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root/jsr166/jsr166/src/main/java/util/PriorityQueue.java

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.75 by jsr166, Tue Oct 25 20:29:12 2011 UTC vs.
Revision 1.115 by jsr166, Fri Dec 2 07:11:36 2016 UTC

#	Line 1 | Line 1
1		/*
2	<	* Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.
2	>	* Copyright (c) 2003, 2013, 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	+
30		/**
31		* An unbounded priority {@linkplain Queue queue} based on a priority heap.
32		* The elements of the priority queue are ordered according to their
#	Line 52 | Line 54 | package java.util;
54		* <p>This class and its iterator implement all of the
55		* <em>optional</em> methods of the {@link Collection} and {@link
56		* Iterator} interfaces.  The Iterator provided in method {@link
57	<	* #iterator()} is <em>not</em> guaranteed to traverse the elements of
57	>	* #iterator()} and the Spliterator provided in method {@link #spliterator()}
58	>	* are <em>not</em> guaranteed to traverse the elements of
59		* the priority queue in any particular order. If you need ordered
60		* traversal, consider using {@code Arrays.sort(pq.toArray())}.
61		*
62	<	* <p> <strong>Note that this implementation is not synchronized.</strong>
62	>	* <p><strong>Note that this implementation is not synchronized.</strong>
63		* Multiple threads should not access a {@code PriorityQueue}
64		* instance concurrently if any of the threads modifies the queue.
65		* Instead, use the thread-safe {@link
66		* java.util.concurrent.PriorityBlockingQueue} class.
67		*
68		* <p>Implementation note: this implementation provides
69	<	* O(log(n)) time for the enqueing and dequeing methods
69	>	* O(log(n)) time for the enqueuing and dequeuing methods
70		* ({@code offer}, {@code poll}, {@code remove()} and {@code add});
71		* linear time for the {@code remove(Object)} and {@code contains(Object)}
72		* methods; and constant time for the retrieval methods
#	Line 75 | Line 78 | package java.util;
78		*
79		* @since 1.5
80		* @author Josh Bloch, Doug Lea
81	<	* @param <E> the type of elements held in this collection
81	>	* @param <E> the type of elements held in this queue
82		*/
83		public class PriorityQueue<E> extends AbstractQueue<E>
84		implements java.io.Serializable {
#	Line 92 | Line 95 | public class PriorityQueue<E> extends Ab
95		* heap and each descendant d of n, n <= d.  The element with the
96		* lowest value is in queue[0], assuming the queue is nonempty.
97		*/
98	<	private transient Object[] queue;
98	>	transient Object[] queue; // non-private to simplify nested class access
99
100		/**
101		* The number of elements in the priority queue.
102		*/
103	<	private int size = 0;
103	>	int size;
104
105		/**
106		* The comparator, or null if priority queue uses elements'
#	Line 109 | Line 112 | public class PriorityQueue<E> extends Ab
112		* The number of times this priority queue has been
113		* <i>structurally modified</i>.  See AbstractList for gory details.
114		*/
115	<	private transient int modCount = 0;
115	>	transient int modCount;     // non-private to simplify nested class access
116
117		/**
118		* Creates a {@code PriorityQueue} with the default initial
#	Line 134 | Line 137 | public class PriorityQueue<E> extends Ab
137		}
138
139		/**
140	+	* Creates a {@code PriorityQueue} with the default initial capacity and
141	+	* whose elements are ordered according to the specified comparator.
142	+	*
143	+	* @param  comparator the comparator that will be used to order this
144	+	*         priority queue.  If {@code null}, the {@linkplain Comparable
145	+	*         natural ordering} of the elements will be used.
146	+	* @since 1.8
147	+	*/
148	+	public PriorityQueue(Comparator<? super E> comparator) {
149	+	this(DEFAULT_INITIAL_CAPACITY, comparator);
150	+	}
151	+
152	+	/**
153		* Creates a {@code PriorityQueue} with the specified initial capacity
154		* that orders its elements according to the specified comparator.
155		*
#	Line 243 | Line 259 | public class PriorityQueue<E> extends Ab
259		a = Arrays.copyOf(a, a.length, Object[].class);
260		int len = a.length;
261		if (len == 1 || this.comparator != null)
262	<	for (int i = 0; i < len; i++)
263	<	if (a[i] == null)
262	>	for (Object e : a)
263	>	if (e == null)
264		throw new NullPointerException();
265		this.queue = a;
266		this.size = a.length;
#	Line 322 | Line 338 | public class PriorityQueue<E> extends Ab
338		int i = size;
339		if (i >= queue.length)
340		grow(i + 1);
341	+	siftUp(i, e);
342		size = i + 1;
326	–	if (i == 0)
327	–	queue[0] = e;
328	–	else
329	–	siftUp(i, e);
343		return true;
344		}
345
346	+	@SuppressWarnings("unchecked")
347		public E peek() {
348		return (size == 0) ? null : (E) queue[0];
349		}
#	Line 390 | Line 404 | public class PriorityQueue<E> extends Ab
404		* @return {@code true} if this queue contains the specified element
405		*/
406		public boolean contains(Object o) {
407	<	return indexOf(o) != -1;
407	>	return indexOf(o) >= 0;
408		}
409
410		/**
#	Line 428 | Line 442 | public class PriorityQueue<E> extends Ab
442		* precise control over the runtime type of the output array, and may,
443		* under certain circumstances, be used to save allocation costs.
444		*
445	<	* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
445	>	* <p>Suppose {@code x} is a queue known to contain only strings.
446		* The following code can be used to dump the queue into a newly
447	<	* allocated array of <tt>String</tt>:
447	>	* allocated array of {@code String}:
448		*
449	<	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
449	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
450		*
451	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
452	<	* <tt>toArray()</tt>.
451	>	* Note that {@code toArray(new Object[0])} is identical in function to
452	>	* {@code toArray()}.
453		*
454		* @param a the array into which the elements of the queue are to
455		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 446 | Line 460 | public class PriorityQueue<E> extends Ab
460		*         this queue
461		* @throws NullPointerException if the specified array is null
462		*/
463	+	@SuppressWarnings("unchecked")
464		public <T> T[] toArray(T[] a) {
465	+	final int size = this.size;
466		if (a.length < size)
467		// Make a new array of a's runtime type, but my contents:
468		return (T[]) Arrays.copyOf(queue, size, a.getClass());
#	Line 471 | Line 487 | public class PriorityQueue<E> extends Ab
487		* Index (into queue array) of element to be returned by
488		* subsequent call to next.
489		*/
490	<	private int cursor = 0;
490	>	private int cursor;
491
492		/**
493		* Index of element returned by most recent call to next,
#	Line 491 | Line 507 | public class PriorityQueue<E> extends Ab
507		* We expect that most iterations, even those involving removals,
508		* will not need to store elements in this field.
509		*/
510	<	private ArrayDeque<E> forgetMeNot = null;
510	>	private ArrayDeque<E> forgetMeNot;
511
512		/**
513		* Element returned by the most recent call to next iff that
514		* element was drawn from the forgetMeNot list.
515		*/
516	<	private E lastRetElt = null;
516	>	private E lastRetElt;
517
518		/**
519		* The modCount value that the iterator believes that the backing
#	Line 511 | Line 527 | public class PriorityQueue<E> extends Ab
527		(forgetMeNot != null && !forgetMeNot.isEmpty());
528		}
529
530	+	@SuppressWarnings("unchecked")
531		public E next() {
532		if (expectedModCount != modCount)
533		throw new ConcurrentModificationException();
#	Line 535 | Line 552 | public class PriorityQueue<E> extends Ab
552		cursor--;
553		else {
554		if (forgetMeNot == null)
555	<	forgetMeNot = new ArrayDeque<E>();
555	>	forgetMeNot = new ArrayDeque<>();
556		forgetMeNot.add(moved);
557		}
558		} else if (lastRetElt != null) {
#	Line 563 | Line 580 | public class PriorityQueue<E> extends Ab
580		size = 0;
581		}
582
583	+	@SuppressWarnings("unchecked")
584		public E poll() {
585		if (size == 0)
586		return null;
#	Line 588 | Line 606 | public class PriorityQueue<E> extends Ab
606		* position before i. This fact is used by iterator.remove so as to
607		* avoid missing traversing elements.
608		*/
609	<	private E removeAt(int i) {
609	>	@SuppressWarnings("unchecked")
610	>	E removeAt(int i) {
611		// assert i >= 0 && i < size;
612		modCount++;
613		int s = --size;
#	Line 626 | Line 645 | public class PriorityQueue<E> extends Ab
645		siftUpComparable(k, x);
646		}
647
648	+	@SuppressWarnings("unchecked")
649		private void siftUpComparable(int k, E x) {
650		Comparable<? super E> key = (Comparable<? super E>) x;
651		while (k > 0) {
#	Line 639 | Line 659 | public class PriorityQueue<E> extends Ab
659		queue[k] = key;
660		}
661
662	+	@SuppressWarnings("unchecked")
663		private void siftUpUsingComparator(int k, E x) {
664		while (k > 0) {
665		int parent = (k - 1) >>> 1;
#	Line 666 | Line 687 | public class PriorityQueue<E> extends Ab
687		siftDownComparable(k, x);
688		}
689
690	+	@SuppressWarnings("unchecked")
691		private void siftDownComparable(int k, E x) {
692		Comparable<? super E> key = (Comparable<? super E>)x;
693		int half = size >>> 1;        // loop while a non-leaf
#	Line 684 | Line 706 | public class PriorityQueue<E> extends Ab
706		queue[k] = key;
707		}
708
709	+	@SuppressWarnings("unchecked")
710		private void siftDownUsingComparator(int k, E x) {
711		int half = size >>> 1;
712		while (k < half) {
#	Line 704 | Line 727 | public class PriorityQueue<E> extends Ab
727		/**
728		* Establishes the heap invariant (described above) in the entire tree,
729		* assuming nothing about the order of the elements prior to the call.
730	+	* This classic algorithm due to Floyd (1964) is known to be O(size).
731		*/
732	+	@SuppressWarnings("unchecked")
733		private void heapify() {
734	<	for (int i = (size >>> 1) - 1; i >= 0; i--)
735	<	siftDown(i, (E) queue[i]);
734	>	final Object[] es = queue;
735	>	final int half = (size >>> 1) - 1;
736	>	if (comparator == null)
737	>	for (int i = half; i >= 0; i--)
738	>	siftDownComparable(i, (E) es[i]);
739	>	else
740	>	for (int i = half; i >= 0; i--)
741	>	siftDownUsingComparator(i, (E) es[i]);
742		}
743
744		/**
#	Line 724 | Line 755 | public class PriorityQueue<E> extends Ab
755		}
756
757		/**
758	<	* Saves the state of the instance to a stream (that
728	<	* is, serializes it).
758	>	* Saves this queue to a stream (that is, serializes it).
759		*
760	+	* @param s the stream
761	+	* @throws java.io.IOException if an I/O error occurs
762		* @serialData The length of the array backing the instance is
763		*             emitted (int), followed by all of its elements
764		*             (each an {@code Object}) in the proper order.
733	–	* @param s the stream
765		*/
766		private void writeObject(java.io.ObjectOutputStream s)
767		throws java.io.IOException {
#	Line 750 | Line 781 | public class PriorityQueue<E> extends Ab
781		* (that is, deserializes it).
782		*
783		* @param s the stream
784	+	* @throws ClassNotFoundException if the class of a serialized object
785	+	*         could not be found
786	+	* @throws java.io.IOException if an I/O error occurs
787		*/
788		private void readObject(java.io.ObjectInputStream s)
789		throws java.io.IOException, ClassNotFoundException {
#	Line 769 | Line 803 | public class PriorityQueue<E> extends Ab
803		// spec has never explained what that might be.
804		heapify();
805		}
806	+
807	+	/**
808	+	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
809	+	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
810	+	* queue. The spliterator does not traverse elements in any particular order
811	+	* (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
812	+	*
813	+	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
814	+	* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.
815	+	* Overriding implementations should document the reporting of additional
816	+	* characteristic values.
817	+	*
818	+	* @return a {@code Spliterator} over the elements in this queue
819	+	* @since 1.8
820	+	*/
821	+	public final Spliterator<E> spliterator() {
822	+	return new PriorityQueueSpliterator(0, -1, 0);
823	+	}
824	+
825	+	final class PriorityQueueSpliterator implements Spliterator<E> {
826	+	private int index;            // current index, modified on advance/split
827	+	private int fence;            // -1 until first use
828	+	private int expectedModCount; // initialized when fence set
829	+
830	+	/** Creates new spliterator covering the given range. */
831	+	PriorityQueueSpliterator(int origin, int fence, int expectedModCount) {
832	+	this.index = origin;
833	+	this.fence = fence;
834	+	this.expectedModCount = expectedModCount;
835	+	}
836	+
837	+	private int getFence() { // initialize fence to size on first use
838	+	int hi;
839	+	if ((hi = fence) < 0) {
840	+	expectedModCount = modCount;
841	+	hi = fence = size;
842	+	}
843	+	return hi;
844	+	}
845	+
846	+	public PriorityQueueSpliterator trySplit() {
847	+	int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
848	+	return (lo >= mid) ? null :
849	+	new PriorityQueueSpliterator(lo, index = mid, expectedModCount);
850	+	}
851	+
852	+	@SuppressWarnings("unchecked")
853	+	public void forEachRemaining(Consumer<? super E> action) {
854	+	if (action == null)
855	+	throw new NullPointerException();
856	+	if (fence < 0) { fence = size; expectedModCount = modCount; }
857	+	final Object[] a = queue;
858	+	int i, hi; E e;
859	+	for (i = index, index = hi = fence; i < hi; i++) {
860	+	if ((e = (E) a[i]) == null)
861	+	break;      // must be CME
862	+	action.accept(e);
863	+	}
864	+	if (modCount != expectedModCount)
865	+	throw new ConcurrentModificationException();
866	+	}
867	+
868	+	@SuppressWarnings("unchecked")
869	+	public boolean tryAdvance(Consumer<? super E> action) {
870	+	if (action == null)
871	+	throw new NullPointerException();
872	+	if (fence < 0) { fence = size; expectedModCount = modCount; }
873	+	int i;
874	+	if ((i = index) < fence) {
875	+	index = i + 1;
876	+	E e;
877	+	if ((e = (E) queue[i]) == null
878	+	|| modCount != expectedModCount)
879	+	throw new ConcurrentModificationException();
880	+	action.accept(e);
881	+	return true;
882	+	}
883	+	return false;
884	+	}
885	+
886	+	public long estimateSize() {
887	+	return getFence() - index;
888	+	}
889	+
890	+	public int characteristics() {
891	+	return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
892	+	}
893	+	}
894		}

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