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

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.15 by dholmes, Thu Jul 31 07:18:02 2003 UTC vs.
Revision 1.19 by tim, Mon Aug 4 16:14:48 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	>	* A 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, and is limited to <tt>Integer.MAX_VALUE-1</tt>.
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 105 | Line 108 | public class PriorityQueue<E> extends Ab
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		throw new IllegalArgumentException();
114	<	queue = (E[]) new Object[initialCapacity + 1];
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; or 1 if the collection is empty.
121	>	* size of the specified collection (bounded by
122	>	* <tt>Integer.MAX_VALUE-1</tt>); 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'
#	Line 132 | Line 136 | public class PriorityQueue<E> extends Ab
136		* @throws NullPointerException if <tt>c</tt> or any element within it
137		* is <tt>null</tt>
138		*/
139	<	public PriorityQueue(Collection<E> c) {
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;
145
146	<	queue = (E[]) new Object[initialCapacity + 1];
146	>	this.queue = new Object[initialCapacity + 1];
147	>
148	>	// FIXME: if c is larger than Integer.MAX_VALUE we'll
149	>	// overflow the array
150
151		if (c instanceof Sorted) {
152	<	// FIXME: this code assumes too much
146	<	comparator = ((Sorted)c).comparator();
147	<	for (Iterator<E> i = c.iterator(); i.hasNext(); )
148	<	queue[++size] = i.next();
152	>	comparator = (Comparator<? super E>)((Sorted)c).comparator();
153		} else {
154		comparator = null;
151	–	for (Iterator<E> i = c.iterator(); i.hasNext(); )
152	–	add(i.next());
155		}
156	+
157	+	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
158	+	add(i.next());
159		}
160
161		// Queue Methods
#	Line 158 | Line 163 | public class PriorityQueue<E> extends Ab
163		/**
164		* Add the specified element to this priority queue.
165		*
161	–	* @param element the element to add.
166		* @return <tt>true</tt>
167		* @throws ClassCastException if the specified element cannot be compared
168		* with elements currently in the priority queue according
169		* to the priority queue's ordering.
170	<	* @throws NullPointerException if the specified element is null.
170	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
171		*/
172	<	public boolean offer(E element) {
173	<	if (element == null)
172	>	public boolean offer(E o) {
173	>	if (o == null)
174		throw new NullPointerException();
175		modCount++;
176		++size;
177
178		// Grow backing store if necessary
179	+	// FIXME: watch for overflow
180	+	// FIXME: what if we're full?
181		while (size >= queue.length) {
182	<	E[] newQueue = (E[]) new Object[2 * queue.length];
182	>	Object[] newQueue = new Object[2 * queue.length];
183		System.arraycopy(queue, 0, newQueue, 0, queue.length);
184		queue = newQueue;
185		}
186
187	<	queue[size] = element;
187	>	queue[size] = o;
188		fixUp(size);
189		return true;
190		}
#	Line 186 | Line 192 | public class PriorityQueue<E> extends Ab
192		public E poll() {
193		if (size == 0)
194		return null;
195	<	return remove(1);
195	>	return (E) remove(1);
196		}
197
198		public E peek() {
199	<	return queue[1];
199	>	return (E) queue[1];
200		}
201
202		// Collection Methods
#	Line 203 | Line 209 | public class PriorityQueue<E> extends Ab
209		* with elements currently in the priority queue according
210		* to the priority queue's ordering.
211		*/
212	<	public boolean add(E element) {
213	<	return super.add(element);
212	>	public boolean add(E o) {
213	>	return super.add(o);
214		}
215
216		/**
211	–	* @throws NullPointerException if any element is <tt>null</tt>.
217		* @throws ClassCastException if any element cannot be compared
218		* with elements currently in the priority queue according
219		* to the priority queue's ordering.
220	+	* @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
221	+	* is <tt>null</tt>
222		*/
223		public boolean addAll(Collection<? extends E> c) {
224		return super.addAll(c);
#	Line 223 | Line 230 | public class PriorityQueue<E> extends Ab
230
231		if (comparator == null) {
232		for (int i = 1; i <= size; i++) {
233	<	if (((Comparable)queue[i]).compareTo(o) == 0) {
233	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
234		remove(i);
235		return true;
236		}
237		}
238		} else {
239		for (int i = 1; i <= size; i++) {
240	<	if (comparator.compare(queue[i], (E)o) == 0) {
240	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
241		remove(i);
242		return true;
243		}
#	Line 272 | Line 279 | public class PriorityQueue<E> extends Ab
279		checkForComodification();
280		if (cursor > size)
281		throw new NoSuchElementException();
282	<	E result = queue[cursor];
282	>	E result = (E) queue[cursor];
283		lastRet = cursor++;
284		return result;
285		}
#	Line 328 | Line 335 | public class PriorityQueue<E> extends Ab
335		assert i <= size;
336		modCount++;
337
338	<	E result = queue[i];
338	>	E result = (E) queue[i];
339		queue[i] = queue[size];
340		queue[size--] = null;  // Drop extra ref to prevent memory leak
341		if (i <= size)
#	Line 349 | Line 356 | public class PriorityQueue<E> extends Ab
356		if (comparator == null) {
357		while (k > 1) {
358		int j = k >> 1;
359	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
359	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
360		break;
361	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
361	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
362		k = j;
363		}
364		} else {
365		while (k > 1) {
366		int j = k >> 1;
367	<	if (comparator.compare(queue[j], queue[k]) <= 0)
367	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
368		break;
369	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
369	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
370		k = j;
371		}
372		}
#	Line 378 | Line 385 | public class PriorityQueue<E> extends Ab
385		int j;
386		if (comparator == null) {
387		while ((j = k << 1) <= size) {
388	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
388	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
389		j++; // j indexes smallest kid
390	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
390	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
391		break;
392	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
392	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
393		k = j;
394		}
395		} else {
396		while ((j = k << 1) <= size) {
397	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
397	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
398		j++; // j indexes smallest kid
399	<	if (comparator.compare(queue[k], queue[j]) <= 0)
399	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
400		break;
401	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
401	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
402		k = j;
403		}
404		}
405		}
406
407	<	public Comparator comparator() {
407	>	public Comparator<? super E> comparator() {
408		return comparator;
409		}
410
#	Line 435 | Line 442 | public class PriorityQueue<E> extends Ab
442
443		// Read in array length and allocate array
444		int arrayLength = s.readInt();
445	<	queue = (E[]) new Object[arrayLength];
445	>	queue = new Object[arrayLength];
446
447		// Read in all elements in the proper order.
448		for (int i=0; i<size; i++)
449	<	queue[i] = (E)s.readObject();
449	>	queue[i] = s.readObject();
450		}
451
452		}

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