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

Question

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 1

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.

Answer 2

Instead of using an anonymous inner class you can use a named class which can then have a property for the Future object you get from the Executor when you schedule a task.

abstract class FutureRunnable implements Runnable {      private Future<?> future;      /* Getter and Setter for future */  } 

When you schedule a task you can then pass the Future to the Runnable.

FutureRunnable runnable = new FutureRunnable() {      public void run() {         if (/* abort condition */)             getFuture().cancel(false);     }  }; Future<?> future = executor.scheduleAtFixedRate(runnable, ...); runnable.setFuture(future); 

Maybe you will have to make sure, that the task is not executed before the Future has been set, because otherwise you will get a NullPointerException.