Programs & Examples On #Mod mono

mod_mono is a module for the Apache HTTP Server that allows for hosting of ASP.NET pages and other assemblies on multiple platforms by use of the Mono development platform.

Javascript: set label text

you are doing several things wrong. The explanation follows the corrected code:

<label id="LblTextCount"></label>
<textarea name="text" onKeyPress="checkLength(this, 512, 'LblTextCount')">

Note the quotes around the id.

function checkLength(object, maxlength, label) {
    charsleft = (maxlength - object.value.length);

    // never allow to exceed the specified limit
    if( charsleft < 0 ) {
        object.value = object.value.substring(0, maxlength-1);

    // set the value of charsleft into the label
    document.getElementById(label).innerHTML = charsleft;

First, on your key press event you need to send the label id as a string for it to read correctly. Second, InnerHTML has a lowercase i. Lastly, because you sent the function the string id you can get the element by that id.

Let me know how that works out for you

EDIT Not that by not declaring charsleft as a var, you are implicitly creating a global variable. a better way would be to do the following when declaring it in the function:

var charsleft = ....

How do you find the current user in a Windows environment?

Via powershell (file.ps1) I use the following

$username = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name

It returns the name of the user in the "Domain\Username" format. If you just want the username just write

$username = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name.Split("\")[1]

The advantage is that It works with windows 10 windows 8 server 2016. As far as I remember with also other OS like Win7 etc. (not older) . And yeah via batch you can simply use

 $username = &whoami

Loading custom functions in PowerShell

You have to dot source them:

. .\build_funtions.ps1
. .\build_builddefs.ps1

Note the extra .

This heyscriptingguy article should be of help - How to Reuse Windows PowerShell Functions in Scripts

What is a Maven artifact?

To maven, the build process is arranged as a set of artifacts. Artifacts include:

  1. The plugins that make up Maven itself.
  2. Dependencies that your code depends on.
  3. Anything that your build produces that can, in turn be consumed by something else.

Artifacts live in repositories.

Application.WorksheetFunction.Match method

You are getting this error because the value cannot be found in the range. String or integer doesn't matter. Best thing to do in my experience is to do a check first to see if the value exists.

I used CountIf below, but there is lots of different ways to check existence of a value in a range.

Public Sub test()

Dim rng As Range
Dim aNumber As Long

aNumber = 666

Set rng = Sheet5.Range("B16:B615")

    If Application.WorksheetFunction.CountIf(rng, aNumber) > 0 Then

        rowNum = Application.WorksheetFunction.Match(aNumber, rng, 0)

        MsgBox aNumber & " does not exist in range " & rng.Address
    End If

End Sub


Public Sub test()
    Dim rng As Range
    Dim aNumber As Variant
    Dim rowNum As Long

    aNumber = "2gg"

    Set rng = Sheet5.Range("B1:B20")

    If Not IsError(Application.Match(aNumber, rng, 0)) Then
        rowNum = Application.Match(aNumber, rng, 0)
        MsgBox rowNum
        MsgBox "error"
    End If
End Sub


Public Sub test()
    Dim rng As Range
    Dim aNumber As Variant
    Dim rowNum As Variant

    aNumber = "2gg"

    Set rng = Sheet5.Range("B1:B20")

    rowNum = Application.Match(aNumber, rng, 0)

    If Not IsError(rowNum) Then
        MsgBox rowNum
        MsgBox "error"
    End If
End Sub

Get first element from a dictionary

For anyone coming to this that wants a linq-less way to get an element from a dictionary

var d = new Dictionary<string, string>();
d.Add("a", "b");
var e = d.GetEnumerator();
var anElement = e.Current;
// anElement/e.Current is a KeyValuePair<string,string>
// where Key = "a", Value = "b"

I'm not sure if this is implementation specific, but if your Dictionary doesn't have any elements, Current will contain a KeyValuePair<string, string> where both the key and value are null.

(I looked at the logic behind linq's First method to come up with this, and tested it via LinqPad 4)

Change div height on button click

Just a silly mistake use quote('') in '200px'


<body >
    <button type="button" onClick = "document.getElementById('chartdiv').style.height = '200px';">Click Me!</button>
    <div id="chartdiv" style="width: 100%; height: 50px; background-color:#E8EDF2"></div>

How to get textLabel of selected row in swift?

Swift 4

To get the label of the selected row:

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let cell = tableView.cellForRow(at: indexPath) as! TableViewCell

To get the label of the deselected row:

func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
    let cell = tableView.cellForRow(at: indexPath) as! TableViewCell

How to set image name in Dockerfile?

How to build an image with custom name without using yml file:

docker build -t image_name .

How to run a container with custom name:

docker run -d --name container_name image_name

Check if one list contains element from the other

With java 8, we can do like below to check if one list contains any element of other list

boolean var = -> list2.contains(element)).findFirst().isPresent();

Why does typeof array with objects return "object" and not "array"?

Quoting the spec

15.4 Array Objects

Array objects give special treatment to a certain class of property names. A property name P (in the form of a String value) is an array index if and only if ToString(ToUint32(P)) is equal to P and ToUint32(P) is not equal to 2^32-1. A property whose property name is an array index is also called an element. Every Array object has a length property whose value is always a nonnegative integer less than 2^32. The value of the length property is numerically greater than the name of every property whose name is an array index; whenever a property of an Array object is created or changed, other properties are adjusted as necessary to maintain this invariant. Specifically, whenever a property is added whose name is an array index, the length property is changed, if necessary, to be one more than the numeric value of that array index; and whenever the length property is changed, every property whose name is an array index whose value is not smaller than the new length is automatically deleted. This constraint applies only to own properties of an Array object and is unaffected by length or array index properties that may be inherited from its prototypes.

And here's a table for typeof

enter image description here

To add some background, there are two data types in JavaScript:

  1. Primitive Data types - This includes null, undefined, string, boolean, number and object.
  2. Derived data types/Special Objects - These include functions, arrays and regular expressions. And yes, these are all derived from "Object" in JavaScript.

An object in JavaScript is similar in structure to the associative array/dictionary seen in most object oriented languages - i.e., it has a set of key-value pairs.

An array can be considered to be an object with the following properties/keys:

  1. Length - This can be 0 or above (non-negative).
  2. The array indices. By this, I mean "0", "1", "2", etc are all properties of array object.

Hope this helped shed more light on why typeof Array returns an object. Cheers!

Bootstrap 4, How do I center-align a button?

Use text-center class in the parent container for Bootstrap 4

How can I specify the schema to run an sql file against in the Postgresql command line

I was facing similar problems trying to do some dat import on an intermediate schema (that later we move on to the final one). As we rely on things like extensions (for example PostGIS), the "run_insert" sql file did not fully solved the problem.

After a while, we've found that at least with Postgres 9.3 the solution is far easier... just create your SQL script always specifying the schema when refering to the table:

CREATE TABLE "my_schema"."my_table" (...); COPY "my_schema"."my_table" (...) FROM stdin;

This way using psql -f xxxxx works perfectly, and you don't need to change search_paths nor use intermediate files (and won't hit extension schema problems).

What is the equivalent of ngShow and ngHide in Angular 2+?

Use hidden like you bind any model with control and specify css for it:


<input type="button" class="view form-control" value="View" [hidden]="true" />


[hidden] {
   display: none;

JavaScript object: access variable property by name as string

Since I was helped with my project by the answer above (I asked a duplicate question and was referred here), I am submitting an answer (my test code) for bracket notation when nesting within the var:

  <script type="text/javascript">_x000D_
    function displayFile(whatOption, whatColor) {_x000D_
      var Test01 = {_x000D_
        rectangle: {_x000D_
          red: "RectangleRedFile",_x000D_
          blue: "RectangleBlueFile"_x000D_
        square: {_x000D_
          red: "SquareRedFile",_x000D_
          blue: "SquareBlueFile"_x000D_
      var filename = Test01[whatOption][whatColor];_x000D_
  <p onclick="displayFile('rectangle', 'red')">[ Rec Red ]</p>_x000D_
  <p onclick="displayFile('square', 'blue')">[ Sq Blue ]</p>_x000D_
  <p onclick="displayFile('square', 'red')">[ Sq Red ]</p>_x000D_

getting a checkbox array value from POST

Check out the implode() function as an alternative. This will convert the array into a list. The first param is how you want the items separated. Here I have used a comma with a space after it.

$invite = implode(', ', $_POST['invite']);
echo $invite;

How can I run a windows batch file but hide the command window?

1,Download the bat to exe converter and install it 2,Run the bat to exe application 3,Download .pco images if you want to make good looking exe 4,specify the bat file location(c:\my.bat) 5,Specify the location for saving the exe(ex:c:/my.exe) 6,Select Version Information Tab 7,Choose the icon file (downloaded .pco image) 8,if you want fill the information like version,comapny name etc 9,change the tab to option 10,Select the invisible application(This will hide the command prompt while running the application) 11,Choose 32 bit(if you select 64 bit exe will work only in 32 bit OS) 12,Compile 13,Copy the exe to the location where bat file executed properly 14,Run the exe

twitter bootstrap typeahead ajax example

All of the responses refer to BootStrap 2 typeahead, which is no longer present in BootStrap 3.

For anyone else directed here looking for an AJAX example using the new post-Bootstrap Twitter typeahead.js, here's a working example. The syntax is a little different:

  hint: true,
  highlight: true,
  minLength: 1
  limit: 12,
  async: true,
  source: function (query, processSync, processAsync) {
    processSync(['This suggestion appears immediately', 'This one too']);
    return $.ajax({
      url: "/ajax/myfilter.php", 
      type: 'GET',
      data: {query: query},
      dataType: 'json',
      success: function (json) {
        // in this example, json is simply an array of strings
        return processAsync(json);

This example uses both synchronous (the call to processSync) and asynchronous suggestion, so you'd see some options appear immediately, then others are added. You can just use one or the other.

There are lots of bindable events and some very powerful options, including working with objects rather than strings, in which case you'd use your own custom display function to render your items as text.

How to validate a url in Python? (Malformed or not)

All of the above solutions recognize a string like "," as valid. This solution always works as it should

import re

# URL-link validation
ip_middle_octet = u"(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5]))"
ip_last_octet = u"(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))"

URL_PATTERN = re.compile(
                        # protocol identifier
                        # user:pass authentication
                        # IP address exclusion
                        # private & local networks
                        u"(?:(?:10|127)" + ip_middle_octet + u"{2}" + ip_last_octet + u")|"
                        u"(?:(?:169\.254|192\.168)" + ip_middle_octet + ip_last_octet + u")|"
                        u"(?:172\.(?:1[6-9]|2\d|3[0-1])" + ip_middle_octet + ip_last_octet + u"))"
                        # IP address dotted notation octets
                        # excludes loopback network
                        # excludes reserved space >=
                        # excludes network & broadcast addresses
                        # (first & last IP address of each class)
                        u"" + ip_middle_octet + u"{2}"
                        u"" + ip_last_octet + u")"
                        # host name
                        # domain name
                        # TLD identifier
                        # port number
                        # resource path
                        # query string
                        re.UNICODE | re.IGNORECASE
def url_validate(url):   
    """ URL string validation
    return re.compile(URL_PATTERN).match(url)

How to get Printer Info in .NET?

As dowski suggested, you could use WMI to get printer properties. The following code displays all properties for a given printer name. Among them you will find: PrinterStatus, Comment, Location, DriverName, PortName, etc.

using System.Management;


string printerName = "YourPrinterName";
string query = string.Format("SELECT * from Win32_Printer WHERE Name LIKE '%{0}'", printerName);

using (ManagementObjectSearcher searcher = new ManagementObjectSearcher(query))
using (ManagementObjectCollection coll = searcher.Get())
        foreach (ManagementObject printer in coll)
            foreach (PropertyData property in printer.Properties)
                Console.WriteLine(string.Format("{0}: {1}", property.Name, property.Value));
    catch (ManagementException ex)

Difference between -XX:+UseParallelGC and -XX:+UseParNewGC

Using -XX:+UseParNewGC along with -XX:+UseConcMarkSweepGC, will cause higher pause time for Minor GCs, when compared to -XX:+UseParallelGC.

This is because, promotion of objects from Young to Old Generation will require running a Best-Fit algorithm (due to old generation fragmentation) to find an address for this object.
Running such an algorithm is not required when using -XX:+UseParallelGC, as +UseParallelGC can be configured only with MarkandCompact Collector, in which case there is no fragmentation.

Do you use source control for your database items?

RedGate is great, we generate new snapshots when database changes are made (a tiny binary file) and keep that file in the projects as a resource. Whenever we need to update the database, we use RedGate's toolkit to update the database, as well as being able to create new databases from empty ones.

RedGate also makes Data snapshots, while I haven't personally worked with them, they are just as robust.

How much should a function trust another function

The addEdge is trusting more than the correction of the addNode method. It's also trusting that the addNode method has been invoked by other method. I'd recommend to include check if m is not null.

Regular Expression: Allow letters, numbers, and spaces (with at least one letter or number)

$("#ValuationName").bind("keypress", function (event) {
    if (event.charCode!=0) {
        var regex = new RegExp("^[a-zA-Z ]+$");
        var key = String.fromCharCode(!event.charCode ? event.which : event.charCode);
        if (!regex.test(key)) {
            return false;

How can I multiply all items in a list together with Python?

I personally like this for a function that multiplies all elements of a generic list together:

def multiply(n):
    total = 1
    for i in range(0, len(n)):
        total *= n[i]
    print total

It's compact, uses simple things (a variable and a for loop), and feels intuitive to me (it looks like how I'd think of the problem, just take one, multiply it, then multiply by the next, and so on!)

Android Linear Layout - How to Keep Element At Bottom Of View?

You should put the parameter gravity to bottom not in the textview but in the Linear Layout. Like this:


Leverage browser caching, how on apache or .htaccess?

I was doing the same thing a couple days ago. Added this to my .htaccess file:

ExpiresActive On
ExpiresByType image/gif A2592000
ExpiresByType image/jpeg A2592000
ExpiresByType image/jpg A2592000
ExpiresByType image/png A2592000
ExpiresByType image/x-icon A2592000
ExpiresByType text/css A86400
ExpiresByType text/javascript A86400
ExpiresByType application/x-shockwave-flash A2592000
<FilesMatch "\.(gif¦jpe?g¦png¦ico¦css¦js¦swf)$">
Header set Cache-Control "public"

And now when I run google speed page, leverage browwer caching is no longer a high priority.

Hope this helps.

Can I underline text in an Android layout?

A simple and flexible solution in xml:

  android:background="@color/your_color" />

How can I Insert data into SQL Server using VBNet

Function ExtSql(ByVal sql As String) As Boolean
    Dim cnn As SqlConnection
    Dim cmd As SqlCommand
    cnn = New SqlConnection(My.Settings.mySqlConnectionString)
        cmd = New SqlCommand
        cmd.Connection = cnn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = sql
    Catch ex As Exception
        Return False
    End Try
    Return True
End Function

Set mouse focus and move cursor to end of input using jQuery

The answer from scorpion9 works. Just to make it more clear see my code below,

<script src="~/js/jquery.js"></script> 
<script type="text/javascript">
    $(function () {
        var input = $("#SomeId");
        var tmpStr = input.val();

How to convert an object to a byte array in C#

To access the memory of an object directly (to do a "core dump") you'll need to head into unsafe code.

If you want something more compact than BinaryWriter or a raw memory dump will give you, then you need to write some custom serialisation code that extracts the critical information from the object and packs it in an optimal way.

edit P.S. It's very easy to wrap the BinaryWriter approach into a DeflateStream to compress the data, which will usually roughly halve the size of the data.

Right mime type for SVG images with fonts embedded

There's only one registered mediatype for SVG, and that's the one you listed, image/svg+xml. You can of course serve SVG as XML too, though browsers tend to behave differently in some scenarios if you do, for example I've seen cases where SVG used in CSS backgrounds fail to display unless served with the image/svg+xml mediatype.

Replace a value if null or undefined in JavaScript

Logical nullish assignment, 2020+ solution

A new operator has been added, ??=. This is equivalent to value = value ?? defaultValue.

||= and &&= are similar, links below.

This checks if left side is undefined or null, short-circuiting if already defined. If not, the left side is assigned the right-side value.

Basic Examples

let a          // undefined
let b = null
let c = false

a ??= true  // true
b ??= true  // true
c ??= true  // false

// Equivalent to
a = a ?? true

Object/Array Examples

let x = ["foo"]
let y = { foo: "fizz" }

x[0] ??= "bar"  // "foo"
x[1] ??= "bar"  // "bar" ??= "buzz"  // "fizz" ??= "buzz"  // "buzz"

x  // Array [ "foo", "bar" ]
y  // Object { foo: "fizz", bar: "buzz" }

Functional Example

function config(options) {
    options.duration ??= 100
    options.speed ??= 25
    return options

config({ duration: 555 })   // { duration: 555, speed: 25 }
config({})                  // { duration: 100, speed: 25 }
config({ duration: null })  // { duration: 100, speed: 25 }

??= Browser Support Nov 2020 - 77%

??= Mozilla Documentation

||= Mozilla Documentation

&&= Mozilla Documentation

Resolve absolute path from relative path and/or file name

Without having to have another batch file to pass arguments to (and use the argument operators), you can use FOR /F:

FOR /F %%i IN ("..\relativePath") DO echo absolute path: %%~fi

where the i in %%~fi is the variable defined at /F %%i. eg. if you changed that to /F %%a then the last part would be %%~fa.

To do the same thing right at the command prompt (and not in a batch file) replace %% with %...

Rounding numbers to 2 digits after comma

UPDATE: Keep in mind, at the time the answer was initially written in 2010, the bellow function toFixed() worked slightly different. toFixed() seems to do some rounding now, but not in the strictly mathematical manner. So be careful with it. Do your tests... The method described bellow will do rounding well, as mathematician would expect.

  • toFixed() - method converts a number into a string, keeping a specified number of decimals. It does not actually rounds up a number, it truncates the number.
  • Math.round(n) - rounds a number to the nearest integer. Thus turning:

0.5 -> 1; 0.05 -> 0

so if you want to round, say number 0.55555, only to the second decimal place; you can do the following(this is step-by-step concept):

  • 0.55555 * 100 = 55.555
  • Math.Round(55.555) -> 56.000
  • 56.000 / 100 = 0.56000
  • (0.56000).toFixed(2) -> 0.56

and this is the code:

(Math.round(number * 100)/100).toFixed(2);

PHP Regex to check date is in YYYY-MM-DD format

I was searching "how to validate date" and found this solution, Its old but i ll share below method that can be use to validate date in php,

checkdate('01', '31', '2019')

How to disable/enable a button with a checkbox if checked

I recommend using jQuery as it will do all the heavy lifting for you. The code is fairly trivial.

$('input:checkbox').click(function () {
  if ($(this).is(':checked')) {
    $('#sendNewSms').click(function () {
      return false;
  } else {

The trick is to override the 'click' event and effectively disable it. You can also follow it up with some CSS magic to make it look "disabled". Here is the code in JavaScript in case you need it. It's not perfect but it gets the point across.

var clickEvent = function () {
  return false;
document.getElementById('#checkbox').onclick(function () {
  if (document.getElementById('#checkbox').checked) {
  } else {
      .removeEventListener('click', clickEvent, false);

What do 1.#INF00, -1.#IND00 and -1.#IND mean?

From IEEE floating-point exceptions in C++ :

This page will answer the following questions.

  • My program just printed out 1.#IND or 1.#INF (on Windows) or nan or inf (on Linux). What happened?
  • How can I tell if a number is really a number and not a NaN or an infinity?
  • How can I find out more details at runtime about kinds of NaNs and infinities?
  • Do you have any sample code to show how this works?
  • Where can I learn more?

These questions have to do with floating point exceptions. If you get some strange non-numeric output where you're expecting a number, you've either exceeded the finite limits of floating point arithmetic or you've asked for some result that is undefined. To keep things simple, I'll stick to working with the double floating point type. Similar remarks hold for float types.

Debugging 1.#IND, 1.#INF, nan, and inf

If your operation would generate a larger positive number than could be stored in a double, the operation will return 1.#INF on Windows or inf on Linux. Similarly your code will return -1.#INF or -inf if the result would be a negative number too large to store in a double. Dividing a positive number by zero produces a positive infinity and dividing a negative number by zero produces a negative infinity. Example code at the end of this page will demonstrate some operations that produce infinities.

Some operations don't make mathematical sense, such as taking the square root of a negative number. (Yes, this operation makes sense in the context of complex numbers, but a double represents a real number and so there is no double to represent the result.) The same is true for logarithms of negative numbers. Both sqrt(-1.0) and log(-1.0) would return a NaN, the generic term for a "number" that is "not a number". Windows displays a NaN as -1.#IND ("IND" for "indeterminate") while Linux displays nan. Other operations that would return a NaN include 0/0, 0*8, and 8/8. See the sample code below for examples.

In short, if you get 1.#INF or inf, look for overflow or division by zero. If you get 1.#IND or nan, look for illegal operations. Maybe you simply have a bug. If it's more subtle and you have something that is difficult to compute, see Avoiding Overflow, Underflow, and Loss of Precision. That article gives tricks for computing results that have intermediate steps overflow if computed directly.

How can we stop a running java process through Windows cmd?

Open the windows cmd. First list all the java processes,

jps -m

now get the name and run below command,

for /f "tokens=1" %i in ('jps -m ^| find "Name_of_the_process"') do ( taskkill /F /PID %i )

or simply kill the process ID

taskkill /F /PID <ProcessID>

sample :)

C:\Users\tk>jps -m
15176 MessagingMain
18072 SoapUI-5.4.0.exe
15164 Jps -m
3420 org.eclipse.equinox.launcher_1.3.201.v20161025-1711.jar -os win32 -ws win32 -arch x86_64 -showsplash -launcher C:\Users\tk\eclipse\jee-neon\eclipse\eclipse.exe -name Eclipse --launcher.library C:\Users\tk\.p2\pool\plugins\org.eclipse.equinox.launcher.win32.win32.x86_64_1.1.401.v20161122-1740\eclipse_1617.dll -startup C:\Users\tk\eclipse\jee-neon\eclipse\\plugins/org.eclipse.equinox.launcher_1.3.201.v20161025-1711.jar --launcher.appendVmargs -exitdata 4b20_d0 -product org.eclipse.epp.package.jee.product -vm C:/Program Files/Java/jre1.8.0_131/bin/javaw.exe -vmargs -Dosgi.requiredJavaVersion=1.8 -XX:+UseG1GC -XX:+UseStringDeduplication -Dosgi.requiredJavaVersion=1.8 -Xms256m -Xmx1024m -Declipse.p2.max.threads=10 -Doomph.update.url= -Doomph.redirection.index.redirection=index:/-> -jar C:\Users\tk\


C:\Users\tk>for /f "tokens=1" %i in ('jps -m ^| find "MessagingMain"') do ( taskkill /F /PID %i )

C:\Users\tk>(taskkill /F /PID 15176  )
SUCCESS: The process with PID 15176 has been terminated.


C:\Users\tk>taskkill /F /PID 15176 
SUCCESS: The process with PID 15176 has been terminated.

How do I revert all local changes in Git managed project to previous state?

This question is more about broader repository reset / revert, but in case if you're interested in reverting individual change - I've added similar answer in here:

Answers to questions:

  • How to revert individual change with or without change preserving in git history

  • How to return back to old version to restart from same state

How do I hide an element on a click event anywhere outside of the element?

$(document).mouseup(function (e)
    var mydiv = $('div#mydiv');
    if (! && mydiv.has( === 0){

Index inside map() function index:

One can access the index via the second argument of the callback function. Here is an example:

const array = [1, 2, 3, 4];_x000D_
const map =, index) => {_x000D_
  return x + index;_x000D_

Other arguments of

  • The third argument of the callback function exposes the array on which map was called upon
  • The second argument of is a object which will be the this value for the callback function. Keep in mind that you have to use the regular function keyword in order to declare the callback since an arrow function doesn't have its own binding to the this keyword.

For example:

const array = [1, 2, 3, 4];_x000D_
const thisObj = {prop1: 1}_x000D_
const map = function (x, index, array) {_x000D_
}, thisObj);

How to sanity check a date in Java

looks like SimpleDateFormat is not checking the pattern strictly even after setLenient(false); method is applied on it, so i have used below method to validate if the date inputted is valid date or not as per supplied pattern.

import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
public boolean isValidFormat(String dateString, String pattern) {
    boolean valid = true;
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
    try {
    } catch (DateTimeParseException e) {
        valid = false;
    return valid;

align divs to the bottom of their container

Why can't you use absolute positioning? Vertical-align does not work (except for tables). Make your container's position: relative. Then absolutely position the internal divs using bottom: 0; Should work like a charm.

EDIT By zoidberg (i will update the answer instead)

<div style="position:relative; border: 1px solid red;width: 40px; height: 40px;">
   <div style="border:1px solid green;position: absolute; bottom: 0; left: 0; width: 20px; height: 20px;"></div>
   <div style="border:1px solid blue;position: absolute; bottom: 0; left: 20px; width: 20px height: 20px;"></div>

How do you dynamically allocate a matrix?

Try boost::multi_array

#include <boost/multi_array.hpp>

int main(){
    int rows;
    int cols;
    boost::multi_array<int, 2> arr(boost::extents[rows][cols] ;

IntelliJ IDEA shows errors when using Spring's @Autowired annotation

Remove .iml file from all your project module and next go to File -> Invalidate Caches/Restart

PermissionError: [WinError 5] Access is denied python using moviepy to write gif

I got the same error when an imported library was trying to create a directory at path "./logs/".

It turns out that the library was trying to create it at the wrong location, i.e. inside the folder of my python interpreter instead of the base project directory. I solved the issue by setting the "Working directory" path to my project folder inside the "Run Configurations" menu of PyCharm. If instead you're using the terminal to run your code, maybe you just need to move inside the project folder before running it.

TypeScript: Property does not exist on type '{}'

let propertyName= data['propertyName'];

Trying to get Laravel 5 email to work

You are getting an authentication error because the username and password in your config file is setup wrong.

Change this:

'username' => env('[email protected]'),
'password' => env('MyPassword'),

To this:

'username' => env('MAIL_USERNAME'),
'password' => env('MAIL_PASSWORD'),

The env method checks your .env file. In your .env file you call these MAIL_USERNAME, so that's what you need to pass to the env method.

One troubleshooting tip: add dd(Config::get('mail')); so that you can see the actual generated config. This will help you spot issues like this, and know exactly what information Laravel is going to try and use. So you may want to stop that in your test route temporarily to examine what you have:

Route::get('test', function()

VB.NET - If string contains "value1" or "value2"

You need this

If strMyString.Contains("Something") or strMyString.Contains("Something2") Then
End if

Run certain code every n seconds

Save yourself a schizophrenic episode and use the Advanced Python scheduler:

The code is so simple:

from apscheduler.scheduler import Scheduler

sched = Scheduler()

def some_job():
    print "Every 10 seconds"

sched.add_interval_job(some_job, seconds = 10)


PowerShell: Format-Table without headers

Here is how I solve this. I just pipe the output to Out-String and then pass that output to the .NET Trim function:

(gci | ft -HideTableHeaders | Out-String).Trim()

This will strip out the line breaks before and after the table.

You can also use TrimStart to just take care of the header's line break if you still want the trailing line breaks.

(gci | ft -HideTableHeaders | Out-String).TrimStart()

JQuery create new select option

A really simple way to do this...

// create the option
var opt = $("<option>").val("myvalue").text("my text");

//append option to the select element

This could be done in lots of ways, even in a single line if really you want to.

OnChange event handler for radio button (INPUT type="radio") doesn't work as one value

var rad = document.myForm.myRadios;_x000D_
var prev = null;_x000D_
for (var i = 0; i < rad.length; i++) {_x000D_
    rad[i].addEventListener('change', function() {_x000D_
        (prev) ? console.log(prev.value): null;_x000D_
        if (this !== prev) {_x000D_
            prev = this;_x000D_
<form name="myForm">_x000D_
  <input type="radio" name="myRadios"  value="1" />_x000D_
  <input type="radio" name="myRadios"  value="2" />_x000D_

Here's a JSFiddle demo:

How can I hide a checkbox in html?

You need to add the element type to the class, otherwise it will not work.

.hide-checkbox { display: none }        /* This will not work! */_x000D_
input.hide-checkbox { display: none }   /* But this will. */ 
<input class="hide-checkbox" id="checkbox" />_x000D_
<label for="checkbox">Checkbox</label>

It looks too simple, but try it out!

How to compare arrays in C#?

You're comparing the object references, and they are not the same. You need to compare the array contents.

.NET2 solution

An option is iterating through the array elements and call Equals() for each element. Remember that you need to override the Equals() method for the array elements, if they are not the same object reference.

An alternative is using this generic method to compare two generic arrays:

static bool ArraysEqual<T>(T[] a1, T[] a2)
    if (ReferenceEquals(a1, a2))
        return true;

    if (a1 == null || a2 == null)
        return false;

    if (a1.Length != a2.Length)
        return false;

    var comparer = EqualityComparer<T>.Default;
    for (int i = 0; i < a1.Length; i++)
        if (!comparer.Equals(a1[i], a2[i])) return false;
    return true;

.NET 3.5 or higher solution

Or use SequenceEqual if Linq is available for you (.NET Framework >= 3.5)

How to lose margin/padding in UITextView?

Building off some of the good answers already given, here is a purely Storyboard / Interface Builder-based solution that works in iOS 7.0+

Set the UITextView's User Defined Runtime Attributes for the following keys:


Interface Builder

Seeking useful Eclipse Java code templates

I know I am kicking a dead post, but wanted to share this for completion sake:

A correct version of singleton generation template, that overcomes the flawed double-checked locking design (discussed above and mentioned else where)

Singleton Creation Template: Name this createsingleton

static enum Singleton {

    private static final ${enclosing_type} singleton = new ${enclosing_type}();

    public ${enclosing_type} getSingleton() {
        return singleton;

To access singletons generated using above:

Singleton reference Template: Name this getsingleton:

${type} ${newName} = ${type}.Singleton.INSTANCE.getSingleton();

ScalaTest in sbt: is there a way to run a single test without tags?

This is now supported (since ScalaTest 2.1.3) within interactive mode:

testOnly *MySuite -- -z foo

to run only the tests whose name includes the substring "foo".

For exact match rather than substring, use -t instead of -z.

get unique machine id

I second Blindy's suggestion to use the MAC address of the (first?) network adapter. Yes, the MAC address can be spoofed, but this has side effects (you don't want two PCs with the same MAC address in the same network), and it's something that "your average pirate" won't do just to be able to use your software. Considering that there's no 100% solution against software piracy, the MAC address is a good compromise, IMO.

Note, however, that the address will change when the user adds, replaces or removes a network card (or replaces his old PC altogether), so be prepared to help your customers and give them a new key when they change their hardware configuration.

Python: import cx_Oracle ImportError: No module named cx_Oracle error is thown

To access Oracle from python you need (additionally) the cx_Oracle module. The module must be located either in the system python path or you have to set the PYTHONPATH appropriate.

SQL Server CTE and recursion example

I haven't tested your code, just tried to help you understand how it operates in comment;

  cteReports (EmpID, FirstName, LastName, MgrID, EmpLevel)
-->>>>>>>>>>Block 1>>>>>>>>>>>>>>>>>
-- In a rCTE, this block is called an [Anchor]
-- The query finds all root nodes as described by WHERE ManagerID IS NULL
    SELECT EmployeeID, FirstName, LastName, ManagerID, 1
    FROM Employees
-->>>>>>>>>>Block 1>>>>>>>>>>>>>>>>>
-->>>>>>>>>>Block 2>>>>>>>>>>>>>>>>>    
-- This is the recursive expression of the rCTE
-- On the first "execution" it will query data in [Employees],
-- relative to the [Anchor] above.
-- This will produce a resultset, we will call it R{1} and it is JOINed to [Employees]
-- as defined by the hierarchy
-- Subsequent "executions" of this block will reference R{n-1}
    SELECT e.EmployeeID, e.FirstName, e.LastName, e.ManagerID,
      r.EmpLevel + 1
    FROM Employees e
      INNER JOIN cteReports r
        ON e.ManagerID = r.EmpID
-->>>>>>>>>>Block 2>>>>>>>>>>>>>>>>>
  FirstName + ' ' + LastName AS FullName,
  (SELECT FirstName + ' ' + LastName FROM Employees
    WHERE EmployeeID = cteReports.MgrID) AS Manager
FROM cteReports
ORDER BY EmpLevel, MgrID

The simplest example of a recursive CTE I can think of to illustrate its operation is;

;WITH Numbers AS
    SELECT n = 1
    SELECT n + 1
    FROM Numbers
    WHERE n+1 <= 10
FROM Numbers

Q 1) how value of N is getting incremented. if value is assign to N every time then N value can be incremented but only first time N value was initialize.

A1: In this case, N is not a variable. N is an alias. It is the equivalent of SELECT 1 AS N. It is a syntax of personal preference. There are 2 main methods of aliasing columns in a CTE in T-SQL. I've included the analog of a simple CTE in Excel to try and illustrate in a more familiar way what is happening.

--  Outside
;WITH CTE (MyColName) AS
    SELECT 1
-- Inside
    SELECT 1 AS MyColName
    -- Or
    SELECT MyColName = 1  
    -- Etc...


Q 2) now here about CTE and recursion of employee relation the moment i add two manager and add few more employee under second manager then problem start. i want to display first manager detail and in the next rows only those employee details will come those who are subordinate of that manager


Does this code answer your question?

-- Synthesise table with non-recursive CTE
;WITH Employee (ID, Name, MgrID) AS 
    SELECT 1,      'Keith',      NULL   UNION ALL
    SELECT 2,      'Josh',       1      UNION ALL
    SELECT 3,      'Robin',      1      UNION ALL
    SELECT 4,      'Raja',       2      UNION ALL
    SELECT 5,      'Tridip',     NULL   UNION ALL
    SELECT 6,      'Arijit',     5      UNION ALL
    SELECT 7,      'Amit',       5      UNION ALL
    SELECT 8,      'Dev',        6   
-- Recursive CTE - Chained to the above CTE
,Hierarchy AS
    --  Anchor
            ,nLevel = 1
            ,Family = ROW_NUMBER() OVER (ORDER BY Name)
    FROM Employee

    --  Recursive query
    FROM Employee   E
    JOIN Hierarchy  H ON E.MgrID = H.ID
FROM Hierarchy
ORDER BY Family, nLevel

Another one sql with tree structure

SELECT ID,space(nLevel+
                    (CASE WHEN nLevel > 1 THEN nLevel ELSE 0 END)
FROM Hierarchy
ORDER BY Family, nLevel

how to add values to an array of objects dynamically in javascript?

You have to instantiate the object first. The simplest way is:

var lab =["1","2","3"];
var val = [42,55,51,22];
var data = [];
for(var i=0; i<4; i++)  {
    data.push({label: lab[i], value: val[i]});

Or an other, less concise way, but closer to your original code:

for(var i=0; i<4; i++)  {
   data[i] = {};              // creates a new object
   data[i].label = lab[i];
   data[i].value = val[i];    

array() will not create a new array (unless you defined that function). Either Array() or new Array() or just [].

I recommend to read the MDN JavaScript Guide.

Difference between Spring MVC and Spring Boot

Spring MVC and Spring Boot are exist for the different purpose. So, it is not wise to compare each other as the contenders.

What is Spring Boot?

Spring Boot is a framework for packaging the spring application with sensible defaults. What does this mean?. You are developing a web application using Spring MVC, Spring Data, Hibernate and Tomcat. How do you package and deploy this application to your web server. As of now, we have to manually write the configurations, XML files, etc. for deploying to web server.

Spring Boot does that for you with Zero XML configuration in your project. Believe me, you don't need deployment descriptor, web server, etc. Spring Boot is magical framework that bundles all the dependencies for you. Finally your web application will be a standalone JAR file with embeded servers.

If you are still confused how this works, please read about microservice framework development using spring boot.

What is Spring MVC?

It is a traditional web application framework that helps you to build web applications. It is similar to Struts framework.

A Spring MVC is a Java framework which is used to build web applications. It follows the Model-View-Controller design pattern. It implements all the basic features of a core spring framework like Inversion of Control, Dependency Injection.

A Spring MVC provides an elegant solution to use MVC in spring framework by the help of DispatcherServlet. Here, DispatcherServlet is a class that receives the incoming request and maps it to the right resource such as controllers, models, and views.

I hope this helps you to understand the difference.

How can I view an old version of a file with Git?

You can use git show with a path from the root of the repository (./ or ../ for relative pathing):

$ git show REVISION:path/to/file

Replace REVISION with your actual revision (could be a Git commit SHA, a tag name, a branch name, a relative commit name, or any other way of identifying a commit in Git)

For example, to view the version of file <repository-root>/src/main.c from 4 commits ago, use:

$ git show HEAD~4:src/main.c

Git for Windows requires forward slashes even in paths relative to the current directory. For more information, check out the man page for git-show.

Difference between HashMap and Map in Java..?

HashMap is an implementation of Map. Map is just an interface for any type of map.

Using Javamail to connect to Gmail smtp server ignores specified port and tries to use 25

For anyone looking for a full solution, I got this working with the following code based on maximdim's answer:

import javax.mail.*
import javax.mail.internet.*

private class SMTPAuthenticator extends Authenticator
    public PasswordAuthentication getPasswordAuthentication()
        return new PasswordAuthentication('[email protected]', 'test1234');

def  d_email = "[email protected]",
        d_uname = "email",
        d_password = "password",
        d_host = "",
        d_port  = "465", //465,587
        m_to = "[email protected]",
        m_subject = "Testing",
        m_text = "Hey, this is the testing email."

def props = new Properties()
props.put("mail.smtp.user", d_email)
props.put("", d_host)
props.put("mail.smtp.port", d_port)
props.put("mail.smtp.debug", "true");
props.put("mail.smtp.auth", "true")
props.put("mail.smtp.socketFactory.port", d_port)
props.put("mail.smtp.socketFactory.class", "")
props.put("mail.smtp.socketFactory.fallback", "false")

def auth = new SMTPAuthenticator()
def session = Session.getInstance(props, auth)

def msg = new MimeMessage(session)
msg.setFrom(new InternetAddress(d_email))
msg.addRecipient(Message.RecipientType.TO, new InternetAddress(m_to))

Transport transport = session.getTransport("smtps");
transport.connect(d_host, 465, d_uname, d_password);
transport.sendMessage(msg, msg.getAllRecipients());

Install dependencies globally and locally using package.json

All modules from package.json are installed to ./node_modules/

I couldn't find this explicitly stated but this is the package.json reference for NPM.

How to set TextView textStyle such as bold, italic

And as explained here Android Developers String Resources if you need to use parameters in your styled text resource, you have to escape the opening brackets

<string name="welcome_messages">Hello, %1$s! You have &lt;b>%2$d new messages&lt;/b>.</string>

and call formatHtml(string)

Resources res = getResources();
String text = String.format(res.getString(R.string.welcome_messages), username, mailCount);
CharSequence styledText = Html.fromHtml(text);

Change default timeout for mocha

By default Mocha will read a file named test/mocha.opts that can contain command line arguments. So you could create such a file that contains:

--timeout 5000

Whenever you run Mocha at the command line, it will read this file and set a timeout of 5 seconds by default.

Another way which may be better depending on your situation is to set it like this in a top level describe call in your test file:

describe("something", function () {

    // tests...

This would allow you to set a timeout only on a per-file basis.

You could use both methods if you want a global default of 5000 but set something different for some files.

Note that you cannot generally use an arrow function if you are going to call this.timeout (or access any other member of this that Mocha sets for you). For instance, this will usually not work:

describe("something", () => {
    this.timeout(5000); //will not work

    // tests...

This is because an arrow function takes this from the scope the function appears in. Mocha will call the function with a good value for this but that value is not passed inside the arrow function. The documentation for Mocha says on this topic:

Passing arrow functions (“lambdas”) to Mocha is discouraged. Due to the lexical binding of this, such functions are unable to access the Mocha context. cannot identify image file - Python?

Seems like a Permissions Issue. I was facing the same error. But when I ran it from the root account, it worked. So either give the read permission to the file using chmod (in linux) or run your script after logging in as a root user.

How to establish ssh key pair when "Host key verification failed"

Its means your remote host key was changed (May be host password change),

Your terminal suggested to execute this command as root user

$ ssh-keygen -f "/root/.ssh/known_hosts" -R []:4231

You have to remove that host name from hosts list on your pc/server. Copy that suggested command and execute as a root user.

$ sudo su                                                            // Login as a root user

$ ssh-keygen -f "/root/.ssh/known_hosts" -R []:4231   // Terminal suggested command execute here
Host []:4231 found: line 16 type ECDSA
/root/.ssh/known_hosts updated.
Original contents retained as /root/.ssh/known_hosts.old

$ exit                                                               // Exist from root user

$ sudo ssh [email protected] -p 4231                              // Try again

I Hope this works.

Property 'value' does not exist on type EventTarget in TypeScript

Passing HTMLInputElement as a generic to the event type should work too:

onUpdatingServerName(event: React.ChangeEvent<HTMLInputElement>) {
  this.newserverName =;

Regex number between 1 and 100

1 - 1000 with leading 0's


it should not accept 0, 00, 000, 0000.

it should accept 1, 01, 001, 0001

How to determine SSL cert expiration date from a PEM encoded certificate?

If you just want to know whether the certificate has expired (or will do so within the next N seconds), the -checkend <seconds> option to openssl x509 will tell you:

if openssl x509 -checkend 86400 -noout -in file.pem
  echo "Certificate is good for another day!"
  echo "Certificate has expired or will do so within 24 hours!"
  echo "(or is invalid/not found)"

This saves having to do date/time comparisons yourself.

openssl will return an exit code of 0 (zero) if the certificate has not expired and will not do so for the next 86400 seconds, in the example above. If the certificate will have expired or has already done so - or some other error like an invalid/nonexistent file - the return code is 1.

(Of course, it assumes the time/date is set correctly)

Be aware that older versions of openssl have a bug which means if the time specified in checkend is too large, 0 will always be returned (

Run Button is Disabled in Android Studio

if you're importing an eclipse project to android studio, you'll also encounter the same issue as above. Double Check if grade>app has apply plugin: '' on the top as sometimes android studio imports it as a library.

Is there a way to use PhantomJS in Python?

The easiest way to use PhantomJS in python is via Selenium. The simplest installation method is

  1. Install NodeJS
  2. Using Node's package manager install phantomjs: npm -g install phantomjs-prebuilt
  3. install selenium (in your virtualenv, if you are using that)

After installation, you may use phantom as simple as:

from selenium import webdriver

driver = webdriver.PhantomJS() # or add to your PATH
driver.set_window_size(1024, 768) # optional
driver.save_screenshot('screen.png') # save a screenshot to disk
sbtn = driver.find_element_by_css_selector('button.gbqfba')

If your system path environment variable isn't set correctly, you'll need to specify the exact path as an argument to webdriver.PhantomJS(). Replace this:

driver = webdriver.PhantomJS() # or add to your PATH

... with the following:

driver = webdriver.PhantomJS(executable_path='/usr/local/lib/node_modules/phantomjs/lib/phantom/bin/phantomjs')


Which selector do I need to select an option by its text?

This worked for me: $("#test").find("option:contains('abc')");

Using a custom (ttf) font in CSS

You need to use the css-property font-face to declare your font. Have a look at this fancy site:


@font-face {
  font-family: MyHelvetica;
  src: local("Helvetica Neue Bold"),
  font-weight: bold;

See also: MDN @font-face

What is the best method of handling currency/money?

Using Virtual Attributes (Link to revised(paid) Railscast) you can store your price_in_cents in an integer column and add a virtual attribute price_in_dollars in your product model as a getter and setter.

# Add a price_in_cents integer column
$ rails g migration add_price_in_cents_to_products price_in_cents:integer

# Use virtual attributes in your Product model
# app/models/product.rb

def price_in_dollars
  price_in_cents.to_d/100 if price_in_cents

def price_in_dollars=(dollars)
  self.price_in_cents = dollars.to_d*100 if dollars.present?

Source: RailsCasts #016: Virtual Attributes: Virtual attributes are a clean way to add form fields that do not map directly to the database. Here I show how to handle validations, associations, and more.

How can I remove a character from a string using JavaScript?

A simple functional javascript way would be

mystring = mystring.split('/r').join('/')

simple, fast, it replace globally and no need for functions or prototypes

npm install error - MSB3428: Could not load the Visual C++ component "VCBuild.exe"

I tried the above suggested npm install --global --production windows-build-tools but found that the installation was always hanging forever.

I managed to fix the problem by installing Node.js 8 instead of Node.js 10.

How to dynamic filter options of <select > with jQuery?

Much simpler code then most of the other solutions. Look for the text (case insensitive) and use CSS to hide/show the contents. Much better than storing a copy of the data.

Pass into this method the id of the select box, and id of the input containing a filter.

function FilterSelectList(selectListId, filterId)
    var filter = $("#" + filterId).val();
    filter = filter.toUpperCase();

    var options = $("#" + selectListId + " option");
    for (var i = 0; i < options.length; i++)
       if (options[i].text.toUpperCase().indexOf(filter) < 0)
           $(options[i]).css("display", "none");
           $(options[i]).css("display", "block");

Using new line(\n) in string and rendering the same in HTML

Set your css in the table cell to


document.body.innerHTML = 'First line\nSecond line\nThird line';
body{ white-space:pre-wrap; }

Reading Space separated input in python

For python 3 it would be like this n,m,p=map(int,input().split())

How to scroll to an element in jQuery?



It'll scroll the window to the item.

 var scrollPos =  $("#branch1").offset().top;

Reliable method to get machine's MAC address in C#

You could go for the NIC ID:

 foreach (NetworkInterface nic in NetworkInterface.GetAllNetworkInterfaces()) {
     if (nic.OperationalStatus == OperationalStatus.Up){
         if (nic.Id == "yay!")

It's not the MAC address, but it is a unique identifier, if that's what you're looking for.

Angular JS POST request not sending JSON data

    url: '/api/user',
    method: "POST",
    data: angular.toJson(yourData)
}).success(function (data, status, headers, config) {
    $scope.users = data.users;
}).error(function (data, status, headers, config) {
    $scope.status = status + ' ' + headers;

How do I exit from a function?

Use the return keyword.

return; //exit this event

Position a CSS background image x pixels from the right?

Just put the pixel padding into the image - add 10px or whatever to the canvas size of the image in photohop and align it right in CSS.

How do I make a checkbox required on an ASP.NET form?

javascript function for client side validation (using jQuery)...

function CheckBoxRequired_ClientValidate(sender, e)
    e.IsValid = jQuery(".AcceptedAgreement input:checkbox").is(':checked');

code-behind for server side validation...

protected void CheckBoxRequired_ServerValidate(object sender, ServerValidateEventArgs e)
    e.IsValid = MyCheckBox.Checked;

ASP.Net code for the checkbox & validator...

<asp:CheckBox runat="server" ID="MyCheckBox" CssClass="AcceptedAgreement" />
<asp:CustomValidator runat="server" ID="CheckBoxRequired" EnableClientScript="true"
    ClientValidationFunction="CheckBoxRequired_ClientValidate">You must select this box to proceed.</asp:CustomValidator>

and finally, in your postback - whether from a button or whatever...

if (Page.IsValid)
    // your code here...

The APK file does not exist on disk

In Android Studio 3.1.1 select File | Sync Project with Gradle Files.

In Android Studio 3, select File | Synchronize.

Then run your project again.

Get Environment Variable from Docker Container

The downside of using docker exec is that it requires a running container, so docker inspect -f might be handy if you're unsure a container is running.

Example #1. Output a list of space-separated environment variables in the specified container:

docker inspect -f \
   '{{range $index, $value := .Config.Env}}{{$value}} {{end}}' container_name

the output will look like this:

ENV_VAR1=value1 ENV_VAR2=value2 ENV_VAR3=value3

Example #2. Output each env var on new line and grep the needed items, for example, the mysql container's settings could be retrieved like this:

docker inspect -f \
    '{{range $index, $value := .Config.Env}}{{println $value}}{{end}}' \
    container_name | grep MYSQL_

will output:


Example #3. Let's modify the example above to get a bash friendly output which can be directly used in your scripts:

docker inspect -f \
   '{{range $index, $value := .Config.Env}}export {{$value}}{{println}}{{end}}' \
   container_name | grep MYSQL

will output:

export MYSQL_PASSWORD=secret
export MYSQL_ROOT_PASSWORD=supersecret
export MYSQL_USER=demo
export MYSQL_DATABASE=demodb
export MYSQL_MAJOR=5.5
export MYSQL_VERSION=5.5.52

If you want to dive deeper, then go to Go’s text/template package documentation with all the details of the format.

REST URI convention - Singular or plural name of resource while creating it

To me plurals manipulate the collection, whereas singulars manipulate the item inside that collection.

Collection allows the methods GET / POST / DELETE

Item allows the methods GET / PUT / DELETE

For example

POST on /students will add a new student in the school.

DELETE on /students will remove all the students in the school.

DELETE on /student/123 will remove student 123 from the school.

It might feel like unimportant but some engineers sometimes forget the id. If the route was always plural and performed a DELETE, you might accidentally wipe your data. Whereas missing the id on the singular will return a 404 route not found.

To further expand the example if the API was supposed to expose multiple schools, then something like

DELETE on /school/abc/students will remove all the students in the school abc.

Choosing the right word sometimes is a challenge on its own, but I like to maintain plurality for the collection. E.g. cart_items or cart/items feels right. In contrast deleting cart, deletes the cart object it self and not the items within the cart ;).

MySQL Orderby a number, Nulls last

You can coalesce your NULLs in the ORDER BY statement:

select * from tablename
where <conditions>
order by
    coalesce(position, 0) ASC, 
    id DESC

If you want the NULLs to sort on the bottom, try coalesce(position, 100000). (Make the second number bigger than all of the other position's in the db.)

How do I remove leading whitespace in Python?

The function strip will remove whitespace from the beginning and end of a string.

my_str = "   text "
my_str = my_str.strip()

will set my_str to "text".

Assembly code vs Machine code vs Object code?

Assembly code is discussed here.

"An assembly language is a low-level language for programming computers. It implements a symbolic representation of the numeric machine codes and other constants needed to program a particular CPU architecture."

Machine code is discussed here.

"Machine code or machine language is a system of instructions and data executed directly by a computer's central processing unit."

Basically, assembler code is the language and it is translated to object code (the native code that the CPU runs) by an assembler (analogous to a compiler).

How do I find the last column with data?

I think we can modify the UsedRange code from @Readify's answer above to get the last used column even if the starting columns are blank or not.

So this lColumn = ws.UsedRange.Columns.Count modified to

this lColumn = ws.UsedRange.Column + ws.UsedRange.Columns.Count - 1 will give reliable results always

enter image description here

?Sheet1.UsedRange.Column + Sheet1.UsedRange.Columns.Count - 1

Above line Yields 9 in the immediate window.

Difference between Return and Break statements

Break statement will break the whole loop and execute the code after loop and Return will not execute the code after that return statement and execute the loop with next increment.


for(int i=0;i<5;i++){

output: 0 1


for(int i=0;i<5;i++)

output: 0 1 3 4

Amazon Linux: apt-get: command not found

There can be 2 issues :=

1. Your are trying the command in machine that does not support apt-get command
because apt-get is suitable for Linux based Ubuntu machines; for MAC, try
apt-get equivalent such as Brew

2. The other issue can be that your installation was not completed properly So

The short answer:

Re-install Ubuntu from a Live CD or USB.

The long version:

The long version would be a waste of your time: your system will never
be clean, but if you insist you could try:

==> Copying everything (missing) except for the /home folder from the Live
CD/USB to your HDD.


==> Do a re-install/repair over the broken system again with the Live
CD / USB stick.


==> Download the deb file for apt-get and install as explained on above posts.
I would definitely go for a fresh new install as there are so many things to
do and so little time.

jQuery UI themes and HTML tables

Why noy just use the theme styles in the table? i.e.

  <thead class="ui-widget-header">
  <tbody class="ui-widget-content">

And you don't need to use any code...

Which equals operator (== vs ===) should be used in JavaScript comparisons?

1 == "1"    =>    true(define)
true === "true"    => false(undefined compare the type of variable)
Case 1
if(true === "true"){
  echo 'true'
 echo 'false undefined'
Ans :- false undefined because case 1 is check data type also with ===  
Case 2
if(1 == "1"){
  echo 'true define'
 echo 'false undefined'
Ans :- true define undefined because case 2 is not check data type with ==

http://localhost:50070 does not work HADOOP


namenode -format

see namenode and datanode are running and browse


If localhost:50070 is still not working, then you need to allows ports. So, check

netstat -anp | grep 50070

DB query builder toArray() laravel 4

If you prefer to use Query Builder instead of Eloquent here is the solutions

$result = DB::table('user')->where('name',=,'Jhon')->get();

First Solution

$array = (array) $result;

Second Solution

$array = get_object_vars($result);

Third Solution

$array = json_decode(json_encode($result), true);

hope it may help

How to use Python's pip to download and keep the zipped files for a package?

In version 7.1.2 pip downloads the wheel of a package (if available) with the following:

pip install package -d /path/to/downloaded/file

The following downloads a source distribution:

pip install package -d /path/to/downloaded/file --no-binary :all:

These download the dependencies as well, if pip is aware of them (e.g., if pip show package lists them).


As noted by Anton Khodak, pip download command is preferred since version 8. In the above examples this means that /path/to/downloaded/file needs to be given with option -d, so replacing install with download works.

What is the best way to convert an array to a hash in Ruby

Simply use Hash[*array_variable.flatten]

For example:

a1 = ['apple', 1, 'banana', 2]
h1 = Hash[*a1.flatten(1)]
puts "h1: #{h1.inspect}"

a2 = [['apple', 1], ['banana', 2]]
h2 = Hash[*a2.flatten(1)]
puts "h2: #{h2.inspect}"

Using Array#flatten(1) limits the recursion so Array keys and values work as expected.

MySql Error: 1364 Field 'display_name' doesn't have default value

MySQL is most likely in STRICT mode, which isn't necessarily a bad thing, as you'll identify bugs/issues early and not just blindly think everything is working as you intended.

Change the column to allow null:

ALTER TABLE `x` CHANGE `display_name` `display_name` TEXT NULL

or, give it a default value as empty string:

ALTER TABLE `x` CHANGE `display_name` `display_name` TEXT NOT NULL DEFAULT ''

Blurring an image via CSS?

You can use CSS3 filters. They are relatively easy to implement, though are only supported on webkit at the minute. Samsung Galaxy 2's browser should support though, as I think that's a webkit browser?

"No Content-Security-Policy meta tag found." error in my phonegap application

You have to add a CSP meta tag in the head section of your app's index.html

As per

Content Security Policy

Controls which network requests (images, XHRs, etc) are allowed to be made (via webview directly).

On Android and iOS, the network request whitelist (see above) is not able to filter all types of requests (e.g. <video> & WebSockets are not blocked). So, in addition to the whitelist, you should use a Content Security Policy <meta> tag on all of your pages.

On Android, support for CSP within the system webview starts with KitKat (but is available on all versions using Crosswalk WebView).

Here are some example CSP declarations for your .html pages:

<!-- Good default declaration:
    * gap: is required only on iOS (when using UIWebView) and is needed for JS->native communication
    * is required only on Android and is needed for TalkBack to function properly
    * Disables use of eval() and inline scripts in order to mitigate risk of XSS vulnerabilities. To change this:
        * Enable inline JS: add 'unsafe-inline' to default-src
        * Enable eval(): add 'unsafe-eval' to default-src
<meta http-equiv="Content-Security-Policy" content="default-src 'self' data: gap:; style-src 'self' 'unsafe-inline'; media-src *">

<!-- Allow requests to -->
<meta http-equiv="Content-Security-Policy" content="default-src 'self'">

<!-- Enable all requests, inline styles, and eval() -->
<meta http-equiv="Content-Security-Policy" content="default-src *; style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline' 'unsafe-eval'">

<!-- Allow XHRs via https only -->
<meta http-equiv="Content-Security-Policy" content="default-src 'self' https:">

<!-- Allow iframe to -->
<meta http-equiv="Content-Security-Policy" content="default-src 'self'; frame-src 'self'">

The definitive guide to form-based website authentication

First, a strong caveat that this answer is not the best fit for this exact question. It should definitely not be the top answer!

I will go ahead and mention Mozilla’s proposed BrowserID (or perhaps more precisely, the Verified Email Protocol) in the spirit of finding an upgrade path to better approaches to authentication in the future.

I’ll summarize it this way:

  1. Mozilla is a nonprofit with values that align well with finding good solutions to this problem.
  2. The reality today is that most websites use form-based authentication
  3. Form-based authentication has a big drawback, which is an increased risk of phishing. Users are asked to enter sensitive information into an area controlled by a remote entity, rather than an area controlled by their User Agent (browser).
  4. Since browsers are implicitly trusted (the whole idea of a User Agent is to act on behalf of the User), they can help improve this situation.
  5. The primary force holding back progress here is deployment deadlock. Solutions must be decomposed into steps which provide some incremental benefit on their own.
  6. The simplest decentralized method for expressing an identity that is built into the internet infrastructure is the domain name.
  7. As a second level of expressing identity, each domain manages its own set of accounts.
  8. The form “account@domain” is concise and supported by a wide range of protocols and URI schemes. Such an identifier is, of course, most universally recognized as an email address.
  9. Email providers are already the de-facto primary identity providers online. Current password reset flows usually let you take control of an account if you can prove that you control that account’s associated email address.
  10. The Verified Email Protocol was proposed to provide a secure method, based on public key cryptography, for streamlining the process of proving to domain B that you have an account on domain A.
  11. For browsers that don’t support the Verified Email Protocol (currently all of them), Mozilla provides a shim which implements the protocol in client-side JavaScript code.
  12. For email services that don’t support the Verified Email Protocol, the protocol allows third parties to act as a trusted intermediary, asserting that they’ve verified a user’s ownership of an account. It is not desirable to have a large number of such third parties; this capability is intended only to allow an upgrade path, and it is much preferred that email services provide these assertions themselves.
  13. Mozilla offers their own service to act like such a trusted third party. Service Providers (that is, Relying Parties) implementing the Verified Email Protocol may choose to trust Mozilla's assertions or not. Mozilla’s service verifies users’ account ownership using the conventional means of sending an email with a confirmation link.
  14. Service Providers may, of course, offer this protocol as an option in addition to any other method(s) of authentication they might wish to offer.
  15. A big user interface benefit being sought here is the “identity selector”. When a user visits a site and chooses to authenticate, their browser shows them a selection of email addresses (“personal”, “work”, “political activism”, etc.) they may use to identify themselves to the site.
  16. Another big user interface benefit being sought as part of this effort is helping the browser know more about the user’s session – who they’re signed in as currently, primarily – so it may display that in the browser chrome.
  17. Because of the distributed nature of this system, it avoids lock-in to major sites like Facebook, Twitter, Google, etc. Any individual can own their own domain and therefore act as their own identity provider.

This is not strictly “form-based authentication for websites”. But it is an effort to transition from the current norm of form-based authentication to something more secure: browser-supported authentication.

OnClick in Excel VBA

In order to trap repeated clicks on the same cell, you need to move the focus to a different cell, so that each time you click, you are in fact moving the selection.

The code below will select the top left cell visible on the screen, when you click on any cell. Obviously, it has the flaw that it won't trap a click on the top left cell, but that can be managed (eg by selecting the top right cell if the activecell is the top left).

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
  'put your code here to process the selection, then..
  ActiveWindow.VisibleRange.Cells(1, 1).Select
End Sub

How to set custom JsonSerializerSettings for Json.NET in ASP.NET Web API?

You can specify JsonSerializerSettings for each JsonConvert, and you can set a global default.

Single JsonConvert with an overload:

// Option #1.
JsonSerializerSettings config = new JsonSerializerSettings { ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore };
this.json = JsonConvert.SerializeObject(YourObject, Formatting.Indented, config);

// Option #2 (inline).
JsonConvert.SerializeObject(YourObject, Formatting.Indented,
    new JsonSerializerSettings() {
        ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore

Global Setting with code in Application_Start() in Global.asax.cs:

JsonConvert.DefaultSettings = () => new JsonSerializerSettings {
     Formatting = Newtonsoft.Json.Formatting.Indented,
     ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore


git: Switch branch and ignore any changes without committing

switching to a new branch losing changes:

git checkout -b YOUR_NEW_BRANCH_NAME --force

switching to an existing branch losing changes:

git checkout YOUR_BRANCH --force

How to get a certain element in a list, given the position?

std::list<Object> l; 
std::list<Object>::iterator ptr;
int i;

for( i = 0 , ptr = l.begin() ; i < N && ptr != l.end() ; i++ , ptr++ );

if( ptr == l.end() ) {
    // list too short  
} else {
    // 'ptr' points to N-th element of list

How to fix "Headers already sent" error in PHP

A simple tip: A simple space (or invisible special char) in your script, right before the very first <?php tag, can cause this ! Especially when you are working in a team and somebody is using a "weak" IDE or has messed around in the files with strange text editors.

I have seen these things ;)

Stacked Tabs in Bootstrap 3

The Bootstrap team seems to have removed it. See here: . @Skelly's answer involves custom css which I didn't want to do so I used the grid system and nav-pills. It worked fine and looked great. The code looks like so:

<div class="row">

  <!-- Navigation Buttons -->
  <div class="col-md-3">
    <ul class="nav nav-pills nav-stacked" id="myTabs">
      <li class="active"><a href="#home" data-toggle="pill">Home</a></li>
      <li><a href="#profile" data-toggle="pill">Profile</a></li>
      <li><a href="#messages" data-toggle="pill">Messages</a></li>

  <!-- Content -->
  <div class="col-md-9">
    <div class="tab-content">
      <div class="tab-pane active" id="home">Home</div>
      <div class="tab-pane" id="profile">Profile</div>
      <div class="tab-pane" id="messages">Messages</div>


You can see this in action here:

[Update] @SeanK gives the option of not having to enable the nav-pills through Javascript and instead using data-toggle="pill". Check it out here: Thanks Sean.

initialize a vector to zeros C++/C++11

You don't need initialization lists for that:

std::vector<int> vector1(length, 0);
std::vector<double> vector2(length, 0.0);

Spring MVC UTF-8 Encoding

Ok guys I found the reason for my encoding issue.

The fault was in my build process. I didn't tell Maven in my pom.xml file to build the project with the UTF-8 encoding. Therefor Maven just took the default encoding from my system which is MacRoman and build it with the MacRoman encoding.

Luckily Maven is warning you about this when building your project (BUT there is a good chance that the warning disappears to fast from your screen because of all the other messages).

Here is the property you need to set in the pom.xml file:


Thank you guys for all your help. Without you guys I wouldn't be able to figure this out!

Difference between int and double

int and double have different semantics. Consider division. 1/2 is 0, 1.0/2.0 is 0.5. In any given situation, one of those answers will be right and the other wrong.

That said, there are programming languages, such as JavaScript, in which 64-bit float is the only numeric data type. You have to explicitly truncate some division results to get the same semantics as Java int. Languages such as Java that support integer types make truncation automatic for integer variables.

In addition to having different semantics from double, int arithmetic is generally faster, and the smaller size (32 bits vs. 64 bits) leads to more efficient use of caches and data transfer bandwidth.

How can I simulate mobile devices and debug in Firefox Browser?

You could use the Firefox add-on User Agent Overrider. With this add-on you can use whatever user agent you want, for examlpe:

Firefox 28/Android: Mozilla/5.0 (Android; Mobile; rv:28.0) Gecko/24.0 Firefox/28.0

If your website detects mobile devices through the user agent then you can test your layout this way.

Update Nov '17:

Due to the release of Firefox 57 and the introduction of web extension this add-on sadly is no longer available. Alternatively you can edit the Firefox preference general.useragent.override in your configuration:

  1. In the address bar type about:config
  2. Search for general.useragent.override
  3. If the preference doesn't exist, right-click on the about:config page, click New, then select String
  4. Name the new preference general.useragent.override
  5. Set the value to the user agent you want

How to change title of Activity in Android?

If you want it one time & let system handle the rest (not dynamic) then do like this in your manifest file:

        android:theme="@style/AppTheme" >
            android:label="@string/app_name_full" > //This is my custom title name on activity. <- The question is about this one.
            <intent-filter android:label="@string/app_launcher_name" > //This is my custom Icon title name (launcher name that you see in android apps/homescreen)
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

JSON character encoding - is UTF-8 well-supported by browsers or should I use numeric escape sequences?

ASCII isn't in it any more. Using UTF-8 encoding means that you aren't using ASCII encoding. What you should use the escaping mechanism for is what the RFC says:

All Unicode characters may be placed within the quotation marks except for the characters that must be escaped: quotation mark, reverse solidus, and the control characters (U+0000 through U+001F)

Script @php artisan package:discover handling the post-autoload-dump event returned with error code 1

in my case the problem was into outdated "../bootstrap/cache/packages.php and services.php"

I have had to. drop those files and rerun composer install...

  Erroneous data format for unserializing 'Symfony\Component\Routing\CompiledRoute'

Script @php artisan package:discover handling the post-autoload-dump event returned with error code 1

How to create a global variable?

if you want to use it in all of your classes you can use:

public var yourVariable = "something"

if you want to use just in one class you can use :

var yourVariable = "something"

How to upload and parse a CSV file in php

This can be done in a much simpler manner now.

$tmpName = $_FILES['csv']['tmp_name'];
$csvAsArray = array_map('str_getcsv', file($tmpName));

This will return you a parsed array of your CSV data. Then you can just loop through it using a foreach statement.

What is ViewModel in MVC?

View model a is simple class which can contain more than one class property. We use it to inherit all the required properties, e.g. I have two classes Student and Subject

Public class Student
public int Id {get; set;}
public string Name {get; set;}
Public class Subject
public int SubjectID {get; set;}
public string SubjectName {get; set;}

Now we want to display records student's Name and Subject's Name in View (In MVC), but it's not possible to add more than one classes like:

 @model ProjectName.Model.Student  
 @model ProjectName.Model.Subject

the code above will throw an error...

Now we create one class and can give it any name, but this format "XyzViewModel" will make it easier to understand. It is inheritance concept. Now we create a third class with the following name:

public class StudentViewModel:Subject
public int ID {get; set;}
public string Name {get; set;}

Now we use this ViewModel in View

@model ProjectName.Model.StudentViewModel

Now we are able to access all the properties of StudentViewModel and inherited class in View.

Error: 'int' object is not subscriptable - Python

It would be a lot more simple just to do this;

name = input("What's your name? ")
age = int(input("How old are you? "))
print ("Hi,{0} you will be 21 in {1} years.".format(name, 21 - age))`

Html ordered list 1.1, 1.2 (Nested counters and scope) not working

After going through other answers I came up with this, just apply class nested-counter-list to root ol tag:

sass code:

ol.nested-counter-list {
  counter-reset: item;

  li {
    display: block;

    &::before {
      content: counters(item, ".") ". ";
      counter-increment: item;
      font-weight: bold;

  ol {
    counter-reset: item;

    & > li {
      display: block;

      &::before {
        content: counters(item, ".") " ";
        counter-increment: item;
        font-weight: bold;

css code:

ol.nested-counter-list {
  counter-reset: item;
ol.nested-counter-list li {
  display: block;
ol.nested-counter-list li::before {
  content: counters(item, ".") ". ";
  counter-increment: item;
  font-weight: bold;
ol.nested-counter-list ol {
  counter-reset: item;
ol.nested-counter-list ol > li {
  display: block;
ol.nested-counter-list ol > li::before {
  content: counters(item, ".") " ";
  counter-increment: item;
  font-weight: bold;

ol.nested-counter-list {
  counter-reset: item;

ol.nested-counter-list li {
  display: block;

ol.nested-counter-list li::before {
  content: counters(item, ".") ". ";
  counter-increment: item;
  font-weight: bold;

ol.nested-counter-list ol {
  counter-reset: item;

ol.nested-counter-list ol>li {
  display: block;

ol.nested-counter-list ol>li::before {
  content: counters(item, ".") " ";
  counter-increment: item;
  font-weight: bold;
<ol class="nested-counter-list">

And if you need trailing . at the end of the nested list's counters use this:

ol.nested-counter-list {
  counter-reset: item;

ol.nested-counter-list li {
  display: block;

ol.nested-counter-list li::before {
  content: counters(item, ".") ". ";
  counter-increment: item;
  font-weight: bold;

ol.nested-counter-list ol {
  counter-reset: item;
<ol class="nested-counter-list">

Exception 'open failed: EACCES (Permission denied)' on Android

Maybe the answer is this:

on the API >= 23 devices, if you install app (the app is not system app), you should check the storage permission in "Setting - applications", there is permission list for every app, you should check it on! try

How to avoid the "Circular view path" exception with Spring MVC test

if you have not used a @RequestBody and are using only @Controller, simplest way to fix this is using @RestController instead of @Controller

Can I hide the HTML5 number input’s spin box?

On Firefox for Ubuntu, just using

    input[type='number'] {

did the trick for me.


input::-webkit-inner-spin-button {
    -webkit-appearance: none;

Would lead me to

Unknown pseudo-class or pseudo-element ‘-webkit-outer-spin-button’. Ruleset ignored due to bad selector.

everytime I tried. Same for the inner spin button.

AngularJS Error: Cross origin requests are only supported for protocol schemes: http, data, chrome-extension, https

This issue is not happening in Firefox and Safari. Make sure you are using the latest version of xml2json.js. Because i faced the XML parser error in IE. In Chrome best way you should open it in server like Apache or XAMPP.

How to assert two list contain the same elements in Python?

Converting your lists to sets will tell you that they contain the same elements. But this method cannot confirm that they contain the same number of all elements. For example, your method will fail in this case:

L1 = [1,2,2,3]
L2 = [1,2,3,3]

You are likely better off sorting the two lists and comparing them:

def checkEqual(L1, L2):
    if sorted(L1) == sorted(L2):
        print "the two lists are the same"
        return True
        print "the two lists are not the same"
        return False

Note that this does not alter the structure/contents of the two lists. Rather, the sorting creates two new lists

Can I override and overload static methods in Java?

Static methods cannot be overridden because they are not dispatched on the object instance at runtime. The compiler decides which method gets called.

This is why you get a compiler warning when you write

 MyClass myObject = new MyClass();
 // should be written as
 // because it is not dispatched on myObject
 myObject = new MySubClass();
 // still calls the static method in MyClass, NOT in MySubClass

Static methods can be overloaded (meaning that you can have the same method name for several methods as long as they have different parameter types).

 Integer.parseInt("AA", 16);

Delete branches in Bitbucket

If you are using a pycharm IDE for development and you already have added Git with it. you can directly delete remote branch from pycharm. From toolbar VCS-->Git-->Branches-->Select branch-->and Delete. It will delete it from remote git server.

How to split a string to 2 strings in C

You can use strtok() for that Example: it works for me

#include <stdio.h>
#include <string.h>

int main ()
    char str[] ="- This, a sample string.";
    char * pch;
    printf ("Splitting string \"%s\" into tokens:\n",str);
    pch = strtok (str," ,.-");
    while (pch != NULL)
        printf ("%s\n",pch);
        pch = strtok (NULL, " ,.-");
    return 0;

Using a bitmask in C#

I have included an example here which demonstrates how you might store the mask in a database column as an int, and how you would reinstate the mask later on:

public enum DaysBitMask { Mon=0, Tues=1, Wed=2, Thu = 4, Fri = 8, Sat = 16, Sun = 32 }

DaysBitMask mask = DaysBitMask.Sat | DaysBitMask.Thu;
bool test;
if ((mask & DaysBitMask.Sat) == DaysBitMask.Sat)
    test = true;
if ((mask & DaysBitMask.Thu) == DaysBitMask.Thu)
    test = true;
if ((mask & DaysBitMask.Wed) != DaysBitMask.Wed)
    test = true;

// Store the value
int storedVal = (int)mask;

// Reinstate the mask and re-test
DaysBitMask reHydratedMask = (DaysBitMask)storedVal;

if ((reHydratedMask & DaysBitMask.Sat) == DaysBitMask.Sat)
    test = true;
if ((reHydratedMask & DaysBitMask.Thu) == DaysBitMask.Thu)
    test = true;
if ((reHydratedMask & DaysBitMask.Wed) != DaysBitMask.Wed)
    test = true;

How to call a SOAP web service on Android

It's true that due to it's overhead SOAP is not the best choice for data exchange with mobile devices. However, you might find yourself in situation in which you do not control the format of server output.

So, if you have to stick with SOAP, there is a kSOAP2 library patched for Android here:

Using the Web.Config to set up my SQL database connection string?

Web.config file

  <add name="MyConnectionString" connectionString="Data Source=SERGIO-DESKTOP\SQLEXPRESS;    Initial Catalog=YourDatabaseName;Integrated Security=True;"/>

.cs file


Bootstrap table without stripe / borders

Bootstrap supports scss, and he has a special variables. If this is a case then you can add in your main variables.scss file

$table-border-width: 0;

More info here

What's the difference between SortedList and SortedDictionary?

Check out the MSDN page for SortedList:

From Remarks section:

The SortedList<(Of <(TKey, TValue>)>) generic class is a binary search tree with O(log n) retrieval, where n is the number of elements in the dictionary. In this, it is similar to the SortedDictionary<(Of <(TKey, TValue>)>) generic class. The two classes have similar object models, and both have O(log n) retrieval. Where the two classes differ is in memory use and speed of insertion and removal:

  • SortedList<(Of <(TKey, TValue>)>) uses less memory than SortedDictionary<(Of <(TKey, TValue>)>).
  • SortedDictionary<(Of <(TKey, TValue>)>) has faster insertion and removal operations for unsorted data, O(log n) as opposed to O(n) for SortedList<(Of <(TKey, TValue>)>).

  • If the list is populated all at once from sorted data, SortedList<(Of <(TKey, TValue>)>) is faster than SortedDictionary<(Of <(TKey, TValue>)>).

GridView must be placed inside a form tag with runat="server" even after the GridView is within a form tag

Here is My Code

protected void btnExcel_Click(object sender, ImageClickEventArgs e)
        if (gvDetail.Rows.Count > 0)
            System.IO.StringWriter stringWrite1 = new System.IO.StringWriter();
            System.Web.UI.HtmlTextWriter htmlWrite1 = new HtmlTextWriter(stringWrite1);

            gvDetail.AllowPaging = false;
            sh.ExportToExcel(gvDetail, "Report");

    public override void VerifyRenderingInServerForm(Control control)
        /* Confirms that an HtmlForm control is rendered for the specified ASP.NET
           server control at run time. */

Solving sslv3 alert handshake failure when trying to use a client certificate

The solution for me on a CentOS 8 system was checking the System Cryptography Policy by verifying the /etc/crypto-policies/config reads the default value of DEFAULT rather than any other value.

Once changing this value to DEFAULT, run the following command:

/usr/bin/update-crypto-policies --set DEFAULT

Rerun the curl command and it should work.

Ping all addresses in network, windows

aping can provide a list of hosts and whether each has responded to pings.

 aping -show all 192.168.1.*

Rotate axis text in python matplotlib

The simplest solution is to use:


but also

# Tweak spacing to prevent clipping of tick-labels

e.g for dates I used rotation=45 and bottom=0.20 but you can do some test for your data

jQuery click event on radio button doesn't get fired

There are a couple of things wrong in this code:

  1. You're using <input> the wrong way. You should use a <label> if you want to make the text behind it clickable.
  2. It's setting the enabled attribute, which does not exist. Use disabled instead.
  3. If it would be an attribute, it's value should not be false, use disabled="disabled" or simply disabled without a value.
  4. If checking for someone clicking on a form event that will CHANGE it's value (like check-boxes and radio-buttons), use .change() instead.

I'm not sure what your code is supposed to do. My guess is that you want to disable the input field with class roomNumber once someone selects "Walk in" (and possibly re-enable when deselected). If so, try this code:


<form class="type">
        <input type="radio" name="type" checked="checked" id="guest" value="guest" />
        <label for="guest">In House</label>
        <input type="radio" name="type" id="walk_in" value="walk_in" />
        <label for="walk_in">Walk in</label>
        <input type="text" name="roomnumber" class="roomNumber" value="12345" />


$("form input:radio").change(function () {
    if ($(this).val() == "walk_in") {
        // Disable your roomnumber element here
        $('.roomNumber').attr('disabled', 'disabled');
    } else {
        // Re-enable here I guess

I created a fiddle here:

Entity framework self referencing loop detected

This happens because you're trying to serialize the EF object collection directly. Since department has an association to employee and employee to department, the JSON serializer will loop infinetly reading d.Employee.Departments.Employee.Departments etc...

To fix this right before the serialization create an anonymous type with the props you want

example (psuedo)code: => new { 
    Employee = new { 
        dep.Employee.Id, dep.Employee.Name 

Generating sql insert into for Oracle

If you have to load a lot of data into tables on a regular basis, check out SQL Loader or external tables. Should be much faster than individual Inserts.

In which case do you use the JPA @JoinTable annotation?

It's the only solution to map a ManyToMany association : you need a join table between the two entities tables to map the association.

It's also used for OneToMany (usually unidirectional) associations when you don't want to add a foreign key in the table of the many side and thus keep it independent of the one side.

Search for @JoinTable in the hibernate documentation for explanations and examples.

How to permanently add a private key with ssh-add on Ubuntu?

I solved that problem on Mac OSX (10.10) by using -K option for ssh-add:

ssh-add -K ~/.ssh/your_private_key

For macOS 10.12 and later you need to additionally edit your ssh config as described here:

H2 in-memory database. Table not found

I had the same problem and changed my configuration in to this:

#Test Properties

And my dependencies:


    <!-- -->

And the annotations used on test class:

public class CommentServicesIntegrationTests {

How to set Grid row and column positions programmatically

Try this:

                Grid grid = new Grid(); //Define the grid
                for (int i = 0; i < 36; i++) //Add 36 rows
                    ColumnDefinition columna = new ColumnDefinition()
                        Name = "Col_" + i,
                        Width = new GridLength(32.5),

                for (int i = 0; i < 36; i++) //Add 36 columns
                    RowDefinition row = new RowDefinition();
                    row.Height = new GridLength(40, GridUnitType.Pixel);

                for (int i = 0; i < 36; i++)
                    for (int j = 0; j < 36; j++)
                        Label t1 = new Label()
                            FontSize = 10,
                            FontFamily = new FontFamily("consolas"),
                            FontWeight = FontWeights.SemiBold,
                            BorderBrush = Brushes.LightGray,
                            BorderThickness = new Thickness(2),
                            HorizontalContentAlignment = HorizontalAlignment.Center,
                            VerticalContentAlignment = VerticalAlignment.Center,
                        Grid.SetRow(t1, i);
                        Grid.SetColumn(t1, j);
                        grid.Children.Add(t1); //Add the Label Control to the Grid created

How to synchronize a static variable among threads running different instances of a class in Java?

If you're simply sharing a counter, consider using an AtomicInteger or another suitable class from the java.util.concurrent.atomic package:

public class Test {

    private final static AtomicInteger count = new AtomicInteger(0); 

    public void foo() {  

What is difference between @RequestBody and @RequestParam?

@RequestParam makes Spring to map request parameters from the GET/POST request to your method argument.

GET Request

public String getCountryFactors(@RequestParam(value = "city") String city, 
                    @RequestParam(value = "country") String country){ }

POST Request

@RequestBody makes Spring to map entire request to a model class and from there you can retrieve or set values from its getter and setter methods. Check below.

You have JSON data as such coming from the front end and hits your controller class

   "city": "Sydney",
   "country": "Australia"

Java Code - backend (@RequestBody)

public String getCountryFactors(@RequestBody Country countryFacts)

public class Country {

    private String city;
    private String country;

    public String getCity() {
        return city;

    public void setCity(String city) { = city;

    public String getCountry() {
        return country;

    public void setCountry(String country) { = country;

Get the number of rows in a HTML table

In the DOM, a tr element is (implicitly or explicitly) a child of tbody, thead, or tfoot, not a child of table (hence the 0 you got). So a general answer is:

var count = $('#gvPerformanceResult > * > tr').length;

This includes the rows of the table but excludes rows of any inner table.

MongoDB: How to update multiple documents with a single command?

Starting in v3.3 You can use updateMany

     upsert: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ]

In v2.2, the update function takes the following form:

   { upsert: <boolean>, multi: <boolean> }

LINQ to Entities how to update a record

They both track your changes to the collection, just call the SaveChanges() method that should update the DB.

What does InitializeComponent() do, and how does it work in WPF?

The call to InitializeComponent() (which is usually called in the default constructor of at least Window and UserControl) is actually a method call to the partial class of the control (rather than a call up the object hierarchy as I first expected).

This method locates a URI to the XAML for the Window/UserControl that is loading, and passes it to the System.Windows.Application.LoadComponent() static method. LoadComponent() loads the XAML file that is located at the passed in URI, and converts it to an instance of the object that is specified by the root element of the XAML file.

In more detail, LoadComponent creates an instance of the XamlParser, and builds a tree of the XAML. Each node is parsed by the XamlParser.ProcessXamlNode(). This gets passed to the BamlRecordWriter class. Some time after this I get a bit lost in how the BAML is converted to objects, but this may be enough to help you on the path to enlightenment.

Note: Interestingly, the InitializeComponent is a method on the System.Windows.Markup.IComponentConnector interface, of which Window/UserControl implement in the partial generated class.

Hope this helps!

OpenCV NoneType object has no attribute shape

I faced the same problem today, please check for the path of the image as mentioned by cybseccrypt. After imread, try printing the image and see. If you get a value, it means the file is open.


img_src = cv2.imread('/home/deepak/python-workout/box2.jpg',0) print img_src

Hope this helps!

How to query SOLR for empty fields?

If you are using SolrSharp, it does not support negative queries.

You need to change QueryParameter.cs (Create a new parameter)

private bool _negativeQuery = false;

public QueryParameter(string field, string value, ParameterJoin parameterJoin = ParameterJoin.AND, bool negativeQuery = false)
    this._field = field;
    this._value = value.Trim();
    this._parameterJoin = parameterJoin;
    this._negativeQuery = negativeQuery;

public bool NegativeQuery
    get { return _negativeQuery; }
    set { _negativeQuery = value; }

And in QueryParameterCollection.cs class, the ToString() override, looks if the Negative parameter is true

arQ[x] = (qp.NegativeQuery ? "-(" : "(") + qp.ToString() + ")" + (qp.Boost != 1 ? "^" + qp.Boost.ToString() : "");

When you call the parameter creator, if it's a negative value. Simple change the propertie

List<QueryParameter> QueryParameters = new List<QueryParameter>();
QueryParameters.Add(new QueryParameter("PartnerList", "[* TO *]", ParameterJoin.AND, true));

Move column by name to front of table in pandas

Here is a very simple answer to this.

Don't forget the two (()) 'brackets' around columns names.Otherwise, it'll give you an error.

# here you can add below line and it should work 
df = df[list(('Mid','Upper', 'Lower', 'Net','Zsore'))]

                             Mid   Upper   Lower  Net  Zsore
Answer option                                                
More than once a day          2   0.22%  -0.12%   0%    65 
Once a day                    3   0.32%  -0.19%   0%    45
Several times a week          4   2.45%   1.10%   2%    78
Once a week                   6   1.63%  -0.40%   1%    65

Excel data validation with suggestions/autocomplete

If you don't want to go down the VBA path, there is this trick from a previous question.

Excel 2010: how to use autocomplete in validation list

It does add some annoying bulk to the top of your sheets, and potential maintenance (should you need more options, adding names of people from a staff list, new projects etc.) but works all the same.

What is the best workaround for the WCF client `using` block issue?

You could also use a DynamicProxy to extend the Dispose() method. This way you could do something like:

using (var wrapperdProxy = new Proxy<yourProxy>())
   // Do whatever and dispose of Proxy<yourProxy> will be called and work properly.

What is the point of WORKDIR on Dockerfile?

Be careful where you set WORKDIR because it can affect the continuous integration flow. For example, setting it to /home/circleci/project will cause error something like .ssh or whatever is the remote circleci is doing at setup time.

Read user input inside a loop

You can redirect the regular stdin through unit 3 to keep the get it inside the pipeline:

{ cat notify-finished | while read line; do
    read -u 3 input
    echo "$input"
done; } 3<&0

BTW, if you really are using cat this way, replace it with a redirect and things become even easier:

while read line; do
    read -u 3 input
    echo "$input"
done 3<&0 <notify-finished

Or, you can swap stdin and unit 3 in that version -- read the file with unit 3, and just leave stdin alone:

while read line <&3; do
    # read & use stdin normally inside the loop
    read input
    echo "$input"
done 3<notify-finished

How can I make git accept a self signed certificate?

Check your antivirus and firewall settings.

From one day to the other, git did not work anymore. With what is described above, I found that Kaspersky puts a self-signed Anti-virus personal root certificate in the middle. I did not manage to let Git accept that certificate following the instructions above. I gave up on that. What works for me is to disable the feature to Scan encrypted connections.

  1. Open Kaspersky
  2. Settings > Additional > Network > Do not scan encrypted connections

After this, git works again with sslVerify enabled.

Note. This is still not satisfying for me, because I would like to have that feature of my Anti-Virus active. In the advanced settings, Kaspersky shows a list of websites that will not work with that feature. Github is not listed as one of them. I will check it at the Kaspersky forum. There seem to be some topics, e.g.

Does a VPN Hide my Location on Android?

Your question can be conveniently divided into several parts:

Does a VPN hide location? Yes, he is capable of this. This is not about GPS determining your location. If you try to change the region via VPN in an application that requires GPS access, nothing will work. However, sites define your region differently. They get an IP address and see what country or region it belongs to. If you can change your IP address, you can change your region. This is exactly what VPNs can do.

How to hide location on Android? There is nothing difficult in figuring out how to set up a VPN on Android, but a couple of nuances still need to be highlighted. Let's start with the fact that not all Android VPNs are created equal. For example, VeePN outperforms many other services in terms of efficiency in circumventing restrictions. It has 2500+ VPN servers and a powerful IP and DNS leak protection system.

You can easily change the location of your Android device by using a VPN. Follow these steps for any device model (Samsung, Sony, Huawei, etc.):

  1. Download and install a trusted VPN.

  2. Install the VPN on your Android device.

  3. Open the application and connect to a server in a different country.

  4. Your Android location will now be successfully changed!

Is it legal? Yes, changing your location on Android is legal. Likewise, you can change VPN settings in Microsoft Edge on your PC, and all this is within the law. VPN allows you to change your IP address, safeguarding your privacy and protecting your actual location from being exposed. However, VPN laws may vary from country to country. There are restrictions in some regions.

Brief summary: Yes, you can change your region on Android and a VPN is a necessary assistant for this. It's simple, safe and legal. Today, VPN is the best way to change the region and unblock sites with regional restrictions.

Do copyright dates need to be updated?

Copyright should be up to the date of publish.

So, if it's a static content (such as the Times article you linked to), it should probably be statically copyrighted.

If it's dynamically generated content, it should be copyrighted to the current year

Is there a way to make text unselectable on an HTML page?

For an example of why it might be desirable to suppress selection, see SIMILE TImeline, which uses drag-and-drop to explore the timeline, during which accidental vertical mouse movement causes the labels to be highlighted unexpectedly, which looks weird.

How to set tint for an image view programmatically in android?

This worked for me

mImageView.setColorFilter(ContextCompat.getColor(getContext(), R.color.green_500));

Get the last element of a std::string

You could write a function template back that delegates to the member function for ordinary containers and a normal function that implements the missing functionality for strings:

template <typename C>
typename C::reference back(C& container)
    return container.back();

template <typename C>
typename C::const_reference back(const C& container)
    return container.back();

char& back(std::string& str)
    return *(str.end() - 1);

char back(const std::string& str)
    return *(str.end() - 1);

Then you can just say back(foo) without worrying whether foo is a string or a vector.

How do I run Visual Studio as an administrator by default?

Right click on the application, Props -> Compatibility -> Check the Run the program as administrator

How to escape double quotes in JSON

For those who would like to use developer powershell. Here are the lines to add to your settings.json:

"": "C:\\Windows\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe",
"": [
    " &{Import-Module 'C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\BuildTools\\Common7\\Tools\\Microsoft.VisualStudio.DevShell.dll'; Enter-VsDevShell b7c50c8d} ",

Multiline text in JLabel

You can do it by putting HTML in the code, so:

JFrame frame = new JFrame();
frame.setLayout(new GridLayout());
JLabel label = new JLabel("<html>First line<br>Second line</html>");

True and False for && logic and || Logic table

I think You ask for Boolean algebra which describes the output of various operations performed on boolean variables. Just look at the article on Wikipedia.

A simple command line to download a remote maven2 artifact to the local repository?

Since version 2.1 of the Maven Dependency Plugin, there is a dependency:get goal for this purpose. To make sure you are using the right version of the plugin, you'll need to use the "fully qualified name":

mvn org.apache.maven.plugins:maven-dependency-plugin:2.1:get \
    -DrepoUrl= \

What are some great online database modeling tools?

The DB Designer Fork project claims that it can generate FireBird sql scripts.

When should I use Async Controllers in ASP.NET MVC?

As you know, MVC supports asynchronous controllers and you should take advantage of it. In case your Controller, performs a lengthy operation, (it might be a disk based I/o or a network call to another remote service), if the request is handled in synchronous manner, the IIS thread is busy the whole time. As a result, the thread is just waiting for the lengthy operation to complete. It can be better utilized by serving other requests while the operation requested in first is under progress. This will help in serving more concurrent requests. Your webservice will be highly scalable and will not easily run into C10k problem. It is a good idea to use async/await for db queries. and yes you can use them as many number of times as you deem fit.

Take a look here for excellent advise.

Only mkdir if it does not exist

if [ ! -d directory ]; then
  mkdir directory


mkdir -p directory

-p ensures creation if directory does not exist

Setting default value in select drop-down using Angularjs

<select ng-init="somethingHere = options[0]" ng-model="somethingHere" ng-options=" for option in options"></select>

This would get you desired result Dude :) Cheers

Verify host key with pysftp

Connect to the server first with a Windows ssh client that uses the known_hosts file. PuTTy stores the data in the windows registry,however OpenSSH uses the known_hosts file, and will add entries in there after you connect. Default location for the file is %USERPROFILE%.ssh. I hope this helps

Error when checking model input: expected convolution2d_input_1 to have 4 dimensions, but got array with shape (32, 32, 3)

Got the same problem, non of the answers worked for me. After a lot of debugging I found out that the size of one image was smaller than 32. This leads to a broken array with wrong dimensions and the above mentioned error.

To solve the problem, make sure that all images have the correct dimensions.

How to sum the values of one column of a dataframe in spark/scala

If you want to sum all values of one column, it's more efficient to use DataFrame's internal RDD and reduce.

import sqlContext.implicits._
import org.apache.spark.sql.functions._

val df = sc.parallelize(Array(10,2,3,4)).toDF("steps")"steps"))[Int]).reduce(_+_)

//res1 Int = 19

Which Java library provides base64 encoding/decoding?

If you're an Android developer you can use android.util.Base64 class for this purpose.

Check if an array is empty or exists

The following is my solution wrapped in a function that also throws errors to manage a couple of problems with object scope and all types of possible data types passed to the function.

Here's my fiddle used to examine this problem (source)

var jill = [0];
var jack;
//"Uncaught ReferenceError: jack is not defined"

//if (typeof jack === 'undefined' || jack === null) {
//if (jack) {
//if (jack in window) {
//if (window.hasOwnP=roperty('jack')){
//if (jack in window){

function isemptyArray (arraynamed){
    //cam also check argument length
  if (arguments.length === 0) { 
    throw "No argument supplied";

  //console.log(arguments.length, "number of arguments found");
  if (typeof arraynamed !== "undefined" && arraynamed !== null) {
      //console.log("found arraynamed has a value");
      if ((arraynamed instanceof Array) === true){
        //console.log("I'm an array");
        if (arraynamed.length === 0) {
            //console.log ("I'm empty");
            return true;
        } else {
          return false;
        }//end length check
      } else {
        //bad type
        throw "Argument is not an array";
      } //end type check
  } else {
    //bad argument
    throw "Argument is invalid, check initialization";;
  }//end argument check

try {
} catch (e) {
    console.log ("error caught:",e);

How to hide "Showing 1 of N Entries" with the dataTables.js library

You can remove it with the bInfo option (

       "bInfo" : false

Update: Since Datatables 1.10.* this option can be used as info, bInfo still works in current nightly build (1.10.10).

C++ floating point to integer type conversions

One thing I want to add. Sometimes, there can be precision loss. You may want to add some epsilon value first before converting. Not sure why that works... but it work.

int someint = (somedouble+epsilon);

Check if null Boolean is true results in exception

If you don't like extra null checks:

if (Boolean.TRUE.equals(value)) {...}

Dynamic instantiation from string name of a class in dynamically imported module?

If you want this sentence from import foo2 to be loaded dynamically, you should do this

foo = __import__("foo")
bar = getattr(foo,"bar")
foo2 = getattr(bar,"foo2")

instance = foo2()

How to embed a PDF?

I recommend using PDFObject for PDF plugin detection.

This will only allow you to display alternate content if the user's browser isn't capable of displaying the PDF directly though. For example, the PDF will display fine in Chrome for most users, but they will need a plugin like Adobe Reader installed if they're using Firefox or Internet Explorer.

At least PDFObject will allow you to display a message with a link to download Adobe Reader and/or the PDF file itself if their browser doesn't already have a PDF plugin installed.

Is it possible to cast a Stream in Java 8?

I don't think there is a way to do that out-of-the-box. A possibly cleaner solution would be:

    .filter(c -> c instanceof Client)
    .map(c -> (Client) c)

or, as suggested in the comments, you could use the cast method - the former may be easier to read though:


Is it necessary to use # for creating temp tables in SQL server?

The difference between this two tables ItemBack1 and #ItemBack1 is that the first on is persistent (permanent) where as the other is temporary.

Now if take a look at your question again

Is it necessary to Use # for creating temp table in sql server?

The answer is Yes, because without this preceding # the table will not be a temporary table, it will be independent of all sessions and scopes.

How to get the size of a JavaScript object?

If your main concern is the memory usage of your Firefox extension, I suggest checking with Mozilla developers.

Mozilla provides on its wiki a list of tools to analyze memory leaks.

Resize image in the wiki of GitHub using Markdown

This addresses the different question, how to get images in gist (as opposed to github) markdown in the first place ?

In December 2015, it seems that only links to files on or or the like work. Steps that worked for me in a gist:

  1. Make a gist, say (and optionally more files)
  2. Go to the "Write Comment" box at the end
  3. Click "Attach files ... by selecting them"; select your local image file
  4. GitHub echos a long long string where it put the image, e.g. ![khan-lasso-squared](
  5. Cut-paste that by hand into your

But: GitHub people may change this behavior tomorrow, without documenting it.

How to put space character into a string name in XML?

Space variants:

<string name="space_demo">|&#x20;|&#x2009;|&#x200A;|</string>