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    <p><code>SynchronousQueue</code> is a very special kind of queue - it implements a rendezvous approach (producer waits until consumer is ready, consumer waits until producer is ready) behind the interface of <code>Queue</code>.</p> <p>Therefore you may need it only in the special cases when you need that particular semantics, for example, <a href="https://stackoverflow.com/questions/4954708/single-threading-a-task-without-queuing-further-requests/4954938#4954938">Single threading a task without queuing further requests</a>.</p> <p>Another reason for using <code>SynchronousQueue</code> is performance. Implementation of <code>SynchronousQueue</code> seems to be heavily optimized, so if you don't need anything more than a rendezvous point (as in the case of <code>Executors.newCachedThreadPool()</code>, where consumers are created "on-demand", so that queue items don't accumulate), you can get a performance gain by using <code>SynchronousQueue</code>. </p> <p>Simple synthetic test shows that in a simple single producer - single consumer scenario on dual-core machine throughput of <code>SynchronousQueue</code> is ~20 time higher that throughput of <code>LinkedBlockingQueue</code> and <code>ArrayBlockingQueue</code> with queue length = 1. When queue length is increased, their throughput rises and almost reaches throughput of <code>SynchronousQueue</code>. It means that <code>SynchronousQueue</code> has low synchronization overhead on multi-core machines compared to other queues. But again, it matters only in specific circumstances when you need a rendezvous point disguised as <code>Queue</code>.</p> <p><strong>EDIT:</strong></p> <p>Here is a test:</p> <pre><code>public class Test { static ExecutorService e = Executors.newFixedThreadPool(2); static int N = 1000000; public static void main(String[] args) throws Exception { for (int i = 0; i &lt; 10; i++) { int length = (i == 0) ? 1 : i * 5; System.out.print(length + "\t"); System.out.print(doTest(new LinkedBlockingQueue&lt;Integer&gt;(length), N) + "\t"); System.out.print(doTest(new ArrayBlockingQueue&lt;Integer&gt;(length), N) + "\t"); System.out.print(doTest(new SynchronousQueue&lt;Integer&gt;(), N)); System.out.println(); } e.shutdown(); } private static long doTest(final BlockingQueue&lt;Integer&gt; q, final int n) throws Exception { long t = System.nanoTime(); e.submit(new Runnable() { public void run() { for (int i = 0; i &lt; n; i++) try { q.put(i); } catch (InterruptedException ex) {} } }); Long r = e.submit(new Callable&lt;Long&gt;() { public Long call() { long sum = 0; for (int i = 0; i &lt; n; i++) try { sum += q.take(); } catch (InterruptedException ex) {} return sum; } }).get(); t = System.nanoTime() - t; return (long)(1000000000.0 * N / t); // Throughput, items/sec } } </code></pre> <p>And here is a result on my machine:</p> <p><img src="https://i.stack.imgur.com/UuEpU.png" alt="enter image description here"></p>
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