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

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.20 by dholmes, Tue Aug 5 06:18:17 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	<	* 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 java.util.TreeSet} and
8		* {@link java.util.TreeMap}: elements are ordered
#	Line 27 | Line 28
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
#	Line 41 | Line 54
54		* @author Josh Bloch
55		*/
56		public class PriorityQueue<E> extends AbstractQueue<E>
57	<	implements Sorted, Queue<E>, java.io.Serializable {
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
#	Line 78 | Line 93 | public class PriorityQueue<E> extends Ab
93		private transient int modCount = 0;
94
95		/**
96	<	* Create a <tt>PriorityQueue</tt> with the default initial capacity
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>.)
98	>	* ordering (using <tt>Comparable</tt>).
99		*/
100		public PriorityQueue() {
101		this(DEFAULT_INITIAL_CAPACITY, null);
102		}
103
104		/**
105	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
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>.)
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 <tt>PriorityQueue</tt> with the specified initial capacity
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.
#	Line 108 | Line 125 | public class PriorityQueue<E> extends Ab
125		* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
126		* than 1
127		*/
128	<	public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
128	>	public PriorityQueue(int initialCapacity,
129	>	Comparator<? super E> comparator) {
130		if (initialCapacity < 1)
131		throw new IllegalArgumentException();
132		this.queue = new Object[initialCapacity + 1];
#	Line 116 | Line 134 | public class PriorityQueue<E> extends Ab
134		}
135
136		/**
137	<	* Create a <tt>PriorityQueue</tt> containing the elements in the specified
138	<	* collection.  The priority queue has an initial capacity of 110% of the
139	<	* size of the specified collection or 1 if the collection is empty.
140	<	* If the specified collection
141	<	* implements the {@link Sorted} interface, the priority queue will be
142	<	* sorted according to the same comparator, or according to its elements'
143	<	* natural order if the collection is sorted according to its elements'
144	<	* natural order.  If the specified collection does not implement
145	<	* <tt>Sorted</tt>, the priority queue is ordered according to
146	<	* its elements' natural order.
137	>	* Common code to initialize underlying queue array across
138	>	* constructors below.
139	>	*/
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;
146	>
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	>	/**
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.
#	Line 136 | Line 189 | public class PriorityQueue<E> extends Ab
189		* is <tt>null</tt>
190		*/
191		public PriorityQueue(Collection<? extends E> c) {
192	<	int sz = c.size();
193	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
194	<	Integer.MAX_VALUE - 1);
195	<	if (initialCapacity < 1)
196	<	initialCapacity = 1;
197	<
198	<	this.queue = new Object[initialCapacity + 1];
199	<
200	<	if (c instanceof Sorted) {
201	<	comparator = (Comparator<? super E>)((Sorted)c).comparator();
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 {
203		comparator = null;
204	+	fillFromUnsorted(c);
205		}
206	+	}
207
208	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
209	<	add(i.next());
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		* Add the specified element to this priority queue.
280		*
#	Line 172 | Line 291 | public class PriorityQueue<E> extends Ab
291		++size;
292
293		// Grow backing store if necessary
294	<	while (size >= queue.length) {
295	<	Object[] newQueue = new Object[2 * queue.length];
177	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
178	<	queue = newQueue;
179	<	}
294	>	if (size >= queue.length)
295	>	grow(size);
296
297		queue[size] = o;
298		fixUp(size);
#	Line 193 | Line 309 | public class PriorityQueue<E> extends Ab
309		return (E) queue[1];
310		}
311
312	<	// Collection Methods
197	<
198	<	// these first two override just to get the throws docs
312	>	// Collection Methods - the first two override to update docs
313
314		/**
315	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
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	>	* @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.
#	Line 207 | Line 325 | public class PriorityQueue<E> extends Ab
325		return super.add(o);
326		}
327
328	+
329		/**
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.
214	–	* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
215	–	* is <tt>null</tt>
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	+	* <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 o) {
363		if (o == null)
364		return false;
#	Line 240 | Line 381 | public class PriorityQueue<E> extends Ab
381		return false;
382		}
383
384	+	/**
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 iterator over the elements in this queue.
389	+	*/
390		public Iterator<E> iterator() {
391		return new Itr();
392		}
#	Line 284 | Line 431 | public class PriorityQueue<E> extends Ab
431		checkForComodification();
432
433		PriorityQueue.this.remove(lastRet);
434	<	if (lastRet < cursor)
288	<	cursor--;
434	>	cursor--;
435		lastRet = 0;
436		expectedModCount = modCount;
437		}
#	Line 296 | Line 442 | public class PriorityQueue<E> extends Ab
442		}
443		}
444
299	–	/**
300	–	* Returns the number of elements in this priority queue.
301	–	*
302	–	* @return the number of elements in this priority queue.
303	–	*/
445		public int size() {
446		return size;
447		}
#	Line 322 | 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		*
325	–	* XXX: Could further special-case i==size, but is it worth it?
326	–	* XXX: Could special-case i==0, but is it worth it?
466		*/
467		private E remove(int i) {
468		assert i <= size;
#	Line 378 | 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) {
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<E>)queue[k]).compareTo((E)queue[j]) <= 0)
#	Line 387 | Line 526 | public class PriorityQueue<E> extends Ab
526		k = j;
527		}
528		} else {
529	<	while ((j = k << 1) <= size) {
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((E)queue[k], (E)queue[j]) <= 0)
#	Line 398 | Line 537 | public class PriorityQueue<E> extends Ab
537		}
538		}
539
540	+
541	+	/**
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 used to order this collection, or <tt>null</tt>
547	+	* if this collection is sorted according to its elements natural ordering.
548	+	*/
549		public Comparator<? super E> comparator() {
550		return comparator;
551		}
#	Line 411 | Line 559 | public class PriorityQueue<E> extends Ab
559		* <tt>Object</tt>) in the proper order.
560		* @param s the stream
561		*/
562	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
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();
#	Line 429 | Line 577 | public class PriorityQueue<E> extends Ab
577		* deserialize it).
578		* @param s the stream
579		*/
580	<	private synchronized void readObject(java.io.ObjectInputStream s)
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();

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