Programs & Examples On #Subforms

Why is there no Constant feature in Java?

There would be two ways to define constants - const and static final, with the exact same semantics. Furthermore static final describes the behaviour better than const

Git merge develop into feature branch outputs "Already up-to-date" while it's not

Step by step self explaining commands for update of feature branch with the latest code from origin "develop" branch:

git checkout develop
git pull -p
git checkout feature_branch
git merge develop
git push origin feature_branch

Create a new object from type parameter in generic class

Because the compiled JavaScript has all the type information erased, you can't use T to new up an object.

You can do this in a non-generic way by passing the type into the constructor.

class TestOne {
    hi() {

class TestTwo {
    constructor(private testType) {

    getNew() {
        return new this.testType();

var test = new TestTwo(TestOne);

var example = test.getNew();

You could extend this example using generics to tighten up the types:

class TestBase {
    hi() {
        alert('Hi from base');

class TestSub extends TestBase {
    hi() {
        alert('Hi from sub');

class TestTwo<T extends TestBase> {
    constructor(private testType: new () => T) {

    getNew() : T {
        return new this.testType();

//var test = new TestTwo<TestBase>(TestBase);
var test = new TestTwo<TestSub>(TestSub);

var example = test.getNew();

Specifying and saving a figure with exact size in pixels

plt.imsave worked for me. You can find the documentation here:

#file_path = directory address where the image will be stored along with file name and extension
#array = variable where the image is stored. I think for the original post this variable is im_np
plt.imsave(file_path, array)

Difference between uint32 and uint32_t

uint32_t is defined in the standard, in

18.4.1 Header <cstdint> synopsis [cstdint.syn]

namespace std {
typedef unsigned integer type uint32_t; // optional

uint32 is not, it's a shortcut provided by some compilers (probably as typedef uint32_t uint32) for ease of use.

How to add subject alernative name to ssl certs?

Although this question was more specifically about IP addresses in Subject Alt. Names, the commands are similar (using DNS entries for a host name and IP entries for IP addresses).

To quote myself:

If you're using keytool, as of Java 7, keytool has an option to include a Subject Alternative Name (see the table in the documentation for -ext): you could use -ext or -ext san=ip:

Note that you only need Java 7's keytool to use this command. Once you've prepared your keystore, it should work with previous versions of Java.

(The rest of this answer also mentions how to do this with OpenSSL, but it doesn't seem to be what you're using.)

/** and /* in Java Comments

I don't think the existing answers adequately addressed this part of the question:

When should I use them?

If you're writing an API that will be published or reused within your organization, you should write comprehensive Javadoc comments for every public class, method, and field, as well as protected methods and fields of non-final classes. Javadoc should cover everything that cannot be conveyed by the method signature, such as preconditions, postconditions, valid arguments, runtime exceptions, internal calls, etc.

If you're writing an internal API (one that's used by different parts of the same program), Javadoc is arguably less important. But for the benefit of maintenance programmers, you should still write Javadoc for any method or field where the correct usage or meaning is not immediately obvious.

The "killer feature" of Javadoc is that it's closely integrated with Eclipse and other IDEs. A developer only needs to hover their mouse pointer over an identifier to learn everything they need to know about it. Constantly referring to the documentation becomes second nature for experienced Java developers, which improves the quality of their own code. If your API isn't documented with Javadoc, experienced developers will not want to use it.

Algorithm for Determining Tic Tac Toe Game Over

I made some optimization in the row, col, diagonal checks. Its mainly decided in the first nested loop if we need to check a particular column or diagonal. So, we avoid checking of columns or diagonals saving time. This makes big impact when the board size is more and a significant number of the cells are not filled.

Here is the java code for that.

    int gameState(int values[][], int boardSz) {

    boolean colCheckNotRequired[] = new boolean[boardSz];//default is false
    boolean diag1CheckNotRequired = false;
    boolean diag2CheckNotRequired = false;
    boolean allFilled = true;

    int x_count = 0;
    int o_count = 0;
    /* Check rows */
    for (int i = 0; i < boardSz; i++) {
        x_count = o_count = 0;
        for (int j = 0; j < boardSz; j++) {
            if(values[i][j] == x_val)x_count++;
            if(values[i][j] == o_val)o_count++;
            if(values[i][j] == 0)
                colCheckNotRequired[j] = true;
                if(i==j)diag1CheckNotRequired = true;
                if(i + j == boardSz - 1)diag2CheckNotRequired = true;
                allFilled = false;
                //No need check further
        if(x_count == boardSz)return X_WIN;
        if(o_count == boardSz)return O_WIN;         

    /* check cols */
    for (int i = 0; i < boardSz; i++) {
        x_count = o_count = 0;
        if(colCheckNotRequired[i] == false)
            for (int j = 0; j < boardSz; j++) {
                if(values[j][i] == x_val)x_count++;
                if(values[j][i] == o_val)o_count++;
                //No need check further
                if(values[i][j] == 0)break;
            if(x_count == boardSz)return X_WIN;
            if(o_count == boardSz)return O_WIN;

    x_count = o_count = 0;
    /* check diagonal 1 */
    if(diag1CheckNotRequired == false)
        for (int i = 0; i < boardSz; i++) {
            if(values[i][i] == x_val)x_count++;
            if(values[i][i] == o_val)o_count++;
            if(values[i][i] == 0)break;
        if(x_count == boardSz)return X_WIN;
        if(o_count == boardSz)return O_WIN;

    x_count = o_count = 0;
    /* check diagonal 2 */
    if( diag2CheckNotRequired == false)
        for (int i = boardSz - 1,j = 0; i >= 0 && j < boardSz; i--,j++) {
            if(values[j][i] == x_val)x_count++;
            if(values[j][i] == o_val)o_count++;
            if(values[j][i] == 0)break;
        if(x_count == boardSz)return X_WIN;
        if(o_count == boardSz)return O_WIN;
        x_count = o_count = 0;

    if( allFilled == true)
        for (int i = 0; i < boardSz; i++) {
            for (int j = 0; j < boardSz; j++) {
                if (values[i][j] == 0) {
                    allFilled = false;

            if (allFilled == false) {

    if (allFilled)
        return DRAW;

    return INPROGRESS;

How to easily initialize a list of Tuples?

One technique I think is a little easier and that hasn't been mentioned before here:

var asdf = new [] { 
    (Age: 1, Name: "cow"), 
    (Age: 2, Name: "bird")

I think that's a little cleaner than:

var asdf = new List<Tuple<int, string>> { 
    (Age: 1, Name: "cow"), 
    (Age: 2, Name: "bird")

How can I check the current status of the GPS receiver?

Maybe it's the best possiblity to create a TimerTask that sets the received Location to a certain value (null?) regularly. If a new value is received by the GPSListener it will update the location with the current data.

I think that would be a working solution.

Scanner vs. StringTokenizer vs. String.Split

Split is slow, but not as slow as Scanner. StringTokenizer is faster than split. However, I found that I could obtain double the speed, by trading some flexibility, to get a speed-boost, which I did at JFastParser

Testing on a string containing one million doubles:

Scanner: 10642 ms
Split: 715 ms
StringTokenizer: 544ms
JFastParser: 290ms

python how to pad numpy array with zeros

NumPy 1.7.0 (when numpy.pad was added) is pretty old now (it was released in 2013) so even though the question asked for a way without using that function I thought it could be useful to know how that could be achieved using numpy.pad.

It's actually pretty simple:

>>> import numpy as np
>>> a = np.array([[ 1.,  1.,  1.,  1.,  1.],
...               [ 1.,  1.,  1.,  1.,  1.],
...               [ 1.,  1.,  1.,  1.,  1.]])
>>> np.pad(a, [(0, 1), (0, 1)], mode='constant')
array([[ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.]])

In this case I used that 0 is the default value for mode='constant'. But it could also be specified by passing it in explicitly:

>>> np.pad(a, [(0, 1), (0, 1)], mode='constant', constant_values=0)
array([[ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.]])

Just in case the second argument ([(0, 1), (0, 1)]) seems confusing: Each list item (in this case tuple) corresponds to a dimension and item therein represents the padding before (first element) and after (second element). So:

[(0, 1), (0, 1)]
         ^^^^^^------ padding for second dimension
 ^^^^^^-------------- padding for first dimension

  ^------------------ no padding at the beginning of the first axis
     ^--------------- pad with one "value" at the end of the first axis.

In this case the padding for the first and second axis are identical, so one could also just pass in the 2-tuple:

>>> np.pad(a, (0, 1), mode='constant')
array([[ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 1.,  1.,  1.,  1.,  1.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.]])

In case the padding before and after is identical one could even omit the tuple (not applicable in this case though):

>>> np.pad(a, 1, mode='constant')
array([[ 0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  1.,  1.,  1.,  1.,  1.,  0.],
       [ 0.,  1.,  1.,  1.,  1.,  1.,  0.],
       [ 0.,  1.,  1.,  1.,  1.,  1.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.]])

Or if the padding before and after is identical but different for the axis, you could also omit the second argument in the inner tuples:

>>> np.pad(a, [(1, ), (2, )], mode='constant')
array([[ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  1.,  1.,  1.,  1.,  1.,  0.,  0.],
       [ 0.,  0.,  1.,  1.,  1.,  1.,  1.,  0.,  0.],
       [ 0.,  0.,  1.,  1.,  1.,  1.,  1.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.]])

However I tend to prefer to always use the explicit one, because it's just to easy to make mistakes (when NumPys expectations differ from your intentions):

>>> np.pad(a, [1, 2], mode='constant')
array([[ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  1.,  1.,  1.,  1.,  1.,  0.,  0.],
       [ 0.,  1.,  1.,  1.,  1.,  1.,  0.,  0.],
       [ 0.,  1.,  1.,  1.,  1.,  1.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.]])

Here NumPy thinks you wanted to pad all axis with 1 element before and 2 elements after each axis! Even if you intended it to pad with 1 element in axis 1 and 2 elements for axis 2.

I used lists of tuples for the padding, note that this is just "my convention", you could also use lists of lists or tuples of tuples, or even tuples of arrays. NumPy just checks the length of the argument (or if it doesn't have a length) and the length of each item (or if it has a length)!

Bash tool to get nth line from a file

head and pipe with tail will be slow for a huge file. I would suggest sed like this:

sed 'NUMq;d' file

Where NUM is the number of the line you want to print; so, for example, sed '10q;d' file to print the 10th line of file.


NUMq will quit immediately when the line number is NUM.

d will delete the line instead of printing it; this is inhibited on the last line because the q causes the rest of the script to be skipped when quitting.

If you have NUM in a variable, you will want to use double quotes instead of single:

sed "${NUM}q;d" file

AppendChild() is not a function javascript

Try the following:

var div = document.createElement("div");
div.innerHTML = "topdiv";

jQuery - Trigger event when an element is removed from the DOM

I couldn't get this answer to work with unbinding (despite the update see here), but was able to figure out a way around it. The answer was to create a 'destroy_proxy' special event that triggered a 'destroyed' event. You put the event listener on both 'destroyed_proxy' and 'destroyed', then when you want to unbind, you just unbind the 'destroyed' event:

var count = 1;
(function ($) {
    $.event.special.destroyed_proxy = {
        remove: function (o) {

$('.remove').on('click', function () {

$('li').on('destroyed_proxy destroyed', function () {
    console.log('Element removed');
    if (count > 2) {

Here is a fiddle

Why is pydot unable to find GraphViz's executables in Windows 8?

For me: (Win10, Anaconda3) Make sure you have done "conda install graphviz"

I have to add to the PATH: C:\Users\username\Anaconda3\Library\bin\graphviz

To modify PATH go to Control Panel > System and Security > System > Advanced System Settings > Environment Variables > Path > Edit > New


Auto detect mobile browser (via user-agent?)

My favorite Mobile Browser Detection mechanism is WURFL. It's updated frequently and it works with every major programming/language platform.

How to loop through an array of objects in swift

Your userPhotos array is option-typed, you should retrieve the actual underlying object with ! (if you want an error in case the object isn't there) or ? (if you want to receive nil in url):

let userPhotos = currentUser?.photos

for var i = 0; i < userPhotos!.count ; ++i {
    let url = userPhotos![i].url

But to preserve safe nil handling, you better use functional approach, for instance, with map, like this:

let urls = userPhotos?.map{ $0.url }

Putting text in top left corner of matplotlib plot

One solution would be to use the plt.legend function, even if you don't want an actual legend. You can specify the placement of the legend box by using the loc keyterm. More information can be found at this website but I've also included an example showing how to place a legend:

ax.scatter(xa,ya, marker='o', s=20, c="lightgreen", alpha=0.9)
ax.scatter(xb,yb, marker='o', s=20, c="dodgerblue", alpha=0.9)
ax.scatter(xc,yc marker='o', s=20, c="firebrick", alpha=1.0)
ax.scatter(xd,xd,xd, marker='o', s=20, c="goldenrod", alpha=0.9)
line1 = Line2D(range(10), range(10), marker='o', color="goldenrod")
line2 = Line2D(range(10), range(10), marker='o',color="firebrick")
line3 = Line2D(range(10), range(10), marker='o',color="lightgreen")
line4 = Line2D(range(10), range(10), marker='o',color="dodgerblue")
plt.legend((line1,line2,line3, line4),('line1','line2', 'line3', 'line4'),numpoints=1, loc=2) 

Note that because loc=2, the legend is in the upper-left corner of the plot. And if the text overlaps with the plot, you can make it smaller by using legend.fontsize, which will then make the legend smaller.

no overload for matches delegate 'system.eventhandler'

You need to wrap button click handler to match the pattern

public void klik(object sender, EventArgs e)

How to compare only Date without Time in DateTime types in Linq to SQL with Entity Framework?

DateTime econvertedDate = Convert.ToDateTime(end_date);
DateTime sconvertedDate = Convert.ToDateTime(start_date);

TimeSpan age = econvertedDate.Subtract(sconvertedDate);
Int32 diff = Convert.ToInt32(age.TotalDays);

The diff value represents the number of days for the age. If the value is negative the start date falls after the end date. This is a good check.

Clicking the back button twice to exit an activity

For the activity whose is having Navigation Drawer, Use the following code for OnBackPressed()

boolean doubleBackToExitPressedOnce = false;

    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(;
        if (drawer.isDrawerOpen(GravityCompat.START)) {
        } else {
            if (doubleBackToExitPressedOnce) {
                if (getFragmentManager().getBackStackEntryCount() ==0) {
                } else {

            if (getFragmentManager().getBackStackEntryCount() ==0) {
                this.doubleBackToExitPressedOnce = true;
                Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();

                new Handler().postDelayed(new Runnable() {

                    public void run() {
                        doubleBackToExitPressedOnce = false;
                }, 2000);
            } else {

Disable clipboard prompt in Excel VBA on workbook close

If I may add one more solution: you can simply cancel the clipboard with this command:

Application.CutCopyMode = False

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - process out of memory

I lost some days with this problem.... until I found that in some file I was importing one static file, a built file. It make the build to never end. Something like:

import PropTypes from "../static/build/prop-types"; 

Fixing to the real source solved all the problem.

Sharing my solution. :)

How to create unit tests easily in eclipse

You can use my plug-in to create tests easily:

  1. highlight the method
  2. press Ctrl+Alt+Shift+U
  3. it will create the unit test for it.

The plug-in is available here. Hope this helps.

set height of imageview as matchparent programmatically

imageView.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));

How to import js-modules into TypeScript file?

2021 Solution

If you're still getting this error message:

TS7016: Could not find a declaration file for module './myjsfile'

Then you might need to add the following to tsconfig.json

  "compilerOptions": {
    "allowJs": true,
    "checkJs": false,

This prevents typescript from trying to apply module types to the imported javascript.

Get value of Span Text

You need to change your code as below:


<span id="span_Id">Click the button to display the content.</span>

<button onclick="displayDate()">Click Me</button>

function displayDate() {
   var span_Text = document.getElementById("span_Id").innerText;
   alert (span_Text);

How to kill all processes matching a name?

I think this command killall is exactly what you need. The command is described as "kill processes by name".It's easy to use.For example

killall chrome

This command will kill all process of Chrome.Here is a link about killall command

Hope this command could help you.

Increasing Heap Size on Linux Machines

Changing Tomcat config wont effect all JVM instances to get theses settings. This is not how it works, the setting will be used only to launch JVMs used by Tomcat, not started in the shell.

Look here for permanently changing the heap size.

How do I change the text size in a label widget, python tkinter

Try passing width=200 as additional paramater when creating the Label.

This should work in creating label with specified width.

If you want to change it later, you can use:


As you want to change the size of font itself you can try:

label.config(font=("Courier", 44))

setting textColor in TextView in layout/main.xml main layout file not referencing colors.xml file. (It wants a #RRGGBB instead of @color/text_color)

After experimenting on that case: android:textColor="@colors/text_color" is wrong since @color is not filename dependant. You can name your resource file foobar.xml, it doesn't matter but if you have defined some colors in it you can access them using @color/some_color.


file location: res/values/colors.xml The filename is arbitrary. The element's name will be used as the resource ID. (Source)

A python class that acts like dict

The problem with this chunk of code:

class myDict(dict):
    def __init__(self):
        self._dict = {}

    def add(id, val):
        self._dict[id] = val

md = myDict()
md.add('id', 123) that your 'add' method (...and any method you want to be a member of a class) needs to have an explicit 'self' declared as its first argument, like:

def add(self, 'id', 23):

To implement the operator overloading to access items by key, look in the docs for the magic methods __getitem__ and __setitem__.

Note that because Python uses Duck Typing, there may actually be no reason to derive your custom dict class from the language's dict class -- without knowing more about what you're trying to do (e.g, if you need to pass an instance of this class into some code someplace that will break unless isinstance(MyDict(), dict) == True), you may be better off just implementing the API that makes your class sufficiently dict-like and stopping there.

Python: subplot within a loop: first panel appears in wrong position

Basically the same solution as provided by Rutger Kassies, but using a more pythonic syntax:

fig, axs = plt.subplots(2,5, figsize=(15, 6), facecolor='w', edgecolor='k')
fig.subplots_adjust(hspace = .5, wspace=.001)

data = np.arange(250, 260)

for ax, d in zip(axs.ravel(), data):
    ax.contourf(np.random.rand(10,10), 5,

Using curl to upload POST data with files

You need to use the -F option:
-F/--form <name=content> Specify HTTP multipart POST data (H)

Try this:

curl \
  -F "userid=1" \
  -F "filecomment=This is an image file" \
  -F "image=@/home/user1/Desktop/test.jpg" \

Creating a .p12 file

The openssl documentation says that file supplied as the -in argument must be in PEM format.

Turns out that, contrary to the CA's manual, the certificate returned by the CA which I stored in myCert.cer is not PEM format rather it is PKCS7.

In order to create my .p12, I had to first convert the certificate to PEM:

openssl pkcs7 -in myCert.cer -print_certs -out certs.pem

and then execute

openssl pkcs12 -export -out keyStore.p12 -inkey myKey.pem -in certs.pem

Bootstrap dropdown sub menu missing

Until today (9 jan 2014) the Bootstrap 3 still not support sub menu dropdown.

I searched Google about responsive navigation menu and found this is the best i though.

It is Smart menus

I hope this is the way out for anyone who want navigation menu with multilevel sub menu.

update 2015-02-17 Smart menus are now fully support Bootstrap element style for submenu. For more information please look at Smart menus website.

Android Gradle Could not reserve enough space for object heap

I ran into the same issue, here's my post:

Android Studio - Gradle build failing - Java Heap Space

exec summary: Windows looks for the file here:


So create that file, and add a line like this:

org.gradle.jvmargs=-XX\:MaxHeapSize\=256m -Xmx256m

as per @Faiz Siddiqui post

How do I include a file over 2 directories back?

following are ways to access your different directories:-

./ = Your current directory
../ = One directory lower
../../ = Two directories lower
../../../ = Three directories lower

What datatype to use when storing latitude and longitude data in SQL databases?

For longitudes use: Decimal(9,6), and latitudes use: Decimal(8,6)

If you're not used to precision and scale parameters, here's a format string visual:

###.###### and ##.######

How to print / echo environment variables?

To bring the existing answers together with an important clarification:

As stated, the problem with NAME=sam echo "$NAME" is that $NAME gets expanded by the current shell before assignment NAME=sam takes effect.

Solutions that preserve the original semantics (of the (ineffective) solution attempt NAME=sam echo "$NAME"):

Use either eval[1] (as in the question itself), or printenv (as added by Aaron McDaid to heemayl's answer), or bash -c (from Ljm Dullaart's answer), in descending order of efficiency:

NAME=sam eval 'echo "$NAME"'  # use `eval` only if you fully control the command string
NAME=sam printenv NAME
NAME=sam bash -c 'echo "$NAME"'

printenv is not a POSIX utility, but it is available on both Linux and macOS/BSD.

What this style of invocation (<var>=<name> cmd ...) does is to define NAME:

  • as an environment variable
  • that is only defined for the command being invoked.

In other words: NAME only exists for the command being invoked, and has no effect on the current shell (if no variable named NAME existed before, there will be none after; a preexisting NAME variable remains unchanged).

POSIX defines the rules for this kind of invocation in its Command Search and Execution chapter.

The following solutions work very differently (from heemayl's answer):

NAME=sam; echo "$NAME"
NAME=sam && echo "$NAME"

While they produce the same output, they instead define:

  • a shell variable NAME (only) rather than an environment variable
    • if echo were a command that relied on environment variable NAME, it wouldn't be defined (or potentially defined differently from earlier).
  • that lives on after the command.

Note that every environment variable is also exposed as a shell variable, but the inverse is not true: shell variables are only visible to the current shell and its subshells, but not to child processes, such as external utilities and (non-sourced) scripts (unless they're marked as environment variables with export or declare -x).

[1] Technically, bash is in violation of POSIX here (as is zsh): Since eval is a special shell built-in, the preceding NAME=sam assignment should cause the the variable $NAME to remain in scope after the command finishes, but that's not what happens.
However, when you run bash in POSIX compatibility mode, it is compliant.
dash and ksh are always compliant.
The exact rules are complicated, and some aspects are left up to the implementations to decide; again, see Command Search and Execution.
Also, the usual disclaimer applies: Use eval only on input you fully control or implicitly trust.

Import SQL file into mysql

For localhost on XAMPP. Open a cmd window and type

cd C:\xampp\mysql\bin
mysql.exe -u root -p

Attention! No semi-colon after -p Enter your password and type

use database_name;

to select the database you need.

Check if your table is there

show tables;

Import from your sql file

source sqlfile.sql;

I have put my file on C:\xampp\mysql\bin location in order to don't mix up with locations of sql file.

Create a BufferedImage from file and make it TYPE_INT_ARGB

Create a BufferedImage from file and make it TYPE_INT_RGB

import java.awt.image.*;
import javax.imageio.*;
public class Main{
    public static void main(String args[]){
            BufferedImage img = new BufferedImage( 
                500, 500, BufferedImage.TYPE_INT_RGB );
            File f = new File("MyFile.png");
            int r = 5;
            int g = 25; 
            int b = 255;
            int col = (r << 16) | (g << 8) | b;
            for(int x = 0; x < 500; x++){
                for(int y = 20; y < 300; y++){
                    img.setRGB(x, y, col);
            ImageIO.write(img, "PNG", f); 
        catch(Exception e){ 

This paints a big blue streak across the top.

If you want it ARGB, do it like this:

        BufferedImage img = new BufferedImage( 
            500, 500, BufferedImage.TYPE_INT_ARGB );
        File f = new File("MyFile.png");
        int r = 255;
        int g = 10;
        int b = 57;
        int alpha = 255;
        int col = (alpha << 24) | (r << 16) | (g << 8) | b;
        for(int x = 0; x < 500; x++){
            for(int y = 20; y < 30; y++){
                img.setRGB(x, y, col);
        ImageIO.write(img, "PNG", f);
    catch(Exception e){

Open up MyFile.png, it has a red streak across the top.

Missing Authentication Token while accessing API Gateway?

If you are using an API with endpoint of type PRIVATE, be sure of:

  1. You are invoking the API from within your AWS account (example: from an EC2 instance created in your account)

  2. Put necessary credential (access and secret keys) in the EC2 instance in route ~/.aws/credentials (this route is for linux instances) If IAM user use MFA aws_session_token value will be required too.

  3. Use vpce (vpc endpoint) based URL. Example: curl

  4. Your EC2 instance have a security group than allow outbound traffic to another security group owned by the vpce like: EC2 instance sg

  5. Your vpce security group allow inbound traffic from another security group (previous sg from ec2 instance) owned by the EC2 instance like: vpce sg


How do relative file paths work in Eclipse?

You need "src/Hankees.txt"

Your file is in the source folder which is not counted as the working directory.\

Or you can move the file up to the root directory of your project and just use "Hankees.txt"

Convert LocalDateTime to LocalDateTime in UTC

public static String convertFromGmtToLocal(String gmtDtStr, String dtFormat, TimeZone lclTimeZone) throws Exception{
        if (gmtDtStr == null || gmtDtStr.trim().equals("")) return null;
        SimpleDateFormat format = new SimpleDateFormat(dtFormat);
        Date dt = format.parse(gmtDtStr);

format.format(dt); }

Total size of the contents of all the files in a directory

stat's "%s" format gives you the actual number of bytes in a file.

 find . -type f |
 xargs stat --format=%s |
 awk '{s+=$1} END {print s}'

Feel free to substitute your favourite method for summing numbers.

Equivalent of Super Keyword in C#

C# equivalent of your code is

  class Imagedata : PDFStreamEngine
     // C# uses "base" keyword whenever Java uses "super" 
     // so instead of super(...) in Java we should call its C# equivalent (base):
     public Imagedata()
       : base(ResourceLoader.loadProperties("org/apache/pdfbox/resources/", true)) 
     { }

     // Java methods are virtual by default, when C# methods aren't.
     // So we should be sure that processOperator method in base class 
     // (that is PDFStreamEngine)
     // declared as "virtual"
     protected override void processOperator(PDFOperator operations, List arguments)
        base.processOperator(operations, arguments);

Change default date time format on a single database in SQL Server

For SQL Server 2008 run:

EXEC sp_defaultlanguage 'username', 'british'

.htaccess not working apache

Most probably, AllowOverride is set to None. in Directory section of apache2.conf located in /etc/apache2 folder

Try setting it to AllowOverride All

Is there a way to disable initial sorting for jquery DataTables?

Well I found the answer set "aaSorting" to an empty array:

$(document).ready( function() {
        /* Disable initial sort */
        "aaSorting": []

For newer versions of Datatables (>= 1.10) use order option:

$(document).ready( function() {
        /* No ordering applied by DataTables during initialisation */
        "order": []

boundingRectWithSize for NSAttributedString returning wrong size

In case you'd like to get bounding box by truncating the tail, this question can help you out.

CGFloat maxTitleWidth = 200;

NSMutableParagraphStyle *paragraph = [[NSMutableParagraphStyle alloc] init];
paragraph.lineBreakMode = NSLineBreakByTruncatingTail;

NSDictionary *attributes = @{NSFontAttributeName : self.textLabel.font,
                             NSParagraphStyleAttributeName: paragraph};

CGRect box = [self.textLabel.text
              boundingRectWithSize:CGSizeMake(maxTitleWidth, CGFLOAT_MAX)
              options:(NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading)
              attributes:attributes context:nil];

Meaning of - <?xml version="1.0" encoding="utf-8"?>

The XML declaration in the document map consists of the following:

The version number, ?xml version="1.0"?. 

This is mandatory. Although the number might change for future versions of XML, 1.0 is the current version.

The encoding declaration,


This is optional. If used, the encoding declaration must appear immediately after the version information in the XML declaration, and must contain a value representing an existing character encoding.

How to set up default schema name in JPA configuration?

For those who uses last versions of spring boot will help this:

.properties:<name of your schema>


                default_schema: <name of your schema>

CSV parsing in Java - working example..?

i had to use a csv parser about 5 years ago. seems there are at least two csv standards: and what microsoft does in excel.

i found this libaray which eats both:, but afaik, it has no way of inferring what data type the columns were.

Adding sheets to end of workbook in Excel (normal method not working?)

Be sure to fully qualify your sheets with which workbook they are referencing!

 mainWB.Sheets.Add(After:=mainWB.Sheets(mainWB.Sheets.Count)).Name = new_sheet_name

Python - Dimension of Data Frame

df.shape, where df is your DataFrame.

Create Map in Java

I use such kind of a Map population thanks to Java 9. In my honest opinion, this approach provides more readability to the code.

  public static void main(String[] args) {
    Map<Integer, Point2D.Double> map = Map.of(
        1, new Point2D.Double(1, 1),
        2, new Point2D.Double(2, 2),
        3, new Point2D.Double(3, 3),
        4, new Point2D.Double(4, 4));

How to Update/Drop a Hive Partition?

You may also need to make database containing table active

use [dbname]

otherwise you may get error (even if you specify database i.e. dbname.table )

FAILED Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.DDLTask. Unable to alter partition. Unable to alter partitions because table or database does not exist.

What's the difference between [ and [[ in Bash?

In bash, contrary to [, [[ prevents word splitting of variable values.

Use RSA private key to generate public key?

People looking for SSH public key...

If you're looking to extract the public key for use with OpenSSH, you will need to get the public key a bit differently

$ ssh-keygen -y -f mykey.pem >

This public key format is compatible with OpenSSH. Append the public key to remote:~/.ssh/authorized_keys and you'll be good to go

docs from SSH-KEYGEN(1)

ssh-keygen -y [-f input_keyfile]  

-y This option will read a private OpenSSH format file and print an OpenSSH public key to stdout.

ECMAScript 6 arrow function that returns an object

ES6 Arrow Function returns an Object

the right ways

  1. normal function return an object

const getUser = user => {return { name:, age: user.age };};

const user = { name: "xgqfrms", age: 21 };

//  {name: "xgqfrms", age: 21}

  1. (js expressions )

const getUser = user => ({ name:, age: user.age });

const user = { name: "xgqfrms", age: 21 };

//  {name: "xgqfrms", age: 21}




coercing to Unicode: need string or buffer, NoneType found when rendering in django admin

This error might occur when you return an object instead of a string in your __unicode__ method. For example:

class Author(models.Model):
    . . . 
    name = models.CharField(...)

class Book(models.Model):
    . . .
    author = models.ForeignKey(Author, ...)
    . . .
    def __unicode__(self):
        return  # <<<<<<<< this causes problems

To avoid this error you can cast the author instance to unicode:

class Book(models.Model):
    . . . 
    def __unicode__(self):
        return unicode(  # <<<<<<<< this is OK

How to do this in Laravel, subquery where in

You can use variable by using keyword "use ($category_id)"

$category_id = array('223','15');
Products::whereIn('id', function($query) use ($category_id){
     ->from(with(new ProductCategory)->getTable())
     ->whereIn('category_id', $category_id )
     ->where('active', 1);

Declare an empty two-dimensional array in Javascript?

If you want to be able access the matrix like so matrix[i][j]

I find it the most convinient to init it in a loop.

var matrix = [],
    cols = 3;

//init the grid matrix
for ( var i = 0; i < cols; i++ ) {
    matrix[i] = []; 

this will give you [ [], [], [] ]

so matrix[0][0] matrix[1][0] return undefined and not the error "Uncaught TypeError: Cannot set property '0' of undefined"

Save a list to a .txt file

Try this, if it helps you

values = ['1', '2', '3']

with open("file.txt", "w") as output:

How to display a readable array - Laravel

For everyone still searching for a nice way to achieve this, the recommended way is the dump() function from symfony/var-dumper.

It is added to documentation since version 5.2:

Converting String to Int with Swift

edit/update: Xcode 11.4 • Swift 5.2

Please check the comments through the code

IntegerField.swift file contents:

import UIKit

class IntegerField: UITextField {

    // returns the textfield contents, removes non digit characters and converts the result to an integer value
    var value: Int { string.digits.integer ?? 0 }

    var maxValue: Int = 999_999_999
    private var lastValue: Int = 0

    override func willMove(toSuperview newSuperview: UIView?) {
        // adds a target to the textfield to monitor when the text changes
        addTarget(self, action: #selector(editingChanged), for: .editingChanged)
        // sets the keyboard type to digits only
        keyboardType = .numberPad
        // set the text alignment to right
        textAlignment = .right
        // sends an editingChanged action to force the textfield to be updated
        sendActions(for: .editingChanged)
    // deletes the last digit of the text field
    override func deleteBackward() {
        // note that the field text property default value is an empty string so force unwrap its value is safe
        // note also that collection remove at requires a non empty collection which is true as well in this case so no need to check if the collection is not empty.
        text!.remove(at: text!.index(before: text!.endIndex))
        // sends an editingChanged action to force the textfield to be updated
        sendActions(for: .editingChanged)
    @objc func editingChanged() {
        guard value <= maxValue else {
            text = Formatter.decimal.string(for: lastValue)
        // This will format the textfield respecting the user device locale and settings
        text = Formatter.decimal.string(for: value)
        print("Value:", value)
        lastValue = value

You would need to add those extensions to your project as well:

Extensions UITextField.swift file contents:

import UIKit
extension UITextField {
    var string: String { text ?? "" }

Extensions Formatter.swift file contents:

import Foundation
extension Formatter {
    static let decimal = NumberFormatter(numberStyle: .decimal)

Extensions NumberFormatter.swift file contents:

import Foundation
extension NumberFormatter {
    convenience init(numberStyle: Style) {
        self.numberStyle = numberStyle

Extensions StringProtocol.swift file contents:

extension StringProtocol where Self: RangeReplaceableCollection {
    var digits: Self { filter(\.isWholeNumber) }
    var integer: Int? { Int(self) }

Sample project

How can I create a marquee effect?

With a small change of the markup, here's my approach (I've just inserted a span inside the paragraph):

.marquee {
  width: 450px;
  margin: 0 auto;
  overflow: hidden;
  box-sizing: border-box;

.marquee span {
  display: inline-block;
  width: max-content;

  padding-left: 100%;
  /* show the marquee just outside the paragraph */
  will-change: transform;
  animation: marquee 15s linear infinite;

.marquee span:hover {
  animation-play-state: paused

@keyframes marquee {
  0% { transform: translate(0, 0); }
  100% { transform: translate(-100%, 0); }

/* Respect user preferences about animations */

@media (prefers-reduced-motion: reduce) {
  .marquee span {
    animation-iteration-count: 1;
    animation-duration: 0.01; 
    /* instead of animation: none, so an animationend event is 
     * still available, if previously attached.
    width: auto;
    padding-left: 0;
<p class="marquee">
       When I had journeyed half of our life's way, I found myself
       within a shadowed forest, for I had lost the path that 
       does not stray. – (Dante Alighieri, <i>Divine Comedy</i>. 

No hardcoded values — dependent on paragraph width — have been inserted.

The animation applies the CSS3 transform property (use prefixes where needed) so it performs well.

If you need to insert a delay just once at the beginning then also set an animation-delay. If you need instead to insert a small delay at every loop then try to play with an higher padding-left (e.g. 150%)

PreparedStatement with list of parameters in a IN clause

public static ResultSet getResult(Connection connection, List values) {
    try {
        String queryString = "Select * from table_name where column_name in";

        StringBuilder parameterBuilder = new StringBuilder();
        parameterBuilder.append(" (");
        for (int i = 0; i < values.size(); i++) {
            if (values.size() > i + 1) {

        PreparedStatement statement = connection.prepareStatement(queryString + parameterBuilder);
        for (int i = 1; i < values.size() + 1; i++) {
            statement.setInt(i, (int) values.get(i - 1));

        return statement.executeQuery();
    } catch (Exception d) {
        return null;

Adding a right click menu to an item

Add a contextmenu to your form and then assign it in the control's properties under ContextMenuStrip. Hope this helps :).

Hope this helps:

ContextMenu cm = new ContextMenu();
cm.MenuItems.Add("Item 1");
cm.MenuItems.Add("Item 2");

pictureBox1.ContextMenu = cm;

How do I kill all the processes in Mysql "show processlist"?

The following will create a simple stored procedure that uses a cursor to kill all processes one by one except for the process currently being used:

DROP PROCEDURE IF EXISTS kill_other_processes;


CREATE PROCEDURE kill_other_processes()
  DECLARE proc_id INT;
  DECLARE proc_id_cursor CURSOR FOR SELECT id FROM information_schema.processlist;

  OPEN proc_id_cursor;
  proc_id_cursor_loop: LOOP
    FETCH proc_id_cursor INTO proc_id;

    IF finished = 1 THEN 
      LEAVE proc_id_cursor_loop;
    END IF;

    IF proc_id <> CONNECTION_ID() THEN
      KILL proc_id;
    END IF;

  END LOOP proc_id_cursor_loop;
  CLOSE proc_id_cursor;


It can be run with SELECTs to show the processes before and after as follows:

SELECT * FROM information_schema.processlist;
CALL kill_other_processes();
SELECT * FROM information_schema.processlist;

Returning JSON object from an ASP.NET page

no problem doing it with asp.... it's most natural to do so with MVC, but can be done with standard asp as well.

The MVC framework has all sorts of helper classes for JSON, if you can, I'd suggest sussing in some MVC-love, if not, you can probably easily just get the JSON helper classes used by MVC in and use them in the context of


here's an example of how to return JSON data with MVC. This would be in your controller class. This is out of the box functionality with MVC--when you crate a new MVC project this stuff gets auto-created so it's nothing special. The only thing that I"m doing is returning an actionResult that is JSON. The JSON method I'm calling is a method on the Controller class. This is all very basic, default MVC stuff:

public ActionResult GetData()
    var data = new { Name="kevin", Age=40 };
    return Json(data, JsonRequestBehavior.AllowGet);

This return data could be called via JQuery as an ajax call thusly:

$.get("/Reader/GetData/", function(data) { someJavacriptMethodOnData(data); });

trigger click event from angularjs directive

This is more the Angular way to do it:

  1. I added $scope.selectedItem that gets you past your first problem (defaulting the image)
  2. I added $scope.setSelectedItem and called it in ng-click. Your final requirements may be different, but using a directive to bind click and change src was overkill, since most of it can be handled with template
  3. Notice use of ngSrc to avoid errant server calls on initial load
  4. You'll need to adjust some styles to get the image positioned right in the div. If you really need to use background-image, then you'll need a directive like ngSrc that defers setting the background-image style until after real data has loaded.

How to set Spinner default value to null?

Base on @Jonik answer I have created fully functional extension to ArrayAdapter

class SpinnerArrayAdapter<T> : ArrayAdapter<T> {

    private val selectText : String
    private val resource: Int
    private val fieldId : Int
    private val inflater : LayoutInflater

    constructor(context: Context?, resource: Int, objects: Array<T>, selectText : String? = null) : super(context, resource, objects) {
        this.selectText = selectText ?: context?.getString(R.string.spinner_default_select_text) ?: ""
        this.resource = resource
        this.fieldId = 0
        this.inflater = LayoutInflater.from(context)
    constructor(context: Context?, resource : Int, objects: List<T>, selectText : String? = null) : super(context, resource, objects) {
        this.selectText = selectText ?: context?.getString(R.string.spinner_default_select_text) ?: ""
        this.resource = resource
        this.fieldId = 0
        this.inflater = LayoutInflater.from(context)
    constructor(context: Context?, resource: Int, textViewResourceId: Int, objects: Array<T>, selectText : String? = null) : super(context, resource, textViewResourceId, objects) {
        this.selectText = selectText ?: context?.getString(R.string.spinner_default_select_text) ?: ""
        this.resource = resource
        this.fieldId = textViewResourceId
        this.inflater = LayoutInflater.from(context)
    constructor(context: Context?, resource : Int, textViewResourceId: Int, objects: List<T>, selectText : String? = null) : super(context, resource, textViewResourceId,  objects) {
        this.selectText = selectText ?: context?.getString(R.string.spinner_default_select_text) ?: ""
        this.resource = resource
        this.fieldId = textViewResourceId
        this.inflater = LayoutInflater.from(context)

    override fun getDropDownView(position: Int, convertView: View?, parent: ViewGroup?): View {
        if(position == 0) {
            return initialSelection(true)

        return createViewFromResource(inflater, position -1, convertView, parent, resource)

    override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View {
        if(position == 0) {
            return initialSelection(false)
        return createViewFromResource(inflater, position -1, convertView, parent, resource)

    override fun getCount(): Int {
        return super.getCount() + 1 // adjust for initial selection

    private fun initialSelection(inDropDown: Boolean) : View {
        // Just simple TextView as initial selection.
        val view = TextView(context)
        view.setPadding(8, 0, 8, 0)

        if(inDropDown) {
            // Hide when dropdown is open
            view.height = 0
        return view

    private fun createViewFromResource(inflater: LayoutInflater, position: Int,
                                       @Nullable convertView: View?, parent: ViewGroup?, resource: Int): View {
        val view: View
        val text: TextView?

        if (convertView == null || (convertView is TextView)) {
            view = inflater.inflate(resource, parent, false)
        } else {
            view = convertView

        try {
            if (fieldId === 0) {
                //  If no custom field is assigned, assume the whole resource is a TextView
                text = view as TextView
            } else {
                //  Otherwise, find the TextView field within the layout
                text = view.findViewById(fieldId)

                if (text == null) {
                    throw RuntimeException("Failed to find view with ID "
                            + context.getResources().getResourceName(fieldId)
                            + " in item layout")
        } catch (e: ClassCastException) {
            Log.e("ArrayAdapter", "You must supply a resource ID for a TextView")
            throw IllegalStateException(
                    "ArrayAdapter requires the resource ID to be a TextView", e)

        val item = getItem(position)
        if (item is CharSequence) {
            text.text = item
        } else {
            text.text = item!!.toString()

        return view

:before and background-image... should it work?

The problem with other answers here is that they use position: absolute;

This makes it difficult to layout the element itself in relation to the ::before pseudo-element. For example, if you wish to show an image before a link like this: enter image description here

Here's how I was able to achieve the layout in the picture:

a::before {_x000D_
  content: "";_x000D_
  float: left;_x000D_
  width: 16px;_x000D_
  height: 16px;_x000D_
  margin-right: 5px;_x000D_
  background: url(../../lhsMenu/images/internal_link.png) no-repeat 0 0;_x000D_
  background-size: 80%;_x000D_

Note that this method allows you to scale the background image, as well as keep the ability to use margins and padding for layout.

Force browser to clear cache

Update 2012

This is an old question but I think it needs a more up to date answer because now there is a way to have more control of website caching.

In Offline Web Applications (which is really any HTML5 website) applicationCache.swapCache() can be used to update the cached version of your website without the need for manually reloading the page.

This is a code example from the Beginner's Guide to Using the Application Cache on HTML5 Rocks explaining how to update users to the newest version of your site:

// Check if a new cache is available on page load.
window.addEventListener('load', function(e) {

  window.applicationCache.addEventListener('updateready', function(e) {
    if (window.applicationCache.status == window.applicationCache.UPDATEREADY) {
      // Browser downloaded a new app cache.
      // Swap it in and reload the page to get the new hotness.
      if (confirm('A new version of this site is available. Load it?')) {
    } else {
      // Manifest didn't changed. Nothing new to server.
  }, false);

}, false);

See also Using the application cache on Mozilla Developer Network for more info.

Update 2016

Things change quickly on the Web. This question was asked in 2009 and in 2012 I posted an update about a new way to handle the problem described in the question. Another 4 years passed and now it seems that it is already deprecated. Thanks to cgaldiolo for pointing it out in the comments.

Currently, as of July 2016, the HTML Standard, Section 7.9, Offline Web applications includes a deprecation warning:

This feature is in the process of being removed from the Web platform. (This is a long process that takes many years.) Using any of the offline Web application features at this time is highly discouraged. Use service workers instead.

So does Using the application cache on Mozilla Developer Network that I referenced in 2012:

This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. Do not use it in old or new projects. Pages or Web apps using it may break at any time.

See also Bug 1204581 - Add a deprecation notice for AppCache if service worker fetch interception is enabled.

jQuery hyperlinks - href value?

I almost had this problem and it was very deceiving. I am providing an answer in case someone winds up in my same position.

  1. I thought I had this problem
  2. But, I was using return false and javascript:void(0);
  3. Then a distinct difference in problem kept surfacing:
  4. I realized it's not going ALL the way to the top - and my problem zone was near the bottom of the page so this jump was strange and annoying.
  5. I realized I was using fadeIn() [jQuery library], which for a short time my content was display:none
  6. And then my content extended the reach of the page! Causing what looks like a jump!
  7. Using visibility hidden toggles now..

Hope this helps the person stuck with jumps!!

Setting paper size in FPDF

/*$mpdf = new mPDF('',    // mode - default ''
 '',    // format - A4, for example, default ''
 0,     // font size - default 0
 '',    // default font family
 15,    // margin_left
 15,    // margin right
 16,     // margin top
 16,    // margin bottom
 9,     // margin header
 9,     // margin footer
 'L');  // L - landscape, P - portrait*/

sqlite3.OperationalError: unable to open database file

In my case, the solution was to use an absolute path, to find an existing file:

import os.path
filepath = os.path.abspath(filepath)
# Leave this out if the file doesn't exist yet
assert os.path.exists(filepath), "The file doesn't exist"
conn = sqlite3.connect(filepath)

I don't know why this fix works: the path only contained ASCII characters and no spaces. Still it made the difference.

For reference: Windows 7, Python 3.6.5 (64-bit).

I was not able to reproduce the issue on another machine (also Windows 7, Python 3.6.4 64-bit), so I have no idea why this fix works.

HTML forms - input type submit problem with action=URL when URL contains index.aspx

This appears to be my "preferred" solution:

<form action="" method="post">  <div>
<input type="submit" value="Gymnastics"></div>

Sorry for the presentation format - I'm still trying to learn how to use this forum....

I do have a follow-up question. In looking at my MySQL database of URL's it appears that ~30% of the URL's will need to use this post/div wrapper approach. This leaves ~70% that cannot accept the "post" attribute. For example:

<form action="" method="post">
    <input type="submit" value="Google"/>

does not work. Do you have a recommendation for how to best handle this get/post condition test. Off the top of my head I'm guessing that using PHP to evaluate the existence of the "?" character in the URL may be my best approach, although I'm not sure how to structure the HTML form to accomplish this.

Thank YOU!

Cmake is not able to find Python-libraries

Paste this into your CMakeLists.txt:

# find python
execute_process(COMMAND python-config --prefix OUTPUT_VARIABLE PYTHON_SEARCH_PATH)
file(GLOB_RECURSE PYTHON_DY_LIBS ${PYTHON_SEARCH_PATH}/lib/libpython*.dylib ${PYTHON_SEARCH_PATH}/lib/libpython*.so)
    message("-- Find shared libpython: ${PYTHON_LIBRARY}")
    message(WARNING "Cannot find shared libpython, try find_package")

find_package(PythonLibs ${PYTHON_VERSION_STRING} EXACT)

Automating the InvokeRequired code pattern

Here's the form I've been using in all my code.

private void DoGUISwitch()
    Invoke( ( MethodInvoker ) delegate {
        object1.Visible = true;
        object2.Visible = false;

I've based this on the blog entry here. I have not had this approach fail me, so I see no reason to complicate my code with a check of the InvokeRequired property.

Hope this helps.

Nginx upstream prematurely closed connection while reading response header from upstream, for large requests


The upstream server is timing out and I don't what is happening.

Where to Look first before increasing read or write timeout if your server is connecting to a database

Server is connecting to a database and that connection is working just fine and within sane response time, and its not the one causing this delay in server response time.

make sure that connection state is not causing a cascading failure on your upstream

Then you can move to look at the read and write timeout configurations of the server and proxy.

Access to ES6 array element index inside for-of loop

Array#entries returns the index and the value, if you need both:

for (let [index, value] of array.entries()) {


How do I create 7-Zip archives with .NET?

SevenZipSharp is another solution. Creates 7-zip archives...

Variable's memory size in Python

Regarding the internal structure of a Python long, check sys.int_info (or sys.long_info for Python 2.7).

>>> import sys
>>> sys.int_info
sys.int_info(bits_per_digit=30, sizeof_digit=4)

Python either stores 30 bits into 4 bytes (most 64-bit systems) or 15 bits into 2 bytes (most 32-bit systems). Comparing the actual memory usage with calculated values, I get

>>> import math, sys
>>> a=0
>>> sys.getsizeof(a)
>>> a=2**100
>>> sys.getsizeof(a)
>>> a=2**1000
>>> sys.getsizeof(a)
>>> 24+4*math.ceil(100/30)
>>> 24+4*math.ceil(1000/30)

There are 24 bytes of overhead for 0 since no bits are stored. The memory requirements for larger values matches the calculated values.

If your numbers are so large that you are concerned about the 6.25% unused bits, you should probably look at the gmpy2 library. The internal representation uses all available bits and computations are significantly faster for large values (say, greater than 100 digits).

How to convert an Stream into a byte[] in C#?

    byte[] buf;  // byte array
    Stream stream=Page.Request.InputStream;  //initialise new stream
    buf = new byte[stream.Length];  //declare arraysize
    stream.Read(buf, 0, buf.Length); // read from stream to byte array

Java - JPA - @Version annotation

Version used to ensure that only one update in a time. JPA provider will check the version, if the expected version already increase then someone else already update the entity so an exception will be thrown.

So updating entity value would be more secure, more optimist.

If the value changes frequent, then you might consider not to use version field. For an example "an entity that has counter field, that will increased everytime a web page accessed"

How to initialize an array of custom objects

Here is a concise way to initialize an array of custom objects in PowerShell.

> $body = @( @{ Prop1="1"; Prop2="2"; Prop3="3" }, @{ Prop1="1"; Prop2="2"; Prop3="3" } )
> $body

Name                           Value
----                           -----
Prop2                          2
Prop1                          1
Prop3                          3
Prop2                          2
Prop1                          1
Prop3                          3  

How do I escape ampersands in batch files?

If you need to echo a string that contains an ampersand, quotes won't help, because you would see them on the output as well. In such a case, use for:

for %a in ("First & Last") do echo %~a a batch script:

for %%a in ("First & Last") do echo %%~a


for %%a in ("%~1") do echo %%~a

How to automate browsing using python?

Selenium2 includes webdriver, which has python bindings and allows one to use the headless htmlUnit driver, or switch to firefox or chrome for graphical debugging.

Android Color Picker

try this open source projects that might help you

unique combinations of values in selected columns in pandas data frame and count

I haven't done time test with this but it was fun to try. Basically convert two columns to one column of tuples. Now convert that to a dataframe, do 'value_counts()' which finds the unique elements and counts them. Fiddle with zip again and put the columns in order you want. You can probably make the steps more elegant but working with tuples seems more natural to me for this problem

b = pd.DataFrame({'A':['yes','yes','yes','yes','no','no','yes','yes','yes','no'],'B':['yes','no','no','no','yes','yes','no','yes','yes','no']})

b['count'] = pd.Series(zip(*[b.A,b.B]))
df = pd.DataFrame(b['count'].value_counts().reset_index())
df['A'], df['B'] = zip(*df['index'])
df = df.drop(columns='index')[['A','B','count']]

How do I change the root directory of an Apache server?

Please note, that this only applies for Ubuntu 14.04 LTS and newer releases.

In my Ubuntu 14.04 LTS, the document root was set to /var/www/html. It was configured in the following file:


So just do a

sudo nano /etc/apache2/sites-available/000-default.conf

and change the following line to what you want:

DocumentRoot /var/www/html

Also do a

sudo nano /etc/apache2/apache2.conf

and find this

<Directory /var/www/html/>
Options Indexes FollowSymLinks
AllowOverride None
Require all granted

and change /var/www/html to your preferred directory

and save it.

After you saved your changes, just restart the apache2 webserver and you'll be done :)

sudo service apache2 restart

If you prefer a graphical text editor, you can just replace the sudo nano by a gksu gedit.

smooth scroll to top

You can simply use

// When the user scrolls down 20px from the top of the document, show the button_x000D_
window.onscroll = function() {scrollFunction()};_x000D_
function scrollFunction() {_x000D_
    if (document.body.scrollTop > 20 || document.documentElement.scrollTop > 20) {_x000D_
        document.getElementById("gotoTop").style.display = "block";_x000D_
    } else {_x000D_
        document.getElementById("gotoTop").style.display = "none";_x000D_
// When the user clicks on the button, scroll to the top of the document_x000D_
function topFunction() {_x000D_
     $('html, body').animate({scrollTop:0}, 'slow');_x000D_
body {_x000D_
  font-family: Arial, Helvetica, sans-serif;_x000D_
  font-size: 20px;_x000D_
#gotoTop {_x000D_
  display: none;_x000D_
  position: fixed;_x000D_
  bottom: 20px;_x000D_
  right: 30px;_x000D_
  z-index: 99;_x000D_
  font-size: 18px;_x000D_
  border: none;_x000D_
  outline: none;_x000D_
  background-color: red;_x000D_
  color: white;_x000D_
  cursor: pointer;_x000D_
  padding: 15px;_x000D_
  border-radius: 4px;_x000D_
#gotoTop:hover {_x000D_
  background-color: #555;_x000D_
<script src=""></script>_x000D_
<button onclick="topFunction()" id="gotoTop" title="Go to top">Top</button>_x000D_
<div style="background-color:black;color:white;padding:30px">Scroll Down</div>_x000D_
<div style="background-color:lightgrey;padding:30px 30px 2500px">This example demonstrates how to create a "scroll to top" button that becomes visible when the user starts to scroll the page.</div>

Using C++ base class constructors?

No, that's not how it is done. Normal way to initialize the base class is in the initialization list :

class A
    A(int val) {}

class B : public A
  B( int v) : A( v )

void main()
    B b(10);

"A referral was returned from the server" exception when accessing AD from C#

In my case I was seeing referrals when I was accessing AD via SSO with an account in a trusted domain. The problem went away when I connected with explicit credentials in the local domain.

i.e. I replaced

DirectoryEntry de = new DirectoryEntry("");


DirectoryEntry de = new DirectoryEntry("", "[email protected]", "supersecret");

and the problem went away.

Saving and loading objects and using pickle

The following works for me:

class Fruits: pass

banana = Fruits()

banana.color = 'yellow'
banana.value = 30

import pickle

filehandler = open("Fruits.obj","wb")

file = open("Fruits.obj",'rb')
object_file = pickle.load(file)

print(object_file.color, object_file.value, sep=', ')
# yellow, 30

How to set the color of "placeholder" text?

Try this

textarea::-webkit-input-placeholder {  color: #999;}

How do I vertically align text in a div?

The correct way to do this in modern browsers is to use Flexbox.

See this answer for details.

See below for some older ways that work in older browsers.

Vertical Centering in CSS

Article summary:

For a CSS 2 browser, one can use display:table/display:table-cell to center content.

A sample is also available at JSFiddle:

div { border:1px solid green;}
<div style="display: table; height: 400px; overflow: hidden;">
  <div style="display: table-cell; vertical-align: middle;">
      everything is vertically centered in modern IE8+ and others.

It is possible to merge hacks for old browsers (Internet Explorer 6/7) into styles with using # to hide styles from newer browsers:

div { border:1px solid green;}
<div style="display: table; height: 400px; #position: relative; overflow: hidden;">
  <div style=
    "#position: absolute; #top: 50%;display: table-cell; vertical-align: middle;">
    <div style=" #position: relative; #top: -50%">
      everything is vertically centered

GitHub center image

You can also resize the image to the desired width and height. For example:

<p align="center">
  <img src="" width="750px" height="300px"/></p>

To add a centered caption to the image, just one more line:

<p align="center">This is a centered caption for the image<p align="center">

Fortunately, this works both for and the GitHub Wiki pages.

Capturing mobile phone traffic on Wireshark

Packet Capture Android app implements a VPN that logs all network traffic on the Android device. You don't need to setup any VPN/proxy server on your PC. Does not needs root. Supports SSL decryption which tPacketCapture does not. It also includes a good log viewer.

Android scale animation on view

Add this code on values anim

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="">


call on styles.xml

<style name="DialogScale">
    <item name="android:windowEnterAnimation">@anim/scale_in</item>
    <item name="android:windowExitAnimation">@anim/scale_out</item>

In Java code: set Onclick

public void onClick(View v) {
            fab_onclick(, "Scale" ,(Activity) context,getWindow().getDecorView().getRootView());
          //  Dialogs.fab_onclick(, "Scale");


setup on method:

alertDialog.getWindow().getAttributes().windowAnimations = type;

How to parse JSON in Java

This blew my mind with how easy it was. You can just pass a String holding your JSON to the constructor of a JSONObject in the default org.json package.

JSONArray rootOfPage =  new JSONArray(JSONString);

Done. Drops microphone. This works with JSONObjects as well. After that, you can just look through your hierarchy of Objects using the get() methods on your objects.

javascript clear field value input

do like

<input name="name" id="name" type="text" value="Name" 
   onblur="fillField(this,'Name');" onfocus="clearField(this,'Name');"/>

and js

function fillField(input,val) {
      if(input.value == "")

function clearField(input,val) {
      if(input.value == val)


here is a demo fiddle of the same

Difference between try-catch and throw in java

Others have already given thorough answers, but if you're looking for even more information, the Oracle Java tutorials are always a good resource. Here's the Java tutorial for Exceptions, which covers all of your questions in great detail;

Authentication plugin 'caching_sha2_password' is not supported

Use pip install mysql-connector-python

Then connect like this:

import mysql.connector

mydb = mysql.connector.connect(
  host="localhost",               #hostname
  user="Harish",                   # the user who has privilege to the db
  passwd="Harish96",               #password for user
  database="Factdb",               #database name
    auth_plugin = 'mysql_native_password',


correct way to define class variables in Python

Neither way is necessarily correct or incorrect, they are just two different kinds of class elements:

  • Elements outside the __init__ method are static elements; they belong to the class.
  • Elements inside the __init__ method are elements of the object (self); they don't belong to the class.

You'll see it more clearly with some code:

class MyClass:
    static_elem = 123

    def __init__(self):
        self.object_elem = 456

c1 = MyClass()
c2 = MyClass()

# Initial values of both elements
>>> print c1.static_elem, c1.object_elem 
123 456
>>> print c2.static_elem, c2.object_elem
123 456

# Nothing new so far ...

# Let's try changing the static element
MyClass.static_elem = 999

>>> print c1.static_elem, c1.object_elem
999 456
>>> print c2.static_elem, c2.object_elem
999 456

# Now, let's try changing the object element
c1.object_elem = 888

>>> print c1.static_elem, c1.object_elem
999 888
>>> print c2.static_elem, c2.object_elem
999 456

As you can see, when we changed the class element, it changed for both objects. But, when we changed the object element, the other object remained unchanged.

How can I limit ngFor repeat to some number of items in Angular?

This works very well:

<template *ngFor="let item of items; let i=index" >
 <ion-slide *ngIf="i<5" >
  <img [src]="item.ItemPic">

get one item from an array of name,value JSON

The easiest approach which I have used is

var found = arr.find(function(element) {
         return === "k1";

//If you print the found :
=> Object { name: "k1", value: "abc" }

//If you need the value
=> "abc"

The similar approach can be used to find the values from the JSON Array based on any input data from the JSON.

Name does not exist in the current context

I solved mine by using an Import directive under my Page directive. You may also want to add the namespace to your Inherits attribute of your Page directive.

Since it appears that your default namespace is "stman.Members", try: <%@ Page Title="" Language="C#" MasterPageFile="~/Members/Members.master" AutoEventWireup="true" CodeFile="Jobs.aspx.cs" Inherits="stman.Members.Members_Jobs" %> <%@ Import Namespace="stman.Members"%>

Additionally, data that I wanted to pass between aspx.cs and aspx, I put inside a static class inside the namespace. That static class was available to move data around in the name space and no longer has a "not in context" error.

Converting an int to a binary string representation in Java?

One more way- By using java.lang.Integer you can get string representation of the first argument i in the radix (Octal - 8, Hex - 16, Binary - 2) specified by the second argument.

 Integer.toString(i, radix)


private void getStrtingRadix() {
        // TODO Auto-generated method stub
         /* returns the string representation of the 
          unsigned integer in concern radix*/
         System.out.println("Binary eqivalent of 100 = " + Integer.toString(100, 2));
         System.out.println("Octal eqivalent of 100 = " + Integer.toString(100, 8));
         System.out.println("Decimal eqivalent of 100 = " + Integer.toString(100, 10));
         System.out.println("Hexadecimal eqivalent of 100 = " + Integer.toString(100, 16));


Binary eqivalent of 100 = 1100100
Octal eqivalent of 100 = 144
Decimal eqivalent of 100 = 100
Hexadecimal eqivalent of 100 = 64

How to reload current page in ReactJS?

use this might help


How to get ALL child controls of a Windows Forms form of a specific type (Button/Textbox)?

    public static IEnumerable<T> GetAllControls<T>(this Control control) where T : Control
        foreach (Control c in control.Controls)
            if (c is T)
                yield return (T)c;
            foreach (T c1 in c.GetAllControls<T>())
                yield return c1;

commands not found on zsh

In my case, it was by mistake the commented code was uncommented at the very first line.

# If you come from bash you might have to change your $PATH.

The hash was removed. After adding it back worked fine.

I just posted this here so someone might find this helpful. Because it's just start of the line and might be deleted by mistake like I had done. And seems there's no solution after trying several ways.

$watch an object

Try this:

function MyController($scope) {
    $scope.form = {
        name: 'my name',
        surname: 'surname'

    function track(newValue, oldValue, scope) {

    $scope.$watch('', track);

Returning IEnumerable<T> vs. IQueryable<T>

There is a blog post with brief source code sample about how misuse of IEnumerable<T> can dramatically impact LINQ query performance: Entity Framework: IQueryable vs. IEnumerable.

If we dig deeper and look into the sources, we can see that there are obviously different extension methods are perfomed for IEnumerable<T>:

// Type: System.Linq.Enumerable
// Assembly: System.Core, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089
// Assembly location: C:\Windows\Microsoft.NET\Framework\v4.0.30319\System.Core.dll
public static class Enumerable
    public static IEnumerable<TSource> Where<TSource>(
        this IEnumerable<TSource> source, 
        Func<TSource, bool> predicate)
        return (IEnumerable<TSource>) 
            new Enumerable.WhereEnumerableIterator<TSource>(source, predicate);

and IQueryable<T>:

// Type: System.Linq.Queryable
// Assembly: System.Core, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089
// Assembly location: C:\Windows\Microsoft.NET\Framework\v4.0.30319\System.Core.dll
public static class Queryable
    public static IQueryable<TSource> Where<TSource>(
        this IQueryable<TSource> source, 
        Expression<Func<TSource, bool>> predicate)
        return source.Provider.CreateQuery<TSource>(
                ((MethodInfo) MethodBase.GetCurrentMethod()).MakeGenericMethod(
                    new Type[] { typeof(TSource) }), 
                    new Expression[] 
                        { source.Expression, Expression.Quote(predicate) }));

The first one returns enumerable iterator, and the second one creates query through the query provider, specified in IQueryable source.

How can I combine hashes in Perl?

This is an old question, but comes out high in my Google search for 'perl merge hashes' - and yet it does not mention the very helpful CPAN module Hash::Merge

Delete all rows with timestamp older than x days

DELETE FROM on_search WHERE search_date < NOW() - INTERVAL N DAY

Replace N with your day count

How do I create a folder in a GitHub repository?

First you have to clone the repository to you local machine

git clone github_url local_directory

Then you can create local folders and files inside your local_directory, and add them to the repository using:

git add file_path

You can also add everything using:

git add .

Note that Git does not track empty folders. A workaround is to create a file inside the empty folder you want to track. I usually name that file empty, but it can be whatever name you choose.

Finally, you commit and push back to GitHub:

git commit
git push

For more information on Git, check out the Pro Git book.

How to check if NSString begins with a certain character

hasPrefix works especially well. for example if you were looking for a http url in a NSString, you would use componentsSeparatedByString to create an NSArray and the iterate the array using hasPrefix to find the elements that begin with http.

NSArray *allStringsArray = 
   [myStringThatHasHttpUrls componentsSeparatedByString:@" "]

for (id myArrayElement in allStringsArray) {
    NSString *theString = [myArrayElement description];
    if ([theString hasPrefix:@"http"]) {
        NSLog(@"The URL  is %@", [myArrayElement description]);


hasPrefix returns a Boolean value that indicates whether a given string matches the beginning characters of the receiver.

- (BOOL)hasPrefix:(NSString *)aString, 

parameter aString is a string that you are looking for Return Value is YES if aString matches the beginning characters of the receiver, otherwise NO. Returns NO if aString is empty.

How to check whether a Button is clicked by using JavaScript

if(button.clicked==true) {
    console.log("Button Clicked");
} ==> // This Code Doesn't Work Properly So Please Use Below One // 

function check() { 
    console.log("Button Clicked");
}; // This Code Works Fine // 

var button= document.querySelector("button"); // Accessing The Button // 
button.addEventListener("click", check); // Adding event to call function when clicked // 

A field initializer cannot reference the nonstatic field, method, or property

private dynamic defaultReminder = reminder.TimeSpanText[TimeSpan.FromMinutes(15)]; is a field initializer and executes first (before any field without an initializer is set to its default value and before the invoked instance constructor is executed). Instance fields that have no initializer will only have a legal (default) value after all instance field initializers are completed. Due to the initialization order, instance constructors are executed last, which is why the instance is not created yet the moment the initializers are executed. Therefore the compiler cannot allow any instance property (or field) to be referenced before the class instance is fully constructed. This is because any access to an instance variable like reminder implicitly references the instance (this) to tell the compiler the concrete memory location of the instance to use.

This is also the reason why this is not allowed in an instance field initializer.

A variable initializer for an instance field cannot reference the instance being created. Thus, it is a compile-time error to reference this in a variable initializer, as it is a compile-time error for a variable initializer to reference any instance member through a simple_name.

The only type members that are guaranteed to be initialized before instance field initializers are executed are class (static) field initializers and class (static) constructors and class methods. Since static members are instance independent, they can be referenced at any time:

class SomeOtherClass
  private static Reminders reminder = new Reminders();

  // This operation is allowed,
  // since the compiler can guarantee that the referenced class member is already initialized
  // when this instance field initializer executes
  private dynamic defaultReminder = reminder.TimeSpanText[TimeSpan.FromMinutes(15)];

That's why instance field initializers are only allowed to reference a class member (static member). This compiler initialization rules will ensure a deterministic type instantiation.

For more details I recommend this document: Microsoft Docs: Class declarations.

This means that an instance field that references another instance member to initialize its value, must be initialized from the instance constructor or the referenced member must be declared static.

How to normalize a 2-dimensional numpy array in python less verbose?

Or using lambda function, like

>>> vec = np.arange(0,27,3).reshape(3,3)
>>> import numpy as np
>>> norm_vec = map(lambda row: row/np.linalg.norm(row), vec)

each vector of vec will have a unit norm.

Programmatically set the initial view controller using Storyboards

You can set Navigation rootviewcontroller as a main view controller. This idea can use for auto login as per application requirement.

UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"Main" bundle: nil];

UIViewController viewController = (HomeController*)[mainStoryboard instantiateViewControllerWithIdentifier: @"HomeController"];

UINavigationController navController = [[UINavigationController alloc] initWithRootViewController:viewController];

 self.window.rootViewController = navController;

if (NSFoundationVersionNumber > NSFoundationVersionNumber_iOS_6_1) {

    // do stuff for iOS 7 and newer

    navController.navigationBar.barTintColor = [UIColor colorWithRed:88/255.0 green:164/255.0 blue:73/255.0 alpha:1.0];

    navController.navigationItem.leftBarButtonItem.tintColor = [UIColor colorWithRed:88/255.0 green:164/255.0 blue:73/255.0 alpha:1.0];

    navController.navigationBar.tintColor = [UIColor whiteColor];

    navController.navigationItem.titleView.tintColor = [UIColor whiteColor];

    NSDictionary *titleAttributes =@{

                                     NSFontAttributeName :[UIFont fontWithName:@"Helvetica-Bold" size:14.0],

                                     NSForegroundColorAttributeName : [UIColor whiteColor]


    navController.navigationBar.titleTextAttributes = titleAttributes;

    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];


else {

    // do stuff for older versions than iOS 7

    navController.navigationBar.tintColor = [UIColor colorWithRed:88/255.0 green:164/255.0 blue:73/255.0 alpha:1.0];

    navController.navigationItem.titleView.tintColor = [UIColor whiteColor];


[self.window makeKeyAndVisible];

For StoryboardSegue Users

UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"Main" bundle: nil];

// Go to Login Screen of story board with Identifier name : LoginViewController_Identifier

LoginViewController *loginViewController = (LoginViewController*)[mainStoryboard instantiateViewControllerWithIdentifier:@“LoginViewController_Identifier”];

navigationController = [[UINavigationController alloc] initWithRootViewController:testViewController];

self.window.rootViewController = navigationController;

[self.window makeKeyAndVisible];

// Go To Main screen if you are already Logged In Just check your saving credential here

if([SavedpreferenceForLogin] > 0){
    [loginViewController performSegueWithIdentifier:@"mainview_action" sender:nil];


What is the difference between conversion specifiers %i and %d in formatted IO functions (*printf / *scanf)

These are identical for printf but different for scanf. For printf, both %d and %i designate a signed decimal integer. For scanf, %d and %i also means a signed integer but %i inteprets the input as a hexadecimal number if preceded by 0x and octal if preceded by 0 and otherwise interprets the input as decimal.

How to make flexbox items the same size?

None of these answers solved my problem, which was that the items weren't the same width in my makeshift flexbox table when it was shrunk to a width too small.

The solution for me was simply to put overflow: hidden; on the flex-grow: 1; cells.

Send email using the GMail SMTP server from a PHP page

Gmail requires port 465, and also it's the code from phpmailer :)

In C#, how to check whether a string contains an integer?

This work for me.

("your string goes here").All(char.IsDigit)

Read from a gzip file in python

Try gzipping some data through the gzip libary like this...

import gzip
content = "Lots of content here"
f ='Onlyfinnaly.log.gz', 'wb')

... then run your code as posted ...

import gzip'Onlyfinnaly.log.gz','rb')
print file_content

This method worked for me as for some reason the gzip library fails to read some files.

How to return part of string before a certain character?

In General a function to return string after substring is

function getStringAfterSubstring(parentString, substring) {_x000D_
    return parentString.substring(parentString.indexOf(substring) + substring.length)_x000D_
function getStringBeforeSubstring(parentString, substring) {_x000D_
    return parentString.substring(0, parentString.indexOf(substring))_x000D_
console.log(getStringAfterSubstring('abcxyz123uvw', '123'))_x000D_
console.log(getStringBeforeSubstring('abcxyz123uvw', '123'))

Vertically align an image inside a div with responsive height

Make another div and add both 'dummy' and 'img-container' inside the div

Do HTML and CSS like follows

html , body {height:100%;}_x000D_
.responsive-container { height:100%; display:table; text-align:center; width:100%;}_x000D_
.inner-container {display:table-cell; vertical-align:middle;}
<div class="responsive-container">_x000D_
    <div class="inner-container">_x000D_
  <div class="dummy">Sample</div>_x000D_
  <div class="img-container">_x000D_
   Image tag_x000D_
 </div> _x000D_

Instead of 100% for the 'responsive-container' you can give the height that you want.,

How can I find out if I have Xcode commandline tools installed?

/usr/bin/xcodebuild -version

will give you the xcode version, run it via Terminal command

Check if specific input file is empty

simple :

if($_FILES['cover_image']['error'] > 0)
    // cover_image is empty

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.)

How to list all the available keyspaces in Cassandra?

describes and desc command will give list of keyspaces in the cluster.Please find below output for more details.

cqlsh> describe keyspaces
reaper_db      system_auth  system_distributed
system_schema  system       system_traces


cqlsh> desc keyspaces
reaper_db      system_auth  system_distributed
system_schema  system       system_traces

If else in stored procedure sql server

You can try below Procedure Sql:

@ParLngId int output
    -- Min will return only 1 value, if 'Extranet Client' is found
    -- IsNull will take care of 'Extranet Client' not found, returning 0 instead of Null
    -- But T_Param must be a Master Table with ParStrNom having a Unique Index, if so Min is not reqd at all
    -- But 'PHY', 'Extranet Client' suggests that Unique Key has 2 columns, not just ParStrNom

    SET @ParLngId = IsNull((Select Min (ParLngId) from T_Param where ParStrNom = 'Extranet Client'), 0);

    -- Nothing changed below

    if  (@ParLngId = 0)
            Insert Into T_Param values ('PHY', 'Extranet Client', Null, Null, 'T', 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, 1, NULL, NULL, NULL)
            SET @ParLngId = @@IDENTITY

    Return  @ParLngId

Terminating a script in PowerShell

I realize this is an old post but I find myself coming back to this thread a lot as it is one of the top search results when searching for this topic. However, I always leave more confused then when I came due to the conflicting information. Ultimately I always have to perform my own tests to figure it out. So this time I will post my findings.

TL;DR Most people will want to use Exit to terminate a running scripts. However, if your script is merely declaring functions to later be used in a shell, then you will want to use Return in the definitions of said functions.

Exit vs Return vs Break

  • Exit: This will "exit" the currently running context. If you call this command from a script it will exit the script. If you call this command from the shell it will exit the shell.

    If a function calls the Exit command it will exit what ever context it is running in. So if that function is only called from within a running script it will exit that script. However, if your script merely declares the function so that it can be used from the current shell and you run that function from the shell, it will exit the shell because the shell is the context in which the function contianing the Exit command is running.

    Note: By default if you right click on a script to run it in PowerShell, once the script is done running, PowerShell will close automatically. This has nothing to do with the Exit command or anything else in your script. It is just a default PowerShell behavior for scripts being ran using this specific method of running a script. The same is true for batch files and the Command Line window.

  • Return: This will return to the previous call point. If you call this command from a script (outside any functions) it will return to the shell. If you call this command from the shell it will return to the shell (which is the previous call point for a single command ran from the shell). If you call this command from a function it will return to where ever the function was called from.

    Execution of any commands after the call point that it is returned to will continue from that point. If a script is called from the shell and it contains the Return command outside any functions then when it returns to the shell there are no more commands to run thus making a Return used in this way essentially the same as Exit.

  • Break: This will break out of loops and switch cases. If you call this command while not in a loop or switch case it will break out of the script. If you call Break inside a loop that is nested inside a loop it will only break out of the loop it was called in.

    There is also an interesting feature of Break where you can prefix a loop with a label and then you can break out of that labeled loop even if the Break command is called within several nested groups within that labeled loop.

    While ($true) {
        # Code here will run
        :myLabel While ($true) {
            # Code here will run
            While ($true) {
                # Code here will run
                While ($true) {
                    # Code here will run
                    Break myLabel
                    # Code here will not run
                # Code here will not run
            # Code here will not run
        # Code here will run

How to reload .bash_profile from the command line?

Simply type:

. ~/.bash_profile

However, if you want to source it to run automatically when terminal starts instead of running it every time you open terminal, you might add . ~/.bash_profile to ~/.bashrc file.


When you open a terminal, the terminal starts bash in (non-login) interactive mode, which means it will source ~/.bashrc.

~/.bash_profile is only sourced by bash when started in interactive login mode. That is typically only when you login at the console (Ctrl+Alt+F1..F6), or connecting via ssh.

convert:not authorized `aaaa` @ error/constitute.c/ReadImage/453

I had this error when trying to convert a pdf to jpg and solved it using this method: sudo vi /etc/ImageMagick*/policy.xml


policy domain="coder" rights="none" pattern="PDF"


policy domain="coder" rights="read|write" pattern="PDF"


How do you run a Python script as a service in Windows?

Yes you can. I do it using the pythoncom libraries that come included with ActivePython or can be installed with pywin32 (Python for Windows extensions).

This is a basic skeleton for a simple service:

import win32serviceutil
import win32service
import win32event
import servicemanager
import socket

class AppServerSvc (win32serviceutil.ServiceFramework):
    _svc_name_ = "TestService"
    _svc_display_name_ = "Test Service"

    def __init__(self,args):
        self.hWaitStop = win32event.CreateEvent(None,0,0,None)

    def SvcStop(self):

    def SvcDoRun(self):

    def main(self):

if __name__ == '__main__':

Your code would go in the main() method—usually with some kind of infinite loop that might be interrupted by checking a flag, which you set in the SvcStop method

HTML / CSS How to add image icon to input type="button"?

What it looks like

This works well for me, and I'm handling hover and click CSS as well (by changing background color):

HTML (here showing 2 images, image1 on top of image2):

<button class="iconButton" style="background-image: url('image1.png'), url('image2.png')"

CSS (my images are 32px X 32px, so I gave them 4px for padding and a 5px border rounding):

.iconButton {
    width: 36px;
    height: 36px;
    background-color: #000000;
    background-position: center;
    background-repeat: no-repeat;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    outline: none;

.iconButton:hover {
    background-color: #303030;

.iconButton:active {
    background-color: #606060;

button::-moz-focus-inner {
    border: 0;

Streaming a video file to an html5 video player with Node.js so that the video controls continue to work?

The accepted answer to this question is awesome and should remain the accepted answer. However I ran into an issue with the code where the read stream was not always being ended/closed. Part of the solution was to send autoClose: true along with start:start, end:end in the second createReadStream arg.

The other part of the solution was to limit the max chunksize being sent in the response. The other answer set end like so:

var end = positions[1] ? parseInt(positions[1], 10) : total - 1;

...which has the effect of sending the rest of the file from the requested start position through its last byte, no matter how many bytes that may be. However the client browser has the option to only read a portion of that stream, and will, if it doesn't need all of the bytes yet. This will cause the stream read to get blocked until the browser decides it's time to get more data (for example a user action like seek/scrub, or just by playing the stream).

I needed this stream to be closed because I was displaying the <video> element on a page that allowed the user to delete the video file. However the file was not being removed from the filesystem until the client (or server) closed the connection, because that is the only way the stream was getting ended/closed.

My solution was just to set a maxChunk configuration variable, set it to 1MB, and never pipe a read a stream of more than 1MB at a time to the response.

// same code as accepted answer
var end = positions[1] ? parseInt(positions[1], 10) : total - 1;
var chunksize = (end - start) + 1;

// poor hack to send smaller chunks to the browser
var maxChunk = 1024 * 1024; // 1MB at a time
if (chunksize > maxChunk) {
  end = start + maxChunk - 1;
  chunksize = (end - start) + 1;

This has the effect of making sure that the read stream is ended/closed after each request, and not kept alive by the browser.

I also wrote a separate StackOverflow question and answer covering this issue.

Can promises have multiple arguments to onFulfilled?

The fulfillment value of a promise parallels the return value of a function and the rejection reason of a promise parallels the thrown exception of a function. Functions cannot return multiple values so promises must not have more than 1 fulfillment value.

Internet Explorer cache location

Are you looking for a Windows API?

Just use SHGetFolderPath function with CSIDL_INTERNET_CACHE flag or SHGetKnownFolderPath with FOLDERID_InternetCache flag to get the exact location. This way you don't have to worry about the OS. The former function works in Windows XP. The latter one works in Windows Vista+.

Counting words in string

Accuracy is also important.

What option 3 does is basically replace all the but any whitespaces with a +1 and then evaluates this to count up the 1's giving you the word count.

It's the most accurate and fastest method of the four that I've done here.

Please note it is slower than return str.split(" ").length; but it's accurate when compared to Microsoft Word.

See file ops/s and returned word count below.

Here's a link to run this bench test.

// This is the fastest at 111,037 ops/s ±2.86% fastest_x000D_
var str = "All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy.";_x000D_
function WordCount(str) {_x000D_
  return str.split(" ").length;_x000D_
// Returns 241 words. Not the same as Microsoft Word count, of by one._x000D_
// This is the 2nd fastest at 46,835 ops/s ±1.76% 57.82% slower_x000D_
var str = "All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy.";_x000D_
function WordCount(str) {_x000D_
  return str.split(/(?!\W)\S+/).length;_x000D_
// Returns 241 words. Not the same as Microsoft Word count, of by one._x000D_
// This is the 3rd fastest at 37,121 ops/s ±1.18% 66.57% slower_x000D_
var str = "All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy.";_x000D_
function countWords(str) {_x000D_
  var str = str.replace(/\S+/g,"\+1");_x000D_
  return eval(str);_x000D_
// Returns 240 words. Same as Microsoft Word count._x000D_
// This is the slowest at 89 ops/s 17,270 ops/s ±2.29% 84.45% slower_x000D_
var str = "All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy. All work and no play makes Jack a dull boy.";_x000D_
function countWords(str) {_x000D_
  var str = str.replace(/(?!\W)\S+/g,"1").replace(/\s*/g,"");_x000D_
  return str.lastIndexOf("");_x000D_
// Returns 240 words. Same as Microsoft Word count.

How to make a window always stay on top in .Net?

I know this is old, but I did not see this response.

In the window (xaml) add:


In the code behind for Window_Deactivated:

private void Window_Deactivated(object sender, EventArgs e)
        Window window = (Window)sender;

This will keep your window on top.

How to create a new variable in a data.frame based on a condition?

One obvious and straightforward possibility is to use "if-else conditions". In that example

x <- c(1, 2, 4)
y <- c(1, 4, 5)
w <- ifelse(x <= 1, "good", ifelse((x >= 3) & (x <= 5), "bad", "fair"))
data.frame(x, y, w)

** For the additional question in the edit** Is that what you expect ?

> d1 <- c("e", "c", "a")
> d2 <- c("e", "a", "b")
> w <- ifelse((d1 == "e") & (d2 == "e"), 1, 
+    ifelse((d1=="a") & (d2 == "b"), 2,
+    ifelse((d1 == "e"), 3, 99)))
> data.frame(d1, d2, w)
  d1 d2  w
1  e  e  1
2  c  a 99
3  a  b  2

If you do not feel comfortable with the ifelse function, you can also work with the if and else statements for such applications.

How to write a JSON file in C#?

Update 2020: It's been 7 years since I wrote this answer. It still seems to be getting a lot of attention. In 2013 Newtonsoft Json.Net was THE answer to this problem. Now it's still a good answer to this problem but it's no longer the the only viable option. To add some up-to-date caveats to this answer:

  • .Net Core now has the spookily similar System.Text.Json serialiser (see below)
  • The days of the JavaScriptSerializer have thankfully passed and this class isn't even in .Net Core. This invalidates a lot of the comparisons ran by Newtonsoft.
  • It's also recently come to my attention, via some vulnerability scanning software we use in work that Json.Net hasn't had an update in some time. Updates in 2020 have dried up and the latest version, 12.0.3, is over a year old.
  • The speed tests quoted below are comparing an older version of Json.Nt (version 6.0 and like I said the latest is 12.0.3) with an outdated .Net Framework serialiser.

Are Json.Net's days numbered? It's still used a LOT and it's still used by MS librarties. So probably not. But this does feel like the beginning of the end for this library that may well of just run it's course.

Update since .Net Core 3.0

A new kid on the block since writing this is System.Text.Json which has been added to .Net Core 3.0. Microsoft makes several claims to how this is, now, better than Newtonsoft. Including that it is faster than Newtonsoft. as below, I'd advise you to test this yourself .

I would recommend Json.Net, see example below:

List<data> _data = new List<data>();
_data.Add(new data()
    Id = 1,
    SSN = 2,
    Message = "A Message"

string json = JsonConvert.SerializeObject(_data.ToArray());

//write string to file
System.IO.File.WriteAllText(@"D:\path.txt", json);

Or the slightly more efficient version of the above code (doesn't use a string as a buffer):

//open file stream
using (StreamWriter file = File.CreateText(@"D:\path.txt"))
     JsonSerializer serializer = new JsonSerializer();
     //serialize object directly into file stream
     serializer.Serialize(file, _data);

Documentation: Serialize JSON to a file

Why? Here's a feature comparison between common serialisers as well as benchmark tests .

Below is a graph of performance taken from the linked article:

enter image description here

This separate post, states that:

Json.NET has always been memory efficient, streaming the reading and writing large documents rather than loading them entirely into memory, but I was able to find a couple of key places where object allocations could be reduced...... (now) Json.Net (6.0) allocates 8 times less memory than JavaScriptSerializer

Benchmarks appear to be Json.Net 5, the current version (on writing) is 10. What version of standard .Net serialisers used is not mentioned

These tests are obviously from the developers who maintain the library. I have not verified their claims. If in doubt test them yourself.

Force hide address bar in Chrome on Android

Check this has everything you need

The Chrome team has recently implemented a feature that tells the browser to launch the page fullscreen when the user has added it to the home screen. It is similar to the iOS Safari model.

<meta name="mobile-web-app-capable" content="yes">

Eclipse : Failed to connect to remote VM. Connection refused.

I faced the same issue. But i resolved it by changing my port numbers to different one.

PHP Deprecated: Methods with the same name

As mentioned in the error, the official manual and the comments:


public function TSStatus($host, $queryPort)


public function __construct($host, $queryPort)

How to check if a value exists in an array in Ruby

You're looking for include?:

>> ['Cat', 'Dog', 'Bird'].include? 'Dog'
=> true

How to reset the bootstrap modal when it gets closed and open it fresh again?

Just reset any content manually when modal is hidden:

$(".modal").on("", function(){

There is more events. More about them here

$(document).ready(function() {_x000D_
  $(".modal").on("", function() {_x000D_
    $(".modal-body1").html("Where did he go?!?!?!");_x000D_
<script src=""></script>_x000D_
<link rel="stylesheet" href="" />_x000D_
<script src=""></script>_x000D_
<button type="button" class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">_x000D_
  Launch modal_x000D_
<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">_x000D_
  <div class="modal-dialog">_x000D_
    <div class="modal-content">_x000D_
      <div class="modal-header">_x000D_
        <button type="button" class="close" data-dismiss="modal"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span>_x000D_
        <h4 class="modal-title" id="myModalLabel">Modal title</h4>_x000D_
      <div class="modal-body">_x000D_
        <div class='modal-body1'>_x000D_
          <h3>Close and open, I will be gone!</h3>_x000D_
      <div class="modal-footer">_x000D_
        <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>_x000D_

Array as session variable

Yes, you can put arrays in sessions, example:

$_SESSION['name_here'] = $your_array;

Now you can use the $_SESSION['name_here'] on any page you want but make sure that you put the session_start() line before using any session functions, so you code should look something like this:

 $_SESSION['name_here'] = $your_array;

Possible Example:

 $_SESSION['name_here'] = $_POST;

Now you can get field values on any page like this:

 echo $_SESSION['name_here']['field_name'];

As for the second part of your question, the session variables remain there unless you assign different array data:

 $_SESSION['name_here'] = $your_array;

Session life time is set into php.ini file.

More Info Here

How to set NODE_ENV to production/development in OS X

No one mentioned .env in here yet? Make a .env file in your app root, then require('dotenv').config() and read the values. Easily changed, easily read, cross platform.

Oracle select most recent date record

you can't use aliases from select list inside the WHERE clause (because of the Order of Evaluation of a SELECT statement)

also you cannot use OVER clause inside WHERE clause - "You can specify analytic functions with this clause in the select list or ORDER BY clause." (citation from

select *
from (select
  staff_id, site_id, pay_level, date, 
  max(date) over (partition by staff_id) max_date
  from owner.table
  where end_enrollment_date is null
where date = max_date

Batch File: ( was unexpected at this time

Oh, dear. A few little problems...

As pointed out by others, you need to quote to protect against empty/space-containing entries, and use the !delayed_expansion! facility.

Two other matters of which you should be aware:

First, set/p will assign a user-input value to a variable. That's not news - but the gotcha is that pressing enter in response will leave the variable UNCHANGED - it will not ASSIGN a zero-length string to the variable (hence deleting the variable from the environment.) The safe method is:

 set "var="
 set /p var=

That is, of course, if you don't WANT enter to repeat the existing value.
Another useful form is

 set "var=default"
 set /p var=


 set "var=default"
 set /p "var=[%var%]"

(which prompts with the default value; !var! if in a block statement with delayedexpansion)

Second issue is that on some Windows versions (although W7 appears to "fix" this issue) ANY label - including a :: comment (which is a broken-label) will terminate any 'block' - that is, parenthesised compound statement)

Why am I getting a "401 Unauthorized" error in Maven?

I had put a not encrypted password in the settings.xml .

I tested the call with curl

curl -u username:password http://url/artifactory/libs-snapshot-local/com/myproject/api/1.0-SNAPSHOT/api-1.0-20160128.114425-1.jar --request PUT --data target/api-1.0-SNAPSHOT.jar 

and I got the error:

  "errors" : [ {
    "status" : 401,
    "message" : "Artifactory configured to accept only encrypted passwords but received a clear text password."
  } ]

I retrieved my encrypted password clicking on my artifactory profile and unlocking it.

Transparent background in JPEG image

How can I set a transparent background on JPEG image?

If you intend to keep the image as a JPEG then you can't. As others have suggested, convert it to PNG and add an alpha channel.

(unicode error) 'unicodeescape' codec can't decode bytes in position 2-3: truncated \UXXXXXXXX escape

This error occurs because you are using a normal string as a path. You can use one of the three following solutions to fix your problem:

1: Just put r before your normal string it converts normal string to raw string:






MongoDB logging all queries

You can log all queries:

$ mongo
MongoDB shell version: 2.4.9
connecting to: test
> use myDb
switched to db myDb
> db.getProfilingLevel()
> db.setProfilingLevel(2)
{ "was" : 0, "slowms" : 1, "ok" : 1 }
> db.getProfilingLevel()
> db.system.profile.find().pretty()


db.setProfilingLevel(2) means "log all operations".

IIS - can't access page by ip address instead of localhost

Try with disabling Windows Firewall, it worked for me, but in my case, I was able to access IIS through

How can I implement the Iterable interface?

First off:

public class ProfileCollection implements Iterable<Profile> {


return m_Profiles.get(m_ActiveProfile);

How is OAuth 2 different from OAuth 1?

Note there are serious security arguments against using Oauth 2:

one bleak article

and a more technical one

Note these are coming from Oauth 2's lead author.

Key points:

  • Oauth 2 offers no security on top of SSL while Oauth 1 is transport-independent.

  • in a sense SSL isn't secure in that the server does not verify the connection and the common client libraries make it easy to ignore failures.

    The problem with SSL/TLS, is that when you fail to verify the certificate on the client side, the connection still works. Any time ignoring an error leads to success, developers are going to do just that. The server has no way of enforcing certificate verification, and even if it could, an attacker will surely not.

  • you can fat-finger away all of your security, which is much harder to do in OAuth 1.0:

    The second common potential problem are typos. Would you consider it a proper design when omitting one character (the ‘s’ in ‘https’) voids the entire security of the token? Or perhaps sending the request (over a valid and verified SSL/TLS connection) to the wrong destination (say ‘’?). Remember, being able to use OAuth bearer tokens from the command line was clearly a use case bearer tokens advocates promoted.

startForeground fail after upgrade to Android 8.1

Works properly on Andorid 8.1:

Updated sample (without any deprecated code):

public NotificationBattery(Context context) {
    this.mCtx = context;

    mBuilder = new NotificationCompat.Builder(context, CHANNEL_ID)
            .setWhen(System.currentTimeMillis() + 500)

    mRemoteViews = new RemoteViews(context.getPackageName(), R.layout.notification_view_battery);



    mNotificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

    if (AesPrefs.getBooleanRes(R.string.SHOW_BATTERY_NOTIFICATION, true)) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(CHANNEL_ID, context.getString(R.string.notification_title_battery),
            channel.setSound(null, null);
    } else {

Old snipped (it's a different app - not related to the code above):

public int onStartCommand(Intent intent, int flags, final int startId) {
    Log.d(TAG, "onStartCommand");

    String CHANNEL_ONE_ID = "";
    String CHANNEL_ONE_NAME = "Channel One";
    NotificationChannel notificationChannel = null;
    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
        notificationChannel = new NotificationChannel(CHANNEL_ONE_ID,
        NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

    Bitmap icon = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);
    Notification notification = new Notification.Builder(getApplicationContext())

    Intent notificationIntent = new Intent(getApplicationContext(), MainActivity.class);
    notificationIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
    notification.contentIntent = PendingIntent.getActivity(getApplicationContext(), 0, notificationIntent, 0);

    startForeground(START_FOREGROUND_ID, notification);

    return START_STICKY;

PHP preg replace only allow numbers

I think you're saying you want to remove all non-numeric characters. If so, \D means "anything that isn't a digit":

preg_replace('/\D/', '', $c)

Null check in VB

Change your Ands to AndAlsos

A standard And will test both expressions. If comp.Container is Nothing, then the second expression will raise a NullReferenceException because you're accessing a property on a null object.

AndAlso will short-circuit the logical evaluation. If comp.Container is Nothing, then the 2nd expression will not be evaluated.

html script src="" triggering redirection with button

First you are linking the file that is here:

<script src="../Script/login.js"> 

Which would lead the website to a file in the Folder Script, but then in the second paragraph you are saying that the folder name is

and also i have onother folder named scripts that contains the the following login.js file

So, this won't work! Because you are not accessing the correct file. To do that please write the code as

<script src="/script/login.js"></script>

Try removing the .. from the beginning of the code too.

This way, you'll reach the js file where the function would run!

Just to make sure:

Just to make sure that the files are attached the HTML DOM, then please open Developer Tools (F12) and in the network workspace note each request that the browser makes to the server. This way you will learn which files were loaded and which weren't, and also why they were not!

Good luck.

Use of 'const' for function parameters

Marking value parameters 'const' is definitely a subjective thing.

However I actually prefer to mark value parameters const, just like in your example.

void func(const int n, const long l) { /* ... */ }

The value to me is in clearly indicating that the function parameter values are never changed by the function. They will have the same value at the beginning as at the end. For me, it is part of keeping to a very functional programming sort of style.

For a short function, it's arguably a waste of time/space to have the 'const' there, since it's usually pretty obvious that the arguments aren't modified by the function.

However for a larger function, its a form of implementation documentation, and it is enforced by the compiler.

I can be sure if I make some computation with 'n' and 'l', I can refactor/move that computation without fear of getting a different result because I missed a place where one or both is changed.

Since it is an implementation detail, you don't need to declare the value parameters const in the header, just like you don't need to declare the function parameters with the same names as the implementation uses.

How to call a function in shell Scripting?


  • Define functions before using them.
  • Once defined, treat them as commands.

Consider this script, called funcdemo:


[ $# = 0 ] && exhort "write nastygram"

    echo "Please, please do not forget to $*"

[ $# != 0 ] && exhort "write begging letter"

In use:

$ funcdemo
./funcdemo: line 3: exhort: command not found
$ funcdemo 1
Please, please do not forget to write begging letter

Note the potential for a missing function to lie undiscovered for a long time (think 'by a customer at the most critical wrong moment'). It only matters whether the function exists when it is executed, the same as it only matters whether any other command exists when you try to execute it. Indeed, until it goes to execute the command, the shell neither knows nor cares whether it is an external command or a function.

gradlew: Permission Denied

Just type this command in Android Studio Terminal (Or your Linux/Mac Terminal)

chmod +x gradlew

and try to :

 ./gradlew assembleDebug

enter image description here

Load json from local file with http.get() in angular 2

You have to change

loadNavItems() {
        this.navItems = this.http.get("../data/navItems.json");


loadNavItems() {
        this.navItems = this.http.get("../data/navItems.json")
                        .map(res => res.json())
                        .do(data => console.log(data));
                        //This is optional, you can remove the last line 
                        // if you don't want to log loaded json in 
                        // console.

Because this.http.get returns an Observable<Response> and you don't want the response, you want its content.

The console.log shows you an observable, which is correct because navItems contains an Observable<Response>.

In order to get data properly in your template, you should use async pipe.

<app-nav-item-comp *ngFor="let item of navItems | async" [item]="item"></app-nav-item-comp>

This should work well, for more informations, please refer to HTTP Client documentation

How do I set response headers in Flask?

Use make_response of Flask something like

def home():
    resp = make_response("hello") #here you could use make_response(render_template(...)) too
    resp.headers['Access-Control-Allow-Origin'] = '*'
    return resp

From flask docs,


Sometimes it is necessary to set additional headers in a view. Because views do not have to return response objects but can return a value that is converted into a response object by Flask itself, it becomes tricky to add headers to it. This function can be called instead of using a return and you will get a response object which you can use to attach headers.

Set database from SINGLE USER mode to MULTI USER

You couldn't do that becouse database in single mode. Above all right but you should know that: when you opened the sql management studio it doesn't know any user on the database but when you click the database it consider you the single user and your command not working. Just do that: Close management studio and re open it. new query window without selecting any database write the command script.

USE [master];

make f5 wolla everything ok !

How to avoid a System.Runtime.InteropServices.COMException?

I came across System.Runtime.InteropServices.COMException while opening a project solution. Sometimes user doesn't have enough priveleges to run some COM Methods. I ran Visual Studio as Administrator and the exception was gone.

Creating a Custom Event

Yes you can do like this :

Creating advanced C# custom events


The Simplest C# Events Example Imaginable

public class Metronome
    public event TickHandler Tick;
    public EventArgs e = null;
    public delegate void TickHandler(Metronome m, EventArgs e);
    public void Start()
        while (true)
            if (Tick != null)
                Tick(this, e);
public class Listener
    public void Subscribe(Metronome m)
        m.Tick += new Metronome.TickHandler(HeardIt);

    private void HeardIt(Metronome m, EventArgs e)
        System.Console.WriteLine("HEARD IT");
class Test
    static void Main()
        Metronome m = new Metronome();
        Listener l = new Listener();

How do I delete a Git branch locally and remotely?

I created the following convenient function in my .bash_aliases file:

    if [[ -n $1 ]]; then
        git checkout master > /dev/null;
        echo "Deleting local $branch_name branch...";
        git branch -D "$branch_name";
        echo "Deleting remote $branch_name branch...";
        git push origin --delete "$branch_name";
        git remote prune origin;
        echo "Your current branches are:";
        git branch -a;
        echo "Usage: git-delete-branch <branch_name>";

Get yesterday's date using Date


There has been recent improvements in datetime API with JSR-310.

Instant now =;
Instant yesterday = now.minus(1, ChronoUnit.DAYS);

Outdated answer

You are subtracting the wrong number:

Use Calendar instead:

private Date yesterday() {
    final Calendar cal = Calendar.getInstance();
    cal.add(Calendar.DATE, -1);
    return cal.getTime();

Then, modify your method to the following:

private String getYesterdayDateString() {
        DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        return dateFormat.format(yesterday());



You can find those maven properties in the super pom.

You find the jar here:


Open the jar with 7-zip or some other archiver (or use the jar tool).

Navigate to


There you'll find the pom-4.0.0.xml.

It contains all those "short cuts":



After some lobbying I am adding a link to the pom-4.0.0.xml. This allows you to see the properties without opening up the local jar file.

CSS Background Image Not Displaying

I had the same issue. For me it worked with:

  background: url("../img/green.jpg") no-repeat center bottom/cover;
  height: 100vh;

Extend contigency table with proportions (percentages)

If it's conciseness you're after, you might like:


and then scale by 100 and round if you like. Or more like your exact output:

tbl <- table(tips$smoker)

If you wanted to do this for multiple columns, there are lots of different directions you could go depending on what your tastes tell you is clean looking output, but here's one option:

tblFun <- function(x){
    tbl <- table(x)
    res <- cbind(tbl,round(prop.table(tbl)*100,2))
    colnames(res) <- c('Count','Percentage')
       Count Percentage
Female    87      35.66
Male     157      64.34
No       151      61.89
Yes       93      38.11
Fri       19       7.79
Sat       87      35.66
Sun       76      31.15
Thur      62      25.41
Dinner   176      72.13
Lunch     68      27.87

If you don't like stack the different tables on top of each other, you can ditch the and leave them in a list.

How to retrieve data from sqlite database in android and display it in TextView

First cast your Edit text like this:

TextView tekst = (TextView) findViewById(;

And after that close the DB not befor this line...


How to get the number of characters in a string

Depends a lot on your definition of what a "character" is. If "rune equals a character " is OK for your task (generally it isn't) then the answer by VonC is perfect for you. Otherwise, it should be probably noted, that there are few situations where the number of runes in a Unicode string is an interesting value. And even in those situations it's better, if possible, to infer the count while "traversing" the string as the runes are processed to avoid doubling the UTF-8 decode effort.

Check if file is already open

Using the Apache Commons IO library...

boolean isFileUnlocked = false;
try {;
    isFileUnlocked = true;
} catch (IOException e) {
    isFileUnlocked = false;

    // Do stuff you need to do with a file that is NOT locked.
} else {
    // Do stuff you need to do with a file that IS locked

What is the dual table in Oracle?

I think this wikipedia article may help clarify.

The DUAL table is a special one-row table present by default in all Oracle database installations. It is suitable for use in selecting a pseudocolumn such as SYSDATE or USER The table has a single VARCHAR2(1) column called DUMMY that has a value of "X"

What is the difference between JVM, JDK, JRE & OpenJDK?

In layman terms:- JDK = JRE + Development/debugging tools, where JDK is our complete package to work with Java, from creating compiling till running it.On the other hand JRE is just of running of code(Byte Code).

Note:- Whether we are installing JDK or JRE, JVM would come bundled with both the packages and JVM is the part where JIT compiler converts the byte code into the machine specific code.

Just read the article on JDK,JRE ,JVM and JIT

Where can I find the Tomcat 7 installation folder on Linux AMI in Elastic Beanstalk?

Following environment variables worked for me on Debian Wheezy 7 and Tomcat 7:


(I did create /tmp/tomcat7 manually)

Error in file(file, "rt") : cannot open the connection

I had a same issue .I removed the extension from the file name.Example my file name was saved as xyz. csv. i saved it as xyz.

Android Studio doesn't see device

In my case the solution was to close to restart Android Studio

How to know Laravel version and where is it defined?

If you want to know the specific version then you need to check composer.lock file and search For

"name": "laravel/framework",

you will find your version in next line

"version": "v5.7.9",

PHP function to make slug (URL string)

Don't use preg_replace for this. There's a php function built just for the task: strtr()

Taken from the comments in the above link (and I tested it myself; it works:

function normalize ($string) {
    $table = array(
        'Š'=>'S', 'š'=>'s', 'Ð'=>'Dj', 'd'=>'dj', 'Ž'=>'Z', 'ž'=>'z', 'C'=>'C', 'c'=>'c', 'C'=>'C', 'c'=>'c',
        'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A', 'Ä'=>'A', 'Å'=>'A', 'Æ'=>'A', 'Ç'=>'C', 'È'=>'E', 'É'=>'E',
        'Ê'=>'E', 'Ë'=>'E', 'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I', 'Ñ'=>'N', 'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O',
        'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O', 'Ù'=>'U', 'Ú'=>'U', 'Û'=>'U', 'Ü'=>'U', 'Ý'=>'Y', 'Þ'=>'B', 'ß'=>'Ss',
        'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a', 'æ'=>'a', 'ç'=>'c', 'è'=>'e', 'é'=>'e',
        'ê'=>'e', 'ë'=>'e', 'ì'=>'i', 'í'=>'i', 'î'=>'i', 'ï'=>'i', 'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o',
        'ô'=>'o', 'õ'=>'o', 'ö'=>'o', 'ø'=>'o', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'ý'=>'y', 'ý'=>'y', 'þ'=>'b',
        'ÿ'=>'y', 'R'=>'R', 'r'=>'r',

    return strtr($string, $table);

Loop through Map in Groovy?

When using the for loop, the value of s is a Map.Entry element, meaning that you can get the key from s.key and the value from s.value

How to properly import a selfsigned certificate into Java keystore that is available to all Java applications by default?

The simple command 'keytool' also works on Windows and/or with Cygwin.

IF you're using Cygwin here is the modified command that I used from the bottom of "S.Botha's" answer :

  1. make sure you identify the JRE inside the JDK that you will be using
  2. Start your prompt/cygwin as admin
  3. go inside the bin directory of that JDK e.g. cd /cygdrive/c/Program\ Files/Java/jdk1.8.0_121/jre/bin
  4. Execute the keytool command from inside it, where you provide the path to your new Cert at the end, like so:

    ./keytool.exe -import -trustcacerts -keystore ../lib/security/cacerts  -storepass changeit -noprompt -alias myownaliasformysystem -file "D:\Stuff\saved-certs\ca.cert"

Notice, because if this is under Cygwin you're giving a path to a non-Cygwin program, so the path is DOS-like and in quotes.