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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.74 by jsr166, Wed Jul 13 11:27:28 2011 UTC vs.
Revision 1.131 by jsr166, Wed May 22 17:36:58 2019 UTC

#	Line 1 | Line 1
1		/*
2	<	* Copyright (c) 2003, 2006, Oracle and/or its affiliates. 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 25 | Line 25
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
#	Line 92 | Line 99 | public class PriorityQueue<E> extends Ab
99		* heap and each descendant d of n, n <= d.  The element with the
100		* lowest value is in queue[0], assuming the queue is nonempty.
101		*/
102	<	private transient Object[] queue;
102	>	transient Object[] queue; // non-private to simplify nested class access
103
104		/**
105		* The number of elements in the priority queue.
106		*/
107	<	private int size = 0;
107	>	int size;
108
109		/**
110		* The comparator, or null if priority queue uses elements'
#	Line 109 | Line 116 | public class PriorityQueue<E> extends Ab
116		* The number of times this priority queue has been
117		* <i>structurally modified</i>.  See AbstractList for gory details.
118		*/
119	<	private transient int modCount = 0;
119	>	transient int modCount;     // non-private to simplify nested class access
120
121		/**
122		* Creates a {@code PriorityQueue} with the default initial
#	Line 134 | Line 141 | public class PriorityQueue<E> extends Ab
141		}
142
143		/**
144	+	* Creates a {@code PriorityQueue} with the default initial capacity and
145	+	* whose elements are ordered according to the specified comparator.
146	+	*
147	+	* @param  comparator the comparator that will be used to order this
148	+	*         priority queue.  If {@code null}, the {@linkplain Comparable
149	+	*         natural ordering} of the elements will be used.
150	+	* @since 1.8
151	+	*/
152	+	public PriorityQueue(Comparator<? super E> comparator) {
153	+	this(DEFAULT_INITIAL_CAPACITY, comparator);
154	+	}
155	+
156	+	/**
157		* Creates a {@code PriorityQueue} with the specified initial capacity
158		* that orders its elements according to the specified comparator.
159		*
#	Line 170 | Line 190 | public class PriorityQueue<E> extends Ab
190		* @throws NullPointerException if the specified collection or any
191		*         of its elements are null
192		*/
173	–	@SuppressWarnings("unchecked")
193		public PriorityQueue(Collection<? extends E> c) {
194		if (c instanceof SortedSet<?>) {
195		SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
#	Line 202 | Line 221 | public class PriorityQueue<E> extends Ab
221		* @throws NullPointerException if the specified priority queue or any
222		*         of its elements are null
223		*/
205	–	@SuppressWarnings("unchecked")
224		public PriorityQueue(PriorityQueue<? extends E> c) {
225		this.comparator = (Comparator<? super E>) c.comparator();
226		initFromPriorityQueue(c);
#	Line 221 | Line 239 | public class PriorityQueue<E> extends Ab
239		* @throws NullPointerException if the specified sorted set or any
240		*         of its elements are null
241		*/
224	–	@SuppressWarnings("unchecked")
242		public PriorityQueue(SortedSet<? extends E> c) {
243		this.comparator = (Comparator<? super E>) c.comparator();
244		initElementsFromCollection(c);
245		}
246
247	+	/** Ensures that queue[0] exists, helping peek() and poll(). */
248	+	private static Object[] ensureNonEmpty(Object[] es) {
249	+	return (es.length > 0) ? es : new Object[1];
250	+	}
251	+
252		private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
253		if (c.getClass() == PriorityQueue.class) {
254	<	this.queue = c.toArray();
254	>	this.queue = ensureNonEmpty(c.toArray());
255		this.size = c.size();
256		} else {
257		initFromCollection(c);
#	Line 237 | Line 259 | public class PriorityQueue<E> extends Ab
259		}
260
261		private void initElementsFromCollection(Collection<? extends E> c) {
262	<	Object[] a = c.toArray();
262	>	Object[] es = c.toArray();
263	>	int len = es.length;
264		// If c.toArray incorrectly doesn't return Object[], copy it.
265	<	if (a.getClass() != Object[].class)
266	<	a = Arrays.copyOf(a, a.length, Object[].class);
244	<	int len = a.length;
265	>	if (es.getClass() != Object[].class)
266	>	es = Arrays.copyOf(es, len, Object[].class);
267		if (len == 1 || this.comparator != null)
268	<	for (int i = 0; i < len; i++)
269	<	if (a[i] == null)
268	>	for (Object e : es)
269	>	if (e == null)
270		throw new NullPointerException();
271	<	this.queue = a;
272	<	this.size = a.length;
271	>	this.queue = ensureNonEmpty(es);
272	>	this.size = len;
273		}
274
275		/**
#	Line 261 | Line 283 | public class PriorityQueue<E> extends Ab
283		}
284
285		/**
264	–	* The maximum size of array to allocate.
265	–	* Some VMs reserve some header words in an array.
266	–	* Attempts to allocate larger arrays may result in
267	–	* OutOfMemoryError: Requested array size exceeds VM limit
268	–	*/
269	–	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
270	–
271	–	/**
286		* Increases the capacity of the array.
287		*
288		* @param minCapacity the desired minimum capacity
#	Line 276 | Line 290 | public class PriorityQueue<E> extends Ab
290		private void grow(int minCapacity) {
291		int oldCapacity = queue.length;
292		// Double size if small; else grow by 50%
293	<	int newCapacity = oldCapacity + ((oldCapacity < 64) ?
294	<	(oldCapacity + 2) :
295	<	(oldCapacity >> 1));
296	<	// overflow-conscious code
283	<	if (newCapacity - MAX_ARRAY_SIZE > 0)
284	<	newCapacity = hugeCapacity(minCapacity);
293	>	int newCapacity = ArraysSupport.newLength(oldCapacity,
294	>	minCapacity - oldCapacity, /* minimum growth */
295	>	oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1
296	>	/* preferred growth */);
297		queue = Arrays.copyOf(queue, newCapacity);
298		}
299
288	–	private static int hugeCapacity(int minCapacity) {
289	–	if (minCapacity < 0) // overflow
290	–	throw new OutOfMemoryError();
291	–	return (minCapacity > MAX_ARRAY_SIZE) ?
292	–	Integer.MAX_VALUE :
293	–	MAX_ARRAY_SIZE;
294	–	}
295	–
300		/**
301		* Inserts the specified element into this priority queue.
302		*
#	Line 322 | Line 326 | public class PriorityQueue<E> extends Ab
326		int i = size;
327		if (i >= queue.length)
328		grow(i + 1);
329	+	siftUp(i, e);
330		size = i + 1;
326	–	if (i == 0)
327	–	queue[0] = e;
328	–	else
329	–	siftUp(i, e);
331		return true;
332		}
333
334		public E peek() {
335	<	return (size == 0) ? null : (E) queue[0];
335	>	return (E) queue[0];
336		}
337
338		private int indexOf(Object o) {
339		if (o != null) {
340	<	for (int i = 0; i < size; i++)
341	<	if (o.equals(queue[i]))
340	>	final Object[] es = queue;
341	>	for (int i = 0, n = size; i < n; i++)
342	>	if (o.equals(es[i]))
343		return i;
344		}
345		return -1;
#	Line 365 | Line 367 | public class PriorityQueue<E> extends Ab
367		}
368
369		/**
370	<	* Version of remove using reference equality, not equals.
369	<	* Needed by iterator.remove.
370	>	* Identity-based version for use in Itr.remove.
371		*
372		* @param o element to be removed from this queue, if present
372	–	* @return {@code true} if removed
373		*/
374	<	boolean removeEq(Object o) {
375	<	for (int i = 0; i < size; i++) {
376	<	if (o == queue[i]) {
374	>	void removeEq(Object o) {
375	>	final Object[] es = queue;
376	>	for (int i = 0, n = size; i < n; i++) {
377	>	if (o == es[i]) {
378		removeAt(i);
379	<	return true;
379	>	break;
380		}
381		}
381	–	return false;
382		}
383
384		/**
#	Line 390 | Line 390 | public class PriorityQueue<E> extends Ab
390		* @return {@code true} if this queue contains the specified element
391		*/
392		public boolean contains(Object o) {
393	<	return indexOf(o) != -1;
393	>	return indexOf(o) >= 0;
394		}
395
396		/**
#	Line 428 | Line 428 | public class PriorityQueue<E> extends Ab
428		* precise control over the runtime type of the output array, and may,
429		* under certain circumstances, be used to save allocation costs.
430		*
431	<	* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
431	>	* <p>Suppose {@code x} is a queue known to contain only strings.
432		* The following code can be used to dump the queue into a newly
433	<	* allocated array of <tt>String</tt>:
433	>	* allocated array of {@code String}:
434		*
435	<	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
435	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
436		*
437	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
438	<	* <tt>toArray()</tt>.
437	>	* Note that {@code toArray(new Object[0])} is identical in function to
438	>	* {@code toArray()}.
439		*
440		* @param a the array into which the elements of the queue are to
441		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 447 | Line 447 | public class PriorityQueue<E> extends Ab
447		* @throws NullPointerException if the specified array is null
448		*/
449		public <T> T[] toArray(T[] a) {
450	+	final int size = this.size;
451		if (a.length < size)
452		// Make a new array of a's runtime type, but my contents:
453		return (T[]) Arrays.copyOf(queue, size, a.getClass());
#	Line 471 | Line 472 | public class PriorityQueue<E> extends Ab
472		* Index (into queue array) of element to be returned by
473		* subsequent call to next.
474		*/
475	<	private int cursor = 0;
475	>	private int cursor;
476
477		/**
478		* Index of element returned by most recent call to next,
#	Line 491 | Line 492 | public class PriorityQueue<E> extends Ab
492		* We expect that most iterations, even those involving removals,
493		* will not need to store elements in this field.
494		*/
495	<	private ArrayDeque<E> forgetMeNot = null;
495	>	private ArrayDeque<E> forgetMeNot;
496
497		/**
498		* Element returned by the most recent call to next iff that
499		* element was drawn from the forgetMeNot list.
500		*/
501	<	private E lastRetElt = null;
501	>	private E lastRetElt;
502
503		/**
504		* The modCount value that the iterator believes that the backing
#	Line 506 | Line 507 | public class PriorityQueue<E> extends Ab
507		*/
508		private int expectedModCount = modCount;
509
510	+	Itr() {}                        // prevent access constructor creation
511	+
512		public boolean hasNext() {
513		return cursor < size ||
514		(forgetMeNot != null && !forgetMeNot.isEmpty());
#	Line 535 | Line 538 | public class PriorityQueue<E> extends Ab
538		cursor--;
539		else {
540		if (forgetMeNot == null)
541	<	forgetMeNot = new ArrayDeque<E>();
541	>	forgetMeNot = new ArrayDeque<>();
542		forgetMeNot.add(moved);
543		}
544		} else if (lastRetElt != null) {
#	Line 558 | Line 561 | public class PriorityQueue<E> extends Ab
561		*/
562		public void clear() {
563		modCount++;
564	<	for (int i = 0; i < size; i++)
565	<	queue[i] = null;
564	>	final Object[] es = queue;
565	>	for (int i = 0, n = size; i < n; i++)
566	>	es[i] = null;
567		size = 0;
568		}
569
570		public E poll() {
571	<	if (size == 0)
572	<	return null;
573	<	int s = --size;
574	<	modCount++;
575	<	E result = (E) queue[0];
576	<	E x = (E) queue[s];
577	<	queue[s] = null;
578	<	if (s != 0)
579	<	siftDown(0, x);
571	>	final Object[] es;
572	>	final E result;
573	>
574	>	if ((result = (E) ((es = queue)[0])) != null) {
575	>	modCount++;
576	>	final int n;
577	>	final E x = (E) es[(n = --size)];
578	>	es[n] = null;
579	>	if (n > 0) {
580	>	final Comparator<? super E> cmp;
581	>	if ((cmp = comparator) == null)
582	>	siftDownComparable(0, x, es, n);
583	>	else
584	>	siftDownUsingComparator(0, x, es, n, cmp);
585	>	}
586	>	}
587		return result;
588		}
589
#	Line 588 | Line 599 | public class PriorityQueue<E> extends Ab
599		* position before i. This fact is used by iterator.remove so as to
600		* avoid missing traversing elements.
601		*/
602	<	private E removeAt(int i) {
602	>	E removeAt(int i) {
603		// assert i >= 0 && i < size;
604	+	final Object[] es = queue;
605		modCount++;
606		int s = --size;
607		if (s == i) // removed last element
608	<	queue[i] = null;
608	>	es[i] = null;
609		else {
610	<	E moved = (E) queue[s];
611	<	queue[s] = null;
610	>	E moved = (E) es[s];
611	>	es[s] = null;
612		siftDown(i, moved);
613	<	if (queue[i] == moved) {
613	>	if (es[i] == moved) {
614		siftUp(i, moved);
615	<	if (queue[i] != moved)
615	>	if (es[i] != moved)
616		return moved;
617		}
618		}
#	Line 612 | Line 624 | public class PriorityQueue<E> extends Ab
624		* promoting x up the tree until it is greater than or equal to
625		* its parent, or is the root.
626		*
627	<	* To simplify and speed up coercions and comparisons. the
627	>	* To simplify and speed up coercions and comparisons, the
628		* Comparable and Comparator versions are separated into different
629		* methods that are otherwise identical. (Similarly for siftDown.)
630		*
#	Line 621 | Line 633 | public class PriorityQueue<E> extends Ab
633		*/
634		private void siftUp(int k, E x) {
635		if (comparator != null)
636	<	siftUpUsingComparator(k, x);
636	>	siftUpUsingComparator(k, x, queue, comparator);
637		else
638	<	siftUpComparable(k, x);
638	>	siftUpComparable(k, x, queue);
639		}
640
641	<	private void siftUpComparable(int k, E x) {
642	<	Comparable<? super E> key = (Comparable<? super E>) x;
641	>	private static <T> void siftUpComparable(int k, T x, Object[] es) {
642	>	Comparable<? super T> key = (Comparable<? super T>) x;
643		while (k > 0) {
644		int parent = (k - 1) >>> 1;
645	<	Object e = queue[parent];
646	<	if (key.compareTo((E) e) >= 0)
645	>	Object e = es[parent];
646	>	if (key.compareTo((T) e) >= 0)
647		break;
648	<	queue[k] = e;
648	>	es[k] = e;
649		k = parent;
650		}
651	<	queue[k] = key;
651	>	es[k] = key;
652		}
653
654	<	private void siftUpUsingComparator(int k, E x) {
654	>	private static <T> void siftUpUsingComparator(
655	>	int k, T x, Object[] es, Comparator<? super T> cmp) {
656		while (k > 0) {
657		int parent = (k - 1) >>> 1;
658	<	Object e = queue[parent];
659	<	if (comparator.compare(x, (E) e) >= 0)
658	>	Object e = es[parent];
659	>	if (cmp.compare(x, (T) e) >= 0)
660		break;
661	<	queue[k] = e;
661	>	es[k] = e;
662		k = parent;
663		}
664	<	queue[k] = x;
664	>	es[k] = x;
665		}
666
667		/**
#	Line 661 | Line 674 | public class PriorityQueue<E> extends Ab
674		*/
675		private void siftDown(int k, E x) {
676		if (comparator != null)
677	<	siftDownUsingComparator(k, x);
677	>	siftDownUsingComparator(k, x, queue, size, comparator);
678		else
679	<	siftDownComparable(k, x);
679	>	siftDownComparable(k, x, queue, size);
680		}
681
682	<	private void siftDownComparable(int k, E x) {
683	<	Comparable<? super E> key = (Comparable<? super E>)x;
684	<	int half = size >>> 1;        // loop while a non-leaf
682	>	private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {
683	>	// assert n > 0;
684	>	Comparable<? super T> key = (Comparable<? super T>)x;
685	>	int half = n >>> 1;           // loop while a non-leaf
686		while (k < half) {
687		int child = (k << 1) + 1; // assume left child is least
688	<	Object c = queue[child];
688	>	Object c = es[child];
689		int right = child + 1;
690	<	if (right < size &&
691	<	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
692	<	c = queue[child = right];
693	<	if (key.compareTo((E) c) <= 0)
690	>	if (right < n &&
691	>	((Comparable<? super T>) c).compareTo((T) es[right]) > 0)
692	>	c = es[child = right];
693	>	if (key.compareTo((T) c) <= 0)
694		break;
695	<	queue[k] = c;
695	>	es[k] = c;
696		k = child;
697		}
698	<	queue[k] = key;
698	>	es[k] = key;
699		}
700
701	<	private void siftDownUsingComparator(int k, E x) {
702	<	int half = size >>> 1;
701	>	private static <T> void siftDownUsingComparator(
702	>	int k, T x, Object[] es, int n, Comparator<? super T> cmp) {
703	>	// assert n > 0;
704	>	int half = n >>> 1;
705		while (k < half) {
706		int child = (k << 1) + 1;
707	<	Object c = queue[child];
707	>	Object c = es[child];
708		int right = child + 1;
709	<	if (right < size &&
710	<	comparator.compare((E) c, (E) queue[right]) > 0)
711	<	c = queue[child = right];
696	<	if (comparator.compare(x, (E) c) <= 0)
709	>	if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
710	>	c = es[child = right];
711	>	if (cmp.compare(x, (T) c) <= 0)
712		break;
713	<	queue[k] = c;
713	>	es[k] = c;
714		k = child;
715		}
716	<	queue[k] = x;
716	>	es[k] = x;
717		}
718
719		/**
720		* Establishes the heap invariant (described above) in the entire tree,
721		* assuming nothing about the order of the elements prior to the call.
722	+	* This classic algorithm due to Floyd (1964) is known to be O(size).
723		*/
724		private void heapify() {
725	<	for (int i = (size >>> 1) - 1; i >= 0; i--)
726	<	siftDown(i, (E) queue[i]);
725	>	final Object[] es = queue;
726	>	int n = size, i = (n >>> 1) - 1;
727	>	final Comparator<? super E> cmp;
728	>	if ((cmp = comparator) == null)
729	>	for (; i >= 0; i--)
730	>	siftDownComparable(i, (E) es[i], es, n);
731	>	else
732	>	for (; i >= 0; i--)
733	>	siftDownUsingComparator(i, (E) es[i], es, n, cmp);
734		}
735
736		/**
#	Line 724 | Line 747 | public class PriorityQueue<E> extends Ab
747		}
748
749		/**
750	<	* Saves the state of the instance to a stream (that
728	<	* is, serializes it).
750	>	* Saves this queue to a stream (that is, serializes it).
751		*
752	+	* @param s the stream
753	+	* @throws java.io.IOException if an I/O error occurs
754		* @serialData The length of the array backing the instance is
755		*             emitted (int), followed by all of its elements
756		*             (each an {@code Object}) in the proper order.
733	–	* @param s the stream
757		*/
758		private void writeObject(java.io.ObjectOutputStream s)
759	<	throws java.io.IOException{
759	>	throws java.io.IOException {
760		// Write out element count, and any hidden stuff
761		s.defaultWriteObject();
762
#	Line 741 | Line 764 | public class PriorityQueue<E> extends Ab
764		s.writeInt(Math.max(2, size + 1));
765
766		// Write out all elements in the "proper order".
767	<	for (int i = 0; i < size; i++)
768	<	s.writeObject(queue[i]);
767	>	final Object[] es = queue;
768	>	for (int i = 0, n = size; i < n; i++)
769	>	s.writeObject(es[i]);
770		}
771
772		/**
#	Line 750 | Line 774 | public class PriorityQueue<E> extends Ab
774		* (that is, deserializes it).
775		*
776		* @param s the stream
777	+	* @throws ClassNotFoundException if the class of a serialized object
778	+	*         could not be found
779	+	* @throws java.io.IOException if an I/O error occurs
780		*/
781		private void readObject(java.io.ObjectInputStream s)
782		throws java.io.IOException, ClassNotFoundException {
#	Line 759 | Line 786 | public class PriorityQueue<E> extends Ab
786		// Read in (and discard) array length
787		s.readInt();
788
789	<	queue = new Object[size];
789	>	jsr166.Platform.checkArray(s, Object[].class, size);
790	>	final Object[] es = queue = new Object[Math.max(size, 1)];
791
792		// Read in all elements.
793	<	for (int i = 0; i < size; i++)
794	<	queue[i] = s.readObject();
793	>	for (int i = 0, n = size; i < n; i++)
794	>	es[i] = s.readObject();
795
796		// Elements are guaranteed to be in "proper order", but the
797		// spec has never explained what that might be.
798		heapify();
799		}
800	+
801	+	/**
802	+	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
803	+	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
804	+	* queue. The spliterator does not traverse elements in any particular order
805	+	* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
806	+	*
807	+	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
808	+	* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.
809	+	* Overriding implementations should document the reporting of additional
810	+	* characteristic values.
811	+	*
812	+	* @return a {@code Spliterator} over the elements in this queue
813	+	* @since 1.8
814	+	*/
815	+	public final Spliterator<E> spliterator() {
816	+	return new PriorityQueueSpliterator(0, -1, 0);
817	+	}
818	+
819	+	final class PriorityQueueSpliterator implements Spliterator<E> {
820	+	private int index;            // current index, modified on advance/split
821	+	private int fence;            // -1 until first use
822	+	private int expectedModCount; // initialized when fence set
823	+
824	+	/** Creates new spliterator covering the given range. */
825	+	PriorityQueueSpliterator(int origin, int fence, int expectedModCount) {
826	+	this.index = origin;
827	+	this.fence = fence;
828	+	this.expectedModCount = expectedModCount;
829	+	}
830	+
831	+	private int getFence() { // initialize fence to size on first use
832	+	int hi;
833	+	if ((hi = fence) < 0) {
834	+	expectedModCount = modCount;
835	+	hi = fence = size;
836	+	}
837	+	return hi;
838	+	}
839	+
840	+	public PriorityQueueSpliterator trySplit() {
841	+	int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
842	+	return (lo >= mid) ? null :
843	+	new PriorityQueueSpliterator(lo, index = mid, expectedModCount);
844	+	}
845	+
846	+	public void forEachRemaining(Consumer<? super E> action) {
847	+	if (action == null)
848	+	throw new NullPointerException();
849	+	if (fence < 0) { fence = size; expectedModCount = modCount; }
850	+	final Object[] es = queue;
851	+	int i, hi; E e;
852	+	for (i = index, index = hi = fence; i < hi; i++) {
853	+	if ((e = (E) es[i]) == null)
854	+	break;      // must be CME
855	+	action.accept(e);
856	+	}
857	+	if (modCount != expectedModCount)
858	+	throw new ConcurrentModificationException();
859	+	}
860	+
861	+	public boolean tryAdvance(Consumer<? super E> action) {
862	+	if (action == null)
863	+	throw new NullPointerException();
864	+	if (fence < 0) { fence = size; expectedModCount = modCount; }
865	+	int i;
866	+	if ((i = index) < fence) {
867	+	index = i + 1;
868	+	E e;
869	+	if ((e = (E) queue[i]) == null
870	+	|| modCount != expectedModCount)
871	+	throw new ConcurrentModificationException();
872	+	action.accept(e);
873	+	return true;
874	+	}
875	+	return false;
876	+	}
877	+
878	+	public long estimateSize() {
879	+	return getFence() - index;
880	+	}
881	+
882	+	public int characteristics() {
883	+	return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
884	+	}
885	+	}
886	+
887	+	/**
888	+	* @throws NullPointerException {@inheritDoc}
889	+	*/
890	+	public boolean removeIf(Predicate<? super E> filter) {
891	+	Objects.requireNonNull(filter);
892	+	return bulkRemove(filter);
893	+	}
894	+
895	+	/**
896	+	* @throws NullPointerException {@inheritDoc}
897	+	*/
898	+	public boolean removeAll(Collection<?> c) {
899	+	Objects.requireNonNull(c);
900	+	return bulkRemove(e -> c.contains(e));
901	+	}
902	+
903	+	/**
904	+	* @throws NullPointerException {@inheritDoc}
905	+	*/
906	+	public boolean retainAll(Collection<?> c) {
907	+	Objects.requireNonNull(c);
908	+	return bulkRemove(e -> !c.contains(e));
909	+	}
910	+
911	+	// A tiny bit set implementation
912	+
913	+	private static long[] nBits(int n) {
914	+	return new long[((n - 1) >> 6) + 1];
915	+	}
916	+	private static void setBit(long[] bits, int i) {
917	+	bits[i >> 6] |= 1L << i;
918	+	}
919	+	private static boolean isClear(long[] bits, int i) {
920	+	return (bits[i >> 6] & (1L << i)) == 0;
921	+	}
922	+
923	+	/** Implementation of bulk remove methods. */
924	+	private boolean bulkRemove(Predicate<? super E> filter) {
925	+	final int expectedModCount = ++modCount;
926	+	final Object[] es = queue;
927	+	final int end = size;
928	+	int i;
929	+	// Optimize for initial run of survivors
930	+	for (i = 0; i < end && !filter.test((E) es[i]); i++)
931	+	;
932	+	if (i >= end) {
933	+	if (modCount != expectedModCount)
934	+	throw new ConcurrentModificationException();
935	+	return false;
936	+	}
937	+	// Tolerate predicates that reentrantly access the collection for
938	+	// read (but writers still get CME), so traverse once to find
939	+	// elements to delete, a second pass to physically expunge.
940	+	final int beg = i;
941	+	final long[] deathRow = nBits(end - beg);
942	+	deathRow[0] = 1L;   // set bit 0
943	+	for (i = beg + 1; i < end; i++)
944	+	if (filter.test((E) es[i]))
945	+	setBit(deathRow, i - beg);
946	+	if (modCount != expectedModCount)
947	+	throw new ConcurrentModificationException();
948	+	int w = beg;
949	+	for (i = beg; i < end; i++)
950	+	if (isClear(deathRow, i - beg))
951	+	es[w++] = es[i];
952	+	for (i = size = w; i < end; i++)
953	+	es[i] = null;
954	+	heapify();
955	+	return true;
956	+	}
957	+
958	+	/**
959	+	* @throws NullPointerException {@inheritDoc}
960	+	*/
961	+	public void forEach(Consumer<? super E> action) {
962	+	Objects.requireNonNull(action);
963	+	final int expectedModCount = modCount;
964	+	final Object[] es = queue;
965	+	for (int i = 0, n = size; i < n; i++)
966	+	action.accept((E) es[i]);
967	+	if (expectedModCount != modCount)
968	+	throw new ConcurrentModificationException();
969	+	}
970		}

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