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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 1.34 by dholmes, Wed Aug 27 01:33:50 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>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
22	<	* as large as the queue size.  As elements are added to a priority list,
23	<	* its capacity grows automatically.  The details of the growth policy are not
24	<	* specified.
21	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
22	>	* not delete, the head of the queue.
23		*
24	<	*<p>Implementation note: this implementation provides O(log(n)) time for
25	<	* the <tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>
26	<	* methods; linear time for the <tt>remove(Object)</tt> and
27	<	* <tt>contains</tt> methods; and constant time for the <tt>peek</tt>,
28	<	* <tt>element</tt>, and <tt>size</tt> methods.
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> <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.PriorityBlockingQueue} class.
41	>	*
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 long serialVersionUID = -7720805057305804111L;
60	>
61		private static final int DEFAULT_INITIAL_CAPACITY = 11;
62
63		/**
64		* Priority queue represented as a balanced binary heap: the two children
65		* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
66		* ordered by comparator, or by the elements' natural ordering, if
67	<	* comparator is null:  For each node n in the heap, and each descendant
68	<	* of n, d, n <= d.
67	>	* comparator is null:  For each node n in the heap and each descendant d
68	>	* of n, n <= d.
69		*
70	<	* The element with the lowest value is in queue[1] (assuming the queue is
71	<	* nonempty). A one-based array is used in preference to the traditional
72	<	* zero-based array to simplify parent and child calculations.
70	>	* The element with the lowest value is in queue[1], assuming the queue is
71	>	* nonempty.  (A one-based array is used in preference to the traditional
72	>	* zero-based array to simplify parent and child calculations.)
73		*
74		* queue.length must be >= 2, even if size == 0.
75		*/
76	<	private E[] queue;
76	>	private transient Object[] queue;
77
78		/**
79		* The number of elements in the priority queue.
#	Line 62 | Line 84 | public class PriorityQueue<E> extends Ab
84		* The comparator, or null if priority queue uses elements'
85		* natural ordering.
86		*/
87	<	private final Comparator<E> comparator;
87	>	private final Comparator<? super E> comparator;
88
89		/**
90		* The number of times this priority queue has been
91		* <i>structurally modified</i>.  See AbstractList for gory details.
92		*/
93	<	private int modCount = 0;
93	>	private transient int modCount = 0;
94
95		/**
96	<	* Create a new priority queue with the default initial capacity (11)
97	<	* that orders its elements according to their natural ordering.
96	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
97	>	* (11) that orders its elements according to their natural
98	>	* ordering (using <tt>Comparable</tt>).
99		*/
100		public PriorityQueue() {
101	<	this(DEFAULT_INITIAL_CAPACITY);
101	>	this(DEFAULT_INITIAL_CAPACITY, null);
102		}
103
104		/**
105	<	* Create a new priority queue with the specified initial capacity
106	<	* that orders its elements according to their natural ordering.
105	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
106	>	* that orders its elements according to their natural ordering
107	>	* (using <tt>Comparable</tt>).
108		*
109		* @param initialCapacity the initial capacity for this priority queue.
110	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
111	+	* than 1
112		*/
113		public PriorityQueue(int initialCapacity) {
114		this(initialCapacity, null);
115		}
116
117		/**
118	<	* Create a new priority queue with the specified initial capacity (11)
118	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
119		* that orders its elements according to the specified comparator.
120		*
121		* @param initialCapacity the initial capacity for this priority queue.
122		* @param comparator the comparator used to order this priority queue.
123	+	* If <tt>null</tt> then the order depends on the elements' natural
124	+	* ordering.
125	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
126	+	* than 1
127		*/
128	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
128	>	public PriorityQueue(int initialCapacity,
129	>	Comparator<? super E> comparator) {
130		if (initialCapacity < 1)
131	<	initialCapacity = 1;
132	<	queue = new E[initialCapacity + 1];
131	>	throw new IllegalArgumentException();
132	>	this.queue = new Object[initialCapacity + 1];
133		this.comparator = comparator;
134		}
135
136		/**
137	<	* Create a new priority queue containing the elements in the specified
138	<	* 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>.
137	>	* Common code to initialize underlying queue array across
138	>	* constructors below.
139		*/
140	<	public PriorityQueue(Collection<E> initialElements) {
141	<	int sz = initialElements.size();
140	>	private void initializeArray(Collection<? extends E> c) {
141	>	int sz = c.size();
142		int initialCapacity = (int)Math.min((sz * 110L) / 100,
143		Integer.MAX_VALUE - 1);
144		if (initialCapacity < 1)
145		initialCapacity = 1;
130	–	queue = new E[initialCapacity + 1];
146
147	<	/* Commented out to compile with generics compiler
147	>	this.queue = new Object[initialCapacity + 1];
148	>	}
149	>
150	>	/**
151	>	* Initially fill elements of the queue array under the
152	>	* knowledge that it is sorted or is another PQ, in which
153	>	* case we can just place the elements without fixups.
154	>	*/
155	>	private void fillFromSorted(Collection<? extends E> c) {
156	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
157	>	queue[++size] = i.next();
158	>	}
159	>
160	>
161	>	/**
162	>	* Initially fill elements of the queue array that is
163	>	* not to our knowledge sorted, so we must add them
164	>	* one by one.
165	>	*/
166	>	private void fillFromUnsorted(Collection<? extends E> c) {
167	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
168	>	add(i.next());
169	>	}
170
171	<	if (initialElements instanceof Sorted) {
172	<	comparator = ((Sorted)initialElements).comparator();
173	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
174	<	queue[++size] = i.next();
171	>	/**
172	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
173	>	* specified collection.  The priority queue has an initial
174	>	* capacity of 110% of the size of the specified collection or 1
175	>	* if the collection is empty.  If the specified collection is an
176	>	* instance of a {@link java.util.SortedSet} or is another
177	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
178	>	* according to the same comparator, or according to its elements'
179	>	* natural order if the collection is sorted according to its
180	>	* elements' natural order.  Otherwise, the priority queue is
181	>	* ordered according to its elements' natural order.
182	>	*
183	>	* @param c the collection whose elements are to be placed
184	>	*        into this priority queue.
185	>	* @throws ClassCastException if elements of the specified collection
186	>	*         cannot be compared to one another according to the priority
187	>	*         queue's ordering.
188	>	* @throws NullPointerException if <tt>c</tt> or any element within it
189	>	* is <tt>null</tt>
190	>	*/
191	>	public PriorityQueue(Collection<? extends E> c) {
192	>	initializeArray(c);
193	>	if (c instanceof SortedSet) {
194	>	// @fixme double-cast workaround for compiler
195	>	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
196	>	comparator = (Comparator<? super E>)s.comparator();
197	>	fillFromSorted(s);
198	>	} else if (c instanceof PriorityQueue) {
199	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
200	>	comparator = (Comparator<? super E>)s.comparator();
201	>	fillFromSorted(s);
202		} else {
139	–	*/
140	–	{
203		comparator = null;
204	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
143	<	add(i.next());
204	>	fillFromUnsorted(c);
205		}
206		}
207
208	+	/**
209	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
210	+	* specified collection.  The priority queue has an initial
211	+	* capacity of 110% of the size of the specified collection or 1
212	+	* if the collection is empty.  This priority queue will be sorted
213	+	* according to the same comparator as the given collection, or
214	+	* according to its elements' natural order if the collection is
215	+	* sorted according to its elements' natural order.
216	+	*
217	+	* @param c the collection whose elements are to be placed
218	+	*        into this priority queue.
219	+	* @throws ClassCastException if elements of the specified collection
220	+	*         cannot be compared to one another according to the priority
221	+	*         queue's ordering.
222	+	* @throws NullPointerException if <tt>c</tt> or any element within it
223	+	* is <tt>null</tt>
224	+	*/
225	+	public PriorityQueue(PriorityQueue<? extends E> c) {
226	+	initializeArray(c);
227	+	comparator = (Comparator<? super E>)c.comparator();
228	+	fillFromSorted(c);
229	+	}
230	+
231	+	/**
232	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
233	+	* specified collection.  The priority queue has an initial
234	+	* capacity of 110% of the size of the specified collection or 1
235	+	* if the collection is empty.  This priority queue will be sorted
236	+	* according to the same comparator as the given collection, or
237	+	* according to its elements' natural order if the collection is
238	+	* sorted according to its elements' natural order.
239	+	*
240	+	* @param c the collection whose elements are to be placed
241	+	*        into this priority queue.
242	+	* @throws ClassCastException if elements of the specified collection
243	+	*         cannot be compared to one another according to the priority
244	+	*         queue's ordering.
245	+	* @throws NullPointerException if <tt>c</tt> or any element within it
246	+	* is <tt>null</tt>
247	+	*/
248	+	public PriorityQueue(SortedSet<? extends E> c) {
249	+	initializeArray(c);
250	+	comparator = (Comparator<? super E>)c.comparator();
251	+	fillFromSorted(c);
252	+	}
253	+
254	+	/**
255	+	* Resize array, if necessary, to be able to hold given index
256	+	*/
257	+	private void grow(int index) {
258	+	int newlen = queue.length;
259	+	if (index < newlen) // don't need to grow
260	+	return;
261	+	if (index == Integer.MAX_VALUE)
262	+	throw new OutOfMemoryError();
263	+	while (newlen <= index) {
264	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
265	+	newlen = Integer.MAX_VALUE;
266	+	else
267	+	newlen <<= 2;
268	+	}
269	+	Object[] newQueue = new Object[newlen];
270	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
271	+	queue = newQueue;
272	+	}
273	+
274		// Queue Methods
275
276	+
277	+
278		/**
279	<	* 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.
279	>	* Add the specified element to this priority queue.
280		*
281	<	* @return the minimal element from this priority queue if it contains
282	<	*         one or more elements, otherwise <tt>null</tt>.
281	>	* @return <tt>true</tt>
282	>	* @throws ClassCastException if the specified element cannot be compared
283	>	* with elements currently in the priority queue according
284	>	* to the priority queue's ordering.
285	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
286		*/
287	+	public boolean offer(E o) {
288	+	if (o == null)
289	+	throw new NullPointerException();
290	+	modCount++;
291	+	++size;
292	+
293	+	// Grow backing store if necessary
294	+	if (size >= queue.length)
295	+	grow(size);
296	+
297	+	queue[size] = o;
298	+	fixUp(size);
299	+	return true;
300	+	}
301	+
302		public E poll() {
303		if (size == 0)
304		return null;
305	<	return remove(1);
305	>	return (E) remove(1);
306		}
307
308	+	public E peek() {
309	+	return (E) queue[1];
310	+	}
311	+
312	+	// Collection Methods - the first two override to update docs
313	+
314		/**
315	<	* Return, but do not remove, the minimal element from the priority queue,
316	<	* or <tt>null</tt> if the queue is empty.  The term <i>minimal</i> is
317	<	* 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.
315	>	* Adds the specified element to this queue.
316	>	* @return <tt>true</tt> (as per the general contract of
317	>	* <tt>Collection.add</tt>).
318		*
319	<	* @return the minimal element from this priority queue if it contains
320	<	*         one or more elements, otherwise <tt>null</tt>.
319	>	* @throws NullPointerException {@inheritDoc}
320	>	* @throws ClassCastException if the specified element cannot be compared
321	>	* with elements currently in the priority queue according
322	>	* to the priority queue's ordering.
323		*/
324	<	public E peek() {
325	<	return queue[1];
324	>	public boolean add(E o) {
325	>	return super.add(o);
326		}
327
328	<	// Collection Methods
179	<
328	>
329		/**
330	<	* Removes a single instance of the specified element from this priority
331	<	* queue, if it is present.  Returns true if this collection contained the
332	<	* specified element (or equivalently, if this collection changed as a
330	>	* Adds all of the elements in the specified collection to this queue.
331	>	* The behavior of this operation is undefined if
332	>	* the specified collection is modified while the operation is in
333	>	* progress.  (This implies that the behavior of this call is undefined if
334	>	* the specified collection is this queue, and this queue is nonempty.)
335	>	* <p>
336	>	* This implementation iterates over the specified collection, and adds
337	>	* each object returned by the iterator to this collection, in turn.
338	>	* @throws NullPointerException {@inheritDoc}
339	>	* @throws ClassCastException if any element cannot be compared
340	>	* with elements currently in the priority queue according
341	>	* to the priority queue's ordering.
342	>	*/
343	>	public boolean addAll(Collection<? extends E> c) {
344	>	return super.addAll(c);
345	>	}
346	>
347	>
348	>	/**
349	>	* Removes a single instance of the specified element from this
350	>	* queue, if it is present.  More formally,
351	>	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
352	>	* o.equals(e))</tt>, if the queue contains one or more such
353	>	* elements.  Returns <tt>true</tt> if the queue contained the
354	>	* specified element (or equivalently, if the queue changed as a
355		* result of the call).
356		*
357	<	* @param o element to be removed from this collection, if present.
358	<	* @return <tt>true</tt> if this collection changed as a result of the
359	<	*         call
360	<	* @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.
357	>	* <p>This implementation iterates over the queue looking for the
358	>	* specified element.  If it finds the element, it removes the element
359	>	* from the queue using the iterator's remove method.<p>
360	>	*
361		*/
362	<	public boolean remove(Object element) {
363	<	if (element == null)
364	<	throw new NullPointerException();
362	>	public boolean remove(Object o) {
363	>	if (o == null)
364	>	return false;
365
366		if (comparator == null) {
367		for (int i = 1; i <= size; i++) {
368	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
368	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
369		remove(i);
370		return true;
371		}
372		}
373		} else {
374		for (int i = 1; i <= size; i++) {
375	<	if (comparator.compare(queue[i], (E) element) == 0) {
375	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
376		remove(i);
377		return true;
378		}
#	Line 214 | Line 382 | public class PriorityQueue<E> extends Ab
382		}
383
384		/**
385	<	* Returns an iterator over the elements in this priority queue.  The
386	<	* first element returned by this iterator is the same element that
219	<	* would be returned by a call to <tt>peek</tt>.
385	>	* Returns an iterator over the elements in this queue. The iterator
386	>	* does not return the elements in any particular order.
387		*
388	<	* @return an <tt>Iterator</tt> over the elements in this priority queue.
388	>	* @return an iterator over the elements in this queue.
389		*/
390		public Iterator<E> iterator() {
391		return new Itr();
#	Line 229 | Line 396 | public class PriorityQueue<E> extends Ab
396		* Index (into queue array) of element to be returned by
397		* subsequent call to next.
398		*/
399	<	int cursor = 1;
399	>	private int cursor = 1;
400
401		/**
402		* Index of element returned by most recent call to next or
403		* previous.  Reset to 0 if this element is deleted by a call
404		* to remove.
405		*/
406	<	int lastRet = 0;
406	>	private int lastRet = 0;
407
408		/**
409		* The modCount value that the iterator believes that the backing
410		* List should have.  If this expectation is violated, the iterator
411		* has detected concurrent modification.
412		*/
413	<	int expectedModCount = modCount;
413	>	private int expectedModCount = modCount;
414
415		public boolean hasNext() {
416		return cursor <= size;
#	Line 253 | Line 420 | public class PriorityQueue<E> extends Ab
420		checkForComodification();
421		if (cursor > size)
422		throw new NoSuchElementException();
423	<	E result = queue[cursor];
423	>	E result = (E) queue[cursor];
424		lastRet = cursor++;
425		return result;
426		}
#	Line 264 | Line 431 | public class PriorityQueue<E> extends Ab
431		checkForComodification();
432
433		PriorityQueue.this.remove(lastRet);
434	<	if (lastRet < cursor)
268	<	cursor--;
434	>	cursor--;
435		lastRet = 0;
436		expectedModCount = modCount;
437		}
#	Line 276 | Line 442 | public class PriorityQueue<E> extends Ab
442		}
443		}
444
279	–	/**
280	–	* Returns the number of elements in this priority queue.
281	–	*
282	–	* @return the number of elements in this priority queue.
283	–	*/
445		public int size() {
446		return size;
447		}
448
449		/**
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	–	/**
450		* Remove all elements from the priority queue.
451		*/
452		public void clear() {
#	Line 329 | Line 463 | public class PriorityQueue<E> extends Ab
463		* Removes and returns the ith element from queue.  Recall
464		* that queue is one-based, so 1 <= i <= size.
465		*
332	–	* XXX: Could further special-case i==size, but is it worth it?
333	–	* XXX: Could special-case i==0, but is it worth it?
466		*/
467		private E remove(int i) {
468		assert i <= size;
469		modCount++;
470
471	<	E result = queue[i];
471	>	E result = (E) queue[i];
472		queue[i] = queue[size];
473		queue[size--] = null;  // Drop extra ref to prevent memory leak
474		if (i <= size)
#	Line 357 | Line 489 | public class PriorityQueue<E> extends Ab
489		if (comparator == null) {
490		while (k > 1) {
491		int j = k >> 1;
492	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
492	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
493		break;
494	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
494	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
495		k = j;
496		}
497		} else {
498		while (k > 1) {
499		int j = k >> 1;
500	<	if (comparator.compare(queue[j], queue[k]) <= 0)
500	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
501		break;
502	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
502	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
503		k = j;
504		}
505		}
#	Line 385 | Line 517 | public class PriorityQueue<E> extends Ab
517		private void fixDown(int k) {
518		int j;
519		if (comparator == null) {
520	<	while ((j = k << 1) <= size) {
521	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
520	>	while ((j = k << 1) <= size && (j > 0)) {
521	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
522		j++; // j indexes smallest kid
523	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
523	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
524		break;
525	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
525	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
526		k = j;
527		}
528		} else {
529	<	while ((j = k << 1) <= size) {
530	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
529	>	while ((j = k << 1) <= size && (j > 0)) {
530	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
531		j++; // j indexes smallest kid
532	<	if (comparator.compare(queue[k], queue[j]) <= 0)
532	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
533		break;
534	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
534	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
535		k = j;
536		}
537		}
538		}
539
540	+
541		/**
542	<	* Returns the comparator associated with this priority queue, or
543	<	* <tt>null</tt> if it uses its elements' natural ordering.
542	>	* Returns the comparator used to order this collection, or <tt>null</tt>
543	>	* if this collection is sorted according to its elements natural ordering
544	>	* (using <tt>Comparable</tt>).
545		*
546	<	* @return the comparator associated with this priority queue, or
547	<	*         <tt>null</tt> if it uses its elements' natural ordering.
546	>	* @return the comparator used to order this collection, or <tt>null</tt>
547	>	* if this collection is sorted according to its elements natural ordering.
548		*/
549	<	Comparator<E> comparator() {
549	>	public Comparator<? super E> comparator() {
550		return comparator;
551		}
552	+
553	+	/**
554	+	* Save the state of the instance to a stream (that
555	+	* is, serialize it).
556	+	*
557	+	* @serialData The length of the array backing the instance is
558	+	* emitted (int), followed by all of its elements (each an
559	+	* <tt>Object</tt>) in the proper order.
560	+	* @param s the stream
561	+	*/
562	+	private void writeObject(java.io.ObjectOutputStream s)
563	+	throws java.io.IOException{
564	+	// Write out element count, and any hidden stuff
565	+	s.defaultWriteObject();
566	+
567	+	// Write out array length
568	+	s.writeInt(queue.length);
569	+
570	+	// Write out all elements in the proper order.
571	+	for (int i=0; i<size; i++)
572	+	s.writeObject(queue[i]);
573	+	}
574	+
575	+	/**
576	+	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
577	+	* deserialize it).
578	+	* @param s the stream
579	+	*/
580	+	private void readObject(java.io.ObjectInputStream s)
581	+	throws java.io.IOException, ClassNotFoundException {
582	+	// Read in size, and any hidden stuff
583	+	s.defaultReadObject();
584	+
585	+	// Read in array length and allocate array
586	+	int arrayLength = s.readInt();
587	+	queue = new Object[arrayLength];
588	+
589	+	// Read in all elements in the proper order.
590	+	for (int i=0; i<size; i++)
591	+	queue[i] = s.readObject();
592	+	}
593	+
594		}
595	+

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