Java.util.concurrent Synchronizers: Difference between revisions

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<syntaxhighlight lang='java'>
<syntaxhighlight lang='java'>
int threadCount = ...;


final CyclicBarrier barrier = new CyclicBarrier(threadCount, new Runnable() {
final CyclicBarrier barrier = new CyclicBarrier(threadCount, () -> System.out.print("ALL threads have finished"));
 
    public void run() {
        System.out.print("ALL threads have finished");
    }
});


for(int i = 0; i < threadCount; i ++) {
for(int i = 0; i < threadCount; i ++) {


     new Thread(new Runnable()  {
     new Thread(() -> {


         @Override
         // do stuff ...
        public void run()  {


            // do stuff ...
        try {


            try {
          barrier.await();
 
        }
                barrier.await();
        catch(Exception e)  {
            }
            catch(Exception e)  {


                log.error("barrier error", e);
            log.error("barrier error", e);


                // ...
            }
         }
         }
     }, "Thread #" + i).start();
     }, "Thread #" + i).start();
}
}
...
</syntaxhighlight>
</syntaxhighlight>

Revision as of 17:00, 23 March 2018

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.

Semaphore

CyclicBarrier

A cyclic barrier is a primitive useful when waiting for all threads in a group to finish work they are doing individually.

int threadCount = ...;

final CyclicBarrier barrier = new CyclicBarrier(threadCount, () -> System.out.print("ALL threads have finished"));

for(int i = 0; i < threadCount; i ++) {

    new Thread(() ->  {

        // do stuff ...

        try {

          barrier.await();
        }
        catch(Exception e)  {

            log.error("barrier error", e);

        }
    }, "Thread #" + i).start();
}