--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/concurrent/PriorityBlockingQueue.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,592 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * 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<E extends Comparable<? super E>>
+ * implements Comparable<FIFOEntry<E>> {
+ * 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<E> other) {
+ * int res = entry.compareTo(other.entry);
+ * if (res == 0 && other.entry != this.entry)
+ * res = (seqNum < 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();
+ }
+ }
+
+}