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Coordinating Runnable tasks using CountDownLatch

/ Published in: Java
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A simple way to parallelize a for loop in Java. Wrapping each iteration (task) with a Runnable, executing them with an ExecutorService (to pool threads) and coordinating them with a simple CountDownLatch.

Due to Java's lack of closures, this simple scenario is rather verbose.

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  1. ExecutorService executorService = Executors.newFixedThreadPool(5);
  2.         int tasksCount = 10;
  3.         final CountDownLatch latch = new CountDownLatch(tasksCount);
  4.         for (int i = 0; i < tasksCount; i++ ) {
  5.             executorService.execute(new Runnable() {
  6.                 public void run() {
  7.                     try {
  8.                         // Do some work;
  9.                     } finally {
  10.                         latch.countDown();
  11.                     }
  12.                 }
  13.             });
  14.         }
  15.         try {
  16.             latch.await();
  17.         } catch (InterruptedException e) {
  18.             // todo >> handle exception
  19.         }
  20.         // All done!
  21.         // Do some more work
  22.     }

URL: http://java.sun.com/j2se/1.6.0/docs/api/java/util/concurrent/CountDownLatch.html

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