Waiting for a Timer to finish in Java

java synchronization timer monitor
ripper234 picture ripper234 · Aug 24, 2009 · Viewed 22.3k times · Source

I'm using java.util.Timer to schedule a periodic task. At one point, I'd like to shut it down, and wait for it to finish.

Timer.cancel() will prevent any future tasks from running. How do I make sure any tasks are not running at the moment (or wait for them if they are?)

I can introduce external synchronization mechanisms, but I don't see how they can cover all cases. For example, if I synchronize on some Monitor within the task, I still miss the case when the task just started executing but didn't take the monitor.

What is the recommended practice for waiting until all tasks are really done, including currently running tasks?

Answer

Mark picture Mark · Aug 24, 2009

You would be better using an ScheduledExecutorService instead of a Timer to schedule your periodic task. ScheduledExecutorService provides a shutdown() method that will execute any pending tasks. You can then call awaitTermination() to wait for shutdown() to finish.

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