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    <p>In the example the that book is giving the Holder class is not directly the cause of the problem, in fact it states that: </p> <p><em>The problem here is not the Holder class itself, but that the Holder is not properly published. However, Holder can be made immune to improper publication by declaring the n field to be final, which would make Holder immutable; see Section 3.5.2.</em></p> <p>Just prior to this it mentions the following code, which it the subject of the problem:</p> <pre><code>// Unsafe publication public Holder holder; public void initialize() { holder = new Holder(42); } </code></pre> <p>So to re-create it you will need to create a publisher class and two threads, one that calls initialize and one that calls the assert.</p> <p>Having said that, I tried to re-create it myself and still failed to do so :( </p> <p>Below is my first attempt, however there is a better explanation of the problem at <a href="http://forums.oracle.com/forums/thread.jspa?threadID=1140814&amp;tstart=195" rel="nofollow">http://forums.oracle.com/forums/thread.jspa?threadID=1140814&amp;tstart=195</a></p> <pre><code>public class HolderTest { @Test public void testHolder() throws Exception { for (int i = 0; i &lt; 1000000000; i++) { final CountDownLatch finished = new CountDownLatch(2); final HolderPublisher publisher = new HolderPublisher(); final Thread publisherThread = new Thread(new Publisher(publisher, finished)); final Thread checkerThread = new Thread(new Checker(publisher, finished)); publisher.holder = null; publisherThread.start(); checkerThread.start(); finished.await(); } } static class Publisher implements Runnable { private final CountDownLatch finished; private final HolderPublisher publisher; public Publisher(final HolderPublisher publisher, final CountDownLatch finished) { this.publisher = publisher; this.finished = finished; } @Override public void run() { try { publisher.initialize(); } finally { finished.countDown(); } } } static class Checker implements Runnable { private final CountDownLatch finished; private final HolderPublisher publisher; public Checker(final HolderPublisher publisher, final CountDownLatch finished) { this.publisher = publisher; this.finished = finished; } @Override public void run() { try { publisher.holder.assertSanity(); } catch (final NullPointerException e) { // This isnt the error we are interested in so swallow it } finally { finished.countDown(); } } } static class HolderPublisher { // Unsafe publication public Holder holder; public void initialize() { holder = new Holder(42); } } } </code></pre>
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    1. POHow to demonstrate race conditions around values that aren't published properly?
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    1. USSteve McDowell
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