Programs & Examples On #Qml

QML (Qt Modeling Language) is a declarative language that allows user interfaces to be described in terms of their visual components and how they interact and relate with one another. It is a highly readable language, JSON-like syntax with support for imperative JavaScript expressions combined with dynamic property bindings. It can be used to build fluid animated user interfaces that can be connected to any backend C++ libraries.

What is the command for cut copy paste a file from one directory to other directory

E:>move "blogger code.txt" d:/"blogger code.txt"

    1 file(s) moved.

"blogger code.txt" is a file name

The file move from E: drive to D: drive

What's the difference between using "let" and "var"?

let vs var. It's all about scope.

var variables are global and can be accessed basically everywhere, while let variables are not global and only exist until a closing parenthesis kills them.

See my example below, and note how the lion (let) variable acts differently in the two console.logs; it becomes out of scope in the 2nd console.log.

var cat = "cat";
let dog = "dog";

var animals = () => {
    var giraffe = "giraffe";
    let lion = "lion";

    console.log(cat);  //will print 'cat'.
    console.log(dog);  //will print 'dog', because dog was declared outside this function (like var cat).

    console.log(giraffe); //will print 'giraffe'.
    console.log(lion); //will print 'lion', as lion is within scope.

console.log(giraffe); //will print 'giraffe', as giraffe is a global variable (var).
console.log(lion); //will print UNDEFINED, as lion is a 'let' variable and is now out of scope.

setInterval in a React app

Manage setInterval with React Hooks:

  const [seconds, setSeconds] = useState(0)

  const interval = useRef(null)

  useEffect(() => { if (seconds === 60) stopCounter() }, [seconds])

  const startCounter = () => interval.current = setInterval(() => {
    setSeconds(prevState => prevState + 1)
  }, 1000)

  const stopCounter = () => clearInterval(interval.current)

Java - Check Not Null/Empty else assign default value

I know the question is really old, but with generics one can add a more generalized method with will work for all types.

public static <T> T getValueOrDefault(T value, T defaultValue) {
    return value == null ? defaultValue : value;

Cannot enqueue Handshake after invoking quit

If you using the node-mysql module, just remove the .connect and .end. Just solved the problem myself. Apparently they pushed in unnecessary code in their last iteration that is also bugged. You don't need to connect if you have already ran the createConnection call

How to create an object property from a variable value in JavaScript?

You could just use this:

function createObject(propName, propValue){
    this[propName] = propValue;
var myObj1 = new createObject('string1','string2');

Anything you pass as the first parameter will be the property name, and the second parameter is the property value.

Entity framework code-first null foreign key

I recommend to read Microsoft guide for use Relationships, Navigation Properties and Foreign Keys in EF Code First, like this picture.

enter image description here

Guide link below:

How do I connect to mongodb with node.js (and authenticate)?

Slight typo with Chris' answer.

Db.authenticate(user, password, function({ // callback }));

should be

Db.authenticate(user, password, function(){ // callback } );

Also depending on your mongodb configuration, you may need to connect to admin and auth there first before going to a different database. This will be the case if you don't add a user to the database you're trying to access. Then you can auth via admin and then switch db and then read or write at will.

How to use both onclick and target="_blank"

onclick="'your_html', '_blank')"

"Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))"


Just looking at the message it sounds like one or more of the components that you reference, or one or more of their dependencies is not registered properly.

If you know which component it is you can use regsvr32.exe to register it, just open a command prompt, go to the directory where the component is and type regsvr32 filename.dll (assuming it's a dll), if it works, try to run the code again otherwise come back here with the error.

If you don't know which component it is, try re-installing/repairing the GIS software (I assume you've installed some GIS software that includes the component you're trying to use).

Add class to <html> with Javascript?


classList is supported since ie10:

Cache an HTTP 'Get' service response in AngularJS?

As AngularJS factories are singletons, you can simply store the result of the http request and retrieve it next time your service is injected into something.

angular.module('myApp', ['ngResource']).factory('myService',
  function($resource) {
    var cache = false;
    return {
      query: function() {
        if(!cache) {
          cache = $resource('').query();
        return cache;

Display Records From MySQL Database using JTable in Java

this is the easy way to do that you just need to download the jar file "rs2xml.jar" add it to your project and do that : 1- creat a connection 2- statment and resultset 3- creat a jtable 4- give the result set to DbUtils.resultSetToTableModel(rs) as define in this methode you well get your jtable so easy.

public void afficherAll(String tableName){
        String sql="select * from "+tableName;
        try {
        } catch (SQLException e) {
            // TODO Auto-generated catch block
             JOptionPane.showMessageDialog(null, e);

anaconda update all possible packages?

To update all possible packages I used conda update --update-all

It works!

json_encode function: special characters

Use the below function.

function utf8_converter($array)
    array_walk_recursive($array, function (&$item, $key) {
        if (!mb_detect_encoding($item, 'utf-8', true)) {
                $item = utf8_encode($item);

    return $array;

Copying PostgreSQL database to another server

Dump your database : pg_dump database_name_name > backup.sql

Import your database back: psql db_name < backup.sql

Facebook Callback appends '#_=_' to Return URL

With angular and angular ui router, you can fix this

    app.config(function ($stateProvider, $urlRouterProvider, $locationProvider) {

      // Make a trailing slash optional for all routes
      // - Note: You'll need to specify all urls with a trailing slash if you use this method.
      $urlRouterProvider.rule(function ($injector, $location) {
        Angular misbehaves when the URL contains a "#_=_" hash.

        From Facebook:
          Change in Session Redirect Behavior
          This week, we started adding a fragment #_=_ to the redirect_uri when this field is left blank.
          Please ensure that your app can handle this behavior.


        if ($location.hash() === '_=_'){

        var path = $location.url();

        // check to see if the path already has a slash where it should be
        if (path[path.length - 1] === '/' || path.indexOf('/?') > -1) {
        else if (path.indexOf('?') > -1) {
          $location.replace().path(path.replace('?', '/?'));
        else {
          $location.replace().path(path + '/');

      // etc ...

Bootstrap 3 Align Text To Bottom of Div

Here's another solution:


<div class="container">
    <div class="row">
        <div class="col-sm-6">
            <img src="//" alt="Logo" class="img-responsive"/>
        <div class="col-sm-6">
            <h3>Some Text</h3>


.row {
    display: table;

.row > div {
    float: none;
    display: table-cell;

Prevent BODY from scrolling when a modal is opened

Most of the pieces are here, but I don't see any answer that puts it all together.

The problem is threefold.

(1) prevent the scroll of the underlying page

$('body').css('overflow', 'hidden')

(2) and remove the scroll bar

var handler = function (e) { e.preventDefault() }
$('.modal').bind('mousewheel touchmove', handler)

(3) clean up when the modal is dismissed

$('.modal').unbind('mousewheel touchmove', handler)
$('body').css('overflow', '')

If the modal is not full-screen then apply the .modal bindings to a full screen overlay.

MySQL root password change

Tried the answer from @kta but didn't work for me.

I am using MySQL 8.0

This worked for me:

mysql> SET PASSWORD FOR 'root'@'localhost' = 'yourpassword'

target input by type and name (selector)

You want a multiple attribute selector

$("input[type='checkbox'][name='ProductCode']").each(function(){ ...


$("input:checkbox[name='ProductCode']").each(function(){ ...

It would be better to use a CSS class to identify those that you want to select however as a lot of the modern browsers implement the document.getElementsByClassName method which will be used to select elements and be much faster than selecting by the name attribute

Remove non-ASCII characters from CSV

As an alternative to sed or perl you may consider to use ed(1) and POSIX character classes.

Note: ed(1) reads the entire file into memory to edit it in-place, so for really large files you should use sed -i ..., perl -i ...

# see:
# -
# -

# test
echo $'aaa \177 bbb \200 \214 ccc \254 ddd\r\n' > testfile
ed -s testfile <<< $',l' 
ed -s testfile <<< $'H\ng/[^[:graph:][:space:][:cntrl:]]/s///g\nwq'
ed -s testfile <<< $',l'

Restarting cron after changing crontab file?

On CentOS with cPanel sudo /etc/init.d/crond reload does the trick.

On CentOS7: sudo systemctl start crond.service

How the single threaded non blocking IO model works in Node.js

Node.js is built upon libuv, a cross-platform library that abstracts apis/syscalls for asynchronous (non-blocking) input/output provided by the supported OSes (Unix, OS X and Windows at least).

Asynchronous IO

In this programming model open/read/write operation on devices and resources (sockets, filesystem, etc.) managed by the file-system don't block the calling thread (as in the typical synchronous c-like model) and just mark the process (in kernel/OS level data structure) to be notified when new data or events are available. In case of a web-server-like app, the process is then responsible to figure out which request/context the notified event belongs to and proceed processing the request from there. Note that this will necessarily mean you'll be on a different stack frame from the one that originated the request to the OS as the latter had to yield to a process' dispatcher in order for a single threaded process to handle new events.

The problem with the model I described is that it's not familiar and hard to reason about for the programmer as it's non-sequential in nature. "You need to make request in function A and handle the result in a different function where your locals from A are usually not available."

Node's model (Continuation Passing Style and Event Loop)

Node tackles the problem leveraging javascript's language features to make this model a little more synchronous-looking by inducing the programmer to employ a certain programming style. Every function that requests IO has a signature like function (... parameters ..., callback) and needs to be given a callback that will be invoked when the requested operation is completed (keep in mind that most of the time is spent waiting for the OS to signal the completion - time that can be spent doing other work). Javascript's support for closures allows you to use variables you've defined in the outer (calling) function inside the body of the callback - this allows to keep state between different functions that will be invoked by the node runtime independently. See also Continuation Passing Style.

Moreover, after invoking a function spawning an IO operation the calling function will usually return control to node's event loop. This loop will invoke the next callback or function that was scheduled for execution (most likely because the corresponding event was notified by the OS) - this allows the concurrent processing of multiple requests.

You can think of node's event loop as somewhat similar to the kernel's dispatcher: the kernel would schedule for execution a blocked thread once its pending IO is completed while node will schedule a callback when the corresponding event has occured.

Highly concurrent, no parallelism

As a final remark, the phrase "everything runs in parallel except your code" does a decent job of capturing the point that node allows your code to handle requests from hundreds of thousands open socket with a single thread concurrently by multiplexing and sequencing all your js logic in a single stream of execution (even though saying "everything runs in parallel" is probably not correct here - see Concurrency vs Parallelism - What is the difference?). This works pretty well for webapp servers as most of the time is actually spent on waiting for network or disk (database / sockets) and the logic is not really CPU intensive - that is to say: this works well for IO-bound workloads.

How can I verify a Google authentication API access token?

I need to somehow query Google and ask: Is this access token valid for [email protected]?

No. All you need is request standard login with Federated Login for Google Account Users from your API domain. And only after that you could compare "persistent user ID" with one you have from 'public interface'.

The value of realm is used on the Google Federated Login page to identify the requesting site to the user. It is also used to determine the value of the persistent user ID returned by Google.

So you need be from same domain as 'public interface'.

And do not forget that user needs to be sure that your API could be trusted ;) So Google will ask user if it allows you to check for his identity.

How do I access previous promise results in a .then() chain?

When using bluebird, you can use .bind method to share variables in promise chain:

.spread(function (aValue, bValue) {
    this.aValue = aValue;
    this.bValue = bValue;
    return somethingElseAsync(aValue, bValue);
.then(function (cValue) {
    return this.aValue + this.bValue + cValue;

please check this link for further information:

Spring Boot default H2 jdbc connection (and H2 console)

If you use Spring Boot's developer tools, it comes with H2 Console enabled by default. It can be accessed from /h2-console/. On the login interface, for input JDBC URL use value jdbc:h2:mem:testdb. Pay attention to mem string.

If you don't use Spring Boot's developer tools, you can enable the console in using spring.h2.console.enabled=true. This will enable console under /h2-console. If you want to change the URL then you can add another entry with spring.h2.console.path=my_console_path.

The default schema name is testdb.

More details in Spring Boot Documentation.

How to create global variables accessible in all views using Express / Node.JS?

For Express 4.0 I found that using application level variables works a little differently & Cory's answer did not work for me.

From the docs:

I found that you could declare a global variable for the app in



app.locals.baseUrl = ""

And then in your application you can access these variables & in your express middleware you can access them in the req object as


//prints out

Excel: the Incredible Shrinking and Expanding Controls

Could it be that the button is defined to stick to the corners of a cell, instead of floating freely ?

Check it with

Format | Properties | Object Positioning

and choose anything but "move and size with cells"

How do I calculate someone's age based on a DateTime type birthday?

int Age = new DateTime((DateTime.Now - BirthDate).Ticks).Year -1;
Console.WriteLine("Age {0}", Age);

What exactly does the .join() method do?

join() is for concatenating all list elements. For concatenating just two strings "+" would make more sense:

strid = repr(595)
print array.array('c', random.sample(string.ascii_letters, 20 - len(strid)))
    .tostring() + strid

What does "export" do in shell programming?

Well, it generally depends on the shell. For bash, it marks the variable as "exportable" meaning that it will show up in the environment for any child processes you run.

Non-exported variables are only visible from the current process (the shell).

From the bash man page:

export [-fn] [name[=word]] ...
export -p

The supplied names are marked for automatic export to the environment of subsequently executed commands.

If the -f option is given, the names refer to functions. If no names are given, or if the -p option is supplied, a list of all names that are exported in this shell is printed.

The -n option causes the export property to be removed from each name.

If a variable name is followed by =word, the value of the variable is set to word.

export returns an exit status of 0 unless an invalid option is encountered, one of the names is not a valid shell variable name, or -f is supplied with a name that is not a function.

You can also set variables as exportable with the typeset command and automatically mark all future variable creations or modifications as such, with set -a.

Disable spell-checking on HTML textfields

Yes, use spellcheck="false", as defined by HTML5, for example:

<textarea spellcheck="false">

Replace a string in shell script using a variable

I had a similar requirement to this but my replace var contained an ampersand. Escaping the ampersand like this solved my problem:

replace="salt & pepper"
echo "pass the salt" | sed "s/salt/${replace/&/\&}/g"

Re-assign host access permission to MySQL user

The accepted answer only renamed the user but the privileges were left behind.

I'd recommend using:

RENAME USER 'foo'@'' TO 'foo'@'';

According to MySQL documentation:

RENAME USER causes the privileges held by the old user to be those held by the new user.

Ignoring upper case and lower case in Java

Use String#toLowerCase() or String#equalsIgnoreCase() methods

Some examples:

    String abc    = "Abc".toLowerCase();
    boolean isAbc = "Abc".equalsIgnoreCase("ABC");

How to obtain the last index of a list?

I guess you want

last_index = len(list1) - 1 

which would store 3 in last_index.

GCC -fPIC option

A minor addition to the answers already posted: object files not compiled to be position independent are relocatable; they contain relocation table entries.

These entries allow the loader (that bit of code that loads a program into memory) to rewrite the absolute addresses to adjust for the actual load address in the virtual address space.

An operating system will try to share a single copy of a "shared object library" loaded into memory with all the programs that are linked to that same shared object library.

Since the code address space (unlike sections of the data space) need not be contiguous, and because most programs that link to a specific library have a fairly fixed library dependency tree, this succeeds most of the time. In those rare cases where there is a discrepancy, yes, it may be necessary to have two or more copies of a shared object library in memory.

Obviously, any attempt to randomize the load address of a library between programs and/or program instances (so as to reduce the possibility of creating an exploitable pattern) will make such cases common, not rare, so where a system has enabled this capability, one should make every attempt to compile all shared object libraries to be position independent.

Since calls into these libraries from the body of the main program will also be made relocatable, this makes it much less likely that a shared library will have to be copied.

Has been compiled by a more recent version of the Java Runtime (class file version 57.0)

I also encountered similar problem which is asked here. The issue was that some applications come with their own JRE and sometimes the installed JDK appears at lower priority level in environment path. Now there are two options:

  1. Uninstall the other application which has their own JDK/JRE.
  2. Sometimes it is not possible to remove the other application, which was my case. So I moved JDk installed by me to higher priority level in environment path.

enter image description here

I also removed the path as suggested by @CrazyCoder

How to list all AWS S3 objects in a bucket using Java

Gray your solution was strange but you seem like a nice guy.

AmazonS3Client s3Client = new AmazonS3Client(new BasicAWSCredentials( ....

ObjectListing images = s3Client.listObjects(bucketName); 

List<S3ObjectSummary> list = images.getObjectSummaries();
for(S3ObjectSummary image: list) {
    S3Object obj = s3Client.getObject(bucketName, image.getKey());

Can a JSON value contain a multiline string

Per the specification, the JSON grammar's char production can take the following values:

  • any-Unicode-character-except-"-or-\-or-control-character
  • \"
  • \\
  • \/
  • \b
  • \f
  • \n
  • \r
  • \t
  • \u four-hex-digits

Newlines are "control characters", so no, you may not have a literal newline within your string. However, you may encode it using whatever combination of \n and \r you require.

The JSONLint tool confirms that your JSON is invalid.

And, if you want to write newlines inside your JSON syntax without actually including newlines in the data, then you're doubly out of luck. While JSON is intended to be human-friendly to a degree, it is still data and you're trying to apply arbitrary formatting to that data. That is absolutely not what JSON is about.

How to avoid the need to specify the WSDL location in a CXF or JAX-WS generated webservice client?

Seriously, the top answer is not working for me. tried cxf.version 2.4.1 and 3.0.10. and generate absolute path with wsdlLocation every times.

My solution is to use the wsdl2java command in the apache-cxf-3.0.10\bin\ with -wsdlLocation classpath:wsdl/QueryService.wsdl.


    wsdl2java -encoding utf-8 -p com.jeiao.boss.testQueryService -impl -wsdlLocation classpath:wsdl/testQueryService.wsdl

PHP server on local machine?

I use WAMP. One easy install wizard, tons of modules to for Apache and PHP preconfigured and easy to turn on and off to match your remote config.

How create Date Object with values in java

import java.util.*;
import java.util.HashMap;

public class Solution 

    public static void main(String[] args)
        HashMap<Integer,String> hm = new HashMap<Integer,String>();
        Scanner in = new Scanner(;
        String month =;
        String day =;
        String year =;

        String format = year + "/" + month + "/" + day;
        Date date = null;
            SimpleDateFormat formatter = new SimpleDateFormat("yyyy/MM/dd");
            date = formatter.parse(format);
        catch(Exception e){
        Calendar c = Calendar.getInstance();
        int dayOfWeek = c.get(Calendar.DAY_OF_WEEK);

How to add image in a TextView text?

This might Help You

  SpannableStringBuilder ssBuilder;

        ssBuilder = new SpannableStringBuilder(" ");
        // working code ImageSpan image = new ImageSpan(textView.getContext(), R.drawable.image);
        Drawable image = ContextCompat.getDrawable(textView.getContext(), R.drawable.image);
        float scale = textView.getContext().getResources().getDisplayMetrics().density;
        int width = (int) (12 * scale + 0.5f);
        int height = (int) (18 * scale + 0.5f);
        image.setBounds(0, 0, width, height);
        ImageSpan imageSpan = new ImageSpan(image, ImageSpan.ALIGN_BASELINE);
                imageSpan, // Span to add
                0, // Start of the span (inclusive)
                1, // End of the span (exclusive)
                Spanned.SPAN_INCLUSIVE_EXCLUSIVE);// Do not extend the span when text add later

        ssBuilder.append(" " + text);
        ssBuilder = new SpannableStringBuilder(text);

Size of Matrix OpenCV

Note that apart from rows and columns there is a number of channels and type. When it is clear what type is, the channels can act as an extra dimension as in CV_8UC3 so you would address a matrix as

uchar a =<Vec3b>(y, x)[i];

So the size in terms of elements of elementary type is M.rows * M.cols *

To find the max element one can use

Mat src;
double minVal, maxVal;
minMaxLoc(src, &minVal, &maxVal);

Min/Max of dates in an array?

Using Moment, Underscore and jQuery, to iterate an array of dates.

Sample JSON:

"workerList": [{        
        "shift_start_dttm": "13/06/2017 20:21",
        "shift_end_dttm": "13/06/2017 23:59"
    }, {
        "shift_start_dttm": "03/04/2018 00:00",
        "shift_end_dttm": "03/05/2018 00:00"        


function getMinStartDttm(workerList) {  
    if(!_.isEmpty(workerList)) {
        var startDtArr = [];
        $.each(d.workerList, function(index,value) {                
            startDtArr.push(moment(value.shift_start_dttm.trim(), 'DD/MM/YYYY HH:mm')); 
         var startDt = _.min(startDtArr);           
         return start.format('DD/MM/YYYY HH:mm');
    } else {
        return '';

Hope it helps.

How to check whether java is installed on the computer

Check the installation directories (typically C:\Program Files (x86) or C:\Program Files) for the java folder. If it contains the JRE you have java installed.

C++ equivalent of StringBuffer/StringBuilder?

std::string's += doesn't work with const char* (what stuff like "string to add" appear to be), so definitely using stringstream is the closest to what is required - you just use << instead of +

HTML table with fixed headers?

The CSS property position: sticky has great support in most modern browsers (I had issues with Edge, see below).

This lets us solve the problem of fixed headers quite easily:

thead th { position: sticky; top: 0; }

Safari needs a vendor prefix: -webkit-sticky.

For Firefox, I had to add min-height: 0 to one the parent elements. I forget exactly why this was needed.

Most unfortunately, the Microsoft Edge implementation seems to be only semi-working. At least, I had some flickering and misaligned table cells in my testing. The table was still usable, but had significant aesthetic issues.

Spring Boot and how to configure connection details to MongoDB?

Here is How you can do in Spring Boot 2.0 by creating custom MongoClient adding Providing more control for Connection ,

Please follow github Link for Full Source Code

@EnableMongoRepositories(basePackages = { "com.frugalis.repository" })
@ComponentScan(basePackages = { "com.frugalis.*" })
public class MongoJPAConfig extends AbstractMongoConfiguration {

    private String database;
    private String host;
    private String port;
    private String username;
    private String password;

    protected String getDatabaseName() {
        return database;

    protected String getMappingBasePackage() {
        return "com.frugalis.entity.mongo";

    public MongoTemplate mongoTemplate() throws Exception {
        return new MongoTemplate(mongoClient(), getDatabaseName());

    public MongoClient mongoClient() {

        List<MongoCredential> allCred = new ArrayList<MongoCredential>();
        System.out.println("???????????????????"+username+" "+database+" "+password+" "+host+" "+port);
        allCred.add(MongoCredential.createCredential(username, database, password.toCharArray()));
        MongoClient client = new MongoClient((new ServerAddress(host, Integer.parseInt(port))), allCred);

        return client;

Reading a .txt file using Scanner class in Java

  1. Make sure the filename is correct (proper capitalisation, matching extension etc - as already suggested).

  2. Use the Class.getResource method to locate your file in the classpath - don't rely on the current directory:

    URL url = insertionSort.class.getResource("10_Random");
    File file = new File(url.toURI());
  3. Specify the absolute file path via command-line arguments:

    File file = new File(args[0]);

In Eclipse:

  1. Choose "Run configurations"
  2. Go to the "Arguments" tab
  3. Put your "c:/my/file/is/here/10_Random.txt.or.whatever" into the "Program arguments" section

How to disable Google Chrome auto update?

We had a problem printing with v49something.

I blocked on localhost temporarily so that I could install previous version and prevent updating to the version that is breaking the label printing.

So, in /etc/hosts I added:

Not a perfect solution, but was perfect for us.

Mapping many-to-many association table with extra column(s)

As said before, with JPA, in order to have the chance to have extra columns, you need to use two OneToMany associations, instead of a single ManyToMany relationship. You can also add a column with autogenerated values; this way, it can work as the primary key of the table, if useful.

For instance, the implementation code of the extra class should look like that:

@Table(name = "USER_SERVICES")
public class UserService{

    // example of auto-generated ID
    @Column(name = "USER_SERVICES_ID", nullable = false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long userServiceID;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "USER_ID")
    private User user;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "SERVICE_ID")
    private Service service;

    // example of extra column
    private boolean visibility;

    public long getUserServiceID() {
        return userServiceID;

    public User getUser() {
        return user;

    public void setUser(User user) {
        this.user = user;

    public Service getService() {
        return service;

    public void setService(Service service) {
        this.service = service;

    public boolean getVisibility() {
        return visibility;

    public void setVisibility(boolean visibility) {
        this.visibility = visibility;


Convert a timedelta to days, hours and minutes

I used the following:

delta = timedelta()
totalMinute, second = divmod(delta.seconds, 60)
hour, minute = divmod(totalMinute, 60)

Static variables in C++

A static variable declared in a header file outside of the class would be file-scoped in every .c file which includes the header. That means separate copy of a variable with same name is accessible in each of the .c files where you include the header file.

A static class variable on the other hand is class-scoped and the same static variable is available to every compilation unit that includes the header containing the class with static variable.

Python Selenium Chrome Webdriver

Here's a simpler solution: install python-chromedrive package, import it in your script, and it's done.

Step by step:
1. pip install chromedriver-binary
2. import the package

from selenium import webdriver
import chromedriver_binary  # Adds chromedriver binary to path

driver = webdriver.Chrome()


Jquery $.ajax fails in IE on cross domain calls

Simply install this jQuery Plugin: jQuery Cross-Domain AJAX for IE8

This 1.4kb plugin works right away in Internet Explorer 8 and 9.

Include the plugin after jQuery, and call your ajax request as normal. Nothing else required.

TypeScript add Object to array with push

If your example represents your real code, the problem is not in the push, it's that your constructor doesn't do anything.

You need to declare and initialize the x and y members.


export class Pixel {
    public x: number;
    public y: number;   
    constructor(x: number, y: number) {
        this.x = x;
        this.y = y;

Or implicitly:

export class Pixel {
    constructor(public x: number, public y: number) {}

Do I commit the package-lock.json file created by npm 5?

Yes, you SHOULD:

  1. commit the package-lock.json.
  2. use npm ci instead of npm install when building your applications both on your CI and your local development machine

The npm ci workflow requires the existence of a package-lock.json.

A big downside of npm install command is its unexpected behavior that it may mutate the package-lock.json, whereas npm ci only uses the versions specified in the lockfile and produces an error

  • if the package-lock.json and package.json are out of sync
  • if a package-lock.json is missing.

Hence, running npm install locally, esp. in larger teams with multiple developers, may lead to lots of conflicts within the package-lock.json and developers to decide to completely delete the package-lock.json instead.

Yet there is a strong use-case for being able to trust that the project's dependencies resolve repeatably in a reliable way across different machines.

From a package-lock.json you get exactly that: a known-to-work state.

In the past, I had projects without package-lock.json / npm-shrinkwrap.json / yarn.lock files whose build would fail one day because a random dependency got a breaking update.

Those issue are hard to resolve as you sometimes have to guess what the last working version was.

If you want to add a new dependency, you still run npm install {dependency}. If you want to upgrade, use either npm update {dependency} or npm install ${dependendency}@{version} and commit the changed package-lock.json.

If an upgrade fails, you can revert to the last known working package-lock.json.

To quote npm doc:

It is highly recommended you commit the generated package lock to source control: this will allow anyone else on your team, your deployments, your CI/continuous integration, and anyone else who runs npm install in your package source to get the exact same dependency tree that you were developing on. Additionally, the diffs from these changes are human-readable and will inform you of any changes npm has made to your node_modules, so you can notice if any transitive dependencies were updated, hoisted, etc.

And in regards to the difference between npm ci vs npm install:

  • The project must have an existing package-lock.json or npm-shrinkwrap.json.
  • If dependencies in the package lock do not match those in package.json, npm ci will exit with an error, instead of updating the package lock.
  • npm ci can only install entire projects at a time: individual dependencies cannot be added with this command.
  • If a node_modules is already present, it will be automatically removed before npm ci begins its install.
  • It will never write to package.json or any of the package-locks: installs are essentially frozen.

Note: I posted a similar answer here

Can anyone explain python's relative imports?

If you are going to call directly and i.e. if you really want to import from a top level module you have to explicitly add it to the sys.path list.
Here is how it should work:

# Add this line to the beginning of file
import sys

# Now you can do imports from one directory top cause it is in the sys.path
import parent

# And even like this:
from parent import Parent

If you think the above can cause some kind of inconsistency you can use this instead:

sys.path.append(sys.path[0] + "/..")

sys.path[0] refers to the path that the entry point was ran from.

Installing a dependency with Bower from URL and specify version

Use the following:

bower install --save git://

More here:

How to encode the filename parameter of Content-Disposition header in HTTP?

In PHP this did it for me (assuming the filename is UTF8 encoded):

header('Content-Disposition: attachment;'
    . 'filename="' . addslashes(utf8_decode($filename)) . '";'
    . 'filename*=utf-8\'\'' . rawurlencode($filename));

Tested against IE8-11, Firefox and Chrome.
If the browser can interpret filename*=utf-8 it will use the UTF8 version of the filename, else it will use the decoded filename. If your filename contains characters that can't be represented in ISO-8859-1 you might want to consider using iconv instead.

<!--[if !IE]> not working

First of all the right syntax is:

<!--[if IE 6]>
<link type="text/css" rel="stylesheet" href="/stylesheets/ie6.css" />

Try this post: and

Another thing you can do:

Check browser with jQuery:

if($.browser.msie){ // do something... }

in this case you can change css rules for some elements or add new css link reference:

read this:

Does the join order matter in SQL?

For INNER joins, no, the order doesn't matter. The queries will return same results, as long as you change your selects from SELECT * to SELECT a.*, b.*, c.*.

For (LEFT, RIGHT or FULL) OUTER joins, yes, the order matters - and (updated) things are much more complicated.

First, outer joins are not commutative, so a LEFT JOIN b is not the same as b LEFT JOIN a

Outer joins are not associative either, so in your examples which involve both (commutativity and associativity) properties:

    ON b.ab_id = a.ab_id
    ON c.ac_id = a.ac_id

is equivalent to:

    ON c.ac_id = a.ac_id
    ON b.ab_id = a.ab_id


    ON  b.ab_id = a.ab_id
    ON  c.ac_id = a.ac_id
    AND c.bc_id = b.bc_id

is not equivalent to:

    ON  c.ac_id = a.ac_id
    ON  b.ab_id = a.ab_id
    AND b.bc_id = c.bc_id

Another (hopefully simpler) associativity example. Think of this as (a LEFT JOIN b) LEFT JOIN c:

    ON b.ab_id = a.ab_id          -- AB condition
    ON c.bc_id = b.bc_id          -- BC condition

This is equivalent to a LEFT JOIN (b LEFT JOIN c):

    b LEFT JOIN c
        ON c.bc_id = b.bc_id          -- BC condition
    ON b.ab_id = a.ab_id          -- AB condition

only because we have "nice" ON conditions. Both ON b.ab_id = a.ab_id and c.bc_id = b.bc_id are equality checks and do not involve NULL comparisons.

You can even have conditions with other operators or more complex ones like: ON a.x <= b.x or ON a.x = 7 or ON a.x LIKE b.x or ON (a.x, a.y) = (b.x, b.y) and the two queries would still be equivalent.

If however, any of these involved IS NULL or a function that is related to nulls like COALESCE(), for example if the condition was b.ab_id IS NULL, then the two queries would not be equivalent.

How to trigger checkbox click event even if it's checked through Javascript code?

Trigger function from jQuery could be your answer.

jQuery docs says: Any event handlers attached with .on() or one of its shortcut methods are triggered when the corresponding event occurs. They can be fired manually, however, with the .trigger() method. A call to .trigger() executes the handlers in the same order they would be if the event were triggered naturally by the user

Thus best one line solution should be:




How to set up a cron job to run an executable every hour?

Did you mean the executable fails to run , if invoked from any other directory? This is rather a bug on the executable. One potential reason could be the executable requires some shared libraires from the installed folder. You may check environment variable LD_LIBRARY_PATH

How do I convert between ISO-8859-1 and UTF-8 in Java?

Regex can also be good and be used effectively (Replaces all UTF-8 characters not covered in ISO-8859-1 with space):

String input = "€Tes¶ti©ng [§] al€l o€f i¶t _ - À ÆÑ with some 9umbers as"
            + " w2921**#$%!@# well Ü, or ü, is a chaŒracte?";
String output = input.replaceAll("[^\\u0020-\\u007e\\u00a0-\\u00ff]", " ");
System.out.println("Input = " + input);
System.out.println("Output = " + output);

Swift - How to detect orientation changes

Swift 4+: I was using this for soft keyboard design, and for some reason the UIDevice.current.orientation.isLandscape method kept telling me it was Portrait, so here's what I used instead:

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)

    if(size.width > self.view.frame.size.width){

Regex for parsing directory and filename


I did a little research through trial and error method. Found out that all the values that are available in keyboard are eligible to be a file or directory except '/' in *nux machine.

I used touch command to create file for following characters and it created a file.

(Comma separated values below)
'!', '@', '#', '$', "'", '%', '^', '&', '*', '(', ')', ' ', '"', '\', '-', ',', '[', ']', '{', '}', '`', '~', '>', '<', '=', '+', ';', ':', '|'

It failed only when I tried creating '/' (because it's root directory) and filename container / because it file separator.

And it changed the modified time of current dir . when I did touch .. However, file.log is possible.

And of course, a-z, A-Z, 0-9, - (hypen), _ (underscore) should work.


So, by the above reasoning we know that a file name or directory name can contain anything except / forward slash. So, our regex will be derived by what will not be present in the file name/directory name.


Step by Step regexp creation process

Pattern Explanation

Step-1: Start with matching root directory

A directory can start with / when it is absolute path and directory name when it's relative. Hence, look for / with zero or one occurrence.


enter image description here

Step-2: Try to find the first directory.

Next, a directory and its child is always separated by /. And a directory name can be anything except /. Let's match /var/ first then.


enter image description here

Step-3: Get full directory path for the file

Next, let's match all directories


enter image description here

Here, single_dir is yz/ because, first it matched var/, then it found next occurrence of same pattern i.e. log/, then it found the next occurrence of same pattern yz/. So, it showed the last occurrence of pattern.

Step-4: Match filename and clean up

Now, we know that we're never going to use the groups like single_dir, filepath, root. Hence let's clean that up.

Let's keep them as groups however don't capture those groups.

And rest_of_the_path is just the filename! So, rename it. And a file will not have / in its name, so it's better to keep [^/]


This brings us to the final result. Of course, there are several other ways you can do it. I am just mentioning one of the ways here.

enter image description here

Regex Rules used above are listed here

^ means string starts with
(?P<dir>pattern) means capture group by group name. We have two groups with group name dir and file
(?:pattern) means don't consider this group or non-capturing group.
? means match zero or one. + means match one or more [^\/] means matches any char except forward slash (/)

[/]? means if it is absolute path then it can start with / otherwise it won't. So, match zero or one occurrence of /.

[^\/]+/ means one or more characters which aren't forward slash (/) which is followed by a forward slash (/). This will match var/ or xyz/. One directory at a time.

Prevent onmouseout when hovering child element of the parent absolute div WITHOUT jQuery

function onMouseOut(event) {
        //this is the original element the event handler was assigned to
        var e = event.toElement || event.relatedTarget;
        if (e.parentNode == this || e == this) {
    // handle mouse event here!


I made a quick JsFiddle demo, with all the CSS and HTML needed, check it out...

EDIT FIXED link for cross-browser support

NOTE that this only checks the immediate parent, if the parent div had nested children then you have to somehow traverse through the elements parents looking for the "Orginal element"

EDIT example for nested children

EDIT Fixed for hopefully cross-browser

function makeMouseOutFn(elem){
    var list = traverseChildren(elem);
    return function onMouseOut(event) {
        var e = event.toElement || event.relatedTarget;
        if (!!~list.indexOf(e)) {
        // handle mouse event here!

//using closure to cache all child elements
var parent = document.getElementById("parent");

//quick and dirty DFS children traversal, 
function traverseChildren(elem){
    var children = [];
    var q = [];
    while (q.length > 0) {
      var elem = q.pop();
    function pushAll(elemArray){
      for(var i=0; i < elemArray.length; i++) {
    return children;

And a new JSFiddle, EDIT updated link

What is pluginManagement in Maven's pom.xml?

You still need to add


in your build, because pluginManagement is only a way to share the same plugin configuration across all your project modules.

From Maven documentation:

pluginManagement: is an element that is seen along side plugins. Plugin Management contains plugin elements in much the same way, except that rather than configuring plugin information for this particular project build, it is intended to configure project builds that inherit from this one. However, this only configures plugins that are actually referenced within the plugins element in the children. The children have every right to override pluginManagement definitions.

How do I list all tables in all databases in SQL Server in a single result set?

This is really handy, but I wanted a way to show all user objects, not just tables, so I adapted it to use sys.objects instead of sys.tables

DECLARE @AllTables table (DbName sysname,SchemaName sysname, ObjectType char(2), ObjectName sysname)
     @SearchDb nvarchar(200)
    ,@SearchSchema nvarchar(200)
    ,@SearchObject nvarchar(200)
    ,@SQL nvarchar(4000)
SET @SearchDb='%'
SET @SearchSchema='%'
SET @SearchObject='%Something%'
SET @SQL='select ''?'' as DbName, as SchemaName, t.type as ObjectType, as ObjectName 
from [?].sys.objects t inner join sys.schemas s on t.schema_id=s.schema_id 
WHERE t.type in (''FN'',''IF'',''U'',''V'',''P'',''TF'') 
AND ''?'' LIKE '''+@SearchDb+''' 
AND LIKE '''+@SearchSchema+''' 
AND LIKE '''+@SearchObject+''''

INSERT INTO @AllTables (DbName, SchemaName, ObjectType, ObjectName)
    EXEC sp_msforeachdb @SQL
SELECT * FROM @AllTables ORDER BY DbName, SchemaName, ObjectType, ObjectName

How do I convert a pandas Series or index to a Numpy array?

I converted the pandas dataframe to list and then used the basic list.index(). Something like this:

dd = list(zone[0]) #Where zone[0] is some specific column of the table
idx = dd.index(filename[i])

You have you index value as idx.

How can I find all matches to a regular expression in Python?

Use re.findall or re.finditer instead.

re.findall(pattern, string) returns a list of matching strings.

re.finditer(pattern, string) returns an iterator over MatchObject objects.


re.findall( r'all (.*?) are', 'all cats are smarter than dogs, all dogs are dumber than cats')
# Output: ['cats', 'dogs']

[ for x in re.finditer( r'all (.*?) are', 'all cats are smarter than dogs, all dogs are dumber than cats')]
# Output: ['all cats are', 'all dogs are']

Spring MVC Controller redirect using URL parameters instead of in response provided me with what I needed to get things working until Spring MVC offers the functionality (potentially in the 3.0.2 release). Although I simply implemented the classes they have temporarily and added the filter to my web application context. Works great!

How to pass object with NSNotificationCenter

Swift 2 Version

As @Johan Karlsson pointed out... I was doing it wrong. Here's the proper way to send and receive information with NSNotificationCenter.

First, we look at the initializer for postNotificationName:

init(name name: String,
   object object: AnyObject?,
 userInfo userInfo: [NSObject : AnyObject]?)


We'll be passing our information using the userInfo param. The [NSObject : AnyObject] type is a hold-over from Objective-C. So, in Swift land, all we need to do is pass in a Swift dictionary that has keys that are derived from NSObject and values which can be AnyObject.

With that knowledge we create a dictionary which we'll pass into the object parameter:

 var userInfo = [String:String]()
 userInfo["UserName"] = "Dan"
 userInfo["Something"] = "Could be any object including a custom Type."

Then we pass the dictionary into our object parameter.


    .postNotificationName("myCustomId", object: nil, userInfo: userInfo)

Receiver Class

First we need to make sure our class is observing for the notification

override func viewDidLoad() {

    NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("btnClicked:"), name: "myCustomId", object: nil)   

Then we can receive our dictionary:

func btnClicked(notification: NSNotification) {
   let userInfo : [String:String!] = notification.userInfo as! [String:String!]
   let name = userInfo["UserName"]

Cross-browser window resize event - JavaScript / jQuery

Besides the window resize functions mentioned it is important to understand that the resize events fire a lot if used without a deboucing the events.

Paul Irish has an excellent function that debounces the resize calls a great deal. Very recommended to use. Works cross-browser. Tested it in IE8 the other day and all was fine.

Make sure to check out the demo to see the difference.

Here is the function for completeness.


  // debouncing function from John Hann
  var debounce = function (func, threshold, execAsap) {
      var timeout;

      return function debounced () {
          var obj = this, args = arguments;
          function delayed () {
              if (!execAsap)
                  func.apply(obj, args);
              timeout = null;

          if (timeout)
          else if (execAsap)
              func.apply(obj, args);

          timeout = setTimeout(delayed, threshold || 100);
  // smartresize 
  jQuery.fn[sr] = function(fn){  return fn ? this.bind('resize', debounce(fn)) : this.trigger(sr); };


// usage:
  // code that takes it easy...

How to update multiple columns in single update statement in DB2

I know it's an old question, but I just had to find solution for multiple rows update where multiple records had to updated with different values based on their IDs and I found that I can use a a scalar-subselect:

  WHERE RESPEMP='000030'

(with WHERE optional, of course)

Also, I found that it is critical to specify that no NULL values would not be used in this update (in case not all records in first table have corresponding record in the second one), this way:



Java - get pixel array from image

I found Mota's answer gave me a 10 times speed increase - so thanks Mota.

I've wrapped up the code in a convenient class which takes the BufferedImage in the constructor and exposes an equivalent getRBG(x,y) method which makes it a drop in replacement for code using BufferedImage.getRGB(x,y)

import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;

public class FastRGB

    private int width;
    private int height;
    private boolean hasAlphaChannel;
    private int pixelLength;
    private byte[] pixels;

    FastRGB(BufferedImage image)

        pixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
        width = image.getWidth();
        height = image.getHeight();
        hasAlphaChannel = image.getAlphaRaster() != null;
        pixelLength = 3;
        if (hasAlphaChannel)
            pixelLength = 4;


    int getRGB(int x, int y)
        int pos = (y * pixelLength * width) + (x * pixelLength);

        int argb = -16777216; // 255 alpha
        if (hasAlphaChannel)
            argb = (((int) pixels[pos++] & 0xff) << 24); // alpha

        argb += ((int) pixels[pos++] & 0xff); // blue
        argb += (((int) pixels[pos++] & 0xff) << 8); // green
        argb += (((int) pixels[pos++] & 0xff) << 16); // red
        return argb;

How to get array keys in Javascript?

For your input data:

let widthRange = new Array()
widthRange[46] = { min:0,  max:52 }
widthRange[61] = { min:52, max:70 }
widthRange[62] = { min:52, max:70 }
widthRange[63] = { min:52, max:70 }
widthRange[66] = { min:52, max:70 }
widthRange[90] = { min:70, max:94 }

Declarative approach:

const relevantKeys = [46,66,90]
const relevantValues = Object.keys(widthRange)
    .filter(index => relevantKeys.includes(parseInt(index)))
    .map(relevantIndex => widthRange[relevantIndex])

Object.keys to get the keys, using parseInt to cast them as numbers. filter to get only ones you want. map to build an array from the original object of just the indices you're after, since Object.keys loses the object values.



Maven: How to run a .java file from command line passing arguments

In addition to running it with mvn exec:java, you can also run it with mvn exec:exec

mvn exec:exec -Dexec.executable="java" -Dexec.args="-classpath %classpath your.package.MainClass"

get and set in TypeScript

If you are looking for way to use get and set on any object (not a class) Proxy may be usefull:

const target = {
  message1: "hello",
  message2: "everyone"

const handler3 = {
  get: function (target, prop, receiver) {
    if (prop === "message2") {
      return "world";
    return Reflect.get(...arguments);

const proxy3 = new Proxy(target, handler3);

console.log(proxy3.message1); // hello
console.log(proxy3.message2); // world

Note: be aware that this is new api not supported and required polifill for older browsers

Rails where condition using NOT NIL

Not sure of this is helpful but this what worked for me in Rails 4

Foo.where.not(bar: nil)

Java code To convert byte to Hexadecimal

The fastest way i've yet found to do this is the following:

private static final String    HEXES    = "0123456789ABCDEF";

static String getHex(byte[] raw) {
    final StringBuilder hex = new StringBuilder(2 * raw.length);
    for (final byte b : raw) {
        hex.append(HEXES.charAt((b & 0xF0) >> 4)).append(HEXES.charAt((b & 0x0F)));
    return hex.toString();

It's ~ 50x faster than String.format. if you want to test it:

public class MyTest{
    private static final String    HEXES        = "0123456789ABCDEF";

    public void test_get_hex() {
        byte[] raw = {
            (byte) 0xd0, (byte) 0x0b, (byte) 0x01, (byte) 0x2a, (byte) 0x63,
            (byte) 0x78, (byte) 0x01, (byte) 0x2e, (byte) 0xe3, (byte) 0x6c,
            (byte) 0xd2, (byte) 0xb0, (byte) 0x78, (byte) 0x51, (byte) 0x73,
            (byte) 0x34, (byte) 0xaf, (byte) 0xbb, (byte) 0xa0, (byte) 0x9f,
            (byte) 0xc3, (byte) 0xa9, (byte) 0x00, (byte) 0x1e, (byte) 0xd5,
            (byte) 0x4b, (byte) 0x89, (byte) 0xa3, (byte) 0x45, (byte) 0x35,
            (byte) 0xd6, (byte) 0x10,

        int N = 77777;
        long t;

            t = System.currentTimeMillis();
            for (int i = 0; i < N; i++) {
                final StringBuilder hex = new StringBuilder(2 * raw.length);
                for (final byte b : raw) {
                    hex.append(HEXES.charAt((b & 0xF0) >> 4)).append(HEXES.charAt((b & 0x0F)));
            System.out.println(System.currentTimeMillis() - t); // 50

            t = System.currentTimeMillis();
            for (int i = 0; i < N; i++) {
                StringBuilder hex = new StringBuilder(2 * raw.length);
                for (byte b : raw) {
                    hex.append(String.format("%02X", b));
            System.out.println(System.currentTimeMillis() - t); // 2535


Edit: Just found something just a lil faster and that holds on one line but is not compatible with JRE 9. Use at your own risks

import javax.xml.bind.DatatypeConverter;


Inline instantiation of a constant List

You are looking for a simple code, like this:

    List<string> tagList = new List<string>(new[]

what is the use of annotations @Id and @GeneratedValue(strategy = GenerationType.IDENTITY)? Why the generationtype is identity?

Simply, @Id: This annotation specifies the primary key of the entity. 

@GeneratedValue: This annotation is used to specify the primary key generation strategy to use. i.e Instructs database to generate a value for this field automatically. If the strategy is not specified by default AUTO will be used. 

GenerationType enum defines four strategies: 
1. Generation Type . TABLE, 
2. Generation Type. SEQUENCE,
3. Generation Type. IDENTITY   
4. Generation Type. AUTO


With this strategy, underlying persistence provider must use a database sequence to get the next unique primary key for the entities. 


With this strategy, underlying persistence provider must use a database table to generate/keep the next unique primary key for the entities. 

This GenerationType indicates that the persistence provider must assign primary keys for the entity using a database identity column. IDENTITY column is typically used in SQL Server. This special type column is populated internally by the table itself without using a separate sequence. If underlying database doesn't support IDENTITY column or some similar variant then the persistence provider can choose an alternative appropriate strategy. In this examples we are using H2 database which doesn't support IDENTITY column.

This GenerationType indicates that the persistence provider should automatically pick an appropriate strategy for the particular database. This is the default GenerationType, i.e. if we just use @GeneratedValue annotation then this value of GenerationType will be used. 


How to get first N elements of a list in C#?

To take first 5 elements better use expression like this one:

var firstFiveArrivals = myList.Where([EXPRESSION]).Take(5);


var firstFiveArrivals = myList.Where([EXPRESSION]).Take(5).OrderBy([ORDER EXPR]);

It will be faster than orderBy variant, because LINQ engine will not scan trough all list due to delayed execution, and will not sort all array.

class MyList : IEnumerable<int>

    int maxCount = 0;

    public int RequestCount
        private set;
    public MyList(int maxCount)
        this.maxCount = maxCount;
    public void Reset()
        RequestCount = 0;
    #region IEnumerable<int> Members

    public IEnumerator<int> GetEnumerator()
        int i = 0;
        while (i < maxCount)
            yield return i++;


    #region IEnumerable Members

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        throw new NotImplementedException();

class Program
    static void Main(string[] args)
        var list = new MyList(15);
        Console.WriteLine(list.RequestCount); // 5;

        list.OrderBy(q => q).Take(5).ToArray();
        Console.WriteLine(list.RequestCount); // 15;

        list.Where(q => (q & 1) == 0).Take(5).ToArray();
        Console.WriteLine(list.RequestCount); // 9; (first 5 odd)

        list.Where(q => (q & 1) == 0).Take(5).OrderBy(q => q).ToArray();
        Console.WriteLine(list.RequestCount); // 9; (first 5 odd)

How to use Git?

this is my blog on git and its for beginners who want to get started on git.

How to split a string by spaces in a Windows batch file?

The following code will split a string with N number of substrings with # separated values. You can use any delimiter

@echo off
if "%1" == "" goto error1

set _myvar="%1"

For /F "tokens=1* delims=#" %%A IN (%_myvar%) DO (
    echo %%A
    set _myvar="%%B"
    if NOT "%_myvar%"=="" goto FORLOOP

goto endofprogram
echo You must provide Argument with # separated

goto endofprogram

Change hover color on a button with Bootstrap customization

I had to add !important to get it to work. I also made my own class button-primary-override.

    background-color: #42A5F5 !important;
    border-color: #42A5F5 !important;
    background-image: none !important;
    border: 0 !important;

Updating a java map entry


table.put(key, val);

to add a new key/value pair or overwrite an existing key's value.

From the Javadocs:

V put(K key, V value): Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for the key, the old value is replaced by the specified value. (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.)

Generate random numbers with a given (numerical) distribution

Here is a more effective way of doing this:

Just call the following function with your 'weights' array (assuming the indices as the corresponding items) and the no. of samples needed. This function can be easily modified to handle ordered pair.

Returns indexes (or items) sampled/picked (with replacement) using their respective probabilities:

def resample(weights, n):
    beta = 0

    # Caveat: Assign max weight to max*2 for best results
    max_w = max(weights)*2

    # Pick an item uniformly at random, to start with
    current_item = random.randint(0,n-1)
    result = []

    for i in range(n):
        beta += random.uniform(0,max_w)

        while weights[current_item] < beta:
            beta -= weights[current_item]
            current_item = (current_item + 1) % n   # cyclic
    return result

A short note on the concept used in the while loop. We reduce the current item's weight from cumulative beta, which is a cumulative value constructed uniformly at random, and increment current index in order to find the item, the weight of which matches the value of beta.

How can I check whether Google Maps is fully loaded?

I'm creating html5 mobile apps and I noticed that the idle, bounds_changed and tilesloaded events fire when the map object is created and rendered (even if it is not visible).

To make my map run code when it is shown for the first time I did the following:

google.maps.event.addListenerOnce(map, 'tilesloaded', function(){
    //this part runs when the mapobject is created and rendered
    google.maps.event.addListenerOnce(map, 'tilesloaded', function(){
        //this part runs when the mapobject shown for the first time

How to get the date and time values in a C program?

The answers given above are good CRT answers, but if you want you can also use the Win32 solution to this. It's almost identical but IMO if you're programming for Windows you might as well just use its API (although I don't know if you are programming in Windows).

char* arrDayNames[7] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}; 
GetLocalTime(&st); // Alternatively use GetSystemTime for the UTC version of the time
printf("The current date and time are: %d/%d/%d %d:%d:%d:%d", st.wDay, st.wMonth, st.wYear, st.wHour, st.wMinute, st.wSecond, st.wMilliseconds);
printf("The day is: %s", arrDayNames[st.wDayOfWeek]);

Anyway, this is a Windows solution. I hope it will be helpful for you sometime!

Split list into smaller lists (split in half)

There is an official Python receipe for the more generalized case of splitting an array into smaller arrays of size n.

from itertools import izip_longest
def grouper(n, iterable, fillvalue=None):
    "Collect data into fixed-length chunks or blocks"
    # grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx
    args = [iter(iterable)] * n
    return izip_longest(fillvalue=fillvalue, *args)

This code snippet is from the python itertools doc page.

How do you append to a file?

The 'a' parameter signifies append mode. If you don't want to use with open each time, you can easily write a function to do it for you:

def append(txt='\nFunction Successfully Executed', file):
    with open(file, 'a') as f:

If you want to write somewhere else other than the end, you can use 'r+':

import os

with open(file, 'r+') as f:, os.SEEK_END)
    f.write("text to add")

Finally, the 'w+' parameter grants even more freedom. Specifically, it allows you to create the file if it doesn't exist, as well as empty the contents of a file that currently exists.

Credit for this function goes to @Primusa

Finding the id of a parent div using Jquery

find() and closest() seems slightly slower than:


Adding data attribute to DOM

to get the text from a

<option value="1" data-sigla="AC">Acre</option>

uf = $("#selectestado option:selected").attr('data-sigla');

Typescript: Type X is missing the following properties from type Y length, pop, push, concat, and 26 more. [2740]

For those newbies like me, don't assign variable to service response, meaning do

export class ShopComponent implements OnInit {
  public productsArray: Product[];

  ngOnInit() {
      this.productService.getProducts().subscribe(res => {
        this.productsArray = res;

Instead of

export class ShopComponent implements OnInit {
    public productsArray: Product[];

    ngOnInit() {
        this.productsArray = this.productService.getProducts().subscribe();

How do I implement onchange of <input type="text"> with jQuery?

Here's the code I use:

$("#tbSearch").on('change keyup paste', function () {

function ApplyFilter() {
    var searchString = $("#tbSearch").val();
    //  ... etc...

<input type="text" id="tbSearch" name="tbSearch" />

This works quite nicely, particularly when paired up with a jqGrid control. You can just type into a textbox and immediately view the results in your jqGrid.

How to add an event after close the modal window?

I find answer. Thanks all but right answer next:

$("#myModal").on("hidden", function () {

Events here


For Bootstrap 3.x need use

$("#myModal").on("", function () {

C# if/then directives for debug vs release

Remove the definitions and check if the conditional is on debug mode. You do not need to check if the directive is on release mode.

Something like this:


What is the SSIS package and what does it do?

Microsoft SQL Server Integration Services (SSIS) is a platform for building high-performance data integration solutions, including extraction, transformation, and load (ETL) packages for data warehousing. SSIS includes graphical tools and wizards for building and debugging packages; tasks for performing workflow functions such as FTP operations, executing SQL statements, and sending e-mail messages; data sources and destinations for extracting and loading data; transformations for cleaning, aggregating, merging, and copying data; a management database, SSISDB, for administering package execution and storage; and application programming interfaces (APIs) for programming the Integration Services object model.

As per Microsoft, the main uses of SSIS Package are:

• Merging Data from Heterogeneous Data Stores Populating Data

• Warehouses and Data Marts Cleaning and Standardizing Data Building

• Business Intelligence into a Data Transformation Process Automating

• Administrative Functions and Data Loading

For developers:

SSIS Package can be integrated with VS development environment for building Business Intelligence solutions. Business Intelligence Development Studio is the Visual Studio environment with enhancements that are specific to business intelligence solutions. It work with 32-bit development environment only.

Download SSDT tools for Visual Studio:

Creating SSIS ETL Package - Basics :

Sample project of SSIS features in 6 lessons:

Are 64 bit programs bigger and faster than 32 bit versions?

More data is transferred between the CPU and RAM for each memory fetch (64 bits instead of 32), so 64-bit programs can be faster provided they are written so that they properly take advantage of this.

Creating an iframe with given HTML dynamically

I know this is an old question but I thought I would provide an example using the srcdoc attribute as this is now widely supported and this is question is viewed often.

Using the srcdoc attribute, you can provide inline HTML to embed. It overrides the src attribute if supported. The browser will fall back to the src attribute if unsupported.

I would also recommend using the sandbox attribute to apply extra restrictions to the content in the frame. This is especially important if the HTML is not your own.

const iframe = document.createElement('iframe');_x000D_
const html = '<body>Foo</body>';_x000D_
iframe.srcdoc = html;_x000D_
iframe.sandbox = '';_x000D_

If you need to support older browsers, you can check for srcdoc support and fallback to one of the other methods from other answers.

function setIframeHTML(iframe, html) {_x000D_
  if (typeof iframe.srcdoc !== 'undefined') {_x000D_
    iframe.srcdoc = html;_x000D_
  } else {_x000D_
    iframe.sandbox = 'allow-same-origin';_x000D_;_x000D_
var iframe = document.createElement('iframe');_x000D_
iframe.sandbox = '';_x000D_
var html = '<body>Foo</body>';_x000D_
setIframeHTML(iframe, html);

SQL Server Format Date DD.MM.YYYY HH:MM:SS


You can concatenate it:


"UnboundLocalError: local variable referenced before assignment" after an if statement

Your if statement is always false and T gets initialized only if a condition is met, so the code doesn't reach the point where T gets a value (and by that, gets defined/bound). You should introduce the variable in a place that always gets executed.


def temp_sky(lreq, breq):
    T = <some_default_value> # None is often a good pick
    for line in tfile:
        data = line.split()
        if abs(float(data[0])-lreq) <= 0.1 and abs(float(data[1])-breq) <= 0.1:            
            T = data[2]
    return T

What is the role of the bias in neural networks?

If you're working with images, you might actually prefer to not use a bias at all. In theory, that way your network will be more independent of data magnitude, as in whether the picture is dark, or bright and vivid. And the net is going to learn to do it's job through studying relativity inside your data. Lots of modern neural networks utilize this.

For other data having biases might be critical. It depends on what type of data you're dealing with. If your information is magnitude-invariant --- if inputting [1,0,0.1] should lead to the same result as if inputting [100,0,10], you might be better off without a bias.

What is a bus error?

One classic instance of a bus error is on certain architecures, such as the SPARC (at least some SPARCs, maybe this has been changed), is when you do a mis-aligned access. For instance:

unsigned char data[6];
(unsigned int *) (data + 2) = 0xdeadf00d;

This snippet tries to write the 32-bit integer value 0xdeadf00d to an address that is (most likely) not properly aligned, and will generate a bus error on architectures that are "picky" in this regard. The Intel x86 is, by the way, not such an architecture, it would allow the access (albeit execute it more slowly).

Wait for page load in Selenium

This seems to be a serious limitation of WebDriver. Obviously waiting for an element will not imply the page being loaded, in particular the DOM can be fully build (onready state) whereby JS is still executing and CSS and images are still loading.

I believe the simplest solution is to set a JS variable upon the onload event after everything is initialized and check and wait for this JS variable in Selenium.

Which characters need to be escaped in HTML?

The exact answer depends on the context. In general, these characters must not be present (HTML 5.2 §

Text nodes and attribute values must consist of Unicode characters, must not contain U+0000 characters, must not contain permanently undefined Unicode characters (noncharacters), and must not contain control characters other than space characters. This specification includes extra constraints on the exact value of Text nodes and attribute values depending on their precise context.

For elements in HTML, the constraints of the Text content model also depends on the kind of element. For instance, an "<" inside a textarea element does not need to be escaped in HTML because textarea is an escapable raw text element.

These restrictions are scattered across the specification. E.g., attribute values (§ must not contain an ambiguous ampersand and be either (i) empty, (ii) within single quotes (and thus must not contain U+0027 APOSTROPHE character '), (iii) within double quotes (must not contain U+0022 QUOTATION MARK character "), or (iv) unquoted — with the following restrictions:

... must not contain any literal space characters, any U+0022 QUOTATION MARK characters ("), U+0027 APOSTROPHE characters ('), U+003D EQUALS SIGN characters (=), U+003C LESS-THAN SIGN characters (<), U+003E GREATER-THAN SIGN characters (>), or U+0060 GRAVE ACCENT characters (`), and must not be the empty string.

Check for special characters (/*-+_@&$#%) in a string?

Use the regular Expression below in to validate a string to make sure it contains numbers, letters, or space only:

[a-zA-Z0-9 ]

How can I pass a file argument to my bash script using a Terminal command in Linux?

It'll be easier (and more "proper", see below) if you just run your script as

myprogram /path/to/file

Then you can access the path within the script as $1 (for argument #1, similarly $2 is argument #2, etc.)

externalprogram "$file" [other parameters]

Or just

externalprogram "$1" [otherparameters]

If you want to extract the path from something like --file=/path/to/file, that's usually done with the getopts shell function. But that's more complicated than just referencing $1, and besides, switches like --file= are intended to be optional. I'm guessing your script requires a file name to be provided, so it doesn't make sense to pass it in an option.

How to lowercase a pandas dataframe string column if it has missing values?

A possible solution:

import pandas as pd
import numpy as np

df=pd.DataFrame(['ONE','Two', np.nan],columns=['x']) 
xLower = df["x"].map(lambda x: x if type(x)!=str else x.lower())
print (xLower)

And a result:

0    one
1    two
2    NaN
Name: x, dtype: object

Not sure about the efficiency though.

Cannot import scipy.misc.imread

If you have Pillow installed with scipy and it is still giving you error then check your scipy version because it has been removed from scipy since 1.3.0rc1.

rather install scipy 1.1.0 by :

pip install scipy==1.1.0


The method imread in scipy.misc requires the forked package of PIL named Pillow. If you are having problem installing the right version of PIL try using imread in other packages:

from matplotlib.pyplot import imread
im = imread(image.png)

To read jpg images without PIL use:

import cv2 as cv
im = cv.imread(image.jpg)

You can try from scipy.misc.pilutil import imread instead of from scipy.misc import imread

Please check the GitHub page : for more details.

How do I get a decimal value when using the division operator in Python?

There are three options:

>>> 4 / float(100)
>>> 4 / 100.0

which is the same behavior as the C, C++, Java etc, or

>>> from __future__ import division
>>> 4 / 100

You can also activate this behavior by passing the argument -Qnew to the Python interpreter:

$ python -Qnew
>>> 4 / 100

The second option will be the default in Python 3.0. If you want to have the old integer division, you have to use the // operator.

Edit: added section about -Qnew, thanks to ??O?????!

Force the origin to start at 0

Simply add these to your ggplot:

+ scale_x_continuous(expand = c(0, 0), limits = c(0, NA)) + 
  scale_y_continuous(expand = c(0, 0), limits = c(0, NA))


df <- data.frame(x = 1:5, y = 1:5)
p <- ggplot(df, aes(x, y)) + geom_point()
p <- p + expand_limits(x = 0, y = 0)
p # not what you are looking for

p + scale_x_continuous(expand = c(0, 0), limits = c(0,NA)) + 
  scale_y_continuous(expand = c(0, 0), limits = c(0, NA))

enter image description here

Lastly, take great care not to unintentionally exclude data off your chart. For example, a position = 'dodge' could cause a bar to get left off the chart entirely (e.g. if its value is zero and you start the axis at zero), so you may not see it and may not even know it's there. I recommend plotting data in full first, inspect, then use the above tip to improve the plot's aesthetics.

Could not transfer artifact org.apache.maven.plugins:maven-surefire-plugin:pom:2.7.1 from/to central (

This problem was solved by following steps -

  1. Go to the local m2 repository and find the directory org/apache/maven/plugins/maven-surefire-plugin.
  2. Delete the problematic version.
  3. maven update the project, then download it again.

Preprocessing in scikit learn - single sample - Depreciation warning

.values.reshape(-1,1) will be accepted without alerts/warnings

.reshape(-1,1) will be accepted, but with deprecation war

Avoid "current URL string parser is deprecated" warning by setting useNewUrlParser to true

We were using:

  (res) => {
   console.log("Connected to Database Successfully.")
).catch(() => {
  console.log("Connection to database failed.");

? This gives a URL parser error

The correct syntax is:

mongoose.connect("mongodb://localhost:27017/mean-course" , { useNewUrlParser: true }).then(
  (res) => {
   console.log("Connected to Database Successfully.")
).catch(() => {
  console.log("Connection to database failed.");

Calculate average in java


you can't do this because result/count is not a String type, and System.out.println() only takes a String parameter. perhaps try:

double avg = (double)result / (double)args.length

Converting File to MultiPartFile

File file = new File("src/test/resources/input.txt");
FileInputStream input = new FileInputStream(file);
MultipartFile multipartFile = new MockMultipartFile("file",
            file.getName(), "text/plain", IOUtils.toByteArray(input));

How can I search (case-insensitive) in a column using LIKE wildcard?

When I want to develop insensitive case searchs, I always convert every string to lower case before do comparasion

Inheriting constructors

Correct Code is

class A
      explicit A(int x) {}

class B: public A

     B(int a):A(a){

    B *b = new B(5);
     delete b;

Error is b/c Class B has not parameter constructor and second it should have base class initializer to call the constructor of Base Class parameter constructor

How to show Snackbar when Activity starts?

Just point to any View inside the Activity's XML. You can give an id to the root viewGroup, for example, and use:

protected void onCreate(Bundle savedInstanceState) {
   View parentLayout = findViewById(;
   Snackbar.make(parentLayout, "This is main activity", Snackbar.LENGTH_LONG) 
        .setAction("CLOSE", new View.OnClickListener() {
            public void onClick(View view) {

        .setActionTextColor(getResources().getColor(android.R.color.holo_red_light ))
   //Other stuff in OnCreate();

Return from a promise then()

Promises don't "return" values, they pass them to a callback (which you supply with .then()).

It's probably trying to say that you're supposed to do resolve(someObject); inside the promise implementation.

Then in your then code you can reference someObject to do what you want.

how to add new <li> to <ul> onclick with javascript

You were almost there:

You just need to append the li to ul and voila!

So just add


to the end of your function so the end function will be like this:

function function1() {
  var ul = document.getElementById("list");
  var li = document.createElement("li");
  li.appendChild(document.createTextNode("Element 4"));

Getting the button into the top right corner inside the div box

Just add position:absolute; top:0; right:0; to the CSS for your button.

 #button {
     line-height: 12px;
     width: 18px;
     font-size: 8pt;
     font-family: tahoma;
     margin-top: 1px;
     margin-right: 2px;

jsFiddle example

How to view log output using docker-compose run?

  1. use the command to start containers in detached mode: docker-compose up -d
  2. to view the containers use: docker ps
  3. to view logs for a container: docker logs <containerid>

How to enable assembly bind failure logging (Fusion) in .NET

I wrote an assembly binding log viewer named Fusion++ and put it on GitHub.

You can get the latest release from here or via chocolatey (choco install fusionplusplus).

I hope you and some of the visitors in here can save some worthy lifetime minutes with it.


Best way to determine user's locale within browser

You can also try to get the language from the document should might be your first port of call, then falling back to other means as often people will want their JS language to match the document language.





No real source is necessarily 100% reliable as people can simply put in the wrong language.

There are language detection libraries that might let you determine the language by content.

SQLException: No suitable Driver Found for jdbc:oracle:thin:@//localhost:1521/orcl

Sometimes it is the simple things. In my case, I had an invalid url. I had left out a colon before the at sign (@). I had "jdbc:oracle:thin@//localhost" instead of "jdbc:oracle:thin:@//localhost" Hope this helps someone else with this issue.

Conflict with dependency ''. Resolved versions for app (23.1.0) and test app (23.0.1) differ

you can try to use

  androidTestCompile('', {
    exclude group: '', module: 'support-annotations'

instead of

androidTestCompile ''

androidTestCompile ''

androidTestCompile ''
androidTestCompile ''

DETERMINISTIC, NO SQL, or READS SQL DATA in its declaration and binary logging is enabled

Try setting the definer for the function!

So instead of

CREATE FUNCTION get_pet_owner

you will write something akin to

CREATE DEFINER=procadmin@% FUNCTION get_pet_owner

which ought to work if the user prodacmin has rights to create functions/procedures.

In my case the function worked when generated through MySQL Workbench but did not work when run directly as an SQL script. Making the changes above fixed the problem.

Why would a JavaScript variable start with a dollar sign?

In the 1st, 2nd, and 3rd Edition of ECMAScript, using $-prefixed variable names was explicitly discouraged by the spec except in the context of autogenerated code:

The dollar sign ($) and the underscore (_) are permitted anywhere in an identifier. The dollar sign is intended for use only in mechanically generated code.

However, in the next version (the 5th Edition, which is current), this restriction was dropped, and the above passage replaced with

The dollar sign ($) and the underscore (_) are permitted anywhere in an IdentifierName.

As such, the $ sign may now be used freely in variable names. Certain frameworks and libraries have their own conventions on the meaning of the symbol, noted in other answers here.

PHP function overloading

PHP doesn't support traditional method overloading, however one way you might be able to achieve what you want, would be to make use of the __call magic method:

class MyClass {
    public function __call($name, $args) {

        switch ($name) {
            case 'funcOne':
                switch (count($args)) {
                    case 1:
                        return call_user_func_array(array($this, 'funcOneWithOneArg'), $args);
                    case 3:
                        return call_user_func_array(array($this, 'funcOneWithThreeArgs'), $args);
            case 'anotherFunc':
                switch (count($args)) {
                    case 0:
                        return $this->anotherFuncWithNoArgs();
                    case 5:
                        return call_user_func_array(array($this, 'anotherFuncWithMoreArgs'), $args);

    protected function funcOneWithOneArg($a) {


    protected function funcOneWithThreeArgs($a, $b, $c) {


    protected function anotherFuncWithNoArgs() {


    protected function anotherFuncWithMoreArgs($a, $b, $c, $d, $e) {



opening html from google drive

  1. Create a new folder in Drive and share it as "Public on the web."
  2. Upload your HTML, JS & CSS files to this folder.
  3. Open the HTML file & you will see "Preview" button in the toolbar.
  4. Share the URL that looks like from the preview window and anyone can view your web page.

How to push files to an emulator instance using Android Studio

I am using Android Studio 3.3.

Go to View -> Tools Window -> Device File Explorer. Or you can find it on the Bottom Right corner of the Android Studio.

enter image description here

If the Emulator is running, the Device File Explorer will display the File structure on Emulator Storage.

enter image description here

Here you can right click on a Folder and select "Upload" to place the file

enter image description here

I usually use mnt - sdcard - download folder. Thanks.

How to get element's width/height within directives and component?

For a bit more flexibility than with micronyks answer, you can do it like that:

1. In your template, add #myIdentifier to the element you want to obtain the width from. Example:

<p #myIdentifier>
  my-component works!

2. In your controller, you can use this with @ViewChild('myIdentifier') to get the width:

import {AfterViewInit, Component, ElementRef, OnInit, ViewChild} from '@angular/core';

  selector: 'app-my-component',
  templateUrl: './my-component.component.html',
  styleUrls: ['./my-component.component.scss']
export class MyComponentComponent implements AfterViewInit {

  constructor() { }

  ngAfterViewInit() {

  myIdentifier: ElementRef;



About the security risk with ElementRef, like this, there is none. There would be a risk, if you would modify the DOM using an ElementRef. But here you are only getting DOM Elements so there is no risk. A risky example of using ElementRef would be: this.myIdentifier.nativeElement.onclick = someFunctionDefinedBySomeUser;. Like this Angular doesn't get a chance to use its sanitisation mechanisms since someFunctionDefinedBySomeUser is inserted directly into the DOM, skipping the Angular sanitisation.

Import PEM into Java Key Store

I got it from internet. It works pretty good for pem files that contains multiple entries.

        # number of certs in the PEM file
        newCert=$(basename "$pemCerts")
        ##echo $newCert $pemCerts $certPass
        CERTS=$(grep 'END CERTIFICATE' $pemCerts| wc -l)
        echo $CERTS
        # For every cert in the PEM file, extract it and import into the JKS keystore
        # awk command: step 1, if line is in the desired cert, print the line
        #              step 2, increment counter when last line of cert is found
        for N in $(seq 0 $(($CERTS - 1))); do
          cat $pemCerts |
                awk "n==$N { print }; /END CERTIFICATE/ { n++ }" |
                $KEYTOOLCMD -noprompt -import -trustcacerts \
                                -alias $ALIAS -keystore $newCert -storepass $certPass
pemToJks <pem to import> <pass for new jks>

Error during installing HAXM, VT-X not working

If your emulators were working and now they aren't due to Avast...

Avast no longer has the option for "Enable Hardware-assisted Virtualization" in Troubleshooting. (it's now March 2017)

Avast captures "emulator.exe", which disables emulators,and stows it in the Virus chest. Open the chest, "Restore and add to exclusions" and your emulator works again...

Pictorial on Avast fix

Overriding the java equals() method - not working?

In Java, the equals() method that is inherited from Object is:

public boolean equals(Object other);

In other words, the parameter must be of type Object. This is called overriding; your method public boolean equals(Book other) does what is called overloading to the equals() method.

The ArrayList uses overridden equals() methods to compare contents (e.g. for its contains() and equals() methods), not overloaded ones. In most of your code, calling the one that didn't properly override Object's equals was fine, but not compatible with ArrayList.

So, not overriding the method correctly can cause problems.

I override equals the following everytime:

public boolean equals(Object other){
    if (other == null) return false;
    if (other == this) return true;
    if (!(other instanceof MyClass)) return false;
    MyClass otherMyClass = (MyClass)other;
    ...test other properties here...

The use of the @Override annotation can help a ton with silly mistakes.

Use it whenever you think you are overriding a super class' or interface's method. That way, if you do it the wrong way, you will get a compile error.

Error : No resource found that matches the given name (at 'icon' with value '@drawable/icon')

In my case, I use Xamarin with Visual Studio 2013. I create Blank App (Android) then deploy without any code update.

You can try:

  • Make sure that icon.png (or whatever files mentioned in the application android:icon tag) is present in the drawable-hdpi folder inside res folder of Android project.

  • If it shows the error even if the icon.png is present,then remove the statement application android:icon from the AndroidManifest.xml and add it again.

  • Check your project folder's path. If it is too long, or contains space, or contains any unicode character, try to relocated.

How to determine MIME type of file in android?

get file object....
File file = new File(filePath);

then....pass as a parameter to...

getMimeType(file); is 

public String getMimeType(File file) {
        String mimetype = MimeTypeMap.getSingleton().getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(Uri.fromFile(file).toString()).toLowerCase());
        if (mimetype == null) {
            return "*/*";
        return mimetype;///return the mimeType

Create a .tar.bz2 file Linux

Try this from different folder:

sudo tar -cvjSf folder.tar.bz2 folder/*

Printing the correct number of decimal points with cout

this an example using a matrix.


Convert this string to datetime

Use DateTime::createFromFormat

$date = date_create_from_format('d/m/Y:H:i:s', $s);

what is Array.any? for javascript

I'm a little late to the party, but...

[].some(x => !!x)

How to store Node.js deployment settings/configuration files?

Are you guys using npm to start your scripts (env etc) ?

If you use .env files you can include them in your package.json and use npm to source/start them.


  "name": "server",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "start": "node test.js",
    "start-dev": "source dev.env; node test.js",
    "start-prod": "source prod.env; node test.js"
  "dependencies": {
    "mysql": "*"

then run the npm scripts:

$ npm start-dev

Its described here All credit to Eric Elliot

How do I redirect with JavaScript?

Compared to window.location="url"; it is much easyer to do just location="url"; I always use that

How to Allow Remote Access to PostgreSQL database

You have to add this to your pg_hba.conf and restart your PostgreSQL.

host all all md5

This works with VirtualBox and host-only adapter enabled. If you don't use Virtualbox you have to replace the IP address.

How do I get Month and Date of JavaScript in 2 digit format?

And another version here, hope to be useful.

var dt = new Date(2016,5,1); // just for the test
var separator = '.';
var strDate = (dt.getFullYear() + separator + (dt.getMonth() + 1) + separator + dt.getDate());
// end of setup

strDate = strDate.replace(/(\b\d{1}\b)/g, "0$1")

How do I catch a PHP fatal (`E_ERROR`) error?

If you are using PHP >= 5.1.0 Just do something like this with the ErrorException class:

    // Define an error handler
    function exception_error_handler($errno, $errstr, $errfile, $errline ) {
        throw new ErrorException($errstr, $errno, 0, $errfile, $errline);

    // Set your error handler

    /* Trigger exception */
        // Try to do something like finding the end of the internet
    catch(ErrorException $e)
        // Anything you want to do with $e

Clean up a fork and restart it from the upstream

Love VonC's answer. Here's an easy version of it for beginners.

There is a git remote called origin which I am sure you are all aware of. Basically, you can add as many remotes to a git repo as you want. So, what we can do is introduce a new remote which is the original repo not the fork. I like to call it original

Let's add original repo's to our fork as a remote.

git remote add original https://git-repo/original/original.git

Now let's fetch the original repo to make sure we have the latest coded

git fetch original

As, VonC suggested, make sure we are on the master.

git checkout master

Now to bring our fork up to speed with the latest code on original repo, all we have to do is hard reset our master branch in accordance with the original remote.

git reset --hard original/master

And you are done :)

Check if boolean is true?

It depends on your situation.

I would say, if your bool has a good name, then:

if (control.IsEnabled)  // Read "If control is enabled."

would be preferred.

If, however, the variable has a not-so-obvious name, checking against true would be helpful in understanding the logic.

if (first == true)  // Read "If first is true."

Animation CSS3: display + opacity

I had the same problem. I tried using animations instead of transitions - as suggested by @MichaelMullany and @Chris - but it only worked for webkit browsers even if I copy-pasted with "-moz" and "-o" prefixes.

I was able to get around the problem by using visibility instead of display. This works for me because my child element is position: absolute, so document flow isn't being affected. It might work for others too.

This is what the original code would look like using my solution:

.child {
    position: absolute;
    opacity: 0;
    visibility: hidden;

    -webkit-transition: opacity 0.5s ease-in-out;
    -moz-transition: opacity 0.5s ease-in-out;
    transition: opacity 0.5s ease-in-out;

.parent:hover .child {
    position: relative;
    opacity: 0.9;
    visibility: visible;

Traits vs. interfaces

Traits are simply for code reuse.

Interface just provides the signature of the functions that is to be defined in the class where it can be used depending on the programmer's discretion. Thus giving us a prototype for a group of classes.

For reference-

How to enable curl in xampp?

In XAMPP installation directory, open %XAMPP_HOME%/php/php.ini file. Uncomment the following line: extension=php_curl.dll

PS: If that doesn't work then check whether %XAMPP_HOME%/php/ext/php_curl.dll file exist or not.

What's the difference between process.cwd() vs __dirname?

As per node js doc process.cwd()

cwd is a method of global object process, returns a string value which is the current working directory of the Node.js process.

As per node js doc __dirname

The directory name of current script as a string value. __dirname is not actually a global but rather local to each module.

Let me explain with example,

suppose we have a main.js file resides inside C:/Project/main.js and running node main.js both these values return same file

or simply with following folder structure

+-- main.js
   +-- script.js


// C:\Project
// C:\Project
// true

suppose we have another file script.js files inside a sub directory of project ie C:/Project/lib/script.js and running node main.js which require script.js


// C:\Project
// C:\Project
// true


// C:\Project
// C:\Project\lib
// false

How can I view the shared preferences file using Android Studio?

I always find these commands useful in console:

  1. Find the correct file name

    adb shell

    ls /data/data/com.your.package/shared_prefs

  2. Get the file to local directory

    adb pull /data/data/com.your.package/shared_prefs/the_file_you_want $local_dir

  3. Check it in your $local_dir.

Unbalanced calls to begin/end appearance transitions for <UITabBarController: 0x197870>

I had this problem when I had navigated from root TVC to TVC A then to TVC B. After tapping the "load" button in TVC B I wanted to jump straight back to the root TVC (no need to revisit TVC A so why do it). I had:

//Pop child from the nav controller
[self.navigationController popViewControllerAnimated:YES];
//Pop self to return to root
[self.navigationController popViewControllerAnimated:YES];

...which gave the error "Unbalanced calls to begin/end etc". The following fixed the error, but no animation:

//Pop child from the nav controller
[self.navigationController popViewControllerAnimated:NO];
//Then pop self to return to root
[self.navigationController popViewControllerAnimated:NO];

This was my final solution, no error and still animated:

//Pop child from the nav controller
[self.navigationController popViewControllerAnimated:NO];
//Then pop self to return to root, only works if first pop above is *not* animated
[self.navigationController popViewControllerAnimated:YES];

Adding Counter in shell script

You may do this with a for loop instead of a while:

for ((count = 0; count < max_loop; count++)); do
  if /home/hadoop/latest/bin/hadoop fs -ls /apps/hdtech/bds/quality-rt/dt=$DATE_YEST_FORMAT2 then
       echo "Files Present" | mailx -s "File Present"  -r [email protected] [email protected]
       echo "Sleeping for half an hour" | mailx -s "Time to Sleep Now"  -r [email protected] [email protected]
       sleep 1800

if [ "$count" -eq "$max_loop" ]; then
  echo "Maximum number of trials reached" >&2
  exit 1

Python: URLError: <urlopen error [Errno 10060]

Answer (Basic is advance!):

Error: 10060 Adding a timeout parameter to request solved the issue for me.

Example 1

import urllib
import urllib2
g = ""
read = urllib2.urlopen(g, timeout=20)

Example 2

A similar error also occurred while I was making a GET request. Again, passing a timeout parameter solved the 10060 Error.

response = requests.get(param_url, timeout=20)

POST JSON fails with 415 Unsupported media type, Spring 3 mvc

A small side note - stumbled upon this same error while developing a web application. The mistake we found, by toying with the service with Firefox Poster, was that both fields and values in the Json should be surrounded by double quotes. For instance..

[ {"idProductCategory" : "1" , "description":"Descrizione1"}, 
  {"idProductCategory" : "2" , "description":"Descrizione2"} ]

In our case we filled the json via javascript, which can be a little confusing when it comes with dealing with single/double quotes, from what I've heard.

What's been said before in this and other posts, like including the 'Accept' and 'Content-Type' headers, applies too.

Hope t'helps.

How to while loop until the end of a file in Python without checking for empty line?

for line in f

reads all file to a memory, and that can be a problem.

My offer is to change the original source by replacing stripping and checking for empty line. Because if it is not last line - You will receive at least newline character in it ('\n'). And '.strip()' removes it. But in last line of a file You will receive truely empty line, without any characters. So the following loop will not give You false EOF, and You do not waste a memory:

with open("blablabla.txt", "r") as fl_in:
   while True:
      line = fl_in.readline()

        if not line:

      line = line.strip()
      # do what You want

What is the difference between And and AndAlso in VB.NET?

In addition to the answers above, AndAlso provides a conditioning process known as short circuiting. Many programming languages have this functionality built in like does, and can provide substantial performance increases in long condition statements by cutting out evaluations that are unneccessary.

Another similar condition is the OrElse condition which would only check the right condition if the left condition is false, thus cutting out unneccessary condition checks after a true condition is found.

I would advise you to always use short circuiting processes and structure your conditional statements in ways that can benefit the most by this. For example, test your most efficient and fastest conditions first so that you only run your long conditions when you absolutely have to and short circuit the other times.

Android - Start service on boot

Just to make searching easier, as mentioned in comments, this is not possible since 3.1

Minimum and maximum value of z-index?

Z-Index only works for elements that have position: relative; or position: absolute; applied to them. If that's not the problem we'll need to see an example page to be more helpful.

EDIT: The good doctor has already put the fullest explanation but the quick version is that the minimum is 0 because it can't be a negative number and the maximum - well, you'll never really need to go above 10 for most designs.

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

While other suggested solutions work, If you really want the solution to be made thread safe you should replace ArrayList with CopyOnWriteArrayList

    //List<String> s = new ArrayList<>(); //Will throw exception
    List<String> s = new CopyOnWriteArrayList<>();
    Iterator<String> it = s.iterator();

    //Below removes only "B" from List
    while (it.hasNext()) {

Printing prime numbers from 1 through 100

#include "stdafx.h"
using namespace std;
void main()
{ int f =0;
 for(int i=2;i<=100;i++)
   for(int j=2;j<=i/2;j++)
     { f=1;
 if (f==0)
  cout<<i<<" ";

Programmatically generate video or animated GIF in Python?

I understand you asked about converting images to a gif; however, if the original format is MP4, you could use FFmpeg:

ffmpeg -i input.mp4 output.gif

Auto generate function documentation in Visual Studio

You can use code snippets to insert any lines you want.

Also, if you type three single quotation marks (''') on the line above the function header, it will insert the XML header template that you can then fill out.

These XML comments can be interpreted by documentation software, and they are included in the build output as an assembly.xml file. If you keep that XML file with the DLL and reference that DLL in another project, those comments become available in intellisense.

Transaction count after EXECUTE indicates a mismatching number of BEGIN and COMMIT statements. Previous count = 1, current count = 0

For me after extensive debugging the fix was a simple missing throw; statement in the catch after the rollback. Without it this ugly error message is what you end up with.

begin catch
    if @@trancount > 0 rollback transaction;
    throw; --allows capture of useful info when an exception happens within the transaction
end catch

Convert Map<String,Object> to Map<String,String>

There are two ways to do this. One is very simple but unsafe:

Map<String, Object> map = new HashMap<String, Object>();
Map<String, String> newMap = new HashMap<String, String>((Map)map);  // unchecked warning

The other way has no compiler warnings and ensures type safety at runtime, which is more robust. (After all, you can't guarantee the original map contains only String values, otherwise why wouldn't it be Map<String, String> in the first place?)

Map<String, Object> map = new HashMap<String, Object>();
Map<String, String> newMap = new HashMap<String, String>();
@SuppressWarnings("unchecked") Map<String, Object> intermediate =
    (Map)Collections.checkedMap(newMap, String.class, String.class);

Centering image and text in R Markdown for a PDF report

You can use raw LaTeX in R Markdown. Try this:


There is, of course, a catch: everything between begin{...} and \end{...} is interpreted as raw LaTeX by Pandoc, so you can't use this technique to center the output of R code chunks, or Markdown content.

How to call external url in jquery?

google the javascript same origin policy

in a nutshell, the url you are trying to use must have the same root and protocol. so cannot access or

is you absolutely MUST bypass this protection (which is at the browser level, as galimy pointed out), consider the ProxyPass module for your favorite web server.

How to declare variable and use it in the same Oracle SQL script?

Just want to add Matas' answer. Maybe it's obvious, but I've searched for a long time to figure out that the variable is accessible only inside the BEGIN-END construction, so if you need to use it in some code later, you need to put this code inside the BEGIN-END block.

Note that these blocks can be nested:

    SELECT PK INTO x FROM table1 WHERE col1 = 'test';

        SELECT PK INTO y FROM table2 WHERE col2 = x;

        INSERT INTO table2 (col1, col2)
        SELECT y,'text'
        FROM dual
        WHERE exists(SELECT * FROM table2);


Is it ok to use `any?` to check if an array is not empty?

The difference between an array evaluating its values to true or if its empty.

The method empty? comes from the Array class

It's used to check if the array contains something or not. This includes things that evaluate to false, such as nil and false.

>> a = []
=> []
>> a.empty?
=> true
>> a = [nil, false]
=> [nil, false]
>> a.empty?
=> false
>> a = [nil]
=> [nil]
>> a.empty?
=> false

The method any? comes from the Enumerable module.

It's used to evaluate if "any" value in the array evaluates to true. Similar methods to this are none?, all? and one?, where they all just check to see how many times true could be evaluated. which has nothing to do with the count of values found in a array.

case 1

>> a = []
=> []
>> a.any?
=> false
=> false
>> a.all?
=> true
>> a.none?
=> true

case 2

>> a = [nil, true]
=> [nil, true]
>> a.any?
=> true
=> true
>> a.all?
=> false
>> a.none?
=> false

case 3

>> a = [true, true]
=> [true, true]
>> a.any?
=> true
=> false
>> a.all?
=> true
>> a.none?
=> false

How to access global variables

I would "inject" the starttime variable instead, otherwise you have a circular dependency between the packages.


var StartTime = time.Now()
func main() {
   otherPackage.StartTime = StartTime


var StartTime time.Time

Python: Find index of minimum item in list of floats

I would use:

val, idx = min((val, idx) for (idx, val) in enumerate(my_list))

Then val will be the minimum value and idx will be its index.

Python Flask, how to set content type

I like and upvoted @Simon Sapin's answer. I ended up taking a slightly different tack, however, and created my own decorator:

from flask import Response
from functools import wraps

def returns_xml(f):
    def decorated_function(*args, **kwargs):
        r = f(*args, **kwargs)
        return Response(r, content_type='text/xml; charset=utf-8')
    return decorated_function

and use it thus:

def ajax_ddl():
    xml = 'foo'
    return xml

I think this is slightly more comfortable.

File inside jar is not visible for spring

The error message is correct (if not very helpful): the file we're trying to load is not a file on the filesystem, but a chunk of bytes in a ZIP inside a ZIP.

Through experimentation (Java 11, Spring Boot 2.3.x), I found this to work without changing any config or even a wildcard:

var resource = ResourceUtils.getURL("classpath:some/resource/in/a/dependency");
new BufferedReader(
  new InputStreamReader(resource.openStream())

What is difference between 'git reset --hard HEAD~1' and 'git reset --soft HEAD~1'?

This is a useful article which graphically shows the explanation of the reset command.

Reset --hard can be quite dangerous as it overwrites your working copy without checking, so if you haven't commited the file at all, it is gone.

As for Source tree, there is no way I know of to undo commits. It would most likely use reset under the covers anyway

Oracle SQL Developer and PostgreSQL

I've just downloaded SQL Developer 4.0 for OS X (10.9), it just got out of beta. I also downloaded the latest Postgres JDBC jar. On a lark I decided to install it (same method as other third party db drivers in SQL Dev), and it accepted it. Whenever I click "new connection", there is a tab now for Postgres... and clicking it shows a panel that asks for the database connection details.

The answer to this question has changed, whether or not it is supported, it seems to work. There is a "choose database" button, that if clicked, gives you a dropdown list filled with available postgres databases. You create the connection, open it, and it lists the schemas in that database. Most postgres commands seem to work, though no psql commands (\list, etc).

Those who need a single tool to connect to multiple database engines can now use SQL Developer.

How much overhead does SSL impose?

Order of magnitude: zero.

In other words, you won't see your throughput cut in half, or anything like it, when you add TLS. Answers to the "duplicate" question focus heavily on application performance, and how that compares to SSL overhead. This question specifically excludes application processing, and seeks to compare non-SSL to SSL only. While it makes sense to take a global view of performance when optimizing, that is not what this question is asking.

The main overhead of SSL is the handshake. That's where the expensive asymmetric cryptography happens. After negotiation, relatively efficient symmetric ciphers are used. That's why it can be very helpful to enable SSL sessions for your HTTPS service, where many connections are made. For a long-lived connection, this "end-effect" isn't as significant, and sessions aren't as useful.

Here's an interesting anecdote. When Google switched Gmail to use HTTPS, no additional resources were required; no network hardware, no new hosts. It only increased CPU load by about 1%.

Cannot create a connection to data source Error (rsErrorOpeningConnection) in SSRS

I had a similar problem, and being the newbie that I am it took me a while to figure out but I learned the user must have a login in SSMS. I created the logins with the following parameters:

  • Under Server Roles - check sysadmin
  • Under User Mapping - I selected the database and the report server. For each I checked datareader and datawriter
  • Under Securables - I checked anything that would allow the user to connect to the database and view anything
  • I also found that one of the existing logins had denydatareader and denydatawriter checked. Once I removed these it worked.

I'm not saying this is the best way to do it, just what worked for me. Hope this helps

reactjs giving error Uncaught TypeError: Super expression must either be null or a function, not undefined

I got this when I tried to use react-i18next's Translation on the parent class and the child. It was being translated twice!

Why am I getting "Thread was being aborted" in ASP.NET?

For a web service hosted in ASP.NET, the configuration property is executionTimeout:

<configuration> <system.web>

<httpRuntime executionTimeout="360" />



Set this and the thread abort exception will go away :)

C# DropDownList with a Dictionary as DataSource

If the DropDownList is declared in your aspx page and not in the codebehind, you can do it like this.


<asp:DropDownList ID="ddlStatus" runat="server" DataSource="<%# Statuses %>"
     DataValueField="Key" DataTextField="Value"></asp:DropDownList>


protected void Page_Load(object sender, EventArgs e)
    // or use Page.DataBind() to bind everything

public Dictionary<int, string> Statuses
        // do database/webservice lookup here to populate Dictionary

Sorting dictionary keys in python

my_list = sorted(dict.items(), key=lambda x: x[1])

select into in mysql


CREATE TABLE new_tbl SELECT * FROM orig_tbl;

What is useState() in React?

Basically React.useState(0) magically sees that it should return the tuple count and setCount (a method to change count). The parameter useState takes sets the initial value of count.

  const [count, setCount] = React.useState(0);
  const [count2, setCount2] = React.useState(0);

  // increments count by 1 when first button clicked
  function handleClick(){
    setCount(count + 1);

  // increments count2 by 1 when second button clicked
  function handleClick2(){
    setCount2(count2 + 1);

  return (
      <h2>A React counter made with the useState Hook!</h2>
      <p>You clicked {count} times</p>
      <p>You clicked {count2} times</p>
      <button onClick={handleClick}>
        Click me
      <button onClick={handleClick2}>
        Click me2

Based off Enmanuel Duran's example, but shows two counters and writes lambda functions as normal functions, so some people might understand it easier.

Simple way to convert datarow array to datatable

.Net 3.5+ added DataTableExtensions, use DataTableExtensions.CopyToDataTable Method

For datarow array just use .CopyToDataTable() and it will return datatable.

For single datarow use

new DataRow[] { myDataRow }.CopyToDataTable()

Git - How to use .netrc file on Windows to save user and password

This will let Git authenticate on HTTPS using .netrc:

  • The file should be named _netrc and located in c:\Users\<username>.
  • You will need to set an environment variable called HOME=%USERPROFILE% (set system-wide environment variables using the System option in the control panel. Depending on the version of Windows, you may need to select "Advanced Options".).
  • The password stored in the _netrc file cannot contain spaces (quoting the password will not work).

What is tail call optimization?

GCC C minimal runnable example with x86 disassembly analysis

Let's see how GCC can automatically do tail call optimizations for us by looking at the generated assembly.

This will serve as an extremely concrete example of what was mentioned in other answers such as that the optimization can convert recursive function calls to a loop.

This in turn saves memory and improves performance, since memory accesses are often the main thing that makes programs slow nowadays.

As an input, we give GCC a non-optimized naive stack based factorial:


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

unsigned factorial(unsigned n) {
    if (n == 1) {
        return 1;
    return n * factorial(n - 1);

int main(int argc, char **argv) {
    int input;
    if (argc > 1) {
        input = strtoul(argv[1], NULL, 0);
    } else {
        input = 5;
    printf("%u\n", factorial(input));
    return EXIT_SUCCESS;

GitHub upstream.

Compile and disassemble:

gcc -O1 -foptimize-sibling-calls -ggdb3 -std=c99 -Wall -Wextra -Wpedantic \
  -o tail_call.out tail_call.c
objdump -d tail_call.out

where -foptimize-sibling-calls is the name of generalization of tail calls according to man gcc:

       Optimize sibling and tail recursive calls.

       Enabled at levels -O2, -O3, -Os.

as mentioned at: How do I check if gcc is performing tail-recursion optimization?

I choose -O1 because:

  • the optimization is not done with -O0. I suspect that this is because there are required intermediate transformations missing.
  • -O3 produces ungodly efficient code that would not be very educative, although it is also tail call optimized.

Disassembly with -fno-optimize-sibling-calls:

0000000000001145 <factorial>:
    1145:       89 f8                   mov    %edi,%eax
    1147:       83 ff 01                cmp    $0x1,%edi
    114a:       74 10                   je     115c <factorial+0x17>
    114c:       53                      push   %rbx
    114d:       89 fb                   mov    %edi,%ebx
    114f:       8d 7f ff                lea    -0x1(%rdi),%edi
    1152:       e8 ee ff ff ff          callq  1145 <factorial>
    1157:       0f af c3                imul   %ebx,%eax
    115a:       5b                      pop    %rbx
    115b:       c3                      retq
    115c:       c3                      retq

With -foptimize-sibling-calls:

0000000000001145 <factorial>:
    1145:       b8 01 00 00 00          mov    $0x1,%eax
    114a:       83 ff 01                cmp    $0x1,%edi
    114d:       74 0e                   je     115d <factorial+0x18>
    114f:       8d 57 ff                lea    -0x1(%rdi),%edx
    1152:       0f af c7                imul   %edi,%eax
    1155:       89 d7                   mov    %edx,%edi
    1157:       83 fa 01                cmp    $0x1,%edx
    115a:       75 f3                   jne    114f <factorial+0xa>
    115c:       c3                      retq
    115d:       89 f8                   mov    %edi,%eax
    115f:       c3                      retq

The key difference between the two is that:

  • the -fno-optimize-sibling-calls uses callq, which is the typical non-optimized function call.

    This instruction pushes the return address to the stack, therefore increasing it.

    Furthermore, this version also does push %rbx, which pushes %rbx to the stack.

    GCC does this because it stores edi, which is the first function argument (n) into ebx, then calls factorial.

    GCC needs to do this because it is preparing for another call to factorial, which will use the new edi == n-1.

    It chooses ebx because this register is callee-saved: What registers are preserved through a linux x86-64 function call so the subcall to factorial won't change it and lose n.

  • the -foptimize-sibling-calls does not use any instructions that push to the stack: it only does goto jumps within factorial with the instructions je and jne.

    Therefore, this version is equivalent to a while loop, without any function calls. Stack usage is constant.

Tested in Ubuntu 18.10, GCC 8.2.