Programs & Examples On #Trading

The act of buying and selling financial instruments, such as money markets spot instruments, stocks, bonds, commodities, virtual currencies, indices, futures, options, CFD-s and other derivatives, performed on a for-profit basis.

What online brokers offer APIs?

Ameritrade also offers an API, as long as you have an Ameritrade account:

Fixed GridView Header with horizontal and vertical scrolling in

It is possible to apply the specific GridView / Table layout via custom CSS rules (as it was discussed in the <table><tbody> scrollable? thread) to fix GridView's Header. However, this approach will not work in all browsers. The 3-rd ASP.NET GridView controls (such as the ASPxGridView from DevExpress component vendor provide this functionality.

Check also the following CodeProject solutions:

How to find a string inside a entire database?

I think you have to options:

  1. Build a dynamic SQL using sys.tables and sys.columns to perform the search (example here).

  2. Use any program that have this function. An example of this is SQL Workbench (free).

CSS: Control space between bullet and <li>

Use padding-left:1em; text-indent:-1em for the <li> tag.
Then, list-style-position: inside for the <ul> tag.

<ul style='list-style-position: inside;'>
  <li style='padding-left: 1em; text-indent: -1em;'>Item 1</li>

Is iterating ConcurrentHashMap values thread safe?

You may use this class to test two accessing threads and one mutating the shared instance of ConcurrentHashMap:

import java.util.Map;
import java.util.Random;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ConcurrentMapIteration
  private final Map<String, String> map = new ConcurrentHashMap<String, String>();

  private final static int MAP_SIZE = 100000;

  public static void main(String[] args)
    new ConcurrentMapIteration().run();

  public ConcurrentMapIteration()
    for (int i = 0; i < MAP_SIZE; i++)
      map.put("key" + i, UUID.randomUUID().toString());

  private final ExecutorService executor = Executors.newCachedThreadPool();

  private final class Accessor implements Runnable
    private final Map<String, String> map;

    public Accessor(Map<String, String> map)
    { = map;

    public void run()
      for (Map.Entry<String, String> entry :
            Thread.currentThread().getName() + " - [" + entry.getKey() + ", " + entry.getValue() + ']'

  private final class Mutator implements Runnable

    private final Map<String, String> map;
    private final Random random = new Random();

    public Mutator(Map<String, String> map)
    { = map;

    public void run()
      for (int i = 0; i < 100; i++)
      {"key" + random.nextInt(MAP_SIZE));"key" + random.nextInt(MAP_SIZE), UUID.randomUUID().toString());
        System.out.println(Thread.currentThread().getName() + ": " + i);

  private void run()
    Accessor a1 = new Accessor(;
    Accessor a2 = new Accessor(;
    Mutator m = new Mutator(;


No exception will be thrown.

Sharing the same iterator between accessor threads can lead to deadlock:

import java.util.Iterator;
import java.util.Map;
import java.util.Random;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ConcurrentMapIteration
  private final Map<String, String> map = new ConcurrentHashMap<String, String>();
  private final Iterator<Map.Entry<String, String>> iterator;

  private final static int MAP_SIZE = 100000;

  public static void main(String[] args)
    new ConcurrentMapIteration().run();

  public ConcurrentMapIteration()
    for (int i = 0; i < MAP_SIZE; i++)
      map.put("key" + i, UUID.randomUUID().toString());
    this.iterator =;

  private final ExecutorService executor = Executors.newCachedThreadPool();

  private final class Accessor implements Runnable
    private final Iterator<Map.Entry<String, String>> iterator;

    public Accessor(Iterator<Map.Entry<String, String>> iterator)
      this.iterator = iterator;

    public void run()
      while(iterator.hasNext()) {
        Map.Entry<String, String> entry =;
          String st = Thread.currentThread().getName() + " - [" + entry.getKey() + ", " + entry.getValue() + ']';
        } catch (Exception e)


  private final class Mutator implements Runnable

    private final Map<String, String> map;
    private final Random random = new Random();

    public Mutator(Map<String, String> map)
    { = map;

    public void run()
      for (int i = 0; i < 100; i++)
      {"key" + random.nextInt(MAP_SIZE));"key" + random.nextInt(MAP_SIZE), UUID.randomUUID().toString());

  private void run()
    Accessor a1 = new Accessor(this.iterator);
    Accessor a2 = new Accessor(this.iterator);
    Mutator m = new Mutator(;


As soon as you start sharing the same Iterator<Map.Entry<String, String>> among accessor and mutator threads java.lang.IllegalStateExceptions will start popping up.

import java.util.Iterator;
import java.util.Map;
import java.util.Random;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ConcurrentMapIteration
  private final Map<String, String> map = new ConcurrentHashMap<String, String>();
  private final Iterator<Map.Entry<String, String>> iterator;

  private final static int MAP_SIZE = 100000;

  public static void main(String[] args)
    new ConcurrentMapIteration().run();

  public ConcurrentMapIteration()
    for (int i = 0; i < MAP_SIZE; i++)
      map.put("key" + i, UUID.randomUUID().toString());
    this.iterator =;

  private final ExecutorService executor = Executors.newCachedThreadPool();

  private final class Accessor implements Runnable
    private final Iterator<Map.Entry<String, String>> iterator;

    public Accessor(Iterator<Map.Entry<String, String>> iterator)
      this.iterator = iterator;

    public void run()
      while (iterator.hasNext())
        Map.Entry<String, String> entry =;
          String st =
              Thread.currentThread().getName() + " - [" + entry.getKey() + ", " + entry.getValue() + ']';
        } catch (Exception e)


  private final class Mutator implements Runnable

    private final Random random = new Random();

    private final Iterator<Map.Entry<String, String>> iterator;

    private final Map<String, String> map;

    public Mutator(Map<String, String> map, Iterator<Map.Entry<String, String>> iterator)
    { = map;
      this.iterator = iterator;

    public void run()
      while (iterator.hasNext())
"key" + random.nextInt(MAP_SIZE), UUID.randomUUID().toString());
        } catch (Exception ex)


  private void run()
    Accessor a1 = new Accessor(this.iterator);
    Accessor a2 = new Accessor(this.iterator);
    Mutator m = new Mutator(map, this.iterator);


How to use SearchView in Toolbar Android

You have to use Appcompat library for that. Which is used like below:


<menu xmlns:android="" 


Activity file (in Java):

public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater menuInflater = getMenuInflater();
    menuInflater.inflate(, menu);

     MenuItem searchItem = menu.findItem(;

    SearchManager searchManager = (SearchManager) MainActivity.this.getSystemService(Context.SEARCH_SERVICE);

    SearchView searchView = null;
    if (searchItem != null) {
        searchView = (SearchView) searchItem.getActionView();
    if (searchView != null) {
        return super.onCreateOptionsMenu(menu);

Activity file (in Kotlin):

override fun onCreateOptionsMenu(menu: Menu?): Boolean {
    menuInflater.inflate(, menu)

    val searchItem: MenuItem? = menu?.findItem(
    val searchManager = getSystemService(Context.SEARCH_SERVICE) as SearchManager
    val searchView: SearchView? = searchItem?.actionView as SearchView

    return super.onCreateOptionsMenu(menu)

manifest file:

      android:value="com.apkgetter.SearchResultsActivity" /> 

            android:launchMode="singleTop" >
                <action android:name="android.intent.action.SEARCH" />
                <action android:name="android.intent.action.VIEW" />

                android:resource="@xml/searchable" />

searchable xml file:

<?xml version="1.0" encoding="utf-8"?>
<searchable xmlns:android=""
    android:label="@string/app_name" />

And at last, your SearchResultsActivity class code. for showing result of your search.

Convert integer to binary in C#

I came across this problem in a coding challenge where you have to convert 32 digit decimal to binary and find the possible combination of the substring.

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Numerics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp2
    class Program

        public static void Main()
            int numberofinputs = int.Parse(Console.ReadLine());
            List<BigInteger> inputdecimal = new List<BigInteger>();
            List<string> outputBinary = new List<string>();

            for (int i = 0; i < numberofinputs; i++)
                inputdecimal.Add(BigInteger.Parse(Console.ReadLine(), CultureInfo.InvariantCulture));
            //processing begins 

            foreach (var n in inputdecimal)
                string binary = (binaryconveter(n));
                subString(binary, binary.Length);

            foreach (var item in outputBinary)

            string binaryconveter(BigInteger n)
                int i;
                StringBuilder output = new StringBuilder();

                for (i = 0; n > 0; i++)
                    output = output.Append(n % 2);
                    n = n / 2;

                return output.ToString();

            void subString(string str, int n)
                int zeroodds = 0;
                int oneodds = 0;

                for (int len = 1; len <= n; len++)

                    for (int i = 0; i <= n - len; i++)
                        int j = i + len - 1;

                        string substring = "";
                        for (int k = i; k <= j; k++)
                            substring = String.Concat(substring, str[k]);

                        var resultofstringanalysis = stringanalysis(substring);
                        if (resultofstringanalysis.Equals("both are odd"))
                        else if (resultofstringanalysis.Equals("zeroes are odd"))
                        else if (resultofstringanalysis.Equals("ones are odd"))

                string outputtest = String.Concat(zeroodds.ToString(), ' ', oneodds.ToString());

            string stringanalysis(string str)
                int n = str.Length;

                int nofZeros = 0;
                int nofOnes = 0;

                for (int i = 0; i < n; i++)
                    if (str[i] == '0')
                    if (str[i] == '1')

                if ((nofZeros != 0 && nofZeros % 2 != 0) && (nofOnes != 0 && nofOnes % 2 != 0))
                    return "both are odd";
                else if (nofZeros != 0 && nofZeros % 2 != 0)
                    return "zeroes are odd";
                else if (nofOnes != 0 && nofOnes % 2 != 0)
                    return "ones are odd";
                    return "nothing";



How to fix "unable to open stdio.h in Turbo C" error?

Just Re install the turbo C++ from your Computer and install again in the Directory C:\TC\ Folder.

Again The Problem exists ,then change the directory from FILE>>CHANGE DIRECTORY to C:\TC\BIN\

Use Font Awesome icon as CSS content

Here's my webpack 4 + font awesome 5 solution:

webpack plugin:

new CopyWebpackPlugin([
    { from: 'node_modules/font-awesome/fonts', to: 'font-awesome' }

global css style:

@font-face {
    font-family: 'FontAwesome';
    src: url('/font-awesome/fontawesome-webfont.eot');
    src: url('/font-awesome/fontawesome-webfont.eot?#iefix') format('embedded-opentype'),
    url('/font-awesome/fontawesome-webfont.woff2') format('woff2'),
    url('/font-awesome/fontawesome-webfont.woff') format('woff'),
    url('/font-awesome/fontawesome-webfont.ttf') format('truetype'),
    url('/font-awesome/fontawesome-webfont.svgfontawesomeregular') format('svg');
    font-weight: normal;
    font-style: normal;

i {
    font-family: "FontAwesome";

How to limit the number of selected checkboxes?

    if ($("input:checkbox:checked").length > 3){
      return false;

All combinations of a list of lists

you need itertools.product:

>>> import itertools
>>> a = [[1,2,3],[4,5,6],[7,8,9,10]]
>>> list(itertools.product(*a))
[(1, 4, 7), (1, 4, 8), (1, 4, 9), (1, 4, 10), (1, 5, 7), (1, 5, 8), (1, 5, 9), (1, 5, 10), (1, 6, 7), (1, 6, 8), (1, 6, 9), (1, 6, 10), (2, 4, 7), (2, 4, 8), (2, 4, 9), (2, 4, 10), (2, 5, 7), (2, 5, 8), (2, 5, 9), (2, 5, 10), (2, 6, 7), (2, 6, 8), (2, 6, 9), (2, 6, 10), (3, 4, 7), (3, 4, 8), (3, 4, 9), (3, 4, 10), (3, 5, 7), (3, 5, 8), (3, 5, 9), (3, 5, 10), (3, 6, 7), (3, 6, 8), (3, 6, 9), (3, 6, 10)]

NoClassDefFoundError in Java: com/google/common/base/Function

you don't have the "google-collections" library on your classpath.

There are a number of ways to add libraries to your classpath, so please provide more info regarding how you are executing your program.

if from the command line, you can add libraries to the classpath via

java -classpath path/lib.jar ...

How to implement a secure REST API with node.js

If you want to have a completely locked down area of your webapplication which can only be accessed by administrators from your company, then SSL authorization maybe for you. It will insure that no one can make a connection to the server instance unless they have an authorized certificate installed in their browser. Last week I wrote an article on how to setup the server: Article

This is one of the most secure setups you will find as there are no username/passwords involved so no one can gain access unless one of your users hands the key files to a potential hacker.

Difference between null and empty string

When Object variables are initially used in a language like Java, they have absolutely no value at all - not zero, but literally no value - that is null

For instance: String s;

If you were to use s, it would actually have a value of null, because it holds absolute nothing.

An empty string, however, is a value - it is a string of no characters.

String s; //Inits to null
String a =""; //A blank string

Null is essentially 'nothing' - it's the default 'value' (to use the term loosely) that Java assigns to any Object variable that was not initialized.

Null isn't really a value - and as such, doesn't have properties. So, calling anything that is meant to return a value - such as .length(), will invariably return an error, because 'nothing' cannot have properties.

To go into more depth, by creating s1 = ""; you are initializing an object, which can have properties, and takes up relevant space in memory. By using s2; you are designating that variable name to be a String, but are not actually assigning any value at that point.

Simplest way to serve static data from outside the application server in a Java web application

Read the InputStream of a file and write it to ServletOutputStream for sending binary data to the client.

  • Local file You can read a file directly using FileInputStream('path/image.png').
  • Mongo DataBase file's you can get InputStream using GridFS.
public class URLStream extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public URLStream() {

    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        File source = new File("D:\\SVN_Commit.PNG");
        long start = System.nanoTime();

        InputStream image = new FileInputStream(source);

        /*String fileID = request.getParameter("id");
        System.out.println("Requested File ID : "+fileID);
        // Mongo DB GridFS -
        image = outputImageFile.getInputStream();*/

        if( image != null ) {
            BufferedInputStream bin = null;
            BufferedOutputStream bout = null;
            ServletOutputStream sos = response.getOutputStream();
            try {
                bin = new BufferedInputStream( image );
                bout = new BufferedOutputStream( sos );
                int ch =0; ;
                while((!=-1) {
            } finally {

        } else {
            PrintWriter writer = response.getWriter();
            writer.append("Something went wrong with your request.");
            System.out.println("Image not available.");
        System.out.println("Time taken by Stream Copy = "+(System.nanoTime()-start));

Result the URL directly to the src attibute.

<img src='' alt="mongodb File"/>
<img src='' alt="local file"/>

<video controls="controls" src=""></video>

How to set a hidden value in Razor

There is a Hidden helper alongside HiddenFor which lets you set the value.

@Html.Hidden("RequiredProperty", "default")

EDIT Based on the edit you've made to the question, you could do this, but I believe you're moving into territory where it will be cheaper and more effective, in the long run, to fight for making the code change. As has been said, even by yourself, the controller or view model should be setting the default.

This code:

        var stacks = new System.Diagnostics.StackTrace().GetFrames();
        foreach (var frame in stacks)
            <li>@frame.GetMethod().Name - @frame.GetMethod().DeclaringType</li>

Will give output like this:

Execute - ASP._Page_Views_ViewDirectoryX__SubView_cshtml
ExecutePageHierarchy - System.Web.WebPages.WebPageBase
ExecutePageHierarchy - System.Web.Mvc.WebViewPage
ExecutePageHierarchy - System.Web.WebPages.WebPageBase
RenderView - System.Web.Mvc.RazorView
Render - System.Web.Mvc.BuildManagerCompiledView
RenderPartialInternal - System.Web.Mvc.HtmlHelper
RenderPartial - System.Web.Mvc.Html.RenderPartialExtensions
Execute - ASP._Page_Views_ViewDirectoryY__MainView_cshtml

So assuming the MVC framework will always go through the same stack, you can grab var frame = stacks[8]; and use the declaring type to determine who your parent view is, and then use that determination to set (or not) the default value. You could also walk the stack instead of directly grabbing [8] which would be safer but even less efficient.

Oracle SQL Developer: Failure - Test failed: The Network Adapter could not establish the connection?

I just had same issue when I installed the oracle 11g and then creating the database.

I don't even know that the listener has to create manually. Hence, I open Net Configuration Assistant and manually create the listener.

And I can connect the database that I created locally through sql developer.

Convert JSONArray to String Array

Bit late for an answer, but here's what I came up with using Gson:

for a jsonarray foo: [{"test": "bar"}, {"test": "bar2"}]

JsonArray foo = getJsonFromWherever();
String[] test = new String[foo.size()]
foo.forEach(x -> {test = ArrayUtils.add(test, x.get("test").getAsString());});

How to parse XML using jQuery?

I assume you are loading the XML from an external file. With $.ajax(), it's quite simple actually:

    url: 'xmlfile.xml',
    dataType: 'xml',
    success: function(data){
        // Extract relevant data from XML
        var xml_node = $('Pages',data);
        console.log( xml_node.find('Page[Name="test"] > controls > test').text() );
    error: function(data){
        console.log('Error loading XML data');

Also, you should be consistent about the XML node naming. You have both lowercase and capitalized node names (<Page> versus <page>) which can be confusing when you try to use XML tree selectors.

Java recursive Fibonacci sequence

public class Fibonaci{      

    static void fibonacci() {
        int ptr1 = 1, ptr2 = 1, ptr3 = 0;
        int temp = 0;
        BufferedReader Data=new BufferedReader (new InputStreamReader(;
        try {
            System.out.println("The Number Value's fib you required ? ");
            ptr3 = Integer.parseInt(Data.readLine());

            System.out.print(ptr1 + " " + ptr2 + " ");
            for (int i = 0; i < ptr3; i++) {
                System.out.print(ptr1 + ptr2 + " ");
                temp = ptr1;
                ptr1 = ptr2;
                ptr2 = temp + ptr2;
        } catch(IOException err) {
            System.out.println("Error!" + err);
        } catch(NumberFormatException err) {
            System.out.println("Invald Input!");

    public static void main(String[]args)throws Exception{    

You can do like this.

Editable 'Select' element

Another sort of workaround might be...

Use the HTML:

<input type="text" id="myselect"/>
<datalist id="myselect">
<option>option 1</option>
<option>option 2</option>
<option>option 3</option>
<option>option 4</option>

In Firefox at least a focus followed by a click drops down the list of known valid values as the <datalist> elements IFF the field happens to be empty. Otherwise, one must clear the field to see valid choices as one types in data. A new value is accepted as typed. One must handle new values in JS or other to persist them.

This is not perfect, but it suffices for my minimalist needs, so I thought I would share.

Can Twitter Bootstrap alerts fade in as well as out?

Add hide class to alert-message. Then put the following code after your jQuery script import:

$(document).ready( function(){
    $(".alert-message").animate({ 'height':'toggle','opacity':'toggle'});
    window.setTimeout( function(){
    }, 2500);

If you want handle multiple messages, this code will hide them in ascending order:

$(document).ready( function(){
   var hide_delay = 2500;  // starting timeout before first message is hidden
   var hide_next = 800;   // time in mS to wait before hiding next message
   $(".alert-message").slideDown().each( function(index,el) {
      window.setTimeout( function(){
         $(el).slideUp();  // hide the message
      }, hide_delay + hide_next*index);

jQuery javascript regex Replace <br> with \n

var str = document.getElementById('mydiv').innerHTML;
document.getElementById('mytextarea').innerHTML = str.replace(/<br\s*[\/]?>/gi, "\n");

or using jQuery:

var str = $("#mydiv").html();
var regex = /<br\s*[\/]?>/gi;
$("#mydiv").html(str.replace(regex, "\n"));


edit: added i flag

edit2: you can use /<br[^>]*>/gi which will match anything between the br and slash if you have for example <br class="clear" />

How to pass a datetime parameter?

This is a solution and a model for possible solutions. Use Moment.js in your client to format dates, convert to unix time.


Setup your route parameters to be long.

public async Task<object[]> Get(long? startDate)
    DateTime? sDate = new DateTime();

        if (startDate != null)
            sDate = new DateTime().FromUnixTime(startDate.Value); 
            sDate = null;
         ... your code here!

Create an extension method for Unix time. Unix DateTime Method

How can I disable selected attribute from select2() dropdown Jquery?

I'm disabling select2 with:


And enabling it with


Could not execute menu item (internal error)[Exception] - When changing PHP version from 5.3.1 to 5.2.9

  • Open Task Manager
  • Go to Details
  • Find and kill Skype... apps

Restart WampServer and it should work

ImportError: No module named pip

I ran into this same issue when I attempted to install the nova client.

spencers-macbook-pro:python-novaclient root# python install    
running install
/usr/bin/python: No module named pip
error: /usr/bin/python -m pip.__init__ install   'pbr>=0.5.21,<1.0' 'iso8601>=0.1.4' 'PrettyTable>=0.6,<0.8' 'requests>=1.1' 'simplejson>=2.0.9' 'six' 'Babel>=0.9.6' returned 1

I use homebrew so I worked around the issue with sudo easy_install pip

spencers-macbook-pro:python-novaclient root# brew search pip
aespipe     brew-pip    lesspipe    pipebench   pipemeter   spiped  pipeviewer

If you meant "pip" precisely:

Homebrew provides pip via: `brew install python`. However you will then
have two Pythons installed on your Mac, so alternatively you can:
    sudo easy_install pip
spencers-macbook-pro:python-novaclient root# sudo easy_install pip

The commands should be similar if you use macports.

How to create a trie in Python

This version is using recursion

import pprint
from collections import deque

pp = pprint.PrettyPrinter(indent=4)

inp = raw_input("Enter a sentence to show as trie\n")
words = inp.split(" ")
trie = {}

def trie_recursion(trie_ds, word):
        letter = word.popleft()
        out = trie_recursion(trie_ds.get(letter, {}), word)
    except IndexError:
        # End of the word
        return {}

    # Dont update if letter already present
    if not trie_ds.has_key(letter):
        trie_ds[letter] = out

    return trie_ds

for word in words:
    # Go through each word
    trie = trie_recursion(trie, deque(word))



Coool <algos>  python
Enter a sentence to show as trie
foo bar baz fun
  'b': {
    'a': {
      'r': {},
      'z': {}
  'f': {
    'o': {
      'o': {}
    'u': {
      'n': {}

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

I would use Joda Time, parse the time as a LocalTime, and then use

time = time.plusMinutes(10);

Short but complete program to demonstrate this:

import org.joda.time.*;
import org.joda.time.format.*;

public class Test {
    public static void main(String[] args) {
        DateTimeFormatter formatter = DateTimeFormat.forPattern("HH:mm");
        LocalTime time = formatter.parseLocalTime("14:10");
        time = time.plusMinutes(10);

Note that I would definitely use Joda Time instead of java.util.Date/Calendar if you possibly can - it's a much nicer API.

Msg 102, Level 15, State 1, Line 1 Incorrect syntax near ' '

For the OP's command:

select compid,2, convert(datetime, '01/01/' + CONVERT(char(4),cal_yr) ,101) ,0,  Update_dt, th1, th2, th3_pc , Update_id, Update_dt,1
from  #tmp_CTF** 

I get this error:

Msg 102, Level 15, State 1, Line 2
Incorrect syntax near '*'.

when debugging something like this split the long line up so you'll get a better row number:

select compid
, convert(datetime
, '01/01/' 
+ CONVERT(char(4)
,  Update_dt
, th1
, th2
, th3_pc 
, Update_id
, Update_dt
from  #tmp_CTF** 

this now results in:

Msg 102, Level 15, State 1, Line 16
Incorrect syntax near '*'.

which is probably just from the OP not putting the entire command in the question, or use [ ] braces to signify the table name:

from [#tmp_CTF**]

if that is the table name.

Best way to represent a Grid or Table in AngularJS with Bootstrap 3?

After trying out ngGrid, ngTable, trNgGrid and Smart Table, I have come to the conclusion that Smart Table is by far the best implementation AngularJS-wise and Bootstrap-wise. It is built exactly the same way as you would build your own, naive table using standard angular. On top of that, they have added a few directives that help you do sorting, filtering etc. Their approach also makes it quite simple to extend yourself. The fact that they use the regular html tags for tables and the standard ng-repeat for the rows and standard bootstrap for formatting makes this my clear winner.

Their JS code depends on angular and your html can depend on bootstrap if you want to. The JS code is 4 kb in total and you can even easily pick stuff out of there if you want to reach an even smaller footprint.

Where the other grids will give you claustrophobia in different areas, Smart Table just feels open and to the point.

If you rely heavily on inline editing and other advanced features, you might get up and running quicker with ngTable for instance. However, you are free to add such features quite easily in Smart Table.

Don't miss Smart Table!!!

I have no relation to Smart Table, except from using it myself.

How can I mock requests and the response?

One possible way to work around requests is using the library betamax, it records all requests and after that if you make a request in the same url with the same parameters the betamax will use the recorded request, I have been using it to test web crawler and it save me a lot time.

import os

import requests
from betamax import Betamax
from betamax_serializers import pretty_json

WORKERS_DIR = os.path.dirname(os.path.abspath(__file__))
CASSETTES_DIR = os.path.join(WORKERS_DIR, u'resources', u'cassettes')
MATCH_REQUESTS_ON = [u'method', u'uri', u'path', u'query']

with Betamax.configure() as config:
    config.cassette_library_dir = CASSETTES_DIR
    config.default_cassette_options[u'serialize_with'] = u'prettyjson'
    config.default_cassette_options[u'match_requests_on'] = MATCH_REQUESTS_ON
    config.default_cassette_options[u'preserve_exact_body_bytes'] = True

class WorkerCertidaoTRT2:
    session = requests.session()

    def make_request(self, input_json):
        with Betamax(self.session) as vcr:
            response = session.get('')

Undo working copy modifications of one file in Git?

Just use

git checkout filename

This will replace filename with the latest version from the current branch.

WARNING: your changes will be discarded — no backup is kept.

How do I detect whether 32-bit Java is installed on x64 Windows, only looking at the filesystem and registry?

just write "java -d64 -version" or d32 and if you have It installed it will give a response with current version installed

How to stop app that node.js express 'npm start'

You can use pm2

after installation just type in terminal

pm2 start app.js and then

pm2 stop 0 to stop your server

How to create a regex for accepting only alphanumeric characters?

Only ASCII or are other characters allowed too?


restricts (in Java) to ASCII letters/digits und underscore,


also allows international characters/digits and "connecting punctuation".

Angular ng-if not true

you are not using the $scope you must use $ctrl.area or $scope.area instead of area

javascript scroll event for iPhone/iPad?

The iPhoneOS does capture onscroll events, except not the way you may expect.

One-finger panning doesn’t generate any events until the user stops panning—an onscroll event is generated when the page stops moving and redraws—as shown in Figure 6-1.

Similarly, scroll with 2 fingers fires onscroll only after you've stopped scrolling.

The usual way of installing the handler works e.g.

window.addEventListener('scroll', function() { alert("Scrolled"); });
// or
$(window).scroll(function() { alert("Scrolled"); });
// or
window.onscroll = function() { alert("Scrolled"); };
// etc 

(See also

PHP: How to get referrer URL?

Underscore. Not space.


Unable to Resolve Module in React Native App

If you recently had a name change in git that only includes changing the case of file. MacOS will ignore the change. So, you will have to go to the file in console and change the name. for example if name change is menu.js -> Menu.js use terminal to do a manual rename after the pull.

mv menu.js Menu.js

angularjs - using {{}} binding inside ng-src but ng-src doesn't load

Changing the ng-src value is actually very simple. Like this:

<html ng-app>
<script src=""></script>
<img ng-src="{{img_url}}">
<button ng-click="img_url = ''">Click</button>

Here is a jsFiddle of a working example:

How to change JFrame icon

JFrame.setIconImage(Image image) pretty standard.

What is the meaning of curly braces?

In languages like C curly braces ({}) are used to create program blocks used in flow control. In Python, curly braces are used to define a data structure called a dictionary (a key/value mapping), while white space indentation is used to define program blocks.

string.split - by multiple character delimiter

string tests = "abc][rfd][5][,][.";
string[] reslts = tests.Split(new char[] { ']', '[' }, StringSplitOptions.RemoveEmptyEntries);

What is the difference between screenX/Y, clientX/Y and pageX/Y?

The difference between those will depend largely on what browser you are currently referring to. Each one implements these properties differently, or not at all. Quirksmode has great documentation regarding browser differences in regards to W3C standards like the DOM and JavaScript Events.

How can I get all sequences in an Oracle database?

select sequence_owner, sequence_name from dba_sequences;

DBA_SEQUENCES -- all sequences that exist 
ALL_SEQUENCES  -- all sequences that you have permission to see 
USER_SEQUENCES  -- all sequences that you own

Note that since you are, by definition, the owner of all the sequences returned from USER_SEQUENCES, there is no SEQUENCE_OWNER column in USER_SEQUENCES.

WAMP won't turn green. And the VCRUNTIME140.dll error

I had the same problem, and I solved it by installing :

NB : 64 bit installation was enough, I had to uninstall / reinstall Wamp after that

How to change an element's title attribute using jQuery

    title: 'New Title'

for first title:


isset in jQuery?

You can use length:

if($("#one").length) { // 0 == false; >0 == true

how do I get eclipse to use a different compiler version for Java?

First off, are you setting your desired JRE or your desired JDK?

Even if your Eclipse is set up properly, there might be a wacky project-specific setting somewhere. You can open up a context menu on a given Java project in the Project Explorer and select Properties > Java Compiler to check on that.

If none of that helps, leave a comment and I'll take another look.

Count records for every month in a year

select count(*) 
from table_emp 

How to horizontally center a floating element of a variable width?

This works better when the id = container (which is the outer div) and id = contained (which is the inner div). The problem with the highly recommended solution is that it results in some cases into an horizontal scrolling bar when the browser is trying to cater for the left: -50% attribute. There is a good reference for this solution

        #container {
            text-align: center;
        #contained {
            text-align: left;
            display: inline-block;

Why does Lua have no "continue" statement?

I've never used Lua before, but I Googled it and came up with this:

Check question 1.26.

This is a common complaint. The Lua authors felt that continue was only one of a number of possible new control flow mechanisms (the fact that it cannot work with the scope rules of repeat/until was a secondary factor.)

In Lua 5.2, there is a goto statement which can be easily used to do the same job.

Change the On/Off text of a toggle button Android

In some cases, you need to force refresh the view in order to make it work.



How to find minimum value from vector?

#include <iostream>
#include <vector>
#include <algorithm> // std::min_element
#include <iterator>  // std::begin, std::end

int main() {
    std::vector<int> v = {5,14,2,4,6};
    auto result = std::min_element(std::begin(v), std::end(v));
    if (std::end(v)!=result)
        std::cout << *result << '\n';

The program you show has a few problems, the primary culprit being the for condition: i<v[n]. You initialize the array, setting the first 5 elements to various values and the rest to zero. n is set to the number of elements you explicitly initialized so v[n] is the first element that was implicitly initialized to zero. Therefore the loop condition is false the first time around and the loop does not run at all; your code simply prints out the first element.

Some minor issues:

  • avoid raw arrays; they behave strangely and inconsistently (e.g., implicit conversion to pointer to the array's first element, can't be assigned, can't be passed to/returned from functions by value)

  • avoid magic numbers. int v[100] is an invitation to a bug if you want your array to get input from somewhere and then try to handle more than 100 elements.

  • avoid using namespace std; It's not a big deal in implementation files, although IMO it's better to just get used to explicit qualification, but it can cause problems if you blindly use it everywhere because you'll put it in header files and start causing unnecessary name conflicts.

Playing HTML5 video on fullscreen in android webview

Edit: please see my other answer, as you probably don't need this now.

As you said, in API levels 11+ a HTML5VideoFullScreen$VideoSurfaceView is passed. But I don't think you are right when you say that "it doens't have a MediaPlayer".

This is the way to reach the MediaPlayer instance from the HTML5VideoFullScreen$VideoSurfaceView instance using reflection:

Class c1 = Class.forName("android.webkit.HTML5VideoFullScreen$VideoSurfaceView");
Field f1 = c1.getDeclaredField("this$0");

Class c2 = f1.getType().getSuperclass();
Field f2 = c2.getDeclaredField("mPlayer");

Object ___html5VideoViewInstance = f1.get(focusedChild); // Look at the code in my other answer to this same question to see whats focusedChild

Object ___mpInstance = f2.get(___html5VideoViewInstance); // This is the MediaPlayer instance.

So, now you could set the onCompletion listener of the MediaPlayer instance like this:

OnCompletionListener ocl = new OnCompletionListener()
    public void onCompletion(MediaPlayer mp)
        // Do stuff

Method m1 = f2.getType().getMethod("setOnCompletionListener", new Class[] { Class.forName("$OnCompletionListener") });
m1.invoke(___mpInstance, ocl);

The code doesn't fail but I'm not completely sure if that onCompletion listener will really be called or if it could be useful to your situation. But just in case someone would like to try it.

python pandas convert index to datetime

It should work as expected. Try to run the following example.

import pandas as pd
import io

data = """value          
"2015-09-25 00:46"    71.925000
"2015-09-25 00:47"    71.625000
"2015-09-25 00:48"    71.333333
"2015-09-25 00:49"    64.571429
"2015-09-25 00:50"    72.285714"""

df = pd.read_table(io.StringIO(data), delim_whitespace=True)

# Converting the index as date
df.index = pd.to_datetime(df.index)

# Extracting hour & minute
df['A'] = df.index.hour
df['B'] = df.index.minute

#                          value  A   B
# 2015-09-25 00:46:00  71.925000  0  46
# 2015-09-25 00:47:00  71.625000  0  47
# 2015-09-25 00:48:00  71.333333  0  48
# 2015-09-25 00:49:00  64.571429  0  49
# 2015-09-25 00:50:00  72.285714  0  50

Operator overloading on class templates

// In MyClass.h
MyClass<T>& operator+=(const MyClass<T>& classObj);

// In MyClass.cpp
template <class T>
MyClass<T>& MyClass<T>::operator+=(const MyClass<T>& classObj) {
  // ...
  return *this;

This is invalid for templates. The full source code of the operator must be in all translation units that it is used in. This typically means that the code is inline in the header.

Edit: Technically, according to the Standard, it is possible to export templates, however very few compilers support it. In addition, you CAN also do the above if the template is explicitly instantiated in MyClass.cpp for all types that are T- but in reality, that normally defies the point of a template.

More edit: I read through your code, and it needs some work, for example overloading operator[]. In addition, typically, I would make the dimensions part of the template parameters, allowing for the failure of + or += to be caught at compile-time, and allowing the type to be meaningfully stack allocated. Your exception class also needs to derive from std::exception. However, none of those involve compile-time errors, they're just not great code.

Whoops, looks like something went wrong. Laravel 5.0

make sure app/storage dir permission is set to 755 and owner is set to admin. and also check permission and owner of files and dir in app/storage too

Error: unable to verify the first certificate in nodejs

Another dirty hack, which will make all your requests insecure:


Why should I use core.autocrlf=true in Git?

Update 2:

Xcode 9 appears to have a "feature" where it will ignore the file's current line endings, and instead just use your default line-ending setting when inserting lines into a file, resulting in files with mixed line endings.

I'm pretty sure this bug didn't exist in Xcode 7; not sure about Xcode 8. The good news is that it appears to be fixed in Xcode 10.

For the time it existed, this bug caused a small amount of hilarity in the codebase I refer to in the question (which to this day uses autocrlf=false), and led to many "EOL" commit messages and eventually to my writing a git pre-commit hook to check for/prevent introducing mixed line endings.


Note: As noted by VonC, starting from Git 2.8, merge markers will not introduce Unix-style line-endings to a Windows-style file.


One little hiccup that I've noticed with this setup is that when there are merge conflicts, the lines git adds to mark up the differences do not have Windows line-endings, even when the rest of the file does, and you can end up with a file with mixed line endings, e.g.:

// Some code<CR><LF>
<<<<<<< Updated upstream<LF>
// Change A<CR><LF>
// Change B<CR><LF>
>>>>>>> Stashed changes<LF>
// More code<CR><LF>

This doesn't cause us any problems (I imagine any tool that can handle both types of line-endings will also deal sensible with mixed line-endings--certainly all the ones we use do), but it's something to be aware of.

The other thing* we've found, is that when using git diff to view changes to a file that has Windows line-endings, lines that have been added display their carriage returns, thus:

    // Not changed

+   // New line added in^M
    // Not changed
    // Not changed

* It doesn't really merit the term: "issue".

How to create an executable .exe file from a .m file

It used to be possible to compile Matlab to C with older versions of Matlab. Check out other tools that Matlab comes with.

Newest Matlab code can be exported as a Java's jar or a .Net Dll, etc. You can then write an executable against that library - it will be obfuscated by the way. The users will have to install a freely available Matlab Runtime.

Like others mentioned, mcc / mcc.exe is what you want to convert matlab code to C code.

What does the Java assert keyword do, and when should it be used?

What does the assert keyword in Java do?

Let's look at the compiled bytecode.

We will conclude that:

public class Assert {
    public static void main(String[] args) {
        assert System.currentTimeMillis() == 0L;

generates almost the exact same bytecode as:

public class Assert {
    static final boolean $assertionsDisabled =
    public static void main(String[] args) {
        if (!$assertionsDisabled) {
            if (System.currentTimeMillis() != 0L) {
                throw new AssertionError();

where Assert.class.desiredAssertionStatus() is true when -ea is passed on the command line, and false otherwise.

We use System.currentTimeMillis() to ensure that it won't get optimized away (assert true; did).

The synthetic field is generated so that Java only needs to call Assert.class.desiredAssertionStatus() once at load time, and it then caches the result there. See also: What is the meaning of "static synthetic"?

We can verify that with:

javap -c -constants -private -verbose Assert.class

With Oracle JDK 1.8.0_45, a synthetic static field was generated (see also: What is the meaning of "static synthetic"?):

static final boolean $assertionsDisabled;
  descriptor: Z

together with a static initializer:

 0: ldc           #6                  // class Assert
 2: invokevirtual #7                  // Method java/lang Class.desiredAssertionStatus:()Z
 5: ifne          12
 8: iconst_1
 9: goto          13
12: iconst_0
13: putstatic     #2                  // Field $assertionsDisabled:Z
16: return

and the main method is:

 0: getstatic     #2                  // Field $assertionsDisabled:Z
 3: ifne          22
 6: invokestatic  #3                  // Method java/lang/System.currentTimeMillis:()J
 9: lconst_0
10: lcmp
11: ifeq          22
14: new           #4                  // class java/lang/AssertionError
17: dup
18: invokespecial #5                  // Method java/lang/AssertionError."<init>":()V
21: athrow
22: return

We conclude that:

  • there is no bytecode level support for assert: it is a Java language concept
  • assert could be emulated pretty well with system properties to replace -ea on the command line, and a throw new AssertionError().

Maven:Failed to execute goal org.apache.maven.plugins:maven-resources-plugin:2.7:resources

I had the same error because of character '@' in my resources/ All I did was replacing the '@' for its unicode value: eureka.client.serviceUrl.defaultZone=http://discUser:discPassword\u0040localhost:8082/eureka/ and it worked like charm. I know the '@' is a perfectly valid character in .properties files and the file was in UTF-8 encoding and it makes me question my career till today but it's worth a shot if you delete content of your resource files to see if you can get pass this error.

Daemon not running. Starting it now on port 5037

Reference link:

Steps I followed 1) Execute the command adb nodaemon server in command prompt Output at command prompt will be: The following error occurred cannot bind 'tcp:5037' The original ADB server port binding failed

2) Enter the following command query which using port 5037 netstat -ano | findstr "5037" The following information will be prompted on command prompt: TCP LISTENING 9288

3) View the task manager, close all adb.exe

4) Restart eclipse or other IDE

The above steps worked for me.

How to specify more spaces for the delimiter using cut?

Another way if you must use cut command

ps axu | grep [j]boss |awk '$1=$1'|cut -d' ' -f5

In Solaris, replace awk with nawk or /usr/xpg4/bin/awk

What is the maximum possible length of a query string?

RFC 2616 (Hypertext Transfer Protocol — HTTP/1.1) states there is no limit to the length of a query string (section 3.2.1). RFC 3986 (Uniform Resource Identifier — URI) also states there is no limit, but indicates the hostname is limited to 255 characters because of DNS limitations (section 2.3.3).

While the specifications do not specify any maximum length, practical limits are imposed by web browser and server software. Based on research which is unfortunately no longer available on its original site (it leads to a shady seeming loan site) but which can still be found at Internet Archive Of

  • Microsoft Internet Explorer (Browser)
    Microsoft states that the maximum length of a URL in Internet Explorer is 2,083 characters, with no more than 2,048 characters in the path portion of the URL. Attempts to use URLs longer than this produced a clear error message in Internet Explorer.

  • Microsoft Edge (Browser)
    The limit appears to be around 81578 characters. See URL Length limitation of Microsoft Edge

  • Chrome
    It stops displaying the URL after 64k characters, but can serve more than 100k characters. No further testing was done beyond that.

  • Firefox (Browser)
    After 65,536 characters, the location bar no longer displays the URL in Windows Firefox 1.5.x. However, longer URLs will work. No further testing was done after 100,000 characters.

  • Safari (Browser)
    At least 80,000 characters will work. Testing was not tried beyond that.

  • Opera (Browser)
    At least 190,000 characters will work. Stopped testing after 190,000 characters. Opera 9 for Windows continued to display a fully editable, copyable and pasteable URL in the location bar even at 190,000 characters.

  • Apache (Server)
    Early attempts to measure the maximum URL length in web browsers bumped into a server URL length limit of approximately 4,000 characters, after which Apache produces a "413 Entity Too Large" error. The current up to date Apache build found in Red Hat Enterprise Linux 4 was used. The official Apache documentation only mentions an 8,192-byte limit on an individual field in a request.

  • Microsoft Internet Information Server (Server)
    The default limit is 16,384 characters (yes, Microsoft's web server accepts longer URLs than Microsoft's web browser). This is configurable.

  • Perl HTTP::Daemon (Server)
    Up to 8,000 bytes will work. Those constructing web application servers with Perl's HTTP::Daemon module will encounter a 16,384 byte limit on the combined size of all HTTP request headers. This does not include POST-method form data, file uploads, etc., but it does include the URL. In practice this resulted in a 413 error when a URL was significantly longer than 8,000 characters. This limitation can be easily removed. Look for all occurrences of 16x1024 in and replace them with a larger value. Of course, this does increase your exposure to denial of service attacks.

How to add Certificate Authority file in CentOS 7

Maybe late to the party but in my case it was RHEL 6.8:

Copy certificate.crt issued by hosting to:



update-ca-trust force-enable (ignore not found warnings)
update-ca-trust extract

Hope it helps

How do I determine the dependencies of a .NET application?

If you are using the Mono toolchain, you can use the monodis utility with the --assemblyref argument to list the dependencies of a .NET assembly. This will work on both .exe and .dll files.

Example usage:

monodis --assemblyref somefile.exe

Example output (.exe):

$ monodis --assemblyref monop.exe
AssemblyRef Table
1: Version=
    Public Key:
0x00000000: B7 7A 5C 56 19 34 E0 89
2: Version=
    Public Key:
0x00000000: B7 7A 5C 56 19 34 E0 89

Example output (.dll):

$ monodis --assemblyref Mono.CSharp.dll
AssemblyRef Table
1: Version=
    Public Key:
0x00000000: B7 7A 5C 56 19 34 E0 89
2: Version=
    Public Key:
0x00000000: B7 7A 5C 56 19 34 E0 89
3: Version=
    Public Key:
0x00000000: B7 7A 5C 56 19 34 E0 89
4: Version=
    Public Key:
0x00000000: B7 7A 5C 56 19 34 E0 89

Virtual Memory Usage from Java under Linux, too much memory used

One way of reducing the heap sice of a system with limited resources may be to play around with the -XX:MaxHeapFreeRatio variable. This is usually set to 70, and is the maximum percentage of the heap that is free before the GC shrinks it. Setting it to a lower value, and you will see in eg the jvisualvm profiler that a smaller heap sice is usually used for your program.

EDIT: To set small values for -XX:MaxHeapFreeRatio you must also set -XX:MinHeapFreeRatio Eg

java -XX:MinHeapFreeRatio=10 -XX:MaxHeapFreeRatio=25 HelloWorld

EDIT2: Added an example for a real application that starts and does the same task, one with default parameters and one with 10 and 25 as parameters. I didn't notice any real speed difference, although java in theory should use more time to increase the heap in the latter example.

Default parameters

At the end, max heap is 905, used heap is 378

MinHeap 10, MaxHeap 25

At the end, max heap is 722, used heap is 378

This actually have some inpact, as our application runs on a remote desktop server, and many users may run it at once.

Get width in pixels from element with style set with %?['cssProperty']

this way you can call the property string dynamically

Get textarea text with javascript or Jquery

To get the value from a textarea with an id you just have to do



If you are having more than one element with the same id in the document then the HTML is invalid.

How do I set the background color of my main screen in Flutter?

      backgroundColor: Constants.defaulBackground,
      body: new Container(
      child: Center(yourtext)


Python "extend" for a dictionary

A beautiful gem in this closed question:

The "oneliner way", altering neither of the input dicts, is

basket = dict(basket_one, **basket_two)

Learn what **basket_two (the **) means here.

In case of conflict, the items from basket_two will override the ones from basket_one. As one-liners go, this is pretty readable and transparent, and I have no compunction against using it any time a dict that's a mix of two others comes in handy (any reader who has trouble understanding it will in fact be very well served by the way this prompts him or her towards learning about dict and the ** form;-). So, for example, uses like:

x = mungesomedict(dict(adict, **anotherdict))

are reasonably frequent occurrences in my code.

Originally submitted by Alex Martelli

Note: In Python 3, this will only work if every key in basket_two is a string.

Use python requests to download CSV

Python3 Supported Code

    with closing(requests.get(PHISHTANK_URL, stream=True})) as r:
        reader = csv.reader(codecs.iterdecode(r.iter_lines(), 'utf-8'), delimiter=',', quotechar='"')
        for record in reader:
           print (record)

ORACLE IIF Statement

In PL/SQL, there is a trick to use the undocumented OWA_UTIL.ITE function.


    x   VARCHAR2(10);
    x := owa_util.ite('a' = 'b','T','F');


PL/SQL procedure successfully completed.

Adding <script> to WordPress in <head> element

Elaborating on the previous answer, you can gather all the required snippets before outputting the header, and only then use an action hook to inject all you need on the head.

In your functions.php file, add

$inject_required_scripts = array();

 * Call this function before calling get_header() to request custom js code to be injected on head.
 * @param code the javascript code to be injected.
function require_script($code) {
  global $inject_required_scripts;
  $inject_required_scripts[] = $code; // store code snippet for later injection

function inject_required_scripts() {
  global $inject_required_scripts;
  foreach($inject_required_scripts as $script)
    // inject all code snippets, if any
    echo '<script type="text/javascript">'.$script.'</script>';
add_action('wp_head', 'inject_required_scripts');

And then in your page or template, use it like

/* Template Name: coolstuff */


  jQuery(function(){jQuery('p,span,a').html('Internet is cool')});


I made it for javascript because it's the most common use, but it can be easily adapted to any tag in the head, and either with inline code or by passing a href/src to an external URL.

What browsers support HTML5 WebSocket API?

Client side

  • Hixie-75:
    • Chrome 4.0 + 5.0
    • Safari 5.0.0
  • HyBi-00/Hixie-76:
  • HyBi-07+:
  • HyBi-10:
    • Chrome 14.0 + 15.0
    • Firefox 7.0 + 8.0 + 9.0 + 10.0 - prefixed: MozWebSocket
    • IE 10 (from Windows 8 developer preview)
  • HyBi-17/RFC 6455
    • Chrome 16
    • Firefox 11
    • Opera 12.10 / Opera Mobile 12.1

Any browser with Flash can support WebSocket using the web-socket-js shim/polyfill.

See caniuse for the current status of WebSockets support in desktop and mobile browsers.

See the test reports from the WS testsuite included in Autobahn WebSockets for feature/protocol conformance tests.

Server side

It depends on which language you use.

In Java/Java EE:

Some other Java implementations:

In C#:


In Python:

In C:

In Node.js:

  • : also has serverside ports for Python, Java, Google GO, Rack
  • sockjs : sockjs also has serverside ports for Python, Java, Erlang and Lua
  • WebSocket-Node - Pure JavaScript Client & Server implementation of HyBi-10.

Vert.x (also known as Node.x) : A node like polyglot implementation running on a Java 7 JVM and based on Netty with :

  • Support for Ruby(JRuby), Java, Groovy, Javascript(Rhino/Nashorn), Scala, ...
  • True threading. (unlike Node.js)
  • Understands multiple network protocols out of the box including: TCP, SSL, UDP, HTTP, HTTPS, Websockets, SockJS as fallback for WebSockets is a Websocket cloud service accessible through a REST API.

DotCloud cloud platform supports Websockets, and Java (Jetty Servlet Container), NodeJS, Python, Ruby, PHP and Perl programming languages.

Openshift cloud platform supports websockets, and Java (Jboss, Spring, Tomcat & Vertx), PHP (ZendServer & CodeIgniter), Ruby (ROR), Node.js, Python (Django & Flask) plateforms.

For other language implementations, see the Wikipedia article for more information.

The RFC for Websockets : RFC6455

Bulk Record Update with SQL

Or you can simply update without using join like this:

Update t1 set  t1.Description = t2.Description from @tbl2 t2,tbl1 t1
where t1.ID= t2.ID

How to check if an app is installed from a web-page on an iPhone?

You can check out this plugin that tries to solve the problem. It is based on the same approach as described by missemisa and Alastair etc, but uses a hidden iframe instead.

Hibernate throws MultipleBagFetchException - cannot simultaneously fetch multiple bags

I think a newer version of hibernate (supporting JPA 2.0) should handle this. But otherwise you can work it around by annotating the collection fields with:


Remember to remove the fetchType attribute from the @*ToMany annotation.

But note that in most cases a Set<Child> is more appropriate than List<Child>, so unless you really need a List - go for Set

But remind that with using sets you won't eliminate the underlaying Cartesian Product as described by Vlad Mihalcea in his answer!

Get class name of object as string in Swift

Swift 5

Here is the extension to get the typeName as a variable (work with both value type or reference type).

protocol NameDescribable {
    var typeName: String { get }
    static var typeName: String { get }

extension NameDescribable {
    var typeName: String {
        return String(describing: type(of: self))

    static var typeName: String {
        return String(describing: self)

How to use:

// Extend with class/struct/enum...
extension NSObject: NameDescribable {}
extension Array: NameDescribable {}
extension UIBarStyle: NameDescribable { }


// Out put:

How to include route handlers in multiple files in Express?

If you're using express-4.x with TypeScript and ES6, this would be the best template to use:


import express, { Router, Request, Response } from "express";

const router: Router = express.Router();
// POST /user/signin'/signin', async (req: Request, res: Response) => {
    try {
    } catch (e) {

export default router;


import express, { Request, Response } from "express";
import compression from "compression";  // compresses requests
import expressValidator from "express-validator";
import bodyParser from "body-parser";
import login from './api/login';

const app = express();

app.use(bodyParser.urlencoded({ extended: true }));

app.get('/public/hc', (req: Request, res: Response) => {

app.use('/user', login);

app.listen(8080, () => {
    console.log("Press CTRL-C to stop\n");

Much cleaner than using var and module.exports.

How can I make my flexbox layout take 100% vertical space?

You should set height of html, body, .wrapper to 100% (in order to inherit full height) and then just set a flex value greater than 1 to .row3 and not on the others.

.wrapper, html, body {
    height: 100%;
    margin: 0;
.wrapper {
    display: flex;
    flex-direction: column;
#row1 {
    background-color: red;
#row2 {
    background-color: blue;
#row3 {
    background-color: green;
    display: flex;
#col1 {
    background-color: yellow;
    flex: 0 0 240px;
    min-height: 100%;/* chrome needed it a question time , not anymore */
#col2 {
    background-color: orange;
    flex: 1 1;
    min-height: 100%;/* chrome needed it a question time , not anymore */
#col3 {
    background-color: purple;
    flex: 0 0 240px;
    min-height: 100%;/* chrome needed it a question time , not anymore */
<div class="wrapper">
    <div id="row1">this is the header</div>
    <div id="row2">this is the second line</div>
    <div id="row3">
        <div id="col1">col1</div>
        <div id="col2">col2</div>
        <div id="col3">col3</div>


How to use session in JSP pages to get information?

<%! String username=(String)session.getAttribute("username"); %>
form action="editinfo" method="post">

            <td>Username: </td><td> <input type="text" value="<%=username %>" /> </td>


add <%! String username=(String)session.getAttribute("username"); %>

How to add data to DataGridView

LINQ is a "query" language (thats the Q), so modifying data is outside its scope.

That said, your DataGridView is presumably bound to an ItemsSource, perhaps of type ObservableCollection<T> or similar. In that case, just do something like X.ToList().ForEach(yourGridSource.Add) (this might have to be adapted based on the type of source in your grid).

The preferred way of creating a new element with jQuery

According to the jQuery official documentation

To create a HTML element, $("<div/>") or $("<div></div>") is preferred.

Then you can use either appendTo, append, before, after and etc,. to insert the new element to the DOM.

PS: jQuery Version 1.11.x

How to include jQuery in ASP.Net project?

There are actually a few ways this can be done:

1: Download

You can download the latest version of jQuery and then include it in your page with a standard HTML script tag. This can be done within the master or an individual page.


<script src="/scripts/jquery-2.1.0.min.js"></script>


<script src="/scripts/jquery-2.1.0.min.js" type="text/javascript"></script>

2: Content Delivery Network

You can include jQuery to your site using a CDN (Content Delivery Network) such as Google's. This should help reduce page load times if the user has already visited a site using the same version from the same CDN.

<script src="//"></script>

3: NuGet Package Manager

Lastly, (my preferred) use NuGet which is shipped with Visual Studio and Visual Studio Express. This is accessed from right-clicking on your project and clicking Manage NuGet Packages.

NuGet is an open source Library Package Manager that comes as a Visual Studio extension and that makes it very easy to add, remove, and update external libraries in your Visual Studio projects and websites. Beginning ASP.NET 4.5 in C# and VB.NET, WROX, 2013

enter image description here

Once installed, a new Folder group will appear in your Solution Explorer called Scripts. Simply drag and drop the file you wish to include onto your page of choice.

This method is ideal for larger projects because if you choose to remove the files, or change versions later (though the package manager) if will automatically remove/update any reference to that file within your project.

The only downside to this approach is it does not use a CDN to host the file so page load time may be slightly slower the first time the user visits your site.

How do I create a master branch in a bare Git repository?

A branch is just a reference to a commit. Until you commit anything to the repository, you don't have any branches. You can see this in a non-bare repository as well.

$ mkdir repo
$ cd repo
$ git init
Initialized empty Git repository in /home/me/repo/.git/
$ git branch
$ touch foo
$ git add foo
$ git commit -m "new file"
1 file changed, 0 insertions(+), 0 deletions(-)
create mode 100644 foo
$ git branch
* master

invalid_client in google oauth2

If you are in Meteor JS, you have to use clientId instead appId:

Since facebook uses appId and google clientId.

    service: "google"
}, {
    $set: {
        clientId: process.env.OAUTH_GOOGLE_APP_ID,
        loginStyle: "popup",
        secret: process.env.OAUTH_GOOGLE_SECRET

I spent some hours to realize over that.

How to see the changes in a Git commit?

To see author and time by commit use git show COMMIT. Which will result in something like this:

commit 13414df70354678b1b9304ebe4b6d204810f867e
Merge: a2a2894 3a1ba8f
Author: You <[email protected]>
Date:   Fri Jul 24 17:46:42 2015 -0700

     Merge remote-tracking branch 'origin/your-feature'

If you want to see which files had been changed, run the following with the values from the Merge line above git diff --stat a2a2894 3a1ba8f.

If you want to see the actual diff, run git --stat a2a2894 3a1ba8f

After installing with pip, "jupyter: command not found"

Execute this in Terminal

export PATH=~/anaconda3/bin:$PATH

Worked for me on Ubuntu 16.10, Python3, Anaconda3


Add path in your ~/.bashrc or ~/.zshrc(if you are using zsh bash) file

vi ~/.bashrc

add the below line to the file


Close the file with

esc + : + wq

How to update/refresh specific item in RecyclerView

That's also my last problem. Here my solution I use data Model and adapter for my RecyclerView

 /*Firstly, register your new data to your model*/
 DataModel detail = new DataModel(id, name, sat, image);

 /*after that, use set to replace old value with the new one*/
 int index = 4;
 mData.set(index, detail);

 /*finally, refresh your adapter*/

How to get the mobile number of current sim card in real device?

You can use the TelephonyManager to do this:

TelephonyManager tm = (TelephonyManager)getSystemService(TELEPHONY_SERVICE); 
String number = tm.getLine1Number();

The documentation for getLine1Number() says this method will return null if the number is "unavailable", but it does not say when the number might be unavailable.

You'll need to give your application permission to make this query by adding the following to your Manifest:

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

(You shouldn't use TelephonyManager.getDefault() to get the TelephonyManager as that is a private undocumented API call and may change in future.)

How to sort a list/tuple of lists/tuples by the element at a given index?

I just want to add to Stephen's answer if you want to sort the array from high to low, another way other than in the comments above is just to add this to the line:

reverse = True

and the result will be as follows:

data.sort(key=lambda tup: tup[1], reverse=True)

Merging two images in C#/.NET

basically i use this in one of our apps: we want to overlay a playicon over a frame of a video:

Image playbutton;
    playbutton = Image.FromFile(/*somekindofpath*/);
catch (Exception ex)

Image frame;
    frame = Image.FromFile(/*somekindofpath*/);
catch (Exception ex)

using (frame)
    using (var bitmap = new Bitmap(width, height))
        using (var canvas = Graphics.FromImage(bitmap))
            canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
                             new Rectangle(0,
                             new Rectangle(0,
                             (bitmap.Width / 2) - (playbutton.Width / 2),
                             (bitmap.Height / 2) - (playbutton.Height / 2));
        catch (Exception ex) { }

How to dynamically create columns in datatable and assign values to it?

If you want to create dynamically/runtime data table in VB.Net then you should follow these steps as mentioned below :

  • Create Data table object.
  • Add columns into that data table object.
  • Add Rows with values into the object.

For eg.

Dim dt As New DataTable

dt.Columns.Add("Id", GetType(Integer))
dt.Columns.Add("FirstName", GetType(String))
dt.Columns.Add("LastName", GetType(String))

dt.Rows.Add(1, "Test", "data")
dt.Rows.Add(15, "Robert", "Wich")
dt.Rows.Add(18, "Merry", "Cylon")
dt.Rows.Add(30, "Tim", "Burst")

Node.js Port 3000 already in use but it actually isn't?

For windows, The Task Manager would definitely show a node process running. Try to kill the process, it will solve the problem.

How to open Emacs inside Bash

Emacs takes many launch options. The one that you are looking for is emacs -nw. This will open Emacs inside the terminal disregarding the DISPLAY environment variable even if it is set. The long form of this flag is emacs --no-window-system.

More information about Emacs launch options can be found in the manual.

How to define a List bean in Spring?

Inject list of strings.

Suppose you have Countries model class that take list of strings like below.

public class Countries {
    private List<String> countries;

    public List<String> getCountries() {
        return countries;

    public void setCountries(List<String> countries) {
        this.countries = countries;


Following xml definition define a bean and inject list of countries.

<bean id="demoCountryCapitals" name="demoCountryCapitals" class="com.sample.pojo.Countries">
   <property name="countries">
         <value>Sri Lanka</value>

Reference link

Inject list of Pojos

Suppose if you have model class like below.

public class Country {
    private String name;
    private String capital;

public class Countries {
    private List<Country> favoriteCountries;

    public List<Country> getFavoriteCountries() {
        return favoriteCountries;

    public void setFavoriteCountries(List<Country> favoriteCountries) {
        this.favoriteCountries = favoriteCountries;


Bean Definitions.

 <bean id="india" class="com.sample.pojo.Country">
  <property name="name" value="India" />
  <property name="capital" value="New Delhi" />

 <bean id="russia" class="com.sample.pojo.Country">
  <property name="name" value="Russia" />
  <property name="capital" value="Moscow" />

 <bean id="demoCountryCapitals" name="demoCountryCapitals" class="com.sample.pojo.Countries">
  <property name="favoriteCountries">
    <ref bean="india" />
    <ref bean="russia" />

Reference Link.

ImportError: No module named win32com.client

win32com.client is a part of pywin32

So, download pywin32 from here

How do I make a column unique and index it in a Ruby on Rails migration?

If you are creating a new table, you can use the inline shortcut:

  def change
    create_table :posts do |t|
      t.string :title, null: false, index: { unique: true }

How do I set a checkbox in razor view?

I had the same issue, luckily I found the below code

@Html.CheckBoxFor(model => model.As, htmlAttributes: new { @checked = true} )

Check Box Checked By Default - Razor Solution

Set keyboard caret position in html textbox

<!DOCTYPE html>
<title>set caret position</title>
<script type="application/javascript">
window.onload = function ()
 setCaret(document.getElementById('input1'), 13, 13)

function setCaret(el, st, end)
 if (el.setSelectionRange)
  el.setSelectionRange(st, end);
  if (el.createTextRange)
   range = el.createTextRange();
   range.moveEnd('character', end);
   range.moveStart('character', st);;

<textarea id="input1" name="input1" rows="10" cols="30">Happy kittens dancing</textarea>



How to remove only 0 (Zero) values from column in excel 2010

Press Control + H, then select Options and check Match entire cell contents and Match case. In the Find what field type a 0, and leave the Replace with field blank. Then Replace All. This will remove all of the zeros that are stand alone.

Scroll to element on click in Angular 4

There is actually a pure javascript way to accomplish this without using setTimeout or requestAnimationFrame or jQuery.

In short, find the element in the scrollView that you want to scroll to, and use scrollIntoView.


Here is a plunkr.

sprintf like functionality in Python

Python has a % operator for this.

>>> a = 5
>>> b = "hello"
>>> buf = "A = %d\n , B = %s\n" % (a, b)
>>> print buf
A = 5
 , B = hello

>>> c = 10
>>> buf = "C = %d\n" % c
>>> print buf
C = 10

See this reference for all supported format specifiers.

You could as well use format:

>>> print "This is the {}th tome of {}".format(5, "knowledge")
This is the 5th tome of knowledge

How to create strings containing double quotes in Excel formulas?

Concatenate " as a ceparate cell:

    A |   B   | C | D
1   " | text  | " | =CONCATENATE(A1; B1; C1);

D1 displays "text"

Google reCAPTCHA: How to get user response and validate in the server side?

A method I use in my login servlet to verify reCaptcha responses. Uses classes from the java.json package. Returns the API response in a JsonObject.

Check the success field for true or false

private JsonObject validateCaptcha(String secret, String response, String remoteip)
    JsonObject jsonObject = null;
    URLConnection connection = null;
    InputStream is = null;
    String charset =;

    String url = "";
    try {            
        String query = String.format("secret=%s&response=%s&remoteip=%s", 
        URLEncoder.encode(secret, charset), 
        URLEncoder.encode(response, charset),
        URLEncoder.encode(remoteip, charset));

        connection = new URL(url + "?" + query).openConnection();
        is = connection.getInputStream();
        JsonReader rdr = Json.createReader(is);
        jsonObject = rdr.readObject();

    } catch (IOException ex) {
        Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
    finally {
        if (is != null) {
            try {
            } catch (IOException e) {

    return jsonObject;

Is it safe to clean docker/overlay2/

I had this issue... It was the log that was huge. Logs are here :

/var/lib/docker/containers/<container id>/<container id>-json.log

You can manage this in the run command line or in the compose file. See there : Configure logging drivers

I personally added these 3 lines to my docker-compose.yml file :

      max-size: 10m

How do you get centered content using Twitter Bootstrap?

My preferred method for centering blocks of information while maintaining responsiveness (mobile compatibility) is to place two empty span1 divs before and after the content you wish to center.

<div class="row-fluid">

    <div class="span1">

        <div class="span10">
          <div class="hero-unit">
            <h1>Reading Resources</h1>
            <p>Read here...</p>

    <div class="span1">


number several equations with only one number

First of all, you probably don't want the align environment if you have only one column of equations. In fact, your example is probably best with the cases environment. But to answer your question directly, used the aligned environment within equation - this way the outside environment gives the number:

  w^T x_i + b &\geq 1-\xi_i &\text{ if }& y_i=1,  \\
  w^T x_i + b &\leq -1+\xi_i & \text{ if } &y_i=-1,

The documentation of the amsmath package explains this and more.

Named placeholders in string formatting

This is an old thread, but just for the record, you could also use Java 8 style, like this:

public static String replaceParams(Map<String, String> hashMap, String template) {
    return hashMap.entrySet().stream().reduce(template, (s, e) -> s.replace("%(" + e.getKey() + ")", e.getValue()),
            (s, s2) -> s);


public static void main(String[] args) {
    final HashMap<String, String> hashMap = new HashMap<String, String>() {
            put("foo", "foo1");
            put("bar", "bar1");
            put("car", "BMW");
            put("truck", "MAN");
    String res = replaceParams(hashMap, "This is '%(foo)' and '%(foo)', but also '%(bar)' '%(bar)' indeed.");
    System.out.println(replaceParams(hashMap, "This is '%(car)' and '%(foo)', but also '%(bar)' '%(bar)' indeed."));
    System.out.println(replaceParams(hashMap, "This is '%(car)' and '%(truck)', but also '%(foo)' '%(bar)' + '%(truck)' indeed."));

The output will be:

This is 'foo1' and 'foo1', but also 'bar1' 'bar1' indeed.
This is 'BMW' and 'foo1', but also 'bar1' 'bar1' indeed.
This is 'BMW' and 'MAN', but also 'foo1' 'bar1' + 'MAN' indeed.

How to join two sets in one line without using "|"

If you are fine with modifying the original set (which you may want to do in some cases), you can use set.update():


The return value is None, but S will be updated to be the union of the original S and T.

How do I resolve the " Address already in use: JVM_Bind" error?

In Windows CMD line, find out the Process ID that hold a connection on the bind port by entering following command:

C:> netstat -a -o

-a show all connections

-o show process identifier

And then Terminate the process.

Get absolute path of initially run script

A simple way to have the absolute path of the initially executed script, in that script and any other script included with include, require, require_once is by using a constant and storing there the current script path at beginning of the main script:

define( 'SCRIPT_ROOT', __FILE__ );

The solution above is suitable when there is a single "main" script that includes every other needed script, as in most web applications.

If that's not the case and there may be several "intital scripts" then to avoid redefinitions and to have the correct path stored inside the constant each script may begin with:

if( ! defined( 'SCRIPT_ROOT' ) ) {
    define( 'SCRIPT_ROOT`, __FILE__ );

A note about the (currently) accepted answer:

the answer states that the initially executed script path is the first element of the array returned by get_included_files().

This is a clever and simple solution and -at the time of writing- (we're almost at PHP 7.4.0) it does work.

However by looking at the documentation there is no mention that the initially executed script is the first item of the array returned by get_included_files().

We only read

The script originally called is considered an "included file," so it will be listed together with the files referenced by include and family.

At the time of writing the "script originally called" is the first one in the array but -technically- there is no guarantee that this won't change in the future.

A note about realpath(), __FILE__, and __DIR__:

Others have suggested in their answers the use of __FILE__, __DIR__, dirname(__FILE__), realpath(__DIR__)...

dirname(__FILE__) is equal to __DIR__ (introduced in PHP 5.3.0), so just use __DIR__.

Both __FILE__ and __DIR__ are always absolute paths so realpath() is unnecessary.

Send an Array with an HTTP Get

I know this post is really old, but I have to reply because although BalusC's answer is marked as correct, it's not completely correct.

You have to write the query adding "[]" to foo like this:


Making view resize to its parent when added with addSubview

that's all you need

childView.frame = parentView.bounds

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

Xcode 11

This is the error I got

Provisioning profile "XXX" doesn't include signing certificate "Apple Development: XXX (XXX)".```

Now Xcode 11 automatically created a certificate "Apple Development: XXX" which is valid for all platforms

You just need to

  1. Go to
  2. Go to your provisioning profile
  3. Check if this certificate is selected

setting request headers in selenium

I had the same issue. I solved it downloading modify-headers firefox add-on and activate it with selenium.

The code in python is the following

fp = webdriver.FirefoxProfile()
path_modify_header = 'C:/xxxxxxx/modify_headers-'

fp.set_preference("modifyheaders.headers.count", 1)
fp.set_preference("modifyheaders.headers.action0", "Add")
fp.set_preference("modifyheaders.headers.name0", "Name_of_header") # Set here the name of the header
fp.set_preference("modifyheaders.headers.value0", "value_of_header") # Set here the value of the header
fp.set_preference("modifyheaders.headers.enabled0", True)
fp.set_preference("", True)
fp.set_preference("modifyheaders.config.alwaysOn", True)

driver = webdriver.Firefox(firefox_profile=fp)

How to convert java.util.Date to java.sql.Date?

java.sql.Date sqlDate = new java.sql.Date(javaDate.getTime());

Here javaDate is the instance of java.util.Date

When to use: Java 8+ interface default method, vs. abstract method

These two are quite different:

Default methods are to add external functionality to existing classes without changing their state.

And abstract classes are a normal type of inheritance, they are normal classes which are intended to be extended.

How to do a https request with bad certificate?

Security note: Disabling security checks is dangerous and should be avoided

You can disable security checks globally for all requests of the default client:

package main

import (

func main() {
    http.DefaultTransport.(*http.Transport).TLSClientConfig = &tls.Config{InsecureSkipVerify: true}
    _, err := http.Get("")
    if err != nil {

You can disable security check for a client:

package main

import (

func main() {
    tr := &http.Transport{
        TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
    client := &http.Client{Transport: tr}
    _, err := client.Get("")
    if err != nil {

CSS: Center block, but align contents to the left

If I understand you well, you need to use to center a container (or block)

margin-left: auto;
margin-right: auto;

and to left align it's contents:

text-align: left;

Save a subplot in matplotlib

Applying the full_extent() function in an answer by @Joe 3 years later from here, you can get exactly what the OP was looking for. Alternatively, you can use Axes.get_tightbbox() which gives a little tighter bounding box

import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np
from matplotlib.transforms import Bbox

def full_extent(ax, pad=0.0):
    """Get the full extent of an axes, including axes labels, tick labels, and
    # For text objects, we need to draw the figure first, otherwise the extents
    # are undefined.
    items = ax.get_xticklabels() + ax.get_yticklabels() 
#    items += [ax, ax.title, ax.xaxis.label, ax.yaxis.label]
    items += [ax, ax.title]
    bbox = Bbox.union([item.get_window_extent() for item in items])

    return bbox.expanded(1.0 + pad, 1.0 + pad)

# Make an example plot with two subplots...
fig = plt.figure()
ax1 = fig.add_subplot(2,1,1)
ax1.plot(range(10), 'b-')

ax2 = fig.add_subplot(2,1,2)
ax2.plot(range(20), 'r^')

# Save the full figure...

# Save just the portion _inside_ the second axis's boundaries
extent = full_extent(ax2).transformed(fig.dpi_scale_trans.inverted())
# Alternatively,
# extent = ax.get_tightbbox(fig.canvas.renderer).transformed(fig.dpi_scale_trans.inverted())
fig.savefig('ax2_figure.png', bbox_inches=extent)

I'd post a pic but I lack the reputation points

Detailed 500 error message, ASP + IIS 7.5

TLDR:First determine where in the pipeline you're getting the error from (scroll looking for screenshots of something that resembles your error), make changes to get something new, repeat.

First determine what error message you are actually seeing.

If you are seeing the file located here...


...which generally looks like this:

IIS Default 500 error

...then you know you are seeing the currently configured error page in **IIS ** and you do NOT need to change the customErrors setting, asp error detail setting, or "show friendly http errors" browser setting.

You may want to look at the above referenced path instead of trusting my screenshot just in case somebody changed it.

"Yes, I see the above described error..."

In this case, you are seeing the setting of <httpErrors> or in IIS Manager it's Error Pages --> Edit Feature Settings. The default for this is errorMode=DetailedLocalOnly at the server node level (as opposed to the site level) which means that while you will see this configured error page while remote, you should be able to log on locally to the server and see the full error which should look something like this:

Detailed HTTP Error

You should have everything that you need at that point to fix the current error.

"But I don't see the detailed error even browsing on the server"

That leaves a couple of possibilities.

  1. The browser you are using on the server is configured to use a proxy in its connection settings so it is not being seen as "local".
  2. You're not actually browsing to the site you think you are browsing to - this commonly happens when there's a load balancer involved. Do a ping check to see if dns gives you an IP on the server or somewhere else.
  3. You're site's httpErrors settings is set for "Custom" only. Change it to "DetailedLocalOnly". However, if you have a configuration error, this may not work since the site level httpErrors is also a configuration item. In that case proceed to #4
  4. The default for httpErrors for all sites is set for "Custom". In this case you need to click on the top level server node in IIS Manager (and not a particular site) and change the httpErrors settings there to DetailedLocalOnly. If this is an internal server and you're not worried about divulging sensitive information, you could also set it to "Detailed" which will allow you to see the error from clients other than the server.
  5. You're missing a module on the server like UrlRewrite (this one bites me a lot, and it often gives the generic message regardless of the httpErrors settings).

"Logging on to the server is not an option for me"

Change your site's httpErrors to "Detailed" so you can see it remotely. But if it doesn't work your error might already be a config error, see #3 immediately above. So you might be stuck with #4 or #5 and you're going to need somebody from your server team.

"I'm not seeing the error page described above. I'm seeing something different"

If you see this...

enter image description here

...and you expect to see something like this...

enter image description here

...then you need to change "Send errors to browser" to true in IIS Manager, under Site --> IIS --> ASP --> Debugging Properties

If you see this...

ie friendly errors 1

or this...

ie friendly errors 2 need to disable friendly errors in your browser or use fiddler's webview to look at the actual response vs what your browser chooses to show you.

If you see this...

Custom errors enabled

...then custom errors is working but you don't have a custom error page (of course at this point were talking about .net and not classic asp). You need to change your customErrors tag in your web.config to RemoteOnly to view on the server, or Off to view remotely.

If you see something that is styled like your site, then custom errors is likely On or RemoteOnly and it's displaying the custom page (Views->Shared->Error.cshtml in MVC for example). That said, it is unlikely but possible that somebody changed the pages in IIS for httpErrors so see the first section on that.

Get selected item value from Bootstrap DropDown with specific ID

Try this code

<input type="TextBox" ID="yearBox" border="0" disabled>

$('#yearSelected li').on('click', function(){

<a href="#" class="dropdown-toggle" data-toggle="dropdown"> <i class="fas fa-calendar-alt"></i> <span>Academic Years</span> <i class="fas fa-chevron-down"></i> </a>
          <ul class="dropdown-menu">
              <ul class="menu" id="yearSelected">
                <li><a href="#">2014-2015</a></li>
                <li><a href="#">2015-2016</a></li>
                <li><a href="#">2016-2017</a></li>
                <li><a href="#">2017-2018</a></li>


its work for me

How do I position an image at the bottom of div?

Using flexbox:


<div class="wrapper">
    <img src="pikachu.gif"/>


.wrapper {
    height: 300px;
    width: 300px;
    display: flex;
    align-items: flex-end;

As requested in some comments on another answer, the image can also be horizontally centred with justify-content: center;

How to modify a text file?

The fileinput module of the Python standard library will rewrite a file inplace if you use the inplace=1 parameter:

import sys
import fileinput

# replace all occurrences of 'sit' with 'SIT' and insert a line after the 5th
for i, line in enumerate(fileinput.input('lorem_ipsum.txt', inplace=1)):
    sys.stdout.write(line.replace('sit', 'SIT'))  # replace 'sit' and write
    if i == 4: sys.stdout.write('\n')  # write a blank line after the 5th line

what's the easiest way to put space between 2 side-by-side buttons in

If you are using bootstrap, add ml-3 to your second button:

 <div class="row justify-content-center mt-5">
        <button class="btn btn-secondary" type="button">Button1</button>
        <button class="btn btn-secondary ml-3" type="button">Button2</button>

NoClassDefFoundError while trying to run my jar with java.exe -jar...what's wrong?

if you use external libraries in your program and you try to pack all together in a jar file it's not that simple, because of classpath issues etc.

I'd prefer to use OneJar for this issue.

Timeout on a function call

I ran across this thread when searching for a timeout call on unit tests. I didn't find anything simple in the answers or 3rd party packages so I wrote the decorator below you can drop right into code:

import multiprocessing.pool
import functools

def timeout(max_timeout):
    """Timeout decorator, parameter in seconds."""
    def timeout_decorator(item):
        """Wrap the original function."""
        def func_wrapper(*args, **kwargs):
            """Closure for function."""
            pool = multiprocessing.pool.ThreadPool(processes=1)
            async_result = pool.apply_async(item, args, kwargs)
            # raises a TimeoutError if execution exceeds max_timeout
            return async_result.get(max_timeout)
        return func_wrapper
    return timeout_decorator

Then it's as simple as this to timeout a test or any function you like:

@timeout(5.0)  # if execution takes longer than 5 seconds, raise a TimeoutError
def test_base_regression(self):

Displaying tooltip on mouse hover of a text

As there is nothing in this question (but its age) that requires a solution in Windows.Forms, here is a way to do this in WPF in code-behind.

TextBlock tb = new TextBlock();
tb.Inlines.Add(new Run("Background indicates packet repeat status:"));
tb.Inlines.Add(new LineBreak());
tb.Inlines.Add(new LineBreak());
Run r = new Run("White");
r.Background = Brushes.White;
r.ToolTip = "This word has a White background";
tb.Inlines.Add(new Run("\t= Identical Packet received at this time."));
tb.Inlines.Add(new LineBreak());
r = new Run("SkyBlue");
r.ToolTip = "This word has a SkyBlue background";
r.Background = new SolidColorBrush(Colors.SkyBlue);
tb.Inlines.Add(new Run("\t= Original Packet received at this time."));

myControl.Content = tb;

How to regex in a MySQL query

In my case (Oracle), it's WHERE REGEXP_LIKE(column, 'regex.*'). See here:

SQL Function



This function searches a character column for a pattern. Use this function in the WHERE clause of a query to return rows matching the regular expression you specify.



This function searches for a pattern in a character column and replaces each occurrence of that pattern with the pattern you specify.



This function searches a string for a given occurrence of a regular expression pattern. You specify which occurrence you want to find and the start position to search from. This function returns an integer indicating the position in the string where the match is found.



This function returns the actual substring matching the regular expression pattern you specify.

(Of course, REGEXP_LIKE only matches queries containing the search string, so if you want a complete match, you'll have to use '^$' for a beginning (^) and end ($) match, e.g.: '^regex.*$'.)

Printing Batch file results to a text file

There's nothing wrong with your redirection of standard out to a file. Move and mkdir commands do not output anything. If you really need to have a log trail of those commands, then you'll need to explicitly echo to standard out indicating what you just executed.

The batch file, example:

cd bob
ECHO I just did this: cd bob

Run from command line:

myfile.bat >> out.txt


myfile.bat > out.txt

Java System.out.print formatting

Since you're using formatters for the rest of it, just use DecimalFormat:

import java.text.DecimalFormat;

DecimalFormat xFormat = new DecimalFormat("000")
System.out.print(xFormat.format(x + 1) + " ");

Alternative you could do whole job in whole line using printf:

System.out.printf("%03d %s  %s    %s    \n",  x + 1, // the payment number
formatter.format(monthlyInterest),  // round our interest rate

.htaccess deny from all

Deny from all 

is an .htaccess command(the actual content of that file you are trying to view). Not a denial of being able to edit the file. Just reopen the .htaccess file in the text viewer of choice and make the alterations as you so desire, save it, then reupload it to your folder of choice.

Though I think inadvertently you are blocking even yourself from viewing said application once uploaded.

I would do something like:

order deny,allow
deny from all
allow from

which will deny everyone but the IP in the allow from line, which you would change the IP to match your IP which you can obtain from or similar site.

Run a controller function whenever a view is opened/shown

For example to @Michael Trouw,

inside your controller put this code. this will run everytime when this state is entered or active, you do not need to worry about disabling cache and it's a better approach.

$scope.$on('$ionicView.enter', function(){
        // Any thing you can think of
        alert("This function just ran away");   

You can have more examples of flexibility like $ionicView.beforeEnter -> which runs before a view is shown. And there are some more to it.

Is there a way to 'uniq' by column?

If you want to retain the last one of the duplicates you could use

 tac a.csv | sort -u -t, -r -k1,1 |tac

Which was my requirement


tac will reverse the file line by line

syntax error when using command line in python

I faced a similar problem, on my Windows computer, please do check that you have set the Environment Variables correctly.

To check that Environment variable is set correctly:

  1. Open cmd.exe

  2. Type Python and press return

  3. (a) If it outputs the version of python then the environment variables are set correctly.

    (b) If it outputs "no such program or file name" then your environment variable are not set correctly.

To set environment variable:

  1. goto Computer-> System Properties-> Advanced System Settings -> Set Environment Variables
  2. Goto path in the system variables; append ;C:\Python27 in the end.

If you have correct variables already set; then you are calling the file inside the python interpreter.

What is "Linting"?

Interpreted languages like Python and JavaScript benefit greatly from linting, as these languages don’t have a compiling phase to display errors before execution.

Linters are also useful for code formatting and/or adhering to language specific best practices.

Lately I have been using ESLint for JS/React and will occasionally use it with an airbnb-config file.

AngularJS view not updating on model change

Do not use $scope.$apply() angular already uses it and it can result in this error

$rootScope:inprog Action Already In Progress

if you use twice, use $timeout or interval

Best cross-browser method to capture CTRL+S with JQuery?

I like this little plugin. It needs a bit more cross browser friendliness though.

PHP Fatal error: Cannot access empty property

This way you can create a new object with a custom property name.

$my_property = 'foo';
$value = 'bar';
$a = (object) array($my_property => $value);

Now you can reach it like:

echo $a->foo;  //returns bar

How do I force "git pull" to overwrite local files?

As I often need a fast way to reset current branch on windows through command prompt, here's a fast way:

for /f "tokens=1* delims= " %a in ('git branch^|findstr /b "*"') do @git reset --hard origin/%b

Uncaught TypeError: Cannot read property 'toLowerCase' of undefined

It fails "when trying to execute the function manually" because you have a different 'this'. This will refer not to the thing you have in mind when invoking the method manually, but something else, probably the window object, or whatever context object you have when invoking manually.

C# ASP.NET Send Email via TLS

TLS (Transport Level Security) is the slightly broader term that has replaced SSL (Secure Sockets Layer) in securing HTTP communications. So what you are being asked to do is enable SSL.

In SQL Server, how do I generate a CREATE TABLE statement for a given table?

If you are using management studio and have the query analyzer window open you can drag the table name to the query analyzer window and ... bingo! you get the table script. I've not tried this in SQL2008

Go / golang time.Now().UnixNano() convert to milliseconds?

As @Jono points out in @OneOfOne's answer, the correct answer should take into account the duration of a nanosecond. Eg:

func makeTimestamp() int64 {
    return time.Now().UnixNano() / (int64(time.Millisecond)/int64(time.Nanosecond))

OneOfOne's answer works because time.Nanosecond happens to be 1, and dividing by 1 has no effect. I don't know enough about go to know how likely this is to change in the future, but for the strictly correct answer I would use this function, not OneOfOne's answer. I doubt there is any performance disadvantage as the compiler should be able to optimize this perfectly well.


Another way of looking at this is that both time.Now().UnixNano() and time.Millisecond use the same units (Nanoseconds). As long as that is true, OneOfOne's answer should work perfectly well.

What is the reason for the error message "System cannot find the path specified"?

You just need to:

Step 1: Go home directory of C:\ with typing cd.. (2 times)

Step 2: It appears now C:\>

Step 3: Type dir Windows\System32\run

That's all, it shows complete files & folder details inside target folder.

enter image description here

Details: I used Windows\System32\com folder as example, you should type your own folder name etc. Windows\System32\run

Combine multiple JavaScript files into one JS file

Just combine the text files and then use something like the YUI Compressor.

Files can be easily combined using the command cat *.js > main.js and main.js can then be run through the YUI compressor using java -jar yuicompressor-x.y.z.jar -o main.min.js main.js.

Update Aug 2014

I've now migrated to using Gulp for javascript concatenation and compression as with various plugins and some minimal configuration you can do things like set up dependencies, compile coffeescript etc as well as compressing your JS.

Rotate a div using javascript

Can be pretty easily done assuming you're using jQuery and css3:


<div id="clicker">Click Here</div>
<div id="rotating"></div>


#clicker { 
    width: 100px; 
    height: 100px; 
    background-color: Green; 

#rotating { 
    width: 100px; 
    height: 100px; 
    background-color: Red; 
    margin-top: 50px; 
    -webkit-transition: all 0.3s ease-in-out;
    -moz-transition: all 0.3s ease-in-out;
    -o-transition: all 0.3s ease-in-out;
    transition: all 0.3s ease-in-out;

.rotated { 


$(document).ready(function() {
    $('#clicker').click(function() {

find -exec with multiple commands

A find+xargs answer.

The example below finds all .html files and creates a copy with the .BAK extension appended (e.g. 1.html > 1.html.BAK).

Single command with multiple placeholders

find . -iname "*.html" -print0 | xargs -0 -I {} cp -- "{}" "{}.BAK"

Multiple commands with multiple placeholders

find . -iname "*.html" -print0 | xargs -0 -I {} echo "cp -- {} {}.BAK ; echo {} >> /tmp/log.txt" | sh

# if you need to do anything bash-specific then pipe to bash instead of sh

This command will also work with files that start with a hyphen or contain spaces such as -my file.html thanks to parameter quoting and the -- after cp which signals to cp the end of parameters and the beginning of the actual file names.

-print0 pipes the results with null-byte terminators.

for xargs the -I {} parameter defines {} as the placeholder; you can use whichever placeholder you like; -0 indicates that input items are null-separated.

How to use comparison operators like >, =, < on BigDecimal

Every object of the Class BigDecimal has a method compareTo you can use to compare it to another BigDecimal. The result of compareTo is then compared > 0, == 0 or < 0 depending on what you need. Read the documentation and you will find out.

The operators ==, <, > and so on can only be used on primitive data types like int, long, double or their wrapper classes like Integerand Double.

From the documentation of compareTo:

Compares this BigDecimal with the specified BigDecimal.

Two BigDecimal objects that are equal in value but have a different scale (like 2.0 and 2.00) are considered equal by this method. This method is provided in preference to individual methods for each of the six boolean comparison operators (<, ==, >, >=, !=, <=). The suggested idiom for performing these comparisons is: (x.compareTo(y) <op> 0), where <op> is one of the six comparison operators.

Returns: -1, 0, or 1 as this BigDecimal is numerically less than, equal to, or greater than val.

Selecting a Linux I/O Scheduler

The aim of having the kernel support different ones is that you can try them out without a reboot; you can then run test workloads through the sytsem, measure performance, and then make that the standard one for your app.

On modern server-grade hardware, only the noop one appears to be at all useful. The others seem slower in my tests.

Which font is used in Visual Studio Code Editor and how to change fonts?

Go to Preferences > User Settings. (Alternatively, Ctrl + , / Cmd + , on macOS)

Then you can type inside the JSON object any settings you want to override. User settings are per user. You can also configure workspace settings, which are for the project that you are currently working on.

Here's an example:

// Controls the font family.
"editor.fontFamily": "Consolas",

// Controls the font size.
"editor.fontSize": 13

Useful links:

Are all Spring Framework Java Configuration injection examples buggy?

In your test, you are comparing the two TestParent beans, not the single TestedChild bean.

Also, Spring proxies your @Configuration class so that when you call one of the @Bean annotated methods, it caches the result and always returns the same object on future calls.

See here:

Use virtualenv with Python with Visual Studio Code in Ubuntu

I got this from YouTube Setting up Python Visual Studio Code... Venv

OK, the video really didn't help me all that much, but... the first comment under (by the person who posted the video) makes a lot of sense and is pure gold.

Basically, open up Visual Studio Code' built-in Terminal. Then source <your path>/, the usual way you choose a venv from the command line. I have a predefined Bash function to find & launch the right script file and that worked just fine.

Quoting that YouTube comment directly (all credit to aneuris ap):

(you really only need steps 5-7)

1. Open your command line/terminal and type `pip virtualenv`.
2. Create a folder in which the virtualenv will be placed in.
3. 'cd' to the script folder in the virtualenv and run activate.bat (CMD).
4. Deactivate to turn of the virtualenv (CMD).
5. Open the project in Visual Studio Code and use its built-in terminal to 'cd' to the script folder in you virtualenv.
6. Type source activates (in Visual Studio Code I use the Git terminal).
7. Deactivate to turn off the virtualenv.

As you may notice, he's talking about activate.bat. So, if it works for me on a Mac, and it works on Windows too, chances are it's pretty robust and portable.

Difference between .keystore file and .jks file

You are confused on this.

A keystore is a container of certificates, private keys etc.

There are specifications of what should be the format of this keystore and the predominant is the #PKCS12

JKS is Java's keystore implementation. There is also BKS etc.

These are all keystore types.

So to answer your question:

difference between .keystore files and .jks files

There is none. JKS are keystore files. There is difference though between keystore types. E.g. JKS vs #PKCS12

I want to add a JSONObject to a JSONArray and that JSONArray included in other JSONObject

JSONArray successObject=new JSONArray();
JSONObject dataObject=new JSONObject();

This works for me.

SOAP or REST for Web Services?

SOAP is useful from a tooling perspective because the WSDL is so easily consumed by tools. So, you can get Web Service clients generated for you in your favorite language.

REST plays well with AJAX'y web pages. If you keep your requests simple, you can make service calls directly from your JavaScript, and that comes in very handy. Try to stay away from having any namespaces in your response XML, I've seen browsers choke on those. So, xsi:type is probably not going to work for you, no overly complex XML Schemas.

REST tends to have better performance as well. CPU requirements of the code generating REST responses tend to be lower than what SOAP frameworks exhibit. And, if you have your XML generation ducks lined up on the server side, you can effectively stream XML out to the client. So, imagine you're reading rows of database cursor. As you read a row, you format it as an XML element, and you write that directly out to the service consumer. This way, you don't have to collect all of the database rows in memory before starting to write your XML output - you read and write at the same time. Look into novel templating engines or XSLT to get the streaming to work for REST.

SOAP on the other hand tends to get generated by tool-generated services as a big blob and only then written. This is not an absolute truth, mind you, there are ways to get streaming characteristics out of SOAP, like by using attachments.

My decision making process is as follows: if I want my service to be easily tooled by consumers, and the messages I write will be medium-to-small-ish (10MB or less), and I don't mind burning some extra CPU cycles on the server, I go with SOAP. If I need to serve to AJAX on web browsers, or I need the thing to stream, or my responses are gigantic, I go REST.

Finally, there are lots of great standards built up around SOAP, like WS-Security and getting stateful Web Services, that you can plug in to if you're using the right tools. That kind of stuff really makes a difference, and can help you satisfy some hairy requirements.

How to downgrade php from 5.5 to 5.3

Short answer is no.

XAMPP is normally built around a specific PHP version to ensure plugins and modules are all compatible and working correctly.

If your project specifically needs PHP 5.3 - the cleanest method is simply reinstalling an older version of XAMPP with PHP 5.3 packaged into it.

XAMPP 1.7.7 was their last update before moving off PHP 5.3.

What is the effect of extern "C" in C++?

Just wanted to add a bit of info, since I haven't seen it posted yet.

You'll very often see code in C headers like so:

#ifdef __cplusplus
extern "C" {

// all of your legacy C code here

#ifdef __cplusplus

What this accomplishes is that it allows you to use that C header file with your C++ code, because the macro "__cplusplus" will be defined. But you can also still use it with your legacy C code, where the macro is NOT defined, so it won't see the uniquely C++ construct.

Although, I have also seen C++ code such as:

extern "C" {
#include "legacy_C_header.h"

which I imagine accomplishes much the same thing.

Not sure which way is better, but I have seen both.

Using @property versus getters and setters

In Python you don't use getters or setters or properties just for the fun of it. You first just use attributes and then later, only if needed, eventually migrate to a property without having to change the code using your classes.

There is indeed a lot of code with extension .py that uses getters and setters and inheritance and pointless classes everywhere where e.g. a simple tuple would do, but it's code from people writing in C++ or Java using Python.

That's not Python code.

I want to convert std::string into a const wchar_t *

You can use the ATL text conversion macros to convert a narrow (char) string to a wide (wchar_t) one. For example, to convert a std::string:

#include <atlconv.h>
std::string str = "Hello, world!";
CA2W pszWide(str.c_str());

You can also specify a code page, so if your std::string contains UTF-8 chars you can use:

CA2W pszWide(str.c_str(), CP_UTF8);

Very useful but Windows only.

How to implement history.back() in angular.js

Or you can simply use code :



<a class="back" ng-class="icons">
   <img src="../media/icons/right_circular.png" onClick="javascript:history.go(-1);" />

Uninstall old versions of Ruby gems

Way to clean out any old versions of gems.

sudo gem cleanup

If you just want to see a list of what would be removed you can use:

sudo gem cleanup -d

You can also cleanup just a specific gem by specifying its name:

sudo gem cleanup gemname

for remove specific version like 1.1.9 only

gem uninstall gemname --version 1.1.9

If you still facing some exception to install gem, like:

invalid gem: package is corrupt, exception while verifying: undefined method `size' for nil:NilClass (NoMethodError) in /home/rails/.rvm/gems/ruby-2.1.1@project/cache/nokogiri-

the, you can remove it from cache:

rm /home/rails/.rvm/gems/ruby-2.1.1@project/cache/nokogiri-

For more detail:

What is a constant reference? (not a reference to a constant)

First I think int&const icr=i; is just int& icr = i, Modifier 'const' makes no sense(It just means you cannot make the reference refer to other variable).

const int x = 10;
// int& const y = x; // Compiler error here

Second, constant reference just means you cannot change the value of variable through reference.

const int x = 10;
const int& y = x;
//y = 20; // Compiler error here

Third, Constant references can bind right-value. Compiler will create a temp variable to bind the reference.

float x = 10;
const int& y = x;
const int& z = y + 10;
cout << (long long)&x << endl; //print 348791766212
cout << (long long)&y << endl; //print 348791766276
cout << (long long)&z << endl; //print 348791766340

How do I calculate r-squared using Python and Numpy?

The wikipedia article on r-squareds suggests that it may be used for general model fitting rather than just linear regression.

XSLT getting last element

You need to put the last() indexing on the nodelist result, rather than as part of the selection criteria. Try:


What is the difference between explicit and implicit cursors in Oracle?

Implicit cursors require anonymous buffer memory.

Explicit cursors can be executed again and again by using their name.They are stored in user defined memory space rather than being stored in an anonymous buffer memory and hence can be easily accessed afterwards.

bootstrap jquery event won't fire

Below are the granular details: works while model dialog loading worked to do any thing after loading. post rendering

How do you return a JSON object from a Java Servlet

Gson is very usefull for this. easier even. here is my example:

public class Bean {
private String nombre="juan";
private String apellido="machado";
private List<InnerBean> datosCriticos;

class InnerBean
    private int edad=12;

public Bean() {
    datosCriticos = new ArrayList<>();
    datosCriticos.add(new InnerBean());


    Bean bean = new Bean();
    Gson gson = new Gson();
    String json =gson.toJson(bean);



Have to say people if yours vars are empty when using gson it wont build the json for you.Just the


What is a good game engine that uses Lua?

World of Warcraft's engine seems all right, and it uses Lua. :)

How can I loop over entries in JSON?

Actually, to query the team_name, just add it in brackets to the last line. Apart from that, it seems to work on Python 2.7.3 on command line.

from urllib2 import urlopen
import json

url = ''
response = urlopen(url)
json_obj = json.load(response)

for i in json_obj['team']:
    print i['team_name']

LOAD DATA INFILE Error Code : 13

I have experienced same problem and applied the solutions above.

First of all my test environment are as follows

  • Ubuntu 14.04.3 64bit
  • mysql Ver 14.14 Distrib 5.5.47, for debian-linux-gnu (x86_64) using readline 6.3 (installed by just 'sudo apt-get install ...' command)

My testing results are

i) AppArmor solution only work for /tmp cases.

ii) Following solution works without AppArmor solution. I would like to appreciate Avnish Mehta for his answer.

$ mysql -u root -p --in-file=1
mysql> LOAD DATA LOCAL INFILE '/home/hongsoog/study/mysql/member.dat'
    -> INTO TABLE member_table;

Important three points are

  • start mysql client with --in-file=1 option
  • check all path element have world read permission from the / to data file path. For example, following subpath should be world readable or mysql group readable if INFILE is targeting for '/home/hongsoog/study/mysql/memer.dat'

    • /home
    • /home/hongsoog
    • /home/hongsoog/study/mysql
    • /home/hongsoog/study/mysql/

When you start mysql client WITHOUT "--in-file=1" option and use

, you will get

ERROR 1148 (42000): The used command is not allowed with this MySQL version

In summary, "--in-file=1" option in mysql client command and "LOAD DATA LOCAL INFILE ..." should go hand in hand.

Hope to helpful to anyone.

What does OpenCV's cvWaitKey( ) function do?

. argument of 0 is interpreted as infinite

. in order to drag the highGUI windows, you need to continually call the cv::waitKey() function. eg for static images:

cv::imshow("winname", img);

while(cv::waitKey(1) != 27); // 27 = ascii value of ESC

Selecting only numeric columns from a data frame

If you have many factor variables, you can use select_if funtion. install the dplyr packages. There are many function that separates data by satisfying a condition. you can set the conditions.

Use like this.


Creating Roles in Identity MVC 5

Here we go:

var roleManager = new RoleManager<Microsoft.AspNet.Identity.EntityFramework.IdentityRole>(new RoleStore<IdentityRole>(new ApplicationDbContext()));

   if(!roleManager.RoleExists("ROLE NAME"))
      var role = new Microsoft.AspNet.Identity.EntityFramework.IdentityRole();
      role.Name = "ROLE NAME";


how to get the one entry from hashmap without iterating

This would get a single entry from the map, which about as close as one can get, given 'first' doesn't really apply.

import java.util.*;

public class Friday {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<String, Integer>();

        map.put("code", 10);
        map.put("to", 11);
        map.put("joy", 12);

        if (! map.isEmpty()) {
            Map.Entry<String, Integer> entry = map.entrySet().iterator().next();

VBA - If a cell in column A is not blank the column B equals

Another way (Using Formulas in VBA). I guess this is the shortest VBA code as well?

Sub Sample()
    Dim ws As Worksheet
    Dim lRow As Long

    Set ws = ThisWorkbook.Sheets("Sheet1")

    With ws
        lRow = .Range("A" & .Rows.Count).End(xlUp).Row

        .Range("B1:B" & lRow).Formula = "=If(A1<>"""",""My Text"","""")"
        .Range("B1:B" & lRow).Value = .Range("B1:B" & lRow).Value
    End With
End Sub

How to show android checkbox at right side?

You can add android:layoutDirection="rtl" but it's only available with API 17.

Update .NET web service to use TLS 1.2

For me below worked:

Step 1: Downloaded and installed the web Installer exe from on the application server. Rebooted the application server after installation was completed.

Step 2: Added below changes in the web.config

    <compilation targetFramework="4.6"/> <!-- Changed framework 4.0 to 4.6 -->
    <!--Added this httpRuntime -->
    <httpRuntime targetFramework="4.6" />

Step 3: After completing step 1 and 2, it gave an error, "WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for 'jquery'. Please add a ScriptResourceMapping named jquery(case-sensitive)" and to resolve this error, I added below key in appsettings in my web.config file

      <add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />

Start / Stop a Windows Service from a non-Administrator user account

There is a free GUI Tool ServiceSecurityEditor

Which allows you to edit Windows Service permissions. I have successfully used it to give a non-Administrator user the rights to start and stop a service.

I had used "sc sdset" before I knew about this tool.

ServiceSecurityEditor feels like cheating, it's that easy :)

Why does flexbox stretch my image rather than retaining aspect ratio?

Adding margin to align images:

Since we wanted the image to be left-aligned, we added:

img {
  margin-right: auto;

Similarly for image to be right-aligned, we can add margin-right: auto;. The snippet shows a demo for both types of alignment.

Good Luck...

div {_x000D_
  display:flex; _x000D_
  border: 2px black solid;_x000D_
h1 {_x000D_
  text-align: center;_x000D_
hr {_x000D_
  border: 1px black solid;_x000D_
  width: 100%_x000D_
}_x000D_ {_x000D_
  margin-right: auto;_x000D_
img.two {_x000D_
  margin-left: auto;_x000D_
  <h1>Flex Box</h1>_x000D_
  <hr />_x000D_
  <img src="" class="one" _x000D_
  <img src="" class="two" _x000D_
  <hr />_x000D_

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

You should use

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

Or change

from datetime import datetime


import datetime

Salt and hash a password in Python

As of Python 3.4, the hashlib module in the standard library contains key derivation functions which are "designed for secure password hashing".

So use one of those, like hashlib.pbkdf2_hmac, with a salt generated using os.urandom:

from typing import Tuple
import os
import hashlib
import hmac

def hash_new_password(password: str) -> Tuple[bytes, bytes]:
    Hash the provided password with a randomly-generated salt and return the
    salt and hash to store in the database.
    salt = os.urandom(16)
    pw_hash = hashlib.pbkdf2_hmac('sha256', password.encode(), salt, 100000)
    return salt, pw_hash

def is_correct_password(salt: bytes, pw_hash: bytes, password: str) -> bool:
    Given a previously-stored salt and hash, and a password provided by a user
    trying to log in, check whether the password is correct.
    return hmac.compare_digest(
        hashlib.pbkdf2_hmac('sha256', password.encode(), salt, 100000)

# Example usage:
salt, pw_hash = hash_new_password('correct horse battery staple')
assert is_correct_password(salt, pw_hash, 'correct horse battery staple')
assert not is_correct_password(salt, pw_hash, 'Tr0ub4dor&3')
assert not is_correct_password(salt, pw_hash, 'rosebud')

Note that:

  • The use of a 16-byte salt and 100000 iterations of PBKDF2 match the minimum numbers recommended in the Python docs. Further increasing the number of iterations will make your hashes slower to compute, and therefore more secure.
  • os.urandom always uses a cryptographically secure source of randomness
  • hmac.compare_digest, used in is_correct_password, is basically just the == operator for strings but without the ability to short-circuit, which makes it immune to timing attacks. That probably doesn't really provide any extra security value, but it doesn't hurt, either, so I've gone ahead and used it.

For theory on what makes a good password hash and a list of other functions appropriate for hashing passwords with, see

How can I get the line number which threw exception?

Check this one

StackTrace st = new StackTrace(ex, true);
//Get the first stack frame
StackFrame frame = st.GetFrame(0);

//Get the file name
string fileName = frame.GetFileName();

//Get the method name
string methodName = frame.GetMethod().Name;

//Get the line number from the stack frame
int line = frame.GetFileLineNumber();

//Get the column number
int col = frame.GetFileColumnNumber();

Group by with union mysql select query

This may be what your after:

SELECT Count(Owner_ID), Name
    SELECT M.Owner_ID, O.Name, T.Type
    FROM Transport As T, Owner As O, Motorbike As M
    WHERE T.Type = 'Motorbike'
    AND O.Owner_ID = M.Owner_ID
    AND T.Type_ID = M.Motorbike_ID


    SELECT C.Owner_ID, O.Name, T.Type
    FROM Transport As T, Owner As O, Car As C
    WHERE T.Type = 'Car'
    AND O.Owner_ID = C.Owner_ID
    AND T.Type_ID = C.Car_ID

Run a Python script from another Python script, passing in arguments

Ideally, the Python script you want to run will be set up with code like this near the end:

def main(arg1, arg2, etc):
    # do whatever the script does

if __name__ == "__main__":
    main(sys.argv[1], sys.argv[2], sys.argv[3])

In other words, if the module is called from the command line, it parses the command line options and then calls another function, main(), to do the actual work. (The actual arguments will vary, and the parsing may be more involved.)

If you want to call such a script from another Python script, however, you can simply import it and call modulename.main() directly, rather than going through the operating system.

os.system will work, but it is the roundabout (read "slow") way to do it, as you are starting a whole new Python interpreter process each time for no raisin.

Split string into tokens and save them in an array

You can use strtok()

char string[]=  "abc/qwe/jkh";
char *array[10];
int i=0;

array[i] = strtok(string,"/");

   array[++i] = strtok(NULL,"/");

Querying DynamoDB by date

Approach I followed to solve this problem is by created a Global Secondary Index as below. Not sure if this is the best approach but hopefully if it is useful to someone.

Hash Key                 | Range Key
Date value of CreatedAt  | CreatedAt

Limitation imposed on the HTTP API user to specify the number of days to retrieve data, defaulted to 24 hr.

This way, I can always specify the HashKey as Current date's day and RangeKey can use > and < operators while retrieving. This way the data is also spread across multiple shards.

How to declare and use 1D and 2D byte arrays in Verilog?

Verilog thinks in bits, so reg [7:0] a[0:3] will give you a 4x8 bit array (=4x1 byte array). You get the first byte out of this with a[0]. The third bit of the 2nd byte is a[1][2].

For a 2D array of bytes, first check your simulator/compiler. Older versions (pre '01, I believe) won't support this. Then reg [7:0] a [0:3] [0:3] will give you a 2D array of bytes. A single bit can be accessed with a[2][0][7] for example.

reg [7:0] a [0:3];
reg [7:0] b [0:3] [0:3];

reg [7:0] c;
reg d;

initial begin

   for (int i=0; i<=3; i++) begin
      a[i] = i[7:0];

   c = a[0];
   d = a[1][2]; 

   // using 2D
   for (int i=0; i<=3; i++)
      for (int j=0; j<=3; j++)
          b[i][j] = i*j;  // watch this if you're building hardware


How to use *ngIf else?

In Angular 4, 5 and 6

We can simply create a template reference variable [2] and link that to the else condition inside an *ngIf directive

The possible Syntaxes [1] are:

<!-- Only If condition -->
<div *ngIf="condition">...</div>
<!-- or -->
<ng-template [ngIf]="condition"><div>...</div></ng-template>

<!-- If and else conditions -->
<div *ngIf="condition; else elseBlock">...</div>
<!-- or -->
<ng-template #elseBlock>...</ng-template>

<!-- If-then-else -->
<div *ngIf="condition; then thenBlock else elseBlock"></div>
<ng-template #thenBlock>...</ng-template>
<ng-template #elseBlock>...</ng-template>

<!-- If and else conditions (storing condition value locally) -->
<div *ngIf="condition as value; else elseBlock">{{value}}</div>
<ng-template #elseBlock>...</ng-template>




Error: Execution failed for task ':app:clean'. Unable to delete file

Deleting the directory intermediates is a quick fix for problem.

The directory will be rebuilt when the project is rebuilt.

Understanding implicit in Scala

In scala implicit works as:


Parameter value injector

Extension method

There are 3 types of use of Implicit

  1. Implicitly type conversion : It converts the error producing assignment into intended type

    val x :String = "1"
    val y:Int = x

String is not the sub type of Int , so error happens in line 2. To resolve the error the compiler will look for such a method in the scope which has implicit keyword and takes a String as argument and returns an Int .


implicit def z(a:String):Int = 2

val x :String = "1"

val y:Int = x // compiler will use z here like val y:Int=z(x)

println(y) // result 2  & no error!
  1. Implicitly receiver conversion: We generally by receiver call object's properties, eg. methods or variables . So to call any property by a receiver the property must be the member of that receiver's class/object.

     class Mahadi{
     val haveCar:String ="BMW"

    class Johnny{

    val haveTv:String = "Sony"


   val mahadi = new Mahadi

   mahadi.haveTv // Error happening

Here mahadi.haveTv will produce an error. Because scala compiler will first look for the haveTv property to mahadi receiver. It will not find. Second it will look for a method in scope having implicit keyword which take Mahadi object as argument and returns Johnny object. But it does not have here. So it will create error. But the following is okay.

class Mahadi{

val haveCar:String ="BMW"


class Johnny{

val haveTv:String = "Sony"


val mahadi = new Mahadi

implicit def z(a:Mahadi):Johnny = new Johnny

mahadi.haveTv // compiler will use z here like new Johnny().haveTv

println(mahadi.haveTv)// result Sony & no error
  1. Implicitly parameter injection: If we call a method and do not pass its parameter value, it will cause an error. The scala compiler works like this - first will try to pass value, but it will get no direct value for the parameter.

     def x(a:Int)= a
     x // ERROR happening

Second if the parameter has any implicit keyword it will look for any val in the scope which have the same type of value. If not get it will cause error.

def x(implicit a:Int)= a

x // error happening here

To slove this problem compiler will look for a implicit val having the type of Int because the parameter a has implicit keyword.

def x(implicit a:Int)=a

implicit val z:Int =10

x // compiler will use implicit like this x(z)
println(x) // will result 10 & no error.

Another example:

def l(implicit b:Int)

def x(implicit a:Int)= l(a)

we can also write it like-

def x(implicit a:Int)= l

Because l has a implicit parameter and in scope of method x's body, there is an implicit local variable(parameters are local variables) a which is the parameter of x, so in the body of x method the method-signature l's implicit argument value is filed by the x method's local implicit variable(parameter) a implicitly.


 def x(implicit a:Int)= l

will be in compiler like this

def x(implicit a:Int)= l(a)

Another example:

def c(implicit k:Int):String = k.toString

def x(a:Int => String):String =a

x => c

it will cause error, because c in x{x=>c} needs explicitly-value-passing in argument or implicit val in scope.

So we can make the function literal's parameter explicitly implicit when we call the method x

implicit x => c // the compiler will set the parameter of c like this c(x)

This has been used in action method of Play-Framework

in view folder of app the template is declared like
@()(implicit requestHreader:RequestHeader)

in controller action is like

def index = Action{
implicit request =>



if you do not mention request parameter as implicit explicitly then you must have been written-

def index = Action{
request =>


  1. Extension Method

Think, we want to add new method with Integer object. The name of the method will be meterToCm,

> 1 .meterToCm 
res0 100 

to do this we need to create an implicit class within a object/class/trait . This class can not be a case class.

object Extensions{
    implicit class MeterToCm(meter:Int){
        def  meterToCm={



Note the implicit class will only take one constructor parameter.

Now import the implicit class in the scope you are wanting to use

import  Extensions._

2.meterToCm // result 200