Programs & Examples On #Formcollection

MVC Form not able to post List of objects

Please read this:
You should set indicies for your html elements "name" attributes like planCompareViewModel[0].PlanId, planCompareViewModel[1].PlanId to make binder able to parse them into IEnumerable.
Instead of @foreach (var planVM in Model) use for loop and render names with indexes.

ASP.Net MVC - Read File from HttpPostedFileBase without save

An alternative is to use StreamReader.

public void FunctionName(HttpPostedFileBase file)
    string result = new StreamReader(file.InputStream).ReadToEnd();

Why ModelState.IsValid always return false in mvc

Please post your Model Class.

To check the errors in your ModelState use the following code:

var errors = ModelState
    .Where(x => x.Value.Errors.Count > 0)
    .Select(x => new { x.Key, x.Value.Errors })

OR: You can also use

var errors = ModelState.Values.SelectMany(v => v.Errors);

Place a break point at the above line and see what are the errors in your ModelState.

How to link HTML5 form action to Controller ActionResult method in ASP.NET MVC 4

you make the use of the HTML Helper and have

        Username: <input type="text" name="username" /> <br />
        Password: <input type="text" name="password" /> <br />
        <input type="submit" value="Login">
        <input type="submit" value="Create Account"/>

or use the Url helper

<form method="post" action="@Url.Action("MyAction", "MyController")" >

Html.BeginForm has several (13) overrides where you can specify more information, for example, a normal use when uploading files is using:

@using(Html.BeginForm("myaction", "mycontroller", FormMethod.Post, new {enctype = "multipart/form-data"}))
    < ... >

If you don't specify any arguments, the Html.BeginForm() will create a POST form that points to your current controller and current action. As an example, let's say you have a controller called Posts and an action called Delete

public ActionResult Delete(int id)
   var model = db.GetPostById(id);
   return View(model);

public ActionResult Delete(int id)
    var model = db.GetPostById(id);
    if(model != null) 

    return RedirectToView("Index");

and your html page would be something like:

<h2>Are you sure you want to delete?</h2>
<p>The Post named <strong>@Model.Title</strong> will be deleted.</p>

    <input type="submit" class="btn btn-danger" value="Delete Post"/>
    @Url.ActionLink("go to list", "Index")

Operation is not valid due to the current state of the object, when I select a dropdown list

This can happen if you call


on an IEnumerable with 2 or more elements.

'Operation is not valid due to the current state of the object' error during postback

For ASP.NET 1.1, this is still due to someone posting more than 1000 form fields, but the setting must be changed in the registry rather than a config file. It should be added as a DWORD named MaxHttpCollectionKeys in the registry under


for 32-bit editions of Windows, and


for 64-bit editions of Windows.

How to convert List<string> to List<int>?

Using Linq ...

List<string> listofIDs = collection.AllKeys.ToList();  
List<int> myStringList = listofIDs.Select(s => int.Parse(s)).ToList();

Validation failed for one or more entities while saving changes to SQL Server Database using Entity Framework

I have faced same issue a couple of days ago while updating the database. In my case, there was few new non nullable columns added for maintenance which was not supplied in the code which is causing the exception. I figure out those fields and supplied values for them and its resolved.

How to handle checkboxes in ASP.NET MVC forms?

From what I can gather, the model doesn't want to guess whether checked = true or false, I got around this by setting a value attribute on the checkbox element with jQuery before submitting the form like this:

 $('input[type="checkbox"]').each(function () {
       $(this).attr('value', $(this).is(':checked'));

This way, you don't need a hidden element just to store the value of the checkbox.

cannot convert data (type interface {}) to type string: need type assertion

According to the Go specification:

For an expression x of interface type and a type T, the primary expression x.(T) asserts that x is not nil and that the value stored in x is of type T.

A "type assertion" allows you to declare an interface value contains a certain concrete type or that its concrete type satisfies another interface.

In your example, you were asserting data (type interface{}) has the concrete type string. If you are wrong, the program will panic at runtime. You do not need to worry about efficiency, checking just requires comparing two pointer values.

If you were unsure if it was a string or not, you could test using the two return syntax.

str, ok := data.(string)

If data is not a string, ok will be false. It is then common to wrap such a statement into an if statement like so:

if str, ok := data.(string); ok {
    /* act on str */
} else {
    /* not string */

Spring Boot Remove Whitelabel Error Page

Here's an alternative method which is very similar to the "old way" of specifying error mappings in web.xml.

Just add this to your Spring Boot configuration:

public class Application implements WebServerFactoryCustomizer<ConfigurableServletWebServerFactory> {

    public void customize(ConfigurableServletWebServerFactory factory) {
        factory.addErrorPages(new ErrorPage(HttpStatus.FORBIDDEN, "/errors/403.html"));
        factory.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/errors/404.html"));
        factory.addErrorPages(new ErrorPage("/errors/500.html"));


Then you can define the error pages in the static content normally.

The customizer can also be a separate @Component, if desired.

PHPDoc type hinting for array of objects?

In NetBeans 7.0 (may be lower too) you could declare the the return type "array with Text objects " just as @return Text and the code hinting will work:

Edit: updated the example with @Bob Fanger suggestion

 * get all Tests
 * @return Test|Array $tests
public function getAllTexts(){
    return array(new Test(), new Test());

and just use it:

$tests =  $controller->getAllTests();
//$tests->         //codehinting works!
//$tests[0]->      //codehinting works!

foreach($tests as $text){
    //$test->      //codehinting works!

It is not perfect but it is better then just to leave it just "mixed", which brings no value.

CONS is you are allowed to tread the array as Text Object which will throw errors.

TypeError: Converting circular structure to JSON in nodejs

Try using this npm package. This helped me decoding the res structure from my node while using passport-azure-ad for integrating login using Microsoft account

You can stringify your circular structure by doing:

const str = CircularJSON.stringify(obj);

then you can convert it onto JSON using JSON parser


Delete specific line number(s) from a text file using sed?

You can delete a particular single line with its line number by

sed -i '33d' file

This will delete the line on 33 line number and save the updated file.

Calculating Covariance with Python and Numpy

When a and b are 1-dimensional sequences, numpy.cov(a,b)[0][1] is equivalent to your cov(a,b).

The 2x2 array returned by np.cov(a,b) has elements equal to

cov(a,a)  cov(a,b)

cov(a,b)  cov(b,b)

(where, again, cov is the function you defined above.)

Enabling/installing GD extension? --without-gd

I've PHP 7.3 and Nginx 1.14 on Ubuntu 18.

# it installs php7.3-gd for the moment
# and restarts PHP 7.3 FastCGI Process Manager: php-fpm7.3.
sudo apt-get install php-gd

# after I've restarted Nginx
sudo /etc/init.d/nginx restart


Expand a div to fill the remaining width

Use calc:

.leftSide {_x000D_
  float: left;_x000D_
  width: 50px;_x000D_
  background-color: green;_x000D_
.rightSide {_x000D_
  float: left;_x000D_
  width: calc(100% - 50px);_x000D_
  background-color: red;_x000D_
<div style="width:200px">_x000D_
  <div class="leftSide">a</div>_x000D_
  <div class="rightSide">b</div>_x000D_

The problem with this is that all widths must be explicitly defined, either as a value(px and em work fine), or as a percent of something explicitly defined itself.

How can I Remove .DS_Store files from a Git repository?

I had to change git-rm to git rm in the above to get it to work:

find . -depth -name '.DS_Store' -exec git rm --cached '{}' \; -print

Pycharm: run only part of my Python file

I found out an easier way.

  • go to File -> Settings -> Keymap
  • Search for Execute Selection in Console and reassign it to a new shortcut, like Crl + Enter.

This is the same shortcut to the same action in Spyder and R-Studio.

Difference between onStart() and onResume()


  1. Called after onCreate(Bundle) or after onRestart() followed by onResume().
  2. you can register a BroadcastReceiver in onStart() to monitor changes that impact your UI, You have to unregister it in onStop()
  3. Derived classes must call through to the super class's implementation of this method. If they do not, an exception will be thrown.


  1. Called after onRestoreInstanceState(Bundle), onRestart(), or onPause()
  2. Begin animations, open exclusive-access devices (such as the camera)

onStart() normally dispatch work to a background thread, whose return values are:

  • START_STICKY to automatically restart if killed, to keep it active.

  • START_REDELIVER_INTENT for auto restart and retry if the service was killed before stopSelf().

onResume() is called by the OS after the device goes to sleep or after an Alert or other partial-screen child activity leaves a portion of the previous window visible so a method is need to re-initialize fields (within a try structure with a catch of exceptions). Such a situation does not cause onStop() to be invoked when the child closes.

onResume() is called without onStart() when the activity resumes from the background

For More details you can visits Android_activity_lifecycle_gotcha And Activity Lifecycle

How to add images in select list?

For a two color image, you can use Fontello, and import any custom glyph you want to use. Just make your image in Illustrator, save to SVG, and drop it onto the Fontello site, then download your custom font ready to import. No JavaScript!

Referencing Row Number in R

These are present by default as rownames when you create a data.frame.

R> df = data.frame('a' = rnorm(10), 'b' = runif(10), 'c' = letters[1:10])
R> df
            a          b c
1   0.3336944 0.39746731 a
2  -0.2334404 0.12242856 b
3   1.4886706 0.07984085 c
4  -1.4853724 0.83163342 d
5   0.7291344 0.10981827 e
6   0.1786753 0.47401690 f
7  -0.9173701 0.73992239 g
8   0.7805941 0.91925413 h
9   0.2469860 0.87979229 i
10  1.2810961 0.53289335 j

and you can access them via the rownames command.

R> rownames(df)
 [1] "1"  "2"  "3"  "4"  "5"  "6"  "7"  "8"  "9"  "10"

if you need them as numbers, simply coerce to numeric by adding as.numeric, as in as.numeric(rownames(df)).

You don't need to add them, as if you know what you are looking for (say item df$c == 'i', you can use the which command:

R> which(df$c =='i')
[1] 9

or if you don't know the column

R> which(df == 'i', arr.ind=T)
     row col
[1,]   9   3

you may access the element using df[9, 'c'], or df$c[9].

If you wanted to add them you could use df$rownumber <- as.numeric(rownames(df)), though this may be less robust than df$rownumber <- 1:nrow(df) as there are cases when you might have assigned to rownames so they will no longer be the default index numbers (the which command will continue to return index numbers even if you do assign to rownames).

Pass Method as Parameter using C#

If you want to pass Method as parameter, use:

using System;

public void Method1()

public void CallingMethod(Action method)
    method();   // This will call the method that has been passed as parameter

public void CalledMethod()
    Console.WriteLine("This method is called by passing parameter");

jQuery - Getting form values for ajax POST

you can use val function to collect data from inputs:


How to find out whether a file is at its `eof`?

You can use tell() method after reaching EOF by calling readlines() method, like this:

eof=fp.tell() # here we store the pointer
              # indicating the end of the file in eof # we bring the cursor at the begining of the file
if eof != fp.tell(): # we check if the cursor
     do_something()  # reaches the end of the file

Combining multiple condition in single case statement in Sql Server

select ROUND(CASE 

WHEN  CONVERT( float, REPLACE( isnull( value1,''),',',''))='' AND CONVERT( float, REPLACE( isnull( value2,''),',',''))='' then  CONVERT( float, REPLACE( isnull( value3,''),',',''))

WHEN  CONVERT( float, REPLACE( isnull( value1,''),',',''))='' AND CONVERT( float, REPLACE( isnull( value2,''),',',''))!='' then  CONVERT( float, REPLACE( isnull( value3,''),',',''))

WHEN  CONVERT( float, REPLACE( isnull( value1,''),',',''))!='' AND CONVERT( float, REPLACE( isnull( value2,''),',',''))='' then  CONVERT( float, REPLACE( isnull( value3,''),',',''))

else CONVERT( float, REPLACE(isnull( value1,''),',','')) end,0)  from Tablename where    ID="123" 

SQL Server convert select a column and convert it to a string

Use LISTAGG function, ex. SELECT LISTAGG(colmn) FROM table_name;

Javascript array search and remove string?


You need to find the location of what you're looking for with .indexOf() then remove it with .splice()

function remove(arr, what) {
    var found = arr.indexOf(what);

    while (found !== -1) {
        arr.splice(found, 1);
        found = arr.indexOf(what);

var array = new Array();
remove(array, 'B');

This will take care of all occurrences.

Set timeout for webClient.DownloadFile()

Assuming you wanted to do this synchronously, using the WebClient.OpenRead(...) method and setting the timeout on the Stream that it returns will give you the desired result:

using (var webClient = new WebClient())
using (var stream = webClient.OpenRead(streamingUri))
     if (stream != null)
          stream.ReadTimeout = Timeout.Infinite;
          using (var reader = new StreamReader(stream, Encoding.UTF8, false))
               string line;
               while ((line = reader.ReadLine()) != null)
                    if (line != String.Empty)
                        Console.WriteLine("Count {0}", count++);

Deriving from WebClient and overriding GetWebRequest(...) to set the timeout @Beniamin suggested, didn't work for me as, but this did.

Is it possible to use vh minus pixels in a CSS calc()?

It does work indeed. Issue was with my less compiler. It was compiled in to:

.container {
  min-height: calc(-51vh);

Fixed with the following code in less file:

.container {
  min-height: calc(~"100vh - 150px");

Thanks to this link: Less Aggressive Compilation with CSS3 calc

Change onClick attribute with javascript

You want to do this - set a function that will be executed to respond to the onclick event:

document.getElementById('buttonLED'+id).onclick = function(){ writeLED(1,1); } ;

The things you are doing don't work because:

  1. The onclick event handler expects to have a function, here you are assigning a string

    document.getElementById('buttonLED'+id).onclick = "writeLED(1,1)";
  2. In this, you are assigning as the onclick event handler the result of executing the writeLED(1,1) function:

    document.getElementById('buttonLED'+id).onclick = writeLED(1,1);

How can I view the allocation unit size of a NTFS partition in Vista?

Open an administrator command prompt, and do this command:

fsutil fsinfo ntfsinfo [your drive]

The Bytes Per Cluster is the equivalent of the allocation unit.

How to set calculation mode to manual when opening an excel file?

The best way around this would be to create an Excel called 'launcher.xlsm' in the same folder as the file you wish to open. In the 'launcher' file put the following code in the 'Workbook' object, but set the constant TargetWBName to be the name of the file you wish to open.

Private Const TargetWBName As String = "myworkbook.xlsx"

'// First, a function to tell us if the workbook is already open...
Function WorkbookOpen(WorkBookName As String) As Boolean
' returns TRUE if the workbook is open
    WorkbookOpen = False
    On Error GoTo WorkBookNotOpen
    If Len(Application.Workbooks(WorkBookName).Name) > 0 Then
        WorkbookOpen = True
        Exit Function
    End If
End Function

Private Sub Workbook_Open()
    'Check if our target workbook is open
    If WorkbookOpen(TargetWBName) = False Then
        'set calculation to manual
        Application.Calculation = xlCalculationManual
        Workbooks.Open ThisWorkbook.Path & "\" & TargetWBName
        Me.Close False
    End If
End Sub

Set the constant 'TargetWBName' to be the name of the workbook that you wish to open. This code will simply switch calculation to manual, then open the file. The launcher file will then automatically close itself. *NOTE: If you do not wish to be prompted to 'Enable Content' every time you open this file (depending on your security settings) you should temporarily remove the 'me.close' to prevent it from closing itself, save the file and set it to be trusted, and then re-enable the 'me.close' call before saving again. Alternatively, you could just set the False to True after Me.Close

"The operation is not valid for the state of the transaction" error and transaction scope

I've encountered this error when my Transaction is nested within another. Is it possible that the stored procedure declares its own transaction or that the calling function declares one?

Why javascript getTime() is not a function?

dat1 and dat2 are Strings in JavaScript. There is no getTime function on the String prototype. I believe you want the Date.parse() function:

You would use it like this:

var date = Date.parse(dat1);

Extract directory path and filename

Using bash "here string":

$ fspec="/exp/home1/abc.txt" 
$ tr  "/"  "\n"  <<< $fspec | tail -1
$ filename=$(tr  "/"  "\n"  <<< $fspec | tail -1)
$ echo $filename

The benefit of the "here string" is that it avoids the need/overhead of running an echo command. In other words, the "here string" is internal to the shell. That is:

$ tr <<< $fspec

as opposed to:

$ echo $fspec | tr

jQuery Ajax error handling, show custom exception messages

If someone is here as in 2016 for the answer, use .fail() for error handling as .error() is deprecated as of jQuery 3.0

$.ajax( "example.php" )
  .done(function() {
    alert( "success" );
  .fail(function(jqXHR, textStatus, errorThrown) {
    //handle error here

I hope it helps

min and max value of data type in C

"But glyph", I hear you asking, "what if I have to determine the maximum value for an opaque type whose maximum might eventually change?" You might continue: "What if it's a typedef in a library I don't control?"

I'm glad you asked, because I just spent a couple of hours cooking up a solution (which I then had to throw away, because it didn't solve my actual problem).

You can use this handy maxof macro to determine the size of any valid integer type.

#define issigned(t) (((t)(-1)) < ((t) 0))

#define umaxof(t) (((0x1ULL << ((sizeof(t) * 8ULL) - 1ULL)) - 1ULL) | \
                    (0xFULL << ((sizeof(t) * 8ULL) - 4ULL)))

#define smaxof(t) (((0x1ULL << ((sizeof(t) * 8ULL) - 1ULL)) - 1ULL) | \
                    (0x7ULL << ((sizeof(t) * 8ULL) - 4ULL)))

#define maxof(t) ((unsigned long long) (issigned(t) ? smaxof(t) : umaxof(t)))

You can use it like so:

int main(int argc, char** argv) {
    printf("schar: %llx uchar: %llx\n", maxof(char), maxof(unsigned char));
    printf("sshort: %llx ushort: %llx\n", maxof(short), maxof(unsigned short));
    printf("sint: %llx uint: %llx\n", maxof(int), maxof(unsigned int));
    printf("slong: %llx ulong: %llx\n", maxof(long), maxof(unsigned long));
    printf("slong long: %llx ulong long: %llx\n",
           maxof(long long), maxof(unsigned long long));
    return 0;

If you'd like, you can toss a '(t)' onto the front of those macros so they give you a result of the type that you're asking about, and you don't have to do casting to avoid warnings.

close vs shutdown socket?

This may be platform specific, I somehow doubt it, but anyway, the best explanation I've seen is here on this msdn page where they explain about shutdown, linger options, socket closure and general connection termination sequences.

In summary, use shutdown to send a shutdown sequence at the TCP level and use close to free up the resources used by the socket data structures in your process. If you haven't issued an explicit shutdown sequence by the time you call close then one is initiated for you.

Writing to a TextBox from another thread?

I would use BeginInvoke instead of Invoke as often as possible, unless you are really required to wait until your control has been updated (which in your example is not the case). BeginInvoke posts the delegate on the WinForms message queue and lets the calling code proceed immediately (in your case the for-loop in the SampleFunction). Invoke not only posts the delegate, but also waits until it has been completed.

So in the method AppendTextBox from your example you would replace Invoke with BeginInvoke like that:

public void AppendTextBox(string value)
    if (InvokeRequired)
        this.BeginInvoke(new Action<string>(AppendTextBox), new object[] {value});
    textBox1.Text += value;

Well and if you want to get even more fancy, there is also the SynchronizationContext class, which lets you basically do the same as Control.Invoke/Control.BeginInvoke, but with the advantage of not needing a WinForms control reference to be known. Here is a small tutorial on SynchronizationContext.

Difference between OpenJDK and Adoptium/AdoptOpenJDK

In short:

  • OpenJDK has multiple meanings and can refer to:
    • free and open source implementation of the Java Platform, Standard Edition (Java SE)
    • open source repository — the Java source code aka OpenJDK project
    • prebuilt OpenJDK binaries maintained by Oracle
    • prebuilt OpenJDK binaries maintained by the OpenJDK community
  • AdoptOpenJDK — prebuilt OpenJDK binaries maintained by community (open source licensed)


Prebuilt OpenJDK (or distribution) — binaries, built from, provided as an archive or installer, offered for various platforms, with a possible support contract.

OpenJDK, the source repository (also called OpenJDK project) - is a Mercurial-based open source repository, hosted at The Java source code. The vast majority of Java features (from the VM and the core libraries to the compiler) are based solely on this source repository. Oracle have an alternate fork of this.

OpenJDK, the distribution (see the list of providers below) - is free as in beer and kind of free as in speech, but, you do not get to call Oracle if you have problems with it. There is no support contract. Furthermore, Oracle will only release updates to any OpenJDK (the distribution) version if that release is the most recent Java release, including LTS (long-term support) releases. The day Oracle releases OpenJDK (the distribution) version 12.0, even if there's a security issue with OpenJDK (the distribution) version 11.0, Oracle will not release an update for 11.0. Maintained solely by Oracle.

Some OpenJDK projects - such as OpenJDK 8 and OpenJDK 11 - are maintained by the OpenJDK community and provide releases for some OpenJDK versions for some platforms. The community members have taken responsibility for releasing fixes for security vulnerabilities in these OpenJDK versions.

AdoptOpenJDK, the distribution is very similar to Oracle's OpenJDK distribution (in that it is free, and it is a build produced by compiling the sources from the OpenJDK source repository). AdoptOpenJDK as an entity will not be backporting patches, i.e. there won't be an AdoptOpenJDK 'fork/version' that is materially different from upstream (except for some build script patches for things like Win32 support). Meaning, if members of the community (Oracle or others, but not AdoptOpenJDK as an entity) backport security fixes to updates of OpenJDK LTS versions, then AdoptOpenJDK will provide builds for those. Maintained by OpenJDK community.

OracleJDK - is yet another distribution. Starting with JDK12 there will be no free version of OracleJDK. Oracle's JDK distribution offering is intended for commercial support. You pay for this, but then you get to rely on Oracle for support. Unlike Oracle's OpenJDK offering, OracleJDK comes with longer support for LTS versions. As a developer you can get a free license for personal/development use only of this particular JDK, but that's mostly a red herring, as 'just the binary' is basically the same as the OpenJDK binary. I guess it means you can download security-patched versions of LTS JDKs from Oracle's websites as long as you promise not to use them commercially.

Note. It may be best to call the OpenJDK builds by Oracle the "Oracle OpenJDK builds".

Donald Smith, Java product manager at Oracle writes:

Ideally, we would simply refer to all Oracle JDK builds as the "Oracle JDK", either under the GPL or the commercial license, depending on your situation. However, for historical reasons, while the small remaining differences exist, we will refer to them separately as Oracle’s OpenJDK builds and the Oracle JDK.

OpenJDK Providers and Comparison

|     Provider      | Free Builds | Free Binary   | Extended | Commercial | Permissive |
|                   | from Source | Distributions | Updates  | Support    | License    |
| AdoptOpenJDK      |    Yes      |    Yes        |   Yes    |   No       |   Yes      |
| Amazon – Corretto |    Yes      |    Yes        |   Yes    |   No       |   Yes      |
| Azul Zulu         |    No       |    Yes        |   Yes    |   Yes      |   Yes      |
| BellSoft Liberica |    No       |    Yes        |   Yes    |   Yes      |   Yes      |
| IBM               |    No       |    No         |   Yes    |   Yes      |   Yes      |
| jClarity          |    No       |    No         |   Yes    |   Yes      |   Yes      |
| OpenJDK           |    Yes      |    Yes        |   Yes    |   No       |   Yes      |
| Oracle JDK        |    No       |    Yes        |   No**   |   Yes      |   No       |
| Oracle OpenJDK    |    Yes      |    Yes        |   No     |   No       |   Yes      |
| ojdkbuild         |    Yes      |    Yes        |   No     |   No       |   Yes      |
| RedHat            |    Yes      |    Yes        |   Yes    |   Yes      |   Yes      |
| SapMachine        |    Yes      |    Yes        |   Yes    |   Yes      |   Yes      |

Free Builds from Source - the distribution source code is publicly available and one can assemble its own build

Free Binary Distributions - the distribution binaries are publicly available for download and usage

Extended Updates - aka LTS (long-term support) - Public Updates beyond the 6-month release lifecycle

Commercial Support - some providers offer extended updates and customer support to paying customers, e.g. Oracle JDK (support details)

Permissive License - the distribution license is non-protective, e.g. Apache 2.0

Which Java Distribution Should I Use?

In the Sun/Oracle days, it was usually Sun/Oracle producing the proprietary downstream JDK distributions based on OpenJDK sources. Recently, Oracle had decided to do their own proprietary builds only with the commercial support attached. They graciously publish the OpenJDK builds as well on their site.

What is happening starting JDK 11 is the shift from single-vendor (Oracle) mindset to the mindset where you select a provider that gives you a distribution for the product, under the conditions you like: platforms they build for, frequency and promptness of releases, how support is structured, etc. If you don't trust any of existing vendors, you can even build OpenJDK yourself.

Each build of OpenJDK is usually made from the same original upstream source repository (OpenJDK “the project”). However each build is quite unique - $free or commercial, branded or unbranded, pure or bundled (e.g., BellSoft Liberica JDK offers bundled JavaFX, which was removed from Oracle builds starting JDK 11).

If no environment (e.g., Linux) and/or license requirement defines specific distribution and if you want the most standard JDK build, then probably the best option is to use OpenJDK by Oracle or AdoptOpenJDK.

Additional information

Time to look beyond Oracle's JDK by Stephen Colebourne

Java Is Still Free by Java Champions community (published on September 17, 2018)

Java is Still Free 2.0.0 by Java Champions community (published on March 3, 2019)

Aleksey Shipilev about JDK updates interview by Opsian (published on June 27, 2019)

Jenkins, specifying JAVA_HOME

In Ubuntu 12.04 I had to install openjdk-7-jdk

then javac was working !

then I could use


as path and jenkins didn't complain anymore.

Getter and Setter?

After reading the other advices, I'm inclined to say that:

As a GENERIC rule, you will not always define setters for ALL properties, specially "internal" ones (semaphores, internal flags...). Read-only properties will not have setters, obviously, so some properties will only have getters; that's where __get() comes to shrink the code:

  • define a __get() (magical global getters) for all those properties which are alike,
  • group them in arrays so:
    • they'll share common characteristics: monetary values will/may come up properly formatted, dates in an specific layout (ISO, US, Intl.), etc.
    • the code itself can verify that only existing & allowed properties are being read using this magical method.
    • whenever you need to create a new similar property, just declare it and add its name to the proper array and it's done. That's way FASTER than defining a new getter, perhaps with some lines of code REPEATED again and again all over the class code.

Yes! we could write a private method to do that, also, but then again, we'll have MANY methods declared (++memory) that end up calling another, always the same, method. Why just not write a SINGLE method to rule them all...? [yep! pun absolutely intended! :)]

Magic setters can also respond ONLY to specific properties, so all date type properties can be screened against invalid values in one method alone. If date type properties were listed in an array, their setters can be defined easily. Just an example, of course. there are way too many situations.

About readability... Well... That's another debate: I don't like to be bound to the uses of an IDE (in fact, I don't use them, they tend to tell me (and force me) how to write... and I have my likes about coding "beauty"). I tend to be consistent about naming, so using ctags and a couple of other aids is sufficient to me... Anyway: once all this magic setters and getters are done, I write the other setters that are too specific or "special" to be generalized in a __set() method. And that covers all I need about getting and setting properties. Of course: there's not always a common ground, or there are such a few properties that is not worth the trouble of coding a magical method, and then there's still the old good traditional setter/getter pair.

Programming languages are just that: human artificial languages. So, each of them has its own intonation or accent, syntax and flavor, so I won't pretend to write a Ruby or Python code using the same "accent" than Java or C#, nor I would write a JavaScript or PHP to resemble Perl or SQL... Use them the way they're meant to be used.

Safely remove migration In Laravel

I accidentally created two times create_users_table. It overrided some classes and turned rollback into ErrorException.

What you need to do is find autoload_classmap.php in vendor/composer folder and look for the specific line of code such as

'CreateUsersTable' => $baseDir . '/app/database/migrations/2013_07_04_014051_create_users_table.php',

and edit path. Then your rollback should be fine.

How to get Android crash logs?

If your app is being downloaded by other people and crashing on remote devices, you may want to look into an Android error reporting library (referenced in this SO post). If it's just on your own local device, you can use LogCat. Even if the device wasn't connected to a host machine when the crash occurred, connecting the device and issuing an adb logcat command will download the entire logcat history (at least to the extent that it is buffered which is usually a loooot of log data, it's just not infinite). Do either of those options answer your question? If not can you attempt to clarify what you're looking for a bit more?

Cannot find module cv2 when using OpenCV

First do run these commands inside Terminal/CMD:

conda update anaconda-navigator  
conda update navigator-updater  

Then the issue for the instruction below will be resolved

For windows if you have anaconda installed, you can simply do

pip install opencv-python


conda install -c opencv

if you are on linux you can do :

pip install opencv-python


conda install opencv 

Link1 Link2

For python3.5+ check these links : Link3 , Link4

if you use anaconda, you may simply use this as well (and hence don't need to add menpo channel):

conda install -c conda-forge opencv

Remove Last Comma from a string

function removeLastComma(str) {
   return str.replace(/,(\s+)?$/, '');   

Regular expressions in C: examples?

It's probably not what you want, but a tool like re2c can compile POSIX(-ish) regular expressions to ANSI C. It's written as a replacement for lex, but this approach allows you to sacrifice flexibility and legibility for the last bit of speed, if you really need it.

CSS: Position text in the middle of the page

Here's a method using display:flex:

.container {_x000D_
  height: 100%;_x000D_
  width: 100%;_x000D_
  display: flex;_x000D_
  position: fixed;_x000D_
  align-items: center;_x000D_
  justify-content: center;_x000D_
<div class="container">_x000D_
  <div>centered text!</div>_x000D_

View on Codepen
Check Browser Compatability

Select a dummy column with a dummy value in SQL?

Try this:

select col1, col2, 'ABC' as col3 from Table1 where col1 = 0;

Write to rails console

I think you should use the Rails debug options:

logger.debug "Person attributes hash: #{@person.attributes.inspect}" "Processing the request..."
logger.fatal "Terminating application, raised unrecoverable error!!!"

How do I put a border around an Android textview?

You can set the border by two methods. One is by drawable and the second is programmatic.

Using Drawable

    <solid android:color="@color/txt_white"/>
    <stroke android:width="1dip" android:color="@color/border_gray"/>
    <corners android:bottomLeftRadius="10dp"
    <padding android:bottom="0dip"


public static GradientDrawable backgroundWithoutBorder(int color) {

    GradientDrawable gdDefault = new GradientDrawable();
    gdDefault.setCornerRadii(new float[] { radius, radius, 0, 0, 0, 0,
                                           radius, radius });
    return gdDefault;

How do I change UIView Size?

This can be achieved in various methods in Swift 3.0 Worked on Latest version MAY- 2019

Directly assign the Height & Width values for a view:

userView.frame.size.height = 0

userView.frame.size.width = 10

Assign the CGRect for the Frame

userView.frame =  CGRect(x:0, y: 0, width:0, height:0)

Method Details:

CGRect(x: point of X, y: point of Y, width: Width of View, height: Height of View)

Using an Extension method for CGRECT

Add following extension code in any swift file,

extension CGRect {

    init(_ x:CGFloat, _ y:CGFloat, _ w:CGFloat, _ h:CGFloat) {

        self.init(x:x, y:y, width:w, height:h)

Use the following code anywhere in your application for the view to set the size parameters

userView.frame =  CGRect(1, 1, 20, 45)

Is it a good idea to index datetime field in mysql?

Here author performed tests showed that integer unix timestamp is better than DateTime. Note, he used MySql. But I feel no matter what DB engine you use comparing integers are slightly faster than comparing dates so int index is better than DateTime index. Take T1 - time of comparing 2 dates, T2 - time of comparing 2 integers. Search on indexed field takes approximately O(log(rows)) time because index based on some balanced tree - it may be different for different DB engines but anyway Log(rows) is common estimation. (if you not use bitmask or r-tree based index). So difference is (T2-T1)*Log(rows) - may play role if you perform your query oftenly.

How open PowerShell as administrator from the run window

Yes, it is possible to run PowerShell through the run window. However, it would be burdensome and you will need to enter in the password for computer. This is similar to how you will need to set up when you run cmd:

runas /user:(ComputerName)\(local admin) powershell.exe

So a basic example would be:

runas /user:MyLaptop\[email protected]  powershell.exe

You can find more information on this subject in Runas.

However, you could also do one more thing :

  • 1: `Windows+R`
  • 2: type: `powershell`
  • 3: type: `Start-Process powershell -verb runAs`

then your system will execute the elevated powershell.

how to install gcc on windows 7 machine?

I use msysgit to install gcc on Windows, it has a nice installer which installs most everything that you might need. Most devs will need more than just the compiler, e.g. the shell, shell tools, make, git, svn, etc. msysgit comes with all of that.

edit: I am now using msys2. Msys2 uses pacman from Arch Linux to install packages, and includes three environments, for building msys2 apps, 32-bit native apps, and 64-bit native apps. (You probably want to build 32-bit native apps.)

You could also go full-monty and install code::blocks or some other gui editor that comes with a compiler. I prefer to use vim and make.

What does 'super' do in Python?

Doesn't all of this assume that the base class is a new-style class?

class A:
    def __init__(self):

class B(A):
    def __init__(self):
        super(B, self).__init__()

Will not work in Python 2. class A must be new-style, i.e: class A(object)

How to set Java SDK path in AndroidStudio?

Generally speaking, it is set in the "Project Structure" dialog.

Go to File > Project Structure > SDK Location. The third field is "JDK Location" where you can set it. This will set it for the current project.

enter image description here

To set the default for new projects, go to File > Other Settings > Default Project Structure > SDK Location and set the "JDK Location".

Older Versions

Go to File > Project Structure > [Platform Settings] > SDKs. You'll need to either update you current SDK configuration to use the new directory, or define a new one and then change your project's settings to use the new one. This will set it for the current project.

To set the default for new projects, go to File > Other Settings > Structure for New Projects > [Platform Settings] > SDKs and set the SDK to use when creating a new project.

How can I stop python.exe from closing immediately after I get an output?

In windows, if Python is installed into the default directory (For me it is):

cd C:\Python27

You then proceed to type

"python.exe "[FULLPATH]\[name].py" 

to run your Python script in Command Prompt

Remove title in Toolbar in appcompat-v7

If you are using Toolbar try below code:


http://localhost:50070 does not work HADOOP

port 50070 changed to 9870 in 3.0.0-alpha1

In fact, lots of others ports changed too. Look:

Namenode ports: 50470 --> 9871, 50070 --> 9870, 8020 --> 9820
Secondary NN ports: 50091 --> 9869, 50090 --> 9868
Datanode ports: 50020 --> 9867, 50010 --> 9866, 50475 --> 9865, 50075 --> 9864


LINQ to Entities how to update a record

//for update

(from x in dataBase.Customers
         where x.Name == "Test"
         select x).ToList().ForEach(xx => xx.Name="New Name");

//for delete


Google Maps V3 - How to calculate the zoom level for a given bounds

For swift version

func getBoundsZoomLevel(bounds: GMSCoordinateBounds, mapDim: CGSize) -> Double {
        var bounds = bounds
        let WORLD_DIM = CGSize(width: 256, height: 256)
        let ZOOM_MAX: Double = 21.0
        func latRad(_ lat: Double) -> Double {
            let sin2 = sin(lat * .pi / 180)
            let radX2 = log10((1 + sin2) / (1 - sin2)) / 2
            return max(min(radX2, .pi), -.pi) / 2
        func zoom(_ mapPx: CGFloat,_ worldPx: CGFloat,_ fraction: Double) -> Double {
            return floor(log10(Double(mapPx) / Double(worldPx) / fraction / log10(2.0)))
        let ne = bounds.northEast
        let sw = bounds.southWest
        let latFraction = (latRad(ne.latitude) - latRad(sw.latitude)) / .pi
        let lngDiff = ne.longitude - sw.longitude
        let lngFraction = lngDiff < 0 ? (lngDiff + 360) : (lngDiff / 360)
        let latZoom = zoom(mapDim.height, WORLD_DIM.height, latFraction);
        let lngZoom = zoom(mapDim.width, WORLD_DIM.width, lngFraction);
        return min(latZoom, lngZoom, ZOOM_MAX)

How to ignore the certificate check when ssl

Expressed explicitly ...

ServicePointManager.ServerCertificateValidationCallback += new System.Net.Security.RemoteCertificateValidationCallback(CertCheck);

private static bool CertCheck(object sender, X509Certificate cert,
X509Chain chain, System.Net.Security.SslPolicyErrors error)
    return true;

what do <form action="#"> and <form method="post" action="#"> do?

action="" will resolve to the page's address. action="#" will resolve to the page's address + #, which will mean an empty fragment identifier.

Doing the latter might prevent a navigation (new load) to the same page and instead try to jump to the element with the id in the fragment identifier. But, since it's empty, it won't jump anywhere.

Usually, authors just put # in href-like attributes when they're not going to use the attribute where they're using scripting instead. In these cases, they could just use action="" (or omit it if validation allows).

Firebase Permission Denied

OK, but you don`t want to open the whole realtime database! You need something like this.

  /* Visit to learn more about security rules. */
  "rules": {
    ".read": "auth.uid !=null",
    ".write": "auth.uid !=null"


  "rules": {
    "users": {
      "$uid": {
        ".write": "$uid === auth.uid"

Ruby 2.0.0p0 IRB warning: "DL is deprecated, please use Fiddle"

You may want to comment out the DL is deprecated, please use Fiddle warning at


since it’s annoying and you are not the irb/pry or some other gems code owner

What exactly is a Context in Java?

In programming terms, it's the larger surrounding part which can have any influence on the behaviour of the current unit of work. E.g. the running environment used, the environment variables, instance variables, local variables, state of other classes, state of the current environment, etcetera.

In some API's you see this name back in an interface/class, e.g. Servlet's ServletContext, JSF's FacesContext, Spring's ApplicationContext, Android's Context, JNDI's InitialContext, etc. They all often follow the Facade Pattern which abstracts the environmental details the enduser doesn't need to know about away in a single interface/class.

PHP MySQL Google Chart JSON - Complete Example

use this, it realy works:

data.addColumn no of your key, you can add more columns or remove

$con=mysql_connect("localhost","USername","Password") or die("Failed to connect with database!!!!");
mysql_select_db("Database Name", $con); 
// The Chart table contain two fields: Weekly_task and percentage
//this example will display a pie chart.if u need other charts such as Bar chart, u will need to change little bit to make work with bar chart and others charts
$sth = mysql_query("SELECT * FROM chart");

while($r = mysql_fetch_assoc($sth)) {


echo "<pre>";

    <!--Load the AJAX API-->
    <script type="text/javascript" src=""></script>
    <script type="text/javascript" src=""></script>
    <script type="text/javascript">

    // Load the Visualization API and the piechart package.
    google.load('visualization', '1', {'packages':['corechart']});

    // Set a callback to run when the Google Visualization API is loaded.

    function drawChart() {

      // Create our data table out of JSON data loaded from server.
     var data = new google.visualization.DataTable();
        data.addColumn("string", "YEAR");
        data.addColumn("number", "NO of record");

        data.addRows(<?php $data ?>);

      var options = {
           title: 'My Weekly Plan',
          is3D: 'true',
          width: 800,
          height: 600
      // Instantiate and draw our chart, passing in some options.
      //do not forget to check ur div ID
      var chart = new google.visualization.PieChart(document.getElementById('chart_div'));
      chart.draw(data, options);

    <!--Div that will hold the pie chart-->
    <div id="chart_div"></div>

How does Python return multiple values from a function?

From Python Cookbook v.30

def myfun():
    return 1, 2, 3

a, b, c = myfun()

Although it looks like myfun() returns multiple values, a tuple is actually being created. It looks a bit peculiar, but it’s actually the comma that forms a tuple, not the parentheses

So yes, what's going on in Python is an internal transformation from multiple comma separated values to a tuple and vice-versa.

Though there's no equivalent in you can easily create this behaviour using array's or some Collections like Lists:

private static int[] sumAndRest(int x, int y) {
    int[] toReturn = new int[2];

    toReturn[0] = x + y;
    toReturn[1] = x - y;

    return toReturn;


Executed in this way:

public static void main(String[] args) {
    int[] results = sumAndRest(10, 5);

    int sum  = results[0];
    int rest = results[1];

    System.out.println("sum = " + sum + "\nrest = " + rest);



sum = 15
rest = 5

Getting a timestamp for today at midnight?

$today_at_midnight = strtotime(date("Ymd"));

should give you what you're after.


What I did was use PHP's date function to get today's date without any references to time, and then pass it to the 'string to time' function which converts a date and time to a epoch timestamp. If it doesn't get a time, it assumes the first second of that day.

References: Date Function:

String To Time:

I want to load another HTML page after a specific amount of time

<meta http-equiv="refresh" content="5;URL='form2.html'">

How can I send a file document to the printer and have it print?

this is a late answer, but you could also use the File.Copy method of the System.IO namespace top send a file to the printer:

System.IO.File.Copy(filename, printerName);

This works fine

How to list only top level directories in Python?

Filter the result using os.path.isdir() (and use os.path.join() to get the real path):

>>> [ name for name in os.listdir(thedir) if os.path.isdir(os.path.join(thedir, name)) ]
['ctypes', 'distutils', 'encodings', 'lib-tk', 'config', 'idlelib', 'xml', 'bsddb', 'hotshot', 'logging', 'doc', 'test', 'compiler', 'curses', 'site-packages', 'email', 'sqlite3', 'lib-dynload', 'wsgiref', 'plat-linux2', 'plat-mac']

Can I get Unix's pthread.h to compile in Windows?

pthread.h isn't on Windows. But Windows has extensive threading functionality, beginning with CreateThread.

My advice is don't get caught looking at WinAPI through the lens of another system's API. These systems are different. It's like insisting on riding the Win32 bike with your comfortable Linux bike seat. Well, the seat might not fit right and in some cases it'll just fall off.

Threads pretty much work the same on different systems, you have ThreadPools and mutexes. Having worked with both pthreads and Windows threads, I can say the Windows threading offers quite a bit more functionality than pthread does.

Learning another API is pretty easy, just think in terms of the concepts (mutex, etc), then look up how to create one of those on MSDN.

How to call a method in MainActivity from another class?

You can make this method static.

public static void startChronometer(){

you can call this function in other class as below:



You can make an object of the main class in second class like,

MainActivity mActivity = new MainActivity();

Sum across multiple columns with dplyr

Using reduce() from purrr is slightly faster than rowSums and definately faster than apply, since you avoid iterating over all the rows and just take advantage of the vectorized operations:

iris %>% mutate(Petal = reduce(select(., starts_with("Petal")), `+`))

See this for timings

Post an object as data using Jquery Ajax

Is not necessary to pass the data as JSON string, you can pass the object directly, without defining contentType or dataType, like this:

    type: "POST",
    url: "TelephoneNumbers.aspx/DeleteNumber",
    data: data0,

    success: function(data)

Convert string to Boolean in javascript

javascript:var string="false";alert(Boolean(string)?'FAIL':'WIN')

will not work because any non-empty string is true

javascript:var string="false";alert(string!=false.toString()?'FAIL':'WIN')

works because compared with string represenation

How to use log4net in core 2.0

I am successfully able to log a file using the following code

public static void Main(string[] args)
    XmlDocument log4netConfig = new XmlDocument();
    var repo = log4net.LogManager.CreateRepository(Assembly.GetEntryAssembly(),
    log4net.Config.XmlConfigurator.Configure(repo, log4netConfig["log4net"]);


log4net.config in website root

<?xml version="1.0" encoding="utf-8" ?>
  <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
    <lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
    <file value="C:\Temp\" />
    <datePattern value="yyyy-MM-dd.'txt'"/>
    <staticLogFileName value="false"/>
    <appendToFile value="true"/>
    <rollingStyle value="Date"/>
    <maxSizeRollBackups value="100"/>
    <maximumFileSize value="15MB"/>
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date [%thread] %-5level App  %newline %message %newline %newline"/>
      <level value="ALL"/>
      <appender-ref ref="RollingLogFileAppender"/>

Nested select statement in SQL Server

You need to alias the subquery.

SELECT name FROM (SELECT name FROM agentinformation) a  

or to be more explicit

SELECT FROM (SELECT name FROM agentinformation) a  

VC++ fatal error LNK1168: cannot open filename.exe for writing

The problem is probably that you forgot to close the program and that you instead have the program running in the background.

Find the console window where the exe file program is running, and close it by clicking the X in the upper right corner. Then try to recompile the program. In my case this solved the problem.

I know this posting is old, but I am answering for the other people like me who find this through the search engines.

Do you need to dispose of objects and set them to null?

I agree with the common answer here that yes you should dispose and no you generally shouldn't set the variable to null... but I wanted to point out that dispose is NOT primarily about memory management. Yes, it can help (and sometimes does) with memory management, but it's primary purpose is to give you deterministic releasing of scarce resources.

For example, if you open a hardware port (serial for example), a TCP/IP socket, a file (in exclusive access mode) or even a database connection you have now prevented any other code from using those items until they are released. Dispose generally releases these items (along with GDI and other "os" handles etc. which there are 1000's of available, but are still limited overall). If you don't call dipose on the owner object and explicitly release these resources, then try to open the same resource again in the future (or another program does) that open attempt will fail because your undisposed, uncollected object still has the item open. Of course, when the GC collects the item (if the Dispose pattern has been implemented correctly) the resource will get released... but you don't know when that will be, so you don't know when it's safe to re-open that resource. This is the primary issue Dispose works around. Of course, releasing these handles often releases memory too, and never releasing them may never release that memory... hence all the talk about memory leaks, or delays in memory clean up.

I have seen real world examples of this causing problems. For instance, I have seen ASP.Net web applications that eventually fail to connect to the database (albeit for short periods of time, or until the web server process is restarted) because the sql server 'connection pool is full'... i.e, so many connections have been created and not explicitly released in so short a period of time that no new connections can be created and many of the connections in the pool, although not active, are still referenced by undiposed and uncollected objects and so can't be reused. Correctly disposing the database connections where necessary ensures this problem doesn't happen (at least not unless you have very high concurrent access).

Using Docker-Compose, how to execute multiple commands

This works for me:

version: '3.1'
    image: postgres
    build: .
      - /bin/bash
      - -c
      - |
        python migrate
        python runserver

      - .:/code
      - "8000:8000"
      - db

docker-compose tries to dereference variables before running the command, so if you want bash to handle variables you'll need to escape the dollar-signs by doubling them...

      - /bin/bash
      - -c
      - |
        var=$$(echo 'foo')
        echo $$var # prints foo

...otherwise you'll get an error:

Invalid interpolation format for "command" option in service "web":

What is the best comment in source code you have ever encountered?

Some years ago I was working in a large code base that had no unit-testing to speak of.

There was a method buried deep within the code that performed some calendar calculations. It was somewhat broken, had to deal with daylight savings in a very clumsy way due to some unfortunate circumstances.

We had to fix it a couple of times, and every time, we would find something broken some months after.

After spending a whole day fixing it and analyzing it, I put the code in source control, along with a comment that said something like this:

// this code was written after a version trying to do {this} failed because of {reason},
// previously we were doing {this} which failed because of {reason}. This is 
// now written {this} way so that {lots of reasons here}. If you want to touch
// this code, please make sure that it produces the right answers when tested with:
// {some sort of unit test}

Ultimately, my team was outsourced. Some days I wonder what happened to this code :)

Working with UTF-8 encoding in Python source

In the source header you can declare:

#!/usr/bin/env python
# -*- coding: utf-8 -*-

It is described in the PEP 0263:

Then you can use UTF-8 in strings:

#!/usr/bin/env python
# -*- coding: utf-8 -*-

u = 'idzie waz waska drózka'
uu = u.decode('utf8')
s = uu.encode('cp1250')

This declaration is not needed in Python 3 as UTF-8 is the default source encoding (see PEP 3120).

In addition, it may be worth verifying that your text editor properly encodes your code in UTF-8. Otherwise, you may have invisible characters that are not interpreted as UTF-8.

Use PPK file in Mac Terminal to connect to remote connection over SSH

There is a way to do this without installing putty on your Mac. You can easily convert your existing PPK file to a PEM file using PuTTYgen on Windows.

Launch PuTTYgen and then load the existing private key file using the Load button. From the "Conversions" menu select "Export OpenSSH key" and save the private key file with the .pem file extension.

Copy the PEM file to your Mac and set it to be read-only by your user:

chmod 400 <private-key-filename>.pem

Then you should be able to use ssh to connect to your remote server

ssh -i <private-key-filename>.pem username@hostname

How to make Git "forget" about a file that was tracked but is now in .gitignore?

I think, that maybe git can't totally forget about file because of its conception (section "Snapshots, Not Differences").

This problem is absent, for example, when using CVS. CVS stores information as a list of file-based changes. Information for CVS is a set of files and the changes made to each file over time.

But in Git every time you commit, or save the state of your project, it basically takes a picture of what all your files look like at that moment and stores a reference to that snapshot. So, if you added file once, it will always be present in that snapshot.

These 2 articles were helpful for me:

git assume-unchanged vs skip-worktree and How to ignore changes in tracked files with Git

Basing on it I do the following, if file is already tracked:

git update-index --skip-worktree <file>

From this moment all local changes in this file will be ignored and will not go to remote. If file is changed on remote, conflict will occure, when git pull. Stash won't work. To resolve it, copy file content to the safe place and follow these steps:

git update-index --no-skip-worktree <file>
git stash
git pull 

File content will be replaced by the remote content. Paste your changes from safe place to file and perform again:

git update-index --skip-worktree <file>

If everyone, who works with project, will perform git update-index --skip-worktree <file>, problems with pull should be absent. This solution is OK for configurations files, when every developer has their own project configuration.

It is not very convenient to do this every time, when file has been changed on remote, but can protect it from overwriting by remote content.

How to retrieve unique count of a field using Kibana + Elastic Search

Using Aggs u can easily do that. Writing down query for now.

GET index/_search
  "aggs": {
    "source": {
      "terms": {
        "field": "field",
        "size": 100000

This would return the different values of field with there doc counts.

Preventing SQL injection in Node.js

The easiest way is to handle all of your database interactions in its own module that you export to your routes. If your route has no context of the database then SQL can't touch it anyway.

Is the ternary operator faster than an "if" condition in Java

Also, the ternary operator enables a form of "optional" parameter. Java does not allow optional parameters in method signatures but the ternary operator enables you to easily inline a default choice when null is supplied for a parameter value.

For example:

public void myMethod(int par1, String optionalPar2) {

    String par2 = ((optionalPar2 == null) ? getDefaultString() : optionalPar2)

In the above example, passing null as the String parameter value gets you a default string value instead of a NullPointerException. It's short and sweet and, I would say, very readable. Moreover, as has been pointed out, at the byte code level there's really no difference between the ternary operator and if-then-else. As in the above example, the decision on which to choose is based wholly on readability.

Moreover, this pattern enables you to make the String parameter truly optional (if it is deemed useful to do so) by overloading the method as follows:

public void myMethod(int par1) {
    return myMethod(par1, null);

How to prevent Browser cache on Angular 2 site?

Found a way to do this, simply add a querystring to load your components, like so:

  selector: 'some-component',
  templateUrl: `./app/component/stuff/component.html?v=${new Date().getTime()}`,
  styleUrls: [`./app/component/stuff/component.css?v=${new Date().getTime()}`]

This should force the client to load the server's copy of the template instead of the browser's. If you would like it to refresh only after a certain period of time you could use this ISOString instead:

new Date().toISOString() //2016-09-24T00:43:21.584Z

And substring some characters so that it will only change after an hour for example:

new Date().toISOString().substr(0,13) //2016-09-24T00

Hope this helps

How do I specify the columns and rows of a multiline Editor-For in ASP.MVC?

One option seems to be using CSS to style the textarea

.multi-line { height:5em; width:5em; }

See this entry on SO or this one.

Amurra's accepted answer seems to imply this class is added automatically when using EditorFor but you'd have to verify this.

EDIT: Confirmed, it does. So yes, if you want to use EditorFor, using this CSS style does what you're looking for.

<textarea class="text-box multi-line" id="StoreSearchCriteria_Location" name="StoreSearchCriteria.Location">

Reset all the items in a form

    function setToggleInputsinPnl(pnlName) {
    var domCount = pnlName.length;
    for (var i = 0; i < domCount; i++) {
        if (pnlName[i].type == 'text') {
            pnlName[i].value = '';
        } else if (pnlName[i].type == 'select-one') {
               pnlName[i].value = '';

How to update /etc/hosts file in Docker image during "docker build"

If this is useful for anyone, the HOSTALIASES env variable worked for me:

echo "fakehost realhost" > /etc/host.aliases
export HOSTALIASES=/etc/host.aliases

how to get 2 digits after decimal point in tsql?

So, something like

SELECT @i / 3

I would however recomend that this be done in the UI/Report layer, as this will cuase loss of precision.

XML Schema minOccurs / maxOccurs default values



<?xml version="1.0" encoding="UTF-8"?> 
<?xml-stylesheet type="text/xsl" href="country.xsl"?>
<country xmlns:xsi="" xsi:noNamespaceSchemaLocation="country.xsd">
    <currency>Australian Dollar</currency>
        <nationalAnthem>Advance Australia Fair</nationalAnthem>
        <nationalDay>Australia Day (26 January)</nationalDay>
        <nationalColour>Green and Gold</nationalColour>
        <nationalFlower>Wattle (Acacia pycnantha)</nationalFlower>
        <newYearDay>1 January</newYearDay>
        <australiaDay>26 January</australiaDay>
        <anzacDay>25 April</anzacDay>
        <christmasDay>25 December</christmasDay>
        <boxingDay>26 December</boxingDay>
        <laborDay>Variable Date</laborDay>
        <easter>Variable Date</easter>
        <queenBirthDay>21 April (Variable Date)</queenBirthDay>
        <stateName><Name>NSW -  New South Wales</Name></stateName>
        <stateName><Name>VIC -  Victoria</Name></stateName>
        <stateName><Name>QLD -  Queensland</Name></stateName>
        <stateName><Name>SA -  South Australia</Name></stateName>
        <stateName><Name>WA -  Western Australia</Name></stateName>
        <stateName><Name>TAS -  Tasmania</Name></stateName>
        <territoryName>ACT -  Australian Capital Territory</territoryName>
        <territoryName>NT -  Northern Territory</territoryName>


<?xml version="1.0" encoding="UTF-8"?> 
<xs:schema xmlns:xs="">
    <xs:element name="country">
                <xs:element name="countryName" type="xs:string"/>
                <xs:element name="capital" type="xs:string"/>
                <xs:element name="nationalLanguage" type="xs:string"/>
                <xs:element name="population" type="xs:double"/>
                <xs:element name="currency" type="xs:string"/>
                <xs:element name="nationalIdentities">
                        <xs:element name="nationalAnthem" type="xs:string"/>
                        <xs:element name="nationalDay" type="xs:string"/>
                        <xs:element name="nationalColour" type="xs:string"/>
                        <xs:element name="nationalGemstone" type="xs:string"/>
                        <xs:element name="nationalFlower" type="xs:string"/>
                <xs:element name="publicHolidays">
                            <xs:element name="newYearDay" maxOccurs="1" type="xs:string"/>
                            <xs:element name="australiaDay" maxOccurs="1" type="xs:string"/>
                            <xs:element name="anzacDay" maxOccurs="1" type="xs:string"/>
                            <xs:element name="christmasDay" maxOccurs="1" type="xs:string"/>
                            <xs:element name="boxingDay" maxOccurs="1" type="xs:string"/>
                            <xs:element name="laborDay" maxOccurs="1" type="xs:string"/>
                            <xs:element name="easter" maxOccurs="1" type="xs:string"/>
                            <xs:element name="queenBirthDay" maxOccurs="1" type="xs:string"/>
                <xs:element name="states">
                            <xs:element name="stateName" minOccurs="1" maxOccurs="unbounded">
                                        <xs:element name="Name" type="xs:string"/>
                <xs:element name="territories">
                            <xs:element name="territoryName" maxOccurs="unbounded"/>


<?xml version="1.0"?> 
<xsl:stylesheet xmlns:xsl="" version="1.0">
    <xsl:output method="html" indent="yes" version="4.0"/>
    <xsl:template match="/">
                <xsl:for-each select="country">         
                    <xsl:value-of select="countryName"/><br/>
                    <xsl:value-of select="capital"/><br/>
                    <xsl:value-of select="nationalLanguage"/><br/>
                    <xsl:value-of select="population"/><br/>
                    <xsl:value-of select="currency"/><br/>              
                    <xsl:for-each select="nationalIdentities">
                        <xsl:value-of select="nationalAnthem"/><br/>
                        <xsl:value-of select="nationalDay"/><br/>
                        <xsl:value-of select="nationalColour"/><br/>
                        <xsl:value-of select="nationalGemstone"/><br/>
                        <xsl:value-of select="nationalFlower"/><br/>
                    <xsl:for-each select="publicHolidays">
                        <xsl:value-of select="newYearDay"/><br/>
                        <xsl:value-of select="australiaDay"/><br/>
                        <xsl:value-of select="anzacDay"/><br/>
                        <xsl:value-of select="christmasDay"/><br/>
                        <xsl:value-of select="boxingDay"/><br/>
                        <xsl:value-of select="laborDay"/><br/>
                        <xsl:value-of select="easter"/><br/>
                        <xsl:value-of select="queenBirthDay"/><br/>
                    <xsl:for-each select="states/stateName">
                        <xsl:value-of select="Name"/><br/>


Australian Dollar
Advance Australia Fair
Australia Day (26 January)
Green and Gold
Wattle (Acacia pycnantha)
1 January
26 January
25 April
25 December
26 December
Variable Date
Variable Date
21 April (Variable Date)
NSW - New South Wales
VIC - Victoria
QLD - Queensland
SA - South Australia
WA - Western Australia
TAS - Tasmania

Display text on MouseOver for image in html

You can use CSS hover
Link to jsfiddle here:


<a><img src=''></a>


div {
    display: none;
    border:1px solid #000;

a:hover + div {
    display: block;

Internet Access in Ubuntu on VirtualBox

I had the same problem.

Solved by sharing internet connection (on the hosting OS).

Network Connection Properties -> advanced -> Allow other users to connect...

Can an AWS Lambda function call another

I'm having the same problem but the Lambda function that I implement will insert an entry in DynamoDB, so my solution uses DynamoDB Triggers.

I make the DB invoke a Lambda function for every insert/update in the table, so this separates the implementation of two Lambda functions.

Documentation is here:

Here is a guided walkthrough:

Java String encoding (UTF-8)

This could be complicated way of doing

String newString = new String(oldString);

This shortens the String is the underlying char[] used is much longer.

However more specifically it will be checking that every character can be UTF-8 encoded.

There are some "characters" you can have in a String which cannot be encoded and these would be turned into ?

Any character between \uD800 and \uDFFF cannot be encoded and will be turned into '?'

String oldString = "\uD800";
String newString = new String(oldString.getBytes("UTF-8"), "UTF-8");



show distinct column values in pyspark dataframe: python

In addition to the dropDuplicates option there is the method named as we know it in pandas drop_duplicates:

drop_duplicates() is an alias for dropDuplicates().


s_df = sqlContext.createDataFrame([("foo", 1),
                                   ("foo", 1),
                                   ("bar", 2),
                                   ("foo", 3)], ('k', 'v'))

|  k|  v|
|foo|  1|
|foo|  1|
|bar|  2|
|foo|  3|

Drop by subset

s_df.drop_duplicates(subset = ['k']).show()

|  k|  v|
|bar|  2|
|foo|  1|

|  k|  v|
|bar|  2|
|foo|  3|
|foo|  1|

Removing unwanted table cell borders with CSS

sometimes even after clearing borders.

the reason is that you have images inside the td, giving the images display:block solves it.

Error in spring application context schema

Referenced file contains errors (

i faced this problem, when i was configuring dispatcher-servlet.xml ,you can remove this:


from your xml and you can also follow the steps go to window -> preferences -> validation -> and unchecked XML validator and XML schema validator.

How to Get a Layout Inflater Given a Context?

You can also use this code to get LayoutInflater:

LayoutInflater li = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE)

The controller for path was not found or does not implement IController

Not sure if this hits the solution from a different angle to the accepted answer, but I found that one of my controllers in the Areas section was sitting in the wrong namespace. Correcting the namespace to:


fixed the issue for me.

I suspect the key factor was to have all the controllers within a given area share the same namespace.

OS X Terminal Colors

If you want to have your ls colorized you have to edit your ~/.bash_profile file and add the following line (if not already written) :

source .bashrc

Then you edit or create ~/.bashrc file and write an alias to the ls command :

alias ls="ls -G"

Now you have to type source .bashrc in a terminal if already launched, or simply open a new terminal.

If you want more options in your ls juste read the manual ( man ls ). Options are not exactly the same as in a GNU/Linux system.

How to get the fields in an Object via reflection?

Here's a quick and dirty method that does what you want in a generic way. You'll need to add exception handling and you'll probably want to cache the BeanInfo types in a weakhashmap.

public Map<String, Object> getNonNullProperties(final Object thingy) {
    final Map<String, Object> nonNullProperties = new TreeMap<String, Object>();
    try {
        final BeanInfo beanInfo = Introspector.getBeanInfo(thingy
        for (final PropertyDescriptor descriptor : beanInfo
                .getPropertyDescriptors()) {
            try {
                final Object propertyValue = descriptor.getReadMethod()
                if (propertyValue != null) {
            } catch (final IllegalArgumentException e) {
                // handle this please
            } catch (final IllegalAccessException e) {
                // and this also
            } catch (final InvocationTargetException e) {
                // and this, too
    } catch (final IntrospectionException e) {
        // do something sensible here
    return nonNullProperties;

See these references:

How to extract epoch from LocalDate and LocalDateTime?

'Millis since unix epoch' represents an instant, so you should use the Instant class:

private long toEpochMilli(LocalDateTime localDateTime)
  return localDateTime.atZone(ZoneId.systemDefault())

What's the fastest way to convert String to Number in JavaScript?

This is probably not that fast, but has the added benefit of making sure your number is at least a certain value (e.g. 0), or at most a certain value:

Math.max(input, 0);

If you need to ensure a minimum value, usually you'd do

var number = Number(input);
if (number < 0) number = 0;

Math.max(..., 0) saves you from writing two statements.

How to check whether a given string is valid JSON in Java

It depends on what you are trying to prove with your validation. Certainly parsing the json as others have suggested is better than using regexes, because the grammar of json is more complicated than can be represented with just regexes.

If the json will only ever be parsed by your java code, then use the same parser to validate it.

But just parsing won't necessarily tell you if it will be accepted in other environments. e.g.

  • many parsers ignore trailing commas in an object or array, but old versions of IE can fail when they hit a trailing comma.
  • Other parsers may accept a trailing comma, but add an undefined/null entry after it.
  • Some parsers may allow unquoted property names.
  • Some parsers may react differently to non-ASCII characters in strings.

If your validation needs to be very thorough, you could:

Compiling problems: cannot find crt1.o

This is a BUG reported in launchpad, but there is a workaround :

Run this to see where these files are located

$ find /usr/ -name crti*

then add this path to LIBRARY_PATH variable

$ export LIBRARY_PATH=/usr/lib/x86_64-linux-gnu:$LIBRARY_PATH

What is the difference between % and %% in a cmd file?

(Explanation in more details can be found in an archived Microsoft KB article.)

Three things to know:

  1. The percent sign is used in batch files to represent command line parameters: %1, %2, ...
  2. Two percent signs with any characters in between them are interpreted as a variable:

    echo %myvar%

  3. Two percent signs without anything in between (in a batch file) are treated like a single percent sign in a command (not a batch file): %%f

Why's that?

For example, if we execute your (simplified) command line

FOR /f %f in ('dir /b .') DO somecommand %f

in a batch file, rule 2 would try to interpret

%f in ('dir /b .') DO somecommand %

as a variable. In order to prevent that, you have to apply rule 3 and escape the % with an second %:

FOR /f %%f in ('dir /b .') DO somecommand %%f

Converting a list to a set changes element order

In case you have a small number of elements in your two initial lists on which you want to do set difference operation, instead of using collections.OrderedDict which complicates the implementation and makes it less readable, you can use:

# initial lists on which you want to do set difference
>>> nums = [1,2,2,3,3,4,4,5]
>>> evens = [2,4,4,6]
>>> evens_set = set(evens)
>>> result = []
>>> for n in nums:
...   if not n in evens_set and not n in result:
...     result.append(n)
>>> result
[1, 3, 5]

Its time complexity is not that good but it is neat and easy to read.

Array vs. Object efficiency in JavaScript

It's not really a performance question at all, since arrays and objects work very differently (or are supposed to, at least). Arrays have a continuous index 0..n, while objects map arbitrary keys to arbitrary values. If you want to supply specific keys, the only choice is an object. If you don't care about the keys, an array it is.

If you try to set arbitrary (numeric) keys on an array, you really have a performance loss, since behaviourally the array will fill in all indexes in-between:

> foo = [];
> foo[100] = 'a';
> foo
  [undefined, undefined, undefined, ..., "a"]

(Note that the array does not actually contain 99 undefined values, but it will behave this way since you're [supposed to be] iterating the array at some point.)

The literals for both options should make it very clear how they can be used:

var arr = ['foo', 'bar', 'baz'];     // no keys, not even the option for it
var obj = { foo : 'bar', baz : 42 }; // associative by its very nature

Converting an integer to a hexadecimal string in Ruby

How about using %/sprintf:

i = 20
"%x" % i  #=> "14"

regular expression for Indian mobile numbers

For Laravel 5.4+

'mobile_number_1' => 'required|numeric|min:0|regex:/^[789]\d{9}$/' should do the trick

Get Specific Columns Using “With()” Function in Laravel Eloquent

If you use PHP 7.4 or later you can also do it using arrow function so it looks cleaner:

Post::with(['user' => fn ($query) => $query->select('id','username')])->get();

Responsive web design is working on desktop but not on mobile device

I have also faced this problem. Finally I got a solution. Use this bellow code. Hope: problem will be solve.

<meta name="viewport" content="initial-scale=1, maximum-scale=1">

Retrieving values from nested JSON Object

You can see that JSONObject extends a HashMap, so you can simply use it as a HashMap:

JSONObject jsonChildObject = (JSONObject)jsonObject.get("LanguageLevels");
for (Map.Entry in jsonChildOBject.entrySet()) {
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());

jQuery Upload Progress and AJAX file upload

Here are some options for using AJAX to upload files:

UPDATE: Here is a JQuery plug-in for Multiple File Uploading.

Best way to remove an event handler in jQuery?

if you set the onclick via html you need to removeAttr ($(this).removeAttr('onclick'))

if you set it via jquery (as the after the first click in my examples above) then you need to unbind($(this).unbind('click'))

CSS performance relative to translateZ(0)

It forces the browser to use hardware acceleration to access the device’s graphical processing unit (GPU) to make pixels fly. Web applications, on the other hand, run in the context of the browser, which lets the software do most (if not all) of the rendering, resulting in less horsepower for transitions. But the Web has been catching up, and most browser vendors now provide graphical hardware acceleration by means of particular CSS rules.

Using -webkit-transform: translate3d(0,0,0); will kick the GPU into action for the CSS transitions, making them smoother (higher FPS).

Note: translate3d(0,0,0) does nothing in terms of what you see. It moves the object by 0px in x,y and z axis. It's only a technique to force the hardware acceleration.

Good read here:

Jquery: Find Text and replace

Change by id or class for each tag

$("#id <tag>:contains('Text want to replaced')").html("Text Want to replaced with");

$(".className <tag>:contains('Text want to replaced')").html("Text Want to replaced with");

NotificationCompat.Builder deprecated in Android O

This constructor was deprecated in API level 26.1.0. use NotificationCompat.Builder(Context, String) instead. All posted Notifications must specify a NotificationChannel Id.

Get pixel color from canvas, on mousemove

I know this is an old question, but here's an alternative. I'd store that image data in an array, then, on mouse move event over the canvas:

var index = (Math.floor(y) * canvasWidth + Math.floor(x)) * 4
var r = data[index]
var g = data[index + 1]
var b = data[index + 2]
var a = data[index + 3]

A lot easier than getting the imageData everytime.

How do I open a URL from C++?

Your question may mean two different things:

1.) Open a web page with a browser.

#include <windows.h>
#include <shellapi.h>
ShellExecute(0, 0, L"", 0, 0 , SW_SHOW );

This should work, it opens the file with the associated program. Should open the browser, which is usually the default web browser.

2.) Get the code of a webpage and you will render it yourself or do some other thing. For this I recommend to read this or/and this.

I hope it's at least a little helpful.

EDIT: Did not notice, what you are asking for UNIX, this only work on Windows.

What's the "average" requests per second for a production web application?

less than 2 seconds per user usually - ie users that see slower responses than this think the system is slow.

Now you tell me how many users you have connected.

Can You Get A Users Local LAN IP Address Via JavaScript?

Now supported in internal-ip!

An RTCPeerConnection can be used. In browsers like Chrome where a getUserMedia permission is required, we can just detect available input devices and request for them.

const internalIp = async () => {
    if (!RTCPeerConnection) {
        throw new Error("Not supported.")

    const peerConnection = new RTCPeerConnection({ iceServers: [] })

    peerConnection.createOffer(peerConnection.setLocalDescription.bind(peerConnection), () => { })

    peerConnection.addEventListener("icecandidateerror", (event) => {
        throw new Error(event.errorText)

    return new Promise(async resolve => {
        peerConnection.addEventListener("icecandidate", async ({candidate}) => {
            if (candidate && candidate.candidate) {
                const result = candidate.candidate.split(" ")[4]
                if (result.endsWith(".local")) {
                    const inputDevices = await navigator.mediaDevices.enumerateDevices()
                    const inputDeviceTypes ={ kind }) => kind)

                    const constraints = {}

                    if (inputDeviceTypes.includes("audioinput")) {
               = true
                    } else if (inputDeviceTypes.includes("videoinput")) {
               = true
                    } else {
                        throw new Error("An audio or video input device is required!")

                    const mediaStream = await navigator.mediaDevices.getUserMedia(constraints)
                    mediaStream.getTracks().forEach(track => track.stop())

How do you configure an OpenFileDialog to select folders?

Exact Audio Copy works this way on Windows XP. The standard file open dialog is shown, but the filename field contains the text "Filename will be ignored".

Just guessing here, but I suspect the string is injected into the combo box edit control every time a significant change is made to the dialog. As long as the field isn't blank, and the dialog flags are set to not check the existence of the file, the dialog can be closed normally.

Edit: this is much easier than I thought. Here's the code in C++/MFC, you can translate it to the environment of your choice.

CFileDialog dlg(true, NULL, "Filename will be ignored", OFN_HIDEREADONLY | OFN_NOVALIDATE | OFN_PATHMUSTEXIST | OFN_READONLY, NULL, this);

Edit 2: This should be the translation to C#, but I'm not fluent in C# so don't shoot me if it doesn't work.

OpenFileDialog openFileDialog1 = new OpenFileDialog();

openFileDialog1.FileName = "Filename will be ignored";
openFileDialog1.CheckPathExists = true;
openFileDialog1.ShowReadOnly = false;
openFileDialog1.ReadOnlyChecked = true;
openFileDialog1.CheckFileExists = false;
openFileDialog1.ValidateNames = false;

if(openFileDialog1.ShowDialog() == DialogResult.OK)
    // openFileDialog1.FileName should contain the folder and a dummy filename

Edit 3: Finally looked at the actual dialog in question, in Visual Studio 2005 (I didn't have access to it earlier). It is not the standard file open dialog! If you inspect the windows in Spy++ and compare them to a standard file open, you'll see that the structure and class names don't match. When you look closely, you can also spot some differences between the contents of the dialogs. My conclusion is that Microsoft completely replaced the standard dialog in Visual Studio to give it this capability. My solution or something similar will be as close as you can get, unless you're willing to code your own from scratch.

How can I use SUM() OVER()

Seems like you expected the query to return running totals, but it must have given you the same values for both partitions of AccountID.

To obtain running totals with SUM() OVER (), you need to add an ORDER BY sub-clause after PARTITION BY …, like this:


But remember, not all database systems support ORDER BY in the OVER clause of a window aggregate function. (For instance, SQL Server didn't support it until the latest version, SQL Server 2012.)

SQL - Rounding off to 2 decimal places

Could you not cast your result as numeric(x,2)? Where x <= 38

    cast(round(630/60.0,2) as numeric(36,2))


10.500000   10.50

SQL UPDATE with sub-query that references the same table in MySQL

Abstract example with clearer table and column names:

UPDATE tableName t1
INNER JOIN tableName t2 ON t2.ref_column = t1.ref_column
SET t1.column_to_update = t2.column_desired_value

As suggested by @Nico

Hope this help someone.

Can not deserialize instance of java.util.ArrayList out of START_OBJECT token

In my case, the error was being shown because when I was reading my JSON file using Jackson library, my JSON file contained only 1 object. Hence it started with "{" and ended with "}". But while reading it and storing it in a variable, I was storing it in an Array object (As in my case, there could be more than 1 object).

Hence, I added "[" in the start and "]" in the end of my JSON file to convert it into an array of object and it worked perfectly fine without any error.

Type or namespace name does not exist

I faced the same issue with an ASP.NET MVC site when I tried to use LINQ to SQL. I fixed the problem by:

Solution Explorer -> References -> Right-click on System.Data.Linq -> Copy Local (True)

What is the instanceof operator in JavaScript?

The other answers here are correct, but they don't get into how instanceof actually works, which may be of interest to some language lawyers out there.

Every object in JavaScript has a prototype, accessible through the __proto__ property. Functions also have a prototype property, which is the initial __proto__ for any objects created by them. When a function is created, it is given a unique object for prototype. The instanceof operator uses this uniqueness to give you an answer. Here's what instanceof might look like if you wrote it as a function.

function instance_of(V, F) {
  var O = F.prototype;
  V = V.__proto__;
  while (true) {
    if (V === null)
      return false;
    if (O === V)
      return true;
    V = V.__proto__;

This is basically paraphrasing ECMA-262 edition 5.1 (also known as ES5), section

Note that you can reassign any object to a function's prototype property, and you can reassign an object's __proto__ property after it is constructed. This will give you some interesting results:

function F() { }
function G() { }
var p = {};
F.prototype = p;
G.prototype = p;
var f = new F();
var g = new G();

f instanceof F;   // returns true
f instanceof G;   // returns true
g instanceof F;   // returns true
g instanceof G;   // returns true

F.prototype = {};
f instanceof F;   // returns false
g.__proto__ = {};
g instanceof G;   // returns false

How to Load RSA Private Key From File

You need to convert your private key to PKCS8 format using following command:

openssl pkcs8 -topk8 -inform PEM -outform DER -in private_key_file  -nocrypt > pkcs8_key

After this your java program can read it.

How do I print out the value of this boolean? (Java)


should work just fine.

Incidentally, in

else if ((year % 4 == 0) && (year % 100 == 0))
    isLeapYear = false;

else if ((year % 4 == 0) && (year % 100 == 0) && (year % 400 == 0))
    isLeapYear = true;

the year % 400 part will never be reached because if (year % 4 == 0) && (year % 100 == 0) && (year % 400 == 0) is true, then (year % 4 == 0) && (year % 100 == 0) must have succeeded.

Maybe swap those two conditions or refactor them:

else if ((year % 4 == 0) && (year % 100 == 0))
    isLeapYear = (year % 400 == 0);

Getting the name / key of a JToken with

JToken is the base class for JObject, JArray, JProperty, JValue, etc. You can use the Children<T>() method to get a filtered list of a JToken's children that are of a certain type, for example JObject. Each JObject has a collection of JProperty objects, which can be accessed via the Properties() method. For each JProperty, you can get its Name. (Of course you can also get the Value if desired, which is another JToken.)

Putting it all together we have:

JArray array = JArray.Parse(json);

foreach (JObject content in array.Children<JObject>())
    foreach (JProperty prop in content.Properties())



Apply style to cells of first row

This should do the work:

.category_table tr:first-child td {
    vertical-align: top;

Replacement for deprecated sizeWithFont: in iOS 7?

- (CGSize) sizeWithMyFont:(UIFont *)fontToUse
    if ([self respondsToSelector:@selector(sizeWithAttributes:)])
        NSDictionary* attribs = @{NSFontAttributeName:fontToUse};
        return ([self sizeWithAttributes:attribs]);
    return ([self sizeWithFont:fontToUse]);

How do I clear the content of a div using JavaScript?

You can do it the DOM way as well:

var div = document.getElementById('cart_item');

How to prevent page scrolling when scrolling a DIV element?

A less hacky solution, in my opinion is to set overflow hidden on the body when you mouse over the scrollable div. This will prevent the body from scrolling, but an unwanted "jumping" effect will occur. The following solution works around that:

    .mouseenter(function(e) {
        // get body width now
        var body_width = jQuery("body").width();
        // set overflow hidden on body. this will prevent it scrolling
        jQuery("body").css("overflow", "hidden"); 
        // get new body width. no scrollbar now, so it will be bigger
        var new_body_width = jQuery("body").width();
        // set the difference between new width and old width as padding to prevent jumps                                     
        jQuery("body").css("padding-right", (new_body_width - body_width)+"px");
    .mouseleave(function(e) {
            overflow: "auto",
            padding-right: "0px"

You could make your code smarter if needed. For example, you could test if the body already has a padding and if yes, add the new padding to that.

ASP.NET MVC Return Json Result?

It should be :

public async Task<ActionResult> GetSomeJsonData()
    var model = // ... get data or build model etc.

    return Json(new { Data = model }, JsonRequestBehavior.AllowGet); 

or more simply:

return Json(model, JsonRequestBehavior.AllowGet); 

I did notice that you are calling GetResources() from another ActionResult which wont work. If you are looking to get JSON back, you should be calling GetResources() from ajax directly...

Send cookies with curl TRUE / FALSE 1560211200 MY_VARIABLE MY_VALUE

The cookies file format apparently consists of a line per cookie and each line consists of the following seven tab-delimited fields:

  • domain - The domain that created AND that can read the variable.
  • flag - A TRUE/FALSE value indicating if all machines within a given domain can access the variable. This value is set automatically by the browser, depending on the value you set for domain.
  • path - The path within the domain that the variable is valid for.
  • secure - A TRUE/FALSE value indicating if a secure connection with the domain is needed to access the variable.
  • expiration - The UNIX time that the variable will expire on. UNIX time is defined as the number of seconds since Jan 1, 1970 00:00:00 GMT.
  • name - The name of the variable.
  • value - The value of the variable.


How to read large text file on windows?

I have been using the BareTail for quite some time for viewing large logs (some GBs) and it is working very well is very fast. There is a free version and a commercial Pro version.

They say that it has

  • Real-time file
  • Optimised real-time viewing engine View files of any size (> 2GB)
  • Scroll to any point in the whole file instantly
  • View files over a network
  • Configurable line wrapping
  • Configurable TAB expansion
  • Configurable font, including spacing and offset to maximise use of screen space

Another alternative is Far Manager. Viewing a several GBs file is no problem (little memory footprint), but attempting to open the text file in the Editing mode might take several GBs of RAM, so be aware of that. I am not aware of the file size limit that can be viewed/edited in Far.

Eclipse comment/uncomment shortcut?


Ctrl + SHIFT + L which will open a list of all major shortcuts for eclipse.

  1. For single line java code comment and uncomment : Ctrl + / (Forward Slash)

  2. For multiple line java code comment : Ctrl + Shift + / (Forward Slash) and

    Multiline uncomment : Ctrl + Shift + \ (Backslash)

  3. For single line xhtml code comment/uncomment : Ctrl + Shift + c

  4. For multiple line xhtml code comment : Ctrl + Shift + / (Forward Slash)

    For multiple uncomment : Ctrl + Shift + \ (Backward Slash)

For Mac user it will be: ? instead of Ctrl

Java Best Practices to Prevent Cross Site Scripting

Use both. In fact refer a guide like the OWASP XSS Prevention cheat sheet, on the possible cases for usage of output encoding and input validation.

Input validation helps when you cannot rely on output encoding in certain cases. For instance, you're better off validating inputs appearing in URLs rather than encoding the URLs themselves (Apache will not serve a URL that is url-encoded). Or for that matter, validate inputs that appear in JavaScript expressions.

Ultimately, a simple thumb rule will help - if you do not trust user input enough or if you suspect that certain sources can result in XSS attacks despite output encoding, validate it against a whitelist.

Do take a look at the OWASP ESAPI source code on how the output encoders and input validators are written in a security library.

How to use Tomcat 8 in Eclipse?

I follow Jason's step, but not works.

And then I find the WTP Update site

Help -> Install new software -> Add > WTP: -> OK

Then Help -> Check for update, just works, I don't know whether Jason's affect this .

php timeout - set_time_limit(0); - don't work

This is an old thread, but I thought I would post this link, as it helped me quite a bit on this issue. Essentially what it's saying is the server configuration can override the php config. From the article:

For example mod_fastcgi has an option called "-idle-timeout" which controls the idle time of the script. So if the script does not output anything to the fastcgi handler for that many seconds then fastcgi would terminate it. The setup is somewhat like this:

Apache <-> mod_fastcgi <-> php processes

The article has other examples and further explanation. Hope this helps somebody else.

capture div into image using html2canvas

I don't know if the answer will be late, but I have used this form.


function getPDF()  {
        var img=canvas.toDataURL("image/png");
        var doc = new jsPDF('l', 'cm'); 


<div id="toPDF"> 
    #your content...

<button  id="getPDF" type="button" class="btn btn-info" onclick="getPDF()">
    Download PDF

How could I create a function with a completion handler in Swift?

I had trouble understanding the answers so I'm assuming any other beginner like myself might have the same problem as me.

My solution does the same as the top answer but hopefully a little more clear and easy to understand for beginners or people just having trouble understanding in general.

To create a function with a completion handler

func yourFunctionName(finished: () -> Void) {

     print("Doing something!")



to use the function

     override func viewDidLoad() {

          yourFunctionName {

          //do something here after running your function


Your output will be

Doing something


Hope this helps!

How to get host name with port from a http or https request

If you use the load balancer & Nginx, config them without modify code.


proxy_set_header       Host $host;  
proxy_set_header  X-Real-IP  $remote_addr;  
proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;  
proxy_set_header X-Forwarded-Proto  $scheme;  

Tomcat's server.xml Engine:

<Valve className="org.apache.catalina.valves.RemoteIpValve"  

If only modify Nginx config file, the java code should be:

String XForwardedProto = request.getHeader("X-Forwarded-Proto");

Finding all cycles in a directed graph

To clarify:

  1. Strongly Connected Components will find all subgraphs that have at least one cycle in them, not all possible cycles in the graph. e.g. if you take all strongly connected components and collapse/group/merge each one of them into one node (i.e. a node per component), you'll get a tree with no cycles (a DAG actually). Each component (which is basically a subgraph with at least one cycle in it) can contain many more possible cycles internally, so SCC will NOT find all possible cycles, it will find all possible groups that have at least one cycle, and if you group them, then the graph will not have cycles.

  2. to find all simple cycles in a graph, as others mentioned, Johnson's algorithm is a candidate.

The cause of "bad magic number" error when loading a workspace and how to avoid it?

The magic number comes from UNIX-type systems where the first few bytes of a file held a marker indicating the file type.

This error indicates you are trying to load a non-valid file type into R. For some reason, R no longer recognizes this file as an R workspace file.

Difference between VARCHAR2(10 CHAR) and NVARCHAR2(10)

  • The NVARCHAR2 stores variable-length character data. When you create a table with the NVARCHAR2 column, the maximum size is always in character length semantics, which is also the default and only length semantics for the NVARCHAR2 data type.

    The NVARCHAR2data type uses AL16UTF16character set which encodes Unicode data in the UTF-16 encoding. The AL16UTF16 use 2 bytes to store a character. In addition, the maximum byte length of an NVARCHAR2 depends on the configured national character set.

  • VARCHAR2 The maximum size of VARCHAR2 can be in either bytes or characters. Its column only can store characters in the default character set while the NVARCHAR2 can store virtually any characters. A single character may require up to 4 bytes.

By defining the field as:

  • VARCHAR2(10 CHAR) you tell Oracle it can use enough space to store 10 characters, no matter how many bytes it takes to store each one. A single character may require up to 4 bytes.
  • NVARCHAR2(10) you tell Oracle it can store 10 characters with 2 bytes per character

In Summary:

  • VARCHAR2(10 CHAR) can store maximum of 10 characters and maximum of 40 bytes (depends on the configured national character set).

  • NVARCHAR2(10) can store maximum of 10 characters and maximum of 20 bytes (depends on the configured national character set).

Note: Character set can be UTF-8, UTF-16,....

Please have a look at this tutorial for more detail.

Have a good day!

What's the fastest way of checking if a point is inside a polygon in python

You can consider shapely:

from shapely.geometry import Point
from shapely.geometry.polygon import Polygon

point = Point(0.5, 0.5)
polygon = Polygon([(0, 0), (0, 1), (1, 1), (1, 0)])

From the methods you've mentioned I've only used the second, path.contains_points, and it works fine. In any case depending on the precision you need for your test I would suggest creating a numpy bool grid with all nodes inside the polygon to be True (False if not). If you are going to make a test for a lot of points this might be faster (although notice this relies you are making a test within a "pixel" tolerance):

from matplotlib import path
import matplotlib.pyplot as plt
import numpy as np

first = -3
size  = (3-first)/100
xv,yv = np.meshgrid(np.linspace(-3,3,100),np.linspace(-3,3,100))
p = path.Path([(0,0), (0, 1), (1, 1), (1, 0)])  # square with legs length 1 and bottom left corner at the origin
flags = p.contains_points(np.hstack((xv.flatten()[:,np.newaxis],yv.flatten()[:,np.newaxis])))
grid = np.zeros((101,101),dtype='bool')
grid[((xv.flatten()-first)/size).astype('int'),((yv.flatten()-first)/size).astype('int')] = flags

xi,yi = np.random.randint(-300,300,100)/100,np.random.randint(-300,300,100)/100
vflag = grid[((xi-first)/size).astype('int'),((yi-first)/size).astype('int')]

, the results is this:

point inside polygon within pixel tolerance

Does return stop a loop?

Yes, once the return statement is executed, the entire function is exited at that very point.

Just imagine what would happen if it did not and continued looping, and executing that return statement each time? It would invalidate it's meaning of returning a value when you think about it.

Use a loop to plot n charts Python

Here are two examples of how to generate graphs in separate windows (frames), and, an example of how to generate graphs and save them into separate graphics files.

Okay, first the on-screen example. Notice that we use a separate instance of plt.figure(), for each graph, with plt.plot(). At the end, we have to call to put it all on the screen.

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace( 0,10 )

for n in range(3):
    y = np.sin( x+n )
    plt.plot( x, y )

Another way to do this, is to use inside the loop:

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace( 0,10 )

for n in range(3):
    y = np.sin( x+n )
    plt.plot( x, y ) block=False )

Now, let's generate the graphs and instead, write them each to a file. Here we replace, with plt.savefig( filename ). The difference from the previous example is that we don't have to account for ''blocking'' at each graph. Note also, that we number the file names. Here we use %03d so that we can conveniently have them in number order afterwards.

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace( 0,10 )

for n in range(3):
    y = np.sin( x+n )
    plt.plot( x, y )

Convert string[] to int[] in one line of code using LINQ

Given an array you can use the Array.ConvertAll method:

int[] myInts = Array.ConvertAll(arr, s => int.Parse(s));

Thanks to Marc Gravell for pointing out that the lambda can be omitted, yielding a shorter version shown below:

int[] myInts = Array.ConvertAll(arr, int.Parse);

A LINQ solution is similar, except you would need the extra ToArray call to get an array:

int[] myInts = arr.Select(int.Parse).ToArray();

How to add style from code behind?

Try this:

Html Markup

<asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl="#">HyperLink</asp:HyperLink>


using System.Drawing;
using System.Web.UI;
using System.Web.UI.WebControls;

protected void Page_Load(object sender, EventArgs e)
    Style style = new Style();
    style.ForeColor = Color.Green;
    this.Page.Header.StyleSheet.CreateStyleRule(style, this, "#" + HyperLink1.ClientID + ":hover");

React: "this" is undefined inside a component function

You can rewrite how your onToggleLoop method is called from your render() method.

render() {
    var shuffleClassName = this.state.toggleActive ? "player-control-icon active" : "player-control-icon"

return (
  <div className="player-controls">
      onClick={(event) => this.onToggleLoop(event)}

The React documentation shows this pattern in making calls to functions from expressions in attributes.

Return list using select new in LINQ

You can do it as following:

class ProjectInfo
    public string Name {get; set; }
    public long Id {get; set; }

    ProjectInfo(string n, long id)
        name = n;   Id = id;

public List<ProjectInfo> GetProjectForCombo()
    using (MyDataContext db = new MyDataContext (DBHelper.GetConnectionString()))
         var query = from pro in db.Projects
                    select new ProjectInfo(pro.ProjectName,pro.ProjectId);

         return query.ToList<ProjectInfo>();

How to share my Docker-Image without using the Docker-Hub?

Docker images are stored as filesystem layers. Every command in the Dockerfile creates a layer. You can also create layers by using docker commit from the command line after making some changes (via docker run probably).

These layers are stored by default under /var/lib/docker. While you could (theoretically) cherry pick files from there and install it in a different docker server, is probably a bad idea to play with the internal representation used by Docker.

When you push your image, these layers are sent to the registry (the docker hub registry, by default… unless you tag your image with another registry prefix) and stored there. When pushing, the layer id is used to check if you already have the layer locally or it needs to be downloaded. You can use docker history to peek at which layers (other images) are used (and, to some extent, which command created the layer).

As for options to share an image without pushing to the docker hub registry, your best options are:

  • docker save an image or docker export a container. This will output a tar file to standard output, so you will like to do something like docker save 'dockerizeit/agent' > dk.agent.latest.tar. Then you can use docker load or docker import in a different host.

  • Host your own private registry. - Outdated, see comments See the docker registry image. We have built an s3 backed registry which you can start and stop as needed (all state is kept on the s3 bucket of your choice) which is trivial to setup. This is also an interesting way of watching what happens when pushing to a registry

  • Use another registry like (I haven't personally tried it), although whatever concerns you have with the docker hub will probably apply here too.

How to check if an array is empty?

Your problem is that you are NOT testing the length of the array until it is too late.

But I just want to point out that the way to solve this problem is to READ THE STACK TRACE.

The exception message will clearly tell you are trying to create an array with length -1, and the trace will tell you exactly which line of your code is doing this. The rest is simple logic ... working back to why the length you are using is -1.

What is a reasonable code coverage % for unit tests (and why)?

I think that what may matter most is knowing what the coverage trend is over time and understanding the reasons for changes in the trend. Whether you view the changes in the trend as good or bad will depend upon your analysis of the reason.

Missing visible-** and hidden-** in Bootstrap v4

i like the bootstrap3 style as the device width of bootstrap4
so i modify the css as below
.visible-xs, .visible-sm, .visible-md, .visible-lg { display:none !important; }
.visible-xs-block, .visible-xs-inline, .visible-xs-inline-block,
.visible-sm-block, .visible-sm-inline, .visible-sm-inline-block,
.visible-md-block, .visible-md-inline, .visible-md-inline-block,
.visible-lg-block, .visible-lg-inline, .visible-lg-inline-block { display:none !important; }
@media (max-width:575px) {
table.visible-xs                { display:table !important; }
tr.visible-xs                   { display:table-row !important; }
th.visible-xs, td.visible-xs    { display:table-cell !important; }

.visible-xs                 { display:block !important; }
.visible-xs-block { display:block !important; }
.visible-xs-inline { display:inline !important; }
.visible-xs-inline-block { display:inline-block !important; }

@media (min-width:576px) and (max-width:767px) {
table.visible-sm { display:table !important; }
tr.visible-sm { display:table-row !important; }
td.visible-sm { display:table-cell !important; }

.visible-sm { display:block !important; }
.visible-sm-block { display:block !important; }
.visible-sm-inline { display:inline !important; }
.visible-sm-inline-block { display:inline-block !important; }

@media (min-width:768px) and (max-width:991px) {
table.visible-md { display:table !important; }
tr.visible-md { display:table-row !important; }
td.visible-md { display:table-cell !important; }

.visible-md { display:block !important; }
.visible-md-block { display:block !important; }
.visible-md-inline { display:inline !important; }
.visible-md-inline-block { display:inline-block !important; }

@media (min-width:992px) and (max-width:1199px) {
table.visible-lg { display:table !important; }
tr.visible-lg { display:table-row !important; }
td.visible-lg { display:table-cell !important; }

.visible-lg { display:block !important; }
.visible-lg-block { display:block !important; }
.visible-lg-inline { display:inline !important; }
.visible-lg-inline-block { display:inline-block !important; }

@media (min-width:1200px) {
table.visible-xl { display:table !important; }
tr.visible-xl { display:table-row !important; }
td.visible-xl { display:table-cell !important; }

.visible-xl { display:block !important; }
.visible-xl-block { display:block !important; }
.visible-xl-inline { display:inline !important; }
.visible-xl-inline-block { display:inline-block !important; }

@media (max-width:575px)                        { .hidden-xs{display:none !important;} }
@media (min-width:576px) and (max-width:767px)  { .hidden-sm{display:none !important;} }
@media (min-width:768px) and (max-width:991px)  { .hidden-md{display:none !important;} }
@media (min-width:992px) and (max-width:1199px) { .hidden-lg{display:none !important;} }
@media (min-width:1200px)                       { .hidden-xl{display:none !important;} }

Dynamic Height Issue for UITableView Cells (Swift)

To make autoresizing of UITableViewCell to work make sure you are doing these changes :

  • In Storyboard your UITableView should only contain Dynamic Prototype Cells (It shouldn't use static cells) otherwise autoresizing won't work.
  • In Storyboard your UITableViewCell's UILabel has configured for all 4 constraints that is top, bottom, leading and trailing constraints.
  • In Storyboard your UITableViewCell's UILabel's number of lines should be 0
  • In your UIViewController's viewDidLoad function set below UITableView Properties :

    self.tableView.estimatedRowHeight = <minimum cell height> 
    self.tableView.rowHeight = UITableViewAutomaticDimension

ctypes - Beginner

Firstly: The >>> code you see in python examples is a way to indicate that it is Python code. It's used to separate Python code from output. Like this:

>>> 4+5

Here we see that the line that starts with >>> is the Python code, and 9 is what it results in. This is exactly how it looks if you start a Python interpreter, which is why it's done like that.

You never enter the >>> part into a .py file.

That takes care of your syntax error.

Secondly, ctypes is just one of several ways of wrapping Python libraries. Other ways are SWIG, which will look at your Python library and generate a Python C extension module that exposes the C API. Another way is to use Cython.

They all have benefits and drawbacks.

SWIG will only expose your C API to Python. That means you don't get any objects or anything, you'll have to make a separate Python file doing that. It is however common to have a module called say "wowza" and a SWIG module called "_wowza" that is the wrapper around the C API. This is a nice and easy way of doing things.

Cython generates a C-Extension file. It has the benefit that all of the Python code you write is made into C, so the objects you write are also in C, which can be a performance improvement. But you'll have to learn how it interfaces with C so it's a little bit extra work to learn how to use it.

ctypes have the benefit that there is no C-code to compile, so it's very nice to use for wrapping standard libraries written by someone else, and already exists in binary versions for Windows and OS X.

How to read one single line of csv data in Python?

The simple way to get any row in csv file

import csv
csvfile = open('some.csv','rb')
csvFileArray = []
for row in csv.reader(csvfile, delimiter = '.'):

Get folder name from full file path

I think you want to get parent folder name from file path. It is easy to get. One way is to create a FileInfo type object and use its Directory property.


FileInfo fInfo = new FileInfo("c:\projects\roott\wsdlproj\devlop\beta2\text\abc.txt");

String dirName = fInfo.Directory.Name;

Check if checkbox is NOT checked on click - jQuery

Do it like this

if (typeof $(this).attr("checked") == "undefined" )

// To check if checkbox is checked
if( $(this).attr("checked")=="checked")

How to work with progress indicator in flutter?

1. Without plugin

    class IndiSampleState extends State<ProgHudPage> {
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('Demo'),
        body: Center(
          child: RaisedButton(
            color: Colors.blueAccent,
            child: Text('Login'),
            onPressed: () async {
                  context: context,
                  builder: (BuildContext context) {
                    return Center(child: CircularProgressIndicator(),);
              await loginAction();

  Future<bool> loginAction() async {
    //replace the below line of code with your login request
    await new Future.delayed(const Duration(seconds: 2));
    return true;

2. With plugin

check this plugin progress_hud

add the dependency in the pubspec.yaml file


import the package

import 'package:progress_hud/progress_hud.dart';

Sample code is given below to show and hide the indicator

class ProgHudPage extends StatefulWidget {
  _ProgHudPageState createState() => _ProgHudPageState();

class _ProgHudPageState extends State<ProgHudPage> {
  ProgressHUD _progressHUD;
  void initState() {
    _progressHUD = new ProgressHUD(
      backgroundColor: Colors.black12,
      color: Colors.white,
      borderRadius: 5.0,
      loading: false,
      text: 'Loading...',

  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('ProgressHUD Demo'),
        body: new Stack(
          children: <Widget>[
            new Positioned(
                child: RaisedButton(
                  color: Colors.blueAccent,
                  child: Text('Login'),
                  onPressed: () async{
                    await loginAction();
                bottom: 30.0,
                right: 10.0)

  Future<bool> loginAction()async{
    //replace the below line of code with your login request
    await new Future.delayed(const Duration(seconds: 2));
    return true;

How do I remove blank pages coming between two chapters in Appendix?

I tried Noah's suggestion which leads to the best solution up to now.

Just insert \let\cleardoublepage\clearpage before all the parts with the blank pages Especially when you use \documentclass[12pt,a4paper]{book}

frederic snyers's advice \documentclass[oneside]{book} is also very good and solves the problem, but if we just want to use the book.cls or article.cls, the one would make a big difference presenting your particles.

Hence, Big support to \let\cleardoublepage\clearpage for the people who will ask the same question in the future.

Synchronous XMLHttpRequest warning and <script>

In my case this was caused by the flexie script which was part of the "CDNJS Selections" app offered by Cloudflare.

According to Cloudflare "This app is being deprecated in March 2015". I turned it off and the message disappeared instantly.

You can access the apps by visiting

ASP.NET page life cycle explanation

There are 10 events in ASP.NET page life cycle, and the sequence is:

  1. Init
  2. Load view state
  3. Post back data
  4. Load
  5. Validate
  6. Events
  7. Pre-render
  8. Save view state
  9. Render
  10. Unload

Below is a pictorial view of ASP.NET Page life cycle with what kind of code is expected in that event. I suggest you read this article I wrote on the ASP.NET Page life cycle, which explains each of the 10 events in detail and when to use them.

ASP.NET life cycle

Image source: my own article at from 19 April 2010

Java Hashmap: How to get key from value?

For Android development targeting API < 19, Vitalii Fedorenko one-to-one relationship solution doesn't work because Objects.equals isn't implemented. Here's a simple alternative:

public <K, V> K getKeyByValue(Map<K, V> map, V value) {
    for (Map.Entry<K, V> entry : map.entrySet()) {
            if (value.equals(entry.getValue())) {
            return entry.getKey();
    return null;

How to download Visual Studio Community Edition 2015 (not 2017)

You can use these links to download Visual Studio 2015

Community Edition:

And for anyone in the future who might be looking for the other editions here are the links for them as well:

Professional Edition:

Enterprise Edition:

Extract a substring using PowerShell

other solution

$template="-----start-------{Value:This is a test 123}------end-------"
$text="-----start-------Hello World------end-------"

$text | ConvertFrom-String -TemplateContent $template

How to find all duplicate from a List<string>?

Using LINQ, ofcourse. The below code would give you dictionary of item as string, and the count of each item in your sourc list.

var item2ItemCount = list.GroupBy(item => item).ToDictionary(x=>x.Key,x=>x.Count());

Sql connection-string for localhost server

string str = @"Data Source=HARIHARAN-PC\SQLEXPRESS;Initial Catalog=master;Integrated Security=True" ;

How can I check that JButton is pressed? If the isEnable() is not work?

Seems you need to use JToggleButton :

JToggleButton tb = new JToggleButton("push me");
tb.addActionListener(new ActionListener() {

    public void actionPerformed(ActionEvent e) {
        JToggleButton btn =  (JToggleButton) e.getSource();
        btn.setText(btn.isSelected() ? "pushed" : "push me");

regular expression for finding 'href' value of a <a> link

I came up with this one, that supports anchor and image tags, and supports single and double quotes.



<a href="/something.ext">click here</a>

Will match:

 Match 1: /something.ext


<a href='/something.ext'>click here</a>

Will match:

 Match 1: /something.ext

Same goes for img src attributes

Can I use multiple "with"?


With DependencedIncidents AS
    SELECT INC.[RecTime],INC.[SQL] AS [str] FROM
        SELECT A.[RecTime] As [RecTime],X.[SQL] As [SQL] FROM [EventView] AS A 
        CROSS JOIN [Incident] AS X
                patindex('%' + A.[Col] + '%', X.[SQL]) > 0
    ) AS INC
lalala AS
    SELECT INC.[RecTime],INC.[SQL] AS [str] FROM
        SELECT A.[RecTime] As [RecTime],X.[SQL] As [SQL] FROM [EventView] AS A 
        CROSS JOIN [Incident] AS X
                patindex('%' + A.[Col] + '%', X.[SQL]) > 0
    ) AS INC

And yes, you can reference common table expression inside common table expression definition. Even recursively. Which leads to some very neat tricks.

Convert to date format dd/mm/yyyy

$test1='2010-04-19 18:31:27';
echo date('d/m/Y',strtotime($test1));

try this

Passing arguments to an interactive program non-interactively

For more complex tasks there is expect ( ). It basically simulates a user, you can code a script how to react to specific program outputs and related stuff.

This also works in cases like ssh that prohibits piping passwords to it.

Given a filesystem path, is there a shorter way to extract the filename without its extension?




string fileName = @"C:\mydir\myfile.ext";
string path = @"C:\mydir\";
string result;

result = Path.GetFileNameWithoutExtension(fileName);
Console.WriteLine("GetFileNameWithoutExtension('{0}') returns '{1}'", 
    fileName, result);

result = Path.GetFileName(path);
Console.WriteLine("GetFileName('{0}') returns '{1}'", 
    path, result);

// This code produces output similar to the following:
// GetFileNameWithoutExtension('C:\mydir\myfile.ext') returns 'myfile'
// GetFileName('C:\mydir\') returns ''

What is the difference between user variables and system variables?

Environment variables are 'evaluated' (ie. they are attributed) in the following order:

  1. System variables
  2. Variables defined in autoexec.bat
  3. User variables

Every process has an environment block that contains a set of environment variables and their values. There are two types of environment variables: user environment variables (set for each user) and system environment variables (set for everyone). A child process inherits the environment variables of its parent process by default.

Programs started by the command processor inherit the command processor's environment variables.

Environment variables specify search paths for files, directories for temporary files, application-specific options, and other similar information. The system maintains an environment block for each user and one for the computer. The system environment block represents environment variables for all users of the particular computer. A user's environment block represents the environment variables the system maintains for that particular user, including the set of system environment variables.

CSS endless rotation animation

@-webkit-keyframes rotating /* Safari and Chrome */ {_x000D_
  from {_x000D_
    -webkit-transform: rotate(0deg);_x000D_
    -o-transform: rotate(0deg);_x000D_
    transform: rotate(0deg);_x000D_
  to {_x000D_
    -webkit-transform: rotate(360deg);_x000D_
    -o-transform: rotate(360deg);_x000D_
    transform: rotate(360deg);_x000D_
@keyframes rotating {_x000D_
  from {_x000D_
    -ms-transform: rotate(0deg);_x000D_
    -moz-transform: rotate(0deg);_x000D_
    -webkit-transform: rotate(0deg);_x000D_
    -o-transform: rotate(0deg);_x000D_
    transform: rotate(0deg);_x000D_
  to {_x000D_
    -ms-transform: rotate(360deg);_x000D_
    -moz-transform: rotate(360deg);_x000D_
    -webkit-transform: rotate(360deg);_x000D_
    -o-transform: rotate(360deg);_x000D_
    transform: rotate(360deg);_x000D_
.rotating {_x000D_
  -webkit-animation: rotating 2s linear infinite;_x000D_
  -moz-animation: rotating 2s linear infinite;_x000D_
  -ms-animation: rotating 2s linear infinite;_x000D_
  -o-animation: rotating 2s linear infinite;_x000D_
  animation: rotating 2s linear infinite;_x000D_
<div _x000D_
  style="width: 100px; height: 100px; line-height: 100px; text-align: center;" _x000D_

Java Wait and Notify: IllegalMonitorStateException

You can't wait() on an object unless the current thread owns that object's monitor. To do that, you must synchronize on it:

class Runner implements Runnable
  public void run()
      synchronized(Main.main) {
    } catch (InterruptedException e) {}
    System.out.println("Runner away!");

The same rule applies to notify()/notifyAll() as well.

The Javadocs for wait() mention this:

This method should only be called by a thread that is the owner of this object's monitor. See the notify method for a description of the ways in which a thread can become the owner of a monitor.


IllegalMonitorStateException – if the current thread is not the owner of this object's monitor.

And from notify():

A thread becomes the owner of the object's monitor in one of three ways:

  • By executing a synchronized instance method of that object.
  • By executing the body of a synchronized statement that synchronizes on the object.
  • For objects of type Class, by executing a synchronized static method of that class.

How can I add a custom HTTP header to ajax request with js or jQuery?

Assuming JQuery ajax, you can add custom headers like -

  url: url,
  beforeSend: function(xhr) {
    xhr.setRequestHeader("custom_header", "value");
  success: function(data) {

Is there a way to "limit" the result with ELOQUENT ORM of Laravel?

Create a Game model which extends Eloquent and use this:


take() here will get 30 records and skip() here will offset to 30 records.

In recent Laravel versions you can also use:


Image style height and width not taken in outlook mails

The px needs to be left off, for some odd reason.

How to set HTML Auto Indent format on Sublime Text 3?

This is an adaptation of the above answer, but should be more complete.

To be clear, this is to re-introduce previous auto-indent features when HTML files are open in Sublime Text. So when you finish a tag, it automatically indents for the next element.

Windows Users

Go to C:\Program Files\Sublime Text 3\Packages extract HTML.sublime-package as if it is a zip file to a directory.

Open Miscellaneous.tmPreferences and copy this contents into the file

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "">
<plist version="1.0">

Then re-zip the file as HTML.sublime-package and replace the existing HTML.sublime-package with the one you just created.

Close and open Sublime Text 3 and you're done!

Condition within JOIN or WHERE

Agree with 2nd most vote answer that it will make big difference when using LEFT JOIN or RIGHT JOIN. Actually, the two statements below are equivalent. So you can see that AND clause is doing a filter before JOIN while the WHERE clause is doing a filter after JOIN.

FROM dbo.Customers AS CUS 
LEFT JOIN dbo.Orders AS ORD 
ON CUS.CustomerID = ORD.CustomerID
AND ORD.OrderDate >'20090515'

FROM dbo.Customers AS CUS 
LEFT JOIN (SELECT * FROM dbo.Orders WHERE OrderDate >'20090515') AS ORD 
ON CUS.CustomerID = ORD.CustomerID

How to skip a iteration/loop in while-loop

while (
  if (f.exists() && !f.isDirectory())


ld.exe: cannot open output file ... : Permission denied

  1. Open task manager -> Processes -> Click on .exe (Fibonacci.exe) -> End Process

    if it doesn't work

  2. Close eclipse IDE (or whatever IDE you use) and repeat step 1.

Import Script from a Parent Directory

If you want to run the script directly, you can:

  1. Add the FolderA's path to the environment variable (PYTHONPATH).
  2. Add the path to sys.path in the your script.


import module_you_wanted

How do I get current date/time on the Windows command line in a suitable format for usage in a file/folder name?

Here's a variant from alt.msdos.batch.nt that works local-independently.

Put this in a text file, e.g. getDate.cmd

-----------8<------8<------------ snip -- snip ----------8<-------------
    :: Works on any NT/2k machine independent of regional date settings
    @ECHO off
    if "%date%A" LSS "A" (set toks=1-3) else (set toks=2-4)
    for /f "tokens=2-4 delims=(-)" %%a in ('echo:^|date') do (
      for /f "tokens=%toks% delims=.-/ " %%i in ('date/t') do (
        set '%%a'=%%i
        set '%%b'=%%j
        set '%%c'=%%k))
    if %'yy'% LSS 100 set 'yy'=20%'yy'%
    set Today=%'yy'%-%'mm'%-%'dd'% 
    ENDLOCAL & SET v_year=%'yy'%& SET v_month=%'mm'%& SET v_day=%'dd'%

    ECHO Today is Year: [%V_Year%] Month: [%V_Month%] Day: [%V_Day%]

-----------8<------8<------------ snip -- snip ----------8<-------------

To get the code to work sans error msg's to stderr, I had to add the single quotes arount the variable assignments for %%a, %%b and %%c. My locale (PT) was causing errors at one stage in the looping/parsing where stuff like "set =20" was getting executed. The quotes yield a token (albeit empty) for the left-hand side of the assignment statement.

The downside is the messy locale variable names: 'yy', 'mm' and 'dd'. But hey, who cares!

how to make a whole row in a table clickable as a link?

Here's an article that explains how to approach doing this in 2020:

The article explains 3 possible solutions:

  1. Using JavaScript.
  2. Wrapping all table cells with anchorm elements.
  3. Using <div> elements instead of native HTML table elements in order to have tables rows as <a> elements.

The article goes into depth on how to implement each solution (with links to CodePens) and also considers edge cases, such as how to approach a situation where you want to add links inside you table cells (having nested <a> elements is not valid HTML, so you need to workaround that).

As @gameliela pointed out, it may also be worth trying to find an approach where you don't make your entire row a link, since it will simplify a lot of things. I do, however, think that it can be a good user experience to have an entire table row clickable as a link since it is convenient for the user to be able to click anywhere on a table to navigate to the corresponding page.

How to find and replace string?

like some say boost::replace_all

here a dummy example:

    #include <boost/algorithm/string/replace.hpp>

    std::string path("file.gz");
    boost::replace_all(path, ".gz", ".zip");

Relational Database Design Patterns?

AskTom is probably the single most helpful resource on best practices on Oracle DBs. (I usually just type "asktom" as the first word of a google query on a particular topic)

I don't think it's really appropriate to speak of design patterns with relational databases. Relational databases are already the application of a "design pattern" to a problem (the problem being "how to represent, store and work with data while maintaining its integrity", and the design being the relational model). Other approches (generally considered obsolete) are the Navigational and Hierarchical models (and I'm nure many others exist).

Having said that, you might consider "Data Warehousing" as a somewhat separate "pattern" or approach in database design. In particular, you might be interested in reading about the Star schema.

download and install visual studio 2008

Microsoft Visual Studio 2008 Service Pack 1 (iso)

Version: SP1 File Name: VS2008SP1ENUX1512962.iso Date Published: 8/11/2008 File Size: 831.3 MB

Supported Operating System

    Windows Server 2003, Windows Server 2008, Windows Vista, Windows XP
    Minimum: 1.6 GHz CPU, 384 MB RAM, 1024x768 display, 5400 RPM hard disk
    Recommended: 2.2 GHz or higher CPU, 1024 MB or more RAM, 1280x1024 display, 7200 RPM or higher hard disk
    On Windows Vista: 2.4 GHz CPU, 768 MB RAM
    Maintain Internet connectivity during the installation of the service pack until seeing the “Installation Completed Successfully” message before disconnecting.