Programs & Examples On

It is a JavaScript method that opens a new window and loads the document specified by a given URL.

Cannot open local file - Chrome: Not allowed to load local resource

This issue come when I am using PHP as server side language and the work around was to generate base64 enconding of my image before sending the result to client

$path = 'E:/pat/rwanda.png';
$type = pathinfo($path, PATHINFO_EXTENSION);
$data = file_get_contents($path);
$base64 = 'data:image/' . $type . ';base64,' . base64_encode($data);

I think may give someone idea to create his own work around


Bypass popup blocker on when JQuery event.preventDefault() is set

The observation that the event had to be initiated by the user helped me to figure out the first part of this, but even after that Chrome and Firefox still blocked the new window. The second part was adding target="_blank" to the link, which was mentioned in one comment.

In summary: you need to call from an event initiated by the user, in this case clicking on a link, and that link needs to have target="_blank".

In the example below the link is using class="button-twitter".

$('.button-twitter').click(function(e) {
  var href = $(this).attr('href');
  var tweet_popup =, 'tweet_popup', 'width=500,height=300');

Window.Open with PDF stream instead of PDF location

Note: I have verified this in the latest version of IE, and other browsers like Mozilla and Chrome and this works for me. Hope it works for others as well.

if (data == "" || data == undefined) {
    alert("Falied to open PDF.");
} else { //For IE using atob convert base64 encoded data to byte array
    if (window.navigator && window.navigator.msSaveOrOpenBlob) {
        var byteCharacters = atob(data);
        var byteNumbers = new Array(byteCharacters.length);
        for (var i = 0; i < byteCharacters.length; i++) {
            byteNumbers[i] = byteCharacters.charCodeAt(i);
        var byteArray = new Uint8Array(byteNumbers);
        var blob = new Blob([byteArray], {
            type: 'application/pdf'
        window.navigator.msSaveOrOpenBlob(blob, fileName);
    } else { // Directly use base 64 encoded data for rest browsers (not IE)
        var base64EncodedPDF = data;
        var dataURI = "data:application/pdf;base64," + base64EncodedPDF;, '_blank');


Chrome, Javascript, in new tab

At the moment (Chrome 39) I use this code to open a new tab:

_x000D_'', '_blank', 'toolbar=yes, location=yes, status=yes, menubar=yes, scrollbars=yes');

Of course this may change in future versions of Chrome.

It is a bad idea to use this if you can't control the browser your users are using. It may not work in future versions or with different settings.

How to use target in location.href

Why not have a hidden anchor tag on the page with the target set as you need, then simulate clicking it when you need the pop out?

How can I simulate a click to an anchor tag?

This would work in the cases where the did not work

JavaScript: location.href to open in new window/tab?
  '_blank' // <- This is what makes it open in a new window.
); with headers

If you are in control of server side, it might be possible to set header value in query string and send it like that? That way you could parse it from query string if it's not found in the headers.

Just an idea... And you asked for a cunning hack :)

Git: which is the default configured remote for branch?

the command to get the effective push remote for the branch, e.g., master, is:

git config branch.master.pushRemote || git config remote.pushDefault || git config branch.master.remote

Here's why (from the "man git config" output): [...] tells git fetch and git push which remote to fetch from/push to [...] [for push] may be overridden with remote.pushDefault (for all branches) [and] for the current branch [..] further overridden by [...]

For some reason, "man git push" only tells about (even though it has the least precedence of the three) + erroneously states that if it is not set, push defaults to origin - it does not, it's just that when you clone a repo, is set to origin, but if you remove this setting, git push will fail, even though you still have the origin remote

Java Switch Statement - Is "or"/"and" possible?

The above are all excellent answers. I just wanted to add that when there are multiple characters to check against, an if-else might turn out better since you could instead write the following.

// switch on vowels, digits, punctuation, or consonants
char c; // assign some character to 'c'
if ("aeiouAEIOU".indexOf(c) != -1) {
  // handle vowel case
} else if ("!@#$%,.".indexOf(c) != -1) {
  // handle punctuation case
} else if ("0123456789".indexOf(c) != -1) {
  // handle digit case
} else {
  // handle consonant case, assuming other characters are not possible

Of course, if this gets any more complicated, I'd recommend a regex matcher.

Mockito match any class argument

the solution from millhouse is not working anymore with recent version of mockito

This solution work with java 8 and mockito 2.2.9

where ArgumentMatcher is an instanceof org.mockito.ArgumentMatcher

public class ClassOrSubclassMatcher<T> implements ArgumentMatcher<Class<T>> {

   private final Class<T> targetClass;

    public ClassOrSubclassMatcher(Class<T> targetClass) {
        this.targetClass = targetClass;

    public boolean matches(Class<T> obj) {
        if (obj != null) {
            if (obj instanceof Class) {
                return targetClass.isAssignableFrom( obj);
        return false;

And the use

when(a.method(ArgumentMatchers.argThat(new ClassOrSubclassMatcher<>(A.class)))).thenReturn(b);

Set value to currency in <input type="number" />

Add step="0.01" to the <input type="number" /> parameters:

<input type="number" min="0.01" step="0.01" max="2500" value="25.67" />


But the Dollar sign must stay outside the textbox... every non-numeric or separator charachter will be cropped automatically.

Otherwise you could use a classic textbox, like described here.

How to find the socket connection state in C?

You should try to use: getpeername function.

now when the connection is down you will get in errno: ENOTCONN - The socket is not connected. which means for you DOWN.

else (if no other failures) there the return code will 0 --> which means UP.

resources: man page:

The difference between the 'Local System' account and the 'Network Service' account?

Since there is so much confusion about functionality of standard service accounts, I'll try to give a quick run down.

First the actual accounts:

  • LocalService account (preferred)

    A limited service account that is very similar to Network Service and meant to run standard least-privileged services. However, unlike Network Service it accesses the network as an Anonymous user.

    • Name: NT AUTHORITY\LocalService
    • the account has no password (any password information you provide is ignored)
    • HKCU represents the LocalService user account
    • has minimal privileges on the local computer
    • presents anonymous credentials on the network
    • SID: S-1-5-19
    • has its own profile under the HKEY_USERS registry key (HKEY_USERS\S-1-5-19)


  • NetworkService account

    Limited service account that is meant to run standard privileged services. This account is far more limited than Local System (or even Administrator) but still has the right to access the network as the machine (see caveat above).

    • NT AUTHORITY\NetworkService
    • the account has no password (any password information you provide is ignored)
    • HKCU represents the NetworkService user account
    • has minimal privileges on the local computer
    • presents the computer's credentials (e.g. MANGO$) to remote servers
    • SID: S-1-5-20
    • has its own profile under the HKEY_USERS registry key (HKEY_USERS\S-1-5-20)
    • If trying to schedule a task using it, enter NETWORK SERVICE into the Select User or Group dialog


  • LocalSystem account (dangerous, don't use!)

    Completely trusted account, more so than the administrator account. There is nothing on a single box that this account cannot do, and it has the right to access the network as the machine (this requires Active Directory and granting the machine account permissions to something)

    • Name: .\LocalSystem (can also use LocalSystem or ComputerName\LocalSystem)
    • the account has no password (any password information you provide is ignored)
    • SID: S-1-5-18
    • does not have any profile of its own (HKCU represents the default user)
    • has extensive privileges on the local computer
    • presents the computer's credentials (e.g. MANGO$) to remote servers


Above when talking about accessing the network, this refers solely to SPNEGO (Negotiate), NTLM and Kerberos and not to any other authentication mechanism. For example, processing running as LocalService can still access the internet.

The general issue with running as a standard out of the box account is that if you modify any of the default permissions you're expanding the set of things everything running as that account can do. So if you grant DBO to a database, not only can your service running as Local Service or Network Service access that database but everything else running as those accounts can too. If every developer does this the computer will have a service account that has permissions to do practically anything (more specifically the superset of all of the different additional privileges granted to that account).

It is always preferable from a security perspective to run as your own service account that has precisely the permissions you need to do what your service does and nothing else. However, the cost of this approach is setting up your service account, and managing the password. It's a balancing act that each application needs to manage.

In your specific case, the issue that you are probably seeing is that the the DCOM or COM+ activation is limited to a given set of accounts. In Windows XP SP2, Windows Server 2003, and above the Activation permission was restricted significantly. You should use the Component Services MMC snapin to examine your specific COM object and see the activation permissions. If you're not accessing anything on the network as the machine account you should seriously consider using Local Service (not Local System which is basically the operating system).

In Windows Server 2003 you cannot run a scheduled task as

  • NT_AUTHORITY\LocalService (aka the Local Service account), or
  • NT AUTHORITY\NetworkService (aka the Network Service account).

That capability only was added with Task Scheduler 2.0, which only exists in Windows Vista/Windows Server 2008 and newer.

A service running as NetworkService presents the machine credentials on the network. This means that if your computer was called mango, it would present as the machine account MANGO$:

enter image description here

How to bring a window to the front?

This simple method worked for me perfectly in Windows 7:

    private void BringToFront() {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                if(jFrame != null) {

Shortcut to comment out a block of code with sublime text

The shortcut to comment out or uncomment the selected text or current line:

  • Windows: Ctrl+/
  • Mac: Command ?+/
  • Linux: Ctrl+Shift+/

Alternatively, use the menu: Edit > Comment

For the block comment you may want to use:

  • Windows: Ctrl+Shift+/
  • Mac: Command ?+Option/Alt+/

How to select lines between two marker patterns which may occur multiple times with awk/sed

something like this works for me:



/^abc$/ {

/^mno$/ {
    print "s="s;

!/^abc|mno$/ {
    if (record==1) {
        s = s"\n"$0

using: awk -f file.awk data...

edit: O_o fedorqui solution is way better/prettier than mine.

Get the index of the object inside an array, matching a condition

var list =  [

var findProp = p => {
    var index = -1;
    $.each(list, (i, o) => {
        if(o.prop2 == p) {
            index = i;
            return false; // break
    return index; // -1 == not found, else == index

Markdown and image alignment

I have an alternative to the methods above that used the ALT tag and a CSS selector on the alt tag... Instead, add a URL hash like this:

First your Markdown image code:

![my image](/img/myImage.jpg#left)
![my image](/img/myImage.jpg#right)
![my image](/img/myImage.jpg#center)

Note the added URL hash #center.

Now add this rule in CSS using CSS 3 attribute selectors to select images with a certain path.

img[src*='#left'] {
    float: left;
img[src*='#right'] {
    float: right;
img[src*='#center'] {
    display: block;
    margin: auto;

You should be able to use a URL hash like this almost like defining a class name and it isn't a misuse of the ALT tag like some people had commented about for that solution. It also won't require any additional extensions. Do one for float right and left as well or any other styles you might want.

How do I turn a python datetime into a string, with readable format date?

Here is how you can accomplish the same using python's general formatting function...

>>>from datetime import datetime
>>>"{:%B %d, %Y}".format(

The formatting characters used here are the same as those used by strftime. Don't miss the leading : in the format specifier.

Using format() instead of strftime() in most cases can make the code more readable, easier to write and consistent with the way formatted output is generated...

>>>"{} today's date is: {:%B %d, %Y}".format("Andre",

Compare the above with the following strftime() alternative...

>>>"{} today's date is {}".format("Andre","%B %d, %Y"))

Moreover, the following is not going to work...

>>>"%s %B %d, %Y" % "Andre")
Traceback (most recent call last):
  File "<pyshell#11>", line 1, in <module>"%s %B %d, %Y" % "Andre")
TypeError: not enough arguments for format string

And so on...

multiple where condition codeigniter

you can use both use array like :

$array = array('tlb_account.crid' =>$value , 'tlb_request.sign'=> 'FALSE' );

and direct assign like:

$this->db->where('tlb_account.crid' =>$value , 'tlb_request.sign'=> 'FALSE');

I wish help you.

Regular expression to match balanced parentheses

This do not fully address the OP question but I though it may be useful to some coming here to search for nested structure regexp:

Parse parmeters from function string (with nested structures) in javascript

Match structures like:
Parse parmeters from function string

  • matches brackets, square brackets, parentheses, single and double quotes

Here you can see generated regexp in action

 * get param content of function string.
 * only params string should be provided without parentheses
 * WORK even if some/all params are not set
 * @return [param1, param2, param3]
exports.getParamsSAFE = (str, nbParams = 3) => {
    const nextParamReg = /^\s*((?:(?:['"([{](?:[^'"()[\]{}]*?|['"([{](?:[^'"()[\]{}]*?|['"([{][^'"()[\]{}]*?['")}\]])*?['")}\]])*?['")}\]])|[^,])*?)\s*(?:,|$)/;
    const params = [];
    while (str.length) { // this is to avoid a BIG performance issue in javascript regexp engine
        str = str.replace(nextParamReg, (full, p1) => {
            return '';
    return params;

Getting datarow values into a string?

I've done this a lot myself. If you just need a comma separated list for all of row values you can do this:

StringBuilder sb = new StringBuilder();
foreach (DataRow row in results.Tables[0].Rows)     
    sb.AppendLine(string.Join(",", row.ItemArray));

A StringBuilder is the preferred method as string concatenation is significantly slower for large amounts of data.

Using Predicate in Swift

Example how to use in swift 2.0

let dataSource = [
    "Domain CheckService",
    "IMEI check",
    "Compliant about service provider",
    "Compliant about TRA",
    "SMS Spam",
    "Poor Coverage",
    "Help Salim"
let searchString = "Enq"
let predicate = NSPredicate(format: "SELF contains %@", searchString)
let searchDataSource = dataSource.filter { predicate.evaluateWithObject($0) }

You will get (playground)

enter image description here

Can't find @Nullable inside javax.annotation.*

You need to include a jar that this class exists in. You can find it here

If using Maven, you can add the following dependency declaration:


and for Gradle:

dependencies {
  testImplementation ''

Multiplying Two Columns in SQL Server


SELECT <Expression>[Arithmetic_Operator]<expression>...
 FROM [Table_Name] 
 WHERE [expression];
  1. Expression : Expression made up of a single constant, variable, scalar function, or column name and can also be the pieces of a SQL query that compare values against other values or perform arithmetic calculations.
  2. Arithmetic_Operator : Plus(+), minus(-), multiply(*), and divide(/).
  3. Table_Name : Name of the table.

Find all elements with a certain attribute value in jquery

It's not called a tag; what you're looking for is called an html attribute.

  //do what ever you wish to this object :) 

Is it possible to Turn page programmatically in UIPageViewController?

Swift 4:

I needed to go to the next controller when i tap next on a pagecontroller view controller and also update the pageControl index, so this was the best and most straightforward solution for me:

let pageController = self.parent as! PageViewController

pageController.setViewControllers([parentVC.orderedViewControllers[1]], direction: .forward, animated: true, completion: nil)

pageController.pageControl.currentPage = 1

m2e lifecycle-mapping not found

I was having the same issue, where:

No marketplace entries found to handle build-helper-maven-plugin:1.8:add-source in Eclipse. Please see Help for more information.

and clicking the Window > Preferences > Maven > Discovery > open catalog button would report no connection.

Updating from 7u40 to 7u45 on Centos 6.4 and OSX fixes the issue.

How to use java.Set

Since it is a HashSet you will need to override hashCode and equals methods. has an example explaining how to implement hashCode and equals methods

javascript onclick increment number

jQuery Example

var $button = $('.increment-btn');
var $counter = $('.counter');

  $counter.val( parseInt($counter.val()) + 1 ); // `parseInt` converts the `value` from a string to a number
<script src=""></script>
<input type="text" value="1" class="counter"/>
<button type="button" class="increment-btn">Increment</button>

'Plain' JavaScript Example

var $button = document.querySelector('.increment-btn');
var $counter = document.querySelector('.counter');

$button.addEventListener('click', function(){
  $counter.value = parseInt($counter.value) + 1; // `parseInt` converts the `value` from a string to a number
}, false);
<input type="text" class="counter" value="1"/>
<button type="button" class="increment-btn">Increment</button>

How to count total lines changed by a specific author in a Git repository?

For windows users you can use following batch script that counts added/removed lines for specified author

@echo off

set added=0
set removed=0

for /f "tokens=1-3 delims= " %%A in ('git log --pretty^=tformat: --numstat --author^=%1') do call :Count %%A %%B %%C

@echo added=%added%
@echo removed=%removed%
goto :eof

  if NOT "%1" == "-" set /a added=%added% + %1
  if NOT "%2" == "-" set /a removed=%removed% + %2
goto :eof

Changing minDate and maxDate on the fly using jQuery DatePicker

For from / to date, here is how I implemented restricting the dates based on the date entered in the other datepicker. Works pretty good:

function activateDatePickers() {
        onClose: function() {
                    { minDate: new Date($('#aDateFrom').val()) }
        onClose: function() {
                    { maxDate: new Date($('#aDateTo').val()) }

Spring Data and Native Query with pagination

You can achieve it by using following code,

@Query(value = "SELECT * FROM users u WHERE  ORDER BY ?#{#pageable}", nativeQuery = true)
List<User> getUsers(String name, Pageable pageable);

Simply use ORDER BY ?#{#pageable} and pass page request to your method.


Using with React components

First argument in update method is SyntheticEvent object that contains common properties and methods to any event, it is not reference to React component where there is property props.

if you need pass argument to update method you can do it like this

onClick={ (e) => this.props.onClick(e, 'home', 'Home') }

and get these arguments inside update method

update(e, space, txt){
   console.log(, space, txt);

Example gives you the native DOMNode, then you need to use the regular DOM APIs to access attributes. For instance getAttribute or dataset

  onClick={ this.props.onClick } 

onClick(e) {


Call PHP function from Twig template

Its not possible to access any PHP function inside Twig directly.

What you can do is write a Twig extension. A common structure is, writing a service with some utility functions, write a Twig extension as bridge to access the service from twig. The Twig extension will use the service and your controller can use the service too.

Take a look:


JQuery Ajax - How to Detect Network Connection error when making Ajax call

Since I can't duplicate the issue I can only suggest to try with a timeout on the ajax call. In jQuery you can set it with the $.ajaxSetup (and it will be global for all your $.ajax calls) or you can set it specifically for your call like this:

    type: 'GET',
    url: '',
    timeout: 15000,
    success: function(data) {},
    error: function(XMLHttpRequest, textStatus, errorThrown) {}

JQuery will register a 15 seconds timeout on your call; after that without an http response code from the server jQuery will execute the error callback with the textStatus value set to "timeout". With this you can at least stop the ajax call but you won't be able to differentiate the real network issues from the loss of connections.

How to pass List<String> in post method using Spring MVC?

I had the same use case, You can change your method defination in the following way :

@RequestMapping(value = "/saveFruits", method = RequestMethod.POST, 
    consumes = "application/json")
public ResultObject saveFruits(@RequestBody Map<String,List<String>> fruits) {

The only problem is it accepts any key in place of "fruits" but You can easily get rid of a wrapper if it is not big functionality.

Javascript equivalent of php's strtotime()?

var strdate = new Date('Tue Feb 07 2017 12:51:48 GMT+0200 (Türkiye Standart Saati)');_x000D_
var date = moment(strdate).format('DD.MM.YYYY');_x000D_
$("#result").text(date); //07.02.2017
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<div id="result"></div>

Last Run Date on a Stored Procedure in SQL Server

The below code should do the trick (>= 2008)

FROM   sys.dm_exec_procedure_stats ps 
       sys.objects o 
       ON ps.object_id = o.object_id 
WHERE  DB_NAME(ps.database_id) = '' 
       ps.last_execution_time DESC  

Edit 1 : Please take note of Jeff Modens advice below. If you find a procedure here, you can be sure that it is accurate. If you do not then you just don't know - you cannot conclude it is not running.

Which is a better way to check if an array has more than one element?

I prefer the count() function instead of sizeOf() as sizeOf() is only an alias of count() and does not mean the same in many other languages. Many programmers expect sizeof() to return the amount of memory allocated.

Where is git.exe located?

I found it at


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

I you are using Visual Studio 2012, download and install Update 2 that Microsoft released recently (as of 4/2013).

Visual Studio 2012 Update 2

There are some bug fixes in that update related to the issue.

How to edit nginx.conf to increase file size upload

You can increase client_max_body_size and upload_max_filesize + post_max_size all day long. Without adjusting HTTP timeout it will never work.

//You need to adjust this, and probably on PHP side also. client_body_timeout 2min // 1GB fileupload

Why is Thread.Sleep so harmful

It is the 1).spinning and 2).polling loop of your examples that people caution against, not the Thread.Sleep() part. I think Thread.Sleep() is usually added to easily improve code that is spinning or in a polling loop, so it is just associated with "bad" code.

In addition people do stuff like:


where the variable inWait is not accessed in a thread-safe manner, which also causes problems.

What programmers want to see is the threads controlled by Events and Signaling and Locking constructs, and when you do that you won't have need for Thread.Sleep(), and the concerns about thread-safe variable access are also eliminated. As an example, could you create an event handler associated with the FileSystemWatcher class and use an event to trigger your 2nd example instead of looping?

As Andreas N. mentioned, read Threading in C#, by Joe Albahari, it is really really good.

How can I combine multiple rows into a comma-delimited list in Oracle?

you can try this query.

select listagg(country_name,',') within group (order by country_name) cnt 
from countries; 

How can I display the current branch and folder path in terminal?

For anyone looking for how to do this in macOS Catalina or above (10.15+ incl. Big Sur 11.0) which has deprecated bash in favour of zsh, here is my .zshrc file:

parse_git_branch() {
    git branch 2> /dev/null | sed -n -e 's/^\* \(.*\)/[\1]/p'
export PROMPT='${COLOR_USR}%n@%M ${COLOR_DIR}%d ${COLOR_GIT}$(parse_git_branch)${COLOR_DEF}${NEWLINE}%% '

If you don't like the colours I have used, replace the 243/197/39 values with the colour codes as defined here:

How can I concatenate strings in VBA?

The main (very interesting) difference for me is that:
"string" & Null -> "string"
"string" + Null -> Null

But that's probably more useful in database apps like Access.

Android – Listen For Incoming SMS Messages

@Mike M. and I found an issue with the accepted answer (see our comments):

Basically, there is no point in going through the for loop if we are not concatenating the multipart message each time:

for (int i = 0; i < msgs.length; i++) {
    msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]);
    msg_from = msgs[i].getOriginatingAddress();
    String msgBody = msgs[i].getMessageBody();

Notice that we just set msgBody to the string value of the respective part of the message no matter what index we are on, which makes the entire point of looping through the different parts of the SMS message useless, since it will just be set to the very last index value. Instead we should use +=, or as Mike noted, StringBuilder:

All in all, here is what my SMS receiving code looks like:

if (myBundle != null) {
    Object[] pdus = (Object[]) myBundle.get("pdus"); // pdus is key for SMS in bundle

    //Object [] pdus now contains array of bytes
    messages = new SmsMessage[pdus.length];
    for (int i = 0; i < messages.length; i++) {
         messages[i] = SmsMessage.createFromPdu((byte[]) pdus[i]); //Returns one message, in array because multipart message due to sms max char
         Message += messages[i].getMessageBody(); // Using +=, because need to add multipart from before also

    contactNumber = messages[0].getOriginatingAddress(); //This could also be inside the loop, but there is no need

Just putting this answer out there in case anyone else has the same confusion.

Xcode source automatic formatting

I also feel xcode should have this function. So I made an extension to do it: Swimat

Simple install by brew cask install swimat preview

You can give it a try, see for more information.

diff current working copy of a file with another branch's committed copy

Also: git diff master..feature foo

Since git diff foo master:foo doesn't work on directories for me.

Call An Asynchronous Javascript Function Synchronously

One thing people might not consider: If you control the async function (which other pieces of code depend on), AND the codepath it would take is not necessarily asynchronous, you can make it synchronous (without breaking those other pieces of code) by creating an optional parameter.


async function myFunc(args_etcetc) {
    // you wrote this
    return 'stuff';

(async function main() {
    var result = await myFunc('argsetcetc');
    console.log('async result:' result);


function myFunc(args_etcetc, opts={}) {
        param opts :: {sync:Boolean} -- whether to return a Promise or not
    var {sync=false} = opts;
    if (sync===true)
        return 'stuff';
        return new Promise((RETURN,REJECT)=> {

// async code still works just like before:
(async function main() {
    var result = await myFunc('argsetcetc');
    console.log('async result:', result);
// prints: 'stuff'

// new sync code works, if you specify sync mode:
(function main() {
    var result = myFunc('argsetcetc', {sync:true});
    console.log('sync result:', result);
// prints: 'stuff'

Of course this doesn't work if the async function relies on inherently async operations (network requests, etc.), in which case the endeavor is futile (without effectively waiting idle-spinning for no reason).

Also this is fairly ugly to return either a value or a Promise depending on the options passed in.

("Why would I have written an async function if it didn't use async constructs?" one might ask? Perhaps some modalities/parameters of the function require asynchronicity and others don't, and due to code duplication you wanted a monolithic block rather than separate modular chunks of code in different functions... For example perhaps the argument is either localDatabase (which doesn't require await) or remoteDatabase (which does). Then you could runtime error if you try to do {sync:true} on the remote database. Perhaps this scenario is indicative of another problem, but there you go.)

Get error message if ModelState.IsValid fails?



How to listen for changes to a MongoDB collection?

After 3.6 one is allowed to use database the following database triggers types:

  • event-driven triggers - useful to update related documents automatically, notify downstream services, propagate data to support mixed workloads, data integrity & auditing
  • scheduled triggers - useful for scheduled data retrieval, propagation, archival and analytics workloads

Log into your Atlas account and select Triggers interface and add new trigger:

enter image description here

Expand each section for more settings or details.

Xcode 6 iPhone Simulator Application Support location

The simulator directory has been moved with Xcode 6 beta to...


Browsing the directory to your app's Documents folder is a bit more arduous, e.g.,


Where is the Docker daemon log?

Using CentOS7, logs are available using the command journalctl -u docker. Answering distinctly, because @sabin's answer might be accurate for older versions of CentOS but was not true for me.

systemd has its own logging system called the journal. The logs for the docker daemon can be viewed using journalctl -u docker


Unzip All Files In A Directory

If by 'current directory' you mean the directory in which the zip file is, then I would use this command:

find . -name '*.zip' -execdir unzip {} \; 

excerpt from find's man page

-execdir command ;
-execdir command {} +

Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec option, the '+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your $PATH environment variable does not reference the current directory; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir.

Check box size change with CSS

Try this

<input type="checkbox" style="zoom:1.5;" />
/* The value 1.5 i.e., the size of checkbox will be increased by 0.5% */

How to add header data in XMLHttpRequest when using formdata?

Use: xmlhttp.setRequestHeader(key, value);

How to add onload event to a div element

we can use MutationObserver to solve the problem in efficient way adding a sample code below

<!DOCTYPE html>
            position: absolute;
            width: 100px;
            height: 100px;
            background-color: #a1a1a1;
<div id="first"></div>
    var callthis = function(element){
        element.onkeydown = handler;
        function handler(){

    var observer = new WebKitMutationObserver(function(mutations) {
        mutations.forEach(function(mutation) {
            for (var i = 0; i < mutation.addedNodes.length; i++)
            if(mutation.addedNodes[i].id === "second"){

    observer.observe(document.getElementById("first"), { childList: true });

    var ele = document.createElement('div'); = "second"




How do I open the "front camera" on the Android platform?

public void surfaceCreated(SurfaceHolder holder) {
    try {
        mCamera =;

        Camera.Parameters p = mCamera.getParameters();
    } catch (IOException e) {
        // TODO Auto-generated catch block

Inline elements shifting when made bold on hover

I really can't stand it when someone tells you not to do something that way when there's a simple solution to the problem. I'm not sure about li elements, but I just fixed the same issue. I have a menu consisting of div tags.

Just set the div tag to be "display: inline-block". Inline so they sit next to each other and block to that you can set a width. Just set the width wide enough to accomodate for the bolded text and have the text center aligned.

(Note: It seems to be stripping out my html [below], but each menu item had a div tag wrapped around it with the corrasponding ID and the class name SearchBar_Cateogory. ie: <div id="ROS_SearchSermons" class="SearchBar_Category">

HTML (I had anchor tags wrapped around each menu item, but i wasn't able to submit them as a new user)

<div id="ROS_SearchSermons" class="SearchBar_Cateogry bold">Sermons</div>|
<div id="ROS_SearchIllustrations" class="SearchBar_Cateogry">Illustrations</div>|
<div id="ROS_SearchVideos" class="SearchBar_Cateogry">Videos</div>|
<div id="ROS_SearchPowerPoints" class="SearchBar_Cateogry">PowerPoints</div>|
<div id="ROS_SearchScripture" class="SearchBar_Cateogry">Scripture</div>|


#ROS_SearchSermons { width: 75px; }
#ROS_SearchIllustrations { width: 90px; }
#ROS_SearchVideos { width: 55px; }
#ROS_SearchPowerPoints { width: 90px; }
#ROS_SearchScripture { width: 70px; }

    display: inline-block;

How can I use an ES6 import in Node.js?

I just wanted to use the import and export in JavaScript files.

Everyone says it's not possible. But, as of May 2018, it's possible to use above in plain Node.js, without any modules like Babel, etc.

Here is a simple way to do it.

Create the below files, run, and see the output for yourself.

Also don't forget to see Explanation below.

File myfile.mjs

function myFunc() {
    console.log("Hello from myFunc")

export default myFunc;

File index.mjs

import myFunc from "./myfile.mjs"  // Simply using "./myfile" may not work in all resolvers



node  --experimental-modules  index.mjs


(node:12020) ExperimentalWarning: The ESM module loader is experimental.

Hello from myFunc


  1. Since it is experimental modules, .js files are named .mjs files
  2. While running you will add --experimental-modules to the node index.mjs
  3. While running with experimental modules in the output you will see: "(node:12020) ExperimentalWarning: The ESM module loader is experimental. "
  4. I have the current release of Node.js, so if I run node --version, it gives me "v10.3.0", though the LTE/stable/recommended version is 8.11.2 LTS.
  5. Someday in the future, you could use .js instead of .mjs, as the features become stable instead of Experimental.
  6. More on experimental features, see:

How to run Tensorflow on CPU

You could use tf.config.set_visible_devices. One possible function that allows you to set if and which GPUs to use is:

import tensorflow as tf

def set_gpu(gpu_ids_list):
    gpus = tf.config.list_physical_devices('GPU')
    if gpus:
            gpus_used = [gpus[i] for i in gpu_ids_list]
            tf.config.set_visible_devices(gpus_used, 'GPU')
            logical_gpus = tf.config.experimental.list_logical_devices('GPU')
            print(len(gpus), "Physical GPUs,", len(logical_gpus), "Logical GPU")
        except RuntimeError as e:
            # Visible devices must be set before GPUs have been initialized

Suppose you are on a system with 4 GPUs and you want to use only two GPUs, the one with id = 0 and the one with id = 2, then the first command of your code, immediately after importing the libraries, would be:

set_gpu([0, 2])

In your case, to use only the CPU, you can invoke the function with an empty list:


For completeness, if you want to avoid that the runtime initialization will allocate all memory on the device, you can use tf.config.experimental.set_memory_growth. Finally, the function to manage which devices to use, occupying the GPUs memory dynamically, becomes:

import tensorflow as tf

def set_gpu(gpu_ids_list):
    gpus = tf.config.list_physical_devices('GPU')
    if gpus:
            gpus_used = [gpus[i] for i in gpu_ids_list]
            tf.config.set_visible_devices(gpus_used, 'GPU')
            for gpu in gpus_used:
                tf.config.experimental.set_memory_growth(gpu, True)
            logical_gpus = tf.config.experimental.list_logical_devices('GPU')
            print(len(gpus), "Physical GPUs,", len(logical_gpus), "Logical GPU")
        except RuntimeError as e:
            # Visible devices must be set before GPUs have been initialized

How to set socket timeout in C when making multiple connections?

am not sure if I fully understand the issue, but guess it's related to the one I had, am using Qt with TCP socket communication, all non-blocking, both Windows and Linux..

wanted to get a quick notification when an already connected client failed or completely disappeared, and not waiting the default 900+ seconds until the disconnect signal got raised. The trick to get this working was to set the TCP_USER_TIMEOUT socket option of the SOL_TCP layer to the required value, given in milliseconds.

this is a comparably new option, pls see, but apparently it's working fine, tried it with WinXP, Win7/x64 and Kubuntu 12.04/x64, my choice of 10 s turned out to be a bit longer, but much better than anything else I've tried before ;-)

the only issue I came across was to find the proper includes, as apparently this isn't added to the standard socket includes (yet..), so finally I defined them myself as follows:

#ifdef WIN32
    #include <winsock2.h>
    #include <sys/socket.h>

#ifndef SOL_TCP
    #define SOL_TCP 6  // socket options TCP level
    #define TCP_USER_TIMEOUT 18  // how long for loss retry before timeout [ms]

setting this socket option only works when the client is already connected, the lines of code look like:

int timeout = 10000;  // user timeout in milliseconds [ms]
setsockopt (fd, SOL_TCP, TCP_USER_TIMEOUT, (char*) &timeout, sizeof (timeout));

and the failure of an initial connect is caught by a timer started when calling connect(), as there will be no signal of Qt for this, the connect signal will no be raised, as there will be no connection, and the disconnect signal will also not be raised, as there hasn't been a connection yet..

How to get selected path and name of the file opened with file dialog?

To extract only the filename from the path, you can do the following:

varFileName = Mid(fDialog.SelectedItems(1), InStrRev(fDialog.SelectedItems(1), "\") + 1, Len(fDialog.SelectedItems(1)))

Where in an Eclipse workspace is the list of projects stored?

In Eclipse 3.3:

It's installed under your Eclipse workspace. Something like:


within your workspace folder.

Under that folder is one folder per project. There's a file in there called .location, but it's binary.

So it looks like you can't do what you want, without interacting w/ Eclipse programmatically.

intellij incorrectly saying no beans of type found for autowired repository

just add below two annotations to your POJO.

public class YourClass {

Add IIS 7 AppPool Identities as SQL Server Logons

The "IIS APPPOOL\AppPoolName" will work, but as mentioned previously, it does not appear to be a valid AD name so when you search for it in the "Select User or Group" dialog box, it won't show up (actually, it will find it, but it will think its an actual system account, and it will try to treat it as such...which won't work, and will give you the error message about it not being found).

How I've gotten it to work is:

  1. In SQL Server Management Studio, look for the Security folder (the security folder at the same level as the Databases, Server Objects, etc. folders...not the security folder within each individual database)
  2. Right click logins and select "New Login"
  3. In the Login name field, type IIS APPPOOL\YourAppPoolName - do not click search
  4. Fill whatever other values you like (i.e., authentication type, default database, etc.)
  5. Click OK

As long as the AppPool name actually exists, the login should now be created.

How can I generate an MD5 hash?

Take a look at the following link, the Example gets an MD5 Hash of a supplied image: MD5 Hash of an Image

javascript create empty array of a given size

You can use both javascript methods repeat() and split() together.

" ".repeat(10).split(" ")

This code will create an array that has 10 item and each item is empty string.

const items = " ".repeat(10).split(" ")

document.getElementById("context").innerHTML =, index) => index)

console.log("items: ", items)
<pre id="context">


How to display a PDF via Android web browser without "downloading" first

I needed this too, and the links above stopped working so this is what I found to work with the New Google Drive:

Google has a service that creates the link for PDF's Not in GDrive: Just add your URL and it creates a link, and IFrame code (Look closely and you will see the pattern and create links without this web service)

Also, there is a way to do it for PDF's stored in Google Drive: (this can be a link or the src URL of an iframe)

I've tested on Android and it brings up the PDF viewer nicely.

How can I assign the output of a function to a variable using bash?


Exactly the same way as for programs.

mvn command is not recognized as an internal or external command

For me it was not working since I was editing Path variable in "User variable" and adding it under "System variable" made it work. Hope it helps.

How do I execute a program from Python? os.system fails due to spaces in path

I suspect it's the same problem as when you use shortcuts in Windows... Try this:

import os;
os.system("\"C:\\Temp\\a b c\\Notepad.exe\" C:\\test.txt");

How to get the index with the key in Python dictionary?

No, there is no straightforward way because Python dictionaries do not have a set ordering.

From the documentation:

Keys and values are listed in an arbitrary order which is non-random, varies across Python implementations, and depends on the dictionary’s history of insertions and deletions.

In other words, the 'index' of b depends entirely on what was inserted into and deleted from the mapping before:

>>> map={}
>>> map['b']=1
>>> map
{'b': 1}
>>> map['a']=1
>>> map
{'a': 1, 'b': 1}
>>> map['c']=1
>>> map
{'a': 1, 'c': 1, 'b': 1}

As of Python 2.7, you could use the collections.OrderedDict() type instead, if insertion order is important to your application.

Remove unused imports in Android Studio

Since Android Studio 3+, this can be done by open the option "Optimize imports".

Alt+Enter the select "Optimize imports".

enter image description here

This must be enough to removed the unused imports.

enter image description here

How can I get the value of a registry key from within a batch script?

@echo off
set KEY_NAME=HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\awhost32.exe
for /F "usebackq tokens=3" %%A IN (`reg query "%KEY_NAME%" /v "%VALUE_NAME%" 2^>nul ^| find "%VALUE_NAME%"`) do (
  echo %%A

How do you handle a space in the %%A variable? This results in C:\Program. The actual path is C:\Program Files\Symantec\pcAnywhere.

How to check file MIME type with javascript before upload?

As stated in other answers, you can check the mime type by checking the signature of the file in the first bytes of the file.

But what other answers are doing is loading the entire file in memory in order to check the signature, which is very wasteful and could easily freeze your browser if you select a big file by accident or not.

 * Load the mime type based on the signature of the first bytes of the file_x000D_
 * @param  {File}   file        A instance of File_x000D_
 * @param  {Function} callback  Callback with the result_x000D_
 * @author Victor www.vitim.us_x000D_
 * @date   2017-03-23_x000D_
function loadMime(file, callback) {_x000D_
    //List of known mimes_x000D_
    var mimes = [_x000D_
            mime: 'image/jpeg',_x000D_
            pattern: [0xFF, 0xD8, 0xFF],_x000D_
            mask: [0xFF, 0xFF, 0xFF],_x000D_
            mime: 'image/png',_x000D_
            pattern: [0x89, 0x50, 0x4E, 0x47],_x000D_
            mask: [0xFF, 0xFF, 0xFF, 0xFF],_x000D_
        // you can expand this list @see
    function check(bytes, mime) {_x000D_
        for (var i = 0, l = mime.mask.length; i < l; ++i) {_x000D_
            if ((bytes[i] & mime.mask[i]) - mime.pattern[i] !== 0) {_x000D_
                return false;_x000D_
        return true;_x000D_
    var blob = file.slice(0, 4); //read the first 4 bytes of the file_x000D_
    var reader = new FileReader();_x000D_
    reader.onloadend = function(e) {_x000D_
        if ( === FileReader.DONE) {_x000D_
            var bytes = new Uint8Array(;_x000D_
            for (var i=0, l = mimes.length; i<l; ++i) {_x000D_
                if (check(bytes, mimes[i])) return callback("Mime: " + mimes[i].mime + " <br> Browser:" + file.type);_x000D_
            return callback("Mime: unknown <br> Browser:" + file.type);_x000D_
//when selecting a file on the input_x000D_
fileInput.onchange = function() {_x000D_
    loadMime(fileInput.files[0], function(mime) {_x000D_
        //print the output to the screen_x000D_
        output.innerHTML = mime;_x000D_
<input type="file" id="fileInput">_x000D_
<div id="output"></div>

How To Auto-Format / Indent XML/HTML in Notepad++

It's been the third time that I install Windows and npp and after some time I realize the tidy function no longer work. So I google for a solution, come to this thread, then with the help of few more so threads I finally fix it. I'll put a summary of all my actions once and for all.

  1. Install TextFX plugin: Plugins -> Plugin Manager -> Show Plugin Manager. Select TextFX Characters and install. After a restart of npp, the menu 'TextFX' should be visible. (credits: @remipod).

  2. Install libtidy.dll by pasting the Config folder from an old npp package: Follow instructions in this answer.

  3. After having a Config folder in your latest npp installation destination (typically C:\Program Files (x86)\Notepad++\plugins), npp needs write access to that folder. Right click Config folder -> Properties -> Security tab -> select Users, click Edit -> check Full control to allow read/write access. Note that you need administrator privileges to do that.

  4. Restart npp and verify TextFX -> TextFX HTML Tidy -> Tidy: Reindent XML works.

The difference between "require(x)" and "import x"

Let me give an example for Including express module with require & import


var express = require('express');


import * as  express from 'express';

So after using any of the above statement we will have a variable called as 'express' with us. Now we can define 'app' variable as,

var app = express(); 

So we use 'require' with 'CommonJS' and 'import' with 'ES6'.

For more info on 'require' & 'import', read through below links.

require - Requiring modules in Node.js: Everything you need to know

import - An Update on ES6 Modules in Node.js

How do I run Google Chrome as root?

I tried this with Kali linux, Debian, CentOs 7,And Ubuntu

(Permanent Method)

  1. Edit the file with any text editor (I used Leafpad) Run this code your terminal leafpad/opt/google/chrome/google-chrome

  2. (Normally its end line) find exec -a "$0" "$HERE/chrome" "$@" or exec -a "$0" "$HERE/chrome" "$PROFILE_DIRECTORY_FLAG" \ "$@"

  3. change as exec -a "$0" "$HERE/chrome" "$@" --no-sandbox --user-data-dir

(Just Simple Method)

Run This command in your terminal

$ google-chrome --no-sandbox --user-data-dir


$ google-chrome-stable --no-sandbox --user-data-dir

Communication between tabs or windows

For those searching for a solution not based on jQuery, this is a plain JavaScript version of the solution provided by Thomas M:

window.addEventListener("storage", message_receive);

function message_broadcast(message) {

function message_receive(ev) {
    if (ev.key == 'message') {
        var message=JSON.parse(ev.newValue);

Best way to find the months between two dates

Get the ending month (relative to the year and month of the start month ex: 2011 January = 13 if your start date starts on 2010 Oct) and then generate the datetimes beginning the start month and that end month like so:

dt1, dt2 = dateRange
end_months=(dt2.year-dt1.year)*12 + dt2.month+1
dates=[datetime.datetime(year=yr, month=mn, day=1) for (yr, mn) in (
          ((m - 1) / 12 + dt1.year, (m - 1) % 12 + 1) for m in range(start_month, end_months)

if both dates are on the same year, it could also be simply written as:

dates=[datetime.datetime(year=dt1.year, month=mn, day=1) for mn in range(dt1.month, dt2.month + 1)]

Error : ORA-01704: string literal too long

What are you using when operate with CLOB?

In all events you can do it with PL/SQL

  str varchar2(32767);
  str := 'Very-very-...-very-very-very-very-very-very long string value';
  update t1 set col1 = str;

Proof link on SQLFiddle

How to add text to a WPF Label in code?

In normal winForms, value of Label object is changed by,

myLabel.Text= "Your desired string";

But in WPF Label control, you have to use .content property of Label control for example,

myLabel.Content= "Your desired string";

How can I split a shell command over multiple lines when using an IF statement?

For Windows/WSL/Cygwin etc users:

Make sure that your line endings are standard Unix line feeds, i.e. \n (LF) only.

Using Windows line endings \r\n (CRLF) line endings will break the command line break.

This is because having \ at the end of a line with Windows line ending translates to \ \r \n.
As Mark correctly explains above:

The line-continuation will fail if you have whitespace after the backslash and before the newline.

This includes not just space () or tabs (\t) but also the carriage return (\r).

Apache HttpClient Interim Error: NoHttpResponseException

Although accepted answer is right, but IMHO is just a workaround.

To be clear: it's a perfectly normal situation that a persistent connection may become stale. But unfortunately it's very bad when the HTTP client library cannot handle it properly.

Since this faulty behavior in Apache HttpClient was not fixed for many years, I definitely would prefer to switch to a library that can easily recover from a stale connection problem, e.g. OkHttp.


  1. OkHttp pools http connections by default.
  2. It gracefully recovers from situations when http connection becomes stale and request cannot be retried due to being not idempotent (e.g. POST). I cannot say it about Apache HttpClient (mentioned NoHttpResponseException).
  3. Supports HTTP/2.0 from early drafts and beta versions.

When I switched to OkHttp, my problems with NoHttpResponseException disappeared forever.

How to pull remote branch from somebody else's repo

The following is a nice expedient solution that works with GitHub for checking out the PR branch from another user's fork. You need to know the pull request ID (which GitHub displays along with the PR title).


Fixing your insecure code #8
alice wants to merge 1 commit into your_repo:master from her_repo:branch

git checkout -b <branch>
git pull origin pull/8/head

Substitute your remote if different from origin.
Substitute 8 with the correct pull request ID.

Get Wordpress Category from Single Post

How about get_the_category?

You can then do

$category = get_the_category();
$firstCategory = $category[0]->cat_name;

Compiler error: "class, interface, or enum expected"

Every method should be within a class. Your method derivativeQuiz is outside a class.

public class ClassName {

 ///your methods

Difference between logical addresses, and physical addresses?

  1. An address generated by the CPU is commonly referred to as a logical address. The set of all logical addresses generated by a program is known as logical address space. Whereas, an address seen by the memory unit- that is, the one loaded into the memory-address register of the memory- is commonly referred to as physical address. The set of all physical addresses corresponding to the logical addresses is known as physical address space.
  2. The compile-time and load-time address-binding methods generate identical logical and physical addresses. However, in the execution-time address-binding scheme, the logical and physical-address spaces differ.
  3. The user program never sees the physical addresses. The program creates a pointer to a logical address, say 346, stores it in memory, manipulate it, compares it to other logical addresses- all as the number 346. Only when a logical address is used as memory address, it is relocated relative to the base/relocation register. The memory-mapping hardware device called the memory- management unit(MMU) converts logical addresses into physical addresses.
  4. Logical addresses range from 0 to max. User program that generates logical address thinks that the process runs in locations 0 to max. Logical addresses must be mapped to physical addresses before they are used. Physical addresses range from (R+0) to (R + max) for a base/relocation register value R.
  5. Example: enter image description here Mapping from logical to physical addresses using memory management unit (MMU) and relocation/base register The value in relocation/base register is added to every logical address generated by a user process, at the time it is sent to memory, to generate corresponding physical address. In the above figure, base/ relocation value is 14000, then an attempt by the user to access the location 346 is mapped to 14346.

CSS: image link, change on hover

If you give generally give a span the property display:block, it'll then behave like a div, i.e you can set width and height.

You can also skip the div or span and just set the a the to display: block and apply the backgound style to it.

<a href="" class="myImage"><!----></a>

      .myImage {display: block; width: 160px; height: 20px; margin:0 0 10px 0; background: url(image.png) center top no-repeat;}

MySQL - Cannot add or update a child row: a foreign key constraint fails

Since you haven't given table definitions, it's hard to guess. But it looks like you are attempting to modify the foreign key in the child table. AFAIK, this is illegal, you can modify it from the parent, but not the child table.

Consider this example:

  parent_id INT NOT NULL,
  parent_data int,

  PRIMARY KEY (parent_id)

  child1_id INT,
  child1_data INT,
  fk_parent_id INT,

  INDEX par_ind1 (fk_parent_id),

  FOREIGN KEY (fk_parent_id)
    REFERENCES parent(parent_id)

  child2_id INT,
  child2_data INT,
  fk_parent_id INT,

  INDEX par_ind2 (fk_parent_id),

  FOREIGN KEY (fk_parent_id)
    REFERENCES parent(parent_id)

  (parent_id, parent_data)
  (1, 11),
  (2, 12);

  (child1_id, child1_data, fk_parent_id)
  (101, 1001, 1),
  (102, 1002, 1),
  (103, 1003, 1),
  (104, 1004, 2),
  (105, 1005, 2);

  (child2_id, child2_data, fk_parent_id)
  (106, 1006, 1),
  (107, 1007, 1),
  (108, 1008, 1),
  (109, 1009, 2),
  (110, 1010, 2);

Then this is allowed:

UPDATE parent
  SET parent_id = 3 WHERE parent_id = 2;

SELECT * FROM parent;
SELECT * FROM child1;
SELECT * FROM child2;

But this is not, because it modifies the parent fk from the child table:

UPDATE child1
  SET fk_parent_id = 4 WHERE fk_parent_id = 1;

It gets an error very similar to your error:

Cannot add or update a child row: a foreign key constraint fails (`db_2_b43a7`.`child1`, CONSTRAINT `child1_ibfk_1` FOREIGN KEY (`fk_parent_id`) REFERENCES `parent` (`parent_id`) ON DELETE CASCADE ON UPDATE CASCADE):

Nested Recycler view height doesn't wrap its content

Used solution from @sinan-kozak, except fixed a few bugs. Specifically, we shouldn't use View.MeasureSpec.UNSPECIFIED for both the width and height when calling measureScrapChild as that won't properly account for wrapped text in the child. Instead, we will pass through the width and height modes from the parent which will allow things to work for both horizontal and vertical layouts.

public class MyLinearLayoutManager extends LinearLayoutManager {

public MyLinearLayoutManager(Context context, int orientation, boolean reverseLayout)    {
    super(context, orientation, reverseLayout);

private int[] mMeasuredDimension = new int[2];

public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state,
                      int widthSpec, int heightSpec) {
    final int widthMode = View.MeasureSpec.getMode(widthSpec);
    final int heightMode = View.MeasureSpec.getMode(heightSpec);
    final int widthSize = View.MeasureSpec.getSize(widthSpec);
    final int heightSize = View.MeasureSpec.getSize(heightSpec);
    int width = 0;
    int height = 0;
    for (int i = 0; i < getItemCount(); i++) {    
        if (getOrientation() == HORIZONTAL) {
            measureScrapChild(recycler, i,
                View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED),
                View.MeasureSpec.makeMeasureSpec(heightSize, heightMode),

            width = width + mMeasuredDimension[0];
            if (i == 0) {
                height = mMeasuredDimension[1];
        } else {
            measureScrapChild(recycler, i,
                View.MeasureSpec.makeMeasureSpec(widthSize, widthMode),
                View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED),

            height = height + mMeasuredDimension[1];
            if (i == 0) {
                width = mMeasuredDimension[0];

    // If child view is more than screen size, there is no need to make it wrap content. We can use original onMeasure() so we can scroll view.
    if (height < heightSize && width < widthSize) {

        switch (widthMode) {
            case View.MeasureSpec.EXACTLY:
                width = widthSize;
            case View.MeasureSpec.AT_MOST:
            case View.MeasureSpec.UNSPECIFIED:

        switch (heightMode) {
            case View.MeasureSpec.EXACTLY:
                height = heightSize;
            case View.MeasureSpec.AT_MOST:
            case View.MeasureSpec.UNSPECIFIED:

        setMeasuredDimension(width, height);
    } else {
        super.onMeasure(recycler, state, widthSpec, heightSpec);

private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
                               int heightSpec, int[] measuredDimension) {

   View view = recycler.getViewForPosition(position);

   // For adding Item Decor Insets to view
   super.measureChildWithMargins(view, 0, 0);
    if (view != null) {
        RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();
        int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
                    getPaddingLeft() + getPaddingRight() + getDecoratedLeft(view) + getDecoratedRight(view), p.width);
            int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
                    getPaddingTop() + getPaddingBottom() + getDecoratedTop(view) + getDecoratedBottom(view) , p.height);
            view.measure(childWidthSpec, childHeightSpec);

            // Get decorated measurements
            measuredDimension[0] = getDecoratedMeasuredWidth(view) + p.leftMargin + p.rightMargin;
            measuredDimension[1] = getDecoratedMeasuredHeight(view) + p.bottomMargin + p.topMargin;


change pgsql port

You can also change the port when starting up:

$ pg_ctl -o "-F -p 5433" start


$ postgres -p 5433

More about this in the manual.

How do I set a fixed background image for a PHP file?

You should consider have other php files included if you're going to derive a website from it. Instead of doing all the css/etc in that file, you can do

    <?php include_once('C:\Users\George\Documents\HTML\style.css'); ?>

Then you can have a separate CSS file that is just being pulled into your php file. It provides some "neater" coding.

CSS rule to apply only if element has BOTH classes

Below applies to all tags with the following two classes {  
  width: 200px !important;

applies to div tags with the following two classes {  
  width: 200px !important;

If you wanted to modify this using jQuery

$(document).ready(function() {

How to make a JTable non-editable

If you are creating the TableModel automatically from a set of values (with "new JTable(Vector, Vector)"), perhaps it is easier to remove editors from columns:

JTable table = new JTable(my_rows, my_header);

for (int c = 0; c < table.getColumnCount(); c++)
    Class<?> col_class = table.getColumnClass(c);
    table.setDefaultEditor(col_class, null);        // remove editor

Without editors, data will be not editable.

How to create a DB link between two oracle instances

Create database link NAME connect to USERNAME identified by PASSWORD using 'SID';

Specify SHARED to use a single network connection to create a public database link that can be shared among multiple users. If you specify SHARED, you must also specify the dblink_authentication clause.

Specify PUBLIC to create a public database link available to all users. If you omit this clause, the database link is private and is available only to you.

How do I open phone settings when a button is clicked?

App-Prefs:root=Privacy&path=LOCATION worked for me for getting to general location settings. Note: only works on a device.

explicit casting from super class to subclass

The code generates a compilation error because your instance type is an Animal:

Animal animal=new Animal();

Downcasting is not allowed in Java for several reasons. See here for details.

What's the difference between implementation and compile in Gradle?


Just replace:

  • compile with implementation (if you don't need transitivity) or api (if you need transitivity)
  • testCompile with testImplementation
  • debugCompile with debugImplementation
  • androidTestCompile with androidTestImplementation
  • compileOnly is still valid. It was added in 3.0 to replace provided and not compile. (provided introduced when Gradle didn't have a configuration name for that use-case and named it after Maven's provided scope.)

It is one of the breaking changes coming with Android Gradle plugin 3.0 that Google announced at IO17.

The compile configuration is now deprecated and should be replaced by implementation or api

From the Gradle documentation:

dependencies {
    api 'commons-httpclient:commons-httpclient:3.1'
    implementation 'org.apache.commons:commons-lang3:3.5'

Dependencies appearing in the api configurations will be transitively exposed to consumers of the library, and as such will appear on the compile classpath of consumers.

Dependencies found in the implementation configuration will, on the other hand, not be exposed to consumers, and therefore not leak into the consumers' compile classpath. This comes with several benefits:

  • dependencies do not leak into the compile classpath of consumers anymore, so you will never accidentally depend on a transitive dependency
  • faster compilation thanks to reduced classpath size
  • less recompilations when implementation dependencies change: consumers would not need to be recompiled
  • cleaner publishing: when used in conjunction with the new maven-publish plugin, Java libraries produce POM files that distinguish exactly between what is required to compile against the library and what is required to use the library at runtime (in other words, don't mix what is needed to compile the library itself and what is needed to compile against the library).

The compile configuration still exists, but should not be used as it will not offer the guarantees that the api and implementation configurations provide.

Note: if you are only using a library in your app module -the common case- you won't notice any difference.
you will only see the difference if you have a complex project with modules depending on each other, or you are creating a library.

Redirecting from cshtml page

You can go to method of same controller..using this line , and if you want to pass some parameters to that action it can be done by writing inside ( new { } ).. Note:- you can add as many parameter as required.

@Html.ActionLink("MethodName", new { parameter = Model.parameter })

Java generating non-repeating random numbers

How about this?

LinkedHashSet<Integer> test = new LinkedHashSet<Integer>();
Random random = new Random();
    test.add(random.nextInt(1000) + 1);
}while(test.size() != 1000);

The user can then iterate through the Set using a for loop.

Master Page Weirdness - "Content controls have to be top-level controls in a content page or a nested master page that references a master page."

I encountered this error after editing a web part (.aspx) page in SharePoint Designer 2013. When I looked at the code in SPD, an H1 element near the top of the page was highlighted yellow. Hovering over that indicated that SharePoint:AjaxDelta was not closed before the H1. Adding the </SharePoint:AjaxDelta> fixed it.

Weird because it appeared SPD introduced the error after I was working on listview web parts or a page viewer web part elsewhere on the page.

How do I align a label and a textarea?

  1. Set the height of your label to the same height as the multiline textbox.
  2. Add the cssClass .alignTop{vertical-align: middle;} for the label control.

        <asp:Label ID="DescriptionLabel" runat="server" Text="Description: " Width="70px" Height="200px" CssClass="alignTop"></asp:Label>
        <asp:Textbox id="DescriptionTextbox" runat="server" Width="400px" Height="200px" TextMode="MultiLine"></asp:Textbox>
        <asp:RequiredFieldValidator id="DescriptionRequiredFieldValidator" runat="server" ForeColor="Red"
        ControlToValidate="DescriptionTextbox" ErrorMessage="Description is a required field.">    

Change value of input and submit form in JavaScript

You're trying to access an element based on the name attribute which works for postbacks to the server, but JavaScript responds to the id attribute. Add an id with the same value as name and all should work fine.

<form name="myform" id="myform" action="action.php">
  <input type="hidden" name="myinput" id="myinput" value="0" />
  <input type="text" name="message" id="message" value="" />
  <input type="submit" name="submit" id="submit" onclick="DoSubmit()" />

function DoSubmit(){
  document.getElementById("myinput").value = '1';
  return true;

How to convert/parse from String to char in java?

 String string = "This is Yasir Shabbir ";
 for(char ch : string.toCharArray()){


or If you want individually then you can as

char ch = string.charAt(1);

Spring CORS No 'Access-Control-Allow-Origin' header is present

I have found the solution in spring boot by using @CrossOrigin annotation.

public class WebConfig extends WebMvcConfigurerAdapter {

    public void addCorsMappings(CorsRegistry registry) {

Handlebars/Mustache - Is there a built in way to loop through the properties of an object?

@Amit's answer is good because it will work in both Mustache and Handlebars.

As far as Handlebars-only solutions, I've seen a few and I like the each_with_key block helper at the best.

  • It allows you to iterate over object literals without having to restructure them first, and
  • It gives you control over what you call the key variable. With many other solutions you have to be careful about using object keys named 'key', or 'property', etc.

Run cron job only if it isn't already running

I do this for a print spooler program that I wrote, it's just a shell script:

if ps -ef | grep -v grep | grep doctype.php ; then
        exit 0
        /home/user/bin/doctype.php >> /home/user/bin/spooler.log &
        #mailing program
        /home/user/bin/simplemail.php "Print spooler was not running...  Restarted." 
        exit 0

It runs every two minutes and is quite effective. I have it email me with special information if for some reason the process is not running.

How to stick text to the bottom of the page?

Try this

 <style type ="text/css" >
       position: fixed;     
       text-align: center;    
       bottom: 0px; 
       width: 100%;
    <div class="footer">All Rights Reserved</div>

Array.size() vs Array.length

array.length isn't necessarily the number of items in the array:

var a = ['car1', 'car2', 'car3'];
a[100] = 'car100';
a.length; // 101

The length of the array is one more than the highest index.

As stated before Array.size() is not a valid method.

More information

SQL: Alias Column Name for Use in CASE Statement

Nor in MsSql

FROM Table1


Msg 207, Level 16, State 3, Line 1
Invalid column name 'o'.
Msg 207, Level 16, State 3, Line 1
Invalid column name 'o'.

However if I change to CASE WHEN col1... THEN col1 it works

How to set background color in jquery

You actually got it. Just forgot some quotes.

$(this).css({backgroundColor: 'red'});


$(this).css('background-color', 'red');

You don't need to pass over a map/object to set only one property. You can just put pass it as string. Note that if passing an object you cannot use a -. All CSS properties which have such a character are mapped with capital letters.

Reference: .css()

What is the 'dynamic' type in C# 4.0 used for?

The best use case of 'dynamic' type variables for me was when, recently, I was writing a data access layer in ADO.NET (using SQLDataReader) and the code was invoking the already written legacy stored procedures. There are hundreds of those legacy stored procedures containing bulk of the business logic. My data access layer needed to return some sort of structured data to the business logic layer, C# based, to do some manipulations (although there are almost none). Every stored procedures returns different set of data (table columns). So instead of creating dozens of classes or structs to hold the returned data and pass it to the BLL, I wrote the below code which looks quite elegant and neat.

public static dynamic GetSomeData(ParameterDTO dto)
            dynamic result = null;
            string SPName = "a_legacy_stored_procedure";
            using (SqlConnection connection = new SqlConnection(DataConnection.ConnectionString))
                SqlCommand command = new SqlCommand(SPName, connection);
                command.CommandType = System.Data.CommandType.StoredProcedure;                
                command.Parameters.Add(new SqlParameter("@empid", dto.EmpID));
                command.Parameters.Add(new SqlParameter("@deptid", dto.DeptID));
                using (SqlDataReader reader = command.ExecuteReader())
                    while (reader.Read())
                        dynamic row = new ExpandoObject();
                        row.EmpName = reader["EmpFullName"].ToString();
                        row.DeptName = reader["DeptName"].ToString();
                        row.AnotherColumn = reader["AnotherColumn"].ToString();                        
                        result = row;
            return result;

Edit and Continue: "Changes are not allowed when..."

I had this happen in a linked class file. The rest of the project allowed E&C, but I got the same error editing the linked file. Solution was to break linked file into it's own project and reference the project.

Spring mvc @PathVariable

suppose you want to write a url to fetch some order, you can say

where 123 is orderId.

So now the url you will use in spring mvc controller would look like


Now order id can be declared a path variable

@RequestMapping(value = " /order/{orderId}", method=RequestMethod.GET)
public String getOrder(@PathVariable String orderId){
//fetch order

if you use url, then orderId variable will be populated by value 123 by spring

Also note that PathVariable differs from requestParam as pathVariable is part of URL. The same url using request param would look like

Spring Official Reference

Angular JS: What is the need of the directive’s link function when we already had directive’s controller with scope?

Why controllers are needed

The difference between link and controller comes into play when you want to nest directives in your DOM and expose API functions from the parent directive to the nested ones.

From the docs:

Best Practice: use controller when you want to expose an API to other directives. Otherwise use link.

Say you want to have two directives my-form and my-text-input and you want my-text-input directive to appear only inside my-form and nowhere else.

In that case, you will say while defining the directive my-text-input that it requires a controller from the parent DOM element using the require argument, like this: require: '^myForm'. Now the controller from the parent element will be injected into the link function as the fourth argument, following $scope, element, attributes. You can call functions on that controller and communicate with the parent directive.

Moreover, if such a controller is not found, an error will be raised.

Why use link at all

There is no real need to use the link function if one is defining the controller since the $scope is available on the controller. Moreover, while defining both link and controller, one does need to be careful about the order of invocation of the two (controller is executed before).

However, in keeping with the Angular way, most DOM manipulation and 2-way binding using $watchers is usually done in the link function while the API for children and $scope manipulation is done in the controller. This is not a hard and fast rule, but doing so will make the code more modular and help in separation of concerns (controller will maintain the directive state and link function will maintain the DOM + outside bindings).

CodeIgniter -> Get current URL relative to base url

 //if you want to get parameter from url use:
 parse_str($_SERVER['QUERY_STRING'], $_GET);
 //then you can use:
      echo $_GET["par"];
 //if you want to get current page url use:
 $current_url = current_url();

Why does NULL = NULL evaluate to false in SQL server

If you are looking for an expression returning true for two NULLs you can use:


It is helpful if you want to replicate data from one table to another.

REST API Login Pattern

TL;DR Login for each request is not a required component to implement API security, authentication is.

It is hard to answer your question about login without talking about security in general. With some authentication schemes, there's no traditional login.

REST does not dictate any security rules, but the most common implementation in practice is OAuth with 3-way authentication (as you've mentioned in your question). There is no log-in per se, at least not with each API request. With 3-way auth, you just use tokens.

  1. User approves API client and grants permission to make requests in the form of a long-lived token
  2. Api client obtains a short-lived token by using the long-lived one.
  3. Api client sends the short-lived token with each request.

This scheme gives the user the option to revoke access at any time. Practially all publicly available RESTful APIs I've seen use OAuth to implement this.

I just don't think you should frame your problem (and question) in terms of login, but rather think about securing the API in general.

For further info on authentication of REST APIs in general, you can look at the following resources:

Tomcat 404 error: The origin server did not find a current representation for the target resource or is not willing to disclose that one exists

Problem solved, I've not added the index.html. Which is point out in the web.xml

enter image description here

Note: a project may have more than one web.xml file.

if there are another web.xml in


Then you might need to add another index (this time index.jsp) to


How to Install Windows Phone 8 SDK on Windows 7

Here is a link from wiki pages, which explains how to install Windows Phone 8 SDK on a Virtual Machine with Working Emulator

And another link here

AFAIK, it is not possible to directly install WP8 SDK in Windows 7, because WP8 sdk is VS 2012 supported and also its emulator works on a Hyper-V (which is integrated into the Windows 8).

Should functions return null or an empty object?

In our Business Objects we have 2 main Get methods:

To keep things simple in the context or you question they would be:

// Returns null if user does not exist
public UserEntity GetUserById(Guid userId)

// Returns a New User if user does not exist
public UserEntity GetNewOrExistingUserById(Guid userId)

The first method is used when getting specific entities, the second method is used specifically when adding or editing entities on web pages.

This enables us to have the best of both worlds in the context where they are used.

Output data from all columns in a dataframe in pandas

In ipython, I use this to print a part of the dataframe that works quite well (prints the first 100 rows):

print paramdata.head(100).to_string()

What does Java option -Xmx stand for?

see here: Java Tool Doc, it says,

Specify the maximum size, in bytes, of the memory allocation pool. This value must a multiple of 1024 greater than 2MB. Append the letter k or K to indicate kilobytes, or m or M to indicate megabytes. The default value is 64MB. The upper limit for this value will be approximately 4000m on Solaris 7 and Solaris 8 SPARC platforms and 2000m on Solaris 2.6 and x86 platforms, minus overhead amounts. Examples:


So, in simple words, you are setting Java heap memory to a maximum of 1024 MB from the available memory, not more.

Notice there is NO SPACE between -Xmx and 1024m

It does not matter if you use uppercase or lowercase. For example: "-Xmx10G" and "-Xmx10g" do the exact same thing.

Auto code completion on Eclipse

Go to Windows--> Preference--->Java--->content assist--->Enable auto activation---(insert ._@abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ in auto activation triggers for java)

Eclipse Preferences

Removing the remembered login and password list in SQL Server Management Studio

Another answer here also mentions since 2012 you can remove Remove cached login via How to remove cached server names from the Connect to Server dialog?. Just confirmed this delete in MRU list works fine in 2016 and 2017.

SQL Server Management Studio 2017 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\SQL Server Management Studio\14.0\SqlStudio.bin

SQL Server Management Studio 2016 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\SQL Server Management Studio\13.0\SqlStudio.bin

SQL Server Management Studio 2014 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\SQL Server Management Studio\12.0\SqlStudio.bin

SQL Server Management Studio 2012 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\SQL Server Management Studio\11.0\SqlStudio.bin

SQL Server Management Studio 2008 delete the file C:\Users\%username%\AppData\Roaming\Microsoft\Microsoft SQL Server\100\Tools\Shell\SqlStudio.bin

SQL Server Management Studio 2005 delete the file – same as above answer but the Vista path. C:\Users\%username%\AppData\Roaming\Microsoft\Microsoft SQL Server\90\Tools\Shell\mru.dat

These are profile paths for Vista / 7 / 8.


Note, AppData is a hidden folder. You need to show hidden folders in explorer.

EDIT: You can simply press delete from the Server / User name drop down (confirmed to be working for SSMS v18.0). Original source from which mentioned that this feature is available since 2012!

jquery find closest previous sibling with class



Tested it with your markup:


will fill up the closest previous li.par_cat with "woohoo".

How to convert JSON string to array

You can change a string to JSON as follows and you can also trim, strip on string if wanted,

$str     = '[{"id":1, "value":"Comfort Stretch"}]';
//here is JSON object
$filters = json_decode($str);

foreach($filters as $obj){
   $filter_id[] = $obj->id;

//here is your array from that JSON

getting error while updating Composer

This works for me with php 7.2

sudo apt-get install php7.2-xml

How to iterate over the files of a certain directory, in Java?

If you want to filter the list prior to iteration (or any more complicated use case), use apache-commons FileUtils. FileUtils.listFiles

Importing a function from a class in another file?


FILENAME is w/o the suffix

How to make an app's background image repeat

Here is a pure-java implementation of background image repeating:

public void onCreate(Bundle savedInstanceState) {
    Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.bg_image);
    BitmapDrawable bitmapDrawable = new BitmapDrawable(bmp);
    bitmapDrawable.setTileModeXY(Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
    LinearLayout layout = new LinearLayout(this);

In this case, our background image would have to be stored in res/drawable/bg_image.png.

cmake and libpthread

The following should be clean (using find_package) and work (the find module is called FindThreads):

cmake_minimum_required (VERSION 2.6) 
find_package (Threads)
add_executable (myapp main.cpp ...)
target_link_libraries (myapp ${CMAKE_THREAD_LIBS_INIT})

How to auto adjust the div size for all mobile / tablet display formats?

You question is a bit unclear as to what you want, but judging from your comments, I assume you want each bubble to cover the screen, both vertically and horizontally. In that case, the vertical part is the tricky part.

As many others have answered, you first need to make sure that you are setting the viewport meta tag to trigger mobile devices to use their "ideal" viewport instead of the emulated "desktop width" viewport. The easiest and most fool proof version of this tag is as follows:

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

Source: PPK, probably the leading expert on how this stuff works. (See

Essentially, the above makes sure that media queries and CSS measurements correspond to the ideal display of a virtual "point" on any given device — instead of shrinking pages to work with non-optimized desktop layouts. You don't need to understand the details of it, but it's important.

Now that we have a correct (non-faked) mobile viewport to work with, adjusting to the height of the viewport is still a tricky subject. Generally, web pages are fine to expand vertically, but not horizontally. So when you set height: 100% on something, that measurement has to relate to something else. At the topmost level, this is the size of the HTML element. But when the HTML element is taller than the screen (and expands to contain the contents), your measurements in percentages will be screwed up.

Enter the vh unit: it works like percentages, but works in relation to the viewport, not the containing block. MDN info page here:

Using that unit works just like you'd expect:

.bubble { height: 100vh; } /* be as tall as the viewport height. Done. */

It works on a lot of browsers (IE9 and up, modern Firefox, Safari, Chrome, Opera etc) but not all (support info here: The downside in the browsers where it does work is that there is a massive bug in iOS6-7 that makes this technique unusable for this very case (details here: It will be fixed in iOS8 though.

Depending on the HTML structure of your project, you may get away with using height: 100% on each element that is supposed to be as tall as the screen, as long as the following conditions are met:

  1. The element is a direct child element of <body>.
  2. Both the html and body elements have a 100% height set.

I have used that technique in the past, but it was long ago and I'm not sure it works on most mobile devices. Try it and see.

The next choice is to use a JavaScript helper to resize your elements to fit the viewport. Either a polyfill fixing the vh issues or something else altogether. Sadly, not every layout is doable in CSS.

Why not use tables for layout in HTML?

CSS layouts are generally much better for accessibility, provided the content comes in a natural order and makes sense without a stylesheet. And it's not just screen readers that struggle with table-based layouts: they also make it much harder for mobile browsers to render a page properly.

Also, with a div-based layout you can very easily do cool things with a print stylesheet such as excluding headers, footers and navigation from printed pages - I think it would be impossible, or at least much more difficult, to do that with a table-based layout.

If you're doubting that separation of content from layout is easier with divs than with tables, take a look at the div-based HTML at CSS Zen Garden, see how changing the stylesheets can drastically change the layout, and think about whether you could achieve the same variety of layouts if the HTML was table based... If you're doing a table-based layout, you're unlikely to be using CSS to control all the spacing and padding in the cells (if you were, you'd almost certainly find it easier to use floating divs etc. in the first place). Without using CSS to control all that, and because of the fact that tables specify the left-to-right and top-to bottom order of things in the HTML, tables tend to mean that your layout becomes very much fixed in the HTML.

Realistically I think it's very hard to completely change the layout of a div-and-CSS-based design without changing the divs a bit. However, with a div-and-CSS-based layout it's much easier to tweak things like the spacing between various blocks, and their relative sizes.

How can I use jQuery to make an input readonly?

There are two attributes, namely readonly and disabled, that can make a semi-read-only input. But there is a tiny difference between them.

<input type="text" readonly />
<input type="text" disabled />
  • The readonly attribute makes your input text disabled, and users are not able to change it anymore.
  • Not only will the disabled attribute make your input-text disabled(unchangeable) but also cannot it be submitted.

jQuery approach (1):

$("#inputID").prop("readonly", true);
$("#inputID").prop("disabled", true);

jQuery approach (2):

$("#inputID").attr("disabled", "disabled");

JavaScript approach:

document.getElementById("inputID").readOnly = true;
document.getElementById("inputID").disabled = true;

PS prop introduced with jQuery 1.6.

How to close jQuery Dialog within the dialog?


Simple, I like to make sure I don't:

  1. hardcode dialog #id values.
  2. Close all dialogs.

How to call an element in a numpy array?

Just use square brackets instead:

print arr[1,1]

Sum values in foreach loop php

foreach($group as $key=>$value)
   echo $key. " = " .$value. "<br>"; 
   $total+= $value;
echo $total;

What is the difference between prefix and postfix operators?

First, note that the function parameter named i and the variable named i in main() are two different variables. I think that doesn't matter that much to the present discussion, but it's important to know.

Second, you use the postincrement operator in fun(). That means the result of the expression is the value before i is incremented; the final value 11 of i is simply discarded, and the function returns 10. The variable i back in main, being a different variable, is assigned the value 10, which you then decrement to get 9.

(Excel) Conditional Formatting based on Adjacent Cell Value

I don't know if maybe it's a difference in Excel version but this question is 6 years old and the accepted answer didn't help me so this is what I figured out:

Under Conditional Formatting > Manage Rules:

  1. Make a new rule with "Use a formula to determine which cells to format"
  2. Make your rule, but put a dollar sign only in front of the letter: $A2<$B2
  3. Under "Applies to", Manually select the second column (It would not work for me if I changed the value in the box, it just kept snapping back to what was already there), so it looks like $B$2:$B$100 (assuming you have 100 rows)

This worked for me in Excel 2016.

Changing cell color using apache poi

Short version: Create styles only once, use them everywhere.

Long version: use a method to create the styles you need (beware of the limit on the amount of styles).

private static Map<String, CellStyle> styles;

private static Map<String, CellStyle> createStyles(Workbook wb){
        Map<String, CellStyle> styles = new HashMap<String, CellStyle>();
        DataFormat df = wb.createDataFormat();

        CellStyle style;
        Font headerFont = wb.createFont();
        headerFont.setFontHeightInPoints((short) 12);
        style = createBorderedStyle(wb);
        styles.put("style1", style);

        style = createBorderedStyle(wb);
        styles.put("date_style", style);
        return styles;

you can also use methods to do repetitive tasks while creating styles hashmap

private static CellStyle createBorderedStyle(Workbook wb) {
        CellStyle style = wb.createCellStyle();
        return style;

then, in your "main" code, set the style from the styles map you have.

Cell cell = xssfCurrentRow.createCell( intCellPosition );       
cell.setCellValue( blah );
cell.setCellStyle( (CellStyle) styles.get("style1") );

C#: How to add subitems in ListView



to the last line of your code so it will look like this in the end.


How to get current foreground activity context in android?

getCurrentActivity() is also in ReactContextBaseJavaModule.
(Since the this question was initially asked, many Android app also has ReactNative component - hybrid app.)

class ReactContext in ReactNative has the whole set of logic to maintain mCurrentActivity which is returned in getCurrentActivity().

Note: I wish getCurrentActivity() is implemented in Android Application class.

MySQL OPTIMIZE all tables?

From command line:

mysqlcheck -o <db_name> -u<username> -p

then type password

How to set environment variables in PyCharm?

This functionality has been added to the IDE now (working Pycharm 2018.3)

Just click the EnvFile tab in the run configuration, click Enable EnvFile and click the + icon to add an env file

Example with the glorious material theme

Update: Essentially the same as the answer by @imguelvargasf but the the plugin was enabled by default for me.

Delete rows containing specific strings in R

This should do the trick:

df[- grep("REVERSE", df$Name),]

Or a safer version would be:

df[!grepl("REVERSE", df$Name),]

How can I run an EXE program from a Windows Service using C#?

You can execute an .exe from a Windows service very well in Windows XP. I have done it myself in the past.

You need to make sure you had checked the option "Allow to interact with the Desktop" in the Windows service properties. If that is not done, it will not execute.

I need to check in Windows 7 or Vista as these versions requires additional security privileges so it may throw an error, but I am quite sure it can be achieved either directly or indirectly. For XP I am certain as I had done it myself.

How do I format a number in Java?

As Robert has pointed out in his answer: DecimalFormat is neither synchronized nor does the API guarantee thread safety (it might depend on the JVM version/vendor you are using).

Use Spring's Numberformatter instead, which is thread safe.

Run react-native application on iOS device directly from command line?

Actually, For the first build, please do it with Xcode and then do the following way:

  1. brew install ios-deploy
  2. npx react-native run-ios --device

The second command will run the app on the first connected device.

CSS: how to get scrollbars for div inside container of fixed height

FWIW, here is my approach = a simple one that works for me:

<div id="outerDivWrapper">
   <div id="outerDiv">
      <div id="scrollableContent">
blah blah blah

html, body {
   height: 100%;
   margin: 0em;

#outerDivWrapper, #outerDiv {
   height: 100%;
   margin: 0em;

#scrollableContent {
   height: 100%;
   margin: 0em;
   overflow-y: auto;

Postgresql column reference "id" is ambiguous

I suppose your p2vg table has also an id field , in that case , postgres cannot find if the id in the SELECT refers to vg or p2vg.

you should use SELECT(, to remove ambiguity

Github Windows 'Failed to sync this branch'

The debug log may provide some insight. I'm using v3.3.4.0, your experience may differ but should be similar. From the settings menu choose 'About Github Desktop...'. Click the link to view the debug log. In my case there was a very clear error:

*** fatal error - cygheap base mismatch detected - 0x1157408/0x1167408. This problem is probably due to using incompatible versions of the cygwin DLL.

It even provided some helpful tips to solve the problem.

I'm not sure why this information isn't exposed in the error prompt, but at least it was available.

Function to calculate distance between two coordinates

I try to make the code a little bit understandable by naming the variables, I hope this can help

function getDistanceFromLatLonInKm(point1, point2) {

  const [lat1, lon1] = point1;
  const [lat2, lon2] = point2;
  const earthRadius = 6371;
  const dLat = convertDegToRad(lat2 - lat1);
  const dLon = convertDegToRad(lon2 - lon1);
  const squarehalfChordLength =
    Math.sin(dLat / 2) * Math.sin(dLat / 2) +
    Math.cos(convertDegToRad(lat1)) * Math.cos(convertDegToRad(lat2)) *
    Math.sin(dLon / 2) * Math.sin(dLon / 2);

  const angularDistance = 2 * Math.atan2(Math.sqrt(squarehalfChordLength), Math.sqrt(1 - squarehalfChordLength));
  const distance = earthRadius * angularDistance;
  return distance;


Add data to JSONObject

In order to have this result:


that holds the same data as:

    "aoColumnDefs": [
     { "aDataSort": [ 0, 1 ], "aTargets": [ 0 ] },
     { "aDataSort": [ 1, 0 ], "aTargets": [ 1 ] },
     { "aDataSort": [ 2, 3, 4 ], "aTargets": [ 2 ] }

you could use this code:

    JSONObject jo = new JSONObject();
    Collection<JSONObject> items = new ArrayList<JSONObject>();

    JSONObject item1 = new JSONObject();
    item1.put("aDataSort", new JSONArray(0, 1));
    item1.put("aTargets", new JSONArray(0));
    JSONObject item2 = new JSONObject();
    item2.put("aDataSort", new JSONArray(1, 0));
    item2.put("aTargets", new JSONArray(1));
    JSONObject item3 = new JSONObject();
    item3.put("aDataSort", new JSONArray(2, 3, 4));
    item3.put("aTargets", new JSONArray(2));

    jo.put("aoColumnDefs", new JSONArray(items));


How can I get the height and width of an uiimage?

UIImage *img = [UIImage imageNamed:@"logo.png"];

CGFloat width = img.size.width;
CGFloat height = img.size.height;

Typescript Type 'string' is not assignable to type

I see this is a little old, but there might be a better solution here.

When you want a string, but you want the string to only match certain values, you can use enums.

For example:

enum Fruit {
    Orange = "Orange",
    Apple  = "Apple",
    Banana = "Banana"

let myFruit: Fruit = Fruit.Banana;

Now you'll know that no matter what, myFruit will always be the string "Banana" (Or whatever other enumerable value you choose). This is useful for many things, whether it be grouping similar values like this, or mapping user-friendly values to machine-friendly values, all while enforcing and restricting the values the compiler will allow.

Best way to work with transactions in MS SQL Server Management Studio

The easisest thing to do is to wrap your code in a transaction, and then execute each batch of T-SQL code line by line.

For example,

Begin Transaction

         -Do some T-SQL queries here.

Rollback transaction -- OR commit transaction

If you want to incorporate error handling you can do so by using a TRY...CATCH BLOCK. Should an error occur you can then rollback the tranasction within the catch block.

For example:

USE AdventureWorks;

    -- Generate a constraint violation error.
    DELETE FROM Production.Product
    WHERE ProductID = 980;
        ERROR_NUMBER() AS ErrorNumber
        ,ERROR_SEVERITY() AS ErrorSeverity
        ,ERROR_STATE() AS ErrorState
        ,ERROR_PROCEDURE() AS ErrorProcedure
        ,ERROR_LINE() AS ErrorLine
        ,ERROR_MESSAGE() AS ErrorMessage;

    IF @@TRANCOUNT > 0


See the following link for more details.

Hope this helps but please let me know if you need more details.

Insert if not exists Oracle

The statement is called MERGE. Look it up, I'm too lazy.

Beware, though, that MERGE is not atomic, which could cause the following effect (thanks, Marius):


create table t1 (pk int primary key, i int);
create table t11 (pk int primary key, i int);
insert into t1 values(1, 1);
insert into t11 values(2, 21);
insert into t11 values(3, 31);

SESS2: insert into t1 values(2, 2);


USING t11 s ON ( =

SESS2: commit;

SESS1: ORA-00001

Programmatically change the src of an img tag

Maybe because you have a tag like a parent of the tag. That why you have to click two time the images.

For me the solution is this:

How to get memory usage at runtime using C++?

in additional to your way
you could call system ps command and get memory usage from it output.
or read info from /proc/pid ( see PIOCPSINFO struct )

mkdir -p functionality in Python

import os
import tempfile

path = tempfile.mktemp(dir=path)

How to set opacity to the background color of a div?

I would say that the easiest way is to use transparent background image.

background: url("") repeat top left;

convert base64 to image in javascript/jquery

Have to add this based on @Joseph's answer. If someone want to create image object:

var image = new Image();
image.onload = function(){
   console.log(image.width); // image is loaded and we have image width 
image.src = 'data:image/png;base64,iVBORw0K...';

Does MySQL ignore null values on unique constraints?

A simple answer would be : No, it doesn't

Explanation : According to the definition of unique constraints (SQL-92)

A unique constraint is satisfied if and only if no two rows in a table have the same non-null values in the unique columns

This statement can have two interpretations as :

  • No two rows can have same values i.e. NULL and NULL is not allowed
  • No two non-null rows can have values i.e NULL and NULL is fine, but StackOverflow and StackOverflow is not allowed

Since MySQL follows second interpretation, multiple NULL values are allowed in UNIQUE constraint column. Second, if you would try to understand the concept of NULL in SQL, you will find that two NULL values can be compared at all since NULL in SQL refers to unavailable or unassigned value (you can't compare nothing with nothing). Now, if you are not allowing multiple NULL values in UNIQUE constraint column, you are contracting the meaning of NULL in SQL. I would summarise my answer by saying :

MySQL supports UNIQUE constraint but not on the cost of ignoring NULL values

Returning http status code from Web Api controller

In MVC 5, things got easier:

return new StatusCodeResult(HttpStatusCode.NotModified, this);

How to generate range of numbers from 0 to n in ES2015 only?

This function will return an integer sequence.

const integerRange = (start, end, n = start, arr = []) =>
  (n === end) ? [...arr, n]
    : integerRange(start, end, start < end ? n + 1 : n - 1, [...arr, n]);

$> integerRange(1, 1)
<- Array [ 1 ]

$> integerRange(1, 3)
<- Array(3) [ 1, 2, 3 ]

$> integerRange(3, -3)
<- Array(7) [ 3, 2, 1, 0, -1, -2, -3 ]

geom_smooth() what are the methods available?

The se argument from the example also isn't in the help or online documentation.

When 'se' in geom_smooth is set 'FALSE', the error shading region is not visible

grep output to show only matching file

You can use the Unix-style -l switch – typically terse and cryptic – or the equivalent --files-with-matches – longer and more readable.

The output of grep --help is not easy to read, but it's there:

-l, --files-with-matches  print only names of FILEs containing matches

Recursive mkdir() system call on Unix

Apparently not, my two suggestions are:

char dirpath[80] = "/path/to/some/directory";
sprintf(mkcmd, "mkdir -p %s", dirpath);

Or if you don't want to use system() try looking at the coreutils mkdir source code and see how they implemented the -p option.

Error: "dictionary update sequence element #0 has length 1; 2 is required" on Django 1.4

You are sending one parameter incorrectly; it should be a dictionary object:

  • Wrong: func(a=r)

  • Correct: func(a={'x':y})

How to add a custom CA Root certificate to the CA Store used by pip in Windows?

Alternative solution on Windows is to install python-certifi-win32 that will allow Python to use Windows Certificate Store.

pip install python-certifi-win32

Show Console in Windows Application?

Easiest way is to start a WinForms application, go to settings and change the type to a console application.

How can I tell which button was clicked in a PHP form submit?

With an HTML form like:

<input type="submit" name="btnSubmit" value="Save Changes" />
<input type="submit" name="btnDelete" value="Delete" />

The PHP code to use would look like:

    // Something posted

    if (isset($_POST['btnDelete'])) {
        // btnDelete
    } else {
        // Assume btnSubmit

You should always assume or default to the first submit button to appear in the form HTML source code. In practice, the various browsers reliably send the name/value of a submit button with the post data when:

  1. The user literally clicks the submit button with the mouse or pointing device
  2. Or there is focus on the submit button (they tabbed to it), and then the Enter key is pressed.

Other ways to submit a form exist, and some browsers/versions decide not to send the name/value of any submit buttons in some of these situations. For example, many users submit forms by pressing the Enter key when the cursor/focus is on a text field. Forms can also be submitted via JavaScript, as well as some more obscure methods.

It's important to pay attention to this detail, otherwise you can really frustrate your users when they submit a form, yet "nothing happens" and their data is lost, because your code failed to detect a form submission, because you did not anticipate the fact that the name/value of a submit button may not be sent with the post data.

Also, the above advice should be used for forms with a single submit button too because you should always assume a default submit button.

I'm aware that the Internet is filled with tons of form-handler tutorials, and almost of all them do nothing more than check for the name and value of a submit button. But, they're just plain wrong!

How to enable cross-origin resource sharing (CORS) in the express.js framework on node.js

app.use(function(req, res, next) {
var allowedOrigins = [
var origin = req.headers.origin;
console.log(allowedOrigins.indexOf(origin) > -1)
// Website you wish to allow to
if (allowedOrigins.indexOf(origin) > -1) {
  res.setHeader("Access-Control-Allow-Origin", origin);

// res.setHeader("Access-Control-Allow-Origin", "http://localhost:4200");

// Request methods you wish to allow

// Request headers you wish to allow

// Set to true if you need the website to include cookies in the requests sent
// to the API (e.g. in case you use sessions)
res.setHeader("Access-Control-Allow-Credentials", true);

// Pass to next layer of middleware


Add this code in your index.js or server.js file and change the allowed origin array according to your requirement.

How to reverse an animation on mouse out after hover

Would you be better off having just the one animation, but having it reverse?

animation-direction: reverse

How to set HTML5 required attribute in Javascript?

let formelems = document.querySelectorAll('input,textarea,select');
formelems.forEach((formelem) => {
  formelem.required = true;


If you wish to make all input, textarea, and select elements required.

How to access global variables

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


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


var StartTime time.Time

How to move Docker containers between different hosts?

What eventually worked for me, after lot's of confusing manuals and confusing tutorials, since Docker is obviously at time of my writing at peek of inflated expectations, is:

  1. Save the docker image into archive:
    docker save image_name > image_name.tar
  2. copy on another machine
  3. on that other docker machine, run docker load in a following way:
    cat image_name.tar | docker load

Export and import, as proposed in another answers does not export ports and variables, which might be required for your container to run. And you might end up with stuff like "No command specified" etc... When you try to load it on another machine.

So, difference between save and export is that save command saves whole image with history and metadata, while export command exports only files structure (without history or metadata).

Needless to say is that, if you already have those ports taken on the docker hyper-visor you are doing import, by some other docker container, you will end-up in conflict, and you will have to reconfigure exposed ports.

Note: In order to move data with docker, you might be having persistent storage somewhere, which should also be moved alongside with containers.

What is the difference between NULL, '\0' and 0?

Note: This answer applies to the C language, not C++.

Null Pointers

The integer constant literal 0 has different meanings depending upon the context in which it's used. In all cases, it is still an integer constant with the value 0, it is just described in different ways.

If a pointer is being compared to the constant literal 0, then this is a check to see if the pointer is a null pointer. This 0 is then referred to as a null pointer constant. The C standard defines that 0 cast to the type void * is both a null pointer and a null pointer constant.

Additionally, to help readability, the macro NULL is provided in the header file stddef.h. Depending upon your compiler it might be possible to #undef NULL and redefine it to something wacky.

Therefore, here are some valid ways to check for a null pointer:

if (pointer == NULL)

NULL is defined to compare equal to a null pointer. It is implementation defined what the actual definition of NULL is, as long as it is a valid null pointer constant.

if (pointer == 0)

0 is another representation of the null pointer constant.

if (!pointer)

This if statement implicitly checks "is not 0", so we reverse that to mean "is 0".

The following are INVALID ways to check for a null pointer:

int mynull = 0;
<some code>
if (pointer == mynull)

To the compiler this is not a check for a null pointer, but an equality check on two variables. This might work if mynull never changes in the code and the compiler optimizations constant fold the 0 into the if statement, but this is not guaranteed and the compiler has to produce at least one diagnostic message (warning or error) according to the C Standard.

Note that the value of a null pointer in the C language does not matter on the underlying architecture. If the underlying architecture has a null pointer value defined as address 0xDEADBEEF, then it is up to the compiler to sort this mess out.

As such, even on this funny architecture, the following ways are still valid ways to check for a null pointer:

if (!pointer)
if (pointer == NULL)
if (pointer == 0)

The following are INVALID ways to check for a null pointer:

#define MYNULL (void *) 0xDEADBEEF
if (pointer == MYNULL)
if (pointer == 0xDEADBEEF)

as these are seen by a compiler as normal comparisons.

Null Characters

'\0' is defined to be a null character - that is a character with all bits set to zero. '\0' is (like all character literals) an integer constant, in this case with the value zero. So '\0' is completely equivalent to an unadorned 0 integer constant - the only difference is in the intent that it conveys to a human reader ("I'm using this as a null character.").

'\0' has nothing to do with pointers. However, you may see something similar to this code:

if (!*char_pointer)

checks if the char pointer is pointing at a null character.

if (*char_pointer)

checks if the char pointer is pointing at a non-null character.

Don't get these confused with null pointers. Just because the bit representation is the same, and this allows for some convenient cross over cases, they are not really the same thing.


See Question 5.3 of the comp.lang.c FAQ for more. See this pdf for the C standard. Check out sections Pointers, paragraph 3.

How do I put hint in a asp:textbox

asp:TextBox ID="txtName" placeholder="any text here"

Removing empty rows of a data file in R

This is similar to some of the above answers, but with this, you can specify if you want to remove rows with a percentage of missing values greater-than or equal-to a given percent (with the argument pct)

drop_rows_all_na <- function(x, pct=1) x[!rowSums( >= ncol(x)*pct,]

Where x is a dataframe and pct is the threshold of NA-filled data you want to get rid of.

pct = 1 means remove rows that have 100% of its values NA. pct = .5 means remome rows that have at least half its values NA

Domain Account keeping locking out with correct password every few minutes

I think this highlights a serious deficiency in Windows. We have a (techincal) user account that we use for our system consisting of a windows service and websites, with the app pools configured to run as this user.

Our company has a security policy that after 5 bad passwords, it locks the account out.

Now finding out what locks out the account is practically impossible in a enterprise. When the account is locked out, the AD server should log from what process and what server caused the lock out.

I've looked into it and it (lock out tools) and it doesnt do this. only possible thing is a tool but you have to run it on the server and wait to see if any process is doing it. But in a enterprise with 1000s of servers thats impossible, you have to guess. Its crazy.

Wi-Fi Direct and iOS Support

According to this thread:

The peer-to-peer Wi-Fi implemented by iOS (and recent versions of OS X) is not compatible with Wi-Fi Direct. Note Just as an aside, you can access peer-to-peer Wi-Fi without using Multipeer Connectivity. The underlying technology is Bonjour + TCP/IP, and you can access that directly from your app. The WiTap sample code shows how.

Servlet Mapping using web.xml

It allows servlets to have multiple servlet mappings:


It allows filters to be mapped on the particular servlet:


Your proposal would support neither of them. Note that the web.xml is read and parsed only once during application's startup, not on every HTTP request as you seem to think.

Since Servlet 3.0, there's the @WebServlet annotation which minimizes this boilerplate:

public class Servlet1 extends HttpServlet {

See also:

Converting string to numeric

I suspect you are having a problem with factors. For example,

> x = factor(4:8)
> x
[1] 4 5 6 7 8
Levels: 4 5 6 7 8
> as.numeric(x)
[1] 1 2 3 4 5
> as.numeric(as.character(x))
[1] 4 5 6 7 8

Some comments:

  • You mention that your vector contains the characters "Down" and "NoData". What do expect/want as.numeric to do with these values?
  • In read.csv, try using the argument stringsAsFactors=FALSE
  • Are you sure it's sep="/t and not sep="\t"
  • Use the command head(pitchman) to check the first fews rows of your data
  • Also, it's very tricky to guess what your problem is when you don't provide data. A minimal working example is always preferable. For example, I can't run the command pichman <- read.csv(file="picman.txt", header=TRUE, sep="/t") since I don't have access to the data set.

How do I find the current executable filename?

If you want the executable:


If you want the assembly that's consuming your library (which could be the same assembly as above, if your code is called directly from a class within your executable):


If you'd like just the filename and not the path, use:


How to make GREP select only numeric values?

No need to used grep here, Try this:

df . -B MB | tail -1 | awk {'print substr($5, 1, length($5)-1)'}

Java - how do I write a file to a specified directory


File file = new File("Z:\\results\\results.txt");

You need to double the backslashes in Windows because the backslash character itself is an escape in Java literal strings.

For POSIX system such as Linux, just use the default file path without doubling the forward slash. this is because forward slash is not a escape character in Java.

File file = new File("/home/userName/Documents/results.txt");

Pipe to/from the clipboard in Bash script

On Windows (with Cygwin) try cat /dev/clipboard or echo "foo" > /dev/clipboard as mentioned in this article.

Why Maven uses JDK 1.6 but my java -version is 1.7

You can also do,


      <!-- maven-compiler-plugin , aka JAVA Compiler 1.7 -->


How to retry image pull in a kubernetes Pods?

Usually in case of "ImagePullBackOff" it's retried after few seconds/minutes. In case you want to try again manually you can delete the old pod and recreate the pod. The one line command to delete and recreate the pod would be:

kubectl replace --force -f <yml_file_describing_pod>

C# Reflection: How to get class reference from string?

Bit late for reply but this should do the trick

Type myType = Type.GetType("AssemblyQualifiedName");

your assembly qualified name should be like this

"Boom.Bam.Class, Boom.Bam, Version=, Culture=neutral, PublicKeyToken=e16dba1a3c4385bd"

How do I get information about an index and table owner in Oracle?

Below are two simple query using which you can check index created on a table in Oracle.

select index_name
  from dba_indexes
 where table_name='&TABLE_NAME'
   and owner='&TABLE_OWNER';
select index_name 
  from user_indexes 
 where table_name='&TABLE_NAME';

Please check for more details and index size below. Index on a table and its size in Oracle

How can I make my custom objects Parcelable?

It is very easy, you can use a plugin on android studio to make objects Parcelables.

public class Persona implements Parcelable {
String nombre;
int edad;
Date fechaNacimiento;

public Persona(String nombre, int edad, Date fechaNacimiento) {
    this.nombre = nombre;
    this.edad = edad;
    this.fechaNacimiento = fechaNacimiento;

public int describeContents() {
    return 0;

public void writeToParcel(Parcel dest, int flags) {
    dest.writeLong(fechaNacimiento != null ? fechaNacimiento.getTime() : -1);

protected Persona(Parcel in) {
    this.nombre = in.readString();
    this.edad = in.readInt();
    long tmpFechaNacimiento = in.readLong();
    this.fechaNacimiento = tmpFechaNacimiento == -1 ? null : new Date(tmpFechaNacimiento);

public static final Parcelable.Creator<Persona> CREATOR = new Parcelable.Creator<Persona>() {
    public Persona createFromParcel(Parcel source) {
        return new Persona(source);

    public Persona[] newArray(int size) {
        return new Persona[size];

Why is lock(this) {...} bad?

Locking on the this pointer can be bad if you are locking over a shared resource. A shared resource can be a static variable or a file on your computer - i.e. something that is shared between all users of the class. The reason is that the this pointer will contain a different reference to a location in memory each time your class is instantiated. So, locking over this in once instance of a class is different than locking over this in another instance of a class.

Check out this code to see what I mean. Add the following code to your main program in a Console application:

    static void Main(string[] args)

    public static void TestThreading()
        Random rand = new Random();
        Thread[] threads = new Thread[10];
        TestLock.balance = 100000;
        for (int i = 0; i < 10; i++)
            TestLock tl = new TestLock();
            Thread t = new Thread(new ThreadStart(tl.WithdrawAmount));
            threads[i] = t;
        for (int i = 0; i < 10; i++)

Create a new class like the below.

 class TestLock
    public static int balance { get; set; }
    public static readonly Object myLock = new Object();

    public void Withdraw(int amount)
      // Try both locks to see what I mean
      //             lock (this)
       lock (myLock)
            Random rand = new Random();
            if (balance >= amount)
                Console.WriteLine("Balance before Withdrawal :  " + balance);
                Console.WriteLine("Withdraw        : -" + amount);
                balance = balance - amount;
                Console.WriteLine("Balance after Withdrawal  :  " + balance);
                Console.WriteLine("Can't process your transaction, current balance is :  " + balance + " and you tried to withdraw " + amount);

    public void WithdrawAmount()
        Random rand = new Random();
        Withdraw(rand.Next(1, 100) * 100);

Here is a run of the program locking on this.

   Balance before Withdrawal :  100000
    Withdraw        : -5600
    Balance after Withdrawal  :  94400
    Balance before Withdrawal :  100000
    Balance before Withdrawal :  100000
    Withdraw        : -5600
    Balance after Withdrawal  :  88800
    Withdraw        : -5600
    Balance after Withdrawal  :  83200
    Balance before Withdrawal :  83200
    Withdraw        : -9100
    Balance after Withdrawal  :  74100
    Balance before Withdrawal :  74100
    Withdraw        : -9100
    Balance before Withdrawal :  74100
    Withdraw        : -9100
    Balance after Withdrawal  :  55900
    Balance after Withdrawal  :  65000
    Balance before Withdrawal :  55900
    Withdraw        : -9100
    Balance after Withdrawal  :  46800
    Balance before Withdrawal :  46800
    Withdraw        : -2800
    Balance after Withdrawal  :  44000
    Balance before Withdrawal :  44000
    Withdraw        : -2800
    Balance after Withdrawal  :  41200
    Balance before Withdrawal :  44000
    Withdraw        : -2800
    Balance after Withdrawal  :  38400

Here is a run of the program locking on myLock.

Balance before Withdrawal :  100000
Withdraw        : -6600
Balance after Withdrawal  :  93400
Balance before Withdrawal :  93400
Withdraw        : -6600
Balance after Withdrawal  :  86800
Balance before Withdrawal :  86800
Withdraw        : -200
Balance after Withdrawal  :  86600
Balance before Withdrawal :  86600
Withdraw        : -8500
Balance after Withdrawal  :  78100
Balance before Withdrawal :  78100
Withdraw        : -8500
Balance after Withdrawal  :  69600
Balance before Withdrawal :  69600
Withdraw        : -8500
Balance after Withdrawal  :  61100
Balance before Withdrawal :  61100
Withdraw        : -2200
Balance after Withdrawal  :  58900
Balance before Withdrawal :  58900
Withdraw        : -2200
Balance after Withdrawal  :  56700
Balance before Withdrawal :  56700
Withdraw        : -2200
Balance after Withdrawal  :  54500
Balance before Withdrawal :  54500
Withdraw        : -500
Balance after Withdrawal  :  54000

How to display hexadecimal numbers in C?

i use it like this:

printf("my number is 0x%02X\n",number);
// output: my number is 0x4A

Just change number "2" to any number of chars You want to print ;)

D3 transform scale and translate

The transforms are SVG transforms (for details, have a look at the standard; here are some examples). Basically, scale and translate apply the respective transformations to the coordinate system, which should work as expected in most cases. You can apply more than one transform however (e.g. first scale and then translate) and then the result might not be what you expect.

When working with the transforms, keep in mind that they transform the coordinate system. In principle, what you say is true -- if you apply a scale > 1 to an object, it will look bigger and a translate will move it to a different position relative to the other objects.

Remove multiple objects with rm()

An other solution rm(list=ls(pattern="temp")), remove all objects matching the pattern.

How do I find the index of a character in a string in Ruby?

index(substring [, offset]) ? fixnum or nil
index(regexp [, offset]) ? fixnum or nil

Returns the index of the first occurrence of the given substring or pattern (regexp) in str. Returns nil if not found. If the second parameter is present, it specifies the position in the string to begin the search.

"hello".index('e')             #=> 1
"hello".index('lo')            #=> 3
"hello".index('a')             #=> nil
"hello".index(?e)              #=> 1
"hello".index(/[aeiou]/, -3)   #=> 4

Check out ruby documents for more information.