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

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.16 by tim, Thu Jul 31 15:44:41 2003 UTC vs.
Revision 1.29 by dl, Sun Aug 24 23:31:53 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		*
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.BlockingPriorityQueue} 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 75 | Line 91 | public class PriorityQueue<E> extends Ab
91		private transient int modCount = 0;
92
93		/**
94	<	* Create a <tt>PriorityQueue</tt> with the default initial capacity
94	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
95		* (11) that orders its elements according to their natural
96	<	* ordering (using <tt>Comparable</tt>.)
96	>	* ordering (using <tt>Comparable</tt>).
97		*/
98		public PriorityQueue() {
99		this(DEFAULT_INITIAL_CAPACITY, null);
100		}
101
102		/**
103	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
103	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
104		* that orders its elements according to their natural ordering
105	<	* (using <tt>Comparable</tt>.)
105	>	* (using <tt>Comparable</tt>).
106		*
107		* @param initialCapacity the initial capacity for this priority queue.
108	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
109	+	* than 1
110		*/
111		public PriorityQueue(int initialCapacity) {
112		this(initialCapacity, null);
113		}
114
115		/**
116	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
116	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
117		* that orders its elements according to the specified comparator.
118		*
119		* @param initialCapacity the initial capacity for this priority queue.
#	Line 105 | Line 123 | public class PriorityQueue<E> extends Ab
123		* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
124		* than 1
125		*/
126	<	public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
126	>	public PriorityQueue(int initialCapacity,
127	>	Comparator<? super E> comparator) {
128		if (initialCapacity < 1)
129		throw new IllegalArgumentException();
130		this.queue = new Object[initialCapacity + 1];
#	Line 113 | Line 132 | public class PriorityQueue<E> extends Ab
132		}
133
134		/**
135	<	* Create a <tt>PriorityQueue</tt> containing the elements in the specified
136	<	* collection.  The priority queue has an initial capacity of 110% of the
137	<	* size of the specified collection; or 1 if the collection is empty.
138	<	* If the specified collection
139	<	* implements the {@link Sorted} interface, the priority queue will be
140	<	* sorted according to the same comparator, or according to its elements'
141	<	* natural order if the collection is sorted according to its elements'
142	<	* natural order.  If the specified collection does not implement
143	<	* <tt>Sorted</tt>, the priority queue is ordered according to
144	<	* its elements' natural order.
135	>	* Common code to initialize underlying queue array across
136	>	* constructors below.
137	>	*/
138	>	private void initializeArray(Collection<? extends E> c) {
139	>	int sz = c.size();
140	>	int initialCapacity = (int)Math.min((sz * 110L) / 100,
141	>	Integer.MAX_VALUE - 1);
142	>	if (initialCapacity < 1)
143	>	initialCapacity = 1;
144	>
145	>	this.queue = new Object[initialCapacity + 1];
146	>	}
147	>
148	>	/**
149	>	* Initially fill elements of the queue array under the
150	>	* knowledge that it is sorted or is another PQ, in which
151	>	* case we can just place the elements without fixups.
152	>	*/
153	>	private void fillFromSorted(Collection<? extends E> c) {
154	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
155	>	queue[++size] = i.next();
156	>	}
157	>
158	>
159	>	/**
160	>	* Initially fill elements of the queue array that is
161	>	* not to our knowledge sorted, so we must add them
162	>	* one by one.
163	>	*/
164	>	private void fillFromUnsorted(Collection<? extends E> c) {
165	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
166	>	add(i.next());
167	>	}
168	>
169	>	/**
170	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
171	>	* specified collection.  The priority queue has an initial
172	>	* capacity of 110% of the size of the specified collection or 1
173	>	* if the collection is empty.  If the specified collection is an
174	>	* instance of a {@link java.util.SortedSet} or is another
175	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
176	>	* according to the same comparator, or according to its elements'
177	>	* natural order if the collection is sorted according to its
178	>	* elements' natural order.  Otherwise, the priority queue is
179	>	* ordered according to its elements' natural order.
180		*
181		* @param c the collection whose elements are to be placed
182		*        into this priority queue.
#	Line 133 | Line 187 | public class PriorityQueue<E> extends Ab
187		* is <tt>null</tt>
188		*/
189		public PriorityQueue(Collection<? extends E> c) {
190	<	int sz = c.size();
191	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
192	<	Integer.MAX_VALUE - 1);
193	<	if (initialCapacity < 1)
194	<	initialCapacity = 1;
195	<
196	<	this.queue = new Object[initialCapacity + 1];
197	<
198	<	if (c instanceof Sorted) {
199	<	// FIXME: this code assumes too much
146	<	this.comparator = (Comparator<? super E>) ((Sorted)c).comparator();
147	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
148	<	queue[++size] = i.next();
190	>	initializeArray(c);
191	>	if (c instanceof SortedSet) {
192	>	// @fixme double-cast workaround for compiler
193	>	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
194	>	comparator = (Comparator<? super E>)s.comparator();
195	>	fillFromSorted(s);
196	>	} else if (c instanceof PriorityQueue) {
197	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
198	>	comparator = (Comparator<? super E>)s.comparator();
199	>	fillFromSorted(s);
200		} else {
201		comparator = null;
202	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
152	<	add(i.next());
202	>	fillFromUnsorted(c);
203		}
204		}
205
206	+	/**
207	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
208	+	* specified collection.  The priority queue has an initial
209	+	* capacity of 110% of the size of the specified collection or 1
210	+	* if the collection is empty.  This priority queue will be sorted
211	+	* according to the same comparator as the given collection, or
212	+	* according to its elements' natural order if the collection is
213	+	* sorted according to its elements' natural order.
214	+	*
215	+	* @param c the collection whose elements are to be placed
216	+	*        into this priority queue.
217	+	* @throws ClassCastException if elements of the specified collection
218	+	*         cannot be compared to one another according to the priority
219	+	*         queue's ordering.
220	+	* @throws NullPointerException if <tt>c</tt> or any element within it
221	+	* is <tt>null</tt>
222	+	*/
223	+	public PriorityQueue(PriorityQueue<? extends E> c) {
224	+	initializeArray(c);
225	+	comparator = (Comparator<? super E>)c.comparator();
226	+	fillFromSorted(c);
227	+	}
228	+
229	+	/**
230	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
231	+	* specified collection.  The priority queue has an initial
232	+	* capacity of 110% of the size of the specified collection or 1
233	+	* if the collection is empty.  This priority queue will be sorted
234	+	* according to the same comparator as the given collection, or
235	+	* according to its elements' natural order if the collection is
236	+	* sorted according to its elements' natural order.
237	+	*
238	+	* @param c the collection whose elements are to be placed
239	+	*        into this priority queue.
240	+	* @throws ClassCastException if elements of the specified collection
241	+	*         cannot be compared to one another according to the priority
242	+	*         queue's ordering.
243	+	* @throws NullPointerException if <tt>c</tt> or any element within it
244	+	* is <tt>null</tt>
245	+	*/
246	+	public PriorityQueue(SortedSet<? extends E> c) {
247	+	initializeArray(c);
248	+	comparator = (Comparator<? super E>)c.comparator();
249	+	fillFromSorted(c);
250	+	}
251	+
252	+	/**
253	+	* Resize array, if necessary, to be able to hold given index
254	+	*/
255	+	private void grow(int index) {
256	+	int newlen = queue.length;
257	+	if (index < newlen) // don't need to grow
258	+	return;
259	+	if (index == Integer.MAX_VALUE)
260	+	throw new OutOfMemoryError();
261	+	while (newlen <= index) {
262	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
263	+	newlen = Integer.MAX_VALUE;
264	+	else
265	+	newlen <<= 2;
266	+	}
267	+	Object[] newQueue = new Object[newlen];
268	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
269	+	queue = newQueue;
270	+	}
271	+
272		// Queue Methods
273
274	+
275	+
276		/**
277		* Add the specified element to this priority queue.
278		*
161	–	* @param element the element to add.
279		* @return <tt>true</tt>
280		* @throws ClassCastException if the specified element cannot be compared
281		* with elements currently in the priority queue according
282		* to the priority queue's ordering.
283	<	* @throws NullPointerException if the specified element is null.
283	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
284		*/
285	<	public boolean offer(E element) {
286	<	if (element == null)
285	>	public boolean offer(E o) {
286	>	if (o == null)
287		throw new NullPointerException();
288		modCount++;
289		++size;
290
291		// Grow backing store if necessary
292	<	while (size >= queue.length) {
293	<	Object[] newQueue = new Object[2 * queue.length];
177	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
178	<	queue = newQueue;
179	<	}
292	>	if (size >= queue.length)
293	>	grow(size);
294
295	<	queue[size] = element;
295	>	queue[size] = o;
296		fixUp(size);
297		return true;
298		}
#	Line 193 | Line 307 | public class PriorityQueue<E> extends Ab
307		return (E) queue[1];
308		}
309
310	<	// Collection Methods
197	<
198	<	// these first two override just to get the throws docs
310	>	// Collection Methods - the first two override to update docs
311
312		/**
313	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
313	>	* Adds the specified element to this queue.
314	>	* @return <tt>true</tt> (as per the general contract of
315	>	* <tt>Collection.add</tt>).
316	>	*
317	>	* @throws NullPointerException {@inheritDoc}
318		* @throws ClassCastException if the specified element cannot be compared
319		* with elements currently in the priority queue according
320		* to the priority queue's ordering.
321		*/
322	<	public boolean add(E element) {
323	<	return super.add(element);
322	>	public boolean add(E o) {
323	>	return super.add(o);
324		}
325
326	+
327		/**
328	<	* @throws NullPointerException if any element is <tt>null</tt>.
328	>	* Adds all of the elements in the specified collection to this queue.
329	>	* The behavior of this operation is undefined if
330	>	* the specified collection is modified while the operation is in
331	>	* progress.  (This implies that the behavior of this call is undefined if
332	>	* the specified collection is this queue, and this queue is nonempty.)
333	>	* <p>
334	>	* This implementation iterates over the specified collection, and adds
335	>	* each object returned by the iterator to this collection, in turn.
336	>	* @throws NullPointerException {@inheritDoc}
337		* @throws ClassCastException if any element cannot be compared
338		* with elements currently in the priority queue according
339		* to the priority queue's ordering.
#	Line 217 | Line 342 | public class PriorityQueue<E> extends Ab
342		return super.addAll(c);
343		}
344
345	+
346	+	/**
347	+	* Removes a single instance of the specified element from this
348	+	* queue, if it is present.  More formally,
349	+	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
350	+	* o.equals(e))</tt>, if the queue contains one or more such
351	+	* elements.  Returns <tt>true</tt> if the queue contained the
352	+	* specified element (or equivalently, if the queue changed as a
353	+	* result of the call).
354	+	*
355	+	* <p>This implementation iterates over the queue looking for the
356	+	* specified element.  If it finds the element, it removes the element
357	+	* from the queue using the iterator's remove method.<p>
358	+	*
359	+	*/
360		public boolean remove(Object o) {
361		if (o == null)
362		return false;
#	Line 239 | Line 379 | public class PriorityQueue<E> extends Ab
379		return false;
380		}
381
382	+	/**
383	+	* Returns an iterator over the elements in this queue. The iterator
384	+	* does not return the elements in any particular order.
385	+	*
386	+	* @return an iterator over the elements in this queue.
387	+	*/
388		public Iterator<E> iterator() {
389		return new Itr();
390		}
#	Line 295 | Line 441 | public class PriorityQueue<E> extends Ab
441		}
442		}
443
298	–	/**
299	–	* Returns the number of elements in this priority queue.
300	–	*
301	–	* @return the number of elements in this priority queue.
302	–	*/
444		public int size() {
445		return size;
446		}
#	Line 397 | Line 538 | public class PriorityQueue<E> extends Ab
538		}
539		}
540
541	+
542	+	/**
543	+	* Returns the comparator used to order this collection, or <tt>null</tt>
544	+	* if this collection is sorted according to its elements natural ordering
545	+	* (using <tt>Comparable</tt>).
546	+	*
547	+	* @return the comparator used to order this collection, or <tt>null</tt>
548	+	* if this collection is sorted according to its elements natural ordering.
549	+	*/
550		public Comparator<? super E> comparator() {
551		return comparator;
552		}
#	Line 410 | Line 560 | public class PriorityQueue<E> extends Ab
560		* <tt>Object</tt>) in the proper order.
561		* @param s the stream
562		*/
563	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
563	>	private void writeObject(java.io.ObjectOutputStream s)
564		throws java.io.IOException{
565		// Write out element count, and any hidden stuff
566		s.defaultWriteObject();
#	Line 428 | Line 578 | public class PriorityQueue<E> extends Ab
578		* deserialize it).
579		* @param s the stream
580		*/
581	<	private synchronized void readObject(java.io.ObjectInputStream s)
581	>	private void readObject(java.io.ObjectInputStream s)
582		throws java.io.IOException, ClassNotFoundException {
583		// Read in size, and any hidden stuff
584		s.defaultReadObject();

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