util/concurrent/DelayQueue.java

/*
 * 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/licenses/publicdomain
 */


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

/**
 * An unbounded {@linkplain BlockingQueue blocking queue} of <tt>Delayed</tt>
 * elements, in which an element can only be taken when its delay has expired.
 * The <em>head</em> of the queue is that <tt>Delayed</tt> element whose delay
 * expired furthest in the past - if no delay has expired there is no head and
 * <tt>poll</tt> will return <tt>null</tt>.
 * This queue does not permit <tt>null</tt> elements.
 * <p>This class implements all of the <em>optional</em> methods
 * of the {@link Collection} and {@link Iterator} interfaces.
 * @since 1.5
 * @author Doug Lea
 * @param <E> the type of elements held in this collection
 */

public class DelayQueue<E extends Delayed> extends AbstractQueue<E>
    implements BlockingQueue<E> {

    private transient final ReentrantLock lock = new ReentrantLock();
    private transient final Condition available = lock.newCondition();
    private final PriorityQueue<E> q = new PriorityQueue<E>();

    /**
     * Creates a new <tt>DelayQueue</tt> that is initially empty.
     */
    public DelayQueue() {}

    /**
     * Creates a <tt>DelayQueue</tt> initially containing the elements of the
     * given collection of {@link Delayed} instances.
     *
     * @param c the collection
     * @throws NullPointerException if <tt>c</tt> or any element within it
     * is <tt>null</tt>
     *
     */
    public DelayQueue(Collection<? extends E> c) {
        this.addAll(c);
    }

    /**
     * Inserts the specified element into this delay queue.
     *
     * @param o the element to add
     * @return <tt>true</tt>
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     */
    public boolean offer(E o) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            E first = q.peek();
            q.offer(o);
            if (first == null || o.compareTo(first) < 0)
                available.signalAll();
            return true;
        } finally {
            lock.unlock();
        }
    }


    /**
     * Adds the specified element to this delay queue. As the queue is
     * unbounded this method will never block.
     * @param o the element to add
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     */
    public void put(E o) {
        offer(o);
    }

    /**
     * Inserts the specified element into this delay queue. As the queue is
     * unbounded this method will never block.
     * @param o the element to add
     * @param timeout This parameter is ignored as the method never blocks
     * @param unit This parameter is ignored as the method never blocks
     * @return <tt>true</tt>
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     */
    public boolean offer(E o, long timeout, TimeUnit unit) {
        return offer(o);
    }

    /**
     * Adds the specified element to this queue.
     * @param o the element to add
     * @return <tt>true</tt> (as per the general contract of
     * <tt>Collection.add</tt>).
     *
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     */
    public boolean add(E o) {
        return offer(o);
    }

    public E take() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            for (;;) {
                E first = q.peek();
                if (first == null) {
                    available.await();
                } else {
                    long delay =  first.getDelay(TimeUnit.NANOSECONDS);
                    if (delay > 0) {
                        long tl = available.awaitNanos(delay);
                    } else {
                        E x = q.poll();
                        assert x != null;
                        if (q.size() != 0)
                            available.signalAll(); // wake up other takers
                        return x;

                    }
                }
            }
        } finally {
            lock.unlock();
        }
    }

    public E poll(long time, TimeUnit unit) throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        long nanos = unit.toNanos(time);
        try {
            for (;;) {
                E first = q.peek();
                if (first == null) {
                    if (nanos <= 0)
                        return null;
                    else
                        nanos = available.awaitNanos(nanos);
                } else {
                    long delay =  first.getDelay(TimeUnit.NANOSECONDS);
                    if (delay > 0) {
                        if (delay > nanos)
                            delay = nanos;
                        long timeLeft = available.awaitNanos(delay);
                        nanos -= delay - timeLeft;
                    } else {
                        E x = q.poll();
                        assert x != null;
                        if (q.size() != 0)
                            available.signalAll();
                        return x;
                    }
                }
            }
        } finally {
            lock.unlock();
        }
    }


    public E poll() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            E first = q.peek();
            if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0)
                return null;
            else {
                E x = q.poll();
                assert x != null;
                if (q.size() != 0)
                    available.signalAll();
                return x;
            }
        } finally {
            lock.unlock();
        }
    }

    public E peek() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.peek();
        } finally {
            lock.unlock();
        }
    }

    public int size() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.size();
        } finally {
            lock.unlock();
        }
    }

    public int drainTo(Collection<? super E> c) {
        if (c == null)
            throw new NullPointerException();
        if (c == this)
            throw new IllegalArgumentException();
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            int n = 0;
            for (;;) {
                E first = q.peek();
                if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0)
                    break;
                c.add(q.poll());
                ++n;
            }
            if (n > 0)
                available.signalAll();
            return n;
        } finally {
            lock.unlock();
        }
    }

    public int drainTo(Collection<? super E> c, int maxElements) {
        if (c == null)
            throw new NullPointerException();
        if (c == this)
            throw new IllegalArgumentException();
        if (maxElements <= 0)
            return 0;
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            int n = 0;
            while (n < maxElements) {
                E first = q.peek();
                if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0)
                    break;
                c.add(q.poll());
                ++n;
            }
            if (n > 0)
                available.signalAll();
            return n;
        } finally {
            lock.unlock();
        }
    }

    /**
     * Atomically removes all of the elements from this delay queue.
     * The queue will be empty after this call returns.
     */
    public void clear() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            q.clear();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Always returns <tt>Integer.MAX_VALUE</tt> because
     * a <tt>DelayQueue</tt> is not capacity constrained.
     * @return <tt>Integer.MAX_VALUE</tt>
     */
    public int remainingCapacity() {
        return Integer.MAX_VALUE;
    }

    public Object[] toArray() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.toArray();
        } finally {
            lock.unlock();
        }
    }

    public <T> T[] toArray(T[] array) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.toArray(array);
        } finally {
            lock.unlock();
        }
    }

    public boolean remove(Object o) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.remove(o);
        } finally {
            lock.unlock();
        }
    }

    /**
     * Returns an iterator over the elements in this queue. The iterator
     * does not return the elements in any particular order. The
     * returned iterator is a thread-safe "fast-fail" iterator that will
     * throw {@link java.util.ConcurrentModificationException}
     * upon detected interference.
     *
     * @return an iterator over the elements in this queue.
     */
    public Iterator<E> iterator() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return new Itr(q.iterator());
        } finally {
            lock.unlock();
        }
    }

    private class Itr<E> implements Iterator<E> {
        private final Iterator<E> iter;
        Itr(Iterator<E> i) {
            iter = i;
        }

        public boolean hasNext() {
            return iter.hasNext();
        }

        public E next() {
            final ReentrantLock lock = DelayQueue.this.lock;
            lock.lock();
            try {
                return iter.next();
            } finally {
                lock.unlock();
            }
        }

        public void remove() {
            final ReentrantLock lock = DelayQueue.this.lock;
            lock.lock();
            try {
                iter.remove();
            } finally {
                lock.unlock();
            }
        }
    }

}
Revision:	1.24
Committed:	Tue Jan 20 04:35:02 2004 UTC (20 years, 4 months ago) by dl
Branch:	MAIN
Changes since 1.23:	+1 -0 lines
Log Message:	javadoc lint; Thread.interrupt shouldn't throw exception if thread dead
#	User	Rev	Content
1	dl	1.2	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.23	* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5	dl	1.2	*/
6
7
8	tim	1.1	package java.util.concurrent;
9	dl	1.5	import java.util.concurrent.locks.*;
10	tim	1.1	import java.util.*;
11
12			/**
13	tim	1.9	* An unbounded {@linkplain BlockingQueue blocking queue} of <tt>Delayed</tt>
14	dholmes	1.7	* elements, in which an element can only be taken when its delay has expired.
15			* The <em>head</em> of the queue is that <tt>Delayed</tt> element whose delay
16			* expired furthest in the past - if no delay has expired there is no head and
17			* <tt>poll</tt> will return <tt>null</tt>.
18			* This queue does not permit <tt>null</tt> elements.
19	dl	1.15	* <p>This class implements all of the <em>optional</em> methods
20			* of the {@link Collection} and {@link Iterator} interfaces.
21	dl	1.4	* @since 1.5
22			* @author Doug Lea
23	dl	1.20	* @param <E> the type of elements held in this collection
24	dl	1.19	*/
25	tim	1.1
26	dl	1.3	public class DelayQueue<E extends Delayed> extends AbstractQueue<E>
27			implements BlockingQueue<E> {
28	tim	1.6
29	dl	1.2	private transient final ReentrantLock lock = new ReentrantLock();
30	dl	1.22	private transient final Condition available = lock.newCondition();
31	dl	1.3	private final PriorityQueue<E> q = new PriorityQueue<E>();
32	tim	1.1
33	dl	1.4	/**
34	dholmes	1.7	* Creates a new <tt>DelayQueue</tt> that is initially empty.
35	dl	1.4	*/
36	tim	1.1	public DelayQueue() {}
37
38	tim	1.6	/**
39	tim	1.9	* Creates a <tt>DelayQueue</tt> initially containing the elements of the
40	dholmes	1.7	* given collection of {@link Delayed} instances.
41			*
42	dl	1.24	* @param c the collection
43	dholmes	1.7	* @throws NullPointerException if <tt>c</tt> or any element within it
44			* is <tt>null</tt>
45	tim	1.6	*
46			*/
47			public DelayQueue(Collection<? extends E> c) {
48			this.addAll(c);
49			}
50
51	dholmes	1.7	/**
52	dl	1.16	* Inserts the specified element into this delay queue.
53	dholmes	1.7	*
54	dl	1.14	* @param o the element to add
55	dholmes	1.7	* @return <tt>true</tt>
56	dl	1.14	* @throws NullPointerException if the specified element is <tt>null</tt>.
57	dholmes	1.7	*/
58			public boolean offer(E o) {
59	dl	1.21	final ReentrantLock lock = this.lock;
60	dl	1.2	lock.lock();
61			try {
62	dl	1.3	E first = q.peek();
63	dholmes	1.7	q.offer(o);
64			if (first == null \|\| o.compareTo(first) < 0)
65	dl	1.4	available.signalAll();
66	dl	1.2	return true;
67	tim	1.13	} finally {
68	dl	1.2	lock.unlock();
69			}
70			}
71
72	dholmes	1.7
73			/**
74			* Adds the specified element to this delay queue. As the queue is
75			* unbounded this method will never block.
76	dl	1.14	* @param o the element to add
77			* @throws NullPointerException if the specified element is <tt>null</tt>.
78	dholmes	1.7	*/
79			public void put(E o) {
80			offer(o);
81	dl	1.2	}
82
83	dholmes	1.7	/**
84	dl	1.16	* Inserts the specified element into this delay queue. As the queue is
85	dholmes	1.7	* unbounded this method will never block.
86	dl	1.14	* @param o the element to add
87			* @param timeout This parameter is ignored as the method never blocks
88	dholmes	1.7	* @param unit This parameter is ignored as the method never blocks
89			* @return <tt>true</tt>
90	dl	1.14	* @throws NullPointerException if the specified element is <tt>null</tt>.
91	dholmes	1.7	*/
92	dl	1.14	public boolean offer(E o, long timeout, TimeUnit unit) {
93	dholmes	1.7	return offer(o);
94	dl	1.2	}
95
96	dholmes	1.7	/**
97			* Adds the specified element to this queue.
98	dl	1.14	* @param o the element to add
99	dholmes	1.7	* @return <tt>true</tt> (as per the general contract of
100			* <tt>Collection.add</tt>).
101			*
102	dl	1.14	* @throws NullPointerException if the specified element is <tt>null</tt>.
103	dholmes	1.7	*/
104			public boolean add(E o) {
105			return offer(o);
106	dl	1.2	}
107
108	dl	1.3	public E take() throws InterruptedException {
109	dl	1.21	final ReentrantLock lock = this.lock;
110	dl	1.2	lock.lockInterruptibly();
111			try {
112			for (;;) {
113	dl	1.3	E first = q.peek();
114	dl	1.12	if (first == null) {
115	dl	1.4	available.await();
116	tim	1.13	} else {
117	dl	1.2	long delay = first.getDelay(TimeUnit.NANOSECONDS);
118	dl	1.12	if (delay > 0) {
119			long tl = available.awaitNanos(delay);
120	tim	1.13	} else {
121	dl	1.3	E x = q.poll();
122	dl	1.2	assert x != null;
123			if (q.size() != 0)
124	dl	1.4	available.signalAll(); // wake up other takers
125	dl	1.2	return x;
126	tim	1.6
127	dl	1.2	}
128			}
129			}
130	tim	1.13	} finally {
131	dl	1.2	lock.unlock();
132			}
133			}
134
135	dl	1.3	public E poll(long time, TimeUnit unit) throws InterruptedException {
136	dl	1.21	final ReentrantLock lock = this.lock;
137	dl	1.2	lock.lockInterruptibly();
138			long nanos = unit.toNanos(time);
139			try {
140			for (;;) {
141	dl	1.3	E first = q.peek();
142	dl	1.2	if (first == null) {
143			if (nanos <= 0)
144			return null;
145			else
146	dl	1.4	nanos = available.awaitNanos(nanos);
147	tim	1.13	} else {
148	dl	1.2	long delay = first.getDelay(TimeUnit.NANOSECONDS);
149			if (delay > 0) {
150			if (delay > nanos)
151			delay = nanos;
152	dl	1.4	long timeLeft = available.awaitNanos(delay);
153	dl	1.2	nanos -= delay - timeLeft;
154	tim	1.13	} else {
155	dl	1.3	E x = q.poll();
156	dl	1.2	assert x != null;
157			if (q.size() != 0)
158	tim	1.6	available.signalAll();
159	dl	1.2	return x;
160			}
161			}
162			}
163	tim	1.13	} finally {
164	dl	1.2	lock.unlock();
165			}
166			}
167
168
169	dl	1.3	public E poll() {
170	dl	1.21	final ReentrantLock lock = this.lock;
171	dl	1.2	lock.lock();
172			try {
173	dl	1.3	E first = q.peek();
174	dl	1.2	if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
175			return null;
176			else {
177	dl	1.3	E x = q.poll();
178	dl	1.2	assert x != null;
179			if (q.size() != 0)
180	tim	1.6	available.signalAll();
181	dl	1.2	return x;
182			}
183	tim	1.13	} finally {
184	dl	1.2	lock.unlock();
185			}
186			}
187
188	dl	1.3	public E peek() {
189	dl	1.21	final ReentrantLock lock = this.lock;
190	dl	1.2	lock.lock();
191			try {
192			return q.peek();
193	tim	1.13	} finally {
194	dl	1.2	lock.unlock();
195			}
196	tim	1.1	}
197
198	dl	1.2	public int size() {
199	dl	1.21	final ReentrantLock lock = this.lock;
200	dl	1.2	lock.lock();
201			try {
202			return q.size();
203	tim	1.13	} finally {
204	dl	1.2	lock.unlock();
205			}
206			}
207
208	dl	1.17	public int drainTo(Collection<? super E> c) {
209			if (c == null)
210			throw new NullPointerException();
211			if (c == this)
212			throw new IllegalArgumentException();
213	dl	1.21	final ReentrantLock lock = this.lock;
214	dl	1.17	lock.lock();
215			try {
216			int n = 0;
217			for (;;) {
218			E first = q.peek();
219			if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
220			break;
221			c.add(q.poll());
222			++n;
223			}
224			if (n > 0)
225			available.signalAll();
226			return n;
227			} finally {
228			lock.unlock();
229			}
230			}
231
232			public int drainTo(Collection<? super E> c, int maxElements) {
233			if (c == null)
234			throw new NullPointerException();
235			if (c == this)
236			throw new IllegalArgumentException();
237			if (maxElements <= 0)
238			return 0;
239	dl	1.21	final ReentrantLock lock = this.lock;
240	dl	1.17	lock.lock();
241			try {
242			int n = 0;
243			while (n < maxElements) {
244			E first = q.peek();
245			if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
246			break;
247			c.add(q.poll());
248			++n;
249			}
250			if (n > 0)
251			available.signalAll();
252			return n;
253			} finally {
254			lock.unlock();
255			}
256			}
257
258	dholmes	1.7	/**
259			* Atomically removes all of the elements from this delay queue.
260			* The queue will be empty after this call returns.
261			*/
262	dl	1.2	public void clear() {
263	dl	1.21	final ReentrantLock lock = this.lock;
264	dl	1.2	lock.lock();
265			try {
266			q.clear();
267	tim	1.13	} finally {
268	dl	1.2	lock.unlock();
269			}
270			}
271	tim	1.1
272	dholmes	1.7	/**
273			* Always returns <tt>Integer.MAX_VALUE</tt> because
274			* a <tt>DelayQueue</tt> is not capacity constrained.
275			* @return <tt>Integer.MAX_VALUE</tt>
276			*/
277	dl	1.2	public int remainingCapacity() {
278			return Integer.MAX_VALUE;
279	tim	1.1	}
280	dl	1.2
281			public Object[] toArray() {
282	dl	1.21	final ReentrantLock lock = this.lock;
283	dl	1.2	lock.lock();
284			try {
285			return q.toArray();
286	tim	1.13	} finally {
287	dl	1.2	lock.unlock();
288			}
289	tim	1.1	}
290	dl	1.2
291			public <T> T[] toArray(T[] array) {
292	dl	1.21	final ReentrantLock lock = this.lock;
293	dl	1.2	lock.lock();
294			try {
295			return q.toArray(array);
296	tim	1.13	} finally {
297	dl	1.2	lock.unlock();
298			}
299	tim	1.1	}
300
301	dholmes	1.7	public boolean remove(Object o) {
302	dl	1.21	final ReentrantLock lock = this.lock;
303	dl	1.2	lock.lock();
304			try {
305	dholmes	1.7	return q.remove(o);
306	tim	1.13	} finally {
307	dl	1.2	lock.unlock();
308			}
309			}
310
311	dholmes	1.7	/**
312			* Returns an iterator over the elements in this queue. The iterator
313	dl	1.8	* does not return the elements in any particular order. The
314	dl	1.15	* returned iterator is a thread-safe "fast-fail" iterator that will
315	dl	1.8	* throw {@link java.util.ConcurrentModificationException}
316			* upon detected interference.
317	dholmes	1.7	*
318			* @return an iterator over the elements in this queue.
319			*/
320	dl	1.3	public Iterator<E> iterator() {
321	dl	1.21	final ReentrantLock lock = this.lock;
322	dl	1.2	lock.lock();
323			try {
324			return new Itr(q.iterator());
325	tim	1.13	} finally {
326	dl	1.2	lock.unlock();
327			}
328			}
329
330	dl	1.3	private class Itr<E> implements Iterator<E> {
331			private final Iterator<E> iter;
332	tim	1.6	Itr(Iterator<E> i) {
333			iter = i;
334	dl	1.2	}
335
336	tim	1.6	public boolean hasNext() {
337	dl	1.2	return iter.hasNext();
338	tim	1.6	}
339
340			public E next() {
341	dl	1.21	final ReentrantLock lock = DelayQueue.this.lock;
342	dl	1.2	lock.lock();
343			try {
344			return iter.next();
345	tim	1.13	} finally {
346	dl	1.2	lock.unlock();
347			}
348	tim	1.6	}
349
350			public void remove() {
351	dl	1.21	final ReentrantLock lock = DelayQueue.this.lock;
352	dl	1.2	lock.lock();
353			try {
354			iter.remove();
355	tim	1.13	} finally {
356	dl	1.2	lock.unlock();
357			}
358	tim	1.6	}
359	tim	1.1	}
360
361			}