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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.8 by dl, Tue Jul 1 16:29:45 2003 UTC vs.
Revision 1.39 by dl, Sun Sep 7 15:06:19 2003 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* %W% %E%
3	>	*
4	>	* Copyright 2003 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 heap.
12	>	* This queue orders elements according to an order specified at construction
13	>	* time, which is specified in the same manner as {@link java.util.TreeSet}
14	>	* and {@link java.util.TreeMap}: elements are ordered either according to
15	>	* their <i>natural order</i> (see {@link Comparable}), or according to a
16	>	* {@link java.util.Comparator}, depending on which constructor is used.
17	>	* <p>The <em>head</em> of this queue is the <em>least</em> element with
18	>	* respect to the specified ordering.  If multiple elements are tied for least
19	>	* value, the head is one of those elements. A priority queue does not permit
20	>	* <tt>null</tt> elements.
21	>	*
22	>	* <p>The {@link #remove()} and {@link #poll()} methods remove and
23	>	* return the head of the queue.
24	>	*
25	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
26	>	* not delete, the head of the queue.
27		*
28		* <p>A priority queue has a <i>capacity</i>.  The capacity is the
29		* size of the array used internally to store the elements on the
30	<	* queue.  It is always at least as large as the queue size.  As
30	>	* queue.
31	>	* It is always at least as large as the queue size.  As
32		* elements are added to a priority queue, its capacity grows
33		* automatically.  The details of the growth policy are not specified.
34		*
35	<	*<p>Implementation note: this implementation provides O(log(n)) time
36	<	*for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
37	<	*<tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
38	<	*<tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
39	<	*constant time for the retrieval methods (<tt>peek</tt>,
40	<	*<tt>element</tt>, and <tt>size</tt>).
35	>	* <p>The Iterator provided in method {@link #iterator()} is <em>not</em>
36	>	* guaranteed to traverse the elements of the PriorityQueue in any
37	>	* particular order. If you need ordered traversal, consider using
38	>	* <tt>Arrays.sort(pq.toArray())</tt>.
39	>	*
40	>	* <p> <strong>Note that this implementation is not synchronized.</strong>
41	>	* Multiple threads should not access a <tt>PriorityQueue</tt>
42	>	* instance concurrently if any of the threads modifies the list
43	>	* structurally. Instead, use the thread-safe {@link
44	>	* java.util.concurrent.PriorityBlockingQueue} class.
45	>	*
46	>	*
47	>	* <p>Implementation note: this implementation provides O(log(n)) time
48	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
49	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
50	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
51	>	* constant time for the retrieval methods (<tt>peek</tt>,
52	>	* <tt>element</tt>, and <tt>size</tt>).
53		*
54		* <p>This class is a member of the
55		* <a href="{@docRoot}/../guide/collections/index.html">
56		* Java Collections Framework</a>.
57		* @since 1.5
58	+	* @version %I%, %G%
59		* @author Josh Bloch
60		*/
61		public class PriorityQueue<E> extends AbstractQueue<E>
62	<	implements Queue<E>,
63	<	java.io.Serializable {
62	>	implements Queue<E>, java.io.Serializable {
63	>
64	>	private static final long serialVersionUID = -7720805057305804111L;
65	>
66		private static final int DEFAULT_INITIAL_CAPACITY = 11;
67
68		/**
#	Line 48 | Line 78 | public class PriorityQueue<E> extends Ab
78		*
79		* queue.length must be >= 2, even if size == 0.
80		*/
81	<	private transient E[] queue;
81	>	private transient Object[] queue;
82
83		/**
84		* The number of elements in the priority queue.
#	Line 59 | Line 89 | public class PriorityQueue<E> extends Ab
89		* The comparator, or null if priority queue uses elements'
90		* natural ordering.
91		*/
92	<	private final Comparator<E> comparator;
92	>	private final Comparator<? super E> comparator;
93
94		/**
95		* The number of times this priority queue has been
#	Line 68 | Line 98 | public class PriorityQueue<E> extends Ab
98		private transient int modCount = 0;
99
100		/**
101	<	* Create a new priority queue with the default initial capacity
101	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
102		* (11) that orders its elements according to their natural
103	<	* ordering (using <tt>Comparable</tt>.)
103	>	* ordering (using <tt>Comparable</tt>).
104		*/
105		public PriorityQueue() {
106	<	this(DEFAULT_INITIAL_CAPACITY);
106	>	this(DEFAULT_INITIAL_CAPACITY, null);
107		}
108
109		/**
110	<	* Create a new priority queue with the specified initial capacity
110	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
111		* that orders its elements according to their natural ordering
112	<	* (using <tt>Comparable</tt>.)
112	>	* (using <tt>Comparable</tt>).
113		*
114		* @param initialCapacity the initial capacity for this priority queue.
115	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
116	+	* than 1
117		*/
118		public PriorityQueue(int initialCapacity) {
119		this(initialCapacity, null);
120		}
121
122		/**
123	<	* Create a new priority queue with the specified initial capacity (11)
123	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
124		* that orders its elements according to the specified comparator.
125		*
126		* @param initialCapacity the initial capacity for this priority queue.
127		* @param comparator the comparator used to order this priority queue.
128	+	* If <tt>null</tt> then the order depends on the elements' natural
129	+	* ordering.
130	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
131	+	* than 1
132		*/
133	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
133	>	public PriorityQueue(int initialCapacity,
134	>	Comparator<? super E> comparator) {
135		if (initialCapacity < 1)
136	<	initialCapacity = 1;
137	<	queue = new E[initialCapacity + 1];
136	>	throw new IllegalArgumentException();
137	>	this.queue = new Object[initialCapacity + 1];
138		this.comparator = comparator;
139		}
140
141		/**
142	<	* Create a new priority queue containing the elements in the specified
143	<	* collection.  The priority queue has an initial capacity of 110% of the
107	<	* size of the specified collection. If the specified collection
108	<	* implements the {@link Sorted} interface, the priority queue will be
109	<	* sorted according to the same comparator, or according to its elements'
110	<	* natural order if the collection is sorted according to its elements'
111	<	* natural order.  If the specified collection does not implement
112	<	* <tt>Sorted</tt>, the priority queue is ordered according to
113	<	* its elements' natural order.
114	<	*
115	<	* @param initialElements the collection whose elements are to be placed
116	<	*        into this priority queue.
117	<	* @throws ClassCastException if elements of the specified collection
118	<	*         cannot be compared to one another according to the priority
119	<	*         queue's ordering.
120	<	* @throws NullPointerException if the specified collection or an
121	<	*         element of the specified collection is <tt>null</tt>.
142	>	* Common code to initialize underlying queue array across
143	>	* constructors below.
144		*/
145	<	public PriorityQueue(Collection<E> initialElements) {
146	<	int sz = initialElements.size();
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;
129	–	queue = new E[initialCapacity + 1];
151
152	+	this.queue = new Object[initialCapacity + 1];
153	+	}
154
155	<	if (initialElements instanceof Sorted) {
156	<	comparator = ((Sorted)initialElements).comparator();
157	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
158	<	queue[++size] = i.next();
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	>	/**
177	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
178	>	* 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
181	>	* instance of a {@link java.util.SortedSet} or is another
182	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
183	>	* according to the same comparator, or according to its elements'
184	>	* 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.
187	>	*
188	>	* @param c the collection whose elements are to be placed
189	>	*        into this priority queue.
190	>	* @throws ClassCastException if elements of the specified collection
191	>	*         cannot be compared to one another according to the priority
192	>	*         queue's ordering.
193	>	* @throws NullPointerException if <tt>c</tt> or any element within it
194	>	* is <tt>null</tt>
195	>	*/
196	>	public PriorityQueue(Collection<? extends E> c) {
197	>	initializeArray(c);
198	>	if (c instanceof SortedSet) {
199	>	// @fixme double-cast workaround for compiler
200	>	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
201	>	comparator = (Comparator<? super E>)s.comparator();
202	>	fillFromSorted(s);
203	>	} else if (c instanceof PriorityQueue) {
204	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
205	>	comparator = (Comparator<? super E>)s.comparator();
206	>	fillFromSorted(s);
207		} else {
208		comparator = null;
209	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
139	<	add(i.next());
209	>	fillFromUnsorted(c);
210		}
211		}
212
213	+	/**
214	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
215	+	* specified collection.  The priority queue has an initial
216	+	* capacity of 110% of the size of the specified collection or 1
217	+	* if the collection is empty.  This priority queue will be sorted
218	+	* according to the same comparator as the given collection, or
219	+	* according to its elements' natural order if the collection is
220	+	* sorted according to its elements' natural order.
221	+	*
222	+	* @param c the collection whose elements are to be placed
223	+	*        into this priority queue.
224	+	* @throws ClassCastException if elements of the specified collection
225	+	*         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>
229	+	*/
230	+	public PriorityQueue(PriorityQueue<? extends E> c) {
231	+	initializeArray(c);
232	+	comparator = (Comparator<? super E>)c.comparator();
233	+	fillFromSorted(c);
234	+	}
235	+
236	+	/**
237	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
238	+	* specified collection.  The priority queue has an initial
239	+	* 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.
244	+	*
245	+	* @param c the collection whose elements are to be placed
246	+	*        into this priority queue.
247	+	* @throws ClassCastException if elements of the specified collection
248	+	*         cannot be compared to one another according to the priority
249	+	*         queue's ordering.
250	+	* @throws NullPointerException if <tt>c</tt> or any element within it
251	+	* is <tt>null</tt>
252	+	*/
253	+	public PriorityQueue(SortedSet<? extends E> c) {
254	+	initializeArray(c);
255	+	comparator = (Comparator<? super E>)c.comparator();
256	+	fillFromSorted(c);
257	+	}
258	+
259	+	/**
260	+	* Resize array, if necessary, to be able to hold given index
261	+	*/
262	+	private void grow(int index) {
263	+	int newlen = queue.length;
264	+	if (index < newlen) // don't need to grow
265	+	return;
266	+	if (index == Integer.MAX_VALUE)
267	+	throw new OutOfMemoryError();
268	+	while (newlen <= index) {
269	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
270	+	newlen = Integer.MAX_VALUE;
271	+	else
272	+	newlen <<= 2;
273	+	}
274	+	Object[] newQueue = new Object[newlen];
275	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
276	+	queue = newQueue;
277	+	}
278	+
279	+
280		// Queue Methods
281
282		/**
283	<	* Remove and return the minimal element from this priority queue
147	<	* if it contains one or more elements, otherwise return
148	<	* <tt>null</tt>.  The term <i>minimal</i> is defined according to
149	<	* this priority queue's order.
283	>	* Add the specified element to 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 poll() {
307		if (size == 0)
308		return null;
309	<	return remove(1);
309	>	return remove();
310		}
311
312	+	public E peek() {
313	+	return (E) queue[1];
314	+	}
315	+
316	+	// Collection Methods - the first two override to update docs
317	+
318		/**
319	<	* Return, but do not remove, the minimal element from the
320	<	* priority queue, or return <tt>null</tt> if the queue is empty.
321	<	* The term <i>minimal</i> is defined according to this priority
164	<	* queue's order.  This method returns the same object reference
165	<	* that would be returned by by the <tt>poll</tt> method.  The two
166	<	* methods differ in that this method does not remove the element
167	<	* from the priority queue.
319	>	* Adds the specified element to this queue.
320	>	* @return <tt>true</tt> (as per the general contract of
321	>	* <tt>Collection.add</tt>).
322		*
323	<	* @return the minimal element from this priority queue if it contains
324	<	*         one or more elements, otherwise <tt>null</tt>.
323	>	* @throws NullPointerException {@inheritDoc}
324	>	* @throws ClassCastException if the specified element cannot be compared
325	>	* with elements currently in the priority queue according
326	>	* to the priority queue's ordering.
327		*/
328	<	public E peek() {
329	<	return queue[1];
328	>	public boolean add(E o) {
329	>	return super.add(o);
330	>	}
331	>
332	>
333	>	/**
334	>	* Adds all of the elements in the specified collection to this queue.
335	>	* The behavior of this operation is undefined if
336	>	* the specified collection is modified while the operation is in
337	>	* progress.  (This implies that the behavior of this call is undefined if
338	>	* the specified collection is this queue, and this queue is nonempty.)
339	>	* <p>
340	>	* This implementation iterates over the specified collection, and adds
341	>	* each object returned by the iterator to this collection, in turn.
342	>	* @throws NullPointerException {@inheritDoc}
343	>	* @throws ClassCastException if any element cannot be compared
344	>	* with elements currently in the priority queue according
345	>	* to the priority queue's ordering.
346	>	*/
347	>	public boolean addAll(Collection<? extends E> c) {
348	>	return super.addAll(c);
349		}
350
176	–	// Collection Methods
351
352		/**
353	<	* Removes a single instance of the specified element from this priority
354	<	* queue, if it is present.  Returns true if this collection contained the
355	<	* specified element (or equivalently, if this collection changed as a
353	>	* Removes a single instance of the specified element from this
354	>	* queue, if it is present.  More formally,
355	>	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
356	>	* o.equals(e))</tt>, if the queue contains one or more such
357	>	* elements.  Returns <tt>true</tt> if the queue contained the
358	>	* specified element (or equivalently, if the queue changed as a
359		* result of the call).
360		*
361	<	* @param element the element to be removed from this collection,
362	<	* if present.
363	<	* @return <tt>true</tt> if this collection changed as a result of the
364	<	*         call
188	<	* @throws ClassCastException if the specified element cannot be compared
189	<	*            with elements currently in the priority queue according
190	<	*            to the priority queue's ordering.
191	<	* @throws NullPointerException if the specified element is null.
361	>	* <p>This implementation iterates over the queue looking for the
362	>	* specified element.  If it finds the element, it removes the element
363	>	* from the queue using the iterator's remove method.<p>
364	>	*
365		*/
366	<	public boolean remove(Object element) {
367	<	if (element == null)
368	<	throw new NullPointerException();
366	>	public boolean remove(Object o) {
367	>	if (o == null)
368	>	return false;
369
370		if (comparator == null) {
371		for (int i = 1; i <= size; i++) {
372	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
373	<	remove(i);
372	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
373	>	removeAt(i);
374		return true;
375		}
376		}
377		} else {
378		for (int i = 1; i <= size; i++) {
379	<	if (comparator.compare(queue[i], (E) element) == 0) {
380	<	remove(i);
379	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
380	>	removeAt(i);
381		return true;
382		}
383		}
#	Line 213 | Line 386 | public class PriorityQueue<E> extends Ab
386		}
387
388		/**
389	<	* Returns an iterator over the elements in this priority queue.  The
390	<	* elements of the priority queue will be returned by this iterator in the
391	<	* order specified by the queue, which is to say the order they would be
392	<	* returned by repeated calls to <tt>poll</tt>.
220	<	*
221	<	* @return an <tt>Iterator</tt> over the elements in this priority queue.
389	>	* Returns an iterator over the elements in this queue. The iterator
390	>	* does not return the elements in any particular order.
391	>	*
392	>	* @return an iterator over the elements in this queue.
393		*/
394		public Iterator<E> iterator() {
395		return new Itr();
396		}
397
398		private class Itr implements Iterator<E> {
399	+
400		/**
401		* Index (into queue array) of element to be returned by
402		* subsequent call to next.
#	Line 232 | Line 404 | public class PriorityQueue<E> extends Ab
404		private int cursor = 1;
405
406		/**
407	<	* Index of element returned by most recent call to next or
408	<	* previous.  Reset to 0 if this element is deleted by a call
409	<	* to remove.
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.
410		*/
411		private int lastRet = 0;
412
#	Line 245 | Line 417 | public class PriorityQueue<E> extends Ab
417		*/
418		private int expectedModCount = modCount;
419
420	+	/**
421	+	* A list of elements that were moved from the unvisited portion of
422	+	* the heap into the visited portion as a result of "unlucky" element
423	+	* removals during the iteration.  (Unlucky element removals are those
424	+	* that require a fixup instead of a fixdown.)  We must visit all of
425	+	* the elements in this list to complete the iteration.  We do this
426	+	* after we've completed the "normal" iteration.
427	+	*
428	+	* We expect that most iterations, even those involving removals,
429	+	* will not use need to store elements in this field.
430	+	*/
431	+	private ArrayList<E> forgetMeNot = null;
432	+
433	+	/**
434	+	* Element returned by the most recent call to next iff that
435	+	* element was drawn from the forgetMeNot list.
436	+	*/
437	+	private Object lastRetElt = null;
438	+
439		public boolean hasNext() {
440	<	return cursor <= size;
440	>	return cursor <= size || forgetMeNot != null;
441		}
442
443		public E next() {
444		checkForComodification();
445	<	if (cursor > size)
445	>	E result;
446	>	if (cursor <= size) {
447	>	result = (E) queue[cursor];
448	>	lastRet = cursor++;
449	>	}
450	>	else if (forgetMeNot == null)
451		throw new NoSuchElementException();
452	<	E result = queue[cursor];
453	<	lastRet = cursor++;
452	>	else {
453	>	int remaining = forgetMeNot.size();
454	>	result = forgetMeNot.remove(remaining - 1);
455	>	if (remaining == 1)
456	>	forgetMeNot = null;
457	>	lastRet = 0;
458	>	lastRetElt = result;
459	>	}
460		return result;
461		}
462
463		public void remove() {
262	–	if (lastRet == 0)
263	–	throw new IllegalStateException();
464		checkForComodification();
465
466	<	PriorityQueue.this.remove(lastRet);
467	<	if (lastRet < cursor)
468	<	cursor--;
469	<	lastRet = 0;
466	>	if (lastRet != 0) {
467	>	E moved = PriorityQueue.this.removeAt(lastRet);
468	>	lastRet = 0;
469	>	if (moved == null) {
470	>	cursor--;
471	>	} else {
472	>	if (forgetMeNot == null)
473	>	forgetMeNot = new ArrayList<E>();
474	>	forgetMeNot.add(moved);
475	>	}
476	>	} else if (lastRetElt != null) {
477	>	PriorityQueue.this.remove(lastRetElt);
478	>	lastRetElt = null;
479	>	} else {
480	>	throw new IllegalStateException();
481	>	}
482	>
483		expectedModCount = modCount;
484		}
485
#	Line 276 | Line 489 | public class PriorityQueue<E> extends Ab
489		}
490		}
491
279	–	/**
280	–	* Returns the number of elements in this priority queue.
281	–	*
282	–	* @return the number of elements in this priority queue.
283	–	*/
492		public int size() {
493		return size;
494		}
495
496		/**
497	<	* Add the specified element to this priority queue.
290	<	*
291	<	* @param element the element to add.
292	<	* @return true
293	<	* @throws ClassCastException if the specified element cannot be compared
294	<	*            with elements currently in the priority queue according
295	<	*            to the priority queue's ordering.
296	<	* @throws NullPointerException if the specified element is null.
497	>	* Remove all elements from the priority queue.
498		*/
499	<	public boolean offer(E element) {
299	<	if (element == null)
300	<	throw new NullPointerException();
499	>	public void clear() {
500		modCount++;
501
502	<	// Grow backing store if necessary
503	<	if (++size == queue.length) {
504	<	E[] newQueue = new E[2 * queue.length];
306	<	System.arraycopy(queue, 0, newQueue, 0, size);
307	<	queue = newQueue;
308	<	}
502	>	// Null out element references to prevent memory leak
503	>	for (int i=1; i<=size; i++)
504	>	queue[i] = null;
505
506	<	queue[size] = element;
311	<	fixUp(size);
312	<	return true;
506	>	size = 0;
507		}
508
509		/**
510	<	* Remove all elements from the priority queue.
510	>	* Removes and returns the first element from queue.
511		*/
512	<	public void clear() {
512	>	public E remove() {
513	>	if (size == 0)
514	>	throw new NoSuchElementException();
515		modCount++;
516
517	<	// Null out element references to prevent memory leak
518	<	for (int i=1; i<=size; i++)
519	<	queue[i] = null;
517	>	E result = (E) queue[1];
518	>	queue[1] = queue[size];
519	>	queue[size--] = null;  // Drop extra ref to prevent memory leak
520	>	if (size > 1)
521	>	fixDown(1);
522
523	<	size = 0;
523	>	return result;
524		}
525
526		/**
527	<	* Removes and returns the ith element from queue.  Recall
528	<	* that queue is one-based, so 1 <= i <= size.
527	>	* Removes and returns the ith element from queue.  (Recall that queue
528	>	* is one-based, so 1 <= i <= size.)
529		*
530	<	* XXX: Could further special-case i==size, but is it worth it?
531	<	* XXX: Could special-case i==0, but is it worth it?
530	>	* Normally this method leaves the elements at positions from 1 up to i-1,
531	>	* inclusive, untouched.  Under these circumstances, it returns null.
532	>	* Occasionally, in order to maintain the heap invariant, it must move
533	>	* the last element of the list to some index in the range [2, i-1],
534	>	* and move the element previously at position (i/2) to position i.
535	>	* Under these circumstances, this method returns the element that was
536	>	* previously at the end of the list and is now at some position between
537	>	* 2 and i-1 inclusive.
538		*/
539	<	private E remove(int i) {
540	<	assert i <= size;
539	>	private E removeAt(int i) {
540	>	assert i > 0 && i <= size;
541		modCount++;
542
543	<	E result = queue[i];
544	<	queue[i] = queue[size];
543	>	E moved = (E) queue[size];
544	>	queue[i] = moved;
545		queue[size--] = null;  // Drop extra ref to prevent memory leak
546	<	if (i <= size)
546	>	if (i <= size) {
547		fixDown(i);
548	<	return result;
548	>	if (queue[i] == moved) {
549	>	fixUp(i);
550	>	if (queue[i] != moved)
551	>	return moved;
552	>	}
553	>	}
554	>	return null;
555		}
556
557		/**
#	Line 357 | Line 567 | public class PriorityQueue<E> extends Ab
567		if (comparator == null) {
568		while (k > 1) {
569		int j = k >> 1;
570	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
570	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
571		break;
572	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
572	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
573		k = j;
574		}
575		} else {
576		while (k > 1) {
577	<	int j = k >> 1;
578	<	if (comparator.compare(queue[j], queue[k]) <= 0)
577	>	int j = k >>> 1;
578	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
579		break;
580	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
580	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
581		k = j;
582		}
583		}
#	Line 385 | Line 595 | public class PriorityQueue<E> extends Ab
595		private void fixDown(int k) {
596		int j;
597		if (comparator == null) {
598	<	while ((j = k << 1) <= size) {
599	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
598	>	while ((j = k << 1) <= size && (j > 0)) {
599	>	if (j<size &&
600	>	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
601		j++; // j indexes smallest kid
602	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
602	>
603	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
604		break;
605	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
605	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
606		k = j;
607		}
608		} else {
609	<	while ((j = k << 1) <= size) {
610	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
609	>	while ((j = k << 1) <= size && (j > 0)) {
610	>	if (j<size &&
611	>	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
612		j++; // j indexes smallest kid
613	<	if (comparator.compare(queue[k], queue[j]) <= 0)
613	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
614		break;
615	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
615	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
616		k = j;
617		}
618		}
619		}
620
621		/**
622	<	* Returns the comparator associated with this priority queue, or
623	<	* <tt>null</tt> if it uses its elements' natural ordering.
622	>	* Establishes the heap invariant (described above) in the entire tree,
623	>	* assuming nothing about the order of the elements prior to the call.
624	>	*/
625	>	private void heapify() {
626	>	for (int i = size/2; i >= 1; i--)
627	>	fixDown(i);
628	>	}
629	>
630	>	/**
631	>	* Returns the comparator used to order this collection, or <tt>null</tt>
632	>	* if this collection is sorted according to its elements natural ordering
633	>	* (using <tt>Comparable</tt>).
634		*
635	<	* @return the comparator associated with this priority queue, or
636	<	*         <tt>null</tt> if it uses its elements' natural ordering.
635	>	* @return the comparator used to order this collection, or <tt>null</tt>
636	>	* if this collection is sorted according to its elements natural ordering.
637		*/
638	<	public Comparator comparator() {
638	>	public Comparator<? super E> comparator() {
639		return comparator;
640		}
641
#	Line 425 | Line 648 | public class PriorityQueue<E> extends Ab
648		* <tt>Object</tt>) in the proper order.
649		* @param s the stream
650		*/
651	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
651	>	private void writeObject(java.io.ObjectOutputStream s)
652		throws java.io.IOException{
653		// Write out element count, and any hidden stuff
654		s.defaultWriteObject();
#	Line 434 | Line 657 | public class PriorityQueue<E> extends Ab
657		s.writeInt(queue.length);
658
659		// Write out all elements in the proper order.
660	<	for (int i=0; i<size; i++)
660	>	for (int i=1; i<=size; i++)
661		s.writeObject(queue[i]);
662		}
663
#	Line 443 | Line 666 | public class PriorityQueue<E> extends Ab
666		* deserialize it).
667		* @param s the stream
668		*/
669	<	private synchronized void readObject(java.io.ObjectInputStream s)
669	>	private void readObject(java.io.ObjectInputStream s)
670		throws java.io.IOException, ClassNotFoundException {
671		// Read in size, and any hidden stuff
672		s.defaultReadObject();
673
674		// Read in array length and allocate array
675		int arrayLength = s.readInt();
676	<	queue = new E[arrayLength];
676	>	queue = new Object[arrayLength];
677
678		// Read in all elements in the proper order.
679	<	for (int i=0; i<size; i++)
680	<	queue[i] = (E)s.readObject();
679	>	for (int i=1; i<=size; i++)
680	>	queue[i] = (E) s.readObject();
681		}
682
683		}

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