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

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.15 by dholmes, Thu Jul 31 07:18:02 2003 UTC vs.
Revision 1.25 by tim, Wed Aug 6 18:42:49 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
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		*
#	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.
#	Line 105 | Line 111 | public class PriorityQueue<E> extends Ab
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		throw new IllegalArgumentException();
118	<	queue = (E[]) new Object[initialCapacity + 1];
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
125	<	* size of the specified collection; or 1 if the collection is empty.
126	<	* If the specified collection
127	<	* implements the {@link Sorted} interface, the priority queue will be
128	<	* sorted according to the same comparator, or according to its elements'
129	<	* natural order if the collection is sorted according to its elements'
130	<	* natural order.  If the specified collection does not implement
131	<	* <tt>Sorted</tt>, the priority queue is ordered according to
132	<	* its elements' natural order.
123	>	* Common code to initialize underlying queue array across
124	>	* constructors below.
125	>	*/
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;
132	>
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.
#	Line 132 | Line 174 | public class PriorityQueue<E> extends Ab
174		* @throws NullPointerException if <tt>c</tt> or any element within it
175		* is <tt>null</tt>
176		*/
177	<	public PriorityQueue(Collection<E> c) {
178	<	int sz = c.size();
179	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
180	<	Integer.MAX_VALUE - 1);
181	<	if (initialCapacity < 1)
182	<	initialCapacity = 1;
183	<
184	<	queue = (E[]) new Object[initialCapacity + 1];
185	<
186	<	if (c instanceof Sorted) {
187	<	// FIXME: this code assumes too much
188	<	comparator = ((Sorted)c).comparator();
189	<	for (Iterator<E> i = c.iterator(); i.hasNext(); )
148	<	queue[++size] = i.next();
149	<	} else {
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	>	}
184	>	else if (c instanceof PriorityQueue<? extends E>) {
185	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
186	>	comparator = (Comparator<? super E>)s.comparator();
187	>	fillFromSorted(s);
188	>	}
189	>	else {
190		comparator = null;
191	<	for (Iterator<E> i = c.iterator(); i.hasNext(); )
152	<	add(i.next());
191	>	fillFromUnsorted(c);
192		}
193		}
194
195	+	/**
196	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
197	+	* specified collection.  The priority queue has an initial
198	+	* capacity of 110% of the size of the specified collection or 1
199	+	* if the collection is empty.  This priority queue will be sorted
200	+	* according to the same comparator as the given collection, or
201	+	* according to its elements' natural order if the collection is
202	+	* sorted according to its elements' natural order.
203	+	*
204	+	* @param c the collection whose elements are to be placed
205	+	*        into this priority queue.
206	+	* @throws ClassCastException if elements of the specified collection
207	+	*         cannot be compared to one another according to the priority
208	+	*         queue's ordering.
209	+	* @throws NullPointerException if <tt>c</tt> or any element within it
210	+	* is <tt>null</tt>
211	+	*/
212	+	public PriorityQueue(PriorityQueue<? extends E> c) {
213	+	initializeArray(c);
214	+	comparator = (Comparator<? super E>)c.comparator();
215	+	fillFromSorted(c);
216	+	}
217	+
218	+	/**
219	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
220	+	* specified collection.  The priority queue has an initial
221	+	* capacity of 110% of the size of the specified collection or 1
222	+	* if the collection is empty.  This priority queue will be sorted
223	+	* according to the same comparator as the given collection, or
224	+	* according to its elements' natural order if the collection is
225	+	* sorted according to its elements' natural order.
226	+	*
227	+	* @param c the collection whose elements are to be placed
228	+	*        into this priority queue.
229	+	* @throws ClassCastException if elements of the specified collection
230	+	*         cannot be compared to one another according to the priority
231	+	*         queue's ordering.
232	+	* @throws NullPointerException if <tt>c</tt> or any element within it
233	+	* is <tt>null</tt>
234	+	*/
235	+	public PriorityQueue(SortedSet<? extends E> c) {
236	+	initializeArray(c);
237	+	comparator = (Comparator<? super E>)c.comparator();
238	+	fillFromSorted(c);
239	+	}
240	+
241	+	/**
242	+	* Resize array, if necessary, to be able to hold given index
243	+	*/
244	+	private void grow(int index) {
245	+	int newlen = queue.length;
246	+	if (index < newlen) // don't need to grow
247	+	return;
248	+	if (index == Integer.MAX_VALUE)
249	+	throw new OutOfMemoryError();
250	+	while (newlen <= index) {
251	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
252	+	newlen = Integer.MAX_VALUE;
253	+	else
254	+	newlen <<= 2;
255	+	}
256	+	Object[] newQueue = new Object[newlen];
257	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
258	+	queue = newQueue;
259	+	}
260	+
261		// Queue Methods
262
263	+
264	+
265		/**
266		* Add the specified element to this priority queue.
267		*
161	–	* @param element the element to add.
268		* @return <tt>true</tt>
269		* @throws ClassCastException if the specified element cannot be compared
270		* with elements currently in the priority queue according
271		* to the priority queue's ordering.
272	<	* @throws NullPointerException if the specified element is null.
272	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
273		*/
274	<	public boolean offer(E element) {
275	<	if (element == null)
274	>	public boolean offer(E o) {
275	>	if (o == null)
276		throw new NullPointerException();
277		modCount++;
278		++size;
279
280		// Grow backing store if necessary
281	<	while (size >= queue.length) {
282	<	E[] newQueue = (E[]) new Object[2 * queue.length];
177	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
178	<	queue = newQueue;
179	<	}
281	>	if (size >= queue.length)
282	>	grow(size);
283
284	<	queue[size] = element;
284	>	queue[size] = o;
285		fixUp(size);
286		return true;
287		}
#	Line 186 | Line 289 | public class PriorityQueue<E> extends Ab
289		public E poll() {
290		if (size == 0)
291		return null;
292	<	return remove(1);
292	>	return (E) remove(1);
293		}
294
295		public E peek() {
296	<	return queue[1];
296	>	return (E) queue[1];
297		}
298
299	<	// Collection Methods
197	<
198	<	// these first two override just to get the throws docs
299	>	// Collection Methods - the first two override to update docs
300
301		/**
302	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
302	>	* Adds the specified element to this queue.
303	>	* @return <tt>true</tt> (as per the general contract of
304	>	* <tt>Collection.add</tt>).
305	>	*
306	>	* @throws NullPointerException {@inheritDoc}
307		* @throws ClassCastException if the specified element cannot be compared
308		* with elements currently in the priority queue according
309		* to the priority queue's ordering.
310		*/
311	<	public boolean add(E element) {
312	<	return super.add(element);
311	>	public boolean add(E o) {
312	>	return super.add(o);
313		}
314
315	+
316		/**
317	<	* @throws NullPointerException if any element is <tt>null</tt>.
317	>	* Adds all of the elements in the specified collection to this queue.
318	>	* The behavior of this operation is undefined if
319	>	* the specified collection is modified while the operation is in
320	>	* progress.  (This implies that the behavior of this call is undefined if
321	>	* the specified collection is this queue, and this queue is nonempty.)
322	>	* <p>
323	>	* This implementation iterates over the specified collection, and adds
324	>	* each object returned by the iterator to this collection, in turn.
325	>	* @throws NullPointerException {@inheritDoc}
326		* @throws ClassCastException if any element cannot be compared
327		* with elements currently in the priority queue according
328		* to the priority queue's ordering.
#	Line 217 | Line 331 | public class PriorityQueue<E> extends Ab
331		return super.addAll(c);
332		}
333
334	+
335	+	/**
336	+	* Removes a single instance of the specified element from this
337	+	* queue, if it is present.  More formally,
338	+	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
339	+	* o.equals(e))</tt>, if the queue contains one or more such
340	+	* elements.  Returns <tt>true</tt> if the queue contained the
341	+	* specified element (or equivalently, if the queue changed as a
342	+	* result of the call).
343	+	*
344	+	* <p>This implementation iterates over the queue looking for the
345	+	* specified element.  If it finds the element, it removes the element
346	+	* from the queue using the iterator's remove method.<p>
347	+	*
348	+	*/
349		public boolean remove(Object o) {
350		if (o == null)
351		return false;
352
353		if (comparator == null) {
354		for (int i = 1; i <= size; i++) {
355	<	if (((Comparable)queue[i]).compareTo(o) == 0) {
355	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
356		remove(i);
357		return true;
358		}
359		}
360		} else {
361		for (int i = 1; i <= size; i++) {
362	<	if (comparator.compare(queue[i], (E)o) == 0) {
362	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
363		remove(i);
364		return true;
365		}
#	Line 239 | Line 368 | public class PriorityQueue<E> extends Ab
368		return false;
369		}
370
371	+	/**
372	+	* Returns an iterator over the elements in this queue. The iterator
373	+	* does not return the elements in any particular order.
374	+	*
375	+	* @return an iterator over the elements in this queue.
376	+	*/
377		public Iterator<E> iterator() {
378		return new Itr();
379		}
#	Line 272 | Line 407 | public class PriorityQueue<E> extends Ab
407		checkForComodification();
408		if (cursor > size)
409		throw new NoSuchElementException();
410	<	E result = queue[cursor];
410	>	E result = (E) queue[cursor];
411		lastRet = cursor++;
412		return result;
413		}
#	Line 295 | Line 430 | public class PriorityQueue<E> extends Ab
430		}
431		}
432
298	–	/**
299	–	* Returns the number of elements in this priority queue.
300	–	*
301	–	* @return the number of elements in this priority queue.
302	–	*/
433		public int size() {
434		return size;
435		}
#	Line 328 | Line 458 | public class PriorityQueue<E> extends Ab
458		assert i <= size;
459		modCount++;
460
461	<	E result = queue[i];
461	>	E result = (E) queue[i];
462		queue[i] = queue[size];
463		queue[size--] = null;  // Drop extra ref to prevent memory leak
464		if (i <= size)
#	Line 349 | Line 479 | public class PriorityQueue<E> extends Ab
479		if (comparator == null) {
480		while (k > 1) {
481		int j = k >> 1;
482	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
482	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
483		break;
484	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
484	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
485		k = j;
486		}
487		} else {
488		while (k > 1) {
489		int j = k >> 1;
490	<	if (comparator.compare(queue[j], queue[k]) <= 0)
490	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
491		break;
492	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
492	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
493		k = j;
494		}
495		}
#	Line 378 | Line 508 | public class PriorityQueue<E> extends Ab
508		int j;
509		if (comparator == null) {
510		while ((j = k << 1) <= size) {
511	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
511	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
512		j++; // j indexes smallest kid
513	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
513	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
514		break;
515	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
515	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
516		k = j;
517		}
518		} else {
519		while ((j = k << 1) <= size) {
520	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
520	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
521		j++; // j indexes smallest kid
522	<	if (comparator.compare(queue[k], queue[j]) <= 0)
522	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
523		break;
524	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
524	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
525		k = j;
526		}
527		}
528		}
529
530	<	public Comparator comparator() {
530	>
531	>	/**
532	>	* Returns the comparator used to order this collection, or <tt>null</tt>
533	>	* if this collection is sorted according to its elements natural ordering
534	>	* (using <tt>Comparable</tt>).
535	>	*
536	>	* @return the comparator used to order this collection, or <tt>null</tt>
537	>	* if this collection is sorted according to its elements natural ordering.
538	>	*/
539	>	public Comparator<? super E> comparator() {
540		return comparator;
541		}
542
#	Line 410 | Line 549 | public class PriorityQueue<E> extends Ab
549		* <tt>Object</tt>) in the proper order.
550		* @param s the stream
551		*/
552	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
552	>	private void writeObject(java.io.ObjectOutputStream s)
553		throws java.io.IOException{
554		// Write out element count, and any hidden stuff
555		s.defaultWriteObject();
#	Line 428 | Line 567 | public class PriorityQueue<E> extends Ab
567		* deserialize it).
568		* @param s the stream
569		*/
570	<	private synchronized void readObject(java.io.ObjectInputStream s)
570	>	private void readObject(java.io.ObjectInputStream s)
571		throws java.io.IOException, ClassNotFoundException {
572		// Read in size, and any hidden stuff
573		s.defaultReadObject();
574
575		// Read in array length and allocate array
576		int arrayLength = s.readInt();
577	<	queue = (E[]) new Object[arrayLength];
577	>	queue = new Object[arrayLength];
578
579		// Read in all elements in the proper order.
580		for (int i=0; i<size; i++)
581	<	queue[i] = (E)s.readObject();
581	>	queue[i] = s.readObject();
582		}
583
584		}

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