edu.emory.mathcs.backport.java.util.concurrent
public interface ScheduledExecutorService extends ExecutorService
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 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.
import static edu.emory.mathcs.backport.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 | |
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ScheduledFuture | schedule(Runnable command, long delay, TimeUnit unit)
Creates and executes a one-shot action that becomes enabled
after the given delay.
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ScheduledFuture | schedule(Callable callable, long delay, TimeUnit unit)
Creates and executes a ScheduledFuture that becomes enabled after the
given delay.
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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.
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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. |
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: RejectedExecutionException if the task cannot be scheduled for execution NullPointerException if command is null
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 the task cannot be scheduled for execution NullPointerException if callable is null
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 task, and whose get() method will throw an exception upon cancellation
Throws: RejectedExecutionException if the task cannot be scheduled for execution NullPointerException if command is null IllegalArgumentException if period less than or equal to zero
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 task, and whose get() method will throw an exception upon cancellation
Throws: RejectedExecutionException if the task cannot be scheduled for execution NullPointerException if command is null IllegalArgumentException if delay less than or equal to zero