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What is mutex and semaphore in Java ? What is the main difference?
...the resource releases. All threads waiting for acquiring resource would be blocked.
Semaphore is used to control the number of threads executing. There will be fixed set of resources. The resource count will gets decremented every time when a thread owns the same. When the semaphore count reaches 0...
Convert MySql DateTime stamp into JavaScript's Date format
...
#MySQL
select date_format(my_date_column,'%Y-%m-%dT%T') from my_table;
#PHP
$php_date_str = substr($mysql_date_str,0,10).'T'.substr($mysql_date_str,11,8);
//JavaScript
js_date_str = mysql_date_str.substr(0,10)+'T'+mysql_date_str.substr(11,8);
...
MySQL “WITH” clause
... a feature request for MySQL since January 2006: http://bugs.mysql.com/bug.php?id=16244
Other RDBMS products that support common table expressions:
Oracle 9i release 2 and later:
http://www.oracle-base.com/articles/misc/with-clause.php
Microsoft SQL Server 2005 and later:
http://msdn.microsoft.com/...
HttpClient.GetAsync(…) never returns when using await/async
...yncAwait_GetSomeDataAsync returns an uncompleted Task.
Test5Controller.Get blocks the current thread until that Task completes.
The HTTP response comes in, and the Task returned by HttpClient.GetAsync is completed.
AsyncAwait_GetSomeDataAsync attempts to resume within the ASP.NET request context. Ho...
Volatile boolean vs AtomicBoolean
...push back a new value then I go with Atomic* vars or locks or synchronized blocks, whatever suits me best. In many concurrent scenarios it boils down to get the value, compare it with another one and update if necessary, hence the compareAndSet and getAndSet methods present in the Atomic* classes.
...
Responsively change div size keeping aspect ratio [duplicate]
...ntuitive) fact that padding-top percentages are relative to the containing block's width. Here's an example:
.wrapper {
width: 50%;
/* whatever width you want */
display: inline-block;
position: relative;
}
.wrapper:after {
padding-top: 56.25%;
/* 16:9 ratio */
display: b...
Why does this async action hang?
...
So the first line kicks off the asynchronous work. The second line then blocks the UI thread. So when the runtime wants to run the "return result" line back on the UI thread, it can't do that until the Result completes. But of course, the Result can't be given until the return happens. Deadlock.
...
“where 1=1” statement [duplicate]
... condition is generated dynamically.
for example lets see this code
<?php
//not that this is just example
//do not use it like that in real environment because it security issue.
$cond = $_REQUEST['cond'];
if ($cond == "age"){
$wherecond = " age > 18";
}
$query = "select * from som...
Class.forName() vs ClassLoader.loadClass() - which to use for dynamic loading? [duplicate]
...o attempt to load a Torque peer class in order to run a static initializer block which maps the peer to a database table. The static block was not executed on this call. However, upon calling Class.forName("..."); for the peer class the static block was executed. +1 for a good explanation and educat...
What are the differences between various threading synchronization options in C#?
... one thread can take ownership of the object's lock & enter the locked block of code. Other threads must wait till the current owner relinquishes the lock by exiting the block of code. Also it is recommended that you lock on a private member object of your class.
Monitors
lock(obj) is imple...