util/concurrent/ScheduledExecutor.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

package java.util.concurrent;
import java.util.concurrent.atomic.*;
import java.util.*;

/**
 * An <tt>Executor</tt> that can schedule command to run after a given
 * delay, or to execute periodically. This class is preferable to
 * <tt>java.util.Timer</tt> when multiple worker threads are needed,
 * or when the additional flexibility or capabilities of
 * <tt>ThreadPoolExecutor</tt> (which this class extends) are
 * required.
 *
 * <p> The <tt>schedule</tt> methods create tasks with various delays
 * and return a task object that can be used to cancel or check
 * execution. The <tt>scheduleAtFixedRate</tt> and
 * <tt>scheduleWithFixedDelay</tt> methods create and execute tasks
 * that run periodically until cancelled.  Commands submitted using
 * the <tt>execute</tt> method are scheduled with a requested delay of
 * zero.
 *
 * <p> Delayed tasks execute no sooner than they are enabled, but
 * without any real-time guarantees about when, after they are enabled
 * they will commence. Tasks tied for the same execution time are
 * enabled in first-in-first-out (FIFO) order of submission. An
 * internal {@link DelayQueue} used for scheduling relies on relative
 * delays, which may drift from absolute times (as returned by
 * <tt>System.currentTimeMillis</tt>) over sufficiently long periods.
 *
 * @since 1.5
 * @see Executors
 *
 * @spec JSR-166
 */
public class ScheduledExecutor extends ThreadPoolExecutor {

    /**
     * Sequence number to break scheduling ties, and in turn to
     * guarantee FIFO order among tied entries.
     */
    private static final AtomicLong sequencer = new AtomicLong(0);

    /**
     * A delayed or periodic action.
     */
    public static class DelayedTask extends CancellableTask implements Delayed {
        private final long sequenceNumber;
        private final long time;
        private final long period;
        private final boolean rateBased; // true if at fixed rate;
                                         // false if fixed delay
        /**
         * Creates a one-shot action with given nanoTime-based trigger time
         */
        DelayedTask(Runnable r, long ns) {
            super(r);
            this.time = ns;
            this.period = 0;
            rateBased = false;
            this.sequenceNumber = sequencer.getAndIncrement();
        }

        /**
         * Creates a periodic action with given nano time and period
         */
        DelayedTask(Runnable r, long ns,  long period, boolean rateBased) {
            super(r);
            if (period <= 0)
                throw new IllegalArgumentException();
            this.time = ns;
            this.period = period;
            this.rateBased = rateBased;
            this.sequenceNumber = sequencer.getAndIncrement();
        }


        public long getDelay(TimeUnit unit) {
            return unit.convert(time - TimeUnit.nanoTime(), 
                                TimeUnit.NANOSECONDS);
        }

        public int compareTo(Object other) {
            DelayedTask x = (DelayedTask)other;
            long diff = time - x.time;
            if (diff < 0)
                return -1;
            else if (diff > 0)
                return 1;
            else if (sequenceNumber < x.sequenceNumber)
                return -1;
            else
                return 1;
        }

        /**
         * Return true if this is a periodic (not a one-shot) action.
         */
        public boolean isPeriodic() {
            return period > 0;
        }

        /**
         * Returns the period, or zero if non-periodic
         */
        public long getPeriod(TimeUnit unit) {
            return unit.convert(period, TimeUnit.NANOSECONDS);
        }

        /**
         * Return a new DelayedTask that will trigger in the period
         * subsequent to current task, or null if non-periodic
         * or canceled.
         */
        DelayedTask nextTask() {
            if (period <= 0 || isCancelled())
                return null;
            long nextTime = period + (rateBased ? time : TimeUnit.nanoTime());
            return new DelayedTask(getRunnable(), nextTime, period, rateBased);
        }

    }

    /**
     * A delayed result-bearing action.
     */
    public static class DelayedFutureTask<V> extends DelayedTask implements Future<V> {
        /**
         * Creates a Future that may trigger after the given delay.
         */
        DelayedFutureTask(Callable<V> callable, long delay,  TimeUnit unit) {
            // must set after super ctor call to use inner class
            super(null, TimeUnit.nanoTime() + unit.toNanos(delay));
            setRunnable(new InnerCancellableFuture<V>(callable));
        }

        /**
         * Creates a one-shot action that may trigger after the given date.
         */
        DelayedFutureTask(Callable<V> callable, Date date) {
            super(null, 
                  TimeUnit.MILLISECONDS.toNanos(date.getTime() - 
                                                System.currentTimeMillis()));
            setRunnable(new InnerCancellableFuture<V>(callable));
        }
    
        public V get() throws InterruptedException, ExecutionException {
            return ((InnerCancellableFuture<V>)getRunnable()).get();
        }

        public V get(long timeout, TimeUnit unit)
            throws InterruptedException, ExecutionException, TimeoutException {
            return ((InnerCancellableFuture<V>)getRunnable()).get(timeout, unit);
        }

        protected void set(V v) {
            ((InnerCancellableFuture<V>)getRunnable()).set(v);
        }

        protected void setException(Throwable t) {
            ((InnerCancellableFuture<V>)getRunnable()).setException(t);
        }
    }


    /**
     * An annoying wrapper class to convince generics compiler to
     * use a DelayQueue<DelayedTask> as a BlockingQueue<Runnable>
     */ 
    private static class DelayedWorkQueue extends AbstractQueue<Runnable> implements BlockingQueue<Runnable> {
        private final DelayQueue<DelayedTask> dq = new DelayQueue<DelayedTask>();
        public Runnable poll() { return dq.poll(); }
        public Runnable peek() { return dq.peek(); }
        public Runnable take() throws InterruptedException { return dq.take(); }
        public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException {
            return dq.poll(timeout, unit);
        }
        public boolean offer(Runnable x) { return dq.offer((DelayedTask)x); }
        public void put(Runnable x) throws InterruptedException {
            dq.put((DelayedTask)x); 
        }
        public boolean offer(Runnable x, long timeout, TimeUnit unit) throws InterruptedException {
            return dq.offer((DelayedTask)x, timeout, unit);
        }
        public int remainingCapacity() { return dq.remainingCapacity(); }
        public boolean remove(Object x) { return dq.remove(x); }
        public boolean contains(Object x) { return dq.contains(x); }
        public int size() { return dq.size(); }
        public boolean isEmpty() { return dq.isEmpty(); }
        public Iterator<Runnable> iterator() { 
            return new Iterator<Runnable>() {
                private Iterator<DelayedTask> it = dq.iterator();
                public boolean hasNext() { return it.hasNext(); }
                public Runnable next() { return it.next(); }
                public void remove() {  it.remove(); }
            };
        }
    }

    /**
     * Creates a new ScheduledExecutor with the given initial parameters.
     * 
     * @param corePoolSize the number of threads to keep in the pool,
     * even if they are idle.
     */
    public ScheduledExecutor(int corePoolSize) {
        super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
              new DelayedWorkQueue());
    }

    /**
     * Creates a new ScheduledExecutor with the given initial parameters.
     * 
     * @param corePoolSize the number of threads to keep in the pool,
     * even if they are idle.
     * @param threadFactory the factory to use when the executor
     * creates a new thread. 
     */
    public ScheduledExecutor(int corePoolSize,
                             ThreadFactory threadFactory) {
        super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
              new DelayedWorkQueue(), threadFactory);
    }

    /**
     * Creates a new ScheduledExecutor with the given initial parameters.
     * 
     * @param corePoolSize the number of threads to keep in the pool,
     * even if they are idle.
     * @param handler the handler to use when execution is blocked
     * because the thread bounds and queue capacities are reached.
     */
    public ScheduledExecutor(int corePoolSize,
                              RejectedExecutionHandler handler) {
        super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
              new DelayedWorkQueue(), handler);
    }

    /**
     * Creates a new ScheduledExecutor with the given initial parameters.
     * 
     * @param corePoolSize the number of threads to keep in the pool,
     * even if they are idle.
     * @param threadFactory the factory to use when the executor
     * creates a new thread. 
     * @param handler the handler to use when execution is blocked
     * because the thread bounds and queue capacities are reached.
     */
    public ScheduledExecutor(int corePoolSize,
                              ThreadFactory threadFactory,
                              RejectedExecutionHandler handler) {
        super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
              new DelayedWorkQueue(), threadFactory, handler);
    }

    /**
     * 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 handle that can be used to cancel the task.
     */

    public DelayedTask schedule(Runnable command, long delay,  TimeUnit unit) {
        DelayedTask t = new DelayedTask(command, TimeUnit.nanoTime() + unit.toNanos(delay));
        super.execute(t);
        return t;
    }

    /**
     * Creates and executes a one-shot action that becomes enabled after the given date.
     * @param command the task to execute.
     * @param date the time to commence excution.
     * @return a handle that can be used to cancel the task.
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution because the executor has been shut down.
     */
    public DelayedTask schedule(Runnable command, Date date) {
        DelayedTask t = new DelayedTask
            (command, 
             TimeUnit.MILLISECONDS.toNanos(date.getTime() - 
                                           System.currentTimeMillis()));
        super.execute(t);
        return t;
    }
    
    /**
     * 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
     * <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then
     * <tt>initialDelay + 2 * period</tt>, and so on.
     * @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 delay and period parameters
     * @return a handle that can be used to cancel the task.
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution because the executor has been shut down.
     */
    public DelayedTask scheduleAtFixedRate(Runnable command, long initialDelay,  long period, TimeUnit unit) {
        DelayedTask t = new DelayedTask
            (command, TimeUnit.nanoTime() + unit.toNanos(initialDelay),
             unit.toNanos(period), true);
        super.execute(t);
        return t;
    }
    
    /**
     * Creates a periodic action that becomes enabled first after the
     * given date, and subsequently with the given period
     * period; that is executions will commence after
     * <tt>initialDate</tt> then <tt>initialDate+period</tt>, then
     * <tt>initialDate + 2 * period</tt>, and so on.
     * @param command the task to execute.
     * @param initialDate the time to delay first execution.
     * @param period the period between commencement of successive
     * executions.
     * @param unit the time unit of the  period parameter.
     * @return a handle that can be used to cancel the task.
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution because the executor has been shut down.
     */
    public DelayedTask scheduleAtFixedRate(Runnable command, Date initialDate, long period, TimeUnit unit) {
        DelayedTask t = new DelayedTask
            (command, 
             TimeUnit.MILLISECONDS.toNanos(initialDate.getTime() - 
                                           System.currentTimeMillis()),
             unit.toNanos(period), true);
        super.execute(t);
        return t;
    }

    /**
     * Creates and executes a periodic action that becomes enabled first
     * after the given initial delay, and and subsequently with the
     * given delay between the termination of one execution and the
     * commencement of the next.
     * @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 delay and delay parameters
     * @return a handle that can be used to cancel the task.
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution because the executor has been shut down.
     */
    public DelayedTask scheduleWithFixedDelay(Runnable command, long initialDelay,  long delay, TimeUnit unit) {
        DelayedTask t = new DelayedTask
            (command, TimeUnit.nanoTime() + unit.toNanos(initialDelay),
             unit.toNanos(delay), false);
        super.execute(t);
        return t;
    }
    
    /**
     * Creates a periodic action that becomes enabled first after the
     * given date, and subsequently with the given delay between
     * the termination of one execution and the commencement of the
     * next.
     * @param command the task to execute.
     * @param initialDate 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  delay parameter.
     * @return a handle that can be used to cancel the task.
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution because the executor has been shut down.
     */
    public DelayedTask scheduleWithFixedDelay(Runnable command, Date initialDate, long delay, TimeUnit unit) {
        DelayedTask t = new DelayedTask
            (command, 
             TimeUnit.MILLISECONDS.toNanos(initialDate.getTime() - 
                                           System.currentTimeMillis()),
             unit.toNanos(delay), false);
        super.execute(t);
        return t;
    }


    /**
     * Creates and executes a Future 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 Future that can be used to extract result or cancel.
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution because the executor has been shut down.
     */
    public <V> DelayedFutureTask<V> schedule(Callable<V> callable, long delay,  TimeUnit unit) {
        DelayedFutureTask<V> t = new DelayedFutureTask<V>
            (callable, delay, unit);
        super.execute(t);
        return t;
    }

    /**
     * Creates and executes a one-shot action that becomes enabled after
     * the given date.
     * @param callable the function to execute.
     * @param date the time to commence excution.
     * @return a Future that can be used to extract result or cancel.
     * @throws RejectedExecutionException if task cannot be scheduled
     * for execution because the executor has been shut down.
     */
    public <V> DelayedFutureTask<V> schedule(Callable<V> callable, Date date) {
        DelayedFutureTask<V> t = new DelayedFutureTask<V>
            (callable, date);
        super.execute(t);
        return t;
    }

    /**
     * Execute command with zero required delay
     * @param command the task to execute
     * @throws RejectedExecutionException at discretion of
     * <tt>RejectedExecutionHandler</tt>, if task cannot be accepted
     * for execution because the executor has been shut down.
     */
    public void execute(Runnable command) {
        schedule(command, 0, TimeUnit.NANOSECONDS);
    }

    /**
     * If executed task was periodic, cause the task for the next
     * period to execute.
     */
    protected void afterExecute(Runnable r, Throwable t) { 
        if (isShutdown()) 
            return;
        super.afterExecute(r, t);
        DelayedTask d = (DelayedTask)r;
        DelayedTask next = d.nextTask();
        if (next == null) 
            return;
        try {
            super.execute(next);
        }
        catch(RejectedExecutionException ex) {
            // lost race to detect shutdown; ignore
        }
    }
}


Revision:	1.8
Committed:	Wed Jun 11 13:17:21 2003 UTC (21 years ago) by dl
Branch:	MAIN
Changes since 1.7:	+2 -8 lines
Log Message:	Removed automatic queue removal on cancel; Added TPE purge; Fixed RL typo
#	User	Rev	Content
1	tim	1.1	/*
2	dl	1.4	* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain. Use, modify, and
4			* redistribute this code in any way without acknowledgement.
5	tim	1.1	*/
6
7			package java.util.concurrent;
8	dl	1.4	import java.util.concurrent.atomic.*;
9	dl	1.2	import java.util.*;
10	tim	1.1
11			/**
12	dl	1.7	* An <tt>Executor</tt> that can schedule command to run after a given
13			* delay, or to execute periodically. This class is preferable to
14	tim	1.1	* <tt>java.util.Timer</tt> when multiple worker threads are needed,
15			* or when the additional flexibility or capabilities of
16	dl	1.7	* <tt>ThreadPoolExecutor</tt> (which this class extends) are
17			* required.
18			*
19			* <p> The <tt>schedule</tt> methods create tasks with various delays
20			* and return a task object that can be used to cancel or check
21			* execution. The <tt>scheduleAtFixedRate</tt> and
22			* <tt>scheduleWithFixedDelay</tt> methods create and execute tasks
23			* that run periodically until cancelled. Commands submitted using
24			* the <tt>execute</tt> method are scheduled with a requested delay of
25			* zero.
26			*
27			* <p> Delayed tasks execute no sooner than they are enabled, but
28			* without any real-time guarantees about when, after they are enabled
29			* they will commence. Tasks tied for the same execution time are
30			* enabled in first-in-first-out (FIFO) order of submission. An
31			* internal {@link DelayQueue} used for scheduling relies on relative
32			* delays, which may drift from absolute times (as returned by
33			* <tt>System.currentTimeMillis</tt>) over sufficiently long periods.
34	tim	1.1	*
35			* @since 1.5
36			* @see Executors
37			*
38			* @spec JSR-166
39			*/
40			public class ScheduledExecutor extends ThreadPoolExecutor {
41
42	dl	1.4	/**
43	dl	1.5	* Sequence number to break scheduling ties, and in turn to
44			* guarantee FIFO order among tied entries.
45			*/
46			private static final AtomicLong sequencer = new AtomicLong(0);
47
48			/**
49	dl	1.4	* A delayed or periodic action.
50			*/
51	dl	1.8	public static class DelayedTask extends CancellableTask implements Delayed {
52	dl	1.4	private final long sequenceNumber;
53			private final long time;
54			private final long period;
55	dl	1.7	private final boolean rateBased; // true if at fixed rate;
56			// false if fixed delay
57	dl	1.4	/**
58	dl	1.5	* Creates a one-shot action with given nanoTime-based trigger time
59	dl	1.4	*/
60			DelayedTask(Runnable r, long ns) {
61			super(r);
62			this.time = ns;
63			this.period = 0;
64	dl	1.7	rateBased = false;
65	dl	1.4	this.sequenceNumber = sequencer.getAndIncrement();
66			}
67
68			/**
69	dl	1.5	* Creates a periodic action with given nano time and period
70	dl	1.4	*/
71	dl	1.7	DelayedTask(Runnable r, long ns, long period, boolean rateBased) {
72	dl	1.4	super(r);
73			if (period <= 0)
74			throw new IllegalArgumentException();
75			this.time = ns;
76			this.period = period;
77	dl	1.7	this.rateBased = rateBased;
78	dl	1.4	this.sequenceNumber = sequencer.getAndIncrement();
79			}
80
81
82			public long getDelay(TimeUnit unit) {
83	dl	1.7	return unit.convert(time - TimeUnit.nanoTime(),
84			TimeUnit.NANOSECONDS);
85	dl	1.4	}
86
87			public int compareTo(Object other) {
88			DelayedTask x = (DelayedTask)other;
89			long diff = time - x.time;
90			if (diff < 0)
91			return -1;
92			else if (diff > 0)
93			return 1;
94			else if (sequenceNumber < x.sequenceNumber)
95			return -1;
96			else
97			return 1;
98			}
99
100			/**
101			* Return true if this is a periodic (not a one-shot) action.
102			*/
103			public boolean isPeriodic() {
104			return period > 0;
105			}
106
107			/**
108			* Returns the period, or zero if non-periodic
109			*/
110			public long getPeriod(TimeUnit unit) {
111			return unit.convert(period, TimeUnit.NANOSECONDS);
112			}
113
114			/**
115			* Return a new DelayedTask that will trigger in the period
116			* subsequent to current task, or null if non-periodic
117			* or canceled.
118			*/
119	dl	1.5	DelayedTask nextTask() {
120	dl	1.4	if (period <= 0 \|\| isCancelled())
121			return null;
122	dl	1.7	long nextTime = period + (rateBased ? time : TimeUnit.nanoTime());
123			return new DelayedTask(getRunnable(), nextTime, period, rateBased);
124	dl	1.4	}
125	dl	1.2
126	dl	1.4	}
127	dl	1.2
128	dl	1.4	/**
129			* A delayed result-bearing action.
130			*/
131	dl	1.8	public static class DelayedFutureTask<V> extends DelayedTask implements Future<V> {
132	dl	1.4	/**
133			* Creates a Future that may trigger after the given delay.
134			*/
135			DelayedFutureTask(Callable<V> callable, long delay, TimeUnit unit) {
136			// must set after super ctor call to use inner class
137			super(null, TimeUnit.nanoTime() + unit.toNanos(delay));
138			setRunnable(new InnerCancellableFuture<V>(callable));
139	dl	1.2	}
140
141	dl	1.4	/**
142			* Creates a one-shot action that may trigger after the given date.
143			*/
144			DelayedFutureTask(Callable<V> callable, Date date) {
145			super(null,
146			TimeUnit.MILLISECONDS.toNanos(date.getTime() -
147			System.currentTimeMillis()));
148			setRunnable(new InnerCancellableFuture<V>(callable));
149			}
150
151			public V get() throws InterruptedException, ExecutionException {
152			return ((InnerCancellableFuture<V>)getRunnable()).get();
153	dl	1.2	}
154
155	dl	1.4	public V get(long timeout, TimeUnit unit)
156			throws InterruptedException, ExecutionException, TimeoutException {
157			return ((InnerCancellableFuture<V>)getRunnable()).get(timeout, unit);
158	dl	1.2	}
159	tim	1.1
160	dl	1.4	protected void set(V v) {
161			((InnerCancellableFuture<V>)getRunnable()).set(v);
162	dl	1.2	}
163	tim	1.1
164	dl	1.4	protected void setException(Throwable t) {
165			((InnerCancellableFuture<V>)getRunnable()).setException(t);
166			}
167			}
168
169
170			/**
171			* An annoying wrapper class to convince generics compiler to
172	dl	1.7	* use a DelayQueue<DelayedTask> as a BlockingQueue<Runnable>
173	dl	1.4	*/
174			private static class DelayedWorkQueue extends AbstractQueue<Runnable> implements BlockingQueue<Runnable> {
175			private final DelayQueue<DelayedTask> dq = new DelayQueue<DelayedTask>();
176			public Runnable poll() { return dq.poll(); }
177			public Runnable peek() { return dq.peek(); }
178			public Runnable take() throws InterruptedException { return dq.take(); }
179			public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException {
180			return dq.poll(timeout, unit);
181	dl	1.2	}
182	dl	1.4	public boolean offer(Runnable x) { return dq.offer((DelayedTask)x); }
183			public void put(Runnable x) throws InterruptedException {
184			dq.put((DelayedTask)x);
185	dl	1.2	}
186	dl	1.4	public boolean offer(Runnable x, long timeout, TimeUnit unit) throws InterruptedException {
187			return dq.offer((DelayedTask)x, timeout, unit);
188	dl	1.2	}
189	dl	1.4	public int remainingCapacity() { return dq.remainingCapacity(); }
190			public boolean remove(Object x) { return dq.remove(x); }
191			public boolean contains(Object x) { return dq.contains(x); }
192			public int size() { return dq.size(); }
193			public boolean isEmpty() { return dq.isEmpty(); }
194			public Iterator<Runnable> iterator() {
195			return new Iterator<Runnable>() {
196			private Iterator<DelayedTask> it = dq.iterator();
197			public boolean hasNext() { return it.hasNext(); }
198			public Runnable next() { return it.next(); }
199			public void remove() { it.remove(); }
200			};
201	tim	1.1	}
202	dl	1.4	}
203	tim	1.1
204	dl	1.4	/**
205			* Creates a new ScheduledExecutor with the given initial parameters.
206			*
207			* @param corePoolSize the number of threads to keep in the pool,
208			* even if they are idle.
209			*/
210			public ScheduledExecutor(int corePoolSize) {
211			super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
212			new DelayedWorkQueue());
213			}
214	tim	1.1
215	dl	1.4	/**
216			* Creates a new ScheduledExecutor with the given initial parameters.
217			*
218			* @param corePoolSize the number of threads to keep in the pool,
219			* even if they are idle.
220			* @param threadFactory the factory to use when the executor
221			* creates a new thread.
222			*/
223			public ScheduledExecutor(int corePoolSize,
224			ThreadFactory threadFactory) {
225			super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
226			new DelayedWorkQueue(), threadFactory);
227	tim	1.1	}
228
229	dl	1.4	/**
230			* Creates a new ScheduledExecutor with the given initial parameters.
231			*
232			* @param corePoolSize the number of threads to keep in the pool,
233			* even if they are idle.
234			* @param handler the handler to use when execution is blocked
235			* because the thread bounds and queue capacities are reached.
236			*/
237			public ScheduledExecutor(int corePoolSize,
238			RejectedExecutionHandler handler) {
239			super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
240			new DelayedWorkQueue(), handler);
241			}
242	dl	1.2
243	tim	1.1	/**
244	dl	1.2	* Creates a new ScheduledExecutor with the given initial parameters.
245			*
246			* @param corePoolSize the number of threads to keep in the pool,
247			* even if they are idle.
248	dl	1.4	* @param threadFactory the factory to use when the executor
249			* creates a new thread.
250			* @param handler the handler to use when execution is blocked
251			* because the thread bounds and queue capacities are reached.
252	tim	1.1	*/
253	dl	1.4	public ScheduledExecutor(int corePoolSize,
254			ThreadFactory threadFactory,
255			RejectedExecutionHandler handler) {
256	dl	1.2	super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
257	dl	1.4	new DelayedWorkQueue(), threadFactory, handler);
258			}
259
260			/**
261	dl	1.7	* Creates and executes a one-shot action that becomes enabled after
262	dl	1.4	* the given delay.
263	dl	1.6	* @param command the task to execute.
264			* @param delay the time from now to delay execution.
265			* @param unit the time unit of the delay parameter.
266			* @return a handle that can be used to cancel the task.
267	dl	1.4	*/
268
269	dl	1.6	public DelayedTask schedule(Runnable command, long delay, TimeUnit unit) {
270			DelayedTask t = new DelayedTask(command, TimeUnit.nanoTime() + unit.toNanos(delay));
271	dl	1.4	super.execute(t);
272			return t;
273			}
274
275			/**
276	dl	1.7	* Creates and executes a one-shot action that becomes enabled after the given date.
277	dl	1.6	* @param command the task to execute.
278			* @param date the time to commence excution.
279			* @return a handle that can be used to cancel the task.
280			* @throws RejectedExecutionException if task cannot be scheduled
281			* for execution because the executor has been shut down.
282	dl	1.4	*/
283	dl	1.6	public DelayedTask schedule(Runnable command, Date date) {
284	dl	1.4	DelayedTask t = new DelayedTask
285	dl	1.6	(command,
286	dl	1.4	TimeUnit.MILLISECONDS.toNanos(date.getTime() -
287			System.currentTimeMillis()));
288			super.execute(t);
289			return t;
290			}
291
292			/**
293	dl	1.7	* Creates and executes a periodic action that becomes enabled first
294	dl	1.4	* after the given initial delay, and subsequently with the given
295	dl	1.7	* period; that is executions will commence after
296			* <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then
297			* <tt>initialDelay + 2 * period</tt>, and so on.
298	dl	1.6	* @param command the task to execute.
299			* @param initialDelay the time to delay first execution.
300			* @param period the period between successive executions.
301			* @param unit the time unit of the delay and period parameters
302			* @return a handle that can be used to cancel the task.
303			* @throws RejectedExecutionException if task cannot be scheduled
304			* for execution because the executor has been shut down.
305	dl	1.4	*/
306	dl	1.7	public DelayedTask scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
307	dl	1.4	DelayedTask t = new DelayedTask
308	dl	1.6	(command, TimeUnit.nanoTime() + unit.toNanos(initialDelay),
309	dl	1.7	unit.toNanos(period), true);
310	dl	1.4	super.execute(t);
311			return t;
312			}
313
314			/**
315	dl	1.7	* Creates a periodic action that becomes enabled first after the
316			* given date, and subsequently with the given period
317			* period; that is executions will commence after
318			* <tt>initialDate</tt> then <tt>initialDate+period</tt>, then
319			* <tt>initialDate + 2 * period</tt>, and so on.
320	dl	1.6	* @param command the task to execute.
321			* @param initialDate the time to delay first execution.
322	dl	1.7	* @param period the period between commencement of successive
323			* executions.
324	dl	1.6	* @param unit the time unit of the period parameter.
325			* @return a handle that can be used to cancel the task.
326			* @throws RejectedExecutionException if task cannot be scheduled
327			* for execution because the executor has been shut down.
328	dl	1.4	*/
329	dl	1.7	public DelayedTask scheduleAtFixedRate(Runnable command, Date initialDate, long period, TimeUnit unit) {
330			DelayedTask t = new DelayedTask
331			(command,
332			TimeUnit.MILLISECONDS.toNanos(initialDate.getTime() -
333			System.currentTimeMillis()),
334			unit.toNanos(period), true);
335			super.execute(t);
336			return t;
337			}
338
339			/**
340			* Creates and executes a periodic action that becomes enabled first
341			* after the given initial delay, and and subsequently with the
342			* given delay between the termination of one execution and the
343			* commencement of the next.
344			* @param command the task to execute.
345			* @param initialDelay the time to delay first execution.
346			* @param delay the delay between the termination of one
347			* execution and the commencement of the next.
348			* @param unit the time unit of the delay and delay parameters
349			* @return a handle that can be used to cancel the task.
350			* @throws RejectedExecutionException if task cannot be scheduled
351			* for execution because the executor has been shut down.
352			*/
353			public DelayedTask scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
354			DelayedTask t = new DelayedTask
355			(command, TimeUnit.nanoTime() + unit.toNanos(initialDelay),
356			unit.toNanos(delay), false);
357			super.execute(t);
358			return t;
359			}
360
361			/**
362			* Creates a periodic action that becomes enabled first after the
363			* given date, and subsequently with the given delay between
364			* the termination of one execution and the commencement of the
365			* next.
366			* @param command the task to execute.
367			* @param initialDate the time to delay first execution.
368			* @param delay the delay between the termination of one
369			* execution and the commencement of the next.
370			* @param unit the time unit of the delay parameter.
371			* @return a handle that can be used to cancel the task.
372			* @throws RejectedExecutionException if task cannot be scheduled
373			* for execution because the executor has been shut down.
374			*/
375			public DelayedTask scheduleWithFixedDelay(Runnable command, Date initialDate, long delay, TimeUnit unit) {
376	dl	1.4	DelayedTask t = new DelayedTask
377	dl	1.6	(command,
378			TimeUnit.MILLISECONDS.toNanos(initialDate.getTime() -
379	dl	1.4	System.currentTimeMillis()),
380	dl	1.7	unit.toNanos(delay), false);
381	dl	1.4	super.execute(t);
382			return t;
383	tim	1.1	}
384
385
386	dl	1.4	/**
387	dl	1.7	* Creates and executes a Future that becomes enabled after the
388			* given delay.
389	dl	1.6	* @param callable the function to execute.
390			* @param delay the time from now to delay execution.
391			* @param unit the time unit of the delay parameter.
392			* @return a Future that can be used to extract result or cancel.
393			* @throws RejectedExecutionException if task cannot be scheduled
394			* for execution because the executor has been shut down.
395	dl	1.4	*/
396			public <V> DelayedFutureTask<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
397			DelayedFutureTask<V> t = new DelayedFutureTask<V>
398			(callable, delay, unit);
399			super.execute(t);
400			return t;
401			}
402
403			/**
404	dl	1.7	* Creates and executes a one-shot action that becomes enabled after
405	dl	1.4	* the given date.
406	dl	1.6	* @param callable the function to execute.
407			* @param date the time to commence excution.
408			* @return a Future that can be used to extract result or cancel.
409			* @throws RejectedExecutionException if task cannot be scheduled
410			* for execution because the executor has been shut down.
411	dl	1.4	*/
412			public <V> DelayedFutureTask<V> schedule(Callable<V> callable, Date date) {
413			DelayedFutureTask<V> t = new DelayedFutureTask<V>
414			(callable, date);
415			super.execute(t);
416			return t;
417	tim	1.1	}
418
419	dl	1.4	/**
420			* Execute command with zero required delay
421	dl	1.6	* @param command the task to execute
422			* @throws RejectedExecutionException at discretion of
423			* <tt>RejectedExecutionHandler</tt>, if task cannot be accepted
424			* for execution because the executor has been shut down.
425	dl	1.4	*/
426			public void execute(Runnable command) {
427			schedule(command, 0, TimeUnit.NANOSECONDS);
428	tim	1.1	}
429
430	dl	1.4	/**
431			* If executed task was periodic, cause the task for the next
432			* period to execute.
433			*/
434			protected void afterExecute(Runnable r, Throwable t) {
435			if (isShutdown())
436			return;
437			super.afterExecute(r, t);
438			DelayedTask d = (DelayedTask)r;
439			DelayedTask next = d.nextTask();
440	dl	1.6	if (next == null)
441			return;
442			try {
443	dl	1.4	super.execute(next);
444	dl	1.6	}
445			catch(RejectedExecutionException ex) {
446			// lost race to detect shutdown; ignore
447			}
448	dl	1.4	}
449	tim	1.1	}
450	dl	1.4
451