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root/jsr166/jsr166/src/main/java/util/PriorityQueue.java

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.41 by dl, Sat Sep 13 18:51:06 2003 UTC vs.
Revision 1.59 by jsr166, Tue Nov 29 08:52:26 2005 UTC

#	Line 1 | Line 1
1		/*
2		* %W% %E%
3		*
4	<	* Copyright 2003 Sun Microsystems, Inc. All rights reserved.
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
13	<	* heap.  This queue orders elements according to an order specified
14	<	* at construction time, which is specified either according to their
15	<	* <i>natural order</i> (see {@link Comparable}), or according to a
16	<	* {@link java.util.Comparator}, depending on which constructor is
17	<	* used. A priority queue does not permit <tt>null</tt> elements.
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 <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 {@link #remove()} and {@link #poll()}
25	<	* methods remove and return the head of the queue, and the {@link
26	<	* #element()} and {@link #peek()} methods return, but do not delete,
24	<	* the head of the queue.
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 is unbounded, but has an internal
29		* <i>capacity</i> governing the size of an array used to store the
#	Line 30 | Line 32 | package java.util;
32		* grows automatically.  The details of the growth policy are not
33		* specified.
34		*
35	<	* <p>This class implements all of the <em>optional</em> methods of
36	<	* the {@link Collection} and {@link Iterator} interfaces.  The
37	<	* Iterator provided in method {@link #iterator()} is <em>not</em>
38	<	* guaranteed to traverse the elements of the PriorityQueue in any
39	<	* particular order. If you need ordered traversal, consider using
40	<	* <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 43 | Line 45 | package java.util;
45		* structurally. Instead, use the thread-safe {@link
46		* java.util.concurrent.PriorityBlockingQueue} class.
47		*
46	–	*
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 55 | Line 56 | package java.util;
56		* <a href="{@docRoot}/../guide/collections/index.html">
57		* Java Collections Framework</a>.
58		* @since 1.5
59	<	* @version %I%, %G%
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	<	*
75	<	* The element with the lowest value is in queue[1], assuming the queue is
76	<	* nonempty.  (A one-based array is used in preference to the traditional
77	<	* zero-based array to simplify parent and child calculations.)
78	<	*
79	<	* 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 98 | 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 123 | 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		/**
142	–	* Common code to initialize underlying queue array across
143	–	* constructors below.
144	–	*/
145	–	private void initializeArray(Collection<? extends E> c) {
146	–	int sz = c.size();
147	–	int initialCapacity = (int)Math.min((sz * 110L) / 100,
148	–	Integer.MAX_VALUE - 1);
149	–	if (initialCapacity < 1)
150	–	initialCapacity = 1;
151	–
152	–	this.queue = new Object[initialCapacity + 1];
153	–	}
154	–
155	–	/**
156	–	* Initially fill elements of the queue array under the
157	–	* knowledge that it is sorted or is another PQ, in which
158	–	* case we can just place the elements in the order presented.
159	–	*/
160	–	private void fillFromSorted(Collection<? extends E> c) {
161	–	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
162	–	queue[++size] = i.next();
163	–	}
164	–
165	–	/**
166	–	* Initially fill elements of the queue array that is not to our knowledge
167	–	* sorted, so we must rearrange the elements to guarantee the heap
168	–	* invariant.
169	–	*/
170	–	private void fillFromUnsorted(Collection<? extends E> c) {
171	–	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
172	–	queue[++size] = i.next();
173	–	heapify();
174	–	}
175	–
176	–	/**
141		* Creates a <tt>PriorityQueue</tt> containing the elements in the
142	<	* specified collection.  The priority queue has an initial
179	<	* capacity of 110% of the size of the specified collection or 1
180	<	* 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
185	<	* elements' natural order.  Otherwise, the priority queue is
186	<	* 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;
205	<	comparator = (Comparator<? super E>)s.comparator();
206	<	fillFromSorted(s);
207	<	} 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
226	<	*         queue's ordering.
227	<	* @throws NullPointerException if <tt>c</tt> or any element within it
228	<	* 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) {
231	–	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
240	<	* if the collection is empty.  This priority queue will be sorted
241	<	* according to the same comparator as the given collection, or
242	<	* according to its elements' natural order if the collection is
243	<	* 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) {
254	–	initializeArray(c);
203		comparator = (Comparator<? super E>)c.comparator();
204	<	fillFromSorted(c);
204	>	initFromCollection(c);
205		}
206
207		/**
208	<	* Resize array, if necessary, to be able to hold given index
208	>	* Initialize queue array with elements from the given Collection.
209	>	* @param c the collection
210		*/
211	<	private void grow(int index) {
212	<	int newlen = queue.length;
213	<	if (index < newlen) // don't need to grow
214	<	return;
215	<	if (index == Integer.MAX_VALUE)
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	>	* Increases the capacity of the array.
222	>	*
223	>	* @param minCapacity the desired minimum capacity
224	>	*/
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);
236	<	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 / 2) * 3));
233	>	if (newCapacity < 0) // overflow
234	>	newCapacity = Integer.MAX_VALUE;
235	>	if (newCapacity < minCapacity)
236	>	newCapacity = minCapacity;
237	>	queue = Arrays.copyOf(queue, newCapacity);
238	>	}
239	>
240	>	/**
241	>	* Inserts the specified element into this priority queue.
242	>	*
243	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
244	>	* @throws ClassCastException if the specified element cannot be
245	>	*         compared with elements currently in this priority queue
246	>	*         according to the priority queue's ordering
247	>	* @throws NullPointerException if the specified element is null
248	>	*/
249	>	public boolean add(E e) {
250	>	return offer(e);
251		}
278	–
252
253		/**
254	<	* Inserts the specified element to this priority queue.
254	>	* Inserts the specified element into this priority queue.
255		*
256	<	* @return <tt>true</tt>
257	<	* @throws ClassCastException if the specified element cannot be compared
258	<	* with elements currently in the priority queue according
259	<	* to the priority queue's ordering.
260	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
256	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
257	>	* @throws ClassCastException if the specified element cannot be
258	>	*         compared with elements currently in this priority queue
259	>	*         according to the priority queue's ordering
260	>	* @throws NullPointerException if the specified element is null
261		*/
262	<	public boolean offer(E o) {
263	<	if (o == null)
262	>	public boolean offer(E e) {
263	>	if (e == null)
264		throw new NullPointerException();
265		modCount++;
266	<	++size;
267	<
268	<	// Grow backing store if necessary
269	<	if (size >= queue.length)
270	<	grow(size);
271	<
272	<	queue[size] = o;
273	<	fixUp(size);
266	>	int i = size;
267	>	if (i >= queue.length)
268	>	grow(i + 1);
269	>	size = i + 1;
270	>	if (i == 0)
271	>	queue[0] = e;
272	>	else
273	>	siftUp(i, e);
274		return true;
275		}
276
277		public E peek() {
278		if (size == 0)
279		return null;
280	<	return (E) queue[1];
280	>	return (E) queue[0];
281		}
282
283	<	// Collection Methods - the first two override to update docs
283	>	private int indexOf(Object o) {
284	>	if (o != null) {
285	>	for (int i = 0; i < size; i++)
286	>	if (o.equals(queue[i]))
287	>	return i;
288	>	}
289	>	return -1;
290	>	}
291
292		/**
293	<	* Adds the specified element to this queue.
294	<	* @return <tt>true</tt> (as per the general contract of
295	<	* <tt>Collection.add</tt>).
296	<	*
297	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
298	<	* @throws ClassCastException if the specified element cannot be compared
299	<	* with elements currently in the priority queue according
300	<	* to the priority queue's ordering.
321	<	*/
322	<	public boolean add(E o) {
323	<	return offer(o);
324	<	}
325	<
326	<
327	<	/**
328	<	* Adds all of the elements in the specified collection to this queue.
329	<	* The behavior of this operation is undefined if
330	<	* the specified collection is modified while the operation is in
331	<	* progress.  (This implies that the behavior of this call is undefined if
332	<	* the specified collection is this queue, and this queue is nonempty.)
333	<	* <p>
334	<	* This implementation iterates over the specified collection, and adds
335	<	* each object returned by the iterator to this collection, in turn.
336	<	* @param c collection whose elements are to be added to this queue
337	<	* @return <tt>true</tt> if this queue changed as a result of the
338	<	*         call.
339	<	* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
340	<	* is <tt>null</tt>
341	<	* @throws ClassCastException if any element cannot be compared
342	<	* with elements currently in the priority queue according
343	<	* to the priority queue's ordering.
293	>	* Removes a single instance of the specified element from this queue,
294	>	* if it is present.  More formally, removes an element <tt>e</tt> such
295	>	* that <tt>o.equals(e)</tt>, if this queue contains one or more such
296	>	* elements.  Returns true if this queue contained the specified element
297	>	* (or equivalently, if this queue changed as a result of the call).
298	>	*
299	>	* @param o element to be removed from this queue, if present
300	>	* @return <tt>true</tt> if this queue changed as a result of the call
301		*/
345	–	public boolean addAll(Collection<? extends E> c) {
346	–	return super.addAll(c);
347	–	}
348	–
302		public boolean remove(Object o) {
303	<	if (o == null)
304	<	return false;
303	>	int i = indexOf(o);
304	>	if (i == -1)
305	>	return false;
306	>	else {
307	>	removeAt(i);
308	>	return true;
309	>	}
310	>	}
311
312	<	if (comparator == null) {
313	<	for (int i = 1; i <= size; i++) {
314	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
315	<	removeAt(i);
316	<	return true;
317	<	}
318	<	}
319	<	} else {
320	<	for (int i = 1; i <= size; i++) {
321	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
322	<	removeAt(i);
323	<	return true;
365	<	}
312	>	/**
313	>	* Version of remove using reference equality, not equals.
314	>	* Needed by iterator.remove.
315	>	*
316	>	* @param o element to be removed from this queue, if present
317	>	* @return <tt>true</tt> if removed
318	>	*/
319	>	boolean removeEq(Object o) {
320	>	for (int i = 0; i < size; i++) {
321	>	if (o == queue[i]) {
322	>	removeAt(i);
323	>	return true;
324		}
325		}
326		return false;
327		}
328
329		/**
330	+	* Returns <tt>true</tt> if this queue contains the specified element.
331	+	* More formally, returns <tt>true</tt> if and only if this queue contains
332	+	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
333	+	*
334	+	* @param o object to be checked for containment in this queue
335	+	* @return <tt>true</tt> if this queue contains the specified element
336	+	*/
337	+	public boolean contains(Object o) {
338	+	return indexOf(o) != -1;
339	+	}
340	+
341	+	/**
342	+	* Returns an array containing all of the elements in this queue,
343	+	* The elements are in no particular order.
344	+	*
345	+	* <p>The returned array will be "safe" in that no references to it are
346	+	* maintained by this list.  (In other words, this method must allocate
347	+	* a new array).  The caller is thus free to modify the returned array.
348	+	*
349	+	* @return an array containing all of the elements in this queue
350	+	*/
351	+	public Object[] toArray() {
352	+	return Arrays.copyOf(queue, size);
353	+	}
354	+
355	+	/**
356	+	* Returns an array containing all of the elements in this queue.
357	+	* The elements are in no particular order.  The runtime type of
358	+	* the returned array is that of the specified array.  If the queue
359	+	* fits in the specified array, it is returned therein.
360	+	* Otherwise, a new array is allocated with the runtime type of
361	+	* the specified array and the size of this queue.
362	+	*
363	+	* <p>If the queue fits in the specified array with room to spare
364	+	* (i.e., the array has more elements than the queue), the element in
365	+	* the array immediately following the end of the collection is set to
366	+	* <tt>null</tt>.  (This is useful in determining the length of the
367	+	* queue <i>only</i> if the caller knows that the queue does not contain
368	+	* any null elements.)
369	+	*
370	+	* @param a the array into which the elements of the queue are to
371	+	*          be stored, if it is big enough; otherwise, a new array of the
372	+	*          same runtime type is allocated for this purpose.
373	+	* @return an array containing the elements of the queue
374	+	* @throws ArrayStoreException if the runtime type of the specified array
375	+	*         is not a supertype of the runtime type of every element in
376	+	*         this queue
377	+	* @throws NullPointerException if the specified array is null
378	+	*/
379	+	public <T> T[] toArray(T[] a) {
380	+	if (a.length < size)
381	+	// Make a new array of a's runtime type, but my contents:
382	+	return (T[]) Arrays.copyOf(queue, size, a.getClass());
383	+	System.arraycopy(queue, 0, a, 0, size);
384	+	if (a.length > size)
385	+	a[size] = null;
386	+	return a;
387	+	}
388	+
389	+	/**
390		* Returns an iterator over the elements in this queue. The iterator
391		* does not return the elements in any particular order.
392		*
393	<	* @return an iterator over the elements in this queue.
393	>	* @return an iterator over the elements in this queue
394		*/
395		public Iterator<E> iterator() {
396		return new Itr();
397		}
398
399	<	private class Itr implements Iterator<E> {
382	<
399	>	private final class Itr implements Iterator<E> {
400		/**
401		* Index (into queue array) of element to be returned by
402		* subsequent call to next.
403		*/
404	<	private int cursor = 1;
404	>	private int cursor = 0;
405
406		/**
407		* Index of element returned by most recent call to next,
408		* unless that element came from the forgetMeNot list.
409	<	* Reset to 0 if element is deleted by a call to remove.
393	<	*/
394	<	private int lastRet = 0;
395	<
396	<	/**
397	<	* The modCount value that the iterator believes that the backing
398	<	* List should have.  If this expectation is violated, the iterator
399	<	* has detected concurrent modification.
409	>	* Set to -1 if element is deleted by a call to remove.
410		*/
411	<	private int expectedModCount = modCount;
411	>	private int lastRet = -1;
412
413		/**
414	<	* A list of elements that were moved from the unvisited portion of
414	>	* A queue of elements that were moved from the unvisited portion of
415		* the heap into the visited portion as a result of "unlucky" element
416		* removals during the iteration.  (Unlucky element removals are those
417	<	* that require a fixup instead of a fixdown.)  We must visit all of
417	>	* that require a siftup instead of a siftdown.)  We must visit all of
418		* the elements in this list to complete the iteration.  We do this
419		* after we've completed the "normal" iteration.
420		*
421		* We expect that most iterations, even those involving removals,
422		* will not use need to store elements in this field.
423		*/
424	<	private ArrayList<E> forgetMeNot = null;
424	>	private ArrayDeque<E> forgetMeNot = null;
425
426		/**
427		* Element returned by the most recent call to next iff that
428		* element was drawn from the forgetMeNot list.
429		*/
430	<	private Object lastRetElt = null;
430	>	private E lastRetElt = null;
431	>
432	>	/**
433	>	* The modCount value that the iterator believes that the backing
434	>	* List should have.  If this expectation is violated, the iterator
435	>	* has detected concurrent modification.
436	>	*/
437	>	private int expectedModCount = modCount;
438
439		public boolean hasNext() {
440	<	return cursor <= size || forgetMeNot != null;
440	>	return cursor < size ||
441	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
442		}
443
444		public E next() {
445	<	checkForComodification();
446	<	E result;
447	<	if (cursor <= size) {
448	<	result = (E) queue[cursor];
449	<	lastRet = cursor++;
450	<	}
451	<	else if (forgetMeNot == null)
452	<	throw new NoSuchElementException();
453	<	else {
436	<	int remaining = forgetMeNot.size();
437	<	result = forgetMeNot.remove(remaining - 1);
438	<	if (remaining == 1)
439	<	forgetMeNot = null;
440	<	lastRet = 0;
441	<	lastRetElt = result;
445	>	if (expectedModCount != modCount)
446	>	throw new ConcurrentModificationException();
447	>	if (cursor < size)
448	>	return (E) queue[lastRet = cursor++];
449	>	if (forgetMeNot != null) {
450	>	lastRet = -1;
451	>	lastRetElt = forgetMeNot.poll();
452	>	if (lastRetElt != null)
453	>	return lastRetElt;
454		}
455	<	return result;
455	>	throw new NoSuchElementException();
456		}
457
458		public void remove() {
459	<	checkForComodification();
460	<
461	<	if (lastRet != 0) {
459	>	if (expectedModCount != modCount)
460	>	throw new ConcurrentModificationException();
461	>	if (lastRet == -1 && lastRetElt == null)
462	>	throw new IllegalStateException();
463	>	if (lastRet != -1) {
464		E moved = PriorityQueue.this.removeAt(lastRet);
465	<	lastRet = 0;
466	<	if (moved == null) {
465	>	lastRet = -1;
466	>	if (moved == null)
467		cursor--;
468	<	} else {
468	>	else {
469		if (forgetMeNot == null)
470	<	forgetMeNot = new ArrayList<E>();
470	>	forgetMeNot = new ArrayDeque<E>();
471		forgetMeNot.add(moved);
472		}
459	–	} else if (lastRetElt != null) {
460	–	PriorityQueue.this.remove(lastRetElt);
461	–	lastRetElt = null;
473		} else {
474	<	throw new IllegalStateException();
474	>	PriorityQueue.this.removeEq(lastRetElt);
475	>	lastRetElt = null;
476		}
465	–
477		expectedModCount = modCount;
478		}
479
469	–	final void checkForComodification() {
470	–	if (modCount != expectedModCount)
471	–	throw new ConcurrentModificationException();
472	–	}
480		}
481
482		public int size() {
#	Line 477 | Line 484 | public class PriorityQueue<E> extends Ab
484		}
485
486		/**
487	<	* Remove all elements from the priority queue.
487	>	* Removes all of the elements from this priority queue.
488	>	* The queue will be empty after this call returns.
489		*/
490		public void clear() {
491		modCount++;
492	<
485	<	// Null out element references to prevent memory leak
486	<	for (int i=1; i<=size; i++)
492	>	for (int i = 0; i < size; i++)
493		queue[i] = null;
488	–
494		size = 0;
495		}
496
497		public E poll() {
498		if (size == 0)
499		return null;
500	+	int s = --size;
501		modCount++;
502	<
503	<	E result = (E) queue[1];
504	<	queue[1] = queue[size];
505	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
506	<	if (size > 1)
501	<	fixDown(1);
502	<
502	>	E result = (E)queue[0];
503	>	E x = (E)queue[s];
504	>	queue[s] = null;
505	>	if (s != 0)
506	>	siftDown(0, x);
507		return result;
508		}
509
510		/**
511	<	* Removes and returns the ith element from queue.  (Recall that queue
508	<	* is one-based, so 1 <= i <= size.)
511	>	* Removes the ith element from queue.
512		*
513	<	* Normally this method leaves the elements at positions from 1 up to i-1,
514	<	* inclusive, untouched.  Under these circumstances, it returns null.
515	<	* Occasionally, in order to maintain the heap invariant, it must move
516	<	* the last element of the list to some index in the range [2, i-1],
517	<	* and move the element previously at position (i/2) to position i.
518	<	* Under these circumstances, this method returns the element that was
519	<	* previously at the end of the list and is now at some position between
520	<	* 2 and i-1 inclusive.
513	>	* Normally this method leaves the elements at up to i-1,
514	>	* inclusive, untouched.  Under these circumstances, it returns
515	>	* null.  Occasionally, in order to maintain the heap invariant,
516	>	* it must swap a later element of the list with one earlier than
517	>	* i.  Under these circumstances, this method returns the element
518	>	* that was previously at the end of the list and is now at some
519	>	* position before i. This fact is used by iterator.remove so as to
520	>	* avoid missing traverseing elements.
521		*/
522	<	private E removeAt(int i) {
523	<	assert i > 0 && i <= size;
522	>	private E removeAt(int i) {
523	>	assert i >= 0 && i < size;
524		modCount++;
525	<
526	<	E moved = (E) queue[size];
527	<	queue[i] = moved;
528	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
529	<	if (i <= size) {
530	<	fixDown(i);
525	>	int s = --size;
526	>	if (s == i) // removed last element
527	>	queue[i] = null;
528	>	else {
529	>	E moved = (E) queue[s];
530	>	queue[s] = null;
531	>	siftDown(i, moved);
532		if (queue[i] == moved) {
533	<	fixUp(i);
533	>	siftUp(i, moved);
534		if (queue[i] != moved)
535		return moved;
536		}
#	Line 535 | Line 539 | public class PriorityQueue<E> extends Ab
539		}
540
541		/**
542	<	* Establishes the heap invariant (described above) assuming the heap
543	<	* satisfies the invariant except possibly for the leaf-node indexed by k
544	<	* (which may have a nextExecutionTime less than its parent's).
545	<	*
546	<	* This method functions by "promoting" queue[k] up the hierarchy
547	<	* (by swapping it with its parent) repeatedly until queue[k]
548	<	* is greater than or equal to its parent.
549	<	*/
550	<	private void fixUp(int k) {
551	<	if (comparator == null) {
552	<	while (k > 1) {
553	<	int j = k >> 1;
554	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
555	<	break;
556	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
557	<	k = j;
558	<	}
559	<	} else {
560	<	while (k > 1) {
561	<	int j = k >>> 1;
562	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
563	<	break;
564	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
565	<	k = j;
566	<	}
542	>	* Inserts item x at position k, maintaining heap invariant by
543	>	* promoting x up the tree until it is greater than or equal to
544	>	* its parent, or is the root.
545	>	*
546	>	* To simplify and speed up coercions and comparisons. the
547	>	* Comparable and Comparator versions are separated into different
548	>	* methods that are otherwise identical. (Similarly for siftDown.)
549	>	*
550	>	* @param k the position to fill
551	>	* @param x the item to insert
552	>	*/
553	>	private void siftUp(int k, E x) {
554	>	if (comparator != null)
555	>	siftUpUsingComparator(k, x);
556	>	else
557	>	siftUpComparable(k, x);
558	>	}
559	>
560	>	private void siftUpComparable(int k, E x) {
561	>	Comparable<? super E> key = (Comparable<? super E>) x;
562	>	while (k > 0) {
563	>	int parent = (k - 1) >>> 1;
564	>	Object e = queue[parent];
565	>	if (key.compareTo((E)e) >= 0)
566	>	break;
567	>	queue[k] = e;
568	>	k = parent;
569	>	}
570	>	queue[k] = key;
571	>	}
572	>
573	>	private void siftUpUsingComparator(int k, E x) {
574	>	while (k > 0) {
575	>	int parent = (k - 1) >>> 1;
576	>	Object e = queue[parent];
577	>	if (comparator.compare(x, (E)e) >= 0)
578	>	break;
579	>	queue[k] = e;
580	>	k = parent;
581		}
582	+	queue[k] = x;
583		}
584
585		/**
586	<	* Establishes the heap invariant (described above) in the subtree
587	<	* rooted at k, which is assumed to satisfy the heap invariant except
588	<	* possibly for node k itself (which may be greater than its children).
589	<	*
590	<	* This method functions by "demoting" queue[k] down the hierarchy
591	<	* (by swapping it with its smaller child) repeatedly until queue[k]
592	<	* is less than or equal to its children.
593	<	*/
594	<	private void fixDown(int k) {
595	<	int j;
596	<	if (comparator == null) {
597	<	while ((j = k << 1) <= size && (j > 0)) {
598	<	if (j<size &&
599	<	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
600	<	j++; // j indexes smallest kid
601	<
602	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
603	<	break;
604	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
605	<	k = j;
606	<	}
607	<	} else {
608	<	while ((j = k << 1) <= size && (j > 0)) {
609	<	if (j<size &&
610	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
611	<	j++; // j indexes smallest kid
612	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
613	<	break;
614	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
615	<	k = j;
616	<	}
586	>	* Inserts item x at position k, maintaining heap invariant by
587	>	* demoting x down the tree repeatedly until it is less than or
588	>	* equal to its children or is a leaf.
589	>	*
590	>	* @param k the position to fill
591	>	* @param x the item to insert
592	>	*/
593	>	private void siftDown(int k, E x) {
594	>	if (comparator != null)
595	>	siftDownUsingComparator(k, x);
596	>	else
597	>	siftDownComparable(k, x);
598	>	}
599	>
600	>	private void siftDownComparable(int k, E x) {
601	>	Comparable<? super E> key = (Comparable<? super E>)x;
602	>	int half = size >>> 1;        // loop while a non-leaf
603	>	while (k < half) {
604	>	int child = (k << 1) + 1; // assume left child is least
605	>	Object c = queue[child];
606	>	int right = child + 1;
607	>	if (right < size &&
608	>	((Comparable<? super E>)c).compareTo((E)queue[right]) > 0)
609	>	c = queue[child = right];
610	>	if (key.compareTo((E)c) <= 0)
611	>	break;
612	>	queue[k] = c;
613	>	k = child;
614	>	}
615	>	queue[k] = key;
616	>	}
617	>
618	>	private void siftDownUsingComparator(int k, E x) {
619	>	int half = size >>> 1;
620	>	while (k < half) {
621	>	int child = (k << 1) + 1;
622	>	Object c = queue[child];
623	>	int right = child + 1;
624	>	if (right < size &&
625	>	comparator.compare((E)c, (E)queue[right]) > 0)
626	>	c = queue[child = right];
627	>	if (comparator.compare(x, (E)c) <= 0)
628	>	break;
629	>	queue[k] = c;
630	>	k = child;
631		}
632	+	queue[k] = x;
633		}
634
635		/**
#	Line 603 | Line 637 | public class PriorityQueue<E> extends Ab
637		* assuming nothing about the order of the elements prior to the call.
638		*/
639		private void heapify() {
640	<	for (int i = size/2; i >= 1; i--)
641	<	fixDown(i);
640	>	for (int i = (size >>> 1) - 1; i >= 0; i--)
641	>	siftDown(i, (E)queue[i]);
642		}
643
644		/**
645	<	* Returns the comparator used to order this collection, or <tt>null</tt>
646	<	* if this collection is sorted according to its elements natural ordering
647	<	* (using <tt>Comparable</tt>).
645	>	* Returns the comparator used to order the elements in this
646	>	* queue, or <tt>null</tt> if this queue is sorted according to
647	>	* the {@linkplain Comparable natural ordering} of its elements.
648		*
649	<	* @return the comparator used to order this collection, or <tt>null</tt>
650	<	* if this collection is sorted according to its elements natural ordering.
649	>	* @return the comparator used to order this queue, or
650	>	*         <tt>null</tt> if this queue is sorted according to the
651	>	*         natural ordering of its elements.
652		*/
653		public Comparator<? super E> comparator() {
654		return comparator;
#	Line 634 | Line 669 | public class PriorityQueue<E> extends Ab
669		s.defaultWriteObject();
670
671		// Write out array length
672	<	s.writeInt(queue.length);
672	>	// For compatibility with 1.5 version, must be at least 2.
673	>	s.writeInt(Math.max(2, queue.length));
674
675		// Write out all elements in the proper order.
676	<	for (int i=1; i<=size; i++)
676	>	for (int i=0; i<size; i++)
677		s.writeObject(queue[i]);
678		}
679
680		/**
681	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
682	<	* deserialize it).
681	>	* Reconstitute the <tt>PriorityQueue</tt> instance from a stream
682	>	* (that is, deserialize it).
683		* @param s the stream
684		*/
685		private void readObject(java.io.ObjectInputStream s)
#	Line 656 | Line 692 | public class PriorityQueue<E> extends Ab
692		queue = new Object[arrayLength];
693
694		// Read in all elements in the proper order.
695	<	for (int i=1; i<=size; i++)
695	>	for (int i=0; i<size; i++)
696		queue[i] = (E) s.readObject();
697		}
698

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