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.  Even though unexpired elements cannot be
 * removed using <tt>take</tt> or <tt>poll</tt>, they are otherwise
 * treated as normal elements. For example, the <tt>size</tt> method
 * returns the count of both expired and unexpired elements.
 * This queue does not permit null 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 specified by {@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 {
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        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 (nanos <= 0)
                            return null;
                        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, or
     * returns <tt>null</tt> if this queue is empty.  Unlike
     * <tt>poll</tt>, if no expired elements are available in the queue,
     * this method returns the element that will expire next,
     * if one exists.
     *
     * @return the head of this queue, or <tt>null</tt> if this
     *         queue is empty.
     */
    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>The following code can be used to dump a delay queue into a newly
     * allocated array of <tt>Delayed</tt>:
     *
     * <pre>
     *     Delayed[] a = q.toArray(new Delayed[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, whether or not it has expired.
     */
    public boolean remove(Object o) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.remove(o);
        } finally {
            lock.unlock();
        }
    }

    /**
     * Returns an iterator over all the elements (both expired and
     * unexpired) in this queue. The iterator does not return the
     * elements in any particular order.  The returned
     * <tt>Iterator</tt> is a "weakly consistent" iterator that will
     * never throw {@link ConcurrentModificationException}, and
     * guarantees to traverse elements as they existed upon
     * construction of the iterator, and may (but is not guaranteed
     * to) reflect any modifications subsequent to construction.
     *
     * @return an iterator over the elements in this queue
     */
    public Iterator<E> iterator() {
        return new Itr(toArray());
    }

    /**
     * Snapshot iterator that works off copy of underlying q array.
     */
    private class Itr implements Iterator<E> {
        final Object[] array; // Array of all elements
        int cursor;           // index of next element to return;
        int lastRet;          // index of last element, or -1 if no such

        Itr(Object[] array) {
            lastRet = -1;
            this.array = array;
        }

        public boolean hasNext() {
            return cursor < array.length;
        }

        public E next() {
            if (cursor >= array.length)
                throw new NoSuchElementException();
            lastRet = cursor;
            return (E)array[cursor++];
        }

        public void remove() {
            if (lastRet < 0)
                throw new IllegalStateException();
            Object x = array[lastRet];
            lastRet = -1;
            // Traverse underlying queue to find == element,
            // not just a .equals element.
            lock.lock();
            try {
                for (Iterator it = q.iterator(); it.hasNext(); ) {
                    if (it.next() == x) {
                        it.remove();
                        return;
                    }
                }
            } finally {
                lock.unlock();
            }
        }
    }

}
Revision:	1.45
Committed:	Tue Feb 7 20:54:24 2006 UTC (18 years, 3 months ago) by jsr166
Branch:	MAIN
Changes since 1.44:	+0 -1 lines
Log Message:	6378729: Remove workaround for 6280605
#	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	dl	1.36	* than or equal to zero. Even though unexpired elements cannot be
21			* removed using <tt>take</tt> or <tt>poll</tt>, they are otherwise
22			* treated as normal elements. For example, the <tt>size</tt> method
23			* returns the count of both expired and unexpired elements.
24	jsr166	1.39	* This queue does not permit null elements.
25	dl	1.25	*
26	dl	1.26	* <p>This class and its iterator implement all of the
27			* <em>optional</em> methods of the {@link Collection} and {@link
28	jsr166	1.29	* Iterator} interfaces.
29	dl	1.26	*
30	dl	1.25	* <p>This class is a member of the
31			* <a href="{@docRoot}/../guide/collections/index.html">
32			* Java Collections Framework</a>.
33			*
34	dl	1.4	* @since 1.5
35			* @author Doug Lea
36	dl	1.20	* @param <E> the type of elements held in this collection
37	dl	1.19	*/
38	tim	1.1
39	dl	1.3	public class DelayQueue<E extends Delayed> extends AbstractQueue<E>
40			implements BlockingQueue<E> {
41	tim	1.6
42	dl	1.2	private transient final ReentrantLock lock = new ReentrantLock();
43	dl	1.22	private transient final Condition available = lock.newCondition();
44	dl	1.3	private final PriorityQueue<E> q = new PriorityQueue<E>();
45	tim	1.1
46	dl	1.4	/**
47	dholmes	1.7	* Creates a new <tt>DelayQueue</tt> that is initially empty.
48	dl	1.4	*/
49	tim	1.1	public DelayQueue() {}
50
51	tim	1.6	/**
52	tim	1.9	* Creates a <tt>DelayQueue</tt> initially containing the elements of the
53	dholmes	1.7	* given collection of {@link Delayed} instances.
54			*
55	jsr166	1.32	* @param c the collection of elements to initially contain
56			* @throws NullPointerException if the specified collection or any
57			* of its elements are null
58	tim	1.6	*/
59			public DelayQueue(Collection<? extends E> c) {
60			this.addAll(c);
61			}
62
63	dholmes	1.7	/**
64	dl	1.16	* Inserts the specified element into this delay queue.
65	dholmes	1.7	*
66	jsr166	1.30	* @param e the element to add
67	jsr166	1.38	* @return <tt>true</tt> (as specified by {@link Collection#add})
68	jsr166	1.32	* @throws NullPointerException if the specified element is null
69			*/
70			public boolean add(E e) {
71			return offer(e);
72			}
73
74			/**
75			* Inserts the specified element into this delay queue.
76			*
77			* @param e the element to add
78	dholmes	1.7	* @return <tt>true</tt>
79	jsr166	1.32	* @throws NullPointerException if the specified element is null
80	dholmes	1.7	*/
81	jsr166	1.30	public boolean offer(E e) {
82	dl	1.21	final ReentrantLock lock = this.lock;
83	dl	1.2	lock.lock();
84			try {
85	dl	1.3	E first = q.peek();
86	jsr166	1.30	q.offer(e);
87			if (first == null \|\| e.compareTo(first) < 0)
88	dl	1.4	available.signalAll();
89	dl	1.2	return true;
90	tim	1.13	} finally {
91	dl	1.2	lock.unlock();
92			}
93			}
94
95	dholmes	1.7	/**
96	jsr166	1.32	* Inserts the specified element into this delay queue. As the queue is
97	dholmes	1.7	* unbounded this method will never block.
98	jsr166	1.32	*
99	jsr166	1.30	* @param e the element to add
100	jsr166	1.32	* @throws NullPointerException {@inheritDoc}
101	dholmes	1.7	*/
102	jsr166	1.30	public void put(E e) {
103			offer(e);
104	dl	1.2	}
105
106	dholmes	1.7	/**
107	dl	1.16	* Inserts the specified element into this delay queue. As the queue is
108	dholmes	1.7	* unbounded this method will never block.
109	jsr166	1.32	*
110	jsr166	1.30	* @param e the element to add
111	dl	1.14	* @param timeout This parameter is ignored as the method never blocks
112	dholmes	1.7	* @param unit This parameter is ignored as the method never blocks
113			* @return <tt>true</tt>
114	jsr166	1.32	* @throws NullPointerException {@inheritDoc}
115	dholmes	1.7	*/
116	jsr166	1.30	public boolean offer(E e, long timeout, TimeUnit unit) {
117			return offer(e);
118	dl	1.2	}
119
120	dholmes	1.7	/**
121	jsr166	1.32	* Retrieves and removes the head of this queue, or returns <tt>null</tt>
122			* if this queue has no elements with an expired delay.
123	dholmes	1.7	*
124	jsr166	1.32	* @return the head of this queue, or <tt>null</tt> if this
125			* queue has no elements with an expired delay
126	dholmes	1.7	*/
127	jsr166	1.32	public E poll() {
128			final ReentrantLock lock = this.lock;
129			lock.lock();
130			try {
131			E first = q.peek();
132			if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
133			return null;
134			else {
135			E x = q.poll();
136			assert x != null;
137			if (q.size() != 0)
138			available.signalAll();
139			return x;
140			}
141			} finally {
142			lock.unlock();
143			}
144	dl	1.2	}
145
146	dl	1.27	/**
147	jsr166	1.32	* Retrieves and removes the head of this queue, waiting if necessary
148			* until an element with an expired delay is available on this queue.
149			*
150	dl	1.27	* @return the head of this queue
151	jsr166	1.32	* @throws InterruptedException {@inheritDoc}
152	dl	1.27	*/
153	dl	1.3	public E take() throws InterruptedException {
154	dl	1.21	final ReentrantLock lock = this.lock;
155	dl	1.2	lock.lockInterruptibly();
156			try {
157			for (;;) {
158	dl	1.3	E first = q.peek();
159	dl	1.12	if (first == null) {
160	dl	1.4	available.await();
161	tim	1.13	} else {
162	dl	1.2	long delay = first.getDelay(TimeUnit.NANOSECONDS);
163	dl	1.12	if (delay > 0) {
164			long tl = available.awaitNanos(delay);
165	tim	1.13	} else {
166	dl	1.3	E x = q.poll();
167	dl	1.2	assert x != null;
168			if (q.size() != 0)
169	dl	1.4	available.signalAll(); // wake up other takers
170	dl	1.2	return x;
171	tim	1.6
172	dl	1.2	}
173			}
174			}
175	tim	1.13	} finally {
176	dl	1.2	lock.unlock();
177			}
178			}
179
180	dl	1.27	/**
181	jsr166	1.32	* Retrieves and removes the head of this queue, waiting if necessary
182			* until an element with an expired delay is available on this queue,
183			* or the specified wait time expires.
184			*
185	dl	1.27	* @return the head of this queue, or <tt>null</tt> if the
186	jsr166	1.32	* specified waiting time elapses before an element with
187			* an expired delay becomes available
188			* @throws InterruptedException {@inheritDoc}
189	dl	1.27	*/
190			public E poll(long timeout, TimeUnit unit) throws InterruptedException {
191	jsr166	1.41	long nanos = unit.toNanos(timeout);
192	dl	1.21	final ReentrantLock lock = this.lock;
193	dl	1.2	lock.lockInterruptibly();
194			try {
195			for (;;) {
196	dl	1.3	E first = q.peek();
197	dl	1.2	if (first == null) {
198			if (nanos <= 0)
199			return null;
200			else
201	dl	1.4	nanos = available.awaitNanos(nanos);
202	tim	1.13	} else {
203	jsr166	1.41	long delay = first.getDelay(TimeUnit.NANOSECONDS);
204	dl	1.2	if (delay > 0) {
205	dl	1.40	if (nanos <= 0)
206			return null;
207	dl	1.2	if (delay > nanos)
208			delay = nanos;
209	dl	1.4	long timeLeft = available.awaitNanos(delay);
210	dl	1.2	nanos -= delay - timeLeft;
211	tim	1.13	} else {
212	dl	1.3	E x = q.poll();
213	dl	1.2	assert x != null;
214			if (q.size() != 0)
215	tim	1.6	available.signalAll();
216	dl	1.2	return x;
217			}
218			}
219			}
220	tim	1.13	} finally {
221	dl	1.2	lock.unlock();
222			}
223			}
224
225	dl	1.27	/**
226	dl	1.36	* Retrieves, but does not remove, the head of this queue, or
227			* returns <tt>null</tt> if this queue is empty. Unlike
228			* <tt>poll</tt>, if no expired elements are available in the queue,
229			* this method returns the element that will expire next,
230			* if one exists.
231	dl	1.27	*
232	jsr166	1.32	* @return the head of this queue, or <tt>null</tt> if this
233	dl	1.35	* queue is empty.
234	dl	1.27	*/
235	dl	1.3	public E peek() {
236	dl	1.21	final ReentrantLock lock = this.lock;
237	dl	1.2	lock.lock();
238			try {
239			return q.peek();
240	tim	1.13	} finally {
241	dl	1.2	lock.unlock();
242			}
243	tim	1.1	}
244
245	dl	1.2	public int size() {
246	dl	1.21	final ReentrantLock lock = this.lock;
247	dl	1.2	lock.lock();
248			try {
249			return q.size();
250	tim	1.13	} finally {
251	dl	1.2	lock.unlock();
252			}
253			}
254
255	jsr166	1.32	/**
256			* @throws UnsupportedOperationException {@inheritDoc}
257			* @throws ClassCastException {@inheritDoc}
258			* @throws NullPointerException {@inheritDoc}
259			* @throws IllegalArgumentException {@inheritDoc}
260			*/
261	dl	1.17	public int drainTo(Collection<? super E> c) {
262			if (c == null)
263			throw new NullPointerException();
264			if (c == this)
265			throw new IllegalArgumentException();
266	dl	1.21	final ReentrantLock lock = this.lock;
267	dl	1.17	lock.lock();
268			try {
269			int n = 0;
270			for (;;) {
271			E first = q.peek();
272			if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
273			break;
274			c.add(q.poll());
275			++n;
276			}
277			if (n > 0)
278			available.signalAll();
279			return n;
280			} finally {
281			lock.unlock();
282			}
283			}
284
285	jsr166	1.32	/**
286			* @throws UnsupportedOperationException {@inheritDoc}
287			* @throws ClassCastException {@inheritDoc}
288			* @throws NullPointerException {@inheritDoc}
289			* @throws IllegalArgumentException {@inheritDoc}
290			*/
291	dl	1.17	public int drainTo(Collection<? super E> c, int maxElements) {
292			if (c == null)
293			throw new NullPointerException();
294			if (c == this)
295			throw new IllegalArgumentException();
296			if (maxElements <= 0)
297			return 0;
298	dl	1.21	final ReentrantLock lock = this.lock;
299	dl	1.17	lock.lock();
300			try {
301			int n = 0;
302			while (n < maxElements) {
303			E first = q.peek();
304			if (first == null \|\| first.getDelay(TimeUnit.NANOSECONDS) > 0)
305			break;
306			c.add(q.poll());
307			++n;
308			}
309			if (n > 0)
310			available.signalAll();
311			return n;
312			} finally {
313			lock.unlock();
314			}
315			}
316
317	dholmes	1.7	/**
318			* Atomically removes all of the elements from this delay queue.
319			* The queue will be empty after this call returns.
320	jsr166	1.32	* Elements with an unexpired delay are not waited for; they are
321			* simply discarded from the queue.
322	dholmes	1.7	*/
323	dl	1.2	public void clear() {
324	dl	1.21	final ReentrantLock lock = this.lock;
325	dl	1.2	lock.lock();
326			try {
327			q.clear();
328	tim	1.13	} finally {
329	dl	1.2	lock.unlock();
330			}
331			}
332	tim	1.1
333	dholmes	1.7	/**
334			* Always returns <tt>Integer.MAX_VALUE</tt> because
335			* a <tt>DelayQueue</tt> is not capacity constrained.
336	jsr166	1.32	*
337	dholmes	1.7	* @return <tt>Integer.MAX_VALUE</tt>
338			*/
339	dl	1.2	public int remainingCapacity() {
340			return Integer.MAX_VALUE;
341	tim	1.1	}
342	dl	1.2
343	jsr166	1.32	/**
344			* Returns an array containing all of the elements in this queue.
345			* The returned array elements are in no particular order.
346			*
347			* <p>The returned array will be "safe" in that no references to it are
348			* maintained by this queue. (In other words, this method must allocate
349			* a new array). The caller is thus free to modify the returned array.
350	jsr166	1.33	*
351	jsr166	1.32	* <p>This method acts as bridge between array-based and collection-based
352			* APIs.
353			*
354			* @return an array containing all of the elements in this queue
355			*/
356	dl	1.2	public Object[] toArray() {
357	dl	1.21	final ReentrantLock lock = this.lock;
358	dl	1.2	lock.lock();
359			try {
360			return q.toArray();
361	tim	1.13	} finally {
362	dl	1.2	lock.unlock();
363			}
364	tim	1.1	}
365	dl	1.2
366	jsr166	1.32	/**
367			* Returns an array containing all of the elements in this queue; the
368			* runtime type of the returned array is that of the specified array.
369			* The returned array elements are in no particular order.
370			* If the queue fits in the specified array, it is returned therein.
371			* Otherwise, a new array is allocated with the runtime type of the
372			* specified array and the size of this queue.
373			*
374			* <p>If this queue fits in the specified array with room to spare
375			* (i.e., the array has more elements than this queue), the element in
376			* the array immediately following the end of the queue is set to
377			* <tt>null</tt>.
378			*
379			* <p>Like the {@link #toArray()} method, this method acts as bridge between
380			* array-based and collection-based APIs. Further, this method allows
381			* precise control over the runtime type of the output array, and may,
382			* under certain circumstances, be used to save allocation costs.
383			*
384	jsr166	1.37	* <p>The following code can be used to dump a delay queue into a newly
385			* allocated array of <tt>Delayed</tt>:
386	jsr166	1.32	*
387			* <pre>
388	jsr166	1.37	* Delayed[] a = q.toArray(new Delayed[0]);</pre>
389	jsr166	1.32	*
390			* Note that <tt>toArray(new Object[0])</tt> is identical in function to
391			* <tt>toArray()</tt>.
392			*
393			* @param a the array into which the elements of the queue are to
394			* be stored, if it is big enough; otherwise, a new array of the
395			* same runtime type is allocated for this purpose
396			* @return an array containing all of the elements in this queue
397			* @throws ArrayStoreException if the runtime type of the specified array
398			* is not a supertype of the runtime type of every element in
399			* this queue
400			* @throws NullPointerException if the specified array is null
401			*/
402			public <T> T[] toArray(T[] a) {
403	dl	1.21	final ReentrantLock lock = this.lock;
404	dl	1.2	lock.lock();
405			try {
406	jsr166	1.32	return q.toArray(a);
407	tim	1.13	} finally {
408	dl	1.2	lock.unlock();
409			}
410	tim	1.1	}
411
412	dl	1.26	/**
413			* Removes a single instance of the specified element from this
414	dl	1.36	* queue, if it is present, whether or not it has expired.
415	dl	1.26	*/
416	dholmes	1.7	public boolean remove(Object o) {
417	dl	1.21	final ReentrantLock lock = this.lock;
418	dl	1.2	lock.lock();
419			try {
420	dholmes	1.7	return q.remove(o);
421	tim	1.13	} finally {
422	dl	1.2	lock.unlock();
423			}
424			}
425
426	dholmes	1.7	/**
427	dl	1.36	* Returns an iterator over all the elements (both expired and
428	dl	1.44	* unexpired) in this queue. The iterator does not return the
429			* elements in any particular order. The returned
430			* <tt>Iterator</tt> is a "weakly consistent" iterator that will
431			* never throw {@link ConcurrentModificationException}, and
432			* guarantees to traverse elements as they existed upon
433			* construction of the iterator, and may (but is not guaranteed
434			* to) reflect any modifications subsequent to construction.
435	dholmes	1.7	*
436	jsr166	1.32	* @return an iterator over the elements in this queue
437	dholmes	1.7	*/
438	dl	1.3	public Iterator<E> iterator() {
439	dl	1.44	return new Itr(toArray());
440	dl	1.2	}
441
442	dl	1.42	/**
443			* Snapshot iterator that works off copy of underlying q array.
444			*/
445	dl	1.44	private class Itr implements Iterator<E> {
446	dl	1.42	final Object[] array; // Array of all elements
447			int cursor; // index of next element to return;
448			int lastRet; // index of last element, or -1 if no such
449	jsr166	1.43
450	dl	1.42	Itr(Object[] array) {
451			lastRet = -1;
452			this.array = array;
453	dl	1.2	}
454
455	tim	1.6	public boolean hasNext() {
456	dl	1.42	return cursor < array.length;
457	tim	1.6	}
458
459			public E next() {
460	dl	1.42	if (cursor >= array.length)
461			throw new NoSuchElementException();
462			lastRet = cursor;
463			return (E)array[cursor++];
464	tim	1.6	}
465
466			public void remove() {
467	jsr166	1.43	if (lastRet < 0)
468	dl	1.42	throw new IllegalStateException();
469			Object x = array[lastRet];
470			lastRet = -1;
471			// Traverse underlying queue to find == element,
472			// not just a .equals element.
473	dl	1.2	lock.lock();
474			try {
475	dl	1.42	for (Iterator it = q.iterator(); it.hasNext(); ) {
476			if (it.next() == x) {
477			it.remove();
478			return;
479			}
480			}
481	tim	1.13	} finally {
482	dl	1.2	lock.unlock();
483			}
484	tim	1.6	}
485	tim	1.1	}
486
487			}