| /* |
| * Written by Doug Lea with assistance from members of JCP JSR-166 |
| * Expert Group and released to the public domain, as explained at |
| * http://creativecommons.org/publicdomain/zero/1.0/ |
| */ |
| |
| package java.util.concurrent; |
| |
| /** |
| * An {@link ExecutorService} that can schedule commands to run after a given |
| * delay, or to execute periodically. |
| * |
| * <p>The {@code schedule} methods create tasks with various delays |
| * and return a task object that can be used to cancel or check |
| * execution. The {@code scheduleAtFixedRate} and |
| * {@code scheduleWithFixedDelay} methods create and execute tasks |
| * that run periodically until cancelled. |
| * |
| * <p>Commands submitted using the {@link Executor#execute(Runnable)} |
| * and {@link ExecutorService} {@code submit} methods are scheduled |
| * with a requested delay of zero. Zero and negative delays (but not |
| * periods) are also allowed in {@code schedule} methods, and are |
| * treated as requests for immediate execution. |
| * |
| * <p>All {@code schedule} methods accept <em>relative</em> 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 {@code date}, you can use: {@code schedule(task, |
| * date.getTime() - System.currentTimeMillis(), |
| * TimeUnit.MILLISECONDS)}. Beware however that expiration of a |
| * relative delay need not coincide with the current {@code Date} at |
| * which the task is enabled due to network time synchronization |
| * protocols, clock drift, or other factors. |
| * |
| * <p>The {@link Executors} class provides convenient factory methods for |
| * the ScheduledExecutorService implementations provided in this package. |
| * |
| * <h3>Usage Example</h3> |
| * |
| * Here is a class with a method that sets up a ScheduledExecutorService |
| * to beep every ten seconds for an hour: |
| * |
| * <pre> {@code |
| * 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); |
| * } |
| * }}</pre> |
| * |
| * @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 ScheduledFuture representing pending completion of |
| * the task and whose {@code get()} method will return |
| * {@code null} upon completion |
| * @throws RejectedExecutionException if the 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 |
| * @param <V> the type of the callable's result |
| * @return a ScheduledFuture that can be used to extract result or cancel |
| * @throws RejectedExecutionException if the task cannot be |
| * scheduled for execution |
| * @throws NullPointerException if callable is null |
| */ |
| public <V> ScheduledFuture<V> schedule(Callable<V> callable, |
| long delay, 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 |
| * {@code initialDelay}, then {@code initialDelay + period}, then |
| * {@code initialDelay + 2 * period}, and so on. |
| * |
| * <p>The sequence of task executions continues indefinitely until |
| * one of the following exceptional completions occur: |
| * <ul> |
| * <li>The task is {@linkplain Future#cancel explicitly cancelled} |
| * via the returned future. |
| * <li>The executor terminates, also resulting in task cancellation. |
| * <li>An execution of the task throws an exception. In this case |
| * calling {@link Future#get() get} on the returned future will |
| * throw {@link ExecutionException}. |
| * </ul> |
| * Subsequent executions are suppressed. Subsequent calls to |
| * {@link Future#isDone isDone()} on the returned future will |
| * return {@code true}. |
| * |
| * <p>If any execution of this task takes longer than its period, then |
| * subsequent executions may start late, but will not concurrently |
| * execute. |
| * |
| * @param command the task to execute |
| * @param initialDelay the time to delay first execution |
| * @param period the period between successive executions |
| * @param unit the time unit of the initialDelay and period parameters |
| * @return a ScheduledFuture representing pending completion of |
| * the series of repeated tasks. The future's {@link |
| * Future#get() get()} method will never return normally, |
| * and will throw an exception upon task cancellation or |
| * abnormal termination of a task execution. |
| * @throws RejectedExecutionException if the task cannot be |
| * scheduled for execution |
| * @throws NullPointerException if command is null |
| * @throws IllegalArgumentException if period less than or equal to zero |
| */ |
| 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 delay between the termination of one execution and the |
| * commencement of the next. |
| * |
| * <p>The sequence of task executions continues indefinitely until |
| * one of the following exceptional completions occur: |
| * <ul> |
| * <li>The task is {@linkplain Future#cancel explicitly cancelled} |
| * via the returned future. |
| * <li>The executor terminates, also resulting in task cancellation. |
| * <li>An execution of the task throws an exception. In this case |
| * calling {@link Future#get() get} on the returned future will |
| * throw {@link ExecutionException}. |
| * </ul> |
| * Subsequent executions are suppressed. Subsequent calls to |
| * {@link Future#isDone isDone()} on the returned future will |
| * return {@code true}. |
| * |
| * @param command the task to execute |
| * @param initialDelay the time to delay first execution |
| * @param delay the delay between the termination of one |
| * execution and the commencement of the next |
| * @param unit the time unit of the initialDelay and delay parameters |
| * @return a ScheduledFuture representing pending completion of |
| * the series of repeated tasks. The future's {@link |
| * Future#get() get()} method will never return normally, |
| * and will throw an exception upon task cancellation or |
| * abnormal termination of a task execution. |
| * @throws RejectedExecutionException if the task cannot be |
| * scheduled for execution |
| * @throws NullPointerException if command is null |
| * @throws IllegalArgumentException if delay less than or equal to zero |
| */ |
| public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, |
| long initialDelay, |
| long delay, |
| TimeUnit unit); |
| |
| } |
