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 {@link Executor#execute} and * {@link 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 {@link * 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 {@link 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() {
* 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
*/
public interface ScheduledExecutorService extends ExecutorService {
/**
* Creates and executes a one-shot action that becomes enabled
* after the given delay.
* @param command the task to execute.
* @param delay the time from now to delay execution.
* @param unit the time unit of the delay parameter.
* @return 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.
* @throws NullPointerException if command is null
*/
public ScheduledFuture schedule(Runnable command, long delay, TimeUnit unit);
/**
* Creates and executes a ScheduledFuture that becomes enabled after the
* given delay.
* @param callable the function to execute.
* @param delay the time from now to delay execution.
* @param unit the time unit of the delay parameter.
* @return a ScheduledFuture that can be used to extract result or cancel.
* @throws RejectedExecutionException if task cannot be scheduled
* for execution.
* @throws NullPointerException if callable is null
*/
public