| java.util.concurrent.ScheduledExecutorService
All known Subclasses: java.util.concurrent.ScheduledThreadPoolExecutor,
ScheduledExecutorService | public interface ScheduledExecutorService extends ExecutorService(Code) | | 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 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.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
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 author: Doug Lea |
Method Summary | |
public ScheduledFuture> | schedule(Runnable command, long delay, TimeUnit unit) Creates and executes a one-shot action that becomes enabled
after the given delay. | public ScheduledFuture<V> | schedule(Callable<V> callable, long delay, TimeUnit unit) Creates and executes a ScheduledFuture that becomes enabled after the
given delay. | public 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. | public 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. |
schedule | public ScheduledFuture> schedule(Runnable command, long delay, TimeUnit unit)(Code) | | Creates and executes a one-shot action that becomes enabled
after the given delay.
Parameters: command - the task to execute Parameters: delay - the time from now to delay execution Parameters: unit - the time unit of the delay parameter a ScheduledFuture representing pending completion ofthe task and whose get() method will returnnull upon completion throws: RejectedExecutionException - if the task cannot bescheduled for execution throws: NullPointerException - if command is null |
schedule | public ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit)(Code) | | Creates and executes a ScheduledFuture that becomes enabled after the
given delay.
Parameters: callable - the function to execute Parameters: delay - the time from now to delay execution Parameters: unit - the time unit of the delay parameter a ScheduledFuture that can be used to extract result or cancel throws: RejectedExecutionException - if the task cannot bescheduled for execution throws: NullPointerException - if callable is null |
scheduleAtFixedRate | public ScheduledFuture> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit)(Code) | | 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 execute Parameters: initialDelay - the time to delay first execution Parameters: period - the period between successive executions Parameters: unit - the time unit of the initialDelay and period parameters a ScheduledFuture representing pending completion ofthe task, and whose get() method will throw anexception upon cancellation throws: RejectedExecutionException - if the task cannot bescheduled for execution throws: NullPointerException - if command is null throws: IllegalArgumentException - if period less than or equal to zero |
scheduleWithFixedDelay | public ScheduledFuture> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit)(Code) | | 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 Parameters: initialDelay - the time to delay first execution Parameters: delay - the delay between the termination of oneexecution and the commencement of the next Parameters: unit - the time unit of the initialDelay and delay parameters a ScheduledFuture representing pending completion ofthe task, and whose get() method will throw anexception upon cancellation throws: RejectedExecutionException - if the task cannot bescheduled for execution throws: NullPointerException - if command is null throws: IllegalArgumentException - if delay less than or equal to zero |
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