Programs & Examples On #Switchers

[Ljava.lang.Object; cannot be cast to

You need to add query.addEntity(SwitcherServiceSource.class) before calling the .list() on query.

Auto increment in phpmyadmin

In phpMyAdmin, navigate to the table in question and click the "Operations" tab. On the left under Table Options you will be allowed to set the current AUTO_INCREMENT value.

How to click on hidden element in Selenium WebDriver?

Here is the script in Python.

You cannot click on elements in selenium that are hidden. However, you can execute JavaScript to click on the hidden element for you.

element = driver.find_element_by_id(buttonID)
driver.execute_script("$(arguments[0]).click();", element)

How do you change the colour of each category within a highcharts column chart?

Also you can set option:

  {plotOptions: {column: {colorByPoint: true}}}

for more information read docs

Why can I not push_back a unique_ptr into a vector?

std::unique_ptr has no copy constructor. You create an instance and then ask the std::vector to copy that instance during initialisation.

error: deleted function 'std::unique_ptr<_Tp, _Tp_Deleter>::uniqu
e_ptr(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = int, _Tp_D
eleter = std::default_delete<int>, std::unique_ptr<_Tp, _Tp_Deleter> =

The class satisfies the requirements of MoveConstructible and MoveAssignable, but not the requirements of either CopyConstructible or CopyAssignable.

The following works with the new emplace calls.

std::vector< std::unique_ptr< int > > vec;
vec.emplace_back( new int( 1984 ) );

See using unique_ptr with standard library containers for further reading.

Construct pandas DataFrame from items in nested dictionary

A pandas MultiIndex consists of a list of tuples. So the most natural approach would be to reshape your input dict so that its keys are tuples corresponding to the multi-index values you require. Then you can just construct your dataframe using pd.DataFrame.from_dict, using the option orient='index':

user_dict = {12: {'Category 1': {'att_1': 1, 'att_2': 'whatever'},
                  'Category 2': {'att_1': 23, 'att_2': 'another'}},
             15: {'Category 1': {'att_1': 10, 'att_2': 'foo'},
                  'Category 2': {'att_1': 30, 'att_2': 'bar'}}}

pd.DataFrame.from_dict({(i,j): user_dict[i][j] 
                           for i in user_dict.keys() 
                           for j in user_dict[i].keys()},

               att_1     att_2
12 Category 1      1  whatever
   Category 2     23   another
15 Category 1     10       foo
   Category 2     30       bar

An alternative approach would be to build your dataframe up by concatenating the component dataframes:

user_ids = []
frames = []

for user_id, d in user_dict.iteritems():
    frames.append(pd.DataFrame.from_dict(d, orient='index'))

pd.concat(frames, keys=user_ids)

               att_1     att_2
12 Category 1      1  whatever
   Category 2     23   another
15 Category 1     10       foo
   Category 2     30       bar

How to remove the arrows from input[type="number"] in Opera

Those arrows are part of the Shadow DOM, which are basically DOM elements on your page which are hidden from you. If you're new to the idea, a good introductory read can be found here.

For the most part, the Shadow DOM saves us time and is good. But there are instances, like this question, where you want to modify it.

You can modify these in Webkit now with the right selectors, but this is still in the early stages of development. The Shadow DOM itself has no unified selectors yet, so the webkit selectors are proprietary (and it isn't just a matter of appending -webkit, like in other cases).

Because of this, it seems likely that Opera just hasn't gotten around to adding this yet. Finding resources about Opera Shadow DOM modifications is tough, though. A few unreliable internet sources I've found all say or suggest that Opera doesn't currently support Shadow DOM manipulation.

I spent a bit of time looking through the Opera website to see if there'd be any mention of it, along with trying to find them in Dragonfly...neither search had any luck. Because of the silence on this issue, and the developing nature of the Shadow DOM + Shadow DOM manipulation, it seems to be a safe conclusion that you just can't do it in Opera, at least for now.

How to build a Debian/Ubuntu package from source?

  • put "debian" directory from original package to your source directory
  • use "dch" to update version of package
  • use "debuild" to build the package

How to specify the port an ASP.NET Core application is hosted on?

Above .net core 2.2 the method Main support args with WebHost.CreateDefaultBuilder(args)

public class Program
    public static void Main(string[] args)

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>

You can build your project and go to bin run command like this

dotnet <yours>.dll --urls=http://localhost:5001

or with multi-urls

dotnet <yours>.dll --urls="http://localhost:5001,https://localhost:5002"

How to create Android Facebook Key Hash?

For Windows:

  1. open command prompt and paste below command

keytool -exportcert -alias androiddebugkey -keystore\debug.keystore | openssl sha1 -binary | openssl base64

  1. Enter password : android --> Hit Enter

  2. Copy Generated Hash Key --> Login Facebook with your developer account

  3. Go to your Facebook App --> Settings--> Paste Hash key in "key hashes" option -->save changes.

  4. Now Test your android app with Facebook Log-in/Share etc.

jQuery if statement to check visibility

You can use .is(':visible') to test if something is visible and .is(':hidden') to test for the opposite:

$('#offers').toggle(!$('#column-left form').is(':visible')); // or:
$('#offers').toggle($('#column-left form').is(':hidden'));


Rank function in MySQL

One option is to use a ranking variable, such as the following:

SELECT    first_name,
          @curRank := @curRank + 1 AS rank
FROM      person p, (SELECT @curRank := 0) r
ORDER BY  age;

The (SELECT @curRank := 0) part allows the variable initialization without requiring a separate SET command.

Test case:

CREATE TABLE person (id int, first_name varchar(20), age int, gender char(1));

INSERT INTO person VALUES (1, 'Bob', 25, 'M');
INSERT INTO person VALUES (2, 'Jane', 20, 'F');
INSERT INTO person VALUES (3, 'Jack', 30, 'M');
INSERT INTO person VALUES (4, 'Bill', 32, 'M');
INSERT INTO person VALUES (5, 'Nick', 22, 'M');
INSERT INTO person VALUES (6, 'Kathy', 18, 'F');
INSERT INTO person VALUES (7, 'Steve', 36, 'M');
INSERT INTO person VALUES (8, 'Anne', 25, 'F');


| first_name | age  | gender | rank |
| Kathy      |   18 | F      |    1 |
| Jane       |   20 | F      |    2 |
| Nick       |   22 | M      |    3 |
| Bob        |   25 | M      |    4 |
| Anne       |   25 | F      |    5 |
| Jack       |   30 | M      |    6 |
| Bill       |   32 | M      |    7 |
| Steve      |   36 | M      |    8 |
8 rows in set (0.02 sec)

Why is textarea filled with mysterious white spaces?

Another work around would be to use javascript:


//without jquery
document.getElementById('someid').innerHTML = document.getElementById('someid').innerHTML.trim();

This is what I did. Removing white-spaces and line-breaks in the code makes the line too long.

Display all items in array using jquery

here is solution, i create a text field to dynamic add new items in array my html code is

 <input type="text" id="name">_x000D_
  <input type="button" id="btn" value="Button">_x000D_
  <div id="names">_x000D_

now type any thing in text field and click on button this will add item onto array and call function dispaly_arry

{  _x000D_
 function display_array()_x000D_
    $('#names').append(value + '<br/>');_x000D_
 var names = ['Alex','Billi','Dale'];_x000D_
  var name = $('#name').val();_x000D_
  names.push(name);// appending value to arry _x000D_

showing array elements into div , you can use span but for this solution use same id .!

What exactly is Apache Camel?

A definition from another perspective:

Apache Camel is an integration framework. It consists of some Java libraries, which helps you implementing integration problems on the Java platform. What this means and how it differs from APIs on the one side and an Enterprise Service Bus (ESB) on the other side is described in my article "When to use Apache Camel".

Deploying website: 500 - Internal server error

I recently got into same problem, the disk space was full on the server. Clearing some space has resolved the issue.

How to pass parameter to click event in Jquery

As DOC says, you can pass data to the handler as next:

// say your selector and click handler looks something like this...
$("some selector").on('click',{param1: "Hello", param2: "World"}, cool_function);

// in your function, just grab the event object and go crazy...
function cool_function(event){

    // access element's id where click occur
    alert( ); 

PhoneGap Eclipse Issue - eglCodecCommon glUtilsParamSize: unknow param errors

I Get the same message, when using Intel XHAM emulator (instead of ARM) and have "Use Host GPU" option enabled. I belive when you disable it, it goes away.

fatal: Not a git repository (or any of the parent directories): .git

The command has to be entered in the directory of the repository. The error is complaining that your current directory isn't a git repo

  1. Are you in the right directory? Does typing ls show the right files?
  2. Have you initialized the repository yet? Typed git init? (git-init documentation)

Either of those would cause your error.

What is the OAuth 2.0 Bearer Token exactly?

As I read your question, I have tried without success to search on the Internet how Bearer tokens are encrypted or signed. I guess bearer tokens are not hashed (maybe partially, but not completely) because in that case, it will not be possible to decrypt it and retrieve users properties from it.

But your question seems to be trying to find answers on Bearer token functionality:

Suppose I am implementing an authorization provider, can I supply any kind of string for the bearer token? Can it be a random string? Does it has to be a base64 encoding of some attributes? Should it be hashed?

So, I'll try to explain how Bearer tokens and Refresh tokens work:

When user requests to the server for a token sending user and password through SSL, the server returns two things: an Access token and a Refresh token.

An Access token is a Bearer token that you will have to add in all request headers to be authenticated as a concrete user.

Authorization: Bearer <access_token>

An Access token is an encrypted string with all User properties, Claims and Roles that you wish. (You can check that the size of a token increases if you add more roles or claims). Once the Resource Server receives an access token, it will be able to decrypt it and read these user properties. This way, the user will be validated and granted along with all the application.

Access tokens have a short expiration (ie. 30 minutes). If access tokens had a long expiration it would be a problem, because theoretically there is no possibility to revoke it. So imagine a user with a role="Admin" that changes to "User". If a user keeps the old token with role="Admin" he will be able to access till the token expiration with Admin rights. That's why access tokens have a short expiration.

But, one issue comes in mind. If an access token has short expiration, we have to send every short period the user and password. Is this secure? No, it isn't. We should avoid it. That's when Refresh tokens appear to solve this problem.

Refresh tokens are stored in DB and will have long expiration (example: 1 month).

A user can get a new Access token (when it expires, every 30 minutes for example) using a refresh token, that the user had received in the first request for a token. When an access token expires, the client must send a refresh token. If this refresh token exists in DB, the server will return to the client a new access token and another refresh token (and will replace the old refresh token by the new one).

In case a user Access token has been compromised, the refresh token of that user must be deleted from DB. This way the token will be valid only till the access token expires because when the hacker tries to get a new access token sending the refresh token, this action will be denied.

Android-java- How to sort a list of objects by a certain value within the object

public class DateComparator implements Comparator<Marker> {
    public int compare(Mark lhs, Mark rhs) {
        Double distance = Double.valueOf(lhs.getDistance());
        Double distance1 = Double.valueOf(rhs.getDistance());
        if (distance.compareTo(distance1) < 0) {
            return -1;
        } else if (distance.compareTo(distance1) > 0) {
            return 1;
        } else {
            return 0;

ArrayList(Marker) arraylist;

How To use:

Collections.sort(arraylist, new DateComparator());

Setting the focus to a text field

I did it by setting an AncesterAdded event on the textField and the requesting focus in the window.

Nodejs - Redirect url

You have to use the following code:

response.writeHead(302 , {
           'Location' : '/view/index.html' // This is your url which you want

How can I change the app display name build with Flutter?

There is a plugin, flutter_launcher_name.

Write file pubspec.yaml:

  flutter_launcher_name: "^0.0.1"

  name: "yourNewAppLauncherName"

And run:

flutter pub get
flutter pub run flutter_launcher_name:main

You can get the same result as editing AndroidManifes.xml and Info.plist.

Mark error in form using Bootstrap

Can use CSS to show error message only on error.

.form-group.has-error .help-block {
    display: block;

.form-group .help-block {
    display: none;

<div class="form-group has-error">
  <label class="control-label" for="inputError">Input with error</label>
  <input type="text" class="form-control" id="inputError">
  <span class="help-block">Please correct the error</span>

Passing HTML input value as a JavaScript Function Parameter

You can get the values with use of ID. But ID should be Unique.

<h1>Adding 'a' and 'b'</h1>
  a: <input type="number" name="a" id="a"><br>
  b: <input type="number" name="b" id="b"><br>
  <button onclick="add()">Add</button>
  function add() {
    a = $('#a').val();
    b = $('#b').val();
    var sum = a + b;

Git "error: The branch 'x' is not fully merged"

to see changes that are not merged, I did this:

git checkout experiment
git merge --no-commit master

git diff --cached

Note: This shows changes in master that are not in experiment.

Don't forget to:

git merge --abort

When you're done lookin.

java.util.Date format SSSSSS: if not microseconds what are the last 3 digits?

I used yet another trick to format date with 6-digit precision (microseconds):

    new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.").format(microseconds/1000)
    +String.format("%06d", microseconds%1000000));

This technique can be extended further, to nanoseconds and up.

How to find distinct rows with field in list using JPA and Spring?

@Query("SELECT DISTINCT name FROM people WHERE name NOT IN (:names)")
List<String> findNonReferencedNames(@Param("names") List<String> names);

Append to the end of a Char array in C++

If your arrays are character arrays(which seems to be the case), You need a strcat().
Your destination array should have enough space to accommodate the appended data though.

In C++, You are much better off using std::string and then you can use std::string::append()

System.Runtime.InteropServices.COMException (0x800A03EC)

It 'a permission problem when IIS is running I had this problem and I solved it in this way

I went on folders

C:\Windows\ System32\config\SystemProfile



are protected system folders, they usually have the lock.

Right-click-> Card security-> Click on Edit-> Add untente "Autenticadet User" and assign permissions.

At this point everything is solved, if you still have problems try to give all permissions to "Everyone"

Binding ConverterParameter

There is also an alternative way to use MarkupExtension in order to use Binding for a ConverterParameter. With this solution you can still use the default IValueConverter instead of the IMultiValueConverter because the ConverterParameter is passed into the IValueConverter just like you expected in your first sample.

Here is my reusable MarkupExtension:

/// <summary>
///     <example>
///         <TextBox>
///             <TextBox.Text>
///                 <wpfAdditions:ConverterBindableParameter Binding="{Binding FirstName}"
///                     Converter="{StaticResource TestValueConverter}"
///                     ConverterParameterBinding="{Binding ConcatSign}" />
///             </TextBox.Text>
///         </TextBox>
///     </example>
/// </summary>
public class ConverterBindableParameter : MarkupExtension
    #region Public Properties

    public Binding Binding { get; set; }
    public BindingMode Mode { get; set; }
    public IValueConverter Converter { get; set; }
    public Binding ConverterParameter { get; set; }


    public ConverterBindableParameter()
    { }

    public ConverterBindableParameter(string path)
        Binding = new Binding(path);

    public ConverterBindableParameter(Binding binding)
        Binding = binding;

    #region Overridden Methods

    public override object ProvideValue(IServiceProvider serviceProvider)
        var multiBinding = new MultiBinding();
        Binding.Mode = Mode;
        if (ConverterParameter != null)
            ConverterParameter.Mode = BindingMode.OneWay;
        var adapter = new MultiValueConverterAdapter
            Converter = Converter
        multiBinding.Converter = adapter;
        return multiBinding.ProvideValue(serviceProvider);


    private class MultiValueConverterAdapter : IMultiValueConverter
        public IValueConverter Converter { get; set; }

        private object lastParameter;

        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
            if (Converter == null) return values[0]; // Required for VS design-time
            if (values.Length > 1) lastParameter = values[1];
            return Converter.Convert(values[0], targetType, lastParameter, culture);

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
            if (Converter == null) return new object[] { value }; // Required for VS design-time

            return new object[] { Converter.ConvertBack(value, targetTypes[0], lastParameter, culture) };

With this MarkupExtension in your code base you can simply bind the ConverterParameter the following way:

<Style TargetType="FrameworkElement">
<Setter Property="Visibility">
     <wpfAdditions:ConverterBindableParameter Binding="{Binding Tag, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UserControl}"
                 Converter="{StaticResource AccessLevelToVisibilityConverter}"
                 ConverterParameterBinding="{Binding RelativeSource={RelativeSource Mode=Self}, Path=Tag}" />          

Which looks almost like your initial proposal.

What is the standard exception to throw in Java for not supported/implemented operations?

If you create a new (not yet implemented) function in NetBeans, then it generates a method body with the following statement:

throw new java.lang.UnsupportedOperationException("Not supported yet.");

Therefore, I recommend to use the UnsupportedOperationException.

How to know elastic search installed version from kibana?

If you have installed x-pack to secure elasticseach, the request should contains the valid credential details.

curl -XGET -u "elastic:passwordForElasticUser" 'localhost:9200'

Infact, if the security enabled all the subsequent requests should follow the same pattern (inline credentials should be provided).

Use .htaccess to redirect HTTP to HTTPs

Just add this code, And it will work like charm:

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteCond %{HTTP_HOST}#%{HTTPS}s ^www\.([^#]+)#(?:off|on(s)) [NC]
    RewriteRule ^ http%2://%1%{REQUEST_URI} [R=301,L]

Scanning Java annotations at runtime

Is it too late to answer. I would say, its better to go by Libraries like ClassPathScanningCandidateComponentProvider or like Scannotations

But even after somebody wants to try some hands on it with classLoader, I have written some on my own to print the annotations from classes in a package:

public class ElementScanner {

public void scanElements(){
    try {
    //Get the package name from configuration file
    String packageName = readConfig();

    //Load the classLoader which loads this class.
    ClassLoader classLoader = getClass().getClassLoader();

    //Change the package structure to directory structure
    String packagePath  = packageName.replace('.', '/');
    URL urls = classLoader.getResource(packagePath);

    //Get all the class files in the specified URL Path.
    File folder = new File(urls.getPath());
    File[] classes = folder.listFiles();

    int size = classes.length;
    List<Class<?>> classList = new ArrayList<Class<?>>();

    for(int i=0;i<size;i++){
        int index = classes[i].getName().indexOf(".");
        String className = classes[i].getName().substring(0, index);
        String classNamePath = packageName+"."+className;
        Class<?> repoClass;
        repoClass = Class.forName(classNamePath);
        Annotation[] annotations = repoClass.getAnnotations();
        for(int j =0;j<annotations.length;j++){
            System.out.println("Annotation in class "+repoClass.getName()+ " is "+annotations[j].annotationType().getName());
    } catch (ClassNotFoundException e) {

 * Unmarshall the configuration file
 * @return
public String readConfig(){
        URL url = getClass().getClassLoader().getResource("WEB-INF/config.xml");
        JAXBContext jContext = JAXBContext.newInstance(RepositoryConfig.class);
         Unmarshaller um =  jContext.createUnmarshaller();
         RepositoryConfig rc = (RepositoryConfig) um.unmarshal(new File(url.getFile()));
         return rc.getRepository().getPackageName();
        }catch(Exception e){
    return null;


And in config File, you put the package name and unmarshall it to a class .

What is the string concatenation operator in Oracle?

It is ||, for example:

select 'Mr ' || ename from emp;

The only "interesting" feature I can think of is that 'x' || null returns 'x', not null as you might perhaps expect.

How to do a join in linq to sql with method syntax?

Justin has correctly shown the expansion in the case where the join is just followed by a select. If you've got something else, it becomes more tricky due to transparent identifiers - the mechanism the C# compiler uses to propagate the scope of both halves of the join.

So to change Justin's example slightly:

var result = from sc in enumerableOfSomeClass
             join soc in enumerableOfSomeOtherClass
             on sc.Property1 equals soc.Property2
             where sc.X + sc.Y == 10
             select new { SomeClass = sc, SomeOtherClass = soc }

would be converted into something like this:

var result = enumerableOfSomeClass
          sc => sc.Property1,
          soc => soc.Property2,
          (sc, soc) => new { sc, soc })
    .Where(z => + == 10)
    .Select(z => new { SomeClass =, SomeOtherClass = z.soc });

The z here is the transparent identifier - but because it's transparent, you can't see it in the original query :)

Spring MVC: how to create a default controller for index page?

One way to achieve it, is by map your welcome-file to your controller request path in the web.xml file:


<web-app ...

<!-- Index -->



public class LoginController{

public String homepage2(ModelMap model, HttpServletRequest request, HttpServletResponse response){
    model.addAttribute("sigh", "lesigh");
    return "index";

How do I query for all dates greater than a certain date in SQL Server?

DateTime start1 = DateTime.Parse(txtDate.Text);

FROM dbo.March2010 A
WHERE A.Date >= start1;

First convert TexBox into the Datetime then....use that variable into the Query

Iterate through dictionary values?

Create the opposite dictionary:

PIX1 = {}
for key in PIX0.keys():
    PIX1[PIX0.get(key)] = key

Then run the same code on this dictionary instead (using PIX1 instead of PIX0).

BTW, I'm not sure about Python 3, but in Python 2 you need to use raw_input instead of input.

How to dynamically change a web page's title?

Maybe you can load on your title all the tabs titles in one string, and then once you load one of the tabs change the title via javascript

ex: at first set your title to

my app | description | contact | about us | 

once you load one of the tabs run:

document.title = "my app | tab title";

How can I get the nth character of a string?

char* str = "HELLO";
char c = str[1];

Keep in mind that arrays and strings in C begin indexing at 0 rather than 1, so "H" is str[0], "E" is str[1], the first "L" is str[2] and so on.

How can I set the value of a DropDownList using jQuery?

If your dropdown is Asp.Net drop down then below code will work fine,


But if your DropDown is HTML drop down then this code will work.


Groovy method with optional parameters

You can use arguments with default values.

def someMethod(def mandatory,def optional=null){}

if argument "optional" not exist, it turns to "null".

Validate select box

you want to make sure that the user selects anything but "Choose an option" (which is the default one). So that it won't validate if you choose the first option. How can this be done?

You can do this by simple adding attribute required = "required" in the select tag. you can see it in below code

<select id="select" required="required">
<option value="">Choose an option</option>
<option value="option1">Option1</option>
<option value="option2">Option2</option>
<option value="option3">Option3</option>

It worked fine for me at chorme, firefox and internet explorer. Thanks

Import Google Play Services library in Android Studio

I solved the problem by installing the google play services package in sdk manager.

After it, create a new application & in the build.gradle add this

compile ''

Like this

dependencies {
    compile ''
    compile ''

Add/remove class with jquery based on vertical scroll?

Add some transition effect to it if you like:,css,js

.clearHeader {

  -webkit-transition: background 2s; /* For Safari 3.1 to 6.0 */
  transition: background 2s;

.clearHeader.darkHeader {

How to resize array in C++?

You can do smth like this for 1D arrays. Here we use int*& because we want our pointer to be changeable.

#include<algorithm> // for copy

void resize(int*& a, size_t& n)
   size_t new_n = 2 * n;
   int* new_a = new int[new_n];
   copy(a, a + n, new_a);
   delete[] a;
   a = new_a;
   n = new_n;

For 2D arrays:

#include<algorithm> // for copy

void resize(int**& a, size_t& n)
   size_t new_n = 2 * n, i = 0;
   int** new_a = new int* [new_n];
   for (i = 0; i != new_n; ++i)
       new_a[i] = new int[100];
   for (i = 0; i != n; ++i)
       copy(a[i], a[i] + 100, new_a[i]);
       delete[] a[i];
   delete[] a;
   a = new_a;
   n = new_n;

Invoking of 1D array:

void myfn(int*& a, size_t& n)
   // do smth
   resize(a, n);

Invoking of 2D array:

void myfn(int**& a, size_t& n)
   // do smth
   resize(a, n);


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

Well, putting together every working approach will result in this (also dealing with deprecated GpsStatus.Listener):

private GnssStatus.Callback mGnssStatusCallback;
@Deprecated private GpsStatus.Listener mStatusListener;
private LocationManager mLocationManager;

public void onCreate() {
    mLocationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

    mLocationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
    if (checkPermission()) {
       mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, GPS_UPDATE_INTERVAL, MIN_DISTANCE, this);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        mGnssStatusCallback = new GnssStatus.Callback() {
            public void onSatelliteStatusChanged(GnssStatus status) {

            public void onFirstFix(int ttffMillis) {

    } else {
        mStatusListener = new GpsStatus.Listener() {
            public void onGpsStatusChanged(int event) {
                switch (event) {
                    case GpsStatus.GPS_EVENT_SATELLITE_STATUS:
                    case GpsStatus.GPS_EVENT_FIRST_FIX:
                        // Do something.

private void gpsFixAcquired() {
    // Do something.
    isGPSFix = true;

private void satelliteStatusChanged() {
    if (mLastLocation != null)
        isGPSFix = (SystemClock.elapsedRealtime() - mLastLocationMillis) < (GPS_UPDATE_INTERVAL * 2);

    if (isGPSFix) { // A fix has been acquired.
        // Do something.
    } else { // The fix has been lost.
        // Do something.

public void onLocationChanged(Location location) {
    if (location == null) return;

    mLastLocationMillis = SystemClock.elapsedRealtime();

    mLastLocation = location;

public void onStatusChanged(String s, int i, Bundle bundle) {


public void onProviderEnabled(String s) {


public void onProviderDisabled(String s) {


Note: this answer is a combination of the answers above.

Filtering a list based on a list of booleans

You're looking for itertools.compress:

>>> from itertools import compress
>>> list_a = [1, 2, 4, 6]
>>> fil = [True, False, True, False]
>>> list(compress(list_a, fil))
[1, 4]

Timing comparisons(py3.x):

>>> list_a = [1, 2, 4, 6]
>>> fil = [True, False, True, False]
>>> %timeit list(compress(list_a, fil))
100000 loops, best of 3: 2.58 us per loop
>>> %timeit [i for (i, v) in zip(list_a, fil) if v]  #winner
100000 loops, best of 3: 1.98 us per loop

>>> list_a = [1, 2, 4, 6]*100
>>> fil = [True, False, True, False]*100
>>> %timeit list(compress(list_a, fil))              #winner
10000 loops, best of 3: 24.3 us per loop
>>> %timeit [i for (i, v) in zip(list_a, fil) if v]
10000 loops, best of 3: 82 us per loop

>>> list_a = [1, 2, 4, 6]*10000
>>> fil = [True, False, True, False]*10000
>>> %timeit list(compress(list_a, fil))              #winner
1000 loops, best of 3: 1.66 ms per loop
>>> %timeit [i for (i, v) in zip(list_a, fil) if v] 
100 loops, best of 3: 7.65 ms per loop

Don't use filter as a variable name, it is a built-in function.

Webclient / HttpWebRequest with Basic Authentication returns 404 not found for valid URL

This part of code worked fine for me:

        WebRequest request = WebRequest.Create(url);
        request.Method = WebRequestMethods.Http.Get;
        NetworkCredential networkCredential = new NetworkCredential(logon, password); // logon in format "domain\username"
        CredentialCache myCredentialCache = new CredentialCache {{new Uri(url), "Basic", networkCredential}};
        request.PreAuthenticate = true;
        request.Credentials = myCredentialCache;
        using (WebResponse response = request.GetResponse())

            using (Stream dataStream = response.GetResponseStream())
                using (StreamReader reader = new StreamReader(dataStream))
                    string responseFromServer = reader.ReadToEnd();

Clearing an input text field in Angular2

This is a solution for reactive forms. Then there is no need to use @ViewChild decorator:

  clear() {

Getting new Twitter API consumer and secret keys

  1. Log into the Twitter Developers section.

    • If you don't already have an account, you can login with your normal Twitter credentials
  2. Go to "Create an app"

  3. Fill in the details of the application you'll be using to connect with the API

    • Your application name must be unique. If someone else is already using it, you won't be able to register your application until you can think of something that isn't being used.
  4. Click on Create your Twitter application

  5. Details of your new app will be shown along with your consumer key and consumer secret.

  6. If you need access tokens, scroll down and click Create my access token

    • The page will then refresh on the "Details" tab with your new access tokens. You can recreate these at any time if you need to.

By default your apps will be granted for read-only access. To change this, go to the Settings tab and change the access level required in the "Application Type" section.

Existing apps

To get the consumer and access tokens for an existing application, go to My applications (which is available from the menu in the upper-right).

Getting the base url of the website and globally passing it to twig in Symfony 2

Also for js/css/image urls there's handy function asset()

<img src="{{ asset('image/logo.png') }}"/>

This creates an absolute url starting with /.

How to revert uncommitted changes including files and folders?

Git 2.23 introduced git restore command to restore working tree files.

To restore all files in the current directory

git restore .

If you want to restore all C source files to match the version in the index, you can do

git restore '*.c'

How to make an ng-click event conditional?

We can add ng-click event conditionally without using disabled class.


<div ng-repeat="object in objects">
<span ng-click="!object.status && disableIt(object)">{{object.value}}</span>

Check file uploaded is in csv format

So I ran into this today.

Was attempting to validate an uploaded CSV file's MIME type by looking at $_FILES['upload_file']['type'], but for certain users on various browsers (and not necessarily the same browsers between said users; for instance it worked fine for me in FF but for another user it didn't work on FF) the $_FILES['upload_file']['type'] was coming up as "application/" instead of the expected "text/csv" or "text/plain".

So I resorted to using the (IMHO) much more reliable finfo_* functions something like this:

$acceptable_mime_types = array('text/plain', 'text/csv', 'text/comma-separated-values');

if (!empty($_FILES) && array_key_exists('upload_file', $_FILES) && $_FILES['upload_file']['error'] == UPLOAD_ERR_OK) {
    $tmpf = $_FILES['upload_file']['tmp_name'];

    // Make sure $tmpf is kosher, then:

    $finfo = finfo_open(FILEINFO_MIME_TYPE);
    $mime_type = finfo_file($finfo, $tmpf);

    if (!in_array($mime_type, $acceptable_mime_types)) {
        // Unacceptable mime type.

Waiting on a list of Future

I've got a utility class that contains these:

public interface CheckedSupplier<X> {
  X get() throws Throwable;

public static <X> Supplier<X> uncheckedSupplier(final CheckedSupplier<X> supplier) {
    return () -> {
        try {
            return supplier.get();
        } catch (final Throwable checkedException) {
            throw new IllegalStateException(checkedException);

Once you have that, using a static import, you can simple wait for all futures like this: -> uncheckedSupplier(future::get).get());

you can also collect all their results like this:

List<MyResultType> results =
    .map(future -> uncheckedSupplier(future::get).get())

Just revisiting my old post and noticing that you had another grief:

But the problem here is if, for example, the 4th future throws an exception, then I will wait unnecessarily for the first 3 futures to be available.

In this case, the simple solution is to do this in parallel:
 .forEach(future -> uncheckedSupplier(future::get).get());

This way the first exception, although it will not stop the future, will break the forEach-statement, like in the serial example, but since all wait in parallel, you won't have to wait for the first 3 to complete.

std::string to float or double

You don't want Boost lexical_cast for string <-> floating point anyway. That subset of use cases is the only set for which boost consistently is worse than the older functions- and they basically concentrated all their failure there, because their own performance results show a 20-25X SLOWER performance than using sscanf and printf for such conversions.

Google it yourself. boost::lexical_cast can handle something like 50 conversions and if you exclude the ones involving floating point #s its as good or better as the obvious alternatives (with the added advantage of being having a single API for all those operations). But bring in floats and its like the Titanic hitting an iceberg in terms of performance.

The old, dedicated str->double functions can all do 10000 parses in something like 30 ms (or better). lexical_cast takes something like 650 ms to do the same job.

Make Iframe to fit 100% of container's remaining height

You can do this by measuring the body size on load/resize events and setting the height to the (full height - banner height).

Note that currently in IE8 Beta2 you can't do this onresize as that event is currently broken in IE8 Beta2.

How to retrieve images from MySQL database and display in an html tag

I have added slashes before inserting into database so on the time of fetching i removed slashes again stripslashes() and it works for me. I am sharing the code which works for me.

How i inserted into mysql db (blob type)

$db = mysqli_connect("localhost","root","","dName"); 
$image = addslashes(file_get_contents($_FILES['images']['tmp_name']));
$query = "INSERT INTO student_img (id,image) VALUES('','$image')";  
$query = mysqli_query($db, $query);

Now to access the image

$sqlQuery = "SELECT * FROM student_img WHERE id = $stid";
$rs = $db->query($sqlQuery);
echo '<img src="data:image/jpeg;base64,'.base64_encode( stripslashes($result['image']) ).'"/>';

Hope it will help someone


Referencing in Visual Studio

I used the VS Project Reference menu and browsed to: C:\windows\assembly\GAC_MSIL\System.Management.Automation and added a reference for the dll and the Runspaces dll.

I did not need to hack the .csprj file and add the reference line mentioned above. I do not have the Windows SDK installed.

I did do the Powershell copy mentioned above: Copy ([PSObject].Assembly.Location) C:\

My test with a Get-Process Powershell command then worked. I used examples from Powershell for developers Chapter 5.

Cannot make Project Lombok work on Eclipse

This sometimes does not work if Eclipse is on one of those strange default windows paths (e.g. c:/Program files (86)/Eclipse).

In that case, do as above, then move the lombok jar to a cleaner path without spaces and braces (e.g. c:\lombok\lombok.jar) and modify eclipse.ini accordingly.

JavaScript/JQuery: $(window).resize how to fire AFTER the resize is completed?

Actually, as I know, you can't do some actions exactly when resize is off, simply because you don't know future user's actions. But you can assume the time passed between two resize events, so if you wait a little more than this time and no resize is made, you can call your function.
Idea is that we use setTimeout and it's id in order to save or delete it. For example we know that time between two resize events is 500ms, therefore we will wait 750ms.

var a;_x000D_
  a = setTimeout(function(){_x000D_
    // call your function_x000D_

Maintaining the final state at end of a CSS3 animation

IF NOT USING THE SHORT HAND VERSION: Make sure the animation-fill-mode: forwards is AFTER the animation declaration or it will not work...

animation-fill-mode: forwards;
animation-name: appear;
animation-duration: 1s;
animation-delay: 1s;


animation-name: appear;
animation-duration: 1s;
animation-fill-mode: forwards;
animation-delay: 1s;

JavaScript - XMLHttpRequest, Access-Control-Allow-Origin errors

I've gotten same problem. The servers logs showed:

DEBUG: <-- origin: null

I've investigated that and it occurred that this is not populated when I've been calling from file from local drive. When I've copied file to the server and used it from server - the request worked perfectly fine

How to get the fields in an Object via reflection?

You can use Class#getDeclaredFields() to get all declared fields of the class. You can use Field#get() to get the value.

In short:

Object someObject = getItSomehow();
for (Field field : someObject.getClass().getDeclaredFields()) {
    field.setAccessible(true); // You might want to set modifier to public first.
    Object value = field.get(someObject); 
    if (value != null) {
        System.out.println(field.getName() + "=" + value);

To learn more about reflection, check the Sun tutorial on the subject.

That said, the fields does not necessarily all represent properties of a VO. You would rather like to determine the public methods starting with get or is and then invoke it to grab the real property values.

for (Method method : someObject.getClass().getDeclaredMethods()) {
    if (Modifier.isPublic(method.getModifiers())
        && method.getParameterTypes().length == 0
        && method.getReturnType() != void.class
        && (method.getName().startsWith("get") || method.getName().startsWith("is"))
    ) {
        Object value = method.invoke(someObject);
        if (value != null) {
            System.out.println(method.getName() + "=" + value);

That in turn said, there may be more elegant ways to solve your actual problem. If you elaborate a bit more about the functional requirement for which you think that this is the right solution, then we may be able to suggest the right solution. There are many, many tools available to massage javabeans.

Compare a string using sh shell

-eq is the shell comparison operator for comparing integers. For comparing strings you need to use =.

RegEx to exclude a specific string constant

You could use negative lookahead, or something like this:


Maybe it could be simplified a bit.

Relational Database Design Patterns?

Your question is a bit vague, but I suppose UPSERT could be considered a design pattern. For languages that don't implement MERGE, a number of alternatives to solve the problem (if a suitable rows exists, UPDATE; else INSERT) exist.

Library not loaded: libmysqlclient.16.dylib error when trying to run 'rails server' on OS X 10.6 with mysql2 gem

Just ran into this problem. All I had to do is uninstall mysql2 gem and reinstall it. Hope this works for other people

How to run .sql file in Oracle SQL developer tool to import database?

As others recommend, you can use Oracle SQL Developer. You can point to the location of the script to run it, as described. A slightly simpler method, though, is to just use drag-and-drop:

  • Click and drag your .sql file over to Oracle SQL Developer
  • The contents will appear in a "SQL Worksheet"
  • Click "Run Script" button, or hit F5, to run

enter image description here

Cannot run Eclipse; JVM terminated. Exit code=13

This error occurred to me on ubuntu, having installed 32bit and 64bit java. Use

sudo update-alternatives --config java

to set the right version to use as default.

Intellij IDEA Java classes not auto compiling on save

Edit your Run/Debug Configuration so that Build option is selected before launching

enter image description here

After Build option is selected

enter image description here

The above solution worked for me while working on my JBehave test suite

How do I get a HttpServletRequest in my spring beans?

@eeezyy's answer didn't work for me, although I'm using Spring Boot (2.0.4) and it may differ, but a variation here in 2018 works thus:

private HttpServletRequest request;

How to select all checkboxes with jQuery?

  $("#select_all").live("click", function(){
            $("input").prop("checked", $(this).prop("checked"));

Reading text files using read.table

From ?read.table: The number of data columns is determined by looking at the first five lines of input (or the whole file if it has less than five lines), or from the length of col.names if it is specified and is longer. This could conceivably be wrong if fill or blank.lines.skip are true, so specify col.names if necessary.

So, perhaps your data file isn't clean. Being more specific will help the data import:

d = read.table("foobar.txt", 
               col.names=c("id", "name"), 

will specify exact columns and fill=FALSE will force a two column data frame.

REST - HTTP Post Multipart with JSON

If I understand you correctly, you want to compose a multipart request manually from an HTTP/REST console. The multipart format is simple; a brief introduction can be found in the HTML 4.01 spec. You need to come up with a boundary, which is a string not found in the content, let’s say HereGoes. You set request header Content-Type: multipart/form-data; boundary=HereGoes. Then this should be a valid request body:

Content-Disposition: form-data; name="myJsonString"
Content-Type: application/json

{"foo": "bar"}
Content-Disposition: form-data; name="photo"
Content-Type: image/jpeg
Content-Transfer-Encoding: base64

<...JPEG content in base64...>

Error "package does not exist"

After Rebuild the project issue resolved..

Angular IE Caching issue for $http

I simply added three meta tags into index.html on angular project, and cache issue was solved on IE.

<meta http-equiv="Pragma" content="no-cache">
<meta http-equiv="Cache-Control" content="no-cache">
<meta http-equiv="Expires" content="Sat, 01 Dec 2001 00:00:00 GMT">

How to find the difference in days between two dates?

If you have GNU date, it allows to print the representation of an arbitrary date (-d option). In this case convert the dates to seconds since EPOCH, subtract and divide by 24*3600.

Or you need a portable way?

How can I see what I am about to push with git?

Just to add my two cents... I wanted to implement this when running jobs in a gitlab pipeline on a gitlab runner. The best way to do this was to use this script:

git diff --name-only $CI_COMMIT_BEFORE_SHA $CI_COMMIT_SHA

Also in my case I wanted to filter files by extension, to achieve this I used:

git diff --name-only $CI_COMMIT_BEFORE_SHA $CI_COMMIT_SHA '*.py'

After that you can for example forward this list somewhere else, a linter perhaps ;)

Hope this will help someone.

Issue with parsing the content from json file with Jackson & message- JsonMappingException -Cannot deserialize as out of START_ARRAY token

As said, JsonMappingException: out of START_ARRAY token exception is thrown by Jackson object mapper as it's expecting an Object {} whereas it found an Array [{}] in response.

A simpler solution could be replacing the method getLocations with:

public static List<Location> getLocations(InputStream inputStream) {
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        TypeReference<List<Location>> typeReference = new TypeReference<>() {};
        return objectMapper.readValue(inputStream, typeReference);
    } catch (IOException e) {
    return null;

On the other hand, if you don't have a pojo like Location, you could use:

TypeReference<List<Map<String, Object>>> typeReference = new TypeReference<>() {};
return objectMapper.readValue(inputStream, typeReference);

Listing all the folders subfolders and files in a directory using php

You can also try this:

function listdirs($dir) {
    static $alldirs = array();
    $dirs = glob($dir . '/*', GLOB_ONLYDIR);
    if (count($dirs) > 0) {
        foreach ($dirs as $d) $alldirs[] = $d;
    foreach ($dirs as $dir) listdirs($dir);
    return $alldirs;

$directory_list = listdirs('xampp');

Spark DataFrame TimestampType - how to get Year, Month, Day values from field?

Actually, we really do not need to import any python library. We can separate the year, month, date using simple SQL. See the below example,

|       _c0|

I have a date column in my data frame which contains the date, month and year and assume I want to extract only the year from the column.

sqlDF = spark.sql("SELECT EXTRACT(year from `_c0`) FROM res ")

Here I'm creating a temporary view and store the year values using this single line and the output will be,

|year(CAST(_c0 AS DATE))|
|                   1872|
|                   1873|
|                   1874|
|                   1875|
|                   1876|
|                   1876|
|                   1877|
|                   1877|
|                   1878|
|                   1878|
|                   1879|
|                   1879|
|                   1879|

How to have a transparent ImageButton: Android

Remove this line :


And in your activity class set

ImageButton btn = (ImageButton)findViewById(;

You can set alpha level 0 to 255

o means transparent and 255 means opaque.

How do you style a TextInput in react native for password input

May 2018 react-native version 0.55.2

secureTextEntry={true} works

password={true} does not work

Getting full-size profile picture

Profile pictures are scaled down to 125x125 on the facebook sever when they're uploaded, so as far as I know you can't get pictures bigger than that. How big is the picture you're getting?

How to retrieve element value of XML using Java?

Since you are using this for configuration, your best bet is apache commons-configuration. For simple files it's way easier to use than "raw" XML parsers.

See the XML how-to

How to enter in a Docker container already running with a new TTY

nsenter does that. However I also needed to enter a container in a simple way and nsenter didn't suffice for my needs. It was buggy in some occasions (black screen plus -wd flag not working). Furthermore I wanted to login as a specific user and in a specific directory.

I ended up making my own tool to enter containers. You can find it at:

Its usage is as easy as

./docker-enter [-u <user>] [-d <directory>] <container ID>

Remove duplicates from a dataframe in PySpark

if you have a data frame and want to remove all duplicates -- with reference to duplicates in a specific column (called 'colName'):

count before dedupe:


do the de-dupe (convert the column you are de-duping to string type):

from pyspark.sql.functions import col
df = df.withColumn('colName',col('colName').cast('string'))


can use a sorted groupby to check to see that duplicates have been removed:


What is the correct syntax of ng-include?

try this

<div ng-app="myApp" ng-controller="customersCtrl"> 
  <div ng-include="'myTable.htm'"></div>

var app = angular.module('myApp', []);
app.controller('customersCtrl', function($scope, $http) {
    $http.get("customers.php").then(function (response) {
        $scope.names =;

echo key and value of an array without and with loop

How to echo key and value of an array without and with loop

$keys = array_keys($page);
echo $keys[0].' is at '.$page['Home'];

How to check if a file exists in a folder?

To check file exists or not you can use


libxml/tree.h no such file or directory

Adding libxml2 in Xcode 4.3 / 5 / 6

Adding libxml2 is a big, fat, finicky pain in the ass. If you're going to do it, do it before you get too far in building your project.

You need to add it in two ways:

1. Target settings

Click on your target (not your project) and select Build Phases.

Click on the reveal triangle titled Link Binary With Libraries. Click on the + to add a library.

Scroll to the bottom of the list and select libxml2.dylib. That adds the libxml2 library to your project.

2. Project settings

Now you have to tell your project where to look for it three more times.

Select the Build Settings tab.

Scroll down to the Linking section. Under your projects columns double click on the Other Linker Flags row. Click the + and add -lxml2 to the list.

Still more.

In the same tab, scroll down to the Search Paths section.

Under your projects column in the Framework Search Paths row add /usr/lib/libxml2.dylib.

In the Header Search Paths and the User Header Search Paths row add $(SDKROOT)/usr/include/libxml2.

In those last two cases make sure that path is entered in Debug and Release.

3. Clean

Under the Product Menu select Clean.

Then, if I were you (and lets face it, I probably am) I'd quit Xcode and walk away. When you come back and launch you should be good to go.

Merge (Concat) Multiple JSONObjects in Java

I used string to concatenate new object to an existing object.

private static void concatJSON() throws IOException, InterruptedException {

    JSONParser parser = new JSONParser();
    Object obj = parser.parse(new FileReader(new File(Main.class.getResource("/file/user.json").toURI())));

    JSONObject jsonObj = (JSONObject) obj; //usernameJsonObj

    String [] values = {"0.9" , Date.from(Calendar.getInstance().toInstant()).toLocaleString()},
            innermost = {"Accomplished", "LatestDate"}, 
            inner = {"Lesson1", "Lesson2", "Lesson3", "Lesson4"};
    String in = "Jayvee Villa";

    JSONObject jo1 = new JSONObject();
    for (int i = 0; i < innermost.length; i++)
        jo1.put(innermost[i], values[i]);

    JSONObject jo2 = new JSONObject();
    for (int i = 0; i < inner.length; i++)
        jo2.put(inner[i], jo1);

    JSONObject jo3 = new JSONObject();
    jo3.put(in, jo2);

    String merger = jsonObj.toString().substring(0, jsonObj.toString().length()-1) + "," +jo3.toString().substring(1);

    FileWriter pr = new FileWriter(file);

Array initialization syntax when not in a declaration

I can't answer the why part.

But if you want something dynamic then why don't you consider Collection ArrayList.

ArrrayList can be of any Object type.

And if as an compulsion you want it as an array you can use the toArray() method on it.

For example:

            ArrayList<String> al = new ArrayList<String>();
            String[] strArray = (String[]) al.toArray(new String[0]);

I hope this might help you.

Vim: faster way to select blocks of text in visual mode

v 35 j

text added for 30 character minimum

Post request with Wget?

Wget currently only supports x-www-form-urlencoded data. --post-file is not for transmitting files as form attachments, it expects data with the form: key=value&otherkey=example.

--post-data and --post-file work the same way: the only difference is that --post-data allows you to specify the data in the command line, while --post-file allows you to specify the path of the file that contain the data to send.

Here's the documentation:

           Use POST as the method for all HTTP requests and send the specified data
           in the request body.  --post-data sends string as data, whereas
           --post-file sends the contents of file.  Other than that, they work in
           exactly the same way. In particular, they both expect content of the
           form "key1=value1&key2=value2", with percent-encoding for special
           characters; the only difference is that one expects its content as a
           command-line parameter and the other accepts its content from a file. In
           particular, --post-file is not for transmitting files as form
           attachments: those must appear as "key=value" data (with appropriate
           percent-coding) just like everything else. Wget does not currently
           support "multipart/form-data" for transmitting POST data; only
           "application/x-www-form-urlencoded". Only one of --post-data and
           --post-file should be specified.

Regarding your authentication token, it should either be provided in the header, in the path of the url, or in the data itself. This must be indicated somewhere in the documentation of the service you use. In a POST request, as in a GET request, you must specify the data using keys and values. This way the server will be able to receive multiple information with specific names. It's similar with variables.

Hence, you can't just send a magic token to the server, you also need to specify the name of the key. If the key is "token", then it should be token=YOUR_TOKEN.

wget --post-data 'user=foo&password=bar'

Also, you should consider using curl if you can because it is easier to send files using it. There are many examples on the Internet for that.

batch file Copy files with certain extensions from multiple directories into one directory

Brandon, short and sweet. Also flexible.

set dSource=C:\Main directory\sub directory
set dTarget=D:\Documents
set fType=*.doc
for /f "delims=" %%f in ('dir /a-d /b /s "%dSource%\%fType%"') do (
    copy /V "%%f" "%dTarget%\" 2>nul

Hope this helps.

I would add some checks after the copy (using '||') but i'm not sure how "copy /v" reacts when it encounters an error.

you may want to try this:

copy /V "%%f" "%dTarget%\" 2>nul|| echo En error occured copying "%%F".&& exit /b 1

As the copy line. let me know if you get something out of it (in no position to test a copy failure atm..)

How to save CSS changes of Styles panel of Chrome Developer Tools?

As long as you haven't been sticking the CSS in

  1. Go to a style you have added. There should be a link saying inspector-stylesheet:

enter image description here

  1. Click on that, and it will open up all the CSS that you have added in the sources panel

  2. Copy and paste it - yay!

If you have been using

You can just right-click on your HTML element, click Edit as HTML and then copy and paste the HTML with the inline styles.

How to randomly select an item from a list?

The following code demonstrates if you need to produce the same items. You can also specify how many samples you want to extract.
The sample method returns a new list containing elements from the population while leaving the original population unchanged. The resulting list is in selection order so that all sub-slices will also be valid random samples.

import random as random
random.seed(0)  # don't use seed function, if you want different results in each run
print(random.sample(foo,3))  # 3 is the number of sample you want to retrieve

Output:['d', 'e', 'a']

What are abstract classes and abstract methods?

An abstract class is a class that can't be instantiated. It's only purpose is for other classes to extend.

Abstract methods are methods in the abstract class (have to be declared abstract) which means the extending concrete class must override them as they have no body.

The main purpose of an abstract class is if you have common code to use in sub classes but the abstract class should not have instances of its own.

You can read more about it here: Abstract Methods and Classes

What is the size of column of int(11) in mysql in bytes?

I think max value of int(11) is 4294967295

Can I escape html special chars in javascript?

It was interesting to find a better solution:

var escapeHTML = function(unsafe) {
  return unsafe.replace(/[&<"']/g, function(m) {
    switch (m) {
      case '&':
        return '&amp;';
      case '<':
        return '&lt;';
      case '"':
        return '&quot;';
        return '&#039;';

I do not parse > because it does not break XML/HTML code in the result.

Here are the benchmarks: Also, I created a universal escape function:

Adding a 'share by email' link to website

Something like this might be the easiest way.

<a href="mailto:?subject=I wanted you to see this site&amp;body=Check out this site"
   title="Share by Email">
  <img src="">

You could find another email image and add that if you wanted.

What does "\r" do in the following script?

'\r' means 'carriage return' and it is similar to '\n' which means 'line break' or more commonly 'new line'

in the old days of typewriters, you would have to move the carriage that writes back to the start of the line, and move the line down in order to write onto the next line.

in the modern computer era we still have this functionality for multiple reasons. but mostly we use only '\n' and automatically assume that we want to start writing from the start of the line, since it would not make much sense otherwise.

however, there are some times when we want to use JUST the '\r' and that would be if i want to write something to an output, and the instead of going down to a new line and writing something else, i want to write something over what i already wrote, this is how many programs in linux or in windows command line are able to have 'progress' information that changes on the same line.

nowadays most systems use only the '\n' to denote a newline. but some systems use both together.

you can see examples of this given in some of the other answers, but the most common are:

  • windows ends lines with '\r\n'
  • mac ends lines with '\r'
  • unix/linux use '\n'

and some other programs also have specific uses for them.

for more information about the history of these characters

Accessing the index in 'for' loops?

Using an additional state variable, such as an index variable (which you would normally use in languages such as C or PHP), is considered non-pythonic.

The better option is to use the built-in function enumerate(), available in both Python 2 and 3:

for idx, val in enumerate(ints):
    print(idx, val)

Check out PEP 279 for more.

How to pass variable as a parameter in Execute SQL Task SSIS?

In your Execute SQL Task, make sure SQLSourceType is set to Direct Input, then your SQL Statement is the name of the stored proc, with questionmarks for each paramter of the proc, like so:

enter image description here

Click the parameter mapping in the left column and add each paramter from your stored proc and map it to your SSIS variable:

enter image description here

Now when this task runs it will pass the SSIS variables to the stored proc.

How to split page into 4 equal parts?

I did not want to add style to <body> tag and <html> tag.

    width: 100%;
    height: 100vh;
    margin: 0;
    padding: 0;

    width: 100%;
    height: 50vh;

    display: inline;
    float: left;
    width: 50%;
    height: 100%;

    top: 0;
    left: 50vh;
    background-color: red;

    top: 0;
    left: 0;
    background-color: yellow;

    top: 50vw;
    left: 0;
    background-color: blue;

    top: 50vw;
    left: 50vh;
    background-color: green;
<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <link type="text/css" rel="stylesheet" href="main.css" />

<div class='quodrant'>
    <div class='qtop'>
        <div class='quodrant1'></div>
        <div class='quodrant2'></div>
    <div class='qbottom'>
        <div class='quodrant3'></div>
        <div class='quodrant4'></div>

<script type="text/javascript" src="main.js"></script>

Or making it looks nicer.

    width: 100%;
    height: 100vh;
    margin: 0;
    padding: 0;

    width: 96%;
    height: 46vh;

    display: inline;
    float: left;
    width: 46%;
    height: 96%;
    border-radius: 30px;
    margin: 2%;

    background-color: #948be5;

    background-color: #22e235;

    background-color: #086e75;

    background-color: #7cf5f9;
<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <link type="text/css" rel="stylesheet" href="main.css" />

<div class='quodrant'>
    <div class='qtop'>
        <div class='quodrant1'></div>
        <div class='quodrant2'></div>
    <div class='qbottom'>
        <div class='quodrant3'></div>
        <div class='quodrant4'></div>

<script type="text/javascript" src="main.js"></script>

how to use "tab space" while writing in text file

use \t instead of space.


How to make a parent div auto size to the width of its children divs

Your interior <div> elements should likely both be float:left. Divs size to 100% the size of their container width automatically. Try using display:inline-block instead of width:auto on the container div. Or possibly float:left the container and also apply overflow:auto. Depends on what you're after exactly.

Is it possible to reference one CSS rule within another?

I had this problem yesterday. @Quentin's answer is ok:

No, you cannot reference one rule-set from another.

but I made a javascript function to simulate inheritance in css (like .Net):

    var inherit_array;_x000D_
    var inherit;_x000D_
    inherit_array = [];_x000D_
    Array.from(document.styleSheets).forEach(function (styleSheet_i, index) {_x000D_
        Array.from(styleSheet_i.cssRules).forEach(function (cssRule_i, index) {_x000D_
            if ( != null) {_x000D_
                inherit ="--inherits").trim();_x000D_
            } else {_x000D_
                inherit = "";_x000D_
            if (inherit != "") {_x000D_
                inherit_array.push({ selector: cssRule_i.selectorText, inherit: inherit });_x000D_
    Array.from(document.styleSheets).forEach(function (styleSheet_i, index) {_x000D_
        Array.from(styleSheet_i.cssRules).forEach(function (cssRule_i, index) {_x000D_
            if (cssRule_i.selectorText != null) {_x000D_
                inherit_array.forEach(function (inherit_i, index) {_x000D_
                    if (cssRule_i.selectorText.split(", ").includesMember(inherit_i.inherit.split(", ")) == true) {_x000D_
                        cssRule_i.selectorText = cssRule_i.selectorText + ", " + inherit_i.selector;_x000D_

Array.prototype.includesMember = function (arr2) {_x000D_
    var arr1;_x000D_
    var includes;_x000D_
    arr1 = this;_x000D_
    includes = false;_x000D_
    arr1.forEach(function (arr1_i, index) {_x000D_
        if (arr2.includes(arr1_i) == true) {_x000D_
            includes = true;_x000D_
    return includes;_x000D_

and equivalent css:

.test {_x000D_
    background-color: yellow;_x000D_
.productBox, .imageBox {_x000D_
    --inherits: .test;_x000D_
    display: inline-block;_x000D_

and equivalent HTML :

<div class="imageBox"></div>

I tested it and worked for me, even if rules are in different css files.

Update: I found a bug in hierarchichal inheritance in this solution, and am solving the bug very soon .

Find all elements with a certain attribute value in jquery

You can use partial value of an attribute to detect a DOM element using (^) sign. For example you have divs like this:

<div id="abc_1"></div>
<div id="abc_2"></div>
<div id="xyz_3"></div>
<div id="xyz_4"></div>...

You can use the code:

var abc = $('div[id^=abc]')

This will return a DOM array of divs which have id starting with abc:

<div id="abc_1"></div>
<div id="abc_2"></div>

Here is the demo:

Is it possible to use Java 8 for Android development?

Easy way

You can enable java 1.8 support for android project.

  • Open Project Structure

    • Either by pressing Ctrl + Shift + Alt + S

    • Or File > Project Structure

  • Update the Source Compatibility and Target Compatibility to 1.8 in the Project Structure dialog as shown (click File > Project Structure).


Or you can use gradle

 android {
   compileOptions {
       sourceCompatibility JavaVersion.VERSION_1_8
       targetCompatibility JavaVersion.VERSION_1_8

Sync project. And that's it!

Note: Java 1.8 support can be enabled for Android Studio 3.0.0 or higher. See Documentation for further reading.

<select> HTML element with height

You can also "center" the text with:

vertical-align: middle;

calling a java servlet from javascript

The code here will use AJAX to print text to an HTML5 document dynamically (Ajax code is similar to book Internet & WWW (Deitel)):

Javascript code:

var asyncRequest;    
function start(){
        asyncRequest = new XMLHttpRequest();
        asyncRequest.addEventListener("readystatechange", stateChange, false);'GET', '/Test', true);    //   /Test is url to Servlet!
    alert("Request failed");

function stateChange(){
if(asyncRequest.readyState == 4 && asyncRequest.status == 200)
    var text = document.getElementById("text");         //  text is an id of a 
    text.innerHTML = asyncRequest.responseText;         //  div in HTML document

window.addEventListener("load", start(), false);

Servlet java code:

public class Test extends HttpServlet{
public void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws IOException{
        resp.getWriter().println("Servlet wrote this! (");

HTML document

 <div id = "text"></div>


I wrote answer above when I was new with web programming. I let it stand, but the javascript part should definitely be in jQuery instead, it is 10 times easier than raw javascript.

How to download videos from youtube on java?

ytd2 is a fully functional YouTube video downloader. Check out its source code if you want to see how it's done.

Alternatively, you can also call an external process like youtube-dl to do the job. This is probably the easiest solution but it isn't in "pure" Java.

Enable/Disable Anchor Tags using AngularJS

Make a toggle function in the respective scope to grey out the link.

First,create the following CSS classes in your .css file.

.disabled {
    pointer-events: none;
    cursor: default;

.enabled {
    pointer-events: visible;
    cursor: auto;

Add a $scope.state and $scope.toggle variable. Edit your controller in the JS file like:

    $scope.changeState = function () {
                $scope.state = $scope.state === 'on' ? 'off' : 'on';
    $scope.toggleEdit = function () {
            if ($scope.state === 'on')
                $scope.toggle = 'enabled';
                $scope.toggle = 'disabled';

Now,in the HTML a tags edit as:

<a href="#" ng-click="create()" class="{{toggle}}">CREATE</a><br/>
<a href="#" ng-click="edit()" class="{{toggle}}">EDIT</a><br/>
<a href="#" ng-click="delete()" class="{{toggle}}">DELETE</a>

To avoid the problem of the link disabling itself, change the DOM CSS class at the end of the function.

document.getElementById("create").className = "enabled";

AngularJS - How can I do a redirect with a full page load?

After searching and giving hit and trial session I am able to solove it by first specifying url like

$window.location.href = '/#/home/stats';

then reload


How can I undo a mysql statement that I just executed?

Basically: If you're doing a transaction just do a rollback. Otherwise, you can't "undo" a MySQL query.

what does "dead beef" mean?

It's a magic number used in various places because it also happens to be readable in English, making it stand out. There's a partial list on Wikipedia.

Query to check index on a table

If you just need the indexed columns EXEC sp_helpindex 'TABLE_NAME'

Marker in leaflet, click event

Additional relevant info: A common need is to pass the ID of the object represented by the marker to some ajax call for the purpose of fetching more info from the server.

It seems that when we do:

marker.on('click', function(e) {...

The e points to a MouseEvent, which does not let us get to the marker object. But there is a built-in this object which strangely, requires us to use this.options to get to the options object which let us pass anything we need. In the above case, we can pass some ID in an option, let's say objid then within the function above, we can get the value by invoking: this.options.objid

How to get the response of XMLHttpRequest?

I'd suggest looking into fetch. It is the ES5 equivalent and uses Promises. It is much more readable and easily customizable.

const url = "";
        response => response.text() // .json(), etc.
        // same as function(response) {return response.text();}
        html => console.log(html)

In Node.js, you'll need to import fetch using:

const fetch = require("node-fetch");

If you want to use it synchronously (doesn't work in top scope):

const json = await fetch(url)
  .then(response => response.json())
  .catch((e) => {});

More Info:

Mozilla Documentation

Can I Use (95% Feb 2020)

Matt Walsh Tutorial

GitHub: How to make a fork of public repository private?

There is one more option now ( January-2015 )

  1. Create a new private repo
  2. On the empty repo screen there is an "import" option/button enter image description here
  3. click it and put the existing github repo url There is no github option mention but it works with github repos too. enter image description here
  4. DONE

How to use a ViewBag to create a dropdownlist?


In the controller:

ViewBag.Accounts= new SelectList(db.Accounts, "AccountId", "AccountName");

In the View:

@Html.DropDownList("AccountId", (IEnumerable<SelectListItem>)ViewBag.Accounts, null, new { @class ="form-control" })

or you can replace the "null" with whatever you want display as default selector, i.e. "Select Account".

jQuery slide left and show

You can add new function to your jQuery library by adding these line on your own script file and you can easily use fadeSlideRight() and fadeSlideLeft().

Note: you can change width of animation as you like instance of 750px.

$.fn.fadeSlideRight = function(speed,fn) {
    return $(this).animate({
        'opacity' : 1,
        'width' : '750px'
    },speed || 400, function() {
        $.isFunction(fn) &&;

$.fn.fadeSlideLeft = function(speed,fn) {
    return $(this).animate({
        'opacity' : 0,
        'width' : '0px'
    },speed || 400,function() {
        $.isFunction(fn) &&;

Bootstrap Alert Auto Close

Tiggers automatically and manually when needed

$(function () {

function TriggerAlertClose() {
    window.setTimeout(function () {
        $(".alert").fadeTo(1000, 0).slideUp(1000, function () {
    }, 5000);

Not equal to != and !== in PHP

$a !== $b TRUE if $a is not equal to $b, or they are not of the same type

Please Refer to

How to read appSettings section in the web.config file?

Since you're accessing a web.config you should probably use

using System.Web.Configuration;


How do I run a batch script from within a batch script?

If you wish to open the batch file in another window, use start. This way, you can basically run two scripts at the same time. In other words, you don't have to wait for the script you just called to finish. All examples below work:

start batch.bat
start call batch.bat
start cmd /c batch.bat

If you want to wait for the script to finish, try start /w call batch.bat, but the batch.bat has to end with exit.

What is Bit Masking?

A mask defines which bits you want to keep, and which bits you want to clear.

Masking is the act of applying a mask to a value. This is accomplished by doing:

  • Bitwise ANDing in order to extract a subset of the bits in the value
  • Bitwise ORing in order to set a subset of the bits in the value
  • Bitwise XORing in order to toggle a subset of the bits in the value

Below is an example of extracting a subset of the bits in the value:

Mask:   00001111b
Value:  01010101b

Applying the mask to the value means that we want to clear the first (higher) 4 bits, and keep the last (lower) 4 bits. Thus we have extracted the lower 4 bits. The result is:

Mask:   00001111b
Value:  01010101b
Result: 00000101b

Masking is implemented using AND, so in C we get:

uint8_t stuff(...) {
  uint8_t mask = 0x0f;   // 00001111b
  uint8_t value = 0x55;  // 01010101b
  return mask & value;

Here is a fairly common use-case: Extracting individual bytes from a larger word. We define the high-order bits in the word as the first byte. We use two operators for this, &, and >> (shift right). This is how we can extract the four bytes from a 32-bit integer:

void more_stuff(uint32_t value) {             // Example value: 0x01020304
    uint32_t byte1 = (value >> 24);           // 0x01020304 >> 24 is 0x01 so
                                              // no masking is necessary
    uint32_t byte2 = (value >> 16) & 0xff;    // 0x01020304 >> 16 is 0x0102 so
                                              // we must mask to get 0x02
    uint32_t byte3 = (value >> 8)  & 0xff;    // 0x01020304 >> 8 is 0x010203 so
                                              // we must mask to get 0x03
    uint32_t byte4 = value & 0xff;            // here we only mask, no shifting
                                              // is necessary

Notice that you could switch the order of the operators above, you could first do the mask, then the shift. The results are the same, but now you would have to use a different mask:

uint32_t byte3 = (value & 0xff00) >> 8;

In c++ what does a tilde "~" before a function name signify?

As others have noted, in the instance you are asking about it is the destructor for class Stack.

But taking your question exactly as it appears in the title:

In c++ what does a tilde “~” before a function name signify?

there is another situation. In any context except immediately before the name of a class (which is the destructor context), ~ is the one's complement (or bitwise not) operator. To be sure it does not come up very often, but you can imagine a case like

if (~getMask()) { ...

which looks similar, but has a very different meaning.

How do you import an Eclipse project into Android Studio now?

Simple steps: 1.Go to Android Studio. 2.Close all open projects if any. 3.There will be an option which says import non Android Studio Projects(Eclipse ect). 4.Click on it and choose ur project Thats't it enjoy!!!

How can I make my own event in C#?

Here's an example of creating and using an event with C#

using System;

namespace Event_Example
    //First we have to define a delegate that acts as a signature for the
    //function that is ultimately called when the event is triggered.
    //You will notice that the second parameter is of MyEventArgs type.
    //This object will contain information about the triggered event.
    public delegate void MyEventHandler(object source, MyEventArgs e);

    //This is a class which describes the event to the class that recieves it.
    //An EventArgs class must always derive from System.EventArgs.
    public class MyEventArgs : EventArgs
        private string EventInfo;
        public MyEventArgs(string Text)
            EventInfo = Text;
        public string GetInfo()
            return EventInfo;

    //This next class is the one which contains an event and triggers it
    //once an action is performed. For example, lets trigger this event
    //once a variable is incremented over a particular value. Notice the
    //event uses the MyEventHandler delegate to create a signature
    //for the called function.
    public class MyClass
        public event MyEventHandler OnMaximum;
        private int i;
        private int Maximum = 10;
        public int MyValue
                return i;
                if(value <= Maximum)
                    i = value;
                    //To make sure we only trigger the event if a handler is present
                    //we check the event to make sure it's not null.
                    if(OnMaximum != null)
                        OnMaximum(this, new MyEventArgs("You've entered " +
                            value.ToString() +
                            ", but the maximum is " +

    class Program
        //This is the actual method that will be assigned to the event handler
        //within the above class. This is where we perform an action once the
        //event has been triggered.
        static void MaximumReached(object source, MyEventArgs e)

        static void Main(string[] args)
            //Now lets test the event contained in the above class.
            MyClass MyObject = new MyClass();
            MyObject.OnMaximum += new MyEventHandler(MaximumReached);

            for(int x = 0; x <= 15; x++)
                MyObject.MyValue = x;


Perform curl request in javascript?

Yes, use getJSONP. It's the only way to make cross domain/server async calls. (*Or it will be in the near future). Something like

$.getJSON('your-api-url/validate.php?'+$(this).serialize+'callback=?', function(data){

The callback parameter will be filled in automatically by the browser, so don't worry.

On the server side ('validate.php') you would have something like this

//if condition is met
echo $_GET['callback'] . '(' . "{'message' : 'success', 'userID':'69', 'serial' : 'XYZ99UAUGDVD&orwhatever'}". ')';
else echo json_encode(array('error'=>'failed'));

How to convert milliseconds to seconds with precision

I had this problem too, somehow my code did not present the exact values but rounded the number in seconds to 0.0 (if milliseconds was under 1 second). What helped me out is adding the decimal to the division value.

double time_seconds = time_milliseconds / 1000.0;   // add the decimal
System.out.println(time_milliseconds);              // Now this should give you the right value.

Wrap text in <td> tag

To Wrap TD text

First set table style

    table-layout: fixed;

then set TD Style


How to convert char* to wchar_t*?

const char* text_char = "example of mbstowcs";
size_t length = strlen(text_char );

Example of usage "mbstowcs"

std::wstring text_wchar(length, L'#');

//#pragma warning (disable : 4996)
// Or add to the preprocessor: _CRT_SECURE_NO_WARNINGS
mbstowcs(&text_wchar[0], text_char , length);

Example of usage "mbstowcs_s"

Microsoft suggest to use "mbstowcs_s" instead of "mbstowcs".


Mbstowcs example

mbstowcs_s, _mbstowcs_s_l

wchar_t text_wchar[30];

mbstowcs_s(&length, text_wchar, text_char, length);

How to download Visual Studio 2017 Community Edition for offline installation?

All I wanted were 1) English only and 2) just enough to build a legacy desktop project written in C. No Azure, no mobile development, no .NET, and no other components that I don't know what to do with.

[Note: Options are in multiple lines for readability, but they should be in 1 line]
    --lang en-US
    --layout ".\Visual Studio Cummunity 2017"
    --add Microsoft.VisualStudio.Workload.NativeDesktop 

I chose "NativeDesktop" from "workload and component ID" site (

The result was about 1.6GB downloaded files and 5GB when installed. I'm sure I could have removed a few unnecessary components to save space, but the list was rather long, so I stopped there.

"--includeRecommended" was the key ingredient for me, which included Windows SDK along with other essential things for building the legacy project.

How do you fix the "element not interactable" exception?

It will be better to use xpath

from selenium import webdriver
button = driver.find_element_by_xpath('xpath')

How to redirect DNS to different ports

Possible solutions:

  1. Use nginx on the server as a proxy that will listen to port A and multiplex to port B or C.

  2. If you use AWS you can use the load balancer to redirect the request to specific port based on the host.

Using msbuild to execute a File System Publish Profile

FYI: Same problem with running on a build server (Jenkins with msbuild 15 installed, driven from VS 2017 on a .NET Core 2.1 web project).

In my case it was the use of the "publish" target with msbuild that ignored the profile.

So my msbuild command started with:

msbuild /t:restore;build;publish

This correctly triggerred the publish process, but no combination or variation of "/p:PublishProfile=FolderProfile" ever worked to select the profile I wanted to use ("FolderProfile").

When I stopped using the publish target:

msbuild /t:restore;build /p:DeployOnBuild=true /p:PublishProfile=FolderProfile

I (foolishly) thought that it would make no difference, but as soon as I used the DeployOnBuild switch it correctly picked up the profile.

How to filter specific apps for ACTION_SEND intent (and set a different text for each app)

This solution shows a list of applications in a ListView dialog that resembles the chooser:


It is up to you to:

  1. obtain the list of relevant application packages
  2. given a package name, invoke the relevant intent

The adapter class:

import java.util.List;

import android.content.Context;
import android.util.TypedValue;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

public class ChooserArrayAdapter extends ArrayAdapter<String> {
    PackageManager mPm;
    int mTextViewResourceId;
    List<String> mPackages;

    public ChooserArrayAdapter(Context context, int resource, int textViewResourceId, List<String> packages) {
        super(context, resource, textViewResourceId, packages);
        mPm = context.getPackageManager();
        mTextViewResourceId = textViewResourceId;
        mPackages = packages;

    public View getView(int position, View convertView, ViewGroup parent) {
        String pkg = mPackages.get(position);
        View view = super.getView(position, convertView, parent);

        try {
            ApplicationInfo ai = mPm.getApplicationInfo(pkg, 0);

            CharSequence appName = mPm.getApplicationLabel(ai);
            Drawable appIcon = mPm.getApplicationIcon(pkg);

            TextView textView = (TextView) view.findViewById(mTextViewResourceId);
            textView.setCompoundDrawablesWithIntrinsicBounds(appIcon, null, null, null);
            textView.setCompoundDrawablePadding((int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 12, getContext().getResources().getDisplayMetrics()));
        } catch (NameNotFoundException e) {

        return view;


and its usage:

    void doXxxButton() {
        final List<String> packages = ...;
        if (packages.size() > 1) {
            ArrayAdapter<String> adapter = new ChooserArrayAdapter(MyActivity.this, android.R.layout.select_dialog_item,, packages);

            new AlertDialog.Builder(MyActivity.this)
            .setAdapter(adapter, new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int item ) {
        } else if (packages.size() == 1) {

    void invokeApplication(String packageName) {
        // given a package name, create an intent and fill it with data
        startActivityForResult(intent, rq);

Difference between the System.Array.CopyTo() and System.Array.Clone()

One other difference not mentioned so far is that

  • with Clone() the destination array need not exist yet since a new one is created from scratch.
  • with CopyTo() not only does the destination array need to already exist, it needs to be large enough to hold all the elements in the source array from the index you specify as the destination.

django no such table:

You can try this!

python migrate --run-syncdb

I have the same problem with Django 1.9 and 1.10. This code works!

Why is a div with "display: table-cell;" not affected by margin?

You can use inner divs to set the margin.

<div style="display: table-cell;">
   <div style="margin:5px;background-color: red;">1</div>
<div style="display: table-cell; ">
  <div style="margin:5px;background-color: green;">1</div>

JS Fiddle

How to force file download with PHP

you can use download attribute to force download a file:

<a href="" download>click here to download</a>

Facebook Open Graph Error - Inferred Property

Are those tags on ''?

Bear in mind the linter will follow the og:url tag as this tag should point to the canonical URL of the piece of content - so if you have a page, e.g. '' with an og:url tag pointing to '', Facebook will go there and read the tags there also.

Failing that, the most common reason i've seen for seemingly correct tags not being detected by the linter is user-agent detection returning different content to Facebook's crawler than the content you're seeing when you manually check

keycode and charcode

It is a conditional statement.

If browser supprts e.keyCode then take e.keyCode else e.charCode.

It is similar to

var code = event.keyCode || event.charCode

event.keyCode: Returns the Unicode value of a non-character key in a keypress event or any key in any other type of keyboard event.

event.charCode: Returns the Unicode value of a character key pressed during a keypress event.

How do I do a HTTP GET in Java?

If you dont want to use external libraries, you can use URL and URLConnection classes from standard Java API.

An example looks like this:

String urlString = "";
URL url = new URL(urlString);
URLConnection conn = url.openConnection();
InputStream is = conn.getInputStream();
// Do what you want with that stream

Can I check if Bootstrap Modal Shown / Hidden?

For me this works

if($("#myModal").css("display") !='none' && $("#myModal").css("visibility") != 'hidden')

alert("modal shown");

jQuery: more than one handler for same event

Suppose that you have two handlers, f and g, and want to make sure that they are executed in a known and fixed order, then just encapsulate them:


In this way there is (from the perspective of jQuery) only one handler, which calls f and g in the specified order.

Bootstrap 3 .col-xs-offset-* doesn't work?

The problem is that you're putting .name class instead of nameclass

Do something if screen width is less than 960 px







Sniff HTTP packets for GET and POST requests from an application

You will have to use some sort of network sniffer if you want to get at this sort of data and you're likely to run into the same problem (pulling out the relevant data from the overall network traffic) with those that you do now with Wireshark.

Apache default VirtualHost

I will say what worked for me, the others answers above didn't help to my case at all. I hope it can help someone.

Actually, I'm using Virtual host configuration (sites-available / sites-enabled) on EC2 Linux AMI with Apache/2.4.39 (Amazon). So, I have 1 ec2 instance to serve many sites (domains).

Considering that you already have Virtual Host installed and working. In my folder /etc/httpd/sites-available, I have some files with domain names (suffix .conf), for example: Create a new file like that.

sudo nano /etc/httpd/sites-available/

<VirtualHost *:80>
    DocumentRoot /var/www/html/domain

For each file.conf in sites-available, I create a symbolic link:

sudo ln -s /etc/httpd/sites-available/ /etc/httpd/sites-enabled/

This is the default configuration, so, if access directly by IP of Server, you will be redirect to DocumentRoot of the first file (.conf) in sites-available folder, sorted by filename.

To have a default DocumentRoot folder when access by IP, you have to create a file named 0a.conf, then apache will serve this site because this new file will be the first in sites-available folder.

You must create a symbolic link:

sudo ln -s /etc/httpd/sites-available/0a.conf /etc/httpd/sites-enabled/0a.conf

To check serving order, use it:

sudo apachectl -S

Now, restart apache, and check out it.

Be happy =)

Disable browser's back button

Try this code. You just need to implement this code in master page and it will work for you on all the pages

<script type="text/javascript">
    window.onload = function () {
    function noBack() {
<body  onpageshow="if (event.persisted) noBack();">

MVC - Set selected value of SelectList

Doug answered my question... But I'll explain what my problem was exactly, and how Doug helped me solve my problem which you could be encountering.

I call jquery $.post and am replacing my div with my partial view, like so.

function AddNewAddress (paramvalue) {
    $.post(url, { param: paramvalue}, function(d) {

When doing so, for some reason when stepping into my model my selected value affiliated property was never set, only until I stepped into the view it came into scope.

So, What I had before

@Html.DropDownListUnobtrusiveFor(model => model.CustomerAddresses[i].YearsAtAddress, Model.CustomerAddresses[i].YearsAtAddressSelectList, new {onchange = "return Address.AddNewAddress(this,'" + @Url.Action("AddNewAddress", "Address") + "'," + i + ")"})

however even though Model.CustomerAddresses[i].YearsAtAddressSelectList, was set... it didn't set the selected value.

So after....

 @Html.DropDownListUnobtrusiveFor(model => model.CustomerAddresses[i].YearsAtAddress, new SelectList(Model.CustomerAddresses[i].YearsAtAddressSelectList, "Value", "Text", Model.CustomerAddresses[i].YearsAtAddress), new { onchange = "return Address.AddNewAddress(this,'" + @Url.Action("AddNewAddress", "Address") + "'," + i + ")" })

and it worked!

I decided not to use DropDownListFor as it has problem when using unobtrusive validation, which is why i reference the following if your curious in a class classed


[SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")]

public static MvcHtmlString DropDownListUnobtrusiveFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IEnumerable<SelectListItem> selectList)
    return DropDownListUnobtrusiveFor(htmlHelper, expression, selectList, null /* optionLabel */, null /* htmlAttributes */);


[SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")]

public static MvcHtmlString DropDownListUnobtrusiveFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IEnumerable<SelectListItem> selectList, object htmlAttributes)
    return DropDownListUnobtrusiveFor(htmlHelper, expression, selectList, null /* optionLabel */, new RouteValueDictionary(htmlAttributes));


[SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")]

public static MvcHtmlString DropDownListUnobtrusiveFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IEnumerable<SelectListItem> selectList, IDictionary<string, object> htmlAttributes)
    return DropDownListUnobtrusiveFor(htmlHelper, expression, selectList, null /* optionLabel */, htmlAttributes);


[SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")]

public static MvcHtmlString DropDownListUnobtrusiveFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IEnumerable<SelectListItem> selectList, string optionLabel)
    return DropDownListUnobtrusiveFor(htmlHelper, expression, selectList, optionLabel, null /* htmlAttributes */);


[SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")]

public static MvcHtmlString DropDownListUnobtrusiveFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IEnumerable<SelectListItem> selectList, string optionLabel, object htmlAttributes)
    return DropDownListUnobtrusiveFor(htmlHelper, expression, selectList, optionLabel, new RouteValueDictionary(htmlAttributes));


[SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters", Justification = "Users cannot use anonymous methods with the LambdaExpression type")]

[SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")]

public static MvcHtmlString DropDownListUnobtrusiveFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IEnumerable<SelectListItem> selectList, string optionLabel, IDictionary<string, object> htmlAttributes)
    if (expression == null)
        throw new ArgumentNullException("expression");

    ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);

    IDictionary<string, object> validationAttributes = htmlHelper
        .GetUnobtrusiveValidationAttributes(ExpressionHelper.GetExpressionText(expression), metadata);

    if (htmlAttributes == null)
        htmlAttributes = validationAttributes;
        htmlAttributes = htmlAttributes.Concat(validationAttributes).ToDictionary(k => k.Key, v => v.Value);

    return SelectExtensions.DropDownListFor(htmlHelper, expression, selectList, optionLabel, htmlAttributes);


Namenode not getting started

Following STEPS worked for me with hadoop 2.2.0,

STEP 1 stop hadoop

hduser@prayagupd$ /usr/local/hadoop-2.2.0/sbin/

STEP 2 remove tmp folder

hduser@prayagupd$ sudo rm -rf /app/hadoop/tmp/

STEP 3 create /app/hadoop/tmp/

hduser@prayagupd$ sudo mkdir -p /app/hadoop/tmp
hduser@prayagupd$ sudo chown hduser:hadoop /app/hadoop/tmp
hduser@prayagupd$ sudo chmod 750 /app/hadoop/tmp

STEP 4 format namenode

hduser@prayagupd$ hdfs namenode -format

STEP 5 start dfs

hduser@prayagupd$ /usr/local/hadoop-2.2.0/sbin/

STEP 6 check jps

hduser@prayagupd$ $ jps
11342 Jps
10804 DataNode
11110 SecondaryNameNode
10558 NameNode

How to copy folders to docker image from Dockerfile?

FROM openjdk:8-jdk-alpine RUN apk update && apk add wget openssl lsof procps curl RUN apk update RUN mkdir -p /apps/agent RUN mkdir -p /apps/lib ADD ./app/agent /apps/agent ADD ./app/lib /apps/lib ADD ./app/* /apps/app/ RUN ls -lrt /apps/app/ CMD sh /apps/app/

by using DockerFile, I'm copying agent and lib directories to /apps/agent,/apps/lib directories and bunch of files to target.

Error: Module not specified (IntelliJ IDEA)

this is how I fix this issue my project structure module enter image description here plus button enter image description here import module,and find the module's pom enter image description here
5.make sure you select the module you want to import,then next next finish:) enter image description here

Span inside anchor or anchor inside span or doesn't matter?

It is perfectly valid (at least by HTML 4.01 and XHTML 1.0 standards) to nest either a <span> inside an <a> or an <a> inside a <span>.

Just to prove it to yourself, you can always check it out an the W3C MarkUp Validation Service

I tried validating:

         <a href=""><span>Google</span></a>

And also the same as above, but with the <a> inside the <span>


<span><a href="">Google</a></span>

with both HTML 4.01 and XHTML 1.0 doctypes, and both passed validation successfully!

Only thing to be aware of is to ensure that you close the tags in the correct order. So if you start with a <span> then an <a>, make sure you close the <a> tag first before closing the <span> and vice-versa.

How to change Hash values?

Since ruby 2.4.0 you can use native Hash#transform_values method:

hash = {"a" => "b", "c" => "d"}
new_hash = hash.transform_values(&:upcase)
# => {"a" => "B", "c" => "D"}

There is also destructive Hash#transform_values! version.

Converting a string to JSON object

var obj = JSON.parse(string);

Where string is your json string.

How to check for an empty struct?

Here are 3 more suggestions or techniques:

With an Additional Field

You can add an additional field to tell if the struct has been populated or it is empty. I intentionally named it ready and not empty because the zero value of a bool is false, so if you create a new struct like Session{} its ready field will be automatically false and it will tell you the truth: that the struct is not-yet ready (it's empty).

type Session struct {
    ready bool

    playerId string
    beehive string
    timestamp time.Time

When you initialize the struct, you have to set ready to true. Your isEmpty() method isn't needed anymore (although you can create one if you want to) because you can just test the ready field itself.

var s Session

if !s.ready {
    // do stuff (populate s)

Significance of this one additional bool field increases as the struct grows bigger or if it contains fields which are not comparable (e.g. slice, map and function values).

Using the Zero Value of an Existing Field

This is similar to the previous suggestion, but it uses the zero value of an existing field which is considered invalid when the struct is not empty. Usability of this is implementation dependant.

For example if in your example your playerId cannot be the empty string "", you can use it to test if your struct is empty like this:

var s Session

if s.playerId == "" {
    // do stuff (populate s, give proper value to playerId)

In this case it's worth incorporating this check into an isEmpty() method because this check is implementation dependant:

func (s Session) isEmpty() bool {
    return s.playerId == ""

And using it:

if s.isEmpty() {
    // do stuff (populate s, give proper value to playerId)

Use Pointer to your struct

The second suggestion is to use a Pointer to your struct: *Session. Pointers can have nil values, so you can test for it:

var s *Session

if s == nil {
    s = new(Session)
    // do stuff (populate s)

Using Math.round to round to one decimal place?

Helpful method I created a while ago...

private static double round (double value, int precision) {
    int scale = (int) Math.pow(10, precision);
    return (double) Math.round(value * scale) / scale;

How to get list of dates between two dates in mysql select query


select * from 
(select adddate('1970-01-01',t4.i*10000 + t3.i*1000 + t2.i*100 + t1.i*10 + t0.i) selected_date from
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t1,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t2,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t3,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t4) v
where selected_date between '2012-02-10' and '2012-02-15'

-for date ranges up to nearly 300 years in the future.

[Corrected following a suggested edit by UrvishAtSynapse.]

PHP file_get_contents() and setting request headers

Using the php cURL libraries will probably be the right way to go, as this library has more features than the simple file_get_contents(...).

An example:

$ch = curl_init();
$headers = array('HTTP_ACCEPT: Something', 'HTTP_ACCEPT_LANGUAGE: fr, en, da, nl', 'HTTP_CONNECTION: Something');

curl_setopt($ch, CURLOPT_URL, "http://localhost"); # URL to post to
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1 ); # return into a variable
curl_setopt($ch, CURLOPT_HTTPHEADER, $header ); # custom headers, see above
$result = curl_exec( $ch ); # run!

Using sessions & session variables in a PHP Login Script


//extract data from submit post 

    if($user=="user" && $pass=="pass")    
        $_SESSION['user']= $user;       
        //if correct password and name store in session 
    } else {
        echo "Invalid user and password";

Set System.Drawing.Color values

You can make extension to just change one color component

static class ColorExtension
    public static Color ChangeG(Color this color,byte g) 
        return Color.FromArgb(color.A,color.R,g,color.B);

then you can use this:

  yourColor = yourColor.ChangeG(100);

Serialize JavaScript object into JSON string

    function ArrayToObject( arr ) {
    var obj = {};
    for (var i = 0; i < arr.length; ++i){
        var name = arr[i].name;
        var value = arr[i].value;
        obj[name] = arr[i].value;
    return obj;

      var form_data = $('#my_form').serializeArray();
            form_data = ArrayToObject( form_data );
            form_data.action =;
            console.log( form_data );
            $.post("/api/v1/control/", form_data, function( response ){
            }).done(function( response ) {
            .fail(function(  ) { $('#message_box').html('FAIL'); })
            .always(function(  ) { /*$('#message_box').html('SUCCESS');*/ });

How to pre-populate the sms body text via an html link

Well not only do you have to worry about iOS and Android, there's also which android messaging app. Google messaging app for Note 9 and some new galaxys do not open with text, but the samsung app works. The solution seems to be add // after the sms:

so sms://15551235555

<a href="sms:/* phone number here */?body=/* body text here */">Link</a>

should be

<a href="sms://15551235555?body=Hello">Link</a>

Is there a way to get rid of accents and convert a whole string to regular letters?

I think the best solution is converting each char to HEX and replace it with another HEX. It's because there are 2 Unicode typing:

Composite Unicode
Precomposed Unicode

For example "Ô`" written by Composite Unicode is different from "?" written by Precomposed Unicode. You can copy my sample chars and convert them to see the difference.

In Composite Unicode, "Ô`" is combined from 2 char: Ô (U+00d4) and ` (U+0300)
In Precomposed Unicode, "?" is single char (U+1ED2)

I have developed this feature for some banks to convert the info before sending it to core-bank (usually don't support Unicode) and faced this issue when the end-users use multiple Unicode typing to input the data. So I think, converting to HEX and replace it is the most reliable way.

How can I make a list of lists in R?

You can easily make lists of lists

list1 <- list(a = 2, b = 3)
list2 <- list(c = "a", d = "b")
mylist <- list(list1, list2)

mylist is now a list that contains two lists. To access list1 you can use mylist[[1]]. If you want to be able to something like mylist$list1 then you need to do somethingl like

mylist <- list(list1 = list1, list2 = list2)
# Now you can do the following

Edit: To reply to your edit. Just use double bracket indexing

a <- list_all[[1]]
#[1] 1
#[1] 2

nodejs mongodb object id to string

try this: objectId.str;

see doc.

m2eclipse not finding maven dependencies, artifacts not found

I had problems with using m2eclipse (i.e. it did not appear to be installed at all) but I develop a project using IAM - maven plugin for eclipse supported by Eclipse Foundation (or hosted or something like that).

I had sometimes problems as sometimes some strange error appeared for project (it couldn't move something) but simple command (run from eclipse as task or from console) + refresh (F5) solved all problems:

mvn clean

However please note that I created project in eclipse. However I modified pom.xml by hand.

Python Script Uploading files via FTP

I just answered a similar question here IMHO, if your FTP server is able to communicate with Fabric please us Fabric. It is far better than doing raw ftp.

I have an FTP account from so I am not sure if this will work for other FTP accounts.


from fabric.api import run, env, sudo, put

env.user = 'username'
env.hosts = ['ftp_host_name',]     # such as

def copy():
    # assuming i have in the same directory as this script
    put('', '/www/public/')

save the file as and run fab copy locally.

yeukhon@yeukhon-P5E-VM-DO:~$ fab copy2
[] Executing task 'copy2'
[] Login password: 
[] put: -> /www/public/

Disconnecting from done.

Once again, if you don't want to input password all the time, just add

env.password = 'my_password'

JSONDecodeError: Expecting value: line 1 column 1 (char 0)

In my case it is because the server is giving http error occasionally. So basically once in a while my script gets the response like this rahter than the expected response:

<head><title>502 Bad Gateway</title></head>
<body bgcolor="white">
<h1>502 Bad Gateway</h1>
<p>The proxy server received an invalid response from an upstream server.<hr/>Powered by Tengine</body>

Clearly this is not in json format and trying to call .json() will yield JSONDecodeError: Expecting value: line 1 column 1 (char 0)

You can print the exact response that causes this error to better debug. For example if you are using requests and then simply print the .text field (before you call .json()) would do.

How do I get a list of files in a directory in C++?

I've just asked a similar question and here's my solution based on answer received (using boost::filesystem library):

#include <string>
#include <iostream>
#include <boost/filesystem.hpp>
using namespace std;
using namespace boost::filesystem;

int main()
    path p("D:/AnyFolder");
    for (auto i = directory_iterator(p); i != directory_iterator(); i++)
        if (!is_directory(i->path())) //we eliminate directories in a list
            cout << i->path().filename().string() << endl;

Output is like:


C#: Printing all properties of an object

Any other solution/library is in the end going to use reflection to introspect the type...

Syntax error: Illegal return statement in JavaScript

If you want to return some value then wrap your statement in function

function my_function(){ 

 return my_thing; 

Problem is with the statement on the 1st line if you are trying to use PHP

var ask = confirm ('".$message."'); 

IF you are trying to use PHP you should use

 var ask = confirm (<?php echo "'".$message."'" ?>); //now message with be the javascript string!!

Determine project root from a running node.js application

Try path._makeLong('some_filename_on_root.js');


cons path = require('path');

That will return full path from root of your node application (same position of package.json)

Apache Spark: The number of cores vs. the number of executors

As you run your spark app on top of HDFS, according to Sandy Ryza

I’ve noticed that the HDFS client has trouble with tons of concurrent threads. A rough guess is that at most five tasks per executor can achieve full write throughput, so it’s good to keep the number of cores per executor below that number.

So I believe that your first configuration is slower than third one is because of bad HDFS I/O throughput

While loop in batch

set /a countfiles-=%countfiles%

This will set countfiles to 0. I think you want to decrease it by 1, so use this instead:

set /a countfiles-=1

I'm not sure if the for loop will work, better try something like this:

cscript /nologo c:\deletefile.vbs %BACKUPDIR%
set /a countfiles-=1
if %countfiles% GTR 21 goto loop

Why are exclamation marks used in Ruby methods?

In general, methods that end in ! indicate that the method will modify the object it's called on. Ruby calls these as "dangerous methods" because they change state that someone else might have a reference to. Here's a simple example for strings:

foo = "A STRING"  # a string called foo
foo.downcase!     # modifies foo itself
puts foo          # prints modified foo

This will output:

a string

In the standard libraries, there are a lot of places you'll see pairs of similarly named methods, one with the ! and one without. The ones without are called "safe methods", and they return a copy of the original with changes applied to the copy, with the callee unchanged. Here's the same example without the !:

foo = "A STRING"    # a string called foo
bar = foo.downcase  # doesn't modify foo; returns a modified string
puts foo            # prints unchanged foo
puts bar            # prints newly created bar

This outputs:

a string

Keep in mind this is just a convention, but a lot of Ruby classes follow it. It also helps you keep track of what's getting modified in your code.

Drag and drop menuitems

jQuery UI draggable and droppable are the two plugins I would use to achieve this effect. As for the insertion marker, I would investigate modifying the div (or container) element that was about to have content dropped into it. It should be possible to modify the border in some way or add a JavaScript/jQuery listener that listens for the hover (element about to be dropped) event and modifies the border or adds an image of the insertion marker in the right place.

Bootstrap: How do I identify the Bootstrap version?

Method 1 - Very Simple

In Package.json - you'll see bootstrap package installed with version mentioned.

"dependencies": {
    // ...
   "bootstrap": "x.x.x"
    // ...

Method 2

  1. Open node_modules folder and under that
  2. Search and open bootstrap folder
  3. Now you'll be able to see version number in the following files
    • package.json
    • scss/bootstrap.scss or css/bootstrap.css

SqlException from Entity Framework - New transaction is not allowed because there are other threads running in the session

If you get this error due to foreach and you really need to save one entity first inside loop and use generated identity further in loop, as was in my case, the easiest solution is to use another DBContext to insert entity which will return Id and use this Id in outer context

For example

    using (var context = new DatabaseContext())
        using (var context1 = new DatabaseContext())
        //get id of inserted object from context1 and use is.   

Is a LINQ statement faster than a 'foreach' loop?

This is actually quite a complex question. Linq makes certain things very easy to do, that if you implement them yourself, you might stumble over (e.g. linq .Except()). This particularly applies to PLinq, and especially to parallel aggregation as implemented by PLinq.

In general, for identical code, linq will be slower, because of the overhead of delegate invocation.

If, however, you are processing a large array of data, and applying relatively simple calculations to the elements, you will get a huge performance increase if:

  1. You use an array to store the data.
  2. You use a for loop to access each element (as opposed to foreach or linq).

    • Note: When benchmarking, please everyone remember - if you use the same array/list for two consecutive tests, the CPU cache will make the second one faster. *

MySQL error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near

How to find out what this MySQL Error is trying to say:

#1064 - You have an error in your SQL syntax;

This error has no clues in it. You have to double check all of these items to see where your mistake is:

  1. You have omitted, or included an unnecessary symbol: !@#$%^&*()-_=+[]{}\|;:'",<>/?
  2. A misplaced, missing or unnecessary keyword: select, into, or countless others.
  3. You have unicode characters that look like ascii characters in your query but are not recognized.
  4. Misplaced, missing or unnecessary whitespace or newlines between keywords.
  5. Unmatched single quotes, double quotes, parenthesis or braces.

Take away as much as you can from the broken query until it starts working. And then use PostgreSQL next time that has a sane syntax reporting system.

Comparing two hashmaps for equal values and same key sets?

Simply use :


Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings

Changing file extension in Python

os.path.splitext(), os.rename()

for example:

# renamee is the file getting renamed, pre is the part of file name before extension and ext is current extension
pre, ext = os.path.splitext(renamee)
os.rename(renamee, pre + new_extension)

Change priorityQueue to max priorityqueue

You can try pushing elements with reverse sign. Eg: To add a=2 & b=5 and then poll b=5.

PriorityQueue<Integer>  pq = new PriorityQueue<>();

Once you poll the head of the queue, reverse the sign for your usage. This will print 5 (larger element). Can be used in naive implementations. Definitely not a reliable fix. I don't recommend it.

Make the console wait for a user input to close

public static void main(String args[])
    Scanner s = new Scanner(;

    System.out.println("Press enter to continue.....");


This nextline is a pretty good option as it will help us run next line whenever the enter key is pressed.