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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.36 by dl, Sat Aug 30 11:40:04 2003 UTC vs.
Revision 1.112 by jsr166, Tue Nov 29 18:11:28 2016 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
3	>	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4	>	*
5	>	* This code is free software; you can redistribute it and/or modify it
6	>	* under the terms of the GNU General Public License version 2 only, as
7	>	* published by the Free Software Foundation.  Oracle designates this
8	>	* particular file as subject to the "Classpath" exception as provided
9	>	* by Oracle in the LICENSE file that accompanied this code.
10	>	*
11	>	* This code is distributed in the hope that it will be useful, but WITHOUT
12	>	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13	>	* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14	>	* version 2 for more details (a copy is included in the LICENSE file that
15	>	* accompanied this code).
16	>	*
17	>	* You should have received a copy of the GNU General Public License version
18	>	* 2 along with this work; if not, write to the Free Software Foundation,
19	>	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20	>	*
21	>	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22	>	* or visit www.oracle.com if you need additional information or have any
23	>	* questions.
24	>	*/
25	>
26	>	package java.util;
27	>
28	>	import java.util.function.Consumer;
29
30		/**
31		* An unbounded priority {@linkplain Queue queue} based on a priority heap.
32	<	* This queue orders elements according to an order specified at construction
33	<	* time, which is specified in the same manner as {@link java.util.TreeSet}
34	<	* and {@link java.util.TreeMap}: elements are ordered either according to
35	<	* their <i>natural order</i> (see {@link Comparable}), or according to a
36	<	* {@link java.util.Comparator}, depending on which constructor is used.
37	<	* <p>The <em>head</em> of this queue is the <em>least</em> element with
38	<	* respect to the specified ordering.  If multiple elements are tied for least
39	<	* value, the head is one of those elements. A priority queue does not permit
40	<	* <tt>null</tt> elements.
41	<	*
42	<	* <p>The {@link #remove()} and {@link #poll()} methods remove and
43	<	* return the head of the queue.
44	<	*
45	<	* <p>The {@link #element()} and {@link #peek()} methods return, but do
46	<	* not delete, the head of the queue.
47	<	*
48	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
49	<	* size of the array used internally to store the elements on the
50	<	* queue.
51	<	* It is always at least as large as the queue size.  As
52	<	* elements are added to a priority queue, its capacity grows
53	<	* automatically.  The details of the growth policy are not specified.
54	<	*
55	<	* <p>The Iterator provided in method {@link #iterator()} is <em>not</em>
56	<	* guaranteed to traverse the elements of the PriorityQueue in any
57	<	* particular order. If you need ordered traversal, consider using
58	<	* <tt>Arrays.sort(pq.toArray())</tt>.
59	<	*
60	<	* <p> <strong>Note that this implementation is not synchronized.</strong>
61	<	* Multiple threads should not access a <tt>PriorityQueue</tt>
62	<	* instance concurrently if any of the threads modifies the list
63	<	* structurally. Instead, use the thread-safe {@link
32	>	* The elements of the priority queue are ordered according to their
33	>	* {@linkplain Comparable natural ordering}, or by a {@link Comparator}
34	>	* provided at queue construction time, depending on which constructor is
35	>	* used.  A priority queue does not permit {@code null} elements.
36	>	* A priority queue relying on natural ordering also does not permit
37	>	* insertion of non-comparable objects (doing so may result in
38	>	* {@code ClassCastException}).
39	>	*
40	>	* <p>The <em>head</em> of this queue is the <em>least</em> element
41	>	* with respect to the specified ordering.  If multiple elements are
42	>	* tied for least value, the head is one of those elements -- ties are
43	>	* broken arbitrarily.  The queue retrieval operations {@code poll},
44	>	* {@code remove}, {@code peek}, and {@code element} access the
45	>	* element at the head of the queue.
46	>	*
47	>	* <p>A priority queue is unbounded, but has an internal
48	>	* <i>capacity</i> governing the size of an array used to store the
49	>	* elements on the queue.  It is always at least as large as the queue
50	>	* size.  As elements are added to a priority queue, its capacity
51	>	* grows automatically.  The details of the growth policy are not
52	>	* specified.
53	>	*
54	>	* <p>This class and its iterator implement all of the
55	>	* <em>optional</em> methods of the {@link Collection} and {@link
56	>	* Iterator} interfaces.  The Iterator provided in method {@link
57	>	* #iterator()} and the Spliterator provided in method {@link #spliterator()}
58	>	* are <em>not</em> guaranteed to traverse the elements of
59	>	* the priority queue in any particular order. If you need ordered
60	>	* traversal, consider using {@code Arrays.sort(pq.toArray())}.
61	>	*
62	>	* <p><strong>Note that this implementation is not synchronized.</strong>
63	>	* Multiple threads should not access a {@code PriorityQueue}
64	>	* instance concurrently if any of the threads modifies the queue.
65	>	* Instead, use the thread-safe {@link
66		* java.util.concurrent.PriorityBlockingQueue} class.
67		*
68	<	*
69	<	* <p>Implementation note: this implementation provides O(log(n)) time
70	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
71	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
72	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
73	<	* constant time for the retrieval methods (<tt>peek</tt>,
45	<	* <tt>element</tt>, and <tt>size</tt>).
68	>	* <p>Implementation note: this implementation provides
69	>	* O(log(n)) time for the enqueuing and dequeuing methods
70	>	* ({@code offer}, {@code poll}, {@code remove()} and {@code add});
71	>	* linear time for the {@code remove(Object)} and {@code contains(Object)}
72	>	* methods; and constant time for the retrieval methods
73	>	* ({@code peek}, {@code element}, and {@code size}).
74		*
75		* <p>This class is a member of the
76	<	* <a href="{@docRoot}/../guide/collections/index.html">
76	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
77		* Java Collections Framework</a>.
78	+	*
79		* @since 1.5
80	<	* @author Josh Bloch
80	>	* @author Josh Bloch, Doug Lea
81	>	* @param <E> the type of elements held in this queue
82		*/
83		public class PriorityQueue<E> extends AbstractQueue<E>
84	<	implements Queue<E>, java.io.Serializable {
84	>	implements java.io.Serializable {
85
86		private static final long serialVersionUID = -7720805057305804111L;
87
88		private static final int DEFAULT_INITIAL_CAPACITY = 11;
89
90		/**
91	<	* Priority queue represented as a balanced binary heap: the two children
92	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
93	<	* ordered by comparator, or by the elements' natural ordering, if
94	<	* comparator is null:  For each node n in the heap and each descendant d
95	<	* of n, n <= d.
96	<	*
67	<	* The element with the lowest value is in queue[1], assuming the queue is
68	<	* nonempty.  (A one-based array is used in preference to the traditional
69	<	* zero-based array to simplify parent and child calculations.)
70	<	*
71	<	* queue.length must be >= 2, even if size == 0.
91	>	* Priority queue represented as a balanced binary heap: the two
92	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
93	>	* priority queue is ordered by comparator, or by the elements'
94	>	* natural ordering, if comparator is null: For each node n in the
95	>	* heap and each descendant d of n, n <= d.  The element with the
96	>	* lowest value is in queue[0], assuming the queue is nonempty.
97		*/
98	<	private transient Object[] queue;
98	>	transient Object[] queue; // non-private to simplify nested class access
99
100		/**
101		* The number of elements in the priority queue.
102		*/
103	<	private int size = 0;
103	>	int size;
104
105		/**
106		* The comparator, or null if priority queue uses elements'
#	Line 87 | Line 112 | public class PriorityQueue<E> extends Ab
112		* The number of times this priority queue has been
113		* <i>structurally modified</i>.  See AbstractList for gory details.
114		*/
115	<	private transient int modCount = 0;
115	>	transient int modCount;     // non-private to simplify nested class access
116
117		/**
118	<	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
119	<	* (11) that orders its elements according to their natural
120	<	* ordering (using <tt>Comparable</tt>).
118	>	* Creates a {@code PriorityQueue} with the default initial
119	>	* capacity (11) that orders its elements according to their
120	>	* {@linkplain Comparable natural ordering}.
121		*/
122		public PriorityQueue() {
123		this(DEFAULT_INITIAL_CAPACITY, null);
124		}
125
126		/**
127	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
128	<	* that orders its elements according to their natural ordering
129	<	* (using <tt>Comparable</tt>).
130	<	*
131	<	* @param initialCapacity the initial capacity for this priority queue.
132	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
133	<	* than 1
127	>	* Creates a {@code PriorityQueue} with the specified initial
128	>	* capacity that orders its elements according to their
129	>	* {@linkplain Comparable natural ordering}.
130	>	*
131	>	* @param initialCapacity the initial capacity for this priority queue
132	>	* @throws IllegalArgumentException if {@code initialCapacity} is less
133	>	*         than 1
134		*/
135		public PriorityQueue(int initialCapacity) {
136		this(initialCapacity, null);
137		}
138
139		/**
140	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
140	>	* Creates a {@code PriorityQueue} with the default initial capacity and
141	>	* whose elements are ordered according to the specified comparator.
142	>	*
143	>	* @param  comparator the comparator that will be used to order this
144	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
145	>	*         natural ordering} of the elements will be used.
146	>	* @since 1.8
147	>	*/
148	>	public PriorityQueue(Comparator<? super E> comparator) {
149	>	this(DEFAULT_INITIAL_CAPACITY, comparator);
150	>	}
151	>
152	>	/**
153	>	* Creates a {@code PriorityQueue} with the specified initial capacity
154		* that orders its elements according to the specified comparator.
155		*
156	<	* @param initialCapacity the initial capacity for this priority queue.
157	<	* @param comparator the comparator used to order this priority queue.
158	<	* If <tt>null</tt> then the order depends on the elements' natural
159	<	* ordering.
160	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
161	<	* than 1
156	>	* @param  initialCapacity the initial capacity for this priority queue
157	>	* @param  comparator the comparator that will be used to order this
158	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
159	>	*         natural ordering} of the elements will be used.
160	>	* @throws IllegalArgumentException if {@code initialCapacity} is
161	>	*         less than 1
162		*/
163	<	public PriorityQueue(int initialCapacity,
163	>	public PriorityQueue(int initialCapacity,
164		Comparator<? super E> comparator) {
165	+	// Note: This restriction of at least one is not actually needed,
166	+	// but continues for 1.5 compatibility
167		if (initialCapacity < 1)
168		throw new IllegalArgumentException();
169	<	this.queue = new Object[initialCapacity + 1];
169	>	this.queue = new Object[initialCapacity];
170		this.comparator = comparator;
171		}
172
173		/**
174	<	* Common code to initialize underlying queue array across
175	<	* constructors below.
174	>	* Creates a {@code PriorityQueue} containing the elements in the
175	>	* specified collection.  If the specified collection is an instance of
176	>	* a {@link SortedSet} or is another {@code PriorityQueue}, this
177	>	* priority queue will be ordered according to the same ordering.
178	>	* Otherwise, this priority queue will be ordered according to the
179	>	* {@linkplain Comparable natural ordering} of its elements.
180	>	*
181	>	* @param  c the collection whose elements are to be placed
182	>	*         into this priority queue
183	>	* @throws ClassCastException if elements of the specified collection
184	>	*         cannot be compared to one another according to the priority
185	>	*         queue's ordering
186	>	* @throws NullPointerException if the specified collection or any
187	>	*         of its elements are null
188		*/
189	<	private void initializeArray(Collection<? extends E> c) {
190	<	int sz = c.size();
191	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
192	<	Integer.MAX_VALUE - 1);
193	<	if (initialCapacity < 1)
194	<	initialCapacity = 1;
195	<
196	<	this.queue = new Object[initialCapacity + 1];
189	>	@SuppressWarnings("unchecked")
190	>	public PriorityQueue(Collection<? extends E> c) {
191	>	if (c instanceof SortedSet<?>) {
192	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
193	>	this.comparator = (Comparator<? super E>) ss.comparator();
194	>	initElementsFromCollection(ss);
195	>	}
196	>	else if (c instanceof PriorityQueue<?>) {
197	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
198	>	this.comparator = (Comparator<? super E>) pq.comparator();
199	>	initFromPriorityQueue(pq);
200	>	}
201	>	else {
202	>	this.comparator = null;
203	>	initFromCollection(c);
204	>	}
205		}
206
207		/**
208	<	* Initially fill elements of the queue array under the
209	<	* knowledge that it is sorted or is another PQ, in which
210	<	* case we can just place the elements in the order presented.
208	>	* Creates a {@code PriorityQueue} containing the elements in the
209	>	* specified priority queue.  This priority queue will be
210	>	* ordered according to the same ordering as the given priority
211	>	* queue.
212	>	*
213	>	* @param  c the priority queue whose elements are to be placed
214	>	*         into this priority queue
215	>	* @throws ClassCastException if elements of {@code c} cannot be
216	>	*         compared to one another according to {@code c}'s
217	>	*         ordering
218	>	* @throws NullPointerException if the specified priority queue or any
219	>	*         of its elements are null
220		*/
221	<	private void fillFromSorted(Collection<? extends E> c) {
222	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
223	<	queue[++size] = i.next();
221	>	@SuppressWarnings("unchecked")
222	>	public PriorityQueue(PriorityQueue<? extends E> c) {
223	>	this.comparator = (Comparator<? super E>) c.comparator();
224	>	initFromPriorityQueue(c);
225		}
226
227		/**
228	<	* Initially fill elements of the queue array that is not to our knowledge
229	<	* sorted, so we must rearrange the elements to guarantee the heap
230	<	* invariant.
228	>	* Creates a {@code PriorityQueue} containing the elements in the
229	>	* specified sorted set.   This priority queue will be ordered
230	>	* according to the same ordering as the given sorted set.
231	>	*
232	>	* @param  c the sorted set whose elements are to be placed
233	>	*         into this priority queue
234	>	* @throws ClassCastException if elements of the specified sorted
235	>	*         set cannot be compared to one another according to the
236	>	*         sorted set's ordering
237	>	* @throws NullPointerException if the specified sorted set or any
238	>	*         of its elements are null
239		*/
240	<	private void fillFromUnsorted(Collection<? extends E> c) {
241	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
242	<	queue[++size] = i.next();
243	<	heapify();
240	>	@SuppressWarnings("unchecked")
241	>	public PriorityQueue(SortedSet<? extends E> c) {
242	>	this.comparator = (Comparator<? super E>) c.comparator();
243	>	initElementsFromCollection(c);
244		}
245
246	<	/**
247	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
248	<	* specified collection.  The priority queue has an initial
249	<	* capacity of 110% of the size of the specified collection or 1
172	<	* if the collection is empty.  If the specified collection is an
173	<	* instance of a {@link java.util.SortedSet} or is another
174	<	* <tt>PriorityQueue</tt>, the priority queue will be sorted
175	<	* according to the same comparator, or according to its elements'
176	<	* natural order if the collection is sorted according to its
177	<	* elements' natural order.  Otherwise, the priority queue is
178	<	* ordered according to its elements' natural order.
179	<	*
180	<	* @param c the collection whose elements are to be placed
181	<	*        into this priority queue.
182	<	* @throws ClassCastException if elements of the specified collection
183	<	*         cannot be compared to one another according to the priority
184	<	*         queue's ordering.
185	<	* @throws NullPointerException if <tt>c</tt> or any element within it
186	<	* is <tt>null</tt>
187	<	*/
188	<	public PriorityQueue(Collection<? extends E> c) {
189	<	initializeArray(c);
190	<	if (c instanceof SortedSet) {
191	<	// @fixme double-cast workaround for compiler
192	<	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
193	<	comparator = (Comparator<? super E>)s.comparator();
194	<	fillFromSorted(s);
195	<	} else if (c instanceof PriorityQueue) {
196	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
197	<	comparator = (Comparator<? super E>)s.comparator();
198	<	fillFromSorted(s);
246	>	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
247	>	if (c.getClass() == PriorityQueue.class) {
248	>	this.queue = c.toArray();
249	>	this.size = c.size();
250		} else {
251	<	comparator = null;
201	<	fillFromUnsorted(c);
251	>	initFromCollection(c);
252		}
253		}
254
255	+	private void initElementsFromCollection(Collection<? extends E> c) {
256	+	Object[] a = c.toArray();
257	+	// If c.toArray incorrectly doesn't return Object[], copy it.
258	+	if (a.getClass() != Object[].class)
259	+	a = Arrays.copyOf(a, a.length, Object[].class);
260	+	int len = a.length;
261	+	if (len == 1 || this.comparator != null)
262	+	for (Object e : a)
263	+	if (e == null)
264	+	throw new NullPointerException();
265	+	this.queue = a;
266	+	this.size = a.length;
267	+	}
268	+
269		/**
270	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
207	<	* specified collection.  The priority queue has an initial
208	<	* capacity of 110% of the size of the specified collection or 1
209	<	* if the collection is empty.  This priority queue will be sorted
210	<	* according to the same comparator as the given collection, or
211	<	* according to its elements' natural order if the collection is
212	<	* sorted according to its elements' natural order.
270	>	* Initializes queue array with elements from the given Collection.
271		*
272	<	* @param c the collection whose elements are to be placed
215	<	*        into this priority queue.
216	<	* @throws ClassCastException if elements of the specified collection
217	<	*         cannot be compared to one another according to the priority
218	<	*         queue's ordering.
219	<	* @throws NullPointerException if <tt>c</tt> or any element within it
220	<	* is <tt>null</tt>
272	>	* @param c the collection
273		*/
274	<	public PriorityQueue(PriorityQueue<? extends E> c) {
275	<	initializeArray(c);
276	<	comparator = (Comparator<? super E>)c.comparator();
225	<	fillFromSorted(c);
274	>	private void initFromCollection(Collection<? extends E> c) {
275	>	initElementsFromCollection(c);
276	>	heapify();
277		}
278
279		/**
280	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
281	<	* specified collection.  The priority queue has an initial
282	<	* capacity of 110% of the size of the specified collection or 1
283	<	* if the collection is empty.  This priority queue will be sorted
233	<	* according to the same comparator as the given collection, or
234	<	* according to its elements' natural order if the collection is
235	<	* sorted according to its elements' natural order.
236	<	*
237	<	* @param c the collection whose elements are to be placed
238	<	*        into this priority queue.
239	<	* @throws ClassCastException if elements of the specified collection
240	<	*         cannot be compared to one another according to the priority
241	<	*         queue's ordering.
242	<	* @throws NullPointerException if <tt>c</tt> or any element within it
243	<	* is <tt>null</tt>
280	>	* The maximum size of array to allocate.
281	>	* Some VMs reserve some header words in an array.
282	>	* Attempts to allocate larger arrays may result in
283	>	* OutOfMemoryError: Requested array size exceeds VM limit
284		*/
285	<	public PriorityQueue(SortedSet<? extends E> c) {
246	<	initializeArray(c);
247	<	comparator = (Comparator<? super E>)c.comparator();
248	<	fillFromSorted(c);
249	<	}
285	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
286
287		/**
288	<	* Resize array, if necessary, to be able to hold given index
288	>	* Increases the capacity of the array.
289	>	*
290	>	* @param minCapacity the desired minimum capacity
291		*/
292	<	private void grow(int index) {
293	<	int newlen = queue.length;
294	<	if (index < newlen) // don't need to grow
295	<	return;
296	<	if (index == Integer.MAX_VALUE)
292	>	private void grow(int minCapacity) {
293	>	int oldCapacity = queue.length;
294	>	// Double size if small; else grow by 50%
295	>	int newCapacity = oldCapacity + ((oldCapacity < 64) ?
296	>	(oldCapacity + 2) :
297	>	(oldCapacity >> 1));
298	>	// overflow-conscious code
299	>	if (newCapacity - MAX_ARRAY_SIZE > 0)
300	>	newCapacity = hugeCapacity(minCapacity);
301	>	queue = Arrays.copyOf(queue, newCapacity);
302	>	}
303	>
304	>	private static int hugeCapacity(int minCapacity) {
305	>	if (minCapacity < 0) // overflow
306		throw new OutOfMemoryError();
307	<	while (newlen <= index) {
308	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
309	<	newlen = Integer.MAX_VALUE;
263	<	else
264	<	newlen <<= 2;
265	<	}
266	<	Object[] newQueue = new Object[newlen];
267	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
268	<	queue = newQueue;
307	>	return (minCapacity > MAX_ARRAY_SIZE) ?
308	>	Integer.MAX_VALUE :
309	>	MAX_ARRAY_SIZE;
310		}
270	–
311
312	<	// Queue Methods
312	>	/**
313	>	* Inserts the specified element into this priority queue.
314	>	*
315	>	* @return {@code true} (as specified by {@link Collection#add})
316	>	* @throws ClassCastException if the specified element cannot be
317	>	*         compared with elements currently in this priority queue
318	>	*         according to the priority queue's ordering
319	>	* @throws NullPointerException if the specified element is null
320	>	*/
321	>	public boolean add(E e) {
322	>	return offer(e);
323	>	}
324
325		/**
326	<	* Add the specified element to this priority queue.
326	>	* Inserts the specified element into this priority queue.
327		*
328	<	* @return <tt>true</tt>
329	<	* @throws ClassCastException if the specified element cannot be compared
330	<	* with elements currently in the priority queue according
331	<	* to the priority queue's ordering.
332	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
328	>	* @return {@code true} (as specified by {@link Queue#offer})
329	>	* @throws ClassCastException if the specified element cannot be
330	>	*         compared with elements currently in this priority queue
331	>	*         according to the priority queue's ordering
332	>	* @throws NullPointerException if the specified element is null
333		*/
334	<	public boolean offer(E o) {
335	<	if (o == null)
334	>	public boolean offer(E e) {
335	>	if (e == null)
336		throw new NullPointerException();
337		modCount++;
338	<	++size;
339	<
340	<	// Grow backing store if necessary
341	<	if (size >= queue.length)
342	<	grow(size);
292	<
293	<	queue[size] = o;
294	<	fixUp(size);
338	>	int i = size;
339	>	if (i >= queue.length)
340	>	grow(i + 1);
341	>	siftUp(i, e);
342	>	size = i + 1;
343		return true;
344		}
345
346	<	public E poll() {
299	<	if (size == 0)
300	<	return null;
301	<	return remove();
302	<	}
303	<
346	>	@SuppressWarnings("unchecked")
347		public E peek() {
348	<	return (E) queue[1];
348	>	return (size == 0) ? null : (E) queue[0];
349		}
350
351	<	// Collection Methods - the first two override to update docs
351	>	private int indexOf(Object o) {
352	>	if (o != null) {
353	>	for (int i = 0; i < size; i++)
354	>	if (o.equals(queue[i]))
355	>	return i;
356	>	}
357	>	return -1;
358	>	}
359
360		/**
361	<	* Adds the specified element to this queue.
362	<	* @return <tt>true</tt> (as per the general contract of
363	<	* <tt>Collection.add</tt>).
361	>	* Removes a single instance of the specified element from this queue,
362	>	* if it is present.  More formally, removes an element {@code e} such
363	>	* that {@code o.equals(e)}, if this queue contains one or more such
364	>	* elements.  Returns {@code true} if and only if this queue contained
365	>	* the specified element (or equivalently, if this queue changed as a
366	>	* result of the call).
367		*
368	<	* @throws NullPointerException {@inheritDoc}
369	<	* @throws ClassCastException if the specified element cannot be compared
317	<	* with elements currently in the priority queue according
318	<	* to the priority queue's ordering.
368	>	* @param o element to be removed from this queue, if present
369	>	* @return {@code true} if this queue changed as a result of the call
370		*/
371	<	public boolean add(E o) {
372	<	return super.add(o);
371	>	public boolean remove(Object o) {
372	>	int i = indexOf(o);
373	>	if (i == -1)
374	>	return false;
375	>	else {
376	>	removeAt(i);
377	>	return true;
378	>	}
379		}
380
324	–
381		/**
382	<	* Adds all of the elements in the specified collection to this queue.
383	<	* The behavior of this operation is undefined if
384	<	* the specified collection is modified while the operation is in
385	<	* progress.  (This implies that the behavior of this call is undefined if
386	<	* the specified collection is this queue, and this queue is nonempty.)
331	<	* <p>
332	<	* This implementation iterates over the specified collection, and adds
333	<	* each object returned by the iterator to this collection, in turn.
334	<	* @throws NullPointerException {@inheritDoc}
335	<	* @throws ClassCastException if any element cannot be compared
336	<	* with elements currently in the priority queue according
337	<	* to the priority queue's ordering.
382	>	* Version of remove using reference equality, not equals.
383	>	* Needed by iterator.remove.
384	>	*
385	>	* @param o element to be removed from this queue, if present
386	>	* @return {@code true} if removed
387		*/
388	<	public boolean addAll(Collection<? extends E> c) {
389	<	return super.addAll(c);
388	>	boolean removeEq(Object o) {
389	>	for (int i = 0; i < size; i++) {
390	>	if (o == queue[i]) {
391	>	removeAt(i);
392	>	return true;
393	>	}
394	>	}
395	>	return false;
396		}
397
398	+	/**
399	+	* Returns {@code true} if this queue contains the specified element.
400	+	* More formally, returns {@code true} if and only if this queue contains
401	+	* at least one element {@code e} such that {@code o.equals(e)}.
402	+	*
403	+	* @param o object to be checked for containment in this queue
404	+	* @return {@code true} if this queue contains the specified element
405	+	*/
406	+	public boolean contains(Object o) {
407	+	return indexOf(o) >= 0;
408	+	}
409
410		/**
411	<	* Removes a single instance of the specified element from this
412	<	* queue, if it is present.  More formally,
413	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
414	<	* o.equals(e))</tt>, if the queue contains one or more such
415	<	* elements.  Returns <tt>true</tt> if the queue contained the
416	<	* specified element (or equivalently, if the queue changed as a
351	<	* result of the call).
411	>	* Returns an array containing all of the elements in this queue.
412	>	* The elements are in no particular order.
413	>	*
414	>	* <p>The returned array will be "safe" in that no references to it are
415	>	* maintained by this queue.  (In other words, this method must allocate
416	>	* a new array).  The caller is thus free to modify the returned array.
417		*
418	<	* <p>This implementation iterates over the queue looking for the
419	<	* specified element.  If it finds the element, it removes the element
355	<	* from the queue using the iterator's remove method.<p>
418	>	* <p>This method acts as bridge between array-based and collection-based
419	>	* APIs.
420		*
421	+	* @return an array containing all of the elements in this queue
422		*/
423	<	public boolean remove(Object o) {
424	<	if (o == null)
425	<	return false;
423	>	public Object[] toArray() {
424	>	return Arrays.copyOf(queue, size);
425	>	}
426
427	<	if (comparator == null) {
428	<	for (int i = 1; i <= size; i++) {
429	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
430	<	removeAt(i);
431	<	return true;
432	<	}
433	<	}
434	<	} else {
435	<	for (int i = 1; i <= size; i++) {
436	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
437	<	removeAt(i);
438	<	return true;
439	<	}
440	<	}
441	<	}
442	<	return false;
427	>	/**
428	>	* Returns an array containing all of the elements in this queue; the
429	>	* runtime type of the returned array is that of the specified array.
430	>	* The returned array elements are in no particular order.
431	>	* If the queue fits in the specified array, it is returned therein.
432	>	* Otherwise, a new array is allocated with the runtime type of the
433	>	* specified array and the size of this queue.
434	>	*
435	>	* <p>If the queue fits in the specified array with room to spare
436	>	* (i.e., the array has more elements than the queue), the element in
437	>	* the array immediately following the end of the collection is set to
438	>	* {@code null}.
439	>	*
440	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
441	>	* array-based and collection-based APIs.  Further, this method allows
442	>	* precise control over the runtime type of the output array, and may,
443	>	* under certain circumstances, be used to save allocation costs.
444	>	*
445	>	* <p>Suppose {@code x} is a queue known to contain only strings.
446	>	* The following code can be used to dump the queue into a newly
447	>	* allocated array of {@code String}:
448	>	*
449	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
450	>	*
451	>	* Note that {@code toArray(new Object[0])} is identical in function to
452	>	* {@code toArray()}.
453	>	*
454	>	* @param a the array into which the elements of the queue are to
455	>	*          be stored, if it is big enough; otherwise, a new array of the
456	>	*          same runtime type is allocated for this purpose.
457	>	* @return an array containing all of the elements in this queue
458	>	* @throws ArrayStoreException if the runtime type of the specified array
459	>	*         is not a supertype of the runtime type of every element in
460	>	*         this queue
461	>	* @throws NullPointerException if the specified array is null
462	>	*/
463	>	@SuppressWarnings("unchecked")
464	>	public <T> T[] toArray(T[] a) {
465	>	final int size = this.size;
466	>	if (a.length < size)
467	>	// Make a new array of a's runtime type, but my contents:
468	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
469	>	System.arraycopy(queue, 0, a, 0, size);
470	>	if (a.length > size)
471	>	a[size] = null;
472	>	return a;
473		}
474
475		/**
476		* Returns an iterator over the elements in this queue. The iterator
477		* does not return the elements in any particular order.
478		*
479	<	* @return an iterator over the elements in this queue.
479	>	* @return an iterator over the elements in this queue
480		*/
481		public Iterator<E> iterator() {
482		return new Itr();
483		}
484
485	<	private class Itr implements Iterator<E> {
391	<
485	>	private final class Itr implements Iterator<E> {
486		/**
487		* Index (into queue array) of element to be returned by
488		* subsequent call to next.
489		*/
490	<	private int cursor = 1;
490	>	private int cursor;
491
492		/**
493		* Index of element returned by most recent call to next,
494		* unless that element came from the forgetMeNot list.
495	<	* Reset to 0 if element is deleted by a call to remove.
495	>	* Set to -1 if element is deleted by a call to remove.
496		*/
497	<	private int lastRet = 0;
497	>	private int lastRet = -1;
498
499		/**
500	<	* The modCount value that the iterator believes that the backing
407	<	* List should have.  If this expectation is violated, the iterator
408	<	* has detected concurrent modification.
409	<	*/
410	<	private int expectedModCount = modCount;
411	<
412	<	/**
413	<	* A list of elements that were moved from the unvisited portion of
500	>	* A queue of elements that were moved from the unvisited portion of
501		* the heap into the visited portion as a result of "unlucky" element
502		* removals during the iteration.  (Unlucky element removals are those
503	<	* that require a fixup instead of a fixdown.)  We must visit all of
503	>	* that require a siftup instead of a siftdown.)  We must visit all of
504		* the elements in this list to complete the iteration.  We do this
505		* after we've completed the "normal" iteration.
506		*
507		* We expect that most iterations, even those involving removals,
508	<	* will not use need to store elements in this field.
508	>	* will not need to store elements in this field.
509		*/
510	<	private ArrayList<E> forgetMeNot = null;
510	>	private ArrayDeque<E> forgetMeNot;
511
512		/**
513		* Element returned by the most recent call to next iff that
514		* element was drawn from the forgetMeNot list.
515		*/
516	<	private Object lastRetElt = null;
516	>	private E lastRetElt;
517	>
518	>	/**
519	>	* The modCount value that the iterator believes that the backing
520	>	* Queue should have.  If this expectation is violated, the iterator
521	>	* has detected concurrent modification.
522	>	*/
523	>	private int expectedModCount = modCount;
524
525		public boolean hasNext() {
526	<	return cursor <= size || forgetMeNot != null;
526	>	return cursor < size ||
527	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
528		}
529
530	+	@SuppressWarnings("unchecked")
531		public E next() {
532	<	checkForComodification();
533	<	E result;
534	<	if (cursor <= size) {
535	<	result = (E) queue[cursor];
536	<	lastRet = cursor++;
537	<	}
538	<	else if (forgetMeNot == null)
539	<	throw new NoSuchElementException();
540	<	else {
445	<	int remaining = forgetMeNot.size();
446	<	result = forgetMeNot.remove(remaining - 1);
447	<	if (remaining == 1)
448	<	forgetMeNot = null;
449	<	lastRet = 0;
450	<	lastRetElt = result;
532	>	if (expectedModCount != modCount)
533	>	throw new ConcurrentModificationException();
534	>	if (cursor < size)
535	>	return (E) queue[lastRet = cursor++];
536	>	if (forgetMeNot != null) {
537	>	lastRet = -1;
538	>	lastRetElt = forgetMeNot.poll();
539	>	if (lastRetElt != null)
540	>	return lastRetElt;
541		}
542	<	return result;
542	>	throw new NoSuchElementException();
543		}
544
545		public void remove() {
546	<	checkForComodification();
547	<
548	<	if (lastRet != 0) {
546	>	if (expectedModCount != modCount)
547	>	throw new ConcurrentModificationException();
548	>	if (lastRet != -1) {
549		E moved = PriorityQueue.this.removeAt(lastRet);
550	<	lastRet = 0;
551	<	if (moved == null) {
550	>	lastRet = -1;
551	>	if (moved == null)
552		cursor--;
553	<	} else {
553	>	else {
554		if (forgetMeNot == null)
555	<	forgetMeNot = new ArrayList();
555	>	forgetMeNot = new ArrayDeque<>();
556		forgetMeNot.add(moved);
557		}
558		} else if (lastRetElt != null) {
559	<	PriorityQueue.this.remove(lastRetElt);
559	>	PriorityQueue.this.removeEq(lastRetElt);
560		lastRetElt = null;
561		} else {
562		throw new IllegalStateException();
563		}
474	–
564		expectedModCount = modCount;
565		}
477	–
478	–	final void checkForComodification() {
479	–	if (modCount != expectedModCount)
480	–	throw new ConcurrentModificationException();
481	–	}
566		}
567
568		public int size() {
#	Line 486 | Line 570 | public class PriorityQueue<E> extends Ab
570		}
571
572		/**
573	<	* Remove all elements from the priority queue.
573	>	* Removes all of the elements from this priority queue.
574	>	* The queue will be empty after this call returns.
575		*/
576		public void clear() {
577		modCount++;
578	<
494	<	// Null out element references to prevent memory leak
495	<	for (int i=1; i<=size; i++)
578	>	for (int i = 0; i < size; i++)
579		queue[i] = null;
497	–
580		size = 0;
581		}
582
583	<	/**
584	<	* Removes and returns the first element from queue.
503	<	*/
504	<	public E remove() {
583	>	@SuppressWarnings("unchecked")
584	>	public E poll() {
585		if (size == 0)
586	<	throw new NoSuchElementException();
586	>	return null;
587	>	int s = --size;
588		modCount++;
589	<
590	<	E result = (E) queue[1];
591	<	queue[1] = queue[size];
592	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
593	<	if (size > 1)
513	<	fixDown(1);
514	<
589	>	E result = (E) queue[0];
590	>	E x = (E) queue[s];
591	>	queue[s] = null;
592	>	if (s != 0)
593	>	siftDown(0, x);
594		return result;
595		}
596
597		/**
598	<	* Removes and returns the ith element from queue.  (Recall that queue
520	<	* is one-based, so 1 <= i <= size.)
598	>	* Removes the ith element from queue.
599		*
600	<	* Normally this method leaves the elements at positions from 1 up to i-1,
601	<	* inclusive, untouched.  Under these circumstances, it returns null.
602	<	* Occasionally, in order to maintain the heap invariant, it must move
603	<	* the last element of the list to some index in the range [2, i-1],
604	<	* and move the element previously at position (i/2) to position i.
605	<	* Under these circumstances, this method returns the element that was
606	<	* previously at the end of the list and is now at some position between
607	<	* 2 and i-1 inclusive.
608	<	*/
609	<	private E removeAt(int i) {
610	<	assert i > 0 && i <= size;
600	>	* Normally this method leaves the elements at up to i-1,
601	>	* inclusive, untouched.  Under these circumstances, it returns
602	>	* null.  Occasionally, in order to maintain the heap invariant,
603	>	* it must swap a later element of the list with one earlier than
604	>	* i.  Under these circumstances, this method returns the element
605	>	* that was previously at the end of the list and is now at some
606	>	* position before i. This fact is used by iterator.remove so as to
607	>	* avoid missing traversing elements.
608	>	*/
609	>	@SuppressWarnings("unchecked")
610	>	E removeAt(int i) {
611	>	// assert i >= 0 && i < size;
612		modCount++;
613	<
614	<	E moved = (E) queue[size];
615	<	queue[i] = moved;
616	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
617	<	if (i <= size) {
618	<	fixDown(i);
613	>	int s = --size;
614	>	if (s == i) // removed last element
615	>	queue[i] = null;
616	>	else {
617	>	E moved = (E) queue[s];
618	>	queue[s] = null;
619	>	siftDown(i, moved);
620		if (queue[i] == moved) {
621	<	fixUp(i);
621	>	siftUp(i, moved);
622		if (queue[i] != moved)
623		return moved;
624		}
#	Line 547 | Line 627 | public class PriorityQueue<E> extends Ab
627		}
628
629		/**
630	<	* Establishes the heap invariant (described above) assuming the heap
631	<	* satisfies the invariant except possibly for the leaf-node indexed by k
632	<	* (which may have a nextExecutionTime less than its parent's).
633	<	*
634	<	* This method functions by "promoting" queue[k] up the hierarchy
635	<	* (by swapping it with its parent) repeatedly until queue[k]
636	<	* is greater than or equal to its parent.
637	<	*/
638	<	private void fixUp(int k) {
639	<	if (comparator == null) {
640	<	while (k > 1) {
641	<	int j = k >> 1;
642	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
643	<	break;
644	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
645	<	k = j;
646	<	}
647	<	} else {
648	<	while (k > 1) {
649	<	int j = k >>> 1;
650	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
651	<	break;
652	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
653	<	k = j;
654	<	}
630	>	* Inserts item x at position k, maintaining heap invariant by
631	>	* promoting x up the tree until it is greater than or equal to
632	>	* its parent, or is the root.
633	>	*
634	>	* To simplify and speed up coercions and comparisons. the
635	>	* Comparable and Comparator versions are separated into different
636	>	* methods that are otherwise identical. (Similarly for siftDown.)
637	>	*
638	>	* @param k the position to fill
639	>	* @param x the item to insert
640	>	*/
641	>	private void siftUp(int k, E x) {
642	>	if (comparator != null)
643	>	siftUpUsingComparator(k, x);
644	>	else
645	>	siftUpComparable(k, x);
646	>	}
647	>
648	>	@SuppressWarnings("unchecked")
649	>	private void siftUpComparable(int k, E x) {
650	>	Comparable<? super E> key = (Comparable<? super E>) x;
651	>	while (k > 0) {
652	>	int parent = (k - 1) >>> 1;
653	>	Object e = queue[parent];
654	>	if (key.compareTo((E) e) >= 0)
655	>	break;
656	>	queue[k] = e;
657	>	k = parent;
658		}
659	+	queue[k] = key;
660	+	}
661	+
662	+	@SuppressWarnings("unchecked")
663	+	private void siftUpUsingComparator(int k, E x) {
664	+	while (k > 0) {
665	+	int parent = (k - 1) >>> 1;
666	+	Object e = queue[parent];
667	+	if (comparator.compare(x, (E) e) >= 0)
668	+	break;
669	+	queue[k] = e;
670	+	k = parent;
671	+	}
672	+	queue[k] = x;
673		}
674
675		/**
676	<	* Establishes the heap invariant (described above) in the subtree
677	<	* rooted at k, which is assumed to satisfy the heap invariant except
678	<	* possibly for node k itself (which may be greater than its children).
679	<	*
680	<	* This method functions by "demoting" queue[k] down the hierarchy
681	<	* (by swapping it with its smaller child) repeatedly until queue[k]
682	<	* is less than or equal to its children.
683	<	*/
684	<	private void fixDown(int k) {
685	<	int j;
686	<	if (comparator == null) {
687	<	while ((j = k << 1) <= size && (j > 0)) {
688	<	if (j<size &&
689	<	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
690	<	j++; // j indexes smallest kid
691	<
692	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
693	<	break;
694	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
695	<	k = j;
696	<	}
697	<	} else {
698	<	while ((j = k << 1) <= size && (j > 0)) {
699	<	if (j<size &&
700	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
701	<	j++; // j indexes smallest kid
702	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
703	<	break;
704	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
608	<	k = j;
609	<	}
676	>	* Inserts item x at position k, maintaining heap invariant by
677	>	* demoting x down the tree repeatedly until it is less than or
678	>	* equal to its children or is a leaf.
679	>	*
680	>	* @param k the position to fill
681	>	* @param x the item to insert
682	>	*/
683	>	private void siftDown(int k, E x) {
684	>	if (comparator != null)
685	>	siftDownUsingComparator(k, x);
686	>	else
687	>	siftDownComparable(k, x);
688	>	}
689	>
690	>	@SuppressWarnings("unchecked")
691	>	private void siftDownComparable(int k, E x) {
692	>	Comparable<? super E> key = (Comparable<? super E>)x;
693	>	int half = size >>> 1;        // loop while a non-leaf
694	>	while (k < half) {
695	>	int child = (k << 1) + 1; // assume left child is least
696	>	Object c = queue[child];
697	>	int right = child + 1;
698	>	if (right < size &&
699	>	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
700	>	c = queue[child = right];
701	>	if (key.compareTo((E) c) <= 0)
702	>	break;
703	>	queue[k] = c;
704	>	k = child;
705		}
706	+	queue[k] = key;
707	+	}
708	+
709	+	@SuppressWarnings("unchecked")
710	+	private void siftDownUsingComparator(int k, E x) {
711	+	int half = size >>> 1;
712	+	while (k < half) {
713	+	int child = (k << 1) + 1;
714	+	Object c = queue[child];
715	+	int right = child + 1;
716	+	if (right < size &&
717	+	comparator.compare((E) c, (E) queue[right]) > 0)
718	+	c = queue[child = right];
719	+	if (comparator.compare(x, (E) c) <= 0)
720	+	break;
721	+	queue[k] = c;
722	+	k = child;
723	+	}
724	+	queue[k] = x;
725		}
726
727		/**
728		* Establishes the heap invariant (described above) in the entire tree,
729		* assuming nothing about the order of the elements prior to the call.
730	+	* This classic algorithm due to Floyd (1964) is known to be O(size).
731		*/
732	+	@SuppressWarnings("unchecked")
733		private void heapify() {
734	<	for (int i = size/2; i >= 1; i--)
735	<	fixDown(i);
734	>	for (int i = (size >>> 1) - 1; i >= 0; i--)
735	>	siftDown(i, (E) queue[i]);
736		}
737
738		/**
739	<	* Returns the comparator used to order this collection, or <tt>null</tt>
740	<	* if this collection is sorted according to its elements natural ordering
741	<	* (using <tt>Comparable</tt>).
739	>	* Returns the comparator used to order the elements in this
740	>	* queue, or {@code null} if this queue is sorted according to
741	>	* the {@linkplain Comparable natural ordering} of its elements.
742		*
743	<	* @return the comparator used to order this collection, or <tt>null</tt>
744	<	* if this collection is sorted according to its elements natural ordering.
743	>	* @return the comparator used to order this queue, or
744	>	*         {@code null} if this queue is sorted according to the
745	>	*         natural ordering of its elements
746		*/
747		public Comparator<? super E> comparator() {
748		return comparator;
749		}
750
751		/**
752	<	* Save the state of the instance to a stream (that
636	<	* is, serialize it).
752	>	* Saves this queue to a stream (that is, serializes it).
753		*
638	–	* @serialData The length of the array backing the instance is
639	–	* emitted (int), followed by all of its elements (each an
640	–	* <tt>Object</tt>) in the proper order.
754		* @param s the stream
755	+	* @throws java.io.IOException if an I/O error occurs
756	+	* @serialData The length of the array backing the instance is
757	+	*             emitted (int), followed by all of its elements
758	+	*             (each an {@code Object}) in the proper order.
759		*/
760		private void writeObject(java.io.ObjectOutputStream s)
761	<	throws java.io.IOException{
761	>	throws java.io.IOException {
762		// Write out element count, and any hidden stuff
763		s.defaultWriteObject();
764
765	<	// Write out array length
766	<	s.writeInt(queue.length);
765	>	// Write out array length, for compatibility with 1.5 version
766	>	s.writeInt(Math.max(2, size + 1));
767
768	<	// Write out all elements in the proper order.
769	<	for (int i=0; i<size; i++)
768	>	// Write out all elements in the "proper order".
769	>	for (int i = 0; i < size; i++)
770		s.writeObject(queue[i]);
771		}
772
773		/**
774	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
775	<	* deserialize it).
774	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
775	>	* (that is, deserializes it).
776	>	*
777		* @param s the stream
778	+	* @throws ClassNotFoundException if the class of a serialized object
779	+	*         could not be found
780	+	* @throws java.io.IOException if an I/O error occurs
781		*/
782		private void readObject(java.io.ObjectInputStream s)
783		throws java.io.IOException, ClassNotFoundException {
784		// Read in size, and any hidden stuff
785		s.defaultReadObject();
786
787	<	// Read in array length and allocate array
788	<	int arrayLength = s.readInt();
789	<	queue = new Object[arrayLength];
787	>	// Read in (and discard) array length
788	>	s.readInt();
789	>
790	>	queue = new Object[size];
791
792	<	// Read in all elements in the proper order.
793	<	for (int i=0; i<size; i++)
792	>	// Read in all elements.
793	>	for (int i = 0; i < size; i++)
794		queue[i] = s.readObject();
795	+
796	+	// Elements are guaranteed to be in "proper order", but the
797	+	// spec has never explained what that might be.
798	+	heapify();
799		}
800
801	+	/**
802	+	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
803	+	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
804	+	* queue. The spliterator does not traverse elements in any particular order
805	+	* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
806	+	*
807	+	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
808	+	* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.
809	+	* Overriding implementations should document the reporting of additional
810	+	* characteristic values.
811	+	*
812	+	* @return a {@code Spliterator} over the elements in this queue
813	+	* @since 1.8
814	+	*/
815	+	public final Spliterator<E> spliterator() {
816	+	return new PriorityQueueSpliterator<>(this, 0, -1, 0);
817	+	}
818	+
819	+	static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
820	+	/*
821	+	* This is very similar to ArrayList Spliterator, except for
822	+	* extra null checks.
823	+	*/
824	+	private final PriorityQueue<E> pq;
825	+	private int index;            // current index, modified on advance/split
826	+	private int fence;            // -1 until first use
827	+	private int expectedModCount; // initialized when fence set
828	+
829	+	/** Creates new spliterator covering the given range. */
830	+	PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
831	+	int expectedModCount) {
832	+	this.pq = pq;
833	+	this.index = origin;
834	+	this.fence = fence;
835	+	this.expectedModCount = expectedModCount;
836	+	}
837	+
838	+	private int getFence() { // initialize fence to size on first use
839	+	int hi;
840	+	if ((hi = fence) < 0) {
841	+	expectedModCount = pq.modCount;
842	+	hi = fence = pq.size;
843	+	}
844	+	return hi;
845	+	}
846	+
847	+	public PriorityQueueSpliterator<E> trySplit() {
848	+	int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
849	+	return (lo >= mid) ? null :
850	+	new PriorityQueueSpliterator<>(pq, lo, index = mid,
851	+	expectedModCount);
852	+	}
853	+
854	+	@SuppressWarnings("unchecked")
855	+	public void forEachRemaining(Consumer<? super E> action) {
856	+	int i, hi, mc; // hoist accesses and checks from loop
857	+	PriorityQueue<E> q; Object[] a;
858	+	if (action == null)
859	+	throw new NullPointerException();
860	+	if ((q = pq) != null && (a = q.queue) != null) {
861	+	if ((hi = fence) < 0) {
862	+	mc = q.modCount;
863	+	hi = q.size;
864	+	}
865	+	else
866	+	mc = expectedModCount;
867	+	if ((i = index) >= 0 && (index = hi) <= a.length) {
868	+	for (E e;; ++i) {
869	+	if (i < hi) {
870	+	if ((e = (E) a[i]) == null) // must be CME
871	+	break;
872	+	action.accept(e);
873	+	}
874	+	else if (q.modCount != mc)
875	+	break;
876	+	else
877	+	return;
878	+	}
879	+	}
880	+	}
881	+	throw new ConcurrentModificationException();
882	+	}
883	+
884	+	public boolean tryAdvance(Consumer<? super E> action) {
885	+	if (action == null)
886	+	throw new NullPointerException();
887	+	int hi = getFence(), lo = index;
888	+	if (lo >= 0 && lo < hi) {
889	+	index = lo + 1;
890	+	@SuppressWarnings("unchecked") E e = (E)pq.queue[lo];
891	+	if (e == null)
892	+	throw new ConcurrentModificationException();
893	+	action.accept(e);
894	+	if (pq.modCount != expectedModCount)
895	+	throw new ConcurrentModificationException();
896	+	return true;
897	+	}
898	+	return false;
899	+	}
900	+
901	+	public long estimateSize() {
902	+	return (long) (getFence() - index);
903	+	}
904	+
905	+	public int characteristics() {
906	+	return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
907	+	}
908	+	}
909		}

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