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

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.5 by dl, Tue Mar 22 01:29:00 2005 UTC vs.
Revision 1.61 by jsr166, Wed Dec 31 07:54:13 2014 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	>	import java.util.stream.Stream;
11
12		/**
13		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 15 | Line 18 | import java.io.*;
18		* {@link Stack} when used as a stack, and faster than {@link LinkedList}
19		* when used as a queue.
20		*
21	<	* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time.
22	<	* Exceptions include {@link #remove(Object) remove}, {@link
23	<	* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
24	<	* removeLastOccurrence}, {@link #contains contains }, {@link #iterator
25	<	* iterator.remove()}, and the bulk operations, all of which run in linear
26	<	* time.
21	>	* <p>Most {@code ArrayDeque} operations run in amortized constant time.
22	>	* Exceptions include
23	>	* {@link #remove(Object) remove},
24	>	* {@link #removeFirstOccurrence removeFirstOccurrence},
25	>	* {@link #removeLastOccurrence removeLastOccurrence},
26	>	* {@link #contains contains},
27	>	* {@link #iterator iterator.remove()},
28	>	* and the bulk operations, all of which run in linear time.
29		*
30	<	* <p>The iterators returned by this class's <tt>iterator</tt> method are
31	<	* <i>fail-fast</i>: If the deque is modified at any time after the iterator
32	<	* is created, in any way except through the iterator's own remove method, the
33	<	* iterator will generally throw a {@link ConcurrentModificationException}.
34	<	* Thus, in the face of concurrent modification, the iterator fails quickly
35	<	* and cleanly, rather than risking arbitrary, non-deterministic behavior at
36	<	* an undetermined time in the future.
30	>	* <p>The iterators returned by this class's {@link #iterator() iterator}
31	>	* method are <em>fail-fast</em>: If the deque is modified at any time after
32	>	* the iterator is created, in any way except through the iterator's own
33	>	* {@code remove} method, the iterator will generally throw a {@link
34	>	* ConcurrentModificationException}.  Thus, in the face of concurrent
35	>	* modification, the iterator fails quickly and cleanly, rather than risking
36	>	* arbitrary, non-deterministic behavior at an undetermined time in the
37	>	* future.
38		*
39		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
40		* as it is, generally speaking, impossible to make any hard guarantees in the
41		* presence of unsynchronized concurrent modification.  Fail-fast iterators
42	<	* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
42	>	* throw {@code ConcurrentModificationException} on a best-effort basis.
43		* Therefore, it would be wrong to write a program that depended on this
44		* exception for its correctness: <i>the fail-fast behavior of iterators
45		* should be used only to detect bugs.</i>
46		*
47		* <p>This class and its iterator implement all of the
48	<	* optional methods of the {@link Collection} and {@link
49	<	* Iterator} interfaces.  This class is a member of the <a
50	<	* href="{@docRoot}/../guide/collections/index.html"> Java Collections
51	<	* Framework</a>.
48	>	* <em>optional</em> methods of the {@link Collection} and {@link
49	>	* Iterator} interfaces.
50	>	*
51	>	* <p>This class is a member of the
52	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
53	>	* Java Collections Framework</a>.
54		*
55		* @author  Josh Bloch and Doug Lea
56		* @since   1.6
57	<	* @param <E> the type of elements held in this collection
57	>	* @param <E> the type of elements held in this deque
58		*/
59		public class ArrayDeque<E> extends AbstractCollection<E>
60		implements Deque<E>, Cloneable, Serializable
#	Line 61 | Line 69 | public class ArrayDeque<E> extends Abstr
69		* other.  We also guarantee that all array cells not holding
70		* deque elements are always null.
71		*/
72	<	private transient E[] elements;
72	>	transient Object[] elements; // non-private to simplify nested class access
73
74		/**
75		* The index of the element at the head of the deque (which is the
76		* element that would be removed by remove() or pop()); or an
77		* arbitrary number equal to tail if the deque is empty.
78		*/
79	<	private transient int head;
79	>	transient int head;
80
81		/**
82		* The index at which the next element would be added to the tail
83		* of the deque (via addLast(E), add(E), or push(E)).
84		*/
85	<	private transient int tail;
85	>	transient int tail;
86
87		/**
88		* The minimum capacity that we'll use for a newly created deque.
#	Line 85 | Line 93 | public class ArrayDeque<E> extends Abstr
93		// ******  Array allocation and resizing utilities ******
94
95		/**
96	<	* Allocate empty array to hold the given number of elements.
96	>	* Allocates empty array to hold the given number of elements.
97		*
98	<	* @param numElements  the number of elements to hold.
98	>	* @param numElements  the number of elements to hold
99		*/
100		private void allocateElements(int numElements) {
101		int initialCapacity = MIN_INITIAL_CAPACITY;
#	Line 105 | Line 113 | public class ArrayDeque<E> extends Abstr
113		if (initialCapacity < 0)   // Too many elements, must back off
114		initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
115		}
116	<	elements = (E[]) new Object[initialCapacity];
116	>	elements = new Object[initialCapacity];
117		}
118
119		/**
120	<	* Double the capacity of this deque.  Call only when full, i.e.,
120	>	* Doubles the capacity of this deque.  Call only when full, i.e.,
121		* when head and tail have wrapped around to become equal.
122		*/
123		private void doubleCapacity() {
#	Line 123 | Line 131 | public class ArrayDeque<E> extends Abstr
131		Object[] a = new Object[newCapacity];
132		System.arraycopy(elements, p, a, 0, r);
133		System.arraycopy(elements, 0, a, r, p);
134	<	elements = (E[])a;
134	>	elements = a;
135		head = 0;
136		tail = n;
137		}
138
139		/**
132	–	* 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	–	/**
140		* Constructs an empty array deque with an initial capacity
141		* sufficient to hold 16 elements.
142		*/
143		public ArrayDeque() {
144	<	elements = (E[]) new Object[16];
144	>	elements = new Object[16];
145		}
146
147		/**
#	Line 186 | Line 176 | public class ArrayDeque<E> extends Abstr
176		/**
177		* Inserts the specified element at the front of this deque.
178		*
179	<	* @param e the element to insert
180	<	* @throws NullPointerException if <tt>e</tt> is null
179	>	* @param e the element to add
180	>	* @throws NullPointerException if the specified element is null
181		*/
182		public void addFirst(E e) {
183		if (e == null)
#	Line 198 | Line 188 | public class ArrayDeque<E> extends Abstr
188		}
189
190		/**
191	<	* Inserts the specified element to the end of this deque.
192	<	* This method is equivalent to {@link Collection#add} and
193	<	* {@link #push}.
191	>	* Inserts the specified element at the end of this deque.
192	>	*
193	>	* <p>This method is equivalent to {@link #add}.
194		*
195	<	* @param e the element to insert
196	<	* @throws NullPointerException if <tt>e</tt> is null
195	>	* @param e the element to add
196	>	* @throws NullPointerException if the specified element is null
197		*/
198		public void addLast(E e) {
199		if (e == null)
#	Line 214 | Line 204 | public class ArrayDeque<E> extends Abstr
204		}
205
206		/**
217	–	* 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	–	/**
207		* Inserts the specified element at the front of this deque.
208		*
209	<	* @param e the element to insert
210	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
211	<	* @throws NullPointerException if <tt>e</tt> is null
209	>	* @param e the element to add
210	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
211	>	* @throws NullPointerException if the specified element is null
212		*/
213		public boolean offerFirst(E e) {
214		addFirst(e);
#	Line 260 | Line 216 | public class ArrayDeque<E> extends Abstr
216		}
217
218		/**
219	<	* Inserts the specified element to the end of this deque.
219	>	* Inserts the specified element at the end of this deque.
220		*
221	<	* @param e the element to insert
222	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
223	<	* @throws NullPointerException if <tt>e</tt> is null
221	>	* @param e the element to add
222	>	* @return {@code true} (as specified by {@link Deque#offerLast})
223	>	* @throws NullPointerException if the specified element is null
224		*/
225		public boolean offerLast(E e) {
226		addLast(e);
#	Line 272 | Line 228 | public class ArrayDeque<E> extends Abstr
228		}
229
230		/**
231	<	* 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
231	>	* @throws NoSuchElementException {@inheritDoc}
232		*/
233		public E removeFirst() {
234		E x = pollFirst();
#	Line 287 | Line 238 | public class ArrayDeque<E> extends Abstr
238		}
239
240		/**
241	<	* 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
241	>	* @throws NoSuchElementException {@inheritDoc}
242		*/
243		public E removeLast() {
244		E x = pollLast();
#	Line 301 | Line 247 | public class ArrayDeque<E> extends Abstr
247		return x;
248		}
249
250	<	/**
251	<	* Retrieves, but does not remove, the first element of this deque,
252	<	* returning <tt>null</tt> if this deque is empty.
253	<	*
254	<	* @return the first element of this deque, or <tt>null</tt> if
255	<	*     this deque is empty
256	<	*/
257	<	public E peekFirst() {
258	<	return elements[head]; // elements[head] is null if deque empty
250	>	public E pollFirst() {
251	>	int h = head;
252	>	@SuppressWarnings("unchecked")
253	>	E result = (E) elements[h];
254	>	// Element is null if deque empty
255	>	if (result == null)
256	>	return null;
257	>	elements[h] = null;     // Must null out slot
258	>	head = (h + 1) & (elements.length - 1);
259	>	return result;
260		}
261
262	<	/**
263	<	* Retrieves, but does not remove, the last element of this deque,
264	<	* returning <tt>null</tt> if this deque is empty.
265	<	*
266	<	* @return the last element of this deque, or <tt>null</tt> if this deque
267	<	*     is empty
268	<	*/
269	<	public E peekLast() {
270	<	return elements[(tail - 1) & (elements.length - 1)];
262	>	public E pollLast() {
263	>	int t = (tail - 1) & (elements.length - 1);
264	>	@SuppressWarnings("unchecked")
265	>	E result = (E) elements[t];
266	>	if (result == null)
267	>	return null;
268	>	elements[t] = null;
269	>	tail = t;
270	>	return result;
271		}
272
273		/**
274	<	* Retrieves, but does not remove, the first element of this
328	<	* deque.  This method differs from the <tt>peekFirst</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
274	>	* @throws NoSuchElementException {@inheritDoc}
275		*/
276		public E getFirst() {
277	<	E x = elements[head];
278	<	if (x == null)
277	>	@SuppressWarnings("unchecked")
278	>	E result = (E) elements[head];
279	>	if (result == null)
280		throw new NoSuchElementException();
281	<	return x;
281	>	return result;
282		}
283
284		/**
285	<	* Retrieves, but does not remove, the last element of this
343	<	* deque.  This method differs from the <tt>peekLast</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
285	>	* @throws NoSuchElementException {@inheritDoc}
286		*/
287		public E getLast() {
288	<	E x = elements[(tail - 1) & (elements.length - 1)];
289	<	if (x == null)
288	>	@SuppressWarnings("unchecked")
289	>	E result = (E) elements[(tail - 1) & (elements.length - 1)];
290	>	if (result == null)
291		throw new NoSuchElementException();
292	<	return x;
292	>	return result;
293	>	}
294	>
295	>	@SuppressWarnings("unchecked")
296	>	public E peekFirst() {
297	>	// elements[head] is null if deque empty
298	>	return (E) elements[head];
299	>	}
300	>
301	>	@SuppressWarnings("unchecked")
302	>	public E peekLast() {
303	>	return (E) elements[(tail - 1) & (elements.length - 1)];
304		}
305
306		/**
307		* Removes the first occurrence of the specified element in this
308	<	* deque (when traversing the deque from head to tail).  More
309	<	* formally, removes the first element e such that (o==null ?
310	<	* e==null : o.equals(e)). If the deque does not contain the
311	<	* element, it is unchanged.
308	>	* deque (when traversing the deque from head to tail).
309	>	* If the deque does not contain the element, it is unchanged.
310	>	* More formally, removes the first element {@code e} such that
311	>	* {@code o.equals(e)} (if such an element exists).
312	>	* Returns {@code true} if this deque contained the specified element
313	>	* (or equivalently, if this deque changed as a result of the call).
314		*
315		* @param o element to be removed from this deque, if present
316	<	* @return <tt>true</tt> if the deque contained the specified element
316	>	* @return {@code true} if the deque contained the specified element
317		*/
318		public boolean removeFirstOccurrence(Object o) {
319	<	if (o == null)
320	<	return false;
321	<	int mask = elements.length - 1;
322	<	int i = head;
323	<	E x;
324	<	while ( (x = elements[i]) != null) {
325	<	if (o.equals(x)) {
326	<	delete(i);
375	<	return true;
319	>	if (o != null) {
320	>	int mask = elements.length - 1;
321	>	int i = head;
322	>	for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
323	>	if (o.equals(x)) {
324	>	delete(i);
325	>	return true;
326	>	}
327		}
377	–	i = (i + 1) & mask;
328		}
329		return false;
330		}
331
332		/**
333		* Removes the last occurrence of the specified element in this
334	<	* deque (when traversing the deque from head to tail). More
335	<	* formally, removes the last element e such that (o==null ?
336	<	* e==null : o.equals(e)). If the deque
337	<	* does not contain the element, it is unchanged.
334	>	* deque (when traversing the deque from head to tail).
335	>	* If the deque does not contain the element, it is unchanged.
336	>	* More formally, removes the last element {@code e} such that
337	>	* {@code o.equals(e)} (if such an element exists).
338	>	* Returns {@code true} if this deque contained the specified element
339	>	* (or equivalently, if this deque changed as a result of the call).
340		*
341		* @param o element to be removed from this deque, if present
342	<	* @return <tt>true</tt> if the deque contained the specified element
342	>	* @return {@code true} if the deque contained the specified element
343		*/
344		public boolean removeLastOccurrence(Object o) {
345	<	if (o == null)
346	<	return false;
347	<	int mask = elements.length - 1;
348	<	int i = (tail - 1) & mask;
349	<	E x;
350	<	while ( (x = elements[i]) != null) {
351	<	if (o.equals(x)) {
352	<	delete(i);
401	<	return true;
345	>	if (o != null) {
346	>	int mask = elements.length - 1;
347	>	int i = (tail - 1) & mask;
348	>	for (Object x; (x = elements[i]) != null; i = (i - 1) & mask) {
349	>	if (o.equals(x)) {
350	>	delete(i);
351	>	return true;
352	>	}
353		}
403	–	i = (i - 1) & mask;
354		}
355		return false;
356		}
#	Line 408 | Line 358 | public class ArrayDeque<E> extends Abstr
358		// *** Queue methods ***
359
360		/**
361	<	* Inserts the specified element to the end of this deque.
412	<	*
413	<	* <p>This method is equivalent to {@link #offerLast}.
414	<	*
415	<	* @param e the element to insert
416	<	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
417	<	* @throws NullPointerException if <tt>e</tt> is null
418	<	*/
419	<	public boolean offer(E e) {
420	<	return offerLast(e);
421	<	}
422	<
423	<	/**
424	<	* Inserts the specified element to the end of this deque.
361	>	* Inserts the specified element at the end of this deque.
362		*
363		* <p>This method is equivalent to {@link #addLast}.
364		*
365	<	* @param e the element to insert
366	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
367	<	* @throws NullPointerException if <tt>e</tt> is null
365	>	* @param e the element to add
366	>	* @return {@code true} (as specified by {@link Collection#add})
367	>	* @throws NullPointerException if the specified element is null
368		*/
369		public boolean add(E e) {
370		addLast(e);
#	Line 435 | Line 372 | public class ArrayDeque<E> extends Abstr
372		}
373
374		/**
375	<	* Retrieves and removes the head of the queue represented by
439	<	* this deque, or <tt>null</tt> if this deque is empty.  In other words,
440	<	* retrieves and removes the first element of this deque, or <tt>null</tt>
441	<	* if this deque is empty.
375	>	* Inserts the specified element at the end of this deque.
376		*
377	<	* <p>This method is equivalent to {@link #pollFirst}.
377	>	* <p>This method is equivalent to {@link #offerLast}.
378		*
379	<	* @return the first element of this deque, or <tt>null</tt> if
380	<	*     this deque is empty
379	>	* @param e the element to add
380	>	* @return {@code true} (as specified by {@link Queue#offer})
381	>	* @throws NullPointerException if the specified element is null
382		*/
383	<	public E poll() {
384	<	return pollFirst();
383	>	public boolean offer(E e) {
384	>	return offerLast(e);
385		}
386
387		/**
388		* Retrieves and removes the head of the queue represented by this deque.
389	<	* This method differs from the <tt>poll</tt> method in that it throws an
389	>	*
390	>	* This method differs from {@link #poll poll} only in that it throws an
391		* exception if this deque is empty.
392		*
393		* <p>This method is equivalent to {@link #removeFirst}.
394		*
395		* @return the head of the queue represented by this deque
396	<	* @throws NoSuchElementException if this deque is empty
396	>	* @throws NoSuchElementException {@inheritDoc}
397		*/
398		public E remove() {
399		return removeFirst();
400		}
401
402		/**
403	<	* Retrieves, but does not remove, the head of the queue represented by
404	<	* this deque, returning <tt>null</tt> if this deque is empty.
403	>	* Retrieves and removes the head of the queue represented by this deque
404	>	* (in other words, the first element of this deque), or returns
405	>	* {@code null} if this deque is empty.
406		*
407	<	* <p>This method is equivalent to {@link #peekFirst}
407	>	* <p>This method is equivalent to {@link #pollFirst}.
408		*
409		* @return the head of the queue represented by this deque, or
410	<	*     <tt>null</tt> if this deque is empty
410	>	*         {@code null} if this deque is empty
411		*/
412	<	public E peek() {
413	<	return peekFirst();
412	>	public E poll() {
413	>	return pollFirst();
414		}
415
416		/**
417		* Retrieves, but does not remove, the head of the queue represented by
418	<	* this deque.  This method differs from the <tt>peek</tt> method only in
418	>	* this deque.  This method differs from {@link #peek peek} only in
419		* that it throws an exception if this deque is empty.
420		*
421	<	* <p>This method is equivalent to {@link #getFirst}
421	>	* <p>This method is equivalent to {@link #getFirst}.
422		*
423		* @return the head of the queue represented by this deque
424	<	* @throws NoSuchElementException if this deque is empty
424	>	* @throws NoSuchElementException {@inheritDoc}
425		*/
426		public E element() {
427		return getFirst();
428		}
429
430	+	/**
431	+	* Retrieves, but does not remove, the head of the queue represented by
432	+	* this deque, or returns {@code null} if this deque is empty.
433	+	*
434	+	* <p>This method is equivalent to {@link #peekFirst}.
435	+	*
436	+	* @return the head of the queue represented by this deque, or
437	+	*         {@code null} if this deque is empty
438	+	*/
439	+	public E peek() {
440	+	return peekFirst();
441	+	}
442	+
443		// *** Stack methods ***
444
445		/**
#	Line 499 | Line 449 | public class ArrayDeque<E> extends Abstr
449		* <p>This method is equivalent to {@link #addFirst}.
450		*
451		* @param e the element to push
452	<	* @throws NullPointerException if <tt>e</tt> is null
452	>	* @throws NullPointerException if the specified element is null
453		*/
454		public void push(E e) {
455		addFirst(e);
#	Line 512 | Line 462 | public class ArrayDeque<E> extends Abstr
462		* <p>This method is equivalent to {@link #removeFirst()}.
463		*
464		* @return the element at the front of this deque (which is the top
465	<	*     of the stack represented by this deque)
466	<	* @throws NoSuchElementException if this deque is empty
465	>	*         of the stack represented by this deque)
466	>	* @throws NoSuchElementException {@inheritDoc}
467		*/
468		public E pop() {
469		return removeFirst();
470		}
471
472	+	private void checkInvariants() {
473	+	assert elements[tail] == null;
474	+	assert head == tail ? elements[head] == null :
475	+	(elements[head] != null &&
476	+	elements[(tail - 1) & (elements.length - 1)] != null);
477	+	assert elements[(head - 1) & (elements.length - 1)] == null;
478	+	}
479	+
480		/**
481	<	* Remove the element at the specified position in the elements array,
482	<	* adjusting head, tail, and size as necessary.  This can result in
483	<	* motion of elements backwards or forwards in the array.
481	>	* Removes the element at the specified position in the elements array,
482	>	* adjusting head and tail as necessary.  This can result in motion of
483	>	* elements backwards or forwards in the array.
484		*
485		* <p>This method is called delete rather than remove to emphasize
486	<	* that its semantics differ from those of List.remove(int).
486	>	* that its semantics differ from those of {@link List#remove(int)}.
487		*
488		* @return true if elements moved backwards
489		*/
490		private boolean delete(int i) {
491	<	// Case 1: Deque doesn't wrap
492	<	// Case 2: Deque does wrap and removed element is in the head portion
493	<	if ((head < tail || tail == 0) || i >= head) {
494	<	System.arraycopy(elements, head, elements, head + 1, i - head);
495	<	elements[head] = null;
496	<	head = (head + 1) & (elements.length - 1);
491	>	checkInvariants();
492	>	final Object[] elements = this.elements;
493	>	final int mask = elements.length - 1;
494	>	final int h = head;
495	>	final int t = tail;
496	>	final int front = (i - h) & mask;
497	>	final int back  = (t - i) & mask;
498	>
499	>	// Invariant: head <= i < tail mod circularity
500	>	if (front >= ((t - h) & mask))
501	>	throw new ConcurrentModificationException();
502	>
503	>	// Optimize for least element motion
504	>	if (front < back) {
505	>	if (h <= i) {
506	>	System.arraycopy(elements, h, elements, h + 1, front);
507	>	} else { // Wrap around
508	>	System.arraycopy(elements, 0, elements, 1, i);
509	>	elements[0] = elements[mask];
510	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
511	>	}
512	>	elements[h] = null;
513	>	head = (h + 1) & mask;
514		return false;
515	+	} else {
516	+	if (i < t) { // Copy the null tail as well
517	+	System.arraycopy(elements, i + 1, elements, i, back);
518	+	tail = t - 1;
519	+	} else { // Wrap around
520	+	System.arraycopy(elements, i + 1, elements, i, mask - i);
521	+	elements[mask] = elements[0];
522	+	System.arraycopy(elements, 1, elements, 0, t);
523	+	tail = (t - 1) & mask;
524	+	}
525	+	return true;
526		}
541	–
542	–	// Case 3: Deque wraps and removed element is in the tail portion
543	–	tail--;
544	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
545	–	elements[tail] = null;
546	–	return true;
527		}
528
529		// *** Collection Methods ***
#	Line 558 | Line 538 | public class ArrayDeque<E> extends Abstr
538		}
539
540		/**
541	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
541	>	* Returns {@code true} if this deque contains no elements.
542		*
543	<	* @return <tt>true</tt> if this collection contains no elements.
543	>	* @return {@code true} if this deque contains no elements
544		*/
545		public boolean isEmpty() {
546		return head == tail;
#	Line 572 | Line 552 | public class ArrayDeque<E> extends Abstr
552		* order that elements would be dequeued (via successive calls to
553		* {@link #remove} or popped (via successive calls to {@link #pop}).
554		*
555	<	* @return an <tt>Iterator</tt> over the elements in this deque
555	>	* @return an iterator over the elements in this deque
556		*/
557		public Iterator<E> iterator() {
558		return new DeqIterator();
559		}
560
561	+	public Iterator<E> descendingIterator() {
562	+	return new DescendingIterator();
563	+	}
564	+
565		private class DeqIterator implements Iterator<E> {
566		/**
567		* Index of element to be returned by subsequent call to next.
#	Line 601 | Line 585 | public class ArrayDeque<E> extends Abstr
585		}
586
587		public E next() {
604	–	E result;
588		if (cursor == fence)
589		throw new NoSuchElementException();
590	+	@SuppressWarnings("unchecked")
591	+	E result = (E) elements[cursor];
592		// This check doesn't catch all possible comodifications,
593		// but does catch the ones that corrupt traversal
594	<	if (tail != fence || (result = elements[cursor]) == null)
594	>	if (tail != fence || result == null)
595		throw new ConcurrentModificationException();
596		lastRet = cursor;
597		cursor = (cursor + 1) & (elements.length - 1);
#	Line 616 | Line 601 | public class ArrayDeque<E> extends Abstr
601		public void remove() {
602		if (lastRet < 0)
603		throw new IllegalStateException();
604	<	if (delete(lastRet))
605	<	cursor--;
604	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
605	>	cursor = (cursor - 1) & (elements.length - 1);
606	>	fence = tail;
607	>	}
608	>	lastRet = -1;
609	>	}
610	>	}
611	>
612	>	/**
613	>	* This class is nearly a mirror-image of DeqIterator, using tail
614	>	* instead of head for initial cursor, and head instead of tail
615	>	* for fence.
616	>	*/
617	>	private class DescendingIterator implements Iterator<E> {
618	>	private int cursor = tail;
619	>	private int fence = head;
620	>	private int lastRet = -1;
621	>
622	>	public boolean hasNext() {
623	>	return cursor != fence;
624	>	}
625	>
626	>	public E next() {
627	>	if (cursor == fence)
628	>	throw new NoSuchElementException();
629	>	cursor = (cursor - 1) & (elements.length - 1);
630	>	@SuppressWarnings("unchecked")
631	>	E result = (E) elements[cursor];
632	>	if (head != fence || result == null)
633	>	throw new ConcurrentModificationException();
634	>	lastRet = cursor;
635	>	return result;
636	>	}
637	>
638	>	public void remove() {
639	>	if (lastRet < 0)
640	>	throw new IllegalStateException();
641	>	if (!delete(lastRet)) {
642	>	cursor = (cursor + 1) & (elements.length - 1);
643	>	fence = head;
644	>	}
645		lastRet = -1;
622	–	fence = tail;
646		}
647		}
648
649		/**
650	<	* Returns <tt>true</tt> if this deque contains the specified
651	<	* element.  More formally, returns <tt>true</tt> if and only if this
652	<	* deque contains at least one element <tt>e</tt> such that
630	<	* <tt>e.equals(o)</tt>.
650	>	* Returns {@code true} if this deque contains the specified element.
651	>	* More formally, returns {@code true} if and only if this deque contains
652	>	* at least one element {@code e} such that {@code o.equals(e)}.
653		*
654		* @param o object to be checked for containment in this deque
655	<	* @return <tt>true</tt> if this deque contains the specified element
655	>	* @return {@code true} if this deque contains the specified element
656		*/
657		public boolean contains(Object o) {
658	<	if (o == null)
659	<	return false;
660	<	int mask = elements.length - 1;
661	<	int i = head;
662	<	E x;
663	<	while ( (x = elements[i]) != null) {
664	<	if (o.equals(x))
643	<	return true;
644	<	i = (i + 1) & mask;
658	>	if (o != null) {
659	>	int mask = elements.length - 1;
660	>	int i = head;
661	>	for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
662	>	if (o.equals(x))
663	>	return true;
664	>	}
665		}
666		return false;
667		}
668
669		/**
670		* Removes a single instance of the specified element from this deque.
671	<	* This method is equivalent to {@link #removeFirstOccurrence}.
671	>	* If the deque does not contain the element, it is unchanged.
672	>	* More formally, removes the first element {@code e} such that
673	>	* {@code o.equals(e)} (if such an element exists).
674	>	* Returns {@code true} if this deque contained the specified element
675	>	* (or equivalently, if this deque changed as a result of the call).
676	>	*
677	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
678		*
679	<	* @param e element to be removed from this deque, if present
680	<	* @return <tt>true</tt> if this deque contained the specified element
679	>	* @param o element to be removed from this deque, if present
680	>	* @return {@code true} if this deque contained the specified element
681		*/
682	<	public boolean remove(Object e) {
683	<	return removeFirstOccurrence(e);
682	>	public boolean remove(Object o) {
683	>	return removeFirstOccurrence(o);
684		}
685
686		/**
687		* Removes all of the elements from this deque.
688	+	* The deque will be empty after this call returns.
689		*/
690		public void clear() {
691		int h = head;
#	Line 670 | Line 697 | public class ArrayDeque<E> extends Abstr
697		do {
698		elements[i] = null;
699		i = (i + 1) & mask;
700	<	} while(i != t);
700	>	} while (i != t);
701		}
702		}
703
704		/**
705		* Returns an array containing all of the elements in this deque
706	<	* in the correct order.
706	>	* in proper sequence (from first to last element).
707	>	*
708	>	* <p>The returned array will be "safe" in that no references to it are
709	>	* maintained by this deque.  (In other words, this method must allocate
710	>	* a new array).  The caller is thus free to modify the returned array.
711	>	*
712	>	* <p>This method acts as bridge between array-based and collection-based
713	>	* APIs.
714		*
715		* @return an array containing all of the elements in this deque
682	–	*         in the correct order
716		*/
717		public Object[] toArray() {
718	<	return copyElements(new Object[size()]);
718	>	final int head = this.head;
719	>	final int tail = this.tail;
720	>	boolean wrap = (tail < head);
721	>	int end = wrap ? tail + elements.length : tail;
722	>	Object[] a = Arrays.copyOfRange(elements, head, end);
723	>	if (wrap)
724	>	System.arraycopy(elements, 0, a, elements.length - head, tail);
725	>	return a;
726		}
727
728		/**
729	<	* Returns an array containing all of the elements in this deque in the
730	<	* correct order; the runtime type of the returned array is that of the
731	<	* specified array.  If the deque fits in the specified array, it is
732	<	* returned therein.  Otherwise, a new array is allocated with the runtime
733	<	* type of the specified array and the size of this deque.
729	>	* Returns an array containing all of the elements in this deque in
730	>	* proper sequence (from first to last element); the runtime type of the
731	>	* returned array is that of the specified array.  If the deque fits in
732	>	* the specified array, it is returned therein.  Otherwise, a new array
733	>	* is allocated with the runtime type of the specified array and the
734	>	* size of this deque.
735	>	*
736	>	* <p>If this deque fits in the specified array with room to spare
737	>	* (i.e., the array has more elements than this deque), the element in
738	>	* the array immediately following the end of the deque is set to
739	>	* {@code null}.
740	>	*
741	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
742	>	* array-based and collection-based APIs.  Further, this method allows
743	>	* precise control over the runtime type of the output array, and may,
744	>	* under certain circumstances, be used to save allocation costs.
745	>	*
746	>	* <p>Suppose {@code x} is a deque known to contain only strings.
747	>	* The following code can be used to dump the deque into a newly
748	>	* allocated array of {@code String}:
749		*
750	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
751	<	* the array has more elements than the deque), the element in the array
752	<	* immediately following the end of the collection is set to <tt>null</tt>.
750	>	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
751	>	*
752	>	* Note that {@code toArray(new Object[0])} is identical in function to
753	>	* {@code toArray()}.
754		*
755		* @param a the array into which the elements of the deque are to
756	<	*          be stored, if it is big enough; otherwise, a new array of the
757	<	*          same runtime type is allocated for this purpose
758	<	* @return an array containing the elements of the deque
759	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
760	<	*         of the runtime type of every element in this deque
756	>	*          be stored, if it is big enough; otherwise, a new array of the
757	>	*          same runtime type is allocated for this purpose
758	>	* @return an array containing all of the elements in this deque
759	>	* @throws ArrayStoreException if the runtime type of the specified array
760	>	*         is not a supertype of the runtime type of every element in
761	>	*         this deque
762	>	* @throws NullPointerException if the specified array is null
763		*/
764	+	@SuppressWarnings("unchecked")
765		public <T> T[] toArray(T[] a) {
766	<	int size = size();
767	<	if (a.length < size)
768	<	a = (T[])java.lang.reflect.Array.newInstance(
769	<	a.getClass().getComponentType(), size);
770	<	copyElements(a);
771	<	if (a.length > size)
772	<	a[size] = null;
766	>	final int head = this.head;
767	>	final int tail = this.tail;
768	>	boolean wrap = (tail < head);
769	>	int size = (tail - head) + (wrap ? elements.length : 0);
770	>	int firstLeg = size - (wrap ? tail : 0);
771	>	int len = a.length;
772	>	if (size > len) {
773	>	a = (T[]) Arrays.copyOfRange(elements, head, head + size,
774	>	a.getClass());
775	>	} else {
776	>	System.arraycopy(elements, head, a, 0, firstLeg);
777	>	if (size < len)
778	>	a[size] = null;
779	>	}
780	>	if (wrap)
781	>	System.arraycopy(elements, 0, a, firstLeg, tail);
782		return a;
783		}
784
#	Line 723 | Line 791 | public class ArrayDeque<E> extends Abstr
791		*/
792		public ArrayDeque<E> clone() {
793		try {
794	+	@SuppressWarnings("unchecked")
795		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
796	<	// These two lines are currently faster than cloning the array:
728	<	result.elements = (E[]) new Object[elements.length];
729	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
796	>	result.elements = Arrays.copyOf(elements, elements.length);
797		return result;
731	–
798		} catch (CloneNotSupportedException e) {
799		throw new AssertionError();
800		}
801		}
802
737	–	/**
738	–	* Appease the serialization gods.
739	–	*/
803		private static final long serialVersionUID = 2340985798034038923L;
804
805		/**
806	<	* Serialize this deque.
806	>	* Saves this deque to a stream (that is, serializes it).
807		*
808	<	* @serialData The current size (<tt>int</tt>) of the deque,
808	>	* @param s the stream
809	>	* @throws java.io.IOException if an I/O error occurs
810	>	* @serialData The current size ({@code int}) of the deque,
811		* followed by all of its elements (each an object reference) in
812		* first-to-last order.
813		*/
814	<	private void writeObject(ObjectOutputStream s) throws IOException {
814	>	private void writeObject(java.io.ObjectOutputStream s)
815	>	throws java.io.IOException {
816		s.defaultWriteObject();
817
818		// Write out size
819	<	int size = size();
754	<	s.writeInt(size);
819	>	s.writeInt(size());
820
821		// Write out elements in order.
757	–	int i = head;
822		int mask = elements.length - 1;
823	<	for (int j = 0; j < size; j++) {
823	>	for (int i = head; i != tail; i = (i + 1) & mask)
824		s.writeObject(elements[i]);
761	–	i = (i + 1) & mask;
762	–	}
825		}
826
827		/**
828	<	* Deserialize this deque.
828	>	* Reconstitutes this deque from a stream (that is, deserializes it).
829	>	* @param s the stream
830	>	* @throws ClassNotFoundException if the class of a serialized object
831	>	*         could not be found
832	>	* @throws java.io.IOException if an I/O error occurs
833		*/
834	<	private void readObject(ObjectInputStream s)
835	<	throws IOException, ClassNotFoundException {
834	>	private void readObject(java.io.ObjectInputStream s)
835	>	throws java.io.IOException, ClassNotFoundException {
836		s.defaultReadObject();
837
838		// Read in size and allocate array
#	Line 777 | Line 843 | public class ArrayDeque<E> extends Abstr
843
844		// Read in all elements in the proper order.
845		for (int i = 0; i < size; i++)
846	<	elements[i] = (E)s.readObject();
846	>	elements[i] = s.readObject();
847	>	}
848
849	+	public Spliterator<E> spliterator() {
850	+	return new DeqSpliterator<E>(this, -1, -1);
851		}
852	+
853	+	static final class DeqSpliterator<E> implements Spliterator<E> {
854	+	private final ArrayDeque<E> deq;
855	+	private int fence;  // -1 until first use
856	+	private int index;  // current index, modified on traverse/split
857	+
858	+	/** Creates new spliterator covering the given array and range */
859	+	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
860	+	this.deq = deq;
861	+	this.index = origin;
862	+	this.fence = fence;
863	+	}
864	+
865	+	private int getFence() { // force initialization
866	+	int t;
867	+	if ((t = fence) < 0) {
868	+	t = fence = deq.tail;
869	+	index = deq.head;
870	+	}
871	+	return t;
872	+	}
873	+
874	+	public Spliterator<E> trySplit() {
875	+	int t = getFence(), h = index, n = deq.elements.length;
876	+	if (h != t && ((h + 1) & (n - 1)) != t) {
877	+	if (h > t)
878	+	t += n;
879	+	int m = ((h + t) >>> 1) & (n - 1);
880	+	return new DeqSpliterator<>(deq, h, index = m);
881	+	}
882	+	return null;
883	+	}
884	+
885	+	public void forEachRemaining(Consumer<? super E> consumer) {
886	+	if (consumer == null)
887	+	throw new NullPointerException();
888	+	Object[] a = deq.elements;
889	+	int m = a.length - 1, f = getFence(), i = index;
890	+	index = f;
891	+	while (i != f) {
892	+	@SuppressWarnings("unchecked") E e = (E)a[i];
893	+	i = (i + 1) & m;
894	+	if (e == null)
895	+	throw new ConcurrentModificationException();
896	+	consumer.accept(e);
897	+	}
898	+	}
899	+
900	+	public boolean tryAdvance(Consumer<? super E> consumer) {
901	+	if (consumer == null)
902	+	throw new NullPointerException();
903	+	Object[] a = deq.elements;
904	+	int m = a.length - 1, f = getFence(), i = index;
905	+	if (i != fence) {
906	+	@SuppressWarnings("unchecked") E e = (E)a[i];
907	+	index = (i + 1) & m;
908	+	if (e == null)
909	+	throw new ConcurrentModificationException();
910	+	consumer.accept(e);
911	+	return true;
912	+	}
913	+	return false;
914	+	}
915	+
916	+	public long estimateSize() {
917	+	int n = getFence() - index;
918	+	if (n < 0)
919	+	n += deq.elements.length;
920	+	return (long) n;
921	+	}
922	+
923	+	@Override
924	+	public int characteristics() {
925	+	return Spliterator.ORDERED | Spliterator.SIZED |
926	+	Spliterator.NONNULL | Spliterator.SUBSIZED;
927	+	}
928	+	}
929	+
930		}

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