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 {@linkplain
 * Comparable natural ordering} also does not permit insertion of
 * non-comparable objects (doing so results in
 * <tt>ClassCastException</tt>).
 *
 * <p>This class and its iterator implement all of the
 * <em>optional</em> methods of the {@link Collection} and {@link
 * Iterator} interfaces.  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>.  Also, method <tt>drainTo</tt>
 * can be used to <em>remove</em> some or all elements in priority
 * order and place them in another collection.
 *
 * <p>Operations on this class make no guarantees about the ordering
 * of elements with equal priority. If you need to enforce an
 * ordering, you can define custom classes or comparators that use a
 * secondary key to break ties in primary priority values.  For
 * example, here is a class that applies first-in-first-out
 * tie-breaking to comparable elements. To use it, you would insert a
 * <tt>new FIFOEntry(anEntry)</tt> instead of a plain entry object.
 *
 * <pre>
 * class FIFOEntry&lt;E extends Comparable&lt;? super E&gt;&gt;
 *     implements Comparable&lt;FIFOEntry&lt;E&gt;&gt; {
 *   final static AtomicLong seq = new AtomicLong();
 *   final long seqNum;
 *   final E entry;
 *   public FIFOEntry(E entry) {
 *     seqNum = seq.getAndIncrement();
 *     this.entry = entry;
 *   }
 *   public E getEntry() { return entry; }
 *   public int compareTo(FIFOEntry&lt;E&gt; other) {
 *     int res = entry.compareTo(other.entry);
 *     if (res == 0 &amp;&amp; other.entry != this.entry)
 *       res = (seqNum &lt; other.seqNum ? -1 : 1);
 *     return res;
 *   }
 * }</pre>
 *
 * <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 {@linkplain Comparable natural ordering}.
     */
    public PriorityBlockingQueue() {
        q = new PriorityQueue<E>();
    }

    /**
     * Creates a <tt>PriorityBlockingQueue</tt> with the specified
     * initial capacity that orders its elements according to their
     * {@linkplain Comparable natural ordering}.
     *
     * @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 the natural ordering of its
     * elements if the collection is sorted according to the natural
     * ordering of its elements.  Otherwise, this priority queue is
     * ordered according to the natural ordering of its elements.
     *
     * @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 the specified collection or any
     *         of its elements are null
     */
    public PriorityBlockingQueue(Collection<? extends E> c) {
        q = new PriorityQueue<E>(c);
    }

    /**
     * Inserts the specified element into this priority queue.
     *
     * @param e the element to add
     * @return <tt>true</tt> (as specified by {@link Collection#add})
     * @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 null
     */
    public boolean add(E e) {
        return offer(e);
    }

    /**
     * Inserts the specified element into this priority queue.
     *
     * @param e the element to add
     * @return <tt>true</tt> (as specified by {@link Queue#offer})
     * @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 null
     */
    public boolean offer(E e) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            boolean ok = q.offer(e);
            assert ok;
            notEmpty.signal();
            return true;
        } finally {
            lock.unlock();
        }
    }

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

    /**
     * Inserts the specified element into this priority 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 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 null
     */
    public boolean offer(E e, long timeout, TimeUnit unit) {
        return offer(e); // never need to block
    }

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

    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(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();
        }
    }

    /**
     * Returns the comparator used to order the elements in this queue,
     * or <tt>null</tt> if this queue uses the {@linkplain Comparable
     * natural ordering} of its elements.
     *
     * @return the comparator used to order the elements in this queue,
     *         or <tt>null</tt> if this queue uses the natural
     *         ordering of its elements.
     */
    public Comparator<? super E> comparator() {
        return q.comparator();
    }

    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 queue,
     * if it is present.  More formally, removes an element <tt>e</tt> such
     * that <tt>o.equals(e)</tt>, if this queue contains one or more such
     * elements.
     * Returns <tt>true</tt> if this queue contained the specified element
     * (or equivalently, if this queue changed as a result of the call).
     *
     * @param o element to be removed from this queue, if present
     * @return <tt>true</tt> if this queue changed as a result of the call
     */
    public boolean remove(Object o) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.remove(o);
        } finally {
            lock.unlock();
        }
    }

    /**
     * Returns <tt>true</tt> if this queue contains the specified element.
     * More formally, returns <tt>true</tt> if and only if this queue contains
     * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
     *
     * @param o object to be checked for containment in this queue
     * @return <tt>true</tt> if this queue contains the specified element
     */
    public boolean contains(Object o) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.contains(o);
        } finally {
            lock.unlock();
        }
    }

    /**
     * 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();
        }
    }


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

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

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

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

        public boolean hasNext() {
            /*
             * 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:	1.48
Committed:	Mon Jul 18 19:14:17 2005 UTC (18 years, 10 months ago) by jsr166
Branch:	MAIN
Changes since 1.47:	+2 -2 lines
Log Message:	doc fixes
#	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	jsr166	1.42	* <tt>null</tt> elements. A priority queue relying on {@linkplain
19			* Comparable natural ordering} also does not permit insertion of
20			* non-comparable objects (doing so results in
21			* <tt>ClassCastException</tt>).
22	dl	1.20	*
23	dl	1.38	* <p>This class and its iterator implement all of the
24			* <em>optional</em> methods of the {@link Collection} and {@link
25	dl	1.41	* Iterator} interfaces. The Iterator provided in method {@link
26			* #iterator()} is <em>not</em> guaranteed to traverse the elements of
27			* the PriorityBlockingQueue in any particular order. If you need
28			* ordered traversal, consider using
29			* <tt>Arrays.sort(pq.toArray())</tt>. Also, method <tt>drainTo</tt>
30			* can be used to <em>remove</em> some or all elements in priority
31			* order and place them in another collection.
32			*
33			* <p>Operations on this class make no guarantees about the ordering
34			* of elements with equal priority. If you need to enforce an
35			* ordering, you can define custom classes or comparators that use a
36			* secondary key to break ties in primary priority values. For
37			* example, here is a class that applies first-in-first-out
38			* tie-breaking to comparable elements. To use it, you would insert a
39			* <tt>new FIFOEntry(anEntry)</tt> instead of a plain entry object.
40			*
41			* <pre>
42			* class FIFOEntry<E extends Comparable<? super E>>
43	jsr166	1.47	* implements Comparable<FIFOEntry<E>> {
44			* final static AtomicLong seq = new AtomicLong();
45	dl	1.41	* final long seqNum;
46			* final E entry;
47			* public FIFOEntry(E entry) {
48			* seqNum = seq.getAndIncrement();
49			* this.entry = entry;
50			* }
51			* public E getEntry() { return entry; }
52			* public int compareTo(FIFOEntry<E> other) {
53			* int res = entry.compareTo(other.entry);
54	jsr166	1.42	* if (res == 0 && other.entry != this.entry)
55	dl	1.41	* res = (seqNum < other.seqNum ? -1 : 1);
56			* return res;
57			* }
58	jsr166	1.42	* }</pre>
59	dl	1.20	*
60	dl	1.35	* <p>This class is a member of the
61			* <a href="{@docRoot}/../guide/collections/index.html">
62			* Java Collections Framework</a>.
63			*
64	dl	1.6	* @since 1.5
65			* @author Doug Lea
66	dl	1.29	* @param <E> the type of elements held in this collection
67	dl	1.28	*/
68	dl	1.5	public class PriorityBlockingQueue<E> extends AbstractQueue<E>
69	dl	1.15	implements BlockingQueue<E>, java.io.Serializable {
70	dl	1.21	private static final long serialVersionUID = 5595510919245408276L;
71	tim	1.1
72	dl	1.5	private final PriorityQueue<E> q;
73	dl	1.9	private final ReentrantLock lock = new ReentrantLock(true);
74	dl	1.32	private final Condition notEmpty = lock.newCondition();
75	dl	1.5
76	dl	1.2	/**
77	jsr166	1.42	* Creates a <tt>PriorityBlockingQueue</tt> with the default
78			* initial capacity (11) that orders its elements according to
79			* their {@linkplain Comparable natural ordering}.
80	dl	1.2	*/
81			public PriorityBlockingQueue() {
82	dl	1.5	q = new PriorityQueue<E>();
83	dl	1.2	}
84
85			/**
86	jsr166	1.42	* Creates a <tt>PriorityBlockingQueue</tt> with the specified
87			* initial capacity that orders its elements according to their
88			* {@linkplain Comparable natural ordering}.
89	dl	1.2	*
90	jsr166	1.42	* @param initialCapacity the initial capacity for this priority queue
91	dholmes	1.16	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
92			* than 1
93	dl	1.2	*/
94			public PriorityBlockingQueue(int initialCapacity) {
95	dl	1.5	q = new PriorityQueue<E>(initialCapacity, null);
96	dl	1.2	}
97
98			/**
99	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> with the specified initial
100	jsr166	1.39	* capacity that orders its elements according to the specified
101			* comparator.
102	dl	1.2	*
103	jsr166	1.42	* @param initialCapacity the initial capacity for this priority queue
104	dl	1.2	* @param comparator the comparator used to order this priority queue.
105	dholmes	1.10	* If <tt>null</tt> then the order depends on the elements' natural
106			* ordering.
107	dholmes	1.16	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
108			* than 1
109	dl	1.2	*/
110	tim	1.13	public PriorityBlockingQueue(int initialCapacity,
111	dholmes	1.14	Comparator<? super E> comparator) {
112	dl	1.5	q = new PriorityQueue<E>(initialCapacity, comparator);
113	dl	1.2	}
114
115			/**
116	dholmes	1.16	* Creates a <tt>PriorityBlockingQueue</tt> containing the elements
117	dl	1.15	* in the specified collection. The priority queue has an initial
118	jsr166	1.39	* capacity of 110% of the size of the specified collection. If
119	dl	1.15	* the specified collection is a {@link SortedSet} or a {@link
120			* PriorityQueue}, this priority queue will be sorted according to
121	jsr166	1.39	* the same comparator, or according to the natural ordering of its
122			* elements if the collection is sorted according to the natural
123			* ordering of its elements. Otherwise, this priority queue is
124			* ordered according to the natural ordering of its elements.
125	dl	1.2	*
126	dholmes	1.14	* @param c the collection whose elements are to be placed
127	dl	1.2	* into this priority queue.
128			* @throws ClassCastException if elements of the specified collection
129			* cannot be compared to one another according to the priority
130			* queue's ordering.
131	jsr166	1.42	* @throws NullPointerException if the specified collection or any
132			* of its elements are null
133	dl	1.2	*/
134	dholmes	1.14	public PriorityBlockingQueue(Collection<? extends E> c) {
135			q = new PriorityQueue<E>(c);
136	dl	1.7	}
137
138	dholmes	1.10	/**
139	jsr166	1.42	* Inserts the specified element into this priority queue.
140			*
141	jsr166	1.40	* @param e the element to add
142	jsr166	1.48	* @return <tt>true</tt> (as specified by {@link Collection#add})
143	dholmes	1.16	* @throws ClassCastException if the specified element cannot be compared
144	jsr166	1.42	* with elements currently in the priority queue according to the
145			* priority queue's ordering
146			* @throws NullPointerException if the specified element is null
147	dholmes	1.10	*/
148	jsr166	1.40	public boolean add(E e) {
149	jsr166	1.42	return offer(e);
150	dl	1.5	}
151
152	dholmes	1.16	/**
153	dl	1.24	* Inserts the specified element into this priority queue.
154	dholmes	1.16	*
155	jsr166	1.40	* @param e the element to add
156	jsr166	1.48	* @return <tt>true</tt> (as specified by {@link Queue#offer})
157	dholmes	1.16	* @throws ClassCastException if the specified element cannot be compared
158	jsr166	1.42	* with elements currently in the priority queue according to the
159			* priority queue's ordering
160			* @throws NullPointerException if the specified element is null
161	dholmes	1.16	*/
162	jsr166	1.40	public boolean offer(E e) {
163	dl	1.31	final ReentrantLock lock = this.lock;
164	dl	1.5	lock.lock();
165			try {
166	jsr166	1.40	boolean ok = q.offer(e);
167	dl	1.5	assert ok;
168			notEmpty.signal();
169			return true;
170	tim	1.19	} finally {
171	tim	1.13	lock.unlock();
172	dl	1.5	}
173			}
174
175	dholmes	1.16	/**
176	jsr166	1.42	* Inserts the specified element into this priority queue. As the queue is
177	dholmes	1.16	* unbounded this method will never block.
178	jsr166	1.42	*
179	jsr166	1.40	* @param e the element to add
180	jsr166	1.42	* @throws ClassCastException if the specified element cannot be compared
181			* with elements currently in the priority queue according to the
182			* priority queue's ordering
183			* @throws NullPointerException if the specified element is null
184	dholmes	1.16	*/
185	jsr166	1.40	public void put(E e) {
186			offer(e); // never need to block
187	dl	1.5	}
188
189	dholmes	1.16	/**
190	dl	1.24	* Inserts the specified element into this priority queue. As the queue is
191	dholmes	1.16	* unbounded this method will never block.
192	jsr166	1.42	*
193	jsr166	1.40	* @param e the element to add
194	dholmes	1.16	* @param timeout This parameter is ignored as the method never blocks
195			* @param unit This parameter is ignored as the method never blocks
196	dl	1.22	* @return <tt>true</tt>
197	jsr166	1.42	* @throws ClassCastException if the specified element cannot be compared
198			* with elements currently in the priority queue according to the
199			* priority queue's ordering
200			* @throws NullPointerException if the specified element is null
201	dholmes	1.16	*/
202	jsr166	1.40	public boolean offer(E e, long timeout, TimeUnit unit) {
203			return offer(e); // never need to block
204	dl	1.5	}
205
206	jsr166	1.42	public E poll() {
207			final ReentrantLock lock = this.lock;
208			lock.lock();
209			try {
210			return q.poll();
211			} finally {
212			lock.unlock();
213			}
214			}
215
216	dl	1.5	public E take() throws InterruptedException {
217	dl	1.31	final ReentrantLock lock = this.lock;
218	dl	1.5	lock.lockInterruptibly();
219			try {
220			try {
221			while (q.size() == 0)
222			notEmpty.await();
223	tim	1.19	} catch (InterruptedException ie) {
224	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
225			throw ie;
226			}
227			E x = q.poll();
228			assert x != null;
229			return x;
230	tim	1.19	} finally {
231	dl	1.5	lock.unlock();
232			}
233			}
234
235			public E poll(long timeout, TimeUnit unit) throws InterruptedException {
236	dholmes	1.10	long nanos = unit.toNanos(timeout);
237	dl	1.31	final ReentrantLock lock = this.lock;
238	dl	1.5	lock.lockInterruptibly();
239			try {
240			for (;;) {
241			E x = q.poll();
242	tim	1.13	if (x != null)
243	dl	1.5	return x;
244			if (nanos <= 0)
245			return null;
246			try {
247			nanos = notEmpty.awaitNanos(nanos);
248	tim	1.19	} catch (InterruptedException ie) {
249	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
250			throw ie;
251			}
252			}
253	tim	1.19	} finally {
254	dl	1.5	lock.unlock();
255			}
256			}
257
258			public E peek() {
259	dl	1.31	final ReentrantLock lock = this.lock;
260	dl	1.5	lock.lock();
261			try {
262			return q.peek();
263	tim	1.19	} finally {
264	tim	1.13	lock.unlock();
265	dl	1.5	}
266			}
267
268	jsr166	1.42	/**
269			* Returns the comparator used to order the elements in this queue,
270			* or <tt>null</tt> if this queue uses the {@linkplain Comparable
271			* natural ordering} of its elements.
272			*
273			* @return the comparator used to order the elements in this queue,
274			* or <tt>null</tt> if this queue uses the natural
275			* ordering of its elements.
276			*/
277			public Comparator<? super E> comparator() {
278			return q.comparator();
279			}
280
281	dl	1.5	public int size() {
282	dl	1.31	final ReentrantLock lock = this.lock;
283	dl	1.5	lock.lock();
284			try {
285			return q.size();
286	tim	1.19	} finally {
287	dl	1.5	lock.unlock();
288			}
289			}
290
291			/**
292			* Always returns <tt>Integer.MAX_VALUE</tt> because
293	dholmes	1.16	* a <tt>PriorityBlockingQueue</tt> is not capacity constrained.
294	dl	1.5	* @return <tt>Integer.MAX_VALUE</tt>
295			*/
296			public int remainingCapacity() {
297			return Integer.MAX_VALUE;
298			}
299
300	dl	1.37	/**
301	jsr166	1.42	* Removes a single instance of the specified element from this queue,
302			* if it is present. More formally, removes an element <tt>e</tt> such
303			* that <tt>o.equals(e)</tt>, if this queue contains one or more such
304			* elements.
305			* Returns <tt>true</tt> if this queue contained the specified element
306			* (or equivalently, if this queue changed as a result of the call).
307			*
308			* @param o element to be removed from this queue, if present
309			* @return <tt>true</tt> if this queue changed as a result of the call
310	dl	1.37	*/
311	dholmes	1.14	public boolean remove(Object o) {
312	dl	1.31	final ReentrantLock lock = this.lock;
313	dl	1.5	lock.lock();
314			try {
315	dholmes	1.14	return q.remove(o);
316	tim	1.19	} finally {
317	dl	1.5	lock.unlock();
318			}
319			}
320
321	jsr166	1.42	/**
322			* Returns <tt>true</tt> if this queue contains the specified element.
323			* More formally, returns <tt>true</tt> if and only if this queue contains
324			* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
325			*
326			* @param o object to be checked for containment in this queue
327			* @return <tt>true</tt> if this queue contains the specified element
328			*/
329	dholmes	1.14	public boolean contains(Object o) {
330	dl	1.31	final ReentrantLock lock = this.lock;
331	dl	1.5	lock.lock();
332			try {
333	dholmes	1.14	return q.contains(o);
334	tim	1.19	} finally {
335	dl	1.5	lock.unlock();
336			}
337			}
338
339	jsr166	1.42	/**
340			* Returns an array containing all of the elements in this queue.
341			* The returned array elements are in no particular order.
342			*
343			* <p>The returned array will be "safe" in that no references to it are
344			* maintained by this queue. (In other words, this method must allocate
345			* a new array). The caller is thus free to modify the returned array.
346	jsr166	1.43	*
347	jsr166	1.42	* <p>This method acts as bridge between array-based and collection-based
348			* APIs.
349			*
350			* @return an array containing all of the elements in this queue
351			*/
352	dl	1.5	public Object[] toArray() {
353	dl	1.31	final ReentrantLock lock = this.lock;
354	dl	1.5	lock.lock();
355			try {
356			return q.toArray();
357	tim	1.19	} finally {
358	dl	1.5	lock.unlock();
359			}
360			}
361
362
363			public String toString() {
364	dl	1.31	final ReentrantLock lock = this.lock;
365	dl	1.5	lock.lock();
366			try {
367			return q.toString();
368	tim	1.19	} finally {
369	dl	1.5	lock.unlock();
370			}
371			}
372
373	jsr166	1.42	/**
374			* @throws UnsupportedOperationException {@inheritDoc}
375			* @throws ClassCastException {@inheritDoc}
376			* @throws NullPointerException {@inheritDoc}
377			* @throws IllegalArgumentException {@inheritDoc}
378			*/
379	dl	1.26	public int drainTo(Collection<? super E> c) {
380			if (c == null)
381			throw new NullPointerException();
382			if (c == this)
383			throw new IllegalArgumentException();
384	dl	1.31	final ReentrantLock lock = this.lock;
385	dl	1.26	lock.lock();
386			try {
387			int n = 0;
388			E e;
389			while ( (e = q.poll()) != null) {
390			c.add(e);
391			++n;
392			}
393			return n;
394			} finally {
395			lock.unlock();
396			}
397			}
398
399	jsr166	1.42	/**
400			* @throws UnsupportedOperationException {@inheritDoc}
401			* @throws ClassCastException {@inheritDoc}
402			* @throws NullPointerException {@inheritDoc}
403			* @throws IllegalArgumentException {@inheritDoc}
404			*/
405	dl	1.26	public int drainTo(Collection<? super E> c, int maxElements) {
406			if (c == null)
407			throw new NullPointerException();
408			if (c == this)
409			throw new IllegalArgumentException();
410			if (maxElements <= 0)
411			return 0;
412	dl	1.31	final ReentrantLock lock = this.lock;
413	dl	1.26	lock.lock();
414			try {
415			int n = 0;
416			E e;
417			while (n < maxElements && (e = q.poll()) != null) {
418			c.add(e);
419			++n;
420			}
421			return n;
422			} finally {
423			lock.unlock();
424			}
425			}
426
427	dl	1.17	/**
428	dl	1.37	* Atomically removes all of the elements from this queue.
429	dl	1.17	* The queue will be empty after this call returns.
430			*/
431			public void clear() {
432	dl	1.31	final ReentrantLock lock = this.lock;
433	dl	1.17	lock.lock();
434			try {
435			q.clear();
436	tim	1.19	} finally {
437	dl	1.17	lock.unlock();
438			}
439			}
440
441	jsr166	1.42	/**
442			* Returns an array containing all of the elements in this queue; the
443			* runtime type of the returned array is that of the specified array.
444			* The returned array elements are in no particular order.
445			* If the queue fits in the specified array, it is returned therein.
446			* Otherwise, a new array is allocated with the runtime type of the
447			* specified array and the size of this queue.
448			*
449			* <p>If this queue fits in the specified array with room to spare
450			* (i.e., the array has more elements than this queue), the element in
451			* the array immediately following the end of the queue is set to
452			* <tt>null</tt>.
453			*
454			* <p>Like the {@link #toArray()} method, this method acts as bridge between
455			* array-based and collection-based APIs. Further, this method allows
456			* precise control over the runtime type of the output array, and may,
457			* under certain circumstances, be used to save allocation costs.
458			*
459			* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
460			* The following code can be used to dump the queue into a newly
461			* allocated array of <tt>String</tt>:
462			*
463			* <pre>
464			* String[] y = x.toArray(new String[0]);</pre>
465			*
466			* Note that <tt>toArray(new Object[0])</tt> is identical in function to
467			* <tt>toArray()</tt>.
468			*
469			* @param a the array into which the elements of the queue are to
470			* be stored, if it is big enough; otherwise, a new array of the
471			* same runtime type is allocated for this purpose
472			* @return an array containing all of the elements in this queue
473			* @throws ArrayStoreException if the runtime type of the specified array
474			* is not a supertype of the runtime type of every element in
475			* this queue
476			* @throws NullPointerException if the specified array is null
477			*/
478	dl	1.5	public <T> T[] toArray(T[] a) {
479	dl	1.31	final ReentrantLock lock = this.lock;
480	dl	1.5	lock.lock();
481			try {
482			return q.toArray(a);
483	tim	1.19	} finally {
484	dl	1.5	lock.unlock();
485			}
486			}
487
488	dholmes	1.16	/**
489	dl	1.23	* Returns an iterator over the elements in this queue. The
490			* iterator does not return the elements in any particular order.
491			* The returned iterator is a thread-safe "fast-fail" iterator
492	jsr166	1.39	* that will throw {@link ConcurrentModificationException} upon
493			* detected interference.
494	dholmes	1.16	*
495	jsr166	1.42	* @return an iterator over the elements in this queue
496	dholmes	1.16	*/
497	dl	1.5	public Iterator<E> iterator() {
498	dl	1.31	final ReentrantLock lock = this.lock;
499	dl	1.5	lock.lock();
500			try {
501	dl	1.44	return new Itr<E>(q.iterator());
502	tim	1.19	} finally {
503	dl	1.5	lock.unlock();
504			}
505			}
506
507			private class Itr<E> implements Iterator<E> {
508			private final Iterator<E> iter;
509	tim	1.13	Itr(Iterator<E> i) {
510			iter = i;
511	dl	1.5	}
512
513	tim	1.13	public boolean hasNext() {
514	dl	1.5	/*
515			* No sync -- we rely on underlying hasNext to be
516			* stateless, in which case we can return true by mistake
517	dl	1.30	* only when next() will subsequently throw
518	dl	1.5	* ConcurrentModificationException.
519			*/
520			return iter.hasNext();
521	tim	1.13	}
522
523			public E next() {
524	dl	1.31	ReentrantLock lock = PriorityBlockingQueue.this.lock;
525	dl	1.5	lock.lock();
526			try {
527			return iter.next();
528	tim	1.19	} finally {
529	dl	1.5	lock.unlock();
530			}
531	tim	1.13	}
532
533			public void remove() {
534	dl	1.31	ReentrantLock lock = PriorityBlockingQueue.this.lock;
535	dl	1.5	lock.lock();
536			try {
537			iter.remove();
538	tim	1.19	} finally {
539	dl	1.5	lock.unlock();
540			}
541	tim	1.13	}
542	dl	1.5	}
543
544			/**
545			* Save the state to a stream (that is, serialize it). This
546			* merely wraps default serialization within lock. The
547			* serialization strategy for items is left to underlying
548			* Queue. Note that locking is not needed on deserialization, so
549			* readObject is not defined, just relying on default.
550			*/
551			private void writeObject(java.io.ObjectOutputStream s)
552			throws java.io.IOException {
553			lock.lock();
554			try {
555			s.defaultWriteObject();
556	tim	1.19	} finally {
557	dl	1.5	lock.unlock();
558			}
559	tim	1.1	}
560
561			}