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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.53 by jsr166, Wed Nov 23 05:33:25 2005 UTC vs.
Revision 1.80 by jsr166, Wed Jan 16 01:59:47 2013 UTC

#	Line 1 | Line 1
1		/*
2	<	* @(#)PriorityQueue.java       1.8 05/08/27
2	>	* Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.
3	>	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4		*
5	<	* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
6	<	* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
5	>	* This code is free software; you can redistribute it and/or modify it
6	>	* under the terms of the GNU General Public License version 2 only, as
7	>	* published by the Free Software Foundation.  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;
9	–	import java.util.*; // for javadoc (till 6280605 is fixed)
27
28		/**
29	<	* An unbounded priority {@linkplain Queue queue} based on a priority
30	<	* heap.  The elements of the priority queue are ordered according to
31	<	* their {@linkplain Comparable natural ordering}, or by a {@link
32	<	* Comparator} provided at queue construction time, depending on which
33	<	* constructor is used.  A priority queue does not permit
34	<	* <tt>null</tt> elements.  A priority queue relying on natural
35	<	* ordering also does not permit insertion of non-comparable objects
36	<	* (doing so may result in <tt>ClassCastException</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 <tt>poll</tt>,
42	<	* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the
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
#	Line 37 | Line 54 | import java.util.*; // for javadoc (till
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 <tt>Arrays.sort(pq.toArray())</tt>.
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
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 O(log(n)) time
66	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
67	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
68	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
69	<	* constant time for the retrieval methods (<tt>peek</tt>,
70	<	* <tt>element</tt>, and <tt>size</tt>).
65	>	* <p>Implementation note: this implementation provides
66	>	* O(log(n)) time for the enqueuing and dequeuing methods
67	>	* ({@code offer}, {@code poll}, {@code remove()} and {@code add});
68	>	* linear time for the {@code remove(Object)} and {@code contains(Object)}
69	>	* methods; and constant time for the retrieval methods
70	>	* ({@code peek}, {@code element}, and {@code size}).
71		*
72		* <p>This class is a member of the
73	<	* <a href="{@docRoot}/../guide/collections/index.html">
73	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
74		* Java Collections Framework</a>.
75	+	*
76		* @since 1.5
77	<	* @version 1.8, 08/27/05
60	<	* @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 java.io.Serializable {
83
#	Line 68 | Line 86 | public class PriorityQueue<E> extends Ab
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	<	*
77	<	* The element with the lowest value is in queue[1], assuming the queue is
78	<	* nonempty.  (A one-based array is used in preference to the traditional
79	<	* zero-based array to simplify parent and child calculations.)
80	<	*
81	<	* queue.length must be >= 2, even if size == 0.
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 100 | 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
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		*/
#	Line 109 | Line 122 | public class PriorityQueue<E> extends Ab
122		}
123
124		/**
125	<	* Creates a <tt>PriorityQueue</tt> with the specified initial
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 <tt>initialCapacity</tt> is less
131	<	* than 1
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 that will be used to order
143	<	*         this priority queue.  If <tt>null</tt>, the <i>natural
144	<	*         ordering</i> of the elements will be used.
145	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is
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,
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,
150	<	Integer.MAX_VALUE - 1);
151	<	if (initialCapacity < 1)
152	<	initialCapacity = 1;
153	<
154	<	this.queue = new Object[initialCapacity + 1];
155	<	}
156	<
157	<	/**
158	<	* Initially fill elements of the queue array under the
159	<	* knowledge that it is sorted or is another PQ, in which
160	<	* case we can just place the elements in the order presented.
161	<	*/
162	<	private void fillFromSorted(Collection<? extends E> c) {
163	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) {
164	<	int k = ++size;
165	<	if (k >= queue.length)
166	<	grow(k);
167	<	queue[k] = i.next();
168	<	}
169	<	}
170	<
171	<	/**
172	<	* Initially fill elements of the queue array that is not to our knowledge
173	<	* sorted, so we must rearrange the elements to guarantee the heap
174	<	* invariant.
175	<	*/
176	<	private void fillFromUnsorted(Collection<? extends E> c) {
177	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) {
178	<	int k = ++size;
179	<	if (k >= queue.length)
180	<	grow(k);
181	<	queue[k] = i.next();
182	<	}
183	<	heapify();
184	<	}
185	<
186	<	/**
187	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
188	<	* specified collection.  The priority queue has an initial
189	<	* capacity of 110% of the size of the specified collection or 1
190	<	* if the collection is empty.  If the specified collection is an
191	<	* instance of a {@link java.util.SortedSet} or is another
192	<	* <tt>PriorityQueue</tt>, the priority queue will be ordered
193	<	* according to the same ordering.  Otherwise, this priority queue
194	<	* will be ordered according to the natural ordering of its elements.
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
#	Line 201 | Line 171 | public class PriorityQueue<E> extends Ab
171		* @throws NullPointerException if the specified collection or any
172		*         of its elements are null
173		*/
174	+	@SuppressWarnings("unchecked")
175		public PriorityQueue(Collection<? extends E> c) {
176	<	initializeArray(c);
177	<	if (c instanceof SortedSet) {
178	<	SortedSet<? extends E> s = (SortedSet<? extends E>)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;
183	<	comparator = (Comparator<? super E>)s.comparator();
184	<	fillFromSorted(s);
185	<	} else {
186	<	comparator = null;
187	<	fillFromUnsorted(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	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
194	<	* specified priority queue.  The priority queue has an initial
223	<	* capacity of 110% of the size of the specified priority queue or
224	<	* 1 if the priority queue is empty.  This priority queue will be
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 <tt>c</tt> cannot be
201	<	*         compared to one another according to <tt>c</tt>'s
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	+	@SuppressWarnings("unchecked")
207		public PriorityQueue(PriorityQueue<? extends E> c) {
208	<	initializeArray(c);
209	<	comparator = (Comparator<? super E>)c.comparator();
239	<	fillFromSorted(c);
208	>	this.comparator = (Comparator<? super E>) c.comparator();
209	>	initFromPriorityQueue(c);
210		}
211
212		/**
213	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
214	<	* specified sorted set.  The priority queue has an initial
245	<	* capacity of 110% of the size of the specified sorted set or 1
246	<	* if the sorted set is empty.  This priority queue will be ordered
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.
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	+	@SuppressWarnings("unchecked")
226		public PriorityQueue(SortedSet<? extends E> c) {
227	<	initializeArray(c);
228	<	comparator = (Comparator<? super E>)c.comparator();
229	<	fillFromSorted(c);
227	>	this.comparator = (Comparator<? super E>) c.comparator();
228	>	initElementsFromCollection(c);
229	>	}
230	>
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	>	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	>	* Initializes queue array with elements from the given Collection.
256	>	*
257	>	* @param c the collection
258	>	*/
259	>	private void initFromCollection(Collection<? extends E> c) {
260	>	initElementsFromCollection(c);
261	>	heapify();
262		}
263
264		/**
265	<	* Resize array, if necessary, to be able to hold given index.
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	<	private void grow(int index) {
271	<	int newlen = queue.length;
272	<	if (index < newlen) // don't need to grow
273	<	return;
274	<	if (index == Integer.MAX_VALUE)
270	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
271	>
272	>	/**
273	>	* Increases the capacity of the array.
274	>	*
275	>	* @param minCapacity the desired minimum capacity
276	>	*/
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	>	}
288	>
289	>	private static int hugeCapacity(int minCapacity) {
290	>	if (minCapacity < 0) // overflow
291		throw new OutOfMemoryError();
292	<	while (newlen <= index) {
293	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
294	<	newlen = Integer.MAX_VALUE;
275	<	else
276	<	newlen <<= 2;
277	<	}
278	<	queue = Arrays.copyOf(queue, newlen);
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 <tt>true</tt> (as specified by {@link Collection#add})
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
#	Line 294 | Line 310 | public class PriorityQueue<E> extends Ab
310		/**
311		* Inserts the specified element into this priority queue.
312		*
313	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
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
#	Line 304 | Line 320 | public class PriorityQueue<E> extends Ab
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] = e;
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
334		public E peek() {
335	<	if (size == 0)
320	<	return null;
321	<	return (E) queue[1];
335	>	return (size == 0) ? null : (E) queue[0];
336		}
337
338		private int indexOf(Object o) {
339	<	if (o == null)
340	<	return -1;
341	<	for (int i = 1; i <= size; i++)
342	<	if (o.equals(queue[i]))
343	<	return i;
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		* Removes a single instance of the specified element from this queue,
349	<	* if it is present.  More formally, removes an element <tt>e</tt> such
350	<	* that <tt>o.equals(e)</tt>, if this queue contains one or more such
351	<	* elements.  Returns true if this queue contained the specified element
352	<	* (or equivalently, if this queue changed as a result of the call).
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		* @param o element to be removed from this queue, if present
356	<	* @return <tt>true</tt> if this queue changed as a result of the call
356	>	* @return {@code true} if this queue changed as a result of the call
357		*/
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	<	}
359	>	int i = indexOf(o);
360	>	if (i == -1)
361	>	return false;
362	>	else {
363	>	removeAt(i);
364	>	return true;
365	>	}
366	>	}
367	>
368	>	/**
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	>	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 <tt>true</tt> if this queue contains the specified element.
387	<	* More formally, returns <tt>true</tt> if and only if this queue contains
388	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
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 <tt>true</tt> if this queue contains the specified element
391	>	* @return {@code true} if this queue contains the specified element
392		*/
393		public boolean contains(Object o) {
394	<	return indexOf(o) != -1;
394	>	return indexOf(o) != -1;
395		}
396
397		/**
398	<	* Returns an array containing all of the elements in this queue,
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 list.  (In other words, this method must allocate
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	<	* @return an array containing all of the elements in this queue.
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 Object[] toArray() {
411	<	return Arrays.copyOfRange(queue, 1, size+1);
411	>	return Arrays.copyOf(queue, size);
412		}
413
414		/**
415	<	* Returns an array containing all of the elements in this queue.
416	<	* The elements are in no particular order.  The runtime type of
417	<	* the returned array is that of the specified array.  If the queue
418	<	* fits in the specified array, it is returned therein.
419	<	* Otherwise, a new array is allocated with the runtime type of
420	<	* the specified array and the size of this queue.
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	<	* <tt>null</tt>.  (This is useful in determining the length of the
426	<	* queue <i>only</i> if the caller knows that the queue does not contain
427	<	* any null elements.)
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 {@code x} 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 {@code String}:
435	>	*
436	>	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
437	>	*
438	>	* Note that {@code toArray(new Object[0])} is identical in function to
439	>	* {@code toArray()}.
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 the elements of the queue
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
#	Line 403 | Line 450 | public class PriorityQueue<E> extends Ab
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.copyOfRange(queue, 1, size+1, a.getClass());
454	<	System.arraycopy(queue, 1, a, 0, size);
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;
#	Line 420 | Line 467 | public class PriorityQueue<E> extends Ab
467		return new Itr();
468		}
469
470	<	private class Itr implements Iterator<E> {
424	<
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,
479		* unless that element came from the forgetMeNot list.
480	<	* Reset to 0 if element is deleted by a call to remove.
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	<	* The modCount value that the iterator believes that the backing
440	<	* List should have.  If this expectation is violated, the iterator
441	<	* has detected concurrent modification.
442	<	*/
443	<	private int expectedModCount = modCount;
444	<
445	<	/**
446	<	* A list of elements that were moved from the unvisited portion of
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 fixup instead of a fixdown.)  We must visit all of
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 use need to store elements in this field.
493	>	* will not need to store elements in this field.
494		*/
495	<	private ArrayList<E> forgetMeNot = null;
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 Object lastRetElt = null;
501	>	private E lastRetElt = null;
502	>
503	>	/**
504	>	* The modCount value that the iterator believes that the backing
505	>	* Queue should have.  If this expectation is violated, the iterator
506	>	* has detected concurrent modification.
507	>	*/
508	>	private int expectedModCount = modCount;
509
510		public boolean hasNext() {
511	<	return cursor <= size || forgetMeNot != null;
511	>	return cursor < size ||
512	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
513		}
514
515		public E next() {
516	<	checkForComodification();
517	<	E result;
518	<	if (cursor <= size) {
519	<	result = (E) queue[cursor];
520	<	lastRet = cursor++;
521	<	}
522	<	else if (forgetMeNot == null)
523	<	throw new NoSuchElementException();
524	<	else {
478	<	int remaining = forgetMeNot.size();
479	<	result = forgetMeNot.remove(remaining - 1);
480	<	if (remaining == 1)
481	<	forgetMeNot = null;
482	<	lastRet = 0;
483	<	lastRetElt = result;
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	<	return result;
526	>	throw new NoSuchElementException();
527		}
528
529		public void remove() {
530	<	checkForComodification();
531	<
532	<	if (lastRet != 0) {
530	>	if (expectedModCount != modCount)
531	>	throw new ConcurrentModificationException();
532	>	if (lastRet != -1) {
533		E moved = PriorityQueue.this.removeAt(lastRet);
534	<	lastRet = 0;
535	<	if (moved == null) {
534	>	lastRet = -1;
535	>	if (moved == null)
536		cursor--;
537	<	} else {
537	>	else {
538		if (forgetMeNot == null)
539	<	forgetMeNot = new ArrayList<E>();
539	>	forgetMeNot = new ArrayDeque<E>();
540		forgetMeNot.add(moved);
541		}
542		} else if (lastRetElt != null) {
543	<	PriorityQueue.this.remove(lastRetElt);
543	>	PriorityQueue.this.removeEq(lastRetElt);
544		lastRetElt = null;
545		} else {
546		throw new IllegalStateException();
547		}
507	–
548		expectedModCount = modCount;
549		}
510	–
511	–	final void checkForComodification() {
512	–	if (modCount != expectedModCount)
513	–	throw new ConcurrentModificationException();
514	–	}
550		}
551
552		public int size() {
#	Line 524 | Line 559 | public class PriorityQueue<E> extends Ab
559		*/
560		public void clear() {
561		modCount++;
562	<
528	<	// Null out element references to prevent memory leak
529	<	for (int i=1; i<=size; i++)
562	>	for (int i = 0; i < size; i++)
563		queue[i] = null;
531	–
564		size = 0;
565		}
566
567		public E poll() {
568		if (size == 0)
569		return null;
570	+	int s = --size;
571		modCount++;
572	<
573	<	E result = (E) queue[1];
574	<	queue[1] = queue[size];
575	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
576	<	if (size > 1)
544	<	fixDown(1);
545	<
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 that queue
551	<	* is one-based, so 1 <= i <= size.)
581	>	* Removes the ith element from queue.
582		*
583	<	* Normally this method leaves the elements at positions from 1 up to i-1,
584	<	* inclusive, untouched.  Under these circumstances, it returns null.
585	<	* Occasionally, in order to maintain the heap invariant, it must move
586	<	* the last element of the list to some index in the range [2, i-1],
587	<	* and move the element previously at position (i/2) to position i.
588	<	* Under these circumstances, this method returns the element that was
589	<	* previously at the end of the list and is now at some position between
590	<	* 2 and i-1 inclusive.
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 removeAt(int i) {
593	<	assert i > 0 && i <= size;
593	>	// assert i >= 0 && i < size;
594		modCount++;
595	<
596	<	E moved = (E) queue[size];
597	<	queue[i] = moved;
598	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
599	<	if (i <= size) {
600	<	fixDown(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	<	fixUp(i);
603	>	siftUp(i, moved);
604		if (queue[i] != moved)
605		return moved;
606		}
#	Line 578 | Line 609 | public class PriorityQueue<E> extends Ab
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<? super 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	<	}
637	<	}
638	<	}
639	<
640	<	/**
641	<	* Establishes the heap invariant (described above) in the subtree
642	<	* rooted at k, which is assumed to satisfy the heap invariant except
643	<	* possibly for node k itself (which may be greater than its children).
644	<	*
645	<	* This method functions by "demoting" queue[k] down the hierarchy
646	<	* (by swapping it with its smaller child) repeatedly until queue[k]
647	<	* is less than or equal to its children.
648	<	*/
649	<	private void fixDown(int k) {
650	<	int j;
651	<	if (comparator == null) {
652	<	while ((j = k << 1) <= size && (j > 0)) {
653	<	if (j<size &&
654	<	((Comparable<? super E>)queue[j]).compareTo((E)queue[j+1]) > 0)
655	<	j++; // j indexes smallest kid
656	<
657	<	if (((Comparable<? super E>)queue[k]).compareTo((E)queue[j]) <= 0)
658	<	break;
659	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
660	<	k = j;
661	<	}
662	<	} else {
663	<	while ((j = k << 1) <= size && (j > 0)) {
664	<	if (j<size &&
665	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
666	<	j++; // j indexes smallest kid
667	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
668	<	break;
669	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
670	<	k = j;
671	<	}
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	>	* 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		/**
#	Line 646 | Line 707 | public class PriorityQueue<E> extends Ab
707		* assuming nothing about the order of the elements prior to the call.
708		*/
709		private void heapify() {
710	<	for (int i = size/2; i >= 1; i--)
711	<	fixDown(i);
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 the elements in this
716	<	* queue, or <tt>null</tt> if this queue is sorted according to
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 queue, or
720	<	*         <tt>null</tt> if this queue is sorted according to the
721	<	*         natural ordering of its elements.
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
668	<	* is, serialize it).
728	>	* Saves this queue to a stream (that is, serializes it).
729		*
730		* @serialData The length of the array backing the instance is
731	<	* emitted (int), followed by all of its elements (each an
732	<	* <tt>Object</tt>) in the proper order.
673	<	* @param s the stream
731	>	*             emitted (int), followed by all of its elements
732	>	*             (each an {@code Object}) in the proper order.
733		*/
734		private void writeObject(java.io.ObjectOutputStream s)
735	<	throws java.io.IOException{
735	>	throws java.io.IOException {
736		// Write out element count, and any hidden stuff
737		s.defaultWriteObject();
738
739	<	// Write out array length
740	<	s.writeInt(queue.length);
739	>	// Write out array length, for compatibility with 1.5 version
740	>	s.writeInt(Math.max(2, size + 1));
741
742	<	// Write out all elements in the proper order.
743	<	for (int i=1; i<=size; i++)
742	>	// Write out all elements in the "proper order".
743	>	for (int i = 0; i < size; i++)
744		s.writeObject(queue[i]);
745		}
746
747		/**
748	<	* Reconstitute the <tt>PriorityQueue</tt> instance from a stream
690	<	* (that is, deserialize it).
691	<	* @param s the stream
748	>	* Reconstitutes this queue from a stream (that is, deserializes it).
749		*/
750		private void readObject(java.io.ObjectInputStream s)
751		throws java.io.IOException, ClassNotFoundException {
752		// Read in size, and any hidden stuff
753		s.defaultReadObject();
754
755	<	// Read in array length and allocate array
756	<	int arrayLength = s.readInt();
757	<	queue = new Object[arrayLength];
758	<
702	<	// Read in all elements in the proper order.
703	<	for (int i=1; i<=size; i++)
704	<	queue[i] = (E) s.readObject();
705	<	}
755	>	// Read in (and discard) array length
756	>	s.readInt();
757	>
758	>	queue = new Object[size];
759
760	+	// Read in all elements.
761	+	for (int i = 0; i < size; i++)
762	+	queue[i] = s.readObject();
763	+
764	+	// Elements are guaranteed to be in "proper order", but the
765	+	// spec has never explained what that might be.
766	+	heapify();
767	+	}
768		}

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