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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.39 by dl, Sun Sep 7 15:06:19 2003 UTC vs.
Revision 1.73 by jsr166, Tue Jun 21 19:29:21 2011 UTC

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1		/*
2	<	* %W% %E%
2	>	* Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.
3	>	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4		*
5	<	* Copyright 2003 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.  Sun designates this
8	>	* particular file as subject to the "Classpath" exception as provided
9	>	* by Sun in the LICENSE file that accompanied this code.
10	>	*
11	>	* This code is distributed in the hope that it will be useful, but WITHOUT
12	>	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13	>	* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14	>	* version 2 for more details (a copy is included in the LICENSE file that
15	>	* accompanied this code).
16	>	*
17	>	* You should have received a copy of the GNU General Public License version
18	>	* 2 along with this work; if not, write to the Free Software Foundation,
19	>	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20	>	*
21	>	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22	>	* or visit www.oracle.com if you need additional information or have any
23	>	* questions.
24		*/
25
26		package java.util;
27
28		/**
29		* An unbounded priority {@linkplain Queue queue} based on a priority heap.
30	<	* This queue orders elements according to an order specified at construction
31	<	* time, which is specified in the same manner as {@link java.util.TreeSet}
32	<	* and {@link java.util.TreeMap}: elements are ordered either according to
33	<	* their <i>natural order</i> (see {@link Comparable}), or according to a
34	<	* {@link java.util.Comparator}, depending on which constructor is used.
35	<	* <p>The <em>head</em> of this queue is the <em>least</em> element with
36	<	* respect to the specified ordering.  If multiple elements are tied for least
37	<	* value, the head is one of those elements. A priority queue does not permit
38	<	* <tt>null</tt> elements.
39	<	*
40	<	* <p>The {@link #remove()} and {@link #poll()} methods remove and
41	<	* return the head of the queue.
42	<	*
43	<	* <p>The {@link #element()} and {@link #peek()} methods return, but do
44	<	* not delete, the head of the queue.
45	<	*
46	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
47	<	* size of the array used internally to store the elements on the
48	<	* queue.
49	<	* It is always at least as large as the queue size.  As
50	<	* elements are added to a priority queue, its capacity grows
51	<	* automatically.  The details of the growth policy are not specified.
52	<	*
53	<	* <p>The Iterator provided in method {@link #iterator()} is <em>not</em>
54	<	* guaranteed to traverse the elements of the PriorityQueue in any
55	<	* particular order. If you need ordered traversal, consider using
56	<	* <tt>Arrays.sort(pq.toArray())</tt>.
30	>	* The elements of the priority queue are ordered according to their
31	>	* {@linkplain Comparable natural ordering}, or by a {@link Comparator}
32	>	* provided at queue construction time, depending on which constructor is
33	>	* used.  A priority queue does not permit {@code null} elements.
34	>	* A priority queue relying on natural ordering also does not permit
35	>	* insertion of non-comparable objects (doing so may result in
36	>	* {@code ClassCastException}).
37	>	*
38	>	* <p>The <em>head</em> of this queue is the <em>least</em> element
39	>	* with respect to the specified ordering.  If multiple elements are
40	>	* tied for least value, the head is one of those elements -- ties are
41	>	* broken arbitrarily.  The queue retrieval operations {@code poll},
42	>	* {@code remove}, {@code peek}, and {@code element} access the
43	>	* element at the head of the queue.
44	>	*
45	>	* <p>A priority queue is unbounded, but has an internal
46	>	* <i>capacity</i> governing the size of an array used to store the
47	>	* elements on the queue.  It is always at least as large as the queue
48	>	* size.  As elements are added to a priority queue, its capacity
49	>	* grows automatically.  The details of the growth policy are not
50	>	* specified.
51	>	*
52	>	* <p>This class and its iterator implement all of the
53	>	* <em>optional</em> methods of the {@link Collection} and {@link
54	>	* Iterator} interfaces.  The Iterator provided in method {@link
55	>	* #iterator()} is <em>not</em> guaranteed to traverse the elements of
56	>	* the priority queue in any particular order. If you need ordered
57	>	* traversal, consider using {@code Arrays.sort(pq.toArray())}.
58		*
59		* <p> <strong>Note that this implementation is not synchronized.</strong>
60	<	* Multiple threads should not access a <tt>PriorityQueue</tt>
61	<	* instance concurrently if any of the threads modifies the list
62	<	* structurally. Instead, use the thread-safe {@link
60	>	* Multiple threads should not access a {@code PriorityQueue}
61	>	* instance concurrently if any of the threads modifies the queue.
62	>	* Instead, use the thread-safe {@link
63		* java.util.concurrent.PriorityBlockingQueue} class.
64		*
65	<	*
66	<	* <p>Implementation note: this implementation provides O(log(n)) time
67	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
68	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
69	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
70	<	* constant time for the retrieval methods (<tt>peek</tt>,
52	<	* <tt>element</tt>, and <tt>size</tt>).
65	>	* <p>Implementation note: this implementation provides
66	>	* O(log(n)) time for the enqueing and dequeing methods
67	>	* ({@code offer}, {@code poll}, {@code remove()} and {@code add});
68	>	* linear time for the {@code remove(Object)} and {@code contains(Object)}
69	>	* methods; and constant time for the retrieval methods
70	>	* ({@code peek}, {@code element}, and {@code size}).
71		*
72		* <p>This class is a member of the
73	<	* <a href="{@docRoot}/../guide/collections/index.html">
73	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
74		* Java Collections Framework</a>.
75	+	*
76		* @since 1.5
77	<	* @version %I%, %G%
78	<	* @author Josh Bloch
77	>	* @author Josh Bloch, Doug Lea
78	>	* @param <E> the type of elements held in this collection
79		*/
80		public class PriorityQueue<E> extends AbstractQueue<E>
81	<	implements Queue<E>, java.io.Serializable {
81	>	implements java.io.Serializable {
82
83		private static final long serialVersionUID = -7720805057305804111L;
84
85		private static final int DEFAULT_INITIAL_CAPACITY = 11;
86
87		/**
88	<	* Priority queue represented as a balanced binary heap: the two children
89	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
90	<	* ordered by comparator, or by the elements' natural ordering, if
91	<	* comparator is null:  For each node n in the heap and each descendant d
92	<	* of n, n <= d.
93	<	*
75	<	* The element with the lowest value is in queue[1], assuming the queue is
76	<	* nonempty.  (A one-based array is used in preference to the traditional
77	<	* zero-based array to simplify parent and child calculations.)
78	<	*
79	<	* queue.length must be >= 2, even if size == 0.
88	>	* Priority queue represented as a balanced binary heap: the two
89	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
90	>	* priority queue is ordered by comparator, or by the elements'
91	>	* natural ordering, if comparator is null: For each node n in the
92	>	* heap and each descendant d of n, n <= d.  The element with the
93	>	* lowest value is in queue[0], assuming the queue is nonempty.
94		*/
95		private transient Object[] queue;
96
#	Line 98 | Line 112 | public class PriorityQueue<E> extends Ab
112		private transient int modCount = 0;
113
114		/**
115	<	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
116	<	* (11) that orders its elements according to their natural
117	<	* ordering (using <tt>Comparable</tt>).
115	>	* Creates a {@code PriorityQueue} with the default initial
116	>	* capacity (11) that orders its elements according to their
117	>	* {@linkplain Comparable natural ordering}.
118		*/
119		public PriorityQueue() {
120		this(DEFAULT_INITIAL_CAPACITY, null);
121		}
122
123		/**
124	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
125	<	* that orders its elements according to their natural ordering
126	<	* (using <tt>Comparable</tt>).
127	<	*
128	<	* @param initialCapacity the initial capacity for this priority queue.
129	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
130	<	* than 1
124	>	* Creates a {@code PriorityQueue} with the specified initial
125	>	* capacity that orders its elements according to their
126	>	* {@linkplain Comparable natural ordering}.
127	>	*
128	>	* @param initialCapacity the initial capacity for this priority queue
129	>	* @throws IllegalArgumentException if {@code initialCapacity} is less
130	>	*         than 1
131		*/
132		public PriorityQueue(int initialCapacity) {
133		this(initialCapacity, null);
134		}
135
136		/**
137	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
137	>	* Creates a {@code PriorityQueue} with the specified initial capacity
138		* that orders its elements according to the specified comparator.
139		*
140	<	* @param initialCapacity the initial capacity for this priority queue.
141	<	* @param comparator the comparator used to order this priority queue.
142	<	* If <tt>null</tt> then the order depends on the elements' natural
143	<	* ordering.
144	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
145	<	* than 1
140	>	* @param  initialCapacity the initial capacity for this priority queue
141	>	* @param  comparator the comparator that will be used to order this
142	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
143	>	*         natural ordering} of the elements will be used.
144	>	* @throws IllegalArgumentException if {@code initialCapacity} is
145	>	*         less than 1
146		*/
147	<	public PriorityQueue(int initialCapacity,
147	>	public PriorityQueue(int initialCapacity,
148		Comparator<? super E> comparator) {
149	+	// Note: This restriction of at least one is not actually needed,
150	+	// but continues for 1.5 compatibility
151		if (initialCapacity < 1)
152		throw new IllegalArgumentException();
153	<	this.queue = new Object[initialCapacity + 1];
153	>	this.queue = new Object[initialCapacity];
154		this.comparator = comparator;
155		}
156
157		/**
158	<	* Common code to initialize underlying queue array across
159	<	* constructors below.
158	>	* Creates a {@code PriorityQueue} containing the elements in the
159	>	* specified collection.  If the specified collection is an instance of
160	>	* a {@link SortedSet} or is another {@code PriorityQueue}, this
161	>	* priority queue will be ordered according to the same ordering.
162	>	* Otherwise, this priority queue will be ordered according to the
163	>	* {@linkplain Comparable natural ordering} of its elements.
164	>	*
165	>	* @param  c the collection whose elements are to be placed
166	>	*         into this priority queue
167	>	* @throws ClassCastException if elements of the specified collection
168	>	*         cannot be compared to one another according to the priority
169	>	*         queue's ordering
170	>	* @throws NullPointerException if the specified collection or any
171	>	*         of its elements are null
172		*/
173	<	private void initializeArray(Collection<? extends E> c) {
174	<	int sz = c.size();
175	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
176	<	Integer.MAX_VALUE - 1);
177	<	if (initialCapacity < 1)
178	<	initialCapacity = 1;
179	<
180	<	this.queue = new Object[initialCapacity + 1];
173	>	@SuppressWarnings("unchecked")
174	>	public PriorityQueue(Collection<? extends E> c) {
175	>	if (c instanceof SortedSet<?>) {
176	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
177	>	this.comparator = (Comparator<? super E>) ss.comparator();
178	>	initElementsFromCollection(ss);
179	>	}
180	>	else if (c instanceof PriorityQueue<?>) {
181	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
182	>	this.comparator = (Comparator<? super E>) pq.comparator();
183	>	initFromPriorityQueue(pq);
184	>	}
185	>	else {
186	>	this.comparator = null;
187	>	initFromCollection(c);
188	>	}
189		}
190
191		/**
192	<	* Initially fill elements of the queue array under the
193	<	* knowledge that it is sorted or is another PQ, in which
194	<	* case we can just place the elements in the order presented.
192	>	* Creates a {@code PriorityQueue} containing the elements in the
193	>	* specified priority queue.  This priority queue will be
194	>	* ordered according to the same ordering as the given priority
195	>	* queue.
196	>	*
197	>	* @param  c the priority queue whose elements are to be placed
198	>	*         into this priority queue
199	>	* @throws ClassCastException if elements of {@code c} cannot be
200	>	*         compared to one another according to {@code c}'s
201	>	*         ordering
202	>	* @throws NullPointerException if the specified priority queue or any
203	>	*         of its elements are null
204		*/
205	<	private void fillFromSorted(Collection<? extends E> c) {
206	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
207	<	queue[++size] = i.next();
205	>	@SuppressWarnings("unchecked")
206	>	public PriorityQueue(PriorityQueue<? extends E> c) {
207	>	this.comparator = (Comparator<? super E>) c.comparator();
208	>	initFromPriorityQueue(c);
209		}
210
211		/**
212	<	* Initially fill elements of the queue array that is not to our knowledge
213	<	* sorted, so we must rearrange the elements to guarantee the heap
214	<	* invariant.
212	>	* Creates a {@code PriorityQueue} containing the elements in the
213	>	* specified sorted set.   This priority queue will be ordered
214	>	* according to the same ordering as the given sorted set.
215	>	*
216	>	* @param  c the sorted set whose elements are to be placed
217	>	*         into this priority queue
218	>	* @throws ClassCastException if elements of the specified sorted
219	>	*         set cannot be compared to one another according to the
220	>	*         sorted set's ordering
221	>	* @throws NullPointerException if the specified sorted set or any
222	>	*         of its elements are null
223		*/
224	<	private void fillFromUnsorted(Collection<? extends E> c) {
225	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
226	<	queue[++size] = i.next();
227	<	heapify();
224	>	@SuppressWarnings("unchecked")
225	>	public PriorityQueue(SortedSet<? extends E> c) {
226	>	this.comparator = (Comparator<? super E>) c.comparator();
227	>	initElementsFromCollection(c);
228		}
229
230	<	/**
231	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
232	<	* specified collection.  The priority queue has an initial
233	<	* capacity of 110% of the size of the specified collection or 1
180	<	* if the collection is empty.  If the specified collection is an
181	<	* instance of a {@link java.util.SortedSet} or is another
182	<	* <tt>PriorityQueue</tt>, the priority queue will be sorted
183	<	* according to the same comparator, or according to its elements'
184	<	* natural order if the collection is sorted according to its
185	<	* elements' natural order.  Otherwise, the priority queue is
186	<	* ordered according to its elements' natural order.
187	<	*
188	<	* @param c the collection whose elements are to be placed
189	<	*        into this priority queue.
190	<	* @throws ClassCastException if elements of the specified collection
191	<	*         cannot be compared to one another according to the priority
192	<	*         queue's ordering.
193	<	* @throws NullPointerException if <tt>c</tt> or any element within it
194	<	* is <tt>null</tt>
195	<	*/
196	<	public PriorityQueue(Collection<? extends E> c) {
197	<	initializeArray(c);
198	<	if (c instanceof SortedSet) {
199	<	// @fixme double-cast workaround for compiler
200	<	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
201	<	comparator = (Comparator<? super E>)s.comparator();
202	<	fillFromSorted(s);
203	<	} else if (c instanceof PriorityQueue) {
204	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
205	<	comparator = (Comparator<? super E>)s.comparator();
206	<	fillFromSorted(s);
230	>	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
231	>	if (c.getClass() == PriorityQueue.class) {
232	>	this.queue = c.toArray();
233	>	this.size = c.size();
234		} else {
235	<	comparator = null;
209	<	fillFromUnsorted(c);
235	>	initFromCollection(c);
236		}
237		}
238
239	+	private void initElementsFromCollection(Collection<? extends E> c) {
240	+	Object[] a = c.toArray();
241	+	// If c.toArray incorrectly doesn't return Object[], copy it.
242	+	if (a.getClass() != Object[].class)
243	+	a = Arrays.copyOf(a, a.length, Object[].class);
244	+	int len = a.length;
245	+	if (len == 1 || this.comparator != null)
246	+	for (int i = 0; i < len; i++)
247	+	if (a[i] == null)
248	+	throw new NullPointerException();
249	+	this.queue = a;
250	+	this.size = a.length;
251	+	}
252	+
253		/**
254	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
215	<	* specified collection.  The priority queue has an initial
216	<	* capacity of 110% of the size of the specified collection or 1
217	<	* if the collection is empty.  This priority queue will be sorted
218	<	* according to the same comparator as the given collection, or
219	<	* according to its elements' natural order if the collection is
220	<	* sorted according to its elements' natural order.
254	>	* Initializes queue array with elements from the given Collection.
255		*
256	<	* @param c the collection whose elements are to be placed
223	<	*        into this priority queue.
224	<	* @throws ClassCastException if elements of the specified collection
225	<	*         cannot be compared to one another according to the priority
226	<	*         queue's ordering.
227	<	* @throws NullPointerException if <tt>c</tt> or any element within it
228	<	* is <tt>null</tt>
256	>	* @param c the collection
257		*/
258	<	public PriorityQueue(PriorityQueue<? extends E> c) {
259	<	initializeArray(c);
260	<	comparator = (Comparator<? super E>)c.comparator();
233	<	fillFromSorted(c);
258	>	private void initFromCollection(Collection<? extends E> c) {
259	>	initElementsFromCollection(c);
260	>	heapify();
261		}
262
263		/**
264	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
265	<	* specified collection.  The priority queue has an initial
266	<	* capacity of 110% of the size of the specified collection or 1
267	<	* if the collection is empty.  This priority queue will be sorted
241	<	* according to the same comparator as the given collection, or
242	<	* according to its elements' natural order if the collection is
243	<	* sorted according to its elements' natural order.
244	<	*
245	<	* @param c the collection whose elements are to be placed
246	<	*        into this priority queue.
247	<	* @throws ClassCastException if elements of the specified collection
248	<	*         cannot be compared to one another according to the priority
249	<	*         queue's ordering.
250	<	* @throws NullPointerException if <tt>c</tt> or any element within it
251	<	* is <tt>null</tt>
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	<	public PriorityQueue(SortedSet<? extends E> c) {
254	<	initializeArray(c);
255	<	comparator = (Comparator<? super E>)c.comparator();
256	<	fillFromSorted(c);
257	<	}
269	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
270
271		/**
272	<	* Resize array, if necessary, to be able to hold given index
272	>	* Increases the capacity of the array.
273	>	*
274	>	* @param minCapacity the desired minimum capacity
275		*/
276	<	private void grow(int index) {
277	<	int newlen = queue.length;
278	<	if (index < newlen) // don't need to grow
279	<	return;
280	<	if (index == Integer.MAX_VALUE)
276	>	private void grow(int minCapacity) {
277	>	int oldCapacity = queue.length;
278	>	// Double size if small; else grow by 50%
279	>	int newCapacity = oldCapacity + ((oldCapacity < 64) ?
280	>	(oldCapacity + 2) :
281	>	(oldCapacity >> 1));
282	>	// overflow-conscious code
283	>	if (newCapacity - MAX_ARRAY_SIZE > 0)
284	>	newCapacity = hugeCapacity(minCapacity);
285	>	queue = Arrays.copyOf(queue, newCapacity);
286	>	}
287	>
288	>	private static int hugeCapacity(int minCapacity) {
289	>	if (minCapacity < 0) // overflow
290		throw new OutOfMemoryError();
291	<	while (newlen <= index) {
292	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
293	<	newlen = Integer.MAX_VALUE;
271	<	else
272	<	newlen <<= 2;
273	<	}
274	<	Object[] newQueue = new Object[newlen];
275	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
276	<	queue = newQueue;
291	>	return (minCapacity > MAX_ARRAY_SIZE) ?
292	>	Integer.MAX_VALUE :
293	>	MAX_ARRAY_SIZE;
294		}
278	–
295
296	<	// Queue Methods
296	>	/**
297	>	* Inserts the specified element into this priority queue.
298	>	*
299	>	* @return {@code true} (as specified by {@link Collection#add})
300	>	* @throws ClassCastException if the specified element cannot be
301	>	*         compared with elements currently in this priority queue
302	>	*         according to the priority queue's ordering
303	>	* @throws NullPointerException if the specified element is null
304	>	*/
305	>	public boolean add(E e) {
306	>	return offer(e);
307	>	}
308
309		/**
310	<	* Add the specified element to this priority queue.
310	>	* Inserts the specified element into this priority queue.
311		*
312	<	* @return <tt>true</tt>
313	<	* @throws ClassCastException if the specified element cannot be compared
314	<	* with elements currently in the priority queue according
315	<	* to the priority queue's ordering.
316	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
312	>	* @return {@code true} (as specified by {@link Queue#offer})
313	>	* @throws ClassCastException if the specified element cannot be
314	>	*         compared with elements currently in this priority queue
315	>	*         according to the priority queue's ordering
316	>	* @throws NullPointerException if the specified element is null
317		*/
318	<	public boolean offer(E o) {
319	<	if (o == null)
318	>	public boolean offer(E e) {
319	>	if (e == null)
320		throw new NullPointerException();
321		modCount++;
322	<	++size;
323	<
324	<	// Grow backing store if necessary
325	<	if (size >= queue.length)
326	<	grow(size);
327	<
328	<	queue[size] = o;
329	<	fixUp(size);
322	>	int i = size;
323	>	if (i >= queue.length)
324	>	grow(i + 1);
325	>	size = i + 1;
326	>	if (i == 0)
327	>	queue[0] = e;
328	>	else
329	>	siftUp(i, e);
330		return true;
331		}
332
306	–	public E poll() {
307	–	if (size == 0)
308	–	return null;
309	–	return remove();
310	–	}
311	–
333		public E peek() {
334	<	return (E) queue[1];
334	>	return (size == 0) ? null : (E) queue[0];
335		}
336
337	<	// Collection Methods - the first two override to update docs
337	>	private int indexOf(Object o) {
338	>	if (o != null) {
339	>	for (int i = 0; i < size; i++)
340	>	if (o.equals(queue[i]))
341	>	return i;
342	>	}
343	>	return -1;
344	>	}
345
346		/**
347	<	* Adds the specified element to this queue.
348	<	* @return <tt>true</tt> (as per the general contract of
349	<	* <tt>Collection.add</tt>).
347	>	* Removes a single instance of the specified element from this queue,
348	>	* if it is present.  More formally, removes an element {@code e} such
349	>	* that {@code o.equals(e)}, if this queue contains one or more such
350	>	* elements.  Returns {@code true} if and only if this queue contained
351	>	* the specified element (or equivalently, if this queue changed as a
352	>	* result of the call).
353		*
354	<	* @throws NullPointerException {@inheritDoc}
355	<	* @throws ClassCastException if the specified element cannot be compared
325	<	* with elements currently in the priority queue according
326	<	* to the priority queue's ordering.
354	>	* @param o element to be removed from this queue, if present
355	>	* @return {@code true} if this queue changed as a result of the call
356		*/
357	<	public boolean add(E o) {
358	<	return super.add(o);
357	>	public boolean remove(Object o) {
358	>	int i = indexOf(o);
359	>	if (i == -1)
360	>	return false;
361	>	else {
362	>	removeAt(i);
363	>	return true;
364	>	}
365		}
366
332	–
367		/**
368	<	* Adds all of the elements in the specified collection to this queue.
369	<	* The behavior of this operation is undefined if
370	<	* the specified collection is modified while the operation is in
371	<	* progress.  (This implies that the behavior of this call is undefined if
372	<	* the specified collection is this queue, and this queue is nonempty.)
339	<	* <p>
340	<	* This implementation iterates over the specified collection, and adds
341	<	* each object returned by the iterator to this collection, in turn.
342	<	* @throws NullPointerException {@inheritDoc}
343	<	* @throws ClassCastException if any element cannot be compared
344	<	* with elements currently in the priority queue according
345	<	* to the priority queue's ordering.
368	>	* Version of remove using reference equality, not equals.
369	>	* Needed by iterator.remove.
370	>	*
371	>	* @param o element to be removed from this queue, if present
372	>	* @return {@code true} if removed
373		*/
374	<	public boolean addAll(Collection<? extends E> c) {
375	<	return super.addAll(c);
374	>	boolean removeEq(Object o) {
375	>	for (int i = 0; i < size; i++) {
376	>	if (o == queue[i]) {
377	>	removeAt(i);
378	>	return true;
379	>	}
380	>	}
381	>	return false;
382		}
383
384	+	/**
385	+	* Returns {@code true} if this queue contains the specified element.
386	+	* More formally, returns {@code true} if and only if this queue contains
387	+	* at least one element {@code e} such that {@code o.equals(e)}.
388	+	*
389	+	* @param o object to be checked for containment in this queue
390	+	* @return {@code true} if this queue contains the specified element
391	+	*/
392	+	public boolean contains(Object o) {
393	+	return indexOf(o) != -1;
394	+	}
395
396		/**
397	<	* Removes a single instance of the specified element from this
398	<	* queue, if it is present.  More formally,
399	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
400	<	* o.equals(e))</tt>, if the queue contains one or more such
401	<	* elements.  Returns <tt>true</tt> if the queue contained the
402	<	* specified element (or equivalently, if the queue changed as a
359	<	* result of the call).
397	>	* Returns an array containing all of the elements in this queue.
398	>	* The elements are in no particular order.
399	>	*
400	>	* <p>The returned array will be "safe" in that no references to it are
401	>	* maintained by this queue.  (In other words, this method must allocate
402	>	* a new array).  The caller is thus free to modify the returned array.
403		*
404	<	* <p>This implementation iterates over the queue looking for the
405	<	* specified element.  If it finds the element, it removes the element
363	<	* from the queue using the iterator's remove method.<p>
404	>	* <p>This method acts as bridge between array-based and collection-based
405	>	* APIs.
406		*
407	+	* @return an array containing all of the elements in this queue
408		*/
409	<	public boolean remove(Object o) {
410	<	if (o == null)
411	<	return false;
409	>	public Object[] toArray() {
410	>	return Arrays.copyOf(queue, size);
411	>	}
412
413	<	if (comparator == null) {
414	<	for (int i = 1; i <= size; i++) {
415	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
416	<	removeAt(i);
417	<	return true;
418	<	}
419	<	}
420	<	} else {
421	<	for (int i = 1; i <= size; i++) {
422	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
423	<	removeAt(i);
424	<	return true;
425	<	}
426	<	}
427	<	}
428	<	return false;
413	>	/**
414	>	* Returns an array containing all of the elements in this queue; the
415	>	* runtime type of the returned array is that of the specified array.
416	>	* The returned array elements are in no particular order.
417	>	* If the queue fits in the specified array, it is returned therein.
418	>	* Otherwise, a new array is allocated with the runtime type of the
419	>	* specified array and the size of this queue.
420	>	*
421	>	* <p>If the queue fits in the specified array with room to spare
422	>	* (i.e., the array has more elements than the queue), the element in
423	>	* the array immediately following the end of the collection is set to
424	>	* {@code null}.
425	>	*
426	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
427	>	* array-based and collection-based APIs.  Further, this method allows
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.
432	>	* The following code can be used to dump the queue into a newly
433	>	* allocated array of <tt>String</tt>:
434	>	*
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>.
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
442	>	*          same runtime type is allocated for this purpose.
443	>	* @return an array containing all of the elements in this queue
444	>	* @throws ArrayStoreException if the runtime type of the specified array
445	>	*         is not a supertype of the runtime type of every element in
446	>	*         this queue
447	>	* @throws NullPointerException if the specified array is null
448	>	*/
449	>	public <T> T[] toArray(T[] a) {
450	>	if (a.length < size)
451	>	// Make a new array of a's runtime type, but my contents:
452	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
453	>	System.arraycopy(queue, 0, a, 0, size);
454	>	if (a.length > size)
455	>	a[size] = null;
456	>	return a;
457		}
458
459		/**
460		* Returns an iterator over the elements in this queue. The iterator
461		* does not return the elements in any particular order.
462		*
463	<	* @return an iterator over the elements in this queue.
463	>	* @return an iterator over the elements in this queue
464		*/
465		public Iterator<E> iterator() {
466		return new Itr();
467		}
468
469	<	private class Itr implements Iterator<E> {
399	<
469	>	private final class Itr implements Iterator<E> {
470		/**
471		* Index (into queue array) of element to be returned by
472		* subsequent call to next.
473		*/
474	<	private int cursor = 1;
474	>	private int cursor = 0;
475
476		/**
477		* Index of element returned by most recent call to next,
478		* unless that element came from the forgetMeNot list.
479	<	* Reset to 0 if element is deleted by a call to remove.
479	>	* Set to -1 if element is deleted by a call to remove.
480		*/
481	<	private int lastRet = 0;
481	>	private int lastRet = -1;
482
483		/**
484	<	* The modCount value that the iterator believes that the backing
415	<	* List should have.  If this expectation is violated, the iterator
416	<	* has detected concurrent modification.
417	<	*/
418	<	private int expectedModCount = modCount;
419	<
420	<	/**
421	<	* A list of elements that were moved from the unvisited portion of
484	>	* A queue of elements that were moved from the unvisited portion of
485		* the heap into the visited portion as a result of "unlucky" element
486		* removals during the iteration.  (Unlucky element removals are those
487	<	* that require a fixup instead of a fixdown.)  We must visit all of
487	>	* that require a siftup instead of a siftdown.)  We must visit all of
488		* the elements in this list to complete the iteration.  We do this
489		* after we've completed the "normal" iteration.
490		*
491		* We expect that most iterations, even those involving removals,
492	<	* will not use need to store elements in this field.
492	>	* will not need to store elements in this field.
493		*/
494	<	private ArrayList<E> forgetMeNot = null;
494	>	private ArrayDeque<E> forgetMeNot = null;
495
496		/**
497		* Element returned by the most recent call to next iff that
498		* element was drawn from the forgetMeNot list.
499		*/
500	<	private Object lastRetElt = null;
500	>	private E lastRetElt = null;
501	>
502	>	/**
503	>	* The modCount value that the iterator believes that the backing
504	>	* Queue should have.  If this expectation is violated, the iterator
505	>	* has detected concurrent modification.
506	>	*/
507	>	private int expectedModCount = modCount;
508
509		public boolean hasNext() {
510	<	return cursor <= size || forgetMeNot != null;
510	>	return cursor < size ||
511	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
512		}
513
514		public E next() {
515	<	checkForComodification();
516	<	E result;
517	<	if (cursor <= size) {
518	<	result = (E) queue[cursor];
519	<	lastRet = cursor++;
520	<	}
521	<	else if (forgetMeNot == null)
522	<	throw new NoSuchElementException();
523	<	else {
453	<	int remaining = forgetMeNot.size();
454	<	result = forgetMeNot.remove(remaining - 1);
455	<	if (remaining == 1)
456	<	forgetMeNot = null;
457	<	lastRet = 0;
458	<	lastRetElt = result;
515	>	if (expectedModCount != modCount)
516	>	throw new ConcurrentModificationException();
517	>	if (cursor < size)
518	>	return (E) queue[lastRet = cursor++];
519	>	if (forgetMeNot != null) {
520	>	lastRet = -1;
521	>	lastRetElt = forgetMeNot.poll();
522	>	if (lastRetElt != null)
523	>	return lastRetElt;
524		}
525	<	return result;
525	>	throw new NoSuchElementException();
526		}
527
528		public void remove() {
529	<	checkForComodification();
530	<
531	<	if (lastRet != 0) {
529	>	if (expectedModCount != modCount)
530	>	throw new ConcurrentModificationException();
531	>	if (lastRet != -1) {
532		E moved = PriorityQueue.this.removeAt(lastRet);
533	<	lastRet = 0;
534	<	if (moved == null) {
533	>	lastRet = -1;
534	>	if (moved == null)
535		cursor--;
536	<	} else {
536	>	else {
537		if (forgetMeNot == null)
538	<	forgetMeNot = new ArrayList<E>();
538	>	forgetMeNot = new ArrayDeque<E>();
539		forgetMeNot.add(moved);
540		}
541		} else if (lastRetElt != null) {
542	<	PriorityQueue.this.remove(lastRetElt);
542	>	PriorityQueue.this.removeEq(lastRetElt);
543		lastRetElt = null;
544		} else {
545		throw new IllegalStateException();
546		}
482	–
547		expectedModCount = modCount;
548		}
485	–
486	–	final void checkForComodification() {
487	–	if (modCount != expectedModCount)
488	–	throw new ConcurrentModificationException();
489	–	}
549		}
550
551		public int size() {
#	Line 494 | Line 553 | public class PriorityQueue<E> extends Ab
553		}
554
555		/**
556	<	* Remove all elements from the priority queue.
556	>	* Removes all of the elements from this priority queue.
557	>	* The queue will be empty after this call returns.
558		*/
559		public void clear() {
560		modCount++;
561	<
502	<	// Null out element references to prevent memory leak
503	<	for (int i=1; i<=size; i++)
561	>	for (int i = 0; i < size; i++)
562		queue[i] = null;
505	–
563		size = 0;
564		}
565
566	<	/**
510	<	* Removes and returns the first element from queue.
511	<	*/
512	<	public E remove() {
566	>	public E poll() {
567		if (size == 0)
568	<	throw new NoSuchElementException();
568	>	return null;
569	>	int s = --size;
570		modCount++;
571	<
572	<	E result = (E) queue[1];
573	<	queue[1] = queue[size];
574	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
575	<	if (size > 1)
521	<	fixDown(1);
522	<
571	>	E result = (E) queue[0];
572	>	E x = (E) queue[s];
573	>	queue[s] = null;
574	>	if (s != 0)
575	>	siftDown(0, x);
576		return result;
577		}
578
579		/**
580	<	* Removes and returns the ith element from queue.  (Recall that queue
528	<	* is one-based, so 1 <= i <= size.)
580	>	* Removes the ith element from queue.
581		*
582	<	* Normally this method leaves the elements at positions from 1 up to i-1,
583	<	* inclusive, untouched.  Under these circumstances, it returns null.
584	<	* Occasionally, in order to maintain the heap invariant, it must move
585	<	* the last element of the list to some index in the range [2, i-1],
586	<	* and move the element previously at position (i/2) to position i.
587	<	* Under these circumstances, this method returns the element that was
588	<	* previously at the end of the list and is now at some position between
589	<	* 2 and i-1 inclusive.
582	>	* Normally this method leaves the elements at up to i-1,
583	>	* inclusive, untouched.  Under these circumstances, it returns
584	>	* null.  Occasionally, in order to maintain the heap invariant,
585	>	* it must swap a later element of the list with one earlier than
586	>	* i.  Under these circumstances, this method returns the element
587	>	* that was previously at the end of the list and is now at some
588	>	* position before i. This fact is used by iterator.remove so as to
589	>	* avoid missing traversing elements.
590		*/
591	<	private E removeAt(int i) {
592	<	assert i > 0 && i <= size;
591	>	private E removeAt(int i) {
592	>	assert i >= 0 && i < size;
593		modCount++;
594	<
595	<	E moved = (E) queue[size];
596	<	queue[i] = moved;
597	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
598	<	if (i <= size) {
599	<	fixDown(i);
594	>	int s = --size;
595	>	if (s == i) // removed last element
596	>	queue[i] = null;
597	>	else {
598	>	E moved = (E) queue[s];
599	>	queue[s] = null;
600	>	siftDown(i, moved);
601		if (queue[i] == moved) {
602	<	fixUp(i);
602	>	siftUp(i, moved);
603		if (queue[i] != moved)
604		return moved;
605		}
#	Line 555 | Line 608 | public class PriorityQueue<E> extends Ab
608		}
609
610		/**
611	<	* Establishes the heap invariant (described above) assuming the heap
612	<	* satisfies the invariant except possibly for the leaf-node indexed by k
613	<	* (which may have a nextExecutionTime less than its parent's).
614	<	*
615	<	* This method functions by "promoting" queue[k] up the hierarchy
616	<	* (by swapping it with its parent) repeatedly until queue[k]
617	<	* is greater than or equal to its parent.
618	<	*/
619	<	private void fixUp(int k) {
620	<	if (comparator == null) {
621	<	while (k > 1) {
622	<	int j = k >> 1;
623	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
624	<	break;
625	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
626	<	k = j;
627	<	}
628	<	} else {
629	<	while (k > 1) {
630	<	int j = k >>> 1;
631	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
632	<	break;
633	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
634	<	k = j;
635	<	}
611	>	* Inserts item x at position k, maintaining heap invariant by
612	>	* promoting x up the tree until it is greater than or equal to
613	>	* its parent, or is the root.
614	>	*
615	>	* To simplify and speed up coercions and comparisons. the
616	>	* Comparable and Comparator versions are separated into different
617	>	* methods that are otherwise identical. (Similarly for siftDown.)
618	>	*
619	>	* @param k the position to fill
620	>	* @param x the item to insert
621	>	*/
622	>	private void siftUp(int k, E x) {
623	>	if (comparator != null)
624	>	siftUpUsingComparator(k, x);
625	>	else
626	>	siftUpComparable(k, x);
627	>	}
628	>
629	>	private void siftUpComparable(int k, E x) {
630	>	Comparable<? super E> key = (Comparable<? super E>) x;
631	>	while (k > 0) {
632	>	int parent = (k - 1) >>> 1;
633	>	Object e = queue[parent];
634	>	if (key.compareTo((E) e) >= 0)
635	>	break;
636	>	queue[k] = e;
637	>	k = parent;
638	>	}
639	>	queue[k] = key;
640	>	}
641	>
642	>	private void siftUpUsingComparator(int k, E x) {
643	>	while (k > 0) {
644	>	int parent = (k - 1) >>> 1;
645	>	Object e = queue[parent];
646	>	if (comparator.compare(x, (E) e) >= 0)
647	>	break;
648	>	queue[k] = e;
649	>	k = parent;
650		}
651	+	queue[k] = x;
652		}
653
654		/**
655	<	* Establishes the heap invariant (described above) in the subtree
656	<	* rooted at k, which is assumed to satisfy the heap invariant except
657	<	* possibly for node k itself (which may be greater than its children).
658	<	*
659	<	* This method functions by "demoting" queue[k] down the hierarchy
660	<	* (by swapping it with its smaller child) repeatedly until queue[k]
661	<	* is less than or equal to its children.
662	<	*/
663	<	private void fixDown(int k) {
664	<	int j;
665	<	if (comparator == null) {
666	<	while ((j = k << 1) <= size && (j > 0)) {
667	<	if (j<size &&
668	<	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
669	<	j++; // j indexes smallest kid
670	<
671	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
672	<	break;
673	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
674	<	k = j;
675	<	}
676	<	} else {
677	<	while ((j = k << 1) <= size && (j > 0)) {
678	<	if (j<size &&
679	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
680	<	j++; // j indexes smallest kid
681	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
682	<	break;
615	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
616	<	k = j;
617	<	}
655	>	* Inserts item x at position k, maintaining heap invariant by
656	>	* demoting x down the tree repeatedly until it is less than or
657	>	* equal to its children or is a leaf.
658	>	*
659	>	* @param k the position to fill
660	>	* @param x the item to insert
661	>	*/
662	>	private void siftDown(int k, E x) {
663	>	if (comparator != null)
664	>	siftDownUsingComparator(k, x);
665	>	else
666	>	siftDownComparable(k, x);
667	>	}
668	>
669	>	private void siftDownComparable(int k, E x) {
670	>	Comparable<? super E> key = (Comparable<? super E>)x;
671	>	int half = size >>> 1;        // loop while a non-leaf
672	>	while (k < half) {
673	>	int child = (k << 1) + 1; // assume left child is least
674	>	Object c = queue[child];
675	>	int right = child + 1;
676	>	if (right < size &&
677	>	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
678	>	c = queue[child = right];
679	>	if (key.compareTo((E) c) <= 0)
680	>	break;
681	>	queue[k] = c;
682	>	k = child;
683		}
684	+	queue[k] = key;
685	+	}
686	+
687	+	private void siftDownUsingComparator(int k, E x) {
688	+	int half = size >>> 1;
689	+	while (k < half) {
690	+	int child = (k << 1) + 1;
691	+	Object c = queue[child];
692	+	int right = child + 1;
693	+	if (right < size &&
694	+	comparator.compare((E) c, (E) queue[right]) > 0)
695	+	c = queue[child = right];
696	+	if (comparator.compare(x, (E) c) <= 0)
697	+	break;
698	+	queue[k] = c;
699	+	k = child;
700	+	}
701	+	queue[k] = x;
702		}
703
704		/**
#	Line 623 | Line 706 | public class PriorityQueue<E> extends Ab
706		* assuming nothing about the order of the elements prior to the call.
707		*/
708		private void heapify() {
709	<	for (int i = size/2; i >= 1; i--)
710	<	fixDown(i);
709	>	for (int i = (size >>> 1) - 1; i >= 0; i--)
710	>	siftDown(i, (E) queue[i]);
711		}
712
713		/**
714	<	* Returns the comparator used to order this collection, or <tt>null</tt>
715	<	* if this collection is sorted according to its elements natural ordering
716	<	* (using <tt>Comparable</tt>).
714	>	* Returns the comparator used to order the elements in this
715	>	* queue, or {@code null} if this queue is sorted according to
716	>	* the {@linkplain Comparable natural ordering} of its elements.
717		*
718	<	* @return the comparator used to order this collection, or <tt>null</tt>
719	<	* if this collection is sorted according to its elements natural ordering.
718	>	* @return the comparator used to order this queue, or
719	>	*         {@code null} if this queue is sorted according to the
720	>	*         natural ordering of its elements
721		*/
722		public Comparator<? super E> comparator() {
723		return comparator;
724		}
725
726		/**
727	<	* Save the state of the instance to a stream (that
728	<	* is, serialize it).
727	>	* Saves the state of the instance to a stream (that
728	>	* is, serializes it).
729		*
730		* @serialData The length of the array backing the instance is
731	<	* emitted (int), followed by all of its elements (each an
732	<	* <tt>Object</tt>) in the proper order.
731	>	*             emitted (int), followed by all of its elements
732	>	*             (each an {@code Object}) in the proper order.
733		* @param s the stream
734		*/
735		private void writeObject(java.io.ObjectOutputStream s)
#	Line 653 | Line 737 | public class PriorityQueue<E> extends Ab
737		// Write out element count, and any hidden stuff
738		s.defaultWriteObject();
739
740	<	// Write out array length
741	<	s.writeInt(queue.length);
740	>	// Write out array length, for compatibility with 1.5 version
741	>	s.writeInt(Math.max(2, size + 1));
742
743	<	// Write out all elements in the proper order.
744	<	for (int i=1; i<=size; i++)
743	>	// Write out all elements in the "proper order".
744	>	for (int i = 0; i < size; i++)
745		s.writeObject(queue[i]);
746		}
747
748		/**
749	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
750	<	* deserialize it).
749	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
750	>	* (that is, deserializes it).
751	>	*
752		* @param s the stream
753		*/
754		private void readObject(java.io.ObjectInputStream s)
#	Line 671 | Line 756 | public class PriorityQueue<E> extends Ab
756		// Read in size, and any hidden stuff
757		s.defaultReadObject();
758
759	<	// Read in array length and allocate array
760	<	int arrayLength = s.readInt();
676	<	queue = new Object[arrayLength];
677	<
678	<	// Read in all elements in the proper order.
679	<	for (int i=1; i<=size; i++)
680	<	queue[i] = (E) s.readObject();
681	<	}
759	>	// Read in (and discard) array length
760	>	s.readInt();
761
762	+	queue = new Object[size];
763	+
764	+	// Read in all elements.
765	+	for (int i = 0; i < size; i++)
766	+	queue[i] = s.readObject();
767	+
768	+	// Elements are guaranteed to be in "proper order", but the
769	+	// spec has never explained what that might be.
770	+	heapify();
771	+	}
772		}

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