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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.23 by dholmes, Wed Aug 6 01:57:53 2003 UTC vs.
Revision 1.69 by jsr166, Sun May 18 23:59:57 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>Implementation note: this implementation provides O(log(n)) time
57	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
58	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
59	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
60	<	* constant time for the retrieval methods (<tt>peek</tt>,
61	<	* <tt>element</tt>, and <tt>size</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 {@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	>	* @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	<	*
56	<	* The element with the lowest value is in queue[1], assuming the queue is
57	<	* nonempty.  (A one-based array is used in preference to the traditional
58	<	* zero-based array to simplify parent and child calculations.)
59	<	*
60	<	* 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 79 | 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.
160	<	*/
161	<	private void initializeArray(Collection<? extends E> c) {
162	<	int sz = c.size();
163	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
129	<	Integer.MAX_VALUE - 1);
130	<	if (initialCapacity < 1)
131	<	initialCapacity = 1;
132	<
133	<	this.queue = new Object[initialCapacity + 1];
134	<	}
135	<
136	<	/**
137	<	* Initially fill elements of the queue array under the
138	<	* knowledge that it is sorted or is another PQ, in which
139	<	* case we can just place the elements without fixups.
140	<	*/
141	<	private void fillFromSorted(Collection<? extends E> c) {
142	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
143	<	queue[++size] = i.next();
144	<	}
145	<
146	<
147	<	/**
148	<	* Initially fill elements of the queue array that is
149	<	* not to our knowledge sorted, so we must add them
150	<	* one by one.
151	<	*/
152	<	private void fillFromUnsorted(Collection<? extends E> c) {
153	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
154	<	add(i.next());
155	<	}
156	<
157	<	/**
158	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
159	<	* specified collection.  The priority queue has an initial
160	<	* capacity of 110% of the size of the specified collection or 1
161	<	* if the collection is empty.  If the specified collection is an
162	<	* instance of a {@link SortedSet} or is another
163	<	* <tt>PriorityQueue</tt>, the priority queue will be sorted
164	<	* according to the same comparator, or according to its elements'
165	<	* natural order if the collection is sorted according to its
166	<	* elements' natural order.  Otherwise, the priority queue is
167	<	* ordered according to its elements' natural order.
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.
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 <tt>c</tt> or any element within it
171	<	* is <tt>null</tt>
169	>	*         queue's ordering
170	>	* @throws NullPointerException if the specified collection or any
171	>	*         of its elements are null
172		*/
173		public PriorityQueue(Collection<? extends E> c) {
174	<	initializeArray(c);
175	<	if (c instanceof SortedSet<? extends E>) {
176	<	SortedSet<? extends E> s = (SortedSet<? extends E>) c;
177	<	comparator = (Comparator<? super E>)s.comparator();
178	<	fillFromSorted(s);
179	<	}
180	<	else if (c instanceof PriorityQueue<? extends E>) {
185	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
186	<	comparator = (Comparator<? super E>)s.comparator();
187	<	fillFromSorted(s);
188	<	}
174	>	initFromCollection(c);
175	>	if (c instanceof SortedSet)
176	>	comparator = (Comparator<? super E>)
177	>	((SortedSet<? extends E>)c).comparator();
178	>	else if (c instanceof PriorityQueue)
179	>	comparator = (Comparator<? super E>)
180	>	((PriorityQueue<? extends E>)c).comparator();
181		else {
182		comparator = null;
183	<	fillFromUnsorted(c);
183	>	heapify();
184		}
185		}
186
187		/**
188	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
189	<	* specified collection.  The priority queue has an initial
190	<	* capacity of 110% of the size of the specified collection or 1
191	<	* if the collection is empty.  This priority queue will be sorted
200	<	* according to the same comparator as the given collection, or
201	<	* according to its elements' natural order if the collection is
202	<	* sorted according to its elements' natural order.
188	>	* Creates a {@code PriorityQueue} containing the elements in the
189	>	* specified priority queue.  This priority queue will be
190	>	* ordered according to the same ordering as the given priority
191	>	* queue.
192		*
193	<	* @param c the collection whose elements are to be placed
194	<	*        into this priority queue.
195	<	* @throws ClassCastException if elements of the specified collection
196	<	*         cannot be compared to one another according to the priority
197	<	*         queue's ordering.
198	<	* @throws NullPointerException if <tt>c</tt> or any element within it
199	<	* is <tt>null</tt>
193	>	* @param  c the priority queue whose elements are to be placed
194	>	*         into this priority queue
195	>	* @throws ClassCastException if elements of {@code c} cannot be
196	>	*         compared to one another according to {@code c}'s
197	>	*         ordering
198	>	* @throws NullPointerException if the specified priority queue or any
199	>	*         of its elements are null
200		*/
201		public PriorityQueue(PriorityQueue<? extends E> c) {
213	–	initializeArray(c);
202		comparator = (Comparator<? super E>)c.comparator();
203	<	fillFromSorted(c);
203	>	initFromCollection(c);
204		}
205
206		/**
207	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
208	<	* specified collection.  The priority queue has an initial
209	<	* capacity of 110% of the size of the specified collection or 1
222	<	* if the collection is empty.  This priority queue will be sorted
223	<	* according to the same comparator as the given collection, or
224	<	* according to its elements' natural order if the collection is
225	<	* sorted according to its elements' natural order.
207	>	* Creates a {@code PriorityQueue} containing the elements in the
208	>	* specified sorted set.   This priority queue will be ordered
209	>	* according to the same ordering as the given sorted set.
210		*
211	<	* @param c the collection whose elements are to be placed
212	<	*        into this priority queue.
213	<	* @throws ClassCastException if elements of the specified collection
214	<	*         cannot be compared to one another according to the priority
215	<	*         queue's ordering.
216	<	* @throws NullPointerException if <tt>c</tt> or any element within it
217	<	* is <tt>null</tt>
211	>	* @param  c the sorted set whose elements are to be placed
212	>	*         into this priority queue
213	>	* @throws ClassCastException if elements of the specified sorted
214	>	*         set cannot be compared to one another according to the
215	>	*         sorted set's ordering
216	>	* @throws NullPointerException if the specified sorted set or any
217	>	*         of its elements are null
218		*/
219		public PriorityQueue(SortedSet<? extends E> c) {
236	–	initializeArray(c);
220		comparator = (Comparator<? super E>)c.comparator();
221	<	fillFromSorted(c);
221	>	initFromCollection(c);
222		}
223
224		/**
225	<	* Resize array, if necessary, to be able to hold given index
225	>	* Initializes queue array with elements from the given Collection.
226	>	*
227	>	* @param c the collection
228		*/
229	<	private void grow(int index) {
230	<	int newlen = queue.length;
231	<	if (index < newlen) // don't need to grow
232	<	return;
233	<	if (index == Integer.MAX_VALUE)
234	<	throw new OutOfMemoryError();
235	<	while (newlen <= index) {
251	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
252	<	newlen = Integer.MAX_VALUE;
253	<	else
254	<	newlen <<= 2;
255	<	}
256	<	Object[] newQueue = new Object[newlen];
257	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
258	<	queue = newQueue;
229	>	private void initFromCollection(Collection<? extends E> c) {
230	>	Object[] a = c.toArray();
231	>	// If c.toArray incorrectly doesn't return Object[], copy it.
232	>	if (a.getClass() != Object[].class)
233	>	a = Arrays.copyOf(a, a.length, Object[].class);
234	>	queue = a;
235	>	size = a.length;
236		}
260	–
261	–	// Queue Methods
237
238	+	/**
239	+	* Increases the capacity of the array.
240	+	*
241	+	* @param minCapacity the desired minimum capacity
242	+	*/
243	+	private void grow(int minCapacity) {
244	+	if (minCapacity < 0) // overflow
245	+	throw new OutOfMemoryError();
246	+	int oldCapacity = queue.length;
247	+	// Double size if small; else grow by 50%
248	+	int newCapacity = ((oldCapacity < 64)?
249	+	((oldCapacity + 1) * 2):
250	+	((oldCapacity / 2) * 3));
251	+	if (newCapacity < 0) // overflow
252	+	newCapacity = Integer.MAX_VALUE;
253	+	if (newCapacity < minCapacity)
254	+	newCapacity = minCapacity;
255	+	queue = Arrays.copyOf(queue, newCapacity);
256	+	}
257
258	+	/**
259	+	* Inserts the specified element into this priority queue.
260	+	*
261	+	* @return {@code true} (as specified by {@link Collection#add})
262	+	* @throws ClassCastException if the specified element cannot be
263	+	*         compared with elements currently in this priority queue
264	+	*         according to the priority queue's ordering
265	+	* @throws NullPointerException if the specified element is null
266	+	*/
267	+	public boolean add(E e) {
268	+	return offer(e);
269	+	}
270
271		/**
272	<	* Add the specified element to this priority queue.
272	>	* Inserts the specified element into this priority queue.
273		*
274	<	* @return <tt>true</tt>
275	<	* @throws ClassCastException if the specified element cannot be compared
276	<	* with elements currently in the priority queue according
277	<	* to the priority queue's ordering.
278	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
274	>	* @return {@code true} (as specified by {@link Queue#offer})
275	>	* @throws ClassCastException if the specified element cannot be
276	>	*         compared with elements currently in this priority queue
277	>	*         according to the priority queue's ordering
278	>	* @throws NullPointerException if the specified element is null
279		*/
280	<	public boolean offer(E o) {
281	<	if (o == null)
280	>	public boolean offer(E e) {
281	>	if (e == null)
282		throw new NullPointerException();
283		modCount++;
284	<	++size;
285	<
286	<	// Grow backing store if necessary
287	<	if (size >= queue.length)
288	<	grow(size);
289	<
290	<	queue[size] = o;
291	<	fixUp(size);
284	>	int i = size;
285	>	if (i >= queue.length)
286	>	grow(i + 1);
287	>	size = i + 1;
288	>	if (i == 0)
289	>	queue[0] = e;
290	>	else
291	>	siftUp(i, e);
292		return true;
293		}
294
295	<	public E poll() {
295	>	public E peek() {
296		if (size == 0)
297		return null;
298	<	return (E) remove(1);
298	>	return (E) queue[0];
299		}
300
301	<	public E peek() {
302	<	return (E) queue[1];
301	>	private int indexOf(Object o) {
302	>	if (o != null) {
303	>	for (int i = 0; i < size; i++)
304	>	if (o.equals(queue[i]))
305	>	return i;
306	>	}
307	>	return -1;
308		}
309
299	–	// Collection Methods - the first two override to update docs
300	–
310		/**
311	<	* Adds the specified element to this queue.
312	<	* @return <tt>true</tt> (as per the general contract of
313	<	* <tt>Collection.add</tt>).
311	>	* Removes a single instance of the specified element from this queue,
312	>	* if it is present.  More formally, removes an element {@code e} such
313	>	* that {@code o.equals(e)}, if this queue contains one or more such
314	>	* elements.  Returns {@code true} if and only if this queue contained
315	>	* the specified element (or equivalently, if this queue changed as a
316	>	* result of the call).
317		*
318	<	* @throws NullPointerException {@inheritDoc}
319	<	* @throws ClassCastException if the specified element cannot be compared
308	<	* with elements currently in the priority queue according
309	<	* to the priority queue's ordering.
318	>	* @param o element to be removed from this queue, if present
319	>	* @return {@code true} if this queue changed as a result of the call
320		*/
321	<	public boolean add(E o) {
322	<	return super.add(o);
321	>	public boolean remove(Object o) {
322	>	int i = indexOf(o);
323	>	if (i == -1)
324	>	return false;
325	>	else {
326	>	removeAt(i);
327	>	return true;
328	>	}
329		}
330
315	–
331		/**
332	<	* Adds all of the elements in the specified collection to this queue.
333	<	* The behavior of this operation is undefined if
334	<	* the specified collection is modified while the operation is in
335	<	* progress.  (This implies that the behavior of this call is undefined if
336	<	* the specified collection is this queue, and this queue is nonempty.)
322	<	* <p>
323	<	* This implementation iterates over the specified collection, and adds
324	<	* each object returned by the iterator to this collection, in turn.
325	<	* @throws NullPointerException {@inheritDoc}
326	<	* @throws ClassCastException if any element cannot be compared
327	<	* with elements currently in the priority queue according
328	<	* to the priority queue's ordering.
332	>	* Version of remove using reference equality, not equals.
333	>	* Needed by iterator.remove.
334	>	*
335	>	* @param o element to be removed from this queue, if present
336	>	* @return {@code true} if removed
337		*/
338	<	public boolean addAll(Collection<? extends E> c) {
339	<	return super.addAll(c);
338	>	boolean removeEq(Object o) {
339	>	for (int i = 0; i < size; i++) {
340	>	if (o == queue[i]) {
341	>	removeAt(i);
342	>	return true;
343	>	}
344	>	}
345	>	return false;
346		}
347
348	+	/**
349	+	* Returns {@code true} if this queue contains the specified element.
350	+	* More formally, returns {@code true} if and only if this queue contains
351	+	* at least one element {@code e} such that {@code o.equals(e)}.
352	+	*
353	+	* @param o object to be checked for containment in this queue
354	+	* @return {@code true} if this queue contains the specified element
355	+	*/
356	+	public boolean contains(Object o) {
357	+	return indexOf(o) != -1;
358	+	}
359
360	<	/**
361	<	* Removes a single instance of the specified element from this
362	<	* queue, if it is present.  More formally,
338	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
339	<	* o.equals(e))</tt>, if the queue contains one or more such
340	<	* elements.  Returns <tt>true</tt> if the queue contained the
341	<	* specified element (or equivalently, if the queue changed as a
342	<	* result of the call).
360	>	/**
361	>	* Returns an array containing all of the elements in this queue.
362	>	* The elements are in no particular order.
363		*
364	<	* <p>This implementation iterates over the queue looking for the
365	<	* specified element.  If it finds the element, it removes the element
366	<	* from the queue using the iterator's remove method.<p>
364	>	* <p>The returned array will be "safe" in that no references to it are
365	>	* maintained by this queue.  (In other words, this method must allocate
366	>	* a new array).  The caller is thus free to modify the returned array.
367		*
368	+	* <p>This method acts as bridge between array-based and collection-based
369	+	* APIs.
370	+	*
371	+	* @return an array containing all of the elements in this queue
372		*/
373	<	public boolean remove(Object o) {
374	<	if (o == null)
375	<	return false;
373	>	public Object[] toArray() {
374	>	return Arrays.copyOf(queue, size);
375	>	}
376
377	<	if (comparator == null) {
378	<	for (int i = 1; i <= size; i++) {
379	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
380	<	remove(i);
381	<	return true;
382	<	}
383	<	}
384	<	} else {
385	<	for (int i = 1; i <= size; i++) {
386	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
387	<	remove(i);
388	<	return true;
389	<	}
390	<	}
391	<	}
392	<	return false;
377	>	/**
378	>	* Returns an array containing all of the elements in this queue; the
379	>	* runtime type of the returned array is that of the specified array.
380	>	* The returned array elements are in no particular order.
381	>	* If the queue fits in the specified array, it is returned therein.
382	>	* Otherwise, a new array is allocated with the runtime type of the
383	>	* specified array and the size of this queue.
384	>	*
385	>	* <p>If the queue fits in the specified array with room to spare
386	>	* (i.e., the array has more elements than the queue), the element in
387	>	* the array immediately following the end of the collection is set to
388	>	* {@code null}.
389	>	*
390	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
391	>	* array-based and collection-based APIs.  Further, this method allows
392	>	* precise control over the runtime type of the output array, and may,
393	>	* under certain circumstances, be used to save allocation costs.
394	>	*
395	>	* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
396	>	* The following code can be used to dump the queue into a newly
397	>	* allocated array of <tt>String</tt>:
398	>	*
399	>	* <pre>
400	>	*     String[] y = x.toArray(new String[0]);</pre>
401	>	*
402	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
403	>	* <tt>toArray()</tt>.
404	>	*
405	>	* @param a the array into which the elements of the queue are to
406	>	*          be stored, if it is big enough; otherwise, a new array of the
407	>	*          same runtime type is allocated for this purpose.
408	>	* @return an array containing all of the elements in this queue
409	>	* @throws ArrayStoreException if the runtime type of the specified array
410	>	*         is not a supertype of the runtime type of every element in
411	>	*         this queue
412	>	* @throws NullPointerException if the specified array is null
413	>	*/
414	>	public <T> T[] toArray(T[] a) {
415	>	if (a.length < size)
416	>	// Make a new array of a's runtime type, but my contents:
417	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
418	>	System.arraycopy(queue, 0, a, 0, size);
419	>	if (a.length > size)
420	>	a[size] = null;
421	>	return a;
422		}
423
424		/**
425		* Returns an iterator over the elements in this queue. The iterator
426		* does not return the elements in any particular order.
427		*
428	<	* @return an iterator over the elements in this queue.
428	>	* @return an iterator over the elements in this queue
429		*/
430		public Iterator<E> iterator() {
431		return new Itr();
432		}
433
434	<	private class Itr implements Iterator<E> {
434	>	private final class Itr implements Iterator<E> {
435		/**
436		* Index (into queue array) of element to be returned by
437		* subsequent call to next.
438		*/
439	<	private int cursor = 1;
439	>	private int cursor = 0;
440	>
441	>	/**
442	>	* Index of element returned by most recent call to next,
443	>	* unless that element came from the forgetMeNot list.
444	>	* Set to -1 if element is deleted by a call to remove.
445	>	*/
446	>	private int lastRet = -1;
447	>
448	>	/**
449	>	* A queue of elements that were moved from the unvisited portion of
450	>	* the heap into the visited portion as a result of "unlucky" element
451	>	* removals during the iteration.  (Unlucky element removals are those
452	>	* that require a siftup instead of a siftdown.)  We must visit all of
453	>	* the elements in this list to complete the iteration.  We do this
454	>	* after we've completed the "normal" iteration.
455	>	*
456	>	* We expect that most iterations, even those involving removals,
457	>	* will not need to store elements in this field.
458	>	*/
459	>	private ArrayDeque<E> forgetMeNot = null;
460
461		/**
462	<	* Index of element returned by most recent call to next or
463	<	* previous.  Reset to 0 if this element is deleted by a call
391	<	* to remove.
462	>	* Element returned by the most recent call to next iff that
463	>	* element was drawn from the forgetMeNot list.
464		*/
465	<	private int lastRet = 0;
465	>	private E lastRetElt = null;
466
467		/**
468		* The modCount value that the iterator believes that the backing
469	<	* List should have.  If this expectation is violated, the iterator
469	>	* Queue should have.  If this expectation is violated, the iterator
470		* has detected concurrent modification.
471		*/
472		private int expectedModCount = modCount;
473
474		public boolean hasNext() {
475	<	return cursor <= size;
475	>	return cursor < size ||
476	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
477		}
478
479		public E next() {
480	<	checkForComodification();
481	<	if (cursor > size)
482	<	throw new NoSuchElementException();
483	<	E result = (E) queue[cursor];
484	<	lastRet = cursor++;
485	<	return result;
480	>	if (expectedModCount != modCount)
481	>	throw new ConcurrentModificationException();
482	>	if (cursor < size)
483	>	return (E) queue[lastRet = cursor++];
484	>	if (forgetMeNot != null) {
485	>	lastRet = -1;
486	>	lastRetElt = forgetMeNot.poll();
487	>	if (lastRetElt != null)
488	>	return lastRetElt;
489	>	}
490	>	throw new NoSuchElementException();
491		}
492
493		public void remove() {
494	<	if (lastRet == 0)
494	>	if (expectedModCount != modCount)
495	>	throw new ConcurrentModificationException();
496	>	if (lastRet != -1) {
497	>	E moved = PriorityQueue.this.removeAt(lastRet);
498	>	lastRet = -1;
499	>	if (moved == null)
500	>	cursor--;
501	>	else {
502	>	if (forgetMeNot == null)
503	>	forgetMeNot = new ArrayDeque<E>();
504	>	forgetMeNot.add(moved);
505	>	}
506	>	} else if (lastRetElt != null) {
507	>	PriorityQueue.this.removeEq(lastRetElt);
508	>	lastRetElt = null;
509	>	} else {
510		throw new IllegalStateException();
511	<	checkForComodification();
419	<
420	<	PriorityQueue.this.remove(lastRet);
421	<	if (lastRet < cursor)
422	<	cursor--;
423	<	lastRet = 0;
511	>	}
512		expectedModCount = modCount;
513		}
426	–
427	–	final void checkForComodification() {
428	–	if (modCount != expectedModCount)
429	–	throw new ConcurrentModificationException();
430	–	}
514		}
515
516		public int size() {
#	Line 435 | Line 518 | public class PriorityQueue<E> extends Ab
518		}
519
520		/**
521	<	* Remove all elements from the priority queue.
521	>	* Removes all of the elements from this priority queue.
522	>	* The queue will be empty after this call returns.
523		*/
524		public void clear() {
525		modCount++;
526	<
443	<	// Null out element references to prevent memory leak
444	<	for (int i=1; i<=size; i++)
526	>	for (int i = 0; i < size; i++)
527		queue[i] = null;
446	–
528		size = 0;
529		}
530
531	+	public E poll() {
532	+	if (size == 0)
533	+	return null;
534	+	int s = --size;
535	+	modCount++;
536	+	E result = (E) queue[0];
537	+	E x = (E) queue[s];
538	+	queue[s] = null;
539	+	if (s != 0)
540	+	siftDown(0, x);
541	+	return result;
542	+	}
543	+
544		/**
545	<	* Removes and returns the ith element from queue.  Recall
452	<	* that queue is one-based, so 1 <= i <= size.
545	>	* Removes the ith element from queue.
546		*
547	<	* XXX: Could further special-case i==size, but is it worth it?
548	<	* XXX: Could special-case i==0, but is it worth it?
547	>	* Normally this method leaves the elements at up to i-1,
548	>	* inclusive, untouched.  Under these circumstances, it returns
549	>	* null.  Occasionally, in order to maintain the heap invariant,
550	>	* it must swap a later element of the list with one earlier than
551	>	* i.  Under these circumstances, this method returns the element
552	>	* that was previously at the end of the list and is now at some
553	>	* position before i. This fact is used by iterator.remove so as to
554	>	* avoid missing traversing elements.
555		*/
556	<	private E remove(int i) {
557	<	assert i <= size;
556	>	private E removeAt(int i) {
557	>	assert i >= 0 && i < size;
558		modCount++;
559	<
560	<	E result = (E) queue[i];
561	<	queue[i] = queue[size];
562	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
563	<	if (i <= size)
564	<	fixDown(i);
565	<	return result;
559	>	int s = --size;
560	>	if (s == i) // removed last element
561	>	queue[i] = null;
562	>	else {
563	>	E moved = (E) queue[s];
564	>	queue[s] = null;
565	>	siftDown(i, moved);
566	>	if (queue[i] == moved) {
567	>	siftUp(i, moved);
568	>	if (queue[i] != moved)
569	>	return moved;
570	>	}
571	>	}
572	>	return null;
573		}
574
575		/**
576	<	* Establishes the heap invariant (described above) assuming the heap
577	<	* satisfies the invariant except possibly for the leaf-node indexed by k
578	<	* (which may have a nextExecutionTime less than its parent's).
579	<	*
580	<	* This method functions by "promoting" queue[k] up the hierarchy
581	<	* (by swapping it with its parent) repeatedly until queue[k]
582	<	* is greater than or equal to its parent.
583	<	*/
584	<	private void fixUp(int k) {
585	<	if (comparator == null) {
586	<	while (k > 1) {
587	<	int j = k >> 1;
588	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
589	<	break;
590	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
591	<	k = j;
592	<	}
593	<	} else {
594	<	while (k > 1) {
595	<	int j = k >> 1;
596	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
597	<	break;
598	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
599	<	k = j;
600	<	}
576	>	* Inserts item x at position k, maintaining heap invariant by
577	>	* promoting x up the tree until it is greater than or equal to
578	>	* its parent, or is the root.
579	>	*
580	>	* To simplify and speed up coercions and comparisons. the
581	>	* Comparable and Comparator versions are separated into different
582	>	* methods that are otherwise identical. (Similarly for siftDown.)
583	>	*
584	>	* @param k the position to fill
585	>	* @param x the item to insert
586	>	*/
587	>	private void siftUp(int k, E x) {
588	>	if (comparator != null)
589	>	siftUpUsingComparator(k, x);
590	>	else
591	>	siftUpComparable(k, x);
592	>	}
593	>
594	>	private void siftUpComparable(int k, E x) {
595	>	Comparable<? super E> key = (Comparable<? super E>) x;
596	>	while (k > 0) {
597	>	int parent = (k - 1) >>> 1;
598	>	Object e = queue[parent];
599	>	if (key.compareTo((E) e) >= 0)
600	>	break;
601	>	queue[k] = e;
602	>	k = parent;
603	>	}
604	>	queue[k] = key;
605	>	}
606	>
607	>	private void siftUpUsingComparator(int k, E x) {
608	>	while (k > 0) {
609	>	int parent = (k - 1) >>> 1;
610	>	Object e = queue[parent];
611	>	if (comparator.compare(x, (E) e) >= 0)
612	>	break;
613	>	queue[k] = e;
614	>	k = parent;
615		}
616	+	queue[k] = x;
617		}
618
619		/**
620	<	* Establishes the heap invariant (described above) in the subtree
621	<	* rooted at k, which is assumed to satisfy the heap invariant except
622	<	* possibly for node k itself (which may be greater than its children).
623	<	*
624	<	* This method functions by "demoting" queue[k] down the hierarchy
625	<	* (by swapping it with its smaller child) repeatedly until queue[k]
626	<	* is less than or equal to its children.
627	<	*/
628	<	private void fixDown(int k) {
629	<	int j;
630	<	if (comparator == null) {
631	<	while ((j = k << 1) <= size) {
632	<	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
633	<	j++; // j indexes smallest kid
634	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
635	<	break;
636	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
637	<	k = j;
638	<	}
639	<	} else {
640	<	while ((j = k << 1) <= size) {
641	<	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
642	<	j++; // j indexes smallest kid
643	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
644	<	break;
645	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
646	<	k = j;
647	<	}
620	>	* Inserts item x at position k, maintaining heap invariant by
621	>	* demoting x down the tree repeatedly until it is less than or
622	>	* equal to its children or is a leaf.
623	>	*
624	>	* @param k the position to fill
625	>	* @param x the item to insert
626	>	*/
627	>	private void siftDown(int k, E x) {
628	>	if (comparator != null)
629	>	siftDownUsingComparator(k, x);
630	>	else
631	>	siftDownComparable(k, x);
632	>	}
633	>
634	>	private void siftDownComparable(int k, E x) {
635	>	Comparable<? super E> key = (Comparable<? super E>)x;
636	>	int half = size >>> 1;        // loop while a non-leaf
637	>	while (k < half) {
638	>	int child = (k << 1) + 1; // assume left child is least
639	>	Object c = queue[child];
640	>	int right = child + 1;
641	>	if (right < size &&
642	>	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
643	>	c = queue[child = right];
644	>	if (key.compareTo((E) c) <= 0)
645	>	break;
646	>	queue[k] = c;
647	>	k = child;
648		}
649	+	queue[k] = key;
650		}
651
652	+	private void siftDownUsingComparator(int k, E x) {
653	+	int half = size >>> 1;
654	+	while (k < half) {
655	+	int child = (k << 1) + 1;
656	+	Object c = queue[child];
657	+	int right = child + 1;
658	+	if (right < size &&
659	+	comparator.compare((E) c, (E) queue[right]) > 0)
660	+	c = queue[child = right];
661	+	if (comparator.compare(x, (E) c) <= 0)
662	+	break;
663	+	queue[k] = c;
664	+	k = child;
665	+	}
666	+	queue[k] = x;
667	+	}
668
669		/**
670	<	* Returns the comparator used to order this collection, or <tt>null</tt>
671	<	* if this collection is sorted according to its elements natural ordering
672	<	* (using <tt>Comparable</tt>.)
670	>	* Establishes the heap invariant (described above) in the entire tree,
671	>	* assuming nothing about the order of the elements prior to the call.
672	>	*/
673	>	private void heapify() {
674	>	for (int i = (size >>> 1) - 1; i >= 0; i--)
675	>	siftDown(i, (E) queue[i]);
676	>	}
677	>
678	>	/**
679	>	* Returns the comparator used to order the elements in this
680	>	* queue, or {@code null} if this queue is sorted according to
681	>	* the {@linkplain Comparable natural ordering} of its elements.
682		*
683	<	* @return the comparator used to order this collection, or <tt>null</tt>
684	<	* if this collection is sorted according to its elements natural ordering.
683	>	* @return the comparator used to order this queue, or
684	>	*         {@code null} if this queue is sorted according to the
685	>	*         natural ordering of its elements
686		*/
687		public Comparator<? super E> comparator() {
688		return comparator;
689		}
690
691		/**
692	<	* Save the state of the instance to a stream (that
693	<	* is, serialize it).
692	>	* Saves the state of the instance to a stream (that
693	>	* is, serializes it).
694		*
695		* @serialData The length of the array backing the instance is
696	<	* emitted (int), followed by all of its elements (each an
697	<	* <tt>Object</tt>) in the proper order.
696	>	*             emitted (int), followed by all of its elements
697	>	*             (each an {@code Object}) in the proper order.
698		* @param s the stream
699		*/
700		private void writeObject(java.io.ObjectOutputStream s)
#	Line 554 | Line 702 | public class PriorityQueue<E> extends Ab
702		// Write out element count, and any hidden stuff
703		s.defaultWriteObject();
704
705	<	// Write out array length
706	<	s.writeInt(queue.length);
705	>	// Write out array length, for compatibility with 1.5 version
706	>	s.writeInt(Math.max(2, size + 1));
707
708	<	// Write out all elements in the proper order.
709	<	for (int i=0; i<size; i++)
708	>	// Write out all elements in the "proper order".
709	>	for (int i = 0; i < size; i++)
710		s.writeObject(queue[i]);
711		}
712
713		/**
714	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
715	<	* deserialize it).
714	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
715	>	* (that is, deserializes it).
716	>	*
717		* @param s the stream
718		*/
719		private void readObject(java.io.ObjectInputStream s)
#	Line 572 | Line 721 | public class PriorityQueue<E> extends Ab
721		// Read in size, and any hidden stuff
722		s.defaultReadObject();
723
724	<	// Read in array length and allocate array
725	<	int arrayLength = s.readInt();
577	<	queue = new Object[arrayLength];
724	>	// Read in (and discard) array length
725	>	s.readInt();
726
727	<	// Read in all elements in the proper order.
728	<	for (int i=0; i<size; i++)
727	>	queue = new Object[size];
728	>
729	>	// Read in all elements.
730	>	for (int i = 0; i < size; i++)
731		queue[i] = s.readObject();
582	–	}
732
733	+	// Elements are guaranteed to be in "proper order", but the
734	+	// spec has never explained what that might be.
735	+	heapify();
736	+	}
737		}
585	–

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