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

Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.10 by tim, Sat Jul 26 13:17:51 2003 UTC vs.
Revision 1.15 by dholmes, Thu Jul 31 07:18:02 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}: elements are ordered
6	>	* specified in the same manner as {@link TreeSet} and {@link TreeMap}:
7	>	* 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.
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
13	>	* <tt>null</tt> elements.
14	>	*
15	>	* <p>The {@link #remove()} and {@link #poll()} methods remove and
16	>	* return the head of the queue.
17	>	*
18	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
19	>	* not delete, the head of the queue.
20		*
21		* <p>A priority queue has a <i>capacity</i>.  The capacity is the
22		* size of the array used internally to store the elements on the
#	Line 17 | Line 24
24		* elements are added to a priority queue, its capacity grows
25		* automatically.  The details of the growth policy are not specified.
26		*
27	<	*<p>Implementation note: this implementation provides O(log(n)) time
28	<	*for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
29	<	*<tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
30	<	*<tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
31	<	*constant time for the retrieval methods (<tt>peek</tt>,
32	<	*<tt>element</tt>, and <tt>size</tt>).
27	>	* <p>Implementation note: this implementation provides O(log(n)) time
28	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
29	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
30	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
31	>	* constant time for the retrieval methods (<tt>peek</tt>,
32	>	* <tt>element</tt>, and <tt>size</tt>).
33		*
34		* <p>This class is a member of the
35		* <a href="{@docRoot}/../guide/collections/index.html">
#	Line 31 | Line 38
38		* @author Josh Bloch
39		*/
40		public class PriorityQueue<E> extends AbstractQueue<E>
41	<	implements Queue<E>,
42	<	java.io.Serializable {
41	>	implements Queue<E>, java.io.Serializable {
42	>
43		private static final int DEFAULT_INITIAL_CAPACITY = 11;
44
45		/**
#	Line 68 | Line 75 | public class PriorityQueue<E> extends Ab
75		private transient int modCount = 0;
76
77		/**
78	<	* Create a new priority queue with the default initial capacity
78	>	* Create a <tt>PriorityQueue</tt> with the default initial capacity
79		* (11) that orders its elements according to their natural
80		* ordering (using <tt>Comparable</tt>.)
81		*/
82		public PriorityQueue() {
83	<	this(DEFAULT_INITIAL_CAPACITY);
83	>	this(DEFAULT_INITIAL_CAPACITY, null);
84		}
85
86		/**
87	<	* Create a new priority queue with the specified initial capacity
87	>	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
88		* that orders its elements according to their natural ordering
89		* (using <tt>Comparable</tt>.)
90		*
#	Line 88 | Line 95 | public class PriorityQueue<E> extends Ab
95		}
96
97		/**
98	<	* Create a new priority queue with the specified initial capacity (11)
98	>	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
99		* that orders its elements according to the specified comparator.
100		*
101		* @param initialCapacity the initial capacity for this priority queue.
102		* @param comparator the comparator used to order this priority queue.
103	+	* If <tt>null</tt> then the order depends on the elements' natural
104	+	* ordering.
105	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
106	+	* than 1
107		*/
108		public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
109		if (initialCapacity < 1)
110	<	initialCapacity = 1;
110	>	throw new IllegalArgumentException();
111		queue = (E[]) new Object[initialCapacity + 1];
112		this.comparator = comparator;
113		}
114
115		/**
116	<	* Create a new priority queue containing the elements in the specified
116	>	* Create a <tt>PriorityQueue</tt> containing the elements in the specified
117		* collection.  The priority queue has an initial capacity of 110% of the
118	<	* size of the specified collection. If the specified collection
118	>	* size of the specified collection; or 1 if the collection is empty.
119	>	* If the specified collection
120		* implements the {@link Sorted} interface, the priority queue will be
121		* sorted according to the same comparator, or according to its elements'
122		* natural order if the collection is sorted according to its elements'
#	Line 112 | Line 124 | public class PriorityQueue<E> extends Ab
124		* <tt>Sorted</tt>, the priority queue is ordered according to
125		* its elements' natural order.
126		*
127	<	* @param initialElements the collection whose elements are to be placed
127	>	* @param c the collection whose elements are to be placed
128		*        into this priority queue.
129		* @throws ClassCastException if elements of the specified collection
130		*         cannot be compared to one another according to the priority
131		*         queue's ordering.
132	<	* @throws NullPointerException if the specified collection or an
133	<	*         element of the specified collection is <tt>null</tt>.
132	>	* @throws NullPointerException if <tt>c</tt> or any element within it
133	>	* is <tt>null</tt>
134		*/
135	<	public PriorityQueue(Collection<E> initialElements) {
136	<	int sz = initialElements.size();
135	>	public PriorityQueue(Collection<E> c) {
136	>	int sz = c.size();
137		int initialCapacity = (int)Math.min((sz * 110L) / 100,
138		Integer.MAX_VALUE - 1);
139		if (initialCapacity < 1)
140		initialCapacity = 1;
129	–	queue = (E[]) new Object[initialCapacity + 1];
141
142	+	queue = (E[]) new Object[initialCapacity + 1];
143
144	<	if (initialElements instanceof Sorted) {
145	<	comparator = ((Sorted)initialElements).comparator();
146	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
144	>	if (c instanceof Sorted) {
145	>	// 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();
149		} else {
150		comparator = null;
151	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
151	>	for (Iterator<E> i = c.iterator(); i.hasNext(); )
152		add(i.next());
153		}
154		}
#	Line 143 | Line 156 | public class PriorityQueue<E> extends Ab
156		// Queue Methods
157
158		/**
159	<	* 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.
159	>	* Add the specified element to this priority queue.
160		*
161	<	* @return the minimal element from this priority queue if it contains
162	<	*         one or more elements, otherwise <tt>null</tt>.
161	>	* @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.
167		*/
168	+	public boolean offer(E element) {
169	+	if (element == 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];
177	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
178	+	queue = newQueue;
179	+	}
180	+
181	+	queue[size] = element;
182	+	fixUp(size);
183	+	return true;
184	+	}
185	+
186		public E poll() {
187		if (size == 0)
188		return null;
189		return remove(1);
190		}
191
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	–	*/
192		public E peek() {
193		return queue[1];
194		}
195
196		// Collection Methods
197
198	+	// these first two override just to get the throws docs
199	+
200		/**
201	<	* 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
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.
191	<	* @throws NullPointerException if the specified element is null.
203	>	* with elements currently in the priority queue according
204	>	* to the priority queue's ordering.
205		*/
206	<	public boolean remove(Object element) {
207	<	if (element == null)
208	<	throw new NullPointerException();
206	>	public boolean add(E element) {
207	>	return super.add(element);
208	>	}
209	>
210	>	/**
211	>	* @throws NullPointerException if any 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	>	*/
216	>	public boolean addAll(Collection<? extends E> c) {
217	>	return super.addAll(c);
218	>	}
219	>
220	>	public boolean remove(Object o) {
221	>	if (o == null)
222	>	return false;
223
224		if (comparator == null) {
225		for (int i = 1; i <= size; i++) {
226	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
226	>	if (((Comparable)queue[i]).compareTo(o) == 0) {
227		remove(i);
228		return true;
229		}
230		}
231		} else {
232		for (int i = 1; i <= size; i++) {
233	<	if (comparator.compare(queue[i], (E) element) == 0) {
233	>	if (comparator.compare(queue[i], (E)o) == 0) {
234		remove(i);
235		return true;
236		}
#	Line 212 | Line 239 | public class PriorityQueue<E> extends Ab
239		return false;
240		}
241
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	–	*/
242		public Iterator<E> iterator() {
243		return new Itr();
244		}
#	Line 286 | Line 305 | public class PriorityQueue<E> extends Ab
305		}
306
307		/**
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 = (E[]) new Object[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	–	/**
308		* Remove all elements from the priority queue.
309		*/
310		public void clear() {
#	Line 406 | Line 397 | public class PriorityQueue<E> extends Ab
397		}
398		}
399
409	–	/**
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	–	*/
400		public Comparator comparator() {
401		return comparator;
402		}
#	Line 459 | Line 443 | public class PriorityQueue<E> extends Ab
443		}
444
445		}
446	+

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