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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.23 by dholmes, Wed Aug 6 01:57:53 2003 UTC vs.
Revision 1.132 by jsr166, Fri Aug 30 18:05:39 2019 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
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	>	* 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
36	<	* elements according to an order specified at construction time, which is
37	<	* specified in the same manner as {@link java.util.TreeSet} and
38	<	* {@link java.util.TreeMap}: elements are ordered
39	<	* either according to their <i>natural order</i> (see {@link Comparable}), or
40	<	* according to a {@link java.util.Comparator}, depending on which
41	<	* constructor is used.
42	<	* <p>The <em>head</em> of this queue is the <em>least</em> element with
43	<	* respect to the specified ordering.
44	<	* If multiple elements are tied for least value, the
45	<	* head is one of those elements. A priority queue does not permit
46	<	* <tt>null</tt> elements.
47	<	*
48	<	* <p>The {@link #remove()} and {@link #poll()} methods remove and
49	<	* return the head of the queue.
50	<	*
51	<	* <p>The {@link #element()} and {@link #peek()} methods return, but do
52	<	* not delete, the head of the queue.
53	<	*
54	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
55	<	* size of the array used internally to store the elements on the
56	<	* queue.
57	<	* It is always at least as large as the queue size.  As
58	<	* elements are added to a priority queue, its capacity grows
59	<	* automatically.  The details of the growth policy are not specified.
60	<	*
61	<	* <p>Implementation note: this implementation provides O(log(n)) time
62	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
63	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
64	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
65	<	* constant time for the retrieval methods (<tt>peek</tt>,
66	<	* <tt>element</tt>, and <tt>size</tt>).
34	>	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
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	>	* <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	<	* @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	<	*
56	<	* The element with the lowest value is in queue[1], assuming the queue is
57	<	* nonempty.  (A one-based array is used in preference to the traditional
58	<	* zero-based array to simplify parent and child calculations.)
59	<	*
60	<	* 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'
#	Line 76 | Line 117 | public class PriorityQueue<E> extends Ab
117		* The number of times this priority queue has been
118		* <i>structurally modified</i>.  See AbstractList for gory details.
119		*/
120	<	private transient int modCount = 0;
120	>	transient int modCount;     // non-private to simplify nested class access
121
122		/**
123	<	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
124	<	* (11) that orders its elements according to their natural
125	<	* ordering (using <tt>Comparable</tt>.)
123	>	* Creates a {@code PriorityQueue} with the default initial
124	>	* capacity (11) that orders its elements according to their
125	>	* {@linkplain Comparable natural ordering}.
126		*/
127		public PriorityQueue() {
128		this(DEFAULT_INITIAL_CAPACITY, null);
129		}
130
131		/**
132	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
133	<	* that orders its elements according to their natural ordering
134	<	* (using <tt>Comparable</tt>.)
135	<	*
136	<	* @param initialCapacity the initial capacity for this priority queue.
137	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
138	<	* than 1
132	>	* Creates a {@code PriorityQueue} with the specified initial
133	>	* capacity that orders its elements according to their
134	>	* {@linkplain Comparable natural ordering}.
135	>	*
136	>	* @param initialCapacity the initial capacity for this priority queue
137	>	* @throws IllegalArgumentException if {@code initialCapacity} is less
138	>	*         than 1
139		*/
140		public PriorityQueue(int initialCapacity) {
141		this(initialCapacity, null);
142		}
143
144		/**
145	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
145	>	* Creates a {@code PriorityQueue} with the default initial capacity and
146	>	* whose elements are ordered according to the specified comparator.
147	>	*
148	>	* @param  comparator the comparator that will be used to order this
149	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
150	>	*         natural ordering} of the elements will be used.
151	>	* @since 1.8
152	>	*/
153	>	public PriorityQueue(Comparator<? super E> comparator) {
154	>	this(DEFAULT_INITIAL_CAPACITY, comparator);
155	>	}
156	>
157	>	/**
158	>	* Creates a {@code PriorityQueue} with the specified initial capacity
159		* that orders its elements according to the specified comparator.
160		*
161	<	* @param initialCapacity the initial capacity for this priority queue.
162	<	* @param comparator the comparator used to order this priority queue.
163	<	* If <tt>null</tt> then the order depends on the elements' natural
164	<	* ordering.
165	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
166	<	* than 1
161	>	* @param  initialCapacity the initial capacity for this priority queue
162	>	* @param  comparator the comparator that will be used to order this
163	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
164	>	*         natural ordering} of the elements will be used.
165	>	* @throws IllegalArgumentException if {@code initialCapacity} is
166	>	*         less than 1
167		*/
168	<	public PriorityQueue(int initialCapacity,
168	>	public PriorityQueue(int initialCapacity,
169		Comparator<? super E> comparator) {
170	+	// Note: This restriction of at least one is not actually needed,
171	+	// but continues for 1.5 compatibility
172		if (initialCapacity < 1)
173		throw new IllegalArgumentException();
174	<	this.queue = new Object[initialCapacity + 1];
174	>	this.queue = new Object[initialCapacity];
175		this.comparator = comparator;
176		}
177
178		/**
179	<	* Common code to initialize underlying queue array across
180	<	* constructors below.
179	>	* Creates a {@code PriorityQueue} containing the elements in the
180	>	* specified collection.  If the specified collection is an instance of
181	>	* a {@link SortedSet} or is another {@code PriorityQueue}, this
182	>	* priority queue will be ordered according to the same ordering.
183	>	* Otherwise, this priority queue will be ordered according to the
184	>	* {@linkplain Comparable natural ordering} of its elements.
185	>	*
186	>	* @param  c the collection whose elements are to be placed
187	>	*         into this priority queue
188	>	* @throws ClassCastException if elements of the specified collection
189	>	*         cannot be compared to one another according to the priority
190	>	*         queue's ordering
191	>	* @throws NullPointerException if the specified collection or any
192	>	*         of its elements are null
193		*/
194	<	private void initializeArray(Collection<? extends E> c) {
195	<	int sz = c.size();
196	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
197	<	Integer.MAX_VALUE - 1);
198	<	if (initialCapacity < 1)
199	<	initialCapacity = 1;
200	<
201	<	this.queue = new Object[initialCapacity + 1];
194	>	public PriorityQueue(Collection<? extends E> c) {
195	>	if (c instanceof SortedSet<?>) {
196	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
197	>	this.comparator = (Comparator<? super E>) ss.comparator();
198	>	initElementsFromCollection(ss);
199	>	}
200	>	else if (c instanceof PriorityQueue<?>) {
201	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
202	>	this.comparator = (Comparator<? super E>) pq.comparator();
203	>	initFromPriorityQueue(pq);
204	>	}
205	>	else {
206	>	this.comparator = null;
207	>	initFromCollection(c);
208	>	}
209		}
210
211		/**
212	<	* Initially fill elements of the queue array under the
213	<	* knowledge that it is sorted or is another PQ, in which
214	<	* case we can just place the elements without fixups.
212	>	* Creates a {@code PriorityQueue} containing the elements in the
213	>	* specified priority queue.  This priority queue will be
214	>	* ordered according to the same ordering as the given priority
215	>	* queue.
216	>	*
217	>	* @param  c the priority queue whose elements are to be placed
218	>	*         into this priority queue
219	>	* @throws ClassCastException if elements of {@code c} cannot be
220	>	*         compared to one another according to {@code c}'s
221	>	*         ordering
222	>	* @throws NullPointerException if the specified priority queue or any
223	>	*         of its elements are null
224		*/
225	<	private void fillFromSorted(Collection<? extends E> c) {
226	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
227	<	queue[++size] = i.next();
225	>	public PriorityQueue(PriorityQueue<? extends E> c) {
226	>	this.comparator = (Comparator<? super E>) c.comparator();
227	>	initFromPriorityQueue(c);
228		}
229
146	–
230		/**
231	<	* Initially fill elements of the queue array that is
232	<	* not to our knowledge sorted, so we must add them
233	<	* one by one.
231	>	* Creates a {@code PriorityQueue} containing the elements in the
232	>	* specified sorted set.   This priority queue will be ordered
233	>	* according to the same ordering as the given sorted set.
234	>	*
235	>	* @param  c the sorted set whose elements are to be placed
236	>	*         into this priority queue
237	>	* @throws ClassCastException if elements of the specified sorted
238	>	*         set cannot be compared to one another according to the
239	>	*         sorted set's ordering
240	>	* @throws NullPointerException if the specified sorted set or any
241	>	*         of its elements are null
242		*/
243	<	private void fillFromUnsorted(Collection<? extends E> c) {
244	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
245	<	add(i.next());
243	>	public PriorityQueue(SortedSet<? extends E> c) {
244	>	this.comparator = (Comparator<? super E>) c.comparator();
245	>	initElementsFromCollection(c);
246		}
247
248	<	/**
249	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
250	<	* specified collection.  The priority queue has an initial
251	<	* capacity of 110% of the size of the specified collection or 1
252	<	* if the collection is empty.  If the specified collection is an
253	<	* instance of a {@link SortedSet} or is another
254	<	* <tt>PriorityQueue</tt>, the priority queue will be sorted
255	<	* according to the same comparator, or according to its elements'
256	<	* natural order if the collection is sorted according to its
257	<	* elements' natural order.  Otherwise, the priority queue is
258	<	* ordered according to its elements' natural order.
168	<	*
169	<	* @param c the collection whose elements are to be placed
170	<	*        into this priority queue.
171	<	* @throws ClassCastException if elements of the specified collection
172	<	*         cannot be compared to one another according to the priority
173	<	*         queue's ordering.
174	<	* @throws NullPointerException if <tt>c</tt> or any element within it
175	<	* is <tt>null</tt>
176	<	*/
177	<	public PriorityQueue(Collection<? extends E> c) {
178	<	initializeArray(c);
179	<	if (c instanceof SortedSet<? extends E>) {
180	<	SortedSet<? extends E> s = (SortedSet<? extends E>) c;
181	<	comparator = (Comparator<? super E>)s.comparator();
182	<	fillFromSorted(s);
183	<	}
184	<	else if (c instanceof PriorityQueue<? extends E>) {
185	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
186	<	comparator = (Comparator<? super E>)s.comparator();
187	<	fillFromSorted(s);
188	<	}
189	<	else {
190	<	comparator = null;
191	<	fillFromUnsorted(c);
248	>	/** Ensures that queue[0] exists, helping peek() and poll(). */
249	>	private static Object[] ensureNonEmpty(Object[] es) {
250	>	return (es.length > 0) ? es : new Object[1];
251	>	}
252	>
253	>	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
254	>	if (c.getClass() == PriorityQueue.class) {
255	>	this.queue = ensureNonEmpty(c.toArray());
256	>	this.size = c.size();
257	>	} else {
258	>	initFromCollection(c);
259		}
260		}
261
262	+	private void initElementsFromCollection(Collection<? extends E> c) {
263	+	Object[] es = c.toArray();
264	+	int len = es.length;
265	+	// If c.toArray incorrectly doesn't return Object[], copy it.
266	+	if (es.getClass() != Object[].class)
267	+	es = Arrays.copyOf(es, len, Object[].class);
268	+	if (len == 1 || this.comparator != null)
269	+	for (Object e : es)
270	+	if (e == null)
271	+	throw new NullPointerException();
272	+	this.queue = ensureNonEmpty(es);
273	+	this.size = len;
274	+	}
275	+
276		/**
277	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
197	<	* specified collection.  The priority queue has an initial
198	<	* capacity of 110% of the size of the specified collection or 1
199	<	* if the collection is empty.  This priority queue will be sorted
200	<	* according to the same comparator as the given collection, or
201	<	* according to its elements' natural order if the collection is
202	<	* sorted according to its elements' natural order.
277	>	* Initializes queue array with elements from the given Collection.
278		*
279	<	* @param c the collection whose elements are to be placed
205	<	*        into this priority queue.
206	<	* @throws ClassCastException if elements of the specified collection
207	<	*         cannot be compared to one another according to the priority
208	<	*         queue's ordering.
209	<	* @throws NullPointerException if <tt>c</tt> or any element within it
210	<	* is <tt>null</tt>
279	>	* @param c the collection
280		*/
281	<	public PriorityQueue(PriorityQueue<? extends E> c) {
282	<	initializeArray(c);
283	<	comparator = (Comparator<? super E>)c.comparator();
215	<	fillFromSorted(c);
281	>	private void initFromCollection(Collection<? extends E> c) {
282	>	initElementsFromCollection(c);
283	>	heapify();
284		}
285
286		/**
287	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
220	<	* specified collection.  The priority queue has an initial
221	<	* capacity of 110% of the size of the specified collection or 1
222	<	* if the collection is empty.  This priority queue will be sorted
223	<	* according to the same comparator as the given collection, or
224	<	* according to its elements' natural order if the collection is
225	<	* sorted according to its elements' natural order.
287	>	* Increases the capacity of the array.
288		*
289	<	* @param c the collection whose elements are to be placed
228	<	*        into this priority queue.
229	<	* @throws ClassCastException if elements of the specified collection
230	<	*         cannot be compared to one another according to the priority
231	<	*         queue's ordering.
232	<	* @throws NullPointerException if <tt>c</tt> or any element within it
233	<	* is <tt>null</tt>
289	>	* @param minCapacity the desired minimum capacity
290		*/
291	<	public PriorityQueue(SortedSet<? extends E> c) {
292	<	initializeArray(c);
293	<	comparator = (Comparator<? super E>)c.comparator();
294	<	fillFromSorted(c);
291	>	private void grow(int minCapacity) {
292	>	int oldCapacity = queue.length;
293	>	// Double size if small; else grow by 50%
294	>	int newCapacity = ArraysSupport.newLength(oldCapacity,
295	>	minCapacity - oldCapacity, /* minimum growth */
296	>	oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1
297	>	/* preferred growth */);
298	>	queue = Arrays.copyOf(queue, newCapacity);
299		}
300
301		/**
302	<	* Resize array, if necessary, to be able to hold given index
302	>	* Inserts the specified element into this priority queue.
303	>	*
304	>	* @return {@code true} (as specified by {@link Collection#add})
305	>	* @throws ClassCastException if the specified element cannot be
306	>	*         compared with elements currently in this priority queue
307	>	*         according to the priority queue's ordering
308	>	* @throws NullPointerException if the specified element is null
309		*/
310	<	private void grow(int index) {
311	<	int newlen = queue.length;
246	<	if (index < newlen) // don't need to grow
247	<	return;
248	<	if (index == Integer.MAX_VALUE)
249	<	throw new OutOfMemoryError();
250	<	while (newlen <= index) {
251	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
252	<	newlen = Integer.MAX_VALUE;
253	<	else
254	<	newlen <<= 2;
255	<	}
256	<	Object[] newQueue = new Object[newlen];
257	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
258	<	queue = newQueue;
310	>	public boolean add(E e) {
311	>	return offer(e);
312		}
260	–
261	–	// Queue Methods
262	–
263	–
313
314		/**
315	<	* Add the specified element to this priority queue.
315	>	* Inserts the specified element into this priority queue.
316		*
317	<	* @return <tt>true</tt>
318	<	* @throws ClassCastException if the specified element cannot be compared
319	<	* with elements currently in the priority queue according
320	<	* to the priority queue's ordering.
321	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
317	>	* @return {@code true} (as specified by {@link Queue#offer})
318	>	* @throws ClassCastException if the specified element cannot be
319	>	*         compared with elements currently in this priority queue
320	>	*         according to the priority queue's ordering
321	>	* @throws NullPointerException if the specified element is null
322		*/
323	<	public boolean offer(E o) {
324	<	if (o == null)
323	>	public boolean offer(E e) {
324	>	if (e == null)
325		throw new NullPointerException();
326		modCount++;
327	<	++size;
328	<
329	<	// Grow backing store if necessary
330	<	if (size >= queue.length)
331	<	grow(size);
283	<
284	<	queue[size] = o;
285	<	fixUp(size);
327	>	int i = size;
328	>	if (i >= queue.length)
329	>	grow(i + 1);
330	>	siftUp(i, e);
331	>	size = i + 1;
332		return true;
333		}
334
335	<	public E poll() {
336	<	if (size == 0)
291	<	return null;
292	<	return (E) remove(1);
335	>	public E peek() {
336	>	return (E) queue[0];
337		}
338
339	<	public E peek() {
340	<	return (E) queue[1];
339	>	private int indexOf(Object o) {
340	>	if (o != null) {
341	>	final Object[] es = queue;
342	>	for (int i = 0, n = size; i < n; i++)
343	>	if (o.equals(es[i]))
344	>	return i;
345	>	}
346	>	return -1;
347		}
348
349	<	// Collection Methods - the first two override to update docs
349	>	/**
350	>	* Removes a single instance of the specified element from this queue,
351	>	* if it is present.  More formally, removes an element {@code e} such
352	>	* that {@code o.equals(e)}, if this queue contains one or more such
353	>	* elements.  Returns {@code true} if and only if this queue contained
354	>	* the specified element (or equivalently, if this queue changed as a
355	>	* result of the call).
356	>	*
357	>	* @param o element to be removed from this queue, if present
358	>	* @return {@code true} if this queue changed as a result of the call
359	>	*/
360	>	public boolean remove(Object o) {
361	>	int i = indexOf(o);
362	>	if (i == -1)
363	>	return false;
364	>	else {
365	>	removeAt(i);
366	>	return true;
367	>	}
368	>	}
369
370		/**
371	<	* Adds the specified element to this queue.
303	<	* @return <tt>true</tt> (as per the general contract of
304	<	* <tt>Collection.add</tt>).
371	>	* Identity-based version for use in Itr.remove.
372		*
373	<	* @throws NullPointerException {@inheritDoc}
374	<	* @throws ClassCastException if the specified element cannot be compared
375	<	* with elements currently in the priority queue according
376	<	* to the priority queue's ordering.
377	<	*/
378	<	public boolean add(E o) {
379	<	return super.add(o);
380	<	}
381	<
382	<
316	<	/**
317	<	* Adds all of the elements in the specified collection to this queue.
318	<	* The behavior of this operation is undefined if
319	<	* the specified collection is modified while the operation is in
320	<	* progress.  (This implies that the behavior of this call is undefined if
321	<	* the specified collection is this queue, and this queue is nonempty.)
322	<	* <p>
323	<	* This implementation iterates over the specified collection, and adds
324	<	* each object returned by the iterator to this collection, in turn.
325	<	* @throws NullPointerException {@inheritDoc}
326	<	* @throws ClassCastException if any element cannot be compared
327	<	* with elements currently in the priority queue according
328	<	* to the priority queue's ordering.
329	<	*/
330	<	public boolean addAll(Collection<? extends E> c) {
331	<	return super.addAll(c);
373	>	* @param o element to be removed from this queue, if present
374	>	*/
375	>	void removeEq(Object o) {
376	>	final Object[] es = queue;
377	>	for (int i = 0, n = size; i < n; i++) {
378	>	if (o == es[i]) {
379	>	removeAt(i);
380	>	break;
381	>	}
382	>	}
383		}
384
385	+	/**
386	+	* Returns {@code true} if this queue contains the specified element.
387	+	* More formally, returns {@code true} if and only if this queue contains
388	+	* at least one element {@code e} such that {@code o.equals(e)}.
389	+	*
390	+	* @param o object to be checked for containment in this queue
391	+	* @return {@code true} if this queue contains the specified element
392	+	*/
393	+	public boolean contains(Object o) {
394	+	return indexOf(o) >= 0;
395	+	}
396
397	<	/**
398	<	* Removes a single instance of the specified element from this
399	<	* queue, if it is present.  More formally,
400	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
401	<	* o.equals(e))</tt>, if the queue contains one or more such
402	<	* elements.  Returns <tt>true</tt> if the queue contained the
403	<	* specified element (or equivalently, if the queue changed as a
342	<	* result of the call).
397	>	/**
398	>	* Returns an array containing all of the elements in this queue.
399	>	* The elements are in no particular order.
400	>	*
401	>	* <p>The returned array will be "safe" in that no references to it are
402	>	* maintained by this queue.  (In other words, this method must allocate
403	>	* a new array).  The caller is thus free to modify the returned array.
404		*
405	<	* <p>This implementation iterates over the queue looking for the
406	<	* specified element.  If it finds the element, it removes the element
346	<	* from the queue using the iterator's remove method.<p>
405	>	* <p>This method acts as bridge between array-based and collection-based
406	>	* APIs.
407		*
408	+	* @return an array containing all of the elements in this queue
409		*/
410	<	public boolean remove(Object o) {
411	<	if (o == null)
412	<	return false;
410	>	public Object[] toArray() {
411	>	return Arrays.copyOf(queue, size);
412	>	}
413
414	<	if (comparator == null) {
415	<	for (int i = 1; i <= size; i++) {
416	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
417	<	remove(i);
418	<	return true;
419	<	}
420	<	}
421	<	} else {
422	<	for (int i = 1; i <= size; i++) {
423	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
424	<	remove(i);
425	<	return true;
426	<	}
427	<	}
428	<	}
429	<	return false;
414	>	/**
415	>	* Returns an array containing all of the elements in this queue; the
416	>	* runtime type of the returned array is that of the specified array.
417	>	* The returned array elements are in no particular order.
418	>	* If the queue fits in the specified array, it is returned therein.
419	>	* Otherwise, a new array is allocated with the runtime type of the
420	>	* specified array and the size of this queue.
421	>	*
422	>	* <p>If the queue fits in the specified array with room to spare
423	>	* (i.e., the array has more elements than the queue), the element in
424	>	* the array immediately following the end of the collection is set to
425	>	* {@code null}.
426	>	*
427	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
428	>	* array-based and collection-based APIs.  Further, this method allows
429	>	* precise control over the runtime type of the output array, and may,
430	>	* under certain circumstances, be used to save allocation costs.
431	>	*
432	>	* <p>Suppose {@code x} is a queue known to contain only strings.
433	>	* The following code can be used to dump the queue into a newly
434	>	* allocated array of {@code String}:
435	>	*
436	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
437	>	*
438	>	* Note that {@code toArray(new Object[0])} is identical in function to
439	>	* {@code toArray()}.
440	>	*
441	>	* @param a the array into which the elements of the queue are to
442	>	*          be stored, if it is big enough; otherwise, a new array of the
443	>	*          same runtime type is allocated for this purpose.
444	>	* @return an array containing all of the elements in this queue
445	>	* @throws ArrayStoreException if the runtime type of the specified array
446	>	*         is not a supertype of the runtime type of every element in
447	>	*         this queue
448	>	* @throws NullPointerException if the specified array is null
449	>	*/
450	>	public <T> T[] toArray(T[] a) {
451	>	final int size = this.size;
452	>	if (a.length < size)
453	>	// Make a new array of a's runtime type, but my contents:
454	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
455	>	System.arraycopy(queue, 0, a, 0, size);
456	>	if (a.length > size)
457	>	a[size] = null;
458	>	return a;
459		}
460
461		/**
462		* Returns an iterator over the elements in this queue. The iterator
463		* does not return the elements in any particular order.
464		*
465	<	* @return an iterator over the elements in this queue.
465	>	* @return an iterator over the elements in this queue
466		*/
467		public Iterator<E> iterator() {
468		return new Itr();
469		}
470
471	<	private class Itr implements Iterator<E> {
471	>	private final class Itr implements Iterator<E> {
472		/**
473		* Index (into queue array) of element to be returned by
474		* subsequent call to next.
475		*/
476	<	private int cursor = 1;
476	>	private int cursor;
477	>
478	>	/**
479	>	* Index of element returned by most recent call to next,
480	>	* unless that element came from the forgetMeNot list.
481	>	* Set to -1 if element is deleted by a call to remove.
482	>	*/
483	>	private int lastRet = -1;
484
485		/**
486	<	* Index of element returned by most recent call to next or
487	<	* previous.  Reset to 0 if this element is deleted by a call
488	<	* to remove.
486	>	* A queue of elements that were moved from the unvisited portion of
487	>	* the heap into the visited portion as a result of "unlucky" element
488	>	* removals during the iteration.  (Unlucky element removals are those
489	>	* that require a siftup instead of a siftdown.)  We must visit all of
490	>	* the elements in this list to complete the iteration.  We do this
491	>	* after we've completed the "normal" iteration.
492	>	*
493	>	* We expect that most iterations, even those involving removals,
494	>	* will not need to store elements in this field.
495		*/
496	<	private int lastRet = 0;
496	>	private ArrayDeque<E> forgetMeNot;
497	>
498	>	/**
499	>	* Element returned by the most recent call to next iff that
500	>	* element was drawn from the forgetMeNot list.
501	>	*/
502	>	private E lastRetElt;
503
504		/**
505		* The modCount value that the iterator believes that the backing
506	<	* List should have.  If this expectation is violated, the iterator
506	>	* Queue should have.  If this expectation is violated, the iterator
507		* has detected concurrent modification.
508		*/
509		private int expectedModCount = modCount;
510
511	+	Itr() {}                        // prevent access constructor creation
512	+
513		public boolean hasNext() {
514	<	return cursor <= size;
514	>	return cursor < size ||
515	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
516		}
517
518		public E next() {
519	<	checkForComodification();
520	<	if (cursor > size)
521	<	throw new NoSuchElementException();
522	<	E result = (E) queue[cursor];
523	<	lastRet = cursor++;
524	<	return result;
519	>	if (expectedModCount != modCount)
520	>	throw new ConcurrentModificationException();
521	>	if (cursor < size)
522	>	return (E) queue[lastRet = cursor++];
523	>	if (forgetMeNot != null) {
524	>	lastRet = -1;
525	>	lastRetElt = forgetMeNot.poll();
526	>	if (lastRetElt != null)
527	>	return lastRetElt;
528	>	}
529	>	throw new NoSuchElementException();
530		}
531
532		public void remove() {
533	<	if (lastRet == 0)
533	>	if (expectedModCount != modCount)
534	>	throw new ConcurrentModificationException();
535	>	if (lastRet != -1) {
536	>	E moved = PriorityQueue.this.removeAt(lastRet);
537	>	lastRet = -1;
538	>	if (moved == null)
539	>	cursor--;
540	>	else {
541	>	if (forgetMeNot == null)
542	>	forgetMeNot = new ArrayDeque<>();
543	>	forgetMeNot.add(moved);
544	>	}
545	>	} else if (lastRetElt != null) {
546	>	PriorityQueue.this.removeEq(lastRetElt);
547	>	lastRetElt = null;
548	>	} else {
549		throw new IllegalStateException();
550	<	checkForComodification();
419	<
420	<	PriorityQueue.this.remove(lastRet);
421	<	if (lastRet < cursor)
422	<	cursor--;
423	<	lastRet = 0;
550	>	}
551		expectedModCount = modCount;
552		}
426	–
427	–	final void checkForComodification() {
428	–	if (modCount != expectedModCount)
429	–	throw new ConcurrentModificationException();
430	–	}
553		}
554
555		public int size() {
#	Line 435 | Line 557 | public class PriorityQueue<E> extends Ab
557		}
558
559		/**
560	<	* Remove all elements from the priority queue.
560	>	* Removes all of the elements from this priority queue.
561	>	* The queue will be empty after this call returns.
562		*/
563		public void clear() {
564		modCount++;
565	<
566	<	// Null out element references to prevent memory leak
567	<	for (int i=1; i<=size; i++)
445	<	queue[i] = null;
446	<
565	>	final Object[] es = queue;
566	>	for (int i = 0, n = size; i < n; i++)
567	>	es[i] = null;
568		size = 0;
569		}
570
571	<	/**
572	<	* Removes and returns the ith element from queue.  Recall
573	<	* that queue is one-based, so 1 <= i <= size.
453	<	*
454	<	* XXX: Could further special-case i==size, but is it worth it?
455	<	* XXX: Could special-case i==0, but is it worth it?
456	<	*/
457	<	private E remove(int i) {
458	<	assert i <= size;
459	<	modCount++;
460	<
461	<	E result = (E) queue[i];
462	<	queue[i] = queue[size];
463	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
464	<	if (i <= size)
465	<	fixDown(i);
466	<	return result;
467	<	}
571	>	public E poll() {
572	>	final Object[] es;
573	>	final E result;
574
575	<	/**
576	<	* Establishes the heap invariant (described above) assuming the heap
577	<	* satisfies the invariant except possibly for the leaf-node indexed by k
578	<	* (which may have a nextExecutionTime less than its parent's).
579	<	*
580	<	* This method functions by "promoting" queue[k] up the hierarchy
581	<	* (by swapping it with its parent) repeatedly until queue[k]
582	<	* is greater than or equal to its parent.
583	<	*/
584	<	private void fixUp(int k) {
585	<	if (comparator == null) {
480	<	while (k > 1) {
481	<	int j = k >> 1;
482	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
483	<	break;
484	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
485	<	k = j;
486	<	}
487	<	} else {
488	<	while (k > 1) {
489	<	int j = k >> 1;
490	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
491	<	break;
492	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
493	<	k = j;
575	>	if ((result = (E) ((es = queue)[0])) != null) {
576	>	modCount++;
577	>	final int n;
578	>	final E x = (E) es[(n = --size)];
579	>	es[n] = null;
580	>	if (n > 0) {
581	>	final Comparator<? super E> cmp;
582	>	if ((cmp = comparator) == null)
583	>	siftDownComparable(0, x, es, n);
584	>	else
585	>	siftDownUsingComparator(0, x, es, n, cmp);
586		}
587		}
588	+	return result;
589		}
590
591		/**
592	<	* Establishes the heap invariant (described above) in the subtree
593	<	* rooted at k, which is assumed to satisfy the heap invariant except
594	<	* possibly for node k itself (which may be greater than its children).
595	<	*
596	<	* This method functions by "demoting" queue[k] down the hierarchy
597	<	* (by swapping it with its smaller child) repeatedly until queue[k]
598	<	* is less than or equal to its children.
599	<	*/
600	<	private void fixDown(int k) {
601	<	int j;
602	<	if (comparator == null) {
603	<	while ((j = k << 1) <= size) {
604	<	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
605	<	j++; // j indexes smallest kid
606	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
607	<	break;
608	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
609	<	k = j;
610	<	}
611	<	} else {
612	<	while ((j = k << 1) <= size) {
613	<	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
614	<	j++; // j indexes smallest kid
615	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
616	<	break;
617	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
525	<	k = j;
592	>	* Removes the ith element from queue.
593	>	*
594	>	* Normally this method leaves the elements at up to i-1,
595	>	* inclusive, untouched.  Under these circumstances, it returns
596	>	* null.  Occasionally, in order to maintain the heap invariant,
597	>	* it must swap a later element of the list with one earlier than
598	>	* i.  Under these circumstances, this method returns the element
599	>	* that was previously at the end of the list and is now at some
600	>	* position before i. This fact is used by iterator.remove so as to
601	>	* avoid missing traversing elements.
602	>	*/
603	>	E removeAt(int i) {
604	>	// assert i >= 0 && i < size;
605	>	final Object[] es = queue;
606	>	modCount++;
607	>	int s = --size;
608	>	if (s == i) // removed last element
609	>	es[i] = null;
610	>	else {
611	>	E moved = (E) es[s];
612	>	es[s] = null;
613	>	siftDown(i, moved);
614	>	if (es[i] == moved) {
615	>	siftUp(i, moved);
616	>	if (es[i] != moved)
617	>	return moved;
618		}
619		}
620	+	return null;
621		}
622
530	–
623		/**
624	<	* Returns the comparator used to order this collection, or <tt>null</tt>
625	<	* if this collection is sorted according to its elements natural ordering
626	<	* (using <tt>Comparable</tt>.)
627	<	*
628	<	* @return the comparator used to order this collection, or <tt>null</tt>
629	<	* if this collection is sorted according to its elements natural ordering.
624	>	* Inserts item x at position k, maintaining heap invariant by
625	>	* promoting x up the tree until it is greater than or equal to
626	>	* its parent, or is the root.
627	>	*
628	>	* To simplify and speed up coercions and comparisons, the
629	>	* Comparable and Comparator versions are separated into different
630	>	* methods that are otherwise identical. (Similarly for siftDown.)
631	>	*
632	>	* @param k the position to fill
633	>	* @param x the item to insert
634	>	*/
635	>	private void siftUp(int k, E x) {
636	>	if (comparator != null)
637	>	siftUpUsingComparator(k, x, queue, comparator);
638	>	else
639	>	siftUpComparable(k, x, queue);
640	>	}
641	>
642	>	private static <T> void siftUpComparable(int k, T x, Object[] es) {
643	>	Comparable<? super T> key = (Comparable<? super T>) x;
644	>	while (k > 0) {
645	>	int parent = (k - 1) >>> 1;
646	>	Object e = es[parent];
647	>	if (key.compareTo((T) e) >= 0)
648	>	break;
649	>	es[k] = e;
650	>	k = parent;
651	>	}
652	>	es[k] = key;
653	>	}
654	>
655	>	private static <T> void siftUpUsingComparator(
656	>	int k, T x, Object[] es, Comparator<? super T> cmp) {
657	>	while (k > 0) {
658	>	int parent = (k - 1) >>> 1;
659	>	Object e = es[parent];
660	>	if (cmp.compare(x, (T) e) >= 0)
661	>	break;
662	>	es[k] = e;
663	>	k = parent;
664	>	}
665	>	es[k] = x;
666	>	}
667	>
668	>	/**
669	>	* Inserts item x at position k, maintaining heap invariant by
670	>	* demoting x down the tree repeatedly until it is less than or
671	>	* equal to its children or is a leaf.
672	>	*
673	>	* @param k the position to fill
674	>	* @param x the item to insert
675	>	*/
676	>	private void siftDown(int k, E x) {
677	>	if (comparator != null)
678	>	siftDownUsingComparator(k, x, queue, size, comparator);
679	>	else
680	>	siftDownComparable(k, x, queue, size);
681	>	}
682	>
683	>	private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
684	>	// assert n > 0;
685	>	Comparable<? super T> key = (Comparable<? super T>)x;
686	>	int half = n >>> 1;           // loop while a non-leaf
687	>	while (k < half) {
688	>	int child = (k << 1) + 1; // assume left child is least
689	>	Object c = es[child];
690	>	int right = child + 1;
691	>	if (right < n &&
692	>	((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
693	>	c = es[child = right];
694	>	if (key.compareTo((T) c) <= 0)
695	>	break;
696	>	es[k] = c;
697	>	k = child;
698	>	}
699	>	es[k] = key;
700	>	}
701	>
702	>	private static <T> void siftDownUsingComparator(
703	>	int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
704	>	// assert n > 0;
705	>	int half = n >>> 1;
706	>	while (k < half) {
707	>	int child = (k << 1) + 1;
708	>	Object c = es[child];
709	>	int right = child + 1;
710	>	if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
711	>	c = es[child = right];
712	>	if (cmp.compare(x, (T) c) <= 0)
713	>	break;
714	>	es[k] = c;
715	>	k = child;
716	>	}
717	>	es[k] = x;
718	>	}
719	>
720	>	/**
721	>	* Establishes the heap invariant (described above) in the entire tree,
722	>	* assuming nothing about the order of the elements prior to the call.
723	>	* This classic algorithm due to Floyd (1964) is known to be O(size).
724	>	*/
725	>	private void heapify() {
726	>	final Object[] es = queue;
727	>	int n = size, i = (n >>> 1) - 1;
728	>	final Comparator<? super E> cmp;
729	>	if ((cmp = comparator) == null)
730	>	for (; i >= 0; i--)
731	>	siftDownComparable(i, (E) es[i], es, n);
732	>	else
733	>	for (; i >= 0; i--)
734	>	siftDownUsingComparator(i, (E) es[i], es, n, cmp);
735	>	}
736	>
737	>	/**
738	>	* Returns the comparator used to order the elements in this
739	>	* queue, or {@code null} if this queue is sorted according to
740	>	* the {@linkplain Comparable natural ordering} of its elements.
741	>	*
742	>	* @return the comparator used to order this queue, or
743	>	*         {@code null} if this queue is sorted according to the
744	>	*         natural ordering of its elements
745		*/
746		public Comparator<? super E> comparator() {
747		return comparator;
748		}
749
750		/**
751	<	* Save the state of the instance to a stream (that
545	<	* is, serialize it).
751	>	* Saves this queue to a stream (that is, serializes it).
752		*
547	–	* @serialData The length of the array backing the instance is
548	–	* emitted (int), followed by all of its elements (each an
549	–	* <tt>Object</tt>) in the proper order.
753		* @param s the stream
754	+	* @throws java.io.IOException if an I/O error occurs
755	+	* @serialData The length of the array backing the instance is
756	+	*             emitted (int), followed by all of its elements
757	+	*             (each an {@code Object}) in the proper order.
758		*/
759	+	// OPENJDK @java.io.Serial
760		private void writeObject(java.io.ObjectOutputStream s)
761	<	throws java.io.IOException{
761	>	throws java.io.IOException {
762		// Write out element count, and any hidden stuff
763		s.defaultWriteObject();
764
765	<	// Write out array length
766	<	s.writeInt(queue.length);
765	>	// Write out array length, for compatibility with 1.5 version
766	>	s.writeInt(Math.max(2, size + 1));
767
768	<	// Write out all elements in the proper order.
769	<	for (int i=0; i<size; i++)
770	<	s.writeObject(queue[i]);
768	>	// Write out all elements in the "proper order".
769	>	final Object[] es = queue;
770	>	for (int i = 0, n = size; i < n; i++)
771	>	s.writeObject(es[i]);
772		}
773
774		/**
775	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
776	<	* deserialize it).
775	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
776	>	* (that is, deserializes it).
777	>	*
778		* @param s the stream
779	+	* @throws ClassNotFoundException if the class of a serialized object
780	+	*         could not be found
781	+	* @throws java.io.IOException if an I/O error occurs
782		*/
783	+	// OPENJDK @java.io.Serial
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	>	jsr166.Platform.checkArray(s, Object[].class, size);
793	>	final Object[] es = queue = new Object[Math.max(size, 1)];
794	>
795	>	// Read in all elements.
796	>	for (int i = 0, n = size; i < n; i++)
797	>	es[i] = s.readObject();
798	>
799	>	// Elements are guaranteed to be in "proper order", but the
800	>	// spec has never explained what that might be.
801	>	heapify();
802		}
803
804	<	}
804	>	/**
805	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
806	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
807	>	* queue. The spliterator does not traverse elements in any particular order
808	>	* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
809	>	*
810	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
811	>	* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.
812	>	* Overriding implementations should document the reporting of additional
813	>	* characteristic values.
814	>	*
815	>	* @return a {@code Spliterator} over the elements in this queue
816	>	* @since 1.8
817	>	*/
818	>	public final Spliterator<E> spliterator() {
819	>	return new PriorityQueueSpliterator(0, -1, 0);
820	>	}
821	>
822	>	final class PriorityQueueSpliterator implements Spliterator<E> {
823	>	private int index;            // current index, modified on advance/split
824	>	private int fence;            // -1 until first use
825	>	private int expectedModCount; // initialized when fence set
826
827	+	/** Creates new spliterator covering the given range. */
828	+	PriorityQueueSpliterator(int origin, int fence, int expectedModCount) {
829	+	this.index = origin;
830	+	this.fence = fence;
831	+	this.expectedModCount = expectedModCount;
832	+	}
833	+
834	+	private int getFence() { // initialize fence to size on first use
835	+	int hi;
836	+	if ((hi = fence) < 0) {
837	+	expectedModCount = modCount;
838	+	hi = fence = size;
839	+	}
840	+	return hi;
841	+	}
842	+
843	+	public PriorityQueueSpliterator trySplit() {
844	+	int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
845	+	return (lo >= mid) ? null :
846	+	new PriorityQueueSpliterator(lo, index = mid, expectedModCount);
847	+	}
848	+
849	+	public void forEachRemaining(Consumer<? super E> action) {
850	+	if (action == null)
851	+	throw new NullPointerException();
852	+	if (fence < 0) { fence = size; expectedModCount = modCount; }
853	+	final Object[] es = queue;
854	+	int i, hi; E e;
855	+	for (i = index, index = hi = fence; i < hi; i++) {
856	+	if ((e = (E) es[i]) == null)
857	+	break;      // must be CME
858	+	action.accept(e);
859	+	}
860	+	if (modCount != expectedModCount)
861	+	throw new ConcurrentModificationException();
862	+	}
863	+
864	+	public boolean tryAdvance(Consumer<? super E> action) {
865	+	if (action == null)
866	+	throw new NullPointerException();
867	+	if (fence < 0) { fence = size; expectedModCount = modCount; }
868	+	int i;
869	+	if ((i = index) < fence) {
870	+	index = i + 1;
871	+	E e;
872	+	if ((e = (E) queue[i]) == null
873	+	|| modCount != expectedModCount)
874	+	throw new ConcurrentModificationException();
875	+	action.accept(e);
876	+	return true;
877	+	}
878	+	return false;
879	+	}
880	+
881	+	public long estimateSize() {
882	+	return getFence() - index;
883	+	}
884	+
885	+	public int characteristics() {
886	+	return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
887	+	}
888	+	}
889	+
890	+	/**
891	+	* @throws NullPointerException {@inheritDoc}
892	+	*/
893	+	public boolean removeIf(Predicate<? super E> filter) {
894	+	Objects.requireNonNull(filter);
895	+	return bulkRemove(filter);
896	+	}
897	+
898	+	/**
899	+	* @throws NullPointerException {@inheritDoc}
900	+	*/
901	+	public boolean removeAll(Collection<?> c) {
902	+	Objects.requireNonNull(c);
903	+	return bulkRemove(e -> c.contains(e));
904	+	}
905	+
906	+	/**
907	+	* @throws NullPointerException {@inheritDoc}
908	+	*/
909	+	public boolean retainAll(Collection<?> c) {
910	+	Objects.requireNonNull(c);
911	+	return bulkRemove(e -> !c.contains(e));
912	+	}
913	+
914	+	// A tiny bit set implementation
915	+
916	+	private static long[] nBits(int n) {
917	+	return new long[((n - 1) >> 6) + 1];
918	+	}
919	+	private static void setBit(long[] bits, int i) {
920	+	bits[i >> 6] |= 1L << i;
921	+	}
922	+	private static boolean isClear(long[] bits, int i) {
923	+	return (bits[i >> 6] & (1L << i)) == 0;
924	+	}
925	+
926	+	/** Implementation of bulk remove methods. */
927	+	private boolean bulkRemove(Predicate<? super E> filter) {
928	+	final int expectedModCount = ++modCount;
929	+	final Object[] es = queue;
930	+	final int end = size;
931	+	int i;
932	+	// Optimize for initial run of survivors
933	+	for (i = 0; i < end && !filter.test((E) es[i]); i++)
934	+	;
935	+	if (i >= end) {
936	+	if (modCount != expectedModCount)
937	+	throw new ConcurrentModificationException();
938	+	return false;
939	+	}
940	+	// Tolerate predicates that reentrantly access the collection for
941	+	// read (but writers still get CME), so traverse once to find
942	+	// elements to delete, a second pass to physically expunge.
943	+	final int beg = i;
944	+	final long[] deathRow = nBits(end - beg);
945	+	deathRow[0] = 1L;   // set bit 0
946	+	for (i = beg + 1; i < end; i++)
947	+	if (filter.test((E) es[i]))
948	+	setBit(deathRow, i - beg);
949	+	if (modCount != expectedModCount)
950	+	throw new ConcurrentModificationException();
951	+	int w = beg;
952	+	for (i = beg; i < end; i++)
953	+	if (isClear(deathRow, i - beg))
954	+	es[w++] = es[i];
955	+	for (i = size = w; i < end; i++)
956	+	es[i] = null;
957	+	heapify();
958	+	return true;
959	+	}
960	+
961	+	/**
962	+	* @throws NullPointerException {@inheritDoc}
963	+	*/
964	+	public void forEach(Consumer<? super E> action) {
965	+	Objects.requireNonNull(action);
966	+	final int expectedModCount = modCount;
967	+	final Object[] es = queue;
968	+	for (int i = 0, n = size; i < n; i++)
969	+	action.accept((E) es[i]);
970	+	if (expectedModCount != modCount)
971	+	throw new ConcurrentModificationException();
972	+	}
973	+	}

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