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; {
 *   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 per the spec for {@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>
     * @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) {
        if (e == null) throw new NullPointerException();
        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(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:	1.43
Committed:	Wed May 18 01:41:16 2005 UTC (19 years ago) by jsr166
Branch:	MAIN
Changes since 1.42:	+1 -1 lines
Log Message:	whitespace
#	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			* implements Comparable<FIFOEntry<E>> {
44			* static AtomicLong seq = new AtomicLong();
45			* 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	1.42	* @return <tt>true</tt> (as per the spec for {@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	dholmes	1.16	* @return <tt>true</tt>
157			* @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			if (e == null) throw new NullPointerException();
164	dl	1.31	final ReentrantLock lock = this.lock;
165	dl	1.5	lock.lock();
166			try {
167	jsr166	1.40	boolean ok = q.offer(e);
168	dl	1.5	assert ok;
169			notEmpty.signal();
170			return true;
171	tim	1.19	} finally {
172	tim	1.13	lock.unlock();
173	dl	1.5	}
174			}
175
176	dholmes	1.16	/**
177	jsr166	1.42	* Inserts the specified element into this priority queue. As the queue is
178	dholmes	1.16	* unbounded this method will never block.
179	jsr166	1.42	*
180	jsr166	1.40	* @param e the element to add
181	jsr166	1.42	* @throws ClassCastException if the specified element cannot be compared
182			* with elements currently in the priority queue according to the
183			* priority queue's ordering
184			* @throws NullPointerException if the specified element is null
185	dholmes	1.16	*/
186	jsr166	1.40	public void put(E e) {
187			offer(e); // never need to block
188	dl	1.5	}
189
190	dholmes	1.16	/**
191	dl	1.24	* Inserts the specified element into this priority queue. As the queue is
192	dholmes	1.16	* unbounded this method will never block.
193	jsr166	1.42	*
194	jsr166	1.40	* @param e the element to add
195	dholmes	1.16	* @param timeout This parameter is ignored as the method never blocks
196			* @param unit This parameter is ignored as the method never blocks
197	dl	1.22	* @return <tt>true</tt>
198	jsr166	1.42	* @throws ClassCastException if the specified element cannot be compared
199			* with elements currently in the priority queue according to the
200			* priority queue's ordering
201			* @throws NullPointerException if the specified element is null
202	dholmes	1.16	*/
203	jsr166	1.40	public boolean offer(E e, long timeout, TimeUnit unit) {
204			return offer(e); // never need to block
205	dl	1.5	}
206
207	jsr166	1.42	public E poll() {
208			final ReentrantLock lock = this.lock;
209			lock.lock();
210			try {
211			return q.poll();
212			} finally {
213			lock.unlock();
214			}
215			}
216
217	dl	1.5	public E take() throws InterruptedException {
218	dl	1.31	final ReentrantLock lock = this.lock;
219	dl	1.5	lock.lockInterruptibly();
220			try {
221			try {
222			while (q.size() == 0)
223			notEmpty.await();
224	tim	1.19	} catch (InterruptedException ie) {
225	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
226			throw ie;
227			}
228			E x = q.poll();
229			assert x != null;
230			return x;
231	tim	1.19	} finally {
232	dl	1.5	lock.unlock();
233			}
234			}
235
236			public E poll(long timeout, TimeUnit unit) throws InterruptedException {
237	dholmes	1.10	long nanos = unit.toNanos(timeout);
238	dl	1.31	final ReentrantLock lock = this.lock;
239	dl	1.5	lock.lockInterruptibly();
240			try {
241			for (;;) {
242			E x = q.poll();
243	tim	1.13	if (x != null)
244	dl	1.5	return x;
245			if (nanos <= 0)
246			return null;
247			try {
248			nanos = notEmpty.awaitNanos(nanos);
249	tim	1.19	} catch (InterruptedException ie) {
250	dl	1.5	notEmpty.signal(); // propagate to non-interrupted thread
251			throw ie;
252			}
253			}
254	tim	1.19	} finally {
255	dl	1.5	lock.unlock();
256			}
257			}
258
259			public E peek() {
260	dl	1.31	final ReentrantLock lock = this.lock;
261	dl	1.5	lock.lock();
262			try {
263			return q.peek();
264	tim	1.19	} finally {
265	tim	1.13	lock.unlock();
266	dl	1.5	}
267			}
268
269	jsr166	1.42	/**
270			* Returns the comparator used to order the elements in this queue,
271			* or <tt>null</tt> if this queue uses the {@linkplain Comparable
272			* natural ordering} of its elements.
273			*
274			* @return the comparator used to order the elements in this queue,
275			* or <tt>null</tt> if this queue uses the natural
276			* ordering of its elements.
277			*/
278			public Comparator<? super E> comparator() {
279			return q.comparator();
280			}
281
282	dl	1.5	public int size() {
283	dl	1.31	final ReentrantLock lock = this.lock;
284	dl	1.5	lock.lock();
285			try {
286			return q.size();
287	tim	1.19	} finally {
288	dl	1.5	lock.unlock();
289			}
290			}
291
292			/**
293			* Always returns <tt>Integer.MAX_VALUE</tt> because
294	dholmes	1.16	* a <tt>PriorityBlockingQueue</tt> is not capacity constrained.
295	dl	1.5	* @return <tt>Integer.MAX_VALUE</tt>
296			*/
297			public int remainingCapacity() {
298			return Integer.MAX_VALUE;
299			}
300
301	dl	1.37	/**
302	jsr166	1.42	* Removes a single instance of the specified element from this queue,
303			* if it is present. More formally, removes an element <tt>e</tt> such
304			* that <tt>o.equals(e)</tt>, if this queue contains one or more such
305			* elements.
306			* Returns <tt>true</tt> if this queue contained the specified element
307			* (or equivalently, if this queue changed as a result of the call).
308			*
309			* @param o element to be removed from this queue, if present
310			* @return <tt>true</tt> if this queue changed as a result of the call
311	dl	1.37	*/
312	dholmes	1.14	public boolean remove(Object o) {
313	dl	1.31	final ReentrantLock lock = this.lock;
314	dl	1.5	lock.lock();
315			try {
316	dholmes	1.14	return q.remove(o);
317	tim	1.19	} finally {
318	dl	1.5	lock.unlock();
319			}
320			}
321
322	jsr166	1.42	/**
323			* Returns <tt>true</tt> if this queue contains the specified element.
324			* More formally, returns <tt>true</tt> if and only if this queue contains
325			* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
326			*
327			* @param o object to be checked for containment in this queue
328			* @return <tt>true</tt> if this queue contains the specified element
329			*/
330	dholmes	1.14	public boolean contains(Object o) {
331	dl	1.31	final ReentrantLock lock = this.lock;
332	dl	1.5	lock.lock();
333			try {
334	dholmes	1.14	return q.contains(o);
335	tim	1.19	} finally {
336	dl	1.5	lock.unlock();
337			}
338			}
339
340	jsr166	1.42	/**
341			* Returns an array containing all of the elements in this queue.
342			* The returned array elements are in no particular order.
343			*
344			* <p>The returned array will be "safe" in that no references to it are
345			* maintained by this queue. (In other words, this method must allocate
346			* a new array). The caller is thus free to modify the returned array.
347	jsr166	1.43	*
348	jsr166	1.42	* <p>This method acts as bridge between array-based and collection-based
349			* APIs.
350			*
351			* @return an array containing all of the elements in this queue
352			*/
353	dl	1.5	public Object[] toArray() {
354	dl	1.31	final ReentrantLock lock = this.lock;
355	dl	1.5	lock.lock();
356			try {
357			return q.toArray();
358	tim	1.19	} finally {
359	dl	1.5	lock.unlock();
360			}
361			}
362
363
364			public String toString() {
365	dl	1.31	final ReentrantLock lock = this.lock;
366	dl	1.5	lock.lock();
367			try {
368			return q.toString();
369	tim	1.19	} finally {
370	dl	1.5	lock.unlock();
371			}
372			}
373
374	jsr166	1.42	/**
375			* @throws UnsupportedOperationException {@inheritDoc}
376			* @throws ClassCastException {@inheritDoc}
377			* @throws NullPointerException {@inheritDoc}
378			* @throws IllegalArgumentException {@inheritDoc}
379			*/
380	dl	1.26	public int drainTo(Collection<? super E> c) {
381			if (c == null)
382			throw new NullPointerException();
383			if (c == this)
384			throw new IllegalArgumentException();
385	dl	1.31	final ReentrantLock lock = this.lock;
386	dl	1.26	lock.lock();
387			try {
388			int n = 0;
389			E e;
390			while ( (e = q.poll()) != null) {
391			c.add(e);
392			++n;
393			}
394			return n;
395			} finally {
396			lock.unlock();
397			}
398			}
399
400	jsr166	1.42	/**
401			* @throws UnsupportedOperationException {@inheritDoc}
402			* @throws ClassCastException {@inheritDoc}
403			* @throws NullPointerException {@inheritDoc}
404			* @throws IllegalArgumentException {@inheritDoc}
405			*/
406	dl	1.26	public int drainTo(Collection<? super E> c, int maxElements) {
407			if (c == null)
408			throw new NullPointerException();
409			if (c == this)
410			throw new IllegalArgumentException();
411			if (maxElements <= 0)
412			return 0;
413	dl	1.31	final ReentrantLock lock = this.lock;
414	dl	1.26	lock.lock();
415			try {
416			int n = 0;
417			E e;
418			while (n < maxElements && (e = q.poll()) != null) {
419			c.add(e);
420			++n;
421			}
422			return n;
423			} finally {
424			lock.unlock();
425			}
426			}
427
428	dl	1.17	/**
429	dl	1.37	* Atomically removes all of the elements from this queue.
430	dl	1.17	* The queue will be empty after this call returns.
431			*/
432			public void clear() {
433	dl	1.31	final ReentrantLock lock = this.lock;
434	dl	1.17	lock.lock();
435			try {
436			q.clear();
437	tim	1.19	} finally {
438	dl	1.17	lock.unlock();
439			}
440			}
441
442	jsr166	1.42	/**
443			* Returns an array containing all of the elements in this queue; the
444			* runtime type of the returned array is that of the specified array.
445			* The returned array elements are in no particular order.
446			* If the queue fits in the specified array, it is returned therein.
447			* Otherwise, a new array is allocated with the runtime type of the
448			* specified array and the size of this queue.
449			*
450			* <p>If this queue fits in the specified array with room to spare
451			* (i.e., the array has more elements than this queue), the element in
452			* the array immediately following the end of the queue is set to
453			* <tt>null</tt>.
454			*
455			* <p>Like the {@link #toArray()} method, this method acts as bridge between
456			* array-based and collection-based APIs. Further, this method allows
457			* precise control over the runtime type of the output array, and may,
458			* under certain circumstances, be used to save allocation costs.
459			*
460			* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
461			* The following code can be used to dump the queue into a newly
462			* allocated array of <tt>String</tt>:
463			*
464			* <pre>
465			* String[] y = x.toArray(new String[0]);</pre>
466			*
467			* Note that <tt>toArray(new Object[0])</tt> is identical in function to
468			* <tt>toArray()</tt>.
469			*
470			* @param a the array into which the elements of the queue are to
471			* be stored, if it is big enough; otherwise, a new array of the
472			* same runtime type is allocated for this purpose
473			* @return an array containing all of the elements in this queue
474			* @throws ArrayStoreException if the runtime type of the specified array
475			* is not a supertype of the runtime type of every element in
476			* this queue
477			* @throws NullPointerException if the specified array is null
478			*/
479	dl	1.5	public <T> T[] toArray(T[] a) {
480	dl	1.31	final ReentrantLock lock = this.lock;
481	dl	1.5	lock.lock();
482			try {
483			return q.toArray(a);
484	tim	1.19	} finally {
485	dl	1.5	lock.unlock();
486			}
487			}
488
489	dholmes	1.16	/**
490	dl	1.23	* Returns an iterator over the elements in this queue. The
491			* iterator does not return the elements in any particular order.
492			* The returned iterator is a thread-safe "fast-fail" iterator
493	jsr166	1.39	* that will throw {@link ConcurrentModificationException} upon
494			* detected interference.
495	dholmes	1.16	*
496	jsr166	1.42	* @return an iterator over the elements in this queue
497	dholmes	1.16	*/
498	dl	1.5	public Iterator<E> iterator() {
499	dl	1.31	final ReentrantLock lock = this.lock;
500	dl	1.5	lock.lock();
501			try {
502			return new Itr(q.iterator());
503	tim	1.19	} finally {
504	dl	1.5	lock.unlock();
505			}
506			}
507
508			private class Itr<E> implements Iterator<E> {
509			private final Iterator<E> iter;
510	tim	1.13	Itr(Iterator<E> i) {
511			iter = i;
512	dl	1.5	}
513
514	tim	1.13	public boolean hasNext() {
515	dl	1.5	/*
516			* No sync -- we rely on underlying hasNext to be
517			* stateless, in which case we can return true by mistake
518	dl	1.30	* only when next() will subsequently throw
519	dl	1.5	* ConcurrentModificationException.
520			*/
521			return iter.hasNext();
522	tim	1.13	}
523
524			public E next() {
525	dl	1.31	ReentrantLock lock = PriorityBlockingQueue.this.lock;
526	dl	1.5	lock.lock();
527			try {
528			return iter.next();
529	tim	1.19	} finally {
530	dl	1.5	lock.unlock();
531			}
532	tim	1.13	}
533
534			public void remove() {
535	dl	1.31	ReentrantLock lock = PriorityBlockingQueue.this.lock;
536	dl	1.5	lock.lock();
537			try {
538			iter.remove();
539	tim	1.19	} finally {
540	dl	1.5	lock.unlock();
541			}
542	tim	1.13	}
543	dl	1.5	}
544
545			/**
546			* Save the state to a stream (that is, serialize it). This
547			* merely wraps default serialization within lock. The
548			* serialization strategy for items is left to underlying
549			* Queue. Note that locking is not needed on deserialization, so
550			* readObject is not defined, just relying on default.
551			*/
552			private void writeObject(java.io.ObjectOutputStream s)
553			throws java.io.IOException {
554			lock.lock();
555			try {
556			s.defaultWriteObject();
557	tim	1.19	} finally {
558	dl	1.5	lock.unlock();
559			}
560	tim	1.1	}
561
562			}