Java.util.concurrent Synchronizers: Difference between revisions
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==Overview== | ==Overview== | ||
A <tt>CountDownLatch</tt> is a synchronization tool that allows one or more threads to wait on it until a certain number of operations being performed in other threads completes. The latch is initialized with a count. Any thread calling <tt>await()</tt> blocks unit the count reaches zero, after which it is released. You can think of those threads as waiting on a gate to open. The count is decremented with <tt>countDown()</tt>, which can be called in a loop from a single thread, or concurrently from multiple threads. Note that the threads invoking <tt>countDown()</tt> are not blocked on the latch - they decrement and continue. | A <tt>CountDownLatch</tt> is a synchronization tool that allows one or more threads to wait on it until a certain number of operations being performed in other threads completes. The latch is initialized with a count. Any thread calling <tt>await()</tt> blocks unit the count reaches zero, after which it is released. You can think of those threads as waiting on a gate to open. The count is decremented with <tt>countDown()</tt>, which can be called in a loop from a single thread, or concurrently from multiple threads. Note that the threads invoking <tt>countDown()</tt> are not blocked on the latch - they decrement and continue. | ||
Once the count reached zero, the latch cannot be reused. If you need a reusable mechanism, use [[#Cyclic_Barrier|Cyclic Barrier]]. | |||
=Semaphore= | =Semaphore= | ||
Revision as of 01:20, 25 January 2016
Internal
CountDownLatch
External
Overview
A CountDownLatch is a synchronization tool that allows one or more threads to wait on it until a certain number of operations being performed in other threads completes. The latch is initialized with a count. Any thread calling await() blocks unit the count reaches zero, after which it is released. You can think of those threads as waiting on a gate to open. The count is decremented with countDown(), which can be called in a loop from a single thread, or concurrently from multiple threads. Note that the threads invoking countDown() are not blocked on the latch - they decrement and continue.
Once the count reached zero, the latch cannot be reused. If you need a reusable mechanism, use Cyclic Barrier.