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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.38 by dl, Mon Sep 1 12:23:28 2003 UTC vs.
Revision 1.133 by jsr166, Thu Oct 10 16:53:08 2019 UTC

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1		/*
2	<	* %W% %E%
2	>	* Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
3	>	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4		*
5	<	* Copyright 2003 Sun Microsystems, Inc. All rights reserved.
6	<	* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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 java.util.function.Predicate;
30	+	// OPENJDK import jdk.internal.access.SharedSecrets;
31	+	import jdk.internal.util.ArraysSupport;
32	+
33		/**
34		* An unbounded priority {@linkplain Queue queue} based on a priority heap.
35	<	* This queue orders elements according to an order specified at construction
36	<	* time, which is specified in the same manner as {@link java.util.TreeSet}
37	<	* and {@link java.util.TreeMap}: elements are ordered either according to
38	<	* their <i>natural order</i> (see {@link Comparable}), or according to a
39	<	* {@link java.util.Comparator}, depending on which constructor is used.
40	<	* <p>The <em>head</em> of this queue is the <em>least</em> element with
41	<	* respect to the specified ordering.  If multiple elements are tied for least
42	<	* value, the 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.
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>The Iterator provided in method {@link #iterator()} is <em>not</em>
59	<	* guaranteed to traverse the elements of the PriorityQueue in any
60	<	* particular order. If you need ordered traversal, consider using
61	<	* <tt>Arrays.sort(pq.toArray())</tt>.
62	<	*
63	<	* <p> <strong>Note that this implementation is not synchronized.</strong>
64	<	* Multiple threads should not access a <tt>PriorityQueue</tt>
65	<	* instance concurrently if any of the threads modifies the list
66	<	* structurally. Instead, use the thread-safe {@link
35	>	* The elements of the priority queue are ordered according to their
36	>	* {@linkplain Comparable natural ordering}, or by a {@link Comparator}
37	>	* provided at queue construction time, depending on which constructor is
38	>	* used.  A priority queue does not permit {@code null} elements.
39	>	* A priority queue relying on natural ordering also does not permit
40	>	* insertion of non-comparable objects (doing so may result in
41	>	* {@code ClassCastException}).
42	>	*
43	>	* <p>The <em>head</em> of this queue is the <em>least</em> element
44	>	* with respect to the specified ordering.  If multiple elements are
45	>	* tied for least value, the head is one of those elements -- ties are
46	>	* broken arbitrarily.  The queue retrieval operations {@code poll},
47	>	* {@code remove}, {@code peek}, and {@code element} access the
48	>	* element at the head of the queue.
49	>	*
50	>	* <p>A priority queue is unbounded, but has an internal
51	>	* <i>capacity</i> governing the size of an array used to store the
52	>	* elements on the queue.  It is always at least as large as the queue
53	>	* size.  As elements are added to a priority queue, its capacity
54	>	* grows automatically.  The details of the growth policy are not
55	>	* specified.
56	>	*
57	>	* <p>This class and its iterator implement all of the
58	>	* <em>optional</em> methods of the {@link Collection} and {@link
59	>	* Iterator} interfaces.  The Iterator provided in method {@link
60	>	* #iterator()} and the Spliterator provided in method {@link #spliterator()}
61	>	* are <em>not</em> guaranteed to traverse the elements of
62	>	* the priority queue in any particular order. If you need ordered
63	>	* traversal, consider using {@code Arrays.sort(pq.toArray())}.
64	>	*
65	>	* <p><strong>Note that this implementation is not synchronized.</strong>
66	>	* Multiple threads should not access a {@code PriorityQueue}
67	>	* instance concurrently if any of the threads modifies the queue.
68	>	* Instead, use the thread-safe {@link
69		* java.util.concurrent.PriorityBlockingQueue} class.
70		*
71	<	*
72	<	* <p>Implementation note: this implementation provides O(log(n)) time
73	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
74	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
75	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
76	<	* constant time for the retrieval methods (<tt>peek</tt>,
52	<	* <tt>element</tt>, and <tt>size</tt>).
71	>	* <p>Implementation note: this implementation provides
72	>	* O(log(n)) time for the enqueuing and dequeuing methods
73	>	* ({@code offer}, {@code poll}, {@code remove()} and {@code add});
74	>	* linear time for the {@code remove(Object)} and {@code contains(Object)}
75	>	* methods; and constant time for the retrieval methods
76	>	* ({@code peek}, {@code element}, and {@code size}).
77		*
78		* <p>This class is a member of the
79	<	* <a href="{@docRoot}/../guide/collections/index.html">
79	>	* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
80		* Java Collections Framework</a>.
81	+	*
82		* @since 1.5
83	<	* @version %I%, %G%
84	<	* @author Josh Bloch
83	>	* @author Josh Bloch, Doug Lea
84	>	* @param <E> the type of elements held in this queue
85		*/
86	+	@SuppressWarnings("unchecked")
87		public class PriorityQueue<E> extends AbstractQueue<E>
88	<	implements Queue<E>, java.io.Serializable {
88	>	implements java.io.Serializable {
89
90	+	// OPENJDK @java.io.Serial
91		private static final long serialVersionUID = -7720805057305804111L;
92
93		private static final int DEFAULT_INITIAL_CAPACITY = 11;
94
95		/**
96	<	* Priority queue represented as a balanced binary heap: the two children
97	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
98	<	* ordered by comparator, or by the elements' natural ordering, if
99	<	* comparator is null:  For each node n in the heap and each descendant d
100	<	* of n, n <= d.
101	<	*
75	<	* The element with the lowest value is in queue[1], assuming the queue is
76	<	* nonempty.  (A one-based array is used in preference to the traditional
77	<	* zero-based array to simplify parent and child calculations.)
78	<	*
79	<	* queue.length must be >= 2, even if size == 0.
96	>	* Priority queue represented as a balanced binary heap: the two
97	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
98	>	* priority queue is ordered by comparator, or by the elements'
99	>	* natural ordering, if comparator is null: For each node n in the
100	>	* heap and each descendant d of n, n <= d.  The element with the
101	>	* lowest value is in queue[0], assuming the queue is nonempty.
102		*/
103	<	private transient Object[] queue;
103	>	transient Object[] queue; // non-private to simplify nested class access
104
105		/**
106		* The number of elements in the priority queue.
107		*/
108	<	private int size = 0;
108	>	int size;
109
110		/**
111		* The comparator, or null if priority queue uses elements'
112		* natural ordering.
113		*/
114	+	@SuppressWarnings("serial") // Conditionally serializable
115		private final Comparator<? super E> comparator;
116
117		/**
118		* The number of times this priority queue has been
119		* <i>structurally modified</i>.  See AbstractList for gory details.
120		*/
121	<	private transient int modCount = 0;
121	>	transient int modCount;     // non-private to simplify nested class access
122
123		/**
124	<	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
125	<	* (11) that orders its elements according to their natural
126	<	* ordering (using <tt>Comparable</tt>).
124	>	* Creates a {@code PriorityQueue} with the default initial
125	>	* capacity (11) that orders its elements according to their
126	>	* {@linkplain Comparable natural ordering}.
127		*/
128		public PriorityQueue() {
129		this(DEFAULT_INITIAL_CAPACITY, null);
130		}
131
132		/**
133	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
134	<	* that orders its elements according to their natural ordering
135	<	* (using <tt>Comparable</tt>).
136	<	*
137	<	* @param initialCapacity the initial capacity for this priority queue.
138	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
139	<	* than 1
133	>	* Creates a {@code PriorityQueue} with the specified initial
134	>	* capacity that orders its elements according to their
135	>	* {@linkplain Comparable natural ordering}.
136	>	*
137	>	* @param initialCapacity the initial capacity for this priority queue
138	>	* @throws IllegalArgumentException if {@code initialCapacity} is less
139	>	*         than 1
140		*/
141		public PriorityQueue(int initialCapacity) {
142		this(initialCapacity, null);
143		}
144
145		/**
146	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
146	>	* Creates a {@code PriorityQueue} with the default initial capacity and
147	>	* whose elements are ordered according to the specified comparator.
148	>	*
149	>	* @param  comparator the comparator that will be used to order this
150	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
151	>	*         natural ordering} of the elements will be used.
152	>	* @since 1.8
153	>	*/
154	>	public PriorityQueue(Comparator<? super E> comparator) {
155	>	this(DEFAULT_INITIAL_CAPACITY, comparator);
156	>	}
157	>
158	>	/**
159	>	* Creates a {@code PriorityQueue} with the specified initial capacity
160		* that orders its elements according to the specified comparator.
161		*
162	<	* @param initialCapacity the initial capacity for this priority queue.
163	<	* @param comparator the comparator used to order this priority queue.
164	<	* If <tt>null</tt> then the order depends on the elements' natural
165	<	* ordering.
166	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
167	<	* than 1
162	>	* @param  initialCapacity the initial capacity for this priority queue
163	>	* @param  comparator the comparator that will be used to order this
164	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
165	>	*         natural ordering} of the elements will be used.
166	>	* @throws IllegalArgumentException if {@code initialCapacity} is
167	>	*         less than 1
168		*/
169	<	public PriorityQueue(int initialCapacity,
169	>	public PriorityQueue(int initialCapacity,
170		Comparator<? super E> comparator) {
171	+	// Note: This restriction of at least one is not actually needed,
172	+	// but continues for 1.5 compatibility
173		if (initialCapacity < 1)
174		throw new IllegalArgumentException();
175	<	this.queue = new Object[initialCapacity + 1];
175	>	this.queue = new Object[initialCapacity];
176		this.comparator = comparator;
177		}
178
179		/**
180	<	* Common code to initialize underlying queue array across
181	<	* constructors below.
180	>	* Creates a {@code PriorityQueue} containing the elements in the
181	>	* specified collection.  If the specified collection is an instance of
182	>	* a {@link SortedSet} or is another {@code PriorityQueue}, this
183	>	* priority queue will be ordered according to the same ordering.
184	>	* Otherwise, this priority queue will be ordered according to the
185	>	* {@linkplain Comparable natural ordering} of its elements.
186	>	*
187	>	* @param  c the collection whose elements are to be placed
188	>	*         into this priority queue
189	>	* @throws ClassCastException if elements of the specified collection
190	>	*         cannot be compared to one another according to the priority
191	>	*         queue's ordering
192	>	* @throws NullPointerException if the specified collection or any
193	>	*         of its elements are null
194		*/
195	<	private void initializeArray(Collection<? extends E> c) {
196	<	int sz = c.size();
197	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
198	<	Integer.MAX_VALUE - 1);
199	<	if (initialCapacity < 1)
200	<	initialCapacity = 1;
201	<
202	<	this.queue = new Object[initialCapacity + 1];
195	>	public PriorityQueue(Collection<? extends E> c) {
196	>	if (c instanceof SortedSet<?>) {
197	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
198	>	this.comparator = (Comparator<? super E>) ss.comparator();
199	>	initElementsFromCollection(ss);
200	>	}
201	>	else if (c instanceof PriorityQueue<?>) {
202	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
203	>	this.comparator = (Comparator<? super E>) pq.comparator();
204	>	initFromPriorityQueue(pq);
205	>	}
206	>	else {
207	>	this.comparator = null;
208	>	initFromCollection(c);
209	>	}
210		}
211
212		/**
213	<	* Initially fill elements of the queue array under the
214	<	* knowledge that it is sorted or is another PQ, in which
215	<	* case we can just place the elements in the order presented.
213	>	* Creates a {@code PriorityQueue} containing the elements in the
214	>	* specified priority queue.  This priority queue will be
215	>	* ordered according to the same ordering as the given priority
216	>	* queue.
217	>	*
218	>	* @param  c the priority queue whose elements are to be placed
219	>	*         into this priority queue
220	>	* @throws ClassCastException if elements of {@code c} cannot be
221	>	*         compared to one another according to {@code c}'s
222	>	*         ordering
223	>	* @throws NullPointerException if the specified priority queue or any
224	>	*         of its elements are null
225		*/
226	<	private void fillFromSorted(Collection<? extends E> c) {
227	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
228	<	queue[++size] = i.next();
226	>	public PriorityQueue(PriorityQueue<? extends E> c) {
227	>	this.comparator = (Comparator<? super E>) c.comparator();
228	>	initFromPriorityQueue(c);
229		}
230
231		/**
232	<	* Initially fill elements of the queue array that is not to our knowledge
233	<	* sorted, so we must rearrange the elements to guarantee the heap
234	<	* invariant.
232	>	* Creates a {@code PriorityQueue} containing the elements in the
233	>	* specified sorted set.   This priority queue will be ordered
234	>	* according to the same ordering as the given sorted set.
235	>	*
236	>	* @param  c the sorted set whose elements are to be placed
237	>	*         into this priority queue
238	>	* @throws ClassCastException if elements of the specified sorted
239	>	*         set cannot be compared to one another according to the
240	>	*         sorted set's ordering
241	>	* @throws NullPointerException if the specified sorted set or any
242	>	*         of its elements are null
243		*/
244	<	private void fillFromUnsorted(Collection<? extends E> c) {
245	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
246	<	queue[++size] = i.next();
173	<	heapify();
244	>	public PriorityQueue(SortedSet<? extends E> c) {
245	>	this.comparator = (Comparator<? super E>) c.comparator();
246	>	initElementsFromCollection(c);
247		}
248
249	<	/**
250	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
251	<	* specified collection.  The priority queue has an initial
252	<	* capacity of 110% of the size of the specified collection or 1
253	<	* if the collection is empty.  If the specified collection is an
254	<	* instance of a {@link java.util.SortedSet} or is another
255	<	* <tt>PriorityQueue</tt>, the priority queue will be sorted
256	<	* according to the same comparator, or according to its elements'
257	<	* natural order if the collection is sorted according to its
185	<	* elements' natural order.  Otherwise, the priority queue is
186	<	* ordered according to its elements' natural order.
187	<	*
188	<	* @param c the collection whose elements are to be placed
189	<	*        into this priority queue.
190	<	* @throws ClassCastException if elements of the specified collection
191	<	*         cannot be compared to one another according to the priority
192	<	*         queue's ordering.
193	<	* @throws NullPointerException if <tt>c</tt> or any element within it
194	<	* is <tt>null</tt>
195	<	*/
196	<	public PriorityQueue(Collection<? extends E> c) {
197	<	initializeArray(c);
198	<	if (c instanceof SortedSet) {
199	<	// @fixme double-cast workaround for compiler
200	<	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
201	<	comparator = (Comparator<? super E>)s.comparator();
202	<	fillFromSorted(s);
203	<	} else if (c instanceof PriorityQueue) {
204	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
205	<	comparator = (Comparator<? super E>)s.comparator();
206	<	fillFromSorted(s);
249	>	/** Ensures that queue[0] exists, helping peek() and poll(). */
250	>	private static Object[] ensureNonEmpty(Object[] es) {
251	>	return (es.length > 0) ? es : new Object[1];
252	>	}
253	>
254	>	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
255	>	if (c.getClass() == PriorityQueue.class) {
256	>	this.queue = ensureNonEmpty(c.toArray());
257	>	this.size = c.size();
258		} else {
259	<	comparator = null;
209	<	fillFromUnsorted(c);
259	>	initFromCollection(c);
260		}
261		}
262
263	+	private void initElementsFromCollection(Collection<? extends E> c) {
264	+	Object[] es = c.toArray();
265	+	int len = es.length;
266	+	// If c.toArray incorrectly doesn't return Object[], copy it.
267	+	if (es.getClass() != Object[].class)
268	+	es = Arrays.copyOf(es, len, Object[].class);
269	+	if (len == 1 || this.comparator != null)
270	+	for (Object e : es)
271	+	if (e == null)
272	+	throw new NullPointerException();
273	+	this.queue = ensureNonEmpty(es);
274	+	this.size = len;
275	+	}
276	+
277		/**
278	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
215	<	* specified collection.  The priority queue has an initial
216	<	* capacity of 110% of the size of the specified collection or 1
217	<	* if the collection is empty.  This priority queue will be sorted
218	<	* according to the same comparator as the given collection, or
219	<	* according to its elements' natural order if the collection is
220	<	* sorted according to its elements' natural order.
278	>	* Initializes queue array with elements from the given Collection.
279		*
280	<	* @param c the collection whose elements are to be placed
223	<	*        into this priority queue.
224	<	* @throws ClassCastException if elements of the specified collection
225	<	*         cannot be compared to one another according to the priority
226	<	*         queue's ordering.
227	<	* @throws NullPointerException if <tt>c</tt> or any element within it
228	<	* is <tt>null</tt>
280	>	* @param c the collection
281		*/
282	<	public PriorityQueue(PriorityQueue<? extends E> c) {
283	<	initializeArray(c);
284	<	comparator = (Comparator<? super E>)c.comparator();
233	<	fillFromSorted(c);
282	>	private void initFromCollection(Collection<? extends E> c) {
283	>	initElementsFromCollection(c);
284	>	heapify();
285		}
286
287		/**
288	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
238	<	* specified collection.  The priority queue has an initial
239	<	* capacity of 110% of the size of the specified collection or 1
240	<	* if the collection is empty.  This priority queue will be sorted
241	<	* according to the same comparator as the given collection, or
242	<	* according to its elements' natural order if the collection is
243	<	* sorted according to its elements' natural order.
288	>	* Increases the capacity of the array.
289		*
290	<	* @param c the collection whose elements are to be placed
246	<	*        into this priority queue.
247	<	* @throws ClassCastException if elements of the specified collection
248	<	*         cannot be compared to one another according to the priority
249	<	*         queue's ordering.
250	<	* @throws NullPointerException if <tt>c</tt> or any element within it
251	<	* is <tt>null</tt>
290	>	* @param minCapacity the desired minimum capacity
291		*/
292	<	public PriorityQueue(SortedSet<? extends E> c) {
293	<	initializeArray(c);
294	<	comparator = (Comparator<? super E>)c.comparator();
295	<	fillFromSorted(c);
292	>	private void grow(int minCapacity) {
293	>	int oldCapacity = queue.length;
294	>	// Double size if small; else grow by 50%
295	>	int newCapacity = ArraysSupport.newLength(oldCapacity,
296	>	minCapacity - oldCapacity, /* minimum growth */
297	>	oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1
298	>	/* preferred growth */);
299	>	queue = Arrays.copyOf(queue, newCapacity);
300		}
301
302		/**
303	<	* Resize array, if necessary, to be able to hold given index
303	>	* Inserts the specified element into this priority queue.
304	>	*
305	>	* @return {@code true} (as specified by {@link Collection#add})
306	>	* @throws ClassCastException if the specified element cannot be
307	>	*         compared with elements currently in this priority queue
308	>	*         according to the priority queue's ordering
309	>	* @throws NullPointerException if the specified element is null
310		*/
311	<	private void grow(int index) {
312	<	int newlen = queue.length;
264	<	if (index < newlen) // don't need to grow
265	<	return;
266	<	if (index == Integer.MAX_VALUE)
267	<	throw new OutOfMemoryError();
268	<	while (newlen <= index) {
269	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
270	<	newlen = Integer.MAX_VALUE;
271	<	else
272	<	newlen <<= 2;
273	<	}
274	<	Object[] newQueue = new Object[newlen];
275	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
276	<	queue = newQueue;
311	>	public boolean add(E e) {
312	>	return offer(e);
313		}
278	–
279	–
280	–	// Queue Methods
314
315		/**
316	<	* Add the specified element to this priority queue.
316	>	* Inserts the specified element into this priority queue.
317		*
318	<	* @return <tt>true</tt>
319	<	* @throws ClassCastException if the specified element cannot be compared
320	<	* with elements currently in the priority queue according
321	<	* to the priority queue's ordering.
322	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
318	>	* @return {@code true} (as specified by {@link Queue#offer})
319	>	* @throws ClassCastException if the specified element cannot be
320	>	*         compared with elements currently in this priority queue
321	>	*         according to the priority queue's ordering
322	>	* @throws NullPointerException if the specified element is null
323		*/
324	<	public boolean offer(E o) {
325	<	if (o == null)
324	>	public boolean offer(E e) {
325	>	if (e == null)
326		throw new NullPointerException();
327		modCount++;
328	<	++size;
329	<
330	<	// Grow backing store if necessary
331	<	if (size >= queue.length)
332	<	grow(size);
300	<
301	<	queue[size] = o;
302	<	fixUp(size);
328	>	int i = size;
329	>	if (i >= queue.length)
330	>	grow(i + 1);
331	>	siftUp(i, e);
332	>	size = i + 1;
333		return true;
334		}
335
336	<	public E poll() {
337	<	if (size == 0)
308	<	return null;
309	<	return remove();
336	>	public E peek() {
337	>	return (E) queue[0];
338		}
339
340	<	public E peek() {
341	<	return (E) queue[1];
340	>	private int indexOf(Object o) {
341	>	if (o != null) {
342	>	final Object[] es = queue;
343	>	for (int i = 0, n = size; i < n; i++)
344	>	if (o.equals(es[i]))
345	>	return i;
346	>	}
347	>	return -1;
348		}
349
350	<	// Collection Methods - the first two override to update docs
350	>	/**
351	>	* Removes a single instance of the specified element from this queue,
352	>	* if it is present.  More formally, removes an element {@code e} such
353	>	* that {@code o.equals(e)}, if this queue contains one or more such
354	>	* elements.  Returns {@code true} if and only if this queue contained
355	>	* the specified element (or equivalently, if this queue changed as a
356	>	* result of the call).
357	>	*
358	>	* @param o element to be removed from this queue, if present
359	>	* @return {@code true} if this queue changed as a result of the call
360	>	*/
361	>	public boolean remove(Object o) {
362	>	int i = indexOf(o);
363	>	if (i == -1)
364	>	return false;
365	>	else {
366	>	removeAt(i);
367	>	return true;
368	>	}
369	>	}
370
371		/**
372	<	* Adds the specified element to this queue.
320	<	* @return <tt>true</tt> (as per the general contract of
321	<	* <tt>Collection.add</tt>).
372	>	* Identity-based version for use in Itr.remove.
373		*
374	<	* @throws NullPointerException {@inheritDoc}
324	<	* @throws ClassCastException if the specified element cannot be compared
325	<	* with elements currently in the priority queue according
326	<	* to the priority queue's ordering.
327	<	*/
328	<	public boolean add(E o) {
329	<	return super.add(o);
330	<	}
331	<
332	<
333	<	/**
334	<	* Adds all of the elements in the specified collection to this queue.
335	<	* The behavior of this operation is undefined if
336	<	* the specified collection is modified while the operation is in
337	<	* progress.  (This implies that the behavior of this call is undefined if
338	<	* the specified collection is this queue, and this queue is nonempty.)
339	<	* <p>
340	<	* This implementation iterates over the specified collection, and adds
341	<	* each object returned by the iterator to this collection, in turn.
342	<	* @throws NullPointerException {@inheritDoc}
343	<	* @throws ClassCastException if any element cannot be compared
344	<	* with elements currently in the priority queue according
345	<	* to the priority queue's ordering.
374	>	* @param o element to be removed from this queue, if present
375		*/
376	<	public boolean addAll(Collection<? extends E> c) {
377	<	return super.addAll(c);
376	>	void removeEq(Object o) {
377	>	final Object[] es = queue;
378	>	for (int i = 0, n = size; i < n; i++) {
379	>	if (o == es[i]) {
380	>	removeAt(i);
381	>	break;
382	>	}
383	>	}
384		}
385
386	+	/**
387	+	* Returns {@code true} if this queue contains the specified element.
388	+	* More formally, returns {@code true} if and only if this queue contains
389	+	* at least one element {@code e} such that {@code o.equals(e)}.
390	+	*
391	+	* @param o object to be checked for containment in this queue
392	+	* @return {@code true} if this queue contains the specified element
393	+	*/
394	+	public boolean contains(Object o) {
395	+	return indexOf(o) >= 0;
396	+	}
397
398		/**
399	<	* Removes a single instance of the specified element from this
400	<	* queue, if it is present.  More formally,
401	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
402	<	* o.equals(e))</tt>, if the queue contains one or more such
403	<	* elements.  Returns <tt>true</tt> if the queue contained the
404	<	* specified element (or equivalently, if the queue changed as a
359	<	* result of the call).
399	>	* Returns an array containing all of the elements in this queue.
400	>	* The elements are in no particular order.
401	>	*
402	>	* <p>The returned array will be "safe" in that no references to it are
403	>	* maintained by this queue.  (In other words, this method must allocate
404	>	* a new array).  The caller is thus free to modify the returned array.
405		*
406	<	* <p>This implementation iterates over the queue looking for the
407	<	* specified element.  If it finds the element, it removes the element
363	<	* from the queue using the iterator's remove method.<p>
406	>	* <p>This method acts as bridge between array-based and collection-based
407	>	* APIs.
408		*
409	+	* @return an array containing all of the elements in this queue
410		*/
411	<	public boolean remove(Object o) {
412	<	if (o == null)
413	<	return false;
411	>	public Object[] toArray() {
412	>	return Arrays.copyOf(queue, size);
413	>	}
414
415	<	if (comparator == null) {
416	<	for (int i = 1; i <= size; i++) {
417	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
418	<	removeAt(i);
419	<	return true;
420	<	}
421	<	}
422	<	} else {
423	<	for (int i = 1; i <= size; i++) {
424	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
425	<	removeAt(i);
426	<	return true;
427	<	}
428	<	}
429	<	}
430	<	return false;
415	>	/**
416	>	* Returns an array containing all of the elements in this queue; the
417	>	* runtime type of the returned array is that of the specified array.
418	>	* The returned array elements are in no particular order.
419	>	* If the queue fits in the specified array, it is returned therein.
420	>	* Otherwise, a new array is allocated with the runtime type of the
421	>	* specified array and the size of this queue.
422	>	*
423	>	* <p>If the queue fits in the specified array with room to spare
424	>	* (i.e., the array has more elements than the queue), the element in
425	>	* the array immediately following the end of the collection is set to
426	>	* {@code null}.
427	>	*
428	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
429	>	* array-based and collection-based APIs.  Further, this method allows
430	>	* precise control over the runtime type of the output array, and may,
431	>	* under certain circumstances, be used to save allocation costs.
432	>	*
433	>	* <p>Suppose {@code x} is a queue known to contain only strings.
434	>	* The following code can be used to dump the queue into a newly
435	>	* allocated array of {@code String}:
436	>	*
437	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
438	>	*
439	>	* Note that {@code toArray(new Object[0])} is identical in function to
440	>	* {@code toArray()}.
441	>	*
442	>	* @param a the array into which the elements of the queue are to
443	>	*          be stored, if it is big enough; otherwise, a new array of the
444	>	*          same runtime type is allocated for this purpose.
445	>	* @return an array containing all of the elements in this queue
446	>	* @throws ArrayStoreException if the runtime type of the specified array
447	>	*         is not a supertype of the runtime type of every element in
448	>	*         this queue
449	>	* @throws NullPointerException if the specified array is null
450	>	*/
451	>	public <T> T[] toArray(T[] a) {
452	>	final int size = this.size;
453	>	if (a.length < size)
454	>	// Make a new array of a's runtime type, but my contents:
455	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
456	>	System.arraycopy(queue, 0, a, 0, size);
457	>	if (a.length > size)
458	>	a[size] = null;
459	>	return a;
460		}
461
462		/**
463		* Returns an iterator over the elements in this queue. The iterator
464		* does not return the elements in any particular order.
465		*
466	<	* @return an iterator over the elements in this queue.
466	>	* @return an iterator over the elements in this queue
467		*/
468		public Iterator<E> iterator() {
469		return new Itr();
470		}
471
472	<	private class Itr implements Iterator<E> {
399	<
472	>	private final class Itr implements Iterator<E> {
473		/**
474		* Index (into queue array) of element to be returned by
475		* subsequent call to next.
476		*/
477	<	private int cursor = 1;
477	>	private int cursor;
478
479		/**
480		* Index of element returned by most recent call to next,
481		* unless that element came from the forgetMeNot list.
482	<	* Reset to 0 if element is deleted by a call to remove.
410	<	*/
411	<	private int lastRet = 0;
412	<
413	<	/**
414	<	* The modCount value that the iterator believes that the backing
415	<	* List should have.  If this expectation is violated, the iterator
416	<	* has detected concurrent modification.
482	>	* Set to -1 if element is deleted by a call to remove.
483		*/
484	<	private int expectedModCount = modCount;
484	>	private int lastRet = -1;
485
486		/**
487	<	* A list of elements that were moved from the unvisited portion of
487	>	* A queue of elements that were moved from the unvisited portion of
488		* the heap into the visited portion as a result of "unlucky" element
489		* removals during the iteration.  (Unlucky element removals are those
490	<	* that require a fixup instead of a fixdown.)  We must visit all of
490	>	* that require a siftup instead of a siftdown.)  We must visit all of
491		* the elements in this list to complete the iteration.  We do this
492		* after we've completed the "normal" iteration.
493		*
494		* We expect that most iterations, even those involving removals,
495	<	* will not use need to store elements in this field.
495	>	* will not need to store elements in this field.
496		*/
497	<	private ArrayList<E> forgetMeNot = null;
497	>	private ArrayDeque<E> forgetMeNot;
498
499		/**
500		* Element returned by the most recent call to next iff that
501		* element was drawn from the forgetMeNot list.
502		*/
503	<	private Object lastRetElt = null;
503	>	private E lastRetElt;
504	>
505	>	/**
506	>	* The modCount value that the iterator believes that the backing
507	>	* Queue should have.  If this expectation is violated, the iterator
508	>	* has detected concurrent modification.
509	>	*/
510	>	private int expectedModCount = modCount;
511	>
512	>	Itr() {}                        // prevent access constructor creation
513
514		public boolean hasNext() {
515	<	return cursor <= size || forgetMeNot != null;
515	>	return cursor < size ||
516	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
517		}
518
519		public E next() {
520	<	checkForComodification();
521	<	E result;
522	<	if (cursor <= size) {
523	<	result = (E) queue[cursor];
524	<	lastRet = cursor++;
525	<	}
526	<	else if (forgetMeNot == null)
527	<	throw new NoSuchElementException();
528	<	else {
453	<	int remaining = forgetMeNot.size();
454	<	result = forgetMeNot.remove(remaining - 1);
455	<	if (remaining == 1)
456	<	forgetMeNot = null;
457	<	lastRet = 0;
458	<	lastRetElt = result;
520	>	if (expectedModCount != modCount)
521	>	throw new ConcurrentModificationException();
522	>	if (cursor < size)
523	>	return (E) queue[lastRet = cursor++];
524	>	if (forgetMeNot != null) {
525	>	lastRet = -1;
526	>	lastRetElt = forgetMeNot.poll();
527	>	if (lastRetElt != null)
528	>	return lastRetElt;
529		}
530	<	return result;
530	>	throw new NoSuchElementException();
531		}
532
533		public void remove() {
534	<	checkForComodification();
535	<
536	<	if (lastRet != 0) {
534	>	if (expectedModCount != modCount)
535	>	throw new ConcurrentModificationException();
536	>	if (lastRet != -1) {
537		E moved = PriorityQueue.this.removeAt(lastRet);
538	<	lastRet = 0;
539	<	if (moved == null) {
538	>	lastRet = -1;
539	>	if (moved == null)
540		cursor--;
541	<	} else {
541	>	else {
542		if (forgetMeNot == null)
543	<	forgetMeNot = new ArrayList<E>();
543	>	forgetMeNot = new ArrayDeque<>();
544		forgetMeNot.add(moved);
545		}
546		} else if (lastRetElt != null) {
547	<	PriorityQueue.this.remove(lastRetElt);
547	>	PriorityQueue.this.removeEq(lastRetElt);
548		lastRetElt = null;
549		} else {
550		throw new IllegalStateException();
551		}
482	–
552		expectedModCount = modCount;
553		}
485	–
486	–	final void checkForComodification() {
487	–	if (modCount != expectedModCount)
488	–	throw new ConcurrentModificationException();
489	–	}
554		}
555
556		public int size() {
#	Line 494 | Line 558 | public class PriorityQueue<E> extends Ab
558		}
559
560		/**
561	<	* Remove all elements from the priority queue.
561	>	* Removes all of the elements from this priority queue.
562	>	* The queue will be empty after this call returns.
563		*/
564		public void clear() {
565		modCount++;
566	<
567	<	// Null out element references to prevent memory leak
568	<	for (int i=1; i<=size; i++)
504	<	queue[i] = null;
505	<
566	>	final Object[] es = queue;
567	>	for (int i = 0, n = size; i < n; i++)
568	>	es[i] = null;
569		size = 0;
570		}
571
572	<	/**
573	<	* Removes and returns the first element from queue.
574	<	*/
512	<	public E remove() {
513	<	if (size == 0)
514	<	throw new NoSuchElementException();
515	<	modCount++;
516	<
517	<	E result = (E) queue[1];
518	<	queue[1] = queue[size];
519	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
520	<	if (size > 1)
521	<	fixDown(1);
572	>	public E poll() {
573	>	final Object[] es;
574	>	final E result;
575
576	+	if ((result = (E) ((es = queue)[0])) != null) {
577	+	modCount++;
578	+	final int n;
579	+	final E x = (E) es[(n = --size)];
580	+	es[n] = null;
581	+	if (n > 0) {
582	+	final Comparator<? super E> cmp;
583	+	if ((cmp = comparator) == null)
584	+	siftDownComparable(0, x, es, n);
585	+	else
586	+	siftDownUsingComparator(0, x, es, n, cmp);
587	+	}
588	+	}
589		return result;
590		}
591
592		/**
593	<	* Removes and returns the ith element from queue.  (Recall that queue
528	<	* is one-based, so 1 <= i <= size.)
593	>	* Removes the ith element from queue.
594		*
595	<	* Normally this method leaves the elements at positions from 1 up to i-1,
596	<	* inclusive, untouched.  Under these circumstances, it returns null.
597	<	* Occasionally, in order to maintain the heap invariant, it must move
598	<	* the last element of the list to some index in the range [2, i-1],
599	<	* and move the element previously at position (i/2) to position i.
600	<	* Under these circumstances, this method returns the element that was
601	<	* previously at the end of the list and is now at some position between
602	<	* 2 and i-1 inclusive.
603	<	*/
604	<	private E removeAt(int i) {
605	<	assert i > 0 && i <= size;
595	>	* Normally this method leaves the elements at up to i-1,
596	>	* inclusive, untouched.  Under these circumstances, it returns
597	>	* null.  Occasionally, in order to maintain the heap invariant,
598	>	* it must swap a later element of the list with one earlier than
599	>	* i.  Under these circumstances, this method returns the element
600	>	* that was previously at the end of the list and is now at some
601	>	* position before i. This fact is used by iterator.remove so as to
602	>	* avoid missing traversing elements.
603	>	*/
604	>	E removeAt(int i) {
605	>	// assert i >= 0 && i < size;
606	>	final Object[] es = queue;
607		modCount++;
608	<
609	<	E moved = (E) queue[size];
610	<	queue[i] = moved;
611	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
612	<	if (i <= size) {
613	<	fixDown(i);
614	<	if (queue[i] == moved) {
615	<	fixUp(i);
616	<	if (queue[i] != moved)
608	>	int s = --size;
609	>	if (s == i) // removed last element
610	>	es[i] = null;
611	>	else {
612	>	E moved = (E) es[s];
613	>	es[s] = null;
614	>	siftDown(i, moved);
615	>	if (es[i] == moved) {
616	>	siftUp(i, moved);
617	>	if (es[i] != moved)
618		return moved;
619		}
620		}
#	Line 555 | Line 622 | public class PriorityQueue<E> extends Ab
622		}
623
624		/**
625	<	* Establishes the heap invariant (described above) assuming the heap
626	<	* satisfies the invariant except possibly for the leaf-node indexed by k
627	<	* (which may have a nextExecutionTime less than its parent's).
628	<	*
629	<	* This method functions by "promoting" queue[k] up the hierarchy
630	<	* (by swapping it with its parent) repeatedly until queue[k]
631	<	* is greater than or equal to its parent.
632	<	*/
633	<	private void fixUp(int k) {
634	<	if (comparator == null) {
635	<	while (k > 1) {
636	<	int j = k >> 1;
637	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
638	<	break;
639	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
640	<	k = j;
641	<	}
642	<	} else {
643	<	while (k > 1) {
644	<	int j = k >>> 1;
645	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
646	<	break;
647	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
648	<	k = j;
649	<	}
625	>	* Inserts item x at position k, maintaining heap invariant by
626	>	* promoting x up the tree until it is greater than or equal to
627	>	* its parent, or is the root.
628	>	*
629	>	* To simplify and speed up coercions and comparisons, the
630	>	* Comparable and Comparator versions are separated into different
631	>	* methods that are otherwise identical. (Similarly for siftDown.)
632	>	*
633	>	* @param k the position to fill
634	>	* @param x the item to insert
635	>	*/
636	>	private void siftUp(int k, E x) {
637	>	if (comparator != null)
638	>	siftUpUsingComparator(k, x, queue, comparator);
639	>	else
640	>	siftUpComparable(k, x, queue);
641	>	}
642	>
643	>	private static <T> void siftUpComparable(int k, T x, Object[] es) {
644	>	Comparable<? super T> key = (Comparable<? super T>) x;
645	>	while (k > 0) {
646	>	int parent = (k - 1) >>> 1;
647	>	Object e = es[parent];
648	>	if (key.compareTo((T) e) >= 0)
649	>	break;
650	>	es[k] = e;
651	>	k = parent;
652		}
653	+	es[k] = key;
654	+	}
655	+
656	+	private static <T> void siftUpUsingComparator(
657	+	int k, T x, Object[] es, Comparator<? super T> cmp) {
658	+	while (k > 0) {
659	+	int parent = (k - 1) >>> 1;
660	+	Object e = es[parent];
661	+	if (cmp.compare(x, (T) e) >= 0)
662	+	break;
663	+	es[k] = e;
664	+	k = parent;
665	+	}
666	+	es[k] = x;
667		}
668
669		/**
670	<	* Establishes the heap invariant (described above) in the subtree
671	<	* rooted at k, which is assumed to satisfy the heap invariant except
672	<	* possibly for node k itself (which may be greater than its children).
673	<	*
674	<	* This method functions by "demoting" queue[k] down the hierarchy
675	<	* (by swapping it with its smaller child) repeatedly until queue[k]
676	<	* is less than or equal to its children.
677	<	*/
678	<	private void fixDown(int k) {
679	<	int j;
680	<	if (comparator == null) {
681	<	while ((j = k << 1) <= size && (j > 0)) {
682	<	if (j<size &&
683	<	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
684	<	j++; // j indexes smallest kid
685	<
686	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
687	<	break;
688	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
689	<	k = j;
690	<	}
691	<	} else {
692	<	while ((j = k << 1) <= size && (j > 0)) {
693	<	if (j<size &&
694	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
695	<	j++; // j indexes smallest kid
696	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
697	<	break;
698	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
699	<	k = j;
700	<	}
670	>	* Inserts item x at position k, maintaining heap invariant by
671	>	* demoting x down the tree repeatedly until it is less than or
672	>	* equal to its children or is a leaf.
673	>	*
674	>	* @param k the position to fill
675	>	* @param x the item to insert
676	>	*/
677	>	private void siftDown(int k, E x) {
678	>	if (comparator != null)
679	>	siftDownUsingComparator(k, x, queue, size, comparator);
680	>	else
681	>	siftDownComparable(k, x, queue, size);
682	>	}
683	>
684	>	private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
685	>	// assert n > 0;
686	>	Comparable<? super T> key = (Comparable<? super T>)x;
687	>	int half = n >>> 1;           // loop while a non-leaf
688	>	while (k < half) {
689	>	int child = (k << 1) + 1; // assume left child is least
690	>	Object c = es[child];
691	>	int right = child + 1;
692	>	if (right < n &&
693	>	((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
694	>	c = es[child = right];
695	>	if (key.compareTo((T) c) <= 0)
696	>	break;
697	>	es[k] = c;
698	>	k = child;
699	>	}
700	>	es[k] = key;
701	>	}
702	>
703	>	private static <T> void siftDownUsingComparator(
704	>	int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
705	>	// assert n > 0;
706	>	int half = n >>> 1;
707	>	while (k < half) {
708	>	int child = (k << 1) + 1;
709	>	Object c = es[child];
710	>	int right = child + 1;
711	>	if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
712	>	c = es[child = right];
713	>	if (cmp.compare(x, (T) c) <= 0)
714	>	break;
715	>	es[k] = c;
716	>	k = child;
717		}
718	+	es[k] = x;
719		}
720
721		/**
722		* Establishes the heap invariant (described above) in the entire tree,
723		* assuming nothing about the order of the elements prior to the call.
724	+	* This classic algorithm due to Floyd (1964) is known to be O(size).
725		*/
726		private void heapify() {
727	<	for (int i = size/2; i >= 1; i--)
728	<	fixDown(i);
727	>	final Object[] es = queue;
728	>	int n = size, i = (n >>> 1) - 1;
729	>	final Comparator<? super E> cmp;
730	>	if ((cmp = comparator) == null)
731	>	for (; i >= 0; i--)
732	>	siftDownComparable(i, (E) es[i], es, n);
733	>	else
734	>	for (; i >= 0; i--)
735	>	siftDownUsingComparator(i, (E) es[i], es, n, cmp);
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>).
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.
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 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
644	<	* is, serialize it).
752	>	* Saves this queue to a stream (that is, serializes it).
753		*
646	–	* @serialData The length of the array backing the instance is
647	–	* emitted (int), followed by all of its elements (each an
648	–	* <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	+	// OPENJDK @java.io.Serial
761		private void writeObject(java.io.ObjectOutputStream s)
762	<	throws java.io.IOException{
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	+	// OPENJDK @java.io.Serial
785		private void readObject(java.io.ObjectInputStream s)
786		throws java.io.IOException, ClassNotFoundException {
787		// Read in size, and any hidden stuff
788		s.defaultReadObject();
789
790	<	// Read in array length and allocate array
791	<	int arrayLength = s.readInt();
792	<	queue = new Object[arrayLength];
793	<
794	<	// Read in all elements in the proper order.
795	<	for (int i=0; i<size; i++)
796	<	queue[i] = (E) s.readObject();
790	>	// Read in (and discard) array length
791	>	s.readInt();
792	>
793	>	jsr166.Platform.checkArray(s, Object[].class, size);
794	>	final Object[] es = queue = new Object[Math.max(size, 1)];
795	>
796	>	// Read in all elements.
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	+	/**
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 boolean removeIf(Predicate<? super E> filter) {
895	+	Objects.requireNonNull(filter);
896	+	return bulkRemove(filter);
897	+	}
898	+
899	+	/**
900	+	* @throws NullPointerException {@inheritDoc}
901	+	*/
902	+	public boolean removeAll(Collection<?> c) {
903	+	Objects.requireNonNull(c);
904	+	return bulkRemove(e -> c.contains(e));
905	+	}
906	+
907	+	/**
908	+	* @throws NullPointerException {@inheritDoc}
909	+	*/
910	+	public boolean retainAll(Collection<?> c) {
911	+	Objects.requireNonNull(c);
912	+	return bulkRemove(e -> !c.contains(e));
913	+	}
914	+
915	+	// A tiny bit set implementation
916	+
917	+	private static long[] nBits(int n) {
918	+	return new long[((n - 1) >> 6) + 1];
919	+	}
920	+	private static void setBit(long[] bits, int i) {
921	+	bits[i >> 6] |= 1L << i;
922	+	}
923	+	private static boolean isClear(long[] bits, int i) {
924	+	return (bits[i >> 6] & (1L << i)) == 0;
925	+	}
926	+
927	+	/** Implementation of bulk remove methods. */
928	+	private boolean bulkRemove(Predicate<? super E> filter) {
929	+	final int expectedModCount = ++modCount;
930	+	final Object[] es = queue;
931	+	final int end = size;
932	+	int i;
933	+	// Optimize for initial run of survivors
934	+	for (i = 0; i < end && !filter.test((E) es[i]); i++)
935	+	;
936	+	if (i >= end) {
937	+	if (modCount != expectedModCount)
938	+	throw new ConcurrentModificationException();
939	+	return false;
940	+	}
941	+	// Tolerate predicates that reentrantly access the collection for
942	+	// read (but writers still get CME), so traverse once to find
943	+	// elements to delete, a second pass to physically expunge.
944	+	final int beg = i;
945	+	final long[] deathRow = nBits(end - beg);
946	+	deathRow[0] = 1L;   // set bit 0
947	+	for (i = beg + 1; i < end; i++)
948	+	if (filter.test((E) es[i]))
949	+	setBit(deathRow, i - beg);
950	+	if (modCount != expectedModCount)
951	+	throw new ConcurrentModificationException();
952	+	int w = beg;
953	+	for (i = beg; i < end; i++)
954	+	if (isClear(deathRow, i - beg))
955	+	es[w++] = es[i];
956	+	for (i = size = w; i < end; i++)
957	+	es[i] = null;
958	+	heapify();
959	+	return true;
960	+	}
961	+
962	+	/**
963	+	* @throws NullPointerException {@inheritDoc}
964	+	*/
965	+	public void forEach(Consumer<? super E> action) {
966	+	Objects.requireNonNull(action);
967	+	final int expectedModCount = modCount;
968	+	final Object[] es = queue;
969	+	for (int i = 0, n = size; i < n; i++)
970	+	action.accept((E) es[i]);
971	+	if (expectedModCount != modCount)
972	+	throw new ConcurrentModificationException();
973	+	}
974		}

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