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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.35 by dl, Wed Aug 27 10:27:07 2003 UTC vs.
Revision 1.76 by jsr166, Fri Dec 2 14:37:32 2011 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
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	>	* 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
31	<	* elements according to an order specified at construction time, which is
32	<	* specified in the same manner as {@link java.util.TreeSet} and
33	<	* {@link java.util.TreeMap}: elements are ordered
34	<	* either according to their <i>natural order</i> (see {@link Comparable}), or
35	<	* according to a {@link java.util.Comparator}, depending on which
36	<	* constructor is used.
37	<	* <p>The <em>head</em> of this queue is the <em>least</em> element with
38	<	* respect to the specified ordering.
39	<	* If multiple elements are tied for least value, the
40	<	* head is one of those elements. A priority queue does not permit
41	<	* <tt>null</tt> elements.
42	<	*
43	<	* <p>The {@link #remove()} and {@link #poll()} methods remove and
44	<	* return the head of the queue.
45	<	*
46	<	* <p>The {@link #element()} and {@link #peek()} methods return, but do
47	<	* not delete, the head of the queue.
48	<	*
49	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
50	<	* size of the array used internally to store the elements on the
51	<	* queue.
52	<	* It is always at least as large as the queue size.  As
53	<	* elements are added to a priority queue, its capacity grows
54	<	* automatically.  The details of the growth policy are not specified.
55	<	*
56	<	* <p>The Iterator provided in method {@link #iterator()} is <em>not</em>
57	<	* guaranteed to traverse the elements of the PriorityQueue in any
33	<	* particular order. If you need ordered traversal, consider using
34	<	* <tt>Arrays.sort(pq.toArray())</tt>.
29	>	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
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>,
48	<	* <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	<	* @author Josh Bloch
77	>	* @author Josh Bloch, Doug Lea
78	>	* @param <E> the type of elements held in this collection
79		*/
80	+	@SuppressWarnings("unchecked")
81		public class PriorityQueue<E> extends AbstractQueue<E>
82	<	implements Queue<E>, java.io.Serializable {
82	>	implements java.io.Serializable {
83
84		private static final long serialVersionUID = -7720805057305804111L;
85
86		private static final int DEFAULT_INITIAL_CAPACITY = 11;
87
88		/**
89	<	* Priority queue represented as a balanced binary heap: the two children
90	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
91	<	* ordered by comparator, or by the elements' natural ordering, if
92	<	* comparator is null:  For each node n in the heap and each descendant d
93	<	* of n, n <= d.
94	<	*
70	<	* The element with the lowest value is in queue[1], assuming the queue is
71	<	* nonempty.  (A one-based array is used in preference to the traditional
72	<	* zero-based array to simplify parent and child calculations.)
73	<	*
74	<	* queue.length must be >= 2, even if size == 0.
89	>	* Priority queue represented as a balanced binary heap: the two
90	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
91	>	* priority queue is ordered by comparator, or by the elements'
92	>	* natural ordering, if comparator is null: For each node n in the
93	>	* heap and each descendant d of n, n <= d.  The element with the
94	>	* lowest value is in queue[0], assuming the queue is nonempty.
95		*/
96		private transient Object[] queue;
97
#	Line 93 | Line 113 | public class PriorityQueue<E> extends Ab
113		private transient int modCount = 0;
114
115		/**
116	<	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
117	<	* (11) that orders its elements according to their natural
118	<	* ordering (using <tt>Comparable</tt>).
116	>	* Creates a {@code PriorityQueue} with the default initial
117	>	* capacity (11) that orders its elements according to their
118	>	* {@linkplain Comparable natural ordering}.
119		*/
120		public PriorityQueue() {
121		this(DEFAULT_INITIAL_CAPACITY, null);
122		}
123
124		/**
125	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
126	<	* that orders its elements according to their natural ordering
127	<	* (using <tt>Comparable</tt>).
128	<	*
129	<	* @param initialCapacity the initial capacity for this priority queue.
130	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
131	<	* than 1
125	>	* Creates a {@code PriorityQueue} with the specified initial
126	>	* capacity that orders its elements according to their
127	>	* {@linkplain Comparable natural ordering}.
128	>	*
129	>	* @param initialCapacity the initial capacity for this priority queue
130	>	* @throws IllegalArgumentException if {@code initialCapacity} is less
131	>	*         than 1
132		*/
133		public PriorityQueue(int initialCapacity) {
134		this(initialCapacity, null);
135		}
136
137		/**
138	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
138	>	* Creates a {@code PriorityQueue} with the specified initial capacity
139		* that orders its elements according to the specified comparator.
140		*
141	<	* @param initialCapacity the initial capacity for this priority queue.
142	<	* @param comparator the comparator used to order this priority queue.
143	<	* If <tt>null</tt> then the order depends on the elements' natural
144	<	* ordering.
145	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
146	<	* than 1
141	>	* @param  initialCapacity the initial capacity for this priority queue
142	>	* @param  comparator the comparator that will be used to order this
143	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
144	>	*         natural ordering} of the elements will be used.
145	>	* @throws IllegalArgumentException if {@code initialCapacity} is
146	>	*         less than 1
147		*/
148	<	public PriorityQueue(int initialCapacity,
148	>	public PriorityQueue(int initialCapacity,
149		Comparator<? super E> comparator) {
150	+	// Note: This restriction of at least one is not actually needed,
151	+	// but continues for 1.5 compatibility
152		if (initialCapacity < 1)
153		throw new IllegalArgumentException();
154	<	this.queue = new Object[initialCapacity + 1];
154	>	this.queue = new Object[initialCapacity];
155		this.comparator = comparator;
156		}
157
158		/**
159	<	* Common code to initialize underlying queue array across
160	<	* constructors below.
159	>	* Creates a {@code PriorityQueue} containing the elements in the
160	>	* specified collection.  If the specified collection is an instance of
161	>	* a {@link SortedSet} or is another {@code PriorityQueue}, this
162	>	* priority queue will be ordered according to the same ordering.
163	>	* Otherwise, this priority queue will be ordered according to the
164	>	* {@linkplain Comparable natural ordering} of its elements.
165	>	*
166	>	* @param  c the collection whose elements are to be placed
167	>	*         into this priority queue
168	>	* @throws ClassCastException if elements of the specified collection
169	>	*         cannot be compared to one another according to the priority
170	>	*         queue's ordering
171	>	* @throws NullPointerException if the specified collection or any
172	>	*         of its elements are null
173		*/
174	<	private void initializeArray(Collection<? extends E> c) {
175	<	int sz = c.size();
176	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
177	<	Integer.MAX_VALUE - 1);
178	<	if (initialCapacity < 1)
179	<	initialCapacity = 1;
180	<
181	<	this.queue = new Object[initialCapacity + 1];
174	>	@SuppressWarnings("unchecked")
175	>	public PriorityQueue(Collection<? extends E> c) {
176	>	if (c instanceof SortedSet<?>) {
177	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
178	>	this.comparator = (Comparator<? super E>) ss.comparator();
179	>	initElementsFromCollection(ss);
180	>	}
181	>	else if (c instanceof PriorityQueue<?>) {
182	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
183	>	this.comparator = (Comparator<? super E>) pq.comparator();
184	>	initFromPriorityQueue(pq);
185	>	}
186	>	else {
187	>	this.comparator = null;
188	>	initFromCollection(c);
189	>	}
190		}
191
192		/**
193	<	* Initially fill elements of the queue array under the
194	<	* knowledge that it is sorted or is another PQ, in which
195	<	* case we can just place the elements without fixups.
193	>	* Creates a {@code PriorityQueue} containing the elements in the
194	>	* specified priority queue.  This priority queue will be
195	>	* ordered according to the same ordering as the given priority
196	>	* queue.
197	>	*
198	>	* @param  c the priority queue whose elements are to be placed
199	>	*         into this priority queue
200	>	* @throws ClassCastException if elements of {@code c} cannot be
201	>	*         compared to one another according to {@code c}'s
202	>	*         ordering
203	>	* @throws NullPointerException if the specified priority queue or any
204	>	*         of its elements are null
205		*/
206	<	private void fillFromSorted(Collection<? extends E> c) {
207	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
208	<	queue[++size] = i.next();
206	>	@SuppressWarnings("unchecked")
207	>	public PriorityQueue(PriorityQueue<? extends E> c) {
208	>	this.comparator = (Comparator<? super E>) c.comparator();
209	>	initFromPriorityQueue(c);
210		}
211
160	–
212		/**
213	<	* Initially fill elements of the queue array that is
214	<	* not to our knowledge sorted, so we must add them
215	<	* one by one.
213	>	* Creates a {@code PriorityQueue} containing the elements in the
214	>	* specified sorted set.   This priority queue will be ordered
215	>	* according to the same ordering as the given sorted set.
216	>	*
217	>	* @param  c the sorted set whose elements are to be placed
218	>	*         into this priority queue
219	>	* @throws ClassCastException if elements of the specified sorted
220	>	*         set cannot be compared to one another according to the
221	>	*         sorted set's ordering
222	>	* @throws NullPointerException if the specified sorted set or any
223	>	*         of its elements are null
224		*/
225	<	private void fillFromUnsorted(Collection<? extends E> c) {
226	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
227	<	add(i.next());
225	>	@SuppressWarnings("unchecked")
226	>	public PriorityQueue(SortedSet<? extends E> c) {
227	>	this.comparator = (Comparator<? super E>) c.comparator();
228	>	initElementsFromCollection(c);
229		}
230
231	<	/**
232	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
233	<	* specified collection.  The priority queue has an initial
234	<	* capacity of 110% of the size of the specified collection or 1
175	<	* if the collection is empty.  If the specified collection is an
176	<	* instance of a {@link java.util.SortedSet} or is another
177	<	* <tt>PriorityQueue</tt>, the priority queue will be sorted
178	<	* according to the same comparator, or according to its elements'
179	<	* natural order if the collection is sorted according to its
180	<	* elements' natural order.  Otherwise, the priority queue is
181	<	* ordered according to its elements' natural order.
182	<	*
183	<	* @param c the collection whose elements are to be placed
184	<	*        into this priority queue.
185	<	* @throws ClassCastException if elements of the specified collection
186	<	*         cannot be compared to one another according to the priority
187	<	*         queue's ordering.
188	<	* @throws NullPointerException if <tt>c</tt> or any element within it
189	<	* is <tt>null</tt>
190	<	*/
191	<	public PriorityQueue(Collection<? extends E> c) {
192	<	initializeArray(c);
193	<	if (c instanceof SortedSet) {
194	<	// @fixme double-cast workaround for compiler
195	<	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
196	<	comparator = (Comparator<? super E>)s.comparator();
197	<	fillFromSorted(s);
198	<	} else if (c instanceof PriorityQueue) {
199	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
200	<	comparator = (Comparator<? super E>)s.comparator();
201	<	fillFromSorted(s);
231	>	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
232	>	if (c.getClass() == PriorityQueue.class) {
233	>	this.queue = c.toArray();
234	>	this.size = c.size();
235		} else {
236	<	comparator = null;
204	<	fillFromUnsorted(c);
236	>	initFromCollection(c);
237		}
238		}
239
240	+	private void initElementsFromCollection(Collection<? extends E> c) {
241	+	Object[] a = c.toArray();
242	+	// If c.toArray incorrectly doesn't return Object[], copy it.
243	+	if (a.getClass() != Object[].class)
244	+	a = Arrays.copyOf(a, a.length, Object[].class);
245	+	int len = a.length;
246	+	if (len == 1 || this.comparator != null)
247	+	for (int i = 0; i < len; i++)
248	+	if (a[i] == null)
249	+	throw new NullPointerException();
250	+	this.queue = a;
251	+	this.size = a.length;
252	+	}
253	+
254		/**
255	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
210	<	* specified collection.  The priority queue has an initial
211	<	* capacity of 110% of the size of the specified collection or 1
212	<	* if the collection is empty.  This priority queue will be sorted
213	<	* according to the same comparator as the given collection, or
214	<	* according to its elements' natural order if the collection is
215	<	* sorted according to its elements' natural order.
255	>	* Initializes queue array with elements from the given Collection.
256		*
257	<	* @param c the collection whose elements are to be placed
218	<	*        into this priority queue.
219	<	* @throws ClassCastException if elements of the specified collection
220	<	*         cannot be compared to one another according to the priority
221	<	*         queue's ordering.
222	<	* @throws NullPointerException if <tt>c</tt> or any element within it
223	<	* is <tt>null</tt>
257	>	* @param c the collection
258		*/
259	<	public PriorityQueue(PriorityQueue<? extends E> c) {
260	<	initializeArray(c);
261	<	comparator = (Comparator<? super E>)c.comparator();
228	<	fillFromSorted(c);
259	>	private void initFromCollection(Collection<? extends E> c) {
260	>	initElementsFromCollection(c);
261	>	heapify();
262		}
263
264		/**
265	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
266	<	* specified collection.  The priority queue has an initial
267	<	* capacity of 110% of the size of the specified collection or 1
268	<	* if the collection is empty.  This priority queue will be sorted
236	<	* according to the same comparator as the given collection, or
237	<	* according to its elements' natural order if the collection is
238	<	* sorted according to its elements' natural order.
239	<	*
240	<	* @param c the collection whose elements are to be placed
241	<	*        into this priority queue.
242	<	* @throws ClassCastException if elements of the specified collection
243	<	*         cannot be compared to one another according to the priority
244	<	*         queue's ordering.
245	<	* @throws NullPointerException if <tt>c</tt> or any element within it
246	<	* is <tt>null</tt>
265	>	* The maximum size of array to allocate.
266	>	* Some VMs reserve some header words in an array.
267	>	* Attempts to allocate larger arrays may result in
268	>	* OutOfMemoryError: Requested array size exceeds VM limit
269		*/
270	<	public PriorityQueue(SortedSet<? extends E> c) {
249	<	initializeArray(c);
250	<	comparator = (Comparator<? super E>)c.comparator();
251	<	fillFromSorted(c);
252	<	}
270	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
271
272		/**
273	<	* Resize array, if necessary, to be able to hold given index
273	>	* Increases the capacity of the array.
274	>	*
275	>	* @param minCapacity the desired minimum capacity
276		*/
277	<	private void grow(int index) {
278	<	int newlen = queue.length;
279	<	if (index < newlen) // don't need to grow
280	<	return;
281	<	if (index == Integer.MAX_VALUE)
282	<	throw new OutOfMemoryError();
283	<	while (newlen <= index) {
284	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
285	<	newlen = Integer.MAX_VALUE;
286	<	else
267	<	newlen <<= 2;
268	<	}
269	<	Object[] newQueue = new Object[newlen];
270	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
271	<	queue = newQueue;
277	>	private void grow(int minCapacity) {
278	>	int oldCapacity = queue.length;
279	>	// Double size if small; else grow by 50%
280	>	int newCapacity = oldCapacity + ((oldCapacity < 64) ?
281	>	(oldCapacity + 2) :
282	>	(oldCapacity >> 1));
283	>	// overflow-conscious code
284	>	if (newCapacity - MAX_ARRAY_SIZE > 0)
285	>	newCapacity = hugeCapacity(minCapacity);
286	>	queue = Arrays.copyOf(queue, newCapacity);
287		}
273	–
274	–	// Queue Methods
288
289	+	private static int hugeCapacity(int minCapacity) {
290	+	if (minCapacity < 0) // overflow
291	+	throw new OutOfMemoryError();
292	+	return (minCapacity > MAX_ARRAY_SIZE) ?
293	+	Integer.MAX_VALUE :
294	+	MAX_ARRAY_SIZE;
295	+	}
296
297	+	/**
298	+	* Inserts the specified element into this priority queue.
299	+	*
300	+	* @return {@code true} (as specified by {@link Collection#add})
301	+	* @throws ClassCastException if the specified element cannot be
302	+	*         compared with elements currently in this priority queue
303	+	*         according to the priority queue's ordering
304	+	* @throws NullPointerException if the specified element is null
305	+	*/
306	+	public boolean add(E e) {
307	+	return offer(e);
308	+	}
309
310		/**
311	<	* Add the specified element to this priority queue.
311	>	* Inserts the specified element into this priority queue.
312		*
313	<	* @return <tt>true</tt>
314	<	* @throws ClassCastException if the specified element cannot be compared
315	<	* with elements currently in the priority queue according
316	<	* to the priority queue's ordering.
317	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
313	>	* @return {@code true} (as specified by {@link Queue#offer})
314	>	* @throws ClassCastException if the specified element cannot be
315	>	*         compared with elements currently in this priority queue
316	>	*         according to the priority queue's ordering
317	>	* @throws NullPointerException if the specified element is null
318		*/
319	<	public boolean offer(E o) {
320	<	if (o == null)
319	>	public boolean offer(E e) {
320	>	if (e == null)
321		throw new NullPointerException();
322		modCount++;
323	<	++size;
324	<
325	<	// Grow backing store if necessary
326	<	if (size >= queue.length)
327	<	grow(size);
328	<
329	<	queue[size] = o;
330	<	fixUp(size);
323	>	int i = size;
324	>	if (i >= queue.length)
325	>	grow(i + 1);
326	>	size = i + 1;
327	>	if (i == 0)
328	>	queue[0] = e;
329	>	else
330	>	siftUp(i, e);
331		return true;
332		}
333
302	–	public E poll() {
303	–	if (size == 0)
304	–	return null;
305	–	return (E) remove(1);
306	–	}
307	–
334		public E peek() {
335	<	return (E) queue[1];
335	>	return (size == 0) ? null : (E) queue[0];
336		}
337
338	<	// Collection Methods - the first two override to update docs
338	>	private int indexOf(Object o) {
339	>	if (o != null) {
340	>	for (int i = 0; i < size; i++)
341	>	if (o.equals(queue[i]))
342	>	return i;
343	>	}
344	>	return -1;
345	>	}
346
347		/**
348	<	* Adds the specified element to this queue.
349	<	* @return <tt>true</tt> (as per the general contract of
350	<	* <tt>Collection.add</tt>).
348	>	* Removes a single instance of the specified element from this queue,
349	>	* if it is present.  More formally, removes an element {@code e} such
350	>	* that {@code o.equals(e)}, if this queue contains one or more such
351	>	* elements.  Returns {@code true} if and only if this queue contained
352	>	* the specified element (or equivalently, if this queue changed as a
353	>	* result of the call).
354		*
355	<	* @throws NullPointerException {@inheritDoc}
356	<	* @throws ClassCastException if the specified element cannot be compared
321	<	* with elements currently in the priority queue according
322	<	* to the priority queue's ordering.
355	>	* @param o element to be removed from this queue, if present
356	>	* @return {@code true} if this queue changed as a result of the call
357		*/
358	<	public boolean add(E o) {
359	<	return super.add(o);
358	>	public boolean remove(Object o) {
359	>	int i = indexOf(o);
360	>	if (i == -1)
361	>	return false;
362	>	else {
363	>	removeAt(i);
364	>	return true;
365	>	}
366		}
367
328	–
368		/**
369	<	* Adds all of the elements in the specified collection to this queue.
370	<	* The behavior of this operation is undefined if
371	<	* the specified collection is modified while the operation is in
372	<	* progress.  (This implies that the behavior of this call is undefined if
373	<	* the specified collection is this queue, and this queue is nonempty.)
335	<	* <p>
336	<	* This implementation iterates over the specified collection, and adds
337	<	* each object returned by the iterator to this collection, in turn.
338	<	* @throws NullPointerException {@inheritDoc}
339	<	* @throws ClassCastException if any element cannot be compared
340	<	* with elements currently in the priority queue according
341	<	* to the priority queue's ordering.
369	>	* Version of remove using reference equality, not equals.
370	>	* Needed by iterator.remove.
371	>	*
372	>	* @param o element to be removed from this queue, if present
373	>	* @return {@code true} if removed
374		*/
375	<	public boolean addAll(Collection<? extends E> c) {
376	<	return super.addAll(c);
375	>	boolean removeEq(Object o) {
376	>	for (int i = 0; i < size; i++) {
377	>	if (o == queue[i]) {
378	>	removeAt(i);
379	>	return true;
380	>	}
381	>	}
382	>	return false;
383		}
384
385	+	/**
386	+	* Returns {@code true} if this queue contains the specified element.
387	+	* More formally, returns {@code true} if and only if this queue contains
388	+	* at least one element {@code e} such that {@code o.equals(e)}.
389	+	*
390	+	* @param o object to be checked for containment in this queue
391	+	* @return {@code true} if this queue contains the specified element
392	+	*/
393	+	public boolean contains(Object o) {
394	+	return indexOf(o) != -1;
395	+	}
396
397	<	/**
398	<	* Removes a single instance of the specified element from this
399	<	* queue, if it is present.  More formally,
400	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
401	<	* o.equals(e))</tt>, if the queue contains one or more such
402	<	* elements.  Returns <tt>true</tt> if the queue contained the
403	<	* specified element (or equivalently, if the queue changed as a
355	<	* result of the call).
397	>	/**
398	>	* Returns an array containing all of the elements in this queue.
399	>	* The elements are in no particular order.
400	>	*
401	>	* <p>The returned array will be "safe" in that no references to it are
402	>	* maintained by this queue.  (In other words, this method must allocate
403	>	* a new array).  The caller is thus free to modify the returned array.
404		*
405	<	* <p>This implementation iterates over the queue looking for the
406	<	* specified element.  If it finds the element, it removes the element
359	<	* from the queue using the iterator's remove method.<p>
405	>	* <p>This method acts as bridge between array-based and collection-based
406	>	* APIs.
407		*
408	+	* @return an array containing all of the elements in this queue
409		*/
410	<	public boolean remove(Object o) {
411	<	if (o == null)
412	<	return false;
410	>	public Object[] toArray() {
411	>	return Arrays.copyOf(queue, size);
412	>	}
413
414	<	if (comparator == null) {
415	<	for (int i = 1; i <= size; i++) {
416	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
417	<	remove(i);
418	<	return true;
419	<	}
420	<	}
421	<	} else {
422	<	for (int i = 1; i <= size; i++) {
423	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
424	<	remove(i);
425	<	return true;
426	<	}
427	<	}
428	<	}
429	<	return false;
414	>	/**
415	>	* Returns an array containing all of the elements in this queue; the
416	>	* runtime type of the returned array is that of the specified array.
417	>	* The returned array elements are in no particular order.
418	>	* If the queue fits in the specified array, it is returned therein.
419	>	* Otherwise, a new array is allocated with the runtime type of the
420	>	* specified array and the size of this queue.
421	>	*
422	>	* <p>If the queue fits in the specified array with room to spare
423	>	* (i.e., the array has more elements than the queue), the element in
424	>	* the array immediately following the end of the collection is set to
425	>	* {@code null}.
426	>	*
427	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
428	>	* array-based and collection-based APIs.  Further, this method allows
429	>	* precise control over the runtime type of the output array, and may,
430	>	* under certain circumstances, be used to save allocation costs.
431	>	*
432	>	* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
433	>	* The following code can be used to dump the queue into a newly
434	>	* allocated array of <tt>String</tt>:
435	>	*
436	>	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
437	>	*
438	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
439	>	* <tt>toArray()</tt>.
440	>	*
441	>	* @param a the array into which the elements of the queue are to
442	>	*          be stored, if it is big enough; otherwise, a new array of the
443	>	*          same runtime type is allocated for this purpose.
444	>	* @return an array containing all of the elements in this queue
445	>	* @throws ArrayStoreException if the runtime type of the specified array
446	>	*         is not a supertype of the runtime type of every element in
447	>	*         this queue
448	>	* @throws NullPointerException if the specified array is null
449	>	*/
450	>	public <T> T[] toArray(T[] a) {
451	>	if (a.length < size)
452	>	// Make a new array of a's runtime type, but my contents:
453	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
454	>	System.arraycopy(queue, 0, a, 0, size);
455	>	if (a.length > size)
456	>	a[size] = null;
457	>	return a;
458		}
459
460		/**
461		* Returns an iterator over the elements in this queue. The iterator
462		* does not return the elements in any particular order.
463		*
464	<	* @return an iterator over the elements in this queue.
464	>	* @return an iterator over the elements in this queue
465		*/
466		public Iterator<E> iterator() {
467		return new Itr();
468		}
469
470	<	private class Itr implements Iterator<E> {
395	<
470	>	private final class Itr implements Iterator<E> {
471		/**
472		* Index (into queue array) of element to be returned by
473		* subsequent call to next.
474		*/
475	<	private int cursor = 1;
475	>	private int cursor = 0;
476
477		/**
478	<	* Index of element returned by most recent call to next or
479	<	* previous.  Reset to 0 if this element is deleted by a call
480	<	* to remove.
478	>	* Index of element returned by most recent call to next,
479	>	* unless that element came from the forgetMeNot list.
480	>	* Set to -1 if element is deleted by a call to remove.
481		*/
482	<	private int lastRet = 0;
482	>	private int lastRet = -1;
483	>
484	>	/**
485	>	* A queue of elements that were moved from the unvisited portion of
486	>	* the heap into the visited portion as a result of "unlucky" element
487	>	* removals during the iteration.  (Unlucky element removals are those
488	>	* that require a siftup instead of a siftdown.)  We must visit all of
489	>	* the elements in this list to complete the iteration.  We do this
490	>	* after we've completed the "normal" iteration.
491	>	*
492	>	* We expect that most iterations, even those involving removals,
493	>	* will not need to store elements in this field.
494	>	*/
495	>	private ArrayDeque<E> forgetMeNot = null;
496	>
497	>	/**
498	>	* Element returned by the most recent call to next iff that
499	>	* element was drawn from the forgetMeNot list.
500	>	*/
501	>	private E lastRetElt = null;
502
503		/**
504		* The modCount value that the iterator believes that the backing
505	<	* List should have.  If this expectation is violated, the iterator
505	>	* Queue should have.  If this expectation is violated, the iterator
506		* has detected concurrent modification.
507		*/
508		private int expectedModCount = modCount;
509
416	–	// Workarounds until version that better handles remove() installed.
417	–	// These are used to copy-on-write the array upon first remove
418	–	private Object[] q = queue;
419	–	private int qsize = size;
420	–
510		public boolean hasNext() {
511	<	return cursor <= qsize;
511	>	return cursor < size ||
512	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
513		}
514
515		public E next() {
516	<	checkForComodification();
517	<	if (cursor > qsize)
518	<	throw new NoSuchElementException();
519	<	E result = (E) q[cursor];
520	<	lastRet = cursor++;
521	<	return result;
516	>	if (expectedModCount != modCount)
517	>	throw new ConcurrentModificationException();
518	>	if (cursor < size)
519	>	return (E) queue[lastRet = cursor++];
520	>	if (forgetMeNot != null) {
521	>	lastRet = -1;
522	>	lastRetElt = forgetMeNot.poll();
523	>	if (lastRetElt != null)
524	>	return lastRetElt;
525	>	}
526	>	throw new NoSuchElementException();
527		}
528
529		public void remove() {
530	<	if (lastRet == 0)
530	>	if (expectedModCount != modCount)
531	>	throw new ConcurrentModificationException();
532	>	if (lastRet != -1) {
533	>	E moved = PriorityQueue.this.removeAt(lastRet);
534	>	lastRet = -1;
535	>	if (moved == null)
536	>	cursor--;
537	>	else {
538	>	if (forgetMeNot == null)
539	>	forgetMeNot = new ArrayDeque<E>();
540	>	forgetMeNot.add(moved);
541	>	}
542	>	} else if (lastRetElt != null) {
543	>	PriorityQueue.this.removeEq(lastRetElt);
544	>	lastRetElt = null;
545	>	} else {
546		throw new IllegalStateException();
437	–	checkForComodification();
438	–
439	–	// Copy on first remove
440	–	if (q == queue) {
441	–	q = new Object[queue.length];
442	–	System.arraycopy(queue, 0, q, 0, queue.length);
547		}
444	–	PriorityQueue.this.remove(q[lastRet]);
445	–
446	–	lastRet = 0;
548		expectedModCount = modCount;
549		}
449	–
450	–	final void checkForComodification() {
451	–	if (modCount != expectedModCount)
452	–	throw new ConcurrentModificationException();
453	–	}
550		}
551
552		public int size() {
#	Line 458 | Line 554 | public class PriorityQueue<E> extends Ab
554		}
555
556		/**
557	<	* Remove all elements from the priority queue.
557	>	* Removes all of the elements from this priority queue.
558	>	* The queue will be empty after this call returns.
559		*/
560		public void clear() {
561		modCount++;
562	<
466	<	// Null out element references to prevent memory leak
467	<	for (int i=1; i<=size; i++)
562	>	for (int i = 0; i < size; i++)
563		queue[i] = null;
469	–
564		size = 0;
565		}
566
567	+	public E poll() {
568	+	if (size == 0)
569	+	return null;
570	+	int s = --size;
571	+	modCount++;
572	+	E result = (E) queue[0];
573	+	E x = (E) queue[s];
574	+	queue[s] = null;
575	+	if (s != 0)
576	+	siftDown(0, x);
577	+	return result;
578	+	}
579	+
580		/**
581	<	* Removes and returns the ith element from queue.  Recall
475	<	* that queue is one-based, so 1 <= i <= size.
581	>	* Removes the ith element from queue.
582		*
583	+	* Normally this method leaves the elements at up to i-1,
584	+	* inclusive, untouched.  Under these circumstances, it returns
585	+	* null.  Occasionally, in order to maintain the heap invariant,
586	+	* it must swap a later element of the list with one earlier than
587	+	* i.  Under these circumstances, this method returns the element
588	+	* that was previously at the end of the list and is now at some
589	+	* position before i. This fact is used by iterator.remove so as to
590	+	* avoid missing traversing elements.
591		*/
592	<	private E remove(int i) {
593	<	assert i <= size;
592	>	private E removeAt(int i) {
593	>	// assert i >= 0 && i < size;
594		modCount++;
595	<
596	<	E result = (E) queue[i];
597	<	queue[i] = queue[size];
598	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
599	<	if (i <= size) {
600	<	fixDown(i);
601	<	fixUp(i);
595	>	int s = --size;
596	>	if (s == i) // removed last element
597	>	queue[i] = null;
598	>	else {
599	>	E moved = (E) queue[s];
600	>	queue[s] = null;
601	>	siftDown(i, moved);
602	>	if (queue[i] == moved) {
603	>	siftUp(i, moved);
604	>	if (queue[i] != moved)
605	>	return moved;
606	>	}
607		}
608	<
490	<	return result;
608	>	return null;
609		}
610
611		/**
612	<	* Establishes the heap invariant (described above) assuming the heap
613	<	* satisfies the invariant except possibly for the leaf-node indexed by k
614	<	* (which may have a nextExecutionTime less than its parent's).
615	<	*
616	<	* This method functions by "promoting" queue[k] up the hierarchy
617	<	* (by swapping it with its parent) repeatedly until queue[k]
618	<	* is greater than or equal to its parent.
619	<	*/
620	<	private void fixUp(int k) {
621	<	if (comparator == null) {
622	<	while (k > 1) {
623	<	int j = k >> 1;
624	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
625	<	break;
626	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
627	<	k = j;
628	<	}
629	<	} else {
630	<	while (k > 1) {
631	<	int j = k >>> 1;
632	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
633	<	break;
634	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
635	<	k = j;
636	<	}
612	>	* Inserts item x at position k, maintaining heap invariant by
613	>	* promoting x up the tree until it is greater than or equal to
614	>	* its parent, or is the root.
615	>	*
616	>	* To simplify and speed up coercions and comparisons. the
617	>	* Comparable and Comparator versions are separated into different
618	>	* methods that are otherwise identical. (Similarly for siftDown.)
619	>	*
620	>	* @param k the position to fill
621	>	* @param x the item to insert
622	>	*/
623	>	private void siftUp(int k, E x) {
624	>	if (comparator != null)
625	>	siftUpUsingComparator(k, x);
626	>	else
627	>	siftUpComparable(k, x);
628	>	}
629	>
630	>	private void siftUpComparable(int k, E x) {
631	>	Comparable<? super E> key = (Comparable<? super E>) x;
632	>	while (k > 0) {
633	>	int parent = (k - 1) >>> 1;
634	>	Object e = queue[parent];
635	>	if (key.compareTo((E) e) >= 0)
636	>	break;
637	>	queue[k] = e;
638	>	k = parent;
639	>	}
640	>	queue[k] = key;
641	>	}
642	>
643	>	private void siftUpUsingComparator(int k, E x) {
644	>	while (k > 0) {
645	>	int parent = (k - 1) >>> 1;
646	>	Object e = queue[parent];
647	>	if (comparator.compare(x, (E) e) >= 0)
648	>	break;
649	>	queue[k] = e;
650	>	k = parent;
651		}
652	+	queue[k] = x;
653		}
654
655		/**
656	<	* Establishes the heap invariant (described above) in the subtree
657	<	* rooted at k, which is assumed to satisfy the heap invariant except
658	<	* possibly for node k itself (which may be greater than its children).
659	<	*
660	<	* This method functions by "demoting" queue[k] down the hierarchy
661	<	* (by swapping it with its smaller child) repeatedly until queue[k]
662	<	* is less than or equal to its children.
663	<	*/
664	<	private void fixDown(int k) {
665	<	int j;
666	<	if (comparator == null) {
667	<	while ((j = k << 1) <= size && (j > 0)) {
668	<	if (j<size &&
669	<	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
670	<	j++; // j indexes smallest kid
671	<
672	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
673	<	break;
674	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
675	<	k = j;
676	<	}
677	<	} else {
678	<	while ((j = k << 1) <= size && (j > 0)) {
679	<	if (j<size &&
680	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
681	<	j++; // j indexes smallest kid
682	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
683	<	break;
551	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
552	<	k = j;
553	<	}
656	>	* Inserts item x at position k, maintaining heap invariant by
657	>	* demoting x down the tree repeatedly until it is less than or
658	>	* equal to its children or is a leaf.
659	>	*
660	>	* @param k the position to fill
661	>	* @param x the item to insert
662	>	*/
663	>	private void siftDown(int k, E x) {
664	>	if (comparator != null)
665	>	siftDownUsingComparator(k, x);
666	>	else
667	>	siftDownComparable(k, x);
668	>	}
669	>
670	>	private void siftDownComparable(int k, E x) {
671	>	Comparable<? super E> key = (Comparable<? super E>)x;
672	>	int half = size >>> 1;        // loop while a non-leaf
673	>	while (k < half) {
674	>	int child = (k << 1) + 1; // assume left child is least
675	>	Object c = queue[child];
676	>	int right = child + 1;
677	>	if (right < size &&
678	>	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
679	>	c = queue[child = right];
680	>	if (key.compareTo((E) c) <= 0)
681	>	break;
682	>	queue[k] = c;
683	>	k = child;
684		}
685	+	queue[k] = key;
686	+	}
687
688	+	private void siftDownUsingComparator(int k, E x) {
689	+	int half = size >>> 1;
690	+	while (k < half) {
691	+	int child = (k << 1) + 1;
692	+	Object c = queue[child];
693	+	int right = child + 1;
694	+	if (right < size &&
695	+	comparator.compare((E) c, (E) queue[right]) > 0)
696	+	c = queue[child = right];
697	+	if (comparator.compare(x, (E) c) <= 0)
698	+	break;
699	+	queue[k] = c;
700	+	k = child;
701	+	}
702	+	queue[k] = x;
703		}
704
705	+	/**
706	+	* Establishes the heap invariant (described above) in the entire tree,
707	+	* assuming nothing about the order of the elements prior to the call.
708	+	*/
709	+	private void heapify() {
710	+	for (int i = (size >>> 1) - 1; i >= 0; i--)
711	+	siftDown(i, (E) queue[i]);
712	+	}
713
714		/**
715	<	* Returns the comparator used to order this collection, or <tt>null</tt>
716	<	* if this collection is sorted according to its elements natural ordering
717	<	* (using <tt>Comparable</tt>).
715	>	* Returns the comparator used to order the elements in this
716	>	* queue, or {@code null} if this queue is sorted according to
717	>	* the {@linkplain Comparable natural ordering} of its elements.
718		*
719	<	* @return the comparator used to order this collection, or <tt>null</tt>
720	<	* if this collection is sorted according to its elements natural ordering.
719	>	* @return the comparator used to order this queue, or
720	>	*         {@code null} if this queue is sorted according to the
721	>	*         natural ordering of its elements
722		*/
723		public Comparator<? super E> comparator() {
724		return comparator;
725		}
726
727		/**
728	<	* Save the state of the instance to a stream (that
729	<	* is, serialize it).
728	>	* Saves the state of the instance to a stream (that
729	>	* is, serializes it).
730		*
731		* @serialData The length of the array backing the instance is
732	<	* emitted (int), followed by all of its elements (each an
733	<	* <tt>Object</tt>) in the proper order.
732	>	*             emitted (int), followed by all of its elements
733	>	*             (each an {@code Object}) in the proper order.
734		* @param s the stream
735		*/
736		private void writeObject(java.io.ObjectOutputStream s)
737	<	throws java.io.IOException{
737	>	throws java.io.IOException {
738		// Write out element count, and any hidden stuff
739		s.defaultWriteObject();
740
741	<	// Write out array length
742	<	s.writeInt(queue.length);
741	>	// Write out array length, for compatibility with 1.5 version
742	>	s.writeInt(Math.max(2, size + 1));
743
744	<	// Write out all elements in the proper order.
745	<	for (int i=0; i<size; i++)
744	>	// Write out all elements in the "proper order".
745	>	for (int i = 0; i < size; i++)
746		s.writeObject(queue[i]);
747		}
748
749		/**
750	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
751	<	* deserialize it).
750	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
751	>	* (that is, deserializes it).
752	>	*
753		* @param s the stream
754		*/
755		private void readObject(java.io.ObjectInputStream s)
#	Line 600 | Line 757 | public class PriorityQueue<E> extends Ab
757		// Read in size, and any hidden stuff
758		s.defaultReadObject();
759
760	<	// Read in array length and allocate array
761	<	int arrayLength = s.readInt();
605	<	queue = new Object[arrayLength];
760	>	// Read in (and discard) array length
761	>	s.readInt();
762
763	<	// Read in all elements in the proper order.
764	<	for (int i=0; i<size; i++)
763	>	queue = new Object[size];
764	>
765	>	// Read in all elements.
766	>	for (int i = 0; i < size; i++)
767		queue[i] = s.readObject();
610	–	}
768
769	+	// Elements are guaranteed to be in "proper order", but the
770	+	// spec has never explained what that might be.
771	+	heapify();
772	+	}
773		}
613	–

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