JavaTM 2 Platform Std. Ed. v1.6.0
java.util.concurrent
Interface ScheduledExecutorService
- All Superinterfaces:
- Executor, ExecutorService
- All Known Implementing Classes:
- ScheduledThreadPoolExecutor
public interface ScheduledExecutorService - extends ExecutorService
An 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) 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.
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 |
|
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
initialDelay then initialDelay+period, then
initialDelay + 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. |
Methods inherited from interface java.util.concurrent.ExecutorService |
awaitTermination, invokeAll, invokeAll, invokeAny, invokeAny, isShutdown, isTerminated, shutdown, shutdownNow, submit, submit, submit |
schedule
ScheduledFuture<?> schedule(Runnable command,
long delay,
TimeUnit unit)
- Creates and executes a one-shot action that becomes enabled
after the given delay.
- Parameters:
command - the task to executedelay - the time from now to delay executionunit - the time unit of the delay parameter
- Returns:
- a ScheduledFuture representing pending completion of
the task and whose get() method will return
null upon completion
- Throws:
RejectedExecutionException - if the task cannot be
scheduled for execution
NullPointerException - if command is null
schedule
<V> ScheduledFuture<V> schedule(Callable<V> callable,
long delay,
TimeUnit unit)
- Creates and executes a ScheduledFuture that becomes enabled after the
given delay.
- Parameters:
callable - the function to executedelay - the time from now to delay executionunit - the time unit of the delay parameter
- Returns:
- a ScheduledFuture that can be used to extract result or cancel
- Throws:
RejectedExecutionException - if the task cannot be
scheduled for execution
NullPointerException - if callable is null
scheduleAtFixedRate
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
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.
- Parameters:
command - the task to executeinitialDelay - the time to delay first executionperiod - the period between successive executionsunit - the time unit of the initialDelay and period parameters
- Returns:
- a ScheduledFuture representing pending completion of
the task, and whose get() method will throw an
exception upon cancellation
- Throws:
RejectedExecutionException - if the task cannot be
scheduled for execution
NullPointerException - if command is null
IllegalArgumentException - if period less than or equal to zero
scheduleWithFixedDelay
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. 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 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 parameters
- Returns:
- a ScheduledFuture representing pending completion of
the task, and whose get() method will throw an
exception upon cancellation
- Throws:
RejectedExecutionException - if the task cannot be
scheduled for execution
NullPointerException - if command is null
IllegalArgumentException - if delay less than or equal to zero
Copyright 2003 Sun Microsystems, Inc. All rights reserved
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