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root/jsr166/jsr166/src/main/java/util/PriorityQueue.java

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.13 by dl, Mon Jul 28 10:08:24 2003 UTC vs.
Revision 1.26 by tim, Fri Aug 8 20:05:07 2003 UTC

#	Line 1 | Line 1
1		package java.util;
2
3		/**
4	<	* An unbounded priority queue based on a priority heap.  This queue orders
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 TreeSet} and {@link TreeMap}:
8	<	* elements are ordered
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 <em>head</em> of this queue is the least element with respect to the
12	<	* specified ordering. If multiple elements are tied for least value, the
13	<	* head is one of those elements. A priority queue does not permit
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	<	*
17	>	*
18		* <p>The {@link #remove()} and {@link #poll()} methods remove and
19		* return the head of the queue.
20		*
#	Line 20 | Line 23
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.  It is always at least as large as the queue size.  As
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		*
#	Line 55 | Line 59 | public class PriorityQueue<E> extends Ab
59		*
60		* queue.length must be >= 2, even if size == 0.
61		*/
62	<	private transient E[] queue;
62	>	private transient Object[] queue;
63
64		/**
65		* The number of elements in the priority queue.
#	Line 66 | Line 70 | public class PriorityQueue<E> extends Ab
70		* The comparator, or null if priority queue uses elements'
71		* natural ordering.
72		*/
73	<	private final Comparator<E> comparator;
73	>	private final Comparator<? super E> comparator;
74
75		/**
76		* The number of times this priority queue has been
#	Line 75 | Line 79 | public class PriorityQueue<E> extends Ab
79		private transient int modCount = 0;
80
81		/**
82	<	* Create a <tt>PriorityQueue</tt> with the default initial capacity
82	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
83		* (11) that orders its elements according to their natural
84	<	* ordering (using <tt>Comparable</tt>.)
84	>	* ordering (using <tt>Comparable</tt>).
85		*/
86		public PriorityQueue() {
87		this(DEFAULT_INITIAL_CAPACITY, null);
88		}
89
90		/**
91	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
91	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
92		* that orders its elements according to their natural ordering
93	<	* (using <tt>Comparable</tt>.)
93	>	* (using <tt>Comparable</tt>).
94		*
95		* @param initialCapacity the initial capacity for this priority queue.
96	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
97	+	* than 1
98		*/
99		public PriorityQueue(int initialCapacity) {
100		this(initialCapacity, null);
101		}
102
103		/**
104	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
104	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
105		* that orders its elements according to the specified comparator.
106		*
107		* @param initialCapacity the initial capacity for this priority queue.
108		* @param comparator the comparator used to order this priority queue.
109		* If <tt>null</tt> then the order depends on the elements' natural
110		* ordering.
111	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
112	+	* than 1
113		*/
114	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
114	>	public PriorityQueue(int initialCapacity,
115	>	Comparator<? super E> comparator) {
116		if (initialCapacity < 1)
117	<	initialCapacity = 1;
118	<	queue = (E[]) new Object[initialCapacity + 1];
117	>	throw new IllegalArgumentException();
118	>	this.queue = new Object[initialCapacity + 1];
119		this.comparator = comparator;
120		}
121
122		/**
123	<	* Create a <tt>PriorityQueue</tt> containing the elements in the specified
124	<	* collection.  The priority queue has an initial capacity of 110% of the
116	<	* size of the specified collection. If the specified collection
117	<	* implements the {@link Sorted} interface, the priority queue will be
118	<	* sorted according to the same comparator, or according to its elements'
119	<	* natural order if the collection is sorted according to its elements'
120	<	* natural order.  If the specified collection does not implement
121	<	* <tt>Sorted</tt>, the priority queue is ordered according to
122	<	* its elements' natural order.
123	<	*
124	<	* @param initialElements the collection whose elements are to be placed
125	<	*        into this priority queue.
126	<	* @throws ClassCastException if elements of the specified collection
127	<	*         cannot be compared to one another according to the priority
128	<	*         queue's ordering.
129	<	* @throws NullPointerException if the specified collection or an
130	<	*         element of the specified collection is <tt>null</tt>.
123	>	* Common code to initialize underlying queue array across
124	>	* constructors below.
125		*/
126	<	public PriorityQueue(Collection<E> initialElements) {
127	<	int sz = initialElements.size();
126	>	private void initializeArray(Collection<? extends E> c) {
127	>	int sz = c.size();
128		int initialCapacity = (int)Math.min((sz * 110L) / 100,
129		Integer.MAX_VALUE - 1);
130		if (initialCapacity < 1)
131		initialCapacity = 1;
138	–	queue = (E[]) new Object[initialCapacity + 1];
132
133	<	if (initialElements instanceof Sorted) {
134	<	comparator = ((Sorted)initialElements).comparator();
135	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
136	<	queue[++size] = i.next();
133	>	this.queue = new Object[initialCapacity + 1];
134	>	}
135	>
136	>	/**
137	>	* Initially fill elements of the queue array under the
138	>	* knowledge that it is sorted or is another PQ, in which
139	>	* case we can just place the elements without fixups.
140	>	*/
141	>	private void fillFromSorted(Collection<? extends E> c) {
142	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
143	>	queue[++size] = i.next();
144	>	}
145	>
146	>
147	>	/**
148	>	* Initially fill elements of the queue array that is
149	>	* not to our knowledge sorted, so we must add them
150	>	* one by one.
151	>	*/
152	>	private void fillFromUnsorted(Collection<? extends E> c) {
153	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
154	>	add(i.next());
155	>	}
156	>
157	>	/**
158	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
159	>	* specified collection.  The priority queue has an initial
160	>	* capacity of 110% of the size of the specified collection or 1
161	>	* if the collection is empty.  If the specified collection is an
162	>	* instance of a {@link java.util.SortedSet} or is another
163	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
164	>	* according to the same comparator, or according to its elements'
165	>	* natural order if the collection is sorted according to its
166	>	* elements' natural order.  Otherwise, the priority queue is
167	>	* ordered according to its elements' natural order.
168	>	*
169	>	* @param c the collection whose elements are to be placed
170	>	*        into this priority queue.
171	>	* @throws ClassCastException if elements of the specified collection
172	>	*         cannot be compared to one another according to the priority
173	>	*         queue's ordering.
174	>	* @throws NullPointerException if <tt>c</tt> or any element within it
175	>	* is <tt>null</tt>
176	>	*/
177	>	public PriorityQueue(Collection<? extends E> c) {
178	>	initializeArray(c);
179	>	if (c instanceof SortedSet<? extends E>) {
180	>	SortedSet<? extends E> s = (SortedSet<? extends E>) c;
181	>	comparator = (Comparator<? super E>)s.comparator();
182	>	fillFromSorted(s);
183	>	} else if (c instanceof PriorityQueue<? extends E>) {
184	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
185	>	comparator = (Comparator<? super E>)s.comparator();
186	>	fillFromSorted(s);
187		} else {
188		comparator = null;
189	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
147	<	add(i.next());
189	>	fillFromUnsorted(c);
190		}
191		}
192
193	+	/**
194	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
195	+	* specified collection.  The priority queue has an initial
196	+	* capacity of 110% of the size of the specified collection or 1
197	+	* if the collection is empty.  This priority queue will be sorted
198	+	* according to the same comparator as the given collection, or
199	+	* according to its elements' natural order if the collection is
200	+	* sorted according to its elements' natural order.
201	+	*
202	+	* @param c the collection whose elements are to be placed
203	+	*        into this priority queue.
204	+	* @throws ClassCastException if elements of the specified collection
205	+	*         cannot be compared to one another according to the priority
206	+	*         queue's ordering.
207	+	* @throws NullPointerException if <tt>c</tt> or any element within it
208	+	* is <tt>null</tt>
209	+	*/
210	+	public PriorityQueue(PriorityQueue<? extends E> c) {
211	+	initializeArray(c);
212	+	comparator = (Comparator<? super E>)c.comparator();
213	+	fillFromSorted(c);
214	+	}
215	+
216	+	/**
217	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
218	+	* specified collection.  The priority queue has an initial
219	+	* capacity of 110% of the size of the specified collection or 1
220	+	* if the collection is empty.  This priority queue will be sorted
221	+	* according to the same comparator as the given collection, or
222	+	* according to its elements' natural order if the collection is
223	+	* sorted according to its elements' natural order.
224	+	*
225	+	* @param c the collection whose elements are to be placed
226	+	*        into this priority queue.
227	+	* @throws ClassCastException if elements of the specified collection
228	+	*         cannot be compared to one another according to the priority
229	+	*         queue's ordering.
230	+	* @throws NullPointerException if <tt>c</tt> or any element within it
231	+	* is <tt>null</tt>
232	+	*/
233	+	public PriorityQueue(SortedSet<? extends E> c) {
234	+	initializeArray(c);
235	+	comparator = (Comparator<? super E>)c.comparator();
236	+	fillFromSorted(c);
237	+	}
238	+
239	+	/**
240	+	* Resize array, if necessary, to be able to hold given index
241	+	*/
242	+	private void grow(int index) {
243	+	int newlen = queue.length;
244	+	if (index < newlen) // don't need to grow
245	+	return;
246	+	if (index == Integer.MAX_VALUE)
247	+	throw new OutOfMemoryError();
248	+	while (newlen <= index) {
249	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
250	+	newlen = Integer.MAX_VALUE;
251	+	else
252	+	newlen <<= 2;
253	+	}
254	+	Object[] newQueue = new Object[newlen];
255	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
256	+	queue = newQueue;
257	+	}
258	+
259		// Queue Methods
260
261	+
262	+
263		/**
264		* Add the specified element to this priority queue.
265		*
156	–	* @param element the element to add.
266		* @return <tt>true</tt>
267		* @throws ClassCastException if the specified element cannot be compared
268		* with elements currently in the priority queue according
269		* to the priority queue's ordering.
270	<	* @throws NullPointerException if the specified element is null.
270	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
271		*/
272	<	public boolean offer(E element) {
273	<	if (element == null)
272	>	public boolean offer(E o) {
273	>	if (o == null)
274		throw new NullPointerException();
275		modCount++;
276		++size;
277
278		// Grow backing store if necessary
279	<	while (size >= queue.length) {
280	<	E[] newQueue = (E[]) new Object[2 * queue.length];
172	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
173	<	queue = newQueue;
174	<	}
279	>	if (size >= queue.length)
280	>	grow(size);
281
282	<	queue[size] = element;
282	>	queue[size] = o;
283		fixUp(size);
284		return true;
285		}
#	Line 181 | Line 287 | public class PriorityQueue<E> extends Ab
287		public E poll() {
288		if (size == 0)
289		return null;
290	<	return remove(1);
290	>	return (E) remove(1);
291		}
292
293		public E peek() {
294	<	return queue[1];
294	>	return (E) queue[1];
295		}
296
297	<	// Collection Methods
297	>	// Collection Methods - the first two override to update docs
298
299	<	// these first two override just to get the throws docs
299	>	/**
300	>	* Adds the specified element to this queue.
301	>	* @return <tt>true</tt> (as per the general contract of
302	>	* <tt>Collection.add</tt>).
303	>	*
304	>	* @throws NullPointerException {@inheritDoc}
305	>	* @throws ClassCastException if the specified element cannot be compared
306	>	* with elements currently in the priority queue according
307	>	* to the priority queue's ordering.
308	>	*/
309	>	public boolean add(E o) {
310	>	return super.add(o);
311	>	}
312
313	+
314		/**
315	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
315	>	* Adds all of the elements in the specified collection to this queue.
316	>	* The behavior of this operation is undefined if
317	>	* the specified collection is modified while the operation is in
318	>	* progress.  (This implies that the behavior of this call is undefined if
319	>	* the specified collection is this queue, and this queue is nonempty.)
320	>	* <p>
321	>	* This implementation iterates over the specified collection, and adds
322	>	* each object returned by the iterator to this collection, in turn.
323	>	* @throws NullPointerException {@inheritDoc}
324	>	* @throws ClassCastException if any element cannot be compared
325	>	* with elements currently in the priority queue according
326	>	* to the priority queue's ordering.
327		*/
328	<	public boolean add(E element) {
329	<	return super.add(element);
328	>	public boolean addAll(Collection<? extends E> c) {
329	>	return super.addAll(c);
330		}
331
202	–	//    /**
203	–	//     * @throws NullPointerException if any element is <tt>null</tt>.
204	–	//     */
205	–	//    public boolean addAll(Collection c) {
206	–	//        return super.addAll(c);
207	–	//    }
332
333	<	/**
334	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
333	>	/**
334	>	* Removes a single instance of the specified element from this
335	>	* queue, if it is present.  More formally,
336	>	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
337	>	* o.equals(e))</tt>, if the queue contains one or more such
338	>	* elements.  Returns <tt>true</tt> if the queue contained the
339	>	* specified element (or equivalently, if the queue changed as a
340	>	* result of the call).
341	>	*
342	>	* <p>This implementation iterates over the queue looking for the
343	>	* specified element.  If it finds the element, it removes the element
344	>	* from the queue using the iterator's remove method.<p>
345	>	*
346		*/
347		public boolean remove(Object o) {
348		if (o == null)
349	<	throw new NullPointerException();
349	>	return false;
350
351		if (comparator == null) {
352		for (int i = 1; i <= size; i++) {
353	<	if (((Comparable)queue[i]).compareTo(o) == 0) {
353	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
354		remove(i);
355		return true;
356		}
357		}
358		} else {
359		for (int i = 1; i <= size; i++) {
360	<	if (comparator.compare(queue[i], (E)o) == 0) {
360	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
361		remove(i);
362		return true;
363		}
#	Line 232 | Line 367 | public class PriorityQueue<E> extends Ab
367		}
368
369		/**
370	<	* Returns an iterator over the elements in this priority queue.  The
371	<	* elements of the priority queue will be returned by this iterator in the
237	<	* order specified by the queue, which is to say the order they would be
238	<	* returned by repeated calls to <tt>poll</tt>.
370	>	* Returns an iterator over the elements in this queue. The iterator
371	>	* does not return the elements in any particular order.
372		*
373	<	* @return an <tt>Iterator</tt> over the elements in this priority queue.
373	>	* @return an iterator over the elements in this queue.
374		*/
375		public Iterator<E> iterator() {
376		return new Itr();
#	Line 272 | Line 405 | public class PriorityQueue<E> extends Ab
405		checkForComodification();
406		if (cursor > size)
407		throw new NoSuchElementException();
408	<	E result = queue[cursor];
408	>	E result = (E) queue[cursor];
409		lastRet = cursor++;
410		return result;
411		}
#	Line 295 | Line 428 | public class PriorityQueue<E> extends Ab
428		}
429		}
430
298	–	/**
299	–	* Returns the number of elements in this priority queue.
300	–	*
301	–	* @return the number of elements in this priority queue.
302	–	*/
431		public int size() {
432		return size;
433		}
#	Line 328 | Line 456 | public class PriorityQueue<E> extends Ab
456		assert i <= size;
457		modCount++;
458
459	<	E result = queue[i];
459	>	E result = (E) queue[i];
460		queue[i] = queue[size];
461		queue[size--] = null;  // Drop extra ref to prevent memory leak
462		if (i <= size)
#	Line 349 | Line 477 | public class PriorityQueue<E> extends Ab
477		if (comparator == null) {
478		while (k > 1) {
479		int j = k >> 1;
480	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
480	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
481		break;
482	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
482	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
483		k = j;
484		}
485		} else {
486		while (k > 1) {
487		int j = k >> 1;
488	<	if (comparator.compare(queue[j], queue[k]) <= 0)
488	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
489		break;
490	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
490	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
491		k = j;
492		}
493		}
#	Line 378 | Line 506 | public class PriorityQueue<E> extends Ab
506		int j;
507		if (comparator == null) {
508		while ((j = k << 1) <= size) {
509	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
509	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
510		j++; // j indexes smallest kid
511	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
511	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
512		break;
513	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
513	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
514		k = j;
515		}
516		} else {
517		while ((j = k << 1) <= size) {
518	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
518	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
519		j++; // j indexes smallest kid
520	<	if (comparator.compare(queue[k], queue[j]) <= 0)
520	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
521		break;
522	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
522	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
523		k = j;
524		}
525		}
526		}
527
528	<	public Comparator comparator() {
528	>
529	>	/**
530	>	* Returns the comparator used to order this collection, or <tt>null</tt>
531	>	* if this collection is sorted according to its elements natural ordering
532	>	* (using <tt>Comparable</tt>).
533	>	*
534	>	* @return the comparator used to order this collection, or <tt>null</tt>
535	>	* if this collection is sorted according to its elements natural ordering.
536	>	*/
537	>	public Comparator<? super E> comparator() {
538		return comparator;
539		}
540
#	Line 410 | Line 547 | public class PriorityQueue<E> extends Ab
547		* <tt>Object</tt>) in the proper order.
548		* @param s the stream
549		*/
550	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
550	>	private void writeObject(java.io.ObjectOutputStream s)
551		throws java.io.IOException{
552		// Write out element count, and any hidden stuff
553		s.defaultWriteObject();
#	Line 428 | Line 565 | public class PriorityQueue<E> extends Ab
565		* deserialize it).
566		* @param s the stream
567		*/
568	<	private synchronized void readObject(java.io.ObjectInputStream s)
568	>	private void readObject(java.io.ObjectInputStream s)
569		throws java.io.IOException, ClassNotFoundException {
570		// Read in size, and any hidden stuff
571		s.defaultReadObject();
572
573		// Read in array length and allocate array
574		int arrayLength = s.readInt();
575	<	queue = (E[]) new Object[arrayLength];
575	>	queue = new Object[arrayLength];
576
577		// Read in all elements in the proper order.
578		for (int i=0; i<size; i++)
579	<	queue[i] = (E)s.readObject();
579	>	queue[i] = s.readObject();
580		}
581
582		}

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