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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.6 by brian, Mon Jun 23 02:26:15 2003 UTC vs.
Revision 1.61 by jsr166, Tue Feb 7 20:54:24 2006 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* %W% %E%
3	>	*
4	>	* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
5	>	* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6	>	*/
7	>
8	>	package java.util;
9
10		/**
11	<	* An unbounded priority queue based on a priority heap.  This queue orders
12	<	* elements according to an order specified at construction time, which is
13	<	* specified in the same manner as {@link TreeSet} and {@link TreeMap}: elements are ordered
14	<	* either according to their <i>natural order</i> (see {@link Comparable}), or
15	<	* according to a {@link Comparator}, depending on which constructor is used.
16	<	* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the
17	<	* minimal element with respect to the specified ordering.  If multiple
18	<	* elements are tied for least value, no guarantees are made as to
19	<	* which of these elements is returned.
11	>	* An unbounded priority {@linkplain Queue queue} based on a priority
12	>	* heap.  The elements of the priority queue are ordered according to
13	>	* their {@linkplain Comparable natural ordering}, or by a {@link
14	>	* Comparator} provided at queue construction time, depending on which
15	>	* constructor is used.  A priority queue does not permit
16	>	* <tt>null</tt> elements.  A priority queue relying on natural
17	>	* ordering also does not permit insertion of non-comparable objects
18	>	* (doing so may result in <tt>ClassCastException</tt>).
19	>	*
20	>	* <p>The <em>head</em> of this queue is the <em>least</em> element
21	>	* with respect to the specified ordering.  If multiple elements are
22	>	* tied for least value, the head is one of those elements -- ties are
23	>	* broken arbitrarily.  The queue retrieval operations <tt>poll</tt>,
24	>	* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the
25	>	* element at the head of the queue.
26		*
27	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the size of
28	<	* the array used internally to store the elements on the queue.  It is always at least
29	<	* as large as the queue size.  As elements are added to a priority queue,
30	<	* its capacity grows automatically.  The details of the growth policy are not
27	>	* <p>A priority queue is unbounded, but has an internal
28	>	* <i>capacity</i> governing the size of an array used to store the
29	>	* elements on the queue.  It is always at least as large as the queue
30	>	* size.  As elements are added to a priority queue, its capacity
31	>	* grows automatically.  The details of the growth policy are not
32		* specified.
33		*
34	<	*<p>Implementation note: this implementation provides O(log(n)) time for
35	<	* the insertion methods (<tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>)
36	<	* methods; linear time for the <tt>remove(Object)</tt> and
37	<	* <tt>contains(Object)</tt> methods; and constant time for the retrieval methods (<tt>peek</tt>,
34	>	* <p>This class and its iterator implement all of the
35	>	* <em>optional</em> methods of the {@link Collection} and {@link
36	>	* Iterator} interfaces.  The Iterator provided in method {@link
37	>	* #iterator()} is <em>not</em> guaranteed to traverse the elements of
38	>	* the priority queue in any particular order. If you need ordered
39	>	* traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.
40	>	*
41	>	* <p> <strong>Note that this implementation is not synchronized.</strong>
42	>	* Multiple threads should not access a <tt>PriorityQueue</tt>
43	>	* instance concurrently if any of the threads modifies the list
44	>	* structurally. Instead, use the thread-safe {@link
45	>	* java.util.concurrent.PriorityBlockingQueue} class.
46	>	*
47	>	* <p>Implementation note: this implementation provides O(log(n)) time
48	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
49	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
50	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
51	>	* constant time for the retrieval methods (<tt>peek</tt>,
52		* <tt>element</tt>, and <tt>size</tt>).
53		*
54		* <p>This class is a member of the
55		* <a href="{@docRoot}/../guide/collections/index.html">
56		* Java Collections Framework</a>.
57	+	* @since 1.5
58	+	* @version 1.8, 08/27/05
59	+	* @author Josh Bloch
60	+	* @param <E> the type of elements held in this collection
61		*/
62		public class PriorityQueue<E> extends AbstractQueue<E>
63	<	implements Queue<E>
64	<	{
63	>	implements java.io.Serializable {
64	>
65	>	private static final long serialVersionUID = -7720805057305804111L;
66	>
67		private static final int DEFAULT_INITIAL_CAPACITY = 11;
68
69		/**
70	<	* Priority queue represented as a balanced binary heap: the two children
71	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
72	<	* ordered by comparator, or by the elements' natural ordering, if
73	<	* comparator is null:  For each node n in the heap and each descendant d
74	<	* of n, n <= d.
75	<	*
42	<	* The element with the lowest value is in queue[1], assuming the queue is
43	<	* nonempty.  (A one-based array is used in preference to the traditional
44	<	* zero-based array to simplify parent and child calculations.)
45	<	*
46	<	* queue.length must be >= 2, even if size == 0.
70	>	* Priority queue represented as a balanced binary heap: the two
71	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
72	>	* priority queue is ordered by comparator, or by the elements'
73	>	* natural ordering, if comparator is null: For each node n in the
74	>	* heap and each descendant d of n, n <= d.  The element with the
75	>	* lowest value is in queue[0], assuming the queue is nonempty.
76		*/
77	<	private transient E[] queue;
77	>	private transient Object[] queue;
78
79		/**
80		* The number of elements in the priority queue.
#	Line 56 | Line 85 | public class PriorityQueue<E> extends Ab
85		* The comparator, or null if priority queue uses elements'
86		* natural ordering.
87		*/
88	<	private final Comparator<E> comparator;
88	>	private final Comparator<? super E> comparator;
89
90		/**
91		* The number of times this priority queue has been
#	Line 65 | Line 94 | public class PriorityQueue<E> extends Ab
94		private transient int modCount = 0;
95
96		/**
97	<	* Create a new priority queue with the default initial capacity (11)
98	<	* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.)
97	>	* Creates a <tt>PriorityQueue</tt> with the default initial
98	>	* capacity (11) that orders its elements according to their
99	>	* {@linkplain Comparable natural ordering}.
100		*/
101		public PriorityQueue() {
102	<	this(DEFAULT_INITIAL_CAPACITY);
102	>	this(DEFAULT_INITIAL_CAPACITY, null);
103		}
104
105		/**
106	<	* Create a new priority queue with the specified initial capacity
107	<	* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.)
106	>	* Creates a <tt>PriorityQueue</tt> with the specified initial
107	>	* capacity that orders its elements according to their
108	>	* {@linkplain Comparable natural ordering}.
109		*
110	<	* @param initialCapacity the initial capacity for this priority queue.
110	>	* @param initialCapacity the initial capacity for this priority queue
111	>	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
112	>	* than 1
113		*/
114		public PriorityQueue(int initialCapacity) {
115		this(initialCapacity, null);
116		}
117
118		/**
119	<	* Create a new priority queue with the specified initial capacity (11)
119	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
120		* that orders its elements according to the specified comparator.
121		*
122	<	* @param initialCapacity the initial capacity for this priority queue.
123	<	* @param comparator the comparator used to order this priority queue.
124	<	*/
125	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
122	>	* @param  initialCapacity the initial capacity for this priority queue
123	>	* @param  comparator the comparator that will be used to order
124	>	*         this priority queue.  If <tt>null</tt>, the <i>natural
125	>	*         ordering</i> of the elements will be used.
126	>	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is
127	>	*         less than 1
128	>	*/
129	>	public PriorityQueue(int initialCapacity,
130	>	Comparator<? super E> comparator) {
131	>	// Note: This restriction of at least one is not actually needed,
132	>	// but continues for 1.5 compatibility
133		if (initialCapacity < 1)
134	<	initialCapacity = 1;
135	<	queue = new E[initialCapacity + 1];
134	>	throw new IllegalArgumentException();
135	>	this.queue = new Object[initialCapacity];
136		this.comparator = comparator;
137		}
138
139		/**
140	<	* Create a new priority queue containing the elements in the specified
141	<	* collection.  The priority queue has an initial capacity of 110% of the
142	<	* size of the specified collection. If the specified collection
143	<	* implements the {@link Sorted} interface, the priority queue will be
144	<	* sorted according to the same comparator, or according to its elements'
145	<	* natural order if the collection is sorted according to its elements'
106	<	* natural order.  If the specified collection does not implement
107	<	* <tt>Sorted</tt>, the priority queue is ordered according to
108	<	* its elements' natural order.
140	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
141	>	* specified collection.   If the specified collection is an
142	>	* instance of a {@link java.util.SortedSet} or is another
143	>	* <tt>PriorityQueue</tt>, the priority queue will be ordered
144	>	* according to the same ordering.  Otherwise, this priority queue
145	>	* will be ordered according to the natural ordering of its elements.
146		*
147	<	* @param initialElements the collection whose elements are to be placed
148	<	*        into this priority queue.
147	>	* @param  c the collection whose elements are to be placed
148	>	*         into this priority queue
149		* @throws ClassCastException if elements of the specified collection
150		*         cannot be compared to one another according to the priority
151	<	*         queue's ordering.
152	<	* @throws NullPointerException if the specified collection or an
153	<	*         element of the specified collection is <tt>null</tt>.
154	<	*/
155	<	public PriorityQueue(Collection<E> initialElements) {
156	<	int sz = initialElements.size();
157	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
158	<	Integer.MAX_VALUE - 1);
159	<	if (initialCapacity < 1)
160	<	initialCapacity = 1;
161	<	queue = new E[initialCapacity + 1];
162	<
163	<	/* Commented out to compile with generics compiler
127	<
128	<	if (initialElements instanceof Sorted) {
129	<	comparator = ((Sorted)initialElements).comparator();
130	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
131	<	queue[++size] = i.next();
132	<	} else {
133	<	*/
134	<	{
151	>	*         queue's ordering
152	>	* @throws NullPointerException if the specified collection or any
153	>	*         of its elements are null
154	>	*/
155	>	public PriorityQueue(Collection<? extends E> c) {
156	>	initFromCollection(c);
157	>	if (c instanceof SortedSet)
158	>	comparator = (Comparator<? super E>)
159	>	((SortedSet<? extends E>)c).comparator();
160	>	else if (c instanceof PriorityQueue)
161	>	comparator = (Comparator<? super E>)
162	>	((PriorityQueue<? extends E>)c).comparator();
163	>	else {
164		comparator = null;
165	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
137	<	add(i.next());
165	>	heapify();
166		}
167		}
168
169	<	// Queue Methods
169	>	/**
170	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
171	>	* specified priority queue.  This priority queue will be
172	>	* ordered according to the same ordering as the given priority
173	>	* queue.
174	>	*
175	>	* @param  c the priority queue whose elements are to be placed
176	>	*         into this priority queue
177	>	* @throws ClassCastException if elements of <tt>c</tt> cannot be
178	>	*         compared to one another according to <tt>c</tt>'s
179	>	*         ordering
180	>	* @throws NullPointerException if the specified priority queue or any
181	>	*         of its elements are null
182	>	*/
183	>	public PriorityQueue(PriorityQueue<? extends E> c) {
184	>	comparator = (Comparator<? super E>)c.comparator();
185	>	initFromCollection(c);
186	>	}
187
188		/**
189	<	* Remove and return the minimal element from this priority queue if
190	<	* it contains one or more elements, otherwise return <tt>null</tt>.  The term
191	<	* <i>minimal</i> is defined according to this priority queue's order.
189	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
190	>	* specified sorted set.  This priority queue will be ordered
191	>	* according to the same ordering as the given sorted set.
192		*
193	<	* @return the minimal element from this priority queue if it contains
194	<	*         one or more elements, otherwise <tt>null</tt>.
193	>	* @param  c the sorted set whose elements are to be placed
194	>	*         into this priority queue.
195	>	* @throws ClassCastException if elements of the specified sorted
196	>	*         set cannot be compared to one another according to the
197	>	*         sorted set's ordering
198	>	* @throws NullPointerException if the specified sorted set or any
199	>	*         of its elements are null
200		*/
201	<	public E poll() {
202	<	if (size == 0)
203	<	return null;
154	<	return remove(1);
201	>	public PriorityQueue(SortedSet<? extends E> c) {
202	>	comparator = (Comparator<? super E>)c.comparator();
203	>	initFromCollection(c);
204		}
205
206		/**
207	<	* Return, but do not remove, the minimal element from the priority queue,
208	<	* or return <tt>null</tt> if the queue is empty.  The term <i>minimal</i> is
209	<	* defined according to this priority queue's order.  This method returns
210	<	* the same object reference that would be returned by by the
211	<	* <tt>poll</tt> method.  The two methods differ in that this method
212	<	* does not remove the element from the priority queue.
207	>	* Initialize queue array with elements from the given Collection.
208	>	* @param c the collection
209	>	*/
210	>	private void initFromCollection(Collection<? extends E> c) {
211	>	Object[] a = c.toArray();
212	>	// If c.toArray incorrectly doesn't return Object[], copy it.
213	>	if (a.getClass() != Object[].class)
214	>	a = Arrays.copyOf(a, a.length, Object[].class);
215	>	queue = a;
216	>	size = a.length;
217	>	}
218	>
219	>	/**
220	>	* Increases the capacity of the array.
221		*
222	<	* @return the minimal element from this priority queue if it contains
166	<	*         one or more elements, otherwise <tt>null</tt>.
222	>	* @param minCapacity the desired minimum capacity
223		*/
224	<	public E peek() {
225	<	return queue[1];
224	>	private void grow(int minCapacity) {
225	>	if (minCapacity < 0) // overflow
226	>	throw new OutOfMemoryError();
227	>	int oldCapacity = queue.length;
228	>	// Double size if small; else grow by 50%
229	>	int newCapacity = ((oldCapacity < 64)?
230	>	((oldCapacity + 1) * 2):
231	>	((oldCapacity / 2) * 3));
232	>	if (newCapacity < 0) // overflow
233	>	newCapacity = Integer.MAX_VALUE;
234	>	if (newCapacity < minCapacity)
235	>	newCapacity = minCapacity;
236	>	queue = Arrays.copyOf(queue, newCapacity);
237		}
238
239	<	// Collection Methods
239	>	/**
240	>	* Inserts the specified element into this priority queue.
241	>	*
242	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
243	>	* @throws ClassCastException if the specified element cannot be
244	>	*         compared with elements currently in this priority queue
245	>	*         according to the priority queue's ordering
246	>	* @throws NullPointerException if the specified element is null
247	>	*/
248	>	public boolean add(E e) {
249	>	return offer(e);
250	>	}
251
252		/**
253	<	* Removes a single instance of the specified element from this priority
176	<	* queue, if it is present.  Returns true if this collection contained the
177	<	* specified element (or equivalently, if this collection changed as a
178	<	* result of the call).
253	>	* Inserts the specified element into this priority queue.
254		*
255	<	* @param element the element to be removed from this collection, if present.
256	<	* @return <tt>true</tt> if this collection changed as a result of the
257	<	*         call
258	<	* @throws ClassCastException if the specified element cannot be compared
259	<	*            with elements currently in the priority queue according
185	<	*            to the priority queue's ordering.
186	<	* @throws NullPointerException if the specified element is null.
255	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
256	>	* @throws ClassCastException if the specified element cannot be
257	>	*         compared with elements currently in this priority queue
258	>	*         according to the priority queue's ordering
259	>	* @throws NullPointerException if the specified element is null
260		*/
261	<	public boolean remove(Object element) {
262	<	if (element == null)
261	>	public boolean offer(E e) {
262	>	if (e == null)
263		throw new NullPointerException();
264	+	modCount++;
265	+	int i = size;
266	+	if (i >= queue.length)
267	+	grow(i + 1);
268	+	size = i + 1;
269	+	if (i == 0)
270	+	queue[0] = e;
271	+	else
272	+	siftUp(i, e);
273	+	return true;
274	+	}
275
276	<	if (comparator == null) {
277	<	for (int i = 1; i <= size; i++) {
278	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
279	<	remove(i);
280	<	return true;
281	<	}
282	<	}
283	<	} else {
284	<	for (int i = 1; i <= size; i++) {
285	<	if (comparator.compare(queue[i], (E) element) == 0) {
286	<	remove(i);
287	<	return true;
288	<	}
276	>	public E peek() {
277	>	if (size == 0)
278	>	return null;
279	>	return (E) queue[0];
280	>	}
281	>
282	>	private int indexOf(Object o) {
283	>	if (o != null) {
284	>	for (int i = 0; i < size; i++)
285	>	if (o.equals(queue[i]))
286	>	return i;
287	>	}
288	>	return -1;
289	>	}
290	>
291	>	/**
292	>	* Removes a single instance of the specified element from this queue,
293	>	* if it is present.  More formally, removes an element <tt>e</tt> such
294	>	* that <tt>o.equals(e)</tt>, if this queue contains one or more such
295	>	* elements.  Returns true if this queue contained the specified element
296	>	* (or equivalently, if this queue changed as a result of the call).
297	>	*
298	>	* @param o element to be removed from this queue, if present
299	>	* @return <tt>true</tt> if this queue changed as a result of the call
300	>	*/
301	>	public boolean remove(Object o) {
302	>	int i = indexOf(o);
303	>	if (i == -1)
304	>	return false;
305	>	else {
306	>	removeAt(i);
307	>	return true;
308	>	}
309	>	}
310	>
311	>	/**
312	>	* Version of remove using reference equality, not equals.
313	>	* Needed by iterator.remove.
314	>	*
315	>	* @param o element to be removed from this queue, if present
316	>	* @return <tt>true</tt> if removed
317	>	*/
318	>	boolean removeEq(Object o) {
319	>	for (int i = 0; i < size; i++) {
320	>	if (o == queue[i]) {
321	>	removeAt(i);
322	>	return true;
323		}
324		}
325		return false;
326		}
327
328		/**
329	<	* Returns an iterator over the elements in this priority queue.  The
330	<	* elements of the priority queue will be returned by this iterator in the
331	<	* order specified by the queue, which is to say the order they would be
332	<	* returned by repeated calls to <tt>poll</tt>.
333	<	*
334	<	* @return an <tt>Iterator</tt> over the elements in this priority queue.
329	>	* Returns <tt>true</tt> if this queue contains the specified element.
330	>	* More formally, returns <tt>true</tt> if and only if this queue contains
331	>	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
332	>	*
333	>	* @param o object to be checked for containment in this queue
334	>	* @return <tt>true</tt> if this queue contains the specified element
335	>	*/
336	>	public boolean contains(Object o) {
337	>	return indexOf(o) != -1;
338	>	}
339	>
340	>	/**
341	>	* Returns an array containing all of the elements in this queue,
342	>	* The elements are in no particular order.
343	>	*
344	>	* <p>The returned array will be "safe" in that no references to it are
345	>	* maintained by this list.  (In other words, this method must allocate
346	>	* a new array).  The caller is thus free to modify the returned array.
347	>	*
348	>	* @return an array containing all of the elements in this queue
349	>	*/
350	>	public Object[] toArray() {
351	>	return Arrays.copyOf(queue, size);
352	>	}
353	>
354	>	/**
355	>	* Returns an array containing all of the elements in this queue.
356	>	* The elements are in no particular order.  The runtime type of
357	>	* the returned array is that of the specified array.  If the queue
358	>	* fits in the specified array, it is returned therein.
359	>	* Otherwise, a new array is allocated with the runtime type of
360	>	* the specified array and the size of this queue.
361	>	*
362	>	* <p>If the queue fits in the specified array with room to spare
363	>	* (i.e., the array has more elements than the queue), the element in
364	>	* the array immediately following the end of the collection is set to
365	>	* <tt>null</tt>.  (This is useful in determining the length of the
366	>	* queue <i>only</i> if the caller knows that the queue does not contain
367	>	* any null elements.)
368	>	*
369	>	* @param a the array into which the elements of the queue are to
370	>	*          be stored, if it is big enough; otherwise, a new array of the
371	>	*          same runtime type is allocated for this purpose.
372	>	* @return an array containing the elements of the queue
373	>	* @throws ArrayStoreException if the runtime type of the specified array
374	>	*         is not a supertype of the runtime type of every element in
375	>	*         this queue
376	>	* @throws NullPointerException if the specified array is null
377	>	*/
378	>	public <T> T[] toArray(T[] a) {
379	>	if (a.length < size)
380	>	// Make a new array of a's runtime type, but my contents:
381	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
382	>	System.arraycopy(queue, 0, a, 0, size);
383	>	if (a.length > size)
384	>	a[size] = null;
385	>	return a;
386	>	}
387	>
388	>	/**
389	>	* Returns an iterator over the elements in this queue. The iterator
390	>	* does not return the elements in any particular order.
391	>	*
392	>	* @return an iterator over the elements in this queue
393		*/
394		public Iterator<E> iterator() {
395	<	return new Itr();
395	>	return new Itr();
396		}
397
398	<	private class Itr implements Iterator<E> {
399	<	/**
400	<	* Index (into queue array) of element to be returned by
398	>	private final class Itr implements Iterator<E> {
399	>	/**
400	>	* Index (into queue array) of element to be returned by
401		* subsequent call to next.
402	<	*/
403	<	int cursor = 1;
402	>	*/
403	>	private int cursor = 0;
404
405	<	/**
406	<	* Index of element returned by most recent call to next or
407	<	* previous.  Reset to 0 if this element is deleted by a call
408	<	* to remove.
409	<	*/
410	<	int lastRet = 0;
411	<
412	<	/**
413	<	* The modCount value that the iterator believes that the backing
414	<	* List should have.  If this expectation is violated, the iterator
415	<	* has detected concurrent modification.
416	<	*/
417	<	int expectedModCount = modCount;
418	<
419	<	public boolean hasNext() {
420	<	return cursor <= size;
421	<	}
405	>	/**
406	>	* Index of element returned by most recent call to next,
407	>	* unless that element came from the forgetMeNot list.
408	>	* Set to -1 if element is deleted by a call to remove.
409	>	*/
410	>	private int lastRet = -1;
411	>
412	>	/**
413	>	* A queue of elements that were moved from the unvisited portion of
414	>	* the heap into the visited portion as a result of "unlucky" element
415	>	* removals during the iteration.  (Unlucky element removals are those
416	>	* that require a siftup instead of a siftdown.)  We must visit all of
417	>	* the elements in this list to complete the iteration.  We do this
418	>	* after we've completed the "normal" iteration.
419	>	*
420	>	* We expect that most iterations, even those involving removals,
421	>	* will not use need to store elements in this field.
422	>	*/
423	>	private ArrayDeque<E> forgetMeNot = null;
424	>
425	>	/**
426	>	* Element returned by the most recent call to next iff that
427	>	* element was drawn from the forgetMeNot list.
428	>	*/
429	>	private E lastRetElt = null;
430	>
431	>	/**
432	>	* The modCount value that the iterator believes that the backing
433	>	* List should have.  If this expectation is violated, the iterator
434	>	* has detected concurrent modification.
435	>	*/
436	>	private int expectedModCount = modCount;
437	>
438	>	public boolean hasNext() {
439	>	return cursor < size ||
440	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
441	>	}
442
443	<	public E next() {
444	<	checkForComodification();
445	<	if (cursor > size)
446	<	throw new NoSuchElementException();
447	<	E result = queue[cursor];
448	<	lastRet = cursor++;
449	<	return result;
450	<	}
443	>	public E next() {
444	>	if (expectedModCount != modCount)
445	>	throw new ConcurrentModificationException();
446	>	if (cursor < size)
447	>	return (E) queue[lastRet = cursor++];
448	>	if (forgetMeNot != null) {
449	>	lastRet = -1;
450	>	lastRetElt = forgetMeNot.poll();
451	>	if (lastRetElt != null)
452	>	return lastRetElt;
453	>	}
454	>	throw new NoSuchElementException();
455	>	}
456
457	<	public void remove() {
458	<	if (lastRet == 0)
459	<	throw new IllegalStateException();
460	<	checkForComodification();
461	<
462	<	PriorityQueue.this.remove(lastRet);
463	<	if (lastRet < cursor)
464	<	cursor--;
465	<	lastRet = 0;
457	>	public void remove() {
458	>	if (expectedModCount != modCount)
459	>	throw new ConcurrentModificationException();
460	>	if (lastRet == -1 && lastRetElt == null)
461	>	throw new IllegalStateException();
462	>	if (lastRet != -1) {
463	>	E moved = PriorityQueue.this.removeAt(lastRet);
464	>	lastRet = -1;
465	>	if (moved == null)
466	>	cursor--;
467	>	else {
468	>	if (forgetMeNot == null)
469	>	forgetMeNot = new ArrayDeque<E>();
470	>	forgetMeNot.add(moved);
471	>	}
472	>	} else {
473	>	PriorityQueue.this.removeEq(lastRetElt);
474	>	lastRetElt = null;
475	>	}
476		expectedModCount = modCount;
477	<	}
477	>	}
478
268	–	final void checkForComodification() {
269	–	if (modCount != expectedModCount)
270	–	throw new ConcurrentModificationException();
271	–	}
479		}
480
274	–	/**
275	–	* Returns the number of elements in this priority queue.
276	–	*
277	–	* @return the number of elements in this priority queue.
278	–	*/
481		public int size() {
482		return size;
483		}
484
485		/**
486	<	* Add the specified element to this priority queue.
487	<	*
286	<	* @param element the element to add.
287	<	* @return true
288	<	* @throws ClassCastException if the specified element cannot be compared
289	<	*            with elements currently in the priority queue according
290	<	*            to the priority queue's ordering.
291	<	* @throws NullPointerException if the specified element is null.
486	>	* Removes all of the elements from this priority queue.
487	>	* The queue will be empty after this call returns.
488		*/
489	<	public boolean offer(E element) {
294	<	if (element == null)
295	<	throw new NullPointerException();
489	>	public void clear() {
490		modCount++;
491	+	for (int i = 0; i < size; i++)
492	+	queue[i] = null;
493	+	size = 0;
494	+	}
495
496	<	// Grow backing store if necessary
497	<	if (++size == queue.length) {
498	<	E[] newQueue = new E[2 * queue.length];
499	<	System.arraycopy(queue, 0, newQueue, 0, size);
500	<	queue = newQueue;
501	<	}
502	<
503	<	queue[size] = element;
504	<	fixUp(size);
505	<	return true;
496	>	public E poll() {
497	>	if (size == 0)
498	>	return null;
499	>	int s = --size;
500	>	modCount++;
501	>	E result = (E)queue[0];
502	>	E x = (E)queue[s];
503	>	queue[s] = null;
504	>	if (s != 0)
505	>	siftDown(0, x);
506	>	return result;
507		}
508
509		/**
510	<	* Remove all elements from the priority queue.
510	>	* Removes the ith element from queue.
511	>	*
512	>	* Normally this method leaves the elements at up to i-1,
513	>	* inclusive, untouched.  Under these circumstances, it returns
514	>	* null.  Occasionally, in order to maintain the heap invariant,
515	>	* it must swap a later element of the list with one earlier than
516	>	* i.  Under these circumstances, this method returns the element
517	>	* that was previously at the end of the list and is now at some
518	>	* position before i. This fact is used by iterator.remove so as to
519	>	* avoid missing traverseing elements.
520		*/
521	<	public void clear() {
521	>	private E removeAt(int i) {
522	>	assert i >= 0 && i < size;
523		modCount++;
524	<
525	<	// Null out element references to prevent memory leak
317	<	for (int i=1; i<=size; i++)
524	>	int s = --size;
525	>	if (s == i) // removed last element
526		queue[i] = null;
527	<
528	<	size = 0;
527	>	else {
528	>	E moved = (E) queue[s];
529	>	queue[s] = null;
530	>	siftDown(i, moved);
531	>	if (queue[i] == moved) {
532	>	siftUp(i, moved);
533	>	if (queue[i] != moved)
534	>	return moved;
535	>	}
536	>	}
537	>	return null;
538		}
539
540		/**
541	<	* Removes and returns the ith element from queue.  Recall
542	<	* that queue is one-based, so 1 <= i <= size.
541	>	* Inserts item x at position k, maintaining heap invariant by
542	>	* promoting x up the tree until it is greater than or equal to
543	>	* its parent, or is the root.
544		*
545	<	* XXX: Could further special-case i==size, but is it worth it?
546	<	* XXX: Could special-case i==0, but is it worth it?
545	>	* To simplify and speed up coercions and comparisons. the
546	>	* Comparable and Comparator versions are separated into different
547	>	* methods that are otherwise identical. (Similarly for siftDown.)
548	>	*
549	>	* @param k the position to fill
550	>	* @param x the item to insert
551		*/
552	<	private E remove(int i) {
553	<	assert i <= size;
554	<	modCount++;
552	>	private void siftUp(int k, E x) {
553	>	if (comparator != null)
554	>	siftUpUsingComparator(k, x);
555	>	else
556	>	siftUpComparable(k, x);
557	>	}
558
559	<	E result = queue[i];
560	<	queue[i] = queue[size];
561	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
562	<	if (i <= size)
563	<	fixDown(i);
564	<	return result;
559	>	private void siftUpComparable(int k, E x) {
560	>	Comparable<? super E> key = (Comparable<? super E>) x;
561	>	while (k > 0) {
562	>	int parent = (k - 1) >>> 1;
563	>	Object e = queue[parent];
564	>	if (key.compareTo((E)e) >= 0)
565	>	break;
566	>	queue[k] = e;
567	>	k = parent;
568	>	}
569	>	queue[k] = key;
570		}
571
572	<	/**
573	<	* Establishes the heap invariant (described above) assuming the heap
574	<	* satisfies the invariant except possibly for the leaf-node indexed by k
575	<	* (which may have a nextExecutionTime less than its parent's).
576	<	*
577	<	* This method functions by "promoting" queue[k] up the hierarchy
578	<	* (by swapping it with its parent) repeatedly until queue[k]
579	<	* is greater than or equal to its parent.
350	<	*/
351	<	private void fixUp(int k) {
352	<	if (comparator == null) {
353	<	while (k > 1) {
354	<	int j = k >> 1;
355	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
356	<	break;
357	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
358	<	k = j;
359	<	}
360	<	} else {
361	<	while (k > 1) {
362	<	int j = k >> 1;
363	<	if (comparator.compare(queue[j], queue[k]) <= 0)
364	<	break;
365	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
366	<	k = j;
367	<	}
572	>	private void siftUpUsingComparator(int k, E x) {
573	>	while (k > 0) {
574	>	int parent = (k - 1) >>> 1;
575	>	Object e = queue[parent];
576	>	if (comparator.compare(x, (E)e) >= 0)
577	>	break;
578	>	queue[k] = e;
579	>	k = parent;
580		}
581	+	queue[k] = x;
582		}
583
584		/**
585	<	* Establishes the heap invariant (described above) in the subtree
586	<	* rooted at k, which is assumed to satisfy the heap invariant except
587	<	* possibly for node k itself (which may be greater than its children).
588	<	*
589	<	* This method functions by "demoting" queue[k] down the hierarchy
590	<	* (by swapping it with its smaller child) repeatedly until queue[k]
591	<	* is less than or equal to its children.
592	<	*/
593	<	private void fixDown(int k) {
594	<	int j;
595	<	if (comparator == null) {
596	<	while ((j = k << 1) <= size) {
597	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
598	<	j++; // j indexes smallest kid
599	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
600	<	break;
601	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
602	<	k = j;
603	<	}
604	<	} else {
605	<	while ((j = k << 1) <= size) {
606	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
607	<	j++; // j indexes smallest kid
608	<	if (comparator.compare(queue[k], queue[j]) <= 0)
609	<	break;
610	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
611	<	k = j;
612	<	}
585	>	* Inserts item x at position k, maintaining heap invariant by
586	>	* demoting x down the tree repeatedly until it is less than or
587	>	* equal to its children or is a leaf.
588	>	*
589	>	* @param k the position to fill
590	>	* @param x the item to insert
591	>	*/
592	>	private void siftDown(int k, E x) {
593	>	if (comparator != null)
594	>	siftDownUsingComparator(k, x);
595	>	else
596	>	siftDownComparable(k, x);
597	>	}
598	>
599	>	private void siftDownComparable(int k, E x) {
600	>	Comparable<? super E> key = (Comparable<? super E>)x;
601	>	int half = size >>> 1;        // loop while a non-leaf
602	>	while (k < half) {
603	>	int child = (k << 1) + 1; // assume left child is least
604	>	Object c = queue[child];
605	>	int right = child + 1;
606	>	if (right < size &&
607	>	((Comparable<? super E>)c).compareTo((E)queue[right]) > 0)
608	>	c = queue[child = right];
609	>	if (key.compareTo((E)c) <= 0)
610	>	break;
611	>	queue[k] = c;
612	>	k = child;
613		}
614	+	queue[k] = key;
615	+	}
616	+
617	+	private void siftDownUsingComparator(int k, E x) {
618	+	int half = size >>> 1;
619	+	while (k < half) {
620	+	int child = (k << 1) + 1;
621	+	Object c = queue[child];
622	+	int right = child + 1;
623	+	if (right < size &&
624	+	comparator.compare((E)c, (E)queue[right]) > 0)
625	+	c = queue[child = right];
626	+	if (comparator.compare(x, (E)c) <= 0)
627	+	break;
628	+	queue[k] = c;
629	+	k = child;
630	+	}
631	+	queue[k] = x;
632	+	}
633	+
634	+	/**
635	+	* Establishes the heap invariant (described above) in the entire tree,
636	+	* assuming nothing about the order of the elements prior to the call.
637	+	*/
638	+	private void heapify() {
639	+	for (int i = (size >>> 1) - 1; i >= 0; i--)
640	+	siftDown(i, (E)queue[i]);
641		}
642
643		/**
644	<	* Returns the comparator associated with this priority queue, or
645	<	* <tt>null</tt> if it uses its elements' natural ordering.
644	>	* Returns the comparator used to order the elements in this
645	>	* queue, or <tt>null</tt> if this queue is sorted according to
646	>	* the {@linkplain Comparable natural ordering} of its elements.
647		*
648	<	* @return the comparator associated with this priority queue, or
649	<	*         <tt>null</tt> if it uses its elements' natural ordering.
648	>	* @return the comparator used to order this queue, or
649	>	*         <tt>null</tt> if this queue is sorted according to the
650	>	*         natural ordering of its elements.
651		*/
652	<	Comparator comparator() {
652	>	public Comparator<? super E> comparator() {
653		return comparator;
654		}
655
#	Line 418 | Line 660 | public class PriorityQueue<E> extends Ab
660		* @serialData The length of the array backing the instance is
661		* emitted (int), followed by all of its elements (each an
662		* <tt>Object</tt>) in the proper order.
663	+	* @param s the stream
664		*/
665	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
665	>	private void writeObject(java.io.ObjectOutputStream s)
666		throws java.io.IOException{
667	<	// Write out element count, and any hidden stuff
668	<	s.defaultWriteObject();
667	>	// Write out element count, and any hidden stuff
668	>	s.defaultWriteObject();
669
670		// Write out array length
671	<	s.writeInt(queue.length);
671	>	// For compatibility with 1.5 version, must be at least 2.
672	>	s.writeInt(Math.max(2, queue.length));
673
674	<	// Write out all elements in the proper order.
675	<	for (int i=0; i<size; i++)
674	>	// Write out all elements in the proper order.
675	>	for (int i=0; i<size; i++)
676		s.writeObject(queue[i]);
677		}
678
679		/**
680	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
681	<	* deserialize it).
680	>	* Reconstitute the <tt>PriorityQueue</tt> instance from a stream
681	>	* (that is, deserialize it).
682	>	* @param s the stream
683		*/
684	<	private synchronized void readObject(java.io.ObjectInputStream s)
684	>	private void readObject(java.io.ObjectInputStream s)
685		throws java.io.IOException, ClassNotFoundException {
686	<	// Read in size, and any hidden stuff
687	<	s.defaultReadObject();
686	>	// Read in size, and any hidden stuff
687	>	s.defaultReadObject();
688
689		// Read in array length and allocate array
690		int arrayLength = s.readInt();
691	<	queue = new E[arrayLength];
691	>	queue = new Object[arrayLength];
692
693	<	// Read in all elements in the proper order.
694	<	for (int i=0; i<size; i++)
695	<	queue[i] = (E)s.readObject();
693	>	// Read in all elements in the proper order.
694	>	for (int i=0; i<size; i++)
695	>	queue[i] = (E) s.readObject();
696		}
697
698		}

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