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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.6 by brian, Mon Jun 23 02:26:15 2003 UTC vs.
Revision 1.49 by dl, Thu May 27 11:05:44 2004 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* %W% %E%
3	>	*
4	>	* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5	>	* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6	>	*/
7	>
8	>	package java.util;
9
10		/**
11	<	* An unbounded priority queue based on a priority heap.  This queue orders
12	<	* elements according to an order specified at construction time, which is
13	<	* specified in the same manner as {@link TreeSet} and {@link TreeMap}: elements are ordered
14	<	* either according to their <i>natural order</i> (see {@link Comparable}), or
15	<	* according to a {@link Comparator}, depending on which constructor is used.
16	<	* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the
17	<	* minimal element with respect to the specified ordering.  If multiple
18	<	* elements are tied for least value, no guarantees are made as to
19	<	* which of these elements is returned.
11	>	* An unbounded priority {@linkplain Queue queue} based on a priority
12	>	* heap.  This queue orders elements according to an order specified
13	>	* at construction time, which is specified either according to their
14	>	* <i>natural order</i> (see {@link Comparable}), or according to a
15	>	* {@link java.util.Comparator}, depending on which constructor is
16	>	* used. A priority queue does not permit <tt>null</tt> elements.
17	>	* A priority queue relying on natural ordering also does not
18	>	* permit insertion of non-comparable objects (doing so may result
19	>	* 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 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 size of
29	<	* the array used internally to store the elements on the queue.  It is always at least
30	<	* as large as the queue size.  As elements are added to a priority queue,
31	<	* its capacity grows automatically.  The details of the growth policy are not
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>Implementation note: this implementation provides O(log(n)) time for
36	<	* the insertion methods (<tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>)
37	<	* methods; linear time for the <tt>remove(Object)</tt> and
38	<	* <tt>contains(Object)</tt> methods; and constant time for the retrieval methods (<tt>peek</tt>,
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>.
41	>	*
42	>	* <p> <strong>Note that this implementation is not synchronized.</strong>
43	>	* Multiple threads should not access a <tt>PriorityQueue</tt>
44	>	* instance concurrently if any of the threads modifies the list
45	>	* structurally. Instead, use the thread-safe {@link
46	>	* java.util.concurrent.PriorityBlockingQueue} class.
47	>	*
48	>	*
49	>	* <p>Implementation note: this implementation provides O(log(n)) time
50	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
51	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
52	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
53	>	* constant time for the retrieval methods (<tt>peek</tt>,
54		* <tt>element</tt>, and <tt>size</tt>).
55		*
56		* <p>This class is a member of the
57		* <a href="{@docRoot}/../guide/collections/index.html">
58		* Java Collections Framework</a>.
59	+	* @since 1.5
60	+	* @version %I%, %G%
61	+	* @author Josh Bloch
62	+	* @param <E> the type of elements held in this collection
63		*/
64		public class PriorityQueue<E> extends AbstractQueue<E>
65	<	implements Queue<E>
66	<	{
65	>	implements java.io.Serializable {
66	>
67	>	private static final long serialVersionUID = -7720805057305804111L;
68	>
69		private static final int DEFAULT_INITIAL_CAPACITY = 11;
70
71		/**
#	Line 45 | Line 81 | public class PriorityQueue<E> extends Ab
81		*
82		* queue.length must be >= 2, even if size == 0.
83		*/
84	<	private transient E[] queue;
84	>	private transient Object[] queue;
85
86		/**
87		* The number of elements in the priority queue.
#	Line 56 | Line 92 | public class PriorityQueue<E> extends Ab
92		* The comparator, or null if priority queue uses elements'
93		* natural ordering.
94		*/
95	<	private final Comparator<E> comparator;
95	>	private final Comparator<? super E> comparator;
96
97		/**
98		* The number of times this priority queue has been
#	Line 65 | Line 101 | public class PriorityQueue<E> extends Ab
101		private transient int modCount = 0;
102
103		/**
104	<	* Create a new priority queue with the default initial capacity (11)
105	<	* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.)
104	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
105	>	* (11) that orders its elements according to their natural
106	>	* ordering (using <tt>Comparable</tt>).
107		*/
108		public PriorityQueue() {
109	<	this(DEFAULT_INITIAL_CAPACITY);
109	>	this(DEFAULT_INITIAL_CAPACITY, null);
110		}
111
112		/**
113	<	* Create a new priority queue with the specified initial capacity
114	<	* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.)
113	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
114	>	* that orders its elements according to their natural ordering
115	>	* (using <tt>Comparable</tt>).
116		*
117		* @param initialCapacity the initial capacity for this priority queue.
118	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
119	+	* than 1
120		*/
121		public PriorityQueue(int initialCapacity) {
122		this(initialCapacity, null);
123		}
124
125		/**
126	<	* Create a new priority queue with the specified initial capacity (11)
126	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
127		* that orders its elements according to the specified comparator.
128		*
129		* @param initialCapacity the initial capacity for this priority queue.
130		* @param comparator the comparator used to order this priority queue.
131	+	* If <tt>null</tt> then the order depends on the elements' natural
132	+	* ordering.
133	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
134	+	* than 1
135		*/
136	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
136	>	public PriorityQueue(int initialCapacity,
137	>	Comparator<? super E> comparator) {
138		if (initialCapacity < 1)
139	<	initialCapacity = 1;
140	<	queue = new E[initialCapacity + 1];
139	>	throw new IllegalArgumentException();
140	>	this.queue = new Object[initialCapacity + 1];
141		this.comparator = comparator;
142		}
143
144		/**
145	<	* Create a new priority queue containing the elements in the specified
146	<	* collection.  The priority queue has an initial capacity of 110% of the
102	<	* size of the specified collection. If the specified collection
103	<	* implements the {@link Sorted} interface, the priority queue will be
104	<	* sorted according to the same comparator, or according to its elements'
105	<	* natural order if the collection is sorted according to its elements'
106	<	* natural order.  If the specified collection does not implement
107	<	* <tt>Sorted</tt>, the priority queue is ordered according to
108	<	* its elements' natural order.
109	<	*
110	<	* @param initialElements the collection whose elements are to be placed
111	<	*        into this priority queue.
112	<	* @throws ClassCastException if elements of the specified collection
113	<	*         cannot be compared to one another according to the priority
114	<	*         queue's ordering.
115	<	* @throws NullPointerException if the specified collection or an
116	<	*         element of the specified collection is <tt>null</tt>.
145	>	* Common code to initialize underlying queue array across
146	>	* constructors below.
147		*/
148	<	public PriorityQueue(Collection<E> initialElements) {
149	<	int sz = initialElements.size();
148	>	private void initializeArray(Collection<? extends E> c) {
149	>	int sz = c.size();
150		int initialCapacity = (int)Math.min((sz * 110L) / 100,
151		Integer.MAX_VALUE - 1);
152		if (initialCapacity < 1)
153		initialCapacity = 1;
124	–	queue = new E[initialCapacity + 1];
154
155	<	/* Commented out to compile with generics compiler
155	>	this.queue = new Object[initialCapacity + 1];
156	>	}
157
158	<	if (initialElements instanceof Sorted) {
159	<	comparator = ((Sorted)initialElements).comparator();
160	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
161	<	queue[++size] = i.next();
158	>	/**
159	>	* Initially fill elements of the queue array under the
160	>	* knowledge that it is sorted or is another PQ, in which
161	>	* case we can just place the elements in the order presented.
162	>	*/
163	>	private void fillFromSorted(Collection<? extends E> c) {
164	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
165	>	queue[++size] = i.next();
166	>	}
167	>
168	>	/**
169	>	* Initially fill elements of the queue array that is not to our knowledge
170	>	* sorted, so we must rearrange the elements to guarantee the heap
171	>	* invariant.
172	>	*/
173	>	private void fillFromUnsorted(Collection<? extends E> c) {
174	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
175	>	queue[++size] = i.next();
176	>	heapify();
177	>	}
178	>
179	>	/**
180	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
181	>	* specified collection.  The priority queue has an initial
182	>	* capacity of 110% of the size of the specified collection or 1
183	>	* if the collection is empty.  If the specified collection is an
184	>	* instance of a {@link java.util.SortedSet} or is another
185	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
186	>	* according to the same comparator, or according to its elements'
187	>	* natural order if the collection is sorted according to its
188	>	* elements' natural order.  Otherwise, the priority queue is
189	>	* ordered according to its elements' natural order.
190	>	*
191	>	* @param c the collection whose elements are to be placed
192	>	*        into this priority queue.
193	>	* @throws ClassCastException if elements of the specified collection
194	>	*         cannot be compared to one another according to the priority
195	>	*         queue's ordering.
196	>	* @throws NullPointerException if <tt>c</tt> or any element within it
197	>	* is <tt>null</tt>
198	>	*/
199	>	public PriorityQueue(Collection<? extends E> c) {
200	>	initializeArray(c);
201	>	if (c instanceof SortedSet) {
202	>	SortedSet<? extends E> s = (SortedSet<? extends E>)c;
203	>	comparator = (Comparator<? super E>)s.comparator();
204	>	fillFromSorted(s);
205	>	} else if (c instanceof PriorityQueue) {
206	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
207	>	comparator = (Comparator<? super E>)s.comparator();
208	>	fillFromSorted(s);
209		} else {
133	–	*/
134	–	{
210		comparator = null;
211	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
137	<	add(i.next());
211	>	fillFromUnsorted(c);
212		}
213		}
214
215	<	// Queue Methods
215	>	/**
216	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
217	>	* specified collection.  The priority queue has an initial
218	>	* capacity of 110% of the size of the specified collection or 1
219	>	* if the collection is empty.  This priority queue will be sorted
220	>	* according to the same comparator as the given collection, or
221	>	* according to its elements' natural order if the collection is
222	>	* sorted according to its elements' natural order.
223	>	*
224	>	* @param c the collection whose elements are to be placed
225	>	*        into this priority queue.
226	>	* @throws ClassCastException if elements of the specified collection
227	>	*         cannot be compared to one another according to the priority
228	>	*         queue's ordering.
229	>	* @throws NullPointerException if <tt>c</tt> or any element within it
230	>	* is <tt>null</tt>
231	>	*/
232	>	public PriorityQueue(PriorityQueue<? extends E> c) {
233	>	initializeArray(c);
234	>	comparator = (Comparator<? super E>)c.comparator();
235	>	fillFromSorted(c);
236	>	}
237
238		/**
239	<	* Remove and return the minimal element from this priority queue if
240	<	* it contains one or more elements, otherwise return <tt>null</tt>.  The term
241	<	* <i>minimal</i> is defined according to this priority queue's order.
239	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
240	>	* specified collection.  The priority queue has an initial
241	>	* capacity of 110% of the size of the specified collection or 1
242	>	* if the collection is empty.  This priority queue will be sorted
243	>	* according to the same comparator as the given collection, or
244	>	* according to its elements' natural order if the collection is
245	>	* sorted according to its elements' natural order.
246		*
247	<	* @return the minimal element from this priority queue if it contains
248	<	*         one or more elements, otherwise <tt>null</tt>.
247	>	* @param c the collection whose elements are to be placed
248	>	*        into this priority queue.
249	>	* @throws ClassCastException if elements of the specified collection
250	>	*         cannot be compared to one another according to the priority
251	>	*         queue's ordering.
252	>	* @throws NullPointerException if <tt>c</tt> or any element within it
253	>	* is <tt>null</tt>
254		*/
255	<	public E poll() {
256	<	if (size == 0)
257	<	return null;
258	<	return remove(1);
255	>	public PriorityQueue(SortedSet<? extends E> c) {
256	>	initializeArray(c);
257	>	comparator = (Comparator<? super E>)c.comparator();
258	>	fillFromSorted(c);
259		}
260
261		/**
262	<	* Return, but do not remove, the minimal element from the priority queue,
263	<	* or return <tt>null</tt> if the queue is empty.  The term <i>minimal</i> is
264	<	* defined according to this priority queue's order.  This method returns
265	<	* the same object reference that would be returned by by the
266	<	* <tt>poll</tt> method.  The two methods differ in that this method
267	<	* does not remove the element from the priority queue.
262	>	* Resize array, if necessary, to be able to hold given index
263	>	*/
264	>	private void grow(int index) {
265	>	int newlen = queue.length;
266	>	if (index < newlen) // don't need to grow
267	>	return;
268	>	if (index == Integer.MAX_VALUE)
269	>	throw new OutOfMemoryError();
270	>	while (newlen <= index) {
271	>	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
272	>	newlen = Integer.MAX_VALUE;
273	>	else
274	>	newlen <<= 2;
275	>	}
276	>	Object[] newQueue = new Object[newlen];
277	>	System.arraycopy(queue, 0, newQueue, 0, queue.length);
278	>	queue = newQueue;
279	>	}
280	>
281	>
282	>	/**
283	>	* Inserts the specified element into this priority queue.
284		*
285	<	* @return the minimal element from this priority queue if it contains
286	<	*         one or more elements, otherwise <tt>null</tt>.
285	>	* @return <tt>true</tt>
286	>	* @throws ClassCastException if the specified element cannot be compared
287	>	* with elements currently in the priority queue according
288	>	* to the priority queue's ordering.
289	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
290		*/
291	+	public boolean offer(E o) {
292	+	if (o == null)
293	+	throw new NullPointerException();
294	+	modCount++;
295	+	++size;
296	+
297	+	// Grow backing store if necessary
298	+	if (size >= queue.length)
299	+	grow(size);
300	+
301	+	queue[size] = o;
302	+	fixUp(size);
303	+	return true;
304	+	}
305	+
306		public E peek() {
307	<	return queue[1];
307	>	if (size == 0)
308	>	return null;
309	>	return (E) queue[1];
310		}
311
312	<	// Collection Methods
312	>	// Collection Methods - the first two override to update docs
313
314		/**
315	<	* Removes a single instance of the specified element from this priority
316	<	* queue, if it is present.  Returns true if this collection contained the
317	<	* specified element (or equivalently, if this collection changed as a
178	<	* result of the call).
315	>	* Adds the specified element to this queue.
316	>	* @return <tt>true</tt> (as per the general contract of
317	>	* <tt>Collection.add</tt>).
318		*
319	<	* @param element the element to be removed from this collection, if present.
181	<	* @return <tt>true</tt> if this collection changed as a result of the
182	<	*         call
319	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
320		* @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.
186	<	* @throws NullPointerException if the specified element is null.
321	>	* with elements currently in the priority queue according
322	>	* to the priority queue's ordering.
323		*/
324	<	public boolean remove(Object element) {
325	<	if (element == null)
326	<	throw new NullPointerException();
324	>	public boolean add(E o) {
325	>	return offer(o);
326	>	}
327	>
328	>	/**
329	>	* Removes a single instance of the specified element from this
330	>	* collection, if it is present.
331	>	*/
332	>	public boolean remove(Object o) {
333	>	if (o == null)
334	>	return false;
335
336		if (comparator == null) {
337		for (int i = 1; i <= size; i++) {
338	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
339	<	remove(i);
338	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
339	>	removeAt(i);
340		return true;
341		}
342		}
343		} else {
344		for (int i = 1; i <= size; i++) {
345	<	if (comparator.compare(queue[i], (E) element) == 0) {
346	<	remove(i);
345	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
346	>	removeAt(i);
347		return true;
348		}
349		}
#	Line 208 | Line 352 | public class PriorityQueue<E> extends Ab
352		}
353
354		/**
355	<	* Returns an iterator over the elements in this priority queue.  The
356	<	* elements of the priority queue will be returned by this iterator in the
357	<	* order specified by the queue, which is to say the order they would be
358	<	* returned by repeated calls to <tt>poll</tt>.
215	<	*
216	<	* @return an <tt>Iterator</tt> over the elements in this priority queue.
355	>	* Returns an iterator over the elements in this queue. The iterator
356	>	* does not return the elements in any particular order.
357	>	*
358	>	* @return an iterator over the elements in this queue.
359		*/
360		public Iterator<E> iterator() {
361	<	return new Itr();
361	>	return new Itr();
362		}
363
364		private class Itr implements Iterator<E> {
365	<	/**
366	<	* Index (into queue array) of element to be returned by
365	>
366	>	/**
367	>	* Index (into queue array) of element to be returned by
368		* subsequent call to next.
369	<	*/
370	<	int cursor = 1;
369	>	*/
370	>	private int cursor = 1;
371
372	<	/**
373	<	* Index of element returned by most recent call to next or
374	<	* previous.  Reset to 0 if this element is deleted by a call
375	<	* to remove.
376	<	*/
377	<	int lastRet = 0;
378	<
379	<	/**
380	<	* The modCount value that the iterator believes that the backing
381	<	* List should have.  If this expectation is violated, the iterator
382	<	* has detected concurrent modification.
383	<	*/
384	<	int expectedModCount = modCount;
385	<
386	<	public boolean hasNext() {
387	<	return cursor <= size;
388	<	}
372	>	/**
373	>	* Index of element returned by most recent call to next,
374	>	* unless that element came from the forgetMeNot list.
375	>	* Reset to 0 if element is deleted by a call to remove.
376	>	*/
377	>	private int lastRet = 0;
378	>
379	>	/**
380	>	* The modCount value that the iterator believes that the backing
381	>	* List should have.  If this expectation is violated, the iterator
382	>	* has detected concurrent modification.
383	>	*/
384	>	private int expectedModCount = modCount;
385	>
386	>	/**
387	>	* A list of elements that were moved from the unvisited portion of
388	>	* the heap into the visited portion as a result of "unlucky" element
389	>	* removals during the iteration.  (Unlucky element removals are those
390	>	* that require a fixup instead of a fixdown.)  We must visit all of
391	>	* the elements in this list to complete the iteration.  We do this
392	>	* after we've completed the "normal" iteration.
393	>	*
394	>	* We expect that most iterations, even those involving removals,
395	>	* will not use need to store elements in this field.
396	>	*/
397	>	private ArrayList<E> forgetMeNot = null;
398	>
399	>	/**
400	>	* Element returned by the most recent call to next iff that
401	>	* element was drawn from the forgetMeNot list.
402	>	*/
403	>	private Object lastRetElt = null;
404	>
405	>	public boolean hasNext() {
406	>	return cursor <= size || forgetMeNot != null;
407	>	}
408
409	<	public E next() {
409	>	public E next() {
410		checkForComodification();
411	<	if (cursor > size)
412	<	throw new NoSuchElementException();
413	<	E result = queue[cursor];
414	<	lastRet = cursor++;
411	>	E result;
412	>	if (cursor <= size) {
413	>	result = (E) queue[cursor];
414	>	lastRet = cursor++;
415	>	}
416	>	else if (forgetMeNot == null)
417	>	throw new NoSuchElementException();
418	>	else {
419	>	int remaining = forgetMeNot.size();
420	>	result = forgetMeNot.remove(remaining - 1);
421	>	if (remaining == 1)
422	>	forgetMeNot = null;
423	>	lastRet = 0;
424	>	lastRetElt = result;
425	>	}
426		return result;
427	<	}
427	>	}
428
429	<	public void remove() {
257	<	if (lastRet == 0)
258	<	throw new IllegalStateException();
429	>	public void remove() {
430		checkForComodification();
431
432	<	PriorityQueue.this.remove(lastRet);
433	<	if (lastRet < cursor)
434	<	cursor--;
435	<	lastRet = 0;
432	>	if (lastRet != 0) {
433	>	E moved = PriorityQueue.this.removeAt(lastRet);
434	>	lastRet = 0;
435	>	if (moved == null) {
436	>	cursor--;
437	>	} else {
438	>	if (forgetMeNot == null)
439	>	forgetMeNot = new ArrayList<E>();
440	>	forgetMeNot.add(moved);
441	>	}
442	>	} else if (lastRetElt != null) {
443	>	PriorityQueue.this.remove(lastRetElt);
444	>	lastRetElt = null;
445	>	} else {
446	>	throw new IllegalStateException();
447	>	}
448	>
449		expectedModCount = modCount;
450	<	}
450	>	}
451
452	<	final void checkForComodification() {
453	<	if (modCount != expectedModCount)
454	<	throw new ConcurrentModificationException();
455	<	}
452	>	final void checkForComodification() {
453	>	if (modCount != expectedModCount)
454	>	throw new ConcurrentModificationException();
455	>	}
456		}
457
274	–	/**
275	–	* Returns the number of elements in this priority queue.
276	–	*
277	–	* @return the number of elements in this priority queue.
278	–	*/
458		public int size() {
459		return size;
460		}
461
462		/**
463	<	* Add the specified element to this priority queue.
464	<	*
286	<	* @param element the element to add.
287	<	* @return true
288	<	* @throws ClassCastException if the specified element cannot be compared
289	<	*            with elements currently in the priority queue according
290	<	*            to the priority queue's ordering.
291	<	* @throws NullPointerException if the specified element is null.
292	<	*/
293	<	public boolean offer(E element) {
294	<	if (element == null)
295	<	throw new NullPointerException();
296	<	modCount++;
297	<
298	<	// Grow backing store if necessary
299	<	if (++size == queue.length) {
300	<	E[] newQueue = new E[2 * queue.length];
301	<	System.arraycopy(queue, 0, newQueue, 0, size);
302	<	queue = newQueue;
303	<	}
304	<
305	<	queue[size] = element;
306	<	fixUp(size);
307	<	return true;
308	<	}
309	<
310	<	/**
311	<	* Remove all elements from the priority queue.
463	>	* Removes all elements from the priority queue.
464	>	* The queue will be empty after this call returns.
465		*/
466		public void clear() {
467		modCount++;
#	Line 320 | Line 473 | public class PriorityQueue<E> extends Ab
473		size = 0;
474		}
475
476	+	public E poll() {
477	+	if (size == 0)
478	+	return null;
479	+	modCount++;
480	+
481	+	E result = (E) queue[1];
482	+	queue[1] = queue[size];
483	+	queue[size--] = null;  // Drop extra ref to prevent memory leak
484	+	if (size > 1)
485	+	fixDown(1);
486	+
487	+	return result;
488	+	}
489	+
490		/**
491	<	* Removes and returns the ith element from queue.  Recall
492	<	* that queue is one-based, so 1 <= i <= size.
491	>	* Removes and returns the ith element from queue.  (Recall that queue
492	>	* is one-based, so 1 <= i <= size.)
493		*
494	<	* XXX: Could further special-case i==size, but is it worth it?
495	<	* XXX: Could special-case i==0, but is it worth it?
494	>	* Normally this method leaves the elements at positions from 1 up to i-1,
495	>	* inclusive, untouched.  Under these circumstances, it returns null.
496	>	* Occasionally, in order to maintain the heap invariant, it must move
497	>	* the last element of the list to some index in the range [2, i-1],
498	>	* and move the element previously at position (i/2) to position i.
499	>	* Under these circumstances, this method returns the element that was
500	>	* previously at the end of the list and is now at some position between
501	>	* 2 and i-1 inclusive.
502		*/
503	<	private E remove(int i) {
504	<	assert i <= size;
503	>	private E removeAt(int i) {
504	>	assert i > 0 && i <= size;
505		modCount++;
506
507	<	E result = queue[i];
508	<	queue[i] = queue[size];
507	>	E moved = (E) queue[size];
508	>	queue[i] = moved;
509		queue[size--] = null;  // Drop extra ref to prevent memory leak
510	<	if (i <= size)
510	>	if (i <= size) {
511		fixDown(i);
512	<	return result;
512	>	if (queue[i] == moved) {
513	>	fixUp(i);
514	>	if (queue[i] != moved)
515	>	return moved;
516	>	}
517	>	}
518	>	return null;
519		}
520
521		/**
#	Line 352 | Line 531 | public class PriorityQueue<E> extends Ab
531		if (comparator == null) {
532		while (k > 1) {
533		int j = k >> 1;
534	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
534	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
535		break;
536	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
536	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
537		k = j;
538		}
539		} else {
540		while (k > 1) {
541	<	int j = k >> 1;
542	<	if (comparator.compare(queue[j], queue[k]) <= 0)
541	>	int j = k >>> 1;
542	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
543		break;
544	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
544	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
545		k = j;
546		}
547		}
#	Line 380 | Line 559 | public class PriorityQueue<E> extends Ab
559		private void fixDown(int k) {
560		int j;
561		if (comparator == null) {
562	<	while ((j = k << 1) <= size) {
563	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
562	>	while ((j = k << 1) <= size && (j > 0)) {
563	>	if (j<size &&
564	>	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
565		j++; // j indexes smallest kid
566	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
566	>
567	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
568		break;
569	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
569	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
570		k = j;
571		}
572		} else {
573	<	while ((j = k << 1) <= size) {
574	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
573	>	while ((j = k << 1) <= size && (j > 0)) {
574	>	if (j<size &&
575	>	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
576		j++; // j indexes smallest kid
577	<	if (comparator.compare(queue[k], queue[j]) <= 0)
577	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
578		break;
579	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
579	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
580		k = j;
581		}
582		}
583		}
584
585		/**
586	<	* Returns the comparator associated with this priority queue, or
587	<	* <tt>null</tt> if it uses its elements' natural ordering.
586	>	* Establishes the heap invariant (described above) in the entire tree,
587	>	* assuming nothing about the order of the elements prior to the call.
588	>	*/
589	>	private void heapify() {
590	>	for (int i = size/2; i >= 1; i--)
591	>	fixDown(i);
592	>	}
593	>
594	>	/**
595	>	* Returns the comparator used to order this collection, or <tt>null</tt>
596	>	* if this collection is sorted according to its elements natural ordering
597	>	* (using <tt>Comparable</tt>).
598		*
599	<	* @return the comparator associated with this priority queue, or
600	<	*         <tt>null</tt> if it uses its elements' natural ordering.
599	>	* @return the comparator used to order this collection, or <tt>null</tt>
600	>	* if this collection is sorted according to its elements natural ordering.
601		*/
602	<	Comparator comparator() {
602	>	public Comparator<? super E> comparator() {
603		return comparator;
604		}
605
#	Line 418 | Line 610 | public class PriorityQueue<E> extends Ab
610		* @serialData The length of the array backing the instance is
611		* emitted (int), followed by all of its elements (each an
612		* <tt>Object</tt>) in the proper order.
613	+	* @param s the stream
614		*/
615	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
615	>	private void writeObject(java.io.ObjectOutputStream s)
616		throws java.io.IOException{
617	<	// Write out element count, and any hidden stuff
618	<	s.defaultWriteObject();
617	>	// Write out element count, and any hidden stuff
618	>	s.defaultWriteObject();
619
620		// Write out array length
621		s.writeInt(queue.length);
622
623	<	// Write out all elements in the proper order.
624	<	for (int i=0; i<size; i++)
623	>	// Write out all elements in the proper order.
624	>	for (int i=1; i<=size; i++)
625		s.writeObject(queue[i]);
626		}
627
628		/**
629		* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
630		* deserialize it).
631	+	* @param s the stream
632		*/
633	<	private synchronized void readObject(java.io.ObjectInputStream s)
633	>	private void readObject(java.io.ObjectInputStream s)
634		throws java.io.IOException, ClassNotFoundException {
635	<	// Read in size, and any hidden stuff
636	<	s.defaultReadObject();
635	>	// Read in size, and any hidden stuff
636	>	s.defaultReadObject();
637
638		// Read in array length and allocate array
639		int arrayLength = s.readInt();
640	<	queue = new E[arrayLength];
640	>	queue = new Object[arrayLength];
641
642	<	// Read in all elements in the proper order.
643	<	for (int i=0; i<size; i++)
644	<	queue[i] = (E)s.readObject();
642	>	// Read in all elements in the proper order.
643	>	for (int i=1; i<=size; i++)
644	>	queue[i] = (E) s.readObject();
645		}
646
647		}

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