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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 1.28 by dl, Wed Aug 13 14:11:59 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 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<? super E> comparator) {
114	>	public PriorityQueue(int initialCapacity,
115	>	Comparator<? super E> comparator) {
116		if (initialCapacity < 1)
117		throw new IllegalArgumentException();
118		this.queue = new Object[initialCapacity + 1];
#	Line 113 | Line 120 | public class PriorityQueue<E> extends Ab
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 133 | Line 175 | public class PriorityQueue<E> extends Ab
175		* is <tt>null</tt>
176		*/
177		public PriorityQueue(Collection<? extends 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	<	this.queue = new Object[initialCapacity + 1];
185	<
186	<	if (c instanceof Sorted) {
187	<	// 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();
178	>	initializeArray(c);
179	>	if (c instanceof SortedSet) {
180	>	// @fixme double-cast workaround for compiler
181	>	SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
182	>	comparator = (Comparator<? super E>)s.comparator();
183	>	fillFromSorted(s);
184	>	} else if (c instanceof PriorityQueue) {
185	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
186	>	comparator = (Comparator<? super E>)s.comparator();
187	>	fillFromSorted(s);
188		} else {
189		comparator = null;
190	<	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
152	<	add(i.next());
190	>	fillFromUnsorted(c);
191		}
192		}
193
194	+	/**
195	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
196	+	* specified collection.  The priority queue has an initial
197	+	* capacity of 110% of the size of the specified collection or 1
198	+	* if the collection is empty.  This priority queue will be sorted
199	+	* according to the same comparator as the given collection, or
200	+	* according to its elements' natural order if the collection is
201	+	* sorted according to its elements' natural order.
202	+	*
203	+	* @param c the collection whose elements are to be placed
204	+	*        into this priority queue.
205	+	* @throws ClassCastException if elements of the specified collection
206	+	*         cannot be compared to one another according to the priority
207	+	*         queue's ordering.
208	+	* @throws NullPointerException if <tt>c</tt> or any element within it
209	+	* is <tt>null</tt>
210	+	*/
211	+	public PriorityQueue(PriorityQueue<? extends E> c) {
212	+	initializeArray(c);
213	+	comparator = (Comparator<? super E>)c.comparator();
214	+	fillFromSorted(c);
215	+	}
216	+
217	+	/**
218	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
219	+	* specified collection.  The priority queue has an initial
220	+	* capacity of 110% of the size of the specified collection or 1
221	+	* if the collection is empty.  This priority queue will be sorted
222	+	* according to the same comparator as the given collection, or
223	+	* according to its elements' natural order if the collection is
224	+	* sorted according to its elements' natural order.
225	+	*
226	+	* @param c the collection whose elements are to be placed
227	+	*        into this priority queue.
228	+	* @throws ClassCastException if elements of the specified collection
229	+	*         cannot be compared to one another according to the priority
230	+	*         queue's ordering.
231	+	* @throws NullPointerException if <tt>c</tt> or any element within it
232	+	* is <tt>null</tt>
233	+	*/
234	+	public PriorityQueue(SortedSet<? extends E> c) {
235	+	initializeArray(c);
236	+	comparator = (Comparator<? super E>)c.comparator();
237	+	fillFromSorted(c);
238	+	}
239	+
240	+	/**
241	+	* Resize array, if necessary, to be able to hold given index
242	+	*/
243	+	private void grow(int index) {
244	+	int newlen = queue.length;
245	+	if (index < newlen) // don't need to grow
246	+	return;
247	+	if (index == Integer.MAX_VALUE)
248	+	throw new OutOfMemoryError();
249	+	while (newlen <= index) {
250	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
251	+	newlen = Integer.MAX_VALUE;
252	+	else
253	+	newlen <<= 2;
254	+	}
255	+	Object[] newQueue = new Object[newlen];
256	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
257	+	queue = newQueue;
258	+	}
259	+
260		// Queue Methods
261
262	+
263	+
264		/**
265		* Add the specified element to this priority queue.
266		*
161	–	* @param element the element to add.
267		* @return <tt>true</tt>
268		* @throws ClassCastException if the specified element cannot be compared
269		* with elements currently in the priority queue according
270		* to the priority queue's ordering.
271	<	* @throws NullPointerException if the specified element is null.
271	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
272		*/
273	<	public boolean offer(E element) {
274	<	if (element == null)
273	>	public boolean offer(E o) {
274	>	if (o == null)
275		throw new NullPointerException();
276		modCount++;
277		++size;
278
279		// Grow backing store if necessary
280	<	while (size >= queue.length) {
281	<	Object[] newQueue = new Object[2 * queue.length];
177	<	System.arraycopy(queue, 0, newQueue, 0, queue.length);
178	<	queue = newQueue;
179	<	}
280	>	if (size >= queue.length)
281	>	grow(size);
282
283	<	queue[size] = element;
283	>	queue[size] = o;
284		fixUp(size);
285		return true;
286		}
#	Line 193 | Line 295 | public class PriorityQueue<E> extends Ab
295		return (E) queue[1];
296		}
297
298	<	// Collection Methods
197	<
198	<	// these first two override just to get the throws docs
298	>	// Collection Methods - the first two override to update docs
299
300		/**
301	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
301	>	* Adds the specified element to this queue.
302	>	* @return <tt>true</tt> (as per the general contract of
303	>	* <tt>Collection.add</tt>).
304	>	*
305	>	* @throws NullPointerException {@inheritDoc}
306		* @throws ClassCastException if the specified element cannot be compared
307		* with elements currently in the priority queue according
308		* to the priority queue's ordering.
309		*/
310	<	public boolean add(E element) {
311	<	return super.add(element);
310	>	public boolean add(E o) {
311	>	return super.add(o);
312		}
313
314	+
315		/**
316	<	* @throws NullPointerException if any element is <tt>null</tt>.
316	>	* Adds all of the elements in the specified collection to this queue.
317	>	* The behavior of this operation is undefined if
318	>	* the specified collection is modified while the operation is in
319	>	* progress.  (This implies that the behavior of this call is undefined if
320	>	* the specified collection is this queue, and this queue is nonempty.)
321	>	* <p>
322	>	* This implementation iterates over the specified collection, and adds
323	>	* each object returned by the iterator to this collection, in turn.
324	>	* @throws NullPointerException {@inheritDoc}
325		* @throws ClassCastException if any element cannot be compared
326		* with elements currently in the priority queue according
327		* to the priority queue's ordering.
#	Line 217 | Line 330 | public class PriorityQueue<E> extends Ab
330		return super.addAll(c);
331		}
332
333	+
334	+	/**
335	+	* Removes a single instance of the specified element from this
336	+	* queue, if it is present.  More formally,
337	+	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
338	+	* o.equals(e))</tt>, if the queue contains one or more such
339	+	* elements.  Returns <tt>true</tt> if the queue contained the
340	+	* specified element (or equivalently, if the queue changed as a
341	+	* result of the call).
342	+	*
343	+	* <p>This implementation iterates over the queue looking for the
344	+	* specified element.  If it finds the element, it removes the element
345	+	* from the queue using the iterator's remove method.<p>
346	+	*
347	+	*/
348		public boolean remove(Object o) {
349		if (o == null)
350		return false;
#	Line 239 | Line 367 | public class PriorityQueue<E> extends Ab
367		return false;
368		}
369
370	+	/**
371	+	* Returns an iterator over the elements in this queue. The iterator
372	+	* does not return the elements in any particular order.
373	+	*
374	+	* @return an iterator over the elements in this queue.
375	+	*/
376		public Iterator<E> iterator() {
377		return new Itr();
378		}
#	Line 295 | Line 429 | public class PriorityQueue<E> extends Ab
429		}
430		}
431
298	–	/**
299	–	* Returns the number of elements in this priority queue.
300	–	*
301	–	* @return the number of elements in this priority queue.
302	–	*/
432		public int size() {
433		return size;
434		}
#	Line 397 | Line 526 | public class PriorityQueue<E> extends Ab
526		}
527		}
528
529	+
530	+	/**
531	+	* Returns the comparator used to order this collection, or <tt>null</tt>
532	+	* if this collection is sorted according to its elements natural ordering
533	+	* (using <tt>Comparable</tt>).
534	+	*
535	+	* @return the comparator used to order this collection, or <tt>null</tt>
536	+	* if this collection is sorted according to its elements natural ordering.
537	+	*/
538		public Comparator<? super E> comparator() {
539		return comparator;
540		}
#	Line 410 | Line 548 | public class PriorityQueue<E> extends Ab
548		* <tt>Object</tt>) in the proper order.
549		* @param s the stream
550		*/
551	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
551	>	private void writeObject(java.io.ObjectOutputStream s)
552		throws java.io.IOException{
553		// Write out element count, and any hidden stuff
554		s.defaultWriteObject();
#	Line 428 | Line 566 | public class PriorityQueue<E> extends Ab
566		* deserialize it).
567		* @param s the stream
568		*/
569	<	private synchronized void readObject(java.io.ObjectInputStream s)
569	>	private void readObject(java.io.ObjectInputStream s)
570		throws java.io.IOException, ClassNotFoundException {
571		// Read in size, and any hidden stuff
572		s.defaultReadObject();

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