Programs & Examples On #Multitasking

Multitasking is the apparent simultaneous execution of two or more tasks by a computer.

iOS - Ensure execution on main thread

This will do it:

[[NSOperationQueue mainQueue] addOperationWithBlock:^ {

   //Your code goes in here
   NSLog(@"Main Thread Code");


Hope this helps!

Difference between multitasking, multithreading and multiprocessing?

Multiple threads can exist in a single process. The threads that belong to the same process share the same memory area (can read from and write to the very same variables, and can interfere with one another). On the contrary, different processes live in different memory areas, and each of them has its own variables. In order to communicate, processes have to use other channels (files, pipes or sockets).

If you want to parallelize a computation, you're probably going to need multithreading, because you probably want the threads to cooperate on the same memory.

Speaking about performance, threads are faster to create and manage than processes (because the OS doesn't need to allocate a whole new virtual memory area), and inter-thread communication is usually faster than inter-process communication. But threads are harder to program. Threads can interfere with one another, and can write to each other's memory, but the way this happens is not always obvious (due to several factors, mainly instruction reordering and memory caching), and so you are going to need synchronization primitives to control access to your variables.


How to override the properties of a CSS class using another CSS class

There are different ways in which properties can be overridden. Assuming you have

.left { background: blue }

e.g. any of the following would override it:

a.background-none { background: none; }
body .background-none { background: none; }
.background-none { background: none !important; }

The first two “win” by selector specificity; the third one wins by !important, a blunt instrument.

You could also organize your style sheets so that e.g. the rule

.background-none { background: none; }

wins simply by order, i.e. by being after an otherwise equally “powerful” rule. But this imposes restrictions and requires you to be careful in any reorganization of style sheets.

These are all examples of the CSS Cascade, a crucial but widely misunderstood concept. It defines the exact rules for resolving conflicts between style sheet rules.

P.S. I used left and background-none as they were used in the question. They are examples of class names that should not be used, since they reflect specific rendering and not structural or semantic roles.

Is it possible to send an array with the Postman Chrome extension?

It is important to know, that the VALUE box is only allowed to contain a numeral value (no specifiers).

If you want to send e.g. an array of "messages" with Postman, each having a list of key/value pairs, enter e.g. messages[][reason] into the KEY box and the value of reason into the VALUE box:

enter image description here

The server will receive:

{"messages"=>[{"reason"=>"scrolled", "tabid"=>"2"}, {"reason"=>"reload", "tabid"=>"1"}], "endpoint"=>{}}

Access 2013 - Cannot open a database created with a previous version of your application

Non-Programming Answer: Download and install an older version of the Access Database Engine (2010 or 2007 for example, rather than 2013). Open Excel, navigate to the "Data" tab on the Ribbon and click "From Access". Import the data into Excel, and then Export to an accdb file or do whatever with it. NOTE! opening Access 2013 will trigger a re-install of the 2013 engine, so keep the 2007/2010 installation .exe around.

Programming Answer: Having installed an older version of Access Database Engine, you can use an OLEDB connection in multiple programming environments (C#, VBA, VBScript, etc.) to read/write and move Access data. Gord Thompson's answer also presents the option of jumping to SQL server and back.

See This post for a similar problem using an OLEDB connection is a great resource

See this post for how to setup an OLEDB connection using C#

Pythonically add header to a csv file

The DictWriter() class expects dictionaries for each row. If all you wanted to do was write an initial header, use a regular csv.writer() and pass in a simple row for the header:

import csv

with open('combined_file.csv', 'w', newline='') as outcsv:
    writer = csv.writer(outcsv)
    writer.writerow(["Date", "temperature 1", "Temperature 2"])

    with open('t1.csv', 'r', newline='') as incsv:
        reader = csv.reader(incsv)
        writer.writerows(row + [0.0] for row in reader)

    with open('t2.csv', 'r', newline='') as incsv:
        reader = csv.reader(incsv)
        writer.writerows(row[:1] + [0.0] + row[1:] for row in reader)

The alternative would be to generate dictionaries when copying across your data:

import csv

with open('combined_file.csv', 'w', newline='') as outcsv:
    writer = csv.DictWriter(outcsv, fieldnames = ["Date", "temperature 1", "Temperature 2"])

    with open('t1.csv', 'r', newline='') as incsv:
        reader = csv.reader(incsv)
        writer.writerows({'Date': row[0], 'temperature 1': row[1], 'temperature 2': 0.0} for row in reader)

    with open('t2.csv', 'r', newline='') as incsv:
        reader = csv.reader(incsv)
        writer.writerows({'Date': row[0], 'temperature 1': 0.0, 'temperature 2': row[1]} for row in reader)

How to sort a List of objects by their date (java collections, List<Object>)

You can use this:

Collections.sort(list, org.joda.time.DateTimeComparator.getInstance());

How to assign pointer address manually in C programming language?

let's say you want a pointer to point at the address 0x28ff4402, the usual way is

uint32_t *ptr;
ptr = (uint32_t*) 0x28ff4402 //type-casting the address value to uint32_t pointer
*ptr |= (1<<13) | (1<<10); //access the address how ever you want

So the short way is to use a MACRO,

#define ptr *(uint32_t *) (0x28ff4402)

How do I pass the this context to a function?

You can use the bind function to set the context of this within a function.

function myFunc() {
const myContext = {str: "my context"}
const boundFunc = myFunc.bind(myContext);
boundFunc(); // "my context"

Normalizing images in OpenCV

If you want to change the range to [0, 1], make sure the output data type is float.

image = cv2.imread("lenacolor512.tiff", cv2.IMREAD_COLOR)  # uint8 image
norm_image = cv2.normalize(image, None, alpha=0, beta=1, norm_type=cv2.NORM_MINMAX, dtype=cv2.CV_32F)

newline character in c# string

A great way of handling this is with regular expressions.

string modifiedString = Regex.Replace(originalString, @"(\r\n)|\n|\r", "<br/>");

This will replace any of the 3 legal types of newline with the html tag.

Manually put files to Android emulator SD card

Use the adb tool that comes with the SDK.

adb push myDirectory /sdcard/targetDir

If you only specify /sdcard/ (with the trailing slash) as destination, then the CONTENTS of myDirectory will end up in the root of /sdcard.

Send multipart/form-data files with angular using $http

Here's an updated answer for Angular 4 & 5. TransformRequest and angular.identity were dropped. I've also included the ability to combine files with JSON data in one request.

Angular 5 Solution:

import {HttpClient} from '@angular/common/http';

uploadFileToUrl(files, restObj, uploadUrl): Promise<any> {
  // Note that setting a content-type header
  // for mutlipart forms breaks some built in
  // request parsers like multer in express.
  const options = {} as any; // Set any options you like
  const formData = new FormData();

  // Append files to the virtual form.
  for (const file of files) {
    formData.append(, file)

  // Optional, append other kev:val rest data to the form.
  Object.keys(restObj).forEach(key => {
    formData.append(key, restObj[key]);

  // Send it.
  return, formData, options)
    .catch((e) => {
      // handle me

Angular 4 Solution:

// Note that these imports below are deprecated in Angular 5
import {Http, RequestOptions} from '@angular/http';

uploadFileToUrl(files, restObj, uploadUrl): Promise<any> {
  // Note that setting a content-type header
  // for mutlipart forms breaks some built in
  // request parsers like multer in express.
  const options = new RequestOptions();
  const formData = new FormData();

  // Append files to the virtual form.
  for (const file of files) {
    formData.append(, file)

  // Optional, append other kev:val rest data to the form.
  Object.keys(restObj).forEach(key => {
    formData.append(key, restObj[key]);

  // Send it.
  return, formData, options)
    .catch((e) => {
      // handle me

Generic deep diff between two objects

I'd like to offer an ES6 solution...This is a one-way diff, meaning that it will return keys/values from o2 that are not identical to their counterparts in o1:

let o1 = {
  one: 1,
  two: 2,
  three: 3

let o2 = {
  two: 2,
  three: 3,
  four: 4

let diff = Object.keys(o2).reduce((diff, key) => {
  if (o1[key] === o2[key]) return diff
  return {
    [key]: o2[key]
}, {})

Xcode 8 shows error that provisioning profile doesn't include signing certificate

For what it's worth automatic signing failed every time until I just manually deleted local profiles in: ~/Library/MobileDevice/Provisioning Profiles

After that automatic signing worked perfectly and it got the right profiles from Apple's servers.

This was affecting only some builds, notably the ones for which I had manually created profiles for watch app.

How to scale Docker containers in production

A sensible approach to scaling Docker could be:

  1. Each service will be a docker container
  2. Intra container service discovery managed through links (new feature from docker 0.6.5)
  3. Containers will be deployed through Dokku
  4. Applications will be managed through Shipyard which in its turn is using hipache

Another docker open sourced project from Yandex:

Whether a variable is undefined

function my_url (base, opt)
    var retval = ["" + base];
    retval.push( opt.page_name ? "&page_name=" + opt.page_name : "");
    retval.push( opt.table_name ? "&table_name=" + opt.table_name : "");
    retval.push( opt.optionResult ? "&optionResult=" + opt.optionResult : "");
    return retval.join("");

my_url("?z=z",  { page_name : "pageX" /* no table_name and optionResult */ } );

/* Returns:

This avoids using typeof whatever === "undefined". (Also, there isn't any string concatenation.)

Excel cell value as string won't store as string

Use Range("A1").Text instead of .Value

post comment edit:
Because the .Text property of Range object returns what is literally visible in the spreadsheet, so if you cell displays for example i100l:25he*_92 then <- Text will return exactly what it in the cell including any formatting.
The .Value and .Value2 properties return what's stored in the cell under the hood excluding formatting. Specially .Value2 for date types, it will return the decimal representation.

If you want to dig deeper into the meaning and performance, I just found this article which seems like a good guide

another edit
Here you go @Santosh
type in (MANUALLY) the values from the DEFAULT (col A) to other columns
Do not format column A at all
Format column B as Text
Format column C as Date[dd/mm/yyyy]
Format column D as Percentage
Dont Format column A, Format B as TEXT, C as Date, D as Percentage
paste this code in a module

Sub main()

    Dim ws As Worksheet, i&, j&
    Set ws = Sheets(1)
    For i = 3 To 7
        For j = 1 To 4
            Debug.Print _
                    "row " & i & vbTab & vbTab & _
                    Cells(i, j).Text & vbTab & _
                    Cells(i, j).Value & vbTab & _
                    Cells(i, j).Value2
        Next j
    Next i
End Sub

and Analyse the output! Its really easy and there isn't much more i can do to help :)

            .TEXT              .VALUE             .VALUE2
row 3       hello             hello               hello
row 3       hello             hello               hello
row 3       hello             hello               hello
row 3       hello             hello               hello
row 4       1                 1                   1
row 4       1                 1                   1
row 4       01/01/1900        31/12/1899          1
row 4       1.00%             0.01                0.01
row 5       helo1$$           helo1$$             helo1$$
row 5       helo1$$           helo1$$             helo1$$
row 5       helo1$$           helo1$$             helo1$$
row 5       helo1$$           helo1$$             helo1$$
row 6       63                63                  63
row 6       =7*9              =7*9                =7*9
row 6       03/03/1900        03/03/1900          63
row 6       6300.00%          63                  63
row 7       29/05/2013        29/05/2013          41423
row 7       29/05/2013        29/05/2013          29/05/2013
row 7       29/05/2013        29/05/2013          41423
row 7       29/05/2013%       29/05/2013%         29/05/2013%

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

The big thing to get your head around is that the File class tries to represent a view of what Sun like to call "hierarchical pathnames" (basically a path like c:/foo.txt or /usr/muggins). This is why you create files in terms of paths. The operations you are describing are all operations upon this "pathname".

  • getPath() fetches the path that the File was created with (../foo.txt)
  • getAbsolutePath() fetches the path that the File was created with, but includes information about the current directory if the path is relative (/usr/bobstuff/../foo.txt)
  • getCanonicalPath() attempts to fetch a unique representation of the absolute path to the file. This eliminates indirection from ".." and "." references (/usr/foo.txt).

Note I say attempts - in forming a Canonical Path, the VM can throw an IOException. This usually occurs because it is performing some filesystem operations, any one of which could fail.

Check whether user has a Chrome extension installed

Another possible solution if you own the website is to use inline installation.

if ( {
  // extension is installed.

I know this an old question but this way was introduced in Chrome 15 and so I thought Id list it for anyone only now looking for an answer.

What is the total amount of public IPv4 addresses?

Public IP Addresses will generate a list of Valid IP Public Addresses including Localities.

'' to '' are the valid public IP Address range exclusive of the reserved Private IP Addresses as follows:

import iptools
## Private IP Addresses
private_ips = iptools.IpRangeList(
    '',      '',     '', '',
    '', '',  '',  '',
    '', '', '', '',
    '', '',    '',   ''

IP Generator

Generates a JSON dump of IP Addresses and associated Geo information. Note that the valid public IP Address range is from '' to '' excluding the reserved Private IP Address ranges shown lower down in this readme.

docker build -t geo-ip .
docker run -e IPRANGE='' geo-ip               ## a few IPs
docker run -e IPRANGE='' geo-ip               ## a few more IPs
docker run -e IPRANGE='' geo-ip               ## a lot more IPs
docker run -e IPRANGE=''   geo-ip               ## ALL IPs ( slooooowwwwww )
docker run -e IPRANGE=''   geo-ip > geo-ip.json ## ALL IPs saved to JSON File
docker run geo-ip 

A little faster option for scanning all valid public addresses:

for i in $(seq 1 191); do \
    docker run -e IPRANGE="$i.0.0.0/8" geo-ip; \
    sleep 1; \ 

This prints less than 4,228,250,625 JSON lines to STDOUT. Here is an example of one of the lines:

{"city": "Palo Alto", "ip": "", "longitude": -122.1274,
 "continent": "North America", "continent_code": "NA",
 "state": "California", "country": "United States", "latitude": 37.418,
 "iso_code": "US", "state_code": "CA", "aso": "PubNub",
 "asn": "11404", "zip_code": "94107"}

Private and Reserved IP Range

The dockerfile in the repo above will exclude non-usable IP addresses following the guide from the wikipedia article:

MaxMind Geo IP

The dockerfile imports a free public Database provided by

How to trigger event in JavaScript?

Just to suggest an alternative that does not involve the need to manually invoke a listener event:

Whatever your event listener does, move it into a function and call that function from the event listener.

Then, you can also call that function anywhere else that you need to accomplish the same thing that the event does when it fires.

I find this less "code intensive" and easier to read.

TNS-12505: TNS:listener does not currently know of SID given in connect descriptor

Check - LSNRCTL> stat I got result like -

Alias                     LISTENER
Version                   TNSLSNR for 32-bit Windows: Version - Production 
Start Date                17-APR-2016 10:12:38 
Uptime                    0 days 10 hr. 6 min. 16 sec 
Trace Level               off 
Security                  ON: Local OS Authentication 
SNMP                      OFF
Listener Parameter File 
Listener Log File        c:\app\admin\diag\tnslsnr\admin-PC\listener\alert\log.xml Listening
Endpoints Summary...  
Services Summary... Service "CLRExtProc" has 1 instance(s).   Instance
 "CLRExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "orcl" has 1 instance(s).   Instance "orcl", status READY, has 1 handler(s) for this service... 
Service "orclXDB" has 1 instance(s). 
  Instance "orcl", status READY, has 1 handler(s) for this service...
The command completed successfully.

From above details - My port no is - 1522 and i am able to create connection using "orcl" instance - so i used port as 1522 and instance as "orcl" -- Now URL is -

DriverManager.getConnection("jdbc:oracle:thin:@localhost:1522:orcl", "SYS as SYSDBA","password");

It worked for me So please check LSNRCTL> stat in command prompt and configure your connection url accordingly.
Hope it will help Someone.

Creating a UICollectionView programmatically

Apple Docs:

- (id)initWithFrame:(CGRect)frame 
      collectionViewLayout:(UICollectionViewLayout *)layoutParameters

Use this method when initializing a collection view object programmatically. If you specify nil for the layout parameter, you must assign a layout object to the collectionViewLayout property before displaying the collection view onscreen. If you do not, the collection view will be unable to present any items onscreen.

This method is the designated initializer.

This method is used to initialize the UICollectionView. here you provide frame and a UICollectionViewLayout object.

UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];

At the end, add UICollectionView as a subview to your view.

Now collection view is added pro grammatically. You can go on learning.
Happy learning!! Hope it helps you.

How to select ALL children (in any level) from a parent in jQuery?

Use jQuery.find() to find children more than one level deep.

The .find() and .children() methods are similar, except that the latter only travels a single level down the DOM tree.


You need the '*' in find():

Unlike in the rest of the tree traversal methods, the selector expression is required in a call to .find(). If we need to retrieve all of the descendant elements, we can pass in the universal selector '*' to accomplish this.

How to extract URL parameters from a URL with Ruby or Rails?

In your Controller, you should be able to access a dictionary (hash) called params. So, if you know what the names of each query parameter is, then just do params[:param1] to access it... If you don't know what the names of the parameters are, you could traverse the dictionary and get the keys.

Some simple examples here.

Is it possible to force Excel recognize UTF-8 CSV files automatically?

Working solution for office 365

  • save in UTF-16 (no LE, BE)
  • use separator \t

Code in PHP

$header = ['císlo', 'vytvoreno', 'ešcržýáíé'];
$fileName = 'excel365.csv';
$fp = fopen($fileName, 'w');
fputcsv($fp, $header, "\t");

$handle = fopen($fileName, "r");
$contents = fread($handle, filesize($fileName));
$contents = iconv('UTF-8', 'UTF-16', $contents);

$handle = fopen($fileName, "w");
fwrite($handle, $contents);

Function pointer as parameter

The correct way to do this is:

typedef void (*callback_function)(void); // type for conciseness

callback_function disconnectFunc; // variable to store function pointer type

void D::setDisconnectFunc(callback_function pFunc)
    disconnectFunc = pFunc; // store

void D::disconnected()
    disconnectFunc(); // call
    connected = false;

What does the ">" (greater-than sign) CSS selector mean?

( child selector) was introduced in css2. div p{ } select all p elements decedent of div elements, whereas div > p selects only child p elements, not grand child, great grand child on so on.

  div p{  color:red  }       /* match both p*/
  div > p{  color:blue  }    /* match only first p*/


   <p>para tag, child and decedent of p.</p>
            <p>para inside list. </p>

For more information on CSS Ce[lectors and their use, check my blog, css selectors and css3 selectors

deny directory listing with htaccess

If Options -Indexes does not work as Bryan Drewery suggested, you could write a recursive method to create blank index.php files.

Place this inside of your base folder you wish to protect, you can name it whatever (I would recommend index.php)



function recurse($path){
    foreach(scandir($path) as $o){
        if($o != "." && $o != ".."){
            $full = $path . "/" . $o;
                if(!file_exists($full . "/index.php")){
                    file_put_contents($full . "/index.php", "");


These blank index.php files can be easily deleted or overwritten, and they'll keep your directories from being listable. target _self v window.location.href?

You can omit window and just use location.href. For example:

location.href = '';

WARNING: Setting property 'source' to 'org.eclipse.jst.jee.server:appname' did not find a matching property

You can change the eclipse tomcat server configuration. Open the server view, double click on you server to open server configuration. Then click to activate "Publish module contents to separate XML files". Finally, restart your server, the message must disappear.


[Vue warn]: Cannot find element

I've solved the problem by add attribute 'defer' to the 'script' element.

iOS - Calling App Delegate method from ViewController

In 2020, iOS13, xCode 11.3. What is working for Objective-C is:

#import "AppDelegate.h"

AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];

It's working for me, i hope the same to you! :D

How do I convert two lists into a dictionary?

  • 2018-04-18

The best solution is still:

In [92]: keys = ('name', 'age', 'food')
...: values = ('Monty', 42, 'spam')

In [93]: dt = dict(zip(keys, values))
In [94]: dt
Out[94]: {'age': 42, 'food': 'spam', 'name': 'Monty'}

Tranpose it:

    lst = [('name', 'Monty'), ('age', 42), ('food', 'spam')]
    keys, values = zip(*lst)
    In [101]: keys
    Out[101]: ('name', 'age', 'food')
    In [102]: values
    Out[102]: ('Monty', 42, 'spam')

Adding parameter to ng-click function inside ng-repeat doesn't seem to work

Above answers are excellent. You can look at the following full code example so that you could exactly know how to use

   var app = angular.module('hyperCrudApp', []);_x000D_
   app.controller('usersCtrl', function($scope, $http) {_x000D_
     $http.get("").then(function (response) {_x000D_
         $scope.users =;_x000D_
          $scope.setKey = function (userId){_x000D_
                localStorage.setItem("userId", userId)_x000D_
              } else {_x000D_
                alert("No support of localStorage")_x000D_
          }//function closed  _x000D_
       color: green;_x000D_
       font-weight: bold;_x000D_
  <!DOCTYPE html>_x000D_
    <meta charset="utf-8">_x000D_
    <meta name="viewport" content="width=device-width, initial-scale=1">_x000D_
    <link rel="stylesheet" href="">_x000D_
    <script src=""></script>_x000D_
    <script src=""></script>_x000D_
    <script src=""></script>_x000D_
    <!-- NAVBAR STARTS -->_x000D_
      <nav class="navbar navbar-default navbar-fixed-top">_x000D_
        <div class="container">_x000D_
          <div class="navbar-header">_x000D_
            <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">_x000D_
              <span class="sr-only">Toggle navigation</span>_x000D_
              <span class="icon-bar"></span>_x000D_
              <span class="icon-bar"></span>_x000D_
              <span class="icon-bar"></span>_x000D_
            <a class="navbar-brand" href="#">HyperCrud</a>_x000D_
          <div id="navbar" class="navbar-collapse collapse">_x000D_
            <ul class="nav navbar-nav">_x000D_
              <li class="active"><a href="/">Home</a></li>_x000D_
              <li><a href="/about/">About</a></li>_x000D_
              <li><a href="/contact/">Contact</a></li>_x000D_
              <li class="dropdown">_x000D_
                <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Apps<span class="caret"></span></a>_x000D_
                <ul class="dropdown-menu">_x000D_
                  <li><a href="/qAlarm/details/">qAlarm &raquo;</a></li>_x000D_
                  <li><a href="/YtEdit/details/">YtEdit &raquo;</a></li>_x000D_
                  <li><a href="/GWeather/details/">GWeather &raquo;</a></li>_x000D_
                  <li role="separator" class="divider"></li>_x000D_
                  <li><a href="/WadStore/details/">WadStore &raquo;</a></li>_x000D_
                  <li><a href="/chatsAll/details/">chatsAll</a></li>_x000D_
            <ul class="nav navbar-nav navbar-right">_x000D_
              <li><a href="/login/">Login</a></li>_x000D_
              <li><a href="/register/">Register</a></li>_x000D_
              <li><a href="/services/">Services<span class="sr-only">(current)</span></a></li>_x000D_
      <!--NAVBAR ENDS-->_x000D_
  <div ng-app="hyperCrudApp" ng-controller="usersCtrl" class="container">_x000D_
    <div class="row">_x000D_
     <div class="col-sm-12 col-md-12">_x000D_
        <h1 id="header"> Users </h1>_x000D_
    <div class="row" >_x000D_
        <!--ITERATING USERS LIST-->_x000D_
      <div class="col-sm-6 col-md-4" ng-repeat="user in users">_x000D_
        <div class="thumbnail">_x000D_
           <img src="" alt="Image - {{}}" class="img-responsive img-circle" style="width: 100px">_x000D_
          <div class="caption">_x000D_
             <p>+91 {{}}</p>_x000D_
            <div class="caption">_x000D_
                <a href="/users/delete/{{}}/" role="button" class="btn btn-danger btn-block" ng-click="setKey(">DELETE</a>_x000D_
                <a href="/users/update/{{}}/" role="button" class="btn btn-success btn-block" ng-click="setKey(">UPDATE</a>_x000D_
        <div class="col-sm-6 col-md-4">_x000D_
          <div class="thumbnail">_x000D_
            <a href="/regiser/">_x000D_
             <img src="" alt="Register Image" class="img-responsive img-circle" style="width: 100%">_x000D_
      <!--ROW ENDS-->_x000D_

Android: Bitmaps loaded from gallery are rotated in ImageView

Use the following code to rotate an image correctly:

private Bitmap rotateImage(Bitmap bitmap, String filePath)
    Bitmap resultBitmap = bitmap;

        ExifInterface exifInterface = new ExifInterface(filePath);
        int orientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION, 1);

        Matrix matrix = new Matrix();

        if (orientation == ExifInterface.ORIENTATION_ROTATE_90)
        else if (orientation == ExifInterface.ORIENTATION_ROTATE_180)
        else if (orientation == ExifInterface.ORIENTATION_ROTATE_270)

        // Rotate the bitmap
        resultBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
    catch (Exception exception)
        Logger.d("Could not rotate the image");
    return resultBitmap;

Where is SQL Profiler in my SQL Server 2008?

first get the profiler Exe from:

then you can add it simply to the Management studio:

Tools -> External tools... ->

a- locate the exe file on your disk (If installed, it's typically C:\Program Files (x86)\ExpressProfiler\ExpressProfiler.exe)

b- give it a name e.g. Express Profiler

that's it :) you have your Profiler with your sql express edition

enter image description here

How to return result of a SELECT inside a function in PostgreSQL?

Hi please check the below link


CREATE FUNCTION sum_n_product_with_tab (x int)
RETURNS TABLE(sum int, product int) AS $$
    SELECT $1 + tab.y, $1 * tab.y FROM tab;

How can I select all elements without a given class in jQuery?

You could use this to pick all li elements without class:

$('ul#list li:not([class])')

How to import js-modules into TypeScript file?

I tested 3 methods to do that...


      const FriendCard:any = require('./../pages/FriendCard')


      import * as FriendCard from './../pages/FriendCard';


if you can find something like this in tsconfig.json:

      { "compilerOptions": { ..., "allowJs": true }

then you can write: import FriendCard from './../pages/FriendCard';

Date validation with ASP.NET validator

I think the following is the easiest way to do it.

<asp:TextBox ID="DateControl" runat="server" Visible="False"></asp:TextBox>
<asp:RangeValidator ID ="rvDate" runat ="server" ControlToValidate="DateControl" ErrorMessage="Invalid Date" Type="Date" MinimumValue="01/01/1900" MaximumValue="01/01/2100" Display="Dynamic"></asp:RangeValidator>

"This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded"

If you have already tried all the other logical solutions on this page, then double check this. In my app.config I had a reference to an old framework.

  <supportedRuntime version="v2.0.50727"/>

should have been

  <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>

The project tab correctly showed v4.0 but the app.config was not committed to our repo with that change. To fix it, I changed the framework to something else and back to 4.0 again, which updated my app.config file.

JS - window.history - Delete a state

You may have moved on by now, but... as far as I know there's no way to delete a history entry (or state).

One option I've been looking into is to handle the history yourself in JavaScript and use the window.history object as a carrier of sorts.

Basically, when the page first loads you create your custom history object (we'll go with an array here, but use whatever makes sense for your situation), then do your initial pushState. I would pass your custom history object as the state object, as it may come in handy if you also need to handle users navigating away from your app and coming back later.

var myHistory = [];

function pageLoad() {
    window.history.pushState(myHistory, "<name>", "<url>");

    //Load page data.

Now when you navigate, you add to your own history object (or don't - the history is now in your hands!) and use replaceState to keep the browser out of the loop.

function nav_to_details() {
    window.history.replaceState(myHistory, "<name>", "<url>");

    //Load page data.

When the user navigates backwards, they'll be hitting your "base" state (your state object will be null) and you can handle the navigation according to your custom history object. Afterward, you do another pushState.

function on_popState() {
    // Note that some browsers fire popState on initial load,
    // so you should check your state object and handle things accordingly.
    // (I did not do that in these examples!)

    if (myHistory.length > 0) {
        var pg = myHistory.pop();
        window.history.pushState(myHistory, "<name>", "<url>");

        //Load page data for "pg".
    } else {
        //No "history" - let them exit or keep them in the app.

The user will never be able to navigate forward using their browser buttons because they are always on the newest page.

From the browser's perspective, every time they go "back", they've immediately pushed forward again.

From the user's perspective, they're able to navigate backwards through the pages but not forward (basically simulating the smartphone "page stack" model).

From the developer's perspective, you now have a high level of control over how the user navigates through your application, while still allowing them to use the familiar navigation buttons on their browser. You can add/remove items from anywhere in the history chain as you please. If you use objects in your history array, you can track extra information about the pages as well (like field contents and whatnot).

If you need to handle user-initiated navigation (like the user changing the URL in a hash-based navigation scheme), then you might use a slightly different approach like...

var myHistory = [];

function pageLoad() {
    // When the user first hits your page...
    // Check the state to see what's going on.

    if (window.history.state === null) {
        // If the state is null, this is a NEW navigation,
        //    the user has navigated to your page directly (not using back/forward).

        // First we establish a "back" page to catch backward navigation.
            { isBackPage: true },

        // Then push an "app" page on top of that - this is where the user will sit.
        // (As browsers vary, it might be safer to put this in a short setTimeout).
            { isBackPage: false },

        // We also need to start our history tracking.


    // If the state is NOT null, then the user is returning to our app via history navigation.

    // (Load up the page based on the last entry of myHistory here)

    if (window.history.state.isBackPage) {
        // If the user came into our app via the back page,
        //     you can either push them forward one more step or just use pushState as above.

        // or window.history.pushState({ isBackPage: false }, "<name>", "<url>");

    setTimeout(function() {
        // Add our popstate event listener - doing it here should remove
        //     the issue of dealing with the browser firing it on initial page load.
        window.addEventListener("popstate", on_popstate);
    }, 100);

function on_popstate(e) {
    if (e.state === null) {
        // If there's no state at all, then the user must have navigated to a new hash.

        // <Look at what they've done, maybe by reading the hash from the URL>
        // <Change/load the new page and push it onto the myHistory stack>
        // <Alternatively, ignore their navigation attempt by NOT loading anything new or adding to myHistory>

        // Undo what they've done (as far as navigation) by kicking them backwards to the "app" page

        // Optionally, you can throw another replaceState in here, e.g. if you want to change the visible URL.
        // This would also prevent them from using the "forward" button to return to the new hash.
            { isBackPage: false },
            "<new name>",
            "<new url>"
    } else {
        if (e.state.isBackPage) {
            // If there is state and it's the 'back' page...

            if (myHistory.length > 0) {
                // Pull/load the page from our custom history...
                var pg = myHistory.pop();
                // <load/render/whatever>

                // And push them to our "app" page again
                    { isBackPage: false },
            } else {
                // No more history - let them exit or keep them in the app.

        // Implied 'else' here - if there is state and it's NOT the 'back' page
        //     then we can ignore it since we're already on the page we want.
        //     (This is the case when we push the user back with window.history.go(-1) above)

Auto-indent in Notepad++

Notepad++ will only auto-insert subsequent indents if you manually indent the first line in a block; otherwise you can re-indent your code after the fact using TextFX > TextFX Edit > Reindent C++ code.

Vim: insert the same characters across multiple lines

Suppose you have this file:



something else
and more ...

You want to add "vendor_" in front of "name", "comment", "phone", and "email", regardless of where they appear in the file.


The c flag will prompt you for confirmation. You can drop that if you don't want the prompt.

Get url parameters from a string in .NET

Here's another alternative if, for any reason, you can't or don't want to use HttpUtility.ParseQueryString().

This is built to be somewhat tolerant to "malformed" query strings, i.e. http://test/test.html?empty= becomes a parameter with an empty value. The caller can verify the parameters if needed.

public static class UriHelper
    public static Dictionary<string, string> DecodeQueryParameters(this Uri uri)
        if (uri == null)
            throw new ArgumentNullException("uri");

        if (uri.Query.Length == 0)
            return new Dictionary<string, string>();

        return uri.Query.TrimStart('?')
                        .Split(new[] { '&', ';' }, StringSplitOptions.RemoveEmptyEntries)
                        .Select(parameter => parameter.Split(new[] { '=' }, StringSplitOptions.RemoveEmptyEntries))
                        .GroupBy(parts => parts[0],
                                 parts => parts.Length > 2 ? string.Join("=", parts, 1, parts.Length - 1) : (parts.Length > 1 ? parts[1] : ""))
                        .ToDictionary(grouping => grouping.Key,
                                      grouping => string.Join(",", grouping));


public class UriHelperTest
    public void DecodeQueryParameters()
        DecodeQueryParametersTest("http://test/test.html", new Dictionary<string, string>());
        DecodeQueryParametersTest("http://test/test.html?", new Dictionary<string, string>());
        DecodeQueryParametersTest("http://test/test.html?key=bla/blub.xml", new Dictionary<string, string> { { "key", "bla/blub.xml" } });
        DecodeQueryParametersTest("http://test/test.html?eins=1&zwei=2", new Dictionary<string, string> { { "eins", "1" }, { "zwei", "2" } });
        DecodeQueryParametersTest("http://test/test.html?empty", new Dictionary<string, string> { { "empty", "" } });
        DecodeQueryParametersTest("http://test/test.html?empty=", new Dictionary<string, string> { { "empty", "" } });
        DecodeQueryParametersTest("http://test/test.html?key=1&", new Dictionary<string, string> { { "key", "1" } });
        DecodeQueryParametersTest("http://test/test.html?key=value?&b=c", new Dictionary<string, string> { { "key", "value?" }, { "b", "c" } });
        DecodeQueryParametersTest("http://test/test.html?key=value=what", new Dictionary<string, string> { { "key", "value=what" } });
            new Dictionary<string, string>
                { "q", "energy+edge" },
                { "rls", "" },
                { "ie", "UTF-8" },
                { "oe", "UTF-8" },
                { "startIndex", "" },
                { "startPage", "1%22" },
        DecodeQueryParametersTest("http://test/test.html?key=value;key=anotherValue", new Dictionary<string, string> { { "key", "value,anotherValue" } });

    private static void DecodeQueryParametersTest(string uri, Dictionary<string, string> expected)
        Dictionary<string, string> parameters = new Uri(uri).DecodeQueryParameters();
        Assert.AreEqual(expected.Count, parameters.Count, "Wrong parameter count. Uri: {0}", uri);
        foreach (var key in expected.Keys)
            Assert.IsTrue(parameters.ContainsKey(key), "Missing parameter key {0}. Uri: {1}", key, uri);
            Assert.AreEqual(expected[key], parameters[key], "Wrong parameter value for {0}. Uri: {1}", parameters[key], uri);

Can't connect to MySQL server on 'localhost' (10061)

run > services.msc > rightclick MySQL57 > properties >set start type option to automatic

after restarting computer

At cmd

cd: C:\

C :\> cd "C:\Program Files\MySQL\MySQL Server 5.7\bin"

it will become

C:\Program Files\MySQL\MySQL Server 5.7\bin>

type mysql -u root -p

ie C:\Program Files\MySQL\MySQL Server 5.7\bin> mysql -u root -p

Enter password: ****

That's all

It will result in


Change a branch name in a Git repo

If you're currently on the branch you want to rename:

git branch -m new_name 

Or else:

git branch -m old_name new_name 

You can check with:

git branch -a

As you can see, only the local name changed Now, to change the name also in the remote you must do:

git push origin :old_name

This removes the branch, then upload it with the new name:

git push origin new_name


How to convert between bytes and strings in Python 3?

This is a Python 101 type question,

It's a simple question but one where the answer is not so simple.

In python3, a "bytes" object represents a sequence of bytes, a "string" object represents a sequence of unicode code points.

To convert between from "bytes" to "string" and from "string" back to "bytes" you use the bytes.decode and string.encode functions. These functions take two parameters, an encoding and an error handling policy.

Sadly there are an awful lot of cases where sequences of bytes are used to represent text, but it is not necessarily well-defined what encoding is being used. Take for example filenames on unix-like systems, as far as the kernel is concerned they are a sequence of bytes with a handful of special values, on most modern distros most filenames will be UTF-8 but there is no gaurantee that all filenames will be.

If you want to write robust software then you need to think carefully about those parameters. You need to think carefully about what encoding the bytes are supposed to be in and how you will handle the case where they turn out not to be a valid sequence of bytes for the encoding you thought they should be in. Python defaults to UTF-8 and erroring out on any byte sequence that is not valid UTF-8.


Python uses "repr" as a fallback conversion to string. repr attempts to produce python code that will recreate the object. In the case of a bytes object this means among other things escaping bytes outside the printable ascii range.

How to install Java 8 on Mac

If you have several Java versions on your machine and you want to choose it dynamically at runtime, i.e, in my case, I have two versions:

ls -la /Library/Java/JavaVirtualMachines
drwxr-xr-x  3 root  wheel    96B Nov 16  2014 jdk1.7.0_71.jdk/
drwxr-xr-x  3 root  wheel    96B Mar  1  2015 jdk1.8.0_31.jdk/

You can change them by modifying the /etc/profile content. Just add (or modify) the following two lines at the end of the file:

export JAVA_HOME=YOUR_JAVA_PATH/Contents/Home
export PATH=$JAVA_HOME/bin:$PATH

In my case, it should be like the following if I want to use:

Java 7:

export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.7.0_71.jdk/Contents/Home
export PATH=$JAVA_HOME/bin:$PATH

Java 8:

export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_31.jdk/Contents/Home
export PATH=$JAVA_HOME/bin:$PATH

After saving the file, please run source /etc/profile and it should work. Here are results when I use the first and second option accordingly:

Java 7:

java -version
java version "1.7.0_71"
Java(TM) SE Runtime Environment (build 1.7.0_71-b14)

Java 8:

java -version 
java version "1.8.0_31"
Java(TM) SE Runtime Environment (build 1.8.0_31-b13)

The process is similar if your java folder is located in different locations.

Prevent wrapping of span or div

Try this:

.slideContainer {_x000D_
    overflow-x: scroll;_x000D_
    white-space: nowrap;_x000D_
.slide {_x000D_
    display: inline-block;_x000D_
    width: 600px;_x000D_
    white-space: normal;_x000D_
<div class="slideContainer">_x000D_
    <span class="slide">Some content</span>_x000D_
    <span class="slide">More content. Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</span>_x000D_
    <span class="slide">Even more content!</span>_x000D_

Note that you can omit .slideContainer { overflow-x: scroll; } (which browsers may or may not support when you read this), and you'll get a scrollbar on the window instead of on this container.

The key here is display: inline-block. This has decent cross-browser support nowadays, but as usual, it's worth testing in all target browsers to be sure.

how to change php version in htaccess in server

Try this to switch to php4:

AddHandler application/x-httpd-php4 .php

Upd. Looks like I didn't understand your question correctly. This will not help if you have only php 4 on your server.

type object 'datetime.datetime' has no attribute 'datetime'

If you have used:

from datetime import datetime

Then simply write the code as:

date = datetime(int(year), int(month), 1)

But if you have used:

import datetime

then only you can write:

date = datetime.datetime(int(2005), int(5), 1)

How to set Default Controller in MVC 4 & MVC 5

In case you have only one controller and you want to access every action on root you can skip controller name like this

        new { controller = "Home", action = "Index", 
        id = UrlParameter.Optional }

Getting Google+ profile picture url with user_id

UPDATE: The method below DOES NOT WORK since 2015

It is possible to get the profile picture, and you can even set the size of it:<user_id>?sz=<your_desired_size>

Example: My profile picture, with size set to 100 pixels:

Usage with an image tag:

<img src="" width="100" height="100">

Hope you get it working!

conversion of a varchar data type to a datetime data type resulted in an out-of-range value

i faced this issue where i was using SQL it is different from MYSQL the solution was puting in this format: =date('m-d-y h:m:s'); rather than =date('y-m-d h:m:s');

TypeError: Missing 1 required positional argument: 'self'

You need to instantiate a class instance here.


p = Pump()

Small example -

>>> class TestClass:
        def __init__(self):
            print("in init")
        def testFunc(self):
            print("in Test Func")

>>> testInstance = TestClass()
in init
>>> testInstance.testFunc()
in Test Func

Declaring and using MySQL varchar variables

In Mysql, We can declare and use variables with set command like below

mysql> set @foo="manjeet";
mysql> select * from table where name = @foo;

How can I change IIS Express port for a site

If we are talking about a WebSite, not web app, my issue was that the actual .sln folder was somewhere else than the website, and I had not noticed. Look for the .sln path and then for the .vs (hidden) folder there.

How to get all subsets of a set? (powerset)

You can do it like this:

def powerset(x):
    if not x:
        A = x[0]
        B = x[1:]
        for z in powerset(B):
            r = [A] + z
    return m

print(powerset([1, 2, 3, 4]))


[[], [1], [2], [1, 2], [3], [1, 3], [2, 3], [1, 2, 3], [4], [1, 4], [2, 4], [1, 2, 4], [3, 4], [1, 3, 4], [2, 3, 4], [1, 2, 3, 4]]

Arduino IDE can't find ESP8266WiFi.h file

Starting with 1.6.4, Arduino IDE can be used to program and upload the NodeMCU board by installing the ESP8266 third-party platform package (refer

  • Start Arduino, go to File > Preferences
  • Add the following link to the Additional Boards Manager URLs: and press OK button
  • Click Tools > Boards menu > Boards Manager, search for ESP8266 and install ESP8266 platform from ESP8266 community (and don't forget to select your ESP8266 boards from Tools > Boards menu after installation)

To install additional ESP8266WiFi library:

  • Click Sketch > Include Library > Manage Libraries, search for ESP8266WiFi and then install with the latest version.

After above steps, you should compile the sketch normally.

What is the correct syntax of ng-include?

On ng-build, file not found(404) error occur. So we can use below code

<ng-include src="'views/transaction/test.html'"></ng-include>

insted of,

<div ng-include="'views/transaction/test.html'"></div>

Git Stash vs Shelve in IntelliJ IDEA

git shelve doesn't exist in Git.

Only git stash:

  • when you want to record the current state of the working directory and the index, but want to go back to a clean working directory.
  • which saves your local modifications away and reverts the working directory to match the HEAD commit.

You had a 2008 old project git shelve to isolate modifications in a branch, but that wouldn't be very useful nowadays.

As documented in Intellij IDEA shelve dialog, the feature "shelving and unshelving" is not linked to a VCS (Version Control System tool) but to the IDE itself, to temporarily storing pending changes you have not committed yet in changelist.

Note that since Git 2.13 (Q2 2017), you now can stash individual files too.

Construct pandas DataFrame from items in nested dictionary

So I used to use a for loop for iterating through the dictionary as well, but one thing I've found that works much faster is to convert to a panel and then to a dataframe. Say you have a dictionary d

import pandas as pd
{'RAY Index': {, 11, 3): {'PX_LAST': 1199.46,
'PX_OPEN': 1200.14},, 11, 4): {'PX_LAST': 1195.323, 'PX_OPEN': 1197.69},, 11, 5): {'PX_LAST': 1200.936, 'PX_OPEN': 1195.32},, 11, 6): {'PX_LAST': 1206.061, 'PX_OPEN': 1200.62}},
'SPX Index': {, 11, 3): {'PX_LAST': 2017.81,
'PX_OPEN': 2018.21},, 11, 4): {'PX_LAST': 2012.1, 'PX_OPEN': 2015.81},, 11, 5): {'PX_LAST': 2023.57, 'PX_OPEN': 2015.29},, 11, 6): {'PX_LAST': 2031.21, 'PX_OPEN': 2023.33}}}

The command

<class 'pandas.core.panel.Panel'>
Dimensions: 2 (items) x 2 (major_axis) x 4 (minor_axis)
Items axis: RAY Index to SPX Index
Major_axis axis: PX_LAST to PX_OPEN
Minor_axis axis: 2014-11-03 to 2014-11-06

where pd.Panel(d)[item] yields a dataframe

pd.Panel(d)['SPX Index']
2014-11-03  2014-11-04  2014-11-05 2014-11-06
PX_LAST 2017.81 2012.10 2023.57 2031.21
PX_OPEN 2018.21 2015.81 2015.29 2023.33

You can then hit the command to_frame() to turn it into a dataframe. I use reset_index as well to turn the major and minor axis into columns rather than have them as indices.

major   minor      RAY Index    SPX Index
PX_LAST 2014-11-03  1199.460    2017.81
PX_LAST 2014-11-04  1195.323    2012.10
PX_LAST 2014-11-05  1200.936    2023.57
PX_LAST 2014-11-06  1206.061    2031.21
PX_OPEN 2014-11-03  1200.140    2018.21
PX_OPEN 2014-11-04  1197.690    2015.81
PX_OPEN 2014-11-05  1195.320    2015.29
PX_OPEN 2014-11-06  1200.620    2023.33

Finally, if you don't like the way the frame looks you can use the transpose function of panel to change the appearance before calling to_frame() see documentation here

Just as an example

major        minor  2014-11-03  2014-11-04  2014-11-05  2014-11-06
RAY Index   PX_LAST 1199.46    1195.323     1200.936    1206.061
RAY Index   PX_OPEN 1200.14    1197.690     1195.320    1200.620
SPX Index   PX_LAST 2017.81    2012.100     2023.570    2031.210
SPX Index   PX_OPEN 2018.21    2015.810     2015.290    2023.330

Hope this helps.

How to print out all the elements of a List in Java?

   List<String> textList=
        public class Message  {

        String name;
        String text;

        public Message(String name, String text) {
   = name;
            this.text = text;

        public String getName() {
            return name;

      public String getText() {
        return text;

Ubuntu says "bash: ./program Permission denied"

chmod u+x program_name. Then execute it.

If that does not work, copy the program from the USB device to a native volume on the system. Then chmod u+x program_name on the local copy and execute that.

Unix and Unix-like systems generally will not execute a program unless it is marked with permission to execute. The way you copied the file from one system to another (or mounted an external volume) may have turned off execute permission (as a safety feature). The command chmod u+x name adds permission for the user that owns the file to execute it.

That command only changes the permissions associated with the file; it does not change the security controls associated with the entire volume. If it is security controls on the volume that are interfering with execution (for example, a noexec option may be specified for a volume in the Unix fstab file, which says not to allow execute permission for files on the volume), then you can remount the volume with options to allow execution. However, copying the file to a local volume may be a quicker and easier solution.

How to connect android emulator to the internet

I encounter this issue when I first run the simulator, I solved it by setting the dns server with

Library/Android/sdk/platform-tools/adb shell getprop net.dns1

get the current dns server of simulator

Then set it to my lan dns server

Library/Android/sdk/platform-tools/adb shell setprop net.dns1

Error starting Tomcat from NetBeans - '*' is not recognized as an internal or external command

I didnt try Sumama Waheed's answer but what worked for me was replacing the bin/catalina.jar with a working jar (I disposed of an older tomcat) and after adding in NetBeans, I put the original catalina.jar again.

Waiting for background processes to finish before exiting script

Even if you do not have the pid, you can trigger 'wait;' after triggering all background processes. For. eg. in

bteq < input_file1.sql > output_file1.sql &
bteq < input_file2.sql > output_file2.sql &
bteq < input_file3.sql > output_file3.sql &

Then when this is triggered, as -['sh', ''])
print('all background processes done.')

This will be printed only after all the background processes are done.

Python module for converting PDF to text

I needed to convert a specific PDF to plain text within a python module. I used PDFMiner 20110515, after reading through their tool I wrote this simple snippet:

from cStringIO import StringIO
from pdfminer.pdfinterp import PDFResourceManager, process_pdf
from pdfminer.converter import TextConverter
from pdfminer.layout import LAParams

def to_txt(pdf_path):
    input_ = file(pdf_path, 'rb')
    output = StringIO()

    manager = PDFResourceManager()
    converter = TextConverter(manager, output, laparams=LAParams())
    process_pdf(manager, converter, input_)

    return output.getvalue() 

Flatten an irregular list of lists

I didn't go through all the already available answers here, but here is a one liner I came up with, borrowing from lisp's way of first and rest list processing

def flatten(l): return flatten(l[0]) + (flatten(l[1:]) if len(l) > 1 else []) if type(l) is list else [l]

here is one simple and one not-so-simple case -

>>> flatten([1,[2,3],4])
[1, 2, 3, 4]

>>> flatten([1, [2, 3], 4, [5, [6, {'name': 'some_name', 'age':30}, 7]], [8, 9, [10, [11, [12, [13, {'some', 'set'}, 14, [15, 'some_string'], 16], 17, 18], 19], 20], 21, 22, [23, 24], 25], 26, 27, 28, 29, 30])
[1, 2, 3, 4, 5, 6, {'age': 30, 'name': 'some_name'}, 7, 8, 9, 10, 11, 12, 13, set(['set', 'some']), 14, 15, 'some_string', 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30]

Sort columns of a dataframe by column name

An alternative option is to use str_sort() from library stringr, with the argument numeric = TRUE. This will correctly order column that include numbers not just alphabetically:

str_sort(c("V3", "V1", "V10"), numeric = TRUE)

# [1] V1 V3 V11

Rails 3.1 and Image Assets

when referencing images in CSS or in an IMG tag, use image-name.jpg

while the image is really located under ./assets/images/image-name.jpg

Android XML Percent Symbol

Try using a backslash in front of it, like below:


How to import existing *.sql files in PostgreSQL 8.4?

Well, the shortest way I know of, is following:

psql -U {user_name} -d {database_name} -f {file_path} -h {host_name}

database_name: Which database should you insert your file data in.

file_path: Absolute path to the file through which you want to perform the importing.

host_name: The name of the host. For development purposes, it is mostly localhost.

Upon entering this command in console, you will be prompted to enter your password.

Android ADB stop application command like "force-stop" for non rooted device

To kill from the application, you can do:


How to read xml file contents in jQuery and display in html elements?

responseText is what you are looking for. Example:

complete: function(xhr, status) {

Where xml is your file. Remember this will be your xml in the form form of a string. You can parse it using xmlparse as some of them mentioned.

Copy data from one column to other column (which is in a different table)

Here the query:

Same Table:

UPDATE table_name 
SET column1 = column2

Different Table:

UPDATE table_name1 
    SET column1 = (
        SELECT column2
        FROM table_name2
        WHERE =

Detecting when the 'back' button is pressed on a navbar

For Swift with a UINavigationController:

override func viewWillDisappear(animated: Bool) {
    if self.navigationController?.topViewController != self {
        print("back button tapped")

Bash Templating: How to build configuration files from templates with Bash?

I think eval works really well. It handles templates with linebreaks, whitespace, and all sorts of bash stuff. If you have full control over the templates themselves of course:

$ cat template.txt
variable1 = ${variable1}
variable2 = $variable2
my-ip = \"$(curl -s\"

$ echo $variable1
$ echo $variable2
$ eval "echo \"$(<template.txt)\"" 2> /dev/null
variable1 = AAA
variable2 = BBB
my-ip = ""

This method should be used with care, of course, since eval can execute arbitrary code. Running this as root is pretty much out of the question. Quotes in the template need to be escaped, otherwise they will be eaten by eval.

You can also use here documents if you prefer cat to echo

$ eval "cat <<< \"$(<template.txt)\"" 2> /dev/null

@plockc provoded a solution that avoids the bash quote escaping issue:

$ eval "cat <<EOF
" 2> /dev/null

Edit: Removed part about running this as root using sudo...

Edit: Added comment about how quotes need to be escaped, added plockc's solution to the mix!

Import and Export Excel - What is the best library?

I'm going to throw my hand in for flat csv files, if only because you've got the greatest control over the code. Just make sure that you read in the rows and process them one at a time (reading the document to the end and splitting will eat up all of your memory - same with writing, stream it out).

Yes, the user will have to save-as CSV in excel before you can process it, but perhaps this limitation can be overcome by training and providing clear instructions on the page?

Finally, when you export to the customer, if you set the mime type to text/csv, Excel is usually mapped to that type so it appears to the user to be 'an Excel file'.

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

I was attempting to find strings with numbers ONLY, no punctuation or anything else. I finally found an answer that would work here.

Using PATINDEX('%[^0-9]%', some_column) = 0 allowed me to filter out everything but actual number strings.

How do I format a date as ISO 8601 in moment.js?

Also possible with vanilla JS

new Date().toISOString() // "2017-08-26T16:31:02.349Z"

Nested iframes, AKA Iframe Inception

var iframeInner = jQuery(iframe).find('iframe').contents();

var iframeContent = jQuery(iframeInner).contents().find('#element');

iframeInner contains elements from

<div id="element">other markup goes here</div> 

and iframeContent will find for elements which are inside of

 <div id="element">other markup goes here</div> 

(find doesn't search on current element) that's why it is returning null.

What is Turing Complete?

I think the importance of the concept "Turing Complete" is in the the ability to identify a computing machine (not necessarily a mechanical/electrical "computer") that can have its processes be deconstructed into "simple" instructions, composed of simpler and simpler instructions, that a Universal machine could interpret and then execute.

I highly recommend The Annotated Turing

@Mark i think what you are explaining is a mix between the description of the Universal Turing Machine and Turing Complete.

Something that is Turing Complete, in a practical sense, would be a machine/process/computation able to be written and represented as a program, to be executed by a Universal Machine (a desktop computer). Though it doesn't take consideration for time or storage, as mentioned by others.

Batch script to install MSI

Here is the batch file which should work for you:

@echo off
Title HOST: Installing updates on %computername%
echo %computername%
set Server=\\SERVERNAME or PATH\msifolder

echo Select one of the following MSI install folders for installation task.
dir "%Server%" /AD /ON /B
set /P "MSI=Please enter the MSI folder to install: "
set "Package=%Server%\%MSI%\%MSI%.msi"

if not exist "%Package%" (
   echo The entered folder/MSI file does not exist ^(typing mistake^).
   setlocal EnableDelayedExpansion
   set /P "Retry=Try again [Y/N]: "
   if /I "!Retry!"=="Y" endlocal & goto select
   goto :EOF

echo Selected installation: %MSI%

echo Is This Correct?
echo    0: ABORT INSTALL
echo    1: YES
echo    2: NO, RE-SELECT
set /p "choice=Select YES, NO or ABORT? [0,1,2]: "
if [%choice%]==[0] goto :EOF
if [%choice%]==[1] goto yes
goto select

echo Running %MSI% installation ...
start "Install MSI" /wait "%SystemRoot%\system32\msiexec.exe" /i /quiet "%Package%"

The characters listed on last page output on entering in a command prompt window either help cmd or cmd /? have special meanings in batch files. Here are used parentheses and square brackets also in strings where those characters should be interpreted literally. Therefore it is necessary to either enclose the string in double quotes or escape those characters with character ^ as it can be seen in code above, otherwise command line interpreter exits batch execution because of a syntax error.

And it is not possible to call a file with extension MSI. A *.msi file is not an executable. On double clicking on a MSI file, Windows looks in registry which application is associated with this file extension for opening action. And the application to use is msiexec with the command line option /i to install the application inside MSI package.

Run msiexec.exe /? to get in a GUI window the available options or look at Msiexec (command-line options).

I have added already /quiet additionally to required option /i for a silent installation.

In batch code above command start is used with option /wait to start Windows application msiexec.exe and hold execution of batch file until installation finished (or aborted).

checking if number entered is a digit in jquery

String.prototype.isNumeric = function() {
    var s = this.replace(',', '.').replace(/\s+/g, '');
return s == 0 || (s/s);


'9.1'.isNumeric() -> 1
'0xabc'.isNumeric() -> 1
'10,1'.isNumeric() -> 1
'str'.isNumeric() -> NaN

Handling the null value from a resultset in JAVA

Since the column may be null in the database, the rs.getString() will throw a NullPointerException()


rs.getString will not throw NullPointer if the column is present in the selected result set (SELECT query columns) For a particular record if value for the 'comumn is null in db, you must do something like this -

String myValue = rs.getString("myColumn");
if (rs.wasNull()) {
    myValue = ""; // set it to empty string as you desire.

You may want to refer to wasNull() documentation -

From java.sql.ResultSet
boolean wasNull() throws SQLException;

* Reports whether
* the last column read had a value of SQL <code>NULL</code>.
* Note that you must first call one of the getter methods
* on a column to try to read its value and then call
* the method <code>wasNull</code> to see if the value read was
* SQL <code>NULL</code>.
* @return <code>true</code> if the last column value read was SQL
*         <code>NULL</code> and <code>false</code> otherwise
* @exception SQLException if a database access error occurs or this method is 
*            called on a closed result set

Unable to compile simple Java 10 / Java 11 project with Maven

As of 30Jul, 2018 to fix the above issue, one can configure the java version used within maven to any up to JDK/11 and make use of the maven-compiler-plugin:3.8.0 to specify a release of either 9,10,11 without any explicit dependencies.

        <release>11</release>  <!--or <release>10</release>-->

Note:- The default value for source/target has been lifted from 1.5 to 1.6 with this version. -- release notes.

Edit [30.12.2018]

In fact, you can make use of the same version of maven-compiler-plugin while compiling the code against JDK/12 as well.

More details and a sample configuration in how to Compile and execute a JDK preview feature with Maven.

How to prevent form resubmission when page is refreshed (F5 / CTRL+R)

You can prevent form resubmission via a session variable.

First you have to set rand() in a textbox and $_SESSION['rand'] on the form page:

<form action="" method="post">
 <input type="hidden" value="<?php echo $rand; ?>" name="randcheck" />
   Your Form's Other Field 
 <input type="submit" name="submitbtn" value="submit" />

After that check $_SESSION['rand'] with textbox $_POST['randcheck'] value like this:

if(isset($_POST['submitbtn']) && $_POST['randcheck']==$_SESSION['rand'])
    // Your code here

Make sure you start the session on every file you are using it with session_start()

jQuery: find element by text

You can use the :contains selector to get elements based on their content.

Demo here

$('div:contains("test")').css('background-color', 'red');
<div>This is a test</div>_x000D_
<div>Another Div</div>_x000D_
<script src=""></script>

How to pass password to scp?

  1. make sure you have "expect" tool before, if not, do it

    # apt-get install expect

  2. create the a script file with following content. (# vi /root/scriptfile)

    spawn scp /path_from/file_name user_name_here@to_host_name:/path_to

    expect "password:"

    send put_password_here\n;


  3. execute the script file with "expect" tool

    # expect /root/scriptfile

Kill python interpeter in linux from the terminal

pgrep -f <your process name> | xargs kill -9

This will kill the your process service. In my case it is

pgrep -f python | xargs kill -9

How to implement LIMIT with SQL Server?

This is a multi step approach that will work in SQL2000.

-- Create a temp table to hold the data
CREATE TABLE #foo(rowID int identity(1, 1), myOtherColumns)

INSERT INTO #foo (myColumns) SELECT myData order By MyCriteria

Select * FROM #foo where rowID > 10

Error retrieving parent for item: No resource found that matches the given name 'android:TextAppearance.Material.Widget.Button.Borderless.Colored'

in my case i was using compile sdk 23 and build tools 25.0.0 just changed compile sdk to 25 and done..

Go doing a GET request and building the Querystring

As a commenter mentioned you can get Values from net/url which has an Encode method. You could do something like this (req.URL.Query() returns the existing url.Values)

package main

import (

func main() {
    req, err := http.NewRequest("GET", "", nil)
    if err != nil {

    q := req.URL.Query()
    q.Add("api_key", "key_from_environment_or_flag")
    q.Add("another_thing", "foo & bar")
    req.URL.RawQuery = q.Encode()

    // Output:

Access-Control-Allow-Origin: * in tomcat

Change this:

    <param-value>Content-Type, Last-Modified</param-value>

To this

    <param-value>Accept, Origin, X-Requested-With, Content-Type, Last-Modified</param-value>

I had to do this to get anything to work.

Creating a JSON dynamically with each input value using jquery

Like this:

function createJSON() {
    jsonObj = [];
    $("input[class=email]").each(function() {

        var id = $(this).attr("title");
        var email = $(this).val();

        item = {}
        item ["title"] = id;
        item ["email"] = email;




You are looking for an array of objects. So, you create a blank array. Create an object for each input by using 'title' and 'email' as keys. Then you add each of the objects to the array.

If you need a string, then do

jsonString = JSON.stringify(jsonObj);

Sample Output


How to test android apps in a real device with Android Studio?

You have to Download the driver for your Device just go to device manager-->> your device-->update driver-->choose the usb driver path from sdk extras folder and click next. You can get the correct driver and you can run on real device

Allow only numbers to be typed in a textbox

You could subscribe for the onkeypress event:

<input type="text" class="textfield" value="" id="extra7" name="extra7" onkeypress="return isNumber(event)" />

and then define the isNumber function:

function isNumber(evt) {
    evt = (evt) ? evt : window.event;
    var charCode = (evt.which) ? evt.which : evt.keyCode;
    if (charCode > 31 && (charCode < 48 || charCode > 57)) {
        return false;
    return true;

You can see it in action here.

How do I delete an exported environment variable?

Because the original question doesn't mention how the variable was set, and because I got to this page looking for this specific answer, I'm adding the following:

In C shell (csh/tcsh) there are two ways to set an environment variable:

  1. set x = "something"
  2. setenv x "something"

The difference in the behaviour is that variables set with setenv command are automatically exported to subshell while variable set with set aren't.

To unset a variable set with set, use

unset x

To unset a variable set with setenv, use

unsetenv x

Note: in all the above, I assume that the variable name is 'x'.


What is the best IDE for C Development / Why use Emacs over an IDE?

Use Code::Blocks. It has everything you need and a very clean GUI.

Char to int conversion in C

Try this :

char c = '5' - '0';

How do I iterate over the words of a string?

Here's my approach, cut and split:

string cut (string& str, const string& del)
    string f = str;

    if (in.find_first_of(del) != string::npos)
        f = str.substr(0,str.find_first_of(del));
        str = str.substr(str.find_first_of(del)+del.length());

    return f;

vector<string> split (const string& in, const string& del=" ")
    vector<string> out();
    string t = in;

    while (t.length() > del.length())

    return out;

BTW, if there's something I can do to optimize this ..

AES Encryption for an NSString on the iPhone

@owlstead, regarding your request for "a cryptographically secure variant of one of the given answers," please see RNCryptor. It was designed to do exactly what you're requesting (and was built in response to the problems with the code listed here).

RNCryptor uses PBKDF2 with salt, provides a random IV, and attaches HMAC (also generated from PBKDF2 with its own salt. It support synchronous and asynchronous operation.

Can't push to GitHub because of large file which I already deleted

I had this issue when I didn't have a gitignore file with my iOS project

I think maybe it was trying to push a humungous file to github and github was probably rejecting that giant file or (files)

How to include files outside of Docker's build context?

One quick and dirty way is to set the build context up as many levels as you need - but this can have consequences. If you're working in a microservices architecture that looks like this:


You can set the build context to the parent Code directory and then access everything, but it turns out that with a large number of repositories, this can result in the build taking a long time.

An example situation could be that another team maintains a database schema in Repo1 and your team's code in Repo2 depends on this. You want to dockerise this dependency with some of your own seed data without worrying about schema changes or polluting the other team's repository (depending on what the changes are you may still have to change your seed data scripts of course) The second approach is hacky but gets around the issue of long builds:

Create a sh (or ps1) script in ./Code/Repo2 to copy the files you need and invoke the docker commands you want, for example:

rm -r ./db/schema
mkdir ./db/schema

cp  -r ../Repo1/db/schema ./db/schema

docker-compose -f docker-compose.yml down
docker container prune -f
docker-compose -f docker-compose.yml up --build

In the docker-compose file, simply set the context as Repo2 root and use the content of the ./db/schema directory in your dockerfile without worrying about the path. Bear in mind that you will run the risk of accidentally committing this directory to source control, but scripting cleanup actions should be easy enough.

Parse rfc3339 date strings in Python?

This has already been answered here: How do I translate a ISO 8601 datetime string into a Python datetime object?

d = datetime.datetime.strptime( "2012-10-09T19:00:55Z", "%Y-%m-%dT%H:%M:%SZ" )

How to move Jenkins from one PC to another

Following the Jenkins wiki, you'll have to:

  • Install a fresh Jenkins instance on the new server
  • Be sure the old and the new Jenkins instances are stopped
  • Archive all the content of the JENKINS_HOME of the old Jenkins instance
  • Extract the archive into the new JENKINS_HOME directory
  • Launch the new Jenkins instance
  • Do not forget to change documentation/links to your new instance of Jenkins :)
  • Do not forget to change the owner of the new Jenkins files : chown -R jenkins:jenkins $JENKINS_HOME

JENKINS_HOME is by default located in ~/.jenkins on a Linux installation, yet to exactly find where it is located, go on the http://your_jenkins_url/configure page and check the value of the first parameter: Home directory; this is the JENKINS_HOME.

Create new project on Android, Error: Studio Unknown host ''

Go to setting option which is on upper strip of android studio and follow the below steps to solve the problem.

setting > Appearance&behavior > HTTP and proxy > click on Auto detect Enable option.(The option with radio box)select this one...

Remove all the children DOM elements in div

From the dojo API documentation:


builder for HashMap

Using java 8:

This is a approach of Java-9 Map.ofEntries(Map.entry(k1,v1), Map.entry(k2,v2), ...)

public class MapUtil {
    import static;

    import java.util.AbstractMap.SimpleEntry;
    import java.util.Map;
    import java.util.Map.Entry;

    private MapUtil() {}

    public static Map<String, Object> ofEntries(SimpleEntry<String, Object>... values) {
        return Stream.of(values).collect(toMap(Entry::getKey, Entry::getValue));

    public static SimpleEntry<String, Object> entry(String key, Object value) {
        return new SimpleEntry<String, Object>(key, value);

How to Use:

import static*;

import java.util.Map;

Map<String, Object> map = ofEntries(
        entry("id", 1),
        entry("description", "xyz"),
        entry("value", 1.05),
        entry("enable", true)

Remove NaN from pandas series

A small usage of np.nan ! = np.nan

0    1.0
1    2.0
2    3.0
3    4.0
5    5.0
dtype: float64

More Info

np.nan == np.nan
Out[954]: False

CSS "color" vs. "font-color"

The same way Boston came up with its street plan. They followed the cow paths already there, and built houses where the streets weren't, and after a while it was too much trouble to change.

Detach (move) subdirectory into separate Git repository

Here is a small modification to CoolAJ86's "The Easy Way™" answer in order to split multiple sub folders (let's say sub1and sub2) into a new git repository.

The Easy Way™ (multiple sub folders)

  1. Prepare the old repo

    pushd <big-repo>
    git filter-branch --tree-filter "mkdir <name-of-folder>; mv <sub1> <sub2> <name-of-folder>/" HEAD
    git subtree split -P <name-of-folder> -b <name-of-new-branch>

    Note: <name-of-folder> must NOT contain leading or trailing characters. For instance, the folder named subproject MUST be passed as subproject, NOT ./subproject/

    Note for windows users: when your folder depth is > 1, <name-of-folder> must have *nix style folder separator (/). For instance, the folder named path1\path2\subproject MUST be passed as path1/path2/subproject. Moreover don't use mvcommand but move.

    Final note: the unique and big difference with the base answer is the second line of the script "git filter-branch..."

  2. Create the new repo

    mkdir <new-repo>
    pushd <new-repo>
    git init
    git pull </path/to/big-repo> <name-of-new-branch>
  3. Link the new repo to Github or wherever

    git remote add origin <[email protected]:my-user/new-repo.git>
    git push origin -u master
  4. Cleanup, if desired

    popd # get out of <new-repo>
    pushd <big-repo>
    git rm -rf <name-of-folder>

    Note: This leaves all the historical references in the repository.See the Appendix in the original answer if you're actually concerned about having committed a password or you need to decreasing the file size of your .git folder.

How to Convert Datetime to Date in dd/MM/yyyy format

Give a different alias

SELECT  Convert(varchar,A.InsertDate,103) as converted_Tran_Date from table as A
order by A.InsertDate 

Select folder dialog WPF

The FolderBrowserDialog class from System.Windows.Forms is the recommended way to display a dialog that allows a user to select a folder.

Until recently, the appearance and behaviour of this dialog was not in keeping with the other filesystem dialogs, which is one of the reasons why people were reluctant to use it.

The good news is that FolderBrowserDialog was "modernized" in NET Core 3.0, so is now a viable option for those writing either Windows Forms or WPF apps targeting that version or later.

In .NET Core 3.0, Windows Forms users [sic] a newer COM-based control that was introduced in Windows Vista: FolderBrowserDialog in NET Core 3.0

To reference System.Windows.Forms in a NET Core WPF app, it is necessary to edit the project file and add the following line:


This can be placed directly after the existing <UseWPF> element.

Then it's just a case of using the dialog:

using System;
using System.Windows.Forms;


using var dialog = new FolderBrowserDialog
    Description = "Time to select a folder",
    UseDescriptionForTitle = true,
    SelectedPath = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory)
        + Path.DirectorySeparatorChar,
    ShowNewFolderButton = true

if (dialog.ShowDialog() == DialogResult.OK)

FolderBrowserDialog has a RootFolder property that supposedly "sets the root folder where the browsing starts from" but whatever I set this to it didn't make any difference; SelectedPath seemed to be the better property to use for this purpose, however the trailing backslash is required.

Also, the ShowNewFolderButton property seems to be ignored as well, the button is always shown regardless.

Creating a Menu in Python

This should do it. You were missing a ) and you only need """ not 4 of them. Also you don't need a elif at the end.

while ans:
    1.Add a Student
    2.Delete a Student
    3.Look Up Student Record
    ans=raw_input("What would you like to do? ")
    if ans=="1":
      print("\nStudent Added")
    elif ans=="2":
      print("\n Student Deleted")
    elif ans=="3":
      print("\n Student Record Found")
    elif ans=="4":
      print("\n Goodbye") 
      ans = None
       print("\n Not Valid Choice Try again")

How to Install gcc 5.3 with yum on CentOS 7.2?

The best approach to use yum and update your devtoolset is to utilize the CentOS SCLo RH Testing repository.

yum install centos-release-scl-rh
yum --enablerepo=centos-sclo-rh-testing install devtoolset-7-gcc devtoolset-7-gcc-c++

Many additional packages are also available, to see them all

yum --enablerepo=centos-sclo-rh-testing list devtoolset-7*

You can use this method to install any dev tool version, just swap the 7 for your desired version. devtoolset-6-gcc, devtoolset-5-gcc etc.

java.lang.IllegalArgumentException: contains a path separator

The solution is:

FileInputStream fis = new FileInputStream (new File(NAME_OF_FILE));  // 2nd line

The openFileInput method doesn't accept path separators.

Don't forget to


at the end.

Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.2:compile (default-compile)

I am adding more points to the solution by @Rushi Shah

mvn clean install -X helps to identify the root cause.

Some of the important phases of Maven build lifecycle are:

clean – the project is clean of all artifacts that came from previous compilations compile – the project is compiled into /target directory of project root install – packaged archive is copied into local maven repository (could in your user's home directory under /.m2) test – unit tests are run package – compiled sources are packaged into archive (JAR by default)

The 1.6 under tag refers to JDK version. We need to ensure that proper jdk version in our dev environment or change the value to 1.7 or 1.5 or whatever if the application can be supported in that JDK version.


We can find the complete details on Maven build lifecycle in Maven site.

Pass Hidden parameters using response.sendRedirect()

TheNewIdiot's answer successfully explains the problem and the reason why you can't send attributes in request through a redirect. Possible solutions:

  1. Using forwarding. This will enable that request attributes could be passed to the view and you can use them in form of ServletRequest#getAttribute or by using Expression Language and JSTL. Short example (reusing TheNewIdiot's answer] code).

    Controller (your servlet)

    request.setAttribute("message", "Hello world");
    RequestDispatcher dispatcher = servletContext().getRequestDispatcher(url);
    dispatcher.forward(request, response);

    View (your JSP)

    Using scriptlets:


    This is just for information purposes. Scriptlets usage must be avoided: How to avoid Java code in JSP files?. Below there is the example using EL and JSTL.

    <c:out value="${message}" />
  2. If you can't use forwarding (because you don't like it or you don't feel it that way or because you must use a redirect) then an option would be saving a message as a session attribute, then redirect to your view, recover the session attribute in your view and remove it from session. Remember to always have your user session with only relevant data. Code example


    //if request is not from HttpServletRequest, you should do a typecast before
    HttpSession session = request.getSession(false);
    //save message in session
    session.setAttribute("helloWorld", "Hello world");


    Again, showing this using scriptlets and then EL + JSTL:

    <c:out value="${sessionScope.message}" />
    <c:remove var="message" scope="session" />

How to implement a Map with multiple keys?

I can see the following approaches:

a) Use 2 different maps. You can wrap them in a class as you suggest, but even that might be an overkill. Just use the maps directly: key1Map.getValue(k1), key2Map.getValue(k2)

b) You can create a type-aware key class, and use that (untested).

public class Key {
  public static enum KeyType { KEY_1, KEY_2 }

  public final Object k;
  public final KeyType t;

  public Key(Object k, KeyType t) {
    this.k = k;
    this.t= t;

  public boolean equals(Object obj) {
    KeyType kt = (KeyType)obj;
    return k.equals(kt.k) && t == kt.t;

  public int hashCode() {
   return k.hashCode() ^ t.hashCode();

By the way, in a lot of common cases the space of key1 and the space of key2 do not intersect. In that case, you don't actually need to do anything special. Just define a map that has entries key1=>v as well as key2=>v

make html text input field grow as I type?

For those strictly looking for a solution that works for input or textarea, this is the simplest solution I've came across. Only a few lines of CSS and one line of JS.

The JavaScript sets a data-* attribute on the element equal to the value of the input. The input is set within a CSS grid, where that grid is a pseudo-element that uses that data-* attribute as its content. That content is what stretches the grid to the appropriate size based on the input value.

Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister

In my case the problem was because of conflicting Jars.

Here is the full list of jars which is working absolutely fine for me.


Oracle SQL Where clause to find date records older than 30 days


 WHERE creation_date <= TRUNC(SYSDATE) - 30

SYSDATE returns the date & time; TRUNC resets the date to being as of midnight so you can omit it if you want the creation_date that is 30 days previous including the current time.

Depending on your needs, you could also look at using ADD_MONTHS:

 WHERE creation_date <= ADD_MONTHS(TRUNC(SYSDATE), -1)

Best way to check if an PowerShell Object exist?

What all of these answers do not highlight is that when comparing a value to $null, you have to put $null on the left-hand side, otherwise you may get into trouble when comparing with a collection-type value. See:

$value = @(1, $null, 2, $null)
if ($value -eq $null) {
    Write-Host "$value is $null"

The above block is (unfortunately) executed. What's even more interesting is that in Powershell a $value can be both $null and not $null:

$value = @(1, $null, 2, $null)
if (($value -eq $null) -and ($value -ne $null)) {
    Write-Host "$value is both $null and not $null"

So it is important to put $null on the left-hand side to make these comparisons work with collections:

$value = @(1, $null, 2, $null)
if (($null -eq $value) -and ($null -ne $value)) {
    Write-Host "$value is both $null and not $null"

I guess this shows yet again the power of Powershell !

CFLAGS, CCFLAGS, CXXFLAGS - what exactly do these variables control?

According to the GNU make manual:

CFLAGS: Extra flags to give to the C compiler.
CXXFLAGS: Extra flags to give to the C++ compiler.
CPPFLAGS: Extra flags to give to the C preprocessor and programs that use it (the C and Fortran compilers).

note: PP stands for PreProcessor (and not Plus Plus), i.e.

CPP: Program for running the C preprocessor, with results to standard output; default ‘$(CC) -E’.

These variables are used by the implicit rules of make

Compiling C programs
n.o is made automatically from n.c with a recipe of the form
‘$(CC) $(CPPFLAGS) $(CFLAGS) -c’.

Compiling C++ programs
n.o is made automatically from, n.cpp, or n.C with a recipe of the form
We encourage you to use the suffix ‘.cc’ for C++ source files instead of ‘.C’.


MySQL Multiple Left Joins

You're missing a GROUP BY clause:

SELECT, users.username, news.title,, news.body, COUNT(
FROM news
ON news.user_id =
LEFT JOIN comments
ON comments.news_id =

The left join is correct. If you used an INNER or RIGHT JOIN then you wouldn't get news items that didn't have comments.

Early exit from function?

Apparently you can do this:

function myFunction() {myFunction:{
    console.log('i get executed');
    break myFunction;
    console.log('i do not get executed');

See block scopes through the use of a label:

I can't see any downsides yet. But it doesn't seem like a common use.

Derived this answer: JavaScript equivalent of PHP’s die

Git Bash won't run my python files?

Tried multiple of these, I switched to Cygwin instead which fixed python and some other problems I was having on Windows:

How to add a JAR in NetBeans

Right click 'libraries' in the project list, then click add.

How do I create a timer in WPF?

Adding to the above. You use the Dispatch timer if you want the tick events marshalled back to the UI thread. Otherwise I would use System.Timers.Timer.

How to get number of rows inserted by a transaction

In case you need further info for your log/audit you can OUTPUT clause: This way, not only you keep the number of rows affected, but also what records.

As an example of the Output Clause during inserts: SQL Server list of insert identities

DECLARE @InsertedIDs table(ID int);

        INTO @InsertedIDs 
    SELECT ...


Python multiprocessing PicklingError: Can't pickle <type 'function'>

Building on @rocksportrocker solution, It would make sense to dill when sending and RECVing the results.

import dill
import itertools
def run_dill_encoded(payload):
    fun, args = dill.loads(payload)
    res = fun(*args)
    res = dill.dumps(res)
    return res

def dill_map_async(pool, fun, args_list,
    if as_tuple:
        args_list = ((x,) for x in args_list)

    it = itertools.izip(
    it = itertools.imap(dill.dumps, it)
    return pool.map_async(run_dill_encoded, it, **kw)

if __name__ == '__main__':
    import multiprocessing as mp
    import sys,os
    p = mp.Pool(4)
    res = dill_map_async(p, lambda x:[sys.stdout.write('%s\n'%os.getpid()),x][-1],
                  [lambda x:x+1]*10,)
    res = res.get(timeout=100)
    res = map(dill.loads,res)

Convert CString to const char*

I used this conversion:

CString cs = "TEST";
char* c = cs.GetBuffer(m_ncs me.GetLength())

I hope this is useful.

How do I enable Java in Microsoft Edge web browser?

You cannot open Java Applets (nor any other NPAPI plugin) in Microsoft Edge - they aren't supported and won't be added in the future.

Further you should be aware that in the next release of Google Chrome (v45 - due September 2015) NPAPI plugins will also no longer be supported.


There are a couple of things that you can do:

Use Internet Explorer 11
You will find that in Windows 10 you will already have Internet Explorer 11 installed. IE 11 continues to support NPAPI (incl Java Applets). IE11 is squirrelled away (c:\program files\internet explorer\iexplore.exe). Just pin this exe to your task bar for easy access.

Use FireFox
You can also install and use a Firefox 32-bit Extended Support Release in Win10. Firefox have disabled NPAPI by default, but this can be overridden. This will only be supported until early 2018.


To display last 3 rows without using order by:

select * from Lms_Books_Details where Book_Code not in 
 (select top((select COUNT(*) from Lms_Books_Details ) -3 ) book_code from Lms_Books_Details) 

What is java pojo class, java bean, normal class?

POJO = Plain Old Java Object. It has properties, getters and setters for respective properties. It may also override Object.toString() and Object.equals().

Java Beans : See Wiki link.

Normal Class : Any java Class.

Lost connection to MySQL server at 'reading initial communication packet', system error: 0

I had this problem and it ended up being the prior sys admin changed the port MySQL was running on. MySQL Workbench was trying to connect to the default 3306 but the server was running on 20300.

The apk must be signed with the same certificates as the previous version

I just had this occur out of the clear blue. I really do not think I changed anything.

However, Build => Clean Project fixed it.

PHP $_SERVER['HTTP_HOST'] vs. $_SERVER['SERVER_NAME'], am I understanding the man pages correctly?

XSS will always be there even if you use $_SERVER['HTTP_HOST'], $_SERVER['SERVER_NAME'] OR $_SERVER['PHP_SELF']

BeautifulSoup: extract text from anchor tag

I would suggest going the lxml route and using xpath.

from lxml import etree
# data is the variable containing the html
data = etree.HTML(data)
anchor = data.xpath('//a[@class="title"]/text()')

PL/SQL print out ref cursor returned by a stored procedure

Note: This code is untested

Define a record for your refCursor return type, call it rec. For example:

TYPE MyRec IS RECORD (col1 VARCHAR2(10), col2 VARCHAR2(20), ...);  --define the record
rec MyRec;        -- instantiate the record

Once you have the refcursor returned from your procedure, you can add the following code where your comments are now:

  FETCH refCursor INTO rec;

How do I change an HTML selected option using JavaScript?

An array Index will start from 0. If you want value=11 (Person1), you will get it with position getElementsByTagName('option')[10].selected.

How to create a simple http proxy in node.js?

I don't think it's a good idea to process response received from the 3rd party server. This will only increase your proxy server's memory footprint. Further, it's the reason why your code is not working.

Instead try passing the response through to the client. Consider following snippet:

var http = require('http');


function onRequest(client_req, client_res) {
  console.log('serve: ' + client_req.url);

  var options = {
    hostname: '',
    port: 80,
    path: client_req.url,
    method: client_req.method,
    headers: client_req.headers

  var proxy = http.request(options, function (res) {
    client_res.writeHead(res.statusCode, res.headers)
    res.pipe(client_res, {
      end: true

  client_req.pipe(proxy, {
    end: true

Create dataframe from a matrix

I've found the following "cheat" to work very neatly and error-free

> dimnames <- list(time=c(0, 0.5, 1), name=c("C_0", "C_1"))
> mat <- matrix(data, ncol=2, nrow=3, dimnames=dimnames)
> head(mat, 2) #this returns the number of rows indicated in a data frame format
> df <- data.frame(head(mat, 2)) #"data.frame" might not be necessary

Et voila!

Convert HTML Character Back to Text Using Java Standard Library

I think the Apache Commons Lang library's StringEscapeUtils.unescapeHtml3() and unescapeHtml4() methods are what you are looking for. See

Change border-bottom color using jquery?

$("selector").css("border-bottom-color", "#fff");
  1. construct your jQuery object which provides callable methods first. In this case, say you got an #mydiv, then $("#mydiv")
  2. call the .css() method provided by jQuery to modify specified object's css property values.

CSS to set A4 paper size seems to solve all my needs.

Paper CSS for happy printing

Front-end printing solution - previewable and live-reloadable!

Add an incremental number in a field in INSERT INTO SELECT query in SQL Server

You can use the row_number() function for this.

INSERT INTO PM_Ingrediants_Arrangements_Temp(AdminID, ArrangementID, IngrediantID, Sequence)
    SELECT @AdminID, @ArrangementID, PM_Ingrediants.ID,
            row_number() over (order by (select NULL))
    FROM PM_Ingrediants 
    WHERE PM_Ingrediants.ID IN (SELECT ID FROM GetIDsTableFromIDsList(@IngrediantsIDs)

If you want to start with the maximum already in the table then do:

INSERT INTO PM_Ingrediants_Arrangements_Temp(AdminID, ArrangementID, IngrediantID, Sequence)
    SELECT @AdminID, @ArrangementID, PM_Ingrediants.ID,
           coalesce(const.maxs, 0) + row_number() over (order by (select NULL))
    FROM PM_Ingrediants cross join
         (select max(sequence) as maxs from PM_Ingrediants_Arrangement_Temp) const
    WHERE PM_Ingrediants.ID IN (SELECT ID FROM GetIDsTableFromIDsList(@IngrediantsIDs)

Finally, you can just make the sequence column an auto-incrementing identity column. This saves the need to increment it each time:

create table PM_Ingrediants_Arrangement_Temp ( . . .
    sequence int identity(1, 1) -- and might consider making this a primary key too
    . . .

Javascript: convert 24-hour time-of-day string to 12-hour time with AM/PM and no timezone

Make sure that your time is in this format HH:MM:SS(PM/AM)

function timeConversion(s) {

    s = s.split(':');
    var time = s[2];
    if(time.charAt(2) === 'A' && parseInt(s[0]) == 12) s[0] = '00';
    if(time.charAt(2) === 'P' && parseInt(s[0]) <12) s[0] = parseInt(s[0])+12;
    if(s[0] >=24) s[0]-=24;
    var x = time.split('').slice(0,2);
    s[2] = x.join('');

What is RSS and VSZ in Linux memory management

I think much has already been said, about RSS vs VSZ. From an administrator/programmer/user perspective, when I design/code applications I am more concerned about the RSZ, (Resident memory), as and when you keep pulling more and more variables (heaped) you will see this value shooting up. Try a simple program to build malloc based space allocation in loop, and make sure you fill data in that malloc'd space. RSS keeps moving up. As far as VSZ is concerned, it's more of virtual memory mapping that linux does, and one of its core features derived out of conventional operating system concepts. The VSZ management is done by Virtual memory management of the kernel, for more info on VSZ, see Robert Love's description on mm_struct and vm_struct, which are part of basic task_struct data structure in kernel.

Set a default font for whole iOS app?

Developing from Hugues BR answer but using method swizzling I've arrived to a solution that is successfully changing all the fonts to a desired font in my app.

An approach with Dynamic Type should be what you should look for on iOS 7. The following solution is not using Dynamic Type.


  • the code below, in its presented state, was never submitted to Apple approval;
  • there is a shorter version of it that passed Apple submission, that is without the - initWithCoder: override. However that won't cover all the cases;
  • the following code is present in a class I use to set the style of my app which is included by my AppDelegate class thus being available everywhere and to all UIFont instances;
  • I'm using Zapfino here just to make the changes much more visible;
  • any improvement you may find to this code is welcome.

This solution uses two different methods to achieve the final result. The first is override the UIFont class methods + systemFontWithSize: and similar with ones that use my alternatives (here I use "Zapfino" to leave no doubts that the replacement was successful).

The other method is to override - initWithCoder: method on UIFont to replace any occurrence of CTFontRegularUsage and similar by my alternatives. This last method was necessary because I've found that UILabel objects encoded in NIB files don't check the + systemFontWithSize: methods to get their system font and instead encode them as UICTFontDescriptor objects. I've tried to override - awakeAfterUsingCoder: but somehow it was getting called for every encoded object in my storyboard and causing crashes. Overriding - awakeFromNib wouldn't allow me to read the NSCoder object.

#import <objc/runtime.h>

NSString *const FORegularFontName = @"Zapfino";
NSString *const FOBoldFontName = @"Zapfino";
NSString *const FOItalicFontName = @"Zapfino";

#pragma mark - UIFont category
@implementation UIFont (CustomFonts)

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wobjc-protocol-method-implementation"
+ (void)replaceClassSelector:(SEL)originalSelector withSelector:(SEL)modifiedSelector {
    Method originalMethod = class_getClassMethod(self, originalSelector);
    Method modifiedMethod = class_getClassMethod(self, modifiedSelector);
    method_exchangeImplementations(originalMethod, modifiedMethod);

+ (void)replaceInstanceSelector:(SEL)originalSelector withSelector:(SEL)modifiedSelector {
    Method originalDecoderMethod = class_getInstanceMethod(self, originalSelector);
    Method modifiedDecoderMethod = class_getInstanceMethod(self, modifiedSelector);
    method_exchangeImplementations(originalDecoderMethod, modifiedDecoderMethod);

+ (UIFont *)regularFontWithSize:(CGFloat)size
    return [UIFont fontWithName:FORegularFontName size:size];

+ (UIFont *)boldFontWithSize:(CGFloat)size
    return [UIFont fontWithName:FOBoldFontName size:size];

+ (UIFont *)italicFontOfSize:(CGFloat)fontSize
    return [UIFont fontWithName:FOItalicFontName size:fontSize];

- (id)initCustomWithCoder:(NSCoder *)aDecoder {
    BOOL result = [aDecoder containsValueForKey:@"UIFontDescriptor"];

    if (result) {
        UIFontDescriptor *descriptor = [aDecoder decodeObjectForKey:@"UIFontDescriptor"];

        NSString *fontName;
        if ([descriptor.fontAttributes[@"NSCTFontUIUsageAttribute"] isEqualToString:@"CTFontRegularUsage"]) {
            fontName = FORegularFontName;
        else if ([descriptor.fontAttributes[@"NSCTFontUIUsageAttribute"] isEqualToString:@"CTFontEmphasizedUsage"]) {
            fontName = FOBoldFontName;
        else if ([descriptor.fontAttributes[@"NSCTFontUIUsageAttribute"] isEqualToString:@"CTFontObliqueUsage"]) {
            fontName = FOItalicFontName;
        else {
            fontName = descriptor.fontAttributes[@"NSFontNameAttribute"];

        return [UIFont fontWithName:fontName size:descriptor.pointSize];

    self = [self initCustomWithCoder:aDecoder];

    return self;

+ (void)load
    [self replaceClassSelector:@selector(systemFontOfSize:) withSelector:@selector(regularFontWithSize:)];
    [self replaceClassSelector:@selector(boldSystemFontOfSize:) withSelector:@selector(boldFontWithSize:)];
    [self replaceClassSelector:@selector(italicSystemFontOfSize:) withSelector:@selector(italicFontOfSize:)];

    [self replaceInstanceSelector:@selector(initWithCoder:) withSelector:@selector(initCustomWithCoder:)];
#pragma clang diagnostic pop


How do I measure execution time of a command on the Windows command line?

There's also TimeMem (March 2012):

This is a Windows utility which executes a program and displays its execution time, memory usage, and IO statistics. It is similar in functionality to the Unix time utility.

Tab key == 4 spaces and auto-indent after curly braces in Vim

Firstly, do not use the Tab key in Vim for manual indentation. Vim has a pair of commands in insert mode for manually increasing or decreasing the indentation amount. Those commands are Ctrl-T and Ctrl-D. These commands observe the values of tabstop, shiftwidth and expandtab, and maintain the correct mixture of spaces and tabs (maximum number of tabs followed by any necessary number of spaces).

Secondly, these manual indenting keys don't have to be used very much anyway if you use automatic indentation.

If Ctrl-T instead of Tab bothers you, you can remap it:

:imap <Tab> ^T

You can also remap Shift-Tab to do the Ctrl-D deindent:

:imap <S-Tab> ^D

Here ^T and ^D are literal control characters that can be inserted as Ctrl-VCtrl-T.

With this mapping in place, you can still type literal Tab into the buffer using Ctrl-VTab. Note that if you do this, even if :set expandtab is on, you get an unexpanded tab character.

A similar effect to the <Tab> map is achieved using :set smarttab, which also causes backspace at the front of a line to behave smart.

In smarttab mode, when Tab is used not at the start of a line, it has no special meaning. That's different from my above mapping of Tab to Ctrl-T, because a Ctrl-T used anywhere in a line (in insert mode) will increase that line's indentation.

Other useful mappings may be:

:map <Tab> >
:map <S-Tab> <

Now we can do things like select some lines, and hit Tab to indent them over. Or hit Tab twice on a line (in command mode) to increase its indentation.

If you use the proper indentation management commands, then everything is controlled by the three parameters: shiftwidth, tabstop and expandtab.

The shiftwidth parameter controls your indentation size; if you want four space indents, use :set shiftwidth=4, or the abbreviation :set sw=4.

If only this is done, then indentation will be created using a mixture of spaces and tabs, because noexpandtab is the default. Use :set expandtab. This causes tab characters which you type into the buffer to expand into spaces, and for Vim-managed indentation to use only spaces.

When expandtab is on, and if you manage your indentation through all the proper Vim mechanisms, the value of tabstop becomes irrelevant. It controls how tabs appear if they happen to occur in the file. If you have set tabstop=8 expandtab and then sneak a hard tab into the file using Ctrl-VTab, it will produce an alignment to the next 8-column-based tab position, as usual.

"UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure." when plotting figure with pyplot on Pycharm

Linux Mint 19. Helped for me:

sudo apt install tk-dev

P.S. Recompile python interpreter after package install.

Java - How to create new Entry (key, value)

I defined a generic Pair class that I use all the time. It's great. As a bonus, by defining a static factory method (Pair.create) I only have to write the type arguments half as often.

public class Pair<A, B> {

    private A component1;
    private B component2;

    public Pair() {

    public Pair(A component1, B component2) {
            this.component1 = component1;
            this.component2 = component2;

    public A fst() {
            return component1;

    public void setComponent1(A component1) {
            this.component1 = component1;

    public B snd() {
            return component2;

    public void setComponent2(B component2) {
            this.component2 = component2;

    public String toString() {
            return "<" + component1 + "," + component2 + ">";

    public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result
                            + ((component1 == null) ? 0 : component1.hashCode());
            result = prime * result
                            + ((component2 == null) ? 0 : component2.hashCode());
            return result;

    public boolean equals(Object obj) {
            if (this == obj)
                    return true;
            if (obj == null)
                    return false;
            if (getClass() != obj.getClass())
                    return false;
            final Pair<?, ?> other = (Pair<?, ?>) obj;
            if (component1 == null) {
                    if (other.component1 != null)
                            return false;
            } else if (!component1.equals(other.component1))
                    return false;
            if (component2 == null) {
                    if (other.component2 != null)
                            return false;
            } else if (!component2.equals(other.component2))
                    return false;
            return true;

    public static <A, B> Pair<A, B> create(A component1, B component2) {
            return new Pair<A, B>(component1, component2);


Getting Serial Port Information

EDIT: Sorry, I zipped past your question too quick. I realize now that you're looking for a list with the port name + port description. I've updated the code accordingly...

Using System.Management, you can query for all the ports, and all the information for each port (just like Device Manager...)

Sample code (make sure to add reference to System.Management):

using System;
using System.Management;
using System.Collections.Generic;
using System.Linq;
using System.IO.Ports;        

namespace ConsoleApplication1
    class Program
        static void Main(string[] args)
            using (var searcher = new ManagementObjectSearcher
                ("SELECT * FROM WIN32_SerialPort"))
                string[] portnames = SerialPort.GetPortNames();
                var ports = searcher.Get().Cast<ManagementBaseObject>().ToList();
                var tList = (from n in portnames
                            join p in ports on n equals p["DeviceID"].ToString()
                            select n + " - " + p["Caption"]).ToList();


            // pause program execution to review results...
            Console.WriteLine("Press enter to exit");

More info here:

How to download a file with Node.js (without using third-party libraries)?

?So if you use pipeline, it would close all other streams and make sure that there are no memory leaks.

Working example:

const http = require('http');
const { pipeline } = require('stream');
const fs = require('fs');

const file = fs.createWriteStream('./file.jpg');

http.get('', response => {
    err => {
      if (err)
        console.error('Pipeline failed.', err);
        console.log('Pipeline succeeded.');

From my answer to "What's the difference between .pipe and .pipeline on streams".

linking problem: fatal error LNK1112: module machine type 'x64' conflicts with target machine type 'X86'

The error is explicit, you are trying to link libraries that were compiled with different CPU targets. An executable image can only contain pure x86 (32-bit) or pure x64 (64-bit) code. Mixing is not possible.

You change the target CPU by creating a new configuration for the project, only changing the linker setting isn't enough. Build + Configuration Manager, Active solution platform combo on upper right, choose New and select x64. That creates a new configuration with several modified project settings, most importantly the compiler that will be used.

Beware that prior to VS2010, the 64-bit compilers are not installed by default. If you don't see x64 in the platform combo then you'll need to re-run setup.exe and turn on the option to install the 64-bit compilers. Then also re-run any service pack installer you may have applied.

A possible approach with less pain points is to use the 32-bit version of the library.

JPA and Hibernate - Criteria vs. JPQL or HQL

For me the biggest win on Criteria is the Example API, where you can pass an object and hibernate will build a query based on those object properties.

Besides that, the criteria API has its quirks (I believe the hibernate team is reworking the api), like:

  • a criteria.createAlias("obj") forces a inner join instead of a possible outer join
  • you can't create the same alias two times
  • some sql clauses have no simple criteria counterpart (like a subselect)
  • etc.

I tend to use HQL when I want queries similar to sql (delete from Users where status='blocked'), and I tend to use criteria when I don't want to use string appending.

Another advantage of HQL is that you can define all your queries before hand, and even externalise them to a file or so.

React hooks useState Array

use state is not always needed you can just simply do this

let paymentList = [
    {"id":249,"txnid":"2","fname":"Rigoberto"}, {"id":249,"txnid":"33","fname":"manuel"},]

then use your data in a map loop like this in my case it was just a table and im sure many of you are looking for the same. here is how you use it.

<div className="card-body">
            <div className="table-responsive">
                <table className="table table-striped">
                            <th>Transaction ID</th>
                  , key) => (
                                <tr key={key}>

Could not calculate build plan: Plugin org.apache.maven.plugins:maven-resources-plugin:2.5 or one of its dependencies could not be resolved

A more subtle reason for this could be a Settings.xml file which has a space in the first line before the doctype

C#: Dynamic runtime cast

Best I got so far:

dynamic DynamicCast(object entity, Type to)
    var openCast = this.GetType().GetMethod("Cast", BindingFlags.Static | BindingFlags.NonPublic);
    var closeCast = openCast.MakeGenericMethod(to);
    return closeCast.Invoke(entity, new[] { entity });
static T Cast<T>(object entity) where T : class
    return entity as T;

Converting NumPy array into Python List structure?

c = np.array([[1,2,3],[4,5,6]])


How to tell if UIViewController's view is visible

Here's @progrmr's solution as a UIViewController category:

// UIViewController+Additions.h

@interface UIViewController (Additions)

- (BOOL)isVisible;


// UIViewController+Additions.m

#import "UIViewController+Additions.h"

@implementation UIViewController (Additions)

- (BOOL)isVisible {
    return [self isViewLoaded] && self.view.window;


What is the difference between __str__ and __repr__?

One aspect that is missing in other answers. It's true that in general the pattern is:

  • Goal of __str__: human-readable
  • Goal of __repr__: unambiguous, possibly machine-readable via eval

Unfortunately, this differentiation is flawed, because the Python REPL and also IPython use __repr__ for printing objects in a REPL console (see related questions for Python and IPython). Thus, projects which are targeted for interactive console work (e.g., Numpy or Pandas) have started to ignore above rules and provide a human-readable __repr__ implementation instead.

Get generic type of java.util.List

Use Reflection to get the Field for these then you can just do: field.genericType to get the type that contains the information about generic as well.

WAMP server, localhost is not working

Goto This link its working..

Update: Using XAMP

After I’ve written this blog post I’ve figured out that XAMP, although very similar to WAMP, doesn’t force you to run Apache as a service, instead it can run it as a regular process. So I ended up using XAMP, and changed Apache port to 8080 so now everything works.

WAMP Issues

If you have Window 7 or later you may have come across issues with WAMP server trying to start Apache service on port 80 and failing.

There are many conflict and issues that might have come up. Before you try anything, check if you have ZoneAlarm, Nod32, or any other program/firewall that might be blocking Apache server. If you’re sure that firewall isn’t the problem here is a couple of fixes that you can try.

NOTE: After every fix you try, you must click on yellow WAMP icon and choose Restart All Services

Checking which process is causing the problem

Open Command Prompt window by typing cmd in Run command box or Start Search, and hit Enter. Type in the following command: netstat -o -n -a | findstr 0.0:80 The last column of each row is the process identified (process ID or PID). Identify which process or application is using the port by matching the PID against PID number in Task Manager. If you don’t see PID column in your Task Manager you need to go to Processes tab -> View Menu -> Select Columns and choose PID from the list Now, you may have identified application that reserves port 80, or you may have found out that System is using your port 80. That means that one of internal services is using your port, in which case continue reading further. Conflict with Skype

If you found out that Skype is using your port 80, you need to change some settings in Skype. On Windows, Skype reserves port 80 which is used for HTTP. Apache requires this port. So if you’re running Skype, you must go to Tools > Options. Then in the Advanced section, select Connection. Un-check the box that says “Use port 80 and 443 as alternatives for incoming connection“. Quit Skype and restart. The issue should be resolved.

Conflict with IIS Server

IIS Server and Apache are both web server that use port 80 so they might be in conflict. Try stopping IIS by:

Going into Control Panel -> Administrative Tools -> Internet Information Services Right click on Default Web Site Click on Stop option in the popup menu, and see of the listener on port 80 has cleared. Conflict with MS SQL Server

MS SQL Server installs “SQL Server Reporting Services (MSSQLSERVER)” that apparently defaults to 80. You can try stopping it to free up port 80.

Go to Control Panel -> Administrative Tools -> Services There find MSSQLSERVER (might be found also under SQL Server) Double click it -> Click Stop Under Startup type: choose Manual Other Services that can cause conflicts

As described above for MS SQL Server:

Go to Control Panel -> Administrative Tools -> Services You can try stopping: Web Deployment Agent Service Windows Remote Management Autodesk EDM Server World Wide Web Publishing Service There are probably more of them, but this where the ones that I tryed.

Try turning off HTTP driver directly

If you’ve tried everything mentioned above and your WAMP server is still not working you could try this (which eventually helped me).

Right click on My Computer icon -> Properties Go to Device Manager Click on View menu and chooseShow hidden devices Now from the list choose Non-Plug and Play devices Double click HTTP -> go to Driver For Type choose Disabled Restart your computer After your computer boots up you should be able to start up WAMP server.

If everything else fails

You could try changing Apache server to listen to some other port other than port 80.

Click on yellow WAMP icon in your taskbar Choose Apache -> httpd.conf Inside find these two lines of code:

Listen 80 ServerName localhost:80 and change them to something like this (they are not one next to the other):

Listen 8080 ServerName localhost:8080 Restart all services, and try typing localhost:8080 into your browser. WAMP server should now be working.

UML diagram shapes missing on Visio 2013

If you don't find Stencils you can locate them in your install location. C:\Program Files\Microsoft Office\Office15\Visio Content\1033 for UML Sequcen Stencies you can open

Why is Java Vector (and Stack) class considered obsolete or deprecated?

java.util.Stack inherits the synchronization overhead of java.util.Vector, which is usually not justified.

It inherits a lot more than that, though. The fact that java.util.Stack extends java.util.Vector is a mistake in object-oriented design. Purists will note that it also offers a lot of methods beyond the operations traditionally associated with a stack (namely: push, pop, peek, size). It's also possible to do search, elementAt, setElementAt, remove, and many other random-access operations. It's basically up to the user to refrain from using the non-stack operations of Stack.

For these performance and OOP design reasons, the JavaDoc for java.util.Stack recommends ArrayDeque as the natural replacement. (A deque is more than a stack, but at least it's restricted to manipulating the two ends, rather than offering random access to everything.)

What is InputStream & Output Stream? Why and when do we use them?

The goal of InputStream and OutputStream is to abstract different ways to input and output: whether the stream is a file, a web page, or the screen shouldn't matter. All that matters is that you receive information from the stream (or send information into that stream.)

InputStream is used for many things that you read from.

OutputStream is used for many things that you write to.

Here's some sample code. It assumes the InputStream instr and OutputStream osstr have already been created:

int i;

while ((i = != -1) {


IE Driver download location Link for Selenium

Use the below link to download IE Driver latest version

IE Driver

How to find and replace string?

Do we really need a Boost library for seemingly such a simple task?

To replace all occurences of a substring use this function:

std::string ReplaceString(std::string subject, const std::string& search,
                          const std::string& replace) {
    size_t pos = 0;
    while ((pos = subject.find(search, pos)) != std::string::npos) {
         subject.replace(pos, search.length(), replace);
         pos += replace.length();
    return subject;

If you need performance, here is an optimized function that modifies the input string, it does not create a copy of the string:

void ReplaceStringInPlace(std::string& subject, const std::string& search,
                          const std::string& replace) {
    size_t pos = 0;
    while ((pos = subject.find(search, pos)) != std::string::npos) {
         subject.replace(pos, search.length(), replace);
         pos += replace.length();


std::string input = "abc abc def";
std::cout << "Input string: " << input << std::endl;

std::cout << "ReplaceString() return value: " 
          << ReplaceString(input, "bc", "!!") << std::endl;
std::cout << "ReplaceString() input string not modified: " 
          << input << std::endl;

ReplaceStringInPlace(input, "bc", "??");
std::cout << "ReplaceStringInPlace() input string modified: " 
          << input << std::endl;


Input string: abc abc def
ReplaceString() return value: a!! a!! def
ReplaceString() input string not modified: abc abc def
ReplaceStringInPlace() input string modified: a?? a?? def

Cast object to interface in TypeScript

Here's another way to force a type-cast even between incompatible types and interfaces where TS compiler normally complains:

export function forceCast<T>(input: any): T {

  // ... do runtime checks here

  // @ts-ignore <-- forces TS compiler to compile this as-is
  return input;

Then you can use it to force cast objects to a certain type:

import { forceCast } from './forceCast';

const randomObject: any = {};
const typedObject = forceCast<IToDoDto>(randomObject);

Note that I left out the part you are supposed to do runtime checks before casting for the sake of reducing complexity. What I do in my project is compiling all my .d.ts interface files into JSON schemas and using ajv to validate in runtime.

How can I check if a string is null or empty in PowerShell?

If it is a parameter in a function, you can validate it with ValidateNotNullOrEmpty as you can see in this example:

Function Test-Something

    #stuff todo

restrict edittext to single line



How does += (plus equal) work?

As everyone said above

var str = "foo"
str += " bar"
console.log(str) //will now give you "foo bar"

Check this out as well

How to invoke a Linux shell command from Java

Building on @Tim's example to make a self-contained method:

import java.util.ArrayList;

public class Shell {

    /** Returns null if it failed for some reason.
    public static ArrayList<String> command(final String cmdline,
    final String directory) {
        try {
            Process process = 
                new ProcessBuilder(new String[] {"bash", "-c", cmdline})
                    .directory(new File(directory))

            ArrayList<String> output = new ArrayList<String>();
            BufferedReader br = new BufferedReader(
                new InputStreamReader(process.getInputStream()));
            String line = null;
            while ( (line = br.readLine()) != null )

            //There should really be a timeout here.
            if (0 != process.waitFor())
                return null;

            return output;

        } catch (Exception e) {
            //Warning: doing this is no good in high quality applications.
            //Instead, present appropriate error messages to the user.
            //But it's perfectly fine for prototyping.

            return null;

    public static void main(String[] args) {
        test("which bash");

        test("find . -type f -printf '%T@\\\\t%p\\\\n' "
            + "| sort -n | cut -f 2- | "
            + "sed -e 's/ /\\\\\\\\ /g' | xargs ls -halt");


    static void test(String cmdline) {
        ArrayList<String> output = command(cmdline, ".");
        if (null == output)
            System.out.println("\n\n\t\tCOMMAND FAILED: " + cmdline);
            for (String line : output)


(The test example is a command that lists all files in a directory and its subdirectories, recursively, in chronological order.)

By the way, if somebody can tell me why I need four and eight backslashes there, instead of two and four, I can learn something. There is one more level of unescaping happening than what I am counting.

Edit: Just tried this same code on Linux, and there it turns out that I need half as many backslashes in the test command! (That is: the expected number of two and four.) Now it's no longer just weird, it's a portability problem.

How to write a function that takes a positive integer N and returns a list of the first N natural numbers

Here are a few ways to create a list with N of continuous natural numbers starting from 1.

1 range:

def numbers(n): 
    return range(1, n+1);

2 List Comprehensions:

def numbers(n):
    return [i for i in range(1, n+1)]

You may want to look into the method xrange and the concepts of generators, those are fun in python. Good luck with your Learning!

Redirecting a page using Javascript, like PHP's Header->Location

You cannot mix JS and PHP that way, PHP is rendered before the page is sent to the browser (i.e. before the JS is run)

You can use window.location to change your current page.

$('.entry a:first').click(function() {
    window.location = "";

Powershell Log Off Remote Session

I am sure my code will be easier and works faster.

    $logon_sessions = get-process -includeusername | Select-Object -Unique -Property UserName, si | ? { $_ -match "server" -and $_ -notmatch "admin" }

    foreach ($id in $ {
        logoff $id

java.lang.ClassNotFoundException: org.apache.jsp.index_jsp

I have had the same problem in my project. I used an IntelliJ Idea 14 and Maven 8. And what I've noticed is that when I added a tomcat destination to to IDE it automaticly linked two jars from tomcat lib directory, they were servlet-api and jsp-api. Also I had them in my pom.xml. I killed a whole day trying to figure out why I'm getting java.lang.ClassNotFoundException: org.apache.jsp.index_jsp. And kewpiedoll99 is right. That is because there are dependency conflicts. When I added provided to those two jars in my pom.xml I found a happiness :)

Line Break in XML formatting?

If you are refering to res strings, use CDATA with \n.

<string name="about">
 Author: Sergio Abreu\n

How to refresh a page with jQuery by passing a parameter to URL

Concision counts: I prefer window.location = "?single"; or window.location += "?single";

How to put labels over geom_bar in R with ggplot2

To plot text on a ggplot you use the geom_text. But I find it helpful to summarise the data first using ddply

dfl <- ddply(df, .(x), summarize, y=length(x))

Since the data is pre-summarized, you need to remember to change add the stat="identity" parameter to geom_bar:

ggplot(dfl, aes(x, y=y, fill=x)) + geom_bar(stat="identity") +
    geom_text(aes(label=y), vjust=0) +

enter image description here

Test if a vector contains a given element

Both the match() (returns the first appearance) and %in% (returns a Boolean) functions are designed for this.

v <- c('a','b','c','e')

'b' %in% v
## returns TRUE

## returns the first location of 'b', in this case: 2

Spring MVC: How to return image in @ResponseBody?

I prefere this one:

private ResourceLoader resourceLoader = new DefaultResourceLoader();

@RequestMapping(value = "/{id}",  produces = "image/bmp")
public Resource texture(@PathVariable("id") String id) {
    return resourceLoader.getResource("classpath:images/" + id + ".bmp");

Change the media type to what ever image format you have.

How to set UITextField height?

You can not change the height of the rounded rect border style. To set the height, just choose any border style other than rounded border in Xcode:

enter image description here

Explanation of JSONB introduced by PostgreSQL

As far as I can tell,

  • hstore as it currently exists (in Postgresql 9.3) does not allow for nesting other objects and arrays as the values of its key/value pairs. however a future hstore patch will allow for nesting. this patch will not be in the 9.4 release and may not be included any time soon.

  • json as it currently exists does allow for nesting, but is text-based, and does not allow for indexing, thus it is "slow"

  • jsonb that will be released with 9.4 will have the current nesting capabilities of json, as well as the GIN/GIST indexing of hstore, so it will be fast

People working on postgresql 9.4 seem to be saying that the new, fast jsonb type will appeal to people who would have chosen to use a noSQL data store like MongoDB, but can now combine a relational database with query-able unstructured data under one roof

Benchmarks of postgresql 9.4 jsonb seem to be on par with or in some cases faster than MongoDB

How to display image with JavaScript?

You could make use of the Javascript DOM API. In particular, look at the createElement() method.

You could create a re-usable function that will create an image like so...

function show_image(src, width, height, alt) {
    var img = document.createElement("img");
    img.src = src;
    img.width = width;
    img.height = height;
    img.alt = alt;

    // This next line will just add it to the <body> tag

Then you could use it like this...

<button onclick=
                 'Google Logo');">Add Google Logo</button> 

See a working example on jsFiddle:

How to run different python versions in cmd

I would suggest using the Python Launcher for Windows utility that was introduced into Python 3.3. You can manually download and install it directly from the author's website for use with earlier versions of Python 2 and 3.

Regardless of how you obtain it, after installation it will have associated itself with all the standard Python file extensions (i.e. .py, .pyw, .pyc, and .pyo files). You'll not only be able to explicitly control which version is used at the command-prompt, but also on a script-by-script basis by adding Linux/Unix-y shebang #!/usr/bin/env pythonX comments at the beginning of your Python scripts.

Exporting results of a Mysql query to excel?

The quick and dirty way I use to export mysql output to a file is

$ mysql <database_name> --tee=<file_path>

and then use the exported output (which you can find in <file_path>) wherever I want.

Note that this is the only way you have in order to avoid databases running using the secure-file-priv option, which prevents the usage of INTO OUTFILE suggested in the previous answers:

ERROR 1290 (HY000): The MySQL server is running with the --secure-file-priv option so it cannot execute this statement

How can I check if a command exists in a shell script?

Check if a program exists from a Bash script covers this very well. In any shell script, you're best off running command -v $command_name for testing if $command_name can be run. In bash you can use hash $command_name, which also hashes the result of any path lookup, or type -P $binary_name if you only want to see binaries (not functions etc.)

ReferenceError: document is not defined (in plain JavaScript)

try: window.document......

var body = window.document.getElementsByTagName("body")[0];

JSON Naming Convention (snake_case, camelCase or PascalCase)

Seems that there's enough variation that people go out of their way to allow conversion from all conventions to others:

Notably, the mentioned Jackson JSON parser prefers bean_naming.