Programs & Examples On #Objectdatasource

ObjectDataSource control acts as a data interface for databound controls for such controls as: GridView, Repeater, FormView and DetailsView.

Error - is not marked as serializable

Leaving my specific solution of this for prosperity, as it's a tricky version of this problem:

Type 'System.Linq.Enumerable+WhereSelectArrayIterator[T...] was not marked as serializable

Due to a class with an attribute IEnumerable<int> eg:

class MySessionData{
    public int ID;
    public IEnumerable<int> RelatedIDs; //This can be an issue

Originally the problem instance of MySessionData was set from a non-serializable list:

MySessionData instance = new MySessionData(){ 
    ID = 123,
    RelatedIDs = nonSerizableList.Select<int>(item => item.ID)

The cause here is the concrete class that the Select<int>(...) returns, has type data that's not serializable, and you need to copy the id's to a fresh List<int> to resolve it.

RelatedIDs = nonSerizableList.Select<int>(item => item.ID).ToList();

Formatting DataBinder.Eval data

There is an optional overload for DataBinder.Eval to supply formatting:

<%# DataBinder.Eval(Container.DataItem, "expression"[, "format"]) %>

The format parameter is a String value, using the value placeholder replacement syntax (called composite formatting) like this:

<asp:Label id="lblNewsDate" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "publishedDate", "{0:dddd d MMMM}") %>'</label>

How to return JSON data from spring Controller using @ResponseBody

I was facing same issue. I did not put @ResponseBody since I was using @RestController. But still I was getting error because I did not put the getter/setter method for the Company class. So after putting the getter/setter my problem was resolved.

Filter object properties by key in ES6

The answers here are definitely suitable but they are a bit slow because they require looping through the whitelist for every property in the object. The solution below is much quicker for large datasets because it only loops through the whitelist once:

const data = {
  allowed1: 'blah',
  allowed2: 'blah blah',
  notAllowed: 'woah',
  superSensitiveInfo: 'whooooah',
  allowed3: 'bleh'

const whitelist = ['allowed1', 'allowed2', 'allowed3'];

function sanitize(data, whitelist) {
    return whitelist.reduce(
      (result, key) =>
        data[key] !== undefined
          ? Object.assign(result, { [key]: data[key] })
          : result,

  sanitize(data, whitelist)

c# replace \" characters

Try it like this:


This will replace occurrences of \" with empty string.


string t = "\\\"the dog is my friend\\\"";
t = t.Replace("\\\"","");

This will result in:

the dog is my friend

Converting char* to float or double

printf("price: %d, %f",temp,ftemp); 

This is your problem. Since the arguments are type double and float, you should be using %f for both (since printf is a variadic function, ftemp will be promoted to double).

%d expects the corresponding argument to be type int, not double.

Variadic functions like printf don't really know the types of the arguments in the variable argument list; you have to tell it with the conversion specifier. Since you told printf that the first argument is supposed to be an int, printf will take the next sizeof (int) bytes from the argument list and interpret it as an integer value; hence the first garbage number.

Now, it's almost guaranteed that sizeof (int) < sizeof (double), so when printf takes the next sizeof (double) bytes from the argument list, it's probably starting with the middle byte of temp, rather than the first byte of ftemp; hence the second garbage number.

Use %f for both.

How do I use su to execute the rest of the bash script as that user?

Use sudo instead

EDIT: As Douglas pointed out, you can not use cd in sudo since it is not an external command. You have to run the commands in a subshell to make the cd work.

sudo -u $USERNAME -H sh -c "cd ~/$PROJECT; svn update"

sudo -u $USERNAME -H cd ~/$PROJECT
sudo -u $USERNAME svn update

You may be asked to input that user's password, but only once.

What is the maximum characters for the NVARCHAR(MAX)?

By default, nvarchar(MAX) values are stored exactly the same as nvarchar(4000) values would be, unless the actual length exceed 4000 characters; in that case, the in-row data is replaced by a pointer to one or more seperate pages where the data is stored.

If you anticipate data possibly exceeding 4000 character, nvarchar(MAX) is definitely the recommended choice.


Defining a `required` field in Bootstrap

To make a field required, use required or required="true"

I think required="required" has been deprecated in version 3 of bootstrap.

how to activate a textbox if I select an other option in drop down box

This will submit the right form response (i.e. Select value most of the time, and Input value when the Select box is set to "others"). Uses jQuery:

    new_value = $(this).val();
    if (new_value == "others") {
    } else {

How to set the range of y-axis for a seaborn boxplot?

It is standard matplotlib.pyplot:

import matplotlib.pyplot as plt
plt.ylim(10, 40)

Or simpler, as mwaskom comments below:

ax.set(ylim=(10, 40))

enter image description here

CSS3 animate border color

You can try this also...

button {
  background: none;
  border: 0;
  box-sizing: border-box;
  margin: 1em;
  padding: 1em 2em;
  box-shadow: inset 0 0 0 2px #f45e61;
  color: #f45e61;
  font-size: inherit;
  font-weight: 700;
  vertical-align: middle;
  position: relative;
button::before, button::after {
  box-sizing: inherit;
  content: '';
  position: absolute;
  width: 100%;
  height: 100%;

.draw {
  -webkit-transition: color 0.25s;
  transition: color 0.25s;
.draw::before, .draw::after {
  border: 2px solid transparent;
  width: 0;
  height: 0;
.draw::before {
  top: 0;
  left: 0;
.draw::after {
  bottom: 0;
  right: 0;
.draw:hover {
  color: #60daaa;
.draw:hover::before, .draw:hover::after {
  width: 100%;
  height: 100%;
.draw:hover::before {
  border-top-color: #60daaa;
  border-right-color: #60daaa;
  -webkit-transition: width 0.25s ease-out, height 0.25s ease-out 0.25s;
  transition: width 0.25s ease-out, height 0.25s ease-out 0.25s;
.draw:hover::after {
  border-bottom-color: #60daaa;
  border-left-color: #60daaa;
  -webkit-transition: border-color 0s ease-out 0.5s, width 0.25s ease-out 0.5s, height 0.25s ease-out 0.75s;
  transition: border-color 0s ease-out 0.5s, width 0.25s ease-out 0.5s, height 0.25s ease-out 0.75s;
<section class="buttons">
  <button class="draw">Draw</button>

throw checked Exceptions from mocks with Mockito

Note that in general, Mockito does allow throwing checked exceptions so long as the exception is declared in the message signature. For instance, given

class BarException extends Exception {
  // this is a checked exception

interface Foo {
  Bar frob() throws BarException

it's legal to write:

Foo foo = mock(Foo.class);

However, if you throw a checked exception not declared in the method signature, e.g.

class QuxException extends Exception {
  // a different checked exception

Foo foo = mock(Foo.class);

Mockito will fail at runtime with the somewhat misleading, generic message:

Checked exception is invalid for this method!
Invalid: QuxException

This may lead you to believe that checked exceptions in general are unsupported, but in fact Mockito is only trying to tell you that this checked exception isn't valid for this method.

How to get hex color value rather than RGB value?

Just to add to @Justin's answer above..

it should be

var rgb = document.querySelector('#selector').style['background-color'];
return '#' + rgb.substr(4, rgb.indexOf(')') - 4).split(',').map((color) => String("0" + parseInt(color).toString(16)).slice(-2)).join('');

As the above parse int functions truncates leading zeroes, thus produces incorrect color codes of 5 or 4 letters may be... i.e. for rgb(216, 160, 10) it produces #d8a0a while it should be #d8a00a.


How to launch html using Chrome at "--allow-file-access-from-files" mode?

Well there is quick to run a html which needs permission or blocked by CORS Just simply open the folder using VSCODE and install an extension called "live server"

And then just click on the bottom which says go live, thats it. Screenshot

Facebook page automatic "like" URL (for QR Code)

The answers above seem partly outdated.

The URL builder on worked nicely for me.

You can configure, preview and the get the code/URL in different flavors: HTML5, XFBML, IFRAME, URL

Parse usable Street Address, City, State, Zip from a string

There is javascript port of perl Geo::StreetAddress::US package: . It's regex-based and works fairly well.

PHP how to get local IP of system

try this (if your server is Linux):

$command="/sbin/ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}'";
$localIP = exec ($command);
echo $localIP;

Why is System.Web.Mvc not listed in Add References?

The desired assembly has appeared in the list now.

I can only speculate what caused it to appear, but I suspect it is the fact that I went File ? New ? Project ? ASP.NET Web Application, which I had never done before. It is possible that this caused some sort of late initialisation to happen and the list to be populated with additional assemblies for Web development.

Set value to an entire column of a pandas dataframe

You can do :

df['industry'] = 'yyy'

Reference alias (calculated in SELECT) in WHERE clause

You can't reference an alias except in ORDER BY because SELECT is the second last clause that's evaluated. Two workarounds:

SELECT BalanceDue FROM (
  SELECT (InvoiceTotal - PaymentTotal - CreditTotal) AS BalanceDue
  FROM Invoices
) AS x
WHERE BalanceDue > 0;

Or just repeat the expression:

SELECT (InvoiceTotal - PaymentTotal - CreditTotal) AS BalanceDue
FROM Invoices
WHERE  (InvoiceTotal - PaymentTotal - CreditTotal)  > 0;

I prefer the latter. If the expression is extremely complex (or costly to calculate) you should probably consider a computed column (and perhaps persisted) instead, especially if a lot of queries refer to this same expression.

PS your fears seem unfounded. In this simple example at least, SQL Server is smart enough to only perform the calculation once, even though you've referenced it twice. Go ahead and compare the plans; you'll see they're identical. If you have a more complex case where you see the expression evaluated multiple times, please post the more complex query and the plans.

Here are 5 example queries that all yield the exact same execution plan:

SELECT LEN(name) + column_id AS x
FROM sys.all_columns
WHERE LEN(name) + column_id > 30;

SELECT LEN(name) + column_id AS x
FROM sys.all_columns
) AS x
WHERE x > 30;

SELECT LEN(name) + column_id AS x
FROM sys.all_columns
WHERE column_id + LEN(name) > 30;

SELECT name, column_id, x FROM (
SELECT name, column_id, LEN(name) + column_id AS x
FROM sys.all_columns
) AS x
WHERE x > 30;

SELECT name, column_id, x FROM (
SELECT name, column_id, LEN(name) + column_id AS x
FROM sys.all_columns
) AS x
WHERE LEN(name) + column_id > 30;

Resulting plan for all five queries:

enter image description here

1067 error on attempt to start MySQL

I have mysql data folder replaced by a windows directory junction. I suspect ib_logfile0/1 and/or ibdata1 is corrupted.

Just try to delete those files and computername.err. Then restart mysql service. That's what I did, with success.

Copying ibdata1 files, after a full reinstallation of mysql, to the junction dir and replacing dir by the junction, restarting mysql, was not enough.

You have to let mysql rebuild those files.

using c# .net libraries to check for IMAP messages from gmail servers has both IMAP client and server code that you can use.

I've used it to download email from Gmail. The object model isn't the best, but it is workable, and seems to be rather flexible and stable.

Here is the partial result of my spike to use it. It fetches the first 10 headers with envelopes, and then fetches the full message:

using (var client = new IMAP_Client())
    client.Connect(_hostname, _port, _useSsl);
    client.Authenticate(_username, _password);
     var sequence = new IMAP_SequenceSet();
    var fetchItems = client.FetchMessages(sequence, IMAP_FetchItem_Flags.Envelope | IMAP_FetchItlags.UID,
                                        false, true);
    foreach (var fetchItem in fetchItems)
        Console.Out.WriteLine("message.UID = {0}", fetchItem.UID);
        Console.Out.WriteLine("message.Envelope.From = {0}", fetchItem.Envelope.From);
        Console.Out.WriteLine("message.Envelope.To = {0}", fetchItem.Envelope.To);
        Console.Out.WriteLine("message.Envelope.Subject = {0}", fetchItem.Envelope.Subject);
        Console.Out.WriteLine("message.Envelope.MessageID = {0}", fetchItem.Envelope.MessageID);
    Console.Out.WriteLine("Fetching bodies");
    foreach (var fetchItem in client.FetchMessages(sequence, IMAP_FetchItem_Flags.All, false, true)
        var email = LumiSoft.Net.Mail.Mail_Message.ParseFromByte(fetchItem.MessageData);             
        Console.Out.WriteLine("email.BodyText = {0}", email.BodyText);


How to select the last record from MySQL table using SQL syntax

User order by with desc order:

select * from t
order by id desc
limit 1

What is the difference between OFFLINE and ONLINE index rebuild in SQL Server?

In ONLINE mode the new index is built while the old index is accessible to reads and writes. any update on the old index will also get applied to the new index. An antimatter column is used to track possible conflicts between the updates and the rebuild (ie. delete of a row which was not yet copied). See Online Index Operations. When the process is completed the table is locked for a brief period and the new index replaces the old index. If the index contains LOB columns, ONLINE operations are not supported in SQL Server 2005/2008/R2.

In OFFLINE mode the table is locked upfront for any read or write, and then the new index gets built from the old index, while holding a lock on the table. No read or write operation is permitted on the table while the index is being rebuilt. Only when the operation is done is the lock on the table released and reads and writes are allowed again.

Note that in SQL Server 2012 the restriction on LOBs was lifted, see Online Index Operations for indexes containing LOB columns.

Non-recursive depth first search algorithm

Stack<Node> stack = new Stack<>();
while (!stack.isEmpty()) {
    Node node = stack.pop();
    System.out.print(node.getData() + " ");

    Node right = node.getRight();
    if (right != null) {

    Node left = node.getLeft();
    if (left != null) {

How to check if an object is a certain type

Some more details in relation with the response from Cody Gray. As it took me some time to digest it I though it might be usefull to others.

First, some definitions:

  1. There are TypeNames, which are string representations of the type of an object, interface, etc. For example, Bar is a TypeName in Public Class Bar, or in Dim Foo as Bar. TypeNames could be seen as "labels" used in the code to tell the compiler which type definition to look for in a dictionary where all available types would be described.
  2. There are System.Type objects which contain a value. This value indicates a type; just like a String would take some text or an Int would take a number, except we are storing types instead of text or numbers. Type objects contain the type definitions, as well as its corresponding TypeName.

Second, the theory:

  1. Foo.GetType() returns a Type object which contains the type for the variable Foo. In other words, it tells you what Foo is an instance of.
  2. GetType(Bar) returns a Type object which contains the type for the TypeName Bar.
  3. In some instances, the type an object has been Cast to is different from the type an object was first instantiated from. In the following example, MyObj is an Integer cast into an Object:

    Dim MyVal As Integer = 42 Dim MyObj As Object = CType(MyVal, Object)

So, is MyObj of type Object or of type Integer? MyObj.GetType() will tell you it is an Integer.

  1. But here comes the Type Of Foo Is Bar feature, which allows you to ascertain a variable Foo is compatible with a TypeName Bar. Type Of MyObj Is Integer and Type Of MyObj Is Object will both return True. For most cases, TypeOf will indicate a variable is compatible with a TypeName if the variable is of that Type or a Type that derives from it. More info here:

The test below illustrate quite well the behaviour and usage of each of the mentionned keywords and properties.

Public Sub TestMethod1()

    Dim MyValInt As Integer = 42
    Dim MyValDble As Double = CType(MyValInt, Double)
    Dim MyObj As Object = CType(MyValDble, Object)

    Debug.Print(MyValInt.GetType.ToString) 'Returns System.Int32
    Debug.Print(MyValDble.GetType.ToString) 'Returns System.Double
    Debug.Print(MyObj.GetType.ToString) 'Returns System.Double

    Debug.Print(MyValInt.GetType.GetType.ToString) 'Returns System.RuntimeType
    Debug.Print(MyValDble.GetType.GetType.ToString) 'Returns System.RuntimeType
    Debug.Print(MyObj.GetType.GetType.ToString) 'Returns System.RuntimeType

    Debug.Print(GetType(Integer).GetType.ToString) 'Returns System.RuntimeType
    Debug.Print(GetType(Double).GetType.ToString) 'Returns System.RuntimeType
    Debug.Print(GetType(Object).GetType.ToString) 'Returns System.RuntimeType

    Debug.Print(MyValInt.GetType = GetType(Integer)) '# Returns True
    Debug.Print(MyValInt.GetType = GetType(Double)) 'Returns False
    Debug.Print(MyValInt.GetType = GetType(Object)) 'Returns False

    Debug.Print(MyValDble.GetType = GetType(Integer)) 'Returns False
    Debug.Print(MyValDble.GetType = GetType(Double)) '# Returns True
    Debug.Print(MyValDble.GetType = GetType(Object)) 'Returns False

    Debug.Print(MyObj.GetType = GetType(Integer)) 'Returns False
    Debug.Print(MyObj.GetType = GetType(Double)) '# Returns True
    Debug.Print(MyObj.GetType = GetType(Object)) 'Returns False

    Debug.Print(TypeOf MyObj Is Integer) 'Returns False
    Debug.Print(TypeOf MyObj Is Double) '# Returns True
    Debug.Print(TypeOf MyObj Is Object) '# Returns True

End Sub


You can also use Information.TypeName(Object) to get the TypeName of a given object. For example,

Dim Foo as Bar
Dim Result as String
Result = TypeName(Foo)
Debug.Print(Result) 'Will display "Bar"

How to create a drop shadow only on one side of an element?

You could also just do a gradient on the bottom - this was helpful for me because the shadow I wanted was on an element that was already semi-transparent, so I didn't have to worry about any clipping:

&:after {
      height: 8px;
      position: absolute;
      bottom: -8px;
      left: 0;
      background: linear-gradient(to bottom, rgba(0,0,0,0.65) 0%,rgba(0,0,0,0) 100%);

Just make the "bottom" and "height" properties match and set your rgba values to whatever you want them to be at the top / bottom of the shadow

Find if variable is divisible by 2

You can do it in a better way (up to 50 % faster than modulo operator):

odd: x & 1 even: !(x & 1)

Reference: High Performance JavaScript, 8. ->Bitwise Operators

Groovy: How to check if a string contains any element of an array?

def valid = pointAddress.findAll { a ->
    validPointTypes.any { a.contains(it) }

Should do it

Messages Using Command prompt in Windows 7

"net send" is a command using a background service called "messenger". This service has been removed from Windows 7. ie You cannot use 'net send' on Vista nor Win7 / Win8.

Pity though , I loved using it.

There is alternatives, but that requires you to download and install software on each pc you want to use, this software runs as background services, and i would advise one to be very very very very careful of using these kind of software as they can potentially cause seriously damage one's system or impair the systems securities.

winsent innocenti / winsent messenger

****This command is risky because of what is stated above***

How to check task status in Celery?

Return the task_id (which is given from .delay()) and ask the celery instance afterwards about the state:

x = method.delay(1,2)
print x.task_id

When asking, get a new AsyncResult using this task_id:

from celery.result import AsyncResult
res = AsyncResult("your-task-id")

JavaScript/regex: Remove text between parentheses

I found this version most suitable for all cases. It doesn't remove all whitespaces.

For example "a (test) b" -> "a b"

"Hello, this is Mike (example)".replace(/ *\([^)]*\) */g, " ").trim(); "Hello, this is (example) Mike ".replace(/ *\([^)]*\) */g, " ").trim();

Can I add extension methods to an existing static class?

Nope. Extension method definitions require an instance of the type you're extending. It's unfortunate; I'm not sure why it's required...

TypeScript sorting an array

The error is completely correct.

As it's trying to tell you, .sort() takes a function that returns number, not boolean.

You need to return negative if the first item is smaller; positive if it it's larger, or zero if they're equal.

Select max value of each group

select name, max(value)
from out_pumptable
group by name

How can I pass a Bitmap object from one activity to another

In my case, the way mentioned above didn't worked for me. Every time I put the bitmap in the intent, the 2nd activity didn't start. The same happened when I passed the bitmap as byte[].

I followed this link and it worked like a charme and very fast:

package your.packagename


public class CommonResources { 
      public static Bitmap photoFinishBitmap = null;

in my 1st acitiviy:

Constants.photoFinishBitmap = photoFinishBitmap;
Intent intent = new Intent(mContext, ImageViewerActivity.class);

and here is the onCreate() of my 2nd Activity:

public void onCreate(Bundle savedInstanceState) {
    Bitmap photo = Constants.photoFinishBitmap;
    if (photo != null) {
        mViewHolder.imageViewerImage.setImageDrawable(new BitmapDrawable(getResources(), photo));

Failed to add the host to the list of know hosts

It happened to me simply because of broken permissions. My user did not have read nor write access to that file. Fixing permissions fixed the problem

How to add buttons dynamically to my form?

Two problems- List is empty. You need to add some buttons to the list first. Second problem: You can't add buttons to "this". "This" is not referencing what you think, I think. Change this to reference a Panel for instance.

//Assume you have on your .aspx page:
<asp:Panel ID="Panel_Controls" runat="server"></asp:Panel>

private void button1_Click(object sender, EventArgs e)
        List<Button> buttons = new List<Button>();

        for (int i = 0; i < buttons.Capacity; i++)

How to get URL parameters with Javascript?

function getURLParameter(name) {
  return decodeURIComponent((new RegExp('[?|&]' + name + '=' + '([^&;]+?)(&|#|;|$)').exec( || [null, ''])[1].replace(/\+/g, '%20')) || null;

So you can use:

myvar = getURLParameter('myvar');

Why does C# XmlDocument.LoadXml(string) fail when an XML header is included?

This really saved my day.

I have written a extension method based on Zach's answer, also I have extended it to use the encoding as a parameter, allowing for different encodings beside from UTF-8 to be used, and I wrapped the MemoryStream in a 'using' statement.

public static class XmlHelperExtentions
    /// <summary>
    /// Loads a string through .Load() instead of .LoadXml()
    /// This prevents character encoding problems.
    /// </summary>
    /// <param name="xmlDocument"></param>
    /// <param name="xmlString"></param>
    public static void LoadString(this XmlDocument xmlDocument, string xmlString, Encoding encoding = null) {

        if (encoding == null) {
            encoding = Encoding.UTF8;

        // Encode the XML string in a byte array
        byte[] encodedString = encoding.GetBytes(xmlString);

        // Put the byte array into a stream and rewind it to the beginning
        using (var ms = new MemoryStream(encodedString)) {
            ms.Position = 0;

            // Build the XmlDocument from the MemorySteam of UTF-8 encoded bytes

Make .gitignore ignore everything except a few files

I had a problem with subfolder.

Does not work:




replacing NA's with 0's in R dataframe

dataset <- matrix(sample(c(NA, 1:5), 25, replace = TRUE), 5);
data <-
[,1] [,2] [,3] [,4] [,5] 
[1,]    2    3    5    5    4
[2,]    2    4    3    2    4
[3,]    2   NA   NA   NA    2
[4,]    2    3   NA    5    5
[5,]    2    3    2    2    3
data[] <- 0

How to get time in milliseconds since the unix epoch in Javascript? returns a unix timestamp in milliseconds.

const now =; // Unix timestamp in milliseconds_x000D_
console.log( now );

Prior to ECMAScript5 (I.E. Internet Explorer 8 and older) you needed to construct a Date object, from which there are several ways to get a unix timestamp in milliseconds:

console.log( +new Date );_x000D_
console.log( (new Date).getTime() );_x000D_
console.log( (new Date).valueOf() );

How to use Visual Studio C++ Compiler?

In Visual Studio, you can't just open a .cpp file and expect it to run. You must create a project first, or open the .cpp in some existing project.

In your case, there is no project, so there is no project to build.

Go to File --> New --> Project --> Visual C++ --> Win32 Console Application. You can uncheck "create a directory for solution". On the next page, be sure to check "Empty project".

Then, You can add .cpp files you created outside the Visual Studio by right clicking in the Solution explorer on folder icon "Source" and Add->Existing Item.

Obviously You can create new .cpp this way too (Add --> New). The .cpp file will be created in your project directory.

Then you can press ctrl+F5 to compile without debugging and can see output on console window.

How to add additional fields to form before submit?

This works:

var form = $(this).closest('form');

form = form.serializeArray();

form = form.concat([
    {name: "customer_id", value: window.username},
    {name: "post_action", value: "Update Information"}

$.post('/change-user-details', form, function(d) {
    if (d.error) {
        alert("There was a problem updating your user details")

Windows 7 environment variable not working in path

Also worth making sure you're using the command prompt as an administrator - the system lock on my work machine meant that the standard cmd just reported mvn could not be found when typing mvn --version

To use click 'start > all programs > accessories', right-click on 'command prompt' and select 'run as administrator'.

Could not load file or assembly 'Microsoft.Web.Infrastructure,

For me Microsoft.Web.Infrastructure.dll was missing from the bin folder, it wasn't set to copy local in the project. Copied the dll from another project in the solution and the page loads.

Calculating average of an array list?

Use a double for the sum, otherwise you are doing an integer division and you won't get any decimals:

private double calculateAverage(List <Integer> marks) {
    if (marks == null || marks.isEmpty()) {
        return 0;

    double sum = 0;
    for (Integer mark : marks) {
        sum += mark;

    return sum / marks.size();

or using the Java 8 stream API:

    return -> i).average().orElse(0);

Inline elements shifting when made bold on hover

I fixed menu when hover bold success. It support responsive, this is my code:

(function ($) {
'use strict';

$(document).ready(function () {
$(window).resize(function () {
function customWidthMenu() {
    $('ul.nav li a').each(function() {
        var this = $(this);
        var width = this.innerWidth();
        this.css({'width': width + 12});

how to get yesterday's date in C#

The code you posted is wrong.

You shouldn't make multiple calls to DateTime.Today. If you happen to run that code just as the date changes you could get completely wrong results. For example if you ran it on December 31st 2011 you might get "2011-1-1".

Use a single call to DateTime.Today then use ToString with an appropriate format string to format the date as you desire.

string result = DateTime.Today.AddDays(-1).ToString("yyyy-MM-dd");

Functional programming vs Object Oriented programming

When do you choose functional programming over object oriented?

When you anticipate a different kind of software evolution:

  • Object-oriented languages are good when you have a fixed set of operations on things, and as your code evolves, you primarily add new things. This can be accomplished by adding new classes which implement existing methods, and the existing classes are left alone.

  • Functional languages are good when you have a fixed set of things, and as your code evolves, you primarily add new operations on existing things. This can be accomplished by adding new functions which compute with existing data types, and the existing functions are left alone.

When evolution goes the wrong way, you have problems:

  • Adding a new operation to an object-oriented program may require editing many class definitions to add a new method.

  • Adding a new kind of thing to a functional program may require editing many function definitions to add a new case.

This problem has been well known for many years; in 1998, Phil Wadler dubbed it the "expression problem". Although some researchers think that the expression problem can be addressed with such language features as mixins, a widely accepted solution has yet to hit the mainstream.

What are the typical problem definitions where functional programming is a better choice?

Functional languages excel at manipulating symbolic data in tree form. A favorite example is compilers, where source and intermediate languages change seldom (mostly the same things), but compiler writers are always adding new translations and code improvements or optimizations (new operations on things). Compilation and translation more generally are "killer apps" for functional languages.

No Spring WebApplicationInitializer types detected on classpath

This turned out to be a stupid error. My log4j wasn't configured to capture my error output. I was throwing configuration errors in the background and once I fixed those I was good to go and my request mappings worked fine.

Angular cookies

I ended creating my own functions:

    selector: 'cookie-consent',
    template: cookieconsent_html,
    styles: [cookieconsent_css]
export class CookieConsent {
    private isConsented: boolean = false;

    constructor() {
        this.isConsented = this.getCookie(COOKIE_CONSENT) === '1';

    private getCookie(name: string) {
        let ca: Array<string> = document.cookie.split(';');
        let caLen: number = ca.length;
        let cookieName = `${name}=`;
        let c: string;

        for (let i: number = 0; i < caLen; i += 1) {
            c = ca[i].replace(/^\s+/g, '');
            if (c.indexOf(cookieName) == 0) {
                return c.substring(cookieName.length, c.length);
        return '';

    private deleteCookie(name) {
        this.setCookie(name, '', -1);

    private setCookie(name: string, value: string, expireDays: number, path: string = '') {
        let d:Date = new Date();
        d.setTime(d.getTime() + expireDays * 24 * 60 * 60 * 1000);
        let expires:string = `expires=${d.toUTCString()}`;
        let cpath:string = path ? `; path=${path}` : '';
        document.cookie = `${name}=${value}; ${expires}${cpath}`;

    private consent(isConsent: boolean, e: any) {
        if (!isConsent) {
            return this.isConsented;
        } else if (isConsent) {
            this.setCookie(COOKIE_CONSENT, '1', COOKIE_CONSENT_EXPIRE_DAYS);
            this.isConsented = true;

Can an int be null in Java?

No, but int[] can be.

int[] hayhay = null; //: allowed (int[] is reference type)
int   hayno  = null; //: error   (int   is primitive type)
                     //: Message: incompatible types: 
                     //: <null> cannot be converted to int

Can I dynamically add HTML within a div tag from C# on load event?

You can add a div with runat="server" to the page:

<div runat="server" id="myDiv">

and then set its InnerHtml property from the code-behind:

myDiv.InnerHtml = "your html here";

If you want to modify the DIV's contents on the client side, then you can use javascript code similar to this:

<script type="text/javascript">
    function MyLoad(sender) {
        $get('<%= div.ClientID %>').innerHTML += " - text added on client";

How do I convert a org.w3c.dom.Document object to a String?

If you are ok to do transformation, you may try this.

DocumentBuilderFactory domFact = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = domFact.newDocumentBuilder();
Document doc = builder.parse(st);
DOMSource domSource = new DOMSource(doc);
StringWriter writer = new StringWriter();
StreamResult result = new StreamResult(writer);
TransformerFactory tf = TransformerFactory.newInstance();
Transformer transformer = tf.newTransformer();
transformer.transform(domSource, result);
System.out.println("XML IN String format is: \n" + writer.toString());

Creating a DateTime in a specific Time Zone in c#

The DateTimeOffset structure was created for exactly this type of use.


Here's an example of creating a DateTimeOffset object with a specific time zone:

DateTimeOffset do1 = new DateTimeOffset(2008, 8, 22, 1, 0, 0, new TimeSpan(-5, 0, 0));

python error: no module named pylab

What you've done by following those directions is created an entirely new Python installation, separate from the system Python that is managed by Ubuntu packages.

Modules you had installed in the system Python (e.g. installed via packages, or by manual installation using the system Python to run the setup process) will not be available, since your /usr/local-based python is configured to look in its own module directories, not the system Python's.

You can re-add missing modules now by building them and installing them using your new /usr/local-based Python.

Rotating a Vector in 3D Space

If you want to rotate a vector you should construct what is known as a rotation matrix.

Rotation in 2D

Say you want to rotate a vector or a point by ?, then trigonometry states that the new coordinates are

    x' = x cos ? - y sin ?
    y' = x sin ? + y cos ?

To demo this, let's take the cardinal axes X and Y; when we rotate the X-axis 90° counter-clockwise, we should end up with the X-axis transformed into Y-axis. Consider

    Unit vector along X axis = <1, 0>
    x' = 1 cos 90 - 0 sin 90 = 0
    y' = 1 sin 90 + 0 cos 90 = 1
    New coordinates of the vector, <x', y'> = <0, 1>  ?  Y-axis

When you understand this, creating a matrix to do this becomes simple. A matrix is just a mathematical tool to perform this in a comfortable, generalized manner so that various transformations like rotation, scale and translation (moving) can be combined and performed in a single step, using one common method. From linear algebra, to rotate a point or vector in 2D, the matrix to be built is

    |cos ?   -sin ?| |x| = |x cos ? - y sin ?| = |x'|
    |sin ?    cos ?| |y|   |x sin ? + y cos ?|   |y'|

Rotation in 3D

That works in 2D, while in 3D we need to take in to account the third axis. Rotating a vector around the origin (a point) in 2D simply means rotating it around the Z-axis (a line) in 3D; since we're rotating around Z-axis, its coordinate should be kept constant i.e. 0° (rotation happens on the XY plane in 3D). In 3D rotating around the Z-axis would be

    |cos ?   -sin ?   0| |x|   |x cos ? - y sin ?|   |x'|
    |sin ?    cos ?   0| |y| = |x sin ? + y cos ?| = |y'|
    |  0       0      1| |z|   |        z        |   |z'|

around the Y-axis would be

    | cos ?    0   sin ?| |x|   | x cos ? + z sin ?|   |x'|
    |   0      1       0| |y| = |         y        | = |y'|
    |-sin ?    0   cos ?| |z|   |-x sin ? + z cos ?|   |z'|

around the X-axis would be

    |1     0           0| |x|   |        x        |   |x'|
    |0   cos ?    -sin ?| |y| = |y cos ? - z sin ?| = |y'|
    |0   sin ?     cos ?| |z|   |y sin ? + z cos ?|   |z'|

Note 1: axis around which rotation is done has no sine or cosine elements in the matrix.

Note 2: This method of performing rotations follows the Euler angle rotation system, which is simple to teach and easy to grasp. This works perfectly fine for 2D and for simple 3D cases; but when rotation needs to be performed around all three axes at the same time then Euler angles may not be sufficient due to an inherent deficiency in this system which manifests itself as Gimbal lock. People resort to Quaternions in such situations, which is more advanced than this but doesn't suffer from Gimbal locks when used correctly.

I hope this clarifies basic rotation.

Rotation not Revolution

The aforementioned matrices rotate an object at a distance r = v(x² + y²) from the origin along a circle of radius r; lookup polar coordinates to know why. This rotation will be with respect to the world space origin a.k.a revolution. Usually we need to rotate an object around its own frame/pivot and not around the world's i.e. local origin. This can also be seen as a special case where r = 0. Since not all objects are at the world origin, simply rotating using these matrices will not give the desired result of rotating around the object's own frame. You'd first translate (move) the object to world origin (so that the object's origin would align with the world's, thereby making r = 0), perform the rotation with one (or more) of these matrices and then translate it back again to its previous location. The order in which the transforms are applied matters. Combining multiple transforms together is called concatenation or composition.


I urge you to read about linear and affine transformations and their composition to perform multiple transformations in one shot, before playing with transformations in code. Without understanding the basic maths behind it, debugging transformations would be a nightmare. I found this lecture video to be a very good resource. Another resource is this tutorial on transformations that aims to be intuitive and illustrates the ideas with animation (caveat: authored by me!).

Rotation around Arbitrary Vector

A product of the aforementioned matrices should be enough if you only need rotations around cardinal axes (X, Y or Z) like in the question posted. However, in many situations you might want to rotate around an arbitrary axis/vector. The Rodrigues' formula (a.k.a. axis-angle formula) is a commonly prescribed solution to this problem. However, resort to it only if you’re stuck with just vectors and matrices. If you're using Quaternions, just build a quaternion with the required vector and angle. Quaternions are a superior alternative for storing and manipulating 3D rotations; it's compact and fast e.g. concatenating two rotations in axis-angle representation is fairly expensive, moderate with matrices but cheap in quaternions. Usually all rotation manipulations are done with quaternions and as the last step converted to matrices when uploading to the rendering pipeline. See Understanding Quaternions for a decent primer on quaternions.

Setting different color for each series in scatter plot on matplotlib

I don't know what you mean by 'manually'. You can choose a colourmap and make a colour array easily enough:

import numpy as np
import matplotlib.pyplot as plt
import as cm

x = np.arange(10)
ys = [i+x+(i*x)**2 for i in range(10)]

colors = cm.rainbow(np.linspace(0, 1, len(ys)))
for y, c in zip(ys, colors):
    plt.scatter(x, y, color=c)

Matplotlib graph with different colors

Or you can make your own colour cycler using itertools.cycle and specifying the colours you want to loop over, using next to get the one you want. For example, with 3 colours:

import itertools

colors = itertools.cycle(["r", "b", "g"])
for y in ys:
    plt.scatter(x, y, color=next(colors))

Matplotlib graph with only 3 colors

Come to think of it, maybe it's cleaner not to use zip with the first one neither:

colors = iter(cm.rainbow(np.linspace(0, 1, len(ys))))
for y in ys:
    plt.scatter(x, y, color=next(colors))

How to use a client certificate to authenticate and authorize in a Web API

Looking at the source code I also think there must be some issue with the private key.

What it is doing is actually to check if the certificate that is passed is of type X509Certificate2 and if it has the private key.

If it doesn't find the private key it tries to find the certificate in the CurrentUser store and then in the LocalMachine store. If it finds the certificate it checks if the private key is present.

(see source code from class SecureChannnel, method EnsurePrivateKey)

So depending on which file you imported (.cer - without private key or .pfx - with private key) and on which store it might not find the right one and Request.ClientCertificate won't be populated.

You can activate Network Tracing to try to debug this. It will give you output like this:

  • Trying to find a matching certificate in the certificate store
  • Cannot find the certificate in either the LocalMachine store or the CurrentUser store.

How to implement the Java comparable interface?

Emp class needs to implement Comaparable interface so we need to Override its compateTo method.

import java.util.ArrayList;
import java.util.Collections;

class Emp implements Comparable< Emp >{

    int empid;
    String name;

    Emp(int empid,String name){
         this.empid = empid;   = name;


    public String toString(){
        return empid+" "+name;

    public int compareTo(Emp o) {

       return 0; 
     else if(this.empid < o.empid){
     return 1;
       return -1;

public class JavaApplication1 {

    public static void main(String[] args) {

    ArrayList<Emp> a= new ArrayList<Emp>();

    a.add(new Emp(10,"Mahadev"));
      a.add(new Emp(50,"Ashish"));
      a.add(new Emp(40,"Amit"));
      for(Emp id:a){


Can a foreign key be NULL and/or duplicate?

Can a Foreign key be NULL?

Existing answers focused on single column scenario. If we consider multi column foreign key we have more options using MATCH [SIMPLE | PARTIAL | FULL] clause defined in SQL Standard:


A value inserted into the referencing column(s) is matched against the values of the referenced table and referenced columns using the given match type. There are three match types: MATCH FULL, MATCH PARTIAL, and MATCH SIMPLE (which is the default). MATCH FULL will not allow one column of a multicolumn foreign key to be null unless all foreign key columns are null; if they are all null, the row is not required to have a match in the referenced table. MATCH SIMPLE allows any of the foreign key columns to be null; if any of them are null, the row is not required to have a match in the referenced table. MATCH PARTIAL is not yet implemented.

(Of course, NOT NULL constraints can be applied to the referencing column(s) to prevent these cases from arising.)


INSERT INTO A(a, b, d) 
VALUES (NULL, NULL, NOW()),('a', NULL, NOW()),(NULL, 'b', NOW()),('c', 'b', NOW());


-- MATCH SIMPLE - default behaviour nulls are allowed

INSERT INTO B(id, ref_a, ref_b) VALUES (1, NULL, 'b');  

-- (NULL/'x') 'x' value does not exists in A table, but insert is valid
INSERT INTO B(id, ref_a, ref_b) VALUES (2, NULL, 'x');  


-- MATCH PARTIAL - not implemented
-- ERROR:  MATCH PARTIAL not yet implemented


-- MATCH FULL nulls are not allowed

-- FK is defined, inserting NULL as part of FK
INSERT INTO B(id, ref_a, ref_b) VALUES (1, NULL, 'b');
-- ERROR:  MATCH FULL does not allow mixing of null and nonnull key values.

-- FK is defined, inserting all NULLs - valid
INSERT INTO B(id, ref_a, ref_b) VALUES (1, NULL, NULL);

db<>fiddle demo

jQuery .attr("disabled", "disabled") not working in Chrome

If you are using jQuery < 1.6 do this:

jQuery("input[type='text']").attr("disabled", 'disabled');

If you are using jQuery 1.6+:

jQuery("input[type='text']").prop("disabled", true);

See this question: .prop() vs .attr() for references why.

Or you can try this:

$('input:text').attr("disabled", 'disabled');

see here for info on :text

Python Tkinter clearing a frame

pack_forget and grid_forget will only remove widgets from view, it doesn't destroy them. If you don't plan on re-using the widgets, your only real choice is to destroy them with the destroy method.

To do that you have two choices: destroy each one individually, or destroy the frame which will cause all of its children to be destroyed. The latter is generally the easiest and most effective.

Since you claim you don't want to destroy the container frame, create a secondary frame. Have this secondary frame be the container for all the widgets you want to delete, and then put this one frame inside the parent you do not want to destroy. Then, it's just a matter of destroying this one frame and all of the interior widgets will be destroyed along with it.

Remove columns from DataTable in C#

To remove all columns after the one you want, below code should work. It will remove at index 10 (remember Columns are 0 based), until the Column count is 10 or less.

DataTable dt;
int desiredSize = 10;

while (dt.Columns.Count > desiredSize)

How to install/start Postman native v4.10.3 on Ubuntu 16.04 LTS 64-bit?

also you need install nodejs:

curl -sL | sudo -E bash -
sudo apt-get install -y nodejs 

What is the difference between match_parent and fill_parent?

Google changed the name to avoid confusion.

Problem with the old name fill parent was that it implies its affecting the dimensions of the parent, while match parent better describes the resulting behavior - match the dimension with the parent.

Both constants resolve to -1 in the end, and so result in the identical behavior in the app. Ironically enough, this name change made to clarify things seems to have added confusion rather than eliminating it.

Add a new item to a dictionary in Python

default_data['item3'] = 3

Easy as py.

Another possible solution:

default_data.update({'item3': 3})

which is nice if you want to insert multiple items at once.

Smooth scroll without the use of jQuery

Native browser smooth scrolling in JavaScript is like this:

// scroll to specific values,
// same as window.scroll() method.
// for scrolling a particular distance, use window.scrollBy().
  top: 2500, 
  left: 0, 
  behavior: 'smooth' 

// scroll certain amounts from current position 
  top: 100, // negative value acceptable
  left: 0, 
  behavior: 'smooth' 

// scroll to a certain element
  behavior: 'smooth' 

How to set up datasource with Spring for HikariCP?

for DB2, please try below configuration.

<bean id="hikariConfig" class="com.zaxxer.hikari.HikariConfig">
    <property name="poolName" value="springHikariCP" />
    <property name="dataSourceClassName" value=""/>

    <property name="maximumPoolSize" value="${db.maxTotal}" />
    <property name="dataSourceProperties">
            <prop key="driverType">4</prop>
            <prop key="serverName"></prop>
            <prop key="databaseName">dbname</prop>
            <prop key="portNumber">50000</prop>
            <prop key="user">db2inst1</prop>
            <prop key="password">password</prop>

    <property name="jdbcUrl" value="${db.url}" />
    <property name="username" value="${db.username}" />
    <property name="password" value="${db.password}" />
<bean id="dataSource" class="com.zaxxer.hikari.HikariDataSource" destroy-method="close">
    <constructor-arg ref="hikariConfig" />

Login failed for user 'IIS APPPOOL\ASP.NET v4.0'

something similar happened to me what worked for me was changing the property Integrated Security = True to Integrated Security = false in the web.config of the website

How to check if the request is an AJAX request with PHP

There is no sure-fire way of knowing that a request was made via Ajax. You can never trust data coming from the client. You could use a couple of different methods but they can be easily overcome by spoofing.

arranging div one below the other

You don't even need the float:left;

It seems the default behavior is to render one below the other, if it doesn't happen it's because they are inheriting some style from above.




<div id="wrapper">
    <div id="inner1">inner1</div>
    <div id="inner2">inner2</div>

MySQL - ERROR 1045 - Access denied

  1. Go to mysql console
  2. Enter use mysql;
  3. UPDATE mysql.user SET Password= PASSWORD ('') WHERE User='root' FLUSH PRIVILEGES; exit PASSWORD ('') is must empty
  4. Then go to wamp/apps/phpmyadmin../
  5. Find $cfg ['Servers']['$I']['password']='root';
  6. Replace the ['password'] with ['your old password']
  7. Save the file
  8. Restart the all services and goto localhost/phpmyadmin

What is a unix command for deleting the first N characters of a line?

Here is simple function, tested in bash. 1st param of function is string, 2nd param is number of characters to be stripped

function stringStripNCharsFromStart { echo ${1:$2:${#1}} }

Usage: enter image description here

How can I list all cookies for the current page with Javascript?

Many people have already mentioned that document.cookie gets you all the cookies (except http-only ones).

I'll just add a snippet to keep up with the times.

document.cookie.split(';').reduce((cookies, cookie) => {
  const [ name, value ] = cookie.split('=').map(c => c.trim());
  cookies[name] = value;
  return cookies;
}, {});

The snippet will return an object with cookie names as the keys with cookie values as the values.

Slightly different syntax:

document.cookie.split(';').reduce((cookies, cookie) => {
  const [ name, value ] = cookie.split('=').map(c => c.trim());
  return { ...cookies, [name]: value };
}, {});

Convert int (number) to string with leading zeros? (4 digits)

Use String.PadLeft like this:

var result = input.ToString().PadLeft(length, '0');

Upgrading PHP on CentOS 6.5 (Final)

Steps for upgrading to PHP7 on CentOS 6 system. Taken from install-php-7-in-centos-6

To install latest PHP 7, you need to add EPEL and Remi repository to your CentOS 6 system

yum install
yum install

Now install yum-utils, a group of useful tools that enhance yum’s default package management features

yum install yum-utils

In this step, you need to enable Remi repository using yum-config-manager utility, as the default repository for installing PHP.

yum-config-manager --enable remi-php70

If you want to install PHP 7.1 or PHP 7.2 on CentOS 6, just enable it as shown.

yum-config-manager --enable remi-php71 
yum-config-manager --enable remi-php72

Then finally install PHP 7 on CentOS 6 with all necessary PHP modules using the following command.

yum install php php-mcrypt php-cli php-gd php-curl php-mysql php-ldap php-zip php-fileinfo

Double check the installed version of PHP on your system as follows.

php -V 

Counting the number of occurences of characters in a string

if this is a real program and not a study project, then look at using the Apache Commons StringUtils class - particularly the countMatches method.

If it is a study project then keep at it and learn from your exploring :)

Share variables between files in Node.js?

a variable declared with or without the var keyword got attached to the global object. This is the basis for creating global variables in Node by declaring variables without the var keyword. While variables declared with the var keyword remain local to a module.

see this article for further understanding -

PDO get the last ID inserted

That's because that's an SQL function, not PHP. You can use PDO::lastInsertId().


$stmt = $db->prepare("...");
$id = $db->lastInsertId();

If you want to do it with SQL instead of the PDO API, you would do it like a normal select query:

$stmt = $db->query("SELECT LAST_INSERT_ID()");
$lastId = $stmt->fetchColumn();

Node.js Best Practice Exception Handling

One instance where using a try-catch might be appropriate is when using a forEach loop. It is synchronous but at the same time you cannot just use a return statement in the inner scope. Instead a try and catch approach can be used to return an Error object in the appropriate scope. Consider:

function processArray() {
    try { 
       [1, 2, 3].forEach(function() { throw new Error('exception'); }); 
    } catch (e) { 
       return e; 

It is a combination of the approaches described by @balupton above.

Custom method names in ASP.NET Web API

I am days into the MVC4 world.

For what its worth, I have a SitesAPIController, and I needed a custom method, that could be called like:


With different values for the last parameter to get record with different dispositions.

What Finally worked for me was:

The method in the SitesAPIController:

// GET api/SitesAPI/Disposition/1
public Site Disposition(int disposition)
    Site site = db.Sites.Where(s => s.Disposition == disposition).First();
    return site;

And this in the WebApiConfig.cs

// this was already there
    name: "DefaultApi",
    routeTemplate: "api/{controller}/{id}",
    defaults: new { id = RouteParameter.Optional }

// this i added
    name: "Action",
    routeTemplate: "api/{controller}/{action}/{disposition}"

For as long as I was naming the {disposition} as {id} i was encountering:

"Message": "No HTTP resource was found that matches the request URI 'http://localhost:9000/api/SitesAPI/Disposition/0'.",
"MessageDetail": "No action was found on the controller 'SitesAPI' that matches the request."

When I renamed it to {disposition} it started working. So apparently the parameter name is matched with the value in the placeholder.

Feel free to edit this answer to make it more accurate/explanatory.

Automatically run %matplotlib inline in IPython Notebook

Further to @Kyle Kelley and @DGrady, here is the entry which can be found in the

$HOME/.ipython/profile_default/ (or whichever profile you have created)


# Configure matplotlib for interactive use with the default matplotlib backend.
# c.IPKernelApp.matplotlib = none


# Configure matplotlib for interactive use with the default matplotlib backend.
c.IPKernelApp.matplotlib = 'inline'

This will then work in both ipython qtconsole and notebook sessions.

Make Error 127 when running trying to compile code

Error 127 means one of two things:

  1. file not found: the path you're using is incorrect. double check that the program is actually in your $PATH, or in this case, the relative path is correct -- remember that the current working directory for a random terminal might not be the same for the IDE you're using. it might be better to just use an absolute path instead.
  2. ldso is not found: you're using a pre-compiled binary and it wants an interpreter that isn't on your system. maybe you're using an x86_64 (64-bit) distro, but the prebuilt is for x86 (32-bit). you can determine whether this is the answer by opening a terminal and attempting to execute it directly. or by running file -L on /bin/sh (to get your default/native format) and on the compiler itself (to see what format it is).

if the problem is (2), then you can solve it in a few diff ways:

  1. get a better binary. talk to the vendor that gave you the toolchain and ask them for one that doesn't suck.
  2. see if your distro can install the multilib set of files. most x86_64 64-bit distros allow you to install x86 32-bit libraries in parallel.
  3. build your own cross-compiler using something like crosstool-ng.
  4. you could switch between an x86_64 & x86 install, but that seems a bit drastic ;).

How to get an Instagram Access Token

The access token is returned as a URI fragment after you authorize the application to use your Instagram data. It should look something like the following: enter image description here

jquery to change style attribute of a div class

In order to change the attribute of the class conditionally,

var css_val = $(".handle").css('left');
if(css_val == '336px')

If id is given as following,

<a id="handle" class="handle" href="#" style="left: 336px;"></a>

Here is an alternative solution:

var css_val = $("#handle").css('left');
if(css_val == '336px')

Xcode/Simulator: How to run older iOS version?

I was searching for how to do this on a much newer version of xcode than the original question and while the answers here got me where I needed to go, they aren't quite accurate for location anymore. Xcode 11.3.1, you need to go into Preferences -> Components, then select the desired Simulators. You can also select tvOS and watchOS similators from the same window.

Components preference window from Xcode 11.3.1

Laravel PHP Command Not Found

My quick way of creating a new project

//install composer locally on web root - run the code from:

Then install laravel:

php composer.phar require laravel/installer

Then create the project without adding anything to any path

vendor/laravel/installer/bin/laravel new [ProjectName]

//add project to git

cd ProjectName
git init
git remote add origin git@...[youGitPathToProject]

Wondering if this way of doing it has any issues - please let me know

MySQL Removing Some Foreign keys

Here's a way to drop foreign key constraint, it will work. ALTER TABLE location.location_id DROP FOREIGN KEY location_ibfk_1;

how to convert a string to an array in php

try json_decode like so


   $var = '["SupplierInvoiceReconciliation"]';
   $var = json_decode($var, TRUE);

Get current date in milliseconds

There are several ways of doing this, although my personal favorite is:

CFAbsoluteTime timeInSeconds = CFAbsoluteTimeGetCurrent();

You can read more about this method here. You can also create a NSDate object and get time by calling timeIntervalSince1970 which returns the seconds since 1/1/1970:

NSTimeInterval timeInSeconds = [[NSDate date] timeIntervalSince1970];

And in Swift:

let timeInSeconds: TimeInterval = Date().timeIntervalSince1970

Align inline-block DIVs to top of container element

<style type="text/css">
        div {
  text-align: center;

            width: 150px;
            height: 150px;
            border-radius: 50%;

            display: block;

<script src=""></script>
  <input type='password' class='secondInput mt-4 mr-1' placeholder="Password">
  <span class='dif'></span>

<script type="text/javascript">

$('button').click(function() {


Position DIV relative to another DIV?

You want to use position: absolute while inside the other div.


Connect to SQL Server Database from PowerShell

I did remove integrated security ... my goal is to log onto a sql server using a connection string WITH active directory username / password. When I do that it always fails. Does not matter the format ... sam company\user ... upn [email protected] ... basic username.

Radio Buttons "Checked" Attribute Not Working

Radio inputs must be inside of a form for 'checked' to work.

Send and receive messages through NSNotificationCenter in Objective-C?

This one helped me:

// Add an observer that will respond to loginComplete
[[NSNotificationCenter defaultCenter] addObserver:self 
                                                 name:@"loginComplete" object:nil];

// Post a notification to loginComplete
[[NSNotificationCenter defaultCenter] postNotificationName:@"loginComplete" object:nil];

// the function specified in the same class where we defined the addObserver
- (void)showMainMenu:(NSNotification *)note {
    NSLog(@"Received Notification - Someone seems to have logged in"); 


How to restart Postgresql

On Windows :

1-Open Run Window by Winkey + R

2-Type services.msc

3-Search Postgres service based on version installed.

4-Click stop, start or restart the service option.

On Linux :

sudo systemctl restart postgresql

also instead of "restart" you can replace : status, stop or status.

Array.size() vs Array.length

we can you use .length property to set or returns number of elements in an array. return value is a number

> set the length: let count = myArray.length;
> return lengthof an array : myArray.length

we can you .size in case we need to filter duplicate values and get the count of elements in a set.

const set = new set([1,1,2,1]); 
 console.log(set.size) ;`

How to pass the button value into my onclick event function?

You can pass the element into the function <input type="button" value="mybutton1" onclick="dosomething(this)">test by passing this. Then in the function you can access the value like this:

function dosomething(element) {

AsyncTask Android example

My full answer is here, but here is an explanatory image to supplement the other answers on this page. For me, understanding where all the variables were going was the most confusing part in the beginning.

enter image description here

Sum all values in every column of a data.frame in R

You can use function colSums() to calculate sum of all values. [,-1] ensures that first column with names of people is excluded.

Height Weight 
   199    425

Assuming there could be multiple columns that are not numeric, or that your column order is not fixed, a more general approach would be:

colSums(Filter(is.numeric, people))

How to get unique device hardware id in Android?

I use following code to get Android id.

String android_id = Secure.getString(this.getContentResolver(),

Log.d("Android","Android ID : "+android_id);

enter image description here

Grep and Python

You might be interested in pyp. Citing my other answer:

"The Pyed Piper", or pyp, is a linux command line text manipulation tool similar to awk or sed, but which uses standard python string and list methods as well as custom functions evolved to generate fast results in an intense production environment.

How can I check which version of Angular I'm using?

For angular 4+ use,

  • ng version
  • ng v

Please note ng -v option does not work in Angular 7+.

commands not found on zsh

A way to edit the .zshrc file without doing it through iTerm2 or native Terminal on macOS is to use a terminal in another application. For example, I used the terminal as part of VSCode and was able to find and edit the file.

How to use sed to extract substring

sed 's/[^"]*"\([^"]*\).*/\1/'

does the job.

explanation of the part inside ' '

  • s - tells sed to substitute
  • / - start of regex string to search for
  • [^"]* - any character that is not ", any number of times. (matching parameter name=)
  • " - just a ".
  • ([^"]*) - anything inside () will be saved for reference to use later. The \ are there so the brackets are not considered as characters to search for. [^"]* means the same as above. (matching RemoteHost for example)
  • .* - any character, any number of times. (matching " access="readWrite"> /parameter)
  • / - end of the search regex, and start of the substitute string.
  • \1 - reference to that string we found in the brackets above.
  • / end of the substitute string.

basically s/search for this/replace with this/ but we're telling him to replace the whole line with just a piece of it we found earlier.

c# .net change label text

Old question, but I had this issue as well, so after assigning the Text property, calling Refresh() will update the text.

Label1.Text = "Du har nu lånat filmen:" + test;

Using classes with the Arduino

Can you provide an example of what did not work? As you likely know, the Wiring language is based on C/C++, however, not all of C++ is supported.

Whether you are allowed to create classes in the Wiring IDE, I'm not sure (my first Arduino is in the mail right now). I do know that if you wrote a C++ class, compiled it using AVR-GCC, then loaded it on your Arduino using AVRDUDE, it would work.

"git pull" or "git merge" between master and development branches

my rule of thumb is:

rebase for branches with the same name, merge otherwise.

examples for same names would be master, origin/master and otherRemote/master.

if develop exists only in the local repository, and it is always based on a recent origin/master commit, you should call it master, and work there directly. it simplifies your life, and presents things as they actually are: you are directly developing on the master branch.

if develop is shared, it should not be rebased on master, just merged back into it with --no-ff. you are developing on develop. master and develop have different names, because we want them to be different things, and stay separate. do not make them same with rebase.

Run a script in Dockerfile

Try to create script with ADD command and specification of working directory Like this("script" is the name of script and /root/ is where you want it in the container, it can be different path:

ADD /root/

In this case ADD has to come before CMD, if you have one BTW it's cool way to import scripts to any location in container from host machine

In CMD place [./script]

It should automatically execute your script

You can also specify WORKDIR as /root, then you'l be automatically placed in root, upon starting a container

Count number of tables in Oracle

If you want to know the number of tables that belong to a certain schema/user, you can also use SQL similar to this one:


Setting the User-Agent header for a WebClient request

This worked for me:

var message = new HttpRequestMessage(method, url);
message.Headers.TryAddWithoutValidation("user-agent", "<user agent header value>");
var client = new HttpClient();
var response = await client.SendAsync(message);

Here you can find the documentation for TryAddWithoutValidation

Sending credentials with cross-domain posts?

You can use the beforeSend callback to set additional parameters (The XMLHTTPRequest object is passed to it as its only parameter).

Just so you know, this type of cross-domain request will not work in a normal site scenario and not with any other browser. I don't even know what security limitations FF 3.5 imposes as well, just so you don't beat your head against the wall for nothing:

    url: 'http://bar.other',
    data: { whatever:'cool' },
    type: 'GET',
    beforeSend: function(xhr){
       xhr.withCredentials = true;

One more thing to beware of, is that jQuery is setup to normalize browser differences. You may find that further limitations are imposed by the jQuery library that prohibit this type of functionality.

EL access a map value by Integer key

If you just happen to have a Map with Integer keys you cannot change, you could write a custom EL function to convert a Long to Integer. This would allow you to do something like:

<c:out value="${map[myLib:longToInteger(1)]}"/>

How to upload a file using Java HttpClient library working with PHP

Ok, the Java code I used was wrong, here comes the right Java class:

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpVersion;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.mime.MultipartEntity;
import org.apache.http.entity.mime.content.ContentBody;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.CoreProtocolPNames;
import org.apache.http.util.EntityUtils;

public class PostFile {
  public static void main(String[] args) throws Exception {
    HttpClient httpclient = new DefaultHttpClient();
    httpclient.getParams().setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1);

    HttpPost httppost = new HttpPost("http://localhost:9001/upload.php");
    File file = new File("c:/TRASH/zaba_1.jpg");

    MultipartEntity mpEntity = new MultipartEntity();
    ContentBody cbFile = new FileBody(file, "image/jpeg");
    mpEntity.addPart("userfile", cbFile);

    System.out.println("executing request " + httppost.getRequestLine());
    HttpResponse response = httpclient.execute(httppost);
    HttpEntity resEntity = response.getEntity();

    if (resEntity != null) {
    if (resEntity != null) {


note using MultipartEntity.

How to set up devices for VS Code for a Flutter emulator

You do not need to create a virtual device using android studio. You can use your android device running on android 8.0 or higher. All you have to do is to activate developer settings, then enable USB DEBUGGING in the developer settings. Your device will show at the bottom right side of the VS Code. Without enabling the USB debugging, the device may not show.enter image description here

Using BigDecimal to work with currencies

I would be radical. No BigDecimal.

Here is a great article

Ideas from here.

import java.math.BigDecimal;

public class Main {

    public static void main(String[] args) {

    private static void testEqualsAndCompare() {
        final BigDecimal zero = new BigDecimal("0.0");
        final BigDecimal zerozero = new BigDecimal("0.00");

        boolean zerosAreEqual = zero.equals(zerozero);
        boolean zerosAreEqual2 = zerozero.equals(zero);

        System.out.println("zerosAreEqual: " + zerosAreEqual + " " + zerosAreEqual2);

        int zerosCompare = zero.compareTo(zerozero);
        int zerosCompare2 = zerozero.compareTo(zero);
        System.out.println("zerosCompare: " + zerosCompare + " " + zerosCompare2);

    private static void testArithmetic() {
        try {
            BigDecimal value = new BigDecimal(1);
            value = value.divide(new BigDecimal(3));
        } catch (ArithmeticException e) {
            System.out.println("Failed to devide. " + e.getMessage());

    private static void testConstructors() {
        double doubleValue = 35.7;
        BigDecimal fromDouble = new BigDecimal(doubleValue);
        BigDecimal fromString = new BigDecimal("35.7");

        boolean decimalsEqual = fromDouble.equals(fromString);
        boolean decimalsEqual2 = fromString.equals(fromDouble);

        System.out.println("From double: " + fromDouble);
        System.out.println("decimalsEqual: " + decimalsEqual + " " + decimalsEqual2);

It prints

From double: 35.7000000000000028421709430404007434844970703125
decimalsEqual: false false
zerosAreEqual: false false
zerosCompare: 0 0
Failed to devide. Non-terminating decimal expansion; no exact representable decimal result.

How about storing BigDecimal into a database? Hell, it also stores as a double value??? At least, if I use mongoDb without any advanced configuration it will store BigDecimal.TEN as 1E1.

Possible solutions?

I came with one - use String to store BigDecimal in Java as a String into the database. You have validation, for example @NotNull, @Min(10), etc... Then you can use a trigger on update or save to check if current string is a number you need. There are no triggers for mongo though. Is there a built-in way for Mongodb trigger function calls?

There is one drawback I am having fun around - BigDecimal as String in Swagger defenition

I need to generate swagger, so our front-end team understands that I pass them a number presented as a String. DateTime for example presented as a String.

There is another cool solution I read in the article above... Use long to store precise numbers.

A standard long value can store the current value of the Unites States national debt (as cents, not dollars) 6477 times without any overflow. Whats more: it’s an integer type, not a floating point. This makes it easier and accurate to work with, and a guaranteed behavior.


Maybe in the future MongoDb will add support for BigDecimal. 3.3.8 seems to have this done.

It is an example of the second approach. Use scaling.

Python: How to pip install opencv2 with specific version 2.4.9?

The following command line pip install opencv-python== works properly. Use one of the versions presented to you. May be:,,,,,,, or, etc.

To make sure, you can see my screenshot.screenshot

Notepad++ cached files location

I lost somehow my temporary notepad++ files, they weren't showing in tabs. So I did some search in appdata folder, and I found all my temporary files there. It seems that they are stored there for a long time.




How to check 'undefined' value in jQuery

You can use shorthand technique to check whether it is undefined or null

 function A(val)
   if(val || "") 
   //do this
 //do this

hope this will help you

ASP MVC in IIS 7 results in: HTTP Error 403.14 - Forbidden

After trying every solution suggested here, I found yet another possible solution: URLScan

The IIS had WebDAV disabled, even in the web.config of my application, WebDAV's handler and module was removed. PUTs still returned a 403 - Forbidden without any log entries in the IIS logs. (GET / POST worked fine).

Turns out the IIS had an active ISAPI Filter (the URLScan) enabled which prevented all PUTs. After removing URLScan, it worked for me.

SELECT list is not in GROUP BY clause and contains nonaggregated column .... incompatible with sql_mode=only_full_group_by

Update for MySQL 8.0

Your sql-mode will not have NO_AUTO_CREATE_USER as it has been removed as mentioned here - how-to-set-sql-mode-in-my-cnf-in-mysql-8


Also if someone doesn't have a my.cnf file then they create a new one in /etc/my.cnf and then add the above lines.

HTTPS connections over proxy servers

Here is my complete Java code that supports both HTTP and HTTPS requests using SOCKS proxy.

import java.nio.charset.StandardCharsets;

import org.apache.http.HttpHost;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.protocol.HttpContext;
import org.apache.http.ssl.SSLContexts;
import org.apache.http.util.EntityUtils;


 * How to send a HTTP or HTTPS request via SOCKS proxy.
public class ClientExecuteSOCKS {

    public static void main(String[] args) throws Exception {
        Registry<ConnectionSocketFactory> reg = RegistryBuilder.<ConnectionSocketFactory>create()
            .register("http", new MyHTTPConnectionSocketFactory())
            .register("https", new MyHTTPSConnectionSocketFactory(SSLContexts.createSystemDefault
        PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager(reg);
        try (CloseableHttpClient httpclient = HttpClients.custom()
            .build()) {
            InetSocketAddress socksaddr = new InetSocketAddress("mysockshost", 1234);
            HttpClientContext context = HttpClientContext.create();
            context.setAttribute("socks.address", socksaddr);

            HttpHost target = new HttpHost("", 80, "http");
            HttpGet request = new HttpGet("/");

            System.out.println("Executing request " + request + " to " + target + " via SOCKS " +
                "proxy " + socksaddr);
            try (CloseableHttpResponse response = httpclient.execute(target, request, context)) {
                System.out.println(EntityUtils.toString(response.getEntity(), StandardCharsets

    static class MyHTTPConnectionSocketFactory extends PlainConnectionSocketFactory {
        public Socket createSocket(final HttpContext context) throws IOException {
            InetSocketAddress socksaddr = (InetSocketAddress) context.getAttribute("socks.address");
            Proxy proxy = new Proxy(Proxy.Type.SOCKS, socksaddr);
            return new Socket(proxy);

    static class MyHTTPSConnectionSocketFactory extends SSLConnectionSocketFactory {
        public MyHTTPSConnectionSocketFactory(final SSLContext sslContext) {

        public Socket createSocket(final HttpContext context) throws IOException {
            InetSocketAddress socksaddr = (InetSocketAddress) context.getAttribute("socks.address");
            Proxy proxy = new Proxy(Proxy.Type.SOCKS, socksaddr);
            return new Socket(proxy);

Finding duplicate integers in an array and display how many times they occurred

using System;
using System.Collections.Generic;

namespace ConsoleApp1
    /// <summary>
    /// How do you find the duplicate number on a given integer array?
    /// </summary>
    class Program
        static void Main(string[] args)
            int[] array = { 10, 5, 10, 2, 2, 3, 4, 5, 5, 6, 7, 8, 9, 11, 12, 12 };

            Dictionary<int, int> duplicates = FindDuplicate(array);



        private static Dictionary<T, int> FindDuplicate<T>(IEnumerable<T> source)
            HashSet<T> set = new HashSet<T>();
            Dictionary<T, int> duplicates = new Dictionary<T, int>();

            foreach (var item in source)
                if (!set.Add(item))
                    if (duplicates.ContainsKey(item))
                        duplicates.Add(item, 2);

            return duplicates;

        private static void Display(Dictionary<int, int> duplicates)
            foreach (var item in duplicates)

SQL Inner-join with 3 tables?

This is correct query for join 3 table with same id**

select a.empname,a.empsalary,b.workstatus,b.bonus,c.dateofbirth from employee a, Report b,birth c where a.empid=b.empid and a.empid=c.empid and b.empid='103';

employee first table. report second table. birth third table

Postgresql - unable to drop database because of some auto connections to DB

1. Shut down Pg server
enter image description here
2. It will disconnect all active connection
3. Restart Pg Server
4. Try your command

Disabling user input for UITextfield in swift

you can use UILabel instead if you don't want the user to be able to modify anything in your UITextField

A programmatic solution would be to use enabled property:

yourTextField.enabled = false

A way to do it in a storyboard:

Uncheck the Enabled checkbox in the properties of your UITextField

enter image description here

How can I export tables to Excel from a webpage

There are practical two ways to do this automaticly while only one solution can be used in all browsers. First of all you should use the open xml specification to build the excel sheet. There are free plugins from Microsoft available that make this format also available for older office versions. The open xml is standard since office 2007. The the two ways are obvious the serverside or the clientside.

The clientside implementation use a new standard of CSS that allow you to store data instead of just the URL to the data. This is a great approach coz you dont need any servercall, just the data and some javascript. The killing downside is that microsoft don't support all parts of it in the current IE (I don't know about IE9) releases. Microsoft restrict the data to be a image but we will need a document. In firefox it works quite fine. For me the IE was the killing point.

The other way is to user a serverside implementation. There should be a lot implementations of open XML for all languages. You just need to grap one. In most cases it will be the simplest way to modify a Viewmodel to result in a Document but for sure you can send all data from Clientside back to server and do the same.

Extract values in Pandas value_counts()

The best way to extract the values is to just do the following


This returns a dictionary which you can use like any other dict. Using values or keys.

 {"apple": 5, "sausage": 2, "banana": 2, "cheese": 1}

How to use `@ts-ignore` for a block

You can't.

As a workaround you can use a // @ts-nocheck comment at the top of a file to disable type-checking for that file:

So to disable checking for a block (function, class, etc.), you can move it into its own file, then use the comment/flag above. (This isn't as flexible as block-based disabling of course, but it's the best option available at the moment.)

add Shadow on UIView using swift 3

Shadow using UIView Extension Swift 4

I would like to add one more line with selected answer! When we rasterizing the layer, It needs to be set to 2.0 for retina displays. Otherwise label text or images on that view will be blurry. So we need to add rasterizationScale also.

  extension UIView {

    func dropShadow() {
        layer.masksToBounds = false
        layer.shadowColor =
        layer.shadowOpacity = 0.5
        layer.shadowOffset = CGSize(width: -1, height: 1)
        layer.shadowRadius = 1
        layer.shadowPath = UIBezierPath(rect: self.bounds).cgPath
        layer.shouldRasterize = true
        layer.rasterizationScale = UIScreen.main.scale

How do I automatically play a Youtube video (IFrame API) muted?

var video1;_x000D_
function onYouTubeIframeAPIReady(){_x000D_
 player = new YT.Player("video1", {_x000D_
  videoId: "id-number",_x000D_
  width: 300,_x000D_
  height: 200, _x000D_
  playerVars: {_x000D_
   "autoplay": 1, // and 0 means off_x000D_
   "controls": 1,_x000D_
   "showinfo": 0,_x000D_
   "modestbranding": 0,_x000D_
   "loop": 1,_x000D_
   "fs": 0,_x000D_
   "cc_load_policy": 0,_x000D_
   "iv_load_policy": 3,_x000D_
  events: {_x000D_
      'onReady': onPlayerReady_x000D_
function onPlayerReady(event) {_x000D_;_x000D_; //this can be set from 0 to 100_x000D_

Remember that the sound will not be muted in IE and Safari.

JRE 1.7 - java version - returns: java/lang/NoClassDefFoundError: java/lang/Object

You are most probably missing a file called rt.jar in your installation which has the class file for java.lang.Object. Check your install files etc.

In particular, note that a 64-bit intsaller overlays (or installs "next to") an existing 32-bit installation. In other words, to get a fully working 64-bit installation, you must first run the 32-bit installation, and follow that up with a 64-bit installation if you have a 64bit capable machine...

If instead you do just a 64-bit installation you will be missing certain files in the installation and will get errors such as the one above.

How to avoid "ConcurrentModificationException" while removing elements from `ArrayList` while iterating it?

List myArrayList  = Collections.synchronizedList(new ArrayList());

//add your elements  

synchronized(myArrayList) {
    Iterator i = myArrayList.iterator(); 
     while (i.hasNext()){
         Object  object =;

How can I autoplay a video using the new embed code style for Youtube?

None of yours are solved my problem. But, I found a good solution for me to work properly right now. In between tags write this code:

<div style="position: fixed; z-index: -99; width: 100%; height: 100%">
  <iframe frameborder="0" height="100%" width="100%" 
    src="**[CHANGE HERE WITH YOUR YOUTUBE VIDEO ID]**?autoplay=1&controls=0&showinfo=0&autohide=1">

Get age from Birthdate


You can calculate with Dates.

var birthdate = new Date("1990/1/1");
var cur = new Date();
var diff = cur-birthdate; // This is the difference in milliseconds
var age = Math.floor(diff/31557600000); // Divide by 1000*60*60*24*365.25

Getting values from JSON using Python

If you want to iterate over both keys and values of the dictionary, do this:

for key, value in data.items():
    print key, value

Changing background color of selected cell?

The default style is gray and it destroys the colors of the cell if it was done programmatically. You can do this to avoid that. (in Swift)
cell.selectionStyle = .None

Double precision - decimal places

It is actually 53 binary places, which translates to 15 stable decimal places, meaning that if you round a start out with a number with 15 decimal places, convert it to a double, and then round the double back to 15 decimal places you'll get the same number. To uniquely represent a double you need 17 decimal places (meaning that for every number with 17 decimal places, there's a unique closest double) which is why 17 places are showing up, but not all 17-decimal numbers map to different double values (like in the examples in the other answers).

How to convert minutes to Hours and minutes (hh:mm) in java

It can be done like this

        int totalMinutesInt = Integer.valueOf(totalMinutes.toString());

        int hours = totalMinutesInt / 60;
        int hoursToDisplay = hours;

        if (hours > 12) {
            hoursToDisplay = hoursToDisplay - 12;

        int minutesToDisplay = totalMinutesInt - (hours * 60);

        String minToDisplay = null;
        if(minutesToDisplay == 0 ) minToDisplay = "00";     
        else if( minutesToDisplay < 10 ) minToDisplay = "0" + minutesToDisplay ;
        else minToDisplay = "" + minutesToDisplay ;

        String displayValue = hoursToDisplay + ":" + minToDisplay;

        if (hours < 12)
            displayValue = displayValue + " AM";
            displayValue = displayValue + " PM";

        return displayValue;
    } catch (Exception e) {
        LOGGER.error("Error while converting currency.");
    return totalMinutes.toString();

Add params to given URL in Python

Yet another answer:

def addGetParameters(url, newParams):
    (scheme, netloc, path, params, query, fragment) = urlparse.urlparse(url)
    queryList = urlparse.parse_qsl(query, keep_blank_values=True)
    for key in newParams:
        queryList.append((key, newParams[key]))
    return urlparse.urlunparse((scheme, netloc, path, params, urllib.urlencode(queryList), fragment))

Base64 String throwing invalid character error

Whether null char is allowed or not really depends on base64 codec in question. Given vagueness of Base64 standard (there is no authoritative exact specification), many implementations would just ignore it as white space. And then others can flag it as a problem. And buggiest ones wouldn't notice and would happily try decoding it... :-/

But it sounds c# implementation does not like it (which is one valid approach) so if removing it helps, that should be done.

One minor additional comment: UTF-8 is not a requirement, ISO-8859-x aka Latin-x, and 7-bit Ascii would work as well. This because Base64 was specifically designed to only use 7-bit subset which works with all 7-bit ascii compatible encodings.

Multiple left joins on multiple tables in one query

This kind of query should work - after rewriting with explicit JOIN syntax:

SELECT something
FROM   master      parent
JOIN   master      child ON child.parent_id =
LEFT   JOIN second parentdata ON = parent.secondary_id
LEFT   JOIN second childdata ON = child.secondary_id
WHERE  parent.parent_id = 'rootID'

The tripping wire here is that an explicit JOIN binds before "old style" CROSS JOIN with comma (,). I quote the manual here:

In any case JOIN binds more tightly than the commas separating FROM-list items.

After rewriting the first, all joins are applied left-to-right (logically - Postgres is free to rearrange tables in the query plan otherwise) and it works.

Just to make my point, this would work, too:

SELECT something
FROM   master parent
LEFT   JOIN second parentdata ON = parent.secondary_id
,      master child
LEFT   JOIN second childdata ON = child.secondary_id
WHERE  child.parent_id =
AND    parent.parent_id = 'rootID'

But explicit JOIN syntax is generally preferable, as your case illustrates once again.

And be aware that multiple (LEFT) JOIN can multiply rows:

Printing out all the objects in array list

Override toString() method in Student class as below:

   public String toString() {
        return ("StudentName:"+this.getStudentName()+
                    " Student No: "+ this.getStudentNo() +
                    " Email: "+ this.getEmail() +
                    " Year : " + this.getYear());

ASP.NET MVC Razor: How to render a Razor Partial View's HTML inside the controller action

Although adequate answers have already been given, I'd like to propose a less verbose solution, that can be used without the helper methods available in an MVC controller class. Using a third party library called "RazorEngine" you can use .Net file IO to get the contents of the razor file and call

string html = Razor.Parse(razorViewContentString, modelObject);

Get the third party library here.

Best way to write to the console in PowerShell

Default behaviour of PowerShell is just to dump everything that falls out of a pipeline without being picked up by another pipeline element or being assigned to a variable (or redirected) into Out-Host. What Out-Host does is obviously host-dependent.

Just letting things fall out of the pipeline is not a substitute for Write-Host which exists for the sole reason of outputting text in the host application.

If you want output, then use the Write-* cmdlets. If you want return values from a function, then just dump the objects there without any cmdlet.

Sort Pandas Dataframe by Date

You can use pd.to_datetime() to convert to a datetime object. It takes a format parameter, but in your case I don't think you need it.

>>> import pandas as pd
>>> df = pd.DataFrame( {'Symbol':['A','A','A'] ,
>>> df
         Date Symbol
0  02/20/2015      A
1  01/15/2016      A
2  08/21/2015      A
>>> df['Date'] =pd.to_datetime(df.Date)
>>> df.sort('Date') # This now sorts in date order
        Date Symbol
0 2015-02-20      A
2 2015-08-21      A
1 2016-01-15      A

For future search, you can change the sort statement:

>>> df.sort_values(by='Date') # This now sorts in date order
        Date Symbol
0 2015-02-20      A
2 2015-08-21      A
1 2016-01-15      A

What is the purpose of a plus symbol before a variable?

Operator + is a unary operator which converts value to number. Below I prepared a table with corresponding results of using this operator for different values.

| Value                       | + (Value) |
| 1                           | 1         |
| '-1'                        | -1        |
| '3.14'                      | 3.14      |
| '3'                         | 3         |
| '0xAA'                      | 170       |
| true                        | 1         |
| false                       | 0         |
| null                        | 0         |
| 'Infinity'                  | Infinity  |
| 'infinity'                  | NaN       |
| '10a'                       | NaN       |
| undefined                   | Nan       |
| ['Apple']                   | Nan       |
| function(val){ return val } | NaN       |

Operator + returns value for objects which have implemented method valueOf.

let something = {
    valueOf: function () {
        return 25;


How to convert a PIL Image into a numpy array?

You're not saying how exactly putdata() is not behaving. I'm assuming you're doing

>>> pic.putdata(a)
Traceback (most recent call last):
  File "...blablabla.../PIL/", line 1185, in putdata, scale, offset)
SystemError: new style getargs format but argument is not a tuple

This is because putdata expects a sequence of tuples and you're giving it a numpy array. This

>>> data = list(tuple(pixel) for pixel in pix)
>>> pic.putdata(data)

will work but it is very slow.

As of PIL 1.1.6, the "proper" way to convert between images and numpy arrays is simply

>>> pix = numpy.array(pic)

although the resulting array is in a different format than yours (3-d array or rows/columns/rgb in this case).

Then, after you make your changes to the array, you should be able to do either pic.putdata(pix) or create a new image with Image.fromarray(pix).

Minimal web server using netcat

mkfifo pipe;
while true ; 
   #use read line from pipe to make it blocks before request comes in,
   #this is the key.
   { read line<pipe;echo -e "HTTP/1.1 200 OK\r\n";echo $(date);
   }  | nc -l -q 0 -p 8080 > pipe;  


How to change package name in flutter?

This is how i renamed package for both ios and android

  1. Go to build.gradle in app module and rename applicationId ""
  2. Go to Manifest.xml in app/src/main and rename package="" and android:label="App Name"
  3. Go to Manifest.xml in app/src/debug and rename package=""
  4. Go to Manifest.xml in app/src/profile and rename package=""
  5. Go to app/src/main/kotlin/com/something/something/MainActivity.kt and rename package=""
  6. Go to app/src/main/kotlin/ and rename each directory so that the structure looks like app/src/main/kotlin/com/company/name/
  7. Go to pubspec.yaml in your project and change name: something to name: name, example :- if package name is the name: xyz
  8. Go to each dart file in lib folder and rename the imports to the modified name.
  9. Open XCode and open the runner file and click on Runner in project explorer.
  10. Go to General -> double click on Bundle Identifier -> rename it to
  11. Go to Info.plist click on Bundle name -> rename it to your App Name.
  12. close everything -> go to your flutter project and run this command in terminal flutter clean

Select count(*) from result query

This counts the rows of the inner query:

select count(*) from (
    select count(SID) 
    from Test 
    where Date = '2012-12-10' 
    group by SID
) t

However, in this case the effect of that is the same as this:

select count(distinct SID) from Test where Date = '2012-12-10'

angular 4: *ngIf with multiple conditions

Besides the redundant ) this expression will always be true because currentStatus will always match one of these two conditions:

currentStatus !== 'open' || currentStatus !== 'reopen'

perhaps you mean one of

!(currentStatus === 'open' || currentStatus === 'reopen')
(currentStatus !== 'open' && currentStatus !== 'reopen')

how to prevent this error : Warning: mysql_fetch_assoc() expects parameter 1 to be resource, boolean given in ... on line 11

The proper syntax is (in example):

$query = mysql_query('SELECT * FROM beer ORDER BY quality');
while($row = mysql_fetch_assoc($query)) $results[] = $row;

How to monitor network calls made from iOS Simulator

I use netfox. It is very easy to use and integrate. You can use it on simulator and device. It shows all of the requests and responses. It supports JSON, XML, HTML, Image and Other types of responses. You can share requests, responses and full log by IOS default sharing formats (Gmail, WhatsApp, email, slack, sms, etc.)

You can check on GitHub:

Netfox provides a quick look on all executed network requests performed by your iOS or OSX app. It grabs all requests - of course yours, requests from 3rd party libraries (such as AFNetworking, Alamofire or else), UIWebViews, and more

MySQL Error #1133 - Can't find any matching row in the user table

I think the answer is here now :

So, you should write :

GRANT ALL PRIVILEGES ON mydb.* to myuser@'' IDENTIFIED BY 'mypassword';

And i think that could be work :

SET PASSWORD FOR myuser@'' IDENTIFIED BY 'old_password' = PASSWORD('new_password');

anaconda - graphviz - can't import after installation

I tried this way and worked for me.

conda install -c anaconda graphviz
pip install graphviz

How to create a popup window (PopupWindow) in Android

Button endDataSendButton = (Button)findViewById(;

Similarly you can get the text view by adding a id to it.

How can I edit a view using phpMyAdmin 3.2.4?

In your database table list it should show View in Type column. To edit View:

  1. Click on your View in table list
  2. Click on Structure tab
  3. Click on Edit View under Check All

enter image description here

Hope this help

update: in PHPMyAdmin 4.x, it doesn't show View in Type, but you can still recognize it:

  1. In Row column: It had zero Row
  2. In Action column: It had greyed empty button

Of course it may be just an empty table, but when you open the structure, you will know whether it's a table or a view.

How to print variables without spaces between values

Don't use print ..., if you don't want spaces. Use string concatenation or formatting.


print 'Value is "' + str(value) + '"'


print 'Value is "{}"'.format(value)

The latter is far more flexible, see the str.format() method documentation and the Formatting String Syntax section.

You'll also come across the older % formatting style:

print 'Value is "%d"' % value
print 'Value is "%d", but math.pi is %.2f' % (value, math.pi)

but this isn't as flexible as the newer str.format() method.

Create an Array of Arraylists

To declare an array of ArrayLists statically for, say, sprite positions as Points:

ArrayList<Point>[] positionList = new ArrayList[2];

public Main(---) {
    positionList[0] = new ArrayList<Point>(); // Important, or you will get a NullPointerException at runtime
    positionList[1] = new ArrayList<Point>();


ArrayList<Point>[] positionList;
int numberOfLists;

public Main(---) {
    numberOfLists = 2;
    positionList = new ArrayList[numberOfLists];
    for(int i = 0; i < numberOfLists; i++) {
        positionList[i] = new ArrayList<Point>();

Despite the cautions and some complex suggestions here, I have found an array of ArrayLists to be an elegant solution to represent related ArrayLists of the same type.

No module named MySQLdb

On Debian Buster, the following solution worked for me with python 3.7:

sudo apt-get install libmysqlclient-dev
sudo apt-get install libssl-dev
pip install mysqlclient

IPython/Jupyter Problems saving notebook as PDF

notebook-as-pdfInstall python -m pip install notebook-as-pdf pyppeteer-install

Use it You can also use it with nbconvert:

jupyter-nbconvert --to PDFviaHTML filename.ipynb

which will create a file called filename.pdf.

or pip install notebook-as-pdf

create pdf from notebook jupyter-nbconvert-toPDFviaHTML

Set up Python simpleHTTPserver on Windows

From Stack Overflow question What is the Python 3 equivalent of "python -m SimpleHTTPServer":

The following works for me:

python -m http.server [<portNo>]

Because I am using Python 3 the module SimpleHTTPServer has been replaced by http.server, at least in Windows.

Getting the source of a specific image element with jQuery

var src = $('img.conversation_img[alt="example"]').attr('src');

If you have multiple matching elements only the src of the first one will be returned.

Can git undo a checkout of unstaged files

Unfortunately your changes are lost. Your private modifications are simply overwritten. Unless you did git stash prior making checkout...

Take it from the brighter side: you can now implement things even better ;)

C++ terminate called without an active exception

As long as your program die, then without detach or join of the thread, this error will occur. Without detaching and joining the thread, you should give endless loop after creating thread.

int main(){

std::thread t(thread,1);


return 0;}

It is also interesting that, after sleeping or looping, thread can be detach or join. Also with this way you do not get this error.

Below example also shows that, third thread can not done his job before main die. But this error can not happen also, as long as you detach somewhere in the code. Third thread sleep for 8 seconds but main will die in 5 seconds.

void thread(int n) {std::this_thread::sleep_for (std::chrono::seconds(n));}

int main() {
std::cout << "Start main\n";
std::thread t(thread,1);
std::thread t2(thread,3);
std::thread t3(thread,8);

return 0;}

Google Maps API: open url by clicking on marker

If anyone wants to add an URL on a single marker which not require for loops, here is how it goes:

if ($('#googleMap').length) {
    var initialize = function() {
        var mapOptions = {
            zoom: 15,
            scrollwheel: false,
            center: new google.maps.LatLng(45.725788, -73.5120818),
            styles: [{
                stylers: [{
                    saturation: -100
        var map = new google.maps.Map(document.getElementById("googleMap"), mapOptions);
        var marker = new google.maps.Marker({
            position: map.getCenter(),
            animation: google.maps.Animation.BOUNCE,
            icon: 'example-marker.png',
            map: map,
            url: ''

        //Add an url to the marker
    google.maps.event.addListener(marker, 'click', function() {
        window.location.href = this.url;
    // Add the map initialize function to the window load function
    google.maps.event.addDomListener(window, "load", initialize);

In which conda environment is Jupyter executing?

You can also switch environments in Anaconda Navigator, install Jupiter and run it. Anaconda Navigator

What's the difference between implementation and compile in Gradle?

The brief difference in layman's term is:

  • If you are working on an interface or module that provides support to other modules by exposing the members of the stated dependency you should be using 'api'.
  • If you are making an application or module that is going to implement or use the stated dependency internally, use 'implementation'.
  • 'compile' worked same as 'api', however, if you are only implementing or using any library, 'implementation' will work better and save you resources.

read the answer by @aldok for a comprehensive example.

Delimiter must not be alphanumeric or backslash and preg_match

Please try with this

 $pattern = "/My name is '\(.*\)' and im fine/"; 

What is the difference between NULL, '\0' and 0?

A one-L NUL, it ends a string.

A two-L NULL points to no thing.

And I will bet a golden bull

That there is no three-L NULLL.

How do you deal with NUL?

Which websocket library to use with Node.js?

npm ws was the answer for me. I found it less intrusive and more straight forward. With it was also trivial to mix websockets with rest services. Shared simple code on this post.

var WebSocketServer = require("ws").Server;
var http = require("http");
var express = require("express");
var port = process.env.PORT || 5000;

var app = express();
    app.use(express.static(__dirname+ "/../"));
    app.get('/someGetRequest', function(req, res, next) {
       console.log('receiving get request');
    });'/somePostRequest', function(req, res, next) {
       console.log('receiving post request');
    app.listen(80); //port 80 need to run as root

    console.log("app listening on %d ", 80);

var server = http.createServer(app);

console.log("http server listening on %d", port);

var userId;
var wss = new WebSocketServer({server: server});
    wss.on("connection", function (ws) {"websocket connection open");

    var timestamp = new Date().getTime();
    userId = timestamp;

    ws.send(JSON.stringify({msgType:"onOpenConnection", msg:{connectionId:timestamp}}));

    ws.on("message", function (data, flags) {
        console.log("websocket received a message");
        var clientMsg = data;



    ws.on("close", function () {
        console.log("websocket connection close");
console.log("websocket server created");

How to escape braces (curly brackets) in a format string in .NET

Escaping Brackets: String Interpolation $("") :

Now, you can also use c# string interpolation like this (feature available in C# 6.0)

var inVal= "1, 2, 3";
var outVal= $" foo {{{inVal}}}";
//Output will be:  foo {1, 2, 3}

Import CSV file with mixed data types

I recommend looking at the dataset array.

The dataset array is a data type that ships with Statistics Toolbox. It is specifically designed to store hetrogeneous data in a single container.

The Statistics Toolbox demo page contains a couple vidoes that show some of the dataset array features. The first is titled "An Introduction to Dataset Arrays". The second is titled "An Introduction to Joins".

The response content cannot be parsed because the Internet Explorer engine is not available, or

You can disable need to run Internet Explorer's first launch configuration by running this PowerShell script, it will adjust corresponding registry property:

Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Internet Explorer\Main" -Name "DisableFirstRunCustomize" -Value 2

After this, WebClient will work without problems

FFMPEG mp4 from http live streaming m3u8 file?

Aergistal's answer works, but I found that converting to mp4 can make some m3u8 videos broken. If you are stuck with this problem, try to convert them to mkv, and convert them to mp4 later.

How to run a command in the background and get no output?

If they are in the same directory as your script that contains:

./ > /dev/null 2>&1 &
./ > /dev/null 2>&1 &

The & at the end is what makes your script run in the background.

The > /dev/null 2>&1 part is not necessary - it redirects the stdout and stderr streams so you don't have to see them on the terminal, which you may want to do for noisy scripts with lots of output.

Making a Simple Ajax call to controller in mvc

Use a Razor to dynamically change your URL by calling your action like this:

    type: "POST",
    url: '@Url.Action("ActionName", "ControllerName")',
    contentType: "application/json; charset=utf-8",
    data: { data: "yourdata" },
    dataType: "json",
    success: function(recData) { alert('Success'); },
    error: function() { alert('A error'); }

How to run .APK file on emulator

Steps (These apply for Linux. For other OS, visit here) -

  1. Copy the apk file to platform-tools in android-sdk linux folder.
  2. Open Terminal and navigate to platform-tools folder in android-sdk.
  3. Then Execute this command -

    ./adb install FileName.apk

  4. If the operation is successful (the result is displayed on the screen), then you will find your file in the launcher of your emulator.

For more info can check this link : android videos

How to increase size of DOSBox window?

  • go to dosbox installation directory (on my machine that is C:\Program Files (x86)\DOSBox-0.74 ) as you see the version number is part of the installation directory name.

  • run "DOSBox 0.74 Options.bat"

  • the script starts notepad with configuration file: here change



(the resolution can't be changed if output=surface - that's the default).

  • safe configuration file changes.

How to capitalize the first letter in a String in Ruby

Rails 5+

As of Active Support and Rails 5.0.0.beta4 you can use one of both methods: String#upcase_first or ActiveSupport::Inflector#upcase_first.

"my API is great".upcase_first #=> "My API is great"
"?????".upcase_first           #=> "?????"
"?????".upcase_first           #=> "?????"
"NASA".upcase_first            #=> "NASA"
"MHz".upcase_first             #=> "MHz"
"sputnik".upcase_first         #=> "Sputnik"

Check "Rails 5: New upcase_first Method" for more info.

jQuery - Fancybox: But I don't want scrollbars!

My 2 cents, write

*{ margin:0; padding:0; }

in your target page main css, add a content div with the height size of all your elements, don't touch the .js, listo, saludos

How to send data to COM PORT using JAVA?

An alternative to javax.comm is the rxtx library which supports more platforms than javax.comm.

How to close the command line window after running a batch file?

I added the start and exit which works. Without both it was not working

start C:/Anaconda3/Library/bin/pyrcc4.exe -py3 {path}/Resourses.qrc -{path}/

How to check the exit status using an if statement

Every command that runs has an exit status.

That check is looking at the exit status of the command that finished most recently before that line runs.

If you want your script to exit when that test returns true (the previous command failed) then you put exit 1 (or whatever) inside that if block after the echo.

That being said if you are running the command and wanting to test its output using the following is often more straight-forward.

if some_command; then
    echo command returned true
    echo command returned some error

Or to turn that around use ! for negation

if ! some_command; then
    echo command returned some error
    echo command returned true

Note though that neither of those cares what the error code is. If you know you only care about a specific error code then you need to check $? manually.

psql: FATAL: role "postgres" does not exist

This is the only one that fixed it for me :

createuser -s -U $USER

Jenkins Pipeline Wipe Out Workspace

Using the 'WipeWorkspace' extension seems to work as well. It requires the longer form:

   $class: 'GitSCM',
   branches: scm.branches,
   extensions: scm.extensions + [[$class: 'WipeWorkspace']],
   userRemoteConfigs: scm.userRemoteConfigs

More details here:

Available GitSCM extensions here:

How do I kill a VMware virtual machine that won't die?

Similar, but using WMIC command line to obtain the process ID and path:

WMIC /OUTPUT:C:\ProcessList.txt PROCESS get Caption,Commandline,Processid

This will create a text file with each process and its parameters. You can search in the file for your VM File Path, and get the correct Process ID to end task with.

Thanks to for the correct command line parameters.

Getting the object's property name

Use Object.keys():

var myObject = { a: 'c', b: 'a', c: 'b' };_x000D_
var keyNames = Object.keys(myObject);_x000D_
console.log(keyNames); // Outputs ["a","b","c"]

Object.keys() gives you an array of property names belonging to the input object.

Using CSS :before and :after pseudo-elements with inline CSS?

As mentioned before, you can't use inline elements for styling pseudo classes. Before and after pseudo classes are states of elements, not actual elements. You could only possibly use JavaScript for this.

How can I hash a password in Java?

You can comput hashes using MessageDigest, but this is wrong in terms of security. Hashes are not to be used for storing passwords, as they are easily breakable.

You should use another algorithm like bcrypt, PBKDF2 and scrypt to store you passwords. See here.

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

My 5 cents:

  1. Use async/await if and only if you do an IO operation, like DB or external service webservice.
  2. Always prefer async calls to DB.
  3. Each time you query the DB.

P.S. There are exceptional cases for point 1, but you need to have a good understanding of async internals for this.

As an additional advantage, you can do few IO calls in parallel if needed:

Task task1 = FooAsync(); // launch it, but don't wait for result
Task task2 = BarAsync(); // launch bar; now both foo and bar are running
await Task.WhenAll(task1, task2); // this is better in regard to exception handling
// use task1.Result, task2.Result

iterating over each character of a String in ruby 1.8.6 (each_char)

there is really a problem in 1.8.6. and it's ok after this edition

in 1.8.6,you can add this:

requre 'jcode'

jQuery ajax post file field

I tried this code to accept files using Ajax and on submit file gets store using my php file. Code modified slightly to work. (Uploaded Files: PDF,JPG)

function verify1() {
        type: 'POST',
        data: new FormData($("#infoForm1")[0]),
        processData: false, 
        contentType: false, 
        success: function(returnval) {

Just print the file details and check. You will get Output. If error let me know.

How to use SVN, Branch? Tag? Trunk?

For committing, I use the following strategies:

  • commit as often as possible.

  • Each feature change/bugfix should get its own commit (don't commit many files at once since that will make the history for that file unclear -- e.g. If I change a logging module and a GUI module independently and I commit both at once, both changes will be visible in both file histories. This makes reading a file history difficult),

  • don't break the build on any commit -- it should be possible to retrieve any version of the repository and build it.

All files that are necessary for building and running the app should be in SVN. Test files and such should not, unless they are part of the unit tests.

Find all paths between two graph nodes

If you actually care about ordering your paths from shortest path to longest path then it would be far better to use a modified A* or Dijkstra Algorithm. With a slight modification the algorithm will return as many of the possible paths as you want in order of shortest path first. So if what you really want are all possible paths ordered from shortest to longest then this is the way to go.

If you want an A* based implementation capable of returning all paths ordered from the shortest to the longest, the following will accomplish that. It has several advantages. First off it is efficient at sorting from shortest to longest. Also it computes each additional path only when needed, so if you stop early because you dont need every single path you save some processing time. It also reuses data for subsequent paths each time it calculates the next path so it is more efficient. Finally if you find some desired path you can abort early saving some computation time. Overall this should be the most efficient algorithm if you care about sorting by path length.

import java.util.*;

public class AstarSearch {
    private final Map<Integer, Set<Neighbor>> adjacency;
    private final int destination;

    private final NavigableSet<Step> pending = new TreeSet<>();

    public AstarSearch(Map<Integer, Set<Neighbor>> adjacency, int source, int destination) {
        this.adjacency = adjacency;
        this.destination = destination;

        this.pending.add(new Step(source, null, 0));

    public List<Integer> nextShortestPath() {
        Step current = this.pending.pollFirst();
        while( current != null) {
            if( current.getId() == this.destination )
                return current.generatePath();
            for (Neighbor neighbor : this.adjacency.get( {
                if(!current.seen(neighbor.getId())) {
                    final Step nextStep = new Step(neighbor.getId(), current, current.cost + neighbor.cost + predictCost(, this.destination));
            current = this.pending.pollFirst();
        return null;

    protected int predictCost(int source, int destination) {
        return 0; //Behaves identical to Dijkstra's algorithm, override to make it A*

    private static class Step implements Comparable<Step> {
        final int id;
        final Step parent;
        final int cost;

        public Step(int id, Step parent, int cost) {
   = id;
            this.parent = parent;
            this.cost = cost;

        public int getId() {
            return id;

        public Step getParent() {
            return parent;

        public int getCost() {
            return cost;

        public boolean seen(int node) {
            if( == node)
                return true;
            else if(parent == null)
                return false;
                return this.parent.seen(node);

        public List<Integer> generatePath() {
            final List<Integer> path;
            if(this.parent != null)
                path = this.parent.generatePath();
                path = new ArrayList<>();
            return path;

        public int compareTo(Step step) {
            if(step == null)
                return 1;
            if( this.cost != step.cost)
                return, step.cost);
            if( != )
            if( this.parent != null )
            if(step.parent == null)
                return 0;
            return -1;

        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            Step step = (Step) o;
            return id == &&
                cost == step.cost &&
                Objects.equals(parent, step.parent);

        public int hashCode() {
            return Objects.hash(id, parent, cost);

   *   Everything below here just sets up your adjacency  *
   *   It will just be helpful for you to be able to test *
   *   It isnt part of the actual A* search algorithm     *

    private static class Neighbor {
        final int id;
        final int cost;

        public Neighbor(int id, int cost) {
   = id;
            this.cost = cost;

        public int getId() {
            return id;

        public int getCost() {
            return cost;

    public static void main(String[] args) {
        final Map<Integer, Set<Neighbor>> adjacency = createAdjacency();
        final AstarSearch search = new AstarSearch(adjacency, 1, 4);
        System.out.println("printing all paths from shortest to longest...");
        List<Integer> path = search.nextShortestPath();
        while(path != null) {
            path = search.nextShortestPath();

    private static Map<Integer, Set<Neighbor>> createAdjacency() {
        final Map<Integer, Set<Neighbor>> adjacency = new HashMap<>();

        //This sets up the adjacencies. In this case all adjacencies have a cost of 1, but they dont need to.
        addAdjacency(adjacency, 1,2,1,5,1);         //{1 | 2,5}
        addAdjacency(adjacency, 2,1,1,3,1,4,1,5,1); //{2 | 1,3,4,5}
        addAdjacency(adjacency, 3,2,1,5,1);         //{3 | 2,5}
        addAdjacency(adjacency, 4,2,1);             //{4 | 2}
        addAdjacency(adjacency, 5,1,1,2,1,3,1);     //{5 | 1,2,3}

        return Collections.unmodifiableMap(adjacency);

    private static void addAdjacency(Map<Integer, Set<Neighbor>> adjacency, int source, Integer... dests) {
        if( dests.length % 2 != 0)
            throw new IllegalArgumentException("dests must have an equal number of arguments, each pair is the id and cost for that traversal");

        final Set<Neighbor> destinations = new HashSet<>();
        for(int i = 0; i < dests.length; i+=2)
            destinations.add(new Neighbor(dests[i], dests[i+1]));
        adjacency.put(source, Collections.unmodifiableSet(destinations));

The output from the above code is the following:

[1, 2, 4]
[1, 5, 2, 4]
[1, 5, 3, 2, 4]

Notice that each time you call nextShortestPath() it generates the next shortest path for you on demand. It only calculates the extra steps needed and doesnt traverse any old paths twice. Moreover if you decide you dont need all the paths and end execution early you've saved yourself considerable computation time. You only compute up to the number of paths you need and no more.

Finally it should be noted that the A* and Dijkstra algorithms do have some minor limitations, though I dont think it would effect you. Namely it will not work right on a graph that has negative weights.

Here is a link to JDoodle where you can run the code yourself in the browser and see it working. You can also change around the graph to show it works on other graphs as well:

Kotlin Android start new Activity

Well, I found these 2 ways to be the simplest of all outcomes:

Way #1:

accoun_btn.setOnClickListener {

Way#2: (In a generic way)

    accoun_btn.setOnClickListener {

    private inline fun <reified T> startActivity(context: Context) {


Select distinct using linq

You should override Equals and GetHashCode meaningfully, in this case to compare the ID:

public class LinqTest
    public int id { get; set; }
    public string value { get; set; }

    public override bool Equals(object obj)
        LinqTest obj2 = obj as LinqTest;
        if (obj2 == null) return false;
        return id ==;

    public override int GetHashCode()
        return id;

Now you can use Distinct:

List<LinqTest> uniqueIDs = myList.Distinct().ToList();