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copied!<p>With <code>ListenableFuture</code>, you can submit any number of tasks and then pass the <code>ListenableFuture</code>s from those tasks to <a href="http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/util/concurrent/Futures.html#allAsList%28com.google.common.util.concurrent.ListenableFuture...%29"><code>Futures.allAsList</code></a>, getting another <code>ListenableFuture</code> that will complete when <em>all</em> of the tasks have completed. There's also <a href="http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/util/concurrent/Futures.html#successfulAsList%28com.google.common.util.concurrent.ListenableFuture...%29"><code>Futures.successfulAsList</code></a>, which succeeds even if some of the tasks fail and gives you a <code>null</code> result for each failed task.</p> <p>You can then either block the current thread to wait for those results (using the normal <code>Future.get()</code>) or you can add a listener/callback to be called when they've completed if you don't want/need to block the current thread.</p> <p>Example:</p> <pre><code>ListeningExecutorService executor = ... List<Callable<Foo>> tasks = ... List<ListenableFuture<Foo>> futures = Lists.newArrayList(); for (Callable<Foo> task : tasks) { futures.add(executor.submit(task)); } final ListenableFuture<List<Foo>> resultsFuture = Futures.allAsList(futures); // block until all tasks are done List<Foo> results = resultsFuture.get(); // or add a callback to get called when the tasks complete Futures.addCallback(resultsFuture, new FutureCallback<List<Foo>>() { @Override public void onSuccess(List<Foo> results) { // ... } @Override public void onFailure(Throwable throwable) { // ... } }, someExecutor); </code></pre>

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