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}/../technotes/guides/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 that will be used to order this
     *         priority queue.  If {@code null}, the {@linkplain Comparable
     *         natural ordering} of the elements will be used.
     * @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.  If the specified collection is a
     * {@link SortedSet} or a {@link PriorityQueue},  this
     * priority queue will be ordered according to the same ordering.
     * Otherwise, this priority queue will be ordered according to the
     * {@linkplain Comparable 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 {@code e} such
     * that {@code o.equals(e)}, if this queue contains one or more such
     * elements.  Returns {@code true} if and only 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 {@code true} if this queue contains the specified element.
     * More formally, returns {@code true} if and only if this queue contains
     * at least one element {@code e} such that {@code o.equals(e)}.
     *
     * @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 <tt>Iterator</tt> is a "weakly consistent"
     * iterator that will never throw {@link
     * ConcurrentModificationException}, and guarantees to traverse
     * elements as they existed upon construction of the iterator, and
     * may (but is not guaranteed to) reflect any modifications
     * subsequent to construction.
     *
     * @return an iterator over the elements in this queue
     */
    public Iterator<E> iterator() {
        return new Itr(toArray());
    }

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

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

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

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

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

    /**
     * Saves the state to a stream (that is, serializes 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:	1.54
Committed:	Sun May 18 23:47:56 2008 UTC (16 years ago) by jsr166
Branch:	MAIN
Changes since 1.53:	+3 -3 lines
Log Message:	Sync with OpenJDK; untabify
#	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	jsr166	1.53	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
62	dl	1.35	* 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	jsr166	1.52	* 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	jsr166	1.52	* @param comparator the comparator that will be used to order this
105			* priority queue. If {@code null}, the {@linkplain Comparable
106			* natural ordering} of the elements will be used.
107	dholmes	1.16	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
108	jsr166	1.52	* 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	jsr166	1.52	* in the specified collection. If the specified collection is a
118			* {@link SortedSet} or a {@link PriorityQueue}, this
119			* priority queue will be ordered according to the same ordering.
120			* Otherwise, this priority queue will be ordered according to the
121			* {@linkplain Comparable natural ordering} of its elements.
122	dl	1.2	*
123	jsr166	1.52	* @param c the collection whose elements are to be placed
124			* into this priority queue
125	dl	1.2	* @throws ClassCastException if elements of the specified collection
126			* cannot be compared to one another according to the priority
127	jsr166	1.52	* queue's ordering
128	jsr166	1.42	* @throws NullPointerException if the specified collection or any
129			* of its elements are null
130	dl	1.2	*/
131	dholmes	1.14	public PriorityBlockingQueue(Collection<? extends E> c) {
132			q = new PriorityQueue<E>(c);
133	dl	1.7	}
134
135	dholmes	1.10	/**
136	jsr166	1.42	* Inserts the specified element into this priority queue.
137			*
138	jsr166	1.40	* @param e the element to add
139	jsr166	1.48	* @return <tt>true</tt> (as specified by {@link Collection#add})
140	dholmes	1.16	* @throws ClassCastException if the specified element cannot be compared
141	jsr166	1.42	* with elements currently in the priority queue according to the
142			* priority queue's ordering
143			* @throws NullPointerException if the specified element is null
144	dholmes	1.10	*/
145	jsr166	1.40	public boolean add(E e) {
146	jsr166	1.42	return offer(e);
147	dl	1.5	}
148
149	dholmes	1.16	/**
150	dl	1.24	* Inserts the specified element into this priority queue.
151	dholmes	1.16	*
152	jsr166	1.40	* @param e the element to add
153	jsr166	1.48	* @return <tt>true</tt> (as specified by {@link Queue#offer})
154	dholmes	1.16	* @throws ClassCastException if the specified element cannot be compared
155	jsr166	1.42	* with elements currently in the priority queue according to the
156			* priority queue's ordering
157			* @throws NullPointerException if the specified element is null
158	dholmes	1.16	*/
159	jsr166	1.40	public boolean offer(E e) {
160	dl	1.31	final ReentrantLock lock = this.lock;
161	dl	1.5	lock.lock();
162			try {
163	jsr166	1.40	boolean ok = q.offer(e);
164	dl	1.5	assert ok;
165			notEmpty.signal();
166			return true;
167	tim	1.19	} finally {
168	tim	1.13	lock.unlock();
169	dl	1.5	}
170			}
171
172	dholmes	1.16	/**
173	jsr166	1.42	* Inserts the specified element into this priority queue. As the queue is
174	dholmes	1.16	* unbounded this method will never block.
175	jsr166	1.42	*
176	jsr166	1.40	* @param e the element to add
177	jsr166	1.42	* @throws ClassCastException if the specified element cannot be compared
178			* with elements currently in the priority queue according to the
179			* priority queue's ordering
180			* @throws NullPointerException if the specified element is null
181	dholmes	1.16	*/
182	jsr166	1.40	public void put(E e) {
183			offer(e); // never need to block
184	dl	1.5	}
185
186	dholmes	1.16	/**
187	dl	1.24	* Inserts the specified element into this priority queue. As the queue is
188	dholmes	1.16	* unbounded this method will never block.
189	jsr166	1.42	*
190	jsr166	1.40	* @param e the element to add
191	dholmes	1.16	* @param timeout This parameter is ignored as the method never blocks
192			* @param unit This parameter is ignored as the method never blocks
193	dl	1.22	* @return <tt>true</tt>
194	jsr166	1.42	* @throws ClassCastException if the specified element cannot be compared
195			* with elements currently in the priority queue according to the
196			* priority queue's ordering
197			* @throws NullPointerException if the specified element is null
198	dholmes	1.16	*/
199	jsr166	1.40	public boolean offer(E e, long timeout, TimeUnit unit) {
200			return offer(e); // never need to block
201	dl	1.5	}
202
203	jsr166	1.42	public E poll() {
204			final ReentrantLock lock = this.lock;
205			lock.lock();
206			try {
207			return q.poll();
208			} finally {
209			lock.unlock();
210			}
211			}
212
213	dl	1.5	public E take() throws InterruptedException {
214	dl	1.31	final ReentrantLock lock = this.lock;
215	dl	1.5	lock.lockInterruptibly();
216			try {
217			try {
218			while (q.size() == 0)
219			notEmpty.await();
220	tim	1.19	} catch (InterruptedException ie) {
221	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
222			throw ie;
223			}
224			E x = q.poll();
225			assert x != null;
226			return x;
227	tim	1.19	} finally {
228	dl	1.5	lock.unlock();
229			}
230			}
231
232			public E poll(long timeout, TimeUnit unit) throws InterruptedException {
233	dholmes	1.10	long nanos = unit.toNanos(timeout);
234	dl	1.31	final ReentrantLock lock = this.lock;
235	dl	1.5	lock.lockInterruptibly();
236			try {
237			for (;;) {
238			E x = q.poll();
239	tim	1.13	if (x != null)
240	dl	1.5	return x;
241			if (nanos <= 0)
242			return null;
243			try {
244			nanos = notEmpty.awaitNanos(nanos);
245	tim	1.19	} catch (InterruptedException ie) {
246	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
247			throw ie;
248			}
249			}
250	tim	1.19	} finally {
251	dl	1.5	lock.unlock();
252			}
253			}
254
255			public E peek() {
256	dl	1.31	final ReentrantLock lock = this.lock;
257	dl	1.5	lock.lock();
258			try {
259			return q.peek();
260	tim	1.19	} finally {
261	tim	1.13	lock.unlock();
262	dl	1.5	}
263			}
264
265	jsr166	1.42	/**
266			* Returns the comparator used to order the elements in this queue,
267			* or <tt>null</tt> if this queue uses the {@linkplain Comparable
268			* natural ordering} of its elements.
269			*
270			* @return the comparator used to order the elements in this queue,
271			* or <tt>null</tt> if this queue uses the natural
272	jsr166	1.52	* ordering of its elements
273	jsr166	1.42	*/
274			public Comparator<? super E> comparator() {
275			return q.comparator();
276			}
277
278	dl	1.5	public int size() {
279	dl	1.31	final ReentrantLock lock = this.lock;
280	dl	1.5	lock.lock();
281			try {
282			return q.size();
283	tim	1.19	} finally {
284	dl	1.5	lock.unlock();
285			}
286			}
287
288			/**
289			* Always returns <tt>Integer.MAX_VALUE</tt> because
290	dholmes	1.16	* a <tt>PriorityBlockingQueue</tt> is not capacity constrained.
291	dl	1.5	* @return <tt>Integer.MAX_VALUE</tt>
292			*/
293			public int remainingCapacity() {
294			return Integer.MAX_VALUE;
295			}
296
297	dl	1.37	/**
298	jsr166	1.42	* Removes a single instance of the specified element from this queue,
299	jsr166	1.52	* if it is present. More formally, removes an element {@code e} such
300			* that {@code o.equals(e)}, if this queue contains one or more such
301			* elements. Returns {@code true} if and only if this queue contained
302			* the specified element (or equivalently, if this queue changed as a
303			* result of the call).
304	jsr166	1.42	*
305			* @param o element to be removed from this queue, if present
306			* @return <tt>true</tt> if this queue changed as a result of the call
307	dl	1.37	*/
308	dholmes	1.14	public boolean remove(Object o) {
309	dl	1.31	final ReentrantLock lock = this.lock;
310	dl	1.5	lock.lock();
311			try {
312	dholmes	1.14	return q.remove(o);
313	tim	1.19	} finally {
314	dl	1.5	lock.unlock();
315			}
316			}
317
318	jsr166	1.42	/**
319	jsr166	1.52	* Returns {@code true} if this queue contains the specified element.
320			* More formally, returns {@code true} if and only if this queue contains
321			* at least one element {@code e} such that {@code o.equals(e)}.
322	jsr166	1.42	*
323			* @param o object to be checked for containment in this queue
324			* @return <tt>true</tt> if this queue contains the specified element
325			*/
326	dholmes	1.14	public boolean contains(Object o) {
327	dl	1.31	final ReentrantLock lock = this.lock;
328	dl	1.5	lock.lock();
329			try {
330	dholmes	1.14	return q.contains(o);
331	tim	1.19	} finally {
332	dl	1.5	lock.unlock();
333			}
334			}
335
336	jsr166	1.42	/**
337			* Returns an array containing all of the elements in this queue.
338			* The returned array elements are in no particular order.
339			*
340			* <p>The returned array will be "safe" in that no references to it are
341			* maintained by this queue. (In other words, this method must allocate
342			* a new array). The caller is thus free to modify the returned array.
343	jsr166	1.43	*
344	jsr166	1.42	* <p>This method acts as bridge between array-based and collection-based
345			* APIs.
346			*
347			* @return an array containing all of the elements in this queue
348			*/
349	dl	1.5	public Object[] toArray() {
350	dl	1.31	final ReentrantLock lock = this.lock;
351	dl	1.5	lock.lock();
352			try {
353			return q.toArray();
354	tim	1.19	} finally {
355	dl	1.5	lock.unlock();
356			}
357			}
358
359	jsr166	1.52
360	dl	1.5	public String toString() {
361	dl	1.31	final ReentrantLock lock = this.lock;
362	dl	1.5	lock.lock();
363			try {
364			return q.toString();
365	tim	1.19	} finally {
366	dl	1.5	lock.unlock();
367			}
368			}
369
370	jsr166	1.42	/**
371			* @throws UnsupportedOperationException {@inheritDoc}
372			* @throws ClassCastException {@inheritDoc}
373			* @throws NullPointerException {@inheritDoc}
374			* @throws IllegalArgumentException {@inheritDoc}
375			*/
376	dl	1.26	public int drainTo(Collection<? super E> c) {
377			if (c == null)
378			throw new NullPointerException();
379			if (c == this)
380			throw new IllegalArgumentException();
381	dl	1.31	final ReentrantLock lock = this.lock;
382	dl	1.26	lock.lock();
383			try {
384			int n = 0;
385			E e;
386			while ( (e = q.poll()) != null) {
387			c.add(e);
388			++n;
389			}
390			return n;
391			} finally {
392			lock.unlock();
393			}
394			}
395
396	jsr166	1.42	/**
397			* @throws UnsupportedOperationException {@inheritDoc}
398			* @throws ClassCastException {@inheritDoc}
399			* @throws NullPointerException {@inheritDoc}
400			* @throws IllegalArgumentException {@inheritDoc}
401			*/
402	dl	1.26	public int drainTo(Collection<? super E> c, int maxElements) {
403			if (c == null)
404			throw new NullPointerException();
405			if (c == this)
406			throw new IllegalArgumentException();
407			if (maxElements <= 0)
408			return 0;
409	dl	1.31	final ReentrantLock lock = this.lock;
410	dl	1.26	lock.lock();
411			try {
412			int n = 0;
413			E e;
414			while (n < maxElements && (e = q.poll()) != null) {
415			c.add(e);
416			++n;
417			}
418			return n;
419			} finally {
420			lock.unlock();
421			}
422			}
423
424	dl	1.17	/**
425	dl	1.37	* Atomically removes all of the elements from this queue.
426	dl	1.17	* The queue will be empty after this call returns.
427			*/
428			public void clear() {
429	dl	1.31	final ReentrantLock lock = this.lock;
430	dl	1.17	lock.lock();
431			try {
432			q.clear();
433	tim	1.19	} finally {
434	dl	1.17	lock.unlock();
435			}
436			}
437
438	jsr166	1.42	/**
439			* Returns an array containing all of the elements in this queue; the
440			* runtime type of the returned array is that of the specified array.
441			* The returned array elements are in no particular order.
442			* If the queue fits in the specified array, it is returned therein.
443			* Otherwise, a new array is allocated with the runtime type of the
444			* specified array and the size of this queue.
445			*
446			* <p>If this queue fits in the specified array with room to spare
447			* (i.e., the array has more elements than this queue), the element in
448			* the array immediately following the end of the queue is set to
449			* <tt>null</tt>.
450			*
451			* <p>Like the {@link #toArray()} method, this method acts as bridge between
452			* array-based and collection-based APIs. Further, this method allows
453			* precise control over the runtime type of the output array, and may,
454			* under certain circumstances, be used to save allocation costs.
455			*
456			* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
457			* The following code can be used to dump the queue into a newly
458			* allocated array of <tt>String</tt>:
459			*
460			* <pre>
461			* String[] y = x.toArray(new String[0]);</pre>
462			*
463			* Note that <tt>toArray(new Object[0])</tt> is identical in function to
464			* <tt>toArray()</tt>.
465			*
466			* @param a the array into which the elements of the queue are to
467			* be stored, if it is big enough; otherwise, a new array of the
468			* same runtime type is allocated for this purpose
469			* @return an array containing all of the elements in this queue
470			* @throws ArrayStoreException if the runtime type of the specified array
471			* is not a supertype of the runtime type of every element in
472			* this queue
473			* @throws NullPointerException if the specified array is null
474			*/
475	dl	1.5	public <T> T[] toArray(T[] a) {
476	dl	1.31	final ReentrantLock lock = this.lock;
477	dl	1.5	lock.lock();
478			try {
479			return q.toArray(a);
480	tim	1.19	} finally {
481	dl	1.5	lock.unlock();
482			}
483			}
484
485	dholmes	1.16	/**
486	dl	1.23	* Returns an iterator over the elements in this queue. The
487			* iterator does not return the elements in any particular order.
488	dl	1.51	* The returned <tt>Iterator</tt> is a "weakly consistent"
489			* iterator that will never throw {@link
490			* ConcurrentModificationException}, and guarantees to traverse
491			* elements as they existed upon construction of the iterator, and
492			* may (but is not guaranteed to) reflect any modifications
493			* subsequent to construction.
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	1.51	return new Itr(toArray());
499	dl	1.5	}
500
501	dl	1.49	/**
502			* Snapshot iterator that works off copy of underlying q array.
503			*/
504	dl	1.51	private class Itr implements Iterator<E> {
505	dl	1.49	final Object[] array; // Array of all elements
506	jsr166	1.54	int cursor; // index of next element to return;
507			int lastRet; // index of last element, or -1 if no such
508	jsr166	1.50
509	dl	1.49	Itr(Object[] array) {
510			lastRet = -1;
511			this.array = array;
512	dl	1.5	}
513
514	tim	1.13	public boolean hasNext() {
515	dl	1.49	return cursor < array.length;
516	tim	1.13	}
517
518			public E next() {
519	dl	1.49	if (cursor >= array.length)
520			throw new NoSuchElementException();
521			lastRet = cursor;
522			return (E)array[cursor++];
523	tim	1.13	}
524
525			public void remove() {
526	jsr166	1.50	if (lastRet < 0)
527	jsr166	1.54	throw new IllegalStateException();
528	dl	1.49	Object x = array[lastRet];
529			lastRet = -1;
530			// Traverse underlying queue to find == element,
531			// not just a .equals element.
532	dl	1.5	lock.lock();
533			try {
534	dl	1.49	for (Iterator it = q.iterator(); it.hasNext(); ) {
535			if (it.next() == x) {
536			it.remove();
537			return;
538			}
539			}
540	tim	1.19	} finally {
541	dl	1.5	lock.unlock();
542			}
543	tim	1.13	}
544	dl	1.5	}
545
546			/**
547	jsr166	1.52	* Saves the state to a stream (that is, serializes it). This
548	dl	1.5	* merely wraps default serialization within lock. The
549			* serialization strategy for items is left to underlying
550			* Queue. Note that locking is not needed on deserialization, so
551			* readObject is not defined, just relying on default.
552			*/
553			private void writeObject(java.io.ObjectOutputStream s)
554			throws java.io.IOException {
555			lock.lock();
556			try {
557			s.defaultWriteObject();
558	tim	1.19	} finally {
559	dl	1.5	lock.unlock();
560			}
561	tim	1.1	}
562
563			}