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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.2 by tim, Sun May 18 18:10:02 2003 UTC vs.
Revision 1.37 by dl, Sat Aug 30 11:44:53 2003 UTC

#	Line 1 | Line 1
1		package java.util;
2
3	–	/*
4	–	* Todo
5	–	*
6	–	*   1) Make it serializable.
7	–	*/
8	–
3		/**
4	<	* An unbounded priority queue based on a priority heap.  This queue orders
5	<	* elements according to the order specified at creation time.  This order is
6	<	* specified as for {@link TreeSet} and {@link TreeMap}: Elements are ordered
7	<	* either according to their <i>natural order</i> (see {@link Comparable}), or
8	<	* according to a {@link Comparator}, depending on which constructor is used.
9	<	* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the
10	<	* minimal element with respect to the specified ordering.  If multiple
11	<	* these elements are tied for least value, no guarantees are made as to
12	<	* which of elements is returned.
4	>	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
5	>	* This queue orders elements according to an order specified at construction
6	>	* time, which is specified in the same manner as {@link java.util.TreeSet}
7	>	* and {@link java.util.TreeMap}: elements are ordered either according to
8	>	* their <i>natural order</i> (see {@link Comparable}), or according to a
9	>	* {@link java.util.Comparator}, depending on which constructor is used.
10	>	* <p>The <em>head</em> of this queue is the <em>least</em> element with
11	>	* respect to the specified ordering.  If multiple elements are tied for least
12	>	* value, the head is one of those elements. A priority queue does not permit
13	>	* <tt>null</tt> elements.
14	>	*
15	>	* <p>The {@link #remove()} and {@link #poll()} methods remove and
16	>	* return the head of the queue.
17	>	*
18	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
19	>	* not delete, the head of the queue.
20		*
21	<	* <p>Each priority queue has a <i>capacity</i>.  The capacity is the size of
22	<	* the array used to store the elements on the queue.  It is always at least
23	<	* as large as the queue size.  As elements are added to a priority list,
24	<	* its capacity grows automatically.  The details of the growth policy are not
25	<	* specified.
21	>	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
22	>	* size of the array used internally to store the elements on the
23	>	* queue.
24	>	* It is always at least as large as the queue size.  As
25	>	* elements are added to a priority queue, its capacity grows
26	>	* automatically.  The details of the growth policy are not specified.
27		*
28	<	*<p>Implementation note: this implementation provides O(log(n)) time for
29	<	* the <tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>
30	<	* methods; linear time for the <tt>remove(Object)</tt> and
31	<	* <tt>contains</tt> methods; and constant time for the <tt>peek</tt>,
32	<	* <tt>element</tt>, and <tt>size</tt> methods.
28	>	* <p>The Iterator provided in method {@link #iterator()} is <em>not</em>
29	>	* guaranteed to traverse the elements of the PriorityQueue in any
30	>	* particular order. If you need ordered traversal, consider using
31	>	* <tt>Arrays.sort(pq.toArray())</tt>.
32	>	*
33	>	* <p> <strong>Note that this implementation is not synchronized.</strong>
34	>	* Multiple threads should not access a <tt>PriorityQueue</tt>
35	>	* instance concurrently if any of the threads modifies the list
36	>	* structurally. Instead, use the thread-safe {@link
37	>	* java.util.concurrent.PriorityBlockingQueue} class.
38	>	*
39	>	*
40	>	* <p>Implementation note: this implementation provides O(log(n)) time
41	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
42	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
43	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
44	>	* constant time for the retrieval methods (<tt>peek</tt>,
45	>	* <tt>element</tt>, and <tt>size</tt>).
46		*
47		* <p>This class is a member of the
48		* <a href="{@docRoot}/../guide/collections/index.html">
49		* Java Collections Framework</a>.
50	+	* @since 1.5
51	+	* @author Josh Bloch
52		*/
53		public class PriorityQueue<E> extends AbstractQueue<E>
54	<	implements Queue<E>
55	<	{
54	>	implements Queue<E>, java.io.Serializable {
55	>
56	>	private static final long serialVersionUID = -7720805057305804111L;
57	>
58		private static final int DEFAULT_INITIAL_CAPACITY = 11;
59
60		/**
61		* Priority queue represented as a balanced binary heap: the two children
62		* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
63		* ordered by comparator, or by the elements' natural ordering, if
64	<	* comparator is null:  For each node n in the heap, and each descendant
65	<	* of n, d, n <= d.
64	>	* comparator is null:  For each node n in the heap and each descendant d
65	>	* of n, n <= d.
66		*
67	<	* The element with the lowest value is in queue[1] (assuming the queue is
68	<	* nonempty). A one-based array is used in preference to the traditional
69	<	* zero-based array to simplify parent and child calculations.
67	>	* The element with the lowest value is in queue[1], assuming the queue is
68	>	* nonempty.  (A one-based array is used in preference to the traditional
69	>	* zero-based array to simplify parent and child calculations.)
70		*
71		* queue.length must be >= 2, even if size == 0.
72		*/
73	<	private E[] queue;
73	>	private transient Object[] queue;
74
75		/**
76		* The number of elements in the priority queue.
#	Line 62 | Line 81 | public class PriorityQueue<E> extends Ab
81		* The comparator, or null if priority queue uses elements'
82		* natural ordering.
83		*/
84	<	private final Comparator<E> comparator;
84	>	private final Comparator<? super E> comparator;
85
86		/**
87		* The number of times this priority queue has been
88		* <i>structurally modified</i>.  See AbstractList for gory details.
89		*/
90	<	private int modCount = 0;
90	>	private transient int modCount = 0;
91
92		/**
93	<	* Create a new priority queue with the default initial capacity (11)
94	<	* that orders its elements according to their natural ordering.
93	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
94	>	* (11) that orders its elements according to their natural
95	>	* ordering (using <tt>Comparable</tt>).
96		*/
97		public PriorityQueue() {
98	<	this(DEFAULT_INITIAL_CAPACITY);
98	>	this(DEFAULT_INITIAL_CAPACITY, null);
99		}
100
101		/**
102	<	* Create a new priority queue with the specified initial capacity
103	<	* that orders its elements according to their natural ordering.
102	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
103	>	* that orders its elements according to their natural ordering
104	>	* (using <tt>Comparable</tt>).
105		*
106		* @param initialCapacity the initial capacity for this priority queue.
107	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
108	+	* than 1
109		*/
110		public PriorityQueue(int initialCapacity) {
111		this(initialCapacity, null);
112		}
113
114		/**
115	<	* Create a new priority queue with the specified initial capacity (11)
115	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
116		* that orders its elements according to the specified comparator.
117		*
118		* @param initialCapacity the initial capacity for this priority queue.
119		* @param comparator the comparator used to order this priority queue.
120	+	* If <tt>null</tt> then the order depends on the elements' natural
121	+	* ordering.
122	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
123	+	* than 1
124		*/
125	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
125	>	public PriorityQueue(int initialCapacity,
126	>	Comparator<? super E> comparator) {
127		if (initialCapacity < 1)
128	<	initialCapacity = 1;
129	<	queue = new E[initialCapacity + 1];
128	>	throw new IllegalArgumentException();
129	>	this.queue = new Object[initialCapacity + 1];
130		this.comparator = comparator;
131		}
132
133		/**
134	<	* Create a new priority queue containing the elements in the specified
135	<	* collection.  The priority queue has an initial capacity of 110% of the
108	<	* size of the specified collection. If the specified collection
109	<	* implements the {@link Sorted} interface, the priority queue will be
110	<	* sorted according to the same comparator, or according to its elements'
111	<	* natural order if the collection is sorted according to its elements'
112	<	* natural order.  If the specified collection does not implement the
113	<	* <tt>Sorted</tt> interface, the priority queue is ordered according to
114	<	* its elements' natural order.
115	<	*
116	<	* @param initialElements the collection whose elements are to be placed
117	<	*        into this priority queue.
118	<	* @throws ClassCastException if elements of the specified collection
119	<	*         cannot be compared to one another according to the priority
120	<	*         queue's ordering.
121	<	* @throws NullPointerException if the specified collection or an
122	<	*         element of the specified collection is <tt>null</tt>.
134	>	* Common code to initialize underlying queue array across
135	>	* constructors below.
136		*/
137	<	public PriorityQueue(Collection<E> initialElements) {
138	<	int sz = initialElements.size();
137	>	private void initializeArray(Collection<? extends E> c) {
138	>	int sz = c.size();
139		int initialCapacity = (int)Math.min((sz * 110L) / 100,
140		Integer.MAX_VALUE - 1);
141		if (initialCapacity < 1)
142		initialCapacity = 1;
130	–	queue = new E[initialCapacity + 1];
143
144	<	/* Commented out to compile with generics compiler
144	>	this.queue = new Object[initialCapacity + 1];
145	>	}
146	>
147	>	/**
148	>	* Initially fill elements of the queue array under the
149	>	* knowledge that it is sorted or is another PQ, in which
150	>	* case we can just place the elements in the order presented.
151	>	*/
152	>	private void fillFromSorted(Collection<? extends E> c) {
153	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
154	>	queue[++size] = i.next();
155	>	}
156	>
157	>	/**
158	>	* Initially fill elements of the queue array that is not to our knowledge
159	>	* sorted, so we must rearrange the elements to guarantee the heap
160	>	* invariant.
161	>	*/
162	>	private void fillFromUnsorted(Collection<? extends E> c) {
163	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
164	>	queue[++size] = i.next();
165	>	heapify();
166	>	}
167
168	<	if (initialElements instanceof Sorted) {
169	<	comparator = ((Sorted)initialElements).comparator();
170	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
171	<	queue[++size] = i.next();
168	>	/**
169	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
170	>	* specified collection.  The priority queue has an initial
171	>	* capacity of 110% of the size of the specified collection or 1
172	>	* if the collection is empty.  If the specified collection is an
173	>	* instance of a {@link java.util.SortedSet} or is another
174	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
175	>	* according to the same comparator, or according to its elements'
176	>	* natural order if the collection is sorted according to its
177	>	* elements' natural order.  Otherwise, the priority queue is
178	>	* ordered according to its elements' natural order.
179	>	*
180	>	* @param c the collection whose elements are to be placed
181	>	*        into this priority queue.
182	>	* @throws ClassCastException if elements of the specified collection
183	>	*         cannot be compared to one another according to the priority
184	>	*         queue's ordering.
185	>	* @throws NullPointerException if <tt>c</tt> or any element within it
186	>	* is <tt>null</tt>
187	>	*/
188	>	public PriorityQueue(Collection<? extends E> c) {
189	>	initializeArray(c);
190	>	if (c instanceof SortedSet) {
191	>	// @fixme double-cast workaround for compiler
192	>	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
193	>	comparator = (Comparator<? super E>)s.comparator();
194	>	fillFromSorted(s);
195	>	} else if (c instanceof PriorityQueue) {
196	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
197	>	comparator = (Comparator<? super E>)s.comparator();
198	>	fillFromSorted(s);
199		} else {
139	–	*/
140	–	{
200		comparator = null;
201	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
143	<	add(i.next());
201	>	fillFromUnsorted(c);
202		}
203		}
204
205	+	/**
206	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
207	+	* specified collection.  The priority queue has an initial
208	+	* capacity of 110% of the size of the specified collection or 1
209	+	* if the collection is empty.  This priority queue will be sorted
210	+	* according to the same comparator as the given collection, or
211	+	* according to its elements' natural order if the collection is
212	+	* sorted according to its elements' natural order.
213	+	*
214	+	* @param c the collection whose elements are to be placed
215	+	*        into this priority queue.
216	+	* @throws ClassCastException if elements of the specified collection
217	+	*         cannot be compared to one another according to the priority
218	+	*         queue's ordering.
219	+	* @throws NullPointerException if <tt>c</tt> or any element within it
220	+	* is <tt>null</tt>
221	+	*/
222	+	public PriorityQueue(PriorityQueue<? extends E> c) {
223	+	initializeArray(c);
224	+	comparator = (Comparator<? super E>)c.comparator();
225	+	fillFromSorted(c);
226	+	}
227	+
228	+	/**
229	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
230	+	* specified collection.  The priority queue has an initial
231	+	* capacity of 110% of the size of the specified collection or 1
232	+	* if the collection is empty.  This priority queue will be sorted
233	+	* according to the same comparator as the given collection, or
234	+	* according to its elements' natural order if the collection is
235	+	* sorted according to its elements' natural order.
236	+	*
237	+	* @param c the collection whose elements are to be placed
238	+	*        into this priority queue.
239	+	* @throws ClassCastException if elements of the specified collection
240	+	*         cannot be compared to one another according to the priority
241	+	*         queue's ordering.
242	+	* @throws NullPointerException if <tt>c</tt> or any element within it
243	+	* is <tt>null</tt>
244	+	*/
245	+	public PriorityQueue(SortedSet<? extends E> c) {
246	+	initializeArray(c);
247	+	comparator = (Comparator<? super E>)c.comparator();
248	+	fillFromSorted(c);
249	+	}
250	+
251	+	/**
252	+	* Resize array, if necessary, to be able to hold given index
253	+	*/
254	+	private void grow(int index) {
255	+	int newlen = queue.length;
256	+	if (index < newlen) // don't need to grow
257	+	return;
258	+	if (index == Integer.MAX_VALUE)
259	+	throw new OutOfMemoryError();
260	+	while (newlen <= index) {
261	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
262	+	newlen = Integer.MAX_VALUE;
263	+	else
264	+	newlen <<= 2;
265	+	}
266	+	Object[] newQueue = new Object[newlen];
267	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
268	+	queue = newQueue;
269	+	}
270	+
271	+
272		// Queue Methods
273
274		/**
275	<	* Remove and return the minimal element from this priority queue if
151	<	* it contains one or more elements, otherwise <tt>null</tt>.  The term
152	<	* <i>minimal</i> is defined according to this priority queue's order.
275	>	* Add the specified element to this priority queue.
276		*
277	<	* @return the minimal element from this priority queue if it contains
278	<	*         one or more elements, otherwise <tt>null</tt>.
277	>	* @return <tt>true</tt>
278	>	* @throws ClassCastException if the specified element cannot be compared
279	>	* with elements currently in the priority queue according
280	>	* to the priority queue's ordering.
281	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
282		*/
283	+	public boolean offer(E o) {
284	+	if (o == null)
285	+	throw new NullPointerException();
286	+	modCount++;
287	+	++size;
288	+
289	+	// Grow backing store if necessary
290	+	if (size >= queue.length)
291	+	grow(size);
292	+
293	+	queue[size] = o;
294	+	fixUp(size);
295	+	return true;
296	+	}
297	+
298		public E poll() {
299		if (size == 0)
300		return null;
301	<	return remove(1);
301	>	return remove();
302	>	}
303	>
304	>	public E peek() {
305	>	return (E) queue[1];
306		}
307
308	+	// Collection Methods - the first two override to update docs
309	+
310		/**
311	<	* Return, but do not remove, the minimal element from the priority queue,
312	<	* or <tt>null</tt> if the queue is empty.  The term <i>minimal</i> is
313	<	* defined according to this priority queue's order.  This method returns
167	<	* the same object reference that would be returned by by the
168	<	* <tt>poll</tt> method.  The two methods differ in that this method
169	<	* does not remove the element from the priority queue.
311	>	* Adds the specified element to this queue.
312	>	* @return <tt>true</tt> (as per the general contract of
313	>	* <tt>Collection.add</tt>).
314		*
315	<	* @return the minimal element from this priority queue if it contains
316	<	*         one or more elements, otherwise <tt>null</tt>.
315	>	* @throws NullPointerException {@inheritDoc}
316	>	* @throws ClassCastException if the specified element cannot be compared
317	>	* with elements currently in the priority queue according
318	>	* to the priority queue's ordering.
319		*/
320	<	public E peek() {
321	<	return queue[1];
320	>	public boolean add(E o) {
321	>	return super.add(o);
322	>	}
323	>
324	>
325	>	/**
326	>	* Adds all of the elements in the specified collection to this queue.
327	>	* The behavior of this operation is undefined if
328	>	* the specified collection is modified while the operation is in
329	>	* progress.  (This implies that the behavior of this call is undefined if
330	>	* the specified collection is this queue, and this queue is nonempty.)
331	>	* <p>
332	>	* This implementation iterates over the specified collection, and adds
333	>	* each object returned by the iterator to this collection, in turn.
334	>	* @throws NullPointerException {@inheritDoc}
335	>	* @throws ClassCastException if any element cannot be compared
336	>	* with elements currently in the priority queue according
337	>	* to the priority queue's ordering.
338	>	*/
339	>	public boolean addAll(Collection<? extends E> c) {
340	>	return super.addAll(c);
341		}
342
178	–	// Collection Methods
343
344		/**
345	<	* Removes a single instance of the specified element from this priority
346	<	* queue, if it is present.  Returns true if this collection contained the
347	<	* specified element (or equivalently, if this collection changed as a
345	>	* Removes a single instance of the specified element from this
346	>	* queue, if it is present.  More formally,
347	>	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
348	>	* o.equals(e))</tt>, if the queue contains one or more such
349	>	* elements.  Returns <tt>true</tt> if the queue contained the
350	>	* specified element (or equivalently, if the queue changed as a
351		* result of the call).
352		*
353	<	* @param o element to be removed from this collection, if present.
354	<	* @return <tt>true</tt> if this collection changed as a result of the
355	<	*         call
356	<	* @throws ClassCastException if the specified element cannot be compared
190	<	*            with elements currently in the priority queue according
191	<	*            to the priority queue's ordering.
192	<	* @throws NullPointerException if the specified element is null.
353	>	* <p>This implementation iterates over the queue looking for the
354	>	* specified element.  If it finds the element, it removes the element
355	>	* from the queue using the iterator's remove method.<p>
356	>	*
357		*/
358	<	public boolean remove(Object element) {
359	<	if (element == null)
360	<	throw new NullPointerException();
358	>	public boolean remove(Object o) {
359	>	if (o == null)
360	>	return false;
361
362		if (comparator == null) {
363		for (int i = 1; i <= size; i++) {
364	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
365	<	remove(i);
364	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
365	>	removeAt(i);
366		return true;
367		}
368		}
369		} else {
370		for (int i = 1; i <= size; i++) {
371	<	if (comparator.compare(queue[i], (E) element) == 0) {
372	<	remove(i);
371	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
372	>	removeAt(i);
373		return true;
374		}
375		}
#	Line 214 | Line 378 | public class PriorityQueue<E> extends Ab
378		}
379
380		/**
381	<	* Returns an iterator over the elements in this priority queue.  The
382	<	* first element returned by this iterator is the same element that
219	<	* would be returned by a call to <tt>peek</tt>.
381	>	* Returns an iterator over the elements in this queue. The iterator
382	>	* does not return the elements in any particular order.
383		*
384	<	* @return an <tt>Iterator</tt> over the elements in this priority queue.
384	>	* @return an iterator over the elements in this queue.
385		*/
386		public Iterator<E> iterator() {
387		return new Itr();
388		}
389
390		private class Itr implements Iterator<E> {
391	+
392		/**
393		* Index (into queue array) of element to be returned by
394		* subsequent call to next.
395		*/
396	<	int cursor = 1;
396	>	private int cursor = 1;
397
398		/**
399	<	* Index of element returned by most recent call to next or
400	<	* previous.  Reset to 0 if this element is deleted by a call
401	<	* to remove.
399	>	* Index of element returned by most recent call to next,
400	>	* unless that element came from the forgetMeNot list.
401	>	* Reset to 0 if element is deleted by a call to remove.
402		*/
403	<	int lastRet = 0;
403	>	private int lastRet = 0;
404
405		/**
406		* The modCount value that the iterator believes that the backing
407		* List should have.  If this expectation is violated, the iterator
408		* has detected concurrent modification.
409		*/
410	<	int expectedModCount = modCount;
410	>	private int expectedModCount = modCount;
411	>
412	>	/**
413	>	* A list of elements that were moved from the unvisited portion of
414	>	* the heap into the visited portion as a result of "unlucky" element
415	>	* removals during the iteration.  (Unlucky element removals are those
416	>	* that require a fixup instead of a fixdown.)  We must visit all of
417	>	* the elements in this list to complete the iteration.  We do this
418	>	* after we've completed the "normal" iteration.
419	>	*
420	>	* We expect that most iterations, even those involving removals,
421	>	* will not use need to store elements in this field.
422	>	*/
423	>	private ArrayList<E> forgetMeNot = null;
424	>
425	>	/**
426	>	* Element returned by the most recent call to next iff that
427	>	* element was drawn from the forgetMeNot list.
428	>	*/
429	>	private Object lastRetElt = null;
430
431		public boolean hasNext() {
432	<	return cursor <= size;
432	>	return cursor <= size || forgetMeNot != null;
433		}
434
435		public E next() {
436		checkForComodification();
437	<	if (cursor > size)
437	>	E result;
438	>	if (cursor <= size) {
439	>	result = (E) queue[cursor];
440	>	lastRet = cursor++;
441	>	}
442	>	else if (forgetMeNot == null)
443		throw new NoSuchElementException();
444	<	E result = queue[cursor];
445	<	lastRet = cursor++;
444	>	else {
445	>	int remaining = forgetMeNot.size();
446	>	result = forgetMeNot.remove(remaining - 1);
447	>	if (remaining == 1)
448	>	forgetMeNot = null;
449	>	lastRet = 0;
450	>	lastRetElt = result;
451	>	}
452		return result;
453		}
454
455		public void remove() {
262	–	if (lastRet == 0)
263	–	throw new IllegalStateException();
456		checkForComodification();
457
458	<	PriorityQueue.this.remove(lastRet);
459	<	if (lastRet < cursor)
460	<	cursor--;
461	<	lastRet = 0;
458	>	if (lastRet != 0) {
459	>	E moved = PriorityQueue.this.removeAt(lastRet);
460	>	lastRet = 0;
461	>	if (moved == null) {
462	>	cursor--;
463	>	} else {
464	>	if (forgetMeNot == null)
465	>	forgetMeNot = new ArrayList<E>();
466	>	forgetMeNot.add(moved);
467	>	}
468	>	} else if (lastRetElt != null) {
469	>	PriorityQueue.this.remove(lastRetElt);
470	>	lastRetElt = null;
471	>	} else {
472	>	throw new IllegalStateException();
473	>	}
474	>
475		expectedModCount = modCount;
476		}
477
#	Line 276 | Line 481 | public class PriorityQueue<E> extends Ab
481		}
482		}
483
279	–	/**
280	–	* Returns the number of elements in this priority queue.
281	–	*
282	–	* @return the number of elements in this priority queue.
283	–	*/
484		public int size() {
485		return size;
486		}
487
488		/**
489	<	* 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.
489	>	* Remove all elements from the priority queue.
490		*/
491	<	public boolean offer(E element) {
299	<	if (element == null)
300	<	throw new NullPointerException();
491	>	public void clear() {
492		modCount++;
493
494	<	// Grow backing store if necessary
495	<	if (++size == queue.length) {
496	<	E[] newQueue = new E[2 * queue.length];
306	<	System.arraycopy(queue, 0, newQueue, 0, size);
307	<	queue = newQueue;
308	<	}
494	>	// Null out element references to prevent memory leak
495	>	for (int i=1; i<=size; i++)
496	>	queue[i] = null;
497
498	<	queue[size] = element;
311	<	fixUp(size);
312	<	return true;
498	>	size = 0;
499		}
500
501		/**
502	<	* Remove all elements from the priority queue.
502	>	* Removes and returns the first element from queue.
503		*/
504	<	public void clear() {
504	>	public E remove() {
505	>	if (size == 0)
506	>	throw new NoSuchElementException();
507		modCount++;
508
509	<	// Null out element references to prevent memory leak
510	<	for (int i=1; i<=size; i++)
511	<	queue[i] = null;
509	>	E result = (E) queue[1];
510	>	queue[1] = queue[size];
511	>	queue[size--] = null;  // Drop extra ref to prevent memory leak
512	>	if (size > 1)
513	>	fixDown(1);
514
515	<	size = 0;
515	>	return result;
516		}
517
518		/**
519	<	* Removes and returns the ith element from queue.  Recall
520	<	* that queue is one-based, so 1 <= i <= size.
519	>	* Removes and returns the ith element from queue.  (Recall that queue
520	>	* is one-based, so 1 <= i <= size.)
521		*
522	<	* XXX: Could further special-case i==size, but is it worth it?
523	<	* XXX: Could special-case i==0, but is it worth it?
522	>	* Normally this method leaves the elements at positions from 1 up to i-1,
523	>	* inclusive, untouched.  Under these circumstances, it returns null.
524	>	* Occasionally, in order to maintain the heap invariant, it must move
525	>	* the last element of the list to some index in the range [2, i-1],
526	>	* and move the element previously at position (i/2) to position i.
527	>	* Under these circumstances, this method returns the element that was
528	>	* previously at the end of the list and is now at some position between
529	>	* 2 and i-1 inclusive.
530		*/
531	<	private E remove(int i) {
532	<	assert i <= size;
531	>	private E removeAt(int i) {
532	>	assert i > 0 && i <= size;
533		modCount++;
534
535	<	E result = queue[i];
536	<	queue[i] = queue[size];
535	>	E moved = (E) queue[size];
536	>	queue[i] = moved;
537		queue[size--] = null;  // Drop extra ref to prevent memory leak
538	<	if (i <= size)
538	>	if (i <= size) {
539		fixDown(i);
540	<	return result;
540	>	if (queue[i] == moved) {
541	>	fixUp(i);
542	>	if (queue[i] != moved)
543	>	return moved;
544	>	}
545	>	}
546	>	return null;
547		}
548
549		/**
#	Line 357 | Line 559 | public class PriorityQueue<E> extends Ab
559		if (comparator == null) {
560		while (k > 1) {
561		int j = k >> 1;
562	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
562	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
563		break;
564	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
564	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
565		k = j;
566		}
567		} else {
568		while (k > 1) {
569	<	int j = k >> 1;
570	<	if (comparator.compare(queue[j], queue[k]) <= 0)
569	>	int j = k >>> 1;
570	>	if (comparator.compare((E)queue[j], (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		}
#	Line 385 | Line 587 | public class PriorityQueue<E> extends Ab
587		private void fixDown(int k) {
588		int j;
589		if (comparator == null) {
590	<	while ((j = k << 1) <= size) {
591	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
590	>	while ((j = k << 1) <= size && (j > 0)) {
591	>	if (j<size &&
592	>	((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
593		j++; // j indexes smallest kid
594	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
594	>
595	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
596		break;
597	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
597	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
598		k = j;
599		}
600		} else {
601	<	while ((j = k << 1) <= size) {
602	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
601	>	while ((j = k << 1) <= size && (j > 0)) {
602	>	if (j<size &&
603	>	comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
604		j++; // j indexes smallest kid
605	<	if (comparator.compare(queue[k], queue[j]) <= 0)
605	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
606		break;
607	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
607	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
608		k = j;
609		}
610		}
611		}
612
613		/**
614	<	* Returns the comparator associated with this priority queue, or
615	<	* <tt>null</tt> if it uses its elements' natural ordering.
614	>	* Establishes the heap invariant (described above) in the entire tree,
615	>	* assuming nothing about the order of the elements prior to the call.
616	>	*/
617	>	private void heapify() {
618	>	for (int i = size/2; i >= 1; i--)
619	>	fixDown(i);
620	>	}
621	>
622	>	/**
623	>	* Returns the comparator used to order this collection, or <tt>null</tt>
624	>	* if this collection is sorted according to its elements natural ordering
625	>	* (using <tt>Comparable</tt>).
626		*
627	<	* @return the comparator associated with this priority queue, or
628	<	*         <tt>null</tt> if it uses its elements' natural ordering.
627	>	* @return the comparator used to order this collection, or <tt>null</tt>
628	>	* if this collection is sorted according to its elements natural ordering.
629		*/
630	<	Comparator comparator() {
630	>	public Comparator<? super E> comparator() {
631		return comparator;
632		}
633	+
634	+	/**
635	+	* Save the state of the instance to a stream (that
636	+	* is, serialize it).
637	+	*
638	+	* @serialData The length of the array backing the instance is
639	+	* emitted (int), followed by all of its elements (each an
640	+	* <tt>Object</tt>) in the proper order.
641	+	* @param s the stream
642	+	*/
643	+	private void writeObject(java.io.ObjectOutputStream s)
644	+	throws java.io.IOException{
645	+	// Write out element count, and any hidden stuff
646	+	s.defaultWriteObject();
647	+
648	+	// Write out array length
649	+	s.writeInt(queue.length);
650	+
651	+	// Write out all elements in the proper order.
652	+	for (int i=0; i<size; i++)
653	+	s.writeObject(queue[i]);
654	+	}
655	+
656	+	/**
657	+	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
658	+	* deserialize it).
659	+	* @param s the stream
660	+	*/
661	+	private void readObject(java.io.ObjectInputStream s)
662	+	throws java.io.IOException, ClassNotFoundException {
663	+	// Read in size, and any hidden stuff
664	+	s.defaultReadObject();
665	+
666	+	// Read in array length and allocate array
667	+	int arrayLength = s.readInt();
668	+	queue = new Object[arrayLength];
669	+
670	+	// Read in all elements in the proper order.
671	+	for (int i=0; i<size; i++)
672	+	queue[i] = (E) s.readObject();
673	+	}
674	+
675		}

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