When does Java s Thread sleep throw InterruptedException

Question

When does Java s Thread sleep throw InterruptedException   Is it safe to ignore it   I am not doing any multithreading   I just want to wait for a few seconds before retrying some operation

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The InterruptedException is usually thrown when a sleep is interrupted

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A solid and easy way to handle it in single threaded code would be to catch it and retrow it in a RuntimeException  to avoid the need to declare it for every method

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If an InterruptedException is thrown it means that something wants to interrupt  usually terminate  that thread  This is triggered by a call to the threads interrupt   method  The wait method detects that and throws an InterruptedException so the catch code can handle the request for termination immediately and does not have to wait till the specified time is up   If you use it in a single-threaded app  and also in some multi-threaded apps   that exception will never be triggered  Ignoring it by having an empty catch clause I would not recommend  The throwing of the InterruptedException clears the interrupted state of the thread  so if not handled properly that info gets lost  Therefore I would propose to run     catch  InterruptedException e      Thread currentThread   interrupt         code for stopping current task so thread stops     Which sets that state again  After that  finish execution  This would be correct behaviour  even tough never used   What might be better is to add this     catch  InterruptedException e      throw new RuntimeException  Unexpected interrupt   e          statement to the catch block  That basically means that it must never happen  So if the code is re-used in an environment where it might happen it will complain about it

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The Java Specialists newsletter   which I can unreservedly recommend  had an interesting article on this  and how to handle the InterruptedException  It s well worth reading and digesting

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You should generally NOT ignore the exception  Take a look at the following paper      Don t swallow interrupts      Sometimes throwing InterruptedException is   not an option  such as when a task defined by Runnable calls an   interruptible method  In this case  you can t rethrow   InterruptedException  but you also do not want to do nothing  When a   blocking method detects interruption and throws InterruptedException    it clears the interrupted status  If you catch InterruptedException   but cannot rethrow it  you should preserve evidence that the   interruption occurred so that code higher up on the call stack can   learn of the interruption and respond to it if it wants to  This task   is accomplished by calling interrupt   to  reinterrupt  the current   thread  as shown in Listing 3  At the very least  whenever you catch   InterruptedException and don t rethrow it  reinterrupt the current   thread before returning   public class TaskRunner implements Runnable       private BlockingQueue lt Task gt  queue       public TaskRunner BlockingQueue lt Task gt  queue             this queue   queue              public void run              try                while  true                     Task task   queue take 10  TimeUnit SECONDS                    task execute                                       catch  InterruptedException e                     Restore the interrupted status              Thread currentThread   interrupt                                From Don t swallow interrupts        See the entire paper here    http   www ibm com developerworks java library j-jtp05236 index html ca drs-

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Methods like sleep   and wait   of class Thread might throw an InterruptedException  This will happen if some other thread wanted to interrupt the thread that is waiting or sleeping

[java] When does Java's Thread.sleep throw InterruptedException?

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