ViewVC Help

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

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

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.2 by dl, Tue Mar 8 12:27:06 2005 UTC vs.
Revision 1.65 by jsr166, Sat Feb 28 20:35:47 2015 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Josh Bloch of Google Inc. and released to the public domain,
3	<	* as explained at http://creativecommons.org/licenses/publicdomain.
3	>	* as explained at http://creativecommons.org/publicdomain/zero/1.0/.
4		*/
5
6		package java.util;
7	<	import java.io.*;
7	>
8	>	import java.io.Serializable;
9	>	import java.util.function.Consumer;
10
11		/**
12		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 15 | Line 17 | import java.io.*;
17		* {@link Stack} when used as a stack, and faster than {@link LinkedList}
18		* when used as a queue.
19		*
20	<	* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time.
21	<	* Exceptions include {@link #remove(Object) remove}, {@link
22	<	* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
23	<	* removeLastOccurrence}, {@link #contains contains }, {@link #iterator
24	<	* iterator.remove()}, and the bulk operations, all of which run in linear
25	<	* time.
20	>	* <p>Most {@code ArrayDeque} operations run in amortized constant time.
21	>	* Exceptions include
22	>	* {@link #remove(Object) remove},
23	>	* {@link #removeFirstOccurrence removeFirstOccurrence},
24	>	* {@link #removeLastOccurrence removeLastOccurrence},
25	>	* {@link #contains contains},
26	>	* {@link #iterator iterator.remove()},
27	>	* and the bulk operations, all of which run in linear time.
28		*
29	<	* <p>The iterators returned by this class's <tt>iterator</tt> method are
30	<	* <i>fail-fast</i>: If the deque is modified at any time after the iterator
31	<	* is created, in any way except through the iterator's own remove method, the
32	<	* iterator will generally throw a {@link ConcurrentModificationException}.
33	<	* Thus, in the face of concurrent modification, the iterator fails quickly
34	<	* and cleanly, rather than risking arbitrary, non-deterministic behavior at
35	<	* an undetermined time in the future.
29	>	* <p>The iterators returned by this class's {@link #iterator() iterator}
30	>	* method are <em>fail-fast</em>: If the deque is modified at any time after
31	>	* the iterator is created, in any way except through the iterator's own
32	>	* {@code remove} method, the iterator will generally throw a {@link
33	>	* ConcurrentModificationException}.  Thus, in the face of concurrent
34	>	* modification, the iterator fails quickly and cleanly, rather than risking
35	>	* arbitrary, non-deterministic behavior at an undetermined time in the
36	>	* future.
37		*
38		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
39		* as it is, generally speaking, impossible to make any hard guarantees in the
40		* presence of unsynchronized concurrent modification.  Fail-fast iterators
41	<	* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
41	>	* throw {@code ConcurrentModificationException} on a best-effort basis.
42		* Therefore, it would be wrong to write a program that depended on this
43		* exception for its correctness: <i>the fail-fast behavior of iterators
44		* should be used only to detect bugs.</i>
45		*
46		* <p>This class and its iterator implement all of the
47	<	* optional methods of the {@link Collection} and {@link
48	<	* Iterator} interfaces.  This class is a member of the <a
49	<	* href="{@docRoot}/../guide/collections/index.html"> Java Collections
50	<	* Framework</a>.
47	>	* <em>optional</em> methods of the {@link Collection} and {@link
48	>	* Iterator} interfaces.
49	>	*
50	>	* <p>This class is a member of the
51	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
52	>	* Java Collections Framework</a>.
53		*
54		* @author  Josh Bloch and Doug Lea
55		* @since   1.6
56	<	* @param <E> the type of elements held in this collection
56	>	* @param <E> the type of elements held in this deque
57		*/
58		public class ArrayDeque<E> extends AbstractCollection<E>
59		implements Deque<E>, Cloneable, Serializable
60		{
61		/**
62	<	* The array in which the elements of in the deque are stored.
62	>	* The array in which the elements of the deque are stored.
63		* The capacity of the deque is the length of this array, which is
64		* always a power of two. The array is never allowed to become
65		* full, except transiently within an addX method where it is
#	Line 61 | Line 68 | public class ArrayDeque<E> extends Abstr
68		* other.  We also guarantee that all array cells not holding
69		* deque elements are always null.
70		*/
71	<	private transient E[] elements;
71	>	transient Object[] elements; // non-private to simplify nested class access
72
73		/**
74		* The index of the element at the head of the deque (which is the
75		* element that would be removed by remove() or pop()); or an
76		* arbitrary number equal to tail if the deque is empty.
77		*/
78	<	private transient int head;
78	>	transient int head;
79
80		/**
81		* The index at which the next element would be added to the tail
82		* of the deque (via addLast(E), add(E), or push(E)).
83		*/
84	<	private transient int tail;
84	>	transient int tail;
85
86		/**
87		* The minimum capacity that we'll use for a newly created deque.
#	Line 85 | Line 92 | public class ArrayDeque<E> extends Abstr
92		// ******  Array allocation and resizing utilities ******
93
94		/**
95	<	* Allocate empty array to hold the given number of elements.
95	>	* Allocates empty array to hold the given number of elements.
96		*
97	<	* @param numElements  the number of elements to hold.
97	>	* @param numElements  the number of elements to hold
98		*/
99	<	private void allocateElements(int numElements) {
99	>	private void allocateElements(int numElements) {
100		int initialCapacity = MIN_INITIAL_CAPACITY;
101		// Find the best power of two to hold elements.
102		// Tests "<=" because arrays aren't kept full.
#	Line 105 | Line 112 | public class ArrayDeque<E> extends Abstr
112		if (initialCapacity < 0)   // Too many elements, must back off
113		initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
114		}
115	<	elements = (E[]) new Object[initialCapacity];
115	>	elements = new Object[initialCapacity];
116		}
117
118		/**
119	<	* Double the capacity of this deque.  Call only when full, i.e.,
119	>	* Doubles the capacity of this deque.  Call only when full, i.e.,
120		* when head and tail have wrapped around to become equal.
121		*/
122		private void doubleCapacity() {
123	<	assert head == tail;
123	>	assert head == tail;
124		int p = head;
125		int n = elements.length;
126		int r = n - p; // number of elements to the right of p
#	Line 123 | Line 130 | public class ArrayDeque<E> extends Abstr
130		Object[] a = new Object[newCapacity];
131		System.arraycopy(elements, p, a, 0, r);
132		System.arraycopy(elements, 0, a, r, p);
133	<	elements = (E[])a;
133	>	elements = a;
134		head = 0;
135		tail = n;
136		}
137
138		/**
139	<	* Copy the elements from our element array into the specified array,
133	<	* in order (from first to last element in the deque).  It is assumed
134	<	* that the array is large enough to hold all elements in the deque.
135	<	*
136	<	* @return its argument
137	<	*/
138	<	private <T> T[] copyElements(T[] a) {
139	<	if (head < tail) {
140	<	System.arraycopy(elements, head, a, 0, size());
141	<	} else if (head > tail) {
142	<	int headPortionLen = elements.length - head;
143	<	System.arraycopy(elements, head, a, 0, headPortionLen);
144	<	System.arraycopy(elements, 0, a, headPortionLen, tail);
145	<	}
146	<	return a;
147	<	}
148	<
149	<	/**
150	<	* Constructs an empty array deque with the an initial capacity
139	>	* Constructs an empty array deque with an initial capacity
140		* sufficient to hold 16 elements.
141		*/
142		public ArrayDeque() {
143	<	elements = (E[]) new Object[16];
143	>	elements = new Object[16];
144		}
145
146		/**
#	Line 184 | Line 173 | public class ArrayDeque<E> extends Abstr
173		// terms of these.
174
175		/**
176	<	* Inserts the specified element to the front this deque.
176	>	* Inserts the specified element at the front of this deque.
177		*
178	<	* @param e the element to insert
179	<	* @throws NullPointerException if <tt>e</tt> is null
178	>	* @param e the element to add
179	>	* @throws NullPointerException if the specified element is null
180		*/
181		public void addFirst(E e) {
182		if (e == null)
183		throw new NullPointerException();
184		elements[head = (head - 1) & (elements.length - 1)] = e;
185	<	if (head == tail)
185	>	if (head == tail)
186		doubleCapacity();
187		}
188
189		/**
190	<	* Inserts the specified element to the end this deque.
191	<	* This method is equivalent to {@link Collection#add} and
192	<	* {@link #push}.
190	>	* Inserts the specified element at the end of this deque.
191	>	*
192	>	* <p>This method is equivalent to {@link #add}.
193		*
194	<	* @param e the element to insert
195	<	* @throws NullPointerException if <tt>e</tt> is null
194	>	* @param e the element to add
195	>	* @throws NullPointerException if the specified element is null
196		*/
197		public void addLast(E e) {
198		if (e == null)
#	Line 214 | Line 203 | public class ArrayDeque<E> extends Abstr
203		}
204
205		/**
206	<	* Retrieves and removes the first element of this deque, or
218	<	* <tt>null</tt> if this deque is empty.
219	<	*
220	<	* @return the first element of this deque, or <tt>null</tt> if
221	<	*     this deque is empty
222	<	*/
223	<	public E pollFirst() {
224	<	int h = head;
225	<	E result = elements[h]; // Element is null if deque empty
226	<	if (result == null)
227	<	return null;
228	<	elements[h] = null;     // Must null out slot
229	<	head = (h + 1) & (elements.length - 1);
230	<	return result;
231	<	}
232	<
233	<	/**
234	<	* Retrieves and removes the last element of this deque, or
235	<	* <tt>null</tt> if this deque is empty.
236	<	*
237	<	* @return the last element of this deque, or <tt>null</tt> if
238	<	*     this deque is empty
239	<	*/
240	<	public E pollLast() {
241	<	int t = (tail - 1) & (elements.length - 1);
242	<	E result = elements[t];
243	<	if (result == null)
244	<	return null;
245	<	elements[t] = null;
246	<	tail = t;
247	<	return result;
248	<	}
249	<
250	<	/**
251	<	* Inserts the specified element to the front this deque.
206	>	* Inserts the specified element at the front of this deque.
207		*
208	<	* @param e the element to insert
209	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
210	<	* @throws NullPointerException if <tt>e</tt> is null
208	>	* @param e the element to add
209	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
210	>	* @throws NullPointerException if the specified element is null
211		*/
212		public boolean offerFirst(E e) {
213		addFirst(e);
#	Line 260 | Line 215 | public class ArrayDeque<E> extends Abstr
215		}
216
217		/**
218	<	* Inserts the specified element to the end this deque.
218	>	* Inserts the specified element at the end of this deque.
219		*
220	<	* @param e the element to insert
221	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
222	<	* @throws NullPointerException if <tt>e</tt> is null
220	>	* @param e the element to add
221	>	* @return {@code true} (as specified by {@link Deque#offerLast})
222	>	* @throws NullPointerException if the specified element is null
223		*/
224		public boolean offerLast(E e) {
225		addLast(e);
#	Line 272 | Line 227 | public class ArrayDeque<E> extends Abstr
227		}
228
229		/**
230	<	* Retrieves and removes the first element of this deque.  This method
276	<	* differs from the <tt>pollFirst</tt> method in that it throws an
277	<	* exception if this deque is empty.
278	<	*
279	<	* @return the first element of this deque
280	<	* @throws NoSuchElementException if this deque is empty
230	>	* @throws NoSuchElementException {@inheritDoc}
231		*/
232		public E removeFirst() {
233		E x = pollFirst();
#	Line 287 | Line 237 | public class ArrayDeque<E> extends Abstr
237		}
238
239		/**
240	<	* Retrieves and removes the last element of this deque.  This method
291	<	* differs from the <tt>pollLast</tt> method in that it throws an
292	<	* exception if this deque is empty.
293	<	*
294	<	* @return the last element of this deque
295	<	* @throws NoSuchElementException if this deque is empty
240	>	* @throws NoSuchElementException {@inheritDoc}
241		*/
242		public E removeLast() {
243		E x = pollLast();
#	Line 301 | Line 246 | public class ArrayDeque<E> extends Abstr
246		return x;
247		}
248
249	<	/**
250	<	* Retrieves, but does not remove, the first element of this deque,
251	<	* returning <tt>null</tt> if this deque is empty.
252	<	*
253	<	* @return the first element of this deque, or <tt>null</tt> if
254	<	*     this deque is empty
255	<	*/
256	<	public E peekFirst() {
257	<	return elements[head]; // elements[head] is null if deque empty
249	>	public E pollFirst() {
250	>	int h = head;
251	>	@SuppressWarnings("unchecked")
252	>	E result = (E) elements[h];
253	>	// Element is null if deque empty
254	>	if (result != null) {
255	>	elements[h] = null; // Must null out slot
256	>	head = (h + 1) & (elements.length - 1);
257	>	}
258	>	return result;
259		}
260
261	<	/**
262	<	* Retrieves, but does not remove, the last element of this deque,
263	<	* returning <tt>null</tt> if this deque is empty.
264	<	*
265	<	* @return the last element of this deque, or <tt>null</tt> if this deque
266	<	*     is empty
267	<	*/
268	<	public E peekLast() {
269	<	return elements[(tail - 1) & (elements.length - 1)];
261	>	public E pollLast() {
262	>	int t = (tail - 1) & (elements.length - 1);
263	>	@SuppressWarnings("unchecked")
264	>	E result = (E) elements[t];
265	>	if (result != null) {
266	>	elements[t] = null;
267	>	tail = t;
268	>	}
269	>	return result;
270		}
271
272		/**
273	<	* Retrieves, but does not remove, the first element of this
328	<	* deque.  This method differs from the <tt>peek</tt> method only
329	<	* in that it throws an exception if this deque is empty.
330	<	*
331	<	* @return the first element of this deque
332	<	* @throws NoSuchElementException if this deque is empty
273	>	* @throws NoSuchElementException {@inheritDoc}
274		*/
275		public E getFirst() {
276	<	E x = elements[head];
277	<	if (x == null)
276	>	@SuppressWarnings("unchecked")
277	>	E result = (E) elements[head];
278	>	if (result == null)
279		throw new NoSuchElementException();
280	<	return x;
280	>	return result;
281		}
282
283		/**
284	<	* Retrieves, but does not remove, the last element of this
343	<	* deque.  This method differs from the <tt>peek</tt> method only
344	<	* in that it throws an exception if this deque is empty.
345	<	*
346	<	* @return the last element of this deque
347	<	* @throws NoSuchElementException if this deque is empty
284	>	* @throws NoSuchElementException {@inheritDoc}
285		*/
286		public E getLast() {
287	<	E x = elements[(tail - 1) & (elements.length - 1)];
288	<	if (x == null)
287	>	@SuppressWarnings("unchecked")
288	>	E result = (E) elements[(tail - 1) & (elements.length - 1)];
289	>	if (result == null)
290		throw new NoSuchElementException();
291	<	return x;
291	>	return result;
292	>	}
293	>
294	>	@SuppressWarnings("unchecked")
295	>	public E peekFirst() {
296	>	// elements[head] is null if deque empty
297	>	return (E) elements[head];
298	>	}
299	>
300	>	@SuppressWarnings("unchecked")
301	>	public E peekLast() {
302	>	return (E) elements[(tail - 1) & (elements.length - 1)];
303		}
304
305		/**
306		* Removes the first occurrence of the specified element in this
307	<	* deque (when traversing the deque from head to tail).  If the deque
308	<	* does not contain the element, it is unchanged.
307	>	* deque (when traversing the deque from head to tail).
308	>	* If the deque does not contain the element, it is unchanged.
309	>	* More formally, removes the first element {@code e} such that
310	>	* {@code o.equals(e)} (if such an element exists).
311	>	* Returns {@code true} if this deque contained the specified element
312	>	* (or equivalently, if this deque changed as a result of the call).
313		*
314	<	* @param e element to be removed from this deque, if present
315	<	* @return <tt>true</tt> if the deque contained the specified element
314	>	* @param o element to be removed from this deque, if present
315	>	* @return {@code true} if the deque contained the specified element
316		*/
317	<	public boolean removeFirstOccurrence(Object e) {
318	<	if (e == null)
319	<	return false;
320	<	int mask = elements.length - 1;
321	<	int i = head;
322	<	E x;
323	<	while ( (x = elements[i]) != null) {
324	<	if (e.equals(x)) {
325	<	delete(i);
373	<	return true;
317	>	public boolean removeFirstOccurrence(Object o) {
318	>	if (o != null) {
319	>	int mask = elements.length - 1;
320	>	int i = head;
321	>	for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
322	>	if (o.equals(x)) {
323	>	delete(i);
324	>	return true;
325	>	}
326		}
375	–	i = (i + 1) & mask;
327		}
328		return false;
329		}
330
331		/**
332		* Removes the last occurrence of the specified element in this
333	<	* deque (when traversing the deque from head to tail).  If the deque
334	<	* does not contain the element, it is unchanged.
333	>	* deque (when traversing the deque from head to tail).
334	>	* If the deque does not contain the element, it is unchanged.
335	>	* More formally, removes the last element {@code e} such that
336	>	* {@code o.equals(e)} (if such an element exists).
337	>	* Returns {@code true} if this deque contained the specified element
338	>	* (or equivalently, if this deque changed as a result of the call).
339		*
340	<	* @param e element to be removed from this deque, if present
341	<	* @return <tt>true</tt> if the deque contained the specified element
340	>	* @param o element to be removed from this deque, if present
341	>	* @return {@code true} if the deque contained the specified element
342		*/
343	<	public boolean removeLastOccurrence(Object e) {
344	<	if (e == null)
345	<	return false;
346	<	int mask = elements.length - 1;
347	<	int i = (tail - 1) & mask;
348	<	E x;
349	<	while ( (x = elements[i]) != null) {
350	<	if (e.equals(x)) {
351	<	delete(i);
397	<	return true;
343	>	public boolean removeLastOccurrence(Object o) {
344	>	if (o != null) {
345	>	int mask = elements.length - 1;
346	>	int i = (tail - 1) & mask;
347	>	for (Object x; (x = elements[i]) != null; i = (i - 1) & mask) {
348	>	if (o.equals(x)) {
349	>	delete(i);
350	>	return true;
351	>	}
352		}
399	–	i = (i - 1) & mask;
353		}
354		return false;
355		}
#	Line 404 | Line 357 | public class ArrayDeque<E> extends Abstr
357		// *** Queue methods ***
358
359		/**
360	<	* Inserts the specified element to the end of this deque.
408	<	*
409	<	* <p>This method is equivalent to {@link #offerLast}.
410	<	*
411	<	* @param e the element to insert
412	<	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
413	<	* @throws NullPointerException if <tt>e</tt> is null
414	<	*/
415	<	public boolean offer(E e) {
416	<	return offerLast(e);
417	<	}
418	<
419	<	/**
420	<	* Inserts the specified element to the end of this deque.
360	>	* Inserts the specified element at the end of this deque.
361		*
362		* <p>This method is equivalent to {@link #addLast}.
363		*
364	<	* @param e the element to insert
365	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
366	<	* @throws NullPointerException if <tt>e</tt> is null
364	>	* @param e the element to add
365	>	* @return {@code true} (as specified by {@link Collection#add})
366	>	* @throws NullPointerException if the specified element is null
367		*/
368		public boolean add(E e) {
369		addLast(e);
#	Line 431 | Line 371 | public class ArrayDeque<E> extends Abstr
371		}
372
373		/**
374	<	* Retrieves and removes the head of the queue represented by
435	<	* this deque, or <tt>null</tt> if this deque is empty.  In other words,
436	<	* retrieves and removes the first element of this deque, or <tt>null</tt>
437	<	* if this deque is empty.
374	>	* Inserts the specified element at the end of this deque.
375		*
376	<	* <p>This method is equivalent to {@link #pollFirst}.
376	>	* <p>This method is equivalent to {@link #offerLast}.
377		*
378	<	* @return the first element of this deque, or <tt>null</tt> if
379	<	*     this deque is empty
378	>	* @param e the element to add
379	>	* @return {@code true} (as specified by {@link Queue#offer})
380	>	* @throws NullPointerException if the specified element is null
381		*/
382	<	public E poll() {
383	<	return pollFirst();
382	>	public boolean offer(E e) {
383	>	return offerLast(e);
384		}
385
386		/**
387		* Retrieves and removes the head of the queue represented by this deque.
388	<	* This method differs from the <tt>poll</tt> method in that it throws an
388	>	*
389	>	* This method differs from {@link #poll poll} only in that it throws an
390		* exception if this deque is empty.
391		*
392		* <p>This method is equivalent to {@link #removeFirst}.
393		*
394		* @return the head of the queue represented by this deque
395	<	* @throws NoSuchElementException if this deque is empty
395	>	* @throws NoSuchElementException {@inheritDoc}
396		*/
397		public E remove() {
398		return removeFirst();
399		}
400
401		/**
402	<	* Retrieves, but does not remove, the head of the queue represented by
403	<	* this deque, returning <tt>null</tt> if this deque is empty.
402	>	* Retrieves and removes the head of the queue represented by this deque
403	>	* (in other words, the first element of this deque), or returns
404	>	* {@code null} if this deque is empty.
405		*
406	<	* <p>This method is equivalent to {@link #peekFirst}
406	>	* <p>This method is equivalent to {@link #pollFirst}.
407		*
408		* @return the head of the queue represented by this deque, or
409	<	*     <tt>null</tt> if this deque is empty
409	>	*         {@code null} if this deque is empty
410		*/
411	<	public E peek() {
412	<	return peekFirst();
411	>	public E poll() {
412	>	return pollFirst();
413		}
414
415		/**
416		* Retrieves, but does not remove, the head of the queue represented by
417	<	* this deque.  This method differs from the <tt>peek</tt> method only in
417	>	* this deque.  This method differs from {@link #peek peek} only in
418		* that it throws an exception if this deque is empty.
419		*
420	<	* <p>This method is equivalent to {@link #getFirst}
420	>	* <p>This method is equivalent to {@link #getFirst}.
421		*
422		* @return the head of the queue represented by this deque
423	<	* @throws NoSuchElementException if this deque is empty
423	>	* @throws NoSuchElementException {@inheritDoc}
424		*/
425		public E element() {
426		return getFirst();
427		}
428
429	+	/**
430	+	* Retrieves, but does not remove, the head of the queue represented by
431	+	* this deque, or returns {@code null} if this deque is empty.
432	+	*
433	+	* <p>This method is equivalent to {@link #peekFirst}.
434	+	*
435	+	* @return the head of the queue represented by this deque, or
436	+	*         {@code null} if this deque is empty
437	+	*/
438	+	public E peek() {
439	+	return peekFirst();
440	+	}
441	+
442		// *** Stack methods ***
443
444		/**
445		* Pushes an element onto the stack represented by this deque.  In other
446	<	* words, inserts the element to the front this deque.
446	>	* words, inserts the element at the front of this deque.
447		*
448		* <p>This method is equivalent to {@link #addFirst}.
449		*
450		* @param e the element to push
451	<	* @throws NullPointerException if <tt>e</tt> is null
451	>	* @throws NullPointerException if the specified element is null
452		*/
453		public void push(E e) {
454		addFirst(e);
#	Line 508 | Line 461 | public class ArrayDeque<E> extends Abstr
461		* <p>This method is equivalent to {@link #removeFirst()}.
462		*
463		* @return the element at the front of this deque (which is the top
464	<	*     of the stack represented by this deque)
465	<	* @throws NoSuchElementException if this deque is empty
464	>	*         of the stack represented by this deque)
465	>	* @throws NoSuchElementException {@inheritDoc}
466		*/
467		public E pop() {
468		return removeFirst();
469		}
470
471	+	private void checkInvariants() {
472	+	assert elements[tail] == null;
473	+	assert head == tail ? elements[head] == null :
474	+	(elements[head] != null &&
475	+	elements[(tail - 1) & (elements.length - 1)] != null);
476	+	assert elements[(head - 1) & (elements.length - 1)] == null;
477	+	}
478	+
479		/**
480	<	* Remove the element at the specified position in the elements array,
481	<	* adjusting head, tail, and size as necessary.  This can result in
482	<	* motion of elements backwards or forwards in the array.
483	<	*
484	<	* <p>This method is called delete rather than remove to emphasize the
485	<	* that its semantics differ from those of List.remove(int).
486	<	*
480	>	* Removes the element at the specified position in the elements array,
481	>	* adjusting head and tail as necessary.  This can result in motion of
482	>	* elements backwards or forwards in the array.
483	>	*
484	>	* <p>This method is called delete rather than remove to emphasize
485	>	* that its semantics differ from those of {@link List#remove(int)}.
486	>	*
487		* @return true if elements moved backwards
488		*/
489		private boolean delete(int i) {
490	<	// Case 1: Deque doesn't wrap
491	<	// Case 2: Deque does wrap and removed element is in the head portion
492	<	if ((head < tail || tail == 0) || i >= head) {
493	<	System.arraycopy(elements, head, elements, head + 1, i - head);
494	<	elements[head] = null;
495	<	head = (head + 1) & (elements.length - 1);
490	>	checkInvariants();
491	>	final Object[] elements = this.elements;
492	>	final int mask = elements.length - 1;
493	>	final int h = head;
494	>	final int t = tail;
495	>	final int front = (i - h) & mask;
496	>	final int back  = (t - i) & mask;
497	>
498	>	// Invariant: head <= i < tail mod circularity
499	>	if (front >= ((t - h) & mask))
500	>	throw new ConcurrentModificationException();
501	>
502	>	// Optimize for least element motion
503	>	if (front < back) {
504	>	if (h <= i) {
505	>	System.arraycopy(elements, h, elements, h + 1, front);
506	>	} else { // Wrap around
507	>	System.arraycopy(elements, 0, elements, 1, i);
508	>	elements[0] = elements[mask];
509	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
510	>	}
511	>	elements[h] = null;
512	>	head = (h + 1) & mask;
513		return false;
514	+	} else {
515	+	if (i < t) { // Copy the null tail as well
516	+	System.arraycopy(elements, i + 1, elements, i, back);
517	+	tail = t - 1;
518	+	} else { // Wrap around
519	+	System.arraycopy(elements, i + 1, elements, i, mask - i);
520	+	elements[mask] = elements[0];
521	+	System.arraycopy(elements, 1, elements, 0, t);
522	+	tail = (t - 1) & mask;
523	+	}
524	+	return true;
525		}
537	–
538	–	// Case 3: Deque wraps and removed element is in the tail portion
539	–	tail--;
540	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
541	–	elements[tail] = null;
542	–	return true;
526		}
527
528		// *** Collection Methods ***
#	Line 554 | Line 537 | public class ArrayDeque<E> extends Abstr
537		}
538
539		/**
540	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
540	>	* Returns {@code true} if this deque contains no elements.
541		*
542	<	* @return <tt>true</tt> if this collection contains no elements.
542	>	* @return {@code true} if this deque contains no elements
543		*/
544		public boolean isEmpty() {
545		return head == tail;
#	Line 567 | Line 550 | public class ArrayDeque<E> extends Abstr
550		* will be ordered from first (head) to last (tail).  This is the same
551		* order that elements would be dequeued (via successive calls to
552		* {@link #remove} or popped (via successive calls to {@link #pop}).
553	<	*
554	<	* @return an <tt>Iterator</tt> over the elements in this deque
553	>	*
554	>	* @return an iterator over the elements in this deque
555		*/
556		public Iterator<E> iterator() {
557		return new DeqIterator();
558		}
559
560	+	public Iterator<E> descendingIterator() {
561	+	return new DescendingIterator();
562	+	}
563	+
564		private class DeqIterator implements Iterator<E> {
565		/**
566		* Index of element to be returned by subsequent call to next.
#	Line 597 | Line 584 | public class ArrayDeque<E> extends Abstr
584		}
585
586		public E next() {
600	–	E result;
587		if (cursor == fence)
588		throw new NoSuchElementException();
589	+	@SuppressWarnings("unchecked")
590	+	E result = (E) elements[cursor];
591		// This check doesn't catch all possible comodifications,
592		// but does catch the ones that corrupt traversal
593	<	if (tail != fence || (result = elements[cursor]) == null)
593	>	if (tail != fence || result == null)
594		throw new ConcurrentModificationException();
595		lastRet = cursor;
596		cursor = (cursor + 1) & (elements.length - 1);
#	Line 612 | Line 600 | public class ArrayDeque<E> extends Abstr
600		public void remove() {
601		if (lastRet < 0)
602		throw new IllegalStateException();
603	<	if (delete(lastRet))
604	<	cursor--;
603	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
604	>	cursor = (cursor - 1) & (elements.length - 1);
605	>	fence = tail;
606	>	}
607		lastRet = -1;
618	–	fence = tail;
608		}
609		}
610
611		/**
612	<	* Returns <tt>true</tt> if this deque contains the specified
613	<	* element.  More formally, returns <tt>true</tt> if and only if this
614	<	* deque contains at least one element <tt>e</tt> such that
615	<	* <tt>e.equals(o)</tt>.
612	>	* This class is nearly a mirror-image of DeqIterator, using tail
613	>	* instead of head for initial cursor, and head instead of tail
614	>	* for fence.
615	>	*/
616	>	private class DescendingIterator implements Iterator<E> {
617	>	private int cursor = tail;
618	>	private int fence = head;
619	>	private int lastRet = -1;
620	>
621	>	public boolean hasNext() {
622	>	return cursor != fence;
623	>	}
624	>
625	>	public E next() {
626	>	if (cursor == fence)
627	>	throw new NoSuchElementException();
628	>	cursor = (cursor - 1) & (elements.length - 1);
629	>	@SuppressWarnings("unchecked")
630	>	E result = (E) elements[cursor];
631	>	if (head != fence || result == null)
632	>	throw new ConcurrentModificationException();
633	>	lastRet = cursor;
634	>	return result;
635	>	}
636	>
637	>	public void remove() {
638	>	if (lastRet < 0)
639	>	throw new IllegalStateException();
640	>	if (!delete(lastRet)) {
641	>	cursor = (cursor + 1) & (elements.length - 1);
642	>	fence = head;
643	>	}
644	>	lastRet = -1;
645	>	}
646	>	}
647	>
648	>	/**
649	>	* Returns {@code true} if this deque contains the specified element.
650	>	* More formally, returns {@code true} if and only if this deque contains
651	>	* at least one element {@code e} such that {@code o.equals(e)}.
652		*
653		* @param o object to be checked for containment in this deque
654	<	* @return <tt>true</tt> if this deque contains the specified element
654	>	* @return {@code true} if this deque contains the specified element
655		*/
656		public boolean contains(Object o) {
657	<	if (o == null)
658	<	return false;
659	<	int mask = elements.length - 1;
660	<	int i = head;
661	<	E x;
662	<	while ( (x = elements[i]) != null) {
663	<	if (o.equals(x))
639	<	return true;
640	<	i = (i + 1) & mask;
657	>	if (o != null) {
658	>	int mask = elements.length - 1;
659	>	int i = head;
660	>	for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
661	>	if (o.equals(x))
662	>	return true;
663	>	}
664		}
665		return false;
666		}
667
668		/**
669		* Removes a single instance of the specified element from this deque.
670	<	* This method is equivalent to {@link #removeFirstOccurrence}.
670	>	* If the deque does not contain the element, it is unchanged.
671	>	* More formally, removes the first element {@code e} such that
672	>	* {@code o.equals(e)} (if such an element exists).
673	>	* Returns {@code true} if this deque contained the specified element
674	>	* (or equivalently, if this deque changed as a result of the call).
675	>	*
676	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
677		*
678	<	* @param e element to be removed from this deque, if present
679	<	* @return <tt>true</tt> if this deque contained the specified element
678	>	* @param o element to be removed from this deque, if present
679	>	* @return {@code true} if this deque contained the specified element
680		*/
681	<	public boolean remove(Object e) {
682	<	return removeFirstOccurrence(e);
681	>	public boolean remove(Object o) {
682	>	return removeFirstOccurrence(o);
683		}
684
685		/**
686		* Removes all of the elements from this deque.
687	+	* The deque will be empty after this call returns.
688		*/
689		public void clear() {
690		int h = head;
#	Line 666 | Line 696 | public class ArrayDeque<E> extends Abstr
696		do {
697		elements[i] = null;
698		i = (i + 1) & mask;
699	<	} while(i != t);
699	>	} while (i != t);
700		}
701		}
702
703		/**
704	<	* Returns an array containing all of the elements in this list
705	<	* in the correct order.
704	>	* Returns an array containing all of the elements in this deque
705	>	* in proper sequence (from first to last element).
706	>	*
707	>	* <p>The returned array will be "safe" in that no references to it are
708	>	* maintained by this deque.  (In other words, this method must allocate
709	>	* a new array).  The caller is thus free to modify the returned array.
710		*
711	<	* @return an array containing all of the elements in this list
712	<	*         in the correct order
711	>	* <p>This method acts as bridge between array-based and collection-based
712	>	* APIs.
713	>	*
714	>	* @return an array containing all of the elements in this deque
715		*/
716		public Object[] toArray() {
717	<	return copyElements(new Object[size()]);
717	>	final int head = this.head;
718	>	final int tail = this.tail;
719	>	boolean wrap = (tail < head);
720	>	int end = wrap ? tail + elements.length : tail;
721	>	Object[] a = Arrays.copyOfRange(elements, head, end);
722	>	if (wrap)
723	>	System.arraycopy(elements, 0, a, elements.length - head, tail);
724	>	return a;
725		}
726
727		/**
728	<	* Returns an array containing all of the elements in this deque in the
729	<	* correct order; the runtime type of the returned array is that of the
730	<	* specified array.  If the deque fits in the specified array, it is
731	<	* returned therein.  Otherwise, a new array is allocated with the runtime
732	<	* type of the specified array and the size of this deque.
728	>	* Returns an array containing all of the elements in this deque in
729	>	* proper sequence (from first to last element); the runtime type of the
730	>	* returned array is that of the specified array.  If the deque fits in
731	>	* the specified array, it is returned therein.  Otherwise, a new array
732	>	* is allocated with the runtime type of the specified array and the
733	>	* size of this deque.
734	>	*
735	>	* <p>If this deque fits in the specified array with room to spare
736	>	* (i.e., the array has more elements than this deque), the element in
737	>	* the array immediately following the end of the deque is set to
738	>	* {@code null}.
739	>	*
740	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
741	>	* array-based and collection-based APIs.  Further, this method allows
742	>	* precise control over the runtime type of the output array, and may,
743	>	* under certain circumstances, be used to save allocation costs.
744	>	*
745	>	* <p>Suppose {@code x} is a deque known to contain only strings.
746	>	* The following code can be used to dump the deque into a newly
747	>	* allocated array of {@code String}:
748	>	*
749	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
750		*
751	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
752	<	* the array has more elements than the deque), the element in the array
693	<	* immediately following the end of the collection is set to <tt>null</tt>.
751	>	* Note that {@code toArray(new Object[0])} is identical in function to
752	>	* {@code toArray()}.
753		*
754		* @param a the array into which the elements of the deque are to
755	<	*          be stored, if it is big enough; otherwise, a new array of the
756	<	*          same runtime type is allocated for this purpose
757	<	* @return an array containing the elements of the deque
758	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
759	<	*         of the runtime type of every element in this deque
755	>	*          be stored, if it is big enough; otherwise, a new array of the
756	>	*          same runtime type is allocated for this purpose
757	>	* @return an array containing all of the elements in this deque
758	>	* @throws ArrayStoreException if the runtime type of the specified array
759	>	*         is not a supertype of the runtime type of every element in
760	>	*         this deque
761	>	* @throws NullPointerException if the specified array is null
762		*/
763	+	@SuppressWarnings("unchecked")
764		public <T> T[] toArray(T[] a) {
765	<	int size = size();
766	<	if (a.length < size)
767	<	a = (T[])java.lang.reflect.Array.newInstance(
768	<	a.getClass().getComponentType(), size);
769	<	copyElements(a);
770	<	if (a.length > size)
771	<	a[size] = null;
765	>	final int head = this.head;
766	>	final int tail = this.tail;
767	>	boolean wrap = (tail < head);
768	>	int size = (tail - head) + (wrap ? elements.length : 0);
769	>	int firstLeg = size - (wrap ? tail : 0);
770	>	int len = a.length;
771	>	if (size > len) {
772	>	a = (T[]) Arrays.copyOfRange(elements, head, head + size,
773	>	a.getClass());
774	>	} else {
775	>	System.arraycopy(elements, head, a, 0, firstLeg);
776	>	if (size < len)
777	>	a[size] = null;
778	>	}
779	>	if (wrap)
780	>	System.arraycopy(elements, 0, a, firstLeg, tail);
781		return a;
782		}
783
#	Line 718 | Line 789 | public class ArrayDeque<E> extends Abstr
789		* @return a copy of this deque
790		*/
791		public ArrayDeque<E> clone() {
792	<	try {
792	>	try {
793	>	@SuppressWarnings("unchecked")
794		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
795	<	// These two lines are currently faster than cloning the array:
724	<	result.elements = (E[]) new Object[elements.length];
725	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
795	>	result.elements = Arrays.copyOf(elements, elements.length);
796		return result;
797	<
728	<	} catch (CloneNotSupportedException e) {
797	>	} catch (CloneNotSupportedException e) {
798		throw new AssertionError();
799		}
800		}
801
733	–	/**
734	–	* Appease the serialization gods.
735	–	*/
802		private static final long serialVersionUID = 2340985798034038923L;
803
804		/**
805	<	* Serialize this deque.
805	>	* Saves this deque to a stream (that is, serializes it).
806		*
807	<	* @serialData The current size (<tt>int</tt>) of the deque,
807	>	* @param s the stream
808	>	* @throws java.io.IOException if an I/O error occurs
809	>	* @serialData The current size ({@code int}) of the deque,
810		* followed by all of its elements (each an object reference) in
811		* first-to-last order.
812		*/
813	<	private void writeObject(ObjectOutputStream s) throws IOException {
813	>	private void writeObject(java.io.ObjectOutputStream s)
814	>	throws java.io.IOException {
815		s.defaultWriteObject();
816
817		// Write out size
818	<	int size = size();
750	<	s.writeInt(size);
818	>	s.writeInt(size());
819
820		// Write out elements in order.
753	–	int i = head;
821		int mask = elements.length - 1;
822	<	for (int j = 0; j < size; j++) {
822	>	for (int i = head; i != tail; i = (i + 1) & mask)
823		s.writeObject(elements[i]);
757	–	i = (i + 1) & mask;
758	–	}
824		}
825
826		/**
827	<	* Deserialize this deque.
827	>	* Reconstitutes this deque from a stream (that is, deserializes it).
828	>	* @param s the stream
829	>	* @throws ClassNotFoundException if the class of a serialized object
830	>	*         could not be found
831	>	* @throws java.io.IOException if an I/O error occurs
832		*/
833	<	private void readObject(ObjectInputStream s)
834	<	throws IOException, ClassNotFoundException {
833	>	private void readObject(java.io.ObjectInputStream s)
834	>	throws java.io.IOException, ClassNotFoundException {
835		s.defaultReadObject();
836
837		// Read in size and allocate array
#	Line 773 | Line 842 | public class ArrayDeque<E> extends Abstr
842
843		// Read in all elements in the proper order.
844		for (int i = 0; i < size; i++)
845	<	elements[i] = (E)s.readObject();
845	>	elements[i] = s.readObject();
846	>	}
847
848	+	public Spliterator<E> spliterator() {
849	+	return new DeqSpliterator<E>(this, -1, -1);
850		}
851	+
852	+	static final class DeqSpliterator<E> implements Spliterator<E> {
853	+	private final ArrayDeque<E> deq;
854	+	private int fence;  // -1 until first use
855	+	private int index;  // current index, modified on traverse/split
856	+
857	+	/** Creates new spliterator covering the given array and range */
858	+	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
859	+	this.deq = deq;
860	+	this.index = origin;
861	+	this.fence = fence;
862	+	}
863	+
864	+	private int getFence() { // force initialization
865	+	int t;
866	+	if ((t = fence) < 0) {
867	+	t = fence = deq.tail;
868	+	index = deq.head;
869	+	}
870	+	return t;
871	+	}
872	+
873	+	public Spliterator<E> trySplit() {
874	+	int t = getFence(), h = index, n = deq.elements.length;
875	+	if (h != t && ((h + 1) & (n - 1)) != t) {
876	+	if (h > t)
877	+	t += n;
878	+	int m = ((h + t) >>> 1) & (n - 1);
879	+	return new DeqSpliterator<>(deq, h, index = m);
880	+	}
881	+	return null;
882	+	}
883	+
884	+	public void forEachRemaining(Consumer<? super E> consumer) {
885	+	if (consumer == null)
886	+	throw new NullPointerException();
887	+	Object[] a = deq.elements;
888	+	int m = a.length - 1, f = getFence(), i = index;
889	+	index = f;
890	+	while (i != f) {
891	+	@SuppressWarnings("unchecked") E e = (E)a[i];
892	+	i = (i + 1) & m;
893	+	if (e == null)
894	+	throw new ConcurrentModificationException();
895	+	consumer.accept(e);
896	+	}
897	+	}
898	+
899	+	public boolean tryAdvance(Consumer<? super E> consumer) {
900	+	if (consumer == null)
901	+	throw new NullPointerException();
902	+	Object[] a = deq.elements;
903	+	int m = a.length - 1, f = getFence(), i = index;
904	+	if (i != f) {
905	+	@SuppressWarnings("unchecked") E e = (E)a[i];
906	+	index = (i + 1) & m;
907	+	if (e == null)
908	+	throw new ConcurrentModificationException();
909	+	consumer.accept(e);
910	+	return true;
911	+	}
912	+	return false;
913	+	}
914	+
915	+	public long estimateSize() {
916	+	int n = getFence() - index;
917	+	if (n < 0)
918	+	n += deq.elements.length;
919	+	return (long) n;
920	+	}
921	+
922	+	@Override
923	+	public int characteristics() {
924	+	return Spliterator.ORDERED | Spliterator.SIZED |
925	+	Spliterator.NONNULL | Spliterator.SUBSIZED;
926	+	}
927	+	}
928	+
929		}

Diff Legend

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