Programs & Examples On #Registerclass

Error LNK2019 unresolved external symbol _main referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)

I got the same error because I created a new object from a templated class using the template name without specifying the type explicitly like this:

int main()

    MyClass<T> Test2(5.60, 6.6); <- This is wrong
    return 0;

The correct way to do it was to specify exactly what T was like this:

int main()

    MyClass<double> Test2(5.60, 6.6); <- This is right
    return 0;

How to detect tableView cell touched or clicked in swift

This worked good for me:

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {_x000D_
        print("section: \(indexPath.section)")_x000D_
        print("row: \(indexPath.row)")_x000D_

The output should be:

section: 0
row: 0

How to set cell spacing and UICollectionView - UICollectionViewFlowLayout size ratio?

In Certain situations, Setting the UICollectionViewFlowLayout in viewDidLoador ViewWillAppear may not effect on the collectionView.

Setting the UICollectionViewFlowLayout in viewDidAppear may cause see the changes of the cells sizes in runtime.

Another Solution, in Swift 3 :

extension YourViewController : UICollectionViewDelegateFlowLayout{

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 20, left: 0, bottom: 10, right: 0)

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let collectionViewWidth = collectionView.bounds.width
        return CGSize(width: collectionViewWidth/3, height: collectionViewWidth/3)

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 20

self.tableView.reloadData() not working in Swift

So, the issue was that I was trying to inappropriately use @lazy, which caused my Business variable to essentially be a constant, and thusly uneditable. Also, instead of loading the local json, I'm now loading only the data returned from the API.

import UIKit

class BusinessTableViewController: UITableViewController {

    var data: NSMutableData = NSMutableData()
    var Business: NSMutableArray = NSMutableArray()

    override func viewDidLoad() {

        navigationItem.titleView = UIImageView(image: UIImage(named: "growler"))

        tableView.registerClass(BeerTableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.separatorStyle = .None


    override func numberOfSectionsInTableView(tableView: UITableView!) -> Int {
        return Business.count

    override func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int {
        if (Business.count > 0) {
            let biz = Business[section] as NSDictionary
            let beers = biz["results"] as NSArray
            return beers.count
        } else {
            return 0;

    override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell? {
        let cell = tableView!.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath!) as BeerTableViewCell
        if let path = indexPath {
            let biz = Business[path.section] as NSDictionary
            let beers = biz["results"] as NSArray
            let beer = beers[path.row] as NSDictionary

            cell.titleLabel.text = beer["BeerName"] as String
        } else {
            cell.titleLabel.text = "Loading"

        return cell

    override func tableView(tableView: UITableView!, viewForHeaderInSection section: Int) -> UIView! {
        let view = LocationHeaderView()
        let biz = Business[section] as NSDictionary
        if (Business.count > 0) {
            let count = "\(Business.count)"
            view.titleLabel.text = (biz["name"] as String).uppercaseString
        return view

    override func tableView(tableView: UITableView!, heightForHeaderInSection section: Int) -> CGFloat {
        return 45

    func fetchKimono() {
        var urlPath = "names have been removed to protect the innocent"
        var url: NSURL = NSURL(string: urlPath)
        var request: NSURLRequest = NSURLRequest(URL: url)
        var connection: NSURLConnection = NSURLConnection(request: request, delegate: self, startImmediately: false)


    func connection(didReceiveResponse: NSURLConnection!, didReceiveResponse response: NSURLResponse!) {
        // Recieved a new request, clear out the data object = NSMutableData()

    func connection(connection: NSURLConnection!, didReceiveData data: NSData!) {
        // Append the recieved chunk of data to our data object

    func connectionDidFinishLoading(connection: NSURLConnection!) {
        // Request complete, should now hold the resulting info
        // Convert the retrieved data in to an object through JSON deserialization
        var err: NSError
        var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
        var results: NSDictionary = jsonResult["results"] as NSDictionary
        var collection: NSArray = results["collection1"] as NSArray
        if jsonResult.count>0 && collection.count>0 {
            Business = jsonResult

Swift Docs on @lazy:

You must always declare a lazy property as a variable (with the var keyword), because its initial value may not be retrieved until after instance initialization completes. Constant properties must always have a value before initialization completes, and therefore cannot be declared as lazy.

Add swipe to delete UITableViewCell

SWIFT 3 -- UIViewController

func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
    return true

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if (editingStyle == UITableViewCellEditingStyle.delete) {
        // handle delete (by removing the data from your array and updating the tableview)
        print("delete tableview cell")

UICollectionView current visible cell index

indexPathsForVisibleItems might work for most situations, but sometimes it returns an array with more than one index path and it can be tricky figuring out the one you want. In those situations, you can do something like this:

CGRect visibleRect = (CGRect){.origin = self.collectionView.contentOffset, .size = self.collectionView.bounds.size};
CGPoint visiblePoint = CGPointMake(CGRectGetMidX(visibleRect), CGRectGetMidY(visibleRect));
NSIndexPath *visibleIndexPath = [self.collectionView indexPathForItemAtPoint:visiblePoint];

This works especially well when each item in your collection view takes up the whole screen.

Swift version

let visibleRect = CGRect(origin: collectionView.contentOffset, size: collectionView.bounds.size)
let visiblePoint = CGPoint(x: visibleRect.midX, y: visibleRect.midY)
let visibleIndexPath = collectionView.indexPathForItem(at: visiblePoint)

Creating a UITableView Programmatically

- (void)viewDidLoad
    [super viewDidLoad];
    tableView = [[UITableView alloc] initWithFrame:self.view.bounds style:UITableViewStylePlain];
    tableView.delegate = self;
    tableView.dataSource = self;

    tableView.backgroundColor = [UIColor grayColor];

    // add to superview
    [self.view addSubview:tableView];

#pragma mark - UITableViewDataSource
- (NSInteger)numberOfSectionsInTableView:(UITableView *)theTableView
    return 1;

- (NSInteger)tableView:(UITableView *)theTableView numberOfRowsInSection:    (NSInteger)section
    return 1;

// the cell will be returned to the tableView
- (UITableViewCell *)tableView:(UITableView *)theTableView  cellForRowAtIndexPath:(NSIndexPath *)indexPath
    static NSString *cellIdentifier = @"HistoryCell";

    // Similar to UITableViewCell, but 
    UITableViewCell *cell = (UITableViewCell *)[theTableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if (cell == nil)
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
    cell.descriptionLabel.text = @"Testing";
    return cell;

What is the best way to get the minimum or maximum value from an Array of numbers?

There isn't any reliable way to get the minimum/maximum without testing every value. You don't want to try a sort or anything like that, walking through the array is O(n), which is better than any sort algorithm can do in the general case.

Can someone post a well formed crossdomain.xml sample?

This is what I've been using for development:

<?xml version="1.0" ?>
<allow-access-from domain="*" />

This is a very liberal approach, but is fine for my application.

As others have pointed out below, beware the risks of this.

Using LIMIT within GROUP BY to get N results per group?

for those like me that had queries time out. I made the below to use limits and anything else by a specific group.

CREATE PROCEDURE count_limit200()
    DECLARE a INT Default 0;
    DECLARE stop_loop INT Default 0;
    DECLARE domain_val VARCHAR(250);

    OPEN domain_list;

    SELECT COUNT(DISTINCT(domain)) INTO stop_loop 
    loop_thru_domains: LOOP
        FETCH domain_list INTO domain_val;
        SET a=a+1;

        INSERT INTO db.two(book,artist,title,title_count,last_updated) 
        SELECT * FROM 
            SELECT book,artist,title,COUNT(ObjectKey) AS titleCount, NOW() 
            WHERE book = domain_val
            GROUP BY artist,title
            ORDER BY book,titleCount DESC
            LIMIT 200
        ) a ON DUPLICATE KEY UPDATE title_count = titleCount, last_updated = NOW();

        IF a = stop_loop THEN
            LEAVE loop_thru_domain;
        END IF;
    END LOOP loop_thru_domain;
END $$

it loops through a list of domains and then inserts only a limit of 200 each

How to permanently export a variable in Linux?

You can add it to your shell configuration file, e.g. $HOME/.bashrc or more globally in /etc/environment. After adding these lines the changes won't reflect instantly in GUI based system's you have to exit the terminal or create a new one and in server logout the session and login to reflect these changes.

how to bypass Access-Control-Allow-Origin?

Put this on top of retrieve.php:

header('Access-Control-Allow-Origin: *');

Note that this effectively disables CORS protection, and leaves your users exposed to attack. If you're not completely certain that you need to allow all origins, you should lock this down to a more specific origin:


Please refer to following stack answer for better understanding of Access-Control-Allow-Origin

javac error: Class names are only accepted if annotation processing is explicitly requested

If you compile multiple files in the same line, ensure that you use javac only once and not for every class file.

Incorrect: enter image description here

Correct: enter image description here

Clearfix with twitter bootstrap

clearfix should contain the floating elements but in your html you have added clearfix only after floating right that is your pull-right so you should do like this:

<div class="clearfix">
  <div id="sidebar">
  <div id="main">
      <div class="pull-right">
  <div>MOVED BELOW Z</div>

see this demo

Happy to know you solved the problem by setting overflow properties. However this is also good idea to clear the float. Where you have floated your elements you could add overflow: hidden; as you have done in your main.

Angular.js: How does $eval work and why is it different from vanilla eval?

From the test,

it('should allow passing locals to the expression', inject(function($rootScope) {
  expect($rootScope.$eval('a+1', {a: 2})).toBe(3);

  $rootScope.$eval(function(scope, locals) {
    scope.c = locals.b + 4;
  }, {b: 3});

We also can pass locals for evaluation expression.

See last changes in svn

If you have not yet commit you last changes before vacation. - Command line to the project folder. - Type 'svn diff'

If you already commit you last changes before vacation.

  • Browse to your project.
  • Find a link "View log". Click it.
  • Select top two revision and Click "Compare Revisions" button in the bottom. This will show you the different between the latest and the previous revision.

Search a whole table in mySQL for a string

A PHP Based Solution for search entire table ! Search string is $string . This is generic and will work with all the tables with any number of fields

$sql="SELECT * from client_wireless";
$logicStr="WHERE ";
for($i=0 ; $i < mysql_num_fields($sql_query) ; $i++){
 if($i == ($count-1) )
$logicStr=$logicStr."".mysql_field_name($sql_query,$i)." LIKE '%".$string."%' ";
$logicStr=$logicStr."".mysql_field_name($sql_query,$i)." LIKE '%".$string."%' OR ";
// start the search in all the fields and when a match is found, go on printing it .
$sql="SELECT * from client_wireless ".$logicStr;
//echo $sql;

C# "internal" access modifier when doing unit testing

Internal classes need to be tested and there is an assemby attribute:

using System.Runtime.CompilerServices;


Add this to the project info file, e.g. Properties\AssemblyInfo.cs.

How to execute an action before close metro app WinJS

If I am not mistaken, it will be onunload event.

"Occurs when the application is about to be unloaded." - MSDN

Align div right in Bootstrap 3

Add offset8 to your class, for example:

<div class="offset8">aligns to the right</div>

How do you convert WSDLs to Java classes using Eclipse?

Using command prompt in windows you can use below command to get class files.

wsimport "complete file path of your .wsdl file"
example : wsimport C:\Users\schemas\com\myprofile\myprofile2019.wsdl

if you want to generate source code you should be using below commnad.

wsimport -keep -s src "complete file path of your .wsdl file"
example : wsimport -keep -s src C:\Users\schemas\com\myprofile\myprofile2019.wsdl

Note : Here "-s" means source directory and "src" is name of folder that should be created before executing this command. Wsimport is a tool which is bundled along with JAVA SE, no seperate download is required.

CSS3 background image transition

You can transition background-image. Use the CSS below on the img element:

-webkit-transition: background-image 0.2s ease-in-out;
transition: background-image 0.2s ease-in-out;

This is supported natively by Chrome, Opera and Safari. Firefox hasn't implemented it yet ( Not sure about IE.

Check orientation on Android phone

The current configuration, as used to determine which resources to retrieve, is available from the Resources' Configuration object:


You can check for orientation by looking at its value:

int orientation = getResources().getConfiguration().orientation;
if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
    // In landscape
} else {
    // In portrait

More information can be found in the Android Developer.

How to reload a page using Angularjs?

Be sure to include the $route service into your scope and do this:


See this:

How to reload or re-render the entire page using AngularJS

Squash the first two commits in Git?

I've reworked VonC's script to do everything automatically and not ask me for anything. You give it two commit SHA1s and it will squash everything between them into one commit named "squashed history":

# Go back to the last commit that we want
# to form the initial commit (detach HEAD)
git checkout $2

# reset the branch pointer to the initial commit (= $1),
# but leaving the index and working tree intact.
git reset --soft $1

# amend the initial tree using the tree from $2
git commit --amend -m "squashed history"

# remember the new commit sha1
TARGET=`git rev-list HEAD --max-count=1`

# go back to the original branch (assume master for this example)
git checkout master

# Replay all the commits after $2 onto the new initial commit
git rebase --onto $TARGET $2

How to flush output of print function?

On Python 3, print can take an optional flush argument

print("Hello world!", flush=True)

On Python 2 you'll have to do

import sys

after calling print. By default, print prints to sys.stdout (see the documentation for more about file objects).

how to delete the content of text file without deleting itself

You can use

FileWriter fw = new FileWriter(/*your file path*/);
PrintWriter pw = new PrintWriter(fw);

Remember not to use

FileWriter fw = new FileWriter(/*your file path*/,true);

True in the filewriter constructor will enable append.

JSON.parse vs. eval()

There is a difference between what JSON.parse() and eval() will accept. Try eval on this:

var x = "{\"shoppingCartName\":\"shopping_cart:2000\"}"

eval(x)         //won't work
JSON.parse(x)   //does work

See this example.

How to detect the device orientation using CSS media queries?

I would go for aspect-ratio, it offers way more possibilities.

/* Exact aspect ratio */
@media (aspect-ratio: 2/1) {

/* Minimum aspect ratio */
@media (min-aspect-ratio: 16/9) {

/* Maximum aspect ratio */
@media (max-aspect-ratio: 8/5) {

Both, orientation and aspect-ratio depend on the actual size of the viewport and have nothing todo with the device orientation itself.

Read more:

show all tables in DB2 using the LIST command

Run this command line on your preferred shell session:

db2 "select tabname from syscat.tables where owner = 'DB2INST1'"

Maybe you'd like to modify the owner name, and need to check the list of current owners?

db2 "select distinct owner from syscat.tables"

Get Unix timestamp with C++

Windows uses a different epoch and time units: see Convert Windows Filetime to second in Unix/Linux

What std::time() returns on Windows is (as yet) unknown to me (;-))

Python code to remove HTML tags from a string

Using a regex

Using a regex, you can clean everything inside <> :

import re

def cleanhtml(raw_html):
  cleanr = re.compile('<.*?>')
  cleantext = re.sub(cleanr, '', raw_html)
  return cleantext

Some HTML texts can also contain entities that are not enclosed in brackets, such as '&nsbm'. If that is the case, then you might want to write the regex as

cleanr = re.compile('<.*?>|&([a-z0-9]+|#[0-9]{1,6}|#x[0-9a-f]{1,6});')

This link contains more details on this.

Using BeautifulSoup

You could also use BeautifulSoup additional package to find out all the raw text.

You will need to explicitly set a parser when calling BeautifulSoup I recommend "lxml" as mentioned in alternative answers (much more robust than the default one (html.parser) (i.e. available without additional install).

from bs4 import BeautifulSoup
cleantext = BeautifulSoup(raw_html, "lxml").text

But it doesn't prevent you from using external libraries, so I recommend the first solution.

EDIT: To use lxml you need to pip install lxml.

How Do I Insert a Byte[] Into an SQL Server VARBINARY Column

My solution would be to use a parameterised query, as the connectivity objects take care of formatting the data correctly (including ensuring the correct data-type, and escaping "dangerous" characters where applicable):

// Assuming "conn" is an open SqlConnection
using(SqlCommand cmd = new SqlCommand("INSERT INTO mssqltable(varbinarycolumn) VALUES (@binaryValue)", conn))
    // Replace 8000, below, with the correct size of the field
    cmd.Parameters.Add("@binaryValue", SqlDbType.VarBinary, 8000).Value = arraytoinsert;

Edit: Added the wrapping "using" statement as suggested by John Saunders to correctly dispose of the SqlCommand after it is finished with

How to write LDAP query to test if user is member of a group?

You should be able to create a query with this filter here:


and when you run that against your LDAP server, if you get a result, your user "yourUserName" is indeed a member of the group "CN=YourGroup,OU=Users,DC=YourDomain,DC=com

Try and see if this works!

If you use C# / VB.Net and System.DirectoryServices, this snippet should do the trick:

DirectoryEntry rootEntry = new DirectoryEntry("LDAP://dc=yourcompany,dc=com");

DirectorySearcher srch = new DirectorySearcher(rootEntry);
srch.SearchScope = SearchScope.Subtree;

srch.Filter = "(&(objectClass=user)(sAMAccountName=yourusername)(memberOf=CN=yourgroup,OU=yourOU,DC=yourcompany,DC=com))";

SearchResultCollection res = srch.FindAll();

if(res == null || res.Count <= 0) {
    Console.WriteLine("This user is *NOT* member of that group");
} else {
    Console.WriteLine("This user is INDEED a member of that group");

Word of caution: this will only test for immediate group memberships, and it will not test for membership in what is called the "primary group" (usually "cn=Users") in your domain. It does not handle nested memberships, e.g. User A is member of Group A which is member of Group B - that fact that User A is really a member of Group B as well doesn't get reflected here.


Convert Mongoose docs to json

First of all, try toObject() instead of toJSON() maybe?

Secondly, you'll need to call it on the actual documents and not the array, so maybe try something more annoying like this:

var flatUsers = {
  return user.toObject();
return res.end(JSON.stringify(flatUsers));

It's a guess, but I hope it helps

How to display custom view in ActionBar?

I struggled with this myself, and tried Tomik's answer. However, this didn't made the layout to full available width on start, only when you add something to the view.

You'll need to set the LayoutParams.FILL_PARENT when adding the view:

//I'm using actionbarsherlock, but it's the same.
LayoutParams layout = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
getSupportActionBar().setCustomView(overlay, layout); 

This way it completely fills the available space. (You may need to use Tomik's solution too).

How do you stretch an image to fill a <div> while keeping the image's aspect-ratio?

This did the trick for me

div img {
    width: 100%;
    min-height: 500px;
    width: 100vw;
    height: 100vh;
    object-fit: cover;

build maven project with propriatery libraries included

Possible solutions is put your dependencies in src/main/resources then in your pom :

groupId ...
artifactId ...
version ...

Note: system dependencies are not copied into resulted jar/war
(see How to include system dependencies in war built using maven)

Connecting PostgreSQL 9.2.1 with Hibernate

This is a hibernate.cfg.xml for posgresql and it will help you with basic hibernate configurations for posgresql.

<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

        <property name="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</property>
        <property name="hibernate.connection.driver_class">org.postgresql.Driver</property>
        <property name="hibernate.connection.username">postgres</property>
        <property name="hibernate.connection.password">password</property>
        <property name="hibernate.connection.url">jdbc:postgresql://localhost:5432/hibernatedb</property>

        <property name="connection_pool_size">1</property>

        <property name="">create</property>

        <property name="show_sql">true</property>

       <mapping class="org.javabrains.sanjaya.dto.UserDetails"/>


Uploading multiple files using formData()

This one worked for me

//Javascript part_x000D_
//file_input is a file input id_x000D_
var formData = new FormData();_x000D_
var filesLength=document.getElementById('file_input').files.length;_x000D_
for(var i=0;i<filesLength;i++){_x000D_
 formData.append("file[]", document.getElementById('file_input').files[i]);_x000D_
   url: 'upload.php',_x000D_
   type: 'POST',_x000D_
   data: formData,_x000D_
   contentType: false,_x000D_
   cache: false,_x000D_
   processData: false,_x000D_
   success: function (html) {_x000D_

//PHP part_x000D_
$file_names = $_FILES["file"]["name"];_x000D_
for ($i = 0; $i < count($file_names); $i++) {_x000D_
   $extension = end(explode(".", $file_name));_x000D_
   $original_file_name = pathinfo($file_name, PATHINFO_FILENAME);_x000D_
   $file_url = $original_file_name . "-" . date("YmdHis") . "." . $extension;_x000D_
 move_uploaded_file($_FILES["file"]["tmp_name"][$i], $absolute_destination . $file_url);_x000D_

Convert from lowercase to uppercase all values in all character variables in dataframe

Starting with the following sample data :

df <- data.frame(v1=letters[1:5],v2=1:5,v3=letters[10:14],stringsAsFactors=FALSE)

  v1 v2 v3
1  a  1  j
2  b  2  k
3  c  3  l
4  d  4  m
5  e  5  n

You can use :

data.frame(lapply(df, function(v) {
  if (is.character(v)) return(toupper(v))
  else return(v)

Which gives :

  v1 v2 v3
1  A  1  J
2  B  2  K
3  C  3  L
4  D  4  M
5  E  5  N

Pandas index column title or name

Setting the index name can also be accomplished at creation:

pd.DataFrame(data={'age': [10,20,30], 'height': [100, 170, 175]}, index=pd.Series(['a', 'b', 'c'], name='Tag'))

How to pass model attributes from one Spring MVC controller to another controller?

By using @ModelAttribute we can pass the model from one controller to another controller

[ Input to the first Controller][1]

[]: from jsp page first controller binds the form data with the @ModelAttribute to the User Bean

public class FirstController {
    public ModelAndView forwardModel(@ModelAttribute("user") User u) {
        ModelAndView m = new ModelAndView("forward:/catchUser");
        m.addObject("usr", u);
        return m;

public class SecondController {
    public ModelAndView catchModel(@ModelAttribute("user")  User u) {
        System.out.println(u); //retrive the data passed by the first contoller
        ModelAndView mv = new ModelAndView("userDetails");
        return mv;

Recursively find files with a specific extension

This q/a shows how to use find with regular expression: How to use regex with find command?

Pattern could be something like


How to save and load cookies using Python + Selenium WebDriver

Remember, you can only add a cookie for the current domain.

If you want to add a cookie for your Google account, do

for cookie in cookies:

what is the difference between $_SERVER['REQUEST_URI'] and $_GET['q']?

Given this example url:

$_SERVER['REQUEST_URI'] will give you:


Whereas $_GET['q'] will give you:


In other words, $_SERVER['REQUEST_URI'] will hold the full request path including the querystring. And $_GET['q'] will give you the value of parameter q in the querystring.

How to round up value C# to the nearest integer?

It is simple. So follow this code.

decimal d = 10.5;
int roundNumber = (int)Math.Floor(d + 0.5);

Result is 11

Open multiple Projects/Folders in Visual Studio Code

What I suggest for now is to create symlinks in a folder, since VSCode isn't supporting that feature.

First, make a folder called whatever you'd like it to be.

$ mkdir random_project_folder
$ cd random_project_folder
$ ln -s /path/to/folder1/you/want/to/open folder1
$ ln -s /path/to/folder2/you/want/to/open folder2
$ ln -s /path/to/folder3/you/want/to/open folder3
$ code .

And you'll see your folders in the same VSCode window.

Simplest way to display current month and year like "Aug 2016" in PHP?

Full version:

<? echo date('F Y'); ?>

Short version:

<? echo date('M Y'); ?>

Here is a good reference for the different date options.


To show the previous month we would have to introduce the mktime() function and make use of the optional timestamp parameter for the date() function. Like this:

echo date('F Y', mktime(0, 0, 0, date('m')-1, 1, date('Y')));

This will also work (it's typically used to get the last day of the previous month):

echo date('F Y', mktime(0, 0, 0, date('m'), 0, date('Y')));

Hope that helps.

How do I set the driver's python version in spark?

Please look at the below snippet:

#setting environment variable for pyspark in linux||ubuntu
#goto --- /usr/local/spark/conf
#create a new file named copy all content of to it
#then add below lines to it, with path to python

PYSPARK_DRIVER_PYTHON_OPTS="notebook --no-browser"
#i was running python 3.6 ||run - 'which python' in terminal to find the path of python

Get a filtered list of files in a directory

Keep it simple:

import os
relevant_path = "[path to folder]"
included_extensions = ['jpg','jpeg', 'bmp', 'png', 'gif']
file_names = [fn for fn in os.listdir(relevant_path)
              if any(fn.endswith(ext) for ext in included_extensions)]

I prefer this form of list comprehensions because it reads well in English.

I read the fourth line as: For each fn in os.listdir for my path, give me only the ones that match any one of my included extensions.

It may be hard for novice python programmers to really get used to using list comprehensions for filtering, and it can have some memory overhead for very large data sets, but for listing a directory and other simple string filtering tasks, list comprehensions lead to more clean documentable code.

The only thing about this design is that it doesn't protect you against making the mistake of passing a string instead of a list. For example if you accidentally convert a string to a list and end up checking against all the characters of a string, you could end up getting a slew of false positives.

But it's better to have a problem that's easy to fix than a solution that's hard to understand.

Getting the HTTP Referrer in ASP.NET

Belonging to other reply, I have added condition clause for getting null.

string ComingUrl = "";
if (Request.UrlReferrer != null)
    ComingUrl = System.Web.HttpContext.Current.Request.UrlReferrer.ToString();
    ComingUrl = "Direct"; // Your code

The multi-part identifier could not be bound

If this error happens in an UPDATE, double-check the JOIN on the table with the column/field that is causing the error.

In my case this was due to the lack of the JOIN itself, which generated the same error due to an unknown field (as Andriy pointed out).

row-level trigger vs statement-level trigger

You may want trigger action to execute once after the client executes a statement that modifies a million rows (statement-level trigger). Or, you may want to trigger the action once for every row that is modified (row-level trigger).

EXAMPLE: Let's say you have a trigger that will make sure all high school seniors graduate. That is, when a senior's grade is 12, and we increase it to 13, we want to set the grade to NULL.

For a statement level trigger, you'd say, after the increase-grade statement runs, check the whole table once to update any nows with grade 13 to NULL.

For a row-level trigger, you'd say, after every row that is updated, update the new row's grade to NULL if it is 13.

A statement-level trigger would look like this:

create trigger stmt_level_trigger
after update on Highschooler
    update Highschooler
    set grade = NULL
    where grade = 13;

and a row-level trigger would look like this:

create trigger row_level_trigger
after update on Highschooler
for each row
when New.grade = 13
    update Highschooler
    set grade = NULL
    where New.ID = Highschooler.ID;

Note that SQLite doesn't support statement-level triggers, so in SQLite, the FOR EACH ROW is optional.

How do you append an int to a string in C++?

Well, if you use cout you can just write the integer directly to it, as in

std::cout << text << i;

The C++ way of converting all kinds of objects to strings is through string streams. If you don't have one handy, just create one.

#include <sstream>

std::ostringstream oss;
oss << text << i;
std::cout << oss.str();

Alternatively, you can just convert the integer and append it to the string.

oss << i;
text += oss.str();

Finally, the Boost libraries provide boost::lexical_cast, which wraps around the stringstream conversion with a syntax like the built-in type casts.

#include <boost/lexical_cast.hpp>

text += boost::lexical_cast<std::string>(i);

This also works the other way around, i.e. to parse strings.

Android - how do I investigate an ANR?

You need to look for "waiting to lock" in /data/anr/traces.txt file

enter image description here

for more details: Engineer for High Performance with Tools from Android & Play (Google I/O '17)

Insert multiple lines into a file after specified pattern using shell script

if you want to do that with a bash script, that's useful.

echo $password | echo 'net.ipv4.ping_group_range=0 2147483647' |  sudo -S tee -a /etc/sysctl.conf

Why does Java have an "unreachable statement" compiler error?

There is no definitive reason why unreachable statements must be not be allowed; other languages allow them without problems. For your specific need, this is the usual trick:

if (true) return;

It looks nonsensical, anyone who reads the code will guess that it must have been done deliberately, not a careless mistake of leaving the rest of statements unreachable.

Java has a little bit support for "conditional compilation"

if (false) { x=3; }

does not result in a compile-time error. An optimizing compiler may realize that the statement x=3; will never be executed and may choose to omit the code for that statement from the generated class file, but the statement x=3; is not regarded as "unreachable" in the technical sense specified here.

The rationale for this differing treatment is to allow programmers to define "flag variables" such as:

static final boolean DEBUG = false;

and then write code such as:

if (DEBUG) { x=3; }

The idea is that it should be possible to change the value of DEBUG from false to true or from true to false and then compile the code correctly with no other changes to the program text.

C - error: storage size of ‘a’ isn’t known

1)declare the structs before the main function. it worked for me. 2) And also fix the spelling mistake of that variable name if any e

Android: how to handle button click

Question#1 - These are the only way to handle view clicks.

Question#2 -
Option#1/Option#4 - There's not much difference between option#1 and option#4. The only difference I see is in one case activity is implementing the OnClickListener, whereas, in the other case, there'd be an anonymous implementation.

Option#2 - In this method an anonymous class will be generated. This method is a bit cumborsome, as, you'd need to do it multiple times, if you have multiple buttons. For Anonymous classes, you have to be careful for handling memory leaks.

Option#3 - Though, this is a easy way. Usually, Programmers try not to use any method until they write it, and hence this method is not widely used. You'd see mostly people use Option#4. Because it is cleaner in term of code.

Error inflating class

I have solved this Issue by this blog:

The problem is you use the wrong theme,you can choose theme that like Theme.AppCompat.NoActionBar, in my project,it works.

I hope to help you?

for or while loop to do something n times

This is lighter weight than xrange (and the while loop) since it doesn't even need to create the int objects. It also works equally well in Python2 and Python3

from itertools import repeat
for i in repeat(None, 10):

Byte array to image conversion

In one line:

Image.FromStream(new MemoryStream(byteArrayIn));

Saving awk output to variable

I think the $() syntax is easier to read...

variable=$(ps -ef | grep "port 10 -" | grep -v "grep port 10 -"| awk '{printf "%s", $12}')

But the real issue is probably that $12 should not be qouted with ""

Edited since the question was changed, This returns valid data, but it is not clear what the expected output of ps -ef is and what is expected in variable.

Vertical align middle with Bootstrap responsive grid

Add !important rule to display: table of your .v-center class.

.v-center {
    display:table !important;
    border:2px solid gray;

Your display property is being overridden by bootstrap to display: block.


How to retrieve the current version of a MySQL database management system (DBMS)?

Try this function -

-> '5.7.22-standard'


Or for more details use :

| Variable_name           | Value                                    |
| protocol_version        | 10                                       |
| version                 | 5.0.27-standard                          |
| version_comment         | MySQL Community Edition - Standard (GPL) |
| version_compile_machine | i686                                     |
| version_compile_os      | pc-linux-gnu                             |
5 rows in set (0.04 sec)

MySQL 5.0 Reference Manual (pdf) - Determining Your Current MySQL Version - page 42

if (boolean == false) vs. if (!boolean)

This is a style choice. It does not impact the performance of the code in the least, it just makes it more verbose for the reader.

Iterate over object in Angular

In addition to @obscur's answer, here is an example of how you can access both the key and value from the @View.


   name: 'keyValueFilter'

export class keyValueFilterPipe {
    transform(value: any, args: any[] = null): any {

        return Object.keys(value).map(function(key) {
            let pair = {};
            let k = 'key';
            let v = 'value'

            pair[k] = key;
            pair[v] = value[key];

            return pair;



<li *ngFor="let u of myObject | 
keyValueFilter">First Name: {{u.key}} <br> Last Name: {{u.value}}</li>

So if the object were to look like:

myObject = {
    Daario: Naharis,
    Victarion: Greyjoy,
    Quentyn: Ball

The generated outcome would be:

First name: Daario
Last Name: Naharis

First name: Victarion
Last Name: Greyjoy

First name: Quentyn
Last Name: Ball

Fatal error: Class 'PHPMailer' not found

This answers in an extension to what avs099 has given above, for those who are still having problems:

1.Makesure that you have php_openssl.dll installed(else find it online and install it);

2.Go to your php.ini; find extension=php_openssl.dll enable it/uncomment

3.Go to github and downland the latetest version :6.0 at this time.

4.Extract the master copy into the path that works better for you(I recommend the same directory as the calling file)

Now copy this code into your foo-mailer.php and render it with your gmail stmp authentications.


    $mail = new PHPMailer\PHPMailer\PHPMailer();

    $mail->Host = "";
    $mail->SMTPDebug = 1; 
    $mail->Port = 465 ; //465 or 587

     $mail->SMTPSecure = 'ssl';  
    $mail->SMTPAuth = true; 

    $mail->Username = "[email protected]";
    $mail->Password = "*******";

    //Set Params
    $mail->SetFrom("[email protected]");
    $mail->AddAddress("[email protected]");
    $mail->Subject = "Test";
    $mail->Body = "hello";

     if(!$mail->Send()) {
        echo "Mailer Error: " . $mail->ErrorInfo;
     } else {
        echo "Message has been sent";

Disclaimer:The original owner of the code above is avs099 with just my little input.

Take note of the additional:

a) (PHPMailer\PHPMailer) namespace:needed for name conflict resolution.

b) The (require("/PHPMailer-master/src/Exception.php");):It was missing in avs099's code thus the problem encountered by aProgger,you need that line to tell the mailer class where the Exception class is located.

CSS: On hover show and hide different div's at the same time?

Have you tried somethig like this?

.showme{display: none;}
.showhim:hover .showme{display : block;}
.showhim:hover .hideme{display:none;}

<div class="showhim">HOVER ME
  <div class="showme">hai</div>
  <div class="hideme">bye</div>

I dont know any reason why it shouldn't be possible.

How to "wait" a Thread in Android

Don't use wait(), use either android.os.SystemClock.sleep(1000); or Thread.sleep(1000);.

The main difference between them is that Thread.sleep() can be interrupted early -- you'll be told, but it's still not the full second. The android.os call will not wake early.

How to create a new component in Angular 4 using CLI

ng g c --dry-run so you can see what you are about to do before you actually do it will save some frustration. Just shows you what it is going to do without actually doing it.

How do I set session timeout of greater than 30 minutes

if you are allowed to do it globally then you can set the session time out in

TOMCAT_HOME/conf/web.xml as below

 <!-- ==================== Default Session Configuration ================= -->
  <!-- You can set the default session timeout (in minutes) for all newly   -->
  <!-- created sessions by modifying the value below.                       -->


Proper way to declare custom exceptions in modern Python?

"Proper way to declare custom exceptions in modern Python?"

This is fine, unless your exception is really a type of a more specific exception:

class MyException(Exception):

Or better (maybe perfect), instead of pass give a docstring:

class MyException(Exception):
    """Raise for my specific kind of exception"""

Subclassing Exception Subclasses

From the docs


All built-in, non-system-exiting exceptions are derived from this class. All user-defined exceptions should also be derived from this class.

That means that if your exception is a type of a more specific exception, subclass that exception instead of the generic Exception (and the result will be that you still derive from Exception as the docs recommend). Also, you can at least provide a docstring (and not be forced to use the pass keyword):

class MyAppValueError(ValueError):
    '''Raise when my specific value is wrong'''

Set attributes you create yourself with a custom __init__. Avoid passing a dict as a positional argument, future users of your code will thank you. If you use the deprecated message attribute, assigning it yourself will avoid a DeprecationWarning:

class MyAppValueError(ValueError):
    '''Raise when a specific subset of values in context of app is wrong'''
    def __init__(self, message, foo, *args):
        self.message = message # without this you may get DeprecationWarning
        # Special attribute you desire with your Error, 
        # perhaps the value that caused the error?: = foo         
        # allow users initialize misc. arguments as any other builtin Error
        super(MyAppValueError, self).__init__(message, foo, *args) 

There's really no need to write your own __str__ or __repr__. The builtin ones are very nice, and your cooperative inheritance ensures that you use it.

Critique of the top answer

Maybe I missed the question, but why not:

class MyException(Exception):

Again, the problem with the above is that in order to catch it, you'll either have to name it specifically (importing it if created elsewhere) or catch Exception, (but you're probably not prepared to handle all types of Exceptions, and you should only catch exceptions you are prepared to handle). Similar criticism to the below, but additionally that's not the way to initialize via super, and you'll get a DeprecationWarning if you access the message attribute:

Edit: to override something (or pass extra args), do this:

class ValidationError(Exception):
    def __init__(self, message, errors):

        # Call the base class constructor with the parameters it needs
        super(ValidationError, self).__init__(message)

        # Now for your custom code...
        self.errors = errors

That way you could pass dict of error messages to the second param, and get to it later with e.errors

It also requires exactly two arguments to be passed in (aside from the self.) No more, no less. That's an interesting constraint that future users may not appreciate.

To be direct - it violates Liskov substitutability.

I'll demonstrate both errors:

>>> ValidationError('foo', 'bar', 'baz').message

Traceback (most recent call last):
  File "<pyshell#10>", line 1, in <module>
    ValidationError('foo', 'bar', 'baz').message
TypeError: __init__() takes exactly 3 arguments (4 given)

>>> ValidationError('foo', 'bar').message
__main__:1: DeprecationWarning: BaseException.message has been deprecated as of Python 2.6

Compared to:

>>> MyAppValueError('foo', 'FOO', 'bar').message

how to set default culture info for entire c# application

Not for entire application or particular class.

CurrentUICulture and CurrentCulture are settable per thread as discussed here Is there a way of setting culture for a whole application? All current threads and new threads?. You can't change InvariantCulture at all.

Sample code to change cultures for current thread:

CultureInfo ci = new CultureInfo(theCultureString);
Thread.CurrentThread.CurrentCulture = ci;
Thread.CurrentThread.CurrentUICulture = ci;

For class you can set/restore culture inside critical methods, but it would be significantly safe to use appropriate overrides for most formatting related methods that take culture as one of arguments:

(3.3).ToString(new CultureInfo("fr-FR"))

How do I stretch a background image to cover the entire HTML element?

Simply make a div to be the direct child of body (with the class name bg for example), encompassing all other elements in the body, and add this to the CSS file:

.bg {
    background-image: url('_images/home.jpg');//Put your appropriate image URL here
    background-size: 100% 100%; //You need to put 100% twice here to stretch width and height

Refer to this link: Scroll down to the part that says:

  1. If the background-size property is set to "100% 100%", the background image will stretch to cover the entire content area

There it shows the 'img_flowers.jpg' stretching to the size of the screen or browser regardless of how you resize it.

Warning: Cannot modify header information - headers already sent by ERROR

Check something with echo, print() or printr() in the include file, header.php.

It might be that this is the problem OR if any MVC file, then check the number of spaces after ?>. This could also make a problem.

How to enable or disable an anchor using jQuery?

It's as simple as return false;


jQuery("li a:eq(0)").click(function(){
   return false;


jQuery("#menu a").click(function(){
   return false;

Composer Update Laravel

You can use :

composer self-update --2

To update to 2.0.8 version (Latest stable version)

How to declare a local variable in Razor?

I think you were pretty close, try this:

@{bool isUserConnected = string.IsNullOrEmpty(Model.CreatorFullName);}
@if (isUserConnected)
{ // meaning that the viewing user has not been saved so continue
        <div> click to join us </div>
        <a id="login" href="javascript:void(0);" style="display: inline; ">join here</a>

Installing specific package versions with pip

Sometimes, the previously installed version is cached.

~$ pip install pillow==5.2.0

It returns the followings:
Requirement already satisfied: pillow==5.2.0 in /home/ubuntu/anaconda3/lib/python3.6/site-packages (5.2.0)

We can use --no-cache-dir together with -I to overwrite this

~$ pip install --no-cache-dir -I pillow==5.2.0

A potentially dangerous Request.Form value was detected from the client

Here are possible solution which may help you. Make server side configuration setting for this. If you want to allow HTML element as input from selected pages in your project than you set this page attribute.

<%@ Page ValidateRequest="false" %>

This ValidateRequest="false" on each page. If you want in all pages in you project than make changes in Web.Config file. Add this tag In section.

If you are using .Net 4.0 than you have to make one more change in Web.Config file. Add this tag In section.

<httpRuntime requestValidationMode="2.0" />

Here are configuration for do not validate request for all pages in .Net 4.0

     <httpRuntime requestValidationMode="2.0" />
  <pages validateRequest="false">

Here is full example on this. Click Here...

How to detect running app using ADB command

If you want to directly get the package name of the current app in focus, use this adb command -

adb shell dumpsys window windows | grep -E 'mFocusedApp'| cut -d / -f 1 | cut -d " " -f 7

Extra info from the result of the adb command is removed using the cut command. Original solution from here.

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

You have to seed it. Seeding it with the time is a good idea:


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

int main ()
  srand ( time(NULL) );
  printf ("Random Number: %d\n", rand() %100);
  return 0;

You get the same sequence because rand() is automatically seeded with the a value of 1 if you do not call srand().


Due to comments

rand() will return a number between 0 and RAND_MAX (defined in the standard library). Using the modulo operator (%) gives the remainder of the division rand() / 100. This will force the random number to be within the range 0-99. For example, to get a random number in the range of 0-999 we would apply rand() % 1000.

How much overhead does SSL impose?

I second @erickson: The pure data-transfer speed penalty is negligible. Modern CPUs reach a crypto/AES throughput of several hundred MBit/s. So unless you are on resource constrained system (mobile phone) TLS/SSL is fast enough for slinging data around.

But keep in mind that encryption makes caching and load balancing much harder. This might result in a huge performance penalty.

But connection setup is really a show stopper for many application. On low bandwidth, high packet loss, high latency connections (mobile device in the countryside) the additional roundtrips required by TLS might render something slow into something unusable.

For example we had to drop the encryption requirement for access to some of our internal web apps - they where next to unusable if used from china.

Using SED with wildcard

The asterisk (*) means "zero or more of the previous item".

If you want to match any single character use

sed -i 's/string-./string-0/g' file.txt

If you want to match any string (i.e. any single character zero or more times) use

sed -i 's/string-.*/string-0/g' file.txt

Custom header to HttpClient request

Here is an answer based on that by Anubis (which is a better approach as it doesn't modify the headers for every request) but which is more equivalent to the code in the original question:

using Newtonsoft.Json;

var client = new HttpClient();
var httpRequestMessage = new HttpRequestMessage
        Method = HttpMethod.Post,
        RequestUri = new Uri(""),
        Headers = { 
            { HttpRequestHeader.Authorization.ToString(), "Bearer xxxxxxxxxxxxxxxxxxx" },
            { HttpRequestHeader.Accept.ToString(), "application/json" },
            { "X-Version", "1" }
        Content = new StringContent(JsonConvert.SerializeObject(svm))

var response = client.SendAsync(httpRequestMessage).Result;

Get Return Value from Stored procedure in

Do it this way (make necessary changes in code)..

            SqlConnection con = new SqlConnection(GetConnectionString());
            SqlCommand cmd = new SqlCommand("CheckUser", con);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlParameter p1 = new SqlParameter("username", username.Text);
            SqlParameter p2 = new SqlParameter("password", password.Text);
            SqlDataReader rd = cmd.ExecuteReader();
                //do the things
                lblinfo.Text = "abc";

Gradle error: Minimum supported Gradle version is 3.3. Current version is 3.2

About Android Studio Gradle plugin version and Required Gradle version, you can see more detailed answer here: What is real Android Studio Gradle Version?

For each version of this Gradle plugin, it requires a minimum Gradle version as listed on below table

(Reference page:gradle-plugin#updating-gradle).

enter image description here

When you update Android Studio, you may receive a prompt to also update Gradle to the latest available version.

For example, Android Gradle Plugin version 3.1.0+ requires a minimal gradle version 4.4.

You can be configured via Android Studio File -> Project Structure -> Project. See below:

enter image description here

Or you can manually modify the file gradle/wrapper/ For example:

distributionUrl = https\://

How to center text vertically with a large font-awesome icon?

a flexbox option - font awesome 4.7 and below

FA 4.x Hosted URL -

div {_x000D_
  display: inline-flex; /* make element size relative to content */_x000D_
  align-items: center; /* vertical alignment of items */_x000D_
  line-height: 40px; /* vertically size by height, line-height or padding */_x000D_
  padding: 0px 10px; /* horizontal with padding-l/r */_x000D_
  border: 1px solid #ccc;_x000D_
/* unnecessary styling below, ignore */_x000D_
body {display: flex;justify-content: center;align-items: center;height: 100vh;}div i {margin-right: 10px;}div {background-color: hsla(0, 0%, 87%, 0.5);}div:hover {background-color: hsla(34, 100%, 52%, 0.5);cursor: pointer;}
<link href="" rel="stylesheet"/>_x000D_
    <i class='fa fa-2x fa-camera'></i>_x000D_
    hello world_x000D_


using flex and font awesome 5

FA 5.x Hosted URL -

div {_x000D_
  display: inline-flex; /* make element size relative to content */_x000D_
  align-items: center; /* vertical alignment of items */_x000D_
  padding: 3px 10px; /* horizontal vertical position with padding */_x000D_
  border: 1px solid #ccc;_x000D_
.svg-inline--fa { /* target all FA icons */_x000D_
  padding-right: 10px;_x000D_
.icon-camera .svg-inline--fa { /* target specific icon */_x000D_
  font-size: 50px;_x000D_
/* unnecessary styling below, ignore */_x000D_
body {display: flex;justify-content: center;align-items: center;height: 100vh; flex-direction: column;}div{margin: 10px 0;}div {background-color: hsla(0, 0%, 87%, 0.5);}div:hover {background-color: hsla(212, 100%, 63%, 1);cursor: pointer;}
<script src=""></script>_x000D_
<div class="icon-camera">_x000D_
    <i class='fas fa-camera'></i>_x000D_
    hello world_x000D_
<div class="icon-clock">_x000D_
    <i class='fas fa-clock'></i>_x000D_
    hello world_x000D_


Postgresql : syntax error at or near "-"

i was trying trying to GRANT read-only privileges to a particular table to a user called walters-ro. So when i ran the sql command # GRANT SELECT ON table_name TO walters-ro; --- i got the following error..`syntax error at or near “-”

The solution to this was basically putting the user_name into double quotes since there is a dash(-) between the name.

# GRANT SELECT ON table_name TO "walters-ro";

That solved the problem.

checking memory_limit in PHP

Thank you for inspiration.

I had the same problem and instead of just copy-pasting some function from the Internet, I wrote an open source tool for it. Feel free to use it or provide feedback!

Just install it using Composer and then you get the current PHP memory limit like this:

$configuration = new \BrandEmbassy\Memory\MemoryConfiguration();
$limitProvider = new \BrandEmbassy\Memory\MemoryLimitProvider($configuration);
$limitInBytes = $memoryLimitProvider->getLimitInBytes();

How do I find out my MySQL URL, host, port and username?

If you use phpMyAdmin, click on Home, then Variables on the top menu. Look for the port setting on the page. The value it is set to is the port your MySQL server is running on.

if checkbox is checked, do this

Probably you can go with this code to take actions as the checkbox is checked or unchecked.


Javascript: Extend a Function

The other methods are great but they don't preserve any prototype functions attached to init. To get around that you can do the following (inspired by the post from Nick Craver).

(function () {
    var old_prototype = init.prototype;
    var old_init = init;
    init = function () {
        old_init.apply(this, arguments);
        // Do something extra
    init.prototype = old_prototype;
}) ();

Constant pointer vs Pointer to constant

Please refer the following link for better understanding about the difference between Const pointer and Pointer on a constant value.

constant pointer vs pointer on a constant value

Eclipse: How do I add the javax.servlet package to a project?

To expound on darioo's answer with a concrete example. Tomcat 7 installed using homebrew on OS X, using Eclipse:

  1. Right click your project folder, select Properties at the bottom of the context menu.
  2. Select "Java Build Path"
  3. Click Libraries" tab
  4. Click "Add Library..." button on right (about halfway down)
  5. Select "Server Runtime" click "Next"
  6. Select your Tomcat version from the list
  7. Click Finish

What? No Tomcat version is listed even though you have it installed via homebrew??

  1. Switch to the Java EE perspective (top right)
  2. In the "Window" menu select "Show View" -> "Servers"
  3. In the Servers tab (typically at bottom) right click and select "New > Server"
  4. Add the path to the homebrew tomcat installation in the dialog/wizard (something like: /usr/local/Cellar/tomcat/7.0.14/libexec)

Hope that helps someone who is just getting started out a little.

Execute a stored procedure in another stored procedure in SQL server

Suppose you have one stored procedure like this

First stored procedure:

Create  PROCEDURE LoginId
     @UserName nvarchar(200),
     @Password nvarchar(200)
    DECLARE  @loginID  int

    SELECT @loginID = LoginId 
    FROM UserLogin 
    WHERE UserName = @UserName AND Password = @Password

    return @loginID

Now you want to call this procedure from another stored procedure like as below

Second stored procedure

Create  PROCEDURE Emprecord
         @UserName nvarchar(200),
         @Password nvarchar(200),
         @Email nvarchar(200),
         @IsAdmin bit,
         @EmpName nvarchar(200),
         @EmpLastName nvarchar(200),
         @EmpAddress nvarchar(200),
         @EmpContactNo nvarchar(150),
         @EmpCompanyName nvarchar(200)

        INSERT INTO UserLogin VALUES(@UserName,@Password,@Email,@IsAdmin)

        DECLARE @EmpLoginid int

        **exec @EmpLoginid= LoginId @UserName,@Password**

        INSERT INTO tblEmployee VALUES(@EmpName,@EmpLastName,@EmpAddress,@EmpContactNo,@EmpCompanyName,@EmpLoginid)

As you seen above, we can call one stored procedure from another

Difference between getContext() , getApplicationContext() , getBaseContext() and "this"

The question "what the Context is" is one of the most difficult questions in the Android universe.

Context defines methods that access system resources, retrieve application's static assets, check permissions, perform UI manipulations and many more. In essence, Context is an example of God Object anti-pattern in production.

When it comes to which kind of Context should we use, it becomes very complicated because except for being God Object, the hierarchy tree of Context subclasses violates Liskov Substitution Principle brutally.

This blog post (now from Wayback Machine) attempts to summarize Context classes applicability in different situations.

Let me copy the main table from that post for completeness:

|                            | Application | Activity | Service | ContentProvider | BroadcastReceiver |
| Show a Dialog              | NO          | YES      | NO      | NO              | NO                |
| Start an Activity          | NO¹         | YES      | NO¹     | NO¹             | NO¹               |
| Layout Inflation           | NO²         | YES      | NO²     | NO²             | NO²               |
| Start a Service            | YES         | YES      | YES     | YES             | YES               |
| Bind to a Service          | YES         | YES      | YES     | YES             | NO                |
| Send a Broadcast           | YES         | YES      | YES     | YES             | YES               |
| Register BroadcastReceiver | YES         | YES      | YES     | YES             | NO³               |
| Load Resource Values       | YES         | YES      | YES     | YES             | YES               |
  1. An application CAN start an Activity from here, but it requires that a new task be created. This may fit specific use cases, but can create non-standard back stack behaviors in your application and is generally not recommended or considered good practice.
  2. This is legal, but inflation will be done with the default theme for the system on which you are running, not what’s defined in your application.
  3. Allowed if the receiver is null, which is used for obtaining the current value of a sticky broadcast, on Android 4.2 and above.


How can I execute Shell script in Jenkinsfile?

Based on the number of views this question has, it looks like a lot of people are visiting this to see how to set up a job that executes a shell script.

These are the steps to execute a shell script in Jenkins:

  • In the main page of Jenkins select New Item.
  • Enter an item name like "my shell script job" and chose Freestyle project. Press OK.
  • On the configuration page, in the Build block click in the Add build step dropdown and select Execute shell.
  • In the textarea you can either paste a script or indicate how to run an existing script. So you can either say:

    echo "hello, today is $(date)" > /tmp/jenkins_test

    or just

  • Click Save.

Now the newly created job should appear in the main page of Jenkins, together with the other ones. Open it and select Build now to see if it works. Once it has finished pick that specific build from the build history and read the Console output to see if everything happened as desired.

You can get more details in the document Create a Jenkins shell script job in GitHub.

Getting error in console : Failed to load resource: net::ERR_CONNECTION_RESET

I'm using chrome too and facing same problem on my localhost. I did a lot of things like clear using CCleaner and restart OS. But my problem was solved with clearing cookie. In order to clear cookie:

  1. Go to Chrome settings > Privacy > Content Settings > Cookie > All cookie and Site Data > Delete domain problem


  1. Right Click > Inspect Element > Tab Resources > Cookie (Left Menu) > Select domain > Delete All cookie One By One (Right Menu)

How to change environment's font size?

Currently it is not possible to change the font family or size outside the editor. You can however zoom the entire user interface in and out from the View menu.

Update for our VS Code 1.0 release:

A newly introduced setting window.zoomLevel allows to persist the zoom level for good! It can have both negative and positive values to zoom in or out.

How to extract img src, title and alt from html using php?

The script must be edited like this

foreach( $result[0] as $img_tag)

because preg_match_all return array of arrays

How do a send an HTTPS request through a proxy in Java?

HTTPS proxy doesn't make sense because you can't terminate your HTTP connection at the proxy for security reasons. With your trust policy, it might work if the proxy server has a HTTPS port. Your error is caused by connecting to HTTP proxy port with HTTPS.

You can connect through a proxy using SSL tunneling (many people call that proxy) using proxy CONNECT command. However, Java doesn't support newer version of proxy tunneling. In that case, you need to handle the tunneling yourself. You can find sample code here,

EDIT: If you want defeat all the security measures in JSSE, you still need your own TrustManager. Something like this,

 public SSLTunnelSocketFactory(String proxyhost, String proxyport){
      tunnelHost = proxyhost;
      tunnelPort = Integer.parseInt(proxyport);
      dfactory = (SSLSocketFactory)sslContext.getSocketFactory();


 connection.setSSLSocketFactory( new SSLTunnelSocketFactory( proxyHost, proxyPort ) );
 connection.setDefaultHostnameVerifier( new HostnameVerifier()
    public boolean verify( String arg0, SSLSession arg1 )
        return true;
 }  );

EDIT 2: I just tried my program I wrote a few years ago using SSLTunnelSocketFactory and it doesn't work either. Apparently, Sun introduced a new bug sometime in Java 5. See this bug report,

The good news is that the SSL tunneling bug is fixed so you can just use the default factory. I just tried with a proxy and everything works as expected. See my code,

public class SSLContextTest {

    public static void main(String[] args) {

        System.setProperty("https.proxyHost", "");
        System.setProperty("https.proxyPort", "8888");

        try {

            SSLContext sslContext = SSLContext.getInstance("SSL");

            // set up a TrustManager that trusts everything
            sslContext.init(null, new TrustManager[] { new X509TrustManager() {
                public X509Certificate[] getAcceptedIssuers() {
                    System.out.println("getAcceptedIssuers =============");
                    return null;

                public void checkClientTrusted(X509Certificate[] certs,
                        String authType) {
                    System.out.println("checkClientTrusted =============");

                public void checkServerTrusted(X509Certificate[] certs,
                        String authType) {
                    System.out.println("checkServerTrusted =============");
            } }, new SecureRandom());


                    .setDefaultHostnameVerifier(new HostnameVerifier() {
                        public boolean verify(String arg0, SSLSession arg1) {
                            System.out.println("hostnameVerifier =============");
                            return true;

            URL url = new URL("");
            URLConnection conn = url.openConnection();
            BufferedReader reader = 
                new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = reader.readLine()) != null) {
        } catch (Exception e) {

This is what I get when I run the program,

checkServerTrusted =============
hostnameVerifier =============
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "">

As you can see, both SSLContext and hostnameVerifier are getting called. HostnameVerifier is only involved when the hostname doesn't match the cert. I used "" to trigger this.

Error retrieving parent for item: No resource found that matches the given name '@android:style/TextAppearance.Holo.Widget.ActionBar.Title'


    android:targetSdkVersion="11" />


Project Properties -> Project Build Target = 11 or above

These 2 things fixed the problem for me!

How to remove anaconda from windows completely?

For windows-

  1. In the Control Panel, choose Add or Remove Programs or Uninstall a program, and then select Python 3.6 (Anaconda) or your version of Python.
  2. Use Windows Explorer to delete the envs and pkgs folders prior to Running the uninstall in the root of your installation.

Mergesort with Python

def merge(x):
    if len(x) == 1:
        return x
        mid = int(len(x) / 2)
        l = merge(x[:mid])
        r = merge(x[mid:])
    i = j = 0
    result = []
    while i < len(l) and j < len(r):
        if l[i] < r[j]:
            i += 1
            j += 1
    result += l[i:]
    result += r[j:]
    return result

JOptionPane Yes or No window

You can do this a whole simpler:

int test = JOptionPane.showConfirmDialog(null, "Would you like green eggs and ham?", "An insane question!");
switch(test) {
    case 0: JOptionPane.showMessageDialog(null, "HELLO!"); //Yes option
    case 1: JOptionPane.showMessageDialog(null, "GOODBYE!"); //No option
    case 2: JOptionPane.showMessageDialog(null, "GOODBYE!"); //Cancel option

What does elementFormDefault do in XSD?

elementFormDefault="qualified" is used to control the usage of namespaces in XML instance documents (.xml file), rather than namespaces in the schema document itself (.xsd file).

By specifying elementFormDefault="qualified" we enforce namespace declaration to be used in documents validated with this schema.

It is common practice to specify this value to declare that the elements should be qualified rather than unqualified. However, since attributeFormDefault="unqualified" is the default value, it doesn't need to be specified in the schema document, if one does not want to qualify the namespaces.

Difference between IISRESET and IIS Stop-Start command

Take IISReset as a suite of commands that helps you manage IIS start / stop etc.

Which means you need to specify option (/switch) what you want to do to carry any operation.

Default behavior OR default switch is /restart with iisreset so you do not need to run command twice with /start and /stop.

Hope this clarifies your question. For reference the output of iisreset /? is:

IISRESET.EXE (c) Microsoft Corp. 1998-2005

iisreset [computername]

    /RESTART            Stop and then restart all Internet services.
    /START              Start all Internet services.
    /STOP               Stop all Internet services.
    /REBOOT             Reboot the computer.
    /REBOOTONERROR      Reboot the computer if an error occurs when starting,
                        stopping, or restarting Internet services.
    /NOFORCE            Do not forcefully terminate Internet services if
                        attempting to stop them gracefully fails.
    /TIMEOUT:val        Specify the timeout value ( in seconds ) to wait for
                        a successful stop of Internet services. On expiration
                        of this timeout the computer can be rebooted if
                        the /REBOOTONERROR parameter is specified.
                        The default value is 20s for restart, 60s for stop,
                        and 0s for reboot.
    /STATUS             Display the status of all Internet services.
    /ENABLE             Enable restarting of Internet Services
                        on the local system.
    /DISABLE            Disable restarting of Internet Services
                        on the local system.

How Do I 'git fetch' and 'git merge' from a Remote Tracking Branch (like 'git pull')

Selecting just one branch: fetch/merge vs. pull

People often advise you to separate "fetching" from "merging". They say instead of this:

    git pull remoteR branchB

do this:

    git fetch remoteR
    git merge remoteR branchB

What they don't mention is that such a fetch command will actually fetch all branches from the remote repo, which is not what that pull command does. If you have thousands of branches in the remote repo, but you do not want to see all of them, you can run this obscure command:

    git fetch remoteR refs/heads/branchB:refs/remotes/remoteR/branchB
    git branch -a  # to verify
    git branch -t branchB remoteR/branchB

Of course, that's ridiculously hard to remember, so if you really want to avoid fetching all branches, it is better to alter your .git/config as described in ProGit.


The best explanation of all this is in Chapter 9-5 of ProGit, Git Internals - The Refspec (or via github). That is amazingly hard to find via Google.

First, we need to clear up some terminology. For remote-branch-tracking, there are typically 3 different branches to be aware of:

  1. The branch on the remote repo: refs/heads/branchB inside the other repo
  2. Your remote-tracking branch: refs/remotes/remoteR/branchB in your repo
  3. Your own branch: refs/heads/branchB inside your repo

Remote-tracking branches (in refs/remotes) are read-only. You do not modify those directly. You modify your own branch, and then you push to the corresponding branch at the remote repo. The result is not reflected in your refs/remotes until after an appropriate pull or fetch. That distinction was difficult for me to understand from the git man-pages, mainly because the local branch (refs/heads/branchB) is said to "track" the remote-tracking branch when .git/config defines branch.branchB.remote = remoteR.

Think of 'refs' as C++ pointers. Physically, they are files containing SHA-digests, but basically they are just pointers into the commit tree. git fetch will add many nodes to your commit-tree, but how git decides what pointers to move is a bit complicated.

As mentioned in another answer, neither

    git pull remoteR branchB


    git fetch remoteR branchB

would move refs/remotes/branches/branchB, and the latter certainly cannot move refs/heads/branchB. However, both move FETCH_HEAD. (You can cat any of these files inside .git/ to see when they change.) And git merge will refer to FETCH_HEAD, while setting MERGE_ORIG, etc.

Git push won't do anything (everything up-to-date)

git push doesn't push all of your local branches: how would it know which remote branches to push them to? It only pushes local branches which have been configured to push to a particular remote branch.

On my version of Git (, when I run git remote show origin it actually prints out which branches are configured for push:

Local refs configured for 'git push':
  master pushes to master (up to date)
  quux   pushes to quux   (fast forwardable)

Q. But I could push to master without worrying about all this!

When you git clone, by default it sets up your local master branch to push to the remote's master branch (locally referred to as origin/master), so if you only commit on master, then a simple git push will always push your changes back.

However, from the output snippet you posted, you're on a branch called develop, which I'm guessing hasn't been set up to push to anything. So git push without arguments won't push commits on that branch.

When it says "Everything up-to-date", it means "all the branches you've told me how to push are up to date".

Q. So how can I push my commits?

If what you want to do is put your changes from develop into origin/master, then you should probably merge them into your local master then push that:

git checkout master
git merge develop
git push             # will push 'master'

If what you want is to create a develop branch on the remote, separate from master, then supply arguments to git push:

git push origin develop

That will: create a new branch on the remote called develop; and bring that branch up to date with your local develop branch; and set develop to push to origin/develop so that in future, git push without arguments will push develop automatically.

If you want to push your local develop to a remote branch called something other than develop, then you can say:

git push origin develop:something-else

However, that form won't set up develop to always push to origin/something-else in future; it's a one-shot operation.

What causes imported Maven project in Eclipse to use Java 1.5 instead of Java 1.6 by default and how can I ensure it doesn't?

In case anyone's wondering why Eclipse still puts a J2SE-1.5 library on the Java Build Path in a Maven project even if a Java version >= 9 is specified by the maven.compiler.release property (as of October 2020, that is Eclipse version 2020-09 including Maven version 3.6.3): Maven by default uses version 3.1 of the Maven compiler plugin, while the release property has been introduced only in version 3.6.

So don't forget to include a current version of the Maven compiler plugin in your pom.xml when using the release property:



Or alternatively but possibly less prominent, specify the Java version directly in the plugin configuration:


This picks up Line's comment on the accepted answer which, had I seen it earlier, would have saved me another hour of searching.

How to change MySQL data directory?

Under SuSE 13.1, this works fine to move the mysql data directory elsewhere, e.g. to /home/example_user/ , and to give it a more informative name:

In /var/lib/ :

# mv -T mysql /home/example_user/mysql_datadir
# ln -s /home/example_user/mysql_datadir ./mysql

I restarted mysql:

# systemctl restart mysql.service

but suspect that even that wasn't necessary.

What is the equivalent of bigint in C#?

You can use long type or Int64

How to increase font size in a plot in R?

For completeness, scaling text by 150% with cex = 1.5, here is a full solution:

cex <- 1.5
par(cex.lab=cex, cex.axis=cex, cex.main=cex)
par(cex.lab=1, cex.axis=1, cex.main=1)

I recommend wrapping things like this to reduce boilerplate, e.g.:

plot_cex <- function(x, y, cex=1.5, ...) {
  par(cex.lab=cex, cex.axis=cex, cex.main=cex)
  plot(x, y, ...)
  par(cex.lab=1, cex.axis=1, cex.main=1)

which you can then use like this:

plot_cex(x=1:5, y=rnorm(5), cex=1.3)

The ... are known as ellipses in R and are used to pass additional parameters on to functions. Hence, they are commonly used for plotting. So, the following works as expected:

plot_cex(x=1:5, y=rnorm(5), cex=1.5, ylim=c(-0.5,0.5))

How to open a website when a Button is clicked in Android application?

In your Java file write the following piece of code...

ImageView Button = (ImageView)findViewById(;

Button.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        Intent intent = new Intent();

Block Comments in a Shell Script

I like a single line open and close:

if [ ]; then ##
fi; ##

The '##' helps me easily find the start and end to the block comment. I can stick a number after the '##' if I've got a bunch of them. To turn off the comment, I just stick a '1' in the '[ ]'. I also avoid some issues I've had with single-quotes in the commented block.

How to convert float value to integer in php?

I just want to WARN you about:

>>> (int) (290.15 * 100);
=> 29014
>>> (int) round((290.15 * 100), 0);
=> 29015

How can I send large messages with Kafka (over 15MB)?

Minor changes required for Kafka 0.10 and the new consumer compared to laughing_man's answer:

  • Broker: No changes, you still need to increase properties message.max.bytes and replica.fetch.max.bytes. message.max.bytes has to be equal or smaller(*) than replica.fetch.max.bytes.
  • Producer: Increase max.request.size to send the larger message.
  • Consumer: Increase max.partition.fetch.bytes to receive larger messages.

(*) Read the comments to learn more about message.max.bytes<=replica.fetch.max.bytes

Import txt file and having each line as a list

with open('file') as file:

Visual Studio 2015 or 2017 does not discover unit tests

Somehow my project was set to compile as a Static Library (.lib). After changing this to a Dynamic Library (.dll), tests where discovered correctly by Visual Studio 2012.

My Unit Test Project ->
Properties ->
Configuration Properties ->
General ->
Configuration Type

How to set the maximum memory usage for JVM?

use the arguments -Xms<memory> -Xmx<memory>. Use M or G after the numbers for indicating Megs and Gigs of bytes respectively. -Xms indicates the minimum and -Xmx the maximum.

Unable to start MySQL server

In my case I had to go to the MySQL installer, then configuration button for the MySQL server, then next until the option to "create the server as a windows service" ticked that, gave it a service name as MySQL8.0, next and then finish, that solved the issue and started a new service

How to get single value from this multi-dimensional PHP array

You can also use array_column(). It's available from PHP 5.5:

It returns the values from a single column of the array, identified by the column_key. Optionally, you may provide an index_key to index the values in the returned array by the values from the index_key column in the input array.

print_r(array_column($myarray, 'email'));

Linq UNION query to select two elements


Ok I found why the int.ToString() in LINQtoEF fails, please read this post: Problem with converting int to string in Linq to entities

This works on my side :

        List<string> materialTypes = (from u in result.Users
                                      select u.LastName)
                       .Union(from u in result.Users
                               select SqlFunctions.StringConvert((double) u.UserId)).ToList();

On yours it should be like this:

    IList<String> materialTypes = ((from tom in context.MaterialTypes
                                       where tom.IsActive == true
                                       select tom.Name)
                                       .Union(from tom in context.MaterialTypes
                                       where tom.IsActive == true
                                       select SqlFunctions.StringConvert((double)tom.ID))).ToList();

Thanks, i've learnt something today :)

How to playback MKV video in web browser?

To use video extensions that are MKV. You should use video, not source

For example :

  <!-- mkv -->
  <video width="320" height="240" controls src="assets/animation.mkv"></video>
<!-- mp4 -->
  <video width="320" height="240" controls>
    <source src="assets/animation.mp4" type="video/mp4" />
_x000D_ My answer may be incomprehensible to you, so if you do not understand, click on this

HTTP Error 500.19 and error code : 0x80070021

On Windows 8.1 or 10 include the .Net framework 4.5 or above as shown below

enter image description here

CSS Styling for a Button: Using <input type="button> instead of <button>

Do you want something like the given fiddle!


<div class="button">
    <input type="button" value="TELL ME MORE" onClick="document.location.reload(true)">


.button input[type="button"] {
    font:2.4em Futura, ‘Century Gothic’, AppleGothic, sans-serif;
    background:url(overlay.png) repeat-x center #ffcc00;
    border:1px solid #ffcc00;
    border-bottom:1px solid #9f9f9f;
    -moz-box-shadow:inset 0 1px 0 rgba(255,255,255,0.5);
    -webkit-box-shadow:inset 0 1px 0 rgba(255,255,255,0.5);
    box-shadow:inset 0 1px 0 rgba(255,255,255,0.5);
.button input[type="button"]:hover {

Angular pass callback function to child component as @Input similar to AngularJS way

The current answer can be simplified to...

  template: '<child [myCallback]="theCallback"></child>',
  directives: [ChildComponent]
export class ParentComponent{
  public theCallback(){

export class ChildComponent{
  //This will be bound to the ParentComponent.theCallback
  public myCallback: Function; 

What is the size of an enum in C?

While the previous answers are correct, some compilers have options to break the standard and use the smallest type that will contain all values.

Example with GCC (documentation in the GCC Manual):

enum ord {
    FIRST = 1,
} __attribute__ ((__packed__));
STATIC_ASSERT( sizeof(enum ord) == 1 )

want current date and time in "dd/MM/yyyy HH:mm:ss.SS" format


  • Use modern java.time classes.
  • Never use Date/Calendar/SimpleDateFormat classes.


ZonedDateTime                                // Represent a moment as seen in the wall-clock time used by the people of a particular region (a time zone).
.now(                                        // Capture the current moment.
    ZoneId.of( "Africa/Tunis" )              // Always specify time zone using proper `Continent/Region` format. Never use 3-4 letter pseudo-zones such as EST, PDT, IST, etc.
.truncatedTo(                                // Lop off finer part of this value.
    ChronoUnit.MILLIS                        // Specify level of truncation via `ChronoUnit` enum object.
)                                            // Returns another separate `ZonedDateTime` object, per immutable objects pattern, rather than alter (“mutate”) the original.
.format(                                     // Generate a `String` object with text representing the value of our `ZonedDateTime` object.
    DateTimeFormatter.ISO_LOCAL_DATE_TIME    // This standard ISO 8601 format is close to your desired output.
)                                            // Returns a `String`.
.replace( "T" , " " )                        // Replace `T` in middle with a SPACE.


The modern approach uses java.time classes that years ago supplanted the terrible old date-time classes such as Calendar & SimpleDateFormat.

want current date and time

Capture the current moment in UTC using Instant.

Instant instant = ;

To view that same moment through the lens of the wall-clock time used by the people of a particular region (a time zone), apply a ZoneId to get a ZonedDateTime.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "Pacific/Auckland" ) ;
ZonedDateTime zdt = instant.atZone( z ) ;

Or, as a shortcut, pass a ZoneId to the method.

ZonedDateTime zdt = ZoneId.of( "Pacific/Auckland" ) ) ;

The java.time classes use a resolution of nanoseconds. That means up to nine digits of a decimal fraction of a second. If you want only three, milliseconds, truncate. Pass your desired limit as a ChronoUnit enum object.

    ZoneId.of( "Pacific/Auckland" ) 

in “dd/MM/yyyy HH:mm:ss.SS” format

I recommend always including the offset-from-UTC or time zone when generating a string, to avoid ambiguity and misunderstanding.

But if you insist, you can specify a specific format when generating a string to represent your date-time value. A built-in pre-defined formatter nearly meets your desired format, but for a T where you want a SPACE.

String output = 
    zdt.format( DateTimeFormatter.ISO_LOCAL_DATE_TIME )
    .replace( "T" , " " )  

sdf1.applyPattern("dd/MM/yyyy HH:mm:ss.SS");

Date date = sdf1.parse(strDate);

Never exchange date-time values using text intended for presentation to humans.

Instead, use the standard formats defined for this very purpose, found in ISO 8601.

The java.time use these ISO 8601 formats by default when parsing/generating strings.

Always include an indicator of the offset-from-UTC or time zone when exchanging a specific moment. So your desired format discussed above is to be avoided for data-exchange. Furthermore, generally best to exchange a moment as UTC. This means an Instant in java.time. You can exchange a Instant from a ZonedDateTime, effectively adjusting from a time zone to UTC for the same moment, same point on the timeline, but a different wall-clock time.

Instant instant = zdt.toInstant() ;
String exchangeThisString = instant.toString() ;


This ISO 8601 format uses a Z on the end to represent UTC, pronounced “Zulu”.

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

How to check if a subclass is an instance of a class at runtime?

If there is polymorphism such as checking SQLRecoverableException vs SQLException, it can be done like that.

try {
    // sth may throw exception
} catch (Exception e) {
        // do sth
        System.out.println("SQLException occurs!");

Simply say,

ChildClass child= new ChildClass();
    // do sth

Show Image View from file path?

       public static Bitmap decodeFile(String path) {
    Bitmap b = null;
    File f = new File(path);
    // Decode image size
    BitmapFactory.Options o = new BitmapFactory.Options();
    o.inJustDecodeBounds = true;

    FileInputStream fis = null;
    try {
        fis = new FileInputStream(f);
        BitmapFactory.decodeStream(fis, null, o);

        int IMAGE_MAX_SIZE = 1024; // maximum dimension limit
        int scale = 1;
        if (o.outHeight > IMAGE_MAX_SIZE || o.outWidth > IMAGE_MAX_SIZE) {
            scale = (int) Math.pow(2, (int) Math.round(Math.log(IMAGE_MAX_SIZE / (double) Math.max(o.outHeight, o.outWidth)) / Math.log(0.5)));

        // Decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;

        fis = new FileInputStream(f);
        b = BitmapFactory.decodeStream(fis, null, o2);

    } catch (Exception e) {
        // TODO Auto-generated catch block

    return b;

public static Bitmap showBitmapFromFile(String file_path)
    try {
        File imgFile = new  File(file_path);

            Bitmap pic_Bitmap = decodeFile(file_path);
            return pic_Bitmap;

    } catch (Exception e) {
        MyLog.e("Exception showBitmapFromFile");
        return null;
    return null;

if you are using image loading in List view then use Aquery concept .

     AQuery  aq= new AQuery((Activity) activity, convertView);
            //load image from file, down sample to target width of 250 pixels .gi 
    File file=new File("//pic/path/here/aaaa.jpg");
    if(aq!=null), 250);

Relative path to absolute path in C#?

Assuming you know the real directory the XML file lives in use Path.Combine, e.g.

var absolute_path = Path.Combine(directoryXmlLivesIn, "..\images\image.jpg");

If you want to get back the full path with any ..'s collapsed then you can use:

Path.GetFullPath((new Uri(absolute_path)).LocalPath);

How to change the status bar background color and text color on iOS 7?

Warning: It does not work anymore with iOS 13 and Xcode 11.


I had to try look for other ways. Which does not involve addSubview on window. Because I am moving up the window when keyboard is presented.


- (void)setStatusBarBackgroundColor:(UIColor *)color {

    UIView *statusBar = [[[UIApplication sharedApplication] valueForKey:@"statusBarWindow"] valueForKey:@"statusBar"];

    if ([statusBar respondsToSelector:@selector(setBackgroundColor:)]) {
        statusBar.backgroundColor = color;


func setStatusBarBackgroundColor(color: UIColor) {

    guard  let statusBar = UIApplication.sharedApplication().valueForKey("statusBarWindow")?.valueForKey("statusBar") as? UIView else {

    statusBar.backgroundColor = color

Swift 3

func setStatusBarBackgroundColor(color: UIColor) {

    guard let statusBar = UIApplication.shared.value(forKeyPath: "statusBarWindow.statusBar") as? UIView else { return }

    statusBar.backgroundColor = color

Calling this form application:didFinishLaunchingWithOptions worked for me.

N.B. We have an app in the app store with this logic. So I guess it is okay with the app store policy.


Use at your own risk. Form the commenter @Sebyddd

I had one app rejected cause of this, while another was accepted just fine. They do consider it private API usage, so you are subject to luck during the reviewing process :) – Sebyddd

no target device found android studio 2.1.1

trick that works for me when target device not found:

  • click the "attach debugger to android process" button. (that will enable adb integration for you)

  • click the run button

How to specify function types for void (not Void) methods in Java8?

Set return type to Void instead of void and return null

// Modify existing method
public static Void displayInt(Integer i) {
    return null;


// Or use Lambda
myForEach(theList, i -> {System.out.println(i);return null;});

SVN change username

I’ve had the exact same problem and found the solution in Where does SVN client store user authentication data?:

  1. cd to ~/.subversion/auth/.
  2. Do fgrep -l <yourworkmatesusernameORtheserverurl> */*.
  3. Delete the file found.
  4. The next operation on the repository will ask you again for username/password information.

(For Windows, the steps are analogous; the auth directory is in %APPDATA%\Subversion\).

Note that this will only work for SVN access schemes where the user name is part of the server login so it’s no use for repositories accessed using file://.

onclick event pass <li> id or value

I prefer to use the HTML5 data API, check this documentation:

A example

$('#some-list li').click(function() {_x000D_
  var textLoaded = 'Loading element with id='_x000D_
         + $(this).data('id');_x000D_
<script src=""></script>_x000D_
<ul id='some-list'>_x000D_
  <li data-id='1'>One </li>_x000D_
  <li data-id='2'>Two </li>_x000D_
  <!-- ... more li -->_x000D_
  <li data-id='n'>Other</li>_x000D_
<h1 id='loading-content'></h1>

Can I convert a C# string value to an escaped string literal

There's a method for this in Roslyn's Microsoft.CodeAnalysis.CSharp package on nuget :

    private static string ToLiteral(string valueTextForCompiler)
        return Microsoft.CodeAnalysis.CSharp.SymbolDisplay.FormatLiteral(valueTextForCompiler, false);

Obviously this didn't exist at the time of the original question, but might help people who end up here from Google.

Remove 'b' character do in front of a string literal in Python 3

Decoding is redundant

You only had this "error" in the first place, because of a misunderstanding of what's happening.

You get the b because you encoded to utf-8 and now it's a bytes object.

 >> type("text".encode("utf-8"))
 >> <class 'bytes'>


  1. You can just print the string first
  2. Redundantly decode it after encoding

Tree implementation in Java (root, parents and children)

import java.util.ArrayList;
import java.util.List;

public class Node<T> {
    private List<Node<T>> children = new ArrayList<Node<T>>();
    private Node<T> parent = null;
    private T data = null;

    public Node(T data) { = data;

    public Node(T data, Node<T> parent) { = data;
        this.parent = parent;

    public List<Node<T>> getChildren() {
        return children;

    public void setParent(Node<T> parent) {
        this.parent = parent;

    public void addChild(T data) {
        Node<T> child = new Node<T>(data);

    public void addChild(Node<T> child) {

    public T getData() {

    public void setData(T data) { = data;

    public boolean isRoot() {
        return (this.parent == null);

    public boolean isLeaf() {
        return this.children.size == 0;

    public void removeParent() {
        this.parent = null;


import java.util.List;

Node<String> parentNode = new Node<String>("Parent"); 
Node<String> childNode1 = new Node<String>("Child 1", parentNode);
Node<String> childNode2 = new Node<String>("Child 2");     


Node<String> grandchildNode = new Node<String>("Grandchild of parentNode. Child of childNode1", childNode1); 
List<Node<String>> childrenNodes = parentNode.getChildren();

PHP script to loop through all of the files in a directory?

Most of the time I imagine you want to skip . and ... Here is that with recursion:

$o_dir = new RecursiveDirectoryIterator('.', FilesystemIterator::SKIP_DOTS);
$o_iter = new RecursiveIteratorIterator($o_dir);
foreach ($o_iter as $o_name) {
   echo $o_name->getFilename();

I get "Http failure response for (unknown url): 0 Unknown Error" instead of actual error message in Angular

A similar error can occur, when you didn't give a valid client certificate and token that your server understands:


Http failure response for (unknown url): 0 Unknown Error

Example code:

import { HttpClient, HttpHeaders } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError, map } from 'rxjs/operators';

class MyCls1 {

  constructor(private http: HttpClient) {

  public myFunc(): void {

    let http: HttpClient;

          new HttpHeaders(
              'Content-Type': 'application/json',
              'X-Requested-With': 'XMLHttpRequest',
              'MyClientCert': '',        // This is empty
              'MyToken': ''              // This is empty
    ).pipe( map(res => res), catchError(err => throwError(err)) );


Note that both MyClientCert & MyToken are empty strings, hence the error.
MyClientCert & MyToken can be any name that your server understands.

Eclipse plugin for generating a class diagram

Must it be an Eclipse plug-in? I use doxygen, just supply your code folder, it handles the rest.

How do I check if a type is a subtype OR the type of an object?

If you're trying to do it in a Xamarin Forms PCL project, the above solutions using IsAssignableFrom gives an error:

Error: 'Type' does not contain a definition for 'IsAssignableFrom' and no extension method 'IsAssignableFrom' accepting a first argument of type 'Type' could be found (are you missing a using directive or an assembly reference?)

because IsAssignableFrom asks for a TypeInfo object. You can use the GetTypeInfo() method from System.Reflection:


cleanest way to skip a foreach if array is empty

foreach((array)$items as $item) {}

How to limit text width


<div style="max-width:200px; word-wrap:break-word;">Texttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt</div>

Checking if a field contains a string

Simplest way to accomplish this task

If you want the query to be case-sensitive


If you want the query to be case-insensitive


Cannot ping AWS EC2 instance

You have to open following security port in the security group. Each rule is for different purposes, as shown below.

enter image description here

  1. ALL ICMP for ping.

  2. HTTP for accessing URL on HTTP port.

  3. HTTPS for accessing URL on Secured HTTP port.

As per your requirement you can change SOURCE

How to get the first 2 letters of a string in Python?

In python strings are list of characters, but they are not explicitly list type, just list-like (i.e. it can be treated like a list). More formally, they're known as sequence (see

>>> a = 'foo bar'
>>> isinstance(a, list)
>>> isinstance(a, str)

Since strings are sequence, you can use slicing to access parts of the list, denoted by list[start_index:end_index] see Explain Python's slice notation . For example:

>>> a = [1,2,3,4]
>>> a[0]
1 # first element, NOT a sequence.
>>> a[0:1]
[1] # a slice from first to second, a list, i.e. a sequence.
>>> a[0:2]
[1, 2]
>>> a[:2]
[1, 2]

>>> x = "foo bar"
>>> x[0:2]
>>> x[:2]

When undefined, the slice notation takes the starting position as the 0, and end position as len(sequence).

In the olden C days, it's an array of characters, the whole issue of dynamic vs static list sounds like legend now, see Python List vs. Array - when to use?

How to get the last row of an Oracle a table

select * from table_name ORDER BY primary_id DESC FETCH FIRST 1 ROWS ONLY;

That's the simplest one without doing sub queries

Difference between "module.exports" and "exports" in the CommonJs Module System

As all answers posted above are well explained, I want to add something which I faced today.

When you export something using exports then you have to use it with variable. Like,


exports.a = 5;

In another file


const A = require("./File1.js");

and using module.exports


module.exports.a = 5;

In File2.js

const A = require("./File1.js");

and default module.exports


module.exports = 5;

in File2.js

const A = require("./File2.js");

Getting unique items from a list

In .Net 2.0 I`m pretty sure about this solution:

public IEnumerable<T> Distinct<T>(IEnumerable<T> source)
     List<T> uniques = new List<T>();
     foreach (T item in source)
         if (!uniques.Contains(item)) uniques.Add(item);
     return uniques;

Forcing anti-aliasing using css: Is this a myth?

Using an opacity setting of 99% (through the DXTransform filters) actually forces Internet Explorer to turn off ClearType, at least in Version 7. Source

How to create a RelativeLayout programmatically with two buttons one on top of the other?

Found the answer in How to lay out Views in RelativeLayout programmatically?

We should explicitly set id's using setId(). Only then, RIGHT_OF rules make sense.

Another mistake I did is, reusing the layoutparams object between the controls. We should create new object for each control

How to persist data in a dockerized postgres database using volumes

Strangely enough, the solution ended up being to change

  - ./postgres-data:/var/lib/postgresql


  - ./postgres-data:/var/lib/postgresql/data

How to configure for SpringJUnit4ClassRunner?

If you don't want to bother with a file, you can do something like this in your code:

    Logger rootLogger = Logger.getRootLogger();
    rootLogger.addAppender(new ConsoleAppender(
               new PatternLayout("%-6r [%p] %c - %m%n")));

How to make script execution wait until jquery is loaded

A tangential note on the approaches here that load use setTimeout or setInterval. In those cases it's possible that when your check runs again, the DOM will already have loaded, and the browser's DOMContentLoaded event will have been fired, so you can't detect that event reliably using these approaches. What I found is that jQuery's ready still works, though, so you can embed your usual

jQuery(document).ready(function ($) { ... }

inside your setTimeout or setInterval and everything should work as normal.

Getting the closest string match

The problem is hard to implement if the input data is too large (say millions of strings). I used elastic search to solve this.

Quick start :

Just insert all the input data into DB and you can search any string based on any edit distance quickly. Here is a C# snippet which will give you a list of results sorted by edit distance (smaller to higher)

var res = client.Search<ClassName>(s => s
    .Query(q => q
    .Match(m => m
        .Field(f => f.VariableName)
        .Query("SAMPLE QUERY")

Remove carriage return in Unix

I've used python for it, here my code;

with open(end1, "rb") as inf:
     with open(end2, "w") as fixed:
        for line in inf:
            line = line.replace("\n", "")
            line = line.replace("\r", "")

What's the best CRLF (carriage return, line feed) handling strategy with Git?

Using core.autocrlf=false stopped all the files from being marked updated as soon as I checked them out in my Visual Studio 2010 project. The other two members of the development team are also using Windows systems so a mixed environment didn't come into play, yet the default settings that came with the repository always marked all files as updated immediately after cloning.

I guess the bottom line is to find what CRLF setting works for your environment. Especially since in many other repositories on our Linux boxes setting autocrlf = true produces better results.

20+ years later and we're still dealing with line ending disparities between OSes... sad.

What is the difference between GitHub and gist?

GitHub Gists

To gist or not to gist. That is the $64 question ...

GitHub Gists are Single ( or, multiple ) Simple Markdown Files with repo-like qualities that can be forked or cloned ( if public ).

Otherwise, not if private.

Kinda like a fancy scratch pad that can be shared.

Similar to this comment scratch pad that I am typing on now, but a bit more elaborate.

Whereas, an official, full GitHub repo is a full blown repository of source code src, supporting documents ( markdown or html, or both ) docs or root, images png, ico, svg, and a config.sys file for running Yaml variables hosted on a Jekyll server.

Does a simple Gist file support Yaml front matter?

Me thinks not.

From the official GitHub Gist documentation ...

The gist editor is powered by CodeMirror.

However, you can copy a public Gist ( or, a private Gist if the owner has granted you access via a link to the private Gist ) ...

And, you can then embed that public Gist into an "official" repo using Visual Studio Code, as follows:

"You can embed a gist in any text field that supports Javascript, such as a blog post."

"To get the embed code, click the clipboard icon next to the Embed URL button of a gist."

Now, that's a cool feature.

Makes me want to search ( discover ) other peoples' gists, or OPG and incorporate their "public" work into my full-blown working repos.

"You can discover the PUBLIC gists others have created by going to the gist home page and clicking on the link ...

All Gists{:title='Click to Review the Discover Feature at GitHub Gists'}{:target='_blank'}."

Caveat. No support for Liquid tags at GitHub Gist.

I suppose if I do find something beneficial, I can always ping-back, or cite that source if I do use the work in my full-blown working repos.

Where is the implicit license posted for all gists made public by their authors?


P.S. This is a good comment. I think I will turn this into a gist and make it publically searchable over at GitHub Gists.

Note. When embedding the <script></script> html tag within the body of a Markdown (.md) file, you may get a warning "MD033" from your linter.

This should not, however, affect the rendering of the data ( src ) called from within the script tag.

To change the default warning flag to accommodate the called contents of a script tag from within Visual Studio Code, add an entry to the Markdownlint Configuration Object within the User Settings Json file, as follows:

// Begin Markdownlint Configuration Object
"markdownlint.config": {
  "MD013": false,
  "MD033": {"allowed_elements": ["script"]}
}// End Markdownlint Configuration Object

Note. Solution derived from GitHub Commit by David Anson

How to make vim paste from (and copy to) system's clipboard?

If you have it, try removing this from your vimrc: set mouse=a

It messes with the paste functionality.

Android Studio Checkout Github Error "CreateProcess=2" (Windows)

I faced same issue in android studio 3.2.1, solved the issue by setting git path in System Environment variable

C:\Program Files\Git\bin\,C:\Program Files\Git\bin\

And I imported the project once again and solved the issue!!!

Note : Check your android studio git settings has properly set the correct path to git.exe

enter image description here

How to check if a json key exists?

You can use has

public boolean has(String key)

Determine if the JSONObject contains a specific key.


JSONObject JsonObj = new JSONObject(Your_API_STRING); //JSONObject is an unordered collection of name/value pairs

if (JsonObj.has("address")) { 
    //Checking address Key Present or not
    String get_address = JsonObj .getString("address"); // Present Key
else {
    //Do Your Staff

Angular ng-repeat Error "Duplicates in a repeater are not allowed."

What do you intend your "range" filter to do?

Here's a working sample of what I think you're trying to do:


<div ng-app="manyminds" ng-controller="MainCtrl">
  <div class="idea item" ng-repeat="item in items" isoatom>    
    Item {{$index}}
    <div class="section comment clearfix" ng-repeat="comment in item.comments | range:1:2">
      Comment {{$index}}


angular.module('manyminds', [], function() {}).filter('range', function() {
    return function(input, min, max) {
        var range = [];
        min = parseInt(min); //Make string input int
        max = parseInt(max);
        for (var i=min; i<=max; i++)
            input[i] && range.push(input[i]);
        return range;

function MainCtrl($scope)
    $scope.items = [
            comments: [
                'comment 0 in item 0',
                'comment 1 in item 0'
            comments: [
                'comment 0 in item 1',
                'comment 1 in item 1',
                'comment 2 in item 1',
                'comment 3 in item 1'

Mod of negative number is melting my brain

A single line implementation of dcastro's answer (the most compliant with other languages):

int Mod(int a, int n)
    return (((a %= n) < 0) && n > 0) || (a > 0 && n < 0) ? a + n : a;

If you'd like to keep the use of % operator (you can't overload native operators in C#):

public class IntM
    private int _value;

    private IntM(int value)
        _value = value;

    private static int Mod(int a, int n)
        return (((a %= n) < 0) && n > 0) || (a > 0 && n < 0) ? a + n : a;

    public static implicit operator int(IntM i) => i._value;
    public static implicit operator IntM(int i) => new IntM(i);
    public static int operator %(IntM a, int n) => Mod(a, n);
    public static int operator %(int a, IntM n) => Mod(a, n);

Use case, both works:

int r = (IntM)a % n;

// Or
int r = a % n(IntM);

How to connect to mysql with laravel?

You probably only forgot to create database. Enter your PHPMyAdmin and do it from there.

Edit: Definitely don't go with Maulik's answer. Not only it is using mysql_ extenstion (which is commonly recognized bad practice), Laravel is also taking care of your connections using PDO.

Disabled UIButton not faded or grey

Set title color for different states:

@IBOutlet weak var loginButton: UIButton! {
        didSet {
            loginButton.setTitleColor(UIColor.init(white: 1, alpha: 0.3), for: .disabled)
            loginButton.setTitleColor(UIColor.init(white: 1, alpha: 1), for: .normal)

Usage: (text color will get change automatically)

loginButton.isEnabled = false

enter image description here

android.widget.Switch - on/off event listener?

You can use DataBinding and ViewModel for Switch Checked Change event

<layout xmlns:android=""


                type="com.example.ui.ViewModel" />
            android:onCheckedChanged="@{(button, on) -> viewModel.onCheckedChange(on)}"

How can I break up this long line in Python?

Personally I dislike hanging open blocks, so I'd format it as:
    'Skipping {0} because its thumbnail was already in our system as {1}.'
    .format(line[indexes['url']], video.title)

In general I wouldn't bother struggle too hard to make code fit exactly within a 80-column line. It's worth keeping line length down to reasonable levels, but the hard 80 limit is a thing of the past.

Unix tail equivalent command in Windows Powershell

Probably too late for an answere but, try this one

Get-Content <filename> -tail <number of items wanted>

Using async/await for multiple tasks

You can use Task.WhenAll function that you can pass n tasks; Task.WhenAll will return a task which runs to completion when all the tasks that you passed to Task.WhenAll complete. You have to wait asynchronously on Task.WhenAll so that you'll not block your UI thread:

   public async Task DoSomeThing() {

       var Task[] tasks = new Task[numTasks];
       for(int i = 0; i < numTask; i++)
          tasks[i] = CallSomeAsync();
       await Task.WhenAll(tasks);
       // code that'll execute on UI thread

Convert pandas dataframe to NumPy array

It seems like df.to_records() will work for you. The exact feature you're looking for was requested and to_records pointed to as an alternative.

I tried this out locally using your example, and that call yields something very similar to the output you were looking for:

rec.array([(1, nan, 0.2, nan), (2, nan, nan, 0.5), (3, nan, 0.2, 0.5),
       (4, 0.1, 0.2, nan), (5, 0.1, 0.2, 0.5), (6, 0.1, nan, 0.5),
       (7, 0.1, nan, nan)],
      dtype=[(u'ID', '<i8'), (u'A', '<f8'), (u'B', '<f8'), (u'C', '<f8')])

Note that this is a recarray rather than an array. You could move the result in to regular numpy array by calling its constructor as np.array(df.to_records()).

C++ Calling a function from another class

Forward declare class B and swap order of A and B definitions: 1st B and 2nd A. You can not call methods of forward declared B class.

PHP/MySQL insert row then get 'id'

Try like this you can get the answer:

// Check connection
if (mysqli_connect_errno())
  echo "Failed to connect to MySQL: " . mysqli_connect_error();

mysqli_query($con,"INSERT INTO new values('nameuser','2015-09-12')");

// Print auto-generated id
echo "New record has id: " . mysqli_insert_id($con);


Have a look at following links:

Also please have a note that this extension was deprecated in PHP 5.5 and removed in PHP 7.0

Creating a custom JButton in Java

When I was first learning Java we had to make Yahtzee and I thought it would be cool to create custom Swing components and containers instead of just drawing everything on one JPanel. The benefit of extending Swing components, of course, is to have the ability to add support for keyboard shortcuts and other accessibility features that you can't do just by having a paint() method print a pretty picture. It may not be done the best way however, but it may be a good starting point for you.

Edit 8/6 - If it wasn't apparent from the images, each Die is a button you can click. This will move it to the DiceContainer below. Looking at the source code you can see that each Die button is drawn dynamically, based on its value.

alt text
alt text
alt text

Here are the basic steps:

  1. Create a class that extends JComponent
  2. Call parent constructor super() in your constructors
  3. Make sure you class implements MouseListener
  4. Put this in the constructor:

  5. Override these methods:

    public Dimension getPreferredSize()  
    public Dimension getMinimumSize()  
    public Dimension getMaximumSize()
  6. Override this method:

    public void paintComponent(Graphics g)

The amount of space you have to work with when drawing your button is defined by getPreferredSize(), assuming getMinimumSize() and getMaximumSize() return the same value. I haven't experimented too much with this but, depending on the layout you use for your GUI your button could look completely different.

And finally, the source code. In case I missed anything.

How to draw a line in android

This one draws 2 lines which form a cross on the top left of the screen:

import android.content.Context;
import android.view.View;

public class DrawView extends View {
    Paint paint = new Paint();

    private void init() {

    public DrawView(Context context) {

    public DrawView(Context context, AttributeSet attrs) {
        super(context, attrs);

    public DrawView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

    public void onDraw(Canvas canvas) {
            canvas.drawLine(0, 0, 20, 20, paint);
            canvas.drawLine(20, 0, 0, 20, paint);


The activity to start it:

import android.os.Bundle;

public class StartDraw extends Activity {
    DrawView drawView;

    public void onCreate(Bundle savedInstanceState) {

        drawView = new DrawView(this);


How to get Git to clone into current directory

I used this to clone a repo to the current directory, which wasn't empty. Not necessarily clean living, but it was in a disposable docker container:

git clone temp
cp -r temp/* .
rm -rf temp

Here, I used cp -r instead of mv, since that copies hidden files and directories. Then dispose of the temporary directory with rm -rf

Why when I transfer a file through SFTP, it takes longer than FTP?

Encryption has not only cpu, but also some network overhead.

Pretty-Print JSON Data to a File using Python

You could redirect a file to python and open using the tool and to read it use more.

The sample code will be,

cat filename.json | python -m json.tool | more

Send string to stdin

cat | /my/bash/script

Enables one to type multiple lines into a program, without that input being saved in history, nor visible in ps. Just press Ctrl + C when finished typing to end cat.

Laravel: Auth::user()->id trying to get a property of a non-object

It's working with me :

echo Auth::guard('guard_name')->user()->id;

Jquery .on('scroll') not firing the event while scrolling

Can you place the #ulId in the document prior to the ajax load (with css display: none;), or wrap it in a containing div (with css display: none;), then just load the inner html during ajax page load, that way the scroll event will be linked to the div that is already there prior to the ajax?

Then you can use:

$('#ulId').on('scroll',function(){ console.log('Event Fired'); })

obviously replacing ulId with whatever the actual id of the scrollable div is.

Then set css display: block; on the #ulId (or containing div) upon load?

How to read values from the querystring with ASP.NET Core?

StringValues is an array of strings. You can get your string value by providing an index, e.g. HttpContext.Request.Query["page"][0].

How to add a primary key to a MySQL table?

Remove quotes to work properly...

alter table goods add column id int(10) unsigned primary KEY AUTO_INCREMENT;

How can I solve Exception in thread "main" java.lang.NullPointerException error

This is the problem

double a[] = null;

Since a is null, NullPointerException will arise every time you use it until you initialize it. So this:

a[i] = var;

will fail.

A possible solution would be initialize it when declaring it:

double a[] = new double[PUT_A_LENGTH_HERE]; //seems like this constant should be 7

IMO more important than solving this exception, is the fact that you should learn to read the stacktrace and understand what it says, so you could detect the problems and solve it.


This exception means there's a variable with null value being used. How to solve? Just make sure the variable is not null before being used.

at twoten.TwoTenB.(

This line has two parts:

  • First, shows the class and method where the error was thrown. In this case, it was at <init> method in class TwoTenB declared in package twoten. When you encounter an error message with SomeClassName.<init>, means the error was thrown while creating a new instance of the class e.g. executing the constructor (in this case that seems to be the problem).
  • Secondly, shows the file and line number location where the error is thrown, which is between parenthesis. This way is easier to spot where the error arose. So you have to look into file, line number 29. This seems to be a[i] = var;.

From this line, other lines will be similar to tell you where the error arose. So when reading this:

at javapractice.JavaPractice.main(

It means that you were trying to instantiate a TwoTenB object reference inside the main method of your class JavaPractice declared in javapractice package.

How to get number of rows using SqlDataReader in C#

You can't get a count of rows directly from a data reader because it's what is known as a firehose cursor - which means that the data is read on a row by row basis based on the read being performed. I'd advise against doing 2 reads on the data because there's the potential that the data has changed between doing the 2 reads, and thus you'd get different results.

What you could do is read the data into a temporary structure, and use that in place of the second read. Alternatively, you'll need to change the mechanism by which you retrieve the data and use something like a DataTable instead.

Making an svg image object clickable with onclick, avoiding absolute positioning

You can have an onclick event in the svg itself, I do this all the time in my work. make a rect over the space of your svg, (so define it last, remember svg uses the painters model)

rect.btn {

then as an attribute to the rect add the onclick (this can be done with js or jquery as well).

<svg xmlns="" version="1.1">
    <circle ... //your img svg
    <rect class="btn" x="0" y="0" width="10" height="10" onclick="alert('click!')" />

this will work in most modern browsers, ...though if you need cross compatability, you can implement Google Chrome Frame.

PostgreSQL Autoincrement

Yes, SERIAL is the equivalent function.

bar varchar);

INSERT INTO foo (bar) values ('blah');
INSERT INTO foo (bar) values ('blah');



SERIAL is just a create table time macro around sequences. You can not alter SERIAL onto an existing column.

Git push rejected after feature branch rebase

My way of avoiding the force push is to create a new branch and continuing work on that new branch and after some stability, remove the old branch that was rebased:

  • Rebasing the checked out branch locally
  • Branching from the rebased branch to a new branch
  • Pushing that branch as a new branch to remote. and deleting the old branch on remote

HTML CSS Invisible Button


<input type="button">



Reusing output from last command in Bash

You can use $(!!) to recompute (not re-use) the output of the last command.

The !! on its own executes the last command.

$ echo pierre
$ echo my name is $(!!)
echo my name is $(echo pierre)
my name is pierre

How to pass multiple parameters in json format to a web service using jquery?

This is a stab in the dark, but maybe do you need to wrap your JSON arguments; like say something like this:

data: "{'Ids':[{'Id1':'2'},{'Id2':'2'}]}"

Make sure your JSON is properly formed?

How to set Apache Spark Executor memory

You need to increase the driver memory.On mac(i.e when running on local master), the default driver-memory is 1024M). By default, thus 380Mb is allotted to the executor.


Upon increasing [--driver-memory 2G], executor memory got increased to ~950Mb. enter image description here

How to join three table by laravel eloquent model


$articles = DB::table('articles')
            ->select(' as articles_id', ..... )
            ->join('categories', 'articles.categories_id', '=', '')
            ->join('users', 'articles.user_id', '=', '')


SQL Sum Multiple rows into one

You're grouping with BillDate, but the bill dates are different for each account so your rows are not being grouped. If you think about it, that doesn't even make sense - they are different bills, and have different dates. The same goes for the Bill - you're attempting to sum bills for an account, why would you group by that?

If you leave BillDate and Bill off of the select and group by clauses you'll get the correct results.

SELECT AccountNumber, SUM(Bill)
FROM Table1
GROUP BY AccountNumber

Codeigniter $this->db->get(), how do I return values for a specific row?

you can use row() instead of result().

$this->db->where('id', '3');
$q = $this->db->get('my_users_table')->row();

Why can't I check if a 'DateTime' is 'Nothing'?

Some examples on working with nullable DateTime values.

(See Nullable Value Types (Visual Basic) for more.)

' An ordinary DateTime declaration. It is *not* nullable. Setting it to
' 'Nothing' actually results in a non-null value.
Dim d1 As DateTime = Nothing
Console.WriteLine(String.Format("d1 = [{0}]\n", d1))
' Output:  d1 = [1/1/0001 12:00:00 AM]

' Console.WriteLine(String.Format("d1 is Nothing? [{0}]\n", (d1 Is Nothing)))
'   Compilation error on above expression '(d1 Is Nothing)':
'      'Is' operator does not accept operands of type 'Date'.
'       Operands must be reference or nullable types.

' Three different but equivalent ways to declare a DateTime
' nullable:
Dim d2? As DateTime = Nothing
Console.WriteLine(String.Format("d2 = [{0}][{1}]\n", d2, (d2 Is Nothing)))
' Output:  d2 = [][True]

Dim d3 As DateTime? = Nothing
Console.WriteLine(String.Format("d3 = [{0}][{1}]\n", d3, (d3 Is Nothing)))
' Output:  d3 = [][True]

Dim d4 As Nullable(Of DateTime) = Nothing
Console.WriteLine(String.Format("d4 = [{0}][{1}]\n", d4, (d4 Is Nothing)))
' Output:  d4 = [][True]

Also, on how to check whether a variable is null (from Nothing (Visual Basic)):

When checking whether a reference (or nullable value type) variable is null, do not use = Nothing or <> Nothing. Always use Is Nothing or IsNot Nothing.

Async await in linq select

var inputs = events.Select(async ev => await ProcessEventAsync(ev))
                   .Select(t => t.Result)
                   .Where(i => i != null)

But this seems very weird to me, first of all the use of async and await in the select. According to this answer by Stephen Cleary I should be able to drop those.

The call to Select is valid. These two lines are essentially identical:

events.Select(async ev => await ProcessEventAsync(ev))
events.Select(ev => ProcessEventAsync(ev))

(There's a minor difference regarding how a synchronous exception would be thrown from ProcessEventAsync, but in the context of this code it doesn't matter at all.)

Then the second Select which selects the result. Doesn't this mean the task isn't async at all and is performed synchronously (so much effort for nothing), or will the task be performed asynchronously and when it's done the rest of the query is executed?

It means that the query is blocking. So it is not really asynchronous.

Breaking it down:

var inputs = events.Select(async ev => await ProcessEventAsync(ev))

will first start an asynchronous operation for each event. Then this line:

                   .Select(t => t.Result)

will wait for those operations to complete one at a time (first it waits for the first event's operation, then the next, then the next, etc).

This is the part I don't care for, because it blocks and also would wrap any exceptions in AggregateException.

and is it completely the same like this?

var tasks = await Task.WhenAll(events.Select(ev => ProcessEventAsync(ev)));
var inputs = tasks.Where(result => result != null).ToList();

var inputs = (await Task.WhenAll(events.Select(ev => ProcessEventAsync(ev))))
                                       .Where(result => result != null).ToList();

Yes, those two examples are equivalent. They both start all asynchronous operations (events.Select(...)), then asynchronously wait for all the operations to complete in any order (await Task.WhenAll(...)), then proceed with the rest of the work (Where...).

Both of these examples are different from the original code. The original code is blocking and will wrap exceptions in AggregateException.