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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.32 by dl, Mon Aug 25 23:47:01 2003 UTC vs.
Revision 1.68 by jsr166, Sun May 18 23:47:56 2008 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* Copyright 2003-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22	>	* CA 95054 USA or visit www.sun.com if you need additional information or
23	>	* have any 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
63	<	* java.util.concurrent.BlockingPriorityQueue} 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>).
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	>	* <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	>	* @version %I%, %G%
78	>	* @author Josh Bloch, Doug Lea
79	>	* @param <E> the type of elements held in this collection
80		*/
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.
161	<	*/
162	<	private void initializeArray(Collection<? extends E> c) {
163	<	int sz = c.size();
164	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
143	<	Integer.MAX_VALUE - 1);
144	<	if (initialCapacity < 1)
145	<	initialCapacity = 1;
146	<
147	<	this.queue = new Object[initialCapacity + 1];
148	<	}
149	<
150	<	/**
151	<	* Initially fill elements of the queue array under the
152	<	* knowledge that it is sorted or is another PQ, in which
153	<	* case we can just place the elements without fixups.
154	<	*/
155	<	private void fillFromSorted(Collection<? extends E> c) {
156	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
157	<	queue[++size] = i.next();
158	<	}
159	<
160	<
161	<	/**
162	<	* Initially fill elements of the queue array that is
163	<	* not to our knowledge sorted, so we must add them
164	<	* one by one.
165	<	*/
166	<	private void fillFromUnsorted(Collection<? extends E> c) {
167	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
168	<	add(i.next());
169	<	}
170	<
171	<	/**
172	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
173	<	* specified collection.  The priority queue has an initial
174	<	* 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.
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.
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 <tt>c</tt> or any element within it
172	<	* is <tt>null</tt>
170	>	*         queue's ordering
171	>	* @throws NullPointerException if the specified collection or any
172	>	*         of its elements are null
173		*/
174		public PriorityQueue(Collection<? extends E> c) {
175	<	initializeArray(c);
176	<	if (c instanceof SortedSet) {
177	<	// @fixme double-cast workaround for compiler
178	<	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
179	<	comparator = (Comparator<? super E>)s.comparator();
180	<	fillFromSorted(s);
181	<	} else if (c instanceof PriorityQueue) {
182	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
200	<	comparator = (Comparator<? super E>)s.comparator();
201	<	fillFromSorted(s);
202	<	} else {
175	>	initFromCollection(c);
176	>	if (c instanceof SortedSet)
177	>	comparator = (Comparator<? super E>)
178	>	((SortedSet<? extends E>)c).comparator();
179	>	else if (c instanceof PriorityQueue)
180	>	comparator = (Comparator<? super E>)
181	>	((PriorityQueue<? extends E>)c).comparator();
182	>	else {
183		comparator = null;
184	<	fillFromUnsorted(c);
184	>	heapify();
185		}
186		}
187
188		/**
189	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
190	<	* specified collection.  The priority queue has an initial
191	<	* capacity of 110% of the size of the specified collection or 1
192	<	* if the collection is empty.  This priority queue will be sorted
193	<	* according to the same comparator as the given collection, or
194	<	* according to its elements' natural order if the collection is
195	<	* sorted according to its elements' natural order.
196	<	*
197	<	* @param c the collection whose elements are to be placed
198	<	*        into this priority queue.
199	<	* @throws ClassCastException if elements of the specified collection
200	<	*         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>
189	>	* Creates a {@code PriorityQueue} containing the elements in the
190	>	* specified priority queue.  This priority queue will be
191	>	* ordered according to the same ordering as the given priority
192	>	* queue.
193	>	*
194	>	* @param  c the priority queue whose elements are to be placed
195	>	*         into this priority queue
196	>	* @throws ClassCastException if elements of {@code c} cannot be
197	>	*         compared to one another according to {@code c}'s
198	>	*         ordering
199	>	* @throws NullPointerException if the specified priority queue or any
200	>	*         of its elements are null
201		*/
202		public PriorityQueue(PriorityQueue<? extends E> c) {
226	–	initializeArray(c);
203		comparator = (Comparator<? super E>)c.comparator();
204	<	fillFromSorted(c);
204	>	initFromCollection(c);
205		}
206
207		/**
208	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
209	<	* specified collection.  The priority queue has an initial
210	<	* capacity of 110% of the size of the specified collection or 1
235	<	* 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.
208	>	* Creates a {@code PriorityQueue} containing the elements in the
209	>	* specified sorted set.   This priority queue will be ordered
210	>	* according to the same ordering as the given sorted set.
211		*
212	<	* @param c the collection whose elements are to be placed
213	<	*        into this priority queue.
214	<	* @throws ClassCastException if elements of the specified collection
215	<	*         cannot be compared to one another according to the priority
216	<	*         queue's ordering.
217	<	* @throws NullPointerException if <tt>c</tt> or any element within it
218	<	* is <tt>null</tt>
212	>	* @param  c the sorted set whose elements are to be placed
213	>	*         into this priority queue
214	>	* @throws ClassCastException if elements of the specified sorted
215	>	*         set cannot be compared to one another according to the
216	>	*         sorted set's ordering
217	>	* @throws NullPointerException if the specified sorted set or any
218	>	*         of its elements are null
219		*/
220		public PriorityQueue(SortedSet<? extends E> c) {
249	–	initializeArray(c);
221		comparator = (Comparator<? super E>)c.comparator();
222	<	fillFromSorted(c);
222	>	initFromCollection(c);
223		}
224
225		/**
226	<	* Resize array, if necessary, to be able to hold given index
226	>	* Initializes queue array with elements from the given Collection.
227	>	*
228	>	* @param c the collection
229		*/
230	<	private void grow(int index) {
231	<	int newlen = queue.length;
232	<	if (index < newlen) // don't need to grow
233	<	return;
234	<	if (index == Integer.MAX_VALUE)
235	<	throw new OutOfMemoryError();
236	<	while (newlen <= index) {
264	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
265	<	newlen = Integer.MAX_VALUE;
266	<	else
267	<	newlen <<= 2;
268	<	}
269	<	Object[] newQueue = new Object[newlen];
270	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
271	<	queue = newQueue;
230	>	private void initFromCollection(Collection<? extends E> c) {
231	>	Object[] a = c.toArray();
232	>	// If c.toArray incorrectly doesn't return Object[], copy it.
233	>	if (a.getClass() != Object[].class)
234	>	a = Arrays.copyOf(a, a.length, Object[].class);
235	>	queue = a;
236	>	size = a.length;
237		}
273	–
274	–	// Queue Methods
238
239	+	/**
240	+	* Increases the capacity of the array.
241	+	*
242	+	* @param minCapacity the desired minimum capacity
243	+	*/
244	+	private void grow(int minCapacity) {
245	+	if (minCapacity < 0) // overflow
246	+	throw new OutOfMemoryError();
247	+	int oldCapacity = queue.length;
248	+	// Double size if small; else grow by 50%
249	+	int newCapacity = ((oldCapacity < 64)?
250	+	((oldCapacity + 1) * 2):
251	+	((oldCapacity / 2) * 3));
252	+	if (newCapacity < 0) // overflow
253	+	newCapacity = Integer.MAX_VALUE;
254	+	if (newCapacity < minCapacity)
255	+	newCapacity = minCapacity;
256	+	queue = Arrays.copyOf(queue, newCapacity);
257	+	}
258
259	+	/**
260	+	* Inserts the specified element into this priority queue.
261	+	*
262	+	* @return {@code true} (as specified by {@link Collection#add})
263	+	* @throws ClassCastException if the specified element cannot be
264	+	*         compared with elements currently in this priority queue
265	+	*         according to the priority queue's ordering
266	+	* @throws NullPointerException if the specified element is null
267	+	*/
268	+	public boolean add(E e) {
269	+	return offer(e);
270	+	}
271
272		/**
273	<	* Add the specified element to this priority queue.
273	>	* Inserts the specified element into this priority queue.
274		*
275	<	* @return <tt>true</tt>
276	<	* @throws ClassCastException if the specified element cannot be compared
277	<	* with elements currently in the priority queue according
278	<	* to the priority queue's ordering.
279	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
275	>	* @return {@code true} (as specified by {@link Queue#offer})
276	>	* @throws ClassCastException if the specified element cannot be
277	>	*         compared with elements currently in this priority queue
278	>	*         according to the priority queue's ordering
279	>	* @throws NullPointerException if the specified element is null
280		*/
281	<	public boolean offer(E o) {
282	<	if (o == null)
281	>	public boolean offer(E e) {
282	>	if (e == null)
283		throw new NullPointerException();
284		modCount++;
285	<	++size;
286	<
287	<	// Grow backing store if necessary
288	<	if (size >= queue.length)
289	<	grow(size);
290	<
291	<	queue[size] = o;
292	<	fixUp(size);
285	>	int i = size;
286	>	if (i >= queue.length)
287	>	grow(i + 1);
288	>	size = i + 1;
289	>	if (i == 0)
290	>	queue[0] = e;
291	>	else
292	>	siftUp(i, e);
293		return true;
294		}
295
296	<	public E poll() {
296	>	public E peek() {
297		if (size == 0)
298		return null;
299	<	return (E) remove(1);
299	>	return (E) queue[0];
300		}
301
302	<	public E peek() {
303	<	return (E) queue[1];
302	>	private int indexOf(Object o) {
303	>	if (o != null) {
304	>	for (int i = 0; i < size; i++)
305	>	if (o.equals(queue[i]))
306	>	return i;
307	>	}
308	>	return -1;
309		}
310
312	–	// Collection Methods - the first two override to update docs
313	–
311		/**
312	<	* Adds the specified element to this queue.
313	<	* @return <tt>true</tt> (as per the general contract of
314	<	* <tt>Collection.add</tt>).
312	>	* Removes a single instance of the specified element from this queue,
313	>	* if it is present.  More formally, removes an element {@code e} such
314	>	* that {@code o.equals(e)}, if this queue contains one or more such
315	>	* elements.  Returns {@code true} if and only if this queue contained
316	>	* the specified element (or equivalently, if this queue changed as a
317	>	* result of the call).
318		*
319	<	* @throws NullPointerException {@inheritDoc}
320	<	* @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.
319	>	* @param o element to be removed from this queue, if present
320	>	* @return {@code true} if this queue changed as a result of the call
321		*/
322	<	public boolean add(E o) {
323	<	return super.add(o);
322	>	public boolean remove(Object o) {
323	>	int i = indexOf(o);
324	>	if (i == -1)
325	>	return false;
326	>	else {
327	>	removeAt(i);
328	>	return true;
329	>	}
330		}
331
328	–
332		/**
333	<	* Adds all of the elements in the specified collection to this queue.
334	<	* The behavior of this operation is undefined if
335	<	* the specified collection is modified while the operation is in
336	<	* progress.  (This implies that the behavior of this call is undefined if
337	<	* 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.
333	>	* Version of remove using reference equality, not equals.
334	>	* Needed by iterator.remove.
335	>	*
336	>	* @param o element to be removed from this queue, if present
337	>	* @return {@code true} if removed
338		*/
339	<	public boolean addAll(Collection<? extends E> c) {
340	<	return super.addAll(c);
339	>	boolean removeEq(Object o) {
340	>	for (int i = 0; i < size; i++) {
341	>	if (o == queue[i]) {
342	>	removeAt(i);
343	>	return true;
344	>	}
345	>	}
346	>	return false;
347		}
348
349	+	/**
350	+	* Returns {@code true} if this queue contains the specified element.
351	+	* More formally, returns {@code true} if and only if this queue contains
352	+	* at least one element {@code e} such that {@code o.equals(e)}.
353	+	*
354	+	* @param o object to be checked for containment in this queue
355	+	* @return {@code true} if this queue contains the specified element
356	+	*/
357	+	public boolean contains(Object o) {
358	+	return indexOf(o) != -1;
359	+	}
360
361	<	/**
362	<	* Removes a single instance of the specified element from this
363	<	* queue, if it is present.  More formally,
364	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
365	<	* o.equals(e))</tt>, if the queue contains one or more such
366	<	* elements.  Returns <tt>true</tt> if the queue contained the
367	<	* specified element (or equivalently, if the queue changed as a
355	<	* result of the call).
361	>	/**
362	>	* Returns an array containing all of the elements in this queue.
363	>	* The elements are in no particular order.
364	>	*
365	>	* <p>The returned array will be "safe" in that no references to it are
366	>	* maintained by this queue.  (In other words, this method must allocate
367	>	* a new array).  The caller is thus free to modify the returned array.
368		*
369	<	* <p>This implementation iterates over the queue looking for the
370	<	* specified element.  If it finds the element, it removes the element
359	<	* from the queue using the iterator's remove method.<p>
369	>	* <p>This method acts as bridge between array-based and collection-based
370	>	* APIs.
371		*
372	+	* @return an array containing all of the elements in this queue
373		*/
374	<	public boolean remove(Object o) {
375	<	if (o == null)
376	<	return false;
374	>	public Object[] toArray() {
375	>	return Arrays.copyOf(queue, size);
376	>	}
377
378	<	if (comparator == null) {
379	<	for (int i = 1; i <= size; i++) {
380	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
381	<	remove(i);
382	<	return true;
383	<	}
384	<	}
385	<	} else {
386	<	for (int i = 1; i <= size; i++) {
387	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
388	<	remove(i);
389	<	return true;
390	<	}
391	<	}
392	<	}
393	<	return false;
378	>	/**
379	>	* Returns an array containing all of the elements in this queue; the
380	>	* runtime type of the returned array is that of the specified array.
381	>	* The returned array elements are in no particular order.
382	>	* If the queue fits in the specified array, it is returned therein.
383	>	* Otherwise, a new array is allocated with the runtime type of the
384	>	* specified array and the size of this queue.
385	>	*
386	>	* <p>If the queue fits in the specified array with room to spare
387	>	* (i.e., the array has more elements than the queue), the element in
388	>	* the array immediately following the end of the collection is set to
389	>	* {@code null}.
390	>	*
391	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
392	>	* array-based and collection-based APIs.  Further, this method allows
393	>	* precise control over the runtime type of the output array, and may,
394	>	* under certain circumstances, be used to save allocation costs.
395	>	*
396	>	* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
397	>	* The following code can be used to dump the queue into a newly
398	>	* allocated array of <tt>String</tt>:
399	>	*
400	>	* <pre>
401	>	*     String[] y = x.toArray(new String[0]);</pre>
402	>	*
403	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
404	>	* <tt>toArray()</tt>.
405	>	*
406	>	* @param a the array into which the elements of the queue are to
407	>	*          be stored, if it is big enough; otherwise, a new array of the
408	>	*          same runtime type is allocated for this purpose.
409	>	* @return an array containing all of the elements in this queue
410	>	* @throws ArrayStoreException if the runtime type of the specified array
411	>	*         is not a supertype of the runtime type of every element in
412	>	*         this queue
413	>	* @throws NullPointerException if the specified array is null
414	>	*/
415	>	public <T> T[] toArray(T[] a) {
416	>	if (a.length < size)
417	>	// Make a new array of a's runtime type, but my contents:
418	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
419	>	System.arraycopy(queue, 0, a, 0, size);
420	>	if (a.length > size)
421	>	a[size] = null;
422	>	return a;
423		}
424
425		/**
426		* Returns an iterator over the elements in this queue. The iterator
427		* does not return the elements in any particular order.
428		*
429	<	* @return an iterator over the elements in this queue.
429	>	* @return an iterator over the elements in this queue
430		*/
431		public Iterator<E> iterator() {
432		return new Itr();
433		}
434
435	<	private class Itr implements Iterator<E> {
435	>	private final class Itr implements Iterator<E> {
436		/**
437		* Index (into queue array) of element to be returned by
438		* subsequent call to next.
439		*/
440	<	private int cursor = 1;
440	>	private int cursor = 0;
441	>
442	>	/**
443	>	* Index of element returned by most recent call to next,
444	>	* unless that element came from the forgetMeNot list.
445	>	* Set to -1 if element is deleted by a call to remove.
446	>	*/
447	>	private int lastRet = -1;
448
449		/**
450	<	* Index of element returned by most recent call to next or
451	<	* previous.  Reset to 0 if this element is deleted by a call
452	<	* to remove.
450	>	* A queue of elements that were moved from the unvisited portion of
451	>	* the heap into the visited portion as a result of "unlucky" element
452	>	* removals during the iteration.  (Unlucky element removals are those
453	>	* that require a siftup instead of a siftdown.)  We must visit all of
454	>	* the elements in this list to complete the iteration.  We do this
455	>	* after we've completed the "normal" iteration.
456	>	*
457	>	* We expect that most iterations, even those involving removals,
458	>	* will not need to store elements in this field.
459		*/
460	<	private int lastRet = 0;
460	>	private ArrayDeque<E> forgetMeNot = null;
461	>
462	>	/**
463	>	* Element returned by the most recent call to next iff that
464	>	* element was drawn from the forgetMeNot list.
465	>	*/
466	>	private E lastRetElt = null;
467
468		/**
469		* The modCount value that the iterator believes that the backing
470	<	* List should have.  If this expectation is violated, the iterator
470	>	* Queue should have.  If this expectation is violated, the iterator
471		* has detected concurrent modification.
472		*/
473		private int expectedModCount = modCount;
474
475		public boolean hasNext() {
476	<	return cursor <= size;
476	>	return cursor < size ||
477	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
478		}
479
480		public E next() {
481	<	checkForComodification();
482	<	if (cursor > size)
483	<	throw new NoSuchElementException();
484	<	E result = (E) queue[cursor];
485	<	lastRet = cursor++;
486	<	return result;
481	>	if (expectedModCount != modCount)
482	>	throw new ConcurrentModificationException();
483	>	if (cursor < size)
484	>	return (E) queue[lastRet = cursor++];
485	>	if (forgetMeNot != null) {
486	>	lastRet = -1;
487	>	lastRetElt = forgetMeNot.poll();
488	>	if (lastRetElt != null)
489	>	return lastRetElt;
490	>	}
491	>	throw new NoSuchElementException();
492		}
493
494		public void remove() {
495	<	if (lastRet == 0)
495	>	if (expectedModCount != modCount)
496	>	throw new ConcurrentModificationException();
497	>	if (lastRet != -1) {
498	>	E moved = PriorityQueue.this.removeAt(lastRet);
499	>	lastRet = -1;
500	>	if (moved == null)
501	>	cursor--;
502	>	else {
503	>	if (forgetMeNot == null)
504	>	forgetMeNot = new ArrayDeque<E>();
505	>	forgetMeNot.add(moved);
506	>	}
507	>	} else if (lastRetElt != null) {
508	>	PriorityQueue.this.removeEq(lastRetElt);
509	>	lastRetElt = null;
510	>	} else {
511		throw new IllegalStateException();
512	<	checkForComodification();
432	<
433	<	PriorityQueue.this.remove(lastRet);
434	<	cursor--;
435	<	lastRet = 0;
512	>	}
513		expectedModCount = modCount;
514		}
438	–
439	–	final void checkForComodification() {
440	–	if (modCount != expectedModCount)
441	–	throw new ConcurrentModificationException();
442	–	}
515		}
516
517		public int size() {
#	Line 447 | Line 519 | public class PriorityQueue<E> extends Ab
519		}
520
521		/**
522	<	* Remove all elements from the priority queue.
522	>	* Removes all of the elements from this priority queue.
523	>	* The queue will be empty after this call returns.
524		*/
525		public void clear() {
526		modCount++;
527	<
455	<	// Null out element references to prevent memory leak
456	<	for (int i=1; i<=size; i++)
527	>	for (int i = 0; i < size; i++)
528		queue[i] = null;
458	–
529		size = 0;
530		}
531
532	+	public E poll() {
533	+	if (size == 0)
534	+	return null;
535	+	int s = --size;
536	+	modCount++;
537	+	E result = (E) queue[0];
538	+	E x = (E) queue[s];
539	+	queue[s] = null;
540	+	if (s != 0)
541	+	siftDown(0, x);
542	+	return result;
543	+	}
544	+
545		/**
546	<	* Removes and returns the ith element from queue.  Recall
464	<	* that queue is one-based, so 1 <= i <= size.
546	>	* Removes the ith element from queue.
547		*
548	+	* Normally this method leaves the elements at up to i-1,
549	+	* inclusive, untouched.  Under these circumstances, it returns
550	+	* null.  Occasionally, in order to maintain the heap invariant,
551	+	* it must swap a later element of the list with one earlier than
552	+	* i.  Under these circumstances, this method returns the element
553	+	* that was previously at the end of the list and is now at some
554	+	* position before i. This fact is used by iterator.remove so as to
555	+	* avoid missing traversing elements.
556		*/
557	<	private E remove(int i) {
558	<	assert i <= size;
557	>	private E removeAt(int i) {
558	>	assert i >= 0 && i < size;
559		modCount++;
560	<
561	<	E result = (E) queue[i];
562	<	queue[i] = queue[size];
563	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
564	<	if (i <= size)
565	<	fixDown(i);
566	<	return result;
560	>	int s = --size;
561	>	if (s == i) // removed last element
562	>	queue[i] = null;
563	>	else {
564	>	E moved = (E) queue[s];
565	>	queue[s] = null;
566	>	siftDown(i, moved);
567	>	if (queue[i] == moved) {
568	>	siftUp(i, moved);
569	>	if (queue[i] != moved)
570	>	return moved;
571	>	}
572	>	}
573	>	return null;
574		}
575
576		/**
577	<	* Establishes the heap invariant (described above) assuming the heap
578	<	* satisfies the invariant except possibly for the leaf-node indexed by k
579	<	* (which may have a nextExecutionTime less than its parent's).
580	<	*
581	<	* This method functions by "promoting" queue[k] up the hierarchy
582	<	* (by swapping it with its parent) repeatedly until queue[k]
583	<	* is greater than or equal to its parent.
584	<	*/
585	<	private void fixUp(int k) {
586	<	if (comparator == null) {
587	<	while (k > 1) {
588	<	int j = k >> 1;
589	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
590	<	break;
591	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
592	<	k = j;
593	<	}
594	<	} else {
595	<	while (k > 1) {
596	<	int j = k >> 1;
597	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
598	<	break;
599	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
600	<	k = j;
601	<	}
577	>	* Inserts item x at position k, maintaining heap invariant by
578	>	* promoting x up the tree until it is greater than or equal to
579	>	* its parent, or is the root.
580	>	*
581	>	* To simplify and speed up coercions and comparisons. the
582	>	* Comparable and Comparator versions are separated into different
583	>	* methods that are otherwise identical. (Similarly for siftDown.)
584	>	*
585	>	* @param k the position to fill
586	>	* @param x the item to insert
587	>	*/
588	>	private void siftUp(int k, E x) {
589	>	if (comparator != null)
590	>	siftUpUsingComparator(k, x);
591	>	else
592	>	siftUpComparable(k, x);
593	>	}
594	>
595	>	private void siftUpComparable(int k, E x) {
596	>	Comparable<? super E> key = (Comparable<? super E>) x;
597	>	while (k > 0) {
598	>	int parent = (k - 1) >>> 1;
599	>	Object e = queue[parent];
600	>	if (key.compareTo((E) e) >= 0)
601	>	break;
602	>	queue[k] = e;
603	>	k = parent;
604		}
605	+	queue[k] = key;
606	+	}
607	+
608	+	private void siftUpUsingComparator(int k, E x) {
609	+	while (k > 0) {
610	+	int parent = (k - 1) >>> 1;
611	+	Object e = queue[parent];
612	+	if (comparator.compare(x, (E) e) >= 0)
613	+	break;
614	+	queue[k] = e;
615	+	k = parent;
616	+	}
617	+	queue[k] = x;
618		}
619
620		/**
621	<	* Establishes the heap invariant (described above) in the subtree
622	<	* rooted at k, which is assumed to satisfy the heap invariant except
623	<	* possibly for node k itself (which may be greater than its children).
624	<	*
625	<	* This method functions by "demoting" queue[k] down the hierarchy
626	<	* (by swapping it with its smaller child) repeatedly until queue[k]
627	<	* is less than or equal to its children.
628	<	*/
629	<	private void fixDown(int k) {
630	<	int j;
631	<	if (comparator == null) {
632	<	while ((j = k << 1) <= size && j > 0) {
633	<	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
634	<	j++; // j indexes smallest kid
635	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
636	<	break;
637	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
638	<	k = j;
639	<	}
640	<	} else {
641	<	while ((j = k << 1) <= size && j > 0) {
642	<	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
643	<	j++; // j indexes smallest kid
644	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
645	<	break;
646	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
647	<	k = j;
648	<	}
621	>	* Inserts item x at position k, maintaining heap invariant by
622	>	* demoting x down the tree repeatedly until it is less than or
623	>	* equal to its children or is a leaf.
624	>	*
625	>	* @param k the position to fill
626	>	* @param x the item to insert
627	>	*/
628	>	private void siftDown(int k, E x) {
629	>	if (comparator != null)
630	>	siftDownUsingComparator(k, x);
631	>	else
632	>	siftDownComparable(k, x);
633	>	}
634	>
635	>	private void siftDownComparable(int k, E x) {
636	>	Comparable<? super E> key = (Comparable<? super E>)x;
637	>	int half = size >>> 1;        // loop while a non-leaf
638	>	while (k < half) {
639	>	int child = (k << 1) + 1; // assume left child is least
640	>	Object c = queue[child];
641	>	int right = child + 1;
642	>	if (right < size &&
643	>	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
644	>	c = queue[child = right];
645	>	if (key.compareTo((E) c) <= 0)
646	>	break;
647	>	queue[k] = c;
648	>	k = child;
649	>	}
650	>	queue[k] = key;
651	>	}
652	>
653	>	private void siftDownUsingComparator(int k, E x) {
654	>	int half = size >>> 1;
655	>	while (k < half) {
656	>	int child = (k << 1) + 1;
657	>	Object c = queue[child];
658	>	int right = child + 1;
659	>	if (right < size &&
660	>	comparator.compare((E) c, (E) queue[right]) > 0)
661	>	c = queue[child = right];
662	>	if (comparator.compare(x, (E) c) <= 0)
663	>	break;
664	>	queue[k] = c;
665	>	k = child;
666		}
667	+	queue[k] = x;
668		}
669
670	+	/**
671	+	* Establishes the heap invariant (described above) in the entire tree,
672	+	* assuming nothing about the order of the elements prior to the call.
673	+	*/
674	+	private void heapify() {
675	+	for (int i = (size >>> 1) - 1; i >= 0; i--)
676	+	siftDown(i, (E) queue[i]);
677	+	}
678
679		/**
680	<	* Returns the comparator used to order this collection, or <tt>null</tt>
681	<	* if this collection is sorted according to its elements natural ordering
682	<	* (using <tt>Comparable</tt>).
680	>	* Returns the comparator used to order the elements in this
681	>	* queue, or {@code null} if this queue is sorted according to
682	>	* the {@linkplain Comparable natural ordering} of its elements.
683		*
684	<	* @return the comparator used to order this collection, or <tt>null</tt>
685	<	* if this collection is sorted according to its elements natural ordering.
684	>	* @return the comparator used to order this queue, or
685	>	*         {@code null} if this queue is sorted according to the
686	>	*         natural ordering of its elements
687		*/
688		public Comparator<? super E> comparator() {
689		return comparator;
690		}
691
692		/**
693	<	* Save the state of the instance to a stream (that
694	<	* is, serialize it).
693	>	* Saves the state of the instance to a stream (that
694	>	* is, serializes it).
695		*
696		* @serialData The length of the array backing the instance is
697	<	* emitted (int), followed by all of its elements (each an
698	<	* <tt>Object</tt>) in the proper order.
697	>	*             emitted (int), followed by all of its elements
698	>	*             (each an {@code Object}) in the proper order.
699		* @param s the stream
700		*/
701		private void writeObject(java.io.ObjectOutputStream s)
#	Line 564 | Line 703 | public class PriorityQueue<E> extends Ab
703		// Write out element count, and any hidden stuff
704		s.defaultWriteObject();
705
706	<	// Write out array length
707	<	s.writeInt(queue.length);
706	>	// Write out array length, for compatibility with 1.5 version
707	>	s.writeInt(Math.max(2, size + 1));
708
709	<	// Write out all elements in the proper order.
710	<	for (int i=0; i<size; i++)
709	>	// Write out all elements in the "proper order".
710	>	for (int i = 0; i < size; i++)
711		s.writeObject(queue[i]);
712		}
713
714		/**
715	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
716	<	* deserialize it).
715	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
716	>	* (that is, deserializes it).
717	>	*
718		* @param s the stream
719		*/
720		private void readObject(java.io.ObjectInputStream s)
#	Line 582 | Line 722 | public class PriorityQueue<E> extends Ab
722		// Read in size, and any hidden stuff
723		s.defaultReadObject();
724
725	<	// Read in array length and allocate array
726	<	int arrayLength = s.readInt();
587	<	queue = new Object[arrayLength];
725	>	// Read in (and discard) array length
726	>	s.readInt();
727
728	<	// Read in all elements in the proper order.
729	<	for (int i=0; i<size; i++)
728	>	queue = new Object[size];
729	>
730	>	// Read in all elements.
731	>	for (int i = 0; i < size; i++)
732		queue[i] = s.readObject();
592	–	}
733
734	+	// Elements are guaranteed to be in "proper order", but the
735	+	// spec has never explained what that might be.
736	+	heapify();
737	+	}
738		}
595	–

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