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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.35 by dl, Wed Aug 27 10:27:07 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 {@linkplain Queue queue} based on a priority heap.
12	<	* This queue orders
13	<	* elements according to an order specified at construction time, which is
14	<	* specified in the same manner as {@link java.util.TreeSet} and
15	<	* {@link java.util.TreeMap}: elements are ordered
16	<	* either according to their <i>natural order</i> (see {@link Comparable}), or
17	<	* according to a {@link java.util.Comparator}, depending on which
18	<	* constructor is used.
12	<	* <p>The <em>head</em> of this queue is the <em>least</em> element with
13	<	* respect to the specified ordering.
14	<	* If multiple elements are tied for least value, the
15	<	* head is one of those elements. A priority queue does not permit
16	<	* <tt>null</tt> elements.
17	<	*
18	<	* <p>The {@link #remove()} and {@link #poll()} methods remove and
19	<	* return the head of the queue.
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 {@link #element()} and {@link #peek()} methods return, but do
21	<	* not delete, the head of the queue.
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
28	<	* size of the array used internally to store the elements on the
29	<	* queue.
30	<	* It is always at least as large as the queue size.  As
31	<	* elements are added to a priority queue, its capacity grows
32	<	* automatically.  The details of the growth policy are not specified.
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>The Iterator provided in method {@link #iterator()} is <em>not</em>
35	<	* guaranteed to traverse the elements of the PriorityQueue in any
36	<	* particular order. If you need ordered traversal, consider using
37	<	* <tt>Arrays.sort(pq.toArray())</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>
#	Line 39 | Line 44
44		* structurally. Instead, use the thread-safe {@link
45		* java.util.concurrent.PriorityBlockingQueue} class.
46		*
42	–	*
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
#	Line 51 | Line 55
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>, java.io.Serializable {
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	<	*
70	<	* The element with the lowest value is in queue[1], assuming the queue is
71	<	* nonempty.  (A one-based array is used in preference to the traditional
72	<	* zero-based array to simplify parent and child calculations.)
73	<	*
74	<	* 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 Object[] queue;
78
#	Line 93 | Line 94 | public class PriorityQueue<E> extends Ab
94		private transient int modCount = 0;
95
96		/**
97	<	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
98	<	* (11) that orders its elements according to their natural
99	<	* 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, null);
103		}
104
105		/**
106	<	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
107	<	* that orders its elements according to their natural ordering
108	<	* (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		*/
#	Line 118 | Line 119 | public class PriorityQueue<E> extends Ab
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	<	* If <tt>null</tt> then the order depends on the elements' natural
125	<	* ordering.
126	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
127	<	* than 1
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,
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		throw new IllegalArgumentException();
135	<	this.queue = new Object[initialCapacity + 1];
135	>	this.queue = new Object[initialCapacity];
136		this.comparator = comparator;
137		}
138
139		/**
137	–	* Common code to initialize underlying queue array across
138	–	* constructors below.
139	–	*/
140	–	private void initializeArray(Collection<? extends E> c) {
141	–	int sz = c.size();
142	–	int initialCapacity = (int)Math.min((sz * 110L) / 100,
143	–	Integer.MAX_VALUE - 1);
144	–	if (initialCapacity < 1)
145	–	initialCapacity = 1;
146	–
147	–	this.queue = new Object[initialCapacity + 1];
148	–	}
149	–
150	–	/**
151	–	* Initially fill elements of the queue array under the
152	–	* knowledge that it is sorted or is another PQ, in which
153	–	* case we can just place the elements without fixups.
154	–	*/
155	–	private void fillFromSorted(Collection<? extends E> c) {
156	–	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
157	–	queue[++size] = i.next();
158	–	}
159	–
160	–
161	–	/**
162	–	* Initially fill elements of the queue array that is
163	–	* not to our knowledge sorted, so we must add them
164	–	* one by one.
165	–	*/
166	–	private void fillFromUnsorted(Collection<? extends E> c) {
167	–	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
168	–	add(i.next());
169	–	}
170	–
171	–	/**
140		* Creates a <tt>PriorityQueue</tt> containing the elements in the
141	<	* specified collection.  The priority queue has an initial
174	<	* capacity of 110% of the size of the specified collection or 1
175	<	* if the collection is empty.  If the specified collection is an
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 sorted
144	<	* according to the same comparator, or according to its elements'
145	<	* natural order if the collection is sorted according to its
180	<	* elements' natural order.  Otherwise, the priority queue is
181	<	* ordered according to its elements' natural order.
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 c 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 <tt>c</tt> or any element within it
153	<	* is <tt>null</tt>
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	<	initializeArray(c);
157	<	if (c instanceof SortedSet) {
158	<	// @fixme double-cast workaround for compiler
159	<	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
160	<	comparator = (Comparator<? super E>)s.comparator();
161	<	fillFromSorted(s);
162	<	} else if (c instanceof PriorityQueue) {
163	<	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
200	<	comparator = (Comparator<? super E>)s.comparator();
201	<	fillFromSorted(s);
202	<	} else {
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	<	fillFromUnsorted(c);
165	>	heapify();
166		}
167		}
168
169		/**
170		* Creates a <tt>PriorityQueue</tt> containing the elements in the
171	<	* specified collection.  The priority queue has an initial
172	<	* capacity of 110% of the size of the specified collection or 1
173	<	* if the collection is empty.  This priority queue will be sorted
174	<	* according to the same comparator as the given collection, or
175	<	* according to its elements' natural order if the collection is
176	<	* sorted according to its elements' natural order.
177	<	*
178	<	* @param c the collection whose elements are to be placed
179	<	*        into this priority queue.
180	<	* @throws ClassCastException if elements of the specified collection
181	<	*         cannot be compared to one another according to the priority
221	<	*         queue's ordering.
222	<	* @throws NullPointerException if <tt>c</tt> or any element within it
223	<	* is <tt>null</tt>
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) {
226	–	initializeArray(c);
184		comparator = (Comparator<? super E>)c.comparator();
185	<	fillFromSorted(c);
185	>	initFromCollection(c);
186		}
187
188		/**
189		* Creates a <tt>PriorityQueue</tt> containing the elements in the
190	<	* specified collection.  The priority queue has an initial
191	<	* capacity of 110% of the size of the specified collection or 1
235	<	* if the collection is empty.  This priority queue will be sorted
236	<	* according to the same comparator as the given collection, or
237	<	* according to its elements' natural order if the collection is
238	<	* sorted according to its elements' natural order.
190	>	* specified sorted set.  This priority queue will be ordered
191	>	* according to the same ordering as the given sorted set.
192		*
193	<	* @param c the collection whose elements are to be placed
194	<	*        into this priority queue.
195	<	* @throws ClassCastException if elements of the specified collection
196	<	*         cannot be compared to one another according to the priority
197	<	*         queue's ordering.
198	<	* @throws NullPointerException if <tt>c</tt> or any element within it
199	<	* is <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 PriorityQueue(SortedSet<? extends E> c) {
249	–	initializeArray(c);
202		comparator = (Comparator<? super E>)c.comparator();
203	<	fillFromSorted(c);
203	>	initFromCollection(c);
204		}
205
206		/**
207	<	* Resize array, if necessary, to be able to hold given index
207	>	* Initialize queue array with elements from the given Collection.
208	>	* @param c the collection
209		*/
210	<	private void grow(int index) {
211	<	int newlen = queue.length;
212	<	if (index < newlen) // don't need to grow
213	<	return;
214	<	if (index == Integer.MAX_VALUE)
215	<	throw new OutOfMemoryError();
216	<	while (newlen <= index) {
264	<	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
265	<	newlen = Integer.MAX_VALUE;
266	<	else
267	<	newlen <<= 2;
268	<	}
269	<	Object[] newQueue = new Object[newlen];
270	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
271	<	queue = newQueue;
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		}
273	–
274	–	// Queue Methods
218
219	+	/**
220	+	* Increases the capacity of the array.
221	+	*
222	+	* @param minCapacity the desired minimum capacity
223	+	*/
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	+	/**
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	<	* Add the specified element to this priority queue.
253	>	* Inserts the specified element into this priority queue.
254		*
255	<	* @return <tt>true</tt>
256	<	* @throws ClassCastException if the specified element cannot be compared
257	<	* with elements currently in the priority queue according
258	<	* to the priority queue's ordering.
259	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
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 offer(E o) {
262	<	if (o == null)
261	>	public boolean offer(E e) {
262	>	if (e == null)
263		throw new NullPointerException();
264		modCount++;
265	<	++size;
266	<
267	<	// Grow backing store if necessary
268	<	if (size >= queue.length)
269	<	grow(size);
270	<
271	<	queue[size] = o;
272	<	fixUp(size);
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	<	public E poll() {
276	>	public E peek() {
277		if (size == 0)
278		return null;
279	<	return (E) remove(1);
279	>	return (E) queue[0];
280		}
281
282	<	public E peek() {
283	<	return (E) queue[1];
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
312	–	// Collection Methods - the first two override to update docs
313	–
291		/**
292	<	* Adds the specified element to this queue.
293	<	* @return <tt>true</tt> (as per the general contract of
294	<	* <tt>Collection.add</tt>).
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	<	* @throws NullPointerException {@inheritDoc}
299	<	* @throws ClassCastException if the specified element cannot be compared
321	<	* with elements currently in the priority queue according
322	<	* to the priority queue's ordering.
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 add(E o) {
302	<	return super.add(o);
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
328	–
311		/**
312	<	* Adds all of the elements in the specified collection to this queue.
313	<	* The behavior of this operation is undefined if
314	<	* the specified collection is modified while the operation is in
315	<	* progress.  (This implies that the behavior of this call is undefined if
316	<	* the specified collection is this queue, and this queue is nonempty.)
317	<	* <p>
318	<	* This implementation iterates over the specified collection, and adds
319	<	* each object returned by the iterator to this collection, in turn.
320	<	* @throws NullPointerException {@inheritDoc}
321	<	* @throws ClassCastException if any element cannot be compared
322	<	* with elements currently in the priority queue according
323	<	* to the priority queue's ordering.
324	<	*/
325	<	public boolean addAll(Collection<? extends E> c) {
344	<	return super.addAll(c);
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 <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	<	* Removes a single instance of the specified element from this
342	<	* queue, if it is present.  More formally,
343	<	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
344	<	* o.equals(e))</tt>, if the queue contains one or more such
345	<	* elements.  Returns <tt>true</tt> if the queue contained the
346	<	* specified element (or equivalently, if the queue changed as a
347	<	* result of the call).
348	<	*
349	<	* <p>This implementation iterates over the queue looking for the
350	<	* specified element.  If it finds the element, it removes the element
351	<	* from the queue using the iterator's remove method.<p>
352	<	*
361	<	*/
362	<	public boolean remove(Object o) {
363	<	if (o == null)
364	<	return false;
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	<	if (comparator == null) {
355	<	for (int i = 1; i <= size; i++) {
356	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
357	<	remove(i);
358	<	return true;
359	<	}
360	<	}
361	<	} else {
362	<	for (int i = 1; i <= size; i++) {
363	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
364	<	remove(i);
365	<	return true;
366	<	}
367	<	}
368	<	}
369	<	return false;
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.
392	>	* @return an iterator over the elements in this queue
393		*/
394		public Iterator<E> iterator() {
395		return new Itr();
396		}
397
398	<	private class Itr implements Iterator<E> {
395	<
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	<	private int cursor = 1;
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.
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 = 0;
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
#	Line 413 | Line 435 | public class PriorityQueue<E> extends Ab
435		*/
436		private int expectedModCount = modCount;
437
416	–	// Workarounds until version that better handles remove() installed.
417	–	// These are used to copy-on-write the array upon first remove
418	–	private Object[] q = queue;
419	–	private int qsize = size;
420	–
438		public boolean hasNext() {
439	<	return cursor <= qsize;
439	>	return cursor < size ||
440	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
441		}
442
443		public E next() {
444	<	checkForComodification();
445	<	if (cursor > qsize)
446	<	throw new NoSuchElementException();
447	<	E result = (E) q[cursor];
448	<	lastRet = cursor++;
449	<	return result;
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)
458	>	if (expectedModCount != modCount)
459	>	throw new ConcurrentModificationException();
460	>	if (lastRet == -1 && lastRetElt == null)
461		throw new IllegalStateException();
462	<	checkForComodification();
463	<
464	<	// Copy on first remove
465	<	if (q == queue) {
466	<	q = new Object[queue.length];
467	<	System.arraycopy(queue, 0, q, 0, queue.length);
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		}
444	–	PriorityQueue.this.remove(q[lastRet]);
445	–
446	–	lastRet = 0;
476		expectedModCount = modCount;
477		}
478
450	–	final void checkForComodification() {
451	–	if (modCount != expectedModCount)
452	–	throw new ConcurrentModificationException();
453	–	}
479		}
480
481		public int size() {
#	Line 458 | Line 483 | public class PriorityQueue<E> extends Ab
483		}
484
485		/**
486	<	* Remove all elements from the priority queue.
486	>	* Removes all of the elements from this priority queue.
487	>	* The queue will be empty after this call returns.
488		*/
489		public void clear() {
490		modCount++;
491	<
466	<	// Null out element references to prevent memory leak
467	<	for (int i=1; i<=size; i++)
491	>	for (int i = 0; i < size; i++)
492		queue[i] = null;
469	–
493		size = 0;
494		}
495
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	<	* Removes and returns the ith element from queue.  Recall
475	<	* that queue is one-based, so 1 <= i <= size.
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	<	private E remove(int i) {
522	<	assert i <= size;
521	>	private E removeAt(int i) {
522	>	assert i >= 0 && i < size;
523		modCount++;
524	<
525	<	E result = (E) queue[i];
526	<	queue[i] = queue[size];
527	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
528	<	if (i <= size) {
529	<	fixDown(i);
530	<	fixUp(i);
524	>	int s = --size;
525	>	if (s == i) // removed last element
526	>	queue[i] = null;
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	<
490	<	return result;
537	>	return null;
538		}
539
540		/**
541	<	* Establishes the heap invariant (described above) assuming the heap
542	<	* satisfies the invariant except possibly for the leaf-node indexed by k
543	<	* (which may have a nextExecutionTime less than its parent's).
544	<	*
545	<	* This method functions by "promoting" queue[k] up the hierarchy
546	<	* (by swapping it with its parent) repeatedly until queue[k]
547	<	* is greater than or equal to its parent.
548	<	*/
549	<	private void fixUp(int k) {
550	<	if (comparator == null) {
551	<	while (k > 1) {
552	<	int j = k >> 1;
553	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
554	<	break;
555	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
556	<	k = j;
557	<	}
558	<	} else {
559	<	while (k > 1) {
560	<	int j = k >>> 1;
561	<	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
562	<	break;
563	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
564	<	k = j;
565	<	}
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	>	* 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 void siftUp(int k, E x) {
553	>	if (comparator != null)
554	>	siftUpUsingComparator(k, x);
555	>	else
556	>	siftUpComparable(k, x);
557	>	}
558	>
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	+	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 && (j > 0)) {
597	<	if (j<size &&
598	<	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
599	<	j++; // j indexes smallest kid
600	<
601	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
602	<	break;
603	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
604	<	k = j;
605	<	}
606	<	} else {
607	<	while ((j = k << 1) <= size && (j > 0)) {
608	<	if (j<size &&
609	<	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
610	<	j++; // j indexes smallest kid
611	<	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
612	<	break;
551	<	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
552	<	k = j;
553	<	}
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 used to order this collection, or <tt>null</tt>
645	<	* if this collection is sorted according to its elements natural ordering
646	<	* (using <tt>Comparable</tt>).
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 used to order this collection, or <tt>null</tt>
649	<	* if this collection is sorted according to 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		public Comparator<? super E> comparator() {
653		return comparator;
#	Line 583 | Line 668 | public class PriorityQueue<E> extends Ab
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++)
#	Line 591 | Line 677 | public class PriorityQueue<E> extends Ab
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 void readObject(java.io.ObjectInputStream s)
#	Line 606 | Line 692 | public class PriorityQueue<E> extends Ab
692
693		// Read in all elements in the proper order.
694		for (int i=0; i<size; i++)
695	<	queue[i] = s.readObject();
695	>	queue[i] = (E) s.readObject();
696		}
697
698		}
613	–

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