Programs & Examples On #Bytecode

bytecode is a blanket term for opcodes that are consumed by a virtual machine. For example, the JVM runs bytecode stored in .class files and the CPython interpreter runs bytecode stored in .pyc files.

Why is 2 * (i * i) faster than 2 * i * i in Java?

Interesting observation using Java 11 and switching off loop unrolling with the following VM option:


The loop with the 2 * (i * i) expression results in more compact native code1:

L0001: add    eax,r11d
       inc    r8d
       mov    r11d,r8d
       imul   r11d,r8d
       shl    r11d,1h
       cmp    r8d,r10d
       jl     L0001

in comparison with the 2 * i * i version:

L0001: add    eax,r11d
       mov    r11d,r8d
       shl    r11d,1h
       add    r11d,2h
       inc    r8d
       imul   r11d,r8d
       cmp    r8d,r10d
       jl     L0001

Java version:

java version "11" 2018-09-25
Java(TM) SE Runtime Environment 18.9 (build 11+28)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11+28, mixed mode)

Benchmark results:

Benchmark          (size)  Mode  Cnt    Score     Error  Units  1000000000  avgt    5  694,868 ±  36,470  ms/op
LoopTest.slow  1000000000  avgt    5  769,840 ± 135,006  ms/op

Benchmark source code:

@Warmup(iterations = 5, time = 5, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 5, time = 5, timeUnit = TimeUnit.SECONDS)
public class LoopTest {

    @Param("1000000000") private int size;

    public static void main(String[] args) throws RunnerException {
        Options opt = new OptionsBuilder()
        new Runner(opt).run();

    public int slow() {
        int n = 0;
        for (int i = 0; i < size; i++)
            n += 2 * i * i;
        return n;

    public int fast() {
        int n = 0;
        for (int i = 0; i < size; i++)
            n += 2 * (i * i);
        return n;

1 - VM options used: -XX:+UnlockDiagnosticVMOptions -XX:+PrintAssembly -XX:LoopUnrollLimit=0

C++ performance vs. Java/C#

The virtual machine languages are unlikely to outperform compiled languages but they can get close enough that it doesn't matter, for (at least) the following reasons (I'm speaking for Java here since I've never done C#).

1/ The Java Runtime Environment is usually able to detect pieces of code that are run frequently and perform just-in-time (JIT) compilation of those sections so that, in future, they run at the full compiled speed.

2/ Vast portions of the Java libraries are compiled so that, when you call a library function, you're executing compiled code, not interpreted. You can see the code (in C) by downloading the OpenJDK.

3/ Unless you're doing massive calculations, much of the time your program is running, it's waiting for input from a very slow (relatively speaking) human.

4/ Since a lot of the validation of Java bytecode is done at the time of loading the class, the normal overhead of runtime checks is greatly reduced.

5/ At the worst case, performance-intensive code can be extracted to a compiled module and called from Java (see JNI) so that it runs at full speed.

In summary, the Java bytecode will never outperform native machine language, but there are ways to mitigate this. The big advantage of Java (as I see it) is the HUGE standard library and the cross-platform nature.

How can I conditionally require form inputs with AngularJS?

For Angular2

<input type='email' 
    [required]='!' >

Spring Boot application can't resolve the org.springframework.boot package

I had the same problem when I was trying to work with a basic spring boot app. I tried to use the latest spring-boot version from the official spring-boot site.

As on today, the latest version is 1.5.4.RELEASE. But I keep getting compilation issues on my eclipse IDE irrespective of multiple cleanups to the project. I lowered the version of spring-boot to 1.5.3.RELEASE and it simply worked !! Some of my earlier projects were using the old version which drove me to try this option.

what is this value means 1.845E-07 in excel?

Highlight the cells, format cells, select Custom then select zero.

How do I pass multiple attributes into an Angular.js attribute directive?

The directive can access any attribute that is defined on the same element, even if the directive itself is not the element.


<div example-directive example-number="99" example-function="exampleCallback()"></div>


app.directive('exampleDirective ', function () {
    return {
        restrict: 'A',   // 'A' is the default, so you could remove this line
        scope: {
            callback : '&exampleFunction',
        link: function (scope, element, attrs) {
            var num = scope.$eval(attrs.exampleNumber);
            scope.callback();  // calls exampleCallback()


If the value of attribute example-number will be hard-coded, I suggest using $eval once, and storing the value. Variable num will have the correct type (a number).

How to get text box value in JavaScript

Provided when you want the text box value. Simple one:

<input type="text" value="software engineer" id="textbox">

var result = document.getElementById("textbox").value;

How to specify font attributes for all elements on an html web page?

If you specify CSS attributes for your body element it should apply to anything within <body></body> so long as you don't override them later in the stylesheet.

How can I pass data from Flask to JavaScript in a template?

You can use {{ variable }} anywhere in your template, not just in the HTML part. So this should work:

    var someJavaScriptVar = '{{ geocode[1] }}';
  <p>Hello World</p>
  <button onclick="alert('Geocode: {{ geocode[0] }} ' + someJavaScriptVar)" />

Think of it as a two-stage process: First, Jinja (the template engine Flask uses) generates your text output. This gets sent to the user who executes the JavaScript he sees. If you want your Flask variable to be available in JavaScript as an array, you have to generate an array definition in your output:

      var myGeocode = ['{{ geocode[0] }}', '{{ geocode[1] }}'];
    <p>Hello World</p>
    <button onclick="alert('Geocode: ' + myGeocode[0] + ' ' + myGeocode[1])" />

Jinja also offers more advanced constructs from Python, so you can shorten it to:

    var myGeocode = [{{ ', '.join(geocode) }}];
  <p>Hello World</p>
  <button onclick="alert('Geocode: ' + myGeocode[0] + ' ' + myGeocode[1])" />

You can also use for loops, if statements and many more, see the Jinja2 documentation for more.

Also, have a look at Ford's answer who points out the tojson filter which is an addition to Jinja2's standard set of filters.

Edit Nov 2018: tojson is now included in Jinja2's standard set of filters.

How to make a phone call programmatically?

Solved..! September 5, 2020.

It is working very well. In this way, you do not need to have permission from user. You can open directly phone calling part.

Trick point, use ACTION_DIAL instead of ACTION_CALL.

private void callPhoneNumber() {
    String phone = "03131693169";
    Intent callIntent = new Intent(Intent.ACTION_DIAL);
    callIntent.setData(Uri.parse("tel:" + phone));

For more question, ask me on Instagram: @canerkaseler

How to get the Development/Staging/production Hosting Environment in ConfigureServices

In .NET Core 2.0 MVC app / Microsoft.AspNetCore.All v2.0.0, you can have environmental specific startup class as described by @vaindil but I don't like that approach.

You can also inject IHostingEnvironment into StartUp constructor. You don't need to store the environment variable in Program class.

public class Startup
    private readonly IHostingEnvironment _currentEnvironment;
    public IConfiguration Configuration { get; private set; }

    public Startup(IConfiguration configuration, IHostingEnvironment env)
        _currentEnvironment = env;
        Configuration = configuration;

    public void ConfigureServices(IServiceCollection services)

        services.AddMvc(config =>
            // Requiring authenticated users on the site globally
            var policy = new AuthorizationPolicyBuilder()
            config.Filters.Add(new AuthorizeFilter(policy));

            // Validate anti-forgery token globally
            config.Filters.Add(new AutoValidateAntiforgeryTokenAttribute());

            // If it's Production, enable HTTPS
            if (_currentEnvironment.IsProduction())      // <------
                config.Filters.Add(new RequireHttpsAttribute());


using setTimeout on promise chain

.then(() => new Promise((resolve) => setTimeout(resolve, 15000)))


when I need sleep in async function I throw in

await new Promise(resolve => setTimeout(resolve, 1000))

Get latitude and longitude based on location name with Google Autocomplete API

You can use the Google Geocoder service in the Google Maps API to convert from your location name to a latitude and longitude. So you need some code like:

var geocoder = new google.maps.Geocoder();
var address = document.getElementById("address").value;
geocoder.geocode( { 'address': address}, function(results, status) {
  if (status == google.maps.GeocoderStatus.OK)
      // do something with the geocoded result
      // results[0].geometry.location.latitude
      // results[0].geometry.location.longitude


Are you including the v3 javascript API?

<script type="text/javascript"

Sass - Converting Hex to RGBa for background opacity

SASS has a built-in rgba() function to evaluate values.

rgba($color, $alpha)


rgba(#00aaff, 0.5) => rgba(0, 170, 255, 0.5)

An example using your own variables:

$my-color: #00aaff;
$my-opacity: 0.5;

.my-element {
  color: rgba($my-color, $my-opacity);


.my-element {
  color: rgba(0, 170, 255, 0.5);

How to center icon and text in a android button with width set to "fill parent"

I adjust it by adding padding left and right as follows:


Split data frame string column into multiple columns

This question is pretty old but I'll add the solution I found the be the simplest at present.

before = data.frame(attr = c(1,30,4,6), type=c('foo_and_bar','foo_and_bar_2'))
newColNames <- c("type1", "type2")
newCols <- colsplit(before$type, "_and_", newColNames)
after <- cbind(before, newCols)
after$type <- NULL

Serializing with Jackson (JSON) - getting "No serializer found"?

For Oracle Java applications, add this after the ObjectMapper instantiation:

mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);

Is it possible to add an array or object to SharedPreferences on Android

Regardless of the API level, Check String arrays and Object arrays in SharedPreferences


public boolean saveArray(String[] array, String arrayName, Context mContext) {   
    SharedPreferences prefs = mContext.getSharedPreferences("preferencename", 0);  
    SharedPreferences.Editor editor = prefs.edit();  
    editor.putInt(arrayName +"_size", array.length);  
    for(int i=0;i<array.length;i++)  
        editor.putString(arrayName + "_" + i, array[i]);  
    return editor.commit();  


public String[] loadArray(String arrayName, Context mContext) {  
    SharedPreferences prefs = mContext.getSharedPreferences("preferencename", 0);  
    int size = prefs.getInt(arrayName + "_size", 0);  
    String array[] = new String[size];  
    for(int i=0;i<size;i++)  
        array[i] = prefs.getString(arrayName + "_" + i, null);  
    return array;  

No authenticationScheme was specified, and there was no DefaultChallengeScheme found with default authentification and custom authorization

Many answer above are correct but same time convoluted with other aspects of authN/authZ. What actually resolves the exception in question is this line:

services.AddScheme<YourAuthenticationOptions, YourAuthenticationHandler>(YourAuthenticationSchemeName, options =>
        options.YourProperty = yourValue;

HTML5 Video Autoplay not working correctly

Try autoplay="autoplay" instead of the "true" value. That's the documented way to enable autoplay. That sounds weirdly redundant, I know.

React passing parameter via onclick event using ES6 syntax


Don't bind function (nor use arrow functions) inside render method. See official recommendations.

So, there's an accepted answer and a couple more that points the same. And also there are some comments preventing people from using bind within the render method, and also avoiding arrow functions there for the same reason (those functions will be created once again and again on each render). But there's no example, so I'm writing one.

Basically, you have to bind your functions in the constructor.

class Actions extends Component {

    static propTypes = {
        entity_id: PropTypes.number,
        contact_id: PropTypes.number,
        onReplace: PropTypes.func.isRequired,
        onTransfer: PropTypes.func.isRequired

    constructor() {
        this.onReplace = this.onReplace.bind(this);
        this.onTransfer = this.onTransfer.bind(this);

    onReplace() {
        this.props.onReplace(this.props.entity_id, this.props.contact_id);

    onTransfer() {
        this.props.onTransfer(this.props.entity_id, this.props.contact_id);

    render() {
        return (
            <div className="actions">
                <button className="btn btn-circle btn-icon-only btn-default"
                        <i className="fa fa-refresh"></i>
                <button className="btn btn-circle btn-icon-only btn-default"
                    <i className="fa fa-share"></i>

export default Actions

Key lines are:


this.onReplace = this.onReplace.bind(this);


onReplace() {
    this.props.onReplace(this.props.entity_id, this.props.contact_id);



How to merge two PDF files into one in Java?

Multiple pdf merged method using org.apache.pdfbox:

public void mergePDFFiles(List<File> files,
                          String mergedFileName) {
    try {
        PDFMergerUtility pdfmerger = new PDFMergerUtility();
        for (File file : files) {
            PDDocument document = PDDocument.load(file);
    } catch (IOException e) {
        logger.error("Error to merge files. Error: " + e.getMessage());

From main program, call mergePDFFiles method using list of files and target file name.

        String mergedFileName = "Merged.pdf";
        mergePDFFiles(files, mergedFileName);

After calling mergePDFFiles, load merged file

        File mergedFile = new File(mergedFileName);

Python unittest passing arguments

Have a same problem. My solution is after you handle with parsing arguments using argparse or other way, remove arguments from sys.argv

sys.argv = sys.argv[:1]  

If you need you can filter unittest arguments from main.parseArgs()

How to copy directories with spaces in the name

robocopy "C:\Users\Angie\My Documents" "C:\test-backup\My Documents" /B /E /R:0 /CREATE /NP /TEE /XJ /LOG+:"CompleteBackupLog.txt"
robocopy "C:\Users\Angie\My Music" "C:\test-backup\My Music" /B /E /R:0 /CREATE /NP /TEE /XJ /LOG+:"CompleteBackupLog.txt"
robocopy "C:\Users\Angie\My Pictures" "C:\test-backup\My Pictures" /B /E /R:0 /CREATE /NP /TEE /XJ /LOG+:"CompleteBackupLog.txt"

How to launch multiple Internet Explorer windows/tabs from batch file?

Try this so you allow enough time for the first process to start.. else it will spawn 2 processes because the first one is not still running when you run the second one... This can happen if your computer is too fast..

@echo off
start /d iexplore.exe
PING -n 1 -w 2000 >NUL
START /d iexplore.exe blablabla

replace blablabla with another address

Find Nth occurrence of a character in a string

string theString = "The String";
int index = theString.NthIndexOf("THEVALUE", 3, true);

Java: Most efficient method to iterate over all elements in a org.w3c.dom.Document?

for (int i = 0; i < nodeList.getLength(); i++)

change to

for (int i = 0, len = nodeList.getLength(); i < len; i++)

to be more efficient.

The second way of javanna answer may be the best as it tends to use a flatter, predictable memory model.

How to edit the legend entry of a chart in Excel?

Left Click on chart. «PivotTable Field List» will appear on right. On the right down quarter of PivotTable Field List (S Values), you see the names of the legends. Left Click on the legend name. Left Click on the «Value field settings». At the top there is «Source Name». You can’t change it. Below there is «Custom Name». Change the Custom Name as you wish. Now the legend name on the chart has the new name you gave.

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

Some cookies, such as referrer urls, have = in them. As a result, simply splitting on = will cause irregular results, and the previous answers here will breakdown over time (or immediately depending on your depth of use).

This takes only the first instance of the equals sign. It returns an object with the cookie's key value pairs.

// Returns an object of key value pairs for this page's cookies
function getPageCookies(){

    // cookie is a string containing a semicolon-separated list, this split puts it into an array
    var cookieArr = document.cookie.split(";");

    // This object will hold all of the key value pairs
    var cookieObj = {};

    // Iterate the array of flat cookies to get their key value pair
    for(var i = 0; i < cookieArr.length; i++){

        // Remove the standardized whitespace
        var cookieSeg = cookieArr[i].trim();

        // Index of the split between key and value
        var firstEq = cookieSeg.indexOf("=");

        // Assignments
        var name = cookieSeg.substr(0,firstEq);
        var value = cookieSeg.substr(firstEq+1);
        cookieObj[name] = value;
   return cookieObj;

Set Focus After Last Character in Text Box

I tried lots of different solutions, the only one that worked for me was based on the solution by Chris G on this page (but with a slight modification).

I have turned it into a jQuery plugin for future use for anyone that needs it

    $.fn.setCursorToTextEnd = function() {
        var $initialVal = this.val();

example of usage:


Using getline() with file input in C++

you should do as:

getline(name, sizeofname, '\n');
strtok(name, " ");

This will give you the "joht" in name then to get next token,

temp = strtok(NULL, " ");

temp will get "smith" in it. then you should use string concatination to append the temp at end of name. as:

strcat(name, temp);

(you may also append space first, to obtain a space in between).

Angular2 *ngFor in select list, set active based on string from object

This should work

<option *ngFor="let title of titleArray" 
    [attr.selected]="passenger.Title==title.Text ? true : null">

I'm not sure the attr. part is necessary.

How to add a line break in an Android TextView?

Used Android Studio 0.8.9. The only way worked for me is using \n. Neither wrapping with CDATA nor <br> or <br /> worked.

What are allowed characters in cookies?

One more consideration. I recently implemented a scheme in which some sensitive data posted to a PHP script needed to convert and return it as an encrypted cookie, that used all base64 values I thought were guaranteed 'safe". So I dutifully encrypted the data items using RC4, ran the output through base64_encode, and happily returned the cookie to the site. Testing seemed to go well until a base64 encoded string contained a "+" symbol. The string was written to the page cookie with no trouble. Using the browser diagnostics I could also verify the cookies was written unchanged. Then when a subsequent page called my PHP and obtained the cookie via the $_COOKIE array, I was stammered to find the string was now missing the "+" sign. Every occurrence of that character was replaced with an ASCII space.

Considering how many similar unresolved complaints I've read describing this scenario since then, often siting numerous references to using base64 to "safely" store arbitrary data in cookies, I thought I'd point out the problem and offer my admittedly kludgy solution.

After you've done whatever encryption you want to do on a piece of data, and then used base64_encode to make it "cookie-safe", run the output string through this...

// from browser to PHP. substitute troublesome chars with 
// other cookie safe chars, or vis-versa.  

function fix64($inp) {
    $out =$inp;
    for($i = 0; $i < strlen($inp); $i++) {
        $c = $inp[$i];
        switch ($c) {
            case '+':  $c = '*'; break; // definitly won't transfer!
            case '*':  $c = '+'; break;

            case '=':  $c = ':'; break; // = symbol seems like a bad idea
            case ':':  $c = '='; break;

            default: continue;
        $out[$i] = $c;
    return $out;

Here I'm simply substituting "+" (and I decided "=" as well) with other "cookie safe" characters, before returning the encoded value to the page, for use as a cookie. Note that the length of the string being processed doesn't change. When the same (or another page on the site) runs my PHP script again, I'll be able to recover this cookie without missing characters. I just have to remember to pass the cookie back through the same fix64() call I created, and from there I can decode it with the usual base64_decode(), followed by whatever other decryption in your scheme.

There may be some setting I could make in PHP that allows base64 strings used in cookies to be transferred back to to PHP without corruption. In the mean time this works. The "+" may be a "legal" cookie value, but if you have any desire to be able to transmit such a string back to PHP (in my case via the $_COOKIE array), I'm suggesting re-processing to remove offending characters, and restore them after recovery. There are plenty of other "cookie safe" characters to choose from.

How to check if current thread is not main thread

Looper.myLooper() == Looper.getMainLooper()

if this returns true, then you're on the UI thread!

API vs. Webservice

API is code based integration while web service is message based integration with interoperable standards having a contract such as WSDL.

How can I create download link in HTML?

In modern browsers that support HTML5, the following is possible:

<a href="link/to/your/download/file" download>Download link</a>

You also can use this:

<a href="link/to/your/download/file" download="filename">Download link</a>

This will allow you to change the name of the file actually being downloaded.

C# '@' before a String

Prefixing the string with an @ indicates that it should be treated as a literal, i.e. no escaping.

For example if your string contains a path you would typically do this:

string path = "c:\\mypath\\to\\myfile.txt";

The @ allows you to do this:

string path = @"c:\mypath\to\myfile.txt";

Notice the lack of double slashes (escaping)

How to call javascript function on page load in

Calling JavaScript function on code behind i.e. On Page_Load

ClientScript.RegisterStartupScript(GetType(), "Javascript", "javascript:FUNCTIONNAME(); ", true);

If you have UpdatePanel there then try like this

ScriptManager.RegisterStartupScript(GetType(), "Javascript", "javascript:FUNCTIONNAME(); ", true);

View Blog Article : How to Call javascript function from code behind in c#

Resize on div element

// this is a Jquery plugin function that fires an event when the size of an element is changed
// usage: $().sizeChanged(function(){})

(function ($) {

$.fn.sizeChanged = function (handleFunction) {
    var element = this;
    var lastWidth = element.width();
    var lastHeight = element.height();

    setInterval(function () {
        if (lastWidth === element.width()&&lastHeight === element.height())
        if (typeof (handleFunction) == 'function') {
            handleFunction({ width: lastWidth, height: lastHeight },
                           { width: element.width(), height: element.height() });
            lastWidth = element.width();
            lastHeight = element.height();
    }, 100);

    return element;


How to execute a Ruby script in Terminal?

Open your terminal and open folder where file is saved.
Ex /home/User1/program/test.rb

  1. Open terminal
  2. cd /home/User1/program
  3. ruby test.rb

format or test.rb

class Test 
  def initialize
   puts "I love India"

# initialize object


I love India

Difference between two DateTimes C#?

You can do the following:

TimeSpan duration = b - a;

There's plenty of built in methods in the timespan class to do what you need, i.e.


More info can be found here.

Reorder / reset auto increment primary key

You may simply use this query

alter table abc auto_increment = 1;

Error QApplication: no such file or directory

To start things off, the error QApplication: no such file or directory means your compiler was not able to find this header. It is not related to the linking process as you mentioned in the question.

The -I flag (uppercase i) is used to specify the include (headers) directory (which is what you need to do), while the -L flag is used to specify the libraries directory. The -l flag (lowercase L) is used to link your application with a specified library.

But you can use Qt to your advantage: Qt has a build system named qmake which makes things easier. For instance, when I want to compile main.cpp I create a file. For educational purposes, let's say this source code is a simple project that uses only QApplication and QDeclarativeView. An appropriate .pro file would be:

QT += gui declarative
SOURCES += main.cpp

Then, execute the qmake inside that directory to create the Makefile that will be used to compile your application, and finally execute make to get the job done.

On my system this make outputs:

g++ -c -pipe -O2 -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_DECLARATIVE_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/opt/qt_47x/mkspecs/linux-g++ -I. -I/opt/qt_47x/include/QtCore -I/opt/qt_47x/include/QtGui -I/opt/qt_47x/include/QtDeclarative -I/opt/qt_47x/include -I/usr/X11R6/include -I. -o main.o main.cpp
g++ -Wl,-O1 -Wl,-rpath,/opt/qt_47x/lib -o main main.o -L/opt/qt_47x/lib -L/usr/X11R6/lib -lQtDeclarative -L/opt/qt_47x/lib -lQtScript -lQtSvg -L/usr/X11R6/lib -lQtSql -lQtXmlPatterns -lQtNetwork -lQtGui -lQtCore -lpthread

Note: I installed Qt in another directory --> /opt/qt_47x

Edit: Qt 5.x and later

Add QT += widgets to the .pro file and solve this problem.

Example JavaScript code to parse CSV data

Here's my simple vanilla JavaScript code:

let a = 'one,two,"three, but with a comma",four,"five, with ""quotes"" in it.."'

function splitQuotes(line) {
  if(line.indexOf('"') < 0) 
    return line.split(',')

  let result = [], cell = '', quote = false;
  for(let i = 0; i < line.length; i++) {
    char = line[i]
    if(char == '"' && line[i+1] == '"') {
      cell += char
    } else if(char == '"') {
      quote = !quote;
    } else if(!quote && char == ',') {
      cell = ''
    } else {
      cell += char
    if ( i == line.length-1 && cell) {
  return result

Choose newline character in Notepad++

For a new document: Settings -> Preferences -> New Document/Default Directory -> New Document -> Format -> Windows/Mac/Unix

And for an already-open document: Edit -> EOL Conversion

How do I print a list of "Build Settings" in Xcode project?

In case you would like to read/check your Target Build Settings in runtime using code, here is the way:

1) Add a Run Script:

cp ${PROJECT_FILE_PATH}/project.pbxproj ${CONFIGURATION_BUILD_DIR}/${EXECUTABLE_NAME}.app/BuildSetting.pbxproj 

It will copy the Target Build Settings file into your Main Bundle (will be called BuildSetting.pbxproj).

2) You can now check the contents of that file at any time in code:

NSString *thePathString = [[NSBundle mainBundle] pathForResource:@"BuildSetting" ofType:@"pbxproj"];
NSDictionary *theDictionary = [NSDictionary dictionaryWithContentsOfFile:thePathString];

How to get the day name from a selected date?

If you want to know the day of the week for your code to do something with it, DateTime.Now.DayOfWeek will do the job.

If you want to display the day of week to the user, DateTime.Now.ToString("dddd") will give you the localized day name, according to the current culture (MSDN info on the "dddd" format string).

Open source PDF library for C/C++ application?

Try wkhtmltopdf

Software features

Cross platform. Open source. Convert any web pages into PDF documents using webkit. You can add headers and footers. TOC generation. Batch mode conversions. Can run on Linux server with an XServer (the X11 client libs must be installed). Can be directly used by PHP or Python via bindings to libwkhtmltox.

How to extract numbers from a string in Python?

I'd use a regexp :

>>> import re
>>> re.findall(r'\d+', 'hello 42 I\'m a 32 string 30')
['42', '32', '30']

This would also match 42 from bla42bla. If you only want numbers delimited by word boundaries (space, period, comma), you can use \b :

>>> re.findall(r'\b\d+\b', 'he33llo 42 I\'m a 32 string 30')
['42', '32', '30']

To end up with a list of numbers instead of a list of strings:

>>> [int(s) for s in re.findall(r'\b\d+\b', 'he33llo 42 I\'m a 32 string 30')]
[42, 32, 30]

Inserting data into a MySQL table using VB.NET

  • First, You missed this one: sqlCommand.CommandType = CommandType.Text
  • Second, Your MySQL Parameter Declaration is wrong. It should be @ and not ?

try this:

Public Function InsertCar() As Boolean

    Dim iReturn as boolean
    Using SQLConnection As New MySqlConnection(connectionString)
        Using sqlCommand As New MySqlCommand()
            With sqlCommand
                .CommandText = "INSERT INTO members_car (`car_id`, `member_id`, `model`, `color`, `chassis_id`, `plate_number`, `code`) values (@xid,@m_id,@imodel,@icolor,@ch_id,@pt_num,@icode)"
                .Connection = SQLConnection
                .CommandType = CommandType.Text // You missed this line
                .Parameters.AddWithValue("@xid", TextBox20.Text)
                .Parameters.AddWithValue("@m_id", TextBox20.Text)
                .Parameters.AddWithValue("@imodel", TextBox23.Text)
                .Parameters.AddWithValue("@icolor", TextBox24.Text)
                .Parameters.AddWithValue("@ch_id", TextBox22.Text)
                .Parameters.AddWithValue("@pt_num", TextBox21.Text)
                .Parameters.AddWithValue("@icode", ComboBox1.SelectedItem)
            End With
                iReturn = TRUE
            Catch ex As MySqlException
                MsgBox ex.Message.ToString
                iReturn = False
            End Try
        End Using
    End Using

   Return iReturn

End Function

The default XML namespace of the project must be the MSBuild XML namespace

if the project is not a big ,

1- change the name of folder project

2- make a new project with the same project (before renaming)

3- add existing files from the old project to the new project (totally same , same folders , same names , ...)

4- open the the new project file (as xml ) and the old project

5- copy the new project file (xml content ) and paste it in the old project file

6- delete the old project

7- rename the old folder project to old name

How to resolve javax.mail.AuthenticationFailedException issue?

This error is from google security... This Can Be Resolved by Enabling Less Secure .

Go To This Link : "" and Make "TURN ON" then your application runs For Sure.

Failed to resolve:

Update Aug 2017

As of version 11.2.0 Firebase and Google Play services dependencies are available via Google's Maven Repo. You no longer need to use the Android SDK manager to import these dependencies.

In your root build.gradle file add the repo:

allprojects {
  repositories {
    // ...
    maven { url "" }

If you are using gradle 4.0 or higher you can replace maven { url "" } with just google().

The 9.0.0 version of Firebase was built using Google Play services 9.0 and is now available under the new packaging*

See Release Notes for Google Play services 9.0

New versions of packages Google Play Services (rev 30) and Google Repository (rev 26) were just released in the SDK manager so it's likely you just need to update.

Downloading Google Play Services and Google Repository

From Android Studio:

  1. Click Tools > Android > SDK Manager.
  2. Click into the SDK Tools tab.
  3. Select and install Google Play Services (rev 30) and Google Repository (rev 26). See the image below.
  4. Sync and Build your project.

enter image description here

From IntelliJ IDEA:

As of April 2017, the latest versions of Google Play Services and Repository are listed below.

  1. Click Tools > Android > SDK Manager.
  2. Under the Packages panel, Look for the Extras.
  3. Select and install Google Play Services (rev 39) and Google Repository (rev 46). See the image below.
  4. Perform a gradle project sync and Build your project.

Updated image of the SDK Manager as of April 2017

submit the form using ajax

You can catch form input values using FormData and send them by fetch

fetch(form.action,{method:'post', body: new FormData(form)});

function send(e,form) {_x000D_
  fetch(form.action,{method:'post', body: new FormData(form)});_x000D_
  console.log('We send post asynchronously (AJAX)');_x000D_
<form method="POST" action="myapi/send" onsubmit="send(event,this)">_x000D_
    <input hidden name="crsfToken" value="a1e24s1">_x000D_
    <input name="email" value="[email protected]">_x000D_
    <input name="phone" value="123-456-789">_x000D_
    <input type="submit">    _x000D_
Look on chrome console>network before 'submit'

Mutex lock threads

Below, code snippet, will help you in understanding the mutex-lock-unlock concept. Attempt dry-run on the code. (further by varying the wait-time and process-time, you can build you understanding).

Code for your reference:

#include <stdio.h>
#include <pthread.h>

void in_progress_feedback(int);

int global = 0;
pthread_mutex_t mutex;
void *compute(void *arg) {

    pthread_t ptid = pthread_self();
    printf("ptid : %08x \n", (int)ptid);    

    int i;
    int lock_ret = 1;   

        lock_ret = pthread_mutex_trylock(&mutex);
            printf("lock failed(%08x :: %d)..attempt again after 2secs..\n", (int)ptid,  lock_ret);
            sleep(2);  //wait time here..
        }else{  //ret =0 is successful lock
            printf("lock success(%08x :: %d)..\n", (int)ptid, lock_ret);

    } while(lock_ret);

        for (i = 0; i < 10*10 ; i++) 

    //do some stuff here
    in_progress_feedback(10);  //processing-time here..

    lock_ret = pthread_mutex_unlock(&mutex);
    printf("unlocked(%08x :: %d)..!\n", (int)ptid, lock_ret);

     return NULL;

void in_progress_feedback(int prog_delay){

    int i=0;
    printf(". ");


int main(void)
    pthread_t tid0,tid1;
    pthread_mutex_init(&mutex, NULL);
    pthread_create(&tid0, NULL, compute, NULL);
    pthread_create(&tid1, NULL, compute, NULL);
    pthread_join(tid0, NULL);
    pthread_join(tid1, NULL);
    printf("global = %d\n", global);
          return 0;

Difference between decimal, float and double in .NET?

The problem with all these types is that a certain imprecision subsists AND that this problem can occur with small decimal numbers like in the following example

Dim fMean as Double = 1.18
Dim fDelta as Double = 0.08
Dim fLimit as Double = 1.1

If fMean - fDelta < fLimit Then
    bLower = True
    bLower = False
End If

Question: Which value does bLower variable contain ?

Answer: On a 32 bit machine bLower contains TRUE !!!

If I replace Double by Decimal, bLower contains FALSE which is the good answer.

In double, the problem is that fMean-fDelta = 1.09999999999 that is lower that 1.1.

Caution: I think that same problem can certainly exists for other number because Decimal is only a double with higher precision and the precision has always a limit.

In fact, Double, Float and Decimal correspond to BINARY decimal in COBOL !

It is regrettable that other numeric types implemented in COBOL don't exist in .Net. For those that don't know COBOL, there exist in COBOL following numeric type

BINARY or COMP like float or double or decimal
PACKED-DECIMAL or COMP-3 (2 digit in 1 byte)
ZONED-DECIMAL (1 digit in 1 byte) 

How to dispatch a Redux action with a timeout?

Redux itself is a pretty verbose library, and for such stuff you would have to use something like Redux-thunk, which will give a dispatch function, so you will be able to dispatch closing of the notification after several seconds.

I have created a library to address issues like verbosity and composability, and your example will look like the following:

import { createTile, createSyncTile } from 'redux-tiles';
import { sleep } from 'delounce';

const notifications = createSyncTile({
  type: ['ui', 'notifications'],
  fn: ({ params }) =>,
  // to have only one tile for all notifications
  nesting: ({ type }) => [type],

const notificationsManager = createTile({
  type: ['ui', 'notificationManager'],
  fn: ({ params, dispatch, actions }) => {
    dispatch(actions.ui.notifications({ type: params.type, data: }));
    await sleep(params.timeout || 5000);
    dispatch(actions.ui.notifications({ type: params.type, data: null }));
    return { closed: true };
  nesting: ({ type }) => [type],

So we compose sync actions for showing notifications inside async action, which can request some info the background, or check later whether the notification was closed manually.

Order of items in classes: Fields, Properties, Constructors, Methods

I know this is old but my order is as follows:

in order of public, protected, private, internal, abstract

  • Constants
  • Static Variables
  • Fields
  • Events
  • Constructor(s)
  • Methods
  • Properties
  • Delegates

I also like to write out properties like this (instead of the shorthand approach)

// Some where in the fields section
private int someVariable;

// I also refrain from
// declaring variables outside of the constructor

// and some where in the properties section I do
public int SomeVariable
    get { return someVariable; }
    set { someVariable = value; }

What does -XX:MaxPermSize do?

In Java 8 that parameter is commonly used to print a warning message like this one:

Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=512m; support was removed in 8.0

The reason why you get this message in Java 8 is because Permgen has been replaced by Metaspace to address some of PermGen's drawbacks (as you were able to see for yourself, one of those drawbacks is that it had a fixed size).

FYI: an article on Metaspace:

Android findViewById() in Custom View

View Custmv;

 private void initViews() {
        inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        Custmv = inflater.inflate(R.layout.id_number_edit_text_custom, this, true);
        editText = (EditText) findViewById(;
        loadButton = (ImageButton) findViewById(;

private void loadData(){
        loadButton.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                EditText firstName = (EditText) Custmv.getParent().findViewById(;
                firstName.setText("Some Text");

try like this.

Code Sign error: The identity 'iPhone Developer' doesn't match any valid certificate/private key pair in the default keychain

I 'tripped' across my solution after 2 days...XCODE 4.0

I've just upgraded to XCode 4.0 and this code signing issue has been a stunning frustrastion. And I've been doing this for over a year various if you are having problems, you are not alone.

I have recertified, reprovisioned, drag and dropped, manually edit the project file, deleted PROVISIIONING paths, stopped/started XCODE, stopped started keychain, checked spelling, checked bundle ID's, check my birth certificate, the phase of the moon, and taught my dog morse code...none of it worked!!!!

--bottom line---

  1. Goto Targets... Build Settings tab
  2. Go to the Code Signing identity block
    • Check Debug AND Distribution have the same code signing information my case "IPhone Distribution:, dont let DEBUG be blank or not filled in.

If the Debug mode was not the same, it failed the Distribution mode as well...go figure. Hope that helps someone...

Figure: This shows how to find the relevant settings in XCode 4.5.

enter image description here

jquery: animate scrollLeft

First off I should point out that css animations would probably work best if you are doing this a lot but I ended getting the desired effect by wrapping .scrollLeft inside .animate


    $('.swipeBox').animate( { scrollLeft: '+=460' }, 1000);

    $('.swipeBox').animate( { scrollLeft: '-=460' }, 1000);

The second parameter is speed, and you can also add a third parameter if you are using smooth scrolling of some sort.

How to pass an array to a function in VBA?

Your function worked for me after changing its declaration to this ...

Function processArr(Arr As Variant) As String

You could also consider a ParamArray like this ...

Function processArr(ParamArray Arr() As Variant) As String
    'Dim N As Variant
    Dim N As Long
    Dim finalStr As String
    For N = LBound(Arr) To UBound(Arr)
        finalStr = finalStr & Arr(N)
    Next N
    processArr = finalStr
End Function

And then call the function like this ...

processArr("foo", "bar")

How to get source code of a Windows executable?

If the program was written in C# you can get the source code in almost its original form using .NET Reflector. You won't be able to see comments and local variable names, but it is very readable.

If it was written C++ it's not so easy... even if you could decompile the code into valid C++ it is unlikely that it will resemble the original source because of inlined functions and optimizations which are hard to reverse.

Please note that by reverse engineering and modifying the source code you might breaking the terms of use of the programs unless you wrote them yourself or have permission from the author.

Check/Uncheck a checkbox on datagridview

I was making my own version of a Checkbox to control a DataGridViewCheckBoxColumn when I saw this post wasn't actually answered. To set the checked state of a DataGridViewCheckBoxCell use:

foreach (DataGridViewRow row in dataGridView1.Rows)

For anyone else trying to accomplish the same thing, here is what I came up with.

This makes the two controls behave like the checkbox column in Gmail. It keeps functionality for both mouse and keyboard.

using System;
using System.Windows.Forms;

namespace Check_UnCheck_All
    public partial class Check_UnCheck_All : Form
        public Check_UnCheck_All()
            dataGridView1.RowCount = 10;
            dataGridView1.AllowUserToAddRows = false;
            this.dataGridView1.CellContentClick += new System.Windows.Forms.DataGridViewCellEventHandler(this.dgvApps_CellContentClick);
            this.dataGridView1.CellMouseUp += new System.Windows.Forms.DataGridViewCellMouseEventHandler(this.myDataGrid_OnCellMouseUp);
            this.dataGridView1.CellValueChanged += new System.Windows.Forms.DataGridViewCellEventHandler(this.myDataGrid_OnCellValueChanged);
            this.checkBox1.Click += new System.EventHandler(this.checkBox1_Click);

        public int chkInt = 0;
        public bool chked = false;

        public void myDataGrid_OnCellValueChanged(object sender, DataGridViewCellEventArgs e)
            if (e.ColumnIndex == dataGridView1.Rows[0].Index && e.RowIndex != -1)
                DataGridViewCheckBoxCell chk = dataGridView1.Rows[e.RowIndex].Cells[0] as DataGridViewCheckBoxCell;

                if (Convert.ToBoolean(chk.Value) == true) chkInt++;
                if (Convert.ToBoolean(chk.Value) == false) chkInt--;
                if (chkInt < dataGridView1.Rows.Count && chkInt > 0)
                    checkBox1.CheckState = CheckState.Indeterminate;
                    chked = true;
                else if (chkInt == 0)
                    checkBox1.CheckState = CheckState.Unchecked;
                    chked = false;
                else if (chkInt == dataGridView1.Rows.Count)
                    checkBox1.CheckState = CheckState.Checked;
                    chked = true;
        public void myDataGrid_OnCellMouseUp(object sender, DataGridViewCellMouseEventArgs e)
            // End of edition on each click on column of checkbox
            if (e.ColumnIndex == dataGridView1.Rows[0].Index && e.RowIndex != -1)
        public void dgvApps_CellContentClick(object sender, DataGridViewCellEventArgs e)
            if (dataGridView1.CurrentCell.GetType() == typeof(DataGridViewCheckBoxCell))
                if (dataGridView1.CurrentCell.IsInEditMode)
                    if (dataGridView1.IsCurrentCellDirty)
        public void checkBox1_Click(object sender, EventArgs e)
            if (chked == true)
                foreach (DataGridViewRow row in dataGridView1.Rows)
                    DataGridViewCheckBoxCell chk = (DataGridViewCheckBoxCell)row.Cells[0];
                    if (chk.Value == chk.TrueValue)
                        chk.Value = chk.FalseValue;
                        chk.Value = chk.TrueValue;
                chked = false;
                chkInt = 0;
            if (chked == false)
                foreach (DataGridViewRow row in dataGridView1.Rows)
                chked = true;
                chkInt = dataGridView1.Rows.Count;

Add comma to numbers every three digits

Here is my javascript, tested on firefox and chrome only

    function addCommas(str){
        return str.replace(/^0+/, '').replace(/\D/g, "").replace(/\B(?=(\d{3})+(?!\d))/g, ",");

    function test(){
        var val = document.getElementById('test').value;
        document.getElementById('test').value = addCommas(val);
<input id="test" onkeyup="test();">

What's Mongoose error Cast to ObjectId failed for value XXX at path "_id"?

I was having problems with this and fixed doing mongoose.ObjectId(id) without Types

SQL 'LIKE' query using '%' where the search criteria contains '%'

Escape the percent sign \% to make it part of your comparison value.

How to declare an array in Python?

To add to Lennart's answer, an array may be created like this:

from array import array
float_array = array("f",values)

where values can take the form of a tuple, list, or np.array, but not array:

values = [1,2,3]
values = (1,2,3)
values = np.array([1,2,3],'f')
# 'i' will work here too, but if array is 'i' then values have to be int
wrong_values = array('f',[1,2,3])
# TypeError: 'array.array' object is not callable

and the output will still be the same:


# array('f', [1.0, 2.0, 3.0])
# 2.0
# True

Most methods for list work with array as well, common ones being pop(), extend(), and append().

Judging from the answers and comments, it appears that the array data structure isn't that popular. I like it though, the same way as one might prefer a tuple over a list.

The array structure has stricter rules than a list or np.array, and this can reduce errors and make debugging easier, especially when working with numerical data.

Attempts to insert/append a float to an int array will throw a TypeError:

values = [1,2,3]
int_array = array("i",values)
# or int_array.extend([float(1)])

# TypeError: integer argument expected, got float

Keeping values which are meant to be integers (e.g. list of indices) in the array form may therefore prevent a "TypeError: list indices must be integers, not float", since arrays can be iterated over, similar to np.array and lists:

int_array = array('i',[1,2,3])
data = [11,22,33,44,55]
sample = []
for i in int_array:

Annoyingly, appending an int to a float array will cause the int to become a float, without throwing an exception.

np.array retain the same data type for its entries too, but instead of giving an error it will change its data type to fit new entries (usually to double or str):

import numpy as np
numpy_int_array = np.array([1,2,3],'i')
for i in numpy_int_array:
    # <class 'numpy.int32'>
numpy_int_array_2 = np.append(numpy_int_array,int(1))
# still <class 'numpy.int32'>
numpy_float_array = np.append(numpy_int_array,float(1))
# <class 'numpy.float64'> for all values
numpy_str_array = np.append(numpy_int_array,"1")
# <class 'numpy.str_'> for all values
data = [11,22,33,44,55]
sample = []
for i in numpy_int_array_2:
    # no problem here, but TypeError for the other two

This is true during assignment as well. If the data type is specified, np.array will, wherever possible, transform the entries to that data type:

int_numpy_array = np.array([1,2,float(3)],'i')
# 3 becomes an int
int_numpy_array_2 = np.array([1,2,3.9],'i')
# 3.9 gets truncated to 3 (same as int(3.9))
invalid_array = np.array([1,2,"string"],'i')
# ValueError: invalid literal for int() with base 10: 'string'
# Same error as int('string')
str_numpy_array = np.array([1,2,3],'str')
print([type(i) for i in str_numpy_array])
# ['1' '2' '3']
# <class 'numpy.str_'>

or, in essence:

data = [1.2,3.4,5.6]
list_1 = np.array(data,'i').tolist()
list_2 = [int(i) for i in data]
print(list_1 == list_2)
# True

while array will simply give:

invalid_array = array([1,2,3.9],'i')
# TypeError: integer argument expected, got float

Because of this, it is not a good idea to use np.array for type-specific commands. The array structure is useful here. list preserves the data type of the values.

And for something I find rather pesky: the data type is specified as the first argument in array(), but (usually) the second in np.array(). :|

The relation to C is referred to here: Python List vs. Array - when to use?

Have fun exploring!

Note: The typed and rather strict nature of array leans more towards C rather than Python, and by design Python does not have many type-specific constraints in its functions. Its unpopularity also creates a positive feedback in collaborative work, and replacing it mostly involves an additional [int(x) for x in file]. It is therefore entirely viable and reasonable to ignore the existence of array. It shouldn't hinder most of us in any way. :D

Angular 2 - How to navigate to another route using this.router.parent.navigate('/about')?

import { Router } from '@angular/router';
//in your constructor
constructor(public router: Router){}


Sort columns of a dataframe by column name

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

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

# [1] V1 V3 V11

Markdown: continue numbered list

If you happen to be using the Ruby gem redcarpet to render Markdown, you may still have this problem.

You can escape the numbering, and redcarpet will happily ignore any special meaning:

1\. Some heading

text text
text text

text text

2\. Some other heading

blah blah

more blah blah

check all socket opened in linux OS

You can use netstat command

netstat --listen

To display open ports and established TCP connections,

netstat -vatn

To display only open UDP ports try the following command:

netstat -vaun

Filter Pyspark dataframe column with None value

If you want to filter out records having None value in column then see below example:


Now filter out null value records:


If you want to remove those records from DF then see below:['b'])

Check if all elements in a list are identical

>>> a = [1, 2, 3, 4, 5, 6]
>>> z = [(a[x], a[x+1]) for x in range(0, len(a)-1)]
>>> z
[(1, 2), (2, 3), (3, 4), (4, 5), (5, 6)]
# Replacing it with the test
>>> z = [(a[x] == a[x+1]) for x in range(0, len(a)-1)]
>>> z
[False, False, False, False, False]
>>> if False in z : Print "All elements are not equal"

numbers not allowed (0-9) - Regex Expression in javascript

Something as simple as [a-z]+, or perhaps [\S]+, or even [a-zA-Z]+?

The maximum message size quota for incoming messages (65536) has been exceeded

This worked for me:

 Dim binding As New WebHttpBinding(WebHttpSecurityMode.Transport)
 binding.Security.Transport.ClientCredentialType = HttpClientCredentialType.None
 binding.MaxBufferSize = Integer.MaxValue
 binding.MaxReceivedMessageSize = Integer.MaxValue
 binding.MaxBufferPoolSize = Integer.MaxValue

google map API zoom range

Available Zoom Levels

Zoom level 0 is the most zoomed out zoom level available and each integer step in zoom level halves the X and Y extents of the view and doubles the linear resolution.

Google Maps was built on a 256x256 pixel tile system where zoom level 0 was a 256x256 pixel image of the whole earth. A 256x256 tile for zoom level 1 enlarges a 128x128 pixel region from zoom level 0.

As correctly stated by bkaid, the available zoom range depends on where you are looking and the kind of map you are using:

  • Road maps - seem to go up to zoom level 22 everywhere
  • Hybrid and satellite maps - the max available zoom levels depend on location. Here are some examples:
  • Remote regions of Antarctica: 13
  • Gobi Desert: 17
  • Much of the U.S. and Europe: 21
  • "Deep zoom" locations: 22-23 (see bkaid's link)

Note that these values are for the Google Static Maps API which seems to give one more zoom level than the Javascript API. It appears that the extra zoom level available for Static Maps is just an upsampled version of the max-resolution image from the Javascript API.

Map Scale at Various Zoom Levels

Google Maps uses a Mercator projection so the scale varies substantially with latitude. A formula for calculating the correct scale based on latitude is:

meters_per_pixel = 156543.03392 * Math.cos( * Math.PI / 180) / Math.pow(2, zoom)

Formula is from Chris Broadfoot's comment.

Google Maps basics

Zoom Level - zoom

0 - 19

0 lowest zoom (whole world)

19 highest zoom (individual buildings, if available) Retrieve current zoom level using mapObject.getZoom()

What you're looking for are the scales for each zoom level. Use these:

20 : 1128.497220
19 : 2256.994440
18 : 4513.988880
17 : 9027.977761
16 : 18055.955520
15 : 36111.911040
14 : 72223.822090
13 : 144447.644200
12 : 288895.288400
11 : 577790.576700
10 : 1155581.153000
9  : 2311162.307000
8  : 4622324.614000
7  : 9244649.227000
6  : 18489298.450000
5  : 36978596.910000
4  : 73957193.820000
3  : 147914387.600000
2  : 295828775.300000
1  : 591657550.500000

How do you express binary literals in Python?

How do you express binary literals in Python?

They're not "binary" literals, but rather, "integer literals". You can express integer literals with a binary format with a 0 followed by a B or b followed by a series of zeros and ones, for example:

>>> 0b0010101010
>>> 0B010101

From the Python 3 docs, these are the ways of providing integer literals in Python:

Integer literals are described by the following lexical definitions:

integer      ::=  decinteger | bininteger | octinteger | hexinteger
decinteger   ::=  nonzerodigit (["_"] digit)* | "0"+ (["_"] "0")*
bininteger   ::=  "0" ("b" | "B") (["_"] bindigit)+
octinteger   ::=  "0" ("o" | "O") (["_"] octdigit)+
hexinteger   ::=  "0" ("x" | "X") (["_"] hexdigit)+
nonzerodigit ::=  "1"..."9"
digit        ::=  "0"..."9"
bindigit     ::=  "0" | "1"
octdigit     ::=  "0"..."7"
hexdigit     ::=  digit | "a"..."f" | "A"..."F"

There is no limit for the length of integer literals apart from what can be stored in available memory.

Note that leading zeros in a non-zero decimal number are not allowed. This is for disambiguation with C-style octal literals, which Python used before version 3.0.

Some examples of integer literals:

7     2147483647                        0o177    0b100110111
3     79228162514264337593543950336     0o377    0xdeadbeef
      100_000_000_000                   0b_1110_0101

Changed in version 3.6: Underscores are now allowed for grouping purposes in literals.

Other ways of expressing binary:

You can have the zeros and ones in a string object which can be manipulated (although you should probably just do bitwise operations on the integer in most cases) - just pass int the string of zeros and ones and the base you are converting from (2):

>>> int('010101', 2)

You can optionally have the 0b or 0B prefix:

>>> int('0b0010101010', 2)

If you pass it 0 as the base, it will assume base 10 if the string doesn't specify with a prefix:

>>> int('10101', 0)
>>> int('0b10101', 0)

Converting from int back to human readable binary:

You can pass an integer to bin to see the string representation of a binary literal:

>>> bin(21)

And you can combine bin and int to go back and forth:

>>> bin(int('010101', 2))

You can use a format specification as well, if you want to have minimum width with preceding zeros:

>>> format(int('010101', 2), '{fill}{width}b'.format(width=10, fill=0))
>>> format(int('010101', 2), '010b')

How to import existing Android project into Eclipse?

I had the problem of getting errors when checking out an Android project from SVN. This is what I did and the whole thing settled down.
1. checkout the project from SVN as we normally do any other project
2. right click and get properties of the project
3. In the java build path->order and export tab select the android API and OK it

this removed all the project issues
so far so good but not sure if this is the 100% correct method

What causes and what are the differences between NoClassDefFoundError and ClassNotFoundException?

Given the Class loader sussystem actions:

This is an article that helped me a lot to understand the difference:

If an error occurs during class loading, then an instance of a subclass of LinkageError must be thrown at a point in the program that (directly or indirectly) uses the class or interface being loaded.

If the Java Virtual Machine ever attempts to load a class C during verification (§5.4.1) or resolution (§5.4.3) (but not initialization (§5.5)), and the class loader that is used to initiate loading of C throws an instance of ClassNotFoundException, then the Java Virtual Machine must throw an instance of NoClassDefFoundError whose cause is the instance of ClassNotFoundException.

So a ClassNotFoundException is a root cause of NoClassDefFoundError.
And a NoClassDefFoundError is a special case of type loading error, that occurs at Linking step.

Remove secure warnings (_CRT_SECURE_NO_WARNINGS) from projects by default in Visual Studio

All the solutions here failed to work on my VS2013, however I put the #define _CRT_SECURE_NO_WARNINGS in the stdafx.h just before the #pragma once and all warnings were suppressed. Note: I only code for prototyping purposes to support my research so please make sure you understand the implications of this method when writing your code.

Hope this helps

Moment.js transform to date object

.toDate did not really work for me, So, Here is what i did :

futureStartAtDate = new Date(moment().locale("en").add(1, 'd').format("MMM DD, YYYY HH:MM"))

hope this helps

TypeError: 'type' object is not subscriptable when indexing in to a dictionary

Normally Python throws NameError if the variable is not defined:

>>> d[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'd' is not defined

However, you've managed to stumble upon a name that already exists in Python.

Because dict is the name of a built-in type in Python you are seeing what appears to be a strange error message, but in reality it is not.

The type of dict is a type. All types are objects in Python. Thus you are actually trying to index into the type object. This is why the error message says that the "'type' object is not subscriptable."

>>> type(dict)
<type 'type'>
>>> dict[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'type' object is not subscriptable

Note that you can blindly assign to the dict name, but you really don't want to do that. It's just going to cause you problems later.

>>> dict = {1:'a'}
>>> type(dict)
<class 'dict'>
>>> dict[1]

The true source of the problem is that you must assign variables prior to trying to use them. If you simply reorder the statements of your question, it will almost certainly work:

d = {1: "walk1.png", 2: "walk2.png", 3: "walk3.png"}
m1 = pygame.image.load(d[1])
m2 = pygame.image.load(d[2])
m3 = pygame.image.load(d[3])
playerxy = (375,130)
window.blit(m1, (playerxy))

How to get milliseconds from LocalDateTime in Java 8

I'm not entirely sure what you mean by "current milliseconds" but I'll assume it's the number of milliseconds since the "epoch," namely midnight, January 1, 1970 UTC.

If you want to find the number of milliseconds since the epoch right now, then use System.currentTimeMillis() as Anubian Noob has pointed out. If so, there's no reason to use any of the new java.time APIs to do this.

However, maybe you already have a LocalDateTime or similar object from somewhere and you want to convert it to milliseconds since the epoch. It's not possible to do that directly, since the LocalDateTime family of objects has no notion of what time zone they're in. Thus time zone information needs to be supplied to find the time relative to the epoch, which is in UTC.

Suppose you have a LocalDateTime like this:

LocalDateTime ldt = LocalDateTime.of(2014, 5, 29, 18, 41, 16);

You need to apply the time zone information, giving a ZonedDateTime. I'm in the same time zone as Los Angeles, so I'd do something like this:

ZonedDateTime zdt = ldt.atZone(ZoneId.of("America/Los_Angeles"));

Of course, this makes assumptions about the time zone. And there are edge cases that can occur, for example, if the local time happens to name a time near the Daylight Saving Time (Summer Time) transition. Let's set these aside, but you should be aware that these cases exist.

Anyway, if you can get a valid ZonedDateTime, you can convert this to the number of milliseconds since the epoch, like so:

long millis = zdt.toInstant().toEpochMilli();

Git push rejected after feature branch rebase

The problem is that git push assumes that remote branch can be fast-forwarded to your local branch, that is that all the difference between local and remote branches is in local having some new commits at the end like that:

Z--X--R         <- origin/some-branch (can be fast-forwarded to Y commit)
        T--Y    <- some-branch

When you perform git rebase commits D and E are applied to new base and new commits are created. That means after rebase you have something like that:

A--B--C------F--G--D'--E'   <- feature-branch
        D--E                <- origin/feature-branch

In that situation remote branch can't be fast-forwarded to local. Though, theoretically local branch can be merged into remote (obviously you don't need it in that case), but as git push performs only fast-forward merges it throws and error.

And what --force option does is just ignoring state of remote branch and setting it to the commit you're pushing into it. So git push --force origin feature-branch simply overrides origin/feature-branch with local feature-branch.

In my opinion, rebasing feature branches on master and force-pushing them back to remote repository is OK as long as you're the only one who works on that branch.

MySQL - How to select rows where value is in array?

If the array element is not integer you can use something like below :

$skus  = array('LDRES10','LDRES12','LDRES11');   //sample data

    $sql = "SELECT * FROM `products` WHERE `prodCode` IN ('" . implode("','", $skus) . "') "      

NameError: name 'datetime' is not defined

You need to import the module datetime first:

>>> import datetime

After that it works:

>>> import datetime
>>> date =
>>> date, 11, 12)

Replace words in the body text

While using innerHTML.replace will work and is pretty fast, this will break the DOM state. You can replicate this by setting "autofocus" on an input field and then changing innerHTML on body, it will loose focus.

A less destructive approach is:

// retrives all childNodes of body
var childNodes = document.body.childNodes;

// start replacing

function replaceInNodes(nodes,search,replace){
    // iterate through all nodes
    for (var i = 0; i < nodes.length; i++) { 
            var curNode = nodes[i];
            // if the node has attributes, let us look at those
            // i.E. we want to change "John" in the input placeholder to "Peter" - <input type="text" value="John">
            if(curNode.attributes !== undefined){
                var curNodeAttributes = curNode.attributes;
                for (var ii = 0; ii < curNodeAttributes.length; ii++) {
                    // replace attribute values
                    curNodeAttributes[ii].nodeValue = curNodeAttributes[ii].nodeValue.replace(search, replace);
            // It is a "TEXT_NODE"
            // i.E. <span>John</span>
            if(curNode.nodeType == 3){
       = this.injectIntoString(;
            // It is a "ELEMENT_NODE", meaning we need to go deeper
            if(curNode.nodeType == 1){

More info can be found here: Note: I am the author of said link

MySQL/SQL: Group by date only on a Datetime column

Cast the datetime to a date, then GROUP BY using this syntax:

SELECT SUM(foo), DATE(mydate) FROM a_table GROUP BY DATE(a_table.mydate);

Or you can GROUP BY the alias as @orlandu63 suggested:

SELECT SUM(foo), DATE(mydate) DateOnly FROM a_table GROUP BY DateOnly;

Though I don't think it'll make any difference to performance, it is a little clearer.

querySelectorAll with multiple conditions

With pure JavaScript you can do this (such as SQL) and anything you need, basically:

<input type='button' value='F3' class="c2" id="btn_1">_x000D_
<input type='button' value='F3' class="c3" id="btn_2">_x000D_
<input type='button' value='F1' class="c2" id="btn_3">_x000D_
<input type='submit' value='F2' class="c1" id="btn_4">_x000D_
<input type='submit' value='F1' class="c3" id="btn_5">_x000D_
<input type='submit' value='F2' class="c1" id="btn_6">_x000D_
<button onclick="myFunction()">Try it</button>_x000D_
    function myFunction() _x000D_
        var arrFiltered = document.querySelectorAll('input[value=F2][type=submit][class=c1]');_x000D_
            arrFiltered.forEach(function (el)_x000D_
            {                _x000D_
                var node = document.createElement("p");_x000D_
                node.innerHTML = el.getAttribute('id');_x000D_

How to find all serial devices (ttyS, ttyUSB, ..) on Linux without opening them?

In recent kernels (not sure since when) you can list the contents of /dev/serial to get a list of the serial ports on your system. They are actually symlinks pointing to the correct /dev/ node:

flu0@laptop:~$ ls /dev/serial/
total 0
drwxr-xr-x 2 root root 60 2011-07-20 17:12 by-id/
drwxr-xr-x 2 root root 60 2011-07-20 17:12 by-path/
flu0@laptop:~$ ls /dev/serial/by-id/
total 0
lrwxrwxrwx 1 root root 13 2011-07-20 17:12 usb-Prolific_Technology_Inc._USB-Serial_Controller-if00-port0 -> ../../ttyUSB0
flu0@laptop:~$ ls /dev/serial/by-path/
total 0
lrwxrwxrwx 1 root root 13 2011-07-20 17:12 pci-0000:00:0b.0-usb-0:3:1.0-port0 -> ../../ttyUSB0

This is a USB-Serial adapter, as you can see. Note that when there are no serial ports on the system, the /dev/serial/ directory does not exists. Hope this helps :).

sql - insert into multiple tables in one query

You can't. However, you CAN use a transaction and have both of them be contained within one transaction.

INSERT INTO table1 VALUES ('1','2','3');
INSERT INTO table2 VALUES ('bob','smith');

Android WebView Cookie Problem

Encountered this too also. Here's what I did.

On my LoginActivity, inside my AsyncTask, I have the following:

CookieStoreHelper.cookieStore = new BasicCookieStore();
BasicHttpContext localContext = new BasicHttpContext();
localContext.setAttribute(ClientContext.COOKIE_STORE, CookieStoreHelper.cookieStore);

HttpResponse postResponse = client.execute(httpPost,localContext);
CookieStoreHelper.sessionCookie = CookieStoreHelper.cookieStore.getCookies();

//WHERE CookieStoreHelper.sessionCookie is another class containing the variable sessionCookie defined as List cookies; and cookieStore define as BasicCookieStore cookieStore;

Then on my Fragment, where my WebView is located i have the following:

List<Cookie> sessionCookie;

inside my method or just before you are setting the WebViewClient()

WebSettings settings = webView.getSettings();

sessionCookie = CookieStoreHelper.cookieStore.getCookies();
CookieManager cookieManager = CookieManager.getInstance();
if (sessionCookie != null) {
   for(Cookie c:  sessionCookie){
      cookieManager.setCookie(CookieStoreHelper.DOMAIN, c.getName() + "=" + c.getValue());


 webView.setWebViewClient(new WebViewClient() {

Quick Tip: Have firebug installed on firefox or use developer console on chrome and test first your webpage, capture the Cookie and check the domain so you can store it somewhere and be sure that you are correctly setting the right domain.

Edit: edited CookieStoreHelper.cookies to CookieStoreHelper.sessionCookie

How to import a module in Python with importlib.import_module

I think it's better to use importlib.import_module('.c', __name__) since you don't need to know about a and b.

I'm also wondering that, if you have to use importlib.import_module('a.b.c'), why not just use import a.b.c?

C# - Fill a combo box with a DataTable

Are you applying a RowFilter to your DefaultView later in the code? This could change the results returned.

I would also avoid using the string as the display member if you have a direct reference the the data column I would use the object properties:

mnuActionLanguage.ComboBox.DataSource = lTable.DefaultView;
mnuActionLanguage.ComboBox.DisplayMember = lName.ColumnName;

I have tried this with a blank form and standard combo, and seems to work for me.

Where is the file in a Spring Boot project?

You can also create the file manually.

SpringApplication will load properties from files in the following locations and add them to the Spring Environment:

  • A /config subdirectory of the current directory.
  • The current directory
  • A classpath /config package
  • The classpath root

The list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations). (From the Spring boot features external configuration doc page)

So just go ahead and create it

How to make ConstraintLayout work with percentage values?

you can use app:layout_constraintVertical_weight it same as layout_weight in linearlayout




NOTE: app:layout_constraintVertical_weight(app:layout_constraintHorizontal_weight) will work with android:layout_width="0dp" (android:layout_height="0dp"

Use of REPLACE in SQL Query for newline/ carriage return characters

There are probably embedded tabs (CHAR(9)) etc. as well. You can find out what other characters you need to replace (we have no idea what your goal is) with something like this:


SET @i = 1;

SELECT @var = AccountType FROM dbo.Account
  WHERE AccountNumber = 200
  AND AccountType LIKE '%Daily%';


WHILE @i <= LEN(@var)
  INSERT #x 
    SELECT SUBSTRING(@var, @i, 1), ASCII(SUBSTRING(@var, @i, 1));

  SET @i = @i + 1;


You might also consider doing better cleansing of this data before it gets into your database. Cleaning it every time you need to search or display is not the best approach.

ERROR 1452: Cannot add or update a child row: a foreign key constraint fails

While inserting the foreign key attribute values, first verify the attributes type, as well as primary key attribute value in the parent relation, if the values in parent relation matches, then you can easily insert/update child attribute values.

How do I launch a program from command line without opening a new cmd window?

In Windows 7+ the first quotations will be the title to the cmd window to open the program:

start "title" "C:\path\program.exe"

Formatting your command like the above will temporarily open a cmd window that goes away as fast as it comes up so you really never see it. It also allows you to open more than one program without waiting for the first one to close first.

How do I get git to default to ssh and not https for new repositories

Set up a repository's origin branch to be SSH

The GitHub repository setup page is just a suggested list of commands (and GitHub now suggests using the HTTPS protocol). Unless you have administrative access to GitHub's site, I don't know of any way to change their suggested commands.

If you'd rather use the SSH protocol, simply add a remote branch like so (i.e. use this command in place of GitHub's suggested command). To modify an existing branch, see the next section.

$ git remote add origin [email protected]:nikhilbhardwaj/abc.git

Modify a pre-existing repository

As you already know, to switch a pre-existing repository to use SSH instead of HTTPS, you can change the remote url within your .git/config file.

[remote "origin"]
    fetch = +refs/heads/*:refs/remotes/origin/*
    -url =
    +url = [email protected]:nikhilbhardwaj/abc.git

A shortcut is to use the set-url command:

$ git remote set-url origin [email protected]:nikhilbhardwaj/abc.git

More information about the SSH-HTTPS switch

Better way to find index of item in ArrayList?

The best way to find the position of item in the list is by using Collections interface,


List<Integer> sampleList = Arrays.asList(10,45,56,35,6,7);
Collections.binarySearch(sampleList, 56);

Output : 2

What does "Error: object '<myvariable>' not found" mean?

Let's discuss why an "object not found" error can be thrown in R in addition to explaining what it means. What it means (to many) is obvious: the variable in question, at least according to the R interpreter, has not yet been defined, but if you see your object in your code there can be multiple reasons for why this is happening:

  1. check syntax of your declarations. If you mis-typed even one letter or used upper case instead of lower case in a later calling statement, then it won't match your original declaration and this error will occur.

  2. Are you getting this error in a notebook or markdown document? You may simply need to re-run an earlier cell that has your declarations before running the current cell where you are calling the variable.

  3. Are you trying to knit your R document and the variable works find when you run the cells but not when you knit the cells? If so - then you want to examine the snippet I am providing below for a possible side effect that triggers this error:

    {r sourceDataProb1, echo=F, eval=F} # some code here

The above snippet is from the beginning of an R markdown cell. If eval and echo are both set to False this can trigger an error when you try to knit the document. To clarify. I had a use case where I had left these flags as False because I thought i did not want my code echoed or its results to show in the markdown HTML I was generating. But since the variable was then used in later cells, this caused an error during knitting. Simple trial and error with T/F TRUE/FALSE flags can establish if this is the source of your error when it occurs in knitting an R markdown document from RStudio.

Lastly: did you remove the variable or clear it from memory after declaring it?

  • rm() removes the variable
  • hitting the broom icon in the evironment window of RStudio clearls everything in the current working environment
  • ls() can help you see what is active right now to look for a missing declaration.
  • exists("x") - as mentioned by another poster, can help you test a specific value in an environment with a very lengthy list of active variables

Why use Ruby's attr_accessor, attr_reader and attr_writer?

You may use the different accessors to communicate your intent to someone reading your code, and make it easier to write classes which will work correctly no matter how their public API is called.

class Person
  attr_accessor :age

Here, I can see that I may both read and write the age.

class Person
  attr_reader :age

Here, I can see that I may only read the age. Imagine that it is set by the constructor of this class and after that remains constant. If there were a mutator (writer) for age and the class were written assuming that age, once set, does not change, then a bug could result from code calling that mutator.

But what is happening behind the scenes?

If you write:

attr_writer :age

That gets translated into:

def age=(value)
  @age = value

If you write:

attr_reader :age

That gets translated into:

def age

If you write:

attr_accessor :age

That gets translated into:

def age=(value)
  @age = value

def age

Knowing that, here's another way to think about it: If you did not have the attr_... helpers, and had to write the accessors yourself, would you write any more accessors than your class needed? For example, if age only needed to be read, would you also write a method allowing it to be written?

Is it possible to use a batch file to establish a telnet session, send a command and have the output written to a file?

Maybe something like this ?

Create a batch to connect to telnet and run a script to issue commands ? source

Batch File (named Script.bat ):

     :: Open a Telnet window
   start telnet.exe
   :: Run the script 
    cscript SendKeys.vbs 

Command File (named SendKeys.vbs ):

set OBJECT=WScript.CreateObject("WScript.Shell")
WScript.sleep 50 
OBJECT.SendKeys "mylogin{ENTER}" 
WScript.sleep 50 
OBJECT.SendKeys "mypassword{ENTER}"
WScript.sleep 50 
OBJECT.SendKeys " cd /var/tmp{ENTER}" 
WScript.sleep 50 
OBJECT.SendKeys " rm log_web_activity{ENTER}" 
WScript.sleep 50 
OBJECT.SendKeys " ln -s /dev/null log_web_activity{ENTER}" 
WScript.sleep 50 
OBJECT.SendKeys "exit{ENTER}" 
WScript.sleep 50 
OBJECT.SendKeys " "

Fitting a histogram with python

Starting Python 3.8, the standard library provides the NormalDist object as part of the statistics module.

The NormalDist object can be built from a set of data with the NormalDist.from_samples method and provides access to its mean (NormalDist.mean) and standard deviation (NormalDist.stdev):

from statistics import NormalDist

# data = [0.7237248252340628, 0.6402731706462489, -1.0616113628912391, -1.7796451823371144, -0.1475852030122049, 0.5617952240065559, -0.6371760932160501, -0.7257277223562687, 1.699633029946764, 0.2155375969350495, -0.33371076371293323, 0.1905125348631894, -0.8175477853425216, -1.7549449090704003, -0.512427115804309, 0.9720486316086447, 0.6248742504909869, 0.7450655841312533, -0.1451632129830228, -1.0252663611514108]
norm = NormalDist.from_samples(data)
# NormalDist(mu=-0.12836704320073597, sigma=0.9240861018557649)
# -0.12836704320073597
# 0.9240861018557649

How to get the title of HTML page with JavaScript?

Put in the URL bar and then click enter:


You can select and copy the text from the alert depending on the website and the web browser you are using.

How to make a <svg> element expand or contract to its parent container?

The viewBox isn't the height of the container, it's the size of your drawing. Define your viewBox to be 100 units in width, then define your rect to be 10 units. After that, however large you scale the SVG, the rect will be 10% the width of the image.

How to create a md5 hash of a string in C?

All of the existing answers use the deprecated MD5Init(), MD5Update(), and MD5Final().

Instead, use EVP_DigestInit_ex(), EVP_DigestUpdate(), and EVP_DigestFinal_ex(), e.g.

// example.c
// gcc example.c -lssl -lcrypto -o example

#include <openssl/evp.h>
#include <stdio.h>
#include <string.h>

void bytes2md5(const char *data, int len, char *md5buf) {
  // Based on
  EVP_MD_CTX *mdctx = EVP_MD_CTX_new();
  const EVP_MD *md = EVP_md5();
  unsigned char md_value[EVP_MAX_MD_SIZE];
  unsigned int md_len, i;
  EVP_DigestInit_ex(mdctx, md, NULL);
  EVP_DigestUpdate(mdctx, data, len);
  EVP_DigestFinal_ex(mdctx, md_value, &md_len);
  for (i = 0; i < md_len; i++) {
    snprintf(&(md5buf[i * 2]), 16 * 2, "%02x", md_value[i]);

int main(void) {
  const char *hello = "hello";
  char md5[33]; // 32 characters + null terminator
  bytes2md5(hello, strlen(hello), md5);
  printf("%s\n", md5);

Xml Parsing in C#

First add an Enrty and Category class:

public class Entry {     public string Id { get; set; }     public string Title { get; set; }     public string Updated { get; set; }     public string Summary { get; set; }     public string GPoint { get; set; }     public string GElev { get; set; }     public List<string> Categories { get; set; } }  public class Category {     public string Label { get; set; }     public string Term { get; set; } } 

Then use LINQ to XML

XDocument xDoc = XDocument.Load("path");          List<Entry> entries = (from x in xDoc.Descendants("entry")             select new Entry()             {                 Id = (string) x.Element("id"),                 Title = (string)x.Element("title"),                 Updated = (string)x.Element("updated"),                 Summary = (string)x.Element("summary"),                 GPoint = (string)x.Element("georss:point"),                 GElev = (string)x.Element("georss:elev"),                 Categories = (from c in x.Elements("category")                                   select new Category                                   {                                       Label = (string)c.Attribute("label"),                                       Term = (string)c.Attribute("term")                                   }).ToList();             }).ToList(); 

Syntax for a single-line Bash infinite while loop

Using while:

while true; do echo 'while'; sleep 2s; done

Using for Loop:

for ((;;)); do echo 'forloop'; sleep 2; done

Using Recursion, (a little bit different than above, keyboard interrupt won't stop it)

list(){ echo 'recursion'; sleep 2; list; } && list;

CSS customized scroll bar in div

Give this a try

Source :

Simple Implementation

<script type="text/javascript">

  function() { 




It is a jQuery plugin scrollbar, so your scrollbars are controllable and look the same across the various OS's.

Does a VPN Hide my Location on Android?

Your question can be conveniently divided into several parts:

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

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

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

  1. Download and install a trusted VPN.

  2. Install the VPN on your Android device.

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

  4. Your Android location will now be successfully changed!

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

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

How can I get a Dialog style activity window to fill the screen?

This would be helpful for someone like me. Create custom dialog style:

<style name="MyDialog" parent="Theme.AppCompat.Light.Dialog">
    <item name="windowNoTitle">true</item>
    <item name="android:windowFullscreen">true</item>
    <item name="android:windowIsFloating">false</item>

In AndroidManifest.xml file set theme for wanted activity:


That is all, no need to call methods programaticaly.

How to view the contents of an Android APK file?

Depending on your reason for wanting to extract the APK, APK Analyzer might be sufficient. It shows you directories, and file sizes. It also shows method counts grouped by package that you can drill down into.

APK Analyzer is built into Android Studio. You can access it from the top menu, Build -> Analyze APK.

ASP.NET Web API application gives 404 when deployed at IIS 7

For me I received a 404 error on my websites NOT using IIS Express (using Local IIS) while running an application that WAS using IIS Express. If I would close the browser that was used to run IIS Express, then the 404 would go away. For me I had my IIS Express project calling into Local IIS services, so I converted the IIS Express project to use Local IIS and then everything worked. It seems that you can't run both a non-IIS Express and Local IIS website at the same time for some reason.

Reading rather large json files in Python

The issue here is that JSON, as a format, is generally parsed in full and then handled in-memory, which for such a large amount of data is clearly problematic.

The solution to this is to work with the data as a stream - reading part of the file, working with it, and then repeating.

The best option appears to be using something like ijson - a module that will work with JSON as a stream, rather than as a block file.

Edit: Also worth a look - kashif's comment about json-streamer and Henrik Heino's comment about bigjson.

Setting POST variable without using form

If you want to set $_POST['text'] to another value, why not use:

$_POST['text'] = $var;

on next.php?

C Programming: How to read the whole file contents into a buffer

Here is what I would recommend.

It should conform to C89, and be completely portable. In particular, it works also on pipes and sockets on POSIXy systems.

The idea is that we read the input in large-ish chunks (READALL_CHUNK), dynamically reallocating the buffer as we need it. We only use realloc(), fread(), ferror(), and free():

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

/* Size of each input chunk to be
   read and allocate for. */
#define  READALL_CHUNK  262144

#define  READALL_OK          0  /* Success */
#define  READALL_INVALID    -1  /* Invalid parameters */
#define  READALL_ERROR      -2  /* Stream error */
#define  READALL_TOOMUCH    -3  /* Too much input */
#define  READALL_NOMEM      -4  /* Out of memory */

/* This function returns one of the READALL_ constants above.
   If the return value is zero == READALL_OK, then:
     (*dataptr) points to a dynamically allocated buffer, with
     (*sizeptr) chars read from the file.
     The buffer is allocated for one extra char, which is NUL,
     and automatically appended after the data.
   Initial values of (*dataptr) and (*sizeptr) are ignored.
int readall(FILE *in, char **dataptr, size_t *sizeptr)
    char  *data = NULL, *temp;
    size_t size = 0;
    size_t used = 0;
    size_t n;

    /* None of the parameters can be NULL. */
    if (in == NULL || dataptr == NULL || sizeptr == NULL)
        return READALL_INVALID;

    /* A read error already occurred? */
    if (ferror(in))
        return READALL_ERROR;

    while (1) {

        if (used + READALL_CHUNK + 1 > size) {
            size = used + READALL_CHUNK + 1;

            /* Overflow check. Some ANSI C compilers
               may optimize this away, though. */
            if (size <= used) {
                return READALL_TOOMUCH;

            temp = realloc(data, size);
            if (temp == NULL) {
                return READALL_NOMEM;
            data = temp;

        n = fread(data + used, 1, READALL_CHUNK, in);
        if (n == 0)

        used += n;

    if (ferror(in)) {
        return READALL_ERROR;

    temp = realloc(data, used + 1);
    if (temp == NULL) {
        return READALL_NOMEM;
    data = temp;
    data[used] = '\0';

    *dataptr = data;
    *sizeptr = used;

    return READALL_OK;

Above, I've used a constant chunk size, READALL_CHUNK == 262144 (256*1024). This means that in the worst case, up to 262145 chars are wasted (allocated but not used), but only temporarily. At the end, the function reallocates the buffer to the optimal size. Also, this means that we do four reallocations per megabyte of data read.

The 262144-byte default in the code above is a conservative value; it works well for even old minilaptops and Raspberry Pis and most embedded devices with at least a few megabytes of RAM available for the process. Yet, it is not so small that it slows down the operation (due to many read calls, and many buffer reallocations) on most systems.

For desktop machines at this time (2017), I recommend a much larger READALL_CHUNK, perhaps #define READALL_CHUNK 2097152 (2 MiB).

Because the definition of READALL_CHUNK is guarded (i.e., it is defined only if it is at that point in the code still undefined), you can override the default value at compile time, by using (in most C compilers) -DREADALL_CHUNK=2097152 command-line option -- but do check your compiler options for defining a preprocessor macro using command-line options.

Beamer: How to show images as step-by-step images

I found a solution to my problem, by using the visble-command.


   \textbf{Some text}

Best way to center a <div> on a page vertically and horizontally?

Is the browser supports it, using translate is powerful.

position: absolute;
background-color: red;

width: 70%;     
height: 30%; 

/* The translate % is relative to the size of the div and not the container*/ 
/* 21.42% = ( (100%-70%/2) / 0.7 ) */
/* 116.666% = ( (100%-30%/2) / 0.3 ) */
transform: translate3d( 21.42%, 116.666%, 0);

How may I align text to the left and text to the right in the same line?

If you just want to change alignment of text just make a classes

.left {
text-align: left;

and span that class through the text

<span class='left'>aligned left</span>

/usr/bin/ld: cannot find

Add -L/opt/lib to your compiler parameters, this makes the compiler and linker search that path for in that folder.

How do I make a stored procedure in MS Access?

Access 2010 has both stored procedures, and also has table triggers. And, both features are available even when you not using a server (so, in 100% file based mode).

If you using SQL Server with Access, then of course the stored procedures are built using SQL Server and not Access.

For Access 2010, you open up the table (non-design view), and then choose the table tab. You see options there to create store procedures and table triggers.

For example:


Note that the stored procedure language is its own flavor just like Oracle or SQL Server (T-SQL). Here is example code to update an inventory of fruits as a result of an update in the fruit order table alt text

Keep in mind these are true engine-level table triggers. In fact if you open up that table with VB6, VB.NET, FoxPro or even modify the table on a computer WITHOUT Access having been installed, the procedural code and the trigger at the table level will execute. So, this is a new feature of the data engine jet (now called ACE) for Access 2010. As noted, this is procedural code that runs, not just a single statement.

How can I use a search engine to search for special characters? doesn't ignore special characters, at least if the whole string is between ""*222%23%22

Receive result from DialogFragment

Just to have it as one of the options (since no one mentioned it yet) - you could use an event bus like Otto. So in the dialog you do: AnswerAvailableEvent(42));

And have your caller (Activity or Fragment) subscribe to it:

@Subscribe public void answerAvailable(AnswerAvailableEvent event) {
   // TODO: React to the event somehow!

Resizing image in Java

If you have an java.awt.Image, rezising it doesn't require any additional libraries. Just do:

Image newImage = yourImage.getScaledInstance(newWidth, newHeight, Image.SCALE_DEFAULT);

Ovbiously, replace newWidth and newHeight with the dimensions of the specified image.
Notice the last parameter: it tells to the runtime the algorithm you want to use for resizing.

There are algorithms that produce a very precise result, however these take a large time to complete.
You can use any of the following algorithms:

See the Javadoc for more info.

What does the 'static' keyword do in a class?

It means that there is only one instance of "clock" in Hello, not one per each separate instance of the "Hello" class, or more-so, it means that there will be one commonly shared "clock" reference among all instances of the "Hello" class.

So if you were to do a "new Hello" anywhere in your code: A- in the first scenario (before the change, without using "static"), it would make a new clock every time a "new Hello" is called, but B- in the second scenario (after the change, using "static"), every "new Hello" instance would still share and use the initial and same "clock" reference first created.

Unless you needed "clock" somewhere outside of main, this would work just as well:

package hello;
public class Hello
    public static void main(String args[])
      Clock clock=new Clock();

How do I convert NSInteger to NSString datatype?

NSNumber may be good for you in this case.

NSString *inStr = [NSString stringWithFormat:@"%d", 
                    [NSNumber numberWithInteger:[month intValue]]];

html5 input for money/currency

var currencyInput = document.querySelector('input[type="currency"]')
var currency = 'USD' //

 // format inital value

// bind event listeners
currencyInput.addEventListener('focus', onFocus)
currencyInput.addEventListener('blur', onBlur)

function localStringToNumber( s ){
  return Number(String(s).replace(/[^0-9.-]+/g,""))

function onFocus(e){
  var value =; = value ? localStringToNumber(value) : ''

function onBlur(e){
  var value =

  var options = {
      maximumFractionDigits : 2,
      currency              : currency,
      style                 : "currency",
      currencyDisplay       : "symbol"
  } = value 
    ? localStringToNumber(value).toLocaleString(undefined, options)
    : ''
  padding: 10px;
  font: 20px Arial;
  width: 70%;
<input type='currency' value="123" placeholder='Type a number & click outside' />

How to print HTML content on click of a button, but not the page?

Here is a pure css version

.example-print {_x000D_
    display: none;_x000D_
@media print {_x000D_
   .example-screen {_x000D_
       display: none;_x000D_
    .example-print {_x000D_
       display: block;_x000D_
<div class="example-screen">You only see me in the browser</div>_x000D_
<div class="example-print">You only see me in the print</div>

How to get today's Date?

Code To Get Today's date in any specific Format

You can define the desired format in SimpleDateFormat instance to get the date in that specific formate

 DateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy");
        Calendar cal = Calendar.getInstance();
        Date date = cal.getTime();
        String todaysdate = dateFormat.format(date);
         System.out.println("Today's date : " + todaysdate);

Follow below links to see the valid date format combination.

CODE : To get x days ahead or Previous from Today's date, To get the past date or Future date.

For Example :

Today date : 11/27/2018

xdayFromTodaysDate = 2 to get date as 11/29/2018

xdayFromTodaysDate = -2 to get date as 11/25/2018

  public String getAniversaryDate(int xdayFromTodaysDate ){

        DateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy");
        Calendar cal = Calendar.getInstance();
        Date date = cal.getTime();
        date = cal.getTime();
        String aniversaryDate = dateFormat.format(date);"Today's date : " + todaysdate);
          return aniversaryDate;


CODE : To get x days ahead or Previous from a Given date

  public String getAniversaryDate(String givendate, int xdayFromTodaysDate ){

        Calendar cal = Calendar.getInstance();
        DateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy");
        try {
            Date date = dateFormat.parse(givendate);
            date = cal.getTime();
            String aniversaryDate = dateFormat.format(date);
  "aniversaryDate : " + aniversaryDate);
            return aniversaryDate;
        } catch (ParseException e) {
            return null;


Warning "Do not Access Superglobal $_POST Array Directly" on Netbeans 7.4 for PHP

Here is part of a line in my code that brought the warning up in NetBeans:

$page = (!empty($_GET['p'])) 

After much research and seeing how there are about a bazillion ways to filter this array, I found one that was simple. And my code works and NetBeans is happy:

$p = filter_input(INPUT_GET, 'p');
$page = (!empty($p))

How to use ClassLoader.getResources() correctly?

Here is code based on bestsss' answer:

    Enumeration<URL> en = getClass().getClassLoader().getResources(
    List<String> profiles = new ArrayList<>();
    while (en.hasMoreElements()) {
        URL url = en.nextElement();
        JarURLConnection urlcon = (JarURLConnection) (url.openConnection());
        try (JarFile jar = urlcon.getJarFile();) {
            Enumeration<JarEntry> entries = jar.entries();
            while (entries.hasMoreElements()) {
                String entry = entries.nextElement().getName();

Handle JSON Decode Error when nothing returned

If you don't mind importing the json module, then the best way to handle it is through json.JSONDecodeError (or json.decoder.JSONDecodeError as they are the same) as using default errors like ValueError could catch also other exceptions not necessarily connected to the json decode one.

from json.decoder import JSONDecodeError

    qByUser =
    qUserData = json.loads(qByUser).decode('utf-8')
    questionSubjs = qUserData["all"]["questions"]
except JSONDecodeError as e:
    # do whatever you want

//EDIT (Oct 2020):

As @Jacob Lee noted in the comment, there could be the basic common TypeError raised when the JSON object is not a str, bytes, or bytearray. Your question is about JSONDecodeError, but still it is worth mentioning here as a note; to handle also this situation, but differentiate between different issues, the following could be used:

from json.decoder import JSONDecodeError

    qByUser =
    qUserData = json.loads(qByUser).decode('utf-8')
    questionSubjs = qUserData["all"]["questions"]
except JSONDecodeError as e:
    # do whatever you want
except TypeError as e:
    # do whatever you want in this case

JavaScript implementation of Gzip

You can use a 1 pixel per 1 pixel Java applet embedded in the page and use that for compression.

It's not JavaScript and the clients will need a Java runtime but it will do what you need.

How do I change the background of a Frame in Tkinter?

The root of the problem is that you are unknowingly using the Frame class from the ttk package rather than from the tkinter package. The one from ttk does not support the background option.

This is the main reason why you shouldn't do global imports -- you can overwrite the definition of classes and commands.

I recommend doing imports like this:

import tkinter as tk
import ttk

Then you prefix the widgets with either tk or ttk :

f1 = tk.Frame(..., bg=..., fg=...)
f2 = ttk.Frame(..., style=...)

It then becomes instantly obvious which widget you are using, at the expense of just a tiny bit more typing. If you had done this, this error in your code would never have happened.

Bootstrap button - remove outline on Chrome OS X

Search and replace

outline: thin dotted;
outline: 5px auto -webkit-focus-ring-color;

Replace to

outline: 0;

How to change font size on part of the page in LaTeX?

use \alltt environment instead. Then set size using the same commands as outside verbatim environment.

TypeError: 'int' object is not callable

As mentioned you might have a variable named round (of type int) in your code and removing that should get rid of the error. For Jupyter notebooks however, simply clearing a cell or deleting it might not take the variable out of scope. In such a case, you can restart your notebook to start afresh after deleting the variable.

Does a `+` in a URL scheme/host/path represent a space?

  • Percent encoding in the path section of a URL is expected to be decoded, but
  • any + characters in the path component is expected to be treated literally.

To be explicit: + is only a special character in the query component.

How to get key names from JSON using jq

To print keys on one line as csv:

echo '{"b":"2","a":"1"}' | jq -r 'keys | [ .[] | tostring ] | @csv'



For csv completeness ... to print values on one line as csv:

echo '{"b":"2","a":"1"}' | jq -rS . | jq -r '. | [ .[] | tostring ] | @csv'



UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2


# encoding=utf8

Try This to starting of python file

System.BadImageFormatException: Could not load file or assembly (from installutil.exe)

In the case of having this message in live tests, but not in unit tests, it's because selected assemblies are copied on the fly to $(SolutionDir)\.vs\$(SolutionName)\lut\0\0\x64\Debug\. But sometime few assemblies can be not selected, eg., VC++ dlls in case of interop c++/c# projects.

Post-build xcopy won't correct the problem, because the copied file will be erased by the live test engine.

The only workaround to date (28 dec 2018), is to avoid Live tests, and do everything in unit tests with the attribute [TestCategory("SkipWhenLiveUnitTesting")] applied to the test class or the test method.

This bug is seen in any Visual Studio 2017 up to 15.9.4, and needs to be addressed by the Visual Studio team.

Download file of any type in Asp.Net MVC using FileResult?

Phil Haack has a nice article where he created a Custom File Download Action Result class. You only need to specify the virtual path of the file and the name to be saved as.

I used it once and here's my code.

        public ActionResult Download(int fileID)
            Data.LinqToSql.File file = _fileService.GetByID(fileID);

            return new DownloadResult { VirtualPath = GetVirtualPath(file.Path),
                                        FileDownloadName = file.Name };

In my example i was storing the physical path of the files so i used this helper method -that i found somewhere i can't remember- to convert it to a virtual path

        private string GetVirtualPath(string physicalPath)
            string rootpath = Server.MapPath("~/");

            physicalPath = physicalPath.Replace(rootpath, "");
            physicalPath = physicalPath.Replace("\\", "/");

            return "~/" + physicalPath;

Here's the full class as taken from Phill Haack's article

public class DownloadResult : ActionResult {

    public DownloadResult() {}

    public DownloadResult(string virtualPath) {
        this.VirtualPath = virtualPath;

    public string VirtualPath {

    public string FileDownloadName {

    public override void ExecuteResult(ControllerContext context) {
        if (!String.IsNullOrEmpty(FileDownloadName)) {
            "attachment; filename=" + this.FileDownloadName)

        string filePath = context.HttpContext.Server.MapPath(this.VirtualPath);

How do I get the raw request body from the Request.Content object using .net 4 api endpoint

For other future users who do not want to make their controllers asynchronous, or cannot access the HttpContext, or are using dotnet core (this answer is the first I found on Google trying to do this), the following worked for me:

public IActionResult Put(int pathId, int subPathId, [FromBody] myViewModel viewModel)

    var body = new StreamReader(Request.Body);
    //The modelbinder has already read the stream and need to reset the stream index
    body.BaseStream.Seek(0, SeekOrigin.Begin); 
    var requestBody = body.ReadToEnd();
    //etc, we use this for an audit trail

Expected block end YAML error

In my case, the error occured when I tried to pass a variable which was looking like a bytes-object (b"xxxx") but was actually a string.

You can convert the string to a real bytes object like this:

foo.strip('b"').replace("\\n", "\n").encode()

React.js: How to append a component on click?

Don't use jQuery to manipulate the DOM when you're using React. React components should render a representation of what they should look like given a certain state; what DOM that translates to is taken care of by React itself.

What you want to do is store the "state which determines what gets rendered" higher up the chain, and pass it down. If you are rendering n children, that state should be "owned" by whatever contains your component. eg:

class AppComponent extends React.Component {
  state = {
    numChildren: 0

  render () {
    const children = [];

    for (var i = 0; i < this.state.numChildren; i += 1) {
      children.push(<ChildComponent key={i} number={i} />);

    return (
      <ParentComponent addChild={this.onAddChild}>

  onAddChild = () => {
      numChildren: this.state.numChildren + 1

const ParentComponent = props => (
  <div className="card calculator">
    <p><a href="#" onClick={props.addChild}>Add Another Child Component</a></p>
    <div id="children-pane">

const ChildComponent = props => <div>{"I am child " + props.number}</div>;

Best HTTP Authorization header type for JWT

Short answer

The Bearer authentication scheme is what you are looking for.

Long answer

Is it related to bears?

Errr... No :)

According to the Oxford Dictionaries, here's the definition of bearer:

bearer /'b??r?/

  1. A person or thing that carries or holds something.

  2. A person who presents a cheque or other order to pay money.

The first definition includes the following synonyms: messenger, agent, conveyor, emissary, carrier, provider.

And here's the definition of bearer token according to the RFC 6750:

1.2. Terminology

Bearer Token

A security token with the property that any party in possession of the token (a "bearer") can use the token in any way that any other party in possession of it can. Using a bearer token does not require a bearer to prove possession of cryptographic key material (proof-of-possession).

The Bearer authentication scheme is registered in IANA and originally defined in the RFC 6750 for the OAuth 2.0 authorization framework, but nothing stops you from using the Bearer scheme for access tokens in applications that don't use OAuth 2.0.

Stick to the standards as much as you can and don't create your own authentication schemes.

An access token must be sent in the Authorization request header using the Bearer authentication scheme:

2.1. Authorization Request Header Field

When sending the access token in the Authorization request header field defined by HTTP/1.1, the client uses the Bearer authentication scheme to transmit the access token.

For example:

GET /resource HTTP/1.1
Authorization: Bearer mF_9.B5f-4.1JqM


Clients SHOULD make authenticated requests with a bearer token using the Authorization request header field with the Bearer HTTP authorization scheme. [...]

In case of invalid or missing token, the Bearer scheme should be included in the WWW-Authenticate response header:

3. The WWW-Authenticate Response Header Field

If the protected resource request does not include authentication credentials or does not contain an access token that enables access to the protected resource, the resource server MUST include the HTTP WWW-Authenticate response header field [...].

All challenges defined by this specification MUST use the auth-scheme value Bearer. This scheme MUST be followed by one or more auth-param values. [...].

For example, in response to a protected resource request without authentication:

HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer realm="example"

And in response to a protected resource request with an authentication attempt using an expired access token:

HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer realm="example",
                         error_description="The access token expired"

Remove a git commit which has not been pushed

IF you have NOT pushed your changes to remote

git reset HEAD~1

Check if the working copy is clean by git status.

ELSE you have pushed your changes to remote

git revert HEAD

This command will revert/remove the local commits/change and then you can push

Find Oracle JDBC driver in Maven repository


  • Please do following settings to resolve the error

This repository needs to be enable for finding Oracle dependecies (this setting needs to be done in Buildconfig.groovy grails.project.dependency.resolver = "ivy" // or ivy

Also use following setting for compile time Oracle driver download

runtime ""

This should solve your issue for not finding the Oracle driver for grails application

jQuery window scroll event does not fire up

My issue was I had this code in my css

body {
    height: 100%;
    width: 100%;
    overflow: auto;

Once I removed it, the scroll event on window fired again

Constructor of an abstract class in C#

It's a way to enforce a set of invariants of the abstract class. That is, no matter what the subclass does, you want to make sure some things are always true of the base class... example:

abstract class Foo
    public DateTime TimeCreated {get; private set;}

    protected Foo()
         this.TimeCreated = DateTime.Now;

abstract class Bar : Foo
    public Bar() : base() //Bar's constructor's must call Foo's parameterless constructor.
    { }

Don't think of a constructor as the dual of the new operator. The constructor's only purpose is to ensure that you have an object in a valid state before you start using it. It just happens to be that we usually call it through a new operator.

Code signing is required for product type Unit Test Bundle in SDK iOS 8.0

I was getting this error when running xcodebuild from commandline for integration tests on my work's CI. I managed to get it working by setting the project level setting to codesign. For some reason the target setting was being ignored and it reverted to the project's setting.

How to clear/remove observable bindings in Knockout.js?

Instead of using KO's internal functions and dealing with JQuery's blanket event handler removal, a much better idea is using with or template bindings. When you do this, ko re-creates that part of DOM and so it automatically gets cleaned. This is also recommended way, see here:

Pandas convert string to int

You need add parameter errors='coerce' to function to_numeric:

ID = pd.to_numeric(ID, errors='coerce')

If ID is column:

df.ID = pd.to_numeric(df.ID, errors='coerce')

but non numeric are converted to NaN, so all values are float.

For int need convert NaN to some value e.g. 0 and then cast to int:

df.ID = pd.to_numeric(df.ID, errors='coerce').fillna(0).astype(np.int64)


df = pd.DataFrame({'ID':['4806105017087','4806105017087','CN414149']})
print (df)
0  4806105017087
1  4806105017087
2       CN414149

print (pd.to_numeric(df.ID, errors='coerce'))
0    4.806105e+12
1    4.806105e+12
2             NaN
Name: ID, dtype: float64

df.ID = pd.to_numeric(df.ID, errors='coerce').fillna(0).astype(np.int64)
print (df)
0  4806105017087
1  4806105017087
2              0

EDIT: If use pandas 0.25+ then is possible use integer_na:

df.ID = pd.to_numeric(df.ID, errors='coerce').astype('Int64')
print (df)
0  4806105017087
1  4806105017087
2            NaN

How can I compare two strings in java and define which of them is smaller than the other alphabetically?

You can use


If str1 is lexicographically less than str2, a negative number will be returned, 0 if equal or a positive number if str1 is greater.


"a".compareTo("b"); // returns a negative number, here -1
"a".compareTo("a"); // returns  0
"b".compareTo("a"); // returns a positive number, here 1
"b".compareTo(null); // throws java.lang.NullPointerException

How can I get client information such as OS and browser

You cannot reliably get this information. The basis of several answers provided here is to examine the User-Agent header of the HTTP request. However, there is no way to know if the information in the User-Agent header is truthful. The client sending the request can write anything in that header. So its content can be spoofed, or not sent at all.

convert a list of objects from one type to another using lambda expression

Try the following

var targetList = origList
  .Select(x => new TargetType() { SomeValue = x.SomeValue })

This is using a combination of Lambdas and LINQ to achieve the solution. The Select function is a projection style method which will apply the passed in delegate (or lambda in this case) to every value in the original collection. The result will be returned in a new IEnumerable<TargetType>. The .ToList call is an extension method which will convert this IEnumerable<TargetType> into a List<TargetType>.

Importing a GitHub project into Eclipse

unanswered core problem persists:

My working directory is now c:\users\projectname.git So then I try to import the project using the eclipse "import" option. When I try to import selecting the option "Use the new projects wizard" the source code is not imported, if I import selecting the option "Import as general project" the source code is imported but the created project created by Eclipse is not a java project. When selecting the option "Use the new projects wizard" and creating a new java project using the wizard should'nt the code be automatically imported ?

Yes it should.

It's a bug. Reported here.

Here is a workaround:

  • Import as general project

  • Notice the imported data is no valid Eclipse project (no build path available)

  • Open the .project xml file in the project folder in Eclipse. If you can't see this file, see How can I get Eclipse to show .* files?.

  • Go to source tab

  • Search for <natures></natures> and change it to <natures><nature>org.eclipse.jdt.core.javanature</nature></natures> and save the file

    (idea comes from here)

  • Right click the src folder, go to Build Path... and click Use as Source Folder

After that, you should be able to run & debug the project, and also use team actions via right-click in the package explorer.

If you still have troubles running the project (something like "main class not found"), make sure the <buildSpec> inside the .project file is set (as described here):


Cannot connect to the Docker daemon on macOS

on OSX assure you have launched the Docker application before issuing

docker ps

or docker build ... etc ... yes it seems strange and somewhat misleading that issuing

docker --version

gives version even though the docker daemon is not running ... ditto for those other version cmds ... I just encountered exactly the same symptoms ... this behavior on OSX is different from on linux

Using %f with strftime() in Python to get microseconds

You can use datetime's strftime function to get this. The problem is that time's strftime accepts a timetuple that does not carry microsecond information.

from datetime import datetime"%H:%M:%S.%f")

Should do the trick!

How do I declare class-level properties in Objective-C?

properties have a specific meaning in Objective-C, but I think you mean something that's equivalent to a static variable? E.g. only one instance for all types of Foo?

To declare class functions in Objective-C you use the + prefix instead of - so your implementation would look something like:

// Foo.h
@interface Foo {

+ (NSDictionary *)dictionary;

// Foo.m
+ (NSDictionary *)dictionary {
  static NSDictionary *fooDict = nil;
  if (fooDict == nil) {
    // create dict
  return fooDict;

VBA Convert String to Date

Looks like it could be throwing the error on the empty data row, have you tried to just make sure itemDate isn't empty before you run the CDate() function? I think this might be your problem.

SQL how to increase or decrease one for a int column in one command

UPDATE Orders Order
SET Order.Quantity =  Order.Quantity - 1
WHERE SomeCondition(Order)

As far as I know there is no build-in support for INSERT-OR-UPDATE in SQL. I suggest to create a stored procedure or use a conditional query to achiev this. Here you can find a collection of solutions for different databases.

SQL Group By with an Order By

In all versions of MySQL, simply alias the aggregate in the SELECT list, and order by the alias:

SELECT COUNT(id) AS theCount, `Tag` from `images-tags`

Oracle SQL - DATE greater than statement

you have to use the To_Date() function to convert the string to date !

.gitignore file for java eclipse project

put .gitignore in your main catalog

git status (you will see which files you can commit)
git add -A
git commit -m "message"
git push

java.lang.Exception: No runnable methods exception in running JUnits

I faced the same with my parent test setUp class which has annotation @RunWith(SpringRunner.class) and was being extended by other testClasses. As there was not test in the setUpclass , and Junit was trying to find one due to annotation @RunWith(SpringRunner.class) ,it didn't find one and threw exception

No runnable methods exception in running JUnits

I made my parent class as abstract and it worked like a charm .

I took help from here . Thanks for help @froh42.

Selecting one row from MySQL using mysql_* API

What you should get as output with this code is:

Array ()

... this is exactly how you get just one row, you don't need a while loop. Are you sure you're printing the right variable?

Is there a way to create interfaces in ES6 / Node 4?

This is my solution for the problem. You can 'implement' multiple interfaces by overriding one Interface with another.

class MyInterface {
    // Declare your JS doc in the Interface to make it acceable while writing the Class and for later inheritance
     * Gives the sum of the given Numbers
     * @param {Number} a The first Number
     * @param {Number} b The second Number
     * @return {Number} The sum of the Numbers
    sum(a, b) { this._WARNING('sum(a, b)'); }

    // delcare a warning generator to notice if a method of the interface is not overridden
    // Needs the function name of the Interface method or any String that gives you a hint ;)
    _WARNING(fName='unknown method') {
        console.warn('WARNING! Function "'+fName+'" is not overridden in ';

class MultipleInterfaces extends MyInterface {
    // this is used for "implement" multiple Interfaces at once
     * Gives the square of the given Number
     * @param {Number} a The Number
     * @return {Number} The square of the Numbers
    square(a) { this._WARNING('square(a)'); }

class MyCorrectUsedClass extends MyInterface {
    // You can easy use the JS doc declared in the interface
    /** @inheritdoc */
    sum(a, b) {
        return a+b;
class MyIncorrectUsedClass extends MyInterface {
    // not overriding the method sum(a, b)

class MyMultipleInterfacesClass extends MultipleInterfaces {
    // nothing overriden to show, that it still works

let working = new MyCorrectUsedClass();

let notWorking = new MyIncorrectUsedClass();

let multipleInterfacesInstance = new MyMultipleInterfacesClass();


console.log('working.sum(1, 2) =', working.sum(1, 2));
// output: 'working.sum(1, 2) = 3'

console.log('notWorking.sum(1, 2) =', notWorking.sum(1, 2));
// output: 'notWorking.sum(1, 2) = undefined'
// but also sends a warn to the console with 'WARNING! Function "sum(a, b)" is not overridden in MyIncorrectUsedClass'

console.log('multipleInterfacesInstance.sum(1, 2) =', multipleInterfacesInstance.sum(1, 2));
// output: 'multipleInterfacesInstance.sum(1, 2) = undefined'
// console warn: 'WARNING! Function "sum(a, b)" is not overridden in MyMultipleInterfacesClass'

console.log('multipleInterfacesInstance.square(2) =', multipleInterfacesInstance.square(2));
// output: 'multipleInterfacesInstance.square(2) = undefined'
// console warn: 'WARNING! Function "square(a)" is not overridden in MyMultipleInterfacesClass'


I improved the code so you now can simply use implement(baseClass, interface1, interface2, ...) in the extend.

* Implements any number of interfaces to a given class.
* @param cls The class you want to use
* @param interfaces Any amount of interfaces separated by comma
* @return The class cls exteded with all methods of all implemented interfaces
function implement(cls, ...interfaces) {
    let clsPrototype = Object.getPrototypeOf(cls).prototype;
    for (let i = 0; i < interfaces.length; i++) {
        let proto = interfaces[i].prototype;
        for (let methodName of Object.getOwnPropertyNames(proto)) {
            if (methodName!== 'constructor')
                if (typeof proto[methodName] === 'function')
                    if (!clsPrototype[methodName]) {
                        console.warn('WARNING! "'+methodName+'" of Interface "'+interfaces[i].name+'" is not declared in class "''"');
                        clsPrototype[methodName] = proto[methodName];
    return cls;

// Basic Interface to warn, whenever an not overridden method is used
class MyBaseInterface {
    // declare a warning generator to notice if a method of the interface is not overridden
    // Needs the function name of the Interface method or any String that gives you a hint ;)
    _WARNING(fName='unknown method') {
        console.warn('WARNING! Function "'+fName+'" is not overridden in ';

// create a custom class
/* This is the simplest example but you could also use
*   class MyCustomClass1 extends implement(MyBaseInterface) {
*       foo() {return 66;}
*   }
class MyCustomClass1 extends MyBaseInterface {
    foo() {return 66;}

// create a custom interface
class MyCustomInterface1 {
     // Declare your JS doc in the Interface to make it acceable while writing the Class and for later inheritance

     * Gives the sum of the given Numbers
     * @param {Number} a The first Number
     * @param {Number} b The second Number
     * @return {Number} The sum of the Numbers
    sum(a, b) { this._WARNING('sum(a, b)'); }

// and another custom interface
class MyCustomInterface2 {
     * Gives the square of the given Number
     * @param {Number} a The Number
     * @return {Number} The square of the Numbers
    square(a) { this._WARNING('square(a)'); }

// Extend your custom class even more and implement the custom interfaces
class AllInterfacesImplemented extends implement(MyCustomClass1, MyCustomInterface1, MyCustomInterface2) {
    * @inheritdoc
    sum(a, b) { return a+b; }

    * Multiplies two Numbers
    * @param {Number} a The first Number
    * @param {Number} b The second Number
    * @return {Number}
    multiply(a, b) {return a*b;}


let x = new AllInterfacesImplemented();

console.log(" =",;
//output: ' = 66'

console.log("x.square(2) =", x.square(2));
// output: 'x.square(2) = undefined
// console warn: 'WARNING! Function "square(a)" is not overridden in AllInterfacesImplemented'

console.log("x.sum(1, 2) =", x.sum(1, 2));
// output: 'x.sum(1, 2) = 3'

console.log("x.multiply(4, 5) =", x.multiply(4, 5));
// output: 'x.multiply(4, 5) = 20'

Why do I always get the same sequence of random numbers with rand()?

Seeding the rand()

void srand (unsigned int seed)

This function establishes seed as the seed for a new series of pseudo-random numbers. If you call rand before a seed has been established with srand, it uses the value 1 as a default seed.

To produce a different pseudo-random series each time your program is run, do srand (time (0))

How can I remove duplicate rows?

I prefer the subquery\having count(*) > 1 solution to the inner join because I found it easier to read and it was very easy to turn into a SELECT statement to verify what would be deleted before you run it.

--DELETE FROM table1 
--WHERE id IN ( 
     SELECT MIN(id) FROM table1 
     GROUP BY col1, col2, col3 
     -- could add a WHERE clause here to further filter
     HAVING count(*) > 1

Change remote repository credentials (authentication) on Intellij IDEA 14

This worked for me on Intellij 12:

Open settings -> passwords, select "Do not remember passwords" and apply/ok.

Do your VCS fetch/update/push/whatever and it should ask you for a password.

Check remember password and OK, it should do the VCS thing correctly.

Go back to settings -> passwords and switch it back to "Remember on disk", then apply/ok.

Select all DIV text with single mouse click

Easily achieved with the css property user-select set to all. Like this:

div.anyClass {_x000D_
  user-select: all;_x000D_

Disable button after click in JQuery


jQuery version would be something like below:

function load(recieving_id){
    $('#roommate_but').prop('disabled', true);
    $.get('' + recieving_id, function(data) {

How to redirect to Login page when Session is expired in Java web application?

i found this posible solution:

public void logout() {
    ExternalContext ctx = FacesContext.getCurrentInstance().getExternalContext();
    String ctxPath = ((ServletContext) ctx.getContext()).getContextPath();
    try {
        //Use the context of JSF for invalidate the session,
        //without servlet
        ((HttpSession) ctx.getSession(false)).invalidate();
        //redirect with JSF context.
        ctx.redirect(ctxPath + "absolute/path/index.jsp");
    } catch (IOException ex) {

How do I quickly rename a MySQL database (change schema name)?

The simple way

Change to the database directory:

cd /var/lib/mysql/

Shut down MySQL... This is important!

/etc/init.d/mysql stop

Okay, this way doesn't work for InnoDB or BDB-Databases.

Rename database:

mv old-name new-name

...or the table...

cd database/

mv old-name.frm new-name.frm

mv old-name.MYD new-name.MYD

mv old-name.MYI new-name.MYI

Restart MySQL

/etc/init.d/mysql start


OK, this way doesn't work with InnoDB or BDB databases. In this case you have to dump the database and re-import it.

method in class cannot be applied to given types

generateNumbers() expects a parameter and you aren't passing one in!

generateNumbers() also returns after it has set the first random number - seems to be some confusion about what it is trying to do.

SQL Server returns error "Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'." in Windows application

Try setting "Integrated Security=False" in the connection string.

<add name="YourContext" connectionString="Data Source=<IPAddressOfDBServer>;Initial Catalog=<DBName>;USER ID=<youruserid>;Password=<yourpassword>;Integrated Security=False;MultipleActiveResultSets=True" providerName="System.Data.SqlClient"/>

How can I check whether Google Maps is fully loaded?

Where the variable map is an object of type GMap2:

    GEvent.addListener(map, "tilesloaded", function() {
      console.log("Map is fully loaded");

Errno 10060] A connection attempt failed because the connected party did not properly respond after a period of time

As ping works, but telnetto port 80 does not, the HTTP port 80 is closed on your machine. I assume that your browser's HTTP connection goes through a proxy (as browsing works, how else would you read stackoverflow?). You need to add some code to your python program, that handles the proxy, like described here:

Using an HTTP PROXY - Python

Convert Current date to integer

Probably You can not, Long is higher datatype than Integer.

or this link might help you

Scroll to bottom of div?

Here's what I use on my site:

var objDiv = document.getElementById("your_div");
objDiv.scrollTop = objDiv.scrollHeight;

How can I remove file extension from a website address?

The problem with creating a directory and keeping index.php in it is that

  1. your links with menu will stop functioning
  2. There will be way too many directories. For eg, there will be a seperate directory for each and every question here on stackoverflow

The solutions are 1. MOD REWRITE (as suggested above) 2. use a php code to dynamically include other files in index file. Read a bit more abt it here

Clear the form field after successful submission of php form

// This file is PHP.
    if ($_POST['submit']) {
        $firstname = $_POST['firstname'];
        $lastname = $_POST['lastname'];
        $email = $_POST['email'];
        $password = $_POST['password'];
        $confirmpassword = $_POST['confirmpassword'];
        $strtadd1 = $_POST['strtadd1'];
        $strtadd2 = $_POST['strtadd2'];
        $city = $_POST['city'];
        $country = $_POST['country'];
        $success = '';

        // Upon Success.
        if ($firstname != '' && $lastname != '' && $email != '' && $password != '' && $confirmpassword != '' && $strtadd1 != '' && $strtadd2 != '' && $city != '' && $country != '') {
            // Change $success variable from an empty string.
            $success = 'success';

            // Insert whatever you want to do upon success.

        } else {
            // Upon Failure.
            echo '<p class="error">Fill in all fields.</p>';

            // Set $success variable to an empty string.
            $success = '';
<form method="POST" action="#">
    <label class="w">Plan :</label>
    <select autofocus="" name="plan" required="required">
        <option value="">Select One</option>
        <option value="FREE Account">FREE Account</option>
        <option value="Premium Account Monthly">Premium Account Monthly</option>
        <option value="Premium Account Yearly">Premium Account Yearly</option>
    <label class="w">First Name :</label><input name="firstname" type="text" placeholder="First Name" required="required" value="<?php if (isset($firstname) && $success == '') {echo $firstname;} ?>"><br>
    <label class="w">Last Name :</label><input name="lastname" type="text" placeholder="Last Name" required="required" value="<?php if (isset($lastname) && $success == '') {echo $lastname;} ?>"><br>
    <label class="w">E-mail ID :</label><input name="email" type="email"  placeholder="Enter Email" required="required" value="<?php if (isset($email) && $success == '') {echo $email;} ?>"><br>
    <label class="w">Password :</label><input name="password" type="password" placeholder="********" required="required" value="<?php if (isset($password) && $success == '') {echo $password;} ?>"><br>
    <label class="w">Re-Enter Password :</label><input name="confirmpassword" type="password" placeholder="********" required="required" value="<?php if (isset($confirmpassword) && $success == '') {echo $confirmpassword;} ?>"><br>
    <label class="w">Street Address 1 :</label><input name="strtadd1" type="text" placeholder="street address first" required="required" value="<?php if (isset($strtadd1) && $success == '') {echo $strtadd1;} ?>"><br>
    <label class="w">Street Address 2 :</label><input name="strtadd2" type="text" placeholder="street address second"  value="<?php if (isset($strtadd2) && $success == '') {echo $strtadd2;} ?>"><br>
    <label class="w">City :</label><input name="city" type="text" placeholder="City" required="required" value="<?php if (isset($city) && $success == '') {echo $city;} ?>"><br>
    <label class="w">Country :</label><select autofocus="" id="a1_txtBox1" name="country" required="required" placeholder="select one" value="<?php if (isset($country) && $success == '') {echo $country;} ?>">
    <input type="submit" name="submit">

Use value="<?php if (isset($firstname) && $success == '') {echo $firstname;} ?>"
You'll then have to create the $success variable--as I did in my example.

Show all current locks from get_lock

From MySQL 5.7 onwards, this is possible, but requires first enabling the mdl instrument in the performance_schema.setup_instruments table. You can do this temporarily (until the server is next restarted) by running:

UPDATE performance_schema.setup_instruments
SET enabled = 'YES'
WHERE name = 'wait/lock/metadata/sql/mdl';

Or permanently, by adding the following incantation to the [mysqld] section of your my.cnf file (or whatever config files MySQL reads from on your installation):

performance_schema_instrument = 'wait/lock/metadata/sql/mdl=ON'

(Naturally, MySQL will need to be restarted to make the config change take effect if you take the latter approach.)

Locks you take out after the mdl instrument has been enabled can be seen by running a SELECT against the performance_schema.metadata_locks table. As noted in the docs, GET_LOCK locks have an OBJECT_TYPE of 'USER LEVEL LOCK', so we can filter our query down to them with a WHERE clause:

mysql> SELECT GET_LOCK('foobarbaz', -1);
| GET_LOCK('foobarbaz', -1) |
|                         1 |
1 row in set (0.00 sec)

mysql> SELECT * FROM performance_schema.metadata_locks 
    -> \G
*************************** 1. row ***************************
          OBJECT_NAME: foobarbaz
OBJECT_INSTANCE_BEGIN: 139872119610944
       OWNER_EVENT_ID: 3
1 row in set (0.00 sec)


The meanings of the columns in this result are mostly adequately documented at, but one point of confusion is worth noting: the OWNER_THREAD_ID column does not contain the connection ID (like would be shown in the PROCESSLIST or returned by CONNECTION_ID()) of the thread that holds the lock. Confusingly, the term "thread ID" is sometimes used as a synonym of "connection ID" in the MySQL documentation, but this is not one of those times. If you want to determine the connection ID of the connection that holds a lock (for instance, in order to kill that connection with KILL), you'll need to look up the PROCESSLIST_ID that corresponds to the THREAD_ID in the performance_schema.threads table. For instance, to kill the connection that was holding my lock above...

mysql> SELECT OWNER_THREAD_ID FROM performance_schema.metadata_locks
    -> AND OBJECT_NAME='foobarbaz';
|              35 |
1 row in set (0.00 sec)

mysql> SELECT PROCESSLIST_ID FROM performance_schema.threads
    -> WHERE THREAD_ID=35;
|             10 |
1 row in set (0.00 sec)

mysql> KILL 10;
Query OK, 0 rows affected (0.00 sec)

Routing with multiple Get methods in ASP.NET Web API

I have two get methods with same or no parameters

public IHttpActionResult FirstList()

public IHttpActionResult SecondList()

Just define custom routes in AppStart=>WebApiConfig.cs => under register method

       name: "GetFirstList",
       routeTemplate: "api/Controllername/FirstList"          
       name: "GetSecondList",
       routeTemplate: "api/Controllername/SecondList"          

extract digits in a simple way from a python string

Without using regex, you can just do:

def get_num(x):
    return int(''.join(ele for ele in x if ele.isdigit()))


>>> get_num(x)
>>> get_num(y)
>>> get_num(banana)
>>> get_num(orange)


Answering the follow up question.

If we know that the only period in a given string is the decimal point, extracting a float is quite easy:

def get_num(x):
    return float(''.join(ele for ele in x if ele.isdigit() or ele == '.'))


>>> get_num('dfgd 45.678fjfjf')

How to detect a route change in Angular?

In Angular 8 you should do like Event) => {})


import { Component } from '@angular/core'; 
import { Router, Event } from '@angular/router';
import { NavigationStart, NavigationError, NavigationEnd } from '@angular/router';

    selector: 'app-root',
    template: `<router-outlet></router-outlet>`
export class AppComponent {

    constructor(private router: Router) {
        //Router subscriber Event) => {
            if (event instanceof NavigationStart) {
                //do something on start activity

            if (event instanceof NavigationError) {
                // Handle error

            if (event instanceof NavigationEnd) {
                //do something on end activity

How do I write a method to calculate total cost for all items in an array?

In your for loop you need to multiply the units * price. That gives you the total for that particular item. Also in the for loop you should add that to a counter that keeps track of the grand total. Your code would look something like

float total;
total += theItem.getUnits() * theItem.getPrice();

total should be scoped so it's accessible from within main unless you want to pass it around between function calls. Then you can either just print out the total or create a method that prints it out for you.

MVC Return Partial View as JSON

You can extract the html string from the PartialViewResult object, similar to the answer to this thread:

Render a view as a string

PartialViewResult and ViewResult both derive from ViewResultBase, so the same method should work on both.

Using the code from the thread above, you would be able to use:

public ActionResult ReturnSpecialJsonIfInvalid(AwesomenessModel model)
    if (ModelState.IsValid)
            return PartialView("NotEvil", model);
        return View(model)
        return Json(new { error = true, message = RenderViewToString(PartialView("Evil", model))});
    return View(model);

How do you share constants in NodeJS modules?

import and export (prob need something like babel as of 2018 to use import)


export const BLUE = 'BLUE'
export const RED = 'RED'


import * as types from './types.js'

const MyApp = () => {
  let colour = types.RED

Disable a textbox using CSS

**just copy paste this code and run you can see the textbox disabled **

<html xmlns="">
<head><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Untitled Document</title> 

       .container input{float:left;width:200px;height:25px;}
      <div class="container">
       <input type="text" value="[email protected]" />
       <div class="overlay">

PSEXEC, access denied errors

I had a case where AV was quarantining Psexec - had to disable On-access scanning

Filtering DataSet

The above were really close. Here's my solution:

Private Sub getDsClone(ByRef inClone As DataSet, ByVal matchStr As String, ByRef outClone As DataSet)
    Dim i As Integer

    outClone = inClone.Clone
    Dim dv As DataView = inClone.Tables(0).DefaultView
    dv.RowFilter = matchStr
    Dim dt As New DataTable
    dt = dv.ToTable
    For i = 0 To dv.Count - 1
End Sub

Method List in Visual Studio Code

Visual Studio Code market place has a very nice extension named Go To Method for navigating only methods in a code file.

Hit Ctrl+Shift+P and type the install extensions and press enter

enter image description here

Now type Add to method in search box of extensions market place and press enter.

enter image description here

Click install to install the extension.

Last step is to bind a keyboard shortcut to the command workbench.action.gotoMethod to make it a real productivity thing for a developer.