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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.69 by jsr166, Sun May 18 23:59:57 2008 UTC vs.
Revision 1.133 by jsr166, Thu Oct 10 16:53:08 2019 UTC

#	Line 1 | Line 1
1		/*
2	<	* Copyright 2003-2006 Sun Microsystems, Inc.  All Rights Reserved.
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.  Sun designates this
7	>	* published by the Free Software Foundation.  Oracle designates this
8		* particular file as subject to the "Classpath" exception as provided
9	<	* by Sun in the LICENSE file that accompanied this code.
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
#	Line 18 | Line 18
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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22	<	* CA 95054 USA or visit www.sun.com if you need additional information or
23	<	* have any questions.
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		* The elements of the priority queue are ordered according to their
#	Line 52 | Line 57 | package java.util;
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()} is <em>not</em> guaranteed to traverse the elements of
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>
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 enqueing and dequeing methods
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}/../technotes/guides/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, Doug Lea
84	<	* @param <E> the type of elements held in this collection
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;
#	Line 92 | Line 100 | public class PriorityQueue<E> extends Ab
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 {@code PriorityQueue} with the default initial
#	Line 134 | Line 143 | public class PriorityQueue<E> extends Ab
143		}
144
145		/**
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		*
#	Line 171 | Line 193 | public class PriorityQueue<E> extends Ab
193		*         of its elements are null
194		*/
195		public PriorityQueue(Collection<? extends E> c) {
196	<	initFromCollection(c);
197	<	if (c instanceof SortedSet)
198	<	comparator = (Comparator<? super E>)
199	<	((SortedSet<? extends E>)c).comparator();
200	<	else if (c instanceof PriorityQueue)
201	<	comparator = (Comparator<? super E>)
202	<	((PriorityQueue<? extends E>)c).comparator();
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	<	comparator = null;
208	<	heapify();
207	>	this.comparator = null;
208	>	initFromCollection(c);
209		}
210		}
211
#	Line 199 | Line 224 | public class PriorityQueue<E> extends Ab
224		*         of its elements are null
225		*/
226		public PriorityQueue(PriorityQueue<? extends E> c) {
227	<	comparator = (Comparator<? super E>)c.comparator();
228	<	initFromCollection(c);
227	>	this.comparator = (Comparator<? super E>) c.comparator();
228	>	initFromPriorityQueue(c);
229		}
230
231		/**
#	Line 217 | Line 242 | public class PriorityQueue<E> extends Ab
242		*         of its elements are null
243		*/
244		public PriorityQueue(SortedSet<? extends E> c) {
245	<	comparator = (Comparator<? super E>)c.comparator();
246	<	initFromCollection(c);
245	>	this.comparator = (Comparator<? super E>) c.comparator();
246	>	initElementsFromCollection(c);
247	>	}
248	>
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	>	initFromCollection(c);
260	>	}
261	>	}
262	>
263	>	private void initElementsFromCollection(Collection<? extends E> c) {
264	>	Object[] es = c.toArray();
265	>	int len = es.length;
266	>	// If c.toArray incorrectly doesn't return Object[], copy it.
267	>	if (es.getClass() != Object[].class)
268	>	es = Arrays.copyOf(es, len, Object[].class);
269	>	if (len == 1 || this.comparator != null)
270	>	for (Object e : es)
271	>	if (e == null)
272	>	throw new NullPointerException();
273	>	this.queue = ensureNonEmpty(es);
274	>	this.size = len;
275		}
276
277		/**
#	Line 227 | Line 280 | public class PriorityQueue<E> extends Ab
280		* @param c the collection
281		*/
282		private void initFromCollection(Collection<? extends E> c) {
283	<	Object[] a = c.toArray();
284	<	// If c.toArray incorrectly doesn't return Object[], copy it.
232	<	if (a.getClass() != Object[].class)
233	<	a = Arrays.copyOf(a, a.length, Object[].class);
234	<	queue = a;
235	<	size = a.length;
283	>	initElementsFromCollection(c);
284	>	heapify();
285		}
286
287		/**
#	Line 241 | Line 290 | public class PriorityQueue<E> extends Ab
290		* @param minCapacity the desired minimum capacity
291		*/
292		private void grow(int minCapacity) {
244	–	if (minCapacity < 0) // overflow
245	–	throw new OutOfMemoryError();
293		int oldCapacity = queue.length;
294		// Double size if small; else grow by 50%
295	<	int newCapacity = ((oldCapacity < 64)?
296	<	((oldCapacity + 1) * 2):
297	<	((oldCapacity / 2) * 3));
298	<	if (newCapacity < 0) // overflow
252	<	newCapacity = Integer.MAX_VALUE;
253	<	if (newCapacity < minCapacity)
254	<	newCapacity = minCapacity;
295	>	int newCapacity = ArraysSupport.newLength(oldCapacity,
296	>	minCapacity - oldCapacity, /* minimum growth */
297	>	oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1
298	>	/* preferred growth */);
299		queue = Arrays.copyOf(queue, newCapacity);
300		}
301
#	Line 284 | Line 328 | public class PriorityQueue<E> extends Ab
328		int i = size;
329		if (i >= queue.length)
330		grow(i + 1);
331	+	siftUp(i, e);
332		size = i + 1;
288	–	if (i == 0)
289	–	queue[0] = e;
290	–	else
291	–	siftUp(i, e);
333		return true;
334		}
335
336		public E peek() {
296	–	if (size == 0)
297	–	return null;
337		return (E) queue[0];
338		}
339
340		private int indexOf(Object o) {
341		if (o != null) {
342	<	for (int i = 0; i < size; i++)
343	<	if (o.equals(queue[i]))
342	>	final Object[] es = queue;
343	>	for (int i = 0, n = size; i < n; i++)
344	>	if (o.equals(es[i]))
345		return i;
346		}
347		return -1;
#	Line 329 | Line 369 | public class PriorityQueue<E> extends Ab
369		}
370
371		/**
372	<	* Version of remove using reference equality, not equals.
333	<	* Needed by iterator.remove.
372	>	* Identity-based version for use in Itr.remove.
373		*
374		* @param o element to be removed from this queue, if present
336	–	* @return {@code true} if removed
375		*/
376	<	boolean removeEq(Object o) {
377	<	for (int i = 0; i < size; i++) {
378	<	if (o == queue[i]) {
376	>	void removeEq(Object o) {
377	>	final Object[] es = queue;
378	>	for (int i = 0, n = size; i < n; i++) {
379	>	if (o == es[i]) {
380		removeAt(i);
381	<	return true;
381	>	break;
382		}
383		}
345	–	return false;
384		}
385
386		/**
#	Line 354 | Line 392 | public class PriorityQueue<E> extends Ab
392		* @return {@code true} if this queue contains the specified element
393		*/
394		public boolean contains(Object o) {
395	<	return indexOf(o) != -1;
395	>	return indexOf(o) >= 0;
396		}
397
398		/**
#	Line 392 | Line 430 | public class PriorityQueue<E> extends Ab
430		* precise control over the runtime type of the output array, and may,
431		* under certain circumstances, be used to save allocation costs.
432		*
433	<	* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
433	>	* <p>Suppose {@code x} is a queue known to contain only strings.
434		* The following code can be used to dump the queue into a newly
435	<	* allocated array of <tt>String</tt>:
435	>	* allocated array of {@code String}:
436		*
437	<	* <pre>
400	<	*     String[] y = x.toArray(new String[0]);</pre>
437	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
438		*
439	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
440	<	* <tt>toArray()</tt>.
439	>	* Note that {@code toArray(new Object[0])} is identical in function to
440	>	* {@code toArray()}.
441		*
442		* @param a the array into which the elements of the queue are to
443		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 412 | Line 449 | public class PriorityQueue<E> extends Ab
449		* @throws NullPointerException if the specified array is null
450		*/
451		public <T> T[] toArray(T[] a) {
452	+	final int size = this.size;
453		if (a.length < size)
454		// Make a new array of a's runtime type, but my contents:
455		return (T[]) Arrays.copyOf(queue, size, a.getClass());
#	Line 436 | Line 474 | public class PriorityQueue<E> extends Ab
474		* Index (into queue array) of element to be returned by
475		* subsequent call to next.
476		*/
477	<	private int cursor = 0;
477	>	private int cursor;
478
479		/**
480		* Index of element returned by most recent call to next,
#	Line 456 | Line 494 | public class PriorityQueue<E> extends Ab
494		* We expect that most iterations, even those involving removals,
495		* will not need to store elements in this field.
496		*/
497	<	private ArrayDeque<E> forgetMeNot = null;
497	>	private ArrayDeque<E> forgetMeNot;
498
499		/**
500		* Element returned by the most recent call to next iff that
501		* element was drawn from the forgetMeNot list.
502		*/
503	<	private E lastRetElt = null;
503	>	private E lastRetElt;
504
505		/**
506		* The modCount value that the iterator believes that the backing
#	Line 471 | Line 509 | public class PriorityQueue<E> extends Ab
509		*/
510		private int expectedModCount = modCount;
511
512	+	Itr() {}                        // prevent access constructor creation
513	+
514		public boolean hasNext() {
515		return cursor < size ||
516		(forgetMeNot != null && !forgetMeNot.isEmpty());
#	Line 500 | Line 540 | public class PriorityQueue<E> extends Ab
540		cursor--;
541		else {
542		if (forgetMeNot == null)
543	<	forgetMeNot = new ArrayDeque<E>();
543	>	forgetMeNot = new ArrayDeque<>();
544		forgetMeNot.add(moved);
545		}
546		} else if (lastRetElt != null) {
#	Line 523 | Line 563 | public class PriorityQueue<E> extends Ab
563		*/
564		public void clear() {
565		modCount++;
566	<	for (int i = 0; i < size; i++)
567	<	queue[i] = null;
566	>	final Object[] es = queue;
567	>	for (int i = 0, n = size; i < n; i++)
568	>	es[i] = null;
569		size = 0;
570		}
571
572		public E poll() {
573	<	if (size == 0)
574	<	return null;
575	<	int s = --size;
576	<	modCount++;
577	<	E result = (E) queue[0];
578	<	E x = (E) queue[s];
579	<	queue[s] = null;
580	<	if (s != 0)
581	<	siftDown(0, x);
573	>	final Object[] es;
574	>	final E result;
575	>
576	>	if ((result = (E) ((es = queue)[0])) != null) {
577	>	modCount++;
578	>	final int n;
579	>	final E x = (E) es[(n = --size)];
580	>	es[n] = null;
581	>	if (n > 0) {
582	>	final Comparator<? super E> cmp;
583	>	if ((cmp = comparator) == null)
584	>	siftDownComparable(0, x, es, n);
585	>	else
586	>	siftDownUsingComparator(0, x, es, n, cmp);
587	>	}
588	>	}
589		return result;
590		}
591
#	Line 553 | Line 601 | public class PriorityQueue<E> extends Ab
601		* position before i. This fact is used by iterator.remove so as to
602		* avoid missing traversing elements.
603		*/
604	<	private E removeAt(int i) {
605	<	assert i >= 0 && i < size;
604	>	E removeAt(int i) {
605	>	// assert i >= 0 && i < size;
606	>	final Object[] es = queue;
607		modCount++;
608		int s = --size;
609		if (s == i) // removed last element
610	<	queue[i] = null;
610	>	es[i] = null;
611		else {
612	<	E moved = (E) queue[s];
613	<	queue[s] = null;
612	>	E moved = (E) es[s];
613	>	es[s] = null;
614		siftDown(i, moved);
615	<	if (queue[i] == moved) {
615	>	if (es[i] == moved) {
616		siftUp(i, moved);
617	<	if (queue[i] != moved)
617	>	if (es[i] != moved)
618		return moved;
619		}
620		}
#	Line 577 | Line 626 | public class PriorityQueue<E> extends Ab
626		* promoting x up the tree until it is greater than or equal to
627		* its parent, or is the root.
628		*
629	<	* To simplify and speed up coercions and comparisons. the
629	>	* To simplify and speed up coercions and comparisons, the
630		* Comparable and Comparator versions are separated into different
631		* methods that are otherwise identical. (Similarly for siftDown.)
632		*
#	Line 586 | Line 635 | public class PriorityQueue<E> extends Ab
635		*/
636		private void siftUp(int k, E x) {
637		if (comparator != null)
638	<	siftUpUsingComparator(k, x);
638	>	siftUpUsingComparator(k, x, queue, comparator);
639		else
640	<	siftUpComparable(k, x);
640	>	siftUpComparable(k, x, queue);
641		}
642
643	<	private void siftUpComparable(int k, E x) {
644	<	Comparable<? super E> key = (Comparable<? super E>) x;
643	>	private static <T> void siftUpComparable(int k, T x, Object[] es) {
644	>	Comparable<? super T> key = (Comparable<? super T>) x;
645		while (k > 0) {
646		int parent = (k - 1) >>> 1;
647	<	Object e = queue[parent];
648	<	if (key.compareTo((E) e) >= 0)
647	>	Object e = es[parent];
648	>	if (key.compareTo((T) e) >= 0)
649		break;
650	<	queue[k] = e;
650	>	es[k] = e;
651		k = parent;
652		}
653	<	queue[k] = key;
653	>	es[k] = key;
654		}
655
656	<	private void siftUpUsingComparator(int k, E x) {
656	>	private static <T> void siftUpUsingComparator(
657	>	int k, T x, Object[] es, Comparator<? super T> cmp) {
658		while (k > 0) {
659		int parent = (k - 1) >>> 1;
660	<	Object e = queue[parent];
661	<	if (comparator.compare(x, (E) e) >= 0)
660	>	Object e = es[parent];
661	>	if (cmp.compare(x, (T) e) >= 0)
662		break;
663	<	queue[k] = e;
663	>	es[k] = e;
664		k = parent;
665		}
666	<	queue[k] = x;
666	>	es[k] = x;
667		}
668
669		/**
#	Line 626 | Line 676 | public class PriorityQueue<E> extends Ab
676		*/
677		private void siftDown(int k, E x) {
678		if (comparator != null)
679	<	siftDownUsingComparator(k, x);
679	>	siftDownUsingComparator(k, x, queue, size, comparator);
680		else
681	<	siftDownComparable(k, x);
681	>	siftDownComparable(k, x, queue, size);
682		}
683
684	<	private void siftDownComparable(int k, E x) {
685	<	Comparable<? super E> key = (Comparable<? super E>)x;
686	<	int half = size >>> 1;        // loop while a non-leaf
684	>	private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
685	>	// assert n > 0;
686	>	Comparable<? super T> key = (Comparable<? super T>)x;
687	>	int half = n >>> 1;           // loop while a non-leaf
688		while (k < half) {
689		int child = (k << 1) + 1; // assume left child is least
690	<	Object c = queue[child];
690	>	Object c = es[child];
691		int right = child + 1;
692	<	if (right < size &&
693	<	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
694	<	c = queue[child = right];
695	<	if (key.compareTo((E) c) <= 0)
692	>	if (right < n &&
693	>	((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
694	>	c = es[child = right];
695	>	if (key.compareTo((T) c) <= 0)
696		break;
697	<	queue[k] = c;
697	>	es[k] = c;
698		k = child;
699		}
700	<	queue[k] = key;
700	>	es[k] = key;
701		}
702
703	<	private void siftDownUsingComparator(int k, E x) {
704	<	int half = size >>> 1;
703	>	private static <T> void siftDownUsingComparator(
704	>	int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
705	>	// assert n > 0;
706	>	int half = n >>> 1;
707		while (k < half) {
708		int child = (k << 1) + 1;
709	<	Object c = queue[child];
709	>	Object c = es[child];
710		int right = child + 1;
711	<	if (right < size &&
712	<	comparator.compare((E) c, (E) queue[right]) > 0)
713	<	c = queue[child = right];
661	<	if (comparator.compare(x, (E) c) <= 0)
711	>	if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
712	>	c = es[child = right];
713	>	if (cmp.compare(x, (T) c) <= 0)
714		break;
715	<	queue[k] = c;
715	>	es[k] = c;
716		k = child;
717		}
718	<	queue[k] = x;
718	>	es[k] = x;
719		}
720
721		/**
722		* Establishes the heap invariant (described above) in the entire tree,
723		* assuming nothing about the order of the elements prior to the call.
724	+	* This classic algorithm due to Floyd (1964) is known to be O(size).
725		*/
726		private void heapify() {
727	<	for (int i = (size >>> 1) - 1; i >= 0; i--)
728	<	siftDown(i, (E) queue[i]);
727	>	final Object[] es = queue;
728	>	int n = size, i = (n >>> 1) - 1;
729	>	final Comparator<? super E> cmp;
730	>	if ((cmp = comparator) == null)
731	>	for (; i >= 0; i--)
732	>	siftDownComparable(i, (E) es[i], es, n);
733	>	else
734	>	for (; i >= 0; i--)
735	>	siftDownUsingComparator(i, (E) es[i], es, n, cmp);
736		}
737
738		/**
#	Line 689 | Line 749 | public class PriorityQueue<E> extends Ab
749		}
750
751		/**
752	<	* Saves the state of the instance to a stream (that
693	<	* is, serializes it).
752	>	* Saves this queue to a stream (that is, serializes it).
753		*
754	+	* @param s the stream
755	+	* @throws java.io.IOException if an I/O error occurs
756		* @serialData The length of the array backing the instance is
757		*             emitted (int), followed by all of its elements
758		*             (each an {@code Object}) in the proper order.
698	–	* @param s the stream
759		*/
760	+	// OPENJDK @java.io.Serial
761		private void writeObject(java.io.ObjectOutputStream s)
762	<	throws java.io.IOException{
762	>	throws java.io.IOException {
763		// Write out element count, and any hidden stuff
764		s.defaultWriteObject();
765
#	Line 706 | Line 767 | public class PriorityQueue<E> extends Ab
767		s.writeInt(Math.max(2, size + 1));
768
769		// Write out all elements in the "proper order".
770	<	for (int i = 0; i < size; i++)
771	<	s.writeObject(queue[i]);
770	>	final Object[] es = queue;
771	>	for (int i = 0, n = size; i < n; i++)
772	>	s.writeObject(es[i]);
773		}
774
775		/**
#	Line 715 | Line 777 | public class PriorityQueue<E> extends Ab
777		* (that is, deserializes it).
778		*
779		* @param s the stream
780	+	* @throws ClassNotFoundException if the class of a serialized object
781	+	*         could not be found
782	+	* @throws java.io.IOException if an I/O error occurs
783		*/
784	+	// OPENJDK @java.io.Serial
785		private void readObject(java.io.ObjectInputStream s)
786		throws java.io.IOException, ClassNotFoundException {
787		// Read in size, and any hidden stuff
#	Line 724 | Line 790 | public class PriorityQueue<E> extends Ab
790		// Read in (and discard) array length
791		s.readInt();
792
793	<	queue = new Object[size];
793	>	jsr166.Platform.checkArray(s, Object[].class, size);
794	>	final Object[] es = queue = new Object[Math.max(size, 1)];
795
796		// Read in all elements.
797	<	for (int i = 0; i < size; i++)
798	<	queue[i] = s.readObject();
797	>	for (int i = 0, n = size; i < n; i++)
798	>	es[i] = s.readObject();
799
800		// Elements are guaranteed to be in "proper order", but the
801		// spec has never explained what that might be.
802		heapify();
803		}
804	+
805	+	/**
806	+	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
807	+	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
808	+	* queue. The spliterator does not traverse elements in any particular order
809	+	* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
810	+	*
811	+	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
812	+	* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.
813	+	* Overriding implementations should document the reporting of additional
814	+	* characteristic values.
815	+	*
816	+	* @return a {@code Spliterator} over the elements in this queue
817	+	* @since 1.8
818	+	*/
819	+	public final Spliterator<E> spliterator() {
820	+	return new PriorityQueueSpliterator(0, -1, 0);
821	+	}
822	+
823	+	final class PriorityQueueSpliterator implements Spliterator<E> {
824	+	private int index;            // current index, modified on advance/split
825	+	private int fence;            // -1 until first use
826	+	private int expectedModCount; // initialized when fence set
827	+
828	+	/** Creates new spliterator covering the given range. */
829	+	PriorityQueueSpliterator(int origin, int fence, int expectedModCount) {
830	+	this.index = origin;
831	+	this.fence = fence;
832	+	this.expectedModCount = expectedModCount;
833	+	}
834	+
835	+	private int getFence() { // initialize fence to size on first use
836	+	int hi;
837	+	if ((hi = fence) < 0) {
838	+	expectedModCount = modCount;
839	+	hi = fence = size;
840	+	}
841	+	return hi;
842	+	}
843	+
844	+	public PriorityQueueSpliterator trySplit() {
845	+	int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
846	+	return (lo >= mid) ? null :
847	+	new PriorityQueueSpliterator(lo, index = mid, expectedModCount);
848	+	}
849	+
850	+	public void forEachRemaining(Consumer<? super E> action) {
851	+	if (action == null)
852	+	throw new NullPointerException();
853	+	if (fence < 0) { fence = size; expectedModCount = modCount; }
854	+	final Object[] es = queue;
855	+	int i, hi; E e;
856	+	for (i = index, index = hi = fence; i < hi; i++) {
857	+	if ((e = (E) es[i]) == null)
858	+	break;      // must be CME
859	+	action.accept(e);
860	+	}
861	+	if (modCount != expectedModCount)
862	+	throw new ConcurrentModificationException();
863	+	}
864	+
865	+	public boolean tryAdvance(Consumer<? super E> action) {
866	+	if (action == null)
867	+	throw new NullPointerException();
868	+	if (fence < 0) { fence = size; expectedModCount = modCount; }
869	+	int i;
870	+	if ((i = index) < fence) {
871	+	index = i + 1;
872	+	E e;
873	+	if ((e = (E) queue[i]) == null
874	+	|| modCount != expectedModCount)
875	+	throw new ConcurrentModificationException();
876	+	action.accept(e);
877	+	return true;
878	+	}
879	+	return false;
880	+	}
881	+
882	+	public long estimateSize() {
883	+	return getFence() - index;
884	+	}
885	+
886	+	public int characteristics() {
887	+	return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
888	+	}
889	+	}
890	+
891	+	/**
892	+	* @throws NullPointerException {@inheritDoc}
893	+	*/
894	+	public boolean removeIf(Predicate<? super E> filter) {
895	+	Objects.requireNonNull(filter);
896	+	return bulkRemove(filter);
897	+	}
898	+
899	+	/**
900	+	* @throws NullPointerException {@inheritDoc}
901	+	*/
902	+	public boolean removeAll(Collection<?> c) {
903	+	Objects.requireNonNull(c);
904	+	return bulkRemove(e -> c.contains(e));
905	+	}
906	+
907	+	/**
908	+	* @throws NullPointerException {@inheritDoc}
909	+	*/
910	+	public boolean retainAll(Collection<?> c) {
911	+	Objects.requireNonNull(c);
912	+	return bulkRemove(e -> !c.contains(e));
913	+	}
914	+
915	+	// A tiny bit set implementation
916	+
917	+	private static long[] nBits(int n) {
918	+	return new long[((n - 1) >> 6) + 1];
919	+	}
920	+	private static void setBit(long[] bits, int i) {
921	+	bits[i >> 6] |= 1L << i;
922	+	}
923	+	private static boolean isClear(long[] bits, int i) {
924	+	return (bits[i >> 6] & (1L << i)) == 0;
925	+	}
926	+
927	+	/** Implementation of bulk remove methods. */
928	+	private boolean bulkRemove(Predicate<? super E> filter) {
929	+	final int expectedModCount = ++modCount;
930	+	final Object[] es = queue;
931	+	final int end = size;
932	+	int i;
933	+	// Optimize for initial run of survivors
934	+	for (i = 0; i < end && !filter.test((E) es[i]); i++)
935	+	;
936	+	if (i >= end) {
937	+	if (modCount != expectedModCount)
938	+	throw new ConcurrentModificationException();
939	+	return false;
940	+	}
941	+	// Tolerate predicates that reentrantly access the collection for
942	+	// read (but writers still get CME), so traverse once to find
943	+	// elements to delete, a second pass to physically expunge.
944	+	final int beg = i;
945	+	final long[] deathRow = nBits(end - beg);
946	+	deathRow[0] = 1L;   // set bit 0
947	+	for (i = beg + 1; i < end; i++)
948	+	if (filter.test((E) es[i]))
949	+	setBit(deathRow, i - beg);
950	+	if (modCount != expectedModCount)
951	+	throw new ConcurrentModificationException();
952	+	int w = beg;
953	+	for (i = beg; i < end; i++)
954	+	if (isClear(deathRow, i - beg))
955	+	es[w++] = es[i];
956	+	for (i = size = w; i < end; i++)
957	+	es[i] = null;
958	+	heapify();
959	+	return true;
960	+	}
961	+
962	+	/**
963	+	* @throws NullPointerException {@inheritDoc}
964	+	*/
965	+	public void forEach(Consumer<? super E> action) {
966	+	Objects.requireNonNull(action);
967	+	final int expectedModCount = modCount;
968	+	final Object[] es = queue;
969	+	for (int i = 0, n = size; i < n; i++)
970	+	action.accept((E) es[i]);
971	+	if (expectedModCount != modCount)
972	+	throw new ConcurrentModificationException();
973	+	}
974		}

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