util/concurrent/PriorityBlockingQueue.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} that uses
 * the same ordering rules as class {@link PriorityQueue} and supplies
 * blocking retrieval operations.  While this queue is logically
 * unbounded, attempted additions may fail due to resource exhaustion
 * (causing <tt>OutOfMemoryError</tt>). This class does not permit
 * <tt>null</tt> elements.  A priority queue relying on natural
 * ordering also does not permit insertion of non-comparable objects
 * (doing so results in <tt>ClassCastException</tt>).
 *
 * <p>This class implements all of the <em>optional</em> methods
 * of the {@link Collection} and {@link Iterator} interfaces.
 * <p>The Iterator provided in method {@link #iterator()} is
 * <em>not</em> guaranteed to traverse the elements of the
 * PriorityBlockingQueue in any particular order. If you need ordered
 * traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.
 *
 * @since 1.5
 * @author Doug Lea
 * @param <E> the type of elements held in this collection
 */
public class PriorityBlockingQueue<E> extends AbstractQueue<E>
    implements BlockingQueue<E>, java.io.Serializable {
    private static final long serialVersionUID = 5595510919245408276L;

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

    /**
     * Creates a <tt>PriorityBlockingQueue</tt> with the default initial 
     * capacity
     * (11) that orders its elements according to their natural
     * ordering (using <tt>Comparable</tt>).
     */
    public PriorityBlockingQueue() {
        q = new PriorityQueue<E>();
    }

    /**
     * Creates a <tt>PriorityBlockingQueue</tt> with the specified initial
     * capacity
     * that orders its elements according to their natural ordering
     * (using <tt>Comparable</tt>).
     *
     * @param initialCapacity the initial capacity for this priority queue.
     * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
     * than 1
     */
    public PriorityBlockingQueue(int initialCapacity) {
        q = new PriorityQueue<E>(initialCapacity, null);
    }

    /**
     * Creates a <tt>PriorityBlockingQueue</tt> with the specified initial
     * capacity
     * that orders its elements according to the specified comparator.
     *
     * @param initialCapacity the initial capacity for this priority queue.
     * @param comparator the comparator used to order this priority queue.
     * If <tt>null</tt> then the order depends on the elements' natural
     * ordering.
     * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
     * than 1
     */
    public PriorityBlockingQueue(int initialCapacity,
                                 Comparator<? super E> comparator) {
        q = new PriorityQueue<E>(initialCapacity, comparator);
    }

    /**
     * Creates a <tt>PriorityBlockingQueue</tt> containing the elements
     * in the specified collection.  The priority queue has an initial
     * capacity of 110% of the size of the specified collection. If
     * the specified collection is a {@link SortedSet} or a {@link
     * PriorityQueue}, this priority queue will be sorted according to
     * the same comparator, or according to its elements' natural
     * order if the collection is sorted according to its elements'
     * natural order.  Otherwise, this priority queue is ordered
     * according to its elements' natural order.
     *
     * @param c the collection whose elements are to be placed
     *        into this priority queue.
     * @throws ClassCastException if elements of the specified collection
     *         cannot be compared to one another according to the priority
     *         queue's ordering.
     * @throws NullPointerException if <tt>c</tt> or any element within it
     * is <tt>null</tt>
     */
    public PriorityBlockingQueue(Collection<? extends E> c) {
        q = new PriorityQueue<E>(c);
    }


    // these first few override just to update doc comments

    /**
     * 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>.
     * @throws ClassCastException if the specified element cannot be compared
     * with elements currently in the priority queue according
     * to the priority queue's ordering.
     */
    public boolean add(E o) {
        return super.add(o);
    }

    /**
     * Returns the comparator used to order this collection, or <tt>null</tt>
     * if this collection is sorted according to its elements natural ordering
     * (using <tt>Comparable</tt>).
     *
     * @return the comparator used to order this collection, or <tt>null</tt>
     * if this collection is sorted according to its elements natural ordering.
     */
    public Comparator comparator() {
        return q.comparator();
    }

    /**
     * Inserts the specified element into this priority queue.
     *
     * @param o the element to add
     * @return <tt>true</tt>
     * @throws ClassCastException if the specified element cannot be compared
     * with elements currently in the priority queue according
     * to the priority queue's ordering.
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     */
    public boolean offer(E o) {
        if (o == null) throw new NullPointerException();
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            boolean ok = q.offer(o);
            assert ok;
            notEmpty.signal();
            return true;
        } finally {
            lock.unlock();
        }
    }

    /**
     * Adds the specified element to this priority queue. As the queue is
     * unbounded this method will never block.
     * @param o the element to add
     * @throws ClassCastException if the element cannot be compared
     * with elements currently in the priority queue according
     * to the priority queue's ordering.
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     */
    public void put(E o) {
        offer(o); // never need to block
    }

    /**
     * Inserts the specified element into this priority 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 ClassCastException if the element cannot be compared
     * with elements currently in the priority queue according
     * to the priority queue's ordering.
     * @throws NullPointerException if the specified element is <tt>null</tt>.
     */
    public boolean offer(E o, long timeout, TimeUnit unit) {
        return offer(o); // never need to block
    }

    public E take() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            try {
                while (q.size() == 0)
                    notEmpty.await();
            } catch (InterruptedException ie) {
                notEmpty.signal(); // propagate to non-interrupted thread
                throw ie;
            }
            E x = q.poll();
            assert x != null;
            return x;
        } finally {
            lock.unlock();
        }
    }


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

    public E poll(long timeout, TimeUnit unit) throws InterruptedException {
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            for (;;) {
                E x = q.poll();
                if (x != null)
                    return x;
                if (nanos <= 0)
                    return null;
                try {
                    nanos = notEmpty.awaitNanos(nanos);
                } catch (InterruptedException ie) {
                    notEmpty.signal(); // propagate to non-interrupted thread
                    throw ie;
                }
            }
        } 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();
        }
    }

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

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

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

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


    public String toString() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.toString();
        } 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;
            E e;
            while ( (e = q.poll()) != null) {
                c.add(e);
                ++n;
            }
            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;
            E e;
            while (n < maxElements && (e = q.poll()) != null) {
                c.add(e);
                ++n;
            }
            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();
        }
    }

    public <T> T[] toArray(T[] a) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.toArray(a);
        } 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() {
            /*
             * No sync -- we rely on underlying hasNext to be
             * stateless, in which case we can return true by mistake
             * only when next() will subsequently throw
             * ConcurrentModificationException.
             */
            return iter.hasNext();
        }

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

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

    /**
     * Save the state to a stream (that is, serialize it).  This
     * merely wraps default serialization within lock.  The
     * serialization strategy for items is left to underlying
     * Queue. Note that locking is not needed on deserialization, so
     * readObject is not defined, just relying on default.
     */
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException {
        lock.lock();
        try {
            s.defaultWriteObject();
        } finally {
            lock.unlock();
        }
    }

}
Revision:	1.34
Committed:	Tue Jan 20 04:35:02 2004 UTC (20 years, 4 months ago) by dl
Branch:	MAIN
Changes since 1.33:	+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	1.33	* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5	dl	1.2	*/
6
7	tim	1.1	package java.util.concurrent;
8	tim	1.13
9	dl	1.8	import java.util.concurrent.locks.*;
10	tim	1.1	import java.util.*;
11
12			/**
13	dl	1.25	* An unbounded {@linkplain BlockingQueue blocking queue} that uses
14			* the same ordering rules as class {@link PriorityQueue} and supplies
15			* blocking retrieval operations. While this queue is logically
16	dl	1.24	* unbounded, attempted additions may fail due to resource exhaustion
17	dl	1.25	* (causing <tt>OutOfMemoryError</tt>). This class does not permit
18			* <tt>null</tt> elements. A priority queue relying on natural
19	dl	1.24	* ordering also does not permit insertion of non-comparable objects
20			* (doing so results in <tt>ClassCastException</tt>).
21	dl	1.20	*
22	dl	1.23	* <p>This class implements all of the <em>optional</em> methods
23			* of the {@link Collection} and {@link Iterator} interfaces.
24	dl	1.20	* <p>The Iterator provided in method {@link #iterator()} is
25			* <em>not</em> guaranteed to traverse the elements of the
26			* PriorityBlockingQueue in any particular order. If you need ordered
27			* traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.
28			*
29	dl	1.6	* @since 1.5
30			* @author Doug Lea
31	dl	1.29	* @param <E> the type of elements held in this collection
32	dl	1.28	*/
33	dl	1.5	public class PriorityBlockingQueue<E> extends AbstractQueue<E>
34	dl	1.15	implements BlockingQueue<E>, java.io.Serializable {
35	dl	1.21	private static final long serialVersionUID = 5595510919245408276L;
36	tim	1.1
37	dl	1.5	private final PriorityQueue<E> q;
38	dl	1.9	private final ReentrantLock lock = new ReentrantLock(true);
39	dl	1.32	private final Condition notEmpty = lock.newCondition();
40	dl	1.5
41	dl	1.2	/**
42	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> with the default initial
43	dholmes	1.14	* capacity
44	dholmes	1.10	* (11) that orders its elements according to their natural
45	tim	1.18	* ordering (using <tt>Comparable</tt>).
46	dl	1.2	*/
47			public PriorityBlockingQueue() {
48	dl	1.5	q = new PriorityQueue<E>();
49	dl	1.2	}
50
51			/**
52	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> with the specified initial
53	dholmes	1.10	* capacity
54			* that orders its elements according to their natural ordering
55	tim	1.18	* (using <tt>Comparable</tt>).
56	dl	1.2	*
57			* @param initialCapacity the initial capacity for this priority queue.
58	dholmes	1.16	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
59			* than 1
60	dl	1.2	*/
61			public PriorityBlockingQueue(int initialCapacity) {
62	dl	1.5	q = new PriorityQueue<E>(initialCapacity, null);
63	dl	1.2	}
64
65			/**
66	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> with the specified initial
67	dholmes	1.10	* capacity
68	dl	1.2	* that orders its elements according to the specified comparator.
69			*
70			* @param initialCapacity the initial capacity for this priority queue.
71			* @param comparator the comparator used to order this priority queue.
72	dholmes	1.10	* If <tt>null</tt> then the order depends on the elements' natural
73			* ordering.
74	dholmes	1.16	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
75			* than 1
76	dl	1.2	*/
77	tim	1.13	public PriorityBlockingQueue(int initialCapacity,
78	dholmes	1.14	Comparator<? super E> comparator) {
79	dl	1.5	q = new PriorityQueue<E>(initialCapacity, comparator);
80	dl	1.2	}
81
82			/**
83	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> containing the elements
84	dl	1.15	* in the specified collection. The priority queue has an initial
85			* capacity of 110% of the size of the specified collection. If
86			* the specified collection is a {@link SortedSet} or a {@link
87			* PriorityQueue}, this priority queue will be sorted according to
88			* the same comparator, or according to its elements' natural
89			* order if the collection is sorted according to its elements'
90			* natural order. Otherwise, this priority queue is ordered
91			* according to its elements' natural order.
92	dl	1.2	*
93	dholmes	1.14	* @param c the collection whose elements are to be placed
94	dl	1.2	* into this priority queue.
95			* @throws ClassCastException if elements of the specified collection
96			* cannot be compared to one another according to the priority
97			* queue's ordering.
98	dholmes	1.14	* @throws NullPointerException if <tt>c</tt> or any element within it
99			* is <tt>null</tt>
100	dl	1.2	*/
101	dholmes	1.14	public PriorityBlockingQueue(Collection<? extends E> c) {
102			q = new PriorityQueue<E>(c);
103	dl	1.7	}
104
105	dholmes	1.10
106	dholmes	1.16	// these first few override just to update doc comments
107	dholmes	1.10
108			/**
109	dholmes	1.16	* Adds the specified element to this queue.
110	dl	1.34	* @param o the element to add
111	dholmes	1.16	* @return <tt>true</tt> (as per the general contract of
112			* <tt>Collection.add</tt>).
113			*
114	dl	1.22	* @throws NullPointerException if the specified element is <tt>null</tt>.
115	dholmes	1.16	* @throws ClassCastException if the specified element cannot be compared
116			* with elements currently in the priority queue according
117			* to the priority queue's ordering.
118	dholmes	1.10	*/
119	dholmes	1.16	public boolean add(E o) {
120			return super.add(o);
121	dholmes	1.10	}
122
123	tim	1.13	/**
124	dholmes	1.16	* Returns the comparator used to order this collection, or <tt>null</tt>
125			* if this collection is sorted according to its elements natural ordering
126	tim	1.18	* (using <tt>Comparable</tt>).
127	dholmes	1.16	*
128			* @return the comparator used to order this collection, or <tt>null</tt>
129			* if this collection is sorted according to its elements natural ordering.
130			*/
131	dl	1.7	public Comparator comparator() {
132			return q.comparator();
133	dl	1.5	}
134
135	dholmes	1.16	/**
136	dl	1.24	* Inserts the specified element into this priority queue.
137	dholmes	1.16	*
138	dl	1.22	* @param o the element to add
139	dholmes	1.16	* @return <tt>true</tt>
140			* @throws ClassCastException if the specified element cannot be compared
141			* with elements currently in the priority queue according
142			* to the priority queue's ordering.
143	dl	1.22	* @throws NullPointerException if the specified element is <tt>null</tt>.
144	dholmes	1.16	*/
145	dholmes	1.14	public boolean offer(E o) {
146			if (o == null) throw new NullPointerException();
147	dl	1.31	final ReentrantLock lock = this.lock;
148	dl	1.5	lock.lock();
149			try {
150	dholmes	1.14	boolean ok = q.offer(o);
151	dl	1.5	assert ok;
152			notEmpty.signal();
153			return true;
154	tim	1.19	} finally {
155	tim	1.13	lock.unlock();
156	dl	1.5	}
157			}
158
159	dholmes	1.16	/**
160			* Adds the specified element to this priority queue. As the queue is
161			* unbounded this method will never block.
162	dl	1.22	* @param o the element to add
163	dholmes	1.16	* @throws ClassCastException if the element cannot be compared
164			* with elements currently in the priority queue according
165			* to the priority queue's ordering.
166	dl	1.22	* @throws NullPointerException if the specified element is <tt>null</tt>.
167	dholmes	1.16	*/
168			public void put(E o) {
169	dholmes	1.14	offer(o); // never need to block
170	dl	1.5	}
171
172	dholmes	1.16	/**
173	dl	1.24	* Inserts the specified element into this priority queue. As the queue is
174	dholmes	1.16	* unbounded this method will never block.
175	dl	1.22	* @param o the element to add
176	dholmes	1.16	* @param timeout This parameter is ignored as the method never blocks
177			* @param unit This parameter is ignored as the method never blocks
178	dl	1.22	* @return <tt>true</tt>
179	dholmes	1.16	* @throws ClassCastException if the element cannot be compared
180			* with elements currently in the priority queue according
181			* to the priority queue's ordering.
182	dl	1.22	* @throws NullPointerException if the specified element is <tt>null</tt>.
183	dholmes	1.16	*/
184			public boolean offer(E o, long timeout, TimeUnit unit) {
185	dholmes	1.14	return offer(o); // never need to block
186	dl	1.5	}
187
188			public E take() throws InterruptedException {
189	dl	1.31	final ReentrantLock lock = this.lock;
190	dl	1.5	lock.lockInterruptibly();
191			try {
192			try {
193			while (q.size() == 0)
194			notEmpty.await();
195	tim	1.19	} catch (InterruptedException ie) {
196	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
197			throw ie;
198			}
199			E x = q.poll();
200			assert x != null;
201			return x;
202	tim	1.19	} finally {
203	dl	1.5	lock.unlock();
204			}
205			}
206
207
208			public E poll() {
209	dl	1.31	final ReentrantLock lock = this.lock;
210	dl	1.5	lock.lock();
211			try {
212			return q.poll();
213	tim	1.19	} finally {
214	tim	1.13	lock.unlock();
215	dl	1.5	}
216			}
217
218			public E poll(long timeout, TimeUnit unit) throws InterruptedException {
219	dholmes	1.10	long nanos = unit.toNanos(timeout);
220	dl	1.31	final ReentrantLock lock = this.lock;
221	dl	1.5	lock.lockInterruptibly();
222			try {
223			for (;;) {
224			E x = q.poll();
225	tim	1.13	if (x != null)
226	dl	1.5	return x;
227			if (nanos <= 0)
228			return null;
229			try {
230			nanos = notEmpty.awaitNanos(nanos);
231	tim	1.19	} catch (InterruptedException ie) {
232	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
233			throw ie;
234			}
235			}
236	tim	1.19	} finally {
237	dl	1.5	lock.unlock();
238			}
239			}
240
241			public E peek() {
242	dl	1.31	final ReentrantLock lock = this.lock;
243	dl	1.5	lock.lock();
244			try {
245			return q.peek();
246	tim	1.19	} finally {
247	tim	1.13	lock.unlock();
248	dl	1.5	}
249			}
250
251			public int size() {
252	dl	1.31	final ReentrantLock lock = this.lock;
253	dl	1.5	lock.lock();
254			try {
255			return q.size();
256	tim	1.19	} finally {
257	dl	1.5	lock.unlock();
258			}
259			}
260
261			/**
262			* Always returns <tt>Integer.MAX_VALUE</tt> because
263	dholmes	1.16	* a <tt>PriorityBlockingQueue</tt> is not capacity constrained.
264	dl	1.5	* @return <tt>Integer.MAX_VALUE</tt>
265			*/
266			public int remainingCapacity() {
267			return Integer.MAX_VALUE;
268			}
269
270	dholmes	1.14	public boolean remove(Object o) {
271	dl	1.31	final ReentrantLock lock = this.lock;
272	dl	1.5	lock.lock();
273			try {
274	dholmes	1.14	return q.remove(o);
275	tim	1.19	} finally {
276	dl	1.5	lock.unlock();
277			}
278			}
279
280	dholmes	1.14	public boolean contains(Object o) {
281	dl	1.31	final ReentrantLock lock = this.lock;
282	dl	1.5	lock.lock();
283			try {
284	dholmes	1.14	return q.contains(o);
285	tim	1.19	} finally {
286	dl	1.5	lock.unlock();
287			}
288			}
289
290			public Object[] toArray() {
291	dl	1.31	final ReentrantLock lock = this.lock;
292	dl	1.5	lock.lock();
293			try {
294			return q.toArray();
295	tim	1.19	} finally {
296	dl	1.5	lock.unlock();
297			}
298			}
299
300
301			public String toString() {
302	dl	1.31	final ReentrantLock lock = this.lock;
303	dl	1.5	lock.lock();
304			try {
305			return q.toString();
306	tim	1.19	} finally {
307	dl	1.5	lock.unlock();
308			}
309			}
310
311	dl	1.26	public int drainTo(Collection<? super E> c) {
312			if (c == null)
313			throw new NullPointerException();
314			if (c == this)
315			throw new IllegalArgumentException();
316	dl	1.31	final ReentrantLock lock = this.lock;
317	dl	1.26	lock.lock();
318			try {
319			int n = 0;
320			E e;
321			while ( (e = q.poll()) != null) {
322			c.add(e);
323			++n;
324			}
325			return n;
326			} finally {
327			lock.unlock();
328			}
329			}
330
331			public int drainTo(Collection<? super E> c, int maxElements) {
332			if (c == null)
333			throw new NullPointerException();
334			if (c == this)
335			throw new IllegalArgumentException();
336			if (maxElements <= 0)
337			return 0;
338	dl	1.31	final ReentrantLock lock = this.lock;
339	dl	1.26	lock.lock();
340			try {
341			int n = 0;
342			E e;
343			while (n < maxElements && (e = q.poll()) != null) {
344			c.add(e);
345			++n;
346			}
347			return n;
348			} finally {
349			lock.unlock();
350			}
351			}
352
353	dl	1.17	/**
354			* Atomically removes all of the elements from this delay queue.
355			* The queue will be empty after this call returns.
356			*/
357			public void clear() {
358	dl	1.31	final ReentrantLock lock = this.lock;
359	dl	1.17	lock.lock();
360			try {
361			q.clear();
362	tim	1.19	} finally {
363	dl	1.17	lock.unlock();
364			}
365			}
366
367	dl	1.5	public <T> T[] toArray(T[] a) {
368	dl	1.31	final ReentrantLock lock = this.lock;
369	dl	1.5	lock.lock();
370			try {
371			return q.toArray(a);
372	tim	1.19	} finally {
373	dl	1.5	lock.unlock();
374			}
375			}
376
377	dholmes	1.16	/**
378	dl	1.23	* Returns an iterator over the elements in this queue. The
379			* iterator does not return the elements in any particular order.
380			* The returned iterator is a thread-safe "fast-fail" iterator
381			* that will throw {@link
382			* java.util.ConcurrentModificationException} upon detected
383			* interference.
384	dholmes	1.16	*
385			* @return an iterator over the elements in this queue.
386			*/
387	dl	1.5	public Iterator<E> iterator() {
388	dl	1.31	final ReentrantLock lock = this.lock;
389	dl	1.5	lock.lock();
390			try {
391			return new Itr(q.iterator());
392	tim	1.19	} finally {
393	dl	1.5	lock.unlock();
394			}
395			}
396
397			private class Itr<E> implements Iterator<E> {
398			private final Iterator<E> iter;
399	tim	1.13	Itr(Iterator<E> i) {
400			iter = i;
401	dl	1.5	}
402
403	tim	1.13	public boolean hasNext() {
404	dl	1.5	/*
405			* No sync -- we rely on underlying hasNext to be
406			* stateless, in which case we can return true by mistake
407	dl	1.30	* only when next() will subsequently throw
408	dl	1.5	* ConcurrentModificationException.
409			*/
410			return iter.hasNext();
411	tim	1.13	}
412
413			public E next() {
414	dl	1.31	ReentrantLock lock = PriorityBlockingQueue.this.lock;
415	dl	1.5	lock.lock();
416			try {
417			return iter.next();
418	tim	1.19	} finally {
419	dl	1.5	lock.unlock();
420			}
421	tim	1.13	}
422
423			public void remove() {
424	dl	1.31	ReentrantLock lock = PriorityBlockingQueue.this.lock;
425	dl	1.5	lock.lock();
426			try {
427			iter.remove();
428	tim	1.19	} finally {
429	dl	1.5	lock.unlock();
430			}
431	tim	1.13	}
432	dl	1.5	}
433
434			/**
435			* Save the state to a stream (that is, serialize it). This
436			* merely wraps default serialization within lock. The
437			* serialization strategy for items is left to underlying
438			* Queue. Note that locking is not needed on deserialization, so
439			* readObject is not defined, just relying on default.
440			*/
441			private void writeObject(java.io.ObjectOutputStream s)
442			throws java.io.IOException {
443			lock.lock();
444			try {
445			s.defaultWriteObject();
446	tim	1.19	} finally {
447	dl	1.5	lock.unlock();
448			}
449	tim	1.1	}
450
451			}