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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.53 by jsr166, Wed Nov 23 05:33:25 2005 UTC vs.
Revision 1.102 by jsr166, Wed Dec 31 07:54:13 2014 UTC

#	Line 1 | Line 1
1		/*
2	<	* @(#)PriorityQueue.java       1.8 05/08/27
2	>	* Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
3	>	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4		*
5	<	* Copyright 2005 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	<	import java.util.*; // for javadoc (till 6280605 is fixed)
27	>
28	>	import java.util.function.Consumer;
29	>	import java.util.stream.Stream;
30
31		/**
32	<	* An unbounded priority {@linkplain Queue queue} based on a priority
33	<	* heap.  The elements of the priority queue are ordered according to
34	<	* their {@linkplain Comparable natural ordering}, or by a {@link
35	<	* Comparator} provided at queue construction time, depending on which
36	<	* constructor is used.  A priority queue does not permit
37	<	* <tt>null</tt> elements.  A priority queue relying on natural
38	<	* ordering also does not permit insertion of non-comparable objects
39	<	* (doing so may result in <tt>ClassCastException</tt>).
32	>	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
33	>	* The elements of the priority queue are ordered according to their
34	>	* {@linkplain Comparable natural ordering}, or by a {@link Comparator}
35	>	* provided at queue construction time, depending on which constructor is
36	>	* used.  A priority queue does not permit {@code null} elements.
37	>	* A priority queue relying on natural ordering also does not permit
38	>	* insertion of non-comparable objects (doing so may result in
39	>	* {@code ClassCastException}).
40		*
41		* <p>The <em>head</em> of this queue is the <em>least</em> element
42		* with respect to the specified ordering.  If multiple elements are
43		* tied for least value, the head is one of those elements -- ties are
44	<	* broken arbitrarily.  The queue retrieval operations <tt>poll</tt>,
45	<	* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the
44	>	* broken arbitrarily.  The queue retrieval operations {@code poll},
45	>	* {@code remove}, {@code peek}, and {@code element} access the
46		* element at the head of the queue.
47		*
48		* <p>A priority queue is unbounded, but has an internal
#	Line 37 | Line 57 | import java.util.*; // for javadoc (till
57		* Iterator} interfaces.  The Iterator provided in method {@link
58		* #iterator()} is <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 <tt>Arrays.sort(pq.toArray())</tt>.
60	>	* traversal, consider using {@code Arrays.sort(pq.toArray())}.
61		*
62	<	* <p> <strong>Note that this implementation is not synchronized.</strong>
63	<	* Multiple threads should not access a <tt>PriorityQueue</tt>
64	<	* instance concurrently if any of the threads modifies the list
65	<	* structurally. Instead, use the thread-safe {@link
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 O(log(n)) time
69	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
70	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
71	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
72	<	* constant time for the retrieval methods (<tt>peek</tt>,
73	<	* <tt>element</tt>, and <tt>size</tt>).
68	>	* <p>Implementation note: this implementation provides
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
73	>	* ({@code peek}, {@code element}, and {@code size}).
74		*
75		* <p>This class is a member of the
76	<	* <a href="{@docRoot}/../guide/collections/index.html">
76	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
77		* Java Collections Framework</a>.
78	+	*
79		* @since 1.5
80	<	* @version 1.8, 08/27/05
81	<	* @author Josh Bloch
61	<	* @param <E> the type of elements held in this collection
80	>	* @author Josh Bloch, Doug Lea
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 68 | Line 88 | public class PriorityQueue<E> extends Ab
88		private static final int DEFAULT_INITIAL_CAPACITY = 11;
89
90		/**
91	<	* Priority queue represented as a balanced binary heap: the two children
92	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
93	<	* ordered by comparator, or by the elements' natural ordering, if
94	<	* comparator is null:  For each node n in the heap and each descendant d
95	<	* of n, n <= d.
96	<	*
77	<	* The element with the lowest value is in queue[1], assuming the queue is
78	<	* nonempty.  (A one-based array is used in preference to the traditional
79	<	* zero-based array to simplify parent and child calculations.)
80	<	*
81	<	* queue.length must be >= 2, even if size == 0.
91	>	* Priority queue represented as a balanced binary heap: the two
92	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
93	>	* priority queue is ordered by comparator, or by the elements'
94	>	* natural ordering, if comparator is null: For each node n in the
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	>	private int size;
104
105		/**
106		* The comparator, or null if priority queue uses elements'
#	Line 97 | 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 = 0; // non-private to simplify nested class access
116
117		/**
118	<	* Creates a <tt>PriorityQueue</tt> with the default initial
118	>	* Creates a {@code PriorityQueue} with the default initial
119		* capacity (11) that orders its elements according to their
120		* {@linkplain Comparable natural ordering}.
121		*/
#	Line 109 | Line 124 | public class PriorityQueue<E> extends Ab
124		}
125
126		/**
127	<	* Creates a <tt>PriorityQueue</tt> with the specified initial
127	>	* Creates a {@code PriorityQueue} with the specified initial
128		* capacity that orders its elements according to their
129		* {@linkplain Comparable natural ordering}.
130		*
131		* @param initialCapacity the initial capacity for this priority queue
132	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
133	<	* than 1
132	>	* @throws IllegalArgumentException if {@code initialCapacity} is less
133	>	*         than 1
134		*/
135		public PriorityQueue(int initialCapacity) {
136		this(initialCapacity, null);
137		}
138
139		/**
140	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
140	>	* Creates a {@code PriorityQueue} with the specified initial capacity
141		* that orders its elements according to the specified comparator.
142		*
143		* @param  initialCapacity the initial capacity for this priority queue
144	<	* @param  comparator the comparator that will be used to order
145	<	*         this priority queue.  If <tt>null</tt>, the <i>natural
146	<	*         ordering</i> of the elements will be used.
147	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is
144	>	* @param  comparator the comparator that will be used to order this
145	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
146	>	*         natural ordering} of the elements will be used.
147	>	* @throws IllegalArgumentException if {@code initialCapacity} is
148		*         less than 1
149		*/
150		public PriorityQueue(int initialCapacity,
151		Comparator<? super E> comparator) {
152	+	// Note: This restriction of at least one is not actually needed,
153	+	// but continues for 1.5 compatibility
154		if (initialCapacity < 1)
155		throw new IllegalArgumentException();
156	<	this.queue = new Object[initialCapacity + 1];
156	>	this.queue = new Object[initialCapacity];
157		this.comparator = comparator;
158		}
159
160		/**
161	<	* Common code to initialize underlying queue array across
162	<	* constructors below.
163	<	*/
164	<	private void initializeArray(Collection<? extends E> c) {
165	<	int sz = c.size();
166	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
150	<	Integer.MAX_VALUE - 1);
151	<	if (initialCapacity < 1)
152	<	initialCapacity = 1;
153	<
154	<	this.queue = new Object[initialCapacity + 1];
155	<	}
156	<
157	<	/**
158	<	* Initially fill elements of the queue array under the
159	<	* knowledge that it is sorted or is another PQ, in which
160	<	* case we can just place the elements in the order presented.
161	<	*/
162	<	private void fillFromSorted(Collection<? extends E> c) {
163	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) {
164	<	int k = ++size;
165	<	if (k >= queue.length)
166	<	grow(k);
167	<	queue[k] = i.next();
168	<	}
169	<	}
170	<
171	<	/**
172	<	* Initially fill elements of the queue array that is not to our knowledge
173	<	* sorted, so we must rearrange the elements to guarantee the heap
174	<	* invariant.
175	<	*/
176	<	private void fillFromUnsorted(Collection<? extends E> c) {
177	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) {
178	<	int k = ++size;
179	<	if (k >= queue.length)
180	<	grow(k);
181	<	queue[k] = i.next();
182	<	}
183	<	heapify();
184	<	}
185	<
186	<	/**
187	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
188	<	* specified collection.  The priority queue has an initial
189	<	* capacity of 110% of the size of the specified collection or 1
190	<	* if the collection is empty.  If the specified collection is an
191	<	* instance of a {@link java.util.SortedSet} or is another
192	<	* <tt>PriorityQueue</tt>, the priority queue will be ordered
193	<	* according to the same ordering.  Otherwise, this priority queue
194	<	* will be ordered according to the natural ordering of its elements.
161	>	* Creates a {@code PriorityQueue} containing the elements in the
162	>	* specified collection.  If the specified collection is an instance of
163	>	* a {@link SortedSet} or is another {@code PriorityQueue}, this
164	>	* priority queue will be ordered according to the same ordering.
165	>	* Otherwise, this priority queue will be ordered according to the
166	>	* {@linkplain Comparable natural ordering} of its elements.
167		*
168		* @param  c the collection whose elements are to be placed
169		*         into this priority queue
#	Line 201 | Line 173 | public class PriorityQueue<E> extends Ab
173		* @throws NullPointerException if the specified collection or any
174		*         of its elements are null
175		*/
176	+	@SuppressWarnings("unchecked")
177		public PriorityQueue(Collection<? extends E> c) {
178	<	initializeArray(c);
179	<	if (c instanceof SortedSet) {
180	<	SortedSet<? extends E> s = (SortedSet<? extends E>)c;
181	<	comparator = (Comparator<? super E>)s.comparator();
182	<	fillFromSorted(s);
183	<	} else if (c instanceof PriorityQueue) {
184	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
185	<	comparator = (Comparator<? super E>)s.comparator();
186	<	fillFromSorted(s);
187	<	} else {
188	<	comparator = null;
189	<	fillFromUnsorted(c);
178	>	if (c instanceof SortedSet<?>) {
179	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
180	>	this.comparator = (Comparator<? super E>) ss.comparator();
181	>	initElementsFromCollection(ss);
182	>	}
183	>	else if (c instanceof PriorityQueue<?>) {
184	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
185	>	this.comparator = (Comparator<? super E>) pq.comparator();
186	>	initFromPriorityQueue(pq);
187	>	}
188	>	else {
189	>	this.comparator = null;
190	>	initFromCollection(c);
191		}
192		}
193
194		/**
195	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
196	<	* specified priority queue.  The priority queue has an initial
223	<	* capacity of 110% of the size of the specified priority queue or
224	<	* 1 if the priority queue is empty.  This priority queue will be
195	>	* Creates a {@code PriorityQueue} containing the elements in the
196	>	* specified priority queue.  This priority queue will be
197		* ordered according to the same ordering as the given priority
198		* queue.
199		*
200		* @param  c the priority queue whose elements are to be placed
201		*         into this priority queue
202	<	* @throws ClassCastException if elements of <tt>c</tt> cannot be
203	<	*         compared to one another according to <tt>c</tt>'s
202	>	* @throws ClassCastException if elements of {@code c} cannot be
203	>	*         compared to one another according to {@code c}'s
204		*         ordering
205		* @throws NullPointerException if the specified priority queue or any
206		*         of its elements are null
207		*/
208	+	@SuppressWarnings("unchecked")
209		public PriorityQueue(PriorityQueue<? extends E> c) {
210	<	initializeArray(c);
211	<	comparator = (Comparator<? super E>)c.comparator();
239	<	fillFromSorted(c);
210	>	this.comparator = (Comparator<? super E>) c.comparator();
211	>	initFromPriorityQueue(c);
212		}
213
214		/**
215	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
216	<	* specified sorted set.  The priority queue has an initial
245	<	* capacity of 110% of the size of the specified sorted set or 1
246	<	* if the sorted set is empty.  This priority queue will be ordered
215	>	* Creates a {@code PriorityQueue} containing the elements in the
216	>	* specified sorted set.   This priority queue will be ordered
217		* according to the same ordering as the given sorted set.
218		*
219		* @param  c the sorted set whose elements are to be placed
220	<	*         into this priority queue.
220	>	*         into this priority queue
221		* @throws ClassCastException if elements of the specified sorted
222		*         set cannot be compared to one another according to the
223		*         sorted set's ordering
224		* @throws NullPointerException if the specified sorted set or any
225		*         of its elements are null
226		*/
227	+	@SuppressWarnings("unchecked")
228		public PriorityQueue(SortedSet<? extends E> c) {
229	<	initializeArray(c);
230	<	comparator = (Comparator<? super E>)c.comparator();
231	<	fillFromSorted(c);
229	>	this.comparator = (Comparator<? super E>) c.comparator();
230	>	initElementsFromCollection(c);
231	>	}
232	>
233	>	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
234	>	if (c.getClass() == PriorityQueue.class) {
235	>	this.queue = c.toArray();
236	>	this.size = c.size();
237	>	} else {
238	>	initFromCollection(c);
239	>	}
240	>	}
241	>
242	>	private void initElementsFromCollection(Collection<? extends E> c) {
243	>	Object[] a = c.toArray();
244	>	// If c.toArray incorrectly doesn't return Object[], copy it.
245	>	if (a.getClass() != Object[].class)
246	>	a = Arrays.copyOf(a, a.length, Object[].class);
247	>	int len = a.length;
248	>	if (len == 1 || this.comparator != null)
249	>	for (int i = 0; i < len; i++)
250	>	if (a[i] == null)
251	>	throw new NullPointerException();
252	>	this.queue = a;
253	>	this.size = a.length;
254	>	}
255	>
256	>	/**
257	>	* Initializes queue array with elements from the given Collection.
258	>	*
259	>	* @param c the collection
260	>	*/
261	>	private void initFromCollection(Collection<? extends E> c) {
262	>	initElementsFromCollection(c);
263	>	heapify();
264		}
265
266		/**
267	<	* Resize array, if necessary, to be able to hold given index.
267	>	* The maximum size of array to allocate.
268	>	* Some VMs reserve some header words in an array.
269	>	* Attempts to allocate larger arrays may result in
270	>	* OutOfMemoryError: Requested array size exceeds VM limit
271	>	*/
272	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
273	>
274	>	/**
275	>	* Increases the capacity of the array.
276	>	*
277	>	* @param minCapacity the desired minimum capacity
278		*/
279	<	private void grow(int index) {
280	<	int newlen = queue.length;
281	<	if (index < newlen) // don't need to grow
282	<	return;
283	<	if (index == Integer.MAX_VALUE)
279	>	private void grow(int minCapacity) {
280	>	int oldCapacity = queue.length;
281	>	// Double size if small; else grow by 50%
282	>	int newCapacity = oldCapacity + ((oldCapacity < 64) ?
283	>	(oldCapacity + 2) :
284	>	(oldCapacity >> 1));
285	>	// overflow-conscious code
286	>	if (newCapacity - MAX_ARRAY_SIZE > 0)
287	>	newCapacity = hugeCapacity(minCapacity);
288	>	queue = Arrays.copyOf(queue, newCapacity);
289	>	}
290	>
291	>	private static int hugeCapacity(int minCapacity) {
292	>	if (minCapacity < 0) // overflow
293		throw new OutOfMemoryError();
294	<	while (newlen <= index) {
295	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
296	<	newlen = Integer.MAX_VALUE;
275	<	else
276	<	newlen <<= 2;
277	<	}
278	<	queue = Arrays.copyOf(queue, newlen);
294	>	return (minCapacity > MAX_ARRAY_SIZE) ?
295	>	Integer.MAX_VALUE :
296	>	MAX_ARRAY_SIZE;
297		}
298
299		/**
300		* Inserts the specified element into this priority queue.
301		*
302	<	* @return <tt>true</tt> (as specified by {@link Collection#add})
302	>	* @return {@code true} (as specified by {@link Collection#add})
303		* @throws ClassCastException if the specified element cannot be
304		*         compared with elements currently in this priority queue
305		*         according to the priority queue's ordering
#	Line 294 | Line 312 | public class PriorityQueue<E> extends Ab
312		/**
313		* Inserts the specified element into this priority queue.
314		*
315	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
315	>	* @return {@code true} (as specified by {@link Queue#offer})
316		* @throws ClassCastException if the specified element cannot be
317		*         compared with elements currently in this priority queue
318		*         according to the priority queue's ordering
#	Line 304 | Line 322 | public class PriorityQueue<E> extends Ab
322		if (e == null)
323		throw new NullPointerException();
324		modCount++;
325	<	++size;
326	<
327	<	// Grow backing store if necessary
328	<	if (size >= queue.length)
329	<	grow(size);
330	<
331	<	queue[size] = e;
332	<	fixUp(size);
325	>	int i = size;
326	>	if (i >= queue.length)
327	>	grow(i + 1);
328	>	size = i + 1;
329	>	if (i == 0)
330	>	queue[0] = e;
331	>	else
332	>	siftUp(i, e);
333		return true;
334		}
335
336	+	@SuppressWarnings("unchecked")
337		public E peek() {
338	<	if (size == 0)
320	<	return null;
321	<	return (E) queue[1];
338	>	return (size == 0) ? null : (E) queue[0];
339		}
340
341		private int indexOf(Object o) {
342	<	if (o == null)
343	<	return -1;
344	<	for (int i = 1; i <= size; i++)
345	<	if (o.equals(queue[i]))
346	<	return i;
342	>	if (o != null) {
343	>	for (int i = 0; i < size; i++)
344	>	if (o.equals(queue[i]))
345	>	return i;
346	>	}
347		return -1;
348		}
349
350		/**
351		* Removes a single instance of the specified element from this queue,
352	<	* if it is present.  More formally, removes an element <tt>e</tt> such
353	<	* that <tt>o.equals(e)</tt>, if this queue contains one or more such
354	<	* elements.  Returns true if this queue contained the specified element
355	<	* (or equivalently, if this queue changed as a result of the call).
352	>	* if it is present.  More formally, removes an element {@code e} such
353	>	* that {@code o.equals(e)}, if this queue contains one or more such
354	>	* elements.  Returns {@code true} if and only if this queue contained
355	>	* the specified element (or equivalently, if this queue changed as a
356	>	* result of the call).
357		*
358		* @param o element to be removed from this queue, if present
359	<	* @return <tt>true</tt> if this queue changed as a result of the call
359	>	* @return {@code true} if this queue changed as a result of the call
360		*/
361		public boolean remove(Object o) {
362	<	int i = indexOf(o);
363	<	if (i == -1)
364	<	return false;
365	<	else {
366	<	removeAt(i);
367	<	return true;
368	<	}
362	>	int i = indexOf(o);
363	>	if (i == -1)
364	>	return false;
365	>	else {
366	>	removeAt(i);
367	>	return true;
368	>	}
369	>	}
370	>
371	>	/**
372	>	* Version of remove using reference equality, not equals.
373	>	* Needed by iterator.remove.
374	>	*
375	>	* @param o element to be removed from this queue, if present
376	>	* @return {@code true} if removed
377	>	*/
378	>	boolean removeEq(Object o) {
379	>	for (int i = 0; i < size; i++) {
380	>	if (o == queue[i]) {
381	>	removeAt(i);
382	>	return true;
383	>	}
384	>	}
385	>	return false;
386		}
387
388		/**
389	<	* Returns <tt>true</tt> if this queue contains the specified element.
390	<	* More formally, returns <tt>true</tt> if and only if this queue contains
391	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
389	>	* Returns {@code true} if this queue contains the specified element.
390	>	* More formally, returns {@code true} if and only if this queue contains
391	>	* at least one element {@code e} such that {@code o.equals(e)}.
392		*
393		* @param o object to be checked for containment in this queue
394	<	* @return <tt>true</tt> if this queue contains the specified element
394	>	* @return {@code true} if this queue contains the specified element
395		*/
396		public boolean contains(Object o) {
397	<	return indexOf(o) != -1;
397	>	return indexOf(o) >= 0;
398		}
399
400		/**
401	<	* Returns an array containing all of the elements in this queue,
401	>	* Returns an array containing all of the elements in this queue.
402		* The elements are in no particular order.
403		*
404		* <p>The returned array will be "safe" in that no references to it are
405	<	* maintained by this list.  (In other words, this method must allocate
405	>	* maintained by this queue.  (In other words, this method must allocate
406		* a new array).  The caller is thus free to modify the returned array.
407		*
408	<	* @return an array containing all of the elements in this queue.
408	>	* <p>This method acts as bridge between array-based and collection-based
409	>	* APIs.
410	>	*
411	>	* @return an array containing all of the elements in this queue
412		*/
413		public Object[] toArray() {
414	<	return Arrays.copyOfRange(queue, 1, size+1);
414	>	return Arrays.copyOf(queue, size);
415		}
416
417		/**
418	<	* Returns an array containing all of the elements in this queue.
419	<	* The elements are in no particular order.  The runtime type of
420	<	* the returned array is that of the specified array.  If the queue
421	<	* fits in the specified array, it is returned therein.
422	<	* Otherwise, a new array is allocated with the runtime type of
423	<	* the specified array and the size of this queue.
418	>	* Returns an array containing all of the elements in this queue; the
419	>	* runtime type of the returned array is that of the specified array.
420	>	* The returned array elements are in no particular order.
421	>	* If the queue fits in the specified array, it is returned therein.
422	>	* Otherwise, a new array is allocated with the runtime type of the
423	>	* specified array and the size of this queue.
424		*
425		* <p>If the queue fits in the specified array with room to spare
426		* (i.e., the array has more elements than the queue), the element in
427		* the array immediately following the end of the collection is set to
428	<	* <tt>null</tt>.  (This is useful in determining the length of the
429	<	* queue <i>only</i> if the caller knows that the queue does not contain
430	<	* any null elements.)
428	>	* {@code null}.
429	>	*
430	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
431	>	* array-based and collection-based APIs.  Further, this method allows
432	>	* precise control over the runtime type of the output array, and may,
433	>	* under certain circumstances, be used to save allocation costs.
434	>	*
435	>	* <p>Suppose {@code x} is a queue known to contain only strings.
436	>	* The following code can be used to dump the queue into a newly
437	>	* allocated array of {@code String}:
438	>	*
439	>	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
440	>	*
441	>	* Note that {@code toArray(new Object[0])} is identical in function to
442	>	* {@code toArray()}.
443		*
444		* @param a the array into which the elements of the queue are to
445		*          be stored, if it is big enough; otherwise, a new array of the
446		*          same runtime type is allocated for this purpose.
447	<	* @return an array containing the elements of the queue
447	>	* @return an array containing all of the elements in this queue
448		* @throws ArrayStoreException if the runtime type of the specified array
449		*         is not a supertype of the runtime type of every element in
450		*         this queue
451		* @throws NullPointerException if the specified array is null
452		*/
453	+	@SuppressWarnings("unchecked")
454		public <T> T[] toArray(T[] a) {
455	+	final int size = this.size;
456		if (a.length < size)
457		// Make a new array of a's runtime type, but my contents:
458	<	return (T[]) Arrays.copyOfRange(queue, 1, size+1, a.getClass());
459	<	System.arraycopy(queue, 1, a, 0, size);
458	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
459	>	System.arraycopy(queue, 0, a, 0, size);
460		if (a.length > size)
461		a[size] = null;
462		return a;
#	Line 420 | Line 472 | public class PriorityQueue<E> extends Ab
472		return new Itr();
473		}
474
475	<	private class Itr implements Iterator<E> {
424	<
475	>	private final class Itr implements Iterator<E> {
476		/**
477		* Index (into queue array) of element to be returned by
478		* subsequent call to next.
479		*/
480	<	private int cursor = 1;
480	>	private int cursor;
481
482		/**
483		* Index of element returned by most recent call to next,
484		* unless that element came from the forgetMeNot list.
485	<	* Reset to 0 if element is deleted by a call to remove.
435	<	*/
436	<	private int lastRet = 0;
437	<
438	<	/**
439	<	* The modCount value that the iterator believes that the backing
440	<	* List should have.  If this expectation is violated, the iterator
441	<	* has detected concurrent modification.
485	>	* Set to -1 if element is deleted by a call to remove.
486		*/
487	<	private int expectedModCount = modCount;
487	>	private int lastRet = -1;
488
489		/**
490	<	* A list of elements that were moved from the unvisited portion of
490	>	* A queue of elements that were moved from the unvisited portion of
491		* the heap into the visited portion as a result of "unlucky" element
492		* removals during the iteration.  (Unlucky element removals are those
493	<	* that require a fixup instead of a fixdown.)  We must visit all of
493	>	* that require a siftup instead of a siftdown.)  We must visit all of
494		* the elements in this list to complete the iteration.  We do this
495		* after we've completed the "normal" iteration.
496		*
497		* We expect that most iterations, even those involving removals,
498	<	* will not use need to store elements in this field.
498	>	* will not need to store elements in this field.
499		*/
500	<	private ArrayList<E> forgetMeNot = null;
500	>	private ArrayDeque<E> forgetMeNot;
501
502		/**
503		* Element returned by the most recent call to next iff that
504		* element was drawn from the forgetMeNot list.
505		*/
506	<	private Object lastRetElt = null;
506	>	private E lastRetElt;
507	>
508	>	/**
509	>	* The modCount value that the iterator believes that the backing
510	>	* Queue should have.  If this expectation is violated, the iterator
511	>	* has detected concurrent modification.
512	>	*/
513	>	private int expectedModCount = modCount;
514
515		public boolean hasNext() {
516	<	return cursor <= size || forgetMeNot != null;
516	>	return cursor < size ||
517	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
518		}
519
520	+	@SuppressWarnings("unchecked")
521		public E next() {
522	<	checkForComodification();
523	<	E result;
524	<	if (cursor <= size) {
525	<	result = (E) queue[cursor];
526	<	lastRet = cursor++;
527	<	}
528	<	else if (forgetMeNot == null)
529	<	throw new NoSuchElementException();
530	<	else {
478	<	int remaining = forgetMeNot.size();
479	<	result = forgetMeNot.remove(remaining - 1);
480	<	if (remaining == 1)
481	<	forgetMeNot = null;
482	<	lastRet = 0;
483	<	lastRetElt = result;
522	>	if (expectedModCount != modCount)
523	>	throw new ConcurrentModificationException();
524	>	if (cursor < size)
525	>	return (E) queue[lastRet = cursor++];
526	>	if (forgetMeNot != null) {
527	>	lastRet = -1;
528	>	lastRetElt = forgetMeNot.poll();
529	>	if (lastRetElt != null)
530	>	return lastRetElt;
531		}
532	<	return result;
532	>	throw new NoSuchElementException();
533		}
534
535		public void remove() {
536	<	checkForComodification();
537	<
538	<	if (lastRet != 0) {
536	>	if (expectedModCount != modCount)
537	>	throw new ConcurrentModificationException();
538	>	if (lastRet != -1) {
539		E moved = PriorityQueue.this.removeAt(lastRet);
540	<	lastRet = 0;
541	<	if (moved == null) {
540	>	lastRet = -1;
541	>	if (moved == null)
542		cursor--;
543	<	} else {
543	>	else {
544		if (forgetMeNot == null)
545	<	forgetMeNot = new ArrayList<E>();
545	>	forgetMeNot = new ArrayDeque<>();
546		forgetMeNot.add(moved);
547		}
548		} else if (lastRetElt != null) {
549	<	PriorityQueue.this.remove(lastRetElt);
549	>	PriorityQueue.this.removeEq(lastRetElt);
550		lastRetElt = null;
551		} else {
552		throw new IllegalStateException();
553		}
507	–
554		expectedModCount = modCount;
555		}
510	–
511	–	final void checkForComodification() {
512	–	if (modCount != expectedModCount)
513	–	throw new ConcurrentModificationException();
514	–	}
556		}
557
558		public int size() {
#	Line 524 | Line 565 | public class PriorityQueue<E> extends Ab
565		*/
566		public void clear() {
567		modCount++;
568	<
528	<	// Null out element references to prevent memory leak
529	<	for (int i=1; i<=size; i++)
568	>	for (int i = 0; i < size; i++)
569		queue[i] = null;
531	–
570		size = 0;
571		}
572
573	+	@SuppressWarnings("unchecked")
574		public E poll() {
575		if (size == 0)
576		return null;
577	+	int s = --size;
578		modCount++;
579	<
580	<	E result = (E) queue[1];
581	<	queue[1] = queue[size];
582	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
583	<	if (size > 1)
544	<	fixDown(1);
545	<
579	>	E result = (E) queue[0];
580	>	E x = (E) queue[s];
581	>	queue[s] = null;
582	>	if (s != 0)
583	>	siftDown(0, x);
584		return result;
585		}
586
587		/**
588	<	* Removes and returns the ith element from queue.  (Recall that queue
551	<	* is one-based, so 1 <= i <= size.)
588	>	* Removes the ith element from queue.
589		*
590	<	* Normally this method leaves the elements at positions from 1 up to i-1,
591	<	* inclusive, untouched.  Under these circumstances, it returns null.
592	<	* Occasionally, in order to maintain the heap invariant, it must move
593	<	* the last element of the list to some index in the range [2, i-1],
594	<	* and move the element previously at position (i/2) to position i.
595	<	* Under these circumstances, this method returns the element that was
596	<	* previously at the end of the list and is now at some position between
597	<	* 2 and i-1 inclusive.
590	>	* Normally this method leaves the elements at up to i-1,
591	>	* inclusive, untouched.  Under these circumstances, it returns
592	>	* null.  Occasionally, in order to maintain the heap invariant,
593	>	* it must swap a later element of the list with one earlier than
594	>	* i.  Under these circumstances, this method returns the element
595	>	* that was previously at the end of the list and is now at some
596	>	* position before i. This fact is used by iterator.remove so as to
597	>	* avoid missing traversing elements.
598		*/
599	+	@SuppressWarnings("unchecked")
600		private E removeAt(int i) {
601	<	assert i > 0 && i <= size;
601	>	// assert i >= 0 && i < size;
602		modCount++;
603	<
604	<	E moved = (E) queue[size];
605	<	queue[i] = moved;
606	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
607	<	if (i <= size) {
608	<	fixDown(i);
603	>	int s = --size;
604	>	if (s == i) // removed last element
605	>	queue[i] = null;
606	>	else {
607	>	E moved = (E) queue[s];
608	>	queue[s] = null;
609	>	siftDown(i, moved);
610		if (queue[i] == moved) {
611	<	fixUp(i);
611	>	siftUp(i, moved);
612		if (queue[i] != moved)
613		return moved;
614		}
#	Line 578 | Line 617 | public class PriorityQueue<E> extends Ab
617		}
618
619		/**
620	<	* Establishes the heap invariant (described above) assuming the heap
621	<	* satisfies the invariant except possibly for the leaf-node indexed by k
622	<	* (which may have a nextExecutionTime less than its parent's).
623	<	*
624	<	* This method functions by "promoting" queue[k] up the hierarchy
625	<	* (by swapping it with its parent) repeatedly until queue[k]
626	<	* is greater than or equal to its parent.
627	<	*/
628	<	private void fixUp(int k) {
629	<	if (comparator == null) {
630	<	while (k > 1) {
631	<	int j = k >> 1;
632	<	if (((Comparable<? super E>)queue[j]).compareTo((E)queue[k]) <= 0)
633	<	break;
634	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
635	<	k = j;
636	<	}
637	<	} else {
638	<	while (k > 1) {
639	<	int j = k >>> 1;
640	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
641	<	break;
642	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
643	<	k = j;
644	<	}
645	<	}
646	<	}
647	<
648	<	/**
649	<	* Establishes the heap invariant (described above) in the subtree
650	<	* rooted at k, which is assumed to satisfy the heap invariant except
651	<	* possibly for node k itself (which may be greater than its children).
652	<	*
653	<	* This method functions by "demoting" queue[k] down the hierarchy
654	<	* (by swapping it with its smaller child) repeatedly until queue[k]
655	<	* is less than or equal to its children.
656	<	*/
657	<	private void fixDown(int k) {
658	<	int j;
659	<	if (comparator == null) {
660	<	while ((j = k << 1) <= size && (j > 0)) {
661	<	if (j<size &&
662	<	((Comparable<? super E>)queue[j]).compareTo((E)queue[j+1]) > 0)
663	<	j++; // j indexes smallest kid
664	<
665	<	if (((Comparable<? super E>)queue[k]).compareTo((E)queue[j]) <= 0)
666	<	break;
667	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
668	<	k = j;
669	<	}
670	<	} else {
671	<	while ((j = k << 1) <= size && (j > 0)) {
672	<	if (j<size &&
673	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
674	<	j++; // j indexes smallest kid
675	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
676	<	break;
677	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
678	<	k = j;
679	<	}
620	>	* Inserts item x at position k, maintaining heap invariant by
621	>	* promoting x up the tree until it is greater than or equal to
622	>	* its parent, or is the root.
623	>	*
624	>	* To simplify and speed up coercions and comparisons. the
625	>	* Comparable and Comparator versions are separated into different
626	>	* methods that are otherwise identical. (Similarly for siftDown.)
627	>	*
628	>	* @param k the position to fill
629	>	* @param x the item to insert
630	>	*/
631	>	private void siftUp(int k, E x) {
632	>	if (comparator != null)
633	>	siftUpUsingComparator(k, x);
634	>	else
635	>	siftUpComparable(k, x);
636	>	}
637	>
638	>	@SuppressWarnings("unchecked")
639	>	private void siftUpComparable(int k, E x) {
640	>	Comparable<? super E> key = (Comparable<? super E>) x;
641	>	while (k > 0) {
642	>	int parent = (k - 1) >>> 1;
643	>	Object e = queue[parent];
644	>	if (key.compareTo((E) e) >= 0)
645	>	break;
646	>	queue[k] = e;
647	>	k = parent;
648	>	}
649	>	queue[k] = key;
650	>	}
651	>
652	>	@SuppressWarnings("unchecked")
653	>	private void siftUpUsingComparator(int k, E x) {
654	>	while (k > 0) {
655	>	int parent = (k - 1) >>> 1;
656	>	Object e = queue[parent];
657	>	if (comparator.compare(x, (E) e) >= 0)
658	>	break;
659	>	queue[k] = e;
660	>	k = parent;
661	>	}
662	>	queue[k] = x;
663	>	}
664	>
665	>	/**
666	>	* Inserts item x at position k, maintaining heap invariant by
667	>	* demoting x down the tree repeatedly until it is less than or
668	>	* equal to its children or is a leaf.
669	>	*
670	>	* @param k the position to fill
671	>	* @param x the item to insert
672	>	*/
673	>	private void siftDown(int k, E x) {
674	>	if (comparator != null)
675	>	siftDownUsingComparator(k, x);
676	>	else
677	>	siftDownComparable(k, x);
678	>	}
679	>
680	>	@SuppressWarnings("unchecked")
681	>	private void siftDownComparable(int k, E x) {
682	>	Comparable<? super E> key = (Comparable<? super E>)x;
683	>	int half = size >>> 1;        // loop while a non-leaf
684	>	while (k < half) {
685	>	int child = (k << 1) + 1; // assume left child is least
686	>	Object c = queue[child];
687	>	int right = child + 1;
688	>	if (right < size &&
689	>	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
690	>	c = queue[child = right];
691	>	if (key.compareTo((E) c) <= 0)
692	>	break;
693	>	queue[k] = c;
694	>	k = child;
695	>	}
696	>	queue[k] = key;
697	>	}
698	>
699	>	@SuppressWarnings("unchecked")
700	>	private void siftDownUsingComparator(int k, E x) {
701	>	int half = size >>> 1;
702	>	while (k < half) {
703	>	int child = (k << 1) + 1;
704	>	Object c = queue[child];
705	>	int right = child + 1;
706	>	if (right < size &&
707	>	comparator.compare((E) c, (E) queue[right]) > 0)
708	>	c = queue[child = right];
709	>	if (comparator.compare(x, (E) c) <= 0)
710	>	break;
711	>	queue[k] = c;
712	>	k = child;
713		}
714	+	queue[k] = x;
715		}
716
717		/**
718		* Establishes the heap invariant (described above) in the entire tree,
719		* assuming nothing about the order of the elements prior to the call.
720		*/
721	+	@SuppressWarnings("unchecked")
722		private void heapify() {
723	<	for (int i = size/2; i >= 1; i--)
724	<	fixDown(i);
723	>	for (int i = (size >>> 1) - 1; i >= 0; i--)
724	>	siftDown(i, (E) queue[i]);
725		}
726
727		/**
728		* Returns the comparator used to order the elements in this
729	<	* queue, or <tt>null</tt> if this queue is sorted according to
729	>	* queue, or {@code null} if this queue is sorted according to
730		* the {@linkplain Comparable natural ordering} of its elements.
731		*
732		* @return the comparator used to order this queue, or
733	<	*         <tt>null</tt> if this queue is sorted according to the
734	<	*         natural ordering of its elements.
733	>	*         {@code null} if this queue is sorted according to the
734	>	*         natural ordering of its elements
735		*/
736		public Comparator<? super E> comparator() {
737		return comparator;
738		}
739
740		/**
741	<	* Save the state of the instance to a stream (that
668	<	* is, serialize it).
741	>	* Saves this queue to a stream (that is, serializes it).
742		*
743		* @serialData The length of the array backing the instance is
744	<	* emitted (int), followed by all of its elements (each an
745	<	* <tt>Object</tt>) in the proper order.
744	>	*             emitted (int), followed by all of its elements
745	>	*             (each an {@code Object}) in the proper order.
746		* @param s the stream
747	+	* @throws java.io.IOException if an I/O error occurs
748		*/
749		private void writeObject(java.io.ObjectOutputStream s)
750	<	throws java.io.IOException{
750	>	throws java.io.IOException {
751		// Write out element count, and any hidden stuff
752		s.defaultWriteObject();
753
754	<	// Write out array length
755	<	s.writeInt(queue.length);
754	>	// Write out array length, for compatibility with 1.5 version
755	>	s.writeInt(Math.max(2, size + 1));
756
757	<	// Write out all elements in the proper order.
758	<	for (int i=1; i<=size; i++)
757	>	// Write out all elements in the "proper order".
758	>	for (int i = 0; i < size; i++)
759		s.writeObject(queue[i]);
760		}
761
762		/**
763	<	* Reconstitute the <tt>PriorityQueue</tt> instance from a stream
764	<	* (that is, deserialize it).
763	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
764	>	* (that is, deserializes it).
765	>	*
766		* @param s the stream
767	+	* @throws ClassNotFoundException if the class of a serialized object
768	+	*         could not be found
769	+	* @throws java.io.IOException if an I/O error occurs
770		*/
771		private void readObject(java.io.ObjectInputStream s)
772		throws java.io.IOException, ClassNotFoundException {
773		// Read in size, and any hidden stuff
774		s.defaultReadObject();
775
776	<	// Read in array length and allocate array
777	<	int arrayLength = s.readInt();
778	<	queue = new Object[arrayLength];
779	<
780	<	// Read in all elements in the proper order.
781	<	for (int i=1; i<=size; i++)
782	<	queue[i] = (E) s.readObject();
776	>	// Read in (and discard) array length
777	>	s.readInt();
778	>
779	>	queue = new Object[size];
780	>
781	>	// Read in all elements.
782	>	for (int i = 0; i < size; i++)
783	>	queue[i] = s.readObject();
784	>
785	>	// Elements are guaranteed to be in "proper order", but the
786	>	// spec has never explained what that might be.
787	>	heapify();
788	>	}
789	>
790	>	public Spliterator<E> spliterator() {
791	>	return new PriorityQueueSpliterator<E>(this, 0, -1, 0);
792		}
793
794	+	/**
795	+	* This is very similar to ArrayList Spliterator, except for extra
796	+	* null checks.
797	+	*/
798	+	static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
799	+	private final PriorityQueue<E> pq;
800	+	private int index;            // current index, modified on advance/split
801	+	private int fence;            // -1 until first use
802	+	private int expectedModCount; // initialized when fence set
803	+
804	+	/** Creates new spliterator covering the given range */
805	+	PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
806	+	int expectedModCount) {
807	+	this.pq = pq;
808	+	this.index = origin;
809	+	this.fence = fence;
810	+	this.expectedModCount = expectedModCount;
811	+	}
812	+
813	+	private int getFence() { // initialize fence to size on first use
814	+	int hi;
815	+	if ((hi = fence) < 0) {
816	+	expectedModCount = pq.modCount;
817	+	hi = fence = pq.size;
818	+	}
819	+	return hi;
820	+	}
821	+
822	+	public Spliterator<E> trySplit() {
823	+	int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
824	+	return (lo >= mid) ? null :
825	+	new PriorityQueueSpliterator<E>(pq, lo, index = mid,
826	+	expectedModCount);
827	+	}
828	+
829	+	@SuppressWarnings("unchecked")
830	+	public void forEachRemaining(Consumer<? super E> action) {
831	+	int i, hi, mc; // hoist accesses and checks from loop
832	+	PriorityQueue<E> q; Object[] a;
833	+	if (action == null)
834	+	throw new NullPointerException();
835	+	if ((q = pq) != null && (a = q.queue) != null) {
836	+	if ((hi = fence) < 0) {
837	+	mc = q.modCount;
838	+	hi = q.size;
839	+	}
840	+	else
841	+	mc = expectedModCount;
842	+	if ((i = index) >= 0 && (index = hi) <= a.length) {
843	+	for (E e;; ++i) {
844	+	if (i < hi) {
845	+	if ((e = (E) a[i]) == null) // must be CME
846	+	break;
847	+	action.accept(e);
848	+	}
849	+	else if (q.modCount != mc)
850	+	break;
851	+	else
852	+	return;
853	+	}
854	+	}
855	+	}
856	+	throw new ConcurrentModificationException();
857	+	}
858	+
859	+	public boolean tryAdvance(Consumer<? super E> action) {
860	+	int hi = getFence(), lo = index;
861	+	if (lo >= 0 && lo < hi) {
862	+	index = lo + 1;
863	+	@SuppressWarnings("unchecked") E e = (E)pq.queue[lo];
864	+	if (e == null)
865	+	throw new ConcurrentModificationException();
866	+	action.accept(e);
867	+	if (pq.modCount != expectedModCount)
868	+	throw new ConcurrentModificationException();
869	+	return true;
870	+	}
871	+	return false;
872	+	}
873	+
874	+	public long estimateSize() {
875	+	return (long) (getFence() - index);
876	+	}
877	+
878	+	public int characteristics() {
879	+	return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
880	+	}
881	+	}
882		}

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