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    <p>I would recommend taking a look at <a href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/ExecutorService.html" rel="noreferrer">ExecutorService</a>.</p> <p>In particular, something like this:</p> <pre><code>ExecutorService EXEC = Executors.newCachedThreadPool(); List&lt;Callable&lt;Result&gt;&gt; tasks = new ArrayList&lt;Callable&lt;Result&gt;&gt;(); for (final Object object: objects) { Callable&lt;Result&gt; c = new Callable&lt;Result&gt;() { @Override public Result call() throws Exception { return compute(object); } }; tasks.add(c); } List&lt;Future&lt;Result&gt;&gt; results = EXEC.invokeAll(tasks); </code></pre> <p>Note that using <code>newCachedThreadPool</code> could be bad if <code>objects</code> is a big list. A cached thread pool could create a thread per task! You may want to use <code>newFixedThreadPool(n)</code> where n is something reasonable (like the number of cores you have, assuming <code>compute()</code> is CPU bound).</p> <p>Here's full code that actually runs:</p> <pre><code>import java.util.ArrayList; import java.util.List; import java.util.Random; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; public class ExecutorServiceExample { private static final Random PRNG = new Random(); private static class Result { private final int wait; public Result(int code) { this.wait = code; } } public static Result compute(Object obj) throws InterruptedException { int wait = PRNG.nextInt(3000); Thread.sleep(wait); return new Result(wait); } public static void main(String[] args) throws InterruptedException, ExecutionException { List&lt;Object&gt; objects = new ArrayList&lt;Object&gt;(); for (int i = 0; i &lt; 100; i++) { objects.add(new Object()); } List&lt;Callable&lt;Result&gt;&gt; tasks = new ArrayList&lt;Callable&lt;Result&gt;&gt;(); for (final Object object : objects) { Callable&lt;Result&gt; c = new Callable&lt;Result&gt;() { @Override public Result call() throws Exception { return compute(object); } }; tasks.add(c); } ExecutorService exec = Executors.newCachedThreadPool(); // some other exectuors you could try to see the different behaviours // ExecutorService exec = Executors.newFixedThreadPool(3); // ExecutorService exec = Executors.newSingleThreadExecutor(); try { long start = System.currentTimeMillis(); List&lt;Future&lt;Result&gt;&gt; results = exec.invokeAll(tasks); int sum = 0; for (Future&lt;Result&gt; fr : results) { sum += fr.get().wait; System.out.println(String.format("Task waited %d ms", fr.get().wait)); } long elapsed = System.currentTimeMillis() - start; System.out.println(String.format("Elapsed time: %d ms", elapsed)); System.out.println(String.format("... but compute tasks waited for total of %d ms; speed-up of %.2fx", sum, sum / (elapsed * 1d))); } finally { exec.shutdown(); } } } </code></pre>
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    1. POWhat is the easiest way to parallelize a task in java?
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    1. COIs there a c# version of this?
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      1. USMalfist
    2. COAlso look at Executors, which functions as a factory for various flavors of executor services.
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      1. USRob H
    3. CO@Malfist in C# there's tasks (well for the upcoming .net 4) that make all of these a breeze :). And there are delegates/lambdas and threads, funcs, threadstart, etc to do it in 3.5
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      1. USFrancisco Noriega
 

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