| JavaTM 2 Platform Std. Ed. v1.5.0
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 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 - if 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 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 - if 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.
- 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 - if 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 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 - if 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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