Interrupting Threads

• When the run() method of a Thread completes, the thread ends naturally.
• What if you need to end that thread prematurely?   You must call the interrupt() method of that thread to request a termination.
• Note, this does not actually stop the thread, it simply requests that the thread stop.
• Calling interrupt() will lead to two possible outcomes:
• If the thread is currently running, it will need to check to see if an interrupt has been requested with the interrupted() method.  If so, it should stop processing.
• If the thread does not periodically check while running, it will never know, until it sleeps!
• It is a good idea to plan this wisely.  Check for interrupts after resources have been closed, variables have been written to a final state, etc.
• On the other hand, the thread cannot check for interrupts if it is sleeping or waiting.  If an interrupt is called at this time, an InterruptedException is called.
• Thus, you need to wrap the contents of the run() method in a try-catch block, and handle InterruptedExceptions gracefully.  This is a good time to close resources, bring variables to their final state, etc.

Created by:  Brandan Jones December 17, 2001