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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.6 by brian, Mon Jun 23 02:26:15 2003 UTC vs.
Revision 1.15 by dholmes, Thu Jul 31 07:18:02 2003 UTC

#	Line 3 | Line 3
3		/**
4		* An unbounded priority queue based on a priority heap.  This queue orders
5		* elements according to an order specified at construction time, which is
6	<	* specified in the same manner as {@link TreeSet} and {@link TreeMap}: elements are ordered
6	>	* specified in the same manner as {@link TreeSet} and {@link TreeMap}:
7	>	* elements are ordered
8		* either according to their <i>natural order</i> (see {@link Comparable}), or
9		* according to a {@link Comparator}, depending on which constructor is used.
10	<	* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the
11	<	* minimal element with respect to the specified ordering.  If multiple
12	<	* elements are tied for least value, no guarantees are made as to
13	<	* which of these elements is returned.
10	>	* The <em>head</em> of this queue is the least element with respect to the
11	>	* specified ordering. If multiple elements are tied for least value, the
12	>	* head is one of those elements. A priority queue does not permit
13	>	* <tt>null</tt> elements.
14		*
15	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the size of
16	<	* the array used internally to store the elements on the queue.  It is always at least
16	<	* as large as the queue size.  As elements are added to a priority queue,
17	<	* its capacity grows automatically.  The details of the growth policy are not
18	<	* specified.
15	>	* <p>The {@link #remove()} and {@link #poll()} methods remove and
16	>	* return the head of the queue.
17		*
18	<	*<p>Implementation note: this implementation provides O(log(n)) time for
19	<	* the insertion methods (<tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>)
20	<	* methods; linear time for the <tt>remove(Object)</tt> and
21	<	* <tt>contains(Object)</tt> methods; and constant time for the retrieval methods (<tt>peek</tt>,
18	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
19	>	* not delete, the head of the queue.
20	>	*
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.  It is always at least as large as the queue size.  As
24	>	* elements are added to a priority queue, its capacity grows
25	>	* automatically.  The details of the growth policy are not specified.
26	>	*
27	>	* <p>Implementation note: this implementation provides O(log(n)) time
28	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
29	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
30	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
31	>	* constant time for the retrieval methods (<tt>peek</tt>,
32		* <tt>element</tt>, and <tt>size</tt>).
33		*
34		* <p>This class is a member of the
35		* <a href="{@docRoot}/../guide/collections/index.html">
36		* Java Collections Framework</a>.
37	+	* @since 1.5
38	+	* @author Josh Bloch
39		*/
40		public class PriorityQueue<E> extends AbstractQueue<E>
41	<	implements Queue<E>
42	<	{
41	>	implements Queue<E>, java.io.Serializable {
42	>
43		private static final int DEFAULT_INITIAL_CAPACITY = 11;
44
45		/**
#	Line 65 | Line 75 | public class PriorityQueue<E> extends Ab
75		private transient int modCount = 0;
76
77		/**
78	<	* Create a new priority queue with the default initial capacity (11)
79	<	* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.)
78	>	* Create a <tt>PriorityQueue</tt> with the default initial capacity
79	>	* (11) that orders its elements according to their natural
80	>	* ordering (using <tt>Comparable</tt>.)
81		*/
82		public PriorityQueue() {
83	<	this(DEFAULT_INITIAL_CAPACITY);
83	>	this(DEFAULT_INITIAL_CAPACITY, null);
84		}
85
86		/**
87	<	* Create a new priority queue with the specified initial capacity
88	<	* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.)
87	>	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
88	>	* that orders its elements according to their natural ordering
89	>	* (using <tt>Comparable</tt>.)
90		*
91		* @param initialCapacity the initial capacity for this priority queue.
92		*/
#	Line 83 | Line 95 | public class PriorityQueue<E> extends Ab
95		}
96
97		/**
98	<	* Create a new priority queue with the specified initial capacity (11)
98	>	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
99		* that orders its elements according to the specified comparator.
100		*
101		* @param initialCapacity the initial capacity for this priority queue.
102		* @param comparator the comparator used to order this priority queue.
103	+	* If <tt>null</tt> then the order depends on the elements' natural
104	+	* ordering.
105	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
106	+	* than 1
107		*/
108		public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
109		if (initialCapacity < 1)
110	<	initialCapacity = 1;
111	<	queue = new E[initialCapacity + 1];
110	>	throw new IllegalArgumentException();
111	>	queue = (E[]) new Object[initialCapacity + 1];
112		this.comparator = comparator;
113		}
114
115		/**
116	<	* Create a new priority queue containing the elements in the specified
116	>	* Create a <tt>PriorityQueue</tt> containing the elements in the specified
117		* collection.  The priority queue has an initial capacity of 110% of the
118	<	* size of the specified collection. If the specified collection
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'
#	Line 107 | Line 124 | public class PriorityQueue<E> extends Ab
124		* <tt>Sorted</tt>, the priority queue is ordered according to
125		* its elements' natural order.
126		*
127	<	* @param initialElements the collection whose elements are to be placed
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 the specified collection or an
133	<	*         element of the specified collection is <tt>null</tt>.
132	>	* @throws NullPointerException if <tt>c</tt> or any element within it
133	>	* is <tt>null</tt>
134		*/
135	<	public PriorityQueue(Collection<E> initialElements) {
136	<	int sz = initialElements.size();
135	>	public PriorityQueue(Collection<E> c) {
136	>	int sz = c.size();
137		int initialCapacity = (int)Math.min((sz * 110L) / 100,
138		Integer.MAX_VALUE - 1);
139		if (initialCapacity < 1)
140		initialCapacity = 1;
124	–	queue = new E[initialCapacity + 1];
141
142	<	/* Commented out to compile with generics compiler
142	>	queue = (E[]) new Object[initialCapacity + 1];
143
144	<	if (initialElements instanceof Sorted) {
145	<	comparator = ((Sorted)initialElements).comparator();
146	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
144	>	if (c instanceof Sorted) {
145	>	// FIXME: this code assumes too much
146	>	comparator = ((Sorted)c).comparator();
147	>	for (Iterator<E> i = c.iterator(); i.hasNext(); )
148		queue[++size] = i.next();
149		} else {
133	–	*/
134	–	{
150		comparator = null;
151	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
151	>	for (Iterator<E> i = c.iterator(); i.hasNext(); )
152		add(i.next());
153		}
154		}
#	Line 141 | Line 156 | public class PriorityQueue<E> extends Ab
156		// Queue Methods
157
158		/**
159	<	* Remove and return the minimal element from this priority queue if
145	<	* it contains one or more elements, otherwise return <tt>null</tt>.  The term
146	<	* <i>minimal</i> is defined according to this priority queue's order.
159	>	* Add the specified element to this priority queue.
160		*
161	<	* @return the minimal element from this priority queue if it contains
162	<	*         one or more elements, otherwise <tt>null</tt>.
161	>	* @param element the element to add.
162	>	* @return <tt>true</tt>
163	>	* @throws ClassCastException if the specified element cannot be compared
164	>	* with elements currently in the priority queue according
165	>	* to the priority queue's ordering.
166	>	* @throws NullPointerException if the specified element is null.
167		*/
168	+	public boolean offer(E element) {
169	+	if (element == null)
170	+	throw new NullPointerException();
171	+	modCount++;
172	+	++size;
173	+
174	+	// Grow backing store if necessary
175	+	while (size >= queue.length) {
176	+	E[] newQueue = (E[]) new Object[2 * queue.length];
177	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
178	+	queue = newQueue;
179	+	}
180	+
181	+	queue[size] = element;
182	+	fixUp(size);
183	+	return true;
184	+	}
185	+
186		public E poll() {
187		if (size == 0)
188		return null;
189		return remove(1);
190		}
191
157	–	/**
158	–	* Return, but do not remove, the minimal element from the priority queue,
159	–	* or return <tt>null</tt> if the queue is empty.  The term <i>minimal</i> is
160	–	* defined according to this priority queue's order.  This method returns
161	–	* the same object reference that would be returned by by the
162	–	* <tt>poll</tt> method.  The two methods differ in that this method
163	–	* does not remove the element from the priority queue.
164	–	*
165	–	* @return the minimal element from this priority queue if it contains
166	–	*         one or more elements, otherwise <tt>null</tt>.
167	–	*/
192		public E peek() {
193		return queue[1];
194		}
195
196		// Collection Methods
197
198	+	// these first two override just to get the throws docs
199	+
200		/**
201	<	* Removes a single instance of the specified element from this priority
176	<	* queue, if it is present.  Returns true if this collection contained the
177	<	* specified element (or equivalently, if this collection changed as a
178	<	* result of the call).
179	<	*
180	<	* @param element the element to be removed from this collection, if present.
181	<	* @return <tt>true</tt> if this collection changed as a result of the
182	<	*         call
201	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
202		* @throws ClassCastException if the specified element cannot be compared
203	<	*            with elements currently in the priority queue according
204	<	*            to the priority queue's ordering.
186	<	* @throws NullPointerException if the specified element is null.
203	>	* with elements currently in the priority queue according
204	>	* to the priority queue's ordering.
205		*/
206	<	public boolean remove(Object element) {
207	<	if (element == null)
208	<	throw new NullPointerException();
206	>	public boolean add(E element) {
207	>	return super.add(element);
208	>	}
209	>
210	>	/**
211	>	* @throws NullPointerException if any element is <tt>null</tt>.
212	>	* @throws ClassCastException if any element cannot be compared
213	>	* with elements currently in the priority queue according
214	>	* to the priority queue's ordering.
215	>	*/
216	>	public boolean addAll(Collection<? extends E> c) {
217	>	return super.addAll(c);
218	>	}
219	>
220	>	public boolean remove(Object o) {
221	>	if (o == null)
222	>	return false;
223
224		if (comparator == null) {
225		for (int i = 1; i <= size; i++) {
226	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
226	>	if (((Comparable)queue[i]).compareTo(o) == 0) {
227		remove(i);
228		return true;
229		}
230		}
231		} else {
232		for (int i = 1; i <= size; i++) {
233	<	if (comparator.compare(queue[i], (E) element) == 0) {
233	>	if (comparator.compare(queue[i], (E)o) == 0) {
234		remove(i);
235		return true;
236		}
#	Line 207 | Line 239 | public class PriorityQueue<E> extends Ab
239		return false;
240		}
241
210	–	/**
211	–	* Returns an iterator over the elements in this priority queue.  The
212	–	* elements of the priority queue will be returned by this iterator in the
213	–	* order specified by the queue, which is to say the order they would be
214	–	* returned by repeated calls to <tt>poll</tt>.
215	–	*
216	–	* @return an <tt>Iterator</tt> over the elements in this priority queue.
217	–	*/
242		public Iterator<E> iterator() {
243	<	return new Itr();
243	>	return new Itr();
244		}
245
246		private class Itr implements Iterator<E> {
247	<	/**
248	<	* Index (into queue array) of element to be returned by
247	>	/**
248	>	* Index (into queue array) of element to be returned by
249		* subsequent call to next.
250	<	*/
251	<	int cursor = 1;
250	>	*/
251	>	private int cursor = 1;
252
253	<	/**
254	<	* Index of element returned by most recent call to next or
255	<	* previous.  Reset to 0 if this element is deleted by a call
256	<	* to remove.
257	<	*/
258	<	int lastRet = 0;
259	<
260	<	/**
261	<	* The modCount value that the iterator believes that the backing
262	<	* List should have.  If this expectation is violated, the iterator
263	<	* has detected concurrent modification.
264	<	*/
265	<	int expectedModCount = modCount;
266	<
267	<	public boolean hasNext() {
268	<	return cursor <= size;
269	<	}
253	>	/**
254	>	* Index of element returned by most recent call to next or
255	>	* previous.  Reset to 0 if this element is deleted by a call
256	>	* to remove.
257	>	*/
258	>	private int lastRet = 0;
259	>
260	>	/**
261	>	* The modCount value that the iterator believes that the backing
262	>	* List should have.  If this expectation is violated, the iterator
263	>	* has detected concurrent modification.
264	>	*/
265	>	private int expectedModCount = modCount;
266	>
267	>	public boolean hasNext() {
268	>	return cursor <= size;
269	>	}
270
271	<	public E next() {
271	>	public E next() {
272		checkForComodification();
273		if (cursor > size)
274	<	throw new NoSuchElementException();
274	>	throw new NoSuchElementException();
275		E result = queue[cursor];
276		lastRet = cursor++;
277		return result;
278	<	}
278	>	}
279
280	<	public void remove() {
281	<	if (lastRet == 0)
282	<	throw new IllegalStateException();
280	>	public void remove() {
281	>	if (lastRet == 0)
282	>	throw new IllegalStateException();
283		checkForComodification();
284
285		PriorityQueue.this.remove(lastRet);
#	Line 263 | Line 287 | public class PriorityQueue<E> extends Ab
287		cursor--;
288		lastRet = 0;
289		expectedModCount = modCount;
290	<	}
290	>	}
291
292	<	final void checkForComodification() {
293	<	if (modCount != expectedModCount)
294	<	throw new ConcurrentModificationException();
295	<	}
292	>	final void checkForComodification() {
293	>	if (modCount != expectedModCount)
294	>	throw new ConcurrentModificationException();
295	>	}
296		}
297
298		/**
299		* Returns the number of elements in this priority queue.
300	<	*
300	>	*
301		* @return the number of elements in this priority queue.
302		*/
303		public int size() {
#	Line 281 | Line 305 | public class PriorityQueue<E> extends Ab
305		}
306
307		/**
284	–	* Add the specified element to this priority queue.
285	–	*
286	–	* @param element the element to add.
287	–	* @return true
288	–	* @throws ClassCastException if the specified element cannot be compared
289	–	*            with elements currently in the priority queue according
290	–	*            to the priority queue's ordering.
291	–	* @throws NullPointerException if the specified element is null.
292	–	*/
293	–	public boolean offer(E element) {
294	–	if (element == null)
295	–	throw new NullPointerException();
296	–	modCount++;
297	–
298	–	// Grow backing store if necessary
299	–	if (++size == queue.length) {
300	–	E[] newQueue = new E[2 * queue.length];
301	–	System.arraycopy(queue, 0, newQueue, 0, size);
302	–	queue = newQueue;
303	–	}
304	–
305	–	queue[size] = element;
306	–	fixUp(size);
307	–	return true;
308	–	}
309	–
310	–	/**
308		* Remove all elements from the priority queue.
309		*/
310		public void clear() {
#	Line 400 | Line 397 | public class PriorityQueue<E> extends Ab
397		}
398		}
399
400	<	/**
404	<	* Returns the comparator associated with this priority queue, or
405	<	* <tt>null</tt> if it uses its elements' natural ordering.
406	<	*
407	<	* @return the comparator associated with this priority queue, or
408	<	*         <tt>null</tt> if it uses its elements' natural ordering.
409	<	*/
410	<	Comparator comparator() {
400	>	public Comparator comparator() {
401		return comparator;
402		}
403
#	Line 418 | Line 408 | public class PriorityQueue<E> extends Ab
408		* @serialData The length of the array backing the instance is
409		* emitted (int), followed by all of its elements (each an
410		* <tt>Object</tt>) in the proper order.
411	+	* @param s the stream
412		*/
413		private synchronized void writeObject(java.io.ObjectOutputStream s)
414		throws java.io.IOException{
415	<	// Write out element count, and any hidden stuff
416	<	s.defaultWriteObject();
415	>	// Write out element count, and any hidden stuff
416	>	s.defaultWriteObject();
417
418		// Write out array length
419		s.writeInt(queue.length);
420
421	<	// Write out all elements in the proper order.
422	<	for (int i=0; i<size; i++)
421	>	// Write out all elements in the proper order.
422	>	for (int i=0; i<size; i++)
423		s.writeObject(queue[i]);
424		}
425
426		/**
427		* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
428		* deserialize it).
429	+	* @param s the stream
430		*/
431		private synchronized void readObject(java.io.ObjectInputStream s)
432		throws java.io.IOException, ClassNotFoundException {
433	<	// Read in size, and any hidden stuff
434	<	s.defaultReadObject();
433	>	// Read in size, and any hidden stuff
434	>	s.defaultReadObject();
435
436		// Read in array length and allocate array
437		int arrayLength = s.readInt();
438	<	queue = new E[arrayLength];
438	>	queue = (E[]) new Object[arrayLength];
439
440	<	// Read in all elements in the proper order.
441	<	for (int i=0; i<size; i++)
440	>	// Read in all elements in the proper order.
441	>	for (int i=0; i<size; i++)
442		queue[i] = (E)s.readObject();
443		}
444
445		}
446	+

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