ScheduledExecutorServicepublic interface ScheduledExecutorService implements ExecutorService| An {@link 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 {@link Executor#execute} and
{@link 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 {@link
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 {@link 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);
}
}
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| Methods Summary |
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| public java.util.concurrent.ScheduledFuture | schedule(java.lang.Runnable command, long delay, java.util.concurrent.TimeUnit unit)Creates and executes a one-shot action that becomes enabled
after the given delay.
| | public java.util.concurrent.ScheduledFuture | schedule(java.util.concurrent.Callable callable, long delay, java.util.concurrent.TimeUnit unit)Creates and executes a ScheduledFuture that becomes enabled after the
given delay.
| | public java.util.concurrent.ScheduledFuture | scheduleAtFixedRate(java.lang.Runnable command, long initialDelay, long period, 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. If any execution of this task
takes longer than its period, then subsequent executions
may start late, but will not concurrently execute.
| | public java.util.concurrent.ScheduledFuture | scheduleWithFixedDelay(java.lang.Runnable command, long initialDelay, long delay, 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.
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