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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.17 by tim, Thu Jul 31 19:49:42 2003 UTC vs.
Revision 1.53 by jsr166, Wed Nov 23 05:33:25 2005 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* @(#)PriorityQueue.java       1.8 05/08/27
3	>	*
4	>	* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
5	>	* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6	>	*/
7	>
8	>	package java.util;
9	>	import java.util.*; // for javadoc (till 6280605 is fixed)
10
11		/**
12	<	* An unbounded priority queue based on a priority heap.  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 {@link java.util.TreeMap}:
15	<	* 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 constructor is used.
18	<	* The <em>head</em> of this queue is the least element with respect to the
19	<	* specified ordering. If multiple elements are tied for least value, the
20	<	* head is one of those elements. A priority queue does not permit
21	<	* <tt>null</tt> elements.
12	>	* An unbounded priority {@linkplain Queue queue} based on a priority
13	>	* heap.  The elements of the priority queue are ordered according to
14	>	* their {@linkplain Comparable natural ordering}, or by a {@link
15	>	* Comparator} provided at queue construction time, depending on which
16	>	* constructor is used.  A priority queue does not permit
17	>	* <tt>null</tt> elements.  A priority queue relying on natural
18	>	* ordering also does not permit insertion of non-comparable objects
19	>	* (doing so may result in <tt>ClassCastException</tt>).
20	>	*
21	>	* <p>The <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>The {@link #remove()} and {@link #poll()} methods remove and
29	<	* return the head of the queue.
28	>	* <p>A priority queue is unbounded, but has an internal
29	>	* <i>capacity</i> governing the size of an array used to store the
30	>	* elements on the queue.  It is always at least as large as the queue
31	>	* size.  As elements are added to a priority queue, its capacity
32	>	* grows automatically.  The details of the growth policy are not
33	>	* specified.
34		*
35	<	* <p>The {@link #element()} and {@link #peek()} methods return, but do
36	<	* not delete, the head of the queue.
35	>	* <p>This class and its iterator implement all of the
36	>	* <em>optional</em> methods of the {@link Collection} and {@link
37	>	* Iterator} interfaces.  The Iterator provided in method {@link
38	>	* #iterator()} is <em>not</em> guaranteed to traverse the elements of
39	>	* the priority queue in any particular order. If you need ordered
40	>	* traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.
41		*
42	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
43	<	* size of the array used internally to store the elements on the
44	<	* queue.  It is always at least as large as the queue size.  As
45	<	* elements are added to a priority queue, its capacity grows
46	<	* automatically.  The details of the growth policy are not specified.
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		* <p>Implementation note: this implementation provides O(log(n)) time
49		* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
#	Line 35 | Line 56
56		* <a href="{@docRoot}/../guide/collections/index.html">
57		* Java Collections Framework</a>.
58		* @since 1.5
59	+	* @version 1.8, 08/27/05
60		* @author Josh Bloch
61	+	* @param <E> the type of elements held in this collection
62		*/
63		public class PriorityQueue<E> extends AbstractQueue<E>
64	<	implements Queue<E>, java.io.Serializable {
64	>	implements java.io.Serializable {
65	>
66	>	private static final long serialVersionUID = -7720805057305804111L;
67
68		private static final int DEFAULT_INITIAL_CAPACITY = 11;
69
#	Line 75 | Line 100 | public class PriorityQueue<E> extends Ab
100		private transient int modCount = 0;
101
102		/**
103	<	* Create a <tt>PriorityQueue</tt> with the default initial capacity
104	<	* (11) that orders its elements according to their natural
105	<	* ordering (using <tt>Comparable</tt>.)
103	>	* Creates a <tt>PriorityQueue</tt> with the default initial
104	>	* capacity (11) that orders its elements according to their
105	>	* {@linkplain Comparable natural ordering}.
106		*/
107		public PriorityQueue() {
108		this(DEFAULT_INITIAL_CAPACITY, null);
109		}
110
111		/**
112	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
113	<	* that orders its elements according to their natural ordering
114	<	* (using <tt>Comparable</tt>.)
112	>	* Creates a <tt>PriorityQueue</tt> with the specified initial
113	>	* capacity that orders its elements according to their
114	>	* {@linkplain Comparable natural ordering}.
115		*
116	<	* @param initialCapacity the initial capacity for this priority queue.
116	>	* @param initialCapacity the initial capacity for this priority queue
117	>	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
118	>	* than 1
119		*/
120		public PriorityQueue(int initialCapacity) {
121		this(initialCapacity, null);
122		}
123
124		/**
125	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
125	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
126		* that orders its elements according to the specified comparator.
127		*
128	<	* @param initialCapacity the initial capacity for this priority queue.
129	<	* @param comparator the comparator used to order this priority queue.
130	<	* If <tt>null</tt> then the order depends on the elements' natural
131	<	* ordering.
132	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
133	<	* than 1
128	>	* @param  initialCapacity the initial capacity for this priority queue
129	>	* @param  comparator the comparator that will be used to order
130	>	*         this priority queue.  If <tt>null</tt>, the <i>natural
131	>	*         ordering</i> of the elements will be used.
132	>	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is
133	>	*         less than 1
134		*/
135	<	public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
135	>	public PriorityQueue(int initialCapacity,
136	>	Comparator<? super E> comparator) {
137		if (initialCapacity < 1)
138		throw new IllegalArgumentException();
139		this.queue = new Object[initialCapacity + 1];
#	Line 113 | Line 141 | public class PriorityQueue<E> extends Ab
141		}
142
143		/**
144	<	* Create a <tt>PriorityQueue</tt> containing the elements in the specified
145	<	* collection.  The priority queue has an initial capacity of 110% of the
118	<	* size of the specified collection; or 1 if the collection is empty.
119	<	* If the specified collection
120	<	* implements the {@link Sorted} interface, the priority queue will be
121	<	* sorted according to the same comparator, or according to its elements'
122	<	* natural order if the collection is sorted according to its elements'
123	<	* natural order.  If the specified collection does not implement
124	<	* <tt>Sorted</tt>, the priority queue is ordered according to
125	<	* its elements' natural order.
126	<	*
127	<	* @param c the collection whose elements are to be placed
128	<	*        into this priority queue.
129	<	* @throws ClassCastException if elements of the specified collection
130	<	*         cannot be compared to one another according to the priority
131	<	*         queue's ordering.
132	<	* @throws NullPointerException if <tt>c</tt> or any element within it
133	<	* is <tt>null</tt>
144	>	* Common code to initialize underlying queue array across
145	>	* constructors below.
146		*/
147	<	public PriorityQueue(Collection<? extends E> c) {
147	>	private void initializeArray(Collection<? extends E> c) {
148		int sz = c.size();
149		int initialCapacity = (int)Math.min((sz * 110L) / 100,
150		Integer.MAX_VALUE - 1);
#	Line 140 | Line 152 | public class PriorityQueue<E> extends Ab
152		initialCapacity = 1;
153
154		this.queue = new Object[initialCapacity + 1];
155	+	}
156
157	<	if (c instanceof Sorted) {
158	<	// FIXME: this code assumes too much
159	<	this.comparator = (Comparator<? super E>) ((Sorted)c).comparator();
160	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
161	<	queue[++size] = i.next();
157	>	/**
158	>	* Initially fill elements of the queue array under the
159	>	* knowledge that it is sorted or is another PQ, in which
160	>	* case we can just place the elements in the order presented.
161	>	*/
162	>	private void fillFromSorted(Collection<? extends E> c) {
163	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) {
164	>	int k = ++size;
165	>	if (k >= queue.length)
166	>	grow(k);
167	>	queue[k] = i.next();
168	>	}
169	>	}
170	>
171	>	/**
172	>	* Initially fill elements of the queue array that is not to our knowledge
173	>	* sorted, so we must rearrange the elements to guarantee the heap
174	>	* invariant.
175	>	*/
176	>	private void fillFromUnsorted(Collection<? extends E> c) {
177	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); ) {
178	>	int k = ++size;
179	>	if (k >= queue.length)
180	>	grow(k);
181	>	queue[k] = i.next();
182	>	}
183	>	heapify();
184	>	}
185	>
186	>	/**
187	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
188	>	* specified collection.  The priority queue has an initial
189	>	* capacity of 110% of the size of the specified collection or 1
190	>	* if the collection is empty.  If the specified collection is an
191	>	* instance of a {@link java.util.SortedSet} or is another
192	>	* <tt>PriorityQueue</tt>, the priority queue will be ordered
193	>	* according to the same ordering.  Otherwise, this priority queue
194	>	* will be ordered according to the natural ordering of its elements.
195	>	*
196	>	* @param  c the collection whose elements are to be placed
197	>	*         into this priority queue
198	>	* @throws ClassCastException if elements of the specified collection
199	>	*         cannot be compared to one another according to the priority
200	>	*         queue's ordering
201	>	* @throws NullPointerException if the specified collection or any
202	>	*         of its elements are null
203	>	*/
204	>	public PriorityQueue(Collection<? extends E> c) {
205	>	initializeArray(c);
206	>	if (c instanceof SortedSet) {
207	>	SortedSet<? extends E> s = (SortedSet<? extends E>)c;
208	>	comparator = (Comparator<? super E>)s.comparator();
209	>	fillFromSorted(s);
210	>	} else if (c instanceof PriorityQueue) {
211	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
212	>	comparator = (Comparator<? super E>)s.comparator();
213	>	fillFromSorted(s);
214		} else {
215		comparator = null;
216	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
217	<	add(i.next());
216	>	fillFromUnsorted(c);
217	>	}
218	>	}
219	>
220	>	/**
221	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
222	>	* specified priority queue.  The priority queue has an initial
223	>	* capacity of 110% of the size of the specified priority queue or
224	>	* 1 if the priority queue is empty.  This priority queue will be
225	>	* ordered according to the same ordering as the given priority
226	>	* queue.
227	>	*
228	>	* @param  c the priority queue whose elements are to be placed
229	>	*         into this priority queue
230	>	* @throws ClassCastException if elements of <tt>c</tt> cannot be
231	>	*         compared to one another according to <tt>c</tt>'s
232	>	*         ordering
233	>	* @throws NullPointerException if the specified priority queue or any
234	>	*         of its elements are null
235	>	*/
236	>	public PriorityQueue(PriorityQueue<? extends E> c) {
237	>	initializeArray(c);
238	>	comparator = (Comparator<? super E>)c.comparator();
239	>	fillFromSorted(c);
240	>	}
241	>
242	>	/**
243	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
244	>	* specified sorted set.  The priority queue has an initial
245	>	* capacity of 110% of the size of the specified sorted set or 1
246	>	* if the sorted set is empty.  This priority queue will be ordered
247	>	* according to the same ordering as the given sorted set.
248	>	*
249	>	* @param  c the sorted set whose elements are to be placed
250	>	*         into this priority queue.
251	>	* @throws ClassCastException if elements of the specified sorted
252	>	*         set cannot be compared to one another according to the
253	>	*         sorted set's ordering
254	>	* @throws NullPointerException if the specified sorted set or any
255	>	*         of its elements are null
256	>	*/
257	>	public PriorityQueue(SortedSet<? extends E> c) {
258	>	initializeArray(c);
259	>	comparator = (Comparator<? super E>)c.comparator();
260	>	fillFromSorted(c);
261	>	}
262	>
263	>	/**
264	>	* Resize array, if necessary, to be able to hold given index.
265	>	*/
266	>	private void grow(int index) {
267	>	int newlen = queue.length;
268	>	if (index < newlen) // don't need to grow
269	>	return;
270	>	if (index == Integer.MAX_VALUE)
271	>	throw new OutOfMemoryError();
272	>	while (newlen <= index) {
273	>	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
274	>	newlen = Integer.MAX_VALUE;
275	>	else
276	>	newlen <<= 2;
277		}
278	+	queue = Arrays.copyOf(queue, newlen);
279		}
280
281	<	// Queue Methods
281	>	/**
282	>	* Inserts the specified element into this priority queue.
283	>	*
284	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
285	>	* @throws ClassCastException if the specified element cannot be
286	>	*         compared with elements currently in this priority queue
287	>	*         according to the priority queue's ordering
288	>	* @throws NullPointerException if the specified element is null
289	>	*/
290	>	public boolean add(E e) {
291	>	return offer(e);
292	>	}
293
294		/**
295	<	* Add the specified element to this priority queue.
295	>	* Inserts the specified element into this priority queue.
296		*
297	<	* @param element the element to add.
298	<	* @return <tt>true</tt>
299	<	* @throws ClassCastException if the specified element cannot be compared
300	<	* with elements currently in the priority queue according
301	<	* to the priority queue's ordering.
166	<	* @throws NullPointerException if the specified element is null.
297	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
298	>	* @throws ClassCastException if the specified element cannot be
299	>	*         compared with elements currently in this priority queue
300	>	*         according to the priority queue's ordering
301	>	* @throws NullPointerException if the specified element is null
302		*/
303	<	public boolean offer(E element) {
304	<	if (element == null)
303	>	public boolean offer(E e) {
304	>	if (e == null)
305		throw new NullPointerException();
306		modCount++;
307		++size;
308
309		// Grow backing store if necessary
310	<	while (size >= queue.length) {
311	<	Object[] newQueue = new Object[2 * queue.length];
177	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
178	<	queue = newQueue;
179	<	}
310	>	if (size >= queue.length)
311	>	grow(size);
312
313	<	queue[size] = element;
313	>	queue[size] = e;
314		fixUp(size);
315		return true;
316		}
317
318	<	public E poll() {
318	>	public E peek() {
319		if (size == 0)
320		return null;
189	–	return (E) remove(1);
190	–	}
191	–
192	–	public E peek() {
321		return (E) queue[1];
322		}
323
324	<	// Collection Methods
325	<
326	<	// these first two override just to get the throws docs
324	>	private int indexOf(Object o) {
325	>	if (o == null)
326	>	return -1;
327	>	for (int i = 1; i <= size; i++)
328	>	if (o.equals(queue[i]))
329	>	return i;
330	>	return -1;
331	>	}
332
333		/**
334	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
335	<	* @throws ClassCastException if the specified element cannot be compared
336	<	* with elements currently in the priority queue according
337	<	* to the priority queue's ordering.
334	>	* Removes a single instance of the specified element from this queue,
335	>	* if it is present.  More formally, removes an element <tt>e</tt> such
336	>	* that <tt>o.equals(e)</tt>, if this queue contains one or more such
337	>	* elements.  Returns true if this queue contained the specified element
338	>	* (or equivalently, if this queue changed as a result of the call).
339	>	*
340	>	* @param o element to be removed from this queue, if present
341	>	* @return <tt>true</tt> if this queue changed as a result of the call
342		*/
343	<	public boolean add(E element) {
344	<	return super.add(element);
343	>	public boolean remove(Object o) {
344	>	int i = indexOf(o);
345	>	if (i == -1)
346	>	return false;
347	>	else {
348	>	removeAt(i);
349	>	return true;
350	>	}
351		}
352
353		/**
354	<	* @throws NullPointerException if any element is <tt>null</tt>.
355	<	* @throws ClassCastException if any element cannot be compared
356	<	* with elements currently in the priority queue according
357	<	* to the priority queue's ordering.
354	>	* Returns <tt>true</tt> if this queue contains the specified element.
355	>	* More formally, returns <tt>true</tt> if and only if this queue contains
356	>	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
357	>	*
358	>	* @param o object to be checked for containment in this queue
359	>	* @return <tt>true</tt> if this queue contains the specified element
360		*/
361	<	public boolean addAll(Collection<? extends E> c) {
362	<	return super.addAll(c);
361	>	public boolean contains(Object o) {
362	>	return indexOf(o) != -1;
363		}
364
365	<	public boolean remove(Object o) {
366	<	if (o == null)
367	<	return false;
365	>	/**
366	>	* Returns an array containing all of the elements in this queue,
367	>	* The elements are in no particular order.
368	>	*
369	>	* <p>The returned array will be "safe" in that no references to it are
370	>	* maintained by this list.  (In other words, this method must allocate
371	>	* a new array).  The caller is thus free to modify the returned array.
372	>	*
373	>	* @return an array containing all of the elements in this queue.
374	>	*/
375	>	public Object[] toArray() {
376	>	return Arrays.copyOfRange(queue, 1, size+1);
377	>	}
378
379	<	if (comparator == null) {
380	<	for (int i = 1; i <= size; i++) {
381	<	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
382	<	remove(i);
383	<	return true;
384	<	}
385	<	}
386	<	} else {
387	<	for (int i = 1; i <= size; i++) {
388	<	if (comparator.compare((E)queue[i], (E)o) == 0) {
389	<	remove(i);
390	<	return true;
391	<	}
392	<	}
393	<	}
394	<	return false;
379	>	/**
380	>	* Returns an array containing all of the elements in this queue.
381	>	* The elements are in no particular order.  The runtime type of
382	>	* the returned array is that of the specified array.  If the queue
383	>	* fits in the specified array, it is returned therein.
384	>	* Otherwise, a new array is allocated with the runtime type of
385	>	* the specified array and the size of this queue.
386	>	*
387	>	* <p>If the queue fits in the specified array with room to spare
388	>	* (i.e., the array has more elements than the queue), the element in
389	>	* the array immediately following the end of the collection is set to
390	>	* <tt>null</tt>.  (This is useful in determining the length of the
391	>	* queue <i>only</i> if the caller knows that the queue does not contain
392	>	* any null elements.)
393	>	*
394	>	* @param a the array into which the elements of the queue are to
395	>	*          be stored, if it is big enough; otherwise, a new array of the
396	>	*          same runtime type is allocated for this purpose.
397	>	* @return an array containing the elements of the queue
398	>	* @throws ArrayStoreException if the runtime type of the specified array
399	>	*         is not a supertype of the runtime type of every element in
400	>	*         this queue
401	>	* @throws NullPointerException if the specified array is null
402	>	*/
403	>	public <T> T[] toArray(T[] a) {
404	>	if (a.length < size)
405	>	// Make a new array of a's runtime type, but my contents:
406	>	return (T[]) Arrays.copyOfRange(queue, 1, size+1, a.getClass());
407	>	System.arraycopy(queue, 1, a, 0, size);
408	>	if (a.length > size)
409	>	a[size] = null;
410	>	return a;
411		}
412
413	+	/**
414	+	* Returns an iterator over the elements in this queue. The iterator
415	+	* does not return the elements in any particular order.
416	+	*
417	+	* @return an iterator over the elements in this queue
418	+	*/
419		public Iterator<E> iterator() {
420		return new Itr();
421		}
422
423		private class Itr implements Iterator<E> {
424	+
425		/**
426		* Index (into queue array) of element to be returned by
427		* subsequent call to next.
#	Line 251 | Line 429 | public class PriorityQueue<E> extends Ab
429		private int cursor = 1;
430
431		/**
432	<	* Index of element returned by most recent call to next or
433	<	* previous.  Reset to 0 if this element is deleted by a call
434	<	* to remove.
432	>	* Index of element returned by most recent call to next,
433	>	* unless that element came from the forgetMeNot list.
434	>	* Reset to 0 if element is deleted by a call to remove.
435		*/
436		private int lastRet = 0;
437
#	Line 264 | Line 442 | public class PriorityQueue<E> extends Ab
442		*/
443		private int expectedModCount = modCount;
444
445	+	/**
446	+	* A list of elements that were moved from the unvisited portion of
447	+	* the heap into the visited portion as a result of "unlucky" element
448	+	* removals during the iteration.  (Unlucky element removals are those
449	+	* that require a fixup instead of a fixdown.)  We must visit all of
450	+	* the elements in this list to complete the iteration.  We do this
451	+	* after we've completed the "normal" iteration.
452	+	*
453	+	* We expect that most iterations, even those involving removals,
454	+	* will not use need to store elements in this field.
455	+	*/
456	+	private ArrayList<E> forgetMeNot = null;
457	+
458	+	/**
459	+	* Element returned by the most recent call to next iff that
460	+	* element was drawn from the forgetMeNot list.
461	+	*/
462	+	private Object lastRetElt = null;
463	+
464		public boolean hasNext() {
465	<	return cursor <= size;
465	>	return cursor <= size || forgetMeNot != null;
466		}
467
468		public E next() {
469		checkForComodification();
470	<	if (cursor > size)
470	>	E result;
471	>	if (cursor <= size) {
472	>	result = (E) queue[cursor];
473	>	lastRet = cursor++;
474	>	}
475	>	else if (forgetMeNot == null)
476		throw new NoSuchElementException();
477	<	E result = (E) queue[cursor];
478	<	lastRet = cursor++;
477	>	else {
478	>	int remaining = forgetMeNot.size();
479	>	result = forgetMeNot.remove(remaining - 1);
480	>	if (remaining == 1)
481	>	forgetMeNot = null;
482	>	lastRet = 0;
483	>	lastRetElt = result;
484	>	}
485		return result;
486		}
487
488		public void remove() {
281	–	if (lastRet == 0)
282	–	throw new IllegalStateException();
489		checkForComodification();
490
491	<	PriorityQueue.this.remove(lastRet);
492	<	if (lastRet < cursor)
493	<	cursor--;
494	<	lastRet = 0;
491	>	if (lastRet != 0) {
492	>	E moved = PriorityQueue.this.removeAt(lastRet);
493	>	lastRet = 0;
494	>	if (moved == null) {
495	>	cursor--;
496	>	} else {
497	>	if (forgetMeNot == null)
498	>	forgetMeNot = new ArrayList<E>();
499	>	forgetMeNot.add(moved);
500	>	}
501	>	} else if (lastRetElt != null) {
502	>	PriorityQueue.this.remove(lastRetElt);
503	>	lastRetElt = null;
504	>	} else {
505	>	throw new IllegalStateException();
506	>	}
507	>
508		expectedModCount = modCount;
509		}
510
#	Line 295 | Line 514 | public class PriorityQueue<E> extends Ab
514		}
515		}
516
298	–	/**
299	–	* Returns the number of elements in this priority queue.
300	–	*
301	–	* @return the number of elements in this priority queue.
302	–	*/
517		public int size() {
518		return size;
519		}
520
521		/**
522	<	* Remove all elements from the priority queue.
522	>	* Removes all of the elements from this priority queue.
523	>	* The queue will be empty after this call returns.
524		*/
525		public void clear() {
526		modCount++;
#	Line 317 | Line 532 | public class PriorityQueue<E> extends Ab
532		size = 0;
533		}
534
535	+	public E poll() {
536	+	if (size == 0)
537	+	return null;
538	+	modCount++;
539	+
540	+	E result = (E) queue[1];
541	+	queue[1] = queue[size];
542	+	queue[size--] = null;  // Drop extra ref to prevent memory leak
543	+	if (size > 1)
544	+	fixDown(1);
545	+
546	+	return result;
547	+	}
548	+
549		/**
550	<	* Removes and returns the ith element from queue.  Recall
551	<	* that queue is one-based, so 1 <= i <= size.
550	>	* Removes and returns the ith element from queue.  (Recall that queue
551	>	* is one-based, so 1 <= i <= size.)
552		*
553	<	* XXX: Could further special-case i==size, but is it worth it?
554	<	* XXX: Could special-case i==0, but is it worth it?
553	>	* Normally this method leaves the elements at positions from 1 up to i-1,
554	>	* inclusive, untouched.  Under these circumstances, it returns null.
555	>	* Occasionally, in order to maintain the heap invariant, it must move
556	>	* the last element of the list to some index in the range [2, i-1],
557	>	* and move the element previously at position (i/2) to position i.
558	>	* Under these circumstances, this method returns the element that was
559	>	* previously at the end of the list and is now at some position between
560	>	* 2 and i-1 inclusive.
561		*/
562	<	private E remove(int i) {
563	<	assert i <= size;
562	>	private E removeAt(int i) {
563	>	assert i > 0 && i <= size;
564		modCount++;
565
566	<	E result = (E) queue[i];
567	<	queue[i] = queue[size];
566	>	E moved = (E) queue[size];
567	>	queue[i] = moved;
568		queue[size--] = null;  // Drop extra ref to prevent memory leak
569	<	if (i <= size)
569	>	if (i <= size) {
570		fixDown(i);
571	<	return result;
571	>	if (queue[i] == moved) {
572	>	fixUp(i);
573	>	if (queue[i] != moved)
574	>	return moved;
575	>	}
576	>	}
577	>	return null;
578		}
579
580		/**
#	Line 349 | Line 590 | public class PriorityQueue<E> extends Ab
590		if (comparator == null) {
591		while (k > 1) {
592		int j = k >> 1;
593	<	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
593	>	if (((Comparable<? super E>)queue[j]).compareTo((E)queue[k]) <= 0)
594		break;
595		Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
596		k = j;
597		}
598		} else {
599		while (k > 1) {
600	<	int j = k >> 1;
600	>	int j = k >>> 1;
601		if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
602		break;
603		Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
#	Line 377 | Line 618 | public class PriorityQueue<E> extends Ab
618		private void fixDown(int k) {
619		int j;
620		if (comparator == null) {
621	<	while ((j = k << 1) <= size) {
622	<	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
621	>	while ((j = k << 1) <= size && (j > 0)) {
622	>	if (j<size &&
623	>	((Comparable<? super E>)queue[j]).compareTo((E)queue[j+1]) > 0)
624		j++; // j indexes smallest kid
625	<	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
625	>
626	>	if (((Comparable<? super E>)queue[k]).compareTo((E)queue[j]) <= 0)
627		break;
628		Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
629		k = j;
630		}
631		} else {
632	<	while ((j = k << 1) <= size) {
633	<	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
632	>	while ((j = k << 1) <= size && (j > 0)) {
633	>	if (j<size &&
634	>	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
635		j++; // j indexes smallest kid
636		if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
637		break;
#	Line 397 | Line 641 | public class PriorityQueue<E> extends Ab
641		}
642		}
643
644	+	/**
645	+	* Establishes the heap invariant (described above) in the entire tree,
646	+	* assuming nothing about the order of the elements prior to the call.
647	+	*/
648	+	private void heapify() {
649	+	for (int i = size/2; i >= 1; i--)
650	+	fixDown(i);
651	+	}
652	+
653	+	/**
654	+	* Returns the comparator used to order the elements in this
655	+	* queue, or <tt>null</tt> if this queue is sorted according to
656	+	* the {@linkplain Comparable natural ordering} of its elements.
657	+	*
658	+	* @return the comparator used to order this queue, or
659	+	*         <tt>null</tt> if this queue is sorted according to the
660	+	*         natural ordering of its elements.
661	+	*/
662		public Comparator<? super E> comparator() {
663		return comparator;
664		}
#	Line 410 | Line 672 | public class PriorityQueue<E> extends Ab
672		* <tt>Object</tt>) in the proper order.
673		* @param s the stream
674		*/
675	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
675	>	private void writeObject(java.io.ObjectOutputStream s)
676		throws java.io.IOException{
677		// Write out element count, and any hidden stuff
678		s.defaultWriteObject();
#	Line 419 | Line 681 | public class PriorityQueue<E> extends Ab
681		s.writeInt(queue.length);
682
683		// Write out all elements in the proper order.
684	<	for (int i=0; i<size; i++)
684	>	for (int i=1; i<=size; i++)
685		s.writeObject(queue[i]);
686		}
687
688		/**
689	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
690	<	* deserialize it).
689	>	* Reconstitute the <tt>PriorityQueue</tt> instance from a stream
690	>	* (that is, deserialize it).
691		* @param s the stream
692		*/
693	<	private synchronized void readObject(java.io.ObjectInputStream s)
693	>	private void readObject(java.io.ObjectInputStream s)
694		throws java.io.IOException, ClassNotFoundException {
695		// Read in size, and any hidden stuff
696		s.defaultReadObject();
#	Line 438 | Line 700 | public class PriorityQueue<E> extends Ab
700		queue = new Object[arrayLength];
701
702		// Read in all elements in the proper order.
703	<	for (int i=0; i<size; i++)
704	<	queue[i] = s.readObject();
703	>	for (int i=1; i<=size; i++)
704	>	queue[i] = (E) s.readObject();
705		}
706
707		}
446	–

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