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 java. 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() {
Runnable beeper = () -> System.out.println("beep");
ScheduledFuture<?> beeperHandle =
scheduler.scheduleAtFixedRate(beeper, 10, 10, SECONDS);
Runnable canceller = () -> beeperHandle.cancel(false);
scheduler.schedule(canceller, 1, HOURS);
}
}
| Modifier and Type | Method and Description |
|---|---|
| public ScheduledFuture | Returns: a ScheduledFuture representing pending completion of the task and whoseget() method will return
null upon completionthe task to execute command, long the time from now to delay execution delay, TimeUnit the time unit of the delay parameter unit)Submits a one-shot task that becomes enabled after the given delay. |
| public < the type of the callable's result V> ScheduledFuture | Returns: a ScheduledFuture that can be used to extract result or cancelthe function to execute callable, long the time from now to delay execution delay, TimeUnit the time unit of the delay parameter unit)Submits a value-returning one-shot task that becomes enabled after the given delay. |
| public ScheduledFuture | Returns: a ScheduledFuture representing pending completion of the series of repeated tasks. The future'sget() method will never return normally,
and will throw an exception upon task cancellation or
abnormal termination of a task execution.the task to execute command, long the time to delay first execution initialDelay, long the period between successive executions period, TimeUnit the time unit of the initialDelay and period parameters unit)Submits a periodic action that becomes enabled first after the
given initial delay, and subsequently with the given period;
that is, executions will commence after
|
| public ScheduledFuture | Returns: a ScheduledFuture representing pending completion of the series of repeated tasks. The future'sget() method will never return normally,
and will throw an exception upon task cancellation or
abnormal termination of a task execution.the task to execute command, long the time to delay first execution initialDelay, long the delay between the termination of one
execution and the commencement of the next delay, TimeUnit the time unit of the initialDelay and delay parameters unit)Submits 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. |
| schedule | back to summary |
|---|---|
| public ScheduledFuture Submits a one-shot task that becomes enabled after the given delay.
| |
| schedule | back to summary |
|---|---|
| public <V> ScheduledFuture Submits a value-returning one-shot task that becomes enabled after the given delay.
| |
| scheduleAtFixedRate | back to summary |
|---|---|
| public ScheduledFuture Submits a periodic action that becomes enabled first after the
given initial delay, and subsequently with the given period;
that is, executions will commence after
The sequence of task executions continues indefinitely until one of the following exceptional completions occur:
isDone() on the returned future will
return true.
If any execution of this task takes longer than its period, then subsequent executions may start late, but will not concurrently execute.
| |
| scheduleWithFixedDelay | back to summary |
|---|---|
| public ScheduledFuture Submits 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. The sequence of task executions continues indefinitely until one of the following exceptional completions occur:
isDone() on the returned future will
return true.
| |