpResponseMessage(HttpStatusCode.OK)
           Content = new ObjectContent<SomeType>(objectToSerialize, 
              new System.Net.Http.Formatting.XmlMediaTypeFormatter { 
                  UseXmlSerializer = true 

Making heatmap from pandas DataFrame

If you don't need a plot per say, and you're simply interested in adding color to represent the values in a table format, you can use the style.background_gradient() method of the pandas data frame. This method colorizes the HTML table that is displayed when viewing pandas data frames in e.g. the JupyterLab Notebook and the result is similar to using "conditional formatting" in spreadsheet software:

import numpy as np 
import pandas as pd

index= ['aaa', 'bbb', 'ccc', 'ddd', 'eee']
cols = ['A', 'B', 'C', 'D']
df = pd.DataFrame(abs(np.random.randn(5, 4)), index=index, columns=cols)'Blues')

enter image description here

For detailed usage, please see the more elaborate answer I provided on the same topic previously and the styling section of the pandas documentation.

PHP refresh window? equivalent to F5 page reload?

with php you can use two redirections. It works same as refresh in some issues.

you can use a page redirect.php and post your last url to it by GET method (for example). then in redirect.php you can change header to location you`ve sent to it by GET method.

like this: your page:




that worked for me good.

How can I pretty-print JSON using node.js?

what about this?



How to align a <div> to the middle (horizontally/width) of the page

div {
  display: table;
  margin-right: auto;
  margin-left: auto;

JavaScript property access: dot notation vs. brackets?

Let me add some more use case of the square-bracket notation. If you want to access a property say x-proxy in a object, then - will be interpreted wrongly. Their are some other cases too like space, dot, etc., where dot operation will not help you. Also if u have the key in a variable then only way to access the value of the key in a object is by bracket notation. Hope you get some more context.

Init array of structs in Go

You can have it this way:

It is important to mind the commas after each struct item or set of items.

earnings := []LineItemsType{


            TypeName: "Earnings",

            Totals: 0.0,

            HasTotal: true,

            items: []LineItems{


                    name: "Basic Pay",

                    amount: 100.0,


                    name: "Commuter Allowance",

                    amount: 100.0,

            TypeName: "Earnings",

            Totals: 0.0,

            HasTotal: true,

            items: []LineItems{


                    name: "Basic Pay",

                    amount: 100.0,


                    name: "Commuter Allowance",

                    amount: 100.0,

How to create a .NET DateTime from ISO 8601 format

This works fine in LINQPad4:

Console.WriteLine(DateTime.Parse("2010-08-20 15:00:00"));

Imply bit with constant 1 or 0 in SQL Server

cast (
    when FC.CourseId is not null then 1 else 0
as bit)

The CAST spec is "CAST (expression AS type)". The CASE is an expression in this context.

If you have multiple such expressions, I'd declare bit vars @true and @false and use them. Or use UDFs if you really wanted...

DECLARE @True bit, @False bit;
SELECT @True = 1, @False = 0;  --can be combined with declare in SQL 2008

    case when FC.CourseId is not null then @True ELSE @False END AS ...

Serving favicon.ico in ASP.NET MVC

Placing favicon.ico in the root of your domain only really affects IE5, IIRC. For more modern browsers you should be able to include a link tag to point to another directory:

<link rel="SHORTCUT ICON" href=""/>

You can also use non-ico files for browsers other than IE, for which I'd maybe use the following conditional statement to serve a PNG to FF,etc, and an ICO to IE:

<link rel="icon" type="image/png" href="" />
<!--[if IE]>
<link rel="shortcut icon" href="" type="image/" />

When should a class be Comparable and/or Comparator?

Comparable is for objects with a natural ordering. The object itself knows how it is to be ordered.
Comparator is for objects without a natural ordering or when you wish to use a different ordering.

How do you force a CIFS connection to unmount

On RHEL 6 this worked for me also:

umount -f -a -t cifs -l FOLDER_NAME

Android EditText delete(backspace) key event

I sent 2 days to find a solution and I figured out a working one :) (on soft keys)

public TextWatcher textWatcher = new TextWatcher() {
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {   } 

    public void onTextChanged(CharSequence s, int start, int before, int count) {
        if (count == 0) {
        //Put your code here.
        //Runs when delete/backspace pressed on soft key (tested on htc m8)
        //You can use EditText.getText().length() to make if statements here

    public void afterTextChanged(Editable s) {

After add the textwatcher to your EditText:


I hope it works on another android devices too (samsung, LG, etc).

Font is not available to the JVM with Jasper Reports

Copy your Fonts on the following directory JDK_HOME\jre\lib\fonts

AngularJS: ng-repeat list is not updated when a model element is spliced from the model array

If you add a $scope.$apply(); right after $scope.pluginsDisplayed.splice(index,1); then it works.

I am not sure why this is happening, but basically when AngularJS doesn't know that the $scope has changed, it requires to call $apply manually. I am also new to AngularJS so cannot explain this better. I need too look more into it.

I found this awesome article that explains it quite properly. Note: I think it might be better to use ng-click (docs) rather than binding to "mousedown". I wrote a simple app here (, source based on AngularJS. It is not very clean, but it might be of help.

Code signing is required for product type Unit Test Bundle in SDK iOS 8.0

Sometimes this happens when you download a project from github or other third party tutorial sites.These apps are usually signed with a different identity or company/name.When this happens,if you can't solve the solution,simply create a new xcode project and copy all the header and implementation files into your new project.Also don't forget the dependency files..such as the framework files.This works for me.

Android Failed to install HelloWorld.apk on device (null) Error

I was getting the same errors with my devices.
First be sure that you do not upload debug apk to a device having already installed the same apk but signed with release cert. In this case you've got to uninstall it first from the device.
In other cases my solution is to reboot everything:

  1. reboot device
  2. pskill emulator-arm.exe
  3. pskill eclipse.exe
  4. pskill adb.exe

After that the device, adb and eclipse are working.

android asynctask sending callbacks to ui

You can create an interface, pass it to AsyncTask (in constructor), and then call method in onPostExecute()

For example:

Your interface:

public interface OnTaskCompleted{
    void onTaskCompleted();

Your Activity:

public class YourActivity implements OnTaskCompleted{
    // your Activity

And your AsyncTask:

public class YourTask extends AsyncTask<Object,Object,Object>{ //change Object to required type
    private OnTaskCompleted listener;

    public YourTask(OnTaskCompleted listener){

    // required methods

    protected void onPostExecute(Object o){
        // your stuff


Since this answer got quite popular, I want to add some things.

If you're a new to Android development, AsyncTask is a fast way to make things work without blocking UI thread. It does solves some problems indeed, there is nothing wrong with how the class works itself. However, it brings some implications, such as:

  • Possibility of memory leaks. If you keep reference to your Activity, it will stay in memory even after user left the screen (or rotated the device).
  • AsyncTask is not delivering result to Activity if Activity was already destroyed. You have to add extra code to manage all this stuff or do you operations twice.
  • Convoluted code which does everything in Activity

When you feel that you matured enough to move on with Android, take a look at this article which, I think, is a better way to go for developing your Android apps with asynchronous operations.

Git merge two local branches

If you or another dev will not work on branchB further, I think it's better to keep commits in order to make reverts without headaches. So ;

git checkout branchA
git pull --rebase branchB

It's important that branchB shouldn't be used anymore.

For more ;

How do I create a HTTP Client Request with a cookie?

You can do that using Requestify, a very simple and cool HTTP client I wrote for nodeJS, it support easy use of cookies and it also supports caching.

To perform a request with a cookie attached just do the following:

var requestify = require('requestify');'', {}, {
    cookies: {
        sessionCookie: 'session-cookie-data'   

Creating new database from a backup of another Database on the same server?

Checking the Options Over Write Database worked for me :)

enter image description here

Use dynamic variable names in JavaScript

It is always better to use create a namespace and declare a variable in it instead of adding it to the global object. We can also create a function to get and set the value

See the below code snippet:

//creating a namespace in which all the variables will be defined.
var myObjects={};

//function that will set the name property in the myObjects namespace
function setName(val){

//function that will return the name property in the myObjects namespace
function getName(){
  return myObjects.Name;

//now we can use it like:
  var x = getName();
  var y = x;
  console.log(y)  //"kevin"
  var z = "y";
  console.log(z); //"y"
  console.log(eval(z)); //"kevin"

In this similar way, we can declare and use multiple variables. Although this will increase the line of code but the code will be more robust and less error-prone.

ggplot2: sorting a plot

You need to make the x-factor into an ordered factor with the ordering you want, e.g

x <- data.frame("variable"=letters[1:5], "value"=rnorm(5)) ## example data
x <- x[with(x,order(-value)), ] ## Sorting
x$variable <- ordered(x$variable, levels=levels(x$variable)[unclass(x$variable)])

ggplot(x, aes(x=variable,y=value)) + geom_bar() +
   scale_y_continuous("",formatter="percent") + coord_flip()

I don't know any better way to do the ordering operation. What I have there will only work if there are no duplicate levels for x$variable.

Change Screen Orientation programmatically using a Button

Yes it is implementable!






Refer the link:

Button buttonSetPortrait = (Button)findViewById(;
Button buttonSetLandscape = (Button)findViewById(;

buttonSetPortrait.setOnClickListener(new Button.OnClickListener(){

   public void onClick(View arg0) {


buttonSetLandscape.setOnClickListener(new Button.OnClickListener(){

   public void onClick(View arg0) {


OpenCV - Apply mask to a color image

Answer given by Abid Rahman K is not completely correct. I also tried it and found very helpful but got stuck.

This is how I copy image with a given mask.

x, y = np.where(mask!=0)
pts = zip(x, y)
# Assuming dst and src are of same sizes
for pt in pts:
   dst[pt] = src[pt]

This is a bit slow but gives correct results.


Pythonic way.

idx = (mask!=0)
dst[idx] = src[idx]

Difference between maven scope compile and provided for JAR packaging

If jar file is like executable spring boot jar file then scope of all dependencies must be compile to include all jar files.

But if jar file used in other packages or applications then it does not need to include all dependencies in jar file because these packages or applications can provide other dependencies themselves.

CORS with spring-boot and angularjs not working

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

public class SimpleCORSFilter implements Filter {

private final Logger log = LoggerFactory.getLogger(SimpleCORSFilter.class);

public SimpleCORSFilter() {"SimpleCORSFilter init");

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {

    HttpServletRequest request = (HttpServletRequest) req;
    HttpServletResponse response = (HttpServletResponse) res;

    response.setHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
    response.setHeader("Access-Control-Allow-Credentials", "true");
    response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
    response.setHeader("Access-Control-Max-Age", "3600");
    response.setHeader("Access-Control-Allow-Headers", "Content-Type, Accept, X-Requested-With, remember-me");

    chain.doFilter(req, res);

public void init(FilterConfig filterConfig) {

public void destroy() {


No need extra define this filter just add this class. Spring will be scan and add it for you. SimpleCORSFilter. Here is the example: spring-enable-cors

How to parse XML in Bash?

Well, you can use xpath utility. I guess perl's XML::Xpath contains it.

How to make one Observable sequence wait for another to complete before emitting?

Here's a custom operator written with TypeScript that waits for a signal before emitting results:

export function waitFor<T>(
    signal$: Observable<any>
) {
    return (source$: Observable<T>) =>
        new Observable<T>(observer => {
            // combineLatest emits the first value only when
            // both source and signal emitted at least once
                .subscribe(([v]) =>;

You can use it like this:

   .subscribe(value => ...);

Bootstrap Columns Not Working

Your Nesting DIV structure was missing, you must add another ".row" div when creating nested divs in bootstrap :

Here is the Code:

<div class="container">
   <div class="row">
            <div class="col-md-12">
                <div class="row">
                    <div class="col-md-4"> <a href="">About</a>
                    <div class="col-md-4">
                        <img src="" width="100px" />
                    <div class="col-md-4"> <a href="#myModal1" data-toggle="modal">SHARE</a>

Refer the Bootstrap example description for the same:

Nesting columns

To nest your content with the default grid, add a new .row and set of .col-sm-* columns within an existing .col-sm-* column. Nested rows should include a set of columns that add up to 12 or less (it is not required that you use all 12 available columns).

Here is the working Fiddle of your code:

Ansible Ignore errors in tasks and fail at end of the playbook if any tasks had errors

Use Fail module.

  1. Use ignore_errors with every task that you need to ignore in case of errors.
  2. Set a flag (say, result = false) whenever there is a failure in any task execution
  3. At the end of the playbook, check if flag is set, and depending on that, fail the execution
- fail: msg="The execution has failed because of errors."
  when: flag == "failed"


Use register to store the result of a task like you have shown in your example. Then, use a task like this:

- name: Set flag
  set_fact: flag = failed
  when: "'FAILED' in command_result.stderr"

How to properly override clone method?

There are two cases in which the CloneNotSupportedException will be thrown:

  1. The class being cloned does not implemented Cloneable (assuming that the actual cloning eventually defers to Object's clone method). If the class you are writing this method in implements Cloneable, this will never happen (since any sub-classes will inherit it appropriately).
  2. The exception is explicitly thrown by an implementation - this is the recommended way to prevent clonability in a subclass when the superclass is Cloneable.

The latter case cannot occur in your class (as you're directly calling the superclass' method in the try block, even if invoked from a subclass calling super.clone()) and the former should not since your class clearly should implement Cloneable.

Basically, you should log the error for sure, but in this particular instance it will only happen if you mess up your class' definition. Thus treat it like a checked version of NullPointerException (or similar) - it will never be thrown if your code is functional.

In other situations you would need to be prepared for this eventuality - there is no guarantee that a given object is cloneable, so when catching the exception you should take appropriate action depending on this condition (continue with the existing object, take an alternative cloning strategy e.g. serialize-deserialize, throw an IllegalParameterException if your method requires the parameter by cloneable, etc. etc.).

Edit: Though overall I should point out that yes, clone() really is difficult to implement correctly and difficult for callers to know whether the return value will be what they want, doubly so when you consider deep vs shallow clones. It's often better just to avoid the whole thing entirely and use another mechanism.

Python 3: ImportError "No Module named Setuptools"

Make sure you are running latest version of pip

Tried to install ansible and it failed with ModuleNotFoundError: No module named 'setuptools_rust'

python3-setuptools already in place so upgrading pip solved it.

pip3 install -U pip 

Show a number to two decimal places

I make my own.

$decimals = 2;
$number = 221.12345;
$number = $number * pow(10, $decimals);
$number = intval($number);
$number = $number / pow(10, $decimals);

Correct way to delete cookies server-side

For GlassFish Jersey JAX-RS implementation I have resolved this issue by common method is describing all common parameters. At least three of parameters have to be equal: name(="name"), path(="/") and domain(=null) :

public static NewCookie createDomainCookie(String value, int maxAgeInMinutes) {
    ZonedDateTime time =;
    Date expiry = time.toInstant().toEpochMilli();
    NewCookie newCookie = new NewCookie("name", value, "/", null, Cookie.DEFAULT_VERSION,null, maxAgeInMinutes*60, expiry, false, false);
    return newCookie;

And use it the common way to set cookie:

NewCookie domainNewCookie = RsCookieHelper.createDomainCookie(token, 60);
Response res = Response.status(Response.Status.OK).cookie(domainNewCookie).build();

and to delete the cookie:

NewCookie domainNewCookie = RsCookieHelper.createDomainCookie("", 0);
Response res = Response.status(Response.Status.OK).cookie(domainNewCookie).build();

How to a convert a date to a number and back again in MATLAB


>> datestr(40189)
ans =

Unfortunately, Excel starts counting at 1-Jan-1900. Find out how to convert serial dates from Matlab to Excel by using DATENUM

>> datenum(2010,1,11)
ans =
>> datenum(2010,1,11)-40189
ans =
>> datestr(40189+693960)
ans =

In other words, to convert any serial Excel date, call

datestr(excelSerialDate + 693960)


To get the date in mm/dd/yyyy format, call datestr with the specified format

excelSerialDate = 40189;
datestr(excelSerialDate + 693960,'mm/dd/yyyy')
ans =

Also, if you want to get rid of the leading zero for the month, you can use REGEXPREP to fix things

excelSerialDate = 40189;
regexprep(datestr(excelSerialDate + 693960,'mm/dd/yyyy'),'^0','')
ans =

array filter in python?

This was just asked a couple of days ago (but I cannot find it):

>>> A = [6, 7, 8, 9, 10, 11, 12]
>>> subset_of_A = set([6, 9, 12])
>>> [i for i in A if i not in subset_of_A]
[7, 8, 10, 11]

It might be better to use sets from the beginning, depending on the context. Then you can use set operations like other answers show.

However, converting lists to sets and back only for these operations is slower than list comprehension.

Error: free(): invalid next size (fast):

I encountered the same problem, even though I did not make any dynamic memory allocation in my program, but I was accessing a vector's index without allocating memory for it. So, if the same case, better allocate some memory using resize() and then access vector elements.

How to find the Vagrant IP?

I know this post is old but i want to add a few points to this!

you can try

vagrant ssh -c "ifconfig | grep inet" hostname 

this will be easy if you have setup a name to your guests individually!

Removing specific rows from a dataframe

DF[ ! ( ( DF$sub ==1 & DF$day==2) | ( DF$sub ==3 & DF$day==4) ) , ]   # note the ! (negation)

Or if sub is a factor as suggested by your use of quotes:

DF[ ! paste(sub,day,sep="_") %in% c("1_2", "3_4"), ]

Could also use subset:

subset(DF,  ! paste(sub,day,sep="_") %in% c("1_2", "3_4") )

(And I endorse the use of which in Dirk's answer when using "[" even though some claim it is not needed.)

Javascript setInterval not working

A lot of other answers are focusing on a pattern that does work, but their explanations aren't really very thorough as to why your current code doesn't work.

Your code, for reference:

function funcName() {

var func = funcName();
var run = setInterval("func",10000)

Let's break this up into chunks. Your function funcName is fine. Note that when you call funcName (in other words, you run it) you will be alerting "test". But notice that funcName() -- the parentheses mean to "call" or "run" the function -- doesn't actually return a value. When a function doesn't have a return value, it defaults to a value known as undefined.

When you call a function, you append its argument list to the end in parentheses. When you don't have any arguments to pass the function, you just add empty parentheses, like funcName(). But when you want to refer to the function itself, and not call it, you don't need the parentheses because the parentheses indicate to run it.

So, when you say:

var func = funcName();

You are actually declaring a variable func that has a value of funcName(). But notice the parentheses. funcName() is actually the return value of funcName. As I said above, since funcName doesn't actually return any value, it defaults to undefined. So, in other words, your variable func actually will have the value undefined.

Then you have this line:

var run = setInterval("func",10000)

The function setInterval takes two arguments. The first is the function to be ran every so often, and the second is the number of milliseconds between each time the function is ran.

However, the first argument really should be a function, not a string. If it is a string, then the JavaScript engine will use eval on that string instead. So, in other words, your setInterval is running the following JavaScript code:

// 10 seconds later....
// and so on

However, func is just a variable (with the value undefined, but that's sort of irrelevant). So every ten seconds, the JS engine evaluates the variable func and returns undefined. But this doesn't really do anything. I mean, it technically is being evaluated every 10 seconds, but you're not going to see any effects from that.

The solution is to give setInterval a function to run instead of a string. So, in this case:

var run = setInterval(funcName, 10000);

Notice that I didn't give it func. This is because func is not a function in your code; it's the value undefined, because you assigned it funcName(). Like I said above, funcName() will call the function funcName and return the return value of the function. Since funcName doesn't return anything, this defaults to undefined. I know I've said that several times now, but it really is a very important concept: when you see funcName(), you should think "the return value of funcName". When you want to refer to a function itself, like a separate entity, you should leave off the parentheses so you don't call it: funcName.

So, another solution for your code would be:

var func = funcName;
var run = setInterval(func, 10000);

However, that's a bit redundant: why use func instead of funcName?

Or you can stay as true as possible to the original code by modifying two bits:

var func = funcName;
var run = setInterval("func()", 10000);

In this case, the JS engine will evaluate func() every ten seconds. In other words, it will alert "test" every ten seconds. However, as the famous phrase goes, eval is evil, so you should try to avoid it whenever possible.

Another twist on this code is to use an anonymous function. In other words, a function that doesn't have a name -- you just drop it in the code because you don't care what it's called.

setInterval(function () {
}, 10000);

In this case, since I don't care what the function is called, I just leave a generic, unnamed (anonymous) function there.

Add marker to Google Map on Click

In 2017, the solution is:

map.addListener('click', function(e) {
    placeMarker(e.latLng, map);

function placeMarker(position, map) {
    var marker = new google.maps.Marker({
        position: position,
        map: map

Flex-box: Align last row to grid

Without any extra markup, just adding ::after worked for me specifying the width of the column.

.grid {
  content: '';
  width: 10em // Same width of .grid__element

With the HTML like this:

<div class=grid">
   <div class="grid__element"></div>
   <div class="grid__element"></div>
   <div class="grid__element"></div>

Python dict how to create key or append an element to key?

You can use defaultdict in collections.

An example from doc:

s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
d = defaultdict(list)
for k, v in s:

java.lang.IllegalStateException: Only fullscreen opaque activities can request orientation

If you haven't resolved your problem just register the ad activity in the manifest like this:


You also need to update to the latest version of the sdk.

Convert Numeric value to Varchar

First convert the numeric value then add the 'S':

 select convert(varchar(10),StandardCost) +'S'
 from DimProduct where ProductKey = 212

increase the java heap size permanently?

Apparently, _JAVA_OPTIONS works on Linux, too:

$ export _JAVA_OPTIONS="-Xmx1g"
$ java -jar jconsole.jar &
Picked up _JAVA_OPTIONS: -Xmx1g

log4j configuration via JVM argument(s)?

Generally, as long as your file is on the classpath, Log4j should just automatically pick it up at JVM startup.

How to set shape's opacity?

Use this one, I've written this to my app,

<?xml version="1.0" encoding="utf-8"?>
<!--  res/drawable/rounded_edittext.xml -->
<shape xmlns:android=""
    android:shape="rectangle" android:padding="10dp">
    <solid android:color="#882C383E"/>

Unit testing with Spring Security

Just do it the usual way and then insert it using SecurityContextHolder.setContext() in your test class, for example:


Authentication a = SecurityContextHolder.getContext().getAuthentication();


Authentication authentication = Mockito.mock(Authentication.class);
// Mockito.whens() for your authorization object
SecurityContext securityContext = Mockito.mock(SecurityContext.class);

Why is `input` in Python 3 throwing NameError: name... is not defined

You're running your Python 3 code with a Python 2 interpreter. If you weren't, your print statement would throw up a SyntaxError before it ever prompted you for input.

The result is that you're using Python 2's input, which tries to eval your input (presumably sdas), finds that it's invalid Python, and dies.

ImportError: cannot import name NUMPY_MKL

I don't have enough reputation to comment but I want to add, that the cp number of the .whl file stands for your python version.

cp35 -> Python 3.5.x

cp36 -> Python 3.6.x

cp37 -> Python 3.7.x

I think it's pretty obvious but still I wasted almost an hour because of this and maybe other people struggle with that, too.

So for me worked version cp36 that I downloaded here: since I am using Python 3.6.8.

Then I uninstalled numpy:

pip uninstall numpy 

Then I installed numpy+mkl:

pip install <destination of your .whl file>

What does "while True" mean in Python?

In some languages True is just and alias for the number. You can learn more why this is by reading more about boolean logic.

Detect the Enter key in a text input field

It may be too late to answer this question. But the following code simply prevents the enter key. Just copy and paste should work.

        <script type="text/javascript"> 
        function stopRKey(evt) { 
          var evt = (evt) ? evt : ((event) ? event : null); 
          var node = ( ? : ((evt.srcElement) ? evt.srcElement : null); 
          if ((evt.keyCode == 13) && (node.type=="text"))  {return false;} 

        document.onkeypress = stopRKey; 


How to open a website when a Button is clicked in Android application?

In your Java file write the following piece of code...

ImageView Button = (ImageView)findViewById(;

Button.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        Intent intent = new Intent();

What are the pros and cons of parquet format compared to other formats?

Avro is a row-based storage format for Hadoop.

Parquet is a column-based storage format for Hadoop.

If your use case typically scans or retrieves all of the fields in a row in each query, Avro is usually the best choice.

If your dataset has many columns, and your use case typically involves working with a subset of those columns rather than entire records, Parquet is optimized for that kind of work.


String contains - ignore case

If you won't go with regex:


Getting the minimum of two values in SQL

Use a CASE statement.

Example B in this page should be close to what you're trying to do:

Here's the code from the page:

USE AdventureWorks;
SELECT   ProductNumber, Name, 'Price Range' = 
         WHEN ListPrice =  0 THEN 'Mfg item - not for resale'
         WHEN ListPrice < 50 THEN 'Under $50'
         WHEN ListPrice >= 50 and ListPrice < 250 THEN 'Under $250'
         WHEN ListPrice >= 250 and ListPrice < 1000 THEN 'Under $1000'
         ELSE 'Over $1000'
FROM Production.Product
ORDER BY ProductNumber ;

Table border left and bottom

you can use these styles:

style="border-left: 1px solid #cdd0d4;"  
style="border-bottom: 1px solid #cdd0d4;"
style="border-top: 1px solid #cdd0d4;"
style="border-right: 1px solid #cdd0d4;"

with this you want u must use

<td style="border-left: 1px solid #cdd0d4;border-bottom: 1px solid #cdd0d4;">  


<img style="border-left: 1px solid #cdd0d4;border-bottom: 1px solid #cdd0d4;"> 

How can I debug my JavaScript code?

Besides using Visual Studio's JavaScript debugger, I wrote my own simple panel that I include to a page. It's simply like the Immediate window of Visual Studio. I can change my variables' values, call my functions, and see variables' values. It simply evaluates the code written in the text field.

Best way to deploy Visual Studio application that can run without installing

First you need to publish the file by:

  1. BUILD -> PUBLISH or by right clicking project on Solution Explorer -> properties -> publish or select project in Solution Explorer and press Alt + Enter NOTE: if you are using Visual Studio 2013 then in properties you have to go to BUILD and then you have to disable define DEBUG constant and define TRACE constant and you are ready to go. Representation

  2. Save your file to a particular folder. Find the produced files (the EXE file and the .config, .manifest, and .application files, along with any DLL files, etc.) - they are all in the same folder and typically in the bin\Debug folder below the project file (.csproj). In Visual Studio they are in the Application Files folder and inside that you just need the .exe and dll files. (You have to delete ClickOnce and other files and then make this folder a zip file and distribute it.)

NOTE: The ClickOnce application does install the project to system, but it has one advantage. You DO NOT require administrative privileges here to run (if your application follows the normal guidelines for which folders to use for application data, etc.).

Match whitespace but not newlines

Perl versions 5.10 and later support subsidiary vertical and horizontal character classes, \v and \h, as well as the generic whitespace character class \s

The cleanest solution is to use the horizontal whitespace character class \h. This will match tab and space from the ASCII set, non-breaking space from extended ASCII, or any of these Unicode characters

U+0020 SPACE
U+00A0 NO-BREAK SPACE (not matched by \s)

U+2000 EN QUAD
U+2001 EM QUAD

The vertical space pattern \v is less useful, but matches these characters

U+0085 NEXT LINE (not matched by \s)


There are seven vertical whitespace characters which match \v and eighteen horizontal ones which match \h. \s matches twenty-three characters

All whitespace characters are either vertical or horizontal with no overlap, but they are not proper subsets because \h also matches U+00A0 NO-BREAK SPACE, and \v also matches U+0085 NEXT LINE, neither of which are matched by \s

R: += (plus equals) and ++ (plus plus) equivalent from c++/c#/java, etc.?

We can override +. If unary + is used and its argument is itself an unary + call, then increment the relevant variable in the calling environment.

`+` <- function(e1,e2){
    # if unary `+`, keep original behavior
    if(missing(e2)) {
      s_e1 <- substitute(e1)
      # if e1 (the argument of unary +) is itself an unary `+` operation
      if(length(s_e1) == 2 && 
         identical(s_e1[[1]], quote(`+`)) && 
         length(s_e1[[2]]) == 1) {
        # increment value in parent environment
        eval.parent(substitute(e1 <- e1 + 1, list(e1 = s_e1[[2]])))
      # else unary `+` should just return it's input
      } else e1
    # if binary `+`, keep original behavior
    } else .Primitive("+")(e1, e2)

x <- 10
# [1] 11

other operations don't change :

x + 2
# [1] 13
x ++ 2
# [1] 13
# [1] 11
# [1] 11

Don't do it though, as you'll slow down everything. Or do it in another environment and make sure you don't have big loops on these instructions.

You can also just do this :

`++` <- function(x) eval.parent(substitute(x <- x + 1))
a <- 1
# [1] 2

AssertionError: View function mapping is overwriting an existing endpoint function: main

use flask 0.9 instead use the following commands sudo pip uninstall flask

sudo pip install flask==0.9

Most efficient way to remove special characters from string

You can use regular expresion as follows:

return Regex.Replace(strIn, @"[^\w\.@-]", "", RegexOptions.None, TimeSpan.FromSeconds(1.0));

How to write asynchronous functions for Node.js

Just passing by callbacks is not enough. You have to use settimer for example, to make function async.

Examples: Not async functions:

function a() {
  var a = 0;    
  for(i=0; i<10000000; i++) {

function b() {
  var a = 0;    
  for(i=0; i<10000000; i++) {

function c() {
  for(i=0; i<10000000; i++) {
  console.log("async finished!");

console.log("This should be good");

If you will run above example, This should be good, will have to wait untill those functions will finish to work.

Pseudo multithread (async) functions:

function a() {
  setTimeout ( function() {
    var a = 0;  
    for(i=0; i<10000000; i++) {
  }, 0);

function b() {
  setTimeout ( function() {
    var a = 0;  
    for(i=0; i<10000000; i++) {
  }, 0);

function c() {
  setTimeout ( function() {
    for(i=0; i<10000000; i++) {
    console.log("async finished!");
  }, 0);

console.log("This should be good");

This one will be trully async. This should be good will be writen before async finished.

How do I make a placeholder for a 'select' box?

Try this for a change:

$("select").css("color", "#757575");
$(document).on("change", "select", function(){
    if ($(this).val() != "") {
        $(this).css("color", "");
    else {
        $(this).css("color", "#757575");

Smooth scroll to div id jQuery

are you sure you are loading the jQuery scrollTo Plugin file?

you might be getting a object: method not found "scrollTo" error in the console.

the scrollTO method is not a native jquery method. to use it you need to include the jquery scroll To plugin file.


soln: add this in the head section.

<script src="\\path\to\the\jquery.scrollTo.js file"></script>

Rerouting stdin and stdout from C

This is a modified version of Tim Post's method; I used /dev/tty instead of /dev/stdout. I don't know why it doesn't work with stdout (which is a link to /proc/self/fd/1):


By using /dev/tty the output is redirected to the terminal from where the app was launched.

Hope this info is useful.

Failed to execute 'atob' on 'Window'

In my case, I was going nuts since there wasn't any issues with the string to be decoded, since I could successfully decode it on online tools. Until I found out that you first have to decodeURIComponent what you are decoding, like so:


Generics/templates in python?

If you using Python 2 or want to rewrite java code. Their is not real solution for this. Here is what I get working in a night: I still get no compiler so you currently using it like that:

class A(GenericObject):
    def __init__(self, *args, **kwargs):
        GenericObject.__init__(self, [
        ], *args, **kwargs)

    def _init(self, c, a, b):
        print "success c="+str(c)+" a="+str(a)+" b="+str(b)


  • Compiler
  • Get Generic Classes and Types working (For things like <? extends List<Number>>)
  • Add super support
  • Add ? support
  • Code Clean Up

What is the correct way to declare a boolean variable in Java?

First of all, you should use none of them. You are using wrapper type, which should rarely be used in case you have a primitive type. So, you should use boolean rather.

Further, we initialize the boolean variable to false to hold an initial default value which is false. In case you have declared it as instance variable, it will automatically be initialized to false.

But, its completely upto you, whether you assign a default value or not. I rather prefer to initialize them at the time of declaration.

But if you are immediately assigning to your variable, then you can directly assign a value to it, without having to define a default value.

So, in your case I would use it like this: -

boolean isMatch = email1.equals (email2);

how to insert date and time in oracle?

Try this:

...(to_date('2011/04/22 08:30:00', 'yyyy/mm/dd hh24:mi:ss'));

How can I change the width and height of slides on Slick Carousel?

You could also use this:

   //other settings ................
   respondTo: 'slider', //makes the slider to change width depending on the container it is in
   adaptiveHeight: true //makes the height change depending on the height of the element inside

How can I redirect a php page to another php page?

Send a Location header to redirect. Keep in mind this only works before any other output is sent.

header('Location: index.php'); // redirect to index.php

How to trigger a file download when clicking an HTML button or JavaScript

If you use the <a> tag, do not forget to use the entire url which leads to the file -- i.e.:

<a href="">Download</a>

How to modify a CSS display property from JavaScript?

I found the solution.

As said in the EDIT of my answer, a <div> is misfunctioning in a <table>. So I wrote this code instead :

<tr id="hidden" style="display:none;">
    <td class="depot_table_left">
        <label for="sexe">Sexe</label>
        <select type="text" name="sexe">
            <option value="1">Sexe</option>
            <option value="2">Joueur</option>
            <option value="3">Joueuse</option>

And this is working fine.

Thanks everybody ;)

Search for an item in a Lua list

you can use this solution:

items = { 'a', 'b' }
for k,v in pairs(items) do 
 if v == 'a' then 
  --do something
  --do something


items = {'a', 'b'}
for k,v in pairs(items) do 
  while v do
    if v == 'a' then 
      return found
return nothing

Python | change text color in shell

I just described very popular library clint. Which has more features apart of coloring the output on terminal.

By the way it support MAC, Linux and Windows terminals.

Here is the example of using it:

Installing (in Ubuntu)

pip install clint

To add color to some string'red string')

Example: Using for color output (django command style)

from import BaseCommand
from clint.textui import colored

class Command(BaseCommand):
    args = ''
    help = 'Starting my own django long process. Use ' +'<Ctrl>+c') + ' to break.'

    def handle(self, *args, **options):
        self.stdout.write('Starting the process (Use ' +'<Ctrl>+c') + ' to break)..')
        # ... Rest of my command code ...

General error: 1364 Field 'user_id' doesn't have a default value

use print_r(Auth);

then see in which format you have user_id / id variable and use it

bootstrap initially collapsed element

another solution is to add toggle=false to the collapse target, this will stop it randomly opening and closing which happens if you just remove the "in"


<div class="accordion-heading">
    <a class="accordion-toggle"
    class="accordion-body collapse"
    <div class="span6">
        <div class="well well-small">
            <div class="accordion-toggle">
                ...some text...
    <div class="span2"></div>                            

Fatal error: Call to undefined function mb_detect_encoding()

There's a much easier way than recompiling PHP. Just yum install the required mbstring library:

Example: How to install PHP mbstring on CentOS 6.2

yum --enablerepo=remi install php-mbstring

Oh, and don't forget to restart apache afterward.

How do you run a js file using npm scripts?

You should use npm run-script build or npm build <project_folder>. More info here:

Android setOnClickListener method - How does it work?

It works by same principle of anonymous inner class where we can instantiate an interface without actually defining a class :


What is the easiest way to push an element to the beginning of the array?

What about using the unshift method?

ary.unshift(obj, ...) ? ary
Prepends objects to the front of self, moving other elements upwards.

And in use:

irb>> a = [ 0, 1, 2]
=> [0, 1, 2]
irb>> a.unshift('x')
=> ["x", 0, 1, 2]
irb>> a.inspect
=> "["x", 0, 1, 2]"

Could not obtain information about Windows NT group user

Just solved this problem. In my case it was domain controller is not accessible, because both dns servers was google dns.

I just add to checklist for this problem:

  • check domain controller is accessible

How to do jquery code AFTER page loading?


$(document).ready(function() { 

can be replaced

$(window).bind("load", function() { 
     // insert your code here 

There is once more way which i'm using to increase the page load time.

$(document).ready(function() { 
  $(window).load(function() { 
     //insert all your ajax callback code here. 
     //Which will run only after page is fully loaded in background.

How do I ALTER a PostgreSQL table and make a column unique?

I figured it out from the PostgreSQL docs, the exact syntax is:

ALTER TABLE the_table ADD CONSTRAINT constraint_name UNIQUE (thecolumn);

Thanks Fred.

How to run .APK file on emulator

Step-by-Step way to do this:

  1. Install Android SDK
  2. Start the emulator by going to $SDK_root/emulator.exe
  3. Go to command prompt and go to the directory $SDK_root/platform-tools (or else add the path to windows environment)
  4. Type in the command adb install
  5. Bingo. Your app should be up and running on the emulator

HttpClient.GetAsync(...) never returns when using await/async

You are misusing the API.

Here's the situation: in ASP.NET, only one thread can handle a request at a time. You can do some parallel processing if necessary (borrowing additional threads from the thread pool), but only one thread would have the request context (the additional threads do not have the request context).

This is managed by the ASP.NET SynchronizationContext.

By default, when you await a Task, the method resumes on a captured SynchronizationContext (or a captured TaskScheduler, if there is no SynchronizationContext). Normally, this is just what you want: an asynchronous controller action will await something, and when it resumes, it resumes with the request context.

So, here's why test5 fails:

  • Test5Controller.Get executes AsyncAwait_GetSomeDataAsync (within the ASP.NET request context).
  • AsyncAwait_GetSomeDataAsync executes HttpClient.GetAsync (within the ASP.NET request context).
  • The HTTP request is sent out, and HttpClient.GetAsync returns an uncompleted Task.
  • AsyncAwait_GetSomeDataAsync awaits the Task; since it is not complete, AsyncAwait_GetSomeDataAsync returns an uncompleted Task.
  • Test5Controller.Get blocks the current thread until that Task completes.
  • The HTTP response comes in, and the Task returned by HttpClient.GetAsync is completed.
  • AsyncAwait_GetSomeDataAsync attempts to resume within the ASP.NET request context. However, there is already a thread in that context: the thread blocked in Test5Controller.Get.
  • Deadlock.

Here's why the other ones work:

  • (test1, test2, and test3): Continuations_GetSomeDataAsync schedules the continuation to the thread pool, outside the ASP.NET request context. This allows the Task returned by Continuations_GetSomeDataAsync to complete without having to re-enter the request context.
  • (test4 and test6): Since the Task is awaited, the ASP.NET request thread is not blocked. This allows AsyncAwait_GetSomeDataAsync to use the ASP.NET request context when it is ready to continue.

And here's the best practices:

  1. In your "library" async methods, use ConfigureAwait(false) whenever possible. In your case, this would change AsyncAwait_GetSomeDataAsync to be var result = await httpClient.GetAsync("", HttpCompletionOption.ResponseHeadersRead).ConfigureAwait(false);
  2. Don't block on Tasks; it's async all the way down. In other words, use await instead of GetResult (Task.Result and Task.Wait should also be replaced with await).

That way, you get both benefits: the continuation (the remainder of the AsyncAwait_GetSomeDataAsync method) is run on a basic thread pool thread that doesn't have to enter the ASP.NET request context; and the controller itself is async (which doesn't block a request thread).

More information:

Update 2012-07-13: Incorporated this answer into a blog post.

Clicking submit button of an HTML form by a Javascript code

You can do :


But this won't call the onclick action of your button, so you will need to call it by hand.

Be aware that you must use the name of your form and not the id to access it.

How to decrypt a password from SQL server?

You realise that you may be making a rod for your own back for the future. The pwdencrypt() and pwdcompare() are undocumented functions and may not behave the same in future versions of SQL Server.

Why not hash the password using a predictable algorithm such as SHA-2 or better before hitting the DB?

How to get every first element in 2 dimensional list

You could use this:

a = ((4.0, 4, 4.0), (3.0, 3, 3.6), (3.5, 6, 4.8))
a = np.array(a)
returns >>> array([4. , 3. , 3.5])

Best way to unselect a <select> in jQuery?

Answers so far only work for multiple selects in IE6/7; for the more common non-multi select, you need to use:

$("#selectID").attr('selectedIndex', '-1');

This is explained in the post linked by flyfishr64. If you look at it, you will see how there are 2 cases - multi / non-multi. There is nothing stopping you chaning both for a complete solution:

$("#selectID").attr('selectedIndex', '-1').find("option:selected").removeAttr("selected");

Update multiple values in a single statement

Have you tried with a sub-query for every field:

    TotalX = (SELECT SUM(X) from DetailTbl where DetailTbl.MasterID = MasterTbl.ID),
    TotalY = (SELECT SUM(Y) from DetailTbl where DetailTbl.MasterID = MasterTbl.ID),
    TotalZ = (SELECT SUM(Z) from DetailTbl where DetailTbl.MasterID = MasterTbl.ID)

Angular 2 http post params and body

Seems like you use Angular 4.3 version, I also faced with same problem. Use Angular 4.0.1 and post with code by @trichetricheand and it will work. I am also not sure how to solve it on Angular 4.3 :S

SSRS Expression for IF, THEN ELSE

You should be able to use

IIF(Fields!ExitReason.Value = 7, 1, 0)

Install / upgrade gradle on Mac OS X

Another alternative is to use sdkman. An advantage of sdkman over brew is that many versions of gradle are supported. (brew only supports the latest version and 2.14.) To install sdkman execute:

curl -s "" | bash

Then follow the instructions. Go here for more installation information. Once sdkman is installed use the command:

sdk install gradle

Or to install a specific version:

sdk install gradle 2.2

Or use to use a specific installed version:

sdk use gradle 2.2

To see which versions are installed and available:

sdk list gradle

For more information go here.

How to clear the entire array?

Find a better use for myself: I usually test if a variant is empty, and all of the above methods fail with the test. I found that you can actually set a variant to empty:

Dim aTable As Variant
If IsEmpty(aTable) Then
    'This is true
End If
ReDim aTable(2)
If IsEmpty(aTable) Then
    'This is False
End If
ReDim aTable(2)
aTable = Empty
If IsEmpty(aTable) Then
    'This is true
End If
ReDim aTable(2)
Erase aTable
If IsEmpty(aTable) Then
    'This is False
End If

this way i get the behaviour i want

How can I convert a DOM element to a jQuery element?

So far best solution that I've made:

function convertHtmlToJQueryObject(html){
    var htmlDOMObject = new DOMParser().parseFromString(html, "text/html");
    return $(htmlDOMObject.documentElement);

Find index of last occurrence of a substring in a string

Use the str.rindex method.

>>> 'hello'.rindex('l')
>>> 'hello'.index('l')

How to reload/refresh an element(image) in jQuery

I simply do this in html:

    $(document).load(function () {
        d = new Date();
        $('#<%= imgpreview.ClientID %>').attr('src','');

And reload the image in code behind like this:

protected void Page_Load(object sender, EventArgs e)
    if (!IsPostBack)
        image.Src = "/image.jpg"; //url caming from database


start/play embedded (iframe) youtube-video on click of an image

You can do this simply like this

$('#image_id').click(function() {
  $("#some_id iframe").attr('src', $("#some_id iframe", parent).attr('src') + '?autoplay=1'); 

where image_id is your image id you are clicking and some_id is id of div in which iframe is also you can use iframe id directly.

ASP.NET 4.5 has not been registered on the Web server

Try this Once go to the Programs and Features window->, hit the "Turn Windows Features on or off" in the left pane.

Now scroll down through the tree and find:

Internet Information Services World Wide Web Services Application Development Features ...and then check all the relevant features you require. I chose .NET 3.5 and 4.6.

and if does not work then go to Let it do its work and then you should be back to happy-development-land in VS before you know it. If not, then it could actually be a bug in Visual Studio. Please check the following patches for your version of VS: VS2010, VS2012 or VS2013. This will surely help you out.

In SQL Server, how to create while loop in select

No functions, no cursors. Try this

with cte as(
select CHAR(65) chr, 65 i 
union all
select CHAR(i+1) chr, i=i+1 from cte
where CHAR(i) <'Z'
select * from(
SELECT id, Case when LEN(data)>len(REPLACE(data, chr,'')) then chr+chr end data 
FROM table1, cte) x
where Data is not null

How to get config parameters in Symfony2 Twig Templates

With a Twig extension, you can create a parameterTwig function:

{{ parameter('jira_host') }}


class TwigExtension extends \Twig_Extension
    public $container;

    public function getFunctions()
        return [
            new \Twig_SimpleFunction('parameter', function($name)
                return $this->container->getParameter($name);

     * Returns the name of the extension.
     * @return string The extension name
    public function getName()
        return 'iz';


    class: IzBundle\Services\TwigExtension
      container: "@service_container"
      - { name: twig.extension }

Replacing .NET WebBrowser control with a better browser, like Chrome?

Chrome uses (a fork of) Webkit if you didn't know, which is also used by Safari. Here's a few questions that are of the same vein:

The webkit one isn't great as the other answer states, one version no longer works (the google code one) and the Mono one is experimental. It'd be nice if someone made the effort to make a decent .NET wrapper for it but it's not something anyone seems to want to do - which is surprising given it now has support for HTML5 and so many other features that the IE(8) engine lacks.

Update (2014)

There's new dual-licensed project that allows you embed Chrome into your .NET applications called Awesomium. It comes with a .NET api but requires quite a few hacks for rendering (the examples draw the browser window to a buffer, paint the buffer as an image and refresh on a timer).

I think this is the browser used by Origin in Battlefield 3.

Update (2016)

There is now DotnetBrowser, a commercial alternative to Awesomium. It's based off Chromium.

Easy way to turn JavaScript array into comma-separated list?

Papa Parse handles commas in values and other edge cases.

(Baby Parse for Node has been deprecated - you can now use Papa Parse in the Browser and in Node.)

Eg. (node)

const csvParser = require('papaparse'); // previously you might have used babyparse
var arr = [1,null,"a,b"] ;
var csv = csvParser.unparse([arr]) ;
console.log(csv) ;


Android EditText for password with android:hint

Actually, I found that if you put the the android:gravity="center" at the end of your xml line, the hint text shows up fine with the android:inputType="textVisiblePassword"

How to programmatically empty browser cache?

Imagine the .js files are placed in /my-site/some/path/ui/js/myfile.js

So normally the script tag would look like:

<script src="/my-site/some/path/ui/js/myfile.js"></script>

Now change that to:

<script src="/my-site/some/path/ui-1111111111/js/myfile.js"></script>

Now of course that will not work. To make it work you need to add one or a few lines to your .htaccess The important line is: (entire .htaccess at the bottom)

RewriteRule ^my-site\/(.*)\/ui\-([0-9]+)\/(.*) my-site/$1/ui/$3 [L]

So what this does is, it kind of removes the 1111111111 from the path and links to the correct path.

So now if you make changes you just have to change the number 1111111111 to whatever number you want. And however you include your files you can set that number via a timestamp when the js-file has last been modified. So cache will work normally if the number does not change. If it changes it will serve the new file (YES ALWAYS) because the browser get's a complete new URL and just believes that file is so new he must go get it.

You can use this for CSS, favicons and what ever gets cached. For CSS just use like so

<link href="" type="text/css" rel="stylesheet">

And it will work! Simple to update, simple to maintain.

The promised full .htaccess

If you have no .htaccess yet this is the minimum you need to have there:

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /

    RewriteRule ^my-site\/(.*)\/ui\-([0-9]+)\/(.*) my-site/$1/ui/$3 [L]

How to preserve insertion order in HashMap?

LinkedHashMap is precisely what you're looking for.

It is exactly like HashMap, except that when you iterate over it, it presents the items in the insertion order.

Using VBA code, how to export Excel worksheets as image in Excel 2003?

Winand, Quality was also an issue for me so I did this:

For Each ws In ActiveWorkbook.Worksheets
    If ws.PageSetup.PrintArea <> "" Then
        'Reverse the effects of page zoom on the exported image
        zoom_coef = 100 / ws.Parent.Windows(1).Zoom
        areas = Split(ws.PageSetup.PrintArea, ",")
        areaNo = 0
        For Each a In areas
            Set area = ws.Range(a)
            ' Change xlPrinter to xlScreen to see zooming white space
            area.CopyPicture Appearance:=xlPrinter, Format:=xlPicture
            Set chartobj = ws.ChartObjects.Add(0, 0, area.Width * zoom_coef, area.Height * zoom_coef)
            'scale the image before export
            ws.Shapes(chartobj.Index).ScaleHeight 3, msoFalse, msoScaleFromTopLeft
            ws.Shapes(chartobj.Index).ScaleWidth 3, msoFalse, msoScaleFromTopLeft
            chartobj.Chart.Export ws.Name & "-" & areaNo & ".png", "png"
            areaNo = areaNo + 1
    End If

See here:

How to solve “Microsoft Visual Studio (VS)” error “Unable to connect to the configured development Web server”

I am using visual studio 2015. Deleting .vs folder in the project folder helped me to fix this. You must close the visual studio first.

IIS w3svc error

This is probably a rarer case, but...

If you are using a custom AppPool Identity configuration be sure to check the AppPool is running. It may be turned off because credentials are invalid (usually due to an expired password). Update your credentials and start the AppPool.

How to read from stdin with fgets()?

Assuming that you only want to read a single line, then use LINE_MAX, which is defined in <limits.h>:

#include <stdio.h>
#include <limits.h>
char line[LINE_MAX];
if (fgets(line, LINE_MAX, stdin) != NULL) {

Rails 4: assets not loading in production

I just had the same problem and found this setting in config/environments/production.rb:

# Rails 4:
config.serve_static_assets = false

# Or for Rails 5:
config.public_file_server.enabled = false

Changing it to true got it working. It seems by default Rails expects you to have configured your front-end webserver to handle requests for files out of the public folder instead of proxying them to the Rails app. Perhaps you've done this for your javascript files but not your CSS stylesheets?

(See Rails 5 documentation). As noted in comments, with Rails 5 you may just set the RAILS_SERVE_STATIC_FILES environment variable, since the default setting is config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?.

Getting permission denied (public key) on gitlab

Nothing worked for me on Windows 10 using Pageant as SSH agent, except adding a enviroment variable to windows (translated from german Windows 10, so the naming may differ):

  1. Search for "variables"
  2. Open System Enviroment Variables
  3. Click Enviroment Variables button at the bottom
  4. Add a new key named "GIT_SSH" and the value "C:\Program Files\PuTTY\plink.exe", to the top section "User Variables xxx"
  5. And you're done.

All thanks go to Benjamin Bortels, source:

How to change the default background color white to something else in twitter bootstrap

how to change background color in html & css with class


on html you write

<div class="pad_menu">

on css

.pad_menu {
   padding: 100px;
   background-color: #A9FFCB;

so your background will be change to Magic Mint, if you want to know the code of the color, i suggest you visit Hope this useful :)

FontAwesome icons not showing. Why?


This answer is created when the latest version of fontawesome is v5.* but yarn and npm version points to v4.* (21.06.2019). In other words, versions installed via package managers is behind latest release !

If you installed font-awesome via package manager (yarn or npm) then, please be aware which version was installed. Alternatively, if you've already installed font-awesome long time ago then, check what version was installed.

Installing font-awesome as new dependency:

$ yarn add font-awesome
success Saved lockfile.
success Saved 1 new dependency.
info Direct dependencies
+- [email protected]
info All dependencies
+- [email protected]
Done in 3.32s.

Checking what version of font-awesome is already installed:

$ yarn list font-awesome
yarn list v1.16.0
warning Filtering by arguments is deprecated. Please use the pattern option instead.
+- [email protected]
Done in 0.79s.


After you installed font-awesome dependency, you incorporate one of these two source files font-awesome.css or font-awesome.min.css (founded in node_modules/font-awesome/css/) into header of your webpage e.g.

  <link type="text/css" rel="stylesheet" href="css/font-awesome.css">

Next, you visit You select free icons and you search for sign-in icon (as an example). You copy the icon e.g. <i class="fas fa-sign-in-alt"></i>, you paste it into your html and, icon is not shown, or is display as square or rectangle !


In essence, versions installed via package managers is behind version that is shown on website. As you can see we installed font-awesome v4.7.0 but, website shows documentation for font-awesome v5.*. Solution, visit the website that documents icons for v4.7.0, copy appropriate icon e.g. <i class="fa fa-sign-in" aria-hidden="true"></i> and incorporate it into your html.

Can someone explain __all__ in Python?

This is defined in PEP8 here:

Global Variable Names

(Let's hope that these variables are meant for use inside one module only.) The conventions are about the same as those for functions.

Modules that are designed for use via from M import * should use the __all__ mechanism to prevent exporting globals, or use the older convention of prefixing such globals with an underscore (which you might want to do to indicate these globals are "module non-public").

PEP8 provides coding conventions for the Python code comprising the standard library in the main Python distribution. The more you follow this, closer you are to the original intent.