public interface ScheduledExecutorService extends ExecutorService
ExecutorService that can schedule commands to run after a given
 delay, 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 Executor.execute(Runnable)
 and ExecutorService submit methods are scheduled
 with a 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 Date to the required form. For example, to schedule at
 a 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 Executors class provides convenient factory methods for
 the ScheduledExecutorService implementations provided in this package.
 
 
 import static 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);
   }
 }| Modifier and Type | Method and Description | 
|---|---|
| <V> ScheduledFuture<V> | schedule(Callable<V> callable,
        long delay,
        TimeUnit unit)Creates and executes a ScheduledFuture that becomes enabled after the
 given delay. | 
| ScheduledFuture<?> | schedule(Runnable command,
        long delay,
        TimeUnit unit)Creates and executes a one-shot action that becomes enabled
 after the given delay. | 
| ScheduledFuture<?> | scheduleAtFixedRate(Runnable command,
                   long initialDelay,
                   long period,
                   TimeUnit unit)Creates and executes a periodic action that becomes enabled first
 after the given initial delay, and subsequently with the given
 period; that is executions will commence after
  initialDelaytheninitialDelay+period, theninitialDelay + 2 * period, and so on. | 
| ScheduledFuture<?> | scheduleWithFixedDelay(Runnable command,
                      long initialDelay,
                      long delay,
                      TimeUnit unit)Creates and executes a periodic action that becomes enabled first
 after the given initial delay, and subsequently with the
 given delay between the termination of one execution and the
 commencement of the next. | 
awaitTermination, invokeAll, invokeAll, invokeAny, invokeAny, isShutdown, isTerminated, shutdown, shutdownNow, submit, submit, submitScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit)
command - the task to executedelay - the time from now to delay executionunit - the time unit of the delay parameterget() method will return
         null upon completionRejectedExecutionException - if the task cannot be
         scheduled for executionNullPointerException - if command is null<V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit)
V - the type of the callable's resultcallable - the function to executedelay - the time from now to delay executionunit - the time unit of the delay parameterRejectedExecutionException - if the task cannot be
         scheduled for executionNullPointerException - if callable is nullScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit)
initialDelay then initialDelay+period, then
 initialDelay + 2 * period, and so on.
 If any execution of the task
 encounters an exception, subsequent executions are suppressed.
 Otherwise, the task will only terminate via cancellation or
 termination of the executor.  If any execution of this task
 takes longer than its period, then subsequent executions
 may start late, but will not concurrently execute.command - the task to executeinitialDelay - the time to delay first executionperiod - the period between successive executionsunit - the time unit of the initialDelay and period parametersget() method will throw an
         exception upon cancellationRejectedExecutionException - if the task cannot be
         scheduled for executionNullPointerException - if command is nullIllegalArgumentException - if period less than or equal to zeroScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit)
command - the task to executeinitialDelay - the time to delay first executiondelay - the delay between the termination of one
 execution and the commencement of the nextunit - the time unit of the initialDelay and delay parametersget() method will throw an
         exception upon cancellationRejectedExecutionException - if the task cannot be
         scheduled for executionNullPointerException - if command is nullIllegalArgumentException - if delay less than or equal to zero Submit a bug or feature 
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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