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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.19 by tim, Mon Aug 4 16:14:48 2003 UTC vs.
Revision 1.124 by jsr166, Sun May 6 19:35:51 2018 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* Copyright (c) 2003, 2018, 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	>	import jdk.internal.misc.SharedSecrets;
30
31		/**
32	<	* A priority queue based on a priority heap.  This queue orders
33	<	* elements according to an order specified at construction time, which is
34	<	* specified in the same manner as {@link java.util.TreeSet} and
35	<	* {@link java.util.TreeMap}: elements are ordered
36	<	* either according to their <i>natural order</i> (see {@link Comparable}), or
37	<	* according to a {@link java.util.Comparator}, depending on which
38	<	* constructor is used.
39	<	* <p>The <em>head</em> of this queue is the <em>least</em> element with
40	<	* respect to the specified ordering.
41	<	* If multiple elements are tied for least value, the
42	<	* head is one of those elements. A priority queue does not permit
43	<	* <tt>null</tt> elements.
44	<	*
45	<	* <p>The {@link #remove()} and {@link #poll()} methods remove and
46	<	* return the head of the queue.
47	<	*
48	<	* <p>The {@link #element()} and {@link #peek()} methods return, but do
49	<	* not delete, the head of the queue.
50	<	*
51	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
52	<	* size of the array used internally to store the elements on the
53	<	* queue, and is limited to <tt>Integer.MAX_VALUE-1</tt>.
54	<	* It is always at least as large as the queue size.  As
55	<	* elements are added to a priority queue, its capacity grows
56	<	* automatically.  The details of the growth policy are not specified.
57	<	*
58	<	* <p>Implementation note: this implementation provides O(log(n)) time
59	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
60	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
61	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
62	<	* constant time for the retrieval methods (<tt>peek</tt>,
63	<	* <tt>element</tt>, and <tt>size</tt>).
32	>	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
33	>	* The elements of the priority queue are ordered according to their
34	>	* {@linkplain Comparable natural ordering}, or by a {@link Comparator}
35	>	* provided at queue construction time, depending on which constructor is
36	>	* used.  A priority queue does not permit {@code null} elements.
37	>	* A priority queue relying on natural ordering also does not permit
38	>	* insertion of non-comparable objects (doing so may result in
39	>	* {@code ClassCastException}).
40	>	*
41	>	* <p>The <em>head</em> of this queue is the <em>least</em> element
42	>	* with respect to the specified ordering.  If multiple elements are
43	>	* tied for least value, the head is one of those elements -- ties are
44	>	* broken arbitrarily.  The queue retrieval operations {@code poll},
45	>	* {@code remove}, {@code peek}, and {@code element} access the
46	>	* element at the head of the queue.
47	>	*
48	>	* <p>A priority queue is unbounded, but has an internal
49	>	* <i>capacity</i> governing the size of an array used to store the
50	>	* elements on the queue.  It is always at least as large as the queue
51	>	* size.  As elements are added to a priority queue, its capacity
52	>	* grows automatically.  The details of the growth policy are not
53	>	* specified.
54	>	*
55	>	* <p>This class and its iterator implement all of the
56	>	* <em>optional</em> methods of the {@link Collection} and {@link
57	>	* Iterator} interfaces.  The Iterator provided in method {@link
58	>	* #iterator()} and the Spliterator provided in method {@link #spliterator()}
59	>	* are <em>not</em> guaranteed to traverse the elements of
60	>	* the priority queue in any particular order. If you need ordered
61	>	* traversal, consider using {@code Arrays.sort(pq.toArray())}.
62	>	*
63	>	* <p><strong>Note that this implementation is not synchronized.</strong>
64	>	* Multiple threads should not access a {@code PriorityQueue}
65	>	* instance concurrently if any of the threads modifies the queue.
66	>	* Instead, use the thread-safe {@link
67	>	* java.util.concurrent.PriorityBlockingQueue} class.
68	>	*
69	>	* <p>Implementation note: this implementation provides
70	>	* O(log(n)) time for the enqueuing and dequeuing methods
71	>	* ({@code offer}, {@code poll}, {@code remove()} and {@code add});
72	>	* linear time for the {@code remove(Object)} and {@code contains(Object)}
73	>	* methods; and constant time for the retrieval methods
74	>	* ({@code peek}, {@code element}, and {@code size}).
75		*
76		* <p>This class is a member of the
77	<	* <a href="{@docRoot}/../guide/collections/index.html">
77	>	* <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
78		* Java Collections Framework</a>.
79	+	*
80		* @since 1.5
81	<	* @author Josh Bloch
81	>	* @author Josh Bloch, Doug Lea
82	>	* @param <E> the type of elements held in this queue
83		*/
84	+	@SuppressWarnings("unchecked")
85		public class PriorityQueue<E> extends AbstractQueue<E>
86	<	implements Sorted, Queue<E>, java.io.Serializable {
86	>	implements java.io.Serializable {
87	>
88	>	private static final long serialVersionUID = -7720805057305804111L;
89
90		private static final int DEFAULT_INITIAL_CAPACITY = 11;
91
92		/**
93	<	* Priority queue represented as a balanced binary heap: the two children
94	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
95	<	* ordered by comparator, or by the elements' natural ordering, if
96	<	* comparator is null:  For each node n in the heap and each descendant d
97	<	* of n, n <= d.
98	<	*
55	<	* The element with the lowest value is in queue[1], assuming the queue is
56	<	* nonempty.  (A one-based array is used in preference to the traditional
57	<	* zero-based array to simplify parent and child calculations.)
58	<	*
59	<	* queue.length must be >= 2, even if size == 0.
93	>	* Priority queue represented as a balanced binary heap: the two
94	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
95	>	* priority queue is ordered by comparator, or by the elements'
96	>	* natural ordering, if comparator is null: For each node n in the
97	>	* heap and each descendant d of n, n <= d.  The element with the
98	>	* lowest value is in queue[0], assuming the queue is nonempty.
99		*/
100	<	private transient Object[] queue;
100	>	transient Object[] queue; // non-private to simplify nested class access
101
102		/**
103		* The number of elements in the priority queue.
104		*/
105	<	private int size = 0;
105	>	int size;
106
107		/**
108		* The comparator, or null if priority queue uses elements'
#	Line 75 | Line 114 | public class PriorityQueue<E> extends Ab
114		* The number of times this priority queue has been
115		* <i>structurally modified</i>.  See AbstractList for gory details.
116		*/
117	<	private transient int modCount = 0;
117	>	transient int modCount;     // non-private to simplify nested class access
118
119		/**
120	<	* Create a <tt>PriorityQueue</tt> with the default initial capacity
121	<	* (11) that orders its elements according to their natural
122	<	* ordering (using <tt>Comparable</tt>.)
120	>	* Creates a {@code PriorityQueue} with the default initial
121	>	* capacity (11) that orders its elements according to their
122	>	* {@linkplain Comparable natural ordering}.
123		*/
124		public PriorityQueue() {
125		this(DEFAULT_INITIAL_CAPACITY, null);
126		}
127
128		/**
129	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
130	<	* that orders its elements according to their natural ordering
131	<	* (using <tt>Comparable</tt>.)
132	<	*
133	<	* @param initialCapacity the initial capacity for this priority queue.
129	>	* Creates a {@code PriorityQueue} with the specified initial
130	>	* capacity that orders its elements according to their
131	>	* {@linkplain Comparable natural ordering}.
132	>	*
133	>	* @param initialCapacity the initial capacity for this priority queue
134	>	* @throws IllegalArgumentException if {@code initialCapacity} is less
135	>	*         than 1
136		*/
137		public PriorityQueue(int initialCapacity) {
138		this(initialCapacity, null);
139		}
140
141		/**
142	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
143	<	* that orders its elements according to the specified comparator.
142	>	* Creates a {@code PriorityQueue} with the default initial capacity and
143	>	* whose elements are ordered according to the specified comparator.
144		*
145	<	* @param initialCapacity the initial capacity for this priority queue.
146	<	* @param comparator the comparator used to order this priority queue.
147	<	* If <tt>null</tt> then the order depends on the elements' natural
148	<	* ordering.
108	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
109	<	* than 1
145	>	* @param  comparator the comparator that will be used to order this
146	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
147	>	*         natural ordering} of the elements will be used.
148	>	* @since 1.8
149		*/
150	<	public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
150	>	public PriorityQueue(Comparator<? super E> comparator) {
151	>	this(DEFAULT_INITIAL_CAPACITY, comparator);
152	>	}
153	>
154	>	/**
155	>	* Creates a {@code PriorityQueue} with the specified initial capacity
156	>	* that orders its elements according to the specified comparator.
157	>	*
158	>	* @param  initialCapacity the initial capacity for this priority queue
159	>	* @param  comparator the comparator that will be used to order this
160	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
161	>	*         natural ordering} of the elements will be used.
162	>	* @throws IllegalArgumentException if {@code initialCapacity} is
163	>	*         less than 1
164	>	*/
165	>	public PriorityQueue(int initialCapacity,
166	>	Comparator<? super E> comparator) {
167	>	// Note: This restriction of at least one is not actually needed,
168	>	// but continues for 1.5 compatibility
169		if (initialCapacity < 1)
170		throw new IllegalArgumentException();
171	<	this.queue = new Object[initialCapacity + 1];
171	>	this.queue = new Object[initialCapacity];
172		this.comparator = comparator;
173		}
174
175		/**
176	<	* Create a <tt>PriorityQueue</tt> containing the elements in the specified
177	<	* collection.  The priority queue has an initial capacity of 110% of the
178	<	* size of the specified collection (bounded by
179	<	* <tt>Integer.MAX_VALUE-1</tt>); or 1 if the collection is empty.
180	<	* If the specified collection
181	<	* implements the {@link Sorted} interface, the priority queue will be
125	<	* sorted according to the same comparator, or according to its elements'
126	<	* natural order if the collection is sorted according to its elements'
127	<	* natural order.  If the specified collection does not implement
128	<	* <tt>Sorted</tt>, the priority queue is ordered according to
129	<	* its elements' natural order.
176	>	* Creates a {@code PriorityQueue} containing the elements in the
177	>	* specified collection.  If the specified collection is an instance of
178	>	* a {@link SortedSet} or is another {@code PriorityQueue}, this
179	>	* priority queue will be ordered according to the same ordering.
180	>	* Otherwise, this priority queue will be ordered according to the
181	>	* {@linkplain Comparable natural ordering} of its elements.
182		*
183	<	* @param c the collection whose elements are to be placed
184	<	*        into this priority queue.
183	>	* @param  c the collection whose elements are to be placed
184	>	*         into this priority queue
185		* @throws ClassCastException if elements of the specified collection
186		*         cannot be compared to one another according to the priority
187	<	*         queue's ordering.
188	<	* @throws NullPointerException if <tt>c</tt> or any element within it
189	<	* is <tt>null</tt>
187	>	*         queue's ordering
188	>	* @throws NullPointerException if the specified collection or any
189	>	*         of its elements are null
190		*/
191		public PriorityQueue(Collection<? extends E> c) {
192	<	int sz = c.size();
193	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
194	<	Integer.MAX_VALUE - 1);
195	<	if (initialCapacity < 1)
196	<	initialCapacity = 1;
197	<
198	<	this.queue = new Object[initialCapacity + 1];
192	>	if (c instanceof SortedSet<?>) {
193	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
194	>	this.comparator = (Comparator<? super E>) ss.comparator();
195	>	initElementsFromCollection(ss);
196	>	}
197	>	else if (c instanceof PriorityQueue<?>) {
198	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
199	>	this.comparator = (Comparator<? super E>) pq.comparator();
200	>	initFromPriorityQueue(pq);
201	>	}
202	>	else {
203	>	this.comparator = null;
204	>	initFromCollection(c);
205	>	}
206	>	}
207
208	<	// FIXME: if c is larger than Integer.MAX_VALUE we'll
209	<	// overflow the array
208	>	/**
209	>	* Creates a {@code PriorityQueue} containing the elements in the
210	>	* specified priority queue.  This priority queue will be
211	>	* ordered according to the same ordering as the given priority
212	>	* queue.
213	>	*
214	>	* @param  c the priority queue whose elements are to be placed
215	>	*         into this priority queue
216	>	* @throws ClassCastException if elements of {@code c} cannot be
217	>	*         compared to one another according to {@code c}'s
218	>	*         ordering
219	>	* @throws NullPointerException if the specified priority queue or any
220	>	*         of its elements are null
221	>	*/
222	>	public PriorityQueue(PriorityQueue<? extends E> c) {
223	>	this.comparator = (Comparator<? super E>) c.comparator();
224	>	initFromPriorityQueue(c);
225	>	}
226
227	<	if (c instanceof Sorted) {
228	<	comparator = (Comparator<? super E>)((Sorted)c).comparator();
227	>	/**
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	>	public PriorityQueue(SortedSet<? extends E> c) {
241	>	this.comparator = (Comparator<? super E>) c.comparator();
242	>	initElementsFromCollection(c);
243	>	}
244	>
245	>	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
246	>	if (c.getClass() == PriorityQueue.class) {
247	>	this.queue = c.toArray();
248	>	this.size = c.size();
249		} else {
250	<	comparator = null;
250	>	initFromCollection(c);
251		}
252	+	}
253	+
254	+	private void initElementsFromCollection(Collection<? extends E> c) {
255	+	Object[] es = c.toArray();
256	+	int len = es.length;
257	+	// If c.toArray incorrectly doesn't return Object[], copy it.
258	+	if (es.getClass() != Object[].class)
259	+	es = Arrays.copyOf(es, len, Object[].class);
260	+	if (len == 1 || this.comparator != null)
261	+	for (Object e : es)
262	+	if (e == null)
263	+	throw new NullPointerException();
264	+	this.queue = es;
265	+	this.size = len;
266	+	}
267
268	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
269	<	add(i.next());
268	>	/**
269	>	* Initializes queue array with elements from the given Collection.
270	>	*
271	>	* @param c the collection
272	>	*/
273	>	private void initFromCollection(Collection<? extends E> c) {
274	>	initElementsFromCollection(c);
275	>	heapify();
276		}
277
278	<	// Queue Methods
278	>	/**
279	>	* The maximum size of array to allocate.
280	>	* Some VMs reserve some header words in an array.
281	>	* Attempts to allocate larger arrays may result in
282	>	* OutOfMemoryError: Requested array size exceeds VM limit
283	>	*/
284	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
285
286		/**
287	<	* Add the specified element to this priority queue.
287	>	* Increases the capacity of the array.
288		*
289	<	* @return <tt>true</tt>
167	<	* @throws ClassCastException if the specified element cannot be compared
168	<	* with elements currently in the priority queue according
169	<	* to the priority queue's ordering.
170	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
289	>	* @param minCapacity the desired minimum capacity
290		*/
291	<	public boolean offer(E o) {
292	<	if (o == null)
293	<	throw new NullPointerException();
294	<	modCount++;
295	<	++size;
291	>	private void grow(int minCapacity) {
292	>	int oldCapacity = queue.length;
293	>	// Double size if small; else grow by 50%
294	>	int newCapacity = oldCapacity + ((oldCapacity < 64) ?
295	>	(oldCapacity + 2) :
296	>	(oldCapacity >> 1));
297	>	// overflow-conscious code
298	>	if (newCapacity - MAX_ARRAY_SIZE > 0)
299	>	newCapacity = hugeCapacity(minCapacity);
300	>	queue = Arrays.copyOf(queue, newCapacity);
301	>	}
302
303	<	// Grow backing store if necessary
304	<	// FIXME: watch for overflow
305	<	// FIXME: what if we're full?
306	<	while (size >= queue.length) {
307	<	Object[] newQueue = new Object[2 * queue.length];
308	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
309	<	queue = newQueue;
185	<	}
303	>	private static int hugeCapacity(int minCapacity) {
304	>	if (minCapacity < 0) // overflow
305	>	throw new OutOfMemoryError();
306	>	return (minCapacity > MAX_ARRAY_SIZE) ?
307	>	Integer.MAX_VALUE :
308	>	MAX_ARRAY_SIZE;
309	>	}
310
311	<	queue[size] = o;
312	<	fixUp(size);
313	<	return true;
311	>	/**
312	>	* Inserts the specified element into this priority queue.
313	>	*
314	>	* @return {@code true} (as specified by {@link Collection#add})
315	>	* @throws ClassCastException if the specified element cannot be
316	>	*         compared with elements currently in this priority queue
317	>	*         according to the priority queue's ordering
318	>	* @throws NullPointerException if the specified element is null
319	>	*/
320	>	public boolean add(E e) {
321	>	return offer(e);
322		}
323
324	<	public E poll() {
325	<	if (size == 0)
326	<	return null;
327	<	return (E) remove(1);
324	>	/**
325	>	* Inserts the specified element into this priority queue.
326	>	*
327	>	* @return {@code true} (as specified by {@link Queue#offer})
328	>	* @throws ClassCastException if the specified element cannot be
329	>	*         compared with elements currently in this priority queue
330	>	*         according to the priority queue's ordering
331	>	* @throws NullPointerException if the specified element is null
332	>	*/
333	>	public boolean offer(E e) {
334	>	if (e == null)
335	>	throw new NullPointerException();
336	>	modCount++;
337	>	int i = size;
338	>	if (i >= queue.length)
339	>	grow(i + 1);
340	>	siftUp(i, e);
341	>	size = i + 1;
342	>	return true;
343		}
344
345		public E peek() {
346	<	return (E) queue[1];
346	>	return (size == 0) ? null : (E) queue[0];
347		}
348
349	<	// Collection Methods
349	>	private int indexOf(Object o) {
350	>	if (o != null) {
351	>	final Object[] es = queue;
352	>	for (int i = 0, n = size; i < n; i++)
353	>	if (o.equals(es[i]))
354	>	return i;
355	>	}
356	>	return -1;
357	>	}
358
359	<	// these first two override just to get the throws docs
359	>	/**
360	>	* Removes a single instance of the specified element from this queue,
361	>	* if it is present.  More formally, removes an element {@code e} such
362	>	* that {@code o.equals(e)}, if this queue contains one or more such
363	>	* elements.  Returns {@code true} if and only if this queue contained
364	>	* the specified element (or equivalently, if this queue changed as a
365	>	* result of the call).
366	>	*
367	>	* @param o element to be removed from this queue, if present
368	>	* @return {@code true} if this queue changed as a result of the call
369	>	*/
370	>	public boolean remove(Object o) {
371	>	int i = indexOf(o);
372	>	if (i == -1)
373	>	return false;
374	>	else {
375	>	removeAt(i);
376	>	return true;
377	>	}
378	>	}
379
380		/**
381	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
382	<	* @throws ClassCastException if the specified element cannot be compared
383	<	* with elements currently in the priority queue according
210	<	* to the priority queue's ordering.
381	>	* Identity-based version for use in Itr.remove.
382	>	*
383	>	* @param o element to be removed from this queue, if present
384		*/
385	<	public boolean add(E o) {
386	<	return super.add(o);
385	>	void removeEq(Object o) {
386	>	final Object[] es = queue;
387	>	for (int i = 0, n = size; i < n; i++) {
388	>	if (o == es[i]) {
389	>	removeAt(i);
390	>	break;
391	>	}
392	>	}
393		}
394
395		/**
396	<	* @throws ClassCastException if any element cannot be compared
397	<	* with elements currently in the priority queue according
398	<	* to the priority queue's ordering.
399	<	* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
400	<	* is <tt>null</tt>
396	>	* Returns {@code true} if this queue contains the specified element.
397	>	* More formally, returns {@code true} if and only if this queue contains
398	>	* at least one element {@code e} such that {@code o.equals(e)}.
399	>	*
400	>	* @param o object to be checked for containment in this queue
401	>	* @return {@code true} if this queue contains the specified element
402		*/
403	<	public boolean addAll(Collection<? extends E> c) {
404	<	return super.addAll(c);
403	>	public boolean contains(Object o) {
404	>	return indexOf(o) >= 0;
405		}
406
407	<	public boolean remove(Object o) {
408	<	if (o == null)
409	<	return false;
407	>	/**
408	>	* Returns an array containing all of the elements in this queue.
409	>	* The elements are in no particular order.
410	>	*
411	>	* <p>The returned array will be "safe" in that no references to it are
412	>	* maintained by this queue.  (In other words, this method must allocate
413	>	* a new array).  The caller is thus free to modify the returned array.
414	>	*
415	>	* <p>This method acts as bridge between array-based and collection-based
416	>	* APIs.
417	>	*
418	>	* @return an array containing all of the elements in this queue
419	>	*/
420	>	public Object[] toArray() {
421	>	return Arrays.copyOf(queue, size);
422	>	}
423
424	<	if (comparator == null) {
425	<	for (int i = 1; i <= size; i++) {
426	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
427	<	remove(i);
428	<	return true;
429	<	}
430	<	}
431	<	} else {
432	<	for (int i = 1; i <= size; i++) {
433	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
434	<	remove(i);
435	<	return true;
436	<	}
437	<	}
438	<	}
439	<	return false;
424	>	/**
425	>	* Returns an array containing all of the elements in this queue; the
426	>	* runtime type of the returned array is that of the specified array.
427	>	* The returned array elements are in no particular order.
428	>	* If the queue fits in the specified array, it is returned therein.
429	>	* Otherwise, a new array is allocated with the runtime type of the
430	>	* specified array and the size of this queue.
431	>	*
432	>	* <p>If the queue fits in the specified array with room to spare
433	>	* (i.e., the array has more elements than the queue), the element in
434	>	* the array immediately following the end of the collection is set to
435	>	* {@code null}.
436	>	*
437	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
438	>	* array-based and collection-based APIs.  Further, this method allows
439	>	* precise control over the runtime type of the output array, and may,
440	>	* under certain circumstances, be used to save allocation costs.
441	>	*
442	>	* <p>Suppose {@code x} is a queue known to contain only strings.
443	>	* The following code can be used to dump the queue into a newly
444	>	* allocated array of {@code String}:
445	>	*
446	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
447	>	*
448	>	* Note that {@code toArray(new Object[0])} is identical in function to
449	>	* {@code toArray()}.
450	>	*
451	>	* @param a the array into which the elements of the queue are to
452	>	*          be stored, if it is big enough; otherwise, a new array of the
453	>	*          same runtime type is allocated for this purpose.
454	>	* @return an array containing all of the elements in this queue
455	>	* @throws ArrayStoreException if the runtime type of the specified array
456	>	*         is not a supertype of the runtime type of every element in
457	>	*         this queue
458	>	* @throws NullPointerException if the specified array is null
459	>	*/
460	>	public <T> T[] toArray(T[] a) {
461	>	final int size = this.size;
462	>	if (a.length < size)
463	>	// Make a new array of a's runtime type, but my contents:
464	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
465	>	System.arraycopy(queue, 0, a, 0, size);
466	>	if (a.length > size)
467	>	a[size] = null;
468	>	return a;
469		}
470
471	+	/**
472	+	* Returns an iterator over the elements in this queue. The iterator
473	+	* does not return the elements in any particular order.
474	+	*
475	+	* @return an iterator over the elements in this queue
476	+	*/
477		public Iterator<E> iterator() {
478		return new Itr();
479		}
480
481	<	private class Itr implements Iterator<E> {
481	>	private final class Itr implements Iterator<E> {
482		/**
483		* Index (into queue array) of element to be returned by
484		* subsequent call to next.
485		*/
486	<	private int cursor = 1;
486	>	private int cursor;
487	>
488	>	/**
489	>	* Index of element returned by most recent call to next,
490	>	* unless that element came from the forgetMeNot list.
491	>	* Set to -1 if element is deleted by a call to remove.
492	>	*/
493	>	private int lastRet = -1;
494	>
495	>	/**
496	>	* A queue of elements that were moved from the unvisited portion of
497	>	* the heap into the visited portion as a result of "unlucky" element
498	>	* removals during the iteration.  (Unlucky element removals are those
499	>	* that require a siftup instead of a siftdown.)  We must visit all of
500	>	* the elements in this list to complete the iteration.  We do this
501	>	* after we've completed the "normal" iteration.
502	>	*
503	>	* We expect that most iterations, even those involving removals,
504	>	* will not need to store elements in this field.
505	>	*/
506	>	private ArrayDeque<E> forgetMeNot;
507
508		/**
509	<	* Index of element returned by most recent call to next or
510	<	* previous.  Reset to 0 if this element is deleted by a call
263	<	* to remove.
509	>	* Element returned by the most recent call to next iff that
510	>	* element was drawn from the forgetMeNot list.
511		*/
512	<	private int lastRet = 0;
512	>	private E lastRetElt;
513
514		/**
515		* The modCount value that the iterator believes that the backing
516	<	* List should have.  If this expectation is violated, the iterator
516	>	* Queue should have.  If this expectation is violated, the iterator
517		* has detected concurrent modification.
518		*/
519		private int expectedModCount = modCount;
520
521	+	Itr() {}                        // prevent access constructor creation
522	+
523		public boolean hasNext() {
524	<	return cursor <= size;
524	>	return cursor < size ||
525	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
526		}
527
528		public E next() {
529	<	checkForComodification();
530	<	if (cursor > size)
531	<	throw new NoSuchElementException();
532	<	E result = (E) queue[cursor];
533	<	lastRet = cursor++;
534	<	return result;
529	>	if (expectedModCount != modCount)
530	>	throw new ConcurrentModificationException();
531	>	if (cursor < size)
532	>	return (E) queue[lastRet = cursor++];
533	>	if (forgetMeNot != null) {
534	>	lastRet = -1;
535	>	lastRetElt = forgetMeNot.poll();
536	>	if (lastRetElt != null)
537	>	return lastRetElt;
538	>	}
539	>	throw new NoSuchElementException();
540		}
541
542		public void remove() {
543	<	if (lastRet == 0)
543	>	if (expectedModCount != modCount)
544	>	throw new ConcurrentModificationException();
545	>	if (lastRet != -1) {
546	>	E moved = PriorityQueue.this.removeAt(lastRet);
547	>	lastRet = -1;
548	>	if (moved == null)
549	>	cursor--;
550	>	else {
551	>	if (forgetMeNot == null)
552	>	forgetMeNot = new ArrayDeque<>();
553	>	forgetMeNot.add(moved);
554	>	}
555	>	} else if (lastRetElt != null) {
556	>	PriorityQueue.this.removeEq(lastRetElt);
557	>	lastRetElt = null;
558	>	} else {
559		throw new IllegalStateException();
560	<	checkForComodification();
291	<
292	<	PriorityQueue.this.remove(lastRet);
293	<	if (lastRet < cursor)
294	<	cursor--;
295	<	lastRet = 0;
560	>	}
561		expectedModCount = modCount;
562		}
298	–
299	–	final void checkForComodification() {
300	–	if (modCount != expectedModCount)
301	–	throw new ConcurrentModificationException();
302	–	}
563		}
564
305	–	/**
306	–	* Returns the number of elements in this priority queue.
307	–	*
308	–	* @return the number of elements in this priority queue.
309	–	*/
565		public int size() {
566		return size;
567		}
568
569		/**
570	<	* Remove all elements from the priority queue.
570	>	* Removes all of the elements from this priority queue.
571	>	* The queue will be empty after this call returns.
572		*/
573		public void clear() {
574		modCount++;
575	<
576	<	// Null out element references to prevent memory leak
577	<	for (int i=1; i<=size; i++)
322	<	queue[i] = null;
323	<
575	>	final Object[] es = queue;
576	>	for (int i = 0, n = size; i < n; i++)
577	>	es[i] = null;
578		size = 0;
579		}
580
581	+	public E poll() {
582	+	if (size == 0)
583	+	return null;
584	+	int s = --size;
585	+	modCount++;
586	+	E result = (E) queue[0];
587	+	E x = (E) queue[s];
588	+	queue[s] = null;
589	+	if (s != 0)
590	+	siftDown(0, x);
591	+	return result;
592	+	}
593	+
594		/**
595	<	* Removes and returns the ith element from queue.  Recall
329	<	* that queue is one-based, so 1 <= i <= size.
595	>	* Removes the ith element from queue.
596		*
597	<	* XXX: Could further special-case i==size, but is it worth it?
598	<	* XXX: Could special-case i==0, but is it worth it?
597	>	* Normally this method leaves the elements at up to i-1,
598	>	* inclusive, untouched.  Under these circumstances, it returns
599	>	* null.  Occasionally, in order to maintain the heap invariant,
600	>	* it must swap a later element of the list with one earlier than
601	>	* i.  Under these circumstances, this method returns the element
602	>	* that was previously at the end of the list and is now at some
603	>	* position before i. This fact is used by iterator.remove so as to
604	>	* avoid missing traversing elements.
605		*/
606	<	private E remove(int i) {
607	<	assert i <= size;
606	>	E removeAt(int i) {
607	>	// assert i >= 0 && i < size;
608		modCount++;
609	<
610	<	E result = (E) queue[i];
611	<	queue[i] = queue[size];
612	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
613	<	if (i <= size)
614	<	fixDown(i);
615	<	return result;
609	>	int s = --size;
610	>	if (s == i) // removed last element
611	>	queue[i] = null;
612	>	else {
613	>	E moved = (E) queue[s];
614	>	queue[s] = null;
615	>	siftDown(i, moved);
616	>	if (queue[i] == moved) {
617	>	siftUp(i, moved);
618	>	if (queue[i] != moved)
619	>	return moved;
620	>	}
621	>	}
622	>	return null;
623		}
624
625		/**
626	<	* Establishes the heap invariant (described above) assuming the heap
627	<	* satisfies the invariant except possibly for the leaf-node indexed by k
628	<	* (which may have a nextExecutionTime less than its parent's).
629	<	*
630	<	* This method functions by "promoting" queue[k] up the hierarchy
631	<	* (by swapping it with its parent) repeatedly until queue[k]
632	<	* is greater than or equal to its parent.
633	<	*/
634	<	private void fixUp(int k) {
635	<	if (comparator == null) {
636	<	while (k > 1) {
637	<	int j = k >> 1;
638	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
639	<	break;
640	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
641	<	k = j;
642	<	}
643	<	} else {
644	<	while (k > 1) {
645	<	int j = k >> 1;
646	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
647	<	break;
648	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
649	<	k = j;
650	<	}
626	>	* Inserts item x at position k, maintaining heap invariant by
627	>	* promoting x up the tree until it is greater than or equal to
628	>	* its parent, or is the root.
629	>	*
630	>	* To simplify and speed up coercions and comparisons, the
631	>	* Comparable and Comparator versions are separated into different
632	>	* methods that are otherwise identical. (Similarly for siftDown.)
633	>	*
634	>	* @param k the position to fill
635	>	* @param x the item to insert
636	>	*/
637	>	private void siftUp(int k, E x) {
638	>	if (comparator != null)
639	>	siftUpUsingComparator(k, x, queue, comparator);
640	>	else
641	>	siftUpComparable(k, x, queue);
642	>	}
643	>
644	>	private static <T> void siftUpComparable(int k, T x, Object[] es) {
645	>	Comparable<? super T> key = (Comparable<? super T>) x;
646	>	while (k > 0) {
647	>	int parent = (k - 1) >>> 1;
648	>	Object e = es[parent];
649	>	if (key.compareTo((T) e) >= 0)
650	>	break;
651	>	es[k] = e;
652	>	k = parent;
653		}
654	+	es[k] = key;
655	+	}
656	+
657	+	private static <T> void siftUpUsingComparator(
658	+	int k, T x, Object[] es, Comparator<? super T> cmp) {
659	+	while (k > 0) {
660	+	int parent = (k - 1) >>> 1;
661	+	Object e = es[parent];
662	+	if (cmp.compare(x, (T) e) >= 0)
663	+	break;
664	+	es[k] = e;
665	+	k = parent;
666	+	}
667	+	es[k] = x;
668		}
669
670		/**
671	<	* Establishes the heap invariant (described above) in the subtree
672	<	* rooted at k, which is assumed to satisfy the heap invariant except
673	<	* possibly for node k itself (which may be greater than its children).
674	<	*
675	<	* This method functions by "demoting" queue[k] down the hierarchy
676	<	* (by swapping it with its smaller child) repeatedly until queue[k]
677	<	* is less than or equal to its children.
678	<	*/
679	<	private void fixDown(int k) {
680	<	int j;
681	<	if (comparator == null) {
682	<	while ((j = k << 1) <= size) {
683	<	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
684	<	j++; // j indexes smallest kid
685	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
686	<	break;
687	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
688	<	k = j;
689	<	}
690	<	} else {
691	<	while ((j = k << 1) <= size) {
692	<	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
693	<	j++; // j indexes smallest kid
694	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
695	<	break;
696	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
697	<	k = j;
698	<	}
671	>	* Inserts item x at position k, maintaining heap invariant by
672	>	* demoting x down the tree repeatedly until it is less than or
673	>	* equal to its children or is a leaf.
674	>	*
675	>	* @param k the position to fill
676	>	* @param x the item to insert
677	>	*/
678	>	private void siftDown(int k, E x) {
679	>	if (comparator != null)
680	>	siftDownUsingComparator(k, x, queue, size, comparator);
681	>	else
682	>	siftDownComparable(k, x, queue, size);
683	>	}
684	>
685	>	private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
686	>	// assert n > 0;
687	>	Comparable<? super T> key = (Comparable<? super T>)x;
688	>	int half = n >>> 1;           // loop while a non-leaf
689	>	while (k < half) {
690	>	int child = (k << 1) + 1; // assume left child is least
691	>	Object c = es[child];
692	>	int right = child + 1;
693	>	if (right < n &&
694	>	((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
695	>	c = es[child = right];
696	>	if (key.compareTo((T) c) <= 0)
697	>	break;
698	>	es[k] = c;
699	>	k = child;
700		}
701	+	es[k] = key;
702		}
703
704	+	private static <T> void siftDownUsingComparator(
705	+	int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
706	+	// assert n > 0;
707	+	int half = n >>> 1;
708	+	while (k < half) {
709	+	int child = (k << 1) + 1;
710	+	Object c = es[child];
711	+	int right = child + 1;
712	+	if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
713	+	c = es[child = right];
714	+	if (cmp.compare(x, (T) c) <= 0)
715	+	break;
716	+	es[k] = c;
717	+	k = child;
718	+	}
719	+	es[k] = x;
720	+	}
721	+
722	+	/**
723	+	* Establishes the heap invariant (described above) in the entire tree,
724	+	* assuming nothing about the order of the elements prior to the call.
725	+	* This classic algorithm due to Floyd (1964) is known to be O(size).
726	+	*/
727	+	private void heapify() {
728	+	final Object[] es = queue;
729	+	int n = size, i = (n >>> 1) - 1;
730	+	Comparator<? super E> cmp = comparator;
731	+	if (cmp == null)
732	+	for (; i >= 0; i--)
733	+	siftDownComparable(i, (E) es[i], es, n);
734	+	else
735	+	for (; i >= 0; i--)
736	+	siftDownUsingComparator(i, (E) es[i], es, n, cmp);
737	+	}
738	+
739	+	/**
740	+	* Returns the comparator used to order the elements in this
741	+	* queue, or {@code null} if this queue is sorted according to
742	+	* the {@linkplain Comparable natural ordering} of its elements.
743	+	*
744	+	* @return the comparator used to order this queue, or
745	+	*         {@code null} if this queue is sorted according to the
746	+	*         natural ordering of its elements
747	+	*/
748		public Comparator<? super E> comparator() {
749		return comparator;
750		}
751
752		/**
753	<	* Save the state of the instance to a stream (that
413	<	* is, serialize it).
753	>	* Saves this queue to a stream (that is, serializes it).
754		*
415	–	* @serialData The length of the array backing the instance is
416	–	* emitted (int), followed by all of its elements (each an
417	–	* <tt>Object</tt>) in the proper order.
755		* @param s the stream
756	+	* @throws java.io.IOException if an I/O error occurs
757	+	* @serialData The length of the array backing the instance is
758	+	*             emitted (int), followed by all of its elements
759	+	*             (each an {@code Object}) in the proper order.
760		*/
761	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
762	<	throws java.io.IOException{
761	>	private void writeObject(java.io.ObjectOutputStream s)
762	>	throws java.io.IOException {
763		// Write out element count, and any hidden stuff
764		s.defaultWriteObject();
765
766	<	// Write out array length
767	<	s.writeInt(queue.length);
766	>	// Write out array length, for compatibility with 1.5 version
767	>	s.writeInt(Math.max(2, size + 1));
768
769	<	// Write out all elements in the proper order.
770	<	for (int i=0; i<size; i++)
771	<	s.writeObject(queue[i]);
769	>	// Write out all elements in the "proper order".
770	>	final Object[] es = queue;
771	>	for (int i = 0, n = size; i < n; i++)
772	>	s.writeObject(es[i]);
773		}
774
775		/**
776	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
777	<	* deserialize it).
776	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
777	>	* (that is, deserializes it).
778	>	*
779		* @param s the stream
780	+	* @throws ClassNotFoundException if the class of a serialized object
781	+	*         could not be found
782	+	* @throws java.io.IOException if an I/O error occurs
783		*/
784	<	private synchronized void readObject(java.io.ObjectInputStream s)
784	>	private void readObject(java.io.ObjectInputStream s)
785		throws java.io.IOException, ClassNotFoundException {
786		// Read in size, and any hidden stuff
787		s.defaultReadObject();
788
789	<	// Read in array length and allocate array
790	<	int arrayLength = s.readInt();
791	<	queue = new Object[arrayLength];
792	<
793	<	// Read in all elements in the proper order.
794	<	for (int i=0; i<size; i++)
795	<	queue[i] = s.readObject();
789	>	// Read in (and discard) array length
790	>	s.readInt();
791	>
792	>	SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size);
793	>	queue = new Object[size];
794	>
795	>	// Read in all elements.
796	>	final Object[] es = queue;
797	>	for (int i = 0, n = size; i < n; i++)
798	>	es[i] = s.readObject();
799	>
800	>	// Elements are guaranteed to be in "proper order", but the
801	>	// spec has never explained what that might be.
802	>	heapify();
803		}
804
805	<	}
805	>	/**
806	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
807	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
808	>	* queue. The spliterator does not traverse elements in any particular order
809	>	* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
810	>	*
811	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
812	>	* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.
813	>	* Overriding implementations should document the reporting of additional
814	>	* characteristic values.
815	>	*
816	>	* @return a {@code Spliterator} over the elements in this queue
817	>	* @since 1.8
818	>	*/
819	>	public final Spliterator<E> spliterator() {
820	>	return new PriorityQueueSpliterator(0, -1, 0);
821	>	}
822	>
823	>	final class PriorityQueueSpliterator implements Spliterator<E> {
824	>	private int index;            // current index, modified on advance/split
825	>	private int fence;            // -1 until first use
826	>	private int expectedModCount; // initialized when fence set
827	>
828	>	/** Creates new spliterator covering the given range. */
829	>	PriorityQueueSpliterator(int origin, int fence, int expectedModCount) {
830	>	this.index = origin;
831	>	this.fence = fence;
832	>	this.expectedModCount = expectedModCount;
833	>	}
834	>
835	>	private int getFence() { // initialize fence to size on first use
836	>	int hi;
837	>	if ((hi = fence) < 0) {
838	>	expectedModCount = modCount;
839	>	hi = fence = size;
840	>	}
841	>	return hi;
842	>	}
843	>
844	>	public PriorityQueueSpliterator trySplit() {
845	>	int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
846	>	return (lo >= mid) ? null :
847	>	new PriorityQueueSpliterator(lo, index = mid, expectedModCount);
848	>	}
849	>
850	>	public void forEachRemaining(Consumer<? super E> action) {
851	>	if (action == null)
852	>	throw new NullPointerException();
853	>	if (fence < 0) { fence = size; expectedModCount = modCount; }
854	>	final Object[] es = queue;
855	>	int i, hi; E e;
856	>	for (i = index, index = hi = fence; i < hi; i++) {
857	>	if ((e = (E) es[i]) == null)
858	>	break;      // must be CME
859	>	action.accept(e);
860	>	}
861	>	if (modCount != expectedModCount)
862	>	throw new ConcurrentModificationException();
863	>	}
864	>
865	>	public boolean tryAdvance(Consumer<? super E> action) {
866	>	if (action == null)
867	>	throw new NullPointerException();
868	>	if (fence < 0) { fence = size; expectedModCount = modCount; }
869	>	int i;
870	>	if ((i = index) < fence) {
871	>	index = i + 1;
872	>	E e;
873	>	if ((e = (E) queue[i]) == null
874	>	|| modCount != expectedModCount)
875	>	throw new ConcurrentModificationException();
876	>	action.accept(e);
877	>	return true;
878	>	}
879	>	return false;
880	>	}
881	>
882	>	public long estimateSize() {
883	>	return getFence() - index;
884	>	}
885	>
886	>	public int characteristics() {
887	>	return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
888	>	}
889	>	}
890
891	+	/**
892	+	* @throws NullPointerException {@inheritDoc}
893	+	*/
894	+	public void forEach(Consumer<? super E> action) {
895	+	Objects.requireNonNull(action);
896	+	final int expectedModCount = modCount;
897	+	final Object[] es = queue;
898	+	for (int i = 0, n = size; i < n; i++)
899	+	action.accept((E) es[i]);
900	+	if (expectedModCount != modCount)
901	+	throw new ConcurrentModificationException();
902	+	}
903	+	}

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