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>. Expiration occurs when an element's
 * <tt>getDelay(TimeUnit.NANOSECONDS)</tt> method returns a value less
 * than or equal to zero.  This queue does not permit <tt>null</tt>
 * elements.
 *
 * <p>This class and its iterator implement all of the
 * <em>optional</em> methods of the {@link Collection} and {@link
 * Iterator} interfaces.
 *
 * <p>This class is a member of the
 * <a href="{@docRoot}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @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 of elements to initially contain
     * @throws NullPointerException if the specified collection or any
     *         of its elements are null
     */
    public DelayQueue(Collection<? extends E> c) {
        this.addAll(c);
    }

    /**
     * Inserts the specified element into this delay queue.
     *
     * @param e the element to add
     * @return <tt>true</tt> (as per the spec for {@link Collection#add})
     * @throws NullPointerException if the specified element is null
     */
    public boolean add(E e) {
        return offer(e);
    }

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

    /**
     * Inserts the specified element into this delay queue. As the queue is
     * unbounded this method will never block.
     *
     * @param e the element to add
     * @throws NullPointerException {@inheritDoc}
     */
    public void put(E e) {
        offer(e);
    }

    /**
     * Inserts the specified element into this delay queue. As the queue is
     * unbounded this method will never block.
     *
     * @param e 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 {@inheritDoc}
     */
    public boolean offer(E e, long timeout, TimeUnit unit) {
        return offer(e);
    }

    /**
     * Retrieves and removes the head of this queue, or returns <tt>null</tt>
     * if this queue has no elements with an expired delay.
     *
     * @return the head of this queue, or <tt>null</tt> if this
     *         queue has no elements with an expired delay
     */
    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();
        }
    }

    /**
     * Retrieves and removes the head of this queue, waiting if necessary
     * until an element with an expired delay is available on this queue.
     *
     * @return the head of this queue
     * @throws InterruptedException {@inheritDoc}
     */
    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();
        }
    }

    /**
     * Retrieves and removes the head of this queue, waiting if necessary
     * until an element with an expired delay is available on this queue,
     * or the specified wait time expires.
     *
     * @return the head of this queue, or <tt>null</tt> if the
     *         specified waiting time elapses before an element with
     *         an expired delay becomes available
     * @throws InterruptedException {@inheritDoc}
     */
    public E poll(long timeout, TimeUnit unit) throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        long nanos = unit.toNanos(timeout);
        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();
        }
    }

    /**
     * Retrieves, but does not remove, the head of this queue,
     * returning <tt>null</tt> if this queue has no elements with an
     * expired delay.
     *
     * @return the head of this queue, or <tt>null</tt> if this
     *         queue has no elements with an expired delay
     */
    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();
        }
    }

    /**
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     */
    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();
        }
    }

    /**
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     */
    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.
     * Elements with an unexpired delay are not waited for; they are
     * simply discarded from the queue.
     */
    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;
    }

    /**
     * Returns an array containing all of the elements in this queue.
     * The returned array elements are in no particular order.
     *
     * <p>The returned array will be "safe" in that no references to it are
     * maintained by this queue.  (In other words, this method must allocate
     * a new array).  The caller is thus free to modify the returned array.
     *
     * <p>This method acts as bridge between array-based and collection-based
     * APIs.
     *
     * @return an array containing all of the elements in this queue
     */
    public Object[] toArray() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.toArray();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Returns an array containing all of the elements in this queue; the
     * runtime type of the returned array is that of the specified array.
     * The returned array elements are in no particular order.
     * If the queue fits in the specified array, it is returned therein.
     * Otherwise, a new array is allocated with the runtime type of the
     * specified array and the size of this queue.
     *
     * <p>If this queue fits in the specified array with room to spare
     * (i.e., the array has more elements than this queue), the element in
     * the array immediately following the end of the queue is set to
     * <tt>null</tt>.
     *
     * <p>Like the {@link #toArray()} method, this method acts as bridge between
     * array-based and collection-based APIs.  Further, this method allows
     * precise control over the runtime type of the output array, and may,
     * under certain circumstances, be used to save allocation costs.
     *
     * <p>Suppose <tt>x</tt> is a queue known to contain only strings.
     * The following code can be used to dump the queue into a newly
     * allocated array of <tt>String</tt>:
     *
     * <pre>
     *     String[] y = x.toArray(new String[0]);</pre>
     *
     * Note that <tt>toArray(new Object[0])</tt> is identical in function to
     * <tt>toArray()</tt>.
     *
     * @param a the array into which the elements of the queue are to
     *          be stored, if it is big enough; otherwise, a new array of the
     *          same runtime type is allocated for this purpose
     * @return an array containing all of the elements in this queue
     * @throws ArrayStoreException if the runtime type of the specified array
     *         is not a supertype of the runtime type of every element in
     *         this queue
     * @throws NullPointerException if the specified array is null
     */
    public <T> T[] toArray(T[] a) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.toArray(a);
        } finally {
            lock.unlock();
        }
    }

    /**
     * Removes a single instance of the specified element from this
     * queue, if it is present.
     */
    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 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<E>(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:	1.34
Committed:	Wed May 25 14:05:27 2005 UTC (19 years ago) by dl
Branch:	MAIN
Changes since 1.33:	+1 -1 lines
Log Message:	Avoid generics warnings; clarify javadocs
#	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	dl	1.27	* An unbounded {@linkplain BlockingQueue blocking queue} of
14			* <tt>Delayed</tt> elements, in which an element can only be taken
15			* when its delay has expired. The <em>head</em> of the queue is that
16			* <tt>Delayed</tt> element whose delay expired furthest in the
17	jsr166	1.32	* past. If no delay has expired there is no head and <tt>poll</tt>
18	dl	1.27	* will return <tt>null</tt>. Expiration occurs when an element's
19			* <tt>getDelay(TimeUnit.NANOSECONDS)</tt> method returns a value less
20			* than or equal to zero. This queue does not permit <tt>null</tt>
21			* elements.
22	dl	1.25	*
23	dl	1.26	* <p>This class and its iterator implement all of the
24			* <em>optional</em> methods of the {@link Collection} and {@link
25	jsr166	1.29	* Iterator} interfaces.
26	dl	1.26	*
27	dl	1.25	* <p>This class is a member of the
28			* <a href="{@docRoot}/../guide/collections/index.html">
29			* Java Collections Framework</a>.
30			*
31	dl	1.4	* @since 1.5
32			* @author Doug Lea
33	dl	1.20	* @param <E> the type of elements held in this collection
34	dl	1.19	*/
35	tim	1.1
36	dl	1.3	public class DelayQueue<E extends Delayed> extends AbstractQueue<E>
37			implements BlockingQueue<E> {
38	tim	1.6
39	dl	1.2	private transient final ReentrantLock lock = new ReentrantLock();
40	dl	1.22	private transient final Condition available = lock.newCondition();
41	dl	1.3	private final PriorityQueue<E> q = new PriorityQueue<E>();
42	tim	1.1
43	dl	1.4	/**
44	dholmes	1.7	* Creates a new <tt>DelayQueue</tt> that is initially empty.
45	dl	1.4	*/
46	tim	1.1	public DelayQueue() {}
47
48	tim	1.6	/**
49	tim	1.9	* Creates a <tt>DelayQueue</tt> initially containing the elements of the
50	dholmes	1.7	* given collection of {@link Delayed} instances.
51			*
52	jsr166	1.32	* @param c the collection of elements to initially contain
53			* @throws NullPointerException if the specified collection or any
54			* of its elements are null
55	tim	1.6	*/
56			public DelayQueue(Collection<? extends E> c) {
57			this.addAll(c);
58			}
59
60	dholmes	1.7	/**
61	dl	1.16	* Inserts the specified element into this delay queue.
62	dholmes	1.7	*
63	jsr166	1.30	* @param e the element to add
64	jsr166	1.32	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
65			* @throws NullPointerException if the specified element is null
66			*/
67			public boolean add(E e) {
68			return offer(e);
69			}
70
71			/**
72			* Inserts the specified element into this delay queue.
73			*
74			* @param e the element to add
75	dholmes	1.7	* @return <tt>true</tt>
76	jsr166	1.32	* @throws NullPointerException if the specified element is null
77	dholmes	1.7	*/
78	jsr166	1.30	public boolean offer(E e) {
79	dl	1.21	final ReentrantLock lock = this.lock;
80	dl	1.2	lock.lock();
81			try {
82	dl	1.3	E first = q.peek();
83	jsr166	1.30	q.offer(e);
84			if (first == null \|\| e.compareTo(first) < 0)
85	dl	1.4	available.signalAll();
86	dl	1.2	return true;
87	tim	1.13	} finally {
88	dl	1.2	lock.unlock();
89			}
90			}
91
92	dholmes	1.7	/**
93	jsr166	1.32	* Inserts the specified element into this delay queue. As the queue is
94	dholmes	1.7	* unbounded this method will never block.
95	jsr166	1.32	*
96	jsr166	1.30	* @param e the element to add
97	jsr166	1.32	* @throws NullPointerException {@inheritDoc}
98	dholmes	1.7	*/
99	jsr166	1.30	public void put(E e) {
100			offer(e);
101	dl	1.2	}
102
103	dholmes	1.7	/**
104	dl	1.16	* Inserts the specified element into this delay queue. As the queue is
105	dholmes	1.7	* unbounded this method will never block.
106	jsr166	1.32	*
107	jsr166	1.30	* @param e the element to add
108	dl	1.14	* @param timeout This parameter is ignored as the method never blocks
109	dholmes	1.7	* @param unit This parameter is ignored as the method never blocks
110			* @return <tt>true</tt>
111	jsr166	1.32	* @throws NullPointerException {@inheritDoc}
112	dholmes	1.7	*/
113	jsr166	1.30	public boolean offer(E e, long timeout, TimeUnit unit) {
114			return offer(e);
115	dl	1.2	}
116
117	dholmes	1.7	/**
118	jsr166	1.32	* Retrieves and removes the head of this queue, or returns <tt>null</tt>
119			* if this queue has no elements with an expired delay.
120	dholmes	1.7	*
121	jsr166	1.32	* @return the head of this queue, or <tt>null</tt> if this
122			* queue has no elements with an expired delay
123	dholmes	1.7	*/
124	jsr166	1.32	public E poll() {
125			final ReentrantLock lock = this.lock;
126			lock.lock();
127			try {
128			E first = q.peek();
129			if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
130			return null;
131			else {
132			E x = q.poll();
133			assert x != null;
134			if (q.size() != 0)
135			available.signalAll();
136			return x;
137			}
138			} finally {
139			lock.unlock();
140			}
141	dl	1.2	}
142
143	dl	1.27	/**
144	jsr166	1.32	* Retrieves and removes the head of this queue, waiting if necessary
145			* until an element with an expired delay is available on this queue.
146			*
147	dl	1.27	* @return the head of this queue
148	jsr166	1.32	* @throws InterruptedException {@inheritDoc}
149	dl	1.27	*/
150	dl	1.3	public E take() throws InterruptedException {
151	dl	1.21	final ReentrantLock lock = this.lock;
152	dl	1.2	lock.lockInterruptibly();
153			try {
154			for (;;) {
155	dl	1.3	E first = q.peek();
156	dl	1.12	if (first == null) {
157	dl	1.4	available.await();
158	tim	1.13	} else {
159	dl	1.2	long delay = first.getDelay(TimeUnit.NANOSECONDS);
160	dl	1.12	if (delay > 0) {
161			long tl = available.awaitNanos(delay);
162	tim	1.13	} else {
163	dl	1.3	E x = q.poll();
164	dl	1.2	assert x != null;
165			if (q.size() != 0)
166	dl	1.4	available.signalAll(); // wake up other takers
167	dl	1.2	return x;
168	tim	1.6
169	dl	1.2	}
170			}
171			}
172	tim	1.13	} finally {
173	dl	1.2	lock.unlock();
174			}
175			}
176
177	dl	1.27	/**
178	jsr166	1.32	* Retrieves and removes the head of this queue, waiting if necessary
179			* until an element with an expired delay is available on this queue,
180			* or the specified wait time expires.
181			*
182	dl	1.27	* @return the head of this queue, or <tt>null</tt> if the
183	jsr166	1.32	* specified waiting time elapses before an element with
184			* an expired delay becomes available
185			* @throws InterruptedException {@inheritDoc}
186	dl	1.27	*/
187			public E poll(long timeout, TimeUnit unit) throws InterruptedException {
188	dl	1.21	final ReentrantLock lock = this.lock;
189	dl	1.2	lock.lockInterruptibly();
190	dl	1.27	long nanos = unit.toNanos(timeout);
191	dl	1.2	try {
192			for (;;) {
193	dl	1.3	E first = q.peek();
194	dl	1.2	if (first == null) {
195			if (nanos <= 0)
196			return null;
197			else
198	dl	1.4	nanos = available.awaitNanos(nanos);
199	tim	1.13	} else {
200	dl	1.2	long delay = first.getDelay(TimeUnit.NANOSECONDS);
201			if (delay > 0) {
202			if (delay > nanos)
203			delay = nanos;
204	dl	1.4	long timeLeft = available.awaitNanos(delay);
205	dl	1.2	nanos -= delay - timeLeft;
206	tim	1.13	} else {
207	dl	1.3	E x = q.poll();
208	dl	1.2	assert x != null;
209			if (q.size() != 0)
210	tim	1.6	available.signalAll();
211	dl	1.2	return x;
212			}
213			}
214			}
215	tim	1.13	} finally {
216	dl	1.2	lock.unlock();
217			}
218			}
219
220	dl	1.27	/**
221			* Retrieves, but does not remove, the head of this queue,
222			* returning <tt>null</tt> if this queue has no elements with an
223	jsr166	1.31	* expired delay.
224	dl	1.27	*
225	jsr166	1.32	* @return the head of this queue, or <tt>null</tt> if this
226			* queue has no elements with an expired delay
227	dl	1.27	*/
228	dl	1.3	public E peek() {
229	dl	1.21	final ReentrantLock lock = this.lock;
230	dl	1.2	lock.lock();
231			try {
232			return q.peek();
233	tim	1.13	} finally {
234	dl	1.2	lock.unlock();
235			}
236	tim	1.1	}
237
238	dl	1.2	public int size() {
239	dl	1.21	final ReentrantLock lock = this.lock;
240	dl	1.2	lock.lock();
241			try {
242			return q.size();
243	tim	1.13	} finally {
244	dl	1.2	lock.unlock();
245			}
246			}
247
248	jsr166	1.32	/**
249			* @throws UnsupportedOperationException {@inheritDoc}
250			* @throws ClassCastException {@inheritDoc}
251			* @throws NullPointerException {@inheritDoc}
252			* @throws IllegalArgumentException {@inheritDoc}
253			*/
254	dl	1.17	public int drainTo(Collection<? super E> c) {
255			if (c == null)
256			throw new NullPointerException();
257			if (c == this)
258			throw new IllegalArgumentException();
259	dl	1.21	final ReentrantLock lock = this.lock;
260	dl	1.17	lock.lock();
261			try {
262			int n = 0;
263			for (;;) {
264			E first = q.peek();
265			if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
266			break;
267			c.add(q.poll());
268			++n;
269			}
270			if (n > 0)
271			available.signalAll();
272			return n;
273			} finally {
274			lock.unlock();
275			}
276			}
277
278	jsr166	1.32	/**
279			* @throws UnsupportedOperationException {@inheritDoc}
280			* @throws ClassCastException {@inheritDoc}
281			* @throws NullPointerException {@inheritDoc}
282			* @throws IllegalArgumentException {@inheritDoc}
283			*/
284	dl	1.17	public int drainTo(Collection<? super E> c, int maxElements) {
285			if (c == null)
286			throw new NullPointerException();
287			if (c == this)
288			throw new IllegalArgumentException();
289			if (maxElements <= 0)
290			return 0;
291	dl	1.21	final ReentrantLock lock = this.lock;
292	dl	1.17	lock.lock();
293			try {
294			int n = 0;
295			while (n < maxElements) {
296			E first = q.peek();
297			if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
298			break;
299			c.add(q.poll());
300			++n;
301			}
302			if (n > 0)
303			available.signalAll();
304			return n;
305			} finally {
306			lock.unlock();
307			}
308			}
309
310	dholmes	1.7	/**
311			* Atomically removes all of the elements from this delay queue.
312			* The queue will be empty after this call returns.
313	jsr166	1.32	* Elements with an unexpired delay are not waited for; they are
314			* simply discarded from the queue.
315	dholmes	1.7	*/
316	dl	1.2	public void clear() {
317	dl	1.21	final ReentrantLock lock = this.lock;
318	dl	1.2	lock.lock();
319			try {
320			q.clear();
321	tim	1.13	} finally {
322	dl	1.2	lock.unlock();
323			}
324			}
325	tim	1.1
326	dholmes	1.7	/**
327			* Always returns <tt>Integer.MAX_VALUE</tt> because
328			* a <tt>DelayQueue</tt> is not capacity constrained.
329	jsr166	1.32	*
330	dholmes	1.7	* @return <tt>Integer.MAX_VALUE</tt>
331			*/
332	dl	1.2	public int remainingCapacity() {
333			return Integer.MAX_VALUE;
334	tim	1.1	}
335	dl	1.2
336	jsr166	1.32	/**
337			* Returns an array containing all of the elements in this queue.
338			* The returned array elements are in no particular order.
339			*
340			* <p>The returned array will be "safe" in that no references to it are
341			* maintained by this queue. (In other words, this method must allocate
342			* a new array). The caller is thus free to modify the returned array.
343	jsr166	1.33	*
344	jsr166	1.32	* <p>This method acts as bridge between array-based and collection-based
345			* APIs.
346			*
347			* @return an array containing all of the elements in this queue
348			*/
349	dl	1.2	public Object[] toArray() {
350	dl	1.21	final ReentrantLock lock = this.lock;
351	dl	1.2	lock.lock();
352			try {
353			return q.toArray();
354	tim	1.13	} finally {
355	dl	1.2	lock.unlock();
356			}
357	tim	1.1	}
358	dl	1.2
359	jsr166	1.32	/**
360			* Returns an array containing all of the elements in this queue; the
361			* runtime type of the returned array is that of the specified array.
362			* The returned array elements are in no particular order.
363			* If the queue fits in the specified array, it is returned therein.
364			* Otherwise, a new array is allocated with the runtime type of the
365			* specified array and the size of this queue.
366			*
367			* <p>If this queue fits in the specified array with room to spare
368			* (i.e., the array has more elements than this queue), the element in
369			* the array immediately following the end of the queue is set to
370			* <tt>null</tt>.
371			*
372			* <p>Like the {@link #toArray()} method, this method acts as bridge between
373			* array-based and collection-based APIs. Further, this method allows
374			* precise control over the runtime type of the output array, and may,
375			* under certain circumstances, be used to save allocation costs.
376			*
377			* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
378			* The following code can be used to dump the queue into a newly
379			* allocated array of <tt>String</tt>:
380			*
381			* <pre>
382			* String[] y = x.toArray(new String[0]);</pre>
383			*
384			* Note that <tt>toArray(new Object[0])</tt> is identical in function to
385			* <tt>toArray()</tt>.
386			*
387			* @param a the array into which the elements of the queue are to
388			* be stored, if it is big enough; otherwise, a new array of the
389			* same runtime type is allocated for this purpose
390			* @return an array containing all of the elements in this queue
391			* @throws ArrayStoreException if the runtime type of the specified array
392			* is not a supertype of the runtime type of every element in
393			* this queue
394			* @throws NullPointerException if the specified array is null
395			*/
396			public <T> T[] toArray(T[] a) {
397	dl	1.21	final ReentrantLock lock = this.lock;
398	dl	1.2	lock.lock();
399			try {
400	jsr166	1.32	return q.toArray(a);
401	tim	1.13	} finally {
402	dl	1.2	lock.unlock();
403			}
404	tim	1.1	}
405
406	dl	1.26	/**
407			* Removes a single instance of the specified element from this
408	dl	1.28	* queue, if it is present.
409	dl	1.26	*/
410	dholmes	1.7	public boolean remove(Object o) {
411	dl	1.21	final ReentrantLock lock = this.lock;
412	dl	1.2	lock.lock();
413			try {
414	dholmes	1.7	return q.remove(o);
415	tim	1.13	} finally {
416	dl	1.2	lock.unlock();
417			}
418			}
419
420	dholmes	1.7	/**
421			* Returns an iterator over the elements in this queue. The iterator
422	dl	1.8	* does not return the elements in any particular order. The
423	dl	1.15	* returned iterator is a thread-safe "fast-fail" iterator that will
424	jsr166	1.29	* throw {@link ConcurrentModificationException}
425	dl	1.8	* upon detected interference.
426	dholmes	1.7	*
427	jsr166	1.32	* @return an iterator over the elements in this queue
428	dholmes	1.7	*/
429	dl	1.3	public Iterator<E> iterator() {
430	dl	1.21	final ReentrantLock lock = this.lock;
431	dl	1.2	lock.lock();
432			try {
433	dl	1.34	return new Itr<E>(q.iterator());
434	tim	1.13	} finally {
435	dl	1.2	lock.unlock();
436			}
437			}
438
439	dl	1.3	private class Itr<E> implements Iterator<E> {
440			private final Iterator<E> iter;
441	tim	1.6	Itr(Iterator<E> i) {
442			iter = i;
443	dl	1.2	}
444
445	tim	1.6	public boolean hasNext() {
446	dl	1.2	return iter.hasNext();
447	tim	1.6	}
448
449			public E next() {
450	dl	1.21	final ReentrantLock lock = DelayQueue.this.lock;
451	dl	1.2	lock.lock();
452			try {
453			return iter.next();
454	tim	1.13	} finally {
455	dl	1.2	lock.unlock();
456			}
457	tim	1.6	}
458
459			public void remove() {
460	dl	1.21	final ReentrantLock lock = DelayQueue.this.lock;
461	dl	1.2	lock.lock();
462			try {
463			iter.remove();
464	tim	1.13	} finally {
465	dl	1.2	lock.unlock();
466			}
467	tim	1.6	}
468	tim	1.1	}
469
470			}