An {@link ExecutorService} that can schedule commands to run after a givendelay, or to execute periodically.
The schedule methods create tasks with various delays and return a task object that can be used to cancel or check execution. The scheduleAtFixedRate and scheduleWithFixedDelay methods create and execute tasks that run periodically until cancelled.
Commands submitted using the {@link Executor#execute} and{@link ExecutorService} submit methods are scheduled witha requested delay of zero. Zero and negative delays (but not periods) are also allowed in schedule methods, and are treated as requests for immediate execution.
All schedule methods accept relative delays and periods as arguments, not absolute times or dates. It is a simple matter to transform an absolute time represented as a {@link edu.emory.mathcs.backport.java.util.Date} to the required form. For example, to schedule ata certain future date, you can use: schedule(task, date.getTime() - System.currentTimeMillis(), TimeUnit.MILLISECONDS). Beware however that expiration of a relative delay need not coincide with the current Date at which the task is enabled due to network time synchronization protocols, clock drift, or other factors. The {@link Executors} class provides convenient factory methods forthe ScheduledExecutorService implementations provided in this package.
Usage Example
Here is a class with a method that sets up a ScheduledExecutorService to beep every ten seconds for an hour:
import static edu.emory.mathcs.backport.java.util.concurrent.TimeUnit.*; class BeeperControl { private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1); public void beepForAnHour() { final Runnable beeper = new Runnable() { public void run() { System.out.println("beep"); } }; final ScheduledFuture<?> beeperHandle = scheduler.scheduleAtFixedRate(beeper, 10, 10, SECONDS); scheduler.schedule(new Runnable() { public void run() { beeperHandle.cancel(true); } }, 60 * 60, SECONDS); } }
@since 1.5
@author Doug Lea