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

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.13 by dl, Mon Jul 28 10:08:24 2003 UTC vs.
Revision 1.21 by dholmes, Tue Aug 5 06:49:51 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
12	<	* head is one of those elements. A priority queue does not permit
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	<	*
16	>	*
17		* <p>The {@link #remove()} and {@link #poll()} methods remove and
18		* return the head of the queue.
19		*
#	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 75 | Line 78 | public class PriorityQueue<E> extends Ab
78		private transient int modCount = 0;
79
80		/**
81	<	* Create a <tt>PriorityQueue</tt> with the default initial capacity
81	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
82		* (11) that orders its elements according to their natural
83		* ordering (using <tt>Comparable</tt>.)
84		*/
#	Line 84 | Line 87 | public class PriorityQueue<E> extends Ab
87		}
88
89		/**
90	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
90	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
91		* that orders its elements according to their natural ordering
92		* (using <tt>Comparable</tt>.)
93		*
#	Line 95 | Line 98 | public class PriorityQueue<E> extends Ab
98		}
99
100		/**
101	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
101	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
102		* that orders its elements according to the specified comparator.
103		*
104		* @param initialCapacity the initial capacity for this priority queue.
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
119	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
120	>	* specified collection.
121	>	* The priority queue has an initial capacity of 110% of the
122	>	* size of the specified collection or 1 if the collection is empty.
123	>	* If the specified collection
124		* implements the {@link Sorted} interface, the priority queue will be
125		* sorted according to the same comparator, or according to its elements'
126		* natural order if the collection is sorted according to its elements'
#	Line 121 | Line 128 | public class PriorityQueue<E> extends Ab
128		* <tt>Sorted</tt>, the priority queue is ordered according to
129		* its elements' natural order.
130		*
131	<	* @param initialElements the collection whose elements are to be placed
131	>	* @param c the collection whose elements are to be placed
132		*        into this priority queue.
133		* @throws ClassCastException if elements of the specified collection
134		*         cannot be compared to one another according to the priority
135		*         queue's ordering.
136	<	* @throws NullPointerException if the specified collection or an
137	<	*         element of the specified collection is <tt>null</tt>.
136	>	* @throws NullPointerException if <tt>c</tt> or any element within it
137	>	* is <tt>null</tt>
138		*/
139	<	public PriorityQueue(Collection<E> initialElements) {
140	<	int sz = initialElements.size();
139	>	public PriorityQueue(Collection<? extends E> c) {
140	>	int sz = c.size();
141		int initialCapacity = (int)Math.min((sz * 110L) / 100,
142		Integer.MAX_VALUE - 1);
143		if (initialCapacity < 1)
144		initialCapacity = 1;
138	–	queue = (E[]) new Object[initialCapacity + 1];
145
146	<	if (initialElements instanceof Sorted) {
147	<	comparator = ((Sorted)initialElements).comparator();
148	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
149	<	queue[++size] = i.next();
146	>	this.queue = new Object[initialCapacity + 1];
147	>
148	>	if (c instanceof Sorted) {
149	>	comparator = (Comparator<? super E>)((Sorted)c).comparator();
150		} else {
151		comparator = null;
146	–	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
147	–	add(i.next());
152		}
153	+
154	+	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
155	+	add(i.next());
156		}
157
158		// Queue Methods
#	Line 153 | Line 160 | public class PriorityQueue<E> extends Ab
160		/**
161		* Add the specified element to this priority queue.
162		*
156	–	* @param element the element to add.
163		* @return <tt>true</tt>
164		* @throws ClassCastException if the specified element cannot be compared
165		* with elements currently in the priority queue according
166		* to the priority queue's ordering.
167	<	* @throws NullPointerException if the specified element is null.
167	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
168		*/
169	<	public boolean offer(E element) {
170	<	if (element == null)
169	>	public boolean offer(E o) {
170	>	if (o == null)
171		throw new NullPointerException();
172		modCount++;
173		++size;
174
175		// Grow backing store if necessary
176		while (size >= queue.length) {
177	<	E[] newQueue = (E[]) new Object[2 * queue.length];
177	>	Object[] newQueue = new Object[2 * queue.length];
178		System.arraycopy(queue, 0, newQueue, 0, queue.length);
179		queue = newQueue;
180		}
181
182	<	queue[size] = element;
182	>	queue[size] = o;
183		fixUp(size);
184		return true;
185		}
#	Line 181 | Line 187 | public class PriorityQueue<E> extends Ab
187		public E poll() {
188		if (size == 0)
189		return null;
190	<	return remove(1);
190	>	return (E) remove(1);
191		}
192
193		public E peek() {
194	<	return queue[1];
194	>	return (E) queue[1];
195		}
196
197		// Collection Methods
#	Line 194 | Line 200 | public class PriorityQueue<E> extends Ab
200
201		/**
202		* @throws NullPointerException if the specified element is <tt>null</tt>.
203	+	* @throws ClassCastException if the specified element cannot be compared
204	+	* with elements currently in the priority queue according
205	+	* to the priority queue's ordering.
206		*/
207	<	public boolean add(E element) {
208	<	return super.add(element);
207	>	public boolean add(E o) {
208	>	return super.add(o);
209		}
210
202	–	//    /**
203	–	//     * @throws NullPointerException if any element is <tt>null</tt>.
204	–	//     */
205	–	//    public boolean addAll(Collection c) {
206	–	//        return super.addAll(c);
207	–	//    }
208	–
211		/**
212	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
212	>	* @throws ClassCastException if any element cannot be compared
213	>	* with elements currently in the priority queue according
214	>	* to the priority queue's ordering.
215	>	* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
216	>	* is <tt>null</tt>
217		*/
218	+	public boolean addAll(Collection<? extends E> c) {
219	+	return super.addAll(c);
220	+	}
221	+
222		public boolean remove(Object o) {
223		if (o == null)
224	<	throw new NullPointerException();
224	>	return false;
225
226		if (comparator == null) {
227		for (int i = 1; i <= size; i++) {
228	<	if (((Comparable)queue[i]).compareTo(o) == 0) {
228	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
229		remove(i);
230		return true;
231		}
232		}
233		} else {
234		for (int i = 1; i <= size; i++) {
235	<	if (comparator.compare(queue[i], (E)o) == 0) {
235	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
236		remove(i);
237		return true;
238		}
#	Line 231 | Line 241 | public class PriorityQueue<E> extends Ab
241		return false;
242		}
243
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	–	*/
244		public Iterator<E> iterator() {
245		return new Itr();
246		}
#	Line 272 | Line 274 | public class PriorityQueue<E> extends Ab
274		checkForComodification();
275		if (cursor > size)
276		throw new NoSuchElementException();
277	<	E result = queue[cursor];
277	>	E result = (E) queue[cursor];
278		lastRet = cursor++;
279		return result;
280		}
#	Line 328 | Line 330 | public class PriorityQueue<E> extends Ab
330		assert i <= size;
331		modCount++;
332
333	<	E result = queue[i];
333	>	E result = (E) queue[i];
334		queue[i] = queue[size];
335		queue[size--] = null;  // Drop extra ref to prevent memory leak
336		if (i <= size)
#	Line 349 | Line 351 | public class PriorityQueue<E> extends Ab
351		if (comparator == null) {
352		while (k > 1) {
353		int j = k >> 1;
354	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
354	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
355		break;
356	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
356	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
357		k = j;
358		}
359		} else {
360		while (k > 1) {
361		int j = k >> 1;
362	<	if (comparator.compare(queue[j], queue[k]) <= 0)
362	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
363		break;
364	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
364	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
365		k = j;
366		}
367		}
#	Line 378 | Line 380 | public class PriorityQueue<E> extends Ab
380		int j;
381		if (comparator == null) {
382		while ((j = k << 1) <= size) {
383	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
383	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
384		j++; // j indexes smallest kid
385	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
385	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
386		break;
387	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
387	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
388		k = j;
389		}
390		} else {
391		while ((j = k << 1) <= size) {
392	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
392	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
393		j++; // j indexes smallest kid
394	<	if (comparator.compare(queue[k], queue[j]) <= 0)
394	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
395		break;
396	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
396	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
397		k = j;
398		}
399		}
400		}
401
402	<	public Comparator comparator() {
402	>	public Comparator<? super E> comparator() {
403		return comparator;
404		}
405
#	Line 435 | Line 437 | public class PriorityQueue<E> extends Ab
437
438		// Read in array length and allocate array
439		int arrayLength = s.readInt();
440	<	queue = (E[]) new Object[arrayLength];
440	>	queue = new Object[arrayLength];
441
442		// Read in all elements in the proper order.
443		for (int i=0; i<size; i++)
444	<	queue[i] = (E)s.readObject();
444	>	queue[i] = s.readObject();
445		}
446
447		}

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