ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

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

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.9 by dl, Sun Jul 13 22:51:22 2003 UTC vs.
Revision 1.18 by dholmes, Mon Aug 4 01:48:39 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}: 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 {@link #peek}, {@link #poll}, and {@link #remove} methods return the
11	<	* minimal element with respect to the specified ordering.  If multiple
12	<	* elements are tied for least value, no guarantees are made as to
13	<	* which of these elements is returned.
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	>	*
17	>	* <p>The {@link #remove()} and {@link #poll()} methods remove and
18	>	* return the head of the queue.
19	>	*
20	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
21	>	* not delete, the head of the queue.
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		*
30	<	*<p>Implementation note: this implementation provides O(log(n)) time
31	<	*for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
32	<	*<tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
33	<	*<tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
34	<	*constant time for the retrieval methods (<tt>peek</tt>,
35	<	*<tt>element</tt>, and <tt>size</tt>).
30	>	* <p>Implementation note: this implementation provides O(log(n)) time
31	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
32	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
33	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
34	>	* constant time for the retrieval methods (<tt>peek</tt>,
35	>	* <tt>element</tt>, and <tt>size</tt>).
36		*
37		* <p>This class is a member of the
38		* <a href="{@docRoot}/../guide/collections/index.html">
#	Line 31 | Line 41
41		* @author Josh Bloch
42		*/
43		public class PriorityQueue<E> extends AbstractQueue<E>
44	<	implements Queue<E>,
45	<	java.io.Serializable {
44	>	implements Sorted, Queue<E>, java.io.Serializable {
45	>
46		private static final int DEFAULT_INITIAL_CAPACITY = 11;
47
48		/**
#	Line 48 | 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 59 | 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 68 | Line 78 | public class PriorityQueue<E> extends Ab
78		private transient int modCount = 0;
79
80		/**
81	<	* Create a new priority queue with the default initial capacity
81	>	* Create 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		*/
85		public PriorityQueue() {
86	<	this(DEFAULT_INITIAL_CAPACITY);
86	>	this(DEFAULT_INITIAL_CAPACITY, null);
87		}
88
89		/**
90	<	* Create a new priority queue with the specified initial capacity
90	>	* Create 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 88 | Line 98 | public class PriorityQueue<E> extends Ab
98		}
99
100		/**
101	<	* Create a new priority queue with the specified initial capacity (11)
101	>	* Create 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 = new E[initialCapacity + 1];
113	>	throw new IllegalArgumentException();
114	>	this.queue = new Object[initialCapacity + 1];
115		this.comparator = comparator;
116		}
117
118		/**
119	<	* Create a new priority queue containing the elements in the specified
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 (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'
126		* natural order if the collection is sorted according to its elements'
#	Line 112 | 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;
129	–	queue = new E[initialCapacity + 1];
145
146	+	this.queue = new Object[initialCapacity + 1];
147
148	<	if (initialElements instanceof Sorted) {
149	<	comparator = ((Sorted)initialElements).comparator();
150	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
151	<	queue[++size] = i.next();
148	>	// FIXME: if c is larger than Integer.MAX_VALUE we'll
149	>	// overflow the array
150	>
151	>	if (c instanceof Sorted) {
152	>	comparator = ((Sorted)c).comparator();
153		} else {
154		comparator = null;
138	–	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
139	–	add(i.next());
155		}
156	+
157	+	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
158	+	add(i.next());
159		}
160
161		// Queue Methods
162
163		/**
164	<	* Remove and return the minimal element from this priority queue
147	<	* if it contains one or more elements, otherwise return
148	<	* <tt>null</tt>.  The term <i>minimal</i> is defined according to
149	<	* this priority queue's order.
164	>	* Add the specified element to this priority queue.
165		*
166	<	* @return the minimal element from this priority queue if it contains
167	<	*         one or more elements, otherwise <tt>null</tt>.
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 <tt>null</tt>.
171		*/
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	+	Object[] newQueue = new Object[2 * queue.length];
183	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
184	+	queue = newQueue;
185	+	}
186	+
187	+	queue[size] = o;
188	+	fixUp(size);
189	+	return true;
190	+	}
191	+
192		public E poll() {
193		if (size == 0)
194		return null;
195	<	return remove(1);
195	>	return (E) remove(1);
196		}
197
160	–	/**
161	–	* Return, but do not remove, the minimal element from the
162	–	* priority queue, or return <tt>null</tt> if the queue is empty.
163	–	* The term <i>minimal</i> is defined according to this priority
164	–	* queue's order.  This method returns the same object reference
165	–	* that would be returned by by the <tt>poll</tt> method.  The two
166	–	* methods differ in that this method does not remove the element
167	–	* from the priority queue.
168	–	*
169	–	* @return the minimal element from this priority queue if it contains
170	–	*         one or more elements, otherwise <tt>null</tt>.
171	–	*/
198		public E peek() {
199	<	return queue[1];
199	>	return (E) queue[1];
200		}
201
202		// Collection Methods
203
204	+	// these first two override just to get the throws docs
205	+
206		/**
207	<	* Removes a single instance of the specified element from this priority
180	<	* queue, if it is present.  Returns true if this collection contained the
181	<	* specified element (or equivalently, if this collection changed as a
182	<	* result of the call).
183	<	*
184	<	* @param element the element to be removed from this collection,
185	<	* if present.
186	<	* @return <tt>true</tt> if this collection changed as a result of the
187	<	*         call
207	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
208		* @throws ClassCastException if the specified element cannot be compared
209	<	*            with elements currently in the priority queue according
210	<	*            to the priority queue's ordering.
191	<	* @throws NullPointerException if the specified element is null.
209	>	* with elements currently in the priority queue according
210	>	* to the priority queue's ordering.
211		*/
212	<	public boolean remove(Object element) {
213	<	if (element == null)
214	<	throw new NullPointerException();
212	>	public boolean add(E o) {
213	>	return super.add(o);
214	>	}
215	>
216	>	/**
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);
225	>	}
226	>
227	>	public boolean remove(Object o) {
228	>	if (o == null)
229	>	return false;
230
231		if (comparator == null) {
232		for (int i = 1; i <= size; i++) {
233	<	if (((Comparable)queue[i]).compareTo(element) == 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) element) == 0) {
240	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
241		remove(i);
242		return true;
243		}
#	Line 212 | Line 246 | public class PriorityQueue<E> extends Ab
246		return false;
247		}
248
215	–	/**
216	–	* Returns an iterator over the elements in this priority queue.  The
217	–	* elements of the priority queue will be returned by this iterator in the
218	–	* order specified by the queue, which is to say the order they would be
219	–	* returned by repeated calls to <tt>poll</tt>.
220	–	*
221	–	* @return an <tt>Iterator</tt> over the elements in this priority queue.
222	–	*/
249		public Iterator<E> iterator() {
250		return new Itr();
251		}
#	Line 253 | 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 278 | Line 304 | public class PriorityQueue<E> extends Ab
304
305		/**
306		* Returns the number of elements in this priority queue.
307	<	*
307	>	*
308		* @return the number of elements in this priority queue.
309		*/
310		public int size() {
#	Line 286 | Line 312 | public class PriorityQueue<E> extends Ab
312		}
313
314		/**
289	–	* Add the specified element to this priority queue.
290	–	*
291	–	* @param element the element to add.
292	–	* @return true
293	–	* @throws ClassCastException if the specified element cannot be compared
294	–	*            with elements currently in the priority queue according
295	–	*            to the priority queue's ordering.
296	–	* @throws NullPointerException if the specified element is null.
297	–	*/
298	–	public boolean offer(E element) {
299	–	if (element == null)
300	–	throw new NullPointerException();
301	–	modCount++;
302	–	++size;
303	–
304	–	// Grow backing store if necessary
305	–	while (size >= queue.length) {
306	–	E[] newQueue = new E[2 * queue.length];
307	–	System.arraycopy(queue, 0, newQueue, 0, queue.length);
308	–	queue = newQueue;
309	–	}
310	–
311	–	queue[size] = element;
312	–	fixUp(size);
313	–	return true;
314	–	}
315	–
316	–	/**
315		* Remove all elements from the priority queue.
316		*/
317		public void clear() {
#	Line 337 | 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 358 | 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 387 | 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	<	/**
410	<	* Returns the comparator associated with this priority queue, or
411	<	* <tt>null</tt> if it uses its elements' natural ordering.
412	<	*
413	<	* @return the comparator associated with this priority queue, or
414	<	*         <tt>null</tt> if it uses its elements' natural ordering.
415	<	*/
416	<	public Comparator comparator() {
407	>	public Comparator<? super E> comparator() {
408		return comparator;
409		}
410
#	Line 451 | Line 442 | public class PriorityQueue<E> extends Ab
442
443		// Read in array length and allocate array
444		int arrayLength = s.readInt();
445	<	queue = new E[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		}
453	+

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines