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POInterrupting a blocking method before the method call
 

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    <p>I'm reading this book, (O'Reillys Java Threads 3rd ed., which for now has very bad explanations), and I have encountered this code:</p> <pre><code>//in RandomCharacterGenerator class public void run( ) { while (!isInterrupted()) { nextCharacter( ); try { Thread.sleep(getPauseTime( )); } catch (InterruptedException ie) { return; } } } </code></pre> <p>And the following explanation (producer is the instance of upper class in the main thread): </p> <pre><code>producer.interrupt( ); </code></pre> <blockquote> <p>If the main thread executes this statement while the RandomCharacterGenerator thread is sleeping, the RandomCharacterGenerator thread gets the interrupted exception and immediately returns from the run() method. Otherwise, when the character-feeding thread next gets to the top of its loop, it sees that the interrupted flag has been set and returns from its run() method then. Either way, the random character generator thread completes its task.</p> <p>Note that this technique does not completely eliminate the possibility that we sleep for some amount of time after the thread is asked to stop. It's possible for the main thread to call the interrupt() method just after the RandomCharacterGenerator has called the isInterrupted() method. The character-reading thread still executes the sleep() method, which won't be interrupted (since the main thread has already completed the interrupt() method). This is another example of a race condition that we solve in the next chapter. Since the race condition in this case is benign (it just means we sleep one more time than we'd like), this is sufficient for our purposes.</p> </blockquote> <p>Second paragraph is completely unclear to me. My first question is: How can we sleep one more cycle? If we interrupt the thread when sleeping it goes out of run, if we interrupt before sleep it will interrupt sleep as soon as it starts sleeping (I tested that, and I think that's true? Am I right), if we interrupt after sleep it will brake the loop.</p> <p>Second question: In this example (this is the whole code from the book) is the check in loop completely unnecessary, and can it stand while (true) with the same outcome, so that first paragraph about the top of the loop is complete nonsense?</p>
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    1. COI think this example does not use Thread.interrupt but a custom boolean interruption flag instead. So producer.interrupt() just sets this boolean flag to true but does not interrupt the sleeping thread.
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    2. CONo, it does not, example before is with setting a flag, this example uses Thread.interrupt, producer extends thread, and does not override interrupt
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    3. COOK, if that's the case, then you're right. Thread interruption will cause the sleeping thread to (more or less) immediately throw an InterruptedException. No race condition.
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