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 1.15 by dholmes, Thu Jul 31 07:18:02 2003 UTC vs.
Revision 1.84 by jsr166, Sat Jan 19 18:11:56 2013 UTC

#	Line 1 | Line 1
1	<	package java.util;
1	>	/*
2	>	* Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
3	>	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4	>	*
5	>	* This code is free software; you can redistribute it and/or modify it
6	>	* under the terms of the GNU General Public License version 2 only, as
7	>	* published by the Free Software Foundation.  Oracle designates this
8	>	* particular file as subject to the "Classpath" exception as provided
9	>	* by Oracle in the LICENSE file that accompanied this code.
10	>	*
11	>	* This code is distributed in the hope that it will be useful, but WITHOUT
12	>	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13	>	* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14	>	* version 2 for more details (a copy is included in the LICENSE file that
15	>	* accompanied this code).
16	>	*
17	>	* You should have received a copy of the GNU General Public License version
18	>	* 2 along with this work; if not, write to the Free Software Foundation,
19	>	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20	>	*
21	>	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22	>	* or visit www.oracle.com if you need additional information or have any
23	>	* questions.
24	>	*/
25	>
26	>	package java.util;
27	>	import java.util.stream.Stream;
28	>	import java.util.Spliterator;
29	>	import java.util.stream.Streams;
30	>	import java.util.function.Block;
31
32		/**
33	<	* An unbounded priority queue based on a priority heap.  This queue orders
34	<	* elements according to an order specified at construction time, which is
35	<	* specified in the same manner as {@link TreeSet} and {@link TreeMap}:
36	<	* elements are ordered
37	<	* either according to their <i>natural order</i> (see {@link Comparable}), or
38	<	* according to a {@link Comparator}, depending on which constructor is used.
39	<	* The <em>head</em> of this queue is the least element with respect to the
40	<	* specified ordering. If multiple elements are tied for least value, the
41	<	* head is one of those elements. A priority queue does not permit
42	<	* <tt>null</tt> elements.
43	<	*
44	<	* <p>The {@link #remove()} and {@link #poll()} methods remove and
45	<	* return the head of the queue.
46	<	*
47	<	* <p>The {@link #element()} and {@link #peek()} methods return, but do
48	<	* not delete, the head of the queue.
49	<	*
50	<	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
51	<	* size of the array used internally to store the elements on the
52	<	* queue.  It is always at least as large as the queue size.  As
53	<	* elements are added to a priority queue, its capacity grows
54	<	* automatically.  The details of the growth policy are not specified.
55	<	*
56	<	* <p>Implementation note: this implementation provides O(log(n)) time
57	<	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
58	<	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
59	<	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
60	<	* constant time for the retrieval methods (<tt>peek</tt>,
61	<	* <tt>element</tt>, and <tt>size</tt>).
33	>	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
34	>	* The elements of the priority queue are ordered according to their
35	>	* {@linkplain Comparable natural ordering}, or by a {@link Comparator}
36	>	* provided at queue construction time, depending on which constructor is
37	>	* used.  A priority queue does not permit {@code null} elements.
38	>	* A priority queue relying on natural ordering also does not permit
39	>	* insertion of non-comparable objects (doing so may result in
40	>	* {@code ClassCastException}).
41	>	*
42	>	* <p>The <em>head</em> of this queue is the <em>least</em> element
43	>	* with respect to the specified ordering.  If multiple elements are
44	>	* tied for least value, the head is one of those elements -- ties are
45	>	* broken arbitrarily.  The queue retrieval operations {@code poll},
46	>	* {@code remove}, {@code peek}, and {@code element} access the
47	>	* element at the head of the queue.
48	>	*
49	>	* <p>A priority queue is unbounded, but has an internal
50	>	* <i>capacity</i> governing the size of an array used to store the
51	>	* elements on the queue.  It is always at least as large as the queue
52	>	* size.  As elements are added to a priority queue, its capacity
53	>	* grows automatically.  The details of the growth policy are not
54	>	* specified.
55	>	*
56	>	* <p>This class and its iterator implement all of the
57	>	* <em>optional</em> methods of the {@link Collection} and {@link
58	>	* Iterator} interfaces.  The Iterator provided in method {@link
59	>	* #iterator()} is <em>not</em> guaranteed to traverse the elements of
60	>	* the priority queue in any particular order. If you need ordered
61	>	* traversal, consider using {@code Arrays.sort(pq.toArray())}.
62	>	*
63	>	* <p><strong>Note that this implementation is not synchronized.</strong>
64	>	* Multiple threads should not access a {@code PriorityQueue}
65	>	* instance concurrently if any of the threads modifies the queue.
66	>	* Instead, use the thread-safe {@link
67	>	* java.util.concurrent.PriorityBlockingQueue} class.
68	>	*
69	>	* <p>Implementation note: this implementation provides
70	>	* O(log(n)) time for the enqueing and dequeing methods
71	>	* ({@code offer}, {@code poll}, {@code remove()} and {@code add});
72	>	* linear time for the {@code remove(Object)} and {@code contains(Object)}
73	>	* methods; and constant time for the retrieval methods
74	>	* ({@code peek}, {@code element}, and {@code size}).
75		*
76		* <p>This class is a member of the
77	<	* <a href="{@docRoot}/../guide/collections/index.html">
77	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
78		* Java Collections Framework</a>.
79	+	*
80		* @since 1.5
81	<	* @author Josh Bloch
81	>	* @author Josh Bloch, Doug Lea
82	>	* @param <E> the type of elements held in this collection
83		*/
84		public class PriorityQueue<E> extends AbstractQueue<E>
85	<	implements Queue<E>, java.io.Serializable {
85	>	implements java.io.Serializable {
86	>
87	>	private static final long serialVersionUID = -7720805057305804111L;
88
89		private static final int DEFAULT_INITIAL_CAPACITY = 11;
90
91		/**
92	<	* Priority queue represented as a balanced binary heap: the two children
93	<	* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
94	<	* ordered by comparator, or by the elements' natural ordering, if
95	<	* comparator is null:  For each node n in the heap and each descendant d
96	<	* of n, n <= d.
97	<	*
52	<	* The element with the lowest value is in queue[1], assuming the queue is
53	<	* nonempty.  (A one-based array is used in preference to the traditional
54	<	* zero-based array to simplify parent and child calculations.)
55	<	*
56	<	* queue.length must be >= 2, even if size == 0.
92	>	* Priority queue represented as a balanced binary heap: the two
93	>	* children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
94	>	* priority queue is ordered by comparator, or by the elements'
95	>	* natural ordering, if comparator is null: For each node n in the
96	>	* heap and each descendant d of n, n <= d.  The element with the
97	>	* lowest value is in queue[0], assuming the queue is nonempty.
98		*/
99	<	private transient E[] queue;
99	>	transient Object[] queue; // non-private to simplify nested class access
100
101		/**
102		* The number of elements in the priority queue.
#	Line 66 | Line 107 | public class PriorityQueue<E> extends Ab
107		* The comparator, or null if priority queue uses elements'
108		* natural ordering.
109		*/
110	<	private final Comparator<E> comparator;
110	>	private final Comparator<? super E> comparator;
111
112		/**
113		* The number of times this priority queue has been
114		* <i>structurally modified</i>.  See AbstractList for gory details.
115		*/
116	<	private transient int modCount = 0;
116	>	transient int modCount = 0; // non-private to simplify nested class access
117
118		/**
119	<	* Create a <tt>PriorityQueue</tt> with the default initial capacity
120	<	* (11) that orders its elements according to their natural
121	<	* ordering (using <tt>Comparable</tt>.)
119	>	* Creates a {@code PriorityQueue} with the default initial
120	>	* capacity (11) that orders its elements according to their
121	>	* {@linkplain Comparable natural ordering}.
122		*/
123		public PriorityQueue() {
124		this(DEFAULT_INITIAL_CAPACITY, null);
125		}
126
127		/**
128	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
129	<	* that orders its elements according to their natural ordering
130	<	* (using <tt>Comparable</tt>.)
131	<	*
132	<	* @param initialCapacity the initial capacity for this priority queue.
128	>	* Creates a {@code PriorityQueue} with the specified initial
129	>	* capacity that orders its elements according to their
130	>	* {@linkplain Comparable natural ordering}.
131	>	*
132	>	* @param initialCapacity the initial capacity for this priority queue
133	>	* @throws IllegalArgumentException if {@code initialCapacity} is less
134	>	*         than 1
135		*/
136		public PriorityQueue(int initialCapacity) {
137		this(initialCapacity, null);
138		}
139
140		/**
141	<	* Create a <tt>PriorityQueue</tt> with the specified initial capacity
141	>	* Creates a {@code PriorityQueue} with the specified initial capacity
142		* that orders its elements according to the specified comparator.
143		*
144	<	* @param initialCapacity the initial capacity for this priority queue.
145	<	* @param comparator the comparator used to order this priority queue.
146	<	* If <tt>null</tt> then the order depends on the elements' natural
147	<	* ordering.
148	<	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
149	<	* than 1
150	<	*/
151	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
144	>	* @param  initialCapacity the initial capacity for this priority queue
145	>	* @param  comparator the comparator that will be used to order this
146	>	*         priority queue.  If {@code null}, the {@linkplain Comparable
147	>	*         natural ordering} of the elements will be used.
148	>	* @throws IllegalArgumentException if {@code initialCapacity} is
149	>	*         less than 1
150	>	*/
151	>	public PriorityQueue(int initialCapacity,
152	>	Comparator<? super E> comparator) {
153	>	// Note: This restriction of at least one is not actually needed,
154	>	// but continues for 1.5 compatibility
155		if (initialCapacity < 1)
156		throw new IllegalArgumentException();
157	<	queue = (E[]) new Object[initialCapacity + 1];
157	>	this.queue = new Object[initialCapacity];
158		this.comparator = comparator;
159		}
160
161		/**
162	<	* Create a <tt>PriorityQueue</tt> containing the elements in the specified
163	<	* collection.  The priority queue has an initial capacity of 110% of the
164	<	* size of the specified collection; or 1 if the collection is empty.
165	<	* If the specified collection
166	<	* implements the {@link Sorted} interface, the priority queue will be
167	<	* sorted according to the same comparator, or according to its elements'
122	<	* natural order if the collection is sorted according to its elements'
123	<	* natural order.  If the specified collection does not implement
124	<	* <tt>Sorted</tt>, the priority queue is ordered according to
125	<	* its elements' natural order.
162	>	* Creates a {@code PriorityQueue} containing the elements in the
163	>	* specified collection.  If the specified collection is an instance of
164	>	* a {@link SortedSet} or is another {@code PriorityQueue}, this
165	>	* priority queue will be ordered according to the same ordering.
166	>	* Otherwise, this priority queue will be ordered according to the
167	>	* {@linkplain Comparable natural ordering} of its elements.
168		*
169	<	* @param c the collection whose elements are to be placed
170	<	*        into this priority queue.
169	>	* @param  c the collection whose elements are to be placed
170	>	*         into this priority queue
171		* @throws ClassCastException if elements of the specified collection
172		*         cannot be compared to one another according to the priority
173	<	*         queue's ordering.
174	<	* @throws NullPointerException if <tt>c</tt> or any element within it
175	<	* is <tt>null</tt>
176	<	*/
177	<	public PriorityQueue(Collection<E> c) {
178	<	int sz = c.size();
179	<	int initialCapacity = (int)Math.min((sz * 110L) / 100,
180	<	Integer.MAX_VALUE - 1);
181	<	if (initialCapacity < 1)
182	<	initialCapacity = 1;
173	>	*         queue's ordering
174	>	* @throws NullPointerException if the specified collection or any
175	>	*         of its elements are null
176	>	*/
177	>	@SuppressWarnings("unchecked")
178	>	public PriorityQueue(Collection<? extends E> c) {
179	>	if (c instanceof SortedSet<?>) {
180	>	SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
181	>	this.comparator = (Comparator<? super E>) ss.comparator();
182	>	initElementsFromCollection(ss);
183	>	}
184	>	else if (c instanceof PriorityQueue<?>) {
185	>	PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
186	>	this.comparator = (Comparator<? super E>) pq.comparator();
187	>	initFromPriorityQueue(pq);
188	>	}
189	>	else {
190	>	this.comparator = null;
191	>	initFromCollection(c);
192	>	}
193	>	}
194
195	<	queue = (E[]) new Object[initialCapacity + 1];
195	>	/**
196	>	* Creates a {@code PriorityQueue} containing the elements in the
197	>	* specified priority queue.  This priority queue will be
198	>	* ordered according to the same ordering as the given priority
199	>	* queue.
200	>	*
201	>	* @param  c the priority queue whose elements are to be placed
202	>	*         into this priority queue
203	>	* @throws ClassCastException if elements of {@code c} cannot be
204	>	*         compared to one another according to {@code c}'s
205	>	*         ordering
206	>	* @throws NullPointerException if the specified priority queue or any
207	>	*         of its elements are null
208	>	*/
209	>	@SuppressWarnings("unchecked")
210	>	public PriorityQueue(PriorityQueue<? extends E> c) {
211	>	this.comparator = (Comparator<? super E>) c.comparator();
212	>	initFromPriorityQueue(c);
213	>	}
214
215	<	if (c instanceof Sorted) {
216	<	// FIXME: this code assumes too much
217	<	comparator = ((Sorted)c).comparator();
218	<	for (Iterator<E> i = c.iterator(); i.hasNext(); )
219	<	queue[++size] = i.next();
215	>	/**
216	>	* Creates a {@code PriorityQueue} containing the elements in the
217	>	* specified sorted set.   This priority queue will be ordered
218	>	* according to the same ordering as the given sorted set.
219	>	*
220	>	* @param  c the sorted set whose elements are to be placed
221	>	*         into this priority queue
222	>	* @throws ClassCastException if elements of the specified sorted
223	>	*         set cannot be compared to one another according to the
224	>	*         sorted set's ordering
225	>	* @throws NullPointerException if the specified sorted set or any
226	>	*         of its elements are null
227	>	*/
228	>	@SuppressWarnings("unchecked")
229	>	public PriorityQueue(SortedSet<? extends E> c) {
230	>	this.comparator = (Comparator<? super E>) c.comparator();
231	>	initElementsFromCollection(c);
232	>	}
233	>
234	>	private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
235	>	if (c.getClass() == PriorityQueue.class) {
236	>	this.queue = c.toArray();
237	>	this.size = c.size();
238		} else {
239	<	comparator = null;
151	<	for (Iterator<E> i = c.iterator(); i.hasNext(); )
152	<	add(i.next());
239	>	initFromCollection(c);
240		}
241		}
242
243	<	// Queue Methods
243	>	private void initElementsFromCollection(Collection<? extends E> c) {
244	>	Object[] a = c.toArray();
245	>	// If c.toArray incorrectly doesn't return Object[], copy it.
246	>	if (a.getClass() != Object[].class)
247	>	a = Arrays.copyOf(a, a.length, Object[].class);
248	>	int len = a.length;
249	>	if (len == 1 || this.comparator != null)
250	>	for (int i = 0; i < len; i++)
251	>	if (a[i] == null)
252	>	throw new NullPointerException();
253	>	this.queue = a;
254	>	this.size = a.length;
255	>	}
256
257		/**
258	<	* Add the specified element to this priority queue.
258	>	* Initializes queue array with elements from the given Collection.
259		*
260	<	* @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.
260	>	* @param c the collection
261		*/
262	<	public boolean offer(E element) {
263	<	if (element == null)
264	<	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;
262	>	private void initFromCollection(Collection<? extends E> c) {
263	>	initElementsFromCollection(c);
264	>	heapify();
265		}
266
267	<	public E poll() {
268	<	if (size == 0)
269	<	return null;
270	<	return remove(1);
271	<	}
267	>	/**
268	>	* The maximum size of array to allocate.
269	>	* Some VMs reserve some header words in an array.
270	>	* Attempts to allocate larger arrays may result in
271	>	* OutOfMemoryError: Requested array size exceeds VM limit
272	>	*/
273	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
274
275	<	public E peek() {
276	<	return queue[1];
275	>	/**
276	>	* Increases the capacity of the array.
277	>	*
278	>	* @param minCapacity the desired minimum capacity
279	>	*/
280	>	private void grow(int minCapacity) {
281	>	int oldCapacity = queue.length;
282	>	// Double size if small; else grow by 50%
283	>	int newCapacity = oldCapacity + ((oldCapacity < 64) ?
284	>	(oldCapacity + 2) :
285	>	(oldCapacity >> 1));
286	>	// overflow-conscious code
287	>	if (newCapacity - MAX_ARRAY_SIZE > 0)
288	>	newCapacity = hugeCapacity(minCapacity);
289	>	queue = Arrays.copyOf(queue, newCapacity);
290		}
291
292	<	// Collection Methods
293	<
294	<	// these first two override just to get the throws docs
292	>	private static int hugeCapacity(int minCapacity) {
293	>	if (minCapacity < 0) // overflow
294	>	throw new OutOfMemoryError();
295	>	return (minCapacity > MAX_ARRAY_SIZE) ?
296	>	Integer.MAX_VALUE :
297	>	MAX_ARRAY_SIZE;
298	>	}
299
300		/**
301	<	* @throws NullPointerException if the specified element is <tt>null</tt>.
302	<	* @throws ClassCastException if the specified element cannot be compared
303	<	* with elements currently in the priority queue according
304	<	* to the priority queue's ordering.
301	>	* Inserts the specified element into this priority queue.
302	>	*
303	>	* @return {@code true} (as specified by {@link Collection#add})
304	>	* @throws ClassCastException if the specified element cannot be
305	>	*         compared with elements currently in this priority queue
306	>	*         according to the priority queue's ordering
307	>	* @throws NullPointerException if the specified element is null
308		*/
309	<	public boolean add(E element) {
310	<	return super.add(element);
309	>	public boolean add(E e) {
310	>	return offer(e);
311		}
312
313		/**
314	<	* @throws NullPointerException if any element is <tt>null</tt>.
315	<	* @throws ClassCastException if any element cannot be compared
316	<	* with elements currently in the priority queue according
317	<	* to the priority queue's ordering.
314	>	* Inserts the specified element into this priority queue.
315	>	*
316	>	* @return {@code true} (as specified by {@link Queue#offer})
317	>	* @throws ClassCastException if the specified element cannot be
318	>	*         compared with elements currently in this priority queue
319	>	*         according to the priority queue's ordering
320	>	* @throws NullPointerException if the specified element is null
321		*/
322	<	public boolean addAll(Collection<? extends E> c) {
323	<	return super.addAll(c);
322	>	public boolean offer(E e) {
323	>	if (e == null)
324	>	throw new NullPointerException();
325	>	modCount++;
326	>	int i = size;
327	>	if (i >= queue.length)
328	>	grow(i + 1);
329	>	size = i + 1;
330	>	if (i == 0)
331	>	queue[0] = e;
332	>	else
333	>	siftUp(i, e);
334	>	return true;
335		}
336
337	+	@SuppressWarnings("unchecked")
338	+	public E peek() {
339	+	return (size == 0) ? null : (E) queue[0];
340	+	}
341	+
342	+	private int indexOf(Object o) {
343	+	if (o != null) {
344	+	for (int i = 0; i < size; i++)
345	+	if (o.equals(queue[i]))
346	+	return i;
347	+	}
348	+	return -1;
349	+	}
350	+
351	+	/**
352	+	* Removes a single instance of the specified element from this queue,
353	+	* if it is present.  More formally, removes an element {@code e} such
354	+	* that {@code o.equals(e)}, if this queue contains one or more such
355	+	* elements.  Returns {@code true} if and only if this queue contained
356	+	* the specified element (or equivalently, if this queue changed as a
357	+	* result of the call).
358	+	*
359	+	* @param o element to be removed from this queue, if present
360	+	* @return {@code true} if this queue changed as a result of the call
361	+	*/
362		public boolean remove(Object o) {
363	<	if (o == null)
363	>	int i = indexOf(o);
364	>	if (i == -1)
365		return false;
366	+	else {
367	+	removeAt(i);
368	+	return true;
369	+	}
370	+	}
371
372	<	if (comparator == null) {
373	<	for (int i = 1; i <= size; i++) {
374	<	if (((Comparable)queue[i]).compareTo(o) == 0) {
375	<	remove(i);
376	<	return true;
377	<	}
378	<	}
379	<	} else {
380	<	for (int i = 1; i <= size; i++) {
381	<	if (comparator.compare(queue[i], (E)o) == 0) {
382	<	remove(i);
383	<	return true;
236	<	}
372	>	/**
373	>	* Version of remove using reference equality, not equals.
374	>	* Needed by iterator.remove.
375	>	*
376	>	* @param o element to be removed from this queue, if present
377	>	* @return {@code true} if removed
378	>	*/
379	>	boolean removeEq(Object o) {
380	>	for (int i = 0; i < size; i++) {
381	>	if (o == queue[i]) {
382	>	removeAt(i);
383	>	return true;
384		}
385		}
386		return false;
387		}
388
389	+	/**
390	+	* Returns {@code true} if this queue contains the specified element.
391	+	* More formally, returns {@code true} if and only if this queue contains
392	+	* at least one element {@code e} such that {@code o.equals(e)}.
393	+	*
394	+	* @param o object to be checked for containment in this queue
395	+	* @return {@code true} if this queue contains the specified element
396	+	*/
397	+	public boolean contains(Object o) {
398	+	return indexOf(o) != -1;
399	+	}
400	+
401	+	/**
402	+	* Returns an array containing all of the elements in this queue.
403	+	* The elements are in no particular order.
404	+	*
405	+	* <p>The returned array will be "safe" in that no references to it are
406	+	* maintained by this queue.  (In other words, this method must allocate
407	+	* a new array).  The caller is thus free to modify the returned array.
408	+	*
409	+	* <p>This method acts as bridge between array-based and collection-based
410	+	* APIs.
411	+	*
412	+	* @return an array containing all of the elements in this queue
413	+	*/
414	+	public Object[] toArray() {
415	+	return Arrays.copyOf(queue, size);
416	+	}
417	+
418	+	/**
419	+	* Returns an array containing all of the elements in this queue; the
420	+	* runtime type of the returned array is that of the specified array.
421	+	* The returned array elements are in no particular order.
422	+	* If the queue fits in the specified array, it is returned therein.
423	+	* Otherwise, a new array is allocated with the runtime type of the
424	+	* specified array and the size of this queue.
425	+	*
426	+	* <p>If the queue fits in the specified array with room to spare
427	+	* (i.e., the array has more elements than the queue), the element in
428	+	* the array immediately following the end of the collection is set to
429	+	* {@code null}.
430	+	*
431	+	* <p>Like the {@link #toArray()} method, this method acts as bridge between
432	+	* array-based and collection-based APIs.  Further, this method allows
433	+	* precise control over the runtime type of the output array, and may,
434	+	* under certain circumstances, be used to save allocation costs.
435	+	*
436	+	* <p>Suppose {@code x} is a queue known to contain only strings.
437	+	* The following code can be used to dump the queue into a newly
438	+	* allocated array of {@code String}:
439	+	*
440	+	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
441	+	*
442	+	* Note that {@code toArray(new Object[0])} is identical in function to
443	+	* {@code toArray()}.
444	+	*
445	+	* @param a the array into which the elements of the queue are to
446	+	*          be stored, if it is big enough; otherwise, a new array of the
447	+	*          same runtime type is allocated for this purpose.
448	+	* @return an array containing all of the elements in this queue
449	+	* @throws ArrayStoreException if the runtime type of the specified array
450	+	*         is not a supertype of the runtime type of every element in
451	+	*         this queue
452	+	* @throws NullPointerException if the specified array is null
453	+	*/
454	+	@SuppressWarnings("unchecked")
455	+	public <T> T[] toArray(T[] a) {
456	+	if (a.length < size)
457	+	// Make a new array of a's runtime type, but my contents:
458	+	return (T[]) Arrays.copyOf(queue, size, a.getClass());
459	+	System.arraycopy(queue, 0, a, 0, size);
460	+	if (a.length > size)
461	+	a[size] = null;
462	+	return a;
463	+	}
464	+
465	+	/**
466	+	* Returns an iterator over the elements in this queue. The iterator
467	+	* does not return the elements in any particular order.
468	+	*
469	+	* @return an iterator over the elements in this queue
470	+	*/
471		public Iterator<E> iterator() {
472		return new Itr();
473		}
474
475	<	private class Itr implements Iterator<E> {
475	>	private final class Itr implements Iterator<E> {
476		/**
477		* Index (into queue array) of element to be returned by
478		* subsequent call to next.
479		*/
480	<	private int cursor = 1;
480	>	private int cursor = 0;
481	>
482	>	/**
483	>	* Index of element returned by most recent call to next,
484	>	* unless that element came from the forgetMeNot list.
485	>	* Set to -1 if element is deleted by a call to remove.
486	>	*/
487	>	private int lastRet = -1;
488
489		/**
490	<	* Index of element returned by most recent call to next or
491	<	* previous.  Reset to 0 if this element is deleted by a call
492	<	* to remove.
490	>	* A queue of elements that were moved from the unvisited portion of
491	>	* the heap into the visited portion as a result of "unlucky" element
492	>	* removals during the iteration.  (Unlucky element removals are those
493	>	* that require a siftup instead of a siftdown.)  We must visit all of
494	>	* the elements in this list to complete the iteration.  We do this
495	>	* after we've completed the "normal" iteration.
496	>	*
497	>	* We expect that most iterations, even those involving removals,
498	>	* will not need to store elements in this field.
499		*/
500	<	private int lastRet = 0;
500	>	private ArrayDeque<E> forgetMeNot = null;
501	>
502	>	/**
503	>	* Element returned by the most recent call to next iff that
504	>	* element was drawn from the forgetMeNot list.
505	>	*/
506	>	private E lastRetElt = null;
507
508		/**
509		* The modCount value that the iterator believes that the backing
510	<	* List should have.  If this expectation is violated, the iterator
510	>	* Queue should have.  If this expectation is violated, the iterator
511		* has detected concurrent modification.
512		*/
513		private int expectedModCount = modCount;
514
515		public boolean hasNext() {
516	<	return cursor <= size;
516	>	return cursor < size ||
517	>	(forgetMeNot != null && !forgetMeNot.isEmpty());
518		}
519
520	+	@SuppressWarnings("unchecked")
521		public E next() {
522	<	checkForComodification();
523	<	if (cursor > size)
524	<	throw new NoSuchElementException();
525	<	E result = queue[cursor];
526	<	lastRet = cursor++;
527	<	return result;
522	>	if (expectedModCount != modCount)
523	>	throw new ConcurrentModificationException();
524	>	if (cursor < size)
525	>	return (E) queue[lastRet = cursor++];
526	>	if (forgetMeNot != null) {
527	>	lastRet = -1;
528	>	lastRetElt = forgetMeNot.poll();
529	>	if (lastRetElt != null)
530	>	return lastRetElt;
531	>	}
532	>	throw new NoSuchElementException();
533		}
534
535		public void remove() {
536	<	if (lastRet == 0)
536	>	if (expectedModCount != modCount)
537	>	throw new ConcurrentModificationException();
538	>	if (lastRet != -1) {
539	>	E moved = PriorityQueue.this.removeAt(lastRet);
540	>	lastRet = -1;
541	>	if (moved == null)
542	>	cursor--;
543	>	else {
544	>	if (forgetMeNot == null)
545	>	forgetMeNot = new ArrayDeque<E>();
546	>	forgetMeNot.add(moved);
547	>	}
548	>	} else if (lastRetElt != null) {
549	>	PriorityQueue.this.removeEq(lastRetElt);
550	>	lastRetElt = null;
551	>	} else {
552		throw new IllegalStateException();
553	<	checkForComodification();
284	<
285	<	PriorityQueue.this.remove(lastRet);
286	<	if (lastRet < cursor)
287	<	cursor--;
288	<	lastRet = 0;
553	>	}
554		expectedModCount = modCount;
555		}
291	–
292	–	final void checkForComodification() {
293	–	if (modCount != expectedModCount)
294	–	throw new ConcurrentModificationException();
295	–	}
556		}
557
298	–	/**
299	–	* Returns the number of elements in this priority queue.
300	–	*
301	–	* @return the number of elements in this priority queue.
302	–	*/
558		public int size() {
559		return size;
560		}
561
562		/**
563	<	* Remove all elements from the priority queue.
563	>	* Removes all of the elements from this priority queue.
564	>	* The queue will be empty after this call returns.
565		*/
566		public void clear() {
567		modCount++;
568	<
313	<	// Null out element references to prevent memory leak
314	<	for (int i=1; i<=size; i++)
568	>	for (int i = 0; i < size; i++)
569		queue[i] = null;
316	–
570		size = 0;
571		}
572
573	<	/**
574	<	* Removes and returns the ith element from queue.  Recall
575	<	* that queue is one-based, so 1 <= i <= size.
576	<	*
577	<	* XXX: Could further special-case i==size, but is it worth it?
325	<	* XXX: Could special-case i==0, but is it worth it?
326	<	*/
327	<	private E remove(int i) {
328	<	assert i <= size;
573	>	@SuppressWarnings("unchecked")
574	>	public E poll() {
575	>	if (size == 0)
576	>	return null;
577	>	int s = --size;
578		modCount++;
579	<
580	<	E result = queue[i];
581	<	queue[i] = queue[size];
582	<	queue[size--] = null;  // Drop extra ref to prevent memory leak
583	<	if (i <= size)
335	<	fixDown(i);
579	>	E result = (E) queue[0];
580	>	E x = (E) queue[s];
581	>	queue[s] = null;
582	>	if (s != 0)
583	>	siftDown(0, x);
584		return result;
585		}
586
587		/**
588	<	* Establishes the heap invariant (described above) assuming the heap
589	<	* satisfies the invariant except possibly for the leaf-node indexed by k
590	<	* (which may have a nextExecutionTime less than its parent's).
591	<	*
592	<	* This method functions by "promoting" queue[k] up the hierarchy
593	<	* (by swapping it with its parent) repeatedly until queue[k]
594	<	* is greater than or equal to its parent.
595	<	*/
596	<	private void fixUp(int k) {
597	<	if (comparator == null) {
598	<	while (k > 1) {
599	<	int j = k >> 1;
600	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
601	<	break;
602	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
603	<	k = j;
604	<	}
605	<	} else {
606	<	while (k > 1) {
607	<	int j = k >> 1;
608	<	if (comparator.compare(queue[j], queue[k]) <= 0)
609	<	break;
610	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
611	<	k = j;
588	>	* Removes the ith element from queue.
589	>	*
590	>	* Normally this method leaves the elements at up to i-1,
591	>	* inclusive, untouched.  Under these circumstances, it returns
592	>	* null.  Occasionally, in order to maintain the heap invariant,
593	>	* it must swap a later element of the list with one earlier than
594	>	* i.  Under these circumstances, this method returns the element
595	>	* that was previously at the end of the list and is now at some
596	>	* position before i. This fact is used by iterator.remove so as to
597	>	* avoid missing traversing elements.
598	>	*/
599	>	@SuppressWarnings("unchecked")
600	>	private E removeAt(int i) {
601	>	// assert i >= 0 && i < size;
602	>	modCount++;
603	>	int s = --size;
604	>	if (s == i) // removed last element
605	>	queue[i] = null;
606	>	else {
607	>	E moved = (E) queue[s];
608	>	queue[s] = null;
609	>	siftDown(i, moved);
610	>	if (queue[i] == moved) {
611	>	siftUp(i, moved);
612	>	if (queue[i] != moved)
613	>	return moved;
614		}
615		}
616	+	return null;
617		}
618
619		/**
620	<	* Establishes the heap invariant (described above) in the subtree
621	<	* rooted at k, which is assumed to satisfy the heap invariant except
622	<	* possibly for node k itself (which may be greater than its children).
623	<	*
624	<	* This method functions by "demoting" queue[k] down the hierarchy
625	<	* (by swapping it with its smaller child) repeatedly until queue[k]
626	<	* is less than or equal to its children.
627	<	*/
628	<	private void fixDown(int k) {
629	<	int j;
630	<	if (comparator == null) {
631	<	while ((j = k << 1) <= size) {
632	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
633	<	j++; // j indexes smallest kid
634	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
635	<	break;
636	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
637	<	k = j;
638	<	}
639	<	} else {
640	<	while ((j = k << 1) <= size) {
641	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
642	<	j++; // j indexes smallest kid
643	<	if (comparator.compare(queue[k], queue[j]) <= 0)
644	<	break;
645	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
646	<	k = j;
647	<	}
620	>	* Inserts item x at position k, maintaining heap invariant by
621	>	* promoting x up the tree until it is greater than or equal to
622	>	* its parent, or is the root.
623	>	*
624	>	* To simplify and speed up coercions and comparisons. the
625	>	* Comparable and Comparator versions are separated into different
626	>	* methods that are otherwise identical. (Similarly for siftDown.)
627	>	*
628	>	* @param k the position to fill
629	>	* @param x the item to insert
630	>	*/
631	>	private void siftUp(int k, E x) {
632	>	if (comparator != null)
633	>	siftUpUsingComparator(k, x);
634	>	else
635	>	siftUpComparable(k, x);
636	>	}
637	>
638	>	@SuppressWarnings("unchecked")
639	>	private void siftUpComparable(int k, E x) {
640	>	Comparable<? super E> key = (Comparable<? super E>) x;
641	>	while (k > 0) {
642	>	int parent = (k - 1) >>> 1;
643	>	Object e = queue[parent];
644	>	if (key.compareTo((E) e) >= 0)
645	>	break;
646	>	queue[k] = e;
647	>	k = parent;
648	>	}
649	>	queue[k] = key;
650	>	}
651	>
652	>	@SuppressWarnings("unchecked")
653	>	private void siftUpUsingComparator(int k, E x) {
654	>	while (k > 0) {
655	>	int parent = (k - 1) >>> 1;
656	>	Object e = queue[parent];
657	>	if (comparator.compare(x, (E) e) >= 0)
658	>	break;
659	>	queue[k] = e;
660	>	k = parent;
661		}
662	+	queue[k] = x;
663		}
664
665	<	public Comparator comparator() {
665	>	/**
666	>	* Inserts item x at position k, maintaining heap invariant by
667	>	* demoting x down the tree repeatedly until it is less than or
668	>	* equal to its children or is a leaf.
669	>	*
670	>	* @param k the position to fill
671	>	* @param x the item to insert
672	>	*/
673	>	private void siftDown(int k, E x) {
674	>	if (comparator != null)
675	>	siftDownUsingComparator(k, x);
676	>	else
677	>	siftDownComparable(k, x);
678	>	}
679	>
680	>	@SuppressWarnings("unchecked")
681	>	private void siftDownComparable(int k, E x) {
682	>	Comparable<? super E> key = (Comparable<? super E>)x;
683	>	int half = size >>> 1;        // loop while a non-leaf
684	>	while (k < half) {
685	>	int child = (k << 1) + 1; // assume left child is least
686	>	Object c = queue[child];
687	>	int right = child + 1;
688	>	if (right < size &&
689	>	((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
690	>	c = queue[child = right];
691	>	if (key.compareTo((E) c) <= 0)
692	>	break;
693	>	queue[k] = c;
694	>	k = child;
695	>	}
696	>	queue[k] = key;
697	>	}
698	>
699	>	@SuppressWarnings("unchecked")
700	>	private void siftDownUsingComparator(int k, E x) {
701	>	int half = size >>> 1;
702	>	while (k < half) {
703	>	int child = (k << 1) + 1;
704	>	Object c = queue[child];
705	>	int right = child + 1;
706	>	if (right < size &&
707	>	comparator.compare((E) c, (E) queue[right]) > 0)
708	>	c = queue[child = right];
709	>	if (comparator.compare(x, (E) c) <= 0)
710	>	break;
711	>	queue[k] = c;
712	>	k = child;
713	>	}
714	>	queue[k] = x;
715	>	}
716	>
717	>	/**
718	>	* Establishes the heap invariant (described above) in the entire tree,
719	>	* assuming nothing about the order of the elements prior to the call.
720	>	*/
721	>	@SuppressWarnings("unchecked")
722	>	private void heapify() {
723	>	for (int i = (size >>> 1) - 1; i >= 0; i--)
724	>	siftDown(i, (E) queue[i]);
725	>	}
726	>
727	>	/**
728	>	* Returns the comparator used to order the elements in this
729	>	* queue, or {@code null} if this queue is sorted according to
730	>	* the {@linkplain Comparable natural ordering} of its elements.
731	>	*
732	>	* @return the comparator used to order this queue, or
733	>	*         {@code null} if this queue is sorted according to the
734	>	*         natural ordering of its elements
735	>	*/
736	>	public Comparator<? super E> comparator() {
737		return comparator;
738		}
739
740		/**
741	<	* Save the state of the instance to a stream (that
406	<	* is, serialize it).
741	>	* Saves this queue to a stream (that is, serializes it).
742		*
743		* @serialData The length of the array backing the instance is
744	<	* emitted (int), followed by all of its elements (each an
745	<	* <tt>Object</tt>) in the proper order.
744	>	*             emitted (int), followed by all of its elements
745	>	*             (each an {@code Object}) in the proper order.
746		* @param s the stream
747		*/
748	<	private synchronized void writeObject(java.io.ObjectOutputStream s)
749	<	throws java.io.IOException{
748	>	private void writeObject(java.io.ObjectOutputStream s)
749	>	throws java.io.IOException {
750		// Write out element count, and any hidden stuff
751		s.defaultWriteObject();
752
753	<	// Write out array length
754	<	s.writeInt(queue.length);
753	>	// Write out array length, for compatibility with 1.5 version
754	>	s.writeInt(Math.max(2, size + 1));
755
756	<	// Write out all elements in the proper order.
757	<	for (int i=0; i<size; i++)
756	>	// Write out all elements in the "proper order".
757	>	for (int i = 0; i < size; i++)
758		s.writeObject(queue[i]);
759		}
760
761		/**
762	<	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
763	<	* deserialize it).
762	>	* Reconstitutes the {@code PriorityQueue} instance from a stream
763	>	* (that is, deserializes it).
764	>	*
765		* @param s the stream
766		*/
767	<	private synchronized void readObject(java.io.ObjectInputStream s)
767	>	private void readObject(java.io.ObjectInputStream s)
768		throws java.io.IOException, ClassNotFoundException {
769		// Read in size, and any hidden stuff
770		s.defaultReadObject();
771
772	<	// Read in array length and allocate array
773	<	int arrayLength = s.readInt();
438	<	queue = (E[]) new Object[arrayLength];
439	<
440	<	// Read in all elements in the proper order.
441	<	for (int i=0; i<size; i++)
442	<	queue[i] = (E)s.readObject();
443	<	}
772	>	// Read in (and discard) array length
773	>	s.readInt();
774
775	<	}
775	>	queue = new Object[size];
776	>
777	>	// Read in all elements.
778	>	for (int i = 0; i < size; i++)
779	>	queue[i] = s.readObject();
780	>
781	>	// Elements are guaranteed to be in "proper order", but the
782	>	// spec has never explained what that might be.
783	>	heapify();
784	>	}
785	>
786	>	// wrapping constructor in method avoids transient javac problems
787	>	final PriorityQueueSpliterator<E> spliterator(int origin, int fence,
788	>	int expectedModCount) {
789	>	return new PriorityQueueSpliterator<E>(this, origin, fence,
790	>	expectedModCount);
791	>	}
792	>
793	>	public Stream<E> stream() {
794	>	int flags = Streams.STREAM_IS_SIZED;
795	>	return Streams.stream
796	>	(() -> spliterator(0, size, modCount), flags);
797	>	}
798	>	public Stream<E> parallelStream() {
799	>	int flags = Streams.STREAM_IS_SIZED;
800	>	return Streams.parallelStream
801	>	(() -> spliterator(0, size, modCount), flags);
802	>	}
803	>
804	>	/** Index-based split-by-two Spliterator */
805	>	static final class PriorityQueueSpliterator<E>
806	>	implements Spliterator<E>, Iterator<E> {
807	>	private final PriorityQueue<E> pq;
808	>	private int index;           // current index, modified on advance/split
809	>	private final int fence;     // one past last index
810	>	private final int expectedModCount; // for comodification checks
811	>
812	>	/** Create new spliterator covering the given  range */
813	>	PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
814	>	int expectedModCount) {
815	>	this.pq = pq; this.index = origin; this.fence = fence;
816	>	this.expectedModCount = expectedModCount;
817	>	}
818	>
819	>	public PriorityQueueSpliterator<E> trySplit() {
820	>	int lo = index, mid = (lo + fence) >>> 1;
821	>	return (lo >= mid) ? null :
822	>	new PriorityQueueSpliterator<E>(pq, lo, index = mid,
823	>	expectedModCount);
824	>	}
825	>
826	>	public void forEach(Block<? super E> block) {
827	>	Object[] a; int i, hi; // hoist accesses and checks from loop
828	>	if (block == null)
829	>	throw new NullPointerException();
830	>	if ((a = pq.queue).length >= (hi = fence) &&
831	>	(i = index) >= 0 && i < hi) {
832	>	index = hi;
833	>	do {
834	>	@SuppressWarnings("unchecked") E e = (E) a[i];
835	>	block.accept(e);
836	>	} while (++i < hi);
837	>	if (pq.modCount != expectedModCount)
838	>	throw new ConcurrentModificationException();
839	>	}
840	>	}
841	>
842	>	public boolean tryAdvance(Block<? super E> block) {
843	>	if (index >= 0 && index < fence) {
844	>	if (pq.modCount != expectedModCount)
845	>	throw new ConcurrentModificationException();
846	>	@SuppressWarnings("unchecked") E e =
847	>	(E)pq.queue[index++];
848	>	block.accept(e);
849	>	return true;
850	>	}
851	>	return false;
852	>	}
853
854	+	public long estimateSize() { return (long)(fence - index); }
855	+	public boolean hasExactSize() { return true; }
856	+	public boolean hasExactSplits() { return true; }
857	+
858	+	// Iterator support
859	+	public Iterator<E> iterator() { return this; }
860	+	public void remove() { throw new UnsupportedOperationException(); }
861	+	public boolean hasNext() { return index >= 0 && index < fence; }
862	+
863	+	public E next() {
864	+	if (index < 0 || index >= fence)
865	+	throw new NoSuchElementException();
866	+	if (pq.modCount != expectedModCount)
867	+	throw new ConcurrentModificationException();
868	+	@SuppressWarnings("unchecked") E e =
869	+	(E) pq.queue[index++];
870	+	return e;
871	+	}
872	+	}
873	+	}

Diff Legend

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