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
 * @author Doug Lea
 */
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 {
        /** Sequence number to break ties FIFO */
        private final long sequenceNumber;
        /** The time the task is enabled to execute in nanoTime units */
        private final long time;
        /** The delay forllowing next time, or <= 0 if non-periodic */
        private final long period;
        /** true if at fixed rate; false if fixed delay */
        private final boolean rateBased; 

        /**
         * 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 - System.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.
         * @return true if periodic
         */
        public boolean isPeriodic() {
            return period > 0;
        }

        /**
         * Returns the period, or zero if non-periodic.
         *
         * @return the period
         */
        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 : System.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, System.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, System.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, System.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, System.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.
     * @param r the task (assumed to be a DelayedTask)
     * @param t the exception
     */
    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:	1.11
Committed:	Wed Aug 6 18:22:09 2003 UTC (20 years, 10 months ago) by tim
Branch:	MAIN
CVS Tags:	JSR166_CR1
Changes since 1.10:	+5 -3 lines
Log Message:	Fixes to minor errors found by DocCheck
#	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	dl	1.9	* @author Doug Lea
40	tim	1.1	*/
41			public class ScheduledExecutor extends ThreadPoolExecutor {
42
43	dl	1.4	/**
44	dl	1.5	* Sequence number to break scheduling ties, and in turn to
45			* guarantee FIFO order among tied entries.
46			*/
47			private static final AtomicLong sequencer = new AtomicLong(0);
48
49			/**
50	dl	1.4	* A delayed or periodic action.
51			*/
52	dl	1.8	public static class DelayedTask extends CancellableTask implements Delayed {
53	dl	1.9	/** Sequence number to break ties FIFO */
54	dl	1.4	private final long sequenceNumber;
55	dl	1.9	/** The time the task is enabled to execute in nanoTime units */
56	dl	1.4	private final long time;
57	dl	1.9	/** The delay forllowing next time, or <= 0 if non-periodic */
58	dl	1.4	private final long period;
59	dl	1.9	/** true if at fixed rate; false if fixed delay */
60			private final boolean rateBased;
61
62	dl	1.4	/**
63	dl	1.5	* Creates a one-shot action with given nanoTime-based trigger time
64	dl	1.4	*/
65			DelayedTask(Runnable r, long ns) {
66			super(r);
67			this.time = ns;
68			this.period = 0;
69	dl	1.7	rateBased = false;
70	dl	1.4	this.sequenceNumber = sequencer.getAndIncrement();
71			}
72
73			/**
74	dl	1.5	* Creates a periodic action with given nano time and period
75	dl	1.4	*/
76	dl	1.7	DelayedTask(Runnable r, long ns, long period, boolean rateBased) {
77	dl	1.4	super(r);
78			if (period <= 0)
79			throw new IllegalArgumentException();
80			this.time = ns;
81			this.period = period;
82	dl	1.7	this.rateBased = rateBased;
83	dl	1.4	this.sequenceNumber = sequencer.getAndIncrement();
84			}
85
86
87			public long getDelay(TimeUnit unit) {
88	dl	1.10	return unit.convert(time - System.nanoTime(),
89	dl	1.7	TimeUnit.NANOSECONDS);
90	dl	1.4	}
91
92			public int compareTo(Object other) {
93			DelayedTask x = (DelayedTask)other;
94			long diff = time - x.time;
95			if (diff < 0)
96			return -1;
97			else if (diff > 0)
98			return 1;
99			else if (sequenceNumber < x.sequenceNumber)
100			return -1;
101			else
102			return 1;
103			}
104
105			/**
106			* Return true if this is a periodic (not a one-shot) action.
107	dl	1.9	* @return true if periodic
108	dl	1.4	*/
109			public boolean isPeriodic() {
110			return period > 0;
111			}
112
113			/**
114	tim	1.11	* Returns the period, or zero if non-periodic.
115			*
116	dl	1.9	* @return the period
117	dl	1.4	*/
118			public long getPeriod(TimeUnit unit) {
119			return unit.convert(period, TimeUnit.NANOSECONDS);
120			}
121
122			/**
123			* Return a new DelayedTask that will trigger in the period
124			* subsequent to current task, or null if non-periodic
125			* or canceled.
126			*/
127	dl	1.5	DelayedTask nextTask() {
128	dl	1.4	if (period <= 0 \|\| isCancelled())
129			return null;
130	dl	1.10	long nextTime = period + (rateBased ? time : System.nanoTime());
131	dl	1.7	return new DelayedTask(getRunnable(), nextTime, period, rateBased);
132	dl	1.4	}
133	dl	1.2
134	dl	1.4	}
135	dl	1.2
136	dl	1.4	/**
137			* A delayed result-bearing action.
138			*/
139	dl	1.8	public static class DelayedFutureTask<V> extends DelayedTask implements Future<V> {
140	dl	1.4	/**
141			* Creates a Future that may trigger after the given delay.
142			*/
143			DelayedFutureTask(Callable<V> callable, long delay, TimeUnit unit) {
144			// must set after super ctor call to use inner class
145	dl	1.10	super(null, System.nanoTime() + unit.toNanos(delay));
146	dl	1.4	setRunnable(new InnerCancellableFuture<V>(callable));
147	dl	1.2	}
148
149	dl	1.4	/**
150			* Creates a one-shot action that may trigger after the given date.
151			*/
152			DelayedFutureTask(Callable<V> callable, Date date) {
153			super(null,
154			TimeUnit.MILLISECONDS.toNanos(date.getTime() -
155			System.currentTimeMillis()));
156			setRunnable(new InnerCancellableFuture<V>(callable));
157			}
158
159			public V get() throws InterruptedException, ExecutionException {
160			return ((InnerCancellableFuture<V>)getRunnable()).get();
161	dl	1.2	}
162
163	dl	1.4	public V get(long timeout, TimeUnit unit)
164			throws InterruptedException, ExecutionException, TimeoutException {
165			return ((InnerCancellableFuture<V>)getRunnable()).get(timeout, unit);
166	dl	1.2	}
167	tim	1.1
168	dl	1.4	protected void set(V v) {
169			((InnerCancellableFuture<V>)getRunnable()).set(v);
170	dl	1.2	}
171	tim	1.1
172	dl	1.4	protected void setException(Throwable t) {
173			((InnerCancellableFuture<V>)getRunnable()).setException(t);
174			}
175			}
176
177
178			/**
179			* An annoying wrapper class to convince generics compiler to
180	dl	1.7	* use a DelayQueue<DelayedTask> as a BlockingQueue<Runnable>
181	dl	1.4	*/
182			private static class DelayedWorkQueue extends AbstractQueue<Runnable> implements BlockingQueue<Runnable> {
183			private final DelayQueue<DelayedTask> dq = new DelayQueue<DelayedTask>();
184			public Runnable poll() { return dq.poll(); }
185			public Runnable peek() { return dq.peek(); }
186			public Runnable take() throws InterruptedException { return dq.take(); }
187			public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException {
188			return dq.poll(timeout, unit);
189	dl	1.2	}
190	dl	1.4	public boolean offer(Runnable x) { return dq.offer((DelayedTask)x); }
191			public void put(Runnable x) throws InterruptedException {
192			dq.put((DelayedTask)x);
193	dl	1.2	}
194	dl	1.4	public boolean offer(Runnable x, long timeout, TimeUnit unit) throws InterruptedException {
195			return dq.offer((DelayedTask)x, timeout, unit);
196	dl	1.2	}
197	dl	1.4	public int remainingCapacity() { return dq.remainingCapacity(); }
198			public boolean remove(Object x) { return dq.remove(x); }
199			public boolean contains(Object x) { return dq.contains(x); }
200			public int size() { return dq.size(); }
201	tim	1.11	public boolean isEmpty() { return dq.isEmpty(); }
202	dl	1.4	public Iterator<Runnable> iterator() {
203			return new Iterator<Runnable>() {
204			private Iterator<DelayedTask> it = dq.iterator();
205			public boolean hasNext() { return it.hasNext(); }
206			public Runnable next() { return it.next(); }
207			public void remove() { it.remove(); }
208			};
209	tim	1.1	}
210	dl	1.4	}
211	tim	1.1
212	dl	1.4	/**
213			* Creates a new ScheduledExecutor with the given initial parameters.
214			*
215			* @param corePoolSize the number of threads to keep in the pool,
216			* even if they are idle.
217			*/
218			public ScheduledExecutor(int corePoolSize) {
219			super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
220			new DelayedWorkQueue());
221			}
222	tim	1.1
223	dl	1.4	/**
224			* Creates a new ScheduledExecutor with the given initial parameters.
225			*
226			* @param corePoolSize the number of threads to keep in the pool,
227			* even if they are idle.
228			* @param threadFactory the factory to use when the executor
229			* creates a new thread.
230			*/
231			public ScheduledExecutor(int corePoolSize,
232			ThreadFactory threadFactory) {
233			super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
234			new DelayedWorkQueue(), threadFactory);
235	tim	1.1	}
236
237	dl	1.4	/**
238			* Creates a new ScheduledExecutor with the given initial parameters.
239			*
240			* @param corePoolSize the number of threads to keep in the pool,
241			* even if they are idle.
242			* @param handler the handler to use when execution is blocked
243			* because the thread bounds and queue capacities are reached.
244			*/
245			public ScheduledExecutor(int corePoolSize,
246			RejectedExecutionHandler handler) {
247			super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
248			new DelayedWorkQueue(), handler);
249			}
250	dl	1.2
251	tim	1.1	/**
252	dl	1.2	* Creates a new ScheduledExecutor with the given initial parameters.
253			*
254			* @param corePoolSize the number of threads to keep in the pool,
255			* even if they are idle.
256	dl	1.4	* @param threadFactory the factory to use when the executor
257			* creates a new thread.
258			* @param handler the handler to use when execution is blocked
259			* because the thread bounds and queue capacities are reached.
260	tim	1.1	*/
261	dl	1.4	public ScheduledExecutor(int corePoolSize,
262			ThreadFactory threadFactory,
263			RejectedExecutionHandler handler) {
264	dl	1.2	super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
265	dl	1.4	new DelayedWorkQueue(), threadFactory, handler);
266			}
267
268			/**
269	dl	1.7	* Creates and executes a one-shot action that becomes enabled after
270	dl	1.4	* the given delay.
271	dl	1.6	* @param command the task to execute.
272			* @param delay the time from now to delay execution.
273			* @param unit the time unit of the delay parameter.
274			* @return a handle that can be used to cancel the task.
275	dl	1.4	*/
276
277	dl	1.6	public DelayedTask schedule(Runnable command, long delay, TimeUnit unit) {
278	dl	1.10	DelayedTask t = new DelayedTask(command, System.nanoTime() + unit.toNanos(delay));
279	dl	1.4	super.execute(t);
280			return t;
281			}
282
283			/**
284	dl	1.9	* Creates and executes a one-shot action that becomes enabled
285			* after the given date.
286	dl	1.6	* @param command the task to execute.
287			* @param date the time to commence excution.
288			* @return a handle that can be used to cancel the task.
289			* @throws RejectedExecutionException if task cannot be scheduled
290			* for execution because the executor has been shut down.
291	dl	1.4	*/
292	dl	1.6	public DelayedTask schedule(Runnable command, Date date) {
293	dl	1.4	DelayedTask t = new DelayedTask
294	dl	1.6	(command,
295	dl	1.4	TimeUnit.MILLISECONDS.toNanos(date.getTime() -
296			System.currentTimeMillis()));
297			super.execute(t);
298			return t;
299			}
300
301			/**
302	dl	1.7	* Creates and executes a periodic action that becomes enabled first
303	dl	1.4	* after the given initial delay, and subsequently with the given
304	dl	1.7	* period; that is executions will commence after
305			* <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then
306			* <tt>initialDelay + 2 * period</tt>, and so on.
307	dl	1.6	* @param command the task to execute.
308			* @param initialDelay the time to delay first execution.
309			* @param period the period between successive executions.
310			* @param unit the time unit of the delay and period parameters
311			* @return a handle that can be used to cancel the task.
312			* @throws RejectedExecutionException if task cannot be scheduled
313			* for execution because the executor has been shut down.
314	dl	1.4	*/
315	dl	1.7	public DelayedTask scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
316	dl	1.4	DelayedTask t = new DelayedTask
317	dl	1.10	(command, System.nanoTime() + unit.toNanos(initialDelay),
318	dl	1.7	unit.toNanos(period), true);
319	dl	1.4	super.execute(t);
320			return t;
321			}
322
323			/**
324	dl	1.7	* Creates a periodic action that becomes enabled first after the
325			* given date, and subsequently with the given period
326			* period; that is executions will commence after
327			* <tt>initialDate</tt> then <tt>initialDate+period</tt>, then
328			* <tt>initialDate + 2 * period</tt>, and so on.
329	dl	1.6	* @param command the task to execute.
330			* @param initialDate the time to delay first execution.
331	dl	1.7	* @param period the period between commencement of successive
332			* executions.
333	dl	1.6	* @param unit the time unit of the period parameter.
334			* @return a handle that can be used to cancel the task.
335			* @throws RejectedExecutionException if task cannot be scheduled
336			* for execution because the executor has been shut down.
337	dl	1.4	*/
338	dl	1.7	public DelayedTask scheduleAtFixedRate(Runnable command, Date initialDate, long period, TimeUnit unit) {
339			DelayedTask t = new DelayedTask
340			(command,
341			TimeUnit.MILLISECONDS.toNanos(initialDate.getTime() -
342			System.currentTimeMillis()),
343			unit.toNanos(period), true);
344			super.execute(t);
345			return t;
346			}
347
348			/**
349			* Creates and executes a periodic action that becomes enabled first
350			* after the given initial delay, and and subsequently with the
351			* given delay between the termination of one execution and the
352			* commencement of the next.
353			* @param command the task to execute.
354			* @param initialDelay the time to delay first execution.
355			* @param delay the delay between the termination of one
356			* execution and the commencement of the next.
357			* @param unit the time unit of the delay and delay parameters
358			* @return a handle that can be used to cancel the task.
359			* @throws RejectedExecutionException if task cannot be scheduled
360			* for execution because the executor has been shut down.
361			*/
362			public DelayedTask scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
363			DelayedTask t = new DelayedTask
364	dl	1.10	(command, System.nanoTime() + unit.toNanos(initialDelay),
365	dl	1.7	unit.toNanos(delay), false);
366			super.execute(t);
367			return t;
368			}
369
370			/**
371			* Creates a periodic action that becomes enabled first after the
372			* given date, and subsequently with the given delay between
373			* the termination of one execution and the commencement of the
374			* next.
375			* @param command the task to execute.
376			* @param initialDate the time to delay first execution.
377			* @param delay the delay between the termination of one
378			* execution and the commencement of the next.
379			* @param unit the time unit of the delay parameter.
380			* @return a handle that can be used to cancel the task.
381			* @throws RejectedExecutionException if task cannot be scheduled
382			* for execution because the executor has been shut down.
383			*/
384			public DelayedTask scheduleWithFixedDelay(Runnable command, Date initialDate, long delay, TimeUnit unit) {
385	dl	1.4	DelayedTask t = new DelayedTask
386	dl	1.6	(command,
387			TimeUnit.MILLISECONDS.toNanos(initialDate.getTime() -
388	dl	1.4	System.currentTimeMillis()),
389	dl	1.7	unit.toNanos(delay), false);
390	dl	1.4	super.execute(t);
391			return t;
392	tim	1.1	}
393
394
395	dl	1.4	/**
396	dl	1.7	* Creates and executes a Future that becomes enabled after the
397			* given delay.
398	dl	1.6	* @param callable the function to execute.
399			* @param delay the time from now to delay execution.
400			* @param unit the time unit of the delay parameter.
401			* @return a Future that can be used to extract result or cancel.
402			* @throws RejectedExecutionException if task cannot be scheduled
403			* for execution because the executor has been shut down.
404	dl	1.4	*/
405			public <V> DelayedFutureTask<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
406			DelayedFutureTask<V> t = new DelayedFutureTask<V>
407			(callable, delay, unit);
408			super.execute(t);
409			return t;
410			}
411
412			/**
413	dl	1.7	* Creates and executes a one-shot action that becomes enabled after
414	dl	1.4	* the given date.
415	dl	1.6	* @param callable the function to execute.
416			* @param date the time to commence excution.
417			* @return a Future that can be used to extract result or cancel.
418			* @throws RejectedExecutionException if task cannot be scheduled
419			* for execution because the executor has been shut down.
420	dl	1.4	*/
421			public <V> DelayedFutureTask<V> schedule(Callable<V> callable, Date date) {
422			DelayedFutureTask<V> t = new DelayedFutureTask<V>
423			(callable, date);
424			super.execute(t);
425			return t;
426	tim	1.1	}
427
428	dl	1.4	/**
429	tim	1.11	* Execute command with zero required delay.
430			*
431	dl	1.6	* @param command the task to execute
432			* @throws RejectedExecutionException at discretion of
433			* <tt>RejectedExecutionHandler</tt>, if task cannot be accepted
434			* for execution because the executor has been shut down.
435	dl	1.4	*/
436			public void execute(Runnable command) {
437			schedule(command, 0, TimeUnit.NANOSECONDS);
438	tim	1.1	}
439
440	dl	1.4	/**
441			* If executed task was periodic, cause the task for the next
442			* period to execute.
443	dl	1.9	* @param r the task (assumed to be a DelayedTask)
444			* @param t the exception
445	dl	1.4	*/
446			protected void afterExecute(Runnable r, Throwable t) {
447			if (isShutdown())
448			return;
449			super.afterExecute(r, t);
450			DelayedTask d = (DelayedTask)r;
451			DelayedTask next = d.nextTask();
452	dl	1.6	if (next == null)
453			return;
454			try {
455	dl	1.4	super.execute(next);
456	dl	1.6	}
457			catch(RejectedExecutionException ex) {
458			// lost race to detect shutdown; ignore
459			}
460	dl	1.4	}
461	tim	1.1	}
462	dl	1.4
463