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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.3 by tim, Sun May 18 20:36:01 2003 UTC vs.
Revision 1.29 by dl, Sun Aug 24 23:31:53 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
4	>	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
5	>	* This queue orders
6	>	* elements according to an order specified at construction time, which is
7	>	* specified in the same manner as {@link java.util.TreeSet} and
8	>	* {@link java.util.TreeMap}: elements are ordered
9		* either according to their <i>natural order</i> (see {@link Comparable}), or
10	<	* according to a {@link Comparator}, depending on which constructor is used.
11	<	* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the
12	<	* minimal element with respect to the specified ordering.  If multiple
13	<	* these elements are tied for least value, no guarantees are made as to
14	<	* which of elements is returned.
10	>	* according to a {@link java.util.Comparator}, depending on which
11	>	* constructor is used.
12	>	* <p>The <em>head</em> of this queue is the <em>least</em> element with
13	>	* respect to the specified ordering.
14	>	* If multiple elements are tied for least value, the
15	>	* head is one of those elements. A priority queue does not permit
16	>	* <tt>null</tt> elements.
17	>	*
18	>	* <p>The {@link #remove()} and {@link #poll()} methods remove and
19	>	* return the head of the queue.
20	>	*
21	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
22	>	* not delete, the head of the queue.
23	>	*
24	>	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
25	>	* size of the array used internally to store the elements on the
26	>	* queue.
27	>	* It is always at least as large as the queue size.  As
28	>	* elements are added to a priority queue, its capacity grows
29	>	* automatically.  The details of the growth policy are not specified.
30	>	*
31	>	* <p>The Iterator provided in method {@link #iterator()} is <em>not</em>
32	>	* guaranteed to traverse the elements of the PriorityQueue in any
33	>	* particular order. If you need ordered traversal, consider using
34	>	* <tt>Arrays.sort(pq.toArray())</tt>.
35		*
36	<	* <p>Each priority queue has a <i>capacity</i>.  The capacity is the size of
37	<	* the array used to store the elements on the queue.  It is always at least
38	<	* as large as the queue size.  As elements are added to a priority list,
39	<	* its capacity grows automatically.  The details of the growth policy are not
40	<	* specified.
36	>	* <p> <strong>Note that this implementation is not synchronized.</strong>
37	>	* Multiple threads should not access a <tt>PriorityQueue</tt>
38	>	* instance concurrently if any of the threads modifies the list
39	>	* structurally. Instead, use the thread-safe {@link
40	>	* java.util.concurrent.BlockingPriorityQueue} class.
41		*
42	<	*<p>Implementation note: this implementation provides O(log(n)) time for
43	<	* the <tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>
44	<	* methods; linear time for the <tt>remove(Object)</tt> and
45	<	* <tt>contains</tt> methods; and constant time for the <tt>peek</tt>,
46	<	* <tt>element</tt>, and <tt>size</tt> methods.
42	>	*
43	>	* <p>Implementation note: this implementation provides O(log(n)) time
44	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
45	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
46	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
47	>	* constant time for the retrieval methods (<tt>peek</tt>,
48	>	* <tt>element</tt>, and <tt>size</tt>).
49		*
50		* <p>This class is a member of the
51		* <a href="{@docRoot}/../guide/collections/index.html">
52		* Java Collections Framework</a>.
53	+	* @since 1.5
54	+	* @author Josh Bloch
55		*/
56		public class PriorityQueue<E> extends AbstractQueue<E>
57	<	implements Queue<E>
58	<	{
57	>	implements Queue<E>, java.io.Serializable {
58	>
59		private static final int DEFAULT_INITIAL_CAPACITY = 11;
60
61		/**
62		* Priority queue represented as a balanced binary heap: the two children
63		* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
64		* ordered by comparator, or by the elements' natural ordering, if
65	<	* comparator is null:  For each node n in the heap, and each descendant
66	<	* of n, d, n <= d.
65	>	* comparator is null:  For each node n in the heap and each descendant d
66	>	* of n, n <= d.
67		*
68	<	* The element with the lowest value is in queue[1] (assuming the queue is
69	<	* nonempty). A one-based array is used in preference to the traditional
70	<	* zero-based array to simplify parent and child calculations.
68	>	* The element with the lowest value is in queue[1], assuming the queue is
69	>	* nonempty.  (A one-based array is used in preference to the traditional
70	>	* zero-based array to simplify parent and child calculations.)
71		*
72		* queue.length must be >= 2, even if size == 0.
73		*/
74	<	private E[] queue;
74	>	private transient Object[] queue;
75
76		/**
77		* The number of elements in the priority queue.
#	Line 62 | Line 82 | public class PriorityQueue<E> extends Ab
82		* The comparator, or null if priority queue uses elements'
83		* natural ordering.
84		*/
85	<	private final Comparator<E> comparator;
85	>	private final Comparator<? super E> comparator;
86
87		/**
88		* The number of times this priority queue has been
89		* <i>structurally modified</i>.  See AbstractList for gory details.
90		*/
91	<	private int modCount = 0;
91	>	private transient int modCount = 0;
92
93		/**
94	<	* Create a new priority queue with the default initial capacity (11)
95	<	* that orders its elements according to their natural ordering.
94	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
95	>	* (11) that orders its elements according to their natural
96	>	* ordering (using <tt>Comparable</tt>).
97		*/
98		public PriorityQueue() {
99	<	this(DEFAULT_INITIAL_CAPACITY);
99	>	this(DEFAULT_INITIAL_CAPACITY, null);
100		}
101
102		/**
103	<	* Create a new priority queue with the specified initial capacity
104	<	* that orders its elements according to their natural ordering.
103	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
104	>	* that orders its elements according to their natural ordering
105	>	* (using <tt>Comparable</tt>).
106		*
107		* @param initialCapacity the initial capacity for this priority queue.
108	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
109	+	* than 1
110		*/
111		public PriorityQueue(int initialCapacity) {
112		this(initialCapacity, null);
113		}
114
115		/**
116	<	* Create a new priority queue with the specified initial capacity (11)
116	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
117		* that orders its elements according to the specified comparator.
118		*
119		* @param initialCapacity the initial capacity for this priority queue.
120		* @param comparator the comparator used to order this priority queue.
121	+	* If <tt>null</tt> then the order depends on the elements' natural
122	+	* ordering.
123	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
124	+	* than 1
125		*/
126	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
126	>	public PriorityQueue(int initialCapacity,
127	>	Comparator<? super E> comparator) {
128		if (initialCapacity < 1)
129	<	initialCapacity = 1;
130	<	queue = new E[initialCapacity + 1];
129	>	throw new IllegalArgumentException();
130	>	this.queue = new Object[initialCapacity + 1];
131		this.comparator = comparator;
132		}
133
134		/**
135	<	* Create a new priority queue containing the elements in the specified
136	<	* 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>.
135	>	* Common code to initialize underlying queue array across
136	>	* constructors below.
137		*/
138	<	public PriorityQueue(Collection<E> initialElements) {
139	<	int sz = initialElements.size();
138	>	private void initializeArray(Collection<? extends E> c) {
139	>	int sz = c.size();
140		int initialCapacity = (int)Math.min((sz * 110L) / 100,
141		Integer.MAX_VALUE - 1);
142		if (initialCapacity < 1)
143		initialCapacity = 1;
130	–	queue = new E[initialCapacity + 1];
144
145	<	/* Commented out to compile with generics compiler
145	>	this.queue = new Object[initialCapacity + 1];
146	>	}
147	>
148	>	/**
149	>	* Initially fill elements of the queue array under the
150	>	* knowledge that it is sorted or is another PQ, in which
151	>	* case we can just place the elements without fixups.
152	>	*/
153	>	private void fillFromSorted(Collection<? extends E> c) {
154	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
155	>	queue[++size] = i.next();
156	>	}
157	>
158	>
159	>	/**
160	>	* Initially fill elements of the queue array that is
161	>	* not to our knowledge sorted, so we must add them
162	>	* one by one.
163	>	*/
164	>	private void fillFromUnsorted(Collection<? extends E> c) {
165	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
166	>	add(i.next());
167	>	}
168
169	<	if (initialElements instanceof Sorted) {
170	<	comparator = ((Sorted)initialElements).comparator();
171	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
172	<	queue[++size] = i.next();
169	>	/**
170	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
171	>	* specified collection.  The priority queue has an initial
172	>	* capacity of 110% of the size of the specified collection or 1
173	>	* if the collection is empty.  If the specified collection is an
174	>	* instance of a {@link java.util.SortedSet} or is another
175	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
176	>	* according to the same comparator, or according to its elements'
177	>	* natural order if the collection is sorted according to its
178	>	* elements' natural order.  Otherwise, the priority queue is
179	>	* ordered according to its elements' natural order.
180	>	*
181	>	* @param c the collection whose elements are to be placed
182	>	*        into this priority queue.
183	>	* @throws ClassCastException if elements of the specified collection
184	>	*         cannot be compared to one another according to the priority
185	>	*         queue's ordering.
186	>	* @throws NullPointerException if <tt>c</tt> or any element within it
187	>	* is <tt>null</tt>
188	>	*/
189	>	public PriorityQueue(Collection<? extends E> c) {
190	>	initializeArray(c);
191	>	if (c instanceof SortedSet) {
192	>	// @fixme double-cast workaround for compiler
193	>	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
194	>	comparator = (Comparator<? super E>)s.comparator();
195	>	fillFromSorted(s);
196	>	} else if (c instanceof PriorityQueue) {
197	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
198	>	comparator = (Comparator<? super E>)s.comparator();
199	>	fillFromSorted(s);
200		} else {
139	–	*/
140	–	{
201		comparator = null;
202	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
143	<	add(i.next());
202	>	fillFromUnsorted(c);
203		}
204		}
205
206	+	/**
207	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
208	+	* specified collection.  The priority queue has an initial
209	+	* capacity of 110% of the size of the specified collection or 1
210	+	* if the collection is empty.  This priority queue will be sorted
211	+	* according to the same comparator as the given collection, or
212	+	* according to its elements' natural order if the collection is
213	+	* sorted according to its elements' natural order.
214	+	*
215	+	* @param c the collection whose elements are to be placed
216	+	*        into this priority queue.
217	+	* @throws ClassCastException if elements of the specified collection
218	+	*         cannot be compared to one another according to the priority
219	+	*         queue's ordering.
220	+	* @throws NullPointerException if <tt>c</tt> or any element within it
221	+	* is <tt>null</tt>
222	+	*/
223	+	public PriorityQueue(PriorityQueue<? extends E> c) {
224	+	initializeArray(c);
225	+	comparator = (Comparator<? super E>)c.comparator();
226	+	fillFromSorted(c);
227	+	}
228	+
229	+	/**
230	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
231	+	* specified collection.  The priority queue has an initial
232	+	* capacity of 110% of the size of the specified collection or 1
233	+	* if the collection is empty.  This priority queue will be sorted
234	+	* according to the same comparator as the given collection, or
235	+	* according to its elements' natural order if the collection is
236	+	* sorted according to its elements' natural order.
237	+	*
238	+	* @param c the collection whose elements are to be placed
239	+	*        into this priority queue.
240	+	* @throws ClassCastException if elements of the specified collection
241	+	*         cannot be compared to one another according to the priority
242	+	*         queue's ordering.
243	+	* @throws NullPointerException if <tt>c</tt> or any element within it
244	+	* is <tt>null</tt>
245	+	*/
246	+	public PriorityQueue(SortedSet<? extends E> c) {
247	+	initializeArray(c);
248	+	comparator = (Comparator<? super E>)c.comparator();
249	+	fillFromSorted(c);
250	+	}
251	+
252	+	/**
253	+	* Resize array, if necessary, to be able to hold given index
254	+	*/
255	+	private void grow(int index) {
256	+	int newlen = queue.length;
257	+	if (index < newlen) // don't need to grow
258	+	return;
259	+	if (index == Integer.MAX_VALUE)
260	+	throw new OutOfMemoryError();
261	+	while (newlen <= index) {
262	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
263	+	newlen = Integer.MAX_VALUE;
264	+	else
265	+	newlen <<= 2;
266	+	}
267	+	Object[] newQueue = new Object[newlen];
268	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
269	+	queue = newQueue;
270	+	}
271	+
272		// Queue Methods
273
274	+
275	+
276		/**
277	<	* 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.
277	>	* Add the specified element to this priority queue.
278		*
279	<	* @return the minimal element from this priority queue if it contains
280	<	*         one or more elements, otherwise <tt>null</tt>.
279	>	* @return <tt>true</tt>
280	>	* @throws ClassCastException if the specified element cannot be compared
281	>	* with elements currently in the priority queue according
282	>	* to the priority queue's ordering.
283	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
284		*/
285	+	public boolean offer(E o) {
286	+	if (o == null)
287	+	throw new NullPointerException();
288	+	modCount++;
289	+	++size;
290	+
291	+	// Grow backing store if necessary
292	+	if (size >= queue.length)
293	+	grow(size);
294	+
295	+	queue[size] = o;
296	+	fixUp(size);
297	+	return true;
298	+	}
299	+
300		public E poll() {
301		if (size == 0)
302		return null;
303	<	return remove(1);
303	>	return (E) remove(1);
304		}
305
306	+	public E peek() {
307	+	return (E) queue[1];
308	+	}
309	+
310	+	// Collection Methods - the first two override to update docs
311	+
312		/**
313	<	* Return, but do not remove, the minimal element from the priority queue,
314	<	* or <tt>null</tt> if the queue is empty.  The term <i>minimal</i> is
315	<	* 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.
313	>	* Adds the specified element to this queue.
314	>	* @return <tt>true</tt> (as per the general contract of
315	>	* <tt>Collection.add</tt>).
316		*
317	<	* @return the minimal element from this priority queue if it contains
318	<	*         one or more elements, otherwise <tt>null</tt>.
317	>	* @throws NullPointerException {@inheritDoc}
318	>	* @throws ClassCastException if the specified element cannot be compared
319	>	* with elements currently in the priority queue according
320	>	* to the priority queue's ordering.
321		*/
322	<	public E peek() {
323	<	return queue[1];
322	>	public boolean add(E o) {
323	>	return super.add(o);
324		}
325
326	<	// Collection Methods
179	<
326	>
327		/**
328	<	* Removes a single instance of the specified element from this priority
329	<	* queue, if it is present.  Returns true if this collection contained the
330	<	* specified element (or equivalently, if this collection changed as a
328	>	* Adds all of the elements in the specified collection to this queue.
329	>	* The behavior of this operation is undefined if
330	>	* the specified collection is modified while the operation is in
331	>	* progress.  (This implies that the behavior of this call is undefined if
332	>	* the specified collection is this queue, and this queue is nonempty.)
333	>	* <p>
334	>	* This implementation iterates over the specified collection, and adds
335	>	* each object returned by the iterator to this collection, in turn.
336	>	* @throws NullPointerException {@inheritDoc}
337	>	* @throws ClassCastException if any element cannot be compared
338	>	* with elements currently in the priority queue according
339	>	* to the priority queue's ordering.
340	>	*/
341	>	public boolean addAll(Collection<? extends E> c) {
342	>	return super.addAll(c);
343	>	}
344	>
345	>
346	>	/**
347	>	* Removes a single instance of the specified element from this
348	>	* queue, if it is present.  More formally,
349	>	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
350	>	* o.equals(e))</tt>, if the queue contains one or more such
351	>	* elements.  Returns <tt>true</tt> if the queue contained the
352	>	* specified element (or equivalently, if the queue changed as a
353		* result of the call).
354		*
355	<	* @param o element to be removed from this collection, if present.
356	<	* @return <tt>true</tt> if this collection changed as a result of the
357	<	*         call
358	<	* @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.
355	>	* <p>This implementation iterates over the queue looking for the
356	>	* specified element.  If it finds the element, it removes the element
357	>	* from the queue using the iterator's remove method.<p>
358	>	*
359		*/
360	<	public boolean remove(Object element) {
361	<	if (element == null)
362	<	throw new NullPointerException();
360	>	public boolean remove(Object o) {
361	>	if (o == null)
362	>	return false;
363
364		if (comparator == null) {
365		for (int i = 1; i <= size; i++) {
366	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
366	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
367		remove(i);
368		return true;
369		}
370		}
371		} else {
372		for (int i = 1; i <= size; i++) {
373	<	if (comparator.compare(queue[i], (E) element) == 0) {
373	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
374		remove(i);
375		return true;
376		}
#	Line 214 | Line 380 | public class PriorityQueue<E> extends Ab
380		}
381
382		/**
383	<	* Returns an iterator over the elements in this priority queue.  The
384	<	* first element returned by this iterator is the same element that
219	<	* would be returned by a call to <tt>peek</tt>.
383	>	* Returns an iterator over the elements in this queue. The iterator
384	>	* does not return the elements in any particular order.
385		*
386	<	* @return an <tt>Iterator</tt> over the elements in this priority queue.
386	>	* @return an iterator over the elements in this queue.
387		*/
388		public Iterator<E> iterator() {
389		return new Itr();
#	Line 229 | Line 394 | public class PriorityQueue<E> extends Ab
394		* Index (into queue array) of element to be returned by
395		* subsequent call to next.
396		*/
397	<	int cursor = 1;
397	>	private int cursor = 1;
398
399		/**
400		* Index of element returned by most recent call to next or
401		* previous.  Reset to 0 if this element is deleted by a call
402		* to remove.
403		*/
404	<	int lastRet = 0;
404	>	private int lastRet = 0;
405
406		/**
407		* The modCount value that the iterator believes that the backing
408		* List should have.  If this expectation is violated, the iterator
409		* has detected concurrent modification.
410		*/
411	<	int expectedModCount = modCount;
411	>	private int expectedModCount = modCount;
412
413		public boolean hasNext() {
414		return cursor <= size;
#	Line 253 | Line 418 | public class PriorityQueue<E> extends Ab
418		checkForComodification();
419		if (cursor > size)
420		throw new NoSuchElementException();
421	<	E result = queue[cursor];
421	>	E result = (E) queue[cursor];
422		lastRet = cursor++;
423		return result;
424		}
#	Line 276 | Line 441 | public class PriorityQueue<E> extends Ab
441		}
442		}
443
279	–	/**
280	–	* Returns the number of elements in this priority queue.
281	–	*
282	–	* @return the number of elements in this priority queue.
283	–	*/
444		public int size() {
445		return size;
446		}
447
448		/**
289	–	* 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.
297	–	*/
298	–	public boolean offer(E element) {
299	–	if (element == null)
300	–	throw new NullPointerException();
301	–	modCount++;
302	–
303	–	// Grow backing store if necessary
304	–	if (++size == queue.length) {
305	–	E[] newQueue = new E[2 * queue.length];
306	–	System.arraycopy(queue, 0, newQueue, 0, size);
307	–	queue = newQueue;
308	–	}
309	–
310	–	queue[size] = element;
311	–	fixUp(size);
312	–	return true;
313	–	}
314	–
315	–	/**
449		* Remove all elements from the priority queue.
450		*/
451		public void clear() {
#	Line 336 | Line 469 | public class PriorityQueue<E> extends Ab
469		assert i <= size;
470		modCount++;
471
472	<	E result = queue[i];
472	>	E result = (E) queue[i];
473		queue[i] = queue[size];
474		queue[size--] = null;  // Drop extra ref to prevent memory leak
475		if (i <= size)
#	Line 357 | Line 490 | public class PriorityQueue<E> extends Ab
490		if (comparator == null) {
491		while (k > 1) {
492		int j = k >> 1;
493	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
493	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
494		break;
495	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
495	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
496		k = j;
497		}
498		} else {
499		while (k > 1) {
500		int j = k >> 1;
501	<	if (comparator.compare(queue[j], queue[k]) <= 0)
501	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
502		break;
503	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
503	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
504		k = j;
505		}
506		}
#	Line 386 | Line 519 | public class PriorityQueue<E> extends Ab
519		int j;
520		if (comparator == null) {
521		while ((j = k << 1) <= size) {
522	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
522	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
523		j++; // j indexes smallest kid
524	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
524	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
525		break;
526	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
526	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
527		k = j;
528		}
529		} else {
530		while ((j = k << 1) <= size) {
531	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
531	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
532		j++; // j indexes smallest kid
533	<	if (comparator.compare(queue[k], queue[j]) <= 0)
533	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
534		break;
535	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
535	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
536		k = j;
537		}
538		}
539		}
540
541	+
542		/**
543	<	* Returns the comparator associated with this priority queue, or
544	<	* <tt>null</tt> if it uses its elements' natural ordering.
543	>	* Returns the comparator used to order this collection, or <tt>null</tt>
544	>	* if this collection is sorted according to its elements natural ordering
545	>	* (using <tt>Comparable</tt>).
546		*
547	<	* @return the comparator associated with this priority queue, or
548	<	*         <tt>null</tt> if it uses its elements' natural ordering.
547	>	* @return the comparator used to order this collection, or <tt>null</tt>
548	>	* if this collection is sorted according to its elements natural ordering.
549		*/
550	<	Comparator<E> comparator() {
550	>	public Comparator<? super E> comparator() {
551		return comparator;
552		}
553	+
554	+	/**
555	+	* Save the state of the instance to a stream (that
556	+	* is, serialize it).
557	+	*
558	+	* @serialData The length of the array backing the instance is
559	+	* emitted (int), followed by all of its elements (each an
560	+	* <tt>Object</tt>) in the proper order.
561	+	* @param s the stream
562	+	*/
563	+	private void writeObject(java.io.ObjectOutputStream s)
564	+	throws java.io.IOException{
565	+	// Write out element count, and any hidden stuff
566	+	s.defaultWriteObject();
567	+
568	+	// Write out array length
569	+	s.writeInt(queue.length);
570	+
571	+	// Write out all elements in the proper order.
572	+	for (int i=0; i<size; i++)
573	+	s.writeObject(queue[i]);
574	+	}
575	+
576	+	/**
577	+	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
578	+	* deserialize it).
579	+	* @param s the stream
580	+	*/
581	+	private void readObject(java.io.ObjectInputStream s)
582	+	throws java.io.IOException, ClassNotFoundException {
583	+	// Read in size, and any hidden stuff
584	+	s.defaultReadObject();
585	+
586	+	// Read in array length and allocate array
587	+	int arrayLength = s.readInt();
588	+	queue = new Object[arrayLength];
589	+
590	+	// Read in all elements in the proper order.
591	+	for (int i=0; i<size; i++)
592	+	queue[i] = s.readObject();
593	+	}
594	+
595		}
596	+

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