My first initial commit with all of mine experimental changes.

Dmitry Kabak (userdima committed 13 years ago

Commit d37b88d1 parent 3f5b46618352 files · +2598093 −-8690Browse files

Showing the changes to java/pkg/java/util/concurrent/PriorityBlockingQueue.java (1 of 18352 files). Show all

Unified · Split

java/pkg/java/util/concurrent/PriorityBlockingQueue.java+978−0

@@ -0,0 +1,978 @@
	1	+/*
	2	+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	3	+ *
	4	+ * This code is free software; you can redistribute it and/or modify it
	5	+ * under the terms of the GNU General Public License version 2 only, as
	6	+ * published by the Free Software Foundation. Oracle designates this
	7	+ * particular file as subject to the "Classpath" exception as provided
	8	+ * by Oracle in the LICENSE file that accompanied this code.
	9	+ *
	10	+ * This code is distributed in the hope that it will be useful, but WITHOUT
	11	+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	12	+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	13	+ * version 2 for more details (a copy is included in the LICENSE file that
	14	+ * accompanied this code).
	15	+ *
	16	+ * You should have received a copy of the GNU General Public License version
	17	+ * 2 along with this work; if not, write to the Free Software Foundation,
	18	+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	19	+ *
	20	+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	21	+ * or visit www.oracle.com if you need additional information or have any
	22	+ * questions.
	23	+ */
	24	+
	25	+/*
	26	+ * This file is available under and governed by the GNU General Public
	27	+ * License version 2 only, as published by the Free Software Foundation.
	28	+ * However, the following notice accompanied the original version of this
	29	+ * file:
	30	+ *
	31	+ * Written by Doug Lea with assistance from members of JCP JSR-166
	32	+ * Expert Group and released to the public domain, as explained at
	33	+ * http://creativecommons.org/publicdomain/zero/1.0/
	34	+ */
	35	+
	36	+package java.util.concurrent;
	37	+
	38	+import java.util.concurrent.locks.*;
	39	+import java.util.*;
	40	+
	41	+/**
	42	+ * An unbounded {@linkplain BlockingQueue blocking queue} that uses
	43	+ * the same ordering rules as class {@link PriorityQueue} and supplies
	44	+ * blocking retrieval operations. While this queue is logically
	45	+ * unbounded, attempted additions may fail due to resource exhaustion
	46	+ * (causing {@code OutOfMemoryError}). This class does not permit
	47	+ * {@code null} elements. A priority queue relying on {@linkplain
	48	+ * Comparable natural ordering} also does not permit insertion of
	49	+ * non-comparable objects (doing so results in
	50	+ * {@code ClassCastException}).
	51	+ *
	52	+ * <p>This class and its iterator implement all of the
	53	+ * <em>optional</em> methods of the {@link Collection} and {@link
	54	+ * Iterator} interfaces. The Iterator provided in method {@link
	55	+ * #iterator()} is <em>not</em> guaranteed to traverse the elements of
	56	+ * the PriorityBlockingQueue in any particular order. If you need
	57	+ * ordered traversal, consider using
	58	+ * {@code Arrays.sort(pq.toArray())}. Also, method {@code drainTo}
	59	+ * can be used to <em>remove</em> some or all elements in priority
	60	+ * order and place them in another collection.
	61	+ *
	62	+ * <p>Operations on this class make no guarantees about the ordering
	63	+ * of elements with equal priority. If you need to enforce an
	64	+ * ordering, you can define custom classes or comparators that use a
	65	+ * secondary key to break ties in primary priority values. For
	66	+ * example, here is a class that applies first-in-first-out
	67	+ * tie-breaking to comparable elements. To use it, you would insert a
	68	+ * {@code new FIFOEntry(anEntry)} instead of a plain entry object.
	69	+ *
	70	+ * <pre> {@code
	71	+ * class FIFOEntry<E extends Comparable<? super E>>
	72	+ * implements Comparable<FIFOEntry<E>> {
	73	+ * static final AtomicLong seq = new AtomicLong(0);
	74	+ * final long seqNum;
	75	+ * final E entry;
	76	+ * public FIFOEntry(E entry) {
	77	+ * seqNum = seq.getAndIncrement();
	78	+ * this.entry = entry;
	79	+ * }
	80	+ * public E getEntry() { return entry; }
	81	+ * public int compareTo(FIFOEntry<E> other) {
	82	+ * int res = entry.compareTo(other.entry);
	83	+ * if (res == 0 && other.entry != this.entry)
	84	+ * res = (seqNum < other.seqNum ? -1 : 1);
	85	+ * return res;
	86	+ * }
	87	+ * }}</pre>
	88	+ *
	89	+ * <p>This class is a member of the
	90	+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
	91	+ * Java Collections Framework</a>.
	92	+ *
	93	+ * @since 1.5
	94	+ * @author Doug Lea
	95	+ * @param <E> the type of elements held in this collection
	96	+ */
	97	+public class PriorityBlockingQueue<E> extends AbstractQueue<E>
	98	+ implements BlockingQueue<E>, java.io.Serializable {
	99	+ private static final long serialVersionUID = 5595510919245408276L;
	100	+
	101	+ /*
	102	+ * The implementation uses an array-based binary heap, with public
	103	+ * operations protected with a single lock. However, allocation
	104	+ * during resizing uses a simple spinlock (used only while not
	105	+ * holding main lock) in order to allow takes to operate
	106	+ * concurrently with allocation. This avoids repeated
	107	+ * postponement of waiting consumers and consequent element
	108	+ * build-up. The need to back away from lock during allocation
	109	+ * makes it impossible to simply wrap delegated
	110	+ * java.util.PriorityQueue operations within a lock, as was done
	111	+ * in a previous version of this class. To maintain
	112	+ * interoperability, a plain PriorityQueue is still used during
	113	+ * serialization, which maintains compatibility at the espense of
	114	+ * transiently doubling overhead.
	115	+ */
	116	+
	117	+ /**
	118	+ * Default array capacity.
	119	+ */
	120	+ private static final int DEFAULT_INITIAL_CAPACITY = 11;
	121	+
	122	+ /**
	123	+ * The maximum size of array to allocate.
	124	+ * Some VMs reserve some header words in an array.
	125	+ * Attempts to allocate larger arrays may result in
	126	+ * OutOfMemoryError: Requested array size exceeds VM limit
	127	+ */
	128	+ private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
	129	+
	130	+ /**
	131	+ * Priority queue represented as a balanced binary heap: the two
	132	+ * children of queue[n] are queue[2n+1] and queue[2(n+1)]. The
	133	+ * priority queue is ordered by comparator, or by the elements'
	134	+ * natural ordering, if comparator is null: For each node n in the
	135	+ * heap and each descendant d of n, n <= d. The element with the
	136	+ * lowest value is in queue[0], assuming the queue is nonempty.
	137	+ */
	138	+ private transient Object[] queue;
	139	+
	140	+ /**
	141	+ * The number of elements in the priority queue.
	142	+ */
	143	+ private transient int size;
	144	+
	145	+ /**
	146	+ * The comparator, or null if priority queue uses elements'
	147	+ * natural ordering.
	148	+ */
	149	+ private transient Comparator<? super E> comparator;
	150	+
	151	+ /**
	152	+ * Lock used for all public operations
	153	+ */
	154	+ private final ReentrantLock lock;
	155	+
	156	+ /**
	157	+ * Condition for blocking when empty
	158	+ */
	159	+ private final Condition notEmpty;
	160	+
	161	+ /**
	162	+ * Spinlock for allocation, acquired via CAS.
	163	+ */
	164	+ private transient volatile int allocationSpinLock;
	165	+
	166	+ /**
	167	+ * A plain PriorityQueue used only for serialization,
	168	+ * to maintain compatibility with previous versions
	169	+ * of this class. Non-null only during serialization/deserialization.
	170	+ */
	171	+ private PriorityQueue q;
	172	+
	173	+ /**
	174	+ * Creates a {@code PriorityBlockingQueue} with the default
	175	+ * initial capacity (11) that orders its elements according to
	176	+ * their {@linkplain Comparable natural ordering}.
	177	+ */
	178	+ public PriorityBlockingQueue() {
	179	+ this(DEFAULT_INITIAL_CAPACITY, null);
	180	+ }
	181	+
	182	+ /**
	183	+ * Creates a {@code PriorityBlockingQueue} with the specified
	184	+ * initial capacity that orders its elements according to their
	185	+ * {@linkplain Comparable natural ordering}.
	186	+ *
	187	+ * @param initialCapacity the initial capacity for this priority queue
	188	+ * @throws IllegalArgumentException if {@code initialCapacity} is less
	189	+ * than 1
	190	+ */
	191	+ public PriorityBlockingQueue(int initialCapacity) {
	192	+ this(initialCapacity, null);
	193	+ }
	194	+
	195	+ /**
	196	+ * Creates a {@code PriorityBlockingQueue} with the specified initial
	197	+ * capacity that orders its elements according to the specified
	198	+ * comparator.
	199	+ *
	200	+ * @param initialCapacity the initial capacity for this priority queue
	201	+ * @param comparator the comparator that will be used to order this
	202	+ * priority queue. If {@code null}, the {@linkplain Comparable
	203	+ * natural ordering} of the elements will be used.
	204	+ * @throws IllegalArgumentException if {@code initialCapacity} is less
	205	+ * than 1
	206	+ */
	207	+ public PriorityBlockingQueue(int initialCapacity,
	208	+ Comparator<? super E> comparator) {
	209	+ if (initialCapacity < 1)
	210	+ throw new IllegalArgumentException();
	211	+ this.lock = new ReentrantLock();
	212	+ this.notEmpty = lock.newCondition();
	213	+ this.comparator = comparator;
	214	+ this.queue = new Object[initialCapacity];
	215	+ }
	216	+
	217	+ /**
	218	+ * Creates a {@code PriorityBlockingQueue} containing the elements
	219	+ * in the specified collection. If the specified collection is a
	220	+ * {@link SortedSet} or a {@link PriorityQueue}, this
	221	+ * priority queue will be ordered according to the same ordering.
	222	+ * Otherwise, this priority queue will be ordered according to the
	223	+ * {@linkplain Comparable natural ordering} of its elements.
	224	+ *
	225	+ * @param c the collection whose elements are to be placed
	226	+ * into this priority queue
	227	+ * @throws ClassCastException if elements of the specified collection
	228	+ * cannot be compared to one another according to the priority
	229	+ * queue's ordering
	230	+ * @throws NullPointerException if the specified collection or any
	231	+ * of its elements are null
	232	+ */
	233	+ public PriorityBlockingQueue(Collection<? extends E> c) {
	234	+ this.lock = new ReentrantLock();
	235	+ this.notEmpty = lock.newCondition();
	236	+ boolean heapify = true; // true if not known to be in heap order
	237	+ boolean screen = true; // true if must screen for nulls
	238	+ if (c instanceof SortedSet<?>) {
	239	+ SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
	240	+ this.comparator = (Comparator<? super E>) ss.comparator();
	241	+ heapify = false;
	242	+ }
	243	+ else if (c instanceof PriorityBlockingQueue<?>) {
	244	+ PriorityBlockingQueue<? extends E> pq =
	245	+ (PriorityBlockingQueue<? extends E>) c;
	246	+ this.comparator = (Comparator<? super E>) pq.comparator();
	247	+ screen = false;
	248	+ if (pq.getClass() == PriorityBlockingQueue.class) // exact match
	249	+ heapify = false;
	250	+ }
	251	+ Object[] a = c.toArray();
	252	+ int n = a.length;
	253	+ // If c.toArray incorrectly doesn't return Object[], copy it.
	254	+ if (a.getClass() != Object[].class)
	255	+ a = Arrays.copyOf(a, n, Object[].class);
	256	+ if (screen && (n == 1 \|\| this.comparator != null)) {
	257	+ for (int i = 0; i < n; ++i)
	258	+ if (a[i] == null)
	259	+ throw new NullPointerException();
	260	+ }
	261	+ this.queue = a;
	262	+ this.size = n;
	263	+ if (heapify)
	264	+ heapify();
	265	+ }
	266	+
	267	+ /**
	268	+ * Tries to grow array to accommodate at least one more element
	269	+ * (but normally expand by about 50%), giving up (allowing retry)
	270	+ * on contention (which we expect to be rare). Call only while
	271	+ * holding lock.
	272	+ *
	273	+ * @param array the heap array
	274	+ * @param oldCap the length of the array
	275	+ */
	276	+ private void tryGrow(Object[] array, int oldCap) {
	277	+ lock.unlock(); // must release and then re-acquire main lock
	278	+ Object[] newArray = null;
	279	+ if (allocationSpinLock == 0 &&
	280	+ UNSAFE.compareAndSwapInt(this, allocationSpinLockOffset,
	281	+ 0, 1)) {
	282	+ try {
	283	+ int newCap = oldCap + ((oldCap < 64) ?
	284	+ (oldCap + 2) : // grow faster if small
	285	+ (oldCap >> 1));
	286	+ if (newCap - MAX_ARRAY_SIZE > 0) { // possible overflow
	287	+ int minCap = oldCap + 1;
	288	+ if (minCap < 0 \|\| minCap > MAX_ARRAY_SIZE)
	289	+ throw new OutOfMemoryError();
	290	+ newCap = MAX_ARRAY_SIZE;
	291	+ }
	292	+ if (newCap > oldCap && queue == array)
	293	+ newArray = new Object[newCap];
	294	+ } finally {
	295	+ allocationSpinLock = 0;
	296	+ }
	297	+ }
	298	+ if (newArray == null) // back off if another thread is allocating
	299	+ Thread.yield();
	300	+ lock.lock();
	301	+ if (newArray != null && queue == array) {
	302	+ queue = newArray;
	303	+ System.arraycopy(array, 0, newArray, 0, oldCap);
	304	+ }
	305	+ }
	306	+
	307	+ /**
	308	+ * Mechanics for poll(). Call only while holding lock.
	309	+ */
	310	+ private E extract() {
	311	+ E result;
	312	+ int n = size - 1;
	313	+ if (n < 0)
	314	+ result = null;
	315	+ else {
	316	+ Object[] array = queue;
	317	+ result = (E) array[0];
	318	+ E x = (E) array[n];
	319	+ array[n] = null;
	320	+ Comparator<? super E> cmp = comparator;
	321	+ if (cmp == null)
	322	+ siftDownComparable(0, x, array, n);
	323	+ else
	324	+ siftDownUsingComparator(0, x, array, n, cmp);
	325	+ size = n;
	326	+ }
	327	+ return result;
	328	+ }
	329	+
	330	+ /**
	331	+ * Inserts item x at position k, maintaining heap invariant by
	332	+ * promoting x up the tree until it is greater than or equal to
	333	+ * its parent, or is the root.
	334	+ *
	335	+ * To simplify and speed up coercions and comparisons. the
	336	+ * Comparable and Comparator versions are separated into different
	337	+ * methods that are otherwise identical. (Similarly for siftDown.)
	338	+ * These methods are static, with heap state as arguments, to
	339	+ * simplify use in light of possible comparator exceptions.
	340	+ *
	341	+ * @param k the position to fill
	342	+ * @param x the item to insert
	343	+ * @param array the heap array
	344	+ * @param n heap size
	345	+ */
	346	+ private static <T> void siftUpComparable(int k, T x, Object[] array) {
	347	+ Comparable<? super T> key = (Comparable<? super T>) x;
	348	+ while (k > 0) {
	349	+ int parent = (k - 1) >>> 1;
	350	+ Object e = array[parent];
	351	+ if (key.compareTo((T) e) >= 0)
	352	+ break;
	353	+ array[k] = e;
	354	+ k = parent;
	355	+ }
	356	+ array[k] = key;
	357	+ }
	358	+
	359	+ private static <T> void siftUpUsingComparator(int k, T x, Object[] array,
	360	+ Comparator<? super T> cmp) {
	361	+ while (k > 0) {
	362	+ int parent = (k - 1) >>> 1;
	363	+ Object e = array[parent];
	364	+ if (cmp.compare(x, (T) e) >= 0)
	365	+ break;
	366	+ array[k] = e;
	367	+ k = parent;
	368	+ }
	369	+ array[k] = x;
	370	+ }
	371	+
	372	+ /**
	373	+ * Inserts item x at position k, maintaining heap invariant by
	374	+ * demoting x down the tree repeatedly until it is less than or
	375	+ * equal to its children or is a leaf.
	376	+ *
	377	+ * @param k the position to fill
	378	+ * @param x the item to insert
	379	+ * @param array the heap array
	380	+ * @param n heap size
	381	+ */
	382	+ private static <T> void siftDownComparable(int k, T x, Object[] array,
	383	+ int n) {
	384	+ Comparable<? super T> key = (Comparable<? super T>)x;
	385	+ int half = n >>> 1; // loop while a non-leaf
	386	+ while (k < half) {
	387	+ int child = (k << 1) + 1; // assume left child is least
	388	+ Object c = array[child];
	389	+ int right = child + 1;
	390	+ if (right < n &&
	391	+ ((Comparable<? super T>) c).compareTo((T) array[right]) > 0)
	392	+ c = array[child = right];
	393	+ if (key.compareTo((T) c) <= 0)
	394	+ break;
	395	+ array[k] = c;
	396	+ k = child;
	397	+ }
	398	+ array[k] = key;
	399	+ }
	400	+
	401	+ private static <T> void siftDownUsingComparator(int k, T x, Object[] array,
	402	+ int n,
	403	+ Comparator<? super T> cmp) {
	404	+ int half = n >>> 1;
	405	+ while (k < half) {
	406	+ int child = (k << 1) + 1;
	407	+ Object c = array[child];
	408	+ int right = child + 1;
	409	+ if (right < n && cmp.compare((T) c, (T) array[right]) > 0)
	410	+ c = array[child = right];
	411	+ if (cmp.compare(x, (T) c) <= 0)
	412	+ break;
	413	+ array[k] = c;
	414	+ k = child;
	415	+ }
	416	+ array[k] = x;
	417	+ }
	418	+
	419	+ /**
	420	+ * Establishes the heap invariant (described above) in the entire tree,
	421	+ * assuming nothing about the order of the elements prior to the call.
	422	+ */
	423	+ private void heapify() {
	424	+ Object[] array = queue;
	425	+ int n = size;
	426	+ int half = (n >>> 1) - 1;
	427	+ Comparator<? super E> cmp = comparator;
	428	+ if (cmp == null) {
	429	+ for (int i = half; i >= 0; i--)
	430	+ siftDownComparable(i, (E) array[i], array, n);
	431	+ }
	432	+ else {
	433	+ for (int i = half; i >= 0; i--)
	434	+ siftDownUsingComparator(i, (E) array[i], array, n, cmp);
	435	+ }
	436	+ }
	437	+
	438	+ /**
	439	+ * Inserts the specified element into this priority queue.
	440	+ *
	441	+ * @param e the element to add
	442	+ * @return {@code true} (as specified by {@link Collection#add})
	443	+ * @throws ClassCastException if the specified element cannot be compared
	444	+ * with elements currently in the priority queue according to the
	445	+ * priority queue's ordering
	446	+ * @throws NullPointerException if the specified element is null
	447	+ */
	448	+ public boolean add(E e) {
	449	+ return offer(e);
	450	+ }
	451	+
	452	+ /**
	453	+ * Inserts the specified element into this priority queue.
	454	+ * As the queue is unbounded, this method will never return {@code false}.
	455	+ *
	456	+ * @param e the element to add
	457	+ * @return {@code true} (as specified by {@link Queue#offer})
	458	+ * @throws ClassCastException if the specified element cannot be compared
	459	+ * with elements currently in the priority queue according to the
	460	+ * priority queue's ordering
	461	+ * @throws NullPointerException if the specified element is null
	462	+ */
	463	+ public boolean offer(E e) {
	464	+ if (e == null)
	465	+ throw new NullPointerException();
	466	+ final ReentrantLock lock = this.lock;
	467	+ lock.lock();
	468	+ int n, cap;
	469	+ Object[] array;
	470	+ while ((n = size) >= (cap = (array = queue).length))
	471	+ tryGrow(array, cap);
	472	+ try {
	473	+ Comparator<? super E> cmp = comparator;
	474	+ if (cmp == null)
	475	+ siftUpComparable(n, e, array);
	476	+ else
	477	+ siftUpUsingComparator(n, e, array, cmp);
	478	+ size = n + 1;
	479	+ notEmpty.signal();
	480	+ } finally {
	481	+ lock.unlock();
	482	+ }
	483	+ return true;
	484	+ }
	485	+
	486	+ /**
	487	+ * Inserts the specified element into this priority queue.
	488	+ * As the queue is unbounded, this method will never block.
	489	+ *
	490	+ * @param e the element to add
	491	+ * @throws ClassCastException if the specified element cannot be compared
	492	+ * with elements currently in the priority queue according to the
	493	+ * priority queue's ordering
	494	+ * @throws NullPointerException if the specified element is null
	495	+ */
	496	+ public void put(E e) {
	497	+ offer(e); // never need to block
	498	+ }
	499	+
	500	+ /**
	501	+ * Inserts the specified element into this priority queue.
	502	+ * As the queue is unbounded, this method will never block or
	503	+ * return {@code false}.
	504	+ *
	505	+ * @param e the element to add
	506	+ * @param timeout This parameter is ignored as the method never blocks
	507	+ * @param unit This parameter is ignored as the method never blocks
	508	+ * @return {@code true} (as specified by
	509	+ * {@link BlockingQueue#offer(Object,long,TimeUnit) BlockingQueue.offer})
	510	+ * @throws ClassCastException if the specified element cannot be compared
	511	+ * with elements currently in the priority queue according to the
	512	+ * priority queue's ordering
	513	+ * @throws NullPointerException if the specified element is null
	514	+ */
	515	+ public boolean offer(E e, long timeout, TimeUnit unit) {
	516	+ return offer(e); // never need to block
	517	+ }
	518	+
	519	+ public E poll() {
	520	+ final ReentrantLock lock = this.lock;
	521	+ lock.lock();
	522	+ E result;
	523	+ try {
	524	+ result = extract();
	525	+ } finally {
	526	+ lock.unlock();
	527	+ }
	528	+ return result;
	529	+ }
	530	+
	531	+ public E take() throws InterruptedException {
	532	+ final ReentrantLock lock = this.lock;
	533	+ lock.lockInterruptibly();
	534	+ E result;
	535	+ try {
	536	+ while ( (result = extract()) == null)
	537	+ notEmpty.await();
	538	+ } finally {
	539	+ lock.unlock();
	540	+ }
	541	+ return result;
	542	+ }
	543	+
	544	+ public E poll(long timeout, TimeUnit unit) throws InterruptedException {
	545	+ long nanos = unit.toNanos(timeout);
	546	+ final ReentrantLock lock = this.lock;
	547	+ lock.lockInterruptibly();
	548	+ E result;
	549	+ try {
	550	+ while ( (result = extract()) == null && nanos > 0)
	551	+ nanos = notEmpty.awaitNanos(nanos);
	552	+ } finally {
	553	+ lock.unlock();
	554	+ }
	555	+ return result;
	556	+ }
	557	+
	558	+ public E peek() {
	559	+ final ReentrantLock lock = this.lock;
	560	+ lock.lock();
	561	+ E result;
	562	+ try {
	563	+ result = size > 0 ? (E) queue[0] : null;
	564	+ } finally {
	565	+ lock.unlock();
	566	+ }
	567	+ return result;
	568	+ }
	569	+
	570	+ /**
	571	+ * Returns the comparator used to order the elements in this queue,
	572	+ * or {@code null} if this queue uses the {@linkplain Comparable
	573	+ * natural ordering} of its elements.
	574	+ *
	575	+ * @return the comparator used to order the elements in this queue,
	576	+ * or {@code null} if this queue uses the natural
	577	+ * ordering of its elements
	578	+ */
	579	+ public Comparator<? super E> comparator() {
	580	+ return comparator;
	581	+ }
	582	+
	583	+ public int size() {
	584	+ final ReentrantLock lock = this.lock;
	585	+ lock.lock();
	586	+ try {
	587	+ return size;
	588	+ } finally {
	589	+ lock.unlock();
	590	+ }
	591	+ }
	592	+
	593	+ /**
	594	+ * Always returns {@code Integer.MAX_VALUE} because
	595	+ * a {@code PriorityBlockingQueue} is not capacity constrained.
	596	+ * @return {@code Integer.MAX_VALUE} always
	597	+ */
	598	+ public int remainingCapacity() {
	599	+ return Integer.MAX_VALUE;
	600	+ }
	601	+
	602	+ private int indexOf(Object o) {
	603	+ if (o != null) {
	604	+ Object[] array = queue;
	605	+ int n = size;
	606	+ for (int i = 0; i < n; i++)
	607	+ if (o.equals(array[i]))
	608	+ return i;
	609	+ }
	610	+ return -1;
	611	+ }
	612	+
	613	+ /**
	614	+ * Removes the ith element from queue.
	615	+ */
	616	+ private void removeAt(int i) {
	617	+ Object[] array = queue;
	618	+ int n = size - 1;
	619	+ if (n == i) // removed last element
	620	+ array[i] = null;
	621	+ else {
	622	+ E moved = (E) array[n];
	623	+ array[n] = null;
	624	+ Comparator<? super E> cmp = comparator;
	625	+ if (cmp == null)
	626	+ siftDownComparable(i, moved, array, n);
	627	+ else
	628	+ siftDownUsingComparator(i, moved, array, n, cmp);
	629	+ if (array[i] == moved) {
	630	+ if (cmp == null)
	631	+ siftUpComparable(i, moved, array);
	632	+ else
	633	+ siftUpUsingComparator(i, moved, array, cmp);
	634	+ }
	635	+ }
	636	+ size = n;
	637	+ }
	638	+
	639	+ /**
	640	+ * Removes a single instance of the specified element from this queue,
	641	+ * if it is present. More formally, removes an element {@code e} such
	642	+ * that {@code o.equals(e)}, if this queue contains one or more such
	643	+ * elements. Returns {@code true} if and only if this queue contained
	644	+ * the specified element (or equivalently, if this queue changed as a
	645	+ * result of the call).
	646	+ *
	647	+ * @param o element to be removed from this queue, if present
	648	+ * @return {@code true} if this queue changed as a result of the call
	649	+ */
	650	+ public boolean remove(Object o) {
	651	+ boolean removed = false;
	652	+ final ReentrantLock lock = this.lock;
	653	+ lock.lock();
	654	+ try {
	655	+ int i = indexOf(o);
	656	+ if (i != -1) {
	657	+ removeAt(i);
	658	+ removed = true;
	659	+ }
	660	+ } finally {
	661	+ lock.unlock();
	662	+ }
	663	+ return removed;
	664	+ }
	665	+
	666	+
	667	+ /**
	668	+ * Identity-based version for use in Itr.remove
	669	+ */
	670	+ private void removeEQ(Object o) {
	671	+ final ReentrantLock lock = this.lock;
	672	+ lock.lock();
	673	+ try {
	674	+ Object[] array = queue;
	675	+ int n = size;
	676	+ for (int i = 0; i < n; i++) {
	677	+ if (o == array[i]) {
	678	+ removeAt(i);
	679	+ break;
	680	+ }
	681	+ }
	682	+ } finally {
	683	+ lock.unlock();
	684	+ }
	685	+ }
	686	+
	687	+ /**
	688	+ * Returns {@code true} if this queue contains the specified element.
	689	+ * More formally, returns {@code true} if and only if this queue contains
	690	+ * at least one element {@code e} such that {@code o.equals(e)}.
	691	+ *
	692	+ * @param o object to be checked for containment in this queue
	693	+ * @return {@code true} if this queue contains the specified element
	694	+ */
	695	+ public boolean contains(Object o) {
	696	+ int index;
	697	+ final ReentrantLock lock = this.lock;
	698	+ lock.lock();
	699	+ try {
	700	+ index = indexOf(o);
	701	+ } finally {
	702	+ lock.unlock();
	703	+ }
	704	+ return index != -1;
	705	+ }
	706	+
	707	+ /**
	708	+ * Returns an array containing all of the elements in this queue.
	709	+ * The returned array elements are in no particular order.
	710	+ *
	711	+ * <p>The returned array will be "safe" in that no references to it are
	712	+ * maintained by this queue. (In other words, this method must allocate
	713	+ * a new array). The caller is thus free to modify the returned array.
	714	+ *
	715	+ * <p>This method acts as bridge between array-based and collection-based
	716	+ * APIs.
	717	+ *
	718	+ * @return an array containing all of the elements in this queue
	719	+ */
	720	+ public Object[] toArray() {
	721	+ final ReentrantLock lock = this.lock;
	722	+ lock.lock();
	723	+ try {
	724	+ return Arrays.copyOf(queue, size);
	725	+ } finally {
	726	+ lock.unlock();
	727	+ }
	728	+ }
	729	+
	730	+
	731	+ public String toString() {
	732	+ final ReentrantLock lock = this.lock;
	733	+ lock.lock();
	734	+ try {
	735	+ int n = size;
	736	+ if (n == 0)
	737	+ return "[]";
	738	+ StringBuilder sb = new StringBuilder();
	739	+ sb.append('[');
	740	+ for (int i = 0; i < n; ++i) {
	741	+ E e = (E)queue[i];
	742	+ sb.append(e == this ? "(this Collection)" : e);
	743	+ if (i != n - 1)
	744	+ sb.append(',').append(' ');
	745	+ }
	746	+ return sb.append(']').toString();
	747	+ } finally {
	748	+ lock.unlock();
	749	+ }
	750	+ }
	751	+
	752	+ /**
	753	+ * @throws UnsupportedOperationException {@inheritDoc}
	754	+ * @throws ClassCastException {@inheritDoc}
	755	+ * @throws NullPointerException {@inheritDoc}
	756	+ * @throws IllegalArgumentException {@inheritDoc}
	757	+ */
	758	+ public int drainTo(Collection<? super E> c) {
	759	+ if (c == null)
	760	+ throw new NullPointerException();
	761	+ if (c == this)
	762	+ throw new IllegalArgumentException();
	763	+ final ReentrantLock lock = this.lock;
	764	+ lock.lock();
	765	+ try {
	766	+ int n = 0;
	767	+ E e;
	768	+ while ( (e = extract()) != null) {
	769	+ c.add(e);
	770	+ ++n;
	771	+ }
	772	+ return n;
	773	+ } finally {
	774	+ lock.unlock();
	775	+ }
	776	+ }
	777	+
	778	+ /**
	779	+ * @throws UnsupportedOperationException {@inheritDoc}
	780	+ * @throws ClassCastException {@inheritDoc}
	781	+ * @throws NullPointerException {@inheritDoc}
	782	+ * @throws IllegalArgumentException {@inheritDoc}
	783	+ */
	784	+ public int drainTo(Collection<? super E> c, int maxElements) {
	785	+ if (c == null)
	786	+ throw new NullPointerException();
	787	+ if (c == this)
	788	+ throw new IllegalArgumentException();
	789	+ if (maxElements <= 0)
	790	+ return 0;
	791	+ final ReentrantLock lock = this.lock;
	792	+ lock.lock();
	793	+ try {
	794	+ int n = 0;
	795	+ E e;
	796	+ while (n < maxElements && (e = extract()) != null) {
	797	+ c.add(e);
	798	+ ++n;
	799	+ }
	800	+ return n;
	801	+ } finally {
	802	+ lock.unlock();
	803	+ }
	804	+ }
	805	+
	806	+ /**
	807	+ * Atomically removes all of the elements from this queue.
	808	+ * The queue will be empty after this call returns.
	809	+ */
	810	+ public void clear() {
	811	+ final ReentrantLock lock = this.lock;
	812	+ lock.lock();
	813	+ try {
	814	+ Object[] array = queue;
	815	+ int n = size;
	816	+ size = 0;
	817	+ for (int i = 0; i < n; i++)
	818	+ array[i] = null;
	819	+ } finally {
	820	+ lock.unlock();
	821	+ }
	822	+ }
	823	+
	824	+ /**
	825	+ * Returns an array containing all of the elements in this queue; the
	826	+ * runtime type of the returned array is that of the specified array.
	827	+ * The returned array elements are in no particular order.
	828	+ * If the queue fits in the specified array, it is returned therein.
	829	+ * Otherwise, a new array is allocated with the runtime type of the
	830	+ * specified array and the size of this queue.
	831	+ *
	832	+ * <p>If this queue fits in the specified array with room to spare
	833	+ * (i.e., the array has more elements than this queue), the element in
	834	+ * the array immediately following the end of the queue is set to
	835	+ * {@code null}.
	836	+ *
	837	+ * <p>Like the {@link #toArray()} method, this method acts as bridge between
	838	+ * array-based and collection-based APIs. Further, this method allows
	839	+ * precise control over the runtime type of the output array, and may,
	840	+ * under certain circumstances, be used to save allocation costs.
	841	+ *
	842	+ * <p>Suppose {@code x} is a queue known to contain only strings.
	843	+ * The following code can be used to dump the queue into a newly
	844	+ * allocated array of {@code String}:
	845	+ *
	846	+ * <pre>
	847	+ * String[] y = x.toArray(new String[0]);</pre>
	848	+ *
	849	+ * Note that {@code toArray(new Object[0])} is identical in function to
	850	+ * {@code toArray()}.
	851	+ *
	852	+ * @param a the array into which the elements of the queue are to
	853	+ * be stored, if it is big enough; otherwise, a new array of the
	854	+ * same runtime type is allocated for this purpose
	855	+ * @return an array containing all of the elements in this queue
	856	+ * @throws ArrayStoreException if the runtime type of the specified array
	857	+ * is not a supertype of the runtime type of every element in
	858	+ * this queue
	859	+ * @throws NullPointerException if the specified array is null
	860	+ */
	861	+ public <T> T[] toArray(T[] a) {
	862	+ final ReentrantLock lock = this.lock;
	863	+ lock.lock();
	864	+ try {
	865	+ int n = size;
	866	+ if (a.length < n)
	867	+ // Make a new array of a's runtime type, but my contents:
	868	+ return (T[]) Arrays.copyOf(queue, size, a.getClass());
	869	+ System.arraycopy(queue, 0, a, 0, n);
	870	+ if (a.length > n)
	871	+ a[n] = null;
	872	+ return a;
	873	+ } finally {
	874	+ lock.unlock();
	875	+ }
	876	+ }
	877	+
	878	+ /**
	879	+ * Returns an iterator over the elements in this queue. The
	880	+ * iterator does not return the elements in any particular order.
	881	+ *
	882	+ * <p>The returned iterator is a "weakly consistent" iterator that
	883	+ * will never throw {@link java.util.ConcurrentModificationException
	884	+ * ConcurrentModificationException}, and guarantees to traverse
	885	+ * elements as they existed upon construction of the iterator, and
	886	+ * may (but is not guaranteed to) reflect any modifications
	887	+ * subsequent to construction.
	888	+ *
	889	+ * @return an iterator over the elements in this queue
	890	+ */
	891	+ public Iterator<E> iterator() {
	892	+ return new Itr(toArray());
	893	+ }
	894	+
	895	+ /**
	896	+ * Snapshot iterator that works off copy of underlying q array.
	897	+ */
	898	+ final class Itr implements Iterator<E> {
	899	+ final Object[] array; // Array of all elements
	900	+ int cursor; // index of next element to return;
	901	+ int lastRet; // index of last element, or -1 if no such
	902	+
	903	+ Itr(Object[] array) {
	904	+ lastRet = -1;
	905	+ this.array = array;
	906	+ }
	907	+
	908	+ public boolean hasNext() {
	909	+ return cursor < array.length;
	910	+ }
	911	+
	912	+ public E next() {
	913	+ if (cursor >= array.length)
	914	+ throw new NoSuchElementException();
	915	+ lastRet = cursor;
	916	+ return (E)array[cursor++];
	917	+ }
	918	+
	919	+ public void remove() {
	920	+ if (lastRet < 0)
	921	+ throw new IllegalStateException();
	922	+ removeEQ(array[lastRet]);
	923	+ lastRet = -1;
	924	+ }
	925	+ }
	926	+
	927	+ /**
	928	+ * Saves the state to a stream (that is, serializes it). For
	929	+ * compatibility with previous version of this class,
	930	+ * elements are first copied to a java.util.PriorityQueue,
	931	+ * which is then serialized.
	932	+ */
	933	+ private void writeObject(java.io.ObjectOutputStream s)
	934	+ throws java.io.IOException {
	935	+ lock.lock();
	936	+ try {
	937	+ int n = size; // avoid zero capacity argument
	938	+ q = new PriorityQueue<E>(n == 0 ? 1 : n, comparator);
	939	+ q.addAll(this);
	940	+ s.defaultWriteObject();
	941	+ } finally {
	942	+ q = null;
	943	+ lock.unlock();
	944	+ }
	945	+ }
	946	+
	947	+ /**
	948	+ * Reconstitutes the {@code PriorityBlockingQueue} instance from a stream
	949	+ * (that is, deserializes it).
	950	+ *
	951	+ * @param s the stream
	952	+ */
	953	+ private void readObject(java.io.ObjectInputStream s)
	954	+ throws java.io.IOException, ClassNotFoundException {
	955	+ try {
	956	+ s.defaultReadObject();
	957	+ this.queue = new Object[q.size()];
	958	+ comparator = q.comparator();
	959	+ addAll(q);
	960	+ } finally {
	961	+ q = null;
	962	+ }
	963	+ }
	964	+
	965	+ // Unsafe mechanics
	966	+ private static final sun.misc.Unsafe UNSAFE;
	967	+ private static final long allocationSpinLockOffset;
	968	+ static {
	969	+ try {
	970	+ UNSAFE = sun.misc.Unsafe.getUnsafe();
	971	+ Class k = PriorityBlockingQueue.class;
	972	+ allocationSpinLockOffset = UNSAFE.objectFieldOffset
	973	+ (k.getDeclaredField("allocationSpinLock"));
	974	+ } catch (Exception e) {
	975	+ throw new Error(e);
	976	+ }
	977	+ }
	978	+}