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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.50 by dl, Wed Jun 2 23:45:46 2004 UTC vs.
Revision 1.134 by jsr166, Fri Jul 24 20:57:26 2020 UTC

#	Line 1 | Line 1
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 2004 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
35	<	* heap.  This queue orders elements according to an order specified
36	<	* at construction time, which is specified either according to their
37	<	* <i>natural order</i> (see {@link Comparable}), or according to a
38	<	* {@link java.util.Comparator}, depending on which constructor is
39	<	* used. A priority queue does not permit <tt>null</tt> elements.
40	<	* A priority queue relying on natural ordering also does not
41	<	* permit insertion of non-comparable objects (doing so may result
19	<	* in <tt>ClassCastException</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 <tt>poll</tt>,
47	<	* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the
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
#	Line 34 | Line 56 | package java.util;
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.
60	<	* The
61	<	* Iterator provided in method {@link #iterator()} is <em>not</em>
62	<	* guaranteed to traverse the elements of the PriorityQueue in any
63	<	* particular order. If you need ordered traversal, consider using
64	<	* <tt>Arrays.sort(pq.toArray())</tt>.
65	<	*
66	<	* <p> <strong>Note that this implementation is not synchronized.</strong>
67	<	* Multiple threads should not access a <tt>PriorityQueue</tt>
68	<	* instance concurrently if any of the threads modifies the list
47	<	* structurally. Instead, use the thread-safe {@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>,
56	<	* <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
64	<	* @param <E> the type of elements held in this collection
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 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	<	*
80	<	* The element with the lowest value is in queue[1], assuming the queue is
81	<	* nonempty.  (A one-based array is used in preference to the traditional
82	<	* zero-based array to simplify parent and child calculations.)
83	<	*
84	<	* 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();
178	<	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
190	<	* elements' natural order.  Otherwise, the priority queue is
191	<	* ordered according to its elements' natural order.
192	<	*
193	<	* @param c the collection whose elements are to be placed
194	<	*        into this priority queue.
195	<	* @throws ClassCastException if elements of the specified collection
196	<	*         cannot be compared to one another according to the priority
197	<	*         queue's ordering.
198	<	* @throws NullPointerException if <tt>c</tt> or any element within it
199	<	* is <tt>null</tt>
200	<	*/
201	<	public PriorityQueue(Collection<? extends E> c) {
202	<	initializeArray(c);
203	<	if (c instanceof SortedSet) {
204	<	SortedSet<? extends E> s = (SortedSet<? extends E>)c;
205	<	comparator = (Comparator<? super E>)s.comparator();
206	<	fillFromSorted(s);
207	<	} else if (c instanceof PriorityQueue) {
208	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
209	<	comparator = (Comparator<? super E>)s.comparator();
210	<	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;
213	<	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.getClass() != ArrayList.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
219	<	* specified collection.  The priority queue has an initial
220	<	* capacity of 110% of the size of the specified collection or 1
221	<	* if the collection is empty.  This priority queue will be sorted
222	<	* according to the same comparator as the given collection, or
223	<	* according to its elements' natural order if the collection is
224	<	* 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
227	<	*        into this priority queue.
228	<	* @throws ClassCastException if elements of the specified collection
229	<	*         cannot be compared to one another according to the priority
230	<	*         queue's ordering.
231	<	* @throws NullPointerException if <tt>c</tt> or any element within it
232	<	* 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();
237	<	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
242	<	* specified collection.  The priority queue has an initial
243	<	* capacity of 110% of the size of the specified collection or 1
244	<	* if the collection is empty.  This priority queue will be sorted
245	<	* according to the same comparator as the given collection, or
246	<	* according to its elements' natural order if the collection is
247	<	* 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
250	<	*        into this priority queue.
251	<	* @throws ClassCastException if elements of the specified collection
252	<	*         cannot be compared to one another according to the priority
253	<	*         queue's ordering.
254	<	* @throws NullPointerException if <tt>c</tt> or any element within it
255	<	* 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
303	<	*/
304	<	private void grow(int index) {
305	<	int newlen = queue.length;
306	<	if (index < newlen) // don't need to grow
307	<	return;
308	<	if (index == Integer.MAX_VALUE)
309	<	throw new OutOfMemoryError();
310	<	while (newlen <= index) {
311	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
274	<	newlen = Integer.MAX_VALUE;
275	<	else
276	<	newlen <<= 2;
277	<	}
278	<	Object[] newQueue = new Object[newlen];
279	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
280	<	queue = newQueue;
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	>	public boolean add(E e) {
311	>	return offer(e);
312		}
282	–
313
314		/**
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);
302	<
303	<	queue[size] = o;
304	<	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 peek() {
336	<	if (size == 0)
310	<	return null;
311	<	return (E) queue[1];
336	>	return (E) queue[0];
337		}
338
339	<	// Collection Methods - the first two override to update docs
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		/**
350	<	* Adds the specified element to this queue.
351	<	* @return <tt>true</tt> (as per the general contract of
352	<	* <tt>Collection.add</tt>).
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	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
358	<	* @throws ClassCastException if the specified element cannot be compared
323	<	* with elements currently in the priority queue according
324	<	* to the priority queue's ordering.
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 add(E o) {
361	<	return offer(o);
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	<	* Removes a single instance of the specified element from this
372	<	* queue, if it is present.
371	>	* Identity-based version for use in Itr.remove.
372	>	*
373	>	* @param o element to be removed from this queue, if present
374		*/
375	<	public boolean remove(Object o) {
376	<	if (o == null)
377	<	return false;
378	<
379	<	if (comparator == null) {
380	<	for (int i = 1; i <= size; i++) {
340	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
341	<	removeAt(i);
342	<	return true;
343	<	}
344	<	}
345	<	} else {
346	<	for (int i = 1; i <= size; i++) {
347	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
348	<	removeAt(i);
349	<	return true;
350	<	}
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	<	return false;
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	>	* 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 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 Object[] toArray() {
411	>	return Arrays.copyOf(queue, size);
412	>	}
413	>
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> {
367	<
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	<	* Reset to 0 if element is deleted by a call to remove.
481	>	* Set to -1 if element is deleted by a call to remove.
482		*/
483	<	private int lastRet = 0;
483	>	private int lastRet = -1;
484
485		/**
486	<	* The modCount value that the iterator believes that the backing
383	<	* List should have.  If this expectation is violated, the iterator
384	<	* has detected concurrent modification.
385	<	*/
386	<	private int expectedModCount = modCount;
387	<
388	<	/**
389	<	* A list of elements that were moved from the unvisited portion of
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 fixup instead of a fixdown.)  We must visit all of
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 use need to store elements in this field.
494	>	* will not need to store elements in this field.
495		*/
496	<	private ArrayList<E> forgetMeNot = null;
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 Object lastRetElt = null;
502	>	private E lastRetElt;
503	>
504	>	/**
505	>	* The modCount value that the iterator believes that the backing
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 || forgetMeNot != null;
514	>	return cursor < size ||
515	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
516		}
517
518		public E next() {
519	<	checkForComodification();
520	<	E result;
521	<	if (cursor <= size) {
522	<	result = (E) queue[cursor];
523	<	lastRet = cursor++;
524	<	}
525	<	else if (forgetMeNot == null)
526	<	throw new NoSuchElementException();
527	<	else {
421	<	int remaining = forgetMeNot.size();
422	<	result = forgetMeNot.remove(remaining - 1);
423	<	if (remaining == 1)
424	<	forgetMeNot = null;
425	<	lastRet = 0;
426	<	lastRetElt = 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	<	return result;
529	>	throw new NoSuchElementException();
530		}
531
532		public void remove() {
533	<	checkForComodification();
534	<
535	<	if (lastRet != 0) {
533	>	if (expectedModCount != modCount)
534	>	throw new ConcurrentModificationException();
535	>	if (lastRet != -1) {
536		E moved = PriorityQueue.this.removeAt(lastRet);
537	<	lastRet = 0;
538	<	if (moved == null) {
537	>	lastRet = -1;
538	>	if (moved == null)
539		cursor--;
540	<	} else {
540	>	else {
541		if (forgetMeNot == null)
542	<	forgetMeNot = new ArrayList<E>();
542	>	forgetMeNot = new ArrayDeque<>();
543		forgetMeNot.add(moved);
544		}
545		} else if (lastRetElt != null) {
546	<	PriorityQueue.this.remove(lastRetElt);
546	>	PriorityQueue.this.removeEq(lastRetElt);
547		lastRetElt = null;
548		} else {
549		throw new IllegalStateException();
550		}
450	–
551		expectedModCount = modCount;
552		}
453	–
454	–	final void checkForComodification() {
455	–	if (modCount != expectedModCount)
456	–	throw new ConcurrentModificationException();
457	–	}
553		}
554
555		public int size() {
#	Line 462 | Line 557 | public class PriorityQueue<E> extends Ab
557		}
558
559		/**
560	<	* Removes 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++)
473	<	queue[i] = null;
474	<
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		public E poll() {
572	<	if (size == 0)
573	<	return null;
481	<	modCount++;
482	<
483	<	E result = (E) queue[1];
484	<	queue[1] = queue[size];
485	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
486	<	if (size > 1)
487	<	fixDown(1);
572	>	final Object[] es;
573	>	final E result;
574
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	<	* Removes and returns the ith element from queue.  (Recall that queue
494	<	* is one-based, so 1 <= i <= size.)
592	>	* Removes the ith element from queue.
593		*
594	<	* Normally this method leaves the elements at positions from 1 up to i-1,
595	<	* inclusive, untouched.  Under these circumstances, it returns null.
596	<	* Occasionally, in order to maintain the heap invariant, it must move
597	<	* the last element of the list to some index in the range [2, i-1],
598	<	* and move the element previously at position (i/2) to position i.
599	<	* Under these circumstances, this method returns the element that was
600	<	* previously at the end of the list and is now at some position between
601	<	* 2 and i-1 inclusive.
602	<	*/
603	<	private E removeAt(int i) {
604	<	assert i > 0 && i <= size;
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	<
608	<	E moved = (E) queue[size];
609	<	queue[i] = moved;
610	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
611	<	if (i <= size) {
612	<	fixDown(i);
613	<	if (queue[i] == moved) {
614	<	fixUp(i);
615	<	if (queue[i] != moved)
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		}
#	Line 521 | Line 621 | public class PriorityQueue<E> extends Ab
621		}
622
623		/**
624	<	* Establishes the heap invariant (described above) assuming the heap
625	<	* satisfies the invariant except possibly for the leaf-node indexed by k
626	<	* (which may have a nextExecutionTime less than its parent's).
627	<	*
628	<	* This method functions by "promoting" queue[k] up the hierarchy
629	<	* (by swapping it with its parent) repeatedly until queue[k]
630	<	* is greater than or equal to its parent.
631	<	*/
632	<	private void fixUp(int k) {
633	<	if (comparator == null) {
634	<	while (k > 1) {
635	<	int j = k >> 1;
636	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
637	<	break;
638	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
639	<	k = j;
640	<	}
641	<	} else {
642	<	while (k > 1) {
643	<	int j = k >>> 1;
644	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
645	<	break;
646	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
647	<	k = j;
648	<	}
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	<	* Establishes the heap invariant (described above) in the subtree
670	<	* rooted at k, which is assumed to satisfy the heap invariant except
671	<	* possibly for node k itself (which may be greater than its children).
672	<	*
673	<	* This method functions by "demoting" queue[k] down the hierarchy
674	<	* (by swapping it with its smaller child) repeatedly until queue[k]
675	<	* is less than or equal to its children.
676	<	*/
677	<	private void fixDown(int k) {
678	<	int j;
679	<	if (comparator == null) {
680	<	while ((j = k << 1) <= size && (j > 0)) {
681	<	if (j<size &&
682	<	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
683	<	j++; // j indexes smallest kid
684	<
685	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
686	<	break;
687	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
688	<	k = j;
689	<	}
690	<	} else {
691	<	while ((j = k << 1) <= size && (j > 0)) {
692	<	if (j<size &&
693	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
694	<	j++; // j indexes smallest kid
695	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
696	<	break;
697	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
698	<	k = j;
699	<	}
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	<	for (int i = size/2; i >= 1; i--)
727	<	fixDown(i);
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 this collection, or <tt>null</tt>
739	<	* if this collection is sorted according to its elements natural ordering
740	<	* (using <tt>Comparable</tt>).
741	<	*
742	<	* @return the comparator used to order this collection, or <tt>null</tt>
743	<	* if this collection is sorted according to its elements natural ordering.
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
610	<	* is, serialize it).
751	>	* Saves this queue to a stream (that is, serializes it).
752		*
612	–	* @serialData The length of the array backing the instance is
613	–	* emitted (int), followed by all of its elements (each an
614	–	* <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=1; 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=1; i<=size; i++)
795	<	queue[i] = (E) 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	+	/**
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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