Suppose I have a task that is pulling elements from a java.util.concurrent.BlockingQueue and processing them.
public void scheduleTask(int delay, TimeUnit timeUnit)
{
scheduledExecutorService.scheduleWithFixedDelay(new Task(queue), 0, delay, timeUnit);
}
How can I schedule / reschedule the task if the frequency can be changed dynamically?
Use schedule(Callable<V>, long, TimeUnit)
rather than scheduleAtFixedRate
or scheduleWithFixedDelay
. Then ensure that your Callable reschedules itself or a new Callable instance at some point in the future. For example:
// Create Callable instance to schedule.
Callable<Void> c = new Callable<Void>() {
public Void call() {
try {
// Do work.
} finally {
// Reschedule in new Callable, typically with a delay based on the result
// of this Callable. In this example the Callable is stateless so we
// simply reschedule passing a reference to this.
service.schedule(this, 5000L, TimeUnit.MILLISECONDS);
}
return null;
}
}
service.schedule(c);
This approach avoids the need to shut down and recreate the ScheduledExecutorService
.