java.util.concurrent
Interface ScheduledExecutorService

All Superinterfaces:
Executor sample code for java.util.concurrent.Executor definition code for java.util.concurrent.Executor , ExecutorService sample code for java.util.concurrent.ExecutorService definition code for java.util.concurrent.ExecutorService
All Known Implementing Classes:
ScheduledThreadPoolExecutor sample code for java.util.concurrent.ScheduledThreadPoolExecutor definition code for java.util.concurrent.ScheduledThreadPoolExecutor

public interface ScheduledExecutorService
extends ExecutorService sample code for java.util.concurrent.ExecutorService definition code for java.util.concurrent.ExecutorService

An ExecutorService sample code for java.util.concurrent.ExecutorService definition code for java.util.concurrent.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(java.lang.Runnable) sample code for java.util.concurrent.Executor.execute(java.lang.Runnable) definition code for java.util.concurrent.Executor.execute(java.lang.Runnable) and ExecutorService sample code for java.util.concurrent.ExecutorService definition code for java.util.concurrent.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 sample code for java.util.Date definition code for java.util.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 sample code for java.util.concurrent.Executors definition code for java.util.concurrent.Executors class provides convenient factory methods for the 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 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

Method Summary
<V> ScheduledFuture sample code for java.util.concurrent.ScheduledFuture definition code for java.util.concurrent.ScheduledFuture <V>
schedule sample code for java.util.concurrent.ScheduledExecutorService.schedule(java.util.concurrent.Callable, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ScheduledExecutorService.schedule(java.util.concurrent.Callable, long, java.util.concurrent.TimeUnit) (Callable sample code for java.util.concurrent.Callable definition code for java.util.concurrent.Callable <V> callable, long delay, TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.TimeUnit  unit)
          Creates and executes a ScheduledFuture that becomes enabled after the given delay.
 ScheduledFuture sample code for java.util.concurrent.ScheduledFuture definition code for java.util.concurrent.ScheduledFuture <?> schedule sample code for java.util.concurrent.ScheduledExecutorService.schedule(java.lang.Runnable, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ScheduledExecutorService.schedule(java.lang.Runnable, long, java.util.concurrent.TimeUnit) (Runnable sample code for java.lang.Runnable definition code for java.lang.Runnable  command, long delay, TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.TimeUnit  unit)
          Creates and executes a one-shot action that becomes enabled after the given delay.
 ScheduledFuture sample code for java.util.concurrent.ScheduledFuture definition code for java.util.concurrent.ScheduledFuture <?> scheduleAtFixedRate sample code for java.util.concurrent.ScheduledExecutorService.scheduleAtFixedRate(java.lang.Runnable, long, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ScheduledExecutorService.scheduleAtFixedRate(java.lang.Runnable, long, long, java.util.concurrent.TimeUnit) (Runnable sample code for java.lang.Runnable definition code for java.lang.Runnable  command, long initialDelay, long period, TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.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 initialDelay then initialDelay+period, then initialDelay + 2 * period, and so on.
 ScheduledFuture sample code for java.util.concurrent.ScheduledFuture definition code for java.util.concurrent.ScheduledFuture <?> scheduleWithFixedDelay sample code for java.util.concurrent.ScheduledExecutorService.scheduleWithFixedDelay(java.lang.Runnable, long, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ScheduledExecutorService.scheduleWithFixedDelay(java.lang.Runnable, long, long, java.util.concurrent.TimeUnit) (Runnable sample code for java.lang.Runnable definition code for java.lang.Runnable  command, long initialDelay, long delay, TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.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.
 
Methods inherited from interface java.util.concurrent.ExecutorService sample code for java.util.concurrent.ExecutorService definition code for java.util.concurrent.ExecutorService
awaitTermination sample code for java.util.concurrent.ExecutorService.awaitTermination(long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ExecutorService.awaitTermination(long, java.util.concurrent.TimeUnit) , invokeAll sample code for java.util.concurrent.ExecutorService.invokeAll(java.util.Collection) definition code for java.util.concurrent.ExecutorService.invokeAll(java.util.Collection) , invokeAll sample code for java.util.concurrent.ExecutorService.invokeAll(java.util.Collection, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ExecutorService.invokeAll(java.util.Collection, long, java.util.concurrent.TimeUnit) , invokeAny sample code for java.util.concurrent.ExecutorService.invokeAny(java.util.Collection) definition code for java.util.concurrent.ExecutorService.invokeAny(java.util.Collection) , invokeAny sample code for java.util.concurrent.ExecutorService.invokeAny(java.util.Collection, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ExecutorService.invokeAny(java.util.Collection, long, java.util.concurrent.TimeUnit) , isShutdown sample code for java.util.concurrent.ExecutorService.isShutdown() definition code for java.util.concurrent.ExecutorService.isShutdown() , isTerminated sample code for java.util.concurrent.ExecutorService.isTerminated() definition code for java.util.concurrent.ExecutorService.isTerminated() , shutdown sample code for java.util.concurrent.ExecutorService.shutdown() definition code for java.util.concurrent.ExecutorService.shutdown() , shutdownNow sample code for java.util.concurrent.ExecutorService.shutdownNow() definition code for java.util.concurrent.ExecutorService.shutdownNow() , submit sample code for java.util.concurrent.ExecutorService.submit(java.util.concurrent.Callable) definition code for java.util.concurrent.ExecutorService.submit(java.util.concurrent.Callable) , submit sample code for java.util.concurrent.ExecutorService.submit(java.lang.Runnable) definition code for java.util.concurrent.ExecutorService.submit(java.lang.Runnable) , submit sample code for java.util.concurrent.ExecutorService.submit(java.lang.Runnable, T) definition code for java.util.concurrent.ExecutorService.submit(java.lang.Runnable, T)
 
Methods inherited from interface java.util.concurrent.Executor sample code for java.util.concurrent.Executor definition code for java.util.concurrent.Executor
execute sample code for java.util.concurrent.Executor.execute(java.lang.Runnable) definition code for java.util.concurrent.Executor.execute(java.lang.Runnable)
 

Method Detail

schedule sample code for java.util.concurrent.ScheduledExecutorService.schedule(java.lang.Runnable, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ScheduledExecutorService.schedule(java.lang.Runnable, long, java.util.concurrent.TimeUnit)

ScheduledFuture sample code for java.util.concurrent.ScheduledFuture definition code for java.util.concurrent.ScheduledFuture <?> schedule(Runnable sample code for java.lang.Runnable definition code for java.lang.Runnable  command,
                            long delay,
                            TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.TimeUnit  unit)
Creates and executes a one-shot action that becomes enabled after the given delay.

Parameters:
command - the task to execute.
delay - the time from now to delay execution.
unit - the time unit of the delay parameter.
Returns:
a Future representing pending completion of the task, and whose get() method will return null upon completion.
Throws:
RejectedExecutionException sample code for java.util.concurrent.RejectedExecutionException definition code for java.util.concurrent.RejectedExecutionException - if task cannot be scheduled for execution.
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if command is null

schedule sample code for java.util.concurrent.ScheduledExecutorService.<V>schedule(java.util.concurrent.Callable<V>, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ScheduledExecutorService.<V>schedule(java.util.concurrent.Callable<V>, long, java.util.concurrent.TimeUnit)

<V> ScheduledFuture sample code for java.util.concurrent.ScheduledFuture definition code for java.util.concurrent.ScheduledFuture <V> schedule(Callable sample code for java.util.concurrent.Callable definition code for java.util.concurrent.Callable <V> callable,
                                long delay,
                                TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.TimeUnit  unit)
Creates and executes a ScheduledFuture that becomes enabled after the given delay.

Parameters:
callable - the function to execute.
delay - the time from now to delay execution.
unit - the time unit of the delay parameter.
Returns:
a ScheduledFuture that can be used to extract result or cancel.
Throws:
RejectedExecutionException sample code for java.util.concurrent.RejectedExecutionException definition code for java.util.concurrent.RejectedExecutionException - if task cannot be scheduled for execution.
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if callable is null

scheduleAtFixedRate sample code for java.util.concurrent.ScheduledExecutorService.scheduleAtFixedRate(java.lang.Runnable, long, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ScheduledExecutorService.scheduleAtFixedRate(java.lang.Runnable, long, long, java.util.concurrent.TimeUnit)

ScheduledFuture sample code for java.util.concurrent.ScheduledFuture definition code for java.util.concurrent.ScheduledFuture <?> scheduleAtFixedRate(Runnable sample code for java.lang.Runnable definition code for java.lang.Runnable  command,
                                       long initialDelay,
                                       long period,
                                       TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.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 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.

Parameters:
command - the task to execute.
initialDelay - the time to delay first execution.
period - the period between successive executions.
unit - the time unit of the initialDelay and period parameters
Returns:
a Future representing pending completion of the task, and whose get() method will throw an exception upon cancellation.
Throws:
RejectedExecutionException sample code for java.util.concurrent.RejectedExecutionException definition code for java.util.concurrent.RejectedExecutionException - if task cannot be scheduled for execution.
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if command is null
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if period less than or equal to zero.

scheduleWithFixedDelay sample code for java.util.concurrent.ScheduledExecutorService.scheduleWithFixedDelay(java.lang.Runnable, long, long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.ScheduledExecutorService.scheduleWithFixedDelay(java.lang.Runnable, long, long, java.util.concurrent.TimeUnit)

ScheduledFuture sample code for java.util.concurrent.ScheduledFuture definition code for java.util.concurrent.ScheduledFuture <?> scheduleWithFixedDelay(Runnable sample code for java.lang.Runnable definition code for java.lang.Runnable  command,
                                          long initialDelay,
                                          long delay,
                                          TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.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. 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.

Parameters:
command - the task to execute.
initialDelay - the time to delay first execution.
delay - the delay between the termination of one execution and the commencement of the next.
unit - the time unit of the initialDelay and delay parameters
Returns:
a Future representing pending completion of the task, and whose get() method will throw an exception upon cancellation.
Throws:
RejectedExecutionException sample code for java.util.concurrent.RejectedExecutionException definition code for java.util.concurrent.RejectedExecutionException - if task cannot be scheduled for execution.
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if command is null
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if delay less than or equal to zero.