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FlexDoc/Javadoc 2.0 Demo Java Doc |
Interface ScheduledExecutorService
All Superinterfaces:
All Known Implementing Classes:
public interface ScheduledExecutorService
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(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() {
Runnable beeper = () -> System.out.println("beep");
ScheduledFuture<?> beeperHandle =
scheduler.scheduleAtFixedRate(beeper, 10, 10, SECONDS);
Runnable canceller = () -> beeperHandle.cancel(false);
scheduler.schedule(canceller, 1, HOURS);
}
}
Since:
1.5
Author:
Doug Lea
Method Summary |
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Submits a value-returning one-shot task that becomes enabled
after the given delay.
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Submits a one-shot task that becomes enabled after the given delay.
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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
initialDelay, then initialDelay + period, then
initialDelay + 2 * period, and so on.
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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.
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awaitTermination, invokeAll, invokeAll, invokeAny, invokeAny, isShutdown, isTerminated, shutdown, shutdownNow, submit, submit, submit |
Methods inherited from interface java.util.concurrent. Executor |
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Submits a one-shot task 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 ScheduledFuture representing pending completion of
the task and whose get() method will return
null upon completion
Throws:
Submits a value-returning one-shot task that becomes enabled
after the given delay.
Type Parameters:
V - the type of the callable's result
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:
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
initialDelay, then
initialDelay + period, then
initialDelay + 2 * period, and so on.
The sequence of task executions continues indefinitely until
one of the following exceptional completions occur:
- The task is explicitly cancelled
via the returned future.
- The executor terminates, also resulting in task cancellation.
- An execution of the task throws an exception. In this case
calling get on the returned future will throw
ExecutionException, holding the exception as its cause.
Subsequent executions are suppressed. Subsequent calls to
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.
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 ScheduledFuture representing pending completion of
the series of repeated tasks. The future's
get() method will never return normally,
and will throw an exception upon task cancellation or
abnormal termination of a task execution.
Throws:
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:
- The task is explicitly cancelled
via the returned future.
- The executor terminates, also resulting in task cancellation.
- An execution of the task throws an exception. In this case
calling get on the returned future will throw
ExecutionException, holding the exception as its cause.
Subsequent executions are suppressed. Subsequent calls to
isDone() on the returned future will
return
true.
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 ScheduledFuture representing pending completion of
the series of repeated tasks. The future's
get() method will never return normally,
and will throw an exception upon task cancellation or
abnormal termination of a task execution.
Throws:
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