Stop a periodic task from within the task itself running in a ScheduledExecutorService

java concurrency anonymous-class executorservice variable-initialization
akarnokd picture akarnokd · Feb 5, 2011 · Viewed 13.1k times · Source

Is there a nice way to stop the repetition of task from within the task itself when running in a ScheduledExecutorService?

Lets say, I have the following task:

Future<?> f = scheduledExecutor.scheduleAtFixedRate(new Runnable() {
    int count = 0;
    public void run() {
       System.out.println(count++);
       if (count == 10) {
           // ??? cancel self
       }
    }
}, 1, 1, TimeUnit.SECONDS);

From outside, it is easy to cancel via f.cancel(), but how can I stop the repetition at the specified place? (Passing the Future through an AtomicReference is not safe, because there is a potential window when the scheduleAtFixedRate returns f late and the variable is set late too, and the task itself might already run, seeing a null in the reference.)

Answer

Peter Lawrey picture Peter Lawrey · Feb 5, 2011

When a repeating task throws an Exception or Error, it is placed in the Future and the task is not repeated again. You can throw a RuntimeException or Error of your choice.

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