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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.37 by dl, Sat Aug 30 11:44:53 2003 UTC vs.
Revision 1.56 by jsr166, Mon Nov 28 02:35:46 2005 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* @(#)PriorityQueue.java       1.8 05/08/27
3	>	*
4	>	* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
5	>	* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6	>	*/
7	>
8	>	package java.util;
9	>	import java.util.*; // for javadoc (till 6280605 is fixed)
10
11		/**
12	<	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
13	<	* This queue orders elements according to an order specified at construction
14	<	* time, which is specified in the same manner as {@link java.util.TreeSet}
15	<	* and {@link java.util.TreeMap}: elements are ordered either according to
16	<	* their <i>natural order</i> (see {@link Comparable}), or according to a
17	<	* {@link java.util.Comparator}, depending on which constructor is used.
18	<	* <p>The <em>head</em> of this queue is the <em>least</em> element with
19	<	* respect to the specified ordering.  If multiple elements are tied for least
12	<	* value, the head is one of those elements. A priority queue does not permit
13	<	* <tt>null</tt> elements.
14	<	*
15	<	* <p>The {@link #remove()} and {@link #poll()} methods remove and
16	<	* return the head of the queue.
12	>	* An unbounded priority {@linkplain Queue queue} based on a priority
13	>	* heap.  The elements of the priority queue are ordered according to
14	>	* their {@linkplain Comparable natural ordering}, or by a {@link
15	>	* Comparator} provided at queue construction time, depending on which
16	>	* constructor is used.  A priority queue does not permit
17	>	* <tt>null</tt> elements.  A priority queue relying on natural
18	>	* ordering also does not permit insertion of non-comparable objects
19	>	* (doing so may result in <tt>ClassCastException</tt>).
20		*
21	<	* <p>The {@link #element()} and {@link #peek()} methods return, but do
22	<	* not delete, the head of the queue.
21	>	* <p>The <em>head</em> of this queue is the <em>least</em> element
22	>	* with respect to the specified ordering.  If multiple elements are
23	>	* tied for least value, the head is one of those elements -- ties are
24	>	* broken arbitrarily.  The queue retrieval operations <tt>poll</tt>,
25	>	* <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the
26	>	* element at the head of the queue.
27		*
28	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
29	<	* size of the array used internally to store the elements on the
30	<	* queue.
31	<	* It is always at least as large as the queue size.  As
32	<	* elements are added to a priority queue, its capacity grows
33	<	* automatically.  The details of the growth policy are not specified.
28	>	* <p>A priority queue is unbounded, but has an internal
29	>	* <i>capacity</i> governing the size of an array used to store the
30	>	* elements on the queue.  It is always at least as large as the queue
31	>	* size.  As elements are added to a priority queue, its capacity
32	>	* grows automatically.  The details of the growth policy are not
33	>	* specified.
34		*
35	<	* <p>The Iterator provided in method {@link #iterator()} is <em>not</em>
36	<	* guaranteed to traverse the elements of the PriorityQueue in any
37	<	* particular order. If you need ordered traversal, consider using
38	<	* <tt>Arrays.sort(pq.toArray())</tt>.
35	>	* <p>This class and its iterator implement all of the
36	>	* <em>optional</em> methods of the {@link Collection} and {@link
37	>	* Iterator} interfaces.  The Iterator provided in method {@link
38	>	* #iterator()} is <em>not</em> guaranteed to traverse the elements of
39	>	* the priority queue in any particular order. If you need ordered
40	>	* traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.
41		*
42		* <p> <strong>Note that this implementation is not synchronized.</strong>
43		* Multiple threads should not access a <tt>PriorityQueue</tt>
#	Line 36 | Line 45
45		* structurally. Instead, use the thread-safe {@link
46		* java.util.concurrent.PriorityBlockingQueue} class.
47		*
39	–	*
48		* <p>Implementation note: this implementation provides O(log(n)) time
49		* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
50		* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
#	Line 48 | Line 56
56		* <a href="{@docRoot}/../guide/collections/index.html">
57		* Java Collections Framework</a>.
58		* @since 1.5
59	+	* @version 1.8, 08/27/05
60		* @author Josh Bloch
61	+	* @param <E> the type of elements held in this collection
62		*/
63		public class PriorityQueue<E> extends AbstractQueue<E>
64	<	implements Queue<E>, java.io.Serializable {
64	>	implements java.io.Serializable {
65
66		private static final long serialVersionUID = -7720805057305804111L;
67
68		private static final int DEFAULT_INITIAL_CAPACITY = 11;
69
70		/**
71	<	* Priority queue represented as a balanced binary heap: the two children
72	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
73	<	* ordered by comparator, or by the elements' natural ordering, if
74	<	* comparator is null:  For each node n in the heap and each descendant d
75	<	* of n, n <= d.
76	<	*
67	<	* The element with the lowest value is in queue[1], assuming the queue is
68	<	* nonempty.  (A one-based array is used in preference to the traditional
69	<	* zero-based array to simplify parent and child calculations.)
70	<	*
71	<	* queue.length must be >= 2, even if size == 0.
71	>	* Priority queue represented as a balanced binary heap: the two
72	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
73	>	* priority queue is ordered by comparator, or by the elements'
74	>	* natural ordering, if comparator is null: For each node n in the
75	>	* heap and each descendant d of n, n <= d.  The element with the
76	>	* lowest value is in queue[0], assuming the queue is nonempty.
77		*/
78		private transient Object[] queue;
79
#	Line 90 | Line 95 | public class PriorityQueue<E> extends Ab
95		private transient int modCount = 0;
96
97		/**
98	<	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
99	<	* (11) that orders its elements according to their natural
100	<	* ordering (using <tt>Comparable</tt>).
98	>	* Creates a <tt>PriorityQueue</tt> with the default initial
99	>	* capacity (11) that orders its elements according to their
100	>	* {@linkplain Comparable natural ordering}.
101		*/
102		public PriorityQueue() {
103		this(DEFAULT_INITIAL_CAPACITY, null);
104		}
105
106		/**
107	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
108	<	* that orders its elements according to their natural ordering
109	<	* (using <tt>Comparable</tt>).
107	>	* Creates a <tt>PriorityQueue</tt> with the specified initial
108	>	* capacity that orders its elements according to their
109	>	* {@linkplain Comparable natural ordering}.
110		*
111	<	* @param initialCapacity the initial capacity for this priority queue.
111	>	* @param initialCapacity the initial capacity for this priority queue
112		* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
113		* than 1
114		*/
#	Line 115 | Line 120 | public class PriorityQueue<E> extends Ab
120		* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
121		* that orders its elements according to the specified comparator.
122		*
123	<	* @param initialCapacity the initial capacity for this priority queue.
124	<	* @param comparator the comparator used to order this priority queue.
125	<	* If <tt>null</tt> then the order depends on the elements' natural
126	<	* ordering.
127	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
128	<	* than 1
123	>	* @param  initialCapacity the initial capacity for this priority queue
124	>	* @param  comparator the comparator that will be used to order
125	>	*         this priority queue.  If <tt>null</tt>, the <i>natural
126	>	*         ordering</i> of the elements will be used.
127	>	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is
128	>	*         less than 1
129		*/
130	<	public PriorityQueue(int initialCapacity,
130	>	public PriorityQueue(int initialCapacity,
131		Comparator<? super E> comparator) {
132	+	// Note: This restriction of at least one is not actually needed,
133	+	// but continues for 1.5 compatibility
134		if (initialCapacity < 1)
135		throw new IllegalArgumentException();
136	<	this.queue = new Object[initialCapacity + 1];
136	>	this.queue = new Object[initialCapacity];
137		this.comparator = comparator;
138		}
139
140		/**
134	–	* Common code to initialize underlying queue array across
135	–	* constructors below.
136	–	*/
137	–	private void initializeArray(Collection<? extends E> c) {
138	–	int sz = c.size();
139	–	int initialCapacity = (int)Math.min((sz * 110L) / 100,
140	–	Integer.MAX_VALUE - 1);
141	–	if (initialCapacity < 1)
142	–	initialCapacity = 1;
143	–
144	–	this.queue = new Object[initialCapacity + 1];
145	–	}
146	–
147	–	/**
148	–	* Initially fill elements of the queue array under the
149	–	* knowledge that it is sorted or is another PQ, in which
150	–	* case we can just place the elements in the order presented.
151	–	*/
152	–	private void fillFromSorted(Collection<? extends E> c) {
153	–	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
154	–	queue[++size] = i.next();
155	–	}
156	–
157	–	/**
158	–	* Initially fill elements of the queue array that is not to our knowledge
159	–	* sorted, so we must rearrange the elements to guarantee the heap
160	–	* invariant.
161	–	*/
162	–	private void fillFromUnsorted(Collection<? extends E> c) {
163	–	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
164	–	queue[++size] = i.next();
165	–	heapify();
166	–	}
167	–
168	–	/**
141		* Creates a <tt>PriorityQueue</tt> containing the elements in the
142	<	* specified collection.  The priority queue has an initial
171	<	* capacity of 110% of the size of the specified collection or 1
172	<	* if the collection is empty.  If the specified collection is an
142	>	* specified collection.   If the specified collection is an
143		* instance of a {@link java.util.SortedSet} or is another
144	<	* <tt>PriorityQueue</tt>, the priority queue will be sorted
145	<	* according to the same comparator, or according to its elements'
146	<	* natural order if the collection is sorted according to its
177	<	* elements' natural order.  Otherwise, the priority queue is
178	<	* ordered according to its elements' natural order.
144	>	* <tt>PriorityQueue</tt>, the priority queue will be ordered
145	>	* according to the same ordering.  Otherwise, this priority queue
146	>	* will be ordered according to the natural ordering of its elements.
147		*
148	<	* @param c the collection whose elements are to be placed
149	<	*        into this priority queue.
148	>	* @param  c the collection whose elements are to be placed
149	>	*         into this priority queue
150		* @throws ClassCastException if elements of the specified collection
151		*         cannot be compared to one another according to the priority
152	<	*         queue's ordering.
153	<	* @throws NullPointerException if <tt>c</tt> or any element within it
154	<	* is <tt>null</tt>
152	>	*         queue's ordering
153	>	* @throws NullPointerException if the specified collection or any
154	>	*         of its elements are null
155		*/
156		public PriorityQueue(Collection<? extends E> c) {
157	<	initializeArray(c);
158	<	if (c instanceof SortedSet) {
159	<	// @fixme double-cast workaround for compiler
160	<	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
161	<	comparator = (Comparator<? super E>)s.comparator();
162	<	fillFromSorted(s);
163	<	} else if (c instanceof PriorityQueue) {
164	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
197	<	comparator = (Comparator<? super E>)s.comparator();
198	<	fillFromSorted(s);
199	<	} else {
157	>	initFromCollection(c);
158	>	if (c instanceof SortedSet)
159	>	comparator = (Comparator<? super E>)
160	>	((SortedSet<? extends E>)c).comparator();
161	>	else if (c instanceof PriorityQueue)
162	>	comparator = (Comparator<? super E>)
163	>	((PriorityQueue<? extends E>)c).comparator();
164	>	else {
165		comparator = null;
166	<	fillFromUnsorted(c);
166	>	heapify();
167		}
168		}
169
170		/**
171		* Creates a <tt>PriorityQueue</tt> containing the elements in the
172	<	* specified collection.  The priority queue has an initial
173	<	* capacity of 110% of the size of the specified collection or 1
174	<	* if the collection is empty.  This priority queue will be sorted
175	<	* according to the same comparator as the given collection, or
176	<	* according to its elements' natural order if the collection is
177	<	* sorted according to its elements' natural order.
178	<	*
179	<	* @param c the collection whose elements are to be placed
180	<	*        into this priority queue.
181	<	* @throws ClassCastException if elements of the specified collection
182	<	*         cannot be compared to one another according to the priority
218	<	*         queue's ordering.
219	<	* @throws NullPointerException if <tt>c</tt> or any element within it
220	<	* is <tt>null</tt>
172	>	* specified priority queue.  This priority queue will be
173	>	* ordered according to the same ordering as the given priority
174	>	* queue.
175	>	*
176	>	* @param  c the priority queue whose elements are to be placed
177	>	*         into this priority queue
178	>	* @throws ClassCastException if elements of <tt>c</tt> cannot be
179	>	*         compared to one another according to <tt>c</tt>'s
180	>	*         ordering
181	>	* @throws NullPointerException if the specified priority queue or any
182	>	*         of its elements are null
183		*/
184		public PriorityQueue(PriorityQueue<? extends E> c) {
223	–	initializeArray(c);
185		comparator = (Comparator<? super E>)c.comparator();
186	<	fillFromSorted(c);
186	>	initFromCollection(c);
187		}
188
189		/**
190		* Creates a <tt>PriorityQueue</tt> containing the elements in the
191	<	* specified collection.  The priority queue has an initial
192	<	* capacity of 110% of the size of the specified collection or 1
232	<	* if the collection is empty.  This priority queue will be sorted
233	<	* according to the same comparator as the given collection, or
234	<	* according to its elements' natural order if the collection is
235	<	* sorted according to its elements' natural order.
191	>	* specified sorted set.  This priority queue will be ordered
192	>	* according to the same ordering as the given sorted set.
193		*
194	<	* @param c the collection whose elements are to be placed
195	<	*        into this priority queue.
196	<	* @throws ClassCastException if elements of the specified collection
197	<	*         cannot be compared to one another according to the priority
198	<	*         queue's ordering.
199	<	* @throws NullPointerException if <tt>c</tt> or any element within it
200	<	* is <tt>null</tt>
194	>	* @param  c the sorted set whose elements are to be placed
195	>	*         into this priority queue.
196	>	* @throws ClassCastException if elements of the specified sorted
197	>	*         set cannot be compared to one another according to the
198	>	*         sorted set's ordering
199	>	* @throws NullPointerException if the specified sorted set or any
200	>	*         of its elements are null
201		*/
202		public PriorityQueue(SortedSet<? extends E> c) {
246	–	initializeArray(c);
203		comparator = (Comparator<? super E>)c.comparator();
204	<	fillFromSorted(c);
204	>	initFromCollection(c);
205	>	}
206	>
207	>	/**
208	>	* Initialize queue array with elements from the given Collection.
209	>	* @param c the collection
210	>	*/
211	>	private void initFromCollection(Collection<? extends E> c) {
212	>	Object[] a = c.toArray();
213	>	// If c.toArray incorrectly doesn't return Object[], copy it.
214	>	if (a.getClass() != Object[].class)
215	>	a = Arrays.copyOf(a, a.length, Object[].class);
216	>	queue = a;
217	>	size = a.length;
218		}
219
220		/**
221	<	* Resize array, if necessary, to be able to hold given index
221	>	* Increases the capacity of the array.
222	>	*
223	>	* @param minCapacity the desired minimum capacity
224		*/
225	<	private void grow(int index) {
226	<	int newlen = queue.length;
256	<	if (index < newlen) // don't need to grow
257	<	return;
258	<	if (index == Integer.MAX_VALUE)
225	>	private void grow(int minCapacity) {
226	>	if (minCapacity < 0) // overflow
227		throw new OutOfMemoryError();
228	<	while (newlen <= index) {
229	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
230	<	newlen = Integer.MAX_VALUE;
231	<	else
232	<	newlen <<= 2;
233	<	}
234	<	Object[] newQueue = new Object[newlen];
235	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
268	<	queue = newQueue;
228	>	int oldCapacity = queue.length;
229	>	// Double size if small; else grow by 50%
230	>	int newCapacity = ((oldCapacity < 64)?
231	>	((oldCapacity + 1) * 2):
232	>	((oldCapacity * 3) / 2));
233	>	if (newCapacity < minCapacity)
234	>	newCapacity = minCapacity;
235	>	queue = Arrays.copyOf(queue, newCapacity);
236		}
270	–
237
238	<	// Queue Methods
238	>	/**
239	>	* Inserts the specified element into this priority queue.
240	>	*
241	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
242	>	* @throws ClassCastException if the specified element cannot be
243	>	*         compared with elements currently in this priority queue
244	>	*         according to the priority queue's ordering
245	>	* @throws NullPointerException if the specified element is null
246	>	*/
247	>	public boolean add(E e) {
248	>	return offer(e);
249	>	}
250
251		/**
252	<	* Add the specified element to this priority queue.
252	>	* Inserts the specified element into this priority queue.
253		*
254	<	* @return <tt>true</tt>
255	<	* @throws ClassCastException if the specified element cannot be compared
256	<	* with elements currently in the priority queue according
257	<	* to the priority queue's ordering.
258	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
254	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
255	>	* @throws ClassCastException if the specified element cannot be
256	>	*         compared with elements currently in this priority queue
257	>	*         according to the priority queue's ordering
258	>	* @throws NullPointerException if the specified element is null
259		*/
260	<	public boolean offer(E o) {
261	<	if (o == null)
260	>	public boolean offer(E e) {
261	>	if (e == null)
262		throw new NullPointerException();
263		modCount++;
264	<	++size;
265	<
266	<	// Grow backing store if necessary
267	<	if (size >= queue.length)
268	<	grow(size);
269	<
270	<	queue[size] = o;
271	<	fixUp(size);
264	>	int i = size;
265	>	if (i >= queue.length)
266	>	grow(i + 1);
267	>	size = i + 1;
268	>	if (i == 0)
269	>	queue[0] = e;
270	>	else
271	>	siftUp(i, e);
272		return true;
273		}
274
275	<	public E poll() {
275	>	public E peek() {
276		if (size == 0)
277		return null;
278	<	return remove();
278	>	return (E) queue[0];
279		}
280
281	<	public E peek() {
282	<	return (E) queue[1];
281	>	private int indexOf(Object o) {
282	>	if (o != null) {
283	>	for (int i = 0; i < size; i++)
284	>	if (o.equals(queue[i]))
285	>	return i;
286	>	}
287	>	return -1;
288		}
289
308	–	// Collection Methods - the first two override to update docs
309	–
290		/**
291	<	* Adds the specified element to this queue.
292	<	* @return <tt>true</tt> (as per the general contract of
293	<	* <tt>Collection.add</tt>).
291	>	* Removes a single instance of the specified element from this queue,
292	>	* if it is present.  More formally, removes an element <tt>e</tt> such
293	>	* that <tt>o.equals(e)</tt>, if this queue contains one or more such
294	>	* elements.  Returns true if this queue contained the specified element
295	>	* (or equivalently, if this queue changed as a result of the call).
296		*
297	<	* @throws NullPointerException {@inheritDoc}
298	<	* @throws ClassCastException if the specified element cannot be compared
317	<	* with elements currently in the priority queue according
318	<	* to the priority queue's ordering.
297	>	* @param o element to be removed from this queue, if present
298	>	* @return <tt>true</tt> if this queue changed as a result of the call
299		*/
300	<	public boolean add(E o) {
301	<	return super.add(o);
300	>	public boolean remove(Object o) {
301	>	int i = indexOf(o);
302	>	if (i == -1)
303	>	return false;
304	>	else {
305	>	removeAt(i);
306	>	return true;
307	>	}
308		}
309
324	–
310		/**
311	<	* Adds all of the elements in the specified collection to this queue.
312	<	* The behavior of this operation is undefined if
313	<	* the specified collection is modified while the operation is in
314	<	* progress.  (This implies that the behavior of this call is undefined if
315	<	* the specified collection is this queue, and this queue is nonempty.)
316	<	* <p>
317	<	* This implementation iterates over the specified collection, and adds
318	<	* each object returned by the iterator to this collection, in turn.
319	<	* @throws NullPointerException {@inheritDoc}
320	<	* @throws ClassCastException if any element cannot be compared
321	<	* with elements currently in the priority queue according
322	<	* to the priority queue's ordering.
323	<	*/
324	<	public boolean addAll(Collection<? extends E> c) {
340	<	return super.addAll(c);
311	>	* Version of remove using reference equality, not equals.
312	>	* Needed by iterator.remove
313	>	*
314	>	* @param o element to be removed from this queue, if present
315	>	* @return <tt>true</tt> if removed.
316	>	*/
317	>	boolean removeEq(Object o) {
318	>	for (int i = 0; i < size; i++) {
319	>	if (o == queue[i]) {
320	>	removeAt(i);
321	>	return true;
322	>	}
323	>	}
324	>	return false;
325		}
326
327	+	/**
328	+	* Returns <tt>true</tt> if this queue contains the specified element.
329	+	* More formally, returns <tt>true</tt> if and only if this queue contains
330	+	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
331	+	*
332	+	* @param o object to be checked for containment in this queue
333	+	* @return <tt>true</tt> if this queue contains the specified element
334	+	*/
335	+	public boolean contains(Object o) {
336	+	return indexOf(o) != -1;
337	+	}
338
339		/**
340	<	* Removes a single instance of the specified element from this
341	<	* queue, if it is present.  More formally,
342	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
343	<	* o.equals(e))</tt>, if the queue contains one or more such
344	<	* elements.  Returns <tt>true</tt> if the queue contained the
345	<	* specified element (or equivalently, if the queue changed as a
346	<	* result of the call).
347	<	*
348	<	* <p>This implementation iterates over the queue looking for the
349	<	* specified element.  If it finds the element, it removes the element
350	<	* from the queue using the iterator's remove method.<p>
351	<	*
357	<	*/
358	<	public boolean remove(Object o) {
359	<	if (o == null)
360	<	return false;
340	>	* Returns an array containing all of the elements in this queue,
341	>	* The elements are in no particular order.
342	>	*
343	>	* <p>The returned array will be "safe" in that no references to it are
344	>	* maintained by this list.  (In other words, this method must allocate
345	>	* a new array).  The caller is thus free to modify the returned array.
346	>	*
347	>	* @return an array containing all of the elements in this queue.
348	>	*/
349	>	public Object[] toArray() {
350	>	return Arrays.copyOf(queue, size);
351	>	}
352
353	<	if (comparator == null) {
354	<	for (int i = 1; i <= size; i++) {
355	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
356	<	removeAt(i);
357	<	return true;
358	<	}
359	<	}
360	<	} else {
361	<	for (int i = 1; i <= size; i++) {
362	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
363	<	removeAt(i);
364	<	return true;
365	<	}
366	<	}
367	<	}
368	<	return false;
353	>	/**
354	>	* Returns an array containing all of the elements in this queue.
355	>	* The elements are in no particular order.  The runtime type of
356	>	* the returned array is that of the specified array.  If the queue
357	>	* fits in the specified array, it is returned therein.
358	>	* Otherwise, a new array is allocated with the runtime type of
359	>	* the specified array and the size of this queue.
360	>	*
361	>	* <p>If the queue fits in the specified array with room to spare
362	>	* (i.e., the array has more elements than the queue), the element in
363	>	* the array immediately following the end of the collection is set to
364	>	* <tt>null</tt>.  (This is useful in determining the length of the
365	>	* queue <i>only</i> if the caller knows that the queue does not contain
366	>	* any null elements.)
367	>	*
368	>	* @param a the array into which the elements of the queue are to
369	>	*          be stored, if it is big enough; otherwise, a new array of the
370	>	*          same runtime type is allocated for this purpose.
371	>	* @return an array containing the elements of the queue
372	>	* @throws ArrayStoreException if the runtime type of the specified array
373	>	*         is not a supertype of the runtime type of every element in
374	>	*         this queue
375	>	* @throws NullPointerException if the specified array is null
376	>	*/
377	>	public <T> T[] toArray(T[] a) {
378	>	if (a.length < size)
379	>	// Make a new array of a's runtime type, but my contents:
380	>	return (T[]) Arrays.copyOf(queue, size, a.getClass());
381	>	System.arraycopy(queue, 0, a, 0, size);
382	>	if (a.length > size)
383	>	a[size] = null;
384	>	return a;
385		}
386
387		/**
388		* Returns an iterator over the elements in this queue. The iterator
389		* does not return the elements in any particular order.
390		*
391	<	* @return an iterator over the elements in this queue.
391	>	* @return an iterator over the elements in this queue
392		*/
393		public Iterator<E> iterator() {
394		return new Itr();
395		}
396
397	<	private class Itr implements Iterator<E> {
391	<
397	>	private final class Itr implements Iterator<E> {
398		/**
399		* Index (into queue array) of element to be returned by
400		* subsequent call to next.
401		*/
402	<	private int cursor = 1;
402	>	private int cursor = 0;
403
404		/**
405		* Index of element returned by most recent call to next,
406		* unless that element came from the forgetMeNot list.
407	<	* Reset to 0 if element is deleted by a call to remove.
402	<	*/
403	<	private int lastRet = 0;
404	<
405	<	/**
406	<	* The modCount value that the iterator believes that the backing
407	<	* List should have.  If this expectation is violated, the iterator
408	<	* has detected concurrent modification.
407	>	* Set to -1 if element is deleted by a call to remove.
408		*/
409	<	private int expectedModCount = modCount;
409	>	private int lastRet = -1;
410
411		/**
412	<	* A list of elements that were moved from the unvisited portion of
412	>	* A queue of elements that were moved from the unvisited portion of
413		* the heap into the visited portion as a result of "unlucky" element
414		* removals during the iteration.  (Unlucky element removals are those
415	<	* that require a fixup instead of a fixdown.)  We must visit all of
415	>	* that require a siftup instead of a siftdown.)  We must visit all of
416		* the elements in this list to complete the iteration.  We do this
417		* after we've completed the "normal" iteration.
418		*
419		* We expect that most iterations, even those involving removals,
420		* will not use need to store elements in this field.
421		*/
422	<	private ArrayList<E> forgetMeNot = null;
422	>	private ArrayDeque<E> forgetMeNot = null;
423
424		/**
425		* Element returned by the most recent call to next iff that
426		* element was drawn from the forgetMeNot list.
427		*/
428	<	private Object lastRetElt = null;
428	>	private E lastRetElt = null;
429	>
430	>	/**
431	>	* The modCount value that the iterator believes that the backing
432	>	* List should have.  If this expectation is violated, the iterator
433	>	* has detected concurrent modification.
434	>	*/
435	>	private int expectedModCount = modCount;
436
437		public boolean hasNext() {
438	<	return cursor <= size || forgetMeNot != null;
438	>	return cursor < size ||
439	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
440		}
441
442		public E next() {
443	<	checkForComodification();
444	<	E result;
445	<	if (cursor <= size) {
446	<	result = (E) queue[cursor];
447	<	lastRet = cursor++;
448	<	}
449	<	else if (forgetMeNot == null)
450	<	throw new NoSuchElementException();
451	<	else {
445	<	int remaining = forgetMeNot.size();
446	<	result = forgetMeNot.remove(remaining - 1);
447	<	if (remaining == 1)
448	<	forgetMeNot = null;
449	<	lastRet = 0;
450	<	lastRetElt = result;
443	>	if (expectedModCount != modCount)
444	>	throw new ConcurrentModificationException();
445	>	if (cursor < size)
446	>	return (E) queue[lastRet = cursor++];
447	>	if (forgetMeNot != null) {
448	>	lastRet = -1;
449	>	lastRetElt = forgetMeNot.poll();
450	>	if (lastRetElt != null)
451	>	return lastRetElt;
452		}
453	<	return result;
453	>	throw new NoSuchElementException();
454		}
455
456		public void remove() {
457	<	checkForComodification();
458	<
459	<	if (lastRet != 0) {
457	>	if (expectedModCount != modCount)
458	>	throw new ConcurrentModificationException();
459	>	if (lastRet == -1 && lastRetElt == null)
460	>	throw new IllegalStateException();
461	>	if (lastRet != -1) {
462		E moved = PriorityQueue.this.removeAt(lastRet);
463	<	lastRet = 0;
464	<	if (moved == null) {
463	>	lastRet = -1;
464	>	if (moved == null)
465		cursor--;
466	<	} else {
466	>	else {
467		if (forgetMeNot == null)
468	<	forgetMeNot = new ArrayList<E>();
468	>	forgetMeNot = new ArrayDeque<E>();
469		forgetMeNot.add(moved);
470		}
468	–	} else if (lastRetElt != null) {
469	–	PriorityQueue.this.remove(lastRetElt);
470	–	lastRetElt = null;
471		} else {
472	<	throw new IllegalStateException();
472	>	PriorityQueue.this.removeEq(lastRetElt);
473	>	lastRetElt = null;
474		}
474	–
475		expectedModCount = modCount;
476		}
477
478	–	final void checkForComodification() {
479	–	if (modCount != expectedModCount)
480	–	throw new ConcurrentModificationException();
481	–	}
478		}
479
480		public int size() {
#	Line 486 | Line 482 | public class PriorityQueue<E> extends Ab
482		}
483
484		/**
485	<	* Remove all elements from the priority queue.
485	>	* Removes all of the elements from this priority queue.
486	>	* The queue will be empty after this call returns.
487		*/
488		public void clear() {
489		modCount++;
490	<
494	<	// Null out element references to prevent memory leak
495	<	for (int i=1; i<=size; i++)
490	>	for (int i = 0; i < size; i++)
491		queue[i] = null;
497	–
492		size = 0;
493		}
494
495	<	/**
502	<	* Removes and returns the first element from queue.
503	<	*/
504	<	public E remove() {
495	>	public E poll() {
496		if (size == 0)
497	<	throw new NoSuchElementException();
497	>	return null;
498	>	int s = --size;
499		modCount++;
500	<
501	<	E result = (E) queue[1];
502	<	queue[1] = queue[size];
503	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
504	<	if (size > 1)
513	<	fixDown(1);
514	<
500	>	E result = (E)queue[0];
501	>	E x = (E)queue[s];
502	>	queue[s] = null;
503	>	if (s != 0)
504	>	siftDown(0, x);
505		return result;
506		}
507
508		/**
509	<	* Removes and returns the ith element from queue.  (Recall that queue
520	<	* is one-based, so 1 <= i <= size.)
509	>	* Removes the ith element from queue.
510		*
511	<	* Normally this method leaves the elements at positions from 1 up to i-1,
512	<	* inclusive, untouched.  Under these circumstances, it returns null.
513	<	* Occasionally, in order to maintain the heap invariant, it must move
514	<	* the last element of the list to some index in the range [2, i-1],
515	<	* and move the element previously at position (i/2) to position i.
516	<	* Under these circumstances, this method returns the element that was
517	<	* previously at the end of the list and is now at some position between
518	<	* 2 and i-1 inclusive.
511	>	* Normally this method leaves the elements at up to i-1,
512	>	* inclusive, untouched.  Under these circumstances, it returns
513	>	* null.  Occasionally, in order to maintain the heap invariant,
514	>	* it must swap a later element of the list with one earlier than
515	>	* i.  Under these circumstances, this method returns the element
516	>	* that was previously at the end of the list and is now at some
517	>	* position before i. This fact is used by iterator.remove so as to
518	>	* avoid missing traverseing elements.
519		*/
520	<	private E removeAt(int i) {
521	<	assert i > 0 && i <= size;
520	>	private E removeAt(int i) {
521	>	assert i >= 0 && i < size;
522		modCount++;
523	<
524	<	E moved = (E) queue[size];
525	<	queue[i] = moved;
526	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
527	<	if (i <= size) {
528	<	fixDown(i);
523	>	int s = --size;
524	>	if (s == i) // removed last element
525	>	queue[i] = null;
526	>	else {
527	>	E moved = (E) queue[s];
528	>	queue[s] = null;
529	>	siftDown(i, moved);
530		if (queue[i] == moved) {
531	<	fixUp(i);
531	>	siftUp(i, moved);
532		if (queue[i] != moved)
533		return moved;
534		}
#	Line 547 | Line 537 | public class PriorityQueue<E> extends Ab
537		}
538
539		/**
540	<	* Establishes the heap invariant (described above) assuming the heap
541	<	* satisfies the invariant except possibly for the leaf-node indexed by k
542	<	* (which may have a nextExecutionTime less than its parent's).
543	<	*
544	<	* This method functions by "promoting" queue[k] up the hierarchy
545	<	* (by swapping it with its parent) repeatedly until queue[k]
546	<	* is greater than or equal to its parent.
547	<	*/
548	<	private void fixUp(int k) {
549	<	if (comparator == null) {
550	<	while (k > 1) {
551	<	int j = k >> 1;
552	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
553	<	break;
554	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
555	<	k = j;
556	<	}
557	<	} else {
558	<	while (k > 1) {
559	<	int j = k >>> 1;
560	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
561	<	break;
562	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
563	<	k = j;
564	<	}
540	>	* Inserts item x at position k, maintaining heap invariant by
541	>	* promoting x up the tree until it is greater than or equal to
542	>	* its parent, or is the root.
543	>	*
544	>	* To simplify and speed up coercions and comparisons. the
545	>	* Comparable and Comparator versions are separated into different
546	>	* methods that are otherwise identical. (Similarly for siftDown.)
547	>	*
548	>	* @param k the position to fill
549	>	* @param x the item to insert
550	>	*/
551	>	private void siftUp(int k, E x) {
552	>	if (comparator != null)
553	>	siftUpUsingComparator(k, x);
554	>	else
555	>	siftUpComparable(k, x);
556	>	}
557	>
558	>	private void siftUpComparable(int k, E x) {
559	>	Comparable<? super E> key = (Comparable<? super E>) x;
560	>	while (k > 0) {
561	>	int parent = (k - 1) >>> 1;
562	>	Object e = queue[parent];
563	>	if (key.compareTo((E)e) >= 0)
564	>	break;
565	>	queue[k] = e;
566	>	k = parent;
567		}
568	+	queue[k] = key;
569	+	}
570	+
571	+	private void siftUpUsingComparator(int k, E x) {
572	+	while (k > 0) {
573	+	int parent = (k - 1) >>> 1;
574	+	Object e = queue[parent];
575	+	if (comparator.compare(x, (E)e) >= 0)
576	+	break;
577	+	queue[k] = e;
578	+	k = parent;
579	+	}
580	+	queue[k] = x;
581		}
582
583		/**
584	<	* Establishes the heap invariant (described above) in the subtree
585	<	* rooted at k, which is assumed to satisfy the heap invariant except
586	<	* possibly for node k itself (which may be greater than its children).
587	<	*
588	<	* This method functions by "demoting" queue[k] down the hierarchy
589	<	* (by swapping it with its smaller child) repeatedly until queue[k]
590	<	* is less than or equal to its children.
591	<	*/
592	<	private void fixDown(int k) {
593	<	int j;
594	<	if (comparator == null) {
595	<	while ((j = k << 1) <= size && (j > 0)) {
596	<	if (j<size &&
597	<	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
598	<	j++; // j indexes smallest kid
599	<
600	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
601	<	break;
602	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
603	<	k = j;
604	<	}
605	<	} else {
606	<	while ((j = k << 1) <= size && (j > 0)) {
607	<	if (j<size &&
608	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
609	<	j++; // j indexes smallest kid
610	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
611	<	break;
612	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
613	<	k = j;
614	<	}
584	>	* Inserts item x at position k, maintaining heap invariant by
585	>	* demoting x down the tree repeatedly until it is less than or
586	>	* equal to its children or is a leaf.
587	>	*
588	>	* @param k the position to fill
589	>	* @param x the item to insert
590	>	*/
591	>	private void siftDown(int k, E x) {
592	>	if (comparator != null)
593	>	siftDownUsingComparator(k, x);
594	>	else
595	>	siftDownComparable(k, x);
596	>	}
597	>
598	>	private void siftDownComparable(int k, E x) {
599	>	Comparable<? super E> key = (Comparable<? super E>)x;
600	>	int half = size >>> 1;        // loop while a non-leaf
601	>	while (k < half) {
602	>	int child = (k << 1) + 1; // assume left child is least
603	>	Object c = queue[child];
604	>	int right = child + 1;
605	>	if (right < size &&
606	>	((Comparable<? super E>)c).compareTo((E)queue[right]) > 0)
607	>	c = queue[child = right];
608	>	if (key.compareTo((E)c) <= 0)
609	>	break;
610	>	queue[k] = c;
611	>	k = child;
612	>	}
613	>	queue[k] = key;
614	>	}
615	>
616	>	private void siftDownUsingComparator(int k, E x) {
617	>	int half = size >>> 1;
618	>	while (k < half) {
619	>	int child = (k << 1) + 1;
620	>	Object c = queue[child];
621	>	int right = child + 1;
622	>	if (right < size &&
623	>	comparator.compare((E)c, (E)queue[right]) > 0)
624	>	c = queue[child = right];
625	>	if (comparator.compare(x, (E)c) <= 0)
626	>	break;
627	>	queue[k] = c;
628	>	k = child;
629		}
630	+	queue[k] = x;
631		}
632
633		/**
#	Line 615 | Line 635 | public class PriorityQueue<E> extends Ab
635		* assuming nothing about the order of the elements prior to the call.
636		*/
637		private void heapify() {
638	<	for (int i = size/2; i >= 1; i--)
639	<	fixDown(i);
638	>	for (int i = (size >>> 1) - 1; i >= 0; i--)
639	>	siftDown(i, (E)queue[i]);
640		}
641
642		/**
643	<	* Returns the comparator used to order this collection, or <tt>null</tt>
644	<	* if this collection is sorted according to its elements natural ordering
645	<	* (using <tt>Comparable</tt>).
643	>	* Returns the comparator used to order the elements in this
644	>	* queue, or <tt>null</tt> if this queue is sorted according to
645	>	* the {@linkplain Comparable natural ordering} of its elements.
646		*
647	<	* @return the comparator used to order this collection, or <tt>null</tt>
648	<	* if this collection is sorted according to its elements natural ordering.
647	>	* @return the comparator used to order this queue, or
648	>	*         <tt>null</tt> if this queue is sorted according to the
649	>	*         natural ordering of its elements.
650		*/
651		public Comparator<? super E> comparator() {
652		return comparator;
#	Line 646 | Line 667 | public class PriorityQueue<E> extends Ab
667		s.defaultWriteObject();
668
669		// Write out array length
670	<	s.writeInt(queue.length);
670	>	// For compatibility with 1.5 version, must be at least 2.
671	>	s.writeInt(Math.max(2, queue.length));
672
673		// Write out all elements in the proper order.
674		for (int i=0; i<size; i++)
#	Line 654 | Line 676 | public class PriorityQueue<E> extends Ab
676		}
677
678		/**
679	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
680	<	* deserialize it).
679	>	* Reconstitute the <tt>PriorityQueue</tt> instance from a stream
680	>	* (that is, deserialize it).
681		* @param s the stream
682		*/
683		private void readObject(java.io.ObjectInputStream s)

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