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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.52 by dl, Tue Nov 22 11:44:47 2005 UTC vs.
Revision 1.71 by jsr166, Sun Sep 5 21:32:19 2010 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
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 enqueing and dequeing methods
67	>	* ({@code offer}, {@code poll}, {@code remove()} and {@code add});
68	>	* linear time for the {@code remove(Object)} and {@code contains(Object)}
69	>	* methods; and constant time for the retrieval methods
70	>	* ({@code peek}, {@code element}, and {@code size}).
71		*
72		* <p>This class is a member of the
73	<	* <a href="{@docRoot}/../guide/collections/index.html">
73	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
74		* Java Collections Framework</a>.
75	+	*
76		* @since 1.5
77	<	* @version 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		public class PriorityQueue<E> extends AbstractQueue<E>
#	Line 68 | Line 85 | public class PriorityQueue<E> extends Ab
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	<	*
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.
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 100 | 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
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		*/
#	Line 109 | Line 121 | public class PriorityQueue<E> extends Ab
121		}
122
123		/**
124	<	* Creates a <tt>PriorityQueue</tt> with the specified initial
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 <tt>initialCapacity</tt> is less
130	<	* than 1
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 that will be used to order
142	<	*         this priority queue.  If <tt>null</tt>, the <i>natural
143	<	*         ordering</i> of the elements will be used.
144	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is
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,
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,
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.
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
#	Line 201 | Line 170 | public class PriorityQueue<E> extends Ab
170		* @throws NullPointerException if the specified collection or any
171		*         of its elements are null
172		*/
173	+	@SuppressWarnings("unchecked")
174		public PriorityQueue(Collection<? extends E> c) {
175	<	initializeArray(c);
176	<	if (c instanceof SortedSet) {
177	<	SortedSet<? extends E> s = (SortedSet<? extends E>)c;
178	<	comparator = (Comparator<? super E>)s.comparator();
179	<	fillFromSorted(s);
180	<	} else if (c instanceof PriorityQueue) {
181	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
182	<	comparator = (Comparator<? super E>)s.comparator();
183	<	fillFromSorted(s);
184	<	} else {
185	<	comparator = null;
186	<	fillFromUnsorted(c);
175	>	if (c instanceof SortedSet<?>) {
176	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
177	>	this.comparator = (Comparator<? super E>) ss.comparator();
178	>	initElementsFromCollection(ss);
179	>	}
180	>	else if (c instanceof PriorityQueue<?>) {
181	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
182	>	this.comparator = (Comparator<? super E>) pq.comparator();
183	>	initFromPriorityQueue(pq);
184	>	}
185	>	else {
186	>	this.comparator = null;
187	>	initFromCollection(c);
188		}
189		}
190
191		/**
192	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
193	<	* 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
192	>	* Creates a {@code PriorityQueue} containing the elements in the
193	>	* specified priority queue.  This priority queue will be
194		* ordered according to the same ordering as the given priority
195		* queue.
196		*
197		* @param  c the priority queue whose elements are to be placed
198		*         into this priority queue
199	<	* @throws ClassCastException if elements of <tt>c</tt> cannot be
200	<	*         compared to one another according to <tt>c</tt>'s
199	>	* @throws ClassCastException if elements of {@code c} cannot be
200	>	*         compared to one another according to {@code c}'s
201		*         ordering
202		* @throws NullPointerException if the specified priority queue or any
203		*         of its elements are null
204		*/
205	+	@SuppressWarnings("unchecked")
206		public PriorityQueue(PriorityQueue<? extends E> c) {
207	<	initializeArray(c);
208	<	comparator = (Comparator<? super E>)c.comparator();
239	<	fillFromSorted(c);
207	>	this.comparator = (Comparator<? super E>) c.comparator();
208	>	initFromPriorityQueue(c);
209		}
210
211		/**
212	<	* Creates a <tt>PriorityQueue</tt> containing the elements in the
213	<	* 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
212	>	* Creates a {@code PriorityQueue} containing the elements in the
213	>	* specified sorted set.   This priority queue will be ordered
214		* according to the same ordering as the given sorted set.
215		*
216		* @param  c the sorted set whose elements are to be placed
217	<	*         into this priority queue.
217	>	*         into this priority queue
218		* @throws ClassCastException if elements of the specified sorted
219		*         set cannot be compared to one another according to the
220		*         sorted set's ordering
221		* @throws NullPointerException if the specified sorted set or any
222		*         of its elements are null
223		*/
224	+	@SuppressWarnings("unchecked")
225		public PriorityQueue(SortedSet<? extends E> c) {
226	<	initializeArray(c);
227	<	comparator = (Comparator<? super E>)c.comparator();
260	<	fillFromSorted(c);
226	>	this.comparator = (Comparator<? super E>) c.comparator();
227	>	initElementsFromCollection(c);
228		}
229
230	+	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
231	+	if (c.getClass() == PriorityQueue.class) {
232	+	this.queue = c.toArray();
233	+	this.size = c.size();
234	+	} else {
235	+	initFromCollection(c);
236	+	}
237	+	}
238	+
239	+	private void initElementsFromCollection(Collection<? extends E> c) {
240	+	Object[] a = c.toArray();
241	+	// If c.toArray incorrectly doesn't return Object[], copy it.
242	+	if (a.getClass() != Object[].class)
243	+	a = Arrays.copyOf(a, a.length, Object[].class);
244	+	int len = a.length;
245	+	if (len == 1 || this.comparator != null)
246	+	for (int i = 0; i < len; i++)
247	+	if (a[i] == null)
248	+	throw new NullPointerException();
249	+	this.queue = a;
250	+	this.size = a.length;
251	+	}
252	+
253	+	/**
254	+	* Initializes queue array with elements from the given Collection.
255	+	*
256	+	* @param c the collection
257	+	*/
258	+	private void initFromCollection(Collection<? extends E> c) {
259	+	initElementsFromCollection(c);
260	+	heapify();
261	+	}
262	+
263	+	/**
264	+	* The maximum size of array to allocate.
265	+	* Some VMs reserve some header words in an array.
266	+	* Attempts to allocate larger arrays may result in
267	+	* OutOfMemoryError: Requested array size exceeds VM limit
268	+	*/
269	+	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
270	+
271		/**
272	<	* Resize array, if necessary, to be able to hold given index.
272	>	* Increases the capacity of the array.
273	>	*
274	>	* @param minCapacity the desired minimum capacity
275		*/
276	<	private void grow(int index) {
277	<	int newlen = queue.length;
278	<	if (index < newlen) // don't need to grow
279	<	return;
280	<	if (index == Integer.MAX_VALUE)
276	>	private void grow(int minCapacity) {
277	>	int oldCapacity = queue.length;
278	>	// Double size if small; else grow by 50%
279	>	int newCapacity = oldCapacity + ((oldCapacity < 64) ?
280	>	(oldCapacity + 2) :
281	>	(oldCapacity >> 1));
282	>	// overflow-conscious code
283	>	if (newCapacity - MAX_ARRAY_SIZE > 0)
284	>	newCapacity = hugeCapacity(minCapacity);
285	>	queue = Arrays.copyOf(queue, newCapacity);
286	>	}
287	>
288	>	private static int hugeCapacity(int minCapacity) {
289	>	if (minCapacity < 0) // overflow
290		throw new OutOfMemoryError();
291	<	while (newlen <= index) {
292	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
293	<	newlen = Integer.MAX_VALUE;
275	<	else
276	<	newlen <<= 2;
277	<	}
278	<	queue = Arrays.copyOf(queue, newlen);
291	>	return (minCapacity > MAX_ARRAY_SIZE) ?
292	>	Integer.MAX_VALUE :
293	>	MAX_ARRAY_SIZE;
294		}
295
296		/**
297		* Inserts the specified element into this priority queue.
298		*
299	<	* @return <tt>true</tt> (as specified by {@link Collection#add})
299	>	* @return {@code true} (as specified by {@link Collection#add})
300		* @throws ClassCastException if the specified element cannot be
301		*         compared with elements currently in this priority queue
302		*         according to the priority queue's ordering
#	Line 294 | Line 309 | public class PriorityQueue<E> extends Ab
309		/**
310		* Inserts the specified element into this priority queue.
311		*
312	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
312	>	* @return {@code true} (as specified by {@link Queue#offer})
313		* @throws ClassCastException if the specified element cannot be
314		*         compared with elements currently in this priority queue
315		*         according to the priority queue's ordering
#	Line 304 | Line 319 | public class PriorityQueue<E> extends Ab
319		if (e == null)
320		throw new NullPointerException();
321		modCount++;
322	<	++size;
323	<
324	<	// Grow backing store if necessary
325	<	if (size >= queue.length)
326	<	grow(size);
327	<
328	<	queue[size] = e;
329	<	fixUp(size);
322	>	int i = size;
323	>	if (i >= queue.length)
324	>	grow(i + 1);
325	>	size = i + 1;
326	>	if (i == 0)
327	>	queue[0] = e;
328	>	else
329	>	siftUp(i, e);
330		return true;
331		}
332
333		public E peek() {
334		if (size == 0)
335		return null;
336	<	return (E) queue[1];
336	>	return (E) queue[0];
337		}
338
339		private int indexOf(Object o) {
340	<	if (o == null)
341	<	return -1;
342	<	for (int i = 1; i <= size; i++)
343	<	if (o.equals(queue[i]))
344	<	return i;
340	>	if (o != null) {
341	>	for (int i = 0; i < size; i++)
342	>	if (o.equals(queue[i]))
343	>	return i;
344	>	}
345		return -1;
346		}
347
348		/**
349		* Removes a single instance of the specified element from this queue,
350	<	* if it is present.  More formally, removes an element <tt>e</tt> such
351	<	* that <tt>o.equals(e)</tt>, if this queue contains one or more such
352	<	* elements.  Returns true if this queue contained the specified element
353	<	* (or equivalently, if this queue changed as a result of the call).
350	>	* if it is present.  More formally, removes an element {@code e} such
351	>	* that {@code o.equals(e)}, if this queue contains one or more such
352	>	* elements.  Returns {@code true} if and only if this queue contained
353	>	* the specified element (or equivalently, if this queue changed as a
354	>	* result of the call).
355		*
356		* @param o element to be removed from this queue, if present
357	<	* @return <tt>true</tt> if this queue changed as a result of the call
357	>	* @return {@code true} if this queue changed as a result of the call
358		*/
359		public boolean remove(Object o) {
360	<	int i = indexOf(o);
361	<	if (i == -1)
362	<	return false;
363	<	else {
364	<	removeAt(i);
365	<	return true;
366	<	}
360	>	int i = indexOf(o);
361	>	if (i == -1)
362	>	return false;
363	>	else {
364	>	removeAt(i);
365	>	return true;
366	>	}
367	>	}
368	>
369	>	/**
370	>	* Version of remove using reference equality, not equals.
371	>	* Needed by iterator.remove.
372	>	*
373	>	* @param o element to be removed from this queue, if present
374	>	* @return {@code true} if removed
375	>	*/
376	>	boolean removeEq(Object o) {
377	>	for (int i = 0; i < size; i++) {
378	>	if (o == queue[i]) {
379	>	removeAt(i);
380	>	return true;
381	>	}
382	>	}
383	>	return false;
384		}
385
386		/**
387	<	* Returns <tt>true</tt> if this queue contains the specified element.
388	<	* More formally, returns <tt>true</tt> if and only if this queue contains
389	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
387	>	* Returns {@code true} if this queue contains the specified element.
388	>	* More formally, returns {@code true} if and only if this queue contains
389	>	* at least one element {@code e} such that {@code o.equals(e)}.
390		*
391		* @param o object to be checked for containment in this queue
392	<	* @return <tt>true</tt> if this queue contains the specified element
392	>	* @return {@code true} if this queue contains the specified element
393		*/
394		public boolean contains(Object o) {
395	<	return indexOf(o) != -1;
395	>	return indexOf(o) != -1;
396		}
397
398		/**
399	<	* Returns an array containing all of the elements in this queue,
399	>	* Returns an array containing all of the elements in this queue.
400		* The elements are in no particular order.
401		*
402		* <p>The returned array will be "safe" in that no references to it are
403	<	* maintained by this list.  (In other words, this method must allocate
403	>	* maintained by this queue.  (In other words, this method must allocate
404		* a new array).  The caller is thus free to modify the returned array.
405		*
406	<	* @return an array containing all of the elements in this queue.
406	>	* <p>This method acts as bridge between array-based and collection-based
407	>	* APIs.
408	>	*
409	>	* @return an array containing all of the elements in this queue
410		*/
411		public Object[] toArray() {
412	<	return Arrays.copyOfRange(queue, 1, size+1);
412	>	return Arrays.copyOf(queue, size);
413		}
414
415		/**
416	<	* Returns an array containing all of the elements in this queue.
417	<	* The elements are in no particular order.  The runtime type of
418	<	* the returned array is that of the specified array.  If the queue
419	<	* fits in the specified array, it is returned therein.
420	<	* Otherwise, a new array is allocated with the runtime type of
421	<	* the specified array and the size of this queue.
416	>	* Returns an array containing all of the elements in this queue; the
417	>	* runtime type of the returned array is that of the specified array.
418	>	* The returned array elements are in no particular order.
419	>	* If the queue fits in the specified array, it is returned therein.
420	>	* Otherwise, a new array is allocated with the runtime type of the
421	>	* specified array and the size of this queue.
422		*
423		* <p>If the queue fits in the specified array with room to spare
424		* (i.e., the array has more elements than the queue), the element in
425		* the array immediately following the end of the collection is set to
426	<	* <tt>null</tt>.  (This is useful in determining the length of the
427	<	* queue <i>only</i> if the caller knows that the queue does not contain
428	<	* any null elements.)
426	>	* {@code null}.
427	>	*
428	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
429	>	* array-based and collection-based APIs.  Further, this method allows
430	>	* precise control over the runtime type of the output array, and may,
431	>	* under certain circumstances, be used to save allocation costs.
432	>	*
433	>	* <p>Suppose <tt>x</tt> is a queue known to contain only strings.
434	>	* The following code can be used to dump the queue into a newly
435	>	* allocated array of <tt>String</tt>:
436	>	*
437	>	* <pre>
438	>	*     String[] y = x.toArray(new String[0]);</pre>
439	>	*
440	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
441	>	* <tt>toArray()</tt>.
442		*
443		* @param a the array into which the elements of the queue are to
444		*          be stored, if it is big enough; otherwise, a new array of the
445		*          same runtime type is allocated for this purpose.
446	<	* @return an array containing the elements of the queue
446	>	* @return an array containing all of the elements in this queue
447		* @throws ArrayStoreException if the runtime type of the specified array
448		*         is not a supertype of the runtime type of every element in
449		*         this queue
#	Line 403 | Line 452 | public class PriorityQueue<E> extends Ab
452		public <T> T[] toArray(T[] a) {
453		if (a.length < size)
454		// Make a new array of a's runtime type, but my contents:
455	<	return (T[]) Arrays.copyOfRange(queue, 1, size+1, a.getClass());
456	<	System.arraycopy(queue, 1, a, 0, size);
455	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
456	>	System.arraycopy(queue, 0, a, 0, size);
457		if (a.length > size)
458		a[size] = null;
459		return a;
#	Line 420 | Line 469 | public class PriorityQueue<E> extends Ab
469		return new Itr();
470		}
471
472	<	private class Itr implements Iterator<E> {
424	<
472	>	private final class Itr implements Iterator<E> {
473		/**
474		* Index (into queue array) of element to be returned by
475		* subsequent call to next.
476		*/
477	<	private int cursor = 1;
477	>	private int cursor = 0;
478
479		/**
480		* Index of element returned by most recent call to next,
481		* unless that element came from the forgetMeNot list.
482	<	* Reset to 0 if element is deleted by a call to remove.
482	>	* Set to -1 if element is deleted by a call to remove.
483		*/
484	<	private int lastRet = 0;
484	>	private int lastRet = -1;
485
486		/**
487	<	* 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
487	>	* A queue of elements that were moved from the unvisited portion of
488		* the heap into the visited portion as a result of "unlucky" element
489		* removals during the iteration.  (Unlucky element removals are those
490	<	* that require a fixup instead of a fixdown.)  We must visit all of
490	>	* that require a siftup instead of a siftdown.)  We must visit all of
491		* the elements in this list to complete the iteration.  We do this
492		* after we've completed the "normal" iteration.
493		*
494		* We expect that most iterations, even those involving removals,
495	<	* will not use need to store elements in this field.
495	>	* will not need to store elements in this field.
496		*/
497	<	private ArrayList<E> forgetMeNot = null;
497	>	private ArrayDeque<E> forgetMeNot = null;
498
499		/**
500		* Element returned by the most recent call to next iff that
501		* element was drawn from the forgetMeNot list.
502		*/
503	<	private Object lastRetElt = null;
503	>	private E lastRetElt = null;
504	>
505	>	/**
506	>	* The modCount value that the iterator believes that the backing
507	>	* Queue should have.  If this expectation is violated, the iterator
508	>	* has detected concurrent modification.
509	>	*/
510	>	private int expectedModCount = modCount;
511
512		public boolean hasNext() {
513	<	return cursor <= size || forgetMeNot != null;
513	>	return cursor < size ||
514	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
515		}
516
517		public E next() {
518	<	checkForComodification();
519	<	E result;
520	<	if (cursor <= size) {
521	<	result = (E) queue[cursor];
522	<	lastRet = cursor++;
523	<	}
524	<	else if (forgetMeNot == null)
525	<	throw new NoSuchElementException();
526	<	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;
518	>	if (expectedModCount != modCount)
519	>	throw new ConcurrentModificationException();
520	>	if (cursor < size)
521	>	return (E) queue[lastRet = cursor++];
522	>	if (forgetMeNot != null) {
523	>	lastRet = -1;
524	>	lastRetElt = forgetMeNot.poll();
525	>	if (lastRetElt != null)
526	>	return lastRetElt;
527		}
528	<	return result;
528	>	throw new NoSuchElementException();
529		}
530
531		public void remove() {
532	<	checkForComodification();
533	<
534	<	if (lastRet != 0) {
532	>	if (expectedModCount != modCount)
533	>	throw new ConcurrentModificationException();
534	>	if (lastRet != -1) {
535		E moved = PriorityQueue.this.removeAt(lastRet);
536	<	lastRet = 0;
537	<	if (moved == null) {
536	>	lastRet = -1;
537	>	if (moved == null)
538		cursor--;
539	<	} else {
539	>	else {
540		if (forgetMeNot == null)
541	<	forgetMeNot = new ArrayList<E>();
541	>	forgetMeNot = new ArrayDeque<E>();
542		forgetMeNot.add(moved);
543		}
544		} else if (lastRetElt != null) {
545	<	PriorityQueue.this.remove(lastRetElt);
545	>	PriorityQueue.this.removeEq(lastRetElt);
546		lastRetElt = null;
547		} else {
548		throw new IllegalStateException();
549		}
507	–
550		expectedModCount = modCount;
551		}
510	–
511	–	final void checkForComodification() {
512	–	if (modCount != expectedModCount)
513	–	throw new ConcurrentModificationException();
514	–	}
552		}
553
554		public int size() {
#	Line 524 | Line 561 | public class PriorityQueue<E> extends Ab
561		*/
562		public void clear() {
563		modCount++;
564	<
528	<	// Null out element references to prevent memory leak
529	<	for (int i=1; i<=size; i++)
564	>	for (int i = 0; i < size; i++)
565		queue[i] = null;
531	–
566		size = 0;
567		}
568
569		public E poll() {
570		if (size == 0)
571		return null;
572	+	int s = --size;
573		modCount++;
574	<
575	<	E result = (E) queue[1];
576	<	queue[1] = queue[size];
577	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
578	<	if (size > 1)
544	<	fixDown(1);
545	<
574	>	E result = (E) queue[0];
575	>	E x = (E) queue[s];
576	>	queue[s] = null;
577	>	if (s != 0)
578	>	siftDown(0, x);
579		return result;
580		}
581
582		/**
583	<	* Removes and returns the ith element from queue.  (Recall that queue
551	<	* is one-based, so 1 <= i <= size.)
583	>	* Removes the ith element from queue.
584		*
585	<	* Normally this method leaves the elements at positions from 1 up to i-1,
586	<	* inclusive, untouched.  Under these circumstances, it returns null.
587	<	* Occasionally, in order to maintain the heap invariant, it must move
588	<	* the last element of the list to some index in the range [2, i-1],
589	<	* and move the element previously at position (i/2) to position i.
590	<	* Under these circumstances, this method returns the element that was
591	<	* previously at the end of the list and is now at some position between
592	<	* 2 and i-1 inclusive.
585	>	* Normally this method leaves the elements at up to i-1,
586	>	* inclusive, untouched.  Under these circumstances, it returns
587	>	* null.  Occasionally, in order to maintain the heap invariant,
588	>	* it must swap a later element of the list with one earlier than
589	>	* i.  Under these circumstances, this method returns the element
590	>	* that was previously at the end of the list and is now at some
591	>	* position before i. This fact is used by iterator.remove so as to
592	>	* avoid missing traversing elements.
593		*/
594		private E removeAt(int i) {
595	<	assert i > 0 && i <= size;
595	>	assert i >= 0 && i < size;
596		modCount++;
597	<
598	<	E moved = (E) queue[size];
599	<	queue[i] = moved;
600	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
601	<	if (i <= size) {
602	<	fixDown(i);
597	>	int s = --size;
598	>	if (s == i) // removed last element
599	>	queue[i] = null;
600	>	else {
601	>	E moved = (E) queue[s];
602	>	queue[s] = null;
603	>	siftDown(i, moved);
604		if (queue[i] == moved) {
605	<	fixUp(i);
605	>	siftUp(i, moved);
606		if (queue[i] != moved)
607		return moved;
608		}
#	Line 578 | Line 611 | public class PriorityQueue<E> extends Ab
611		}
612
613		/**
614	<	* Establishes the heap invariant (described above) assuming the heap
615	<	* satisfies the invariant except possibly for the leaf-node indexed by k
616	<	* (which may have a nextExecutionTime less than its parent's).
617	<	*
618	<	* This method functions by "promoting" queue[k] up the hierarchy
619	<	* (by swapping it with its parent) repeatedly until queue[k]
620	<	* is greater than or equal to its parent.
621	<	*/
622	<	private void fixUp(int k) {
623	<	if (comparator == null) {
624	<	while (k > 1) {
625	<	int j = k >> 1;
626	<	if (((Comparable<? super E>)queue[j]).compareTo((E)queue[k]) <= 0)
627	<	break;
628	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
629	<	k = j;
630	<	}
631	<	} else {
632	<	while (k > 1) {
633	<	int j = k >>> 1;
634	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
635	<	break;
636	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
637	<	k = j;
638	<	}
639	<	}
640	<	}
641	<
642	<	/**
643	<	* Establishes the heap invariant (described above) in the subtree
644	<	* rooted at k, which is assumed to satisfy the heap invariant except
645	<	* possibly for node k itself (which may be greater than its children).
646	<	*
647	<	* This method functions by "demoting" queue[k] down the hierarchy
648	<	* (by swapping it with its smaller child) repeatedly until queue[k]
649	<	* is less than or equal to its children.
650	<	*/
651	<	private void fixDown(int k) {
652	<	int j;
653	<	if (comparator == null) {
654	<	while ((j = k << 1) <= size && (j > 0)) {
655	<	if (j<size &&
656	<	((Comparable<? super E>)queue[j]).compareTo((E)queue[j+1]) > 0)
657	<	j++; // j indexes smallest kid
658	<
659	<	if (((Comparable<? super E>)queue[k]).compareTo((E)queue[j]) <= 0)
660	<	break;
661	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
662	<	k = j;
663	<	}
664	<	} else {
665	<	while ((j = k << 1) <= size && (j > 0)) {
666	<	if (j<size &&
667	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
668	<	j++; // j indexes smallest kid
669	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
670	<	break;
671	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
672	<	k = j;
673	<	}
614	>	* Inserts item x at position k, maintaining heap invariant by
615	>	* promoting x up the tree until it is greater than or equal to
616	>	* its parent, or is the root.
617	>	*
618	>	* To simplify and speed up coercions and comparisons. the
619	>	* Comparable and Comparator versions are separated into different
620	>	* methods that are otherwise identical. (Similarly for siftDown.)
621	>	*
622	>	* @param k the position to fill
623	>	* @param x the item to insert
624	>	*/
625	>	private void siftUp(int k, E x) {
626	>	if (comparator != null)
627	>	siftUpUsingComparator(k, x);
628	>	else
629	>	siftUpComparable(k, x);
630	>	}
631	>
632	>	private void siftUpComparable(int k, E x) {
633	>	Comparable<? super E> key = (Comparable<? super E>) x;
634	>	while (k > 0) {
635	>	int parent = (k - 1) >>> 1;
636	>	Object e = queue[parent];
637	>	if (key.compareTo((E) e) >= 0)
638	>	break;
639	>	queue[k] = e;
640	>	k = parent;
641	>	}
642	>	queue[k] = key;
643	>	}
644	>
645	>	private void siftUpUsingComparator(int k, E x) {
646	>	while (k > 0) {
647	>	int parent = (k - 1) >>> 1;
648	>	Object e = queue[parent];
649	>	if (comparator.compare(x, (E) e) >= 0)
650	>	break;
651	>	queue[k] = e;
652	>	k = parent;
653	>	}
654	>	queue[k] = x;
655	>	}
656	>
657	>	/**
658	>	* Inserts item x at position k, maintaining heap invariant by
659	>	* demoting x down the tree repeatedly until it is less than or
660	>	* equal to its children or is a leaf.
661	>	*
662	>	* @param k the position to fill
663	>	* @param x the item to insert
664	>	*/
665	>	private void siftDown(int k, E x) {
666	>	if (comparator != null)
667	>	siftDownUsingComparator(k, x);
668	>	else
669	>	siftDownComparable(k, x);
670	>	}
671	>
672	>	private void siftDownComparable(int k, E x) {
673	>	Comparable<? super E> key = (Comparable<? super E>)x;
674	>	int half = size >>> 1;        // loop while a non-leaf
675	>	while (k < half) {
676	>	int child = (k << 1) + 1; // assume left child is least
677	>	Object c = queue[child];
678	>	int right = child + 1;
679	>	if (right < size &&
680	>	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
681	>	c = queue[child = right];
682	>	if (key.compareTo((E) c) <= 0)
683	>	break;
684	>	queue[k] = c;
685	>	k = child;
686	>	}
687	>	queue[k] = key;
688	>	}
689	>
690	>	private void siftDownUsingComparator(int k, E x) {
691	>	int half = size >>> 1;
692	>	while (k < half) {
693	>	int child = (k << 1) + 1;
694	>	Object c = queue[child];
695	>	int right = child + 1;
696	>	if (right < size &&
697	>	comparator.compare((E) c, (E) queue[right]) > 0)
698	>	c = queue[child = right];
699	>	if (comparator.compare(x, (E) c) <= 0)
700	>	break;
701	>	queue[k] = c;
702	>	k = child;
703		}
704	+	queue[k] = x;
705		}
706
707		/**
#	Line 646 | Line 709 | public class PriorityQueue<E> extends Ab
709		* assuming nothing about the order of the elements prior to the call.
710		*/
711		private void heapify() {
712	<	for (int i = size/2; i >= 1; i--)
713	<	fixDown(i);
712	>	for (int i = (size >>> 1) - 1; i >= 0; i--)
713	>	siftDown(i, (E) queue[i]);
714		}
715
716		/**
717		* Returns the comparator used to order the elements in this
718	<	* queue, or <tt>null</tt> if this queue is sorted according to
718	>	* queue, or {@code null} if this queue is sorted according to
719		* the {@linkplain Comparable natural ordering} of its elements.
720		*
721		* @return the comparator used to order this queue, or
722	<	*         <tt>null</tt> if this queue is sorted according to the
723	<	*         natural ordering of its elements.
722	>	*         {@code null} if this queue is sorted according to the
723	>	*         natural ordering of its elements
724		*/
725		public Comparator<? super E> comparator() {
726		return comparator;
727		}
728
729		/**
730	<	* Save the state of the instance to a stream (that
731	<	* is, serialize it).
730	>	* Saves the state of the instance to a stream (that
731	>	* is, serializes it).
732		*
733		* @serialData The length of the array backing the instance is
734	<	* emitted (int), followed by all of its elements (each an
735	<	* <tt>Object</tt>) in the proper order.
734	>	*             emitted (int), followed by all of its elements
735	>	*             (each an {@code Object}) in the proper order.
736		* @param s the stream
737		*/
738		private void writeObject(java.io.ObjectOutputStream s)
#	Line 677 | Line 740 | public class PriorityQueue<E> extends Ab
740		// Write out element count, and any hidden stuff
741		s.defaultWriteObject();
742
743	<	// Write out array length
744	<	s.writeInt(queue.length);
743	>	// Write out array length, for compatibility with 1.5 version
744	>	s.writeInt(Math.max(2, size + 1));
745
746	<	// Write out all elements in the proper order.
747	<	for (int i=1; i<=size; i++)
746	>	// Write out all elements in the "proper order".
747	>	for (int i = 0; i < size; i++)
748		s.writeObject(queue[i]);
749		}
750
751		/**
752	<	* Reconstitute the <tt>PriorityQueue</tt> instance from a stream
753	<	* (that is, deserialize it).
752	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
753	>	* (that is, deserializes it).
754	>	*
755		* @param s the stream
756		*/
757		private void readObject(java.io.ObjectInputStream s)
#	Line 695 | Line 759 | public class PriorityQueue<E> extends Ab
759		// Read in size, and any hidden stuff
760		s.defaultReadObject();
761
762	<	// Read in array length and allocate array
763	<	int arrayLength = s.readInt();
764	<	queue = new Object[arrayLength];
765	<
702	<	// Read in all elements in the proper order.
703	<	for (int i=1; i<=size; i++)
704	<	queue[i] = (E) s.readObject();
705	<	}
762	>	// Read in (and discard) array length
763	>	s.readInt();
764	>
765	>	queue = new Object[size];
766
767	+	// Read in all elements.
768	+	for (int i = 0; i < size; i++)
769	+	queue[i] = s.readObject();
770	+
771	+	// Elements are guaranteed to be in "proper order", but the
772	+	// spec has never explained what that might be.
773	+	heapify();
774	+	}
775		}

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