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

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.14 by tim, Mon Jul 28 16:00:19 2003 UTC vs.
Revision 1.20 by dholmes, Tue Aug 5 06:18:17 2003 UTC

#	Line 3 | Line 3
3		/**
4		* An unbounded priority queue based on a priority heap.  This queue orders
5		* elements according to an order specified at construction time, which is
6	<	* specified in the same manner as {@link TreeSet} and {@link TreeMap}:
7	<	* elements are ordered
6	>	* specified in the same manner as {@link java.util.TreeSet} and
7	>	* {@link java.util.TreeMap}: elements are ordered
8		* either according to their <i>natural order</i> (see {@link Comparable}), or
9	<	* according to a {@link Comparator}, depending on which constructor is used.
10	<	* The <em>head</em> of this queue is the least element with respect to the
11	<	* specified ordering. If multiple elements are tied for least value, the
9	>	* according to a {@link java.util.Comparator}, depending on which
10	>	* constructor is used.
11	>	* <p>The <em>head</em> of this queue is the <em>least</em> element with
12	>	* respect to the specified ordering.
13	>	* If multiple elements are tied for least value, the
14		* head is one of those elements. A priority queue does not permit
15		* <tt>null</tt> elements.
16		*
#	Line 20 | Line 22
22		*
23		* <p>A priority queue has a <i>capacity</i>.  The capacity is the
24		* size of the array used internally to store the elements on the
25	<	* queue.  It is always at least as large as the queue size.  As
25	>	* queue.
26	>	* It is always at least as large as the queue size.  As
27		* elements are added to a priority queue, its capacity grows
28		* automatically.  The details of the growth policy are not specified.
29		*
#	Line 38 | Line 41
41		* @author Josh Bloch
42		*/
43		public class PriorityQueue<E> extends AbstractQueue<E>
44	<	implements Queue<E>, java.io.Serializable {
44	>	implements Sorted, Queue<E>, java.io.Serializable {
45
46		private static final int DEFAULT_INITIAL_CAPACITY = 11;
47
#	Line 55 | Line 58 | public class PriorityQueue<E> extends Ab
58		*
59		* queue.length must be >= 2, even if size == 0.
60		*/
61	<	private transient E[] queue;
61	>	private transient Object[] queue;
62
63		/**
64		* The number of elements in the priority queue.
#	Line 66 | Line 69 | public class PriorityQueue<E> extends Ab
69		* The comparator, or null if priority queue uses elements'
70		* natural ordering.
71		*/
72	<	private final Comparator<E> comparator;
72	>	private final Comparator<? super E> comparator;
73
74		/**
75		* The number of times this priority queue has been
#	Line 102 | Line 105 | public class PriorityQueue<E> extends Ab
105		* @param comparator the comparator used to order this priority queue.
106		* If <tt>null</tt> then the order depends on the elements' natural
107		* ordering.
108	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
109	+	* than 1
110		*/
111	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
111	>	public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
112		if (initialCapacity < 1)
113	<	initialCapacity = 1;
114	<	queue = (E[]) new Object[initialCapacity + 1];
113	>	throw new IllegalArgumentException();
114	>	this.queue = new Object[initialCapacity + 1];
115		this.comparator = comparator;
116		}
117
118		/**
119		* Create a <tt>PriorityQueue</tt> containing the elements in the specified
120		* collection.  The priority queue has an initial capacity of 110% of the
121	<	* size of the specified collection. If the specified collection
121	>	* size of the specified collection or 1 if the collection is empty.
122	>	* If the specified collection
123		* implements the {@link Sorted} interface, the priority queue will be
124		* sorted according to the same comparator, or according to its elements'
125		* natural order if the collection is sorted according to its elements'
#	Line 121 | Line 127 | public class PriorityQueue<E> extends Ab
127		* <tt>Sorted</tt>, the priority queue is ordered according to
128		* its elements' natural order.
129		*
130	<	* @param initialElements the collection whose elements are to be placed
130	>	* @param c the collection whose elements are to be placed
131		*        into this priority queue.
132		* @throws ClassCastException if elements of the specified collection
133		*         cannot be compared to one another according to the priority
134		*         queue's ordering.
135	<	* @throws NullPointerException if the specified collection or an
136	<	*         element of the specified collection is <tt>null</tt>.
135	>	* @throws NullPointerException if <tt>c</tt> or any element within it
136	>	* is <tt>null</tt>
137		*/
138	<	public PriorityQueue(Collection<E> initialElements) {
139	<	int sz = initialElements.size();
138	>	public PriorityQueue(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;
138	–	queue = (E[]) new Object[initialCapacity + 1];
144
145	<	if (initialElements instanceof Sorted) {
146	<	comparator = ((Sorted)initialElements).comparator();
147	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
148	<	queue[++size] = i.next();
145	>	this.queue = new Object[initialCapacity + 1];
146	>
147	>	if (c instanceof Sorted) {
148	>	comparator = (Comparator<? super E>)((Sorted)c).comparator();
149		} else {
150		comparator = null;
146	–	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
147	–	add(i.next());
151		}
152	+
153	+	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
154	+	add(i.next());
155		}
156
157		// Queue Methods
#	Line 153 | Line 159 | public class PriorityQueue<E> extends Ab
159		/**
160		* Add the specified element to this priority queue.
161		*
156	–	* @param element the element to add.
162		* @return <tt>true</tt>
163		* @throws ClassCastException if the specified element cannot be compared
164		* with elements currently in the priority queue according
165		* to the priority queue's ordering.
166	<	* @throws NullPointerException if the specified element is null.
166	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
167		*/
168	<	public boolean offer(E element) {
169	<	if (element == null)
168	>	public boolean offer(E o) {
169	>	if (o == null)
170		throw new NullPointerException();
171		modCount++;
172		++size;
173
174		// Grow backing store if necessary
175		while (size >= queue.length) {
176	<	E[] newQueue = (E[]) new Object[2 * queue.length];
176	>	Object[] newQueue = new Object[2 * queue.length];
177		System.arraycopy(queue, 0, newQueue, 0, queue.length);
178		queue = newQueue;
179		}
180
181	<	queue[size] = element;
181	>	queue[size] = o;
182		fixUp(size);
183		return true;
184		}
#	Line 181 | Line 186 | public class PriorityQueue<E> extends Ab
186		public E poll() {
187		if (size == 0)
188		return null;
189	<	return remove(1);
189	>	return (E) remove(1);
190		}
191
192		public E peek() {
193	<	return queue[1];
193	>	return (E) queue[1];
194		}
195
196		// Collection Methods
#	Line 194 | Line 199 | public class PriorityQueue<E> extends Ab
199
200		/**
201		* @throws NullPointerException if the specified element is <tt>null</tt>.
202	+	* @throws ClassCastException if the specified element cannot be compared
203	+	* with elements currently in the priority queue according
204	+	* to the priority queue's ordering.
205		*/
206	<	public boolean add(E element) {
207	<	return super.add(element);
206	>	public boolean add(E o) {
207	>	return super.add(o);
208		}
209
210		/**
211	<	* @throws NullPointerException if any element is <tt>null</tt>.
211	>	* @throws ClassCastException if any element cannot be compared
212	>	* with elements currently in the priority queue according
213	>	* 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>
216		*/
217		public boolean addAll(Collection<? extends E> c) {
218		return super.addAll(c);
219		}
220
209	–	/**
210	–	* @throws NullPointerException if the specified element is <tt>null</tt>.
211	–	*/
221		public boolean remove(Object o) {
222		if (o == null)
223	<	throw new NullPointerException();
223	>	return false;
224
225		if (comparator == null) {
226		for (int i = 1; i <= size; i++) {
227	<	if (((Comparable)queue[i]).compareTo(o) == 0) {
227	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
228		remove(i);
229		return true;
230		}
231		}
232		} else {
233		for (int i = 1; i <= size; i++) {
234	<	if (comparator.compare(queue[i], (E)o) == 0) {
234	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
235		remove(i);
236		return true;
237		}
#	Line 231 | Line 240 | public class PriorityQueue<E> extends Ab
240		return false;
241		}
242
234	–	/**
235	–	* Returns an iterator over the elements in this priority queue.  The
236	–	* 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>.
239	–	*
240	–	* @return an <tt>Iterator</tt> over the elements in this priority queue.
241	–	*/
243		public Iterator<E> iterator() {
244		return new Itr();
245		}
#	Line 272 | Line 273 | public class PriorityQueue<E> extends Ab
273		checkForComodification();
274		if (cursor > size)
275		throw new NoSuchElementException();
276	<	E result = queue[cursor];
276	>	E result = (E) queue[cursor];
277		lastRet = cursor++;
278		return result;
279		}
#	Line 328 | Line 329 | public class PriorityQueue<E> extends Ab
329		assert i <= size;
330		modCount++;
331
332	<	E result = queue[i];
332	>	E result = (E) queue[i];
333		queue[i] = queue[size];
334		queue[size--] = null;  // Drop extra ref to prevent memory leak
335		if (i <= size)
#	Line 349 | Line 350 | public class PriorityQueue<E> extends Ab
350		if (comparator == null) {
351		while (k > 1) {
352		int j = k >> 1;
353	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
353	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
354		break;
355	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
355	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
356		k = j;
357		}
358		} else {
359		while (k > 1) {
360		int j = k >> 1;
361	<	if (comparator.compare(queue[j], queue[k]) <= 0)
361	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
362		break;
363	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
363	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
364		k = j;
365		}
366		}
#	Line 378 | Line 379 | public class PriorityQueue<E> extends Ab
379		int j;
380		if (comparator == null) {
381		while ((j = k << 1) <= size) {
382	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
382	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
383		j++; // j indexes smallest kid
384	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
384	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
385		break;
386	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
386	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
387		k = j;
388		}
389		} else {
390		while ((j = k << 1) <= size) {
391	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
391	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
392		j++; // j indexes smallest kid
393	<	if (comparator.compare(queue[k], queue[j]) <= 0)
393	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
394		break;
395	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
395	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
396		k = j;
397		}
398		}
399		}
400
401	<	public Comparator comparator() {
401	>	public Comparator<? super E> comparator() {
402		return comparator;
403		}
404
#	Line 435 | Line 436 | public class PriorityQueue<E> extends Ab
436
437		// Read in array length and allocate array
438		int arrayLength = s.readInt();
439	<	queue = (E[]) new Object[arrayLength];
439	>	queue = new Object[arrayLength];
440
441		// Read in all elements in the proper order.
442		for (int i=0; i<size; i++)
443	<	queue[i] = (E)s.readObject();
443	>	queue[i] = s.readObject();
444		}
445
446		}

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