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>.
 *
 * <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 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<? super E> 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;
    }

    /**
     * Removes a single instance of the specified element from this
     * collection, if it is present.
     */
    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 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:	1.37
Committed:	Thu May 27 11:06:11 2004 UTC (20 years ago) by dl
Branch:	MAIN
Changes since 1.36:	+9 -1 lines
Log Message:	Override javadoc specs when overriding AbstractQueue implementations Clarify atomicity in BlockingQueue
#	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	1.37	* <p>This class and its iterator implement all of the
30			* <em>optional</em> methods of the {@link Collection} and {@link
31			* Iterator} interfaces.
32			*
33	dl	1.35	* <p>This class is a member of the
34			* <a href="{@docRoot}/../guide/collections/index.html">
35			* Java Collections Framework</a>.
36			*
37	dl	1.6	* @since 1.5
38			* @author Doug Lea
39	dl	1.29	* @param <E> the type of elements held in this collection
40	dl	1.28	*/
41	dl	1.5	public class PriorityBlockingQueue<E> extends AbstractQueue<E>
42	dl	1.15	implements BlockingQueue<E>, java.io.Serializable {
43	dl	1.21	private static final long serialVersionUID = 5595510919245408276L;
44	tim	1.1
45	dl	1.5	private final PriorityQueue<E> q;
46	dl	1.9	private final ReentrantLock lock = new ReentrantLock(true);
47	dl	1.32	private final Condition notEmpty = lock.newCondition();
48	dl	1.5
49	dl	1.2	/**
50	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> with the default initial
51	dholmes	1.14	* capacity
52	dholmes	1.10	* (11) that orders its elements according to their natural
53	tim	1.18	* ordering (using <tt>Comparable</tt>).
54	dl	1.2	*/
55			public PriorityBlockingQueue() {
56	dl	1.5	q = new PriorityQueue<E>();
57	dl	1.2	}
58
59			/**
60	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> with the specified initial
61	dholmes	1.10	* capacity
62			* that orders its elements according to their natural ordering
63	tim	1.18	* (using <tt>Comparable</tt>).
64	dl	1.2	*
65			* @param initialCapacity the initial capacity for this priority queue.
66	dholmes	1.16	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
67			* than 1
68	dl	1.2	*/
69			public PriorityBlockingQueue(int initialCapacity) {
70	dl	1.5	q = new PriorityQueue<E>(initialCapacity, null);
71	dl	1.2	}
72
73			/**
74	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> with the specified initial
75	dholmes	1.10	* capacity
76	dl	1.2	* that orders its elements according to the specified comparator.
77			*
78			* @param initialCapacity the initial capacity for this priority queue.
79			* @param comparator the comparator used to order this priority queue.
80	dholmes	1.10	* If <tt>null</tt> then the order depends on the elements' natural
81			* ordering.
82	dholmes	1.16	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
83			* than 1
84	dl	1.2	*/
85	tim	1.13	public PriorityBlockingQueue(int initialCapacity,
86	dholmes	1.14	Comparator<? super E> comparator) {
87	dl	1.5	q = new PriorityQueue<E>(initialCapacity, comparator);
88	dl	1.2	}
89
90			/**
91	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> containing the elements
92	dl	1.15	* in the specified collection. The priority queue has an initial
93			* capacity of 110% of the size of the specified collection. If
94			* the specified collection is a {@link SortedSet} or a {@link
95			* PriorityQueue}, this priority queue will be sorted according to
96			* the same comparator, or according to its elements' natural
97			* order if the collection is sorted according to its elements'
98			* natural order. Otherwise, this priority queue is ordered
99			* according to its elements' natural order.
100	dl	1.2	*
101	dholmes	1.14	* @param c the collection whose elements are to be placed
102	dl	1.2	* into this priority queue.
103			* @throws ClassCastException if elements of the specified collection
104			* cannot be compared to one another according to the priority
105			* queue's ordering.
106	dholmes	1.14	* @throws NullPointerException if <tt>c</tt> or any element within it
107			* is <tt>null</tt>
108	dl	1.2	*/
109	dholmes	1.14	public PriorityBlockingQueue(Collection<? extends E> c) {
110			q = new PriorityQueue<E>(c);
111	dl	1.7	}
112
113	dholmes	1.10
114	dholmes	1.16	// these first few override just to update doc comments
115	dholmes	1.10
116			/**
117	dholmes	1.16	* Adds the specified element to this queue.
118	dl	1.34	* @param o the element to add
119	dholmes	1.16	* @return <tt>true</tt> (as per the general contract of
120			* <tt>Collection.add</tt>).
121			*
122	dl	1.22	* @throws NullPointerException if the specified element is <tt>null</tt>.
123	dholmes	1.16	* @throws ClassCastException if the specified element cannot be compared
124			* with elements currently in the priority queue according
125			* to the priority queue's ordering.
126	dholmes	1.10	*/
127	dholmes	1.16	public boolean add(E o) {
128			return super.add(o);
129	dholmes	1.10	}
130
131	tim	1.13	/**
132	dholmes	1.16	* Returns the comparator used to order this collection, or <tt>null</tt>
133			* if this collection is sorted according to its elements natural ordering
134	tim	1.18	* (using <tt>Comparable</tt>).
135	dholmes	1.16	*
136			* @return the comparator used to order this collection, or <tt>null</tt>
137			* if this collection is sorted according to its elements natural ordering.
138			*/
139	dl	1.36	public Comparator<? super E> comparator() {
140	dl	1.7	return q.comparator();
141	dl	1.5	}
142
143	dholmes	1.16	/**
144	dl	1.24	* Inserts the specified element into this priority queue.
145	dholmes	1.16	*
146	dl	1.22	* @param o the element to add
147	dholmes	1.16	* @return <tt>true</tt>
148			* @throws ClassCastException if the specified element cannot be compared
149			* with elements currently in the priority queue according
150			* to the priority queue's ordering.
151	dl	1.22	* @throws NullPointerException if the specified element is <tt>null</tt>.
152	dholmes	1.16	*/
153	dholmes	1.14	public boolean offer(E o) {
154			if (o == null) throw new NullPointerException();
155	dl	1.31	final ReentrantLock lock = this.lock;
156	dl	1.5	lock.lock();
157			try {
158	dholmes	1.14	boolean ok = q.offer(o);
159	dl	1.5	assert ok;
160			notEmpty.signal();
161			return true;
162	tim	1.19	} finally {
163	tim	1.13	lock.unlock();
164	dl	1.5	}
165			}
166
167	dholmes	1.16	/**
168			* Adds the specified element to this priority queue. As the queue is
169			* unbounded this method will never block.
170	dl	1.22	* @param o the element to add
171	dholmes	1.16	* @throws ClassCastException if the element cannot be compared
172			* with elements currently in the priority queue according
173			* to the priority queue's ordering.
174	dl	1.22	* @throws NullPointerException if the specified element is <tt>null</tt>.
175	dholmes	1.16	*/
176			public void put(E o) {
177	dholmes	1.14	offer(o); // never need to block
178	dl	1.5	}
179
180	dholmes	1.16	/**
181	dl	1.24	* Inserts the specified element into this priority queue. As the queue is
182	dholmes	1.16	* unbounded this method will never block.
183	dl	1.22	* @param o the element to add
184	dholmes	1.16	* @param timeout This parameter is ignored as the method never blocks
185			* @param unit This parameter is ignored as the method never blocks
186	dl	1.22	* @return <tt>true</tt>
187	dholmes	1.16	* @throws ClassCastException if the element cannot be compared
188			* with elements currently in the priority queue according
189			* to the priority queue's ordering.
190	dl	1.22	* @throws NullPointerException if the specified element is <tt>null</tt>.
191	dholmes	1.16	*/
192			public boolean offer(E o, long timeout, TimeUnit unit) {
193	dholmes	1.14	return offer(o); // never need to block
194	dl	1.5	}
195
196			public E take() throws InterruptedException {
197	dl	1.31	final ReentrantLock lock = this.lock;
198	dl	1.5	lock.lockInterruptibly();
199			try {
200			try {
201			while (q.size() == 0)
202			notEmpty.await();
203	tim	1.19	} catch (InterruptedException ie) {
204	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
205			throw ie;
206			}
207			E x = q.poll();
208			assert x != null;
209			return x;
210	tim	1.19	} finally {
211	dl	1.5	lock.unlock();
212			}
213			}
214
215
216			public E poll() {
217	dl	1.31	final ReentrantLock lock = this.lock;
218	dl	1.5	lock.lock();
219			try {
220			return q.poll();
221	tim	1.19	} finally {
222	tim	1.13	lock.unlock();
223	dl	1.5	}
224			}
225
226			public E poll(long timeout, TimeUnit unit) throws InterruptedException {
227	dholmes	1.10	long nanos = unit.toNanos(timeout);
228	dl	1.31	final ReentrantLock lock = this.lock;
229	dl	1.5	lock.lockInterruptibly();
230			try {
231			for (;;) {
232			E x = q.poll();
233	tim	1.13	if (x != null)
234	dl	1.5	return x;
235			if (nanos <= 0)
236			return null;
237			try {
238			nanos = notEmpty.awaitNanos(nanos);
239	tim	1.19	} catch (InterruptedException ie) {
240	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
241			throw ie;
242			}
243			}
244	tim	1.19	} finally {
245	dl	1.5	lock.unlock();
246			}
247			}
248
249			public E peek() {
250	dl	1.31	final ReentrantLock lock = this.lock;
251	dl	1.5	lock.lock();
252			try {
253			return q.peek();
254	tim	1.19	} finally {
255	tim	1.13	lock.unlock();
256	dl	1.5	}
257			}
258
259			public int size() {
260	dl	1.31	final ReentrantLock lock = this.lock;
261	dl	1.5	lock.lock();
262			try {
263			return q.size();
264	tim	1.19	} finally {
265	dl	1.5	lock.unlock();
266			}
267			}
268
269			/**
270			* Always returns <tt>Integer.MAX_VALUE</tt> because
271	dholmes	1.16	* a <tt>PriorityBlockingQueue</tt> is not capacity constrained.
272	dl	1.5	* @return <tt>Integer.MAX_VALUE</tt>
273			*/
274			public int remainingCapacity() {
275			return Integer.MAX_VALUE;
276			}
277
278	dl	1.37	/**
279			* Removes a single instance of the specified element from this
280			* collection, if it is present.
281			*/
282	dholmes	1.14	public boolean remove(Object o) {
283	dl	1.31	final ReentrantLock lock = this.lock;
284	dl	1.5	lock.lock();
285			try {
286	dholmes	1.14	return q.remove(o);
287	tim	1.19	} finally {
288	dl	1.5	lock.unlock();
289			}
290			}
291
292	dholmes	1.14	public boolean contains(Object o) {
293	dl	1.31	final ReentrantLock lock = this.lock;
294	dl	1.5	lock.lock();
295			try {
296	dholmes	1.14	return q.contains(o);
297	tim	1.19	} finally {
298	dl	1.5	lock.unlock();
299			}
300			}
301
302			public Object[] toArray() {
303	dl	1.31	final ReentrantLock lock = this.lock;
304	dl	1.5	lock.lock();
305			try {
306			return q.toArray();
307	tim	1.19	} finally {
308	dl	1.5	lock.unlock();
309			}
310			}
311
312
313			public String toString() {
314	dl	1.31	final ReentrantLock lock = this.lock;
315	dl	1.5	lock.lock();
316			try {
317			return q.toString();
318	tim	1.19	} finally {
319	dl	1.5	lock.unlock();
320			}
321			}
322
323	dl	1.26	public int drainTo(Collection<? super E> c) {
324			if (c == null)
325			throw new NullPointerException();
326			if (c == this)
327			throw new IllegalArgumentException();
328	dl	1.31	final ReentrantLock lock = this.lock;
329	dl	1.26	lock.lock();
330			try {
331			int n = 0;
332			E e;
333			while ( (e = q.poll()) != null) {
334			c.add(e);
335			++n;
336			}
337			return n;
338			} finally {
339			lock.unlock();
340			}
341			}
342
343			public int drainTo(Collection<? super E> c, int maxElements) {
344			if (c == null)
345			throw new NullPointerException();
346			if (c == this)
347			throw new IllegalArgumentException();
348			if (maxElements <= 0)
349			return 0;
350	dl	1.31	final ReentrantLock lock = this.lock;
351	dl	1.26	lock.lock();
352			try {
353			int n = 0;
354			E e;
355			while (n < maxElements && (e = q.poll()) != null) {
356			c.add(e);
357			++n;
358			}
359			return n;
360			} finally {
361			lock.unlock();
362			}
363			}
364
365	dl	1.17	/**
366	dl	1.37	* Atomically removes all of the elements from this queue.
367	dl	1.17	* The queue will be empty after this call returns.
368			*/
369			public void clear() {
370	dl	1.31	final ReentrantLock lock = this.lock;
371	dl	1.17	lock.lock();
372			try {
373			q.clear();
374	tim	1.19	} finally {
375	dl	1.17	lock.unlock();
376			}
377			}
378
379	dl	1.5	public <T> T[] toArray(T[] a) {
380	dl	1.31	final ReentrantLock lock = this.lock;
381	dl	1.5	lock.lock();
382			try {
383			return q.toArray(a);
384	tim	1.19	} finally {
385	dl	1.5	lock.unlock();
386			}
387			}
388
389	dholmes	1.16	/**
390	dl	1.23	* Returns an iterator over the elements in this queue. The
391			* iterator does not return the elements in any particular order.
392			* The returned iterator is a thread-safe "fast-fail" iterator
393			* that will throw {@link
394			* java.util.ConcurrentModificationException} upon detected
395			* interference.
396	dholmes	1.16	*
397			* @return an iterator over the elements in this queue.
398			*/
399	dl	1.5	public Iterator<E> iterator() {
400	dl	1.31	final ReentrantLock lock = this.lock;
401	dl	1.5	lock.lock();
402			try {
403			return new Itr(q.iterator());
404	tim	1.19	} finally {
405	dl	1.5	lock.unlock();
406			}
407			}
408
409			private class Itr<E> implements Iterator<E> {
410			private final Iterator<E> iter;
411	tim	1.13	Itr(Iterator<E> i) {
412			iter = i;
413	dl	1.5	}
414
415	tim	1.13	public boolean hasNext() {
416	dl	1.5	/*
417			* No sync -- we rely on underlying hasNext to be
418			* stateless, in which case we can return true by mistake
419	dl	1.30	* only when next() will subsequently throw
420	dl	1.5	* ConcurrentModificationException.
421			*/
422			return iter.hasNext();
423	tim	1.13	}
424
425			public E next() {
426	dl	1.31	ReentrantLock lock = PriorityBlockingQueue.this.lock;
427	dl	1.5	lock.lock();
428			try {
429			return iter.next();
430	tim	1.19	} finally {
431	dl	1.5	lock.unlock();
432			}
433	tim	1.13	}
434
435			public void remove() {
436	dl	1.31	ReentrantLock lock = PriorityBlockingQueue.this.lock;
437	dl	1.5	lock.lock();
438			try {
439			iter.remove();
440	tim	1.19	} finally {
441	dl	1.5	lock.unlock();
442			}
443	tim	1.13	}
444	dl	1.5	}
445
446			/**
447			* Save the state to a stream (that is, serialize it). This
448			* merely wraps default serialization within lock. The
449			* serialization strategy for items is left to underlying
450			* Queue. Note that locking is not needed on deserialization, so
451			* readObject is not defined, just relying on default.
452			*/
453			private void writeObject(java.io.ObjectOutputStream s)
454			throws java.io.IOException {
455			lock.lock();
456			try {
457			s.defaultWriteObject();
458	tim	1.19	} finally {
459	dl	1.5	lock.unlock();
460			}
461	tim	1.1	}
462
463			}