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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.3 by dl, Tue Mar 8 17:52:02 2005 UTC vs.
Revision 1.32 by jsr166, Wed Jun 8 00:21:52 2011 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		/**
9		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 18 | Line 17 | import java.io.*;
17		* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time.
18		* Exceptions include {@link #remove(Object) remove}, {@link
19		* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
20	<	* removeLastOccurrence}, {@link #contains contains }, {@link #iterator
20	>	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
21		* iterator.remove()}, and the bulk operations, all of which run in linear
22		* time.
23		*
24		* <p>The iterators returned by this class's <tt>iterator</tt> method are
25		* <i>fail-fast</i>: If the deque is modified at any time after the iterator
26	<	* is created, in any way except through the iterator's own remove method, the
27	<	* iterator will generally throw a {@link ConcurrentModificationException}.
28	<	* Thus, in the face of concurrent modification, the iterator fails quickly
29	<	* and cleanly, rather than risking arbitrary, non-deterministic behavior at
30	<	* an undetermined time in the future.
26	>	* is created, in any way except through the iterator's own <tt>remove</tt>
27	>	* method, the iterator will generally throw a {@link
28	>	* ConcurrentModificationException}.  Thus, in the face of concurrent
29	>	* modification, the iterator fails quickly and cleanly, rather than risking
30	>	* arbitrary, non-deterministic behavior at an undetermined time in the
31	>	* future.
32		*
33		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
34		* as it is, generally speaking, impossible to make any hard guarantees in the
35		* presence of unsynchronized concurrent modification.  Fail-fast iterators
36	<	* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
36	>	* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
37		* Therefore, it would be wrong to write a program that depended on this
38		* exception for its correctness: <i>the fail-fast behavior of iterators
39		* should be used only to detect bugs.</i>
40		*
41		* <p>This class and its iterator implement all of the
42	<	* optional methods of the {@link Collection} and {@link
43	<	* Iterator} interfaces.  This class is a member of the <a
44	<	* href="{@docRoot}/../guide/collections/index.html"> Java Collections
45	<	* Framework</a>.
42	>	* <em>optional</em> methods of the {@link Collection} and {@link
43	>	* Iterator} interfaces.
44	>	*
45	>	* <p>This class is a member of the
46	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
47	>	* Java Collections Framework</a>.
48		*
49		* @author  Josh Bloch and Doug Lea
50		* @since   1.6
51		* @param <E> the type of elements held in this collection
52		*/
53		public class ArrayDeque<E> extends AbstractCollection<E>
54	<	implements Deque<E>, Cloneable, Serializable
54	>	implements Deque<E>, Cloneable, java.io.Serializable
55		{
56		/**
57	<	* The array in which the elements of in the deque are stored.
57	>	* The array in which the elements of the deque are stored.
58		* The capacity of the deque is the length of this array, which is
59		* always a power of two. The array is never allowed to become
60		* full, except transiently within an addX method where it is
#	Line 87 | Line 89 | public class ArrayDeque<E> extends Abstr
89		/**
90		* Allocate empty array to hold the given number of elements.
91		*
92	<	* @param numElements  the number of elements to hold.
92	>	* @param numElements  the number of elements to hold
93		*/
94	<	private void allocateElements(int numElements) {
94	>	private void allocateElements(int numElements) {
95		int initialCapacity = MIN_INITIAL_CAPACITY;
96		// Find the best power of two to hold elements.
97		// Tests "<=" because arrays aren't kept full.
#	Line 113 | Line 115 | public class ArrayDeque<E> extends Abstr
115		* when head and tail have wrapped around to become equal.
116		*/
117		private void doubleCapacity() {
118	<	assert head == tail;
118	>	assert head == tail;
119		int p = head;
120		int n = elements.length;
121		int r = n - p; // number of elements to the right of p
#	Line 129 | Line 131 | public class ArrayDeque<E> extends Abstr
131		}
132
133		/**
134	<	* Copy the elements from our element array into the specified array,
134	>	* Copies the elements from our element array into the specified array,
135		* in order (from first to last element in the deque).  It is assumed
136		* that the array is large enough to hold all elements in the deque.
137		*
#	Line 147 | Line 149 | public class ArrayDeque<E> extends Abstr
149		}
150
151		/**
152	<	* Constructs an empty array deque with the an initial capacity
152	>	* Constructs an empty array deque with an initial capacity
153		* sufficient to hold 16 elements.
154		*/
155		public ArrayDeque() {
#	Line 184 | Line 186 | public class ArrayDeque<E> extends Abstr
186		// terms of these.
187
188		/**
189	<	* Inserts the specified element to the front this deque.
189	>	* Inserts the specified element at the front of this deque.
190		*
191	<	* @param e the element to insert
192	<	* @throws NullPointerException if <tt>e</tt> is null
191	>	* @param e the element to add
192	>	* @throws NullPointerException if the specified element is null
193		*/
194		public void addFirst(E e) {
195		if (e == null)
196		throw new NullPointerException();
197		elements[head = (head - 1) & (elements.length - 1)] = e;
198	<	if (head == tail)
198	>	if (head == tail)
199		doubleCapacity();
200		}
201
202		/**
203	<	* Inserts the specified element to the end this deque.
204	<	* This method is equivalent to {@link Collection#add} and
205	<	* {@link #push}.
203	>	* Inserts the specified element at the end of this deque.
204	>	*
205	>	* <p>This method is equivalent to {@link #add}.
206		*
207	<	* @param e the element to insert
208	<	* @throws NullPointerException if <tt>e</tt> is null
207	>	* @param e the element to add
208	>	* @throws NullPointerException if the specified element is null
209		*/
210		public void addLast(E e) {
211		if (e == null)
#	Line 214 | Line 216 | public class ArrayDeque<E> extends Abstr
216		}
217
218		/**
219	<	* 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.
219	>	* Inserts the specified element at the front of this deque.
220		*
221	<	* @return the last element of this deque, or <tt>null</tt> if
222	<	*     this deque is empty
223	<	*/
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.
252	<	*
253	<	* @param e the element to insert
254	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
255	<	* @throws NullPointerException if <tt>e</tt> is null
221	>	* @param e the element to add
222	>	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
223	>	* @throws NullPointerException if the specified element is null
224		*/
225		public boolean offerFirst(E e) {
226		addFirst(e);
#	Line 260 | Line 228 | public class ArrayDeque<E> extends Abstr
228		}
229
230		/**
231	<	* Inserts the specified element to the end this deque.
231	>	* Inserts the specified element at the end of this deque.
232		*
233	<	* @param e the element to insert
234	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
235	<	* @throws NullPointerException if <tt>e</tt> is null
233	>	* @param e the element to add
234	>	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
235	>	* @throws NullPointerException if the specified element is null
236		*/
237		public boolean offerLast(E e) {
238		addLast(e);
#	Line 272 | Line 240 | public class ArrayDeque<E> extends Abstr
240		}
241
242		/**
243	<	* 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
243	>	* @throws NoSuchElementException {@inheritDoc}
244		*/
245		public E removeFirst() {
246		E x = pollFirst();
#	Line 287 | Line 250 | public class ArrayDeque<E> extends Abstr
250		}
251
252		/**
253	<	* 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
253	>	* @throws NoSuchElementException {@inheritDoc}
254		*/
255		public E removeLast() {
256		E x = pollLast();
#	Line 301 | Line 259 | public class ArrayDeque<E> extends Abstr
259		return x;
260		}
261
262	<	/**
263	<	* Retrieves, but does not remove, the first element of this deque,
264	<	* returning <tt>null</tt> if this deque is empty.
265	<	*
266	<	* @return the first element of this deque, or <tt>null</tt> if
267	<	*     this deque is empty
268	<	*/
269	<	public E peekFirst() {
312	<	return elements[head]; // elements[head] is null if deque empty
262	>	public E pollFirst() {
263	>	int h = head;
264	>	E result = elements[h]; // Element is null if deque empty
265	>	if (result == null)
266	>	return null;
267	>	elements[h] = null;     // Must null out slot
268	>	head = (h + 1) & (elements.length - 1);
269	>	return result;
270		}
271
272	<	/**
273	<	* Retrieves, but does not remove, the last element of this deque,
274	<	* returning <tt>null</tt> if this deque is empty.
275	<	*
276	<	* @return the last element of this deque, or <tt>null</tt> if this deque
277	<	*     is empty
278	<	*/
279	<	public E peekLast() {
323	<	return elements[(tail - 1) & (elements.length - 1)];
272	>	public E pollLast() {
273	>	int t = (tail - 1) & (elements.length - 1);
274	>	E result = elements[t];
275	>	if (result == null)
276	>	return null;
277	>	elements[t] = null;
278	>	tail = t;
279	>	return result;
280		}
281
282		/**
283	<	* 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
283	>	* @throws NoSuchElementException {@inheritDoc}
284		*/
285		public E getFirst() {
286		E x = elements[head];
#	Line 339 | Line 290 | public class ArrayDeque<E> extends Abstr
290		}
291
292		/**
293	<	* 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
293	>	* @throws NoSuchElementException {@inheritDoc}
294		*/
295		public E getLast() {
296		E x = elements[(tail - 1) & (elements.length - 1)];
#	Line 353 | Line 299 | public class ArrayDeque<E> extends Abstr
299		return x;
300		}
301
302	+	public E peekFirst() {
303	+	return elements[head]; // elements[head] is null if deque empty
304	+	}
305	+
306	+	public E peekLast() {
307	+	return elements[(tail - 1) & (elements.length - 1)];
308	+	}
309	+
310		/**
311		* Removes the first occurrence of the specified element in this
312	<	* deque (when traversing the deque from head to tail).  If the deque
313	<	* does not contain the element, it is unchanged.
312	>	* deque (when traversing the deque from head to tail).
313	>	* If the deque does not contain the element, it is unchanged.
314	>	* More formally, removes the first element <tt>e</tt> such that
315	>	* <tt>o.equals(e)</tt> (if such an element exists).
316	>	* Returns <tt>true</tt> if this deque contained the specified element
317	>	* (or equivalently, if this deque changed as a result of the call).
318		*
319	<	* @param e element to be removed from this deque, if present
319	>	* @param o element to be removed from this deque, if present
320		* @return <tt>true</tt> if the deque contained the specified element
321		*/
322	<	public boolean removeFirstOccurrence(Object e) {
323	<	if (e == null)
322	>	public boolean removeFirstOccurrence(Object o) {
323	>	if (o == null)
324		return false;
325		int mask = elements.length - 1;
326		int i = head;
327		E x;
328		while ( (x = elements[i]) != null) {
329	<	if (e.equals(x)) {
329	>	if (o.equals(x)) {
330		delete(i);
331		return true;
332		}
#	Line 379 | Line 337 | public class ArrayDeque<E> extends Abstr
337
338		/**
339		* Removes the last occurrence of the specified element in this
340	<	* deque (when traversing the deque from head to tail).  If the deque
341	<	* does not contain the element, it is unchanged.
340	>	* deque (when traversing the deque from head to tail).
341	>	* If the deque does not contain the element, it is unchanged.
342	>	* More formally, removes the last element <tt>e</tt> such that
343	>	* <tt>o.equals(e)</tt> (if such an element exists).
344	>	* Returns <tt>true</tt> if this deque contained the specified element
345	>	* (or equivalently, if this deque changed as a result of the call).
346		*
347	<	* @param e element to be removed from this deque, if present
347	>	* @param o element to be removed from this deque, if present
348		* @return <tt>true</tt> if the deque contained the specified element
349		*/
350	<	public boolean removeLastOccurrence(Object e) {
351	<	if (e == null)
350	>	public boolean removeLastOccurrence(Object o) {
351	>	if (o == null)
352		return false;
353		int mask = elements.length - 1;
354		int i = (tail - 1) & mask;
355		E x;
356		while ( (x = elements[i]) != null) {
357	<	if (e.equals(x)) {
357	>	if (o.equals(x)) {
358		delete(i);
359		return true;
360		}
#	Line 404 | Line 366 | public class ArrayDeque<E> extends Abstr
366		// *** Queue methods ***
367
368		/**
369	<	* 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.
369	>	* Inserts the specified element at the end of this deque.
370		*
371		* <p>This method is equivalent to {@link #addLast}.
372		*
373	<	* @param e the element to insert
374	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
375	<	* @throws NullPointerException if <tt>e</tt> is null
373	>	* @param e the element to add
374	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
375	>	* @throws NullPointerException if the specified element is null
376		*/
377		public boolean add(E e) {
378		addLast(e);
#	Line 431 | Line 380 | public class ArrayDeque<E> extends Abstr
380		}
381
382		/**
383	<	* 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.
383	>	* Inserts the specified element at the end of this deque.
384		*
385	<	* <p>This method is equivalent to {@link #pollFirst}.
385	>	* <p>This method is equivalent to {@link #offerLast}.
386		*
387	<	* @return the first element of this deque, or <tt>null</tt> if
388	<	*     this deque is empty
387	>	* @param e the element to add
388	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
389	>	* @throws NullPointerException if the specified element is null
390		*/
391	<	public E poll() {
392	<	return pollFirst();
391	>	public boolean offer(E e) {
392	>	return offerLast(e);
393		}
394
395		/**
396		* Retrieves and removes the head of the queue represented by this deque.
397	<	* This method differs from the <tt>poll</tt> method in that it throws an
397	>	*
398	>	* This method differs from {@link #poll poll} only in that it throws an
399		* exception if this deque is empty.
400		*
401		* <p>This method is equivalent to {@link #removeFirst}.
402		*
403		* @return the head of the queue represented by this deque
404	<	* @throws NoSuchElementException if this deque is empty
404	>	* @throws NoSuchElementException {@inheritDoc}
405		*/
406		public E remove() {
407		return removeFirst();
408		}
409
410		/**
411	<	* Retrieves, but does not remove, the head of the queue represented by
412	<	* this deque, returning <tt>null</tt> if this deque is empty.
411	>	* Retrieves and removes the head of the queue represented by this deque
412	>	* (in other words, the first element of this deque), or returns
413	>	* <tt>null</tt> if this deque is empty.
414		*
415	<	* <p>This method is equivalent to {@link #peekFirst}
415	>	* <p>This method is equivalent to {@link #pollFirst}.
416		*
417		* @return the head of the queue represented by this deque, or
418	<	*     <tt>null</tt> if this deque is empty
418	>	*         <tt>null</tt> if this deque is empty
419		*/
420	<	public E peek() {
421	<	return peekFirst();
420	>	public E poll() {
421	>	return pollFirst();
422		}
423
424		/**
425		* Retrieves, but does not remove, the head of the queue represented by
426	<	* this deque.  This method differs from the <tt>peek</tt> method only in
426	>	* this deque.  This method differs from {@link #peek peek} only in
427		* that it throws an exception if this deque is empty.
428		*
429	<	* <p>This method is equivalent to {@link #getFirst}
429	>	* <p>This method is equivalent to {@link #getFirst}.
430		*
431		* @return the head of the queue represented by this deque
432	<	* @throws NoSuchElementException if this deque is empty
432	>	* @throws NoSuchElementException {@inheritDoc}
433		*/
434		public E element() {
435		return getFirst();
436		}
437
438	+	/**
439	+	* Retrieves, but does not remove, the head of the queue represented by
440	+	* this deque, or returns <tt>null</tt> if this deque is empty.
441	+	*
442	+	* <p>This method is equivalent to {@link #peekFirst}.
443	+	*
444	+	* @return the head of the queue represented by this deque, or
445	+	*         <tt>null</tt> if this deque is empty
446	+	*/
447	+	public E peek() {
448	+	return peekFirst();
449	+	}
450	+
451		// *** Stack methods ***
452
453		/**
454		* Pushes an element onto the stack represented by this deque.  In other
455	<	* words, inserts the element to the front this deque.
455	>	* words, inserts the element at the front of this deque.
456		*
457		* <p>This method is equivalent to {@link #addFirst}.
458		*
459		* @param e the element to push
460	<	* @throws NullPointerException if <tt>e</tt> is null
460	>	* @throws NullPointerException if the specified element is null
461		*/
462		public void push(E e) {
463		addFirst(e);
#	Line 508 | Line 470 | public class ArrayDeque<E> extends Abstr
470		* <p>This method is equivalent to {@link #removeFirst()}.
471		*
472		* @return the element at the front of this deque (which is the top
473	<	*     of the stack represented by this deque)
474	<	* @throws NoSuchElementException if this deque is empty
473	>	*         of the stack represented by this deque)
474	>	* @throws NoSuchElementException {@inheritDoc}
475		*/
476		public E pop() {
477		return removeFirst();
478		}
479
480	+	private void checkInvariants() {
481	+	assert elements[tail] == null;
482	+	assert head == tail ? elements[head] == null :
483	+	(elements[head] != null &&
484	+	elements[(tail - 1) & (elements.length - 1)] != null);
485	+	assert elements[(head - 1) & (elements.length - 1)] == null;
486	+	}
487	+
488		/**
489	<	* Remove the element at the specified position in the elements array,
490	<	* adjusting head, tail, and size as necessary.  This can result in
491	<	* motion of elements backwards or forwards in the array.
492	<	*
493	<	* <p>This method is called delete rather than remove to emphasize
494	<	* that its semantics differ from those of List.remove(int).
495	<	*
489	>	* Removes the element at the specified position in the elements array,
490	>	* adjusting head and tail as necessary.  This can result in motion of
491	>	* elements backwards or forwards in the array.
492	>	*
493	>	* <p>This method is called delete rather than remove to emphasize
494	>	* that its semantics differ from those of {@link List#remove(int)}.
495	>	*
496		* @return true if elements moved backwards
497		*/
498		private boolean delete(int i) {
499	<	// Case 1: Deque doesn't wrap
500	<	// Case 2: Deque does wrap and removed element is in the head portion
501	<	if ((head < tail || tail == 0) || i >= head) {
502	<	System.arraycopy(elements, head, elements, head + 1, i - head);
503	<	elements[head] = null;
504	<	head = (head + 1) & (elements.length - 1);
499	>	checkInvariants();
500	>	final E[] elements = this.elements;
501	>	final int mask = elements.length - 1;
502	>	final int h = head;
503	>	final int t = tail;
504	>	final int front = (i - h) & mask;
505	>	final int back  = (t - i) & mask;
506	>
507	>	// Invariant: head <= i < tail mod circularity
508	>	if (front >= ((t - h) & mask))
509	>	throw new ConcurrentModificationException();
510	>
511	>	// Optimize for least element motion
512	>	if (front < back) {
513	>	if (h <= i) {
514	>	System.arraycopy(elements, h, elements, h + 1, front);
515	>	} else { // Wrap around
516	>	System.arraycopy(elements, 0, elements, 1, i);
517	>	elements[0] = elements[mask];
518	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
519	>	}
520	>	elements[h] = null;
521	>	head = (h + 1) & mask;
522		return false;
523	+	} else {
524	+	if (i < t) { // Copy the null tail as well
525	+	System.arraycopy(elements, i + 1, elements, i, back);
526	+	tail = t - 1;
527	+	} else { // Wrap around
528	+	System.arraycopy(elements, i + 1, elements, i, mask - i);
529	+	elements[mask] = elements[0];
530	+	System.arraycopy(elements, 1, elements, 0, t);
531	+	tail = (t - 1) & mask;
532	+	}
533	+	return true;
534		}
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;
535		}
536
537		// *** Collection Methods ***
#	Line 554 | Line 546 | public class ArrayDeque<E> extends Abstr
546		}
547
548		/**
549	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
549	>	* Returns <tt>true</tt> if this deque contains no elements.
550		*
551	<	* @return <tt>true</tt> if this collection contains no elements.
551	>	* @return <tt>true</tt> if this deque contains no elements
552		*/
553		public boolean isEmpty() {
554		return head == tail;
#	Line 567 | Line 559 | public class ArrayDeque<E> extends Abstr
559		* will be ordered from first (head) to last (tail).  This is the same
560		* order that elements would be dequeued (via successive calls to
561		* {@link #remove} or popped (via successive calls to {@link #pop}).
562	<	*
563	<	* @return an <tt>Iterator</tt> over the elements in this deque
562	>	*
563	>	* @return an iterator over the elements in this deque
564		*/
565		public Iterator<E> iterator() {
566		return new DeqIterator();
567		}
568
569	+	public Iterator<E> descendingIterator() {
570	+	return new DescendingIterator();
571	+	}
572	+
573		private class DeqIterator implements Iterator<E> {
574		/**
575		* Index of element to be returned by subsequent call to next.
#	Line 597 | Line 593 | public class ArrayDeque<E> extends Abstr
593		}
594
595		public E next() {
600	–	E result;
596		if (cursor == fence)
597		throw new NoSuchElementException();
598	+	E result = elements[cursor];
599		// This check doesn't catch all possible comodifications,
600		// but does catch the ones that corrupt traversal
601	<	if (tail != fence || (result = elements[cursor]) == null)
601	>	if (tail != fence || result == null)
602		throw new ConcurrentModificationException();
603		lastRet = cursor;
604		cursor = (cursor + 1) & (elements.length - 1);
#	Line 612 | Line 608 | public class ArrayDeque<E> extends Abstr
608		public void remove() {
609		if (lastRet < 0)
610		throw new IllegalStateException();
611	<	if (delete(lastRet))
612	<	cursor--;
611	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
612	>	cursor = (cursor - 1) & (elements.length - 1);
613	>	fence = tail;
614	>	}
615	>	lastRet = -1;
616	>	}
617	>	}
618	>
619	>	private class DescendingIterator implements Iterator<E> {
620	>	/*
621	>	* This class is nearly a mirror-image of DeqIterator, using
622	>	* tail instead of head for initial cursor, and head instead of
623	>	* tail for fence.
624	>	*/
625	>	private int cursor = tail;
626	>	private int fence = head;
627	>	private int lastRet = -1;
628	>
629	>	public boolean hasNext() {
630	>	return cursor != fence;
631	>	}
632	>
633	>	public E next() {
634	>	if (cursor == fence)
635	>	throw new NoSuchElementException();
636	>	cursor = (cursor - 1) & (elements.length - 1);
637	>	E result = elements[cursor];
638	>	if (head != fence || result == null)
639	>	throw new ConcurrentModificationException();
640	>	lastRet = cursor;
641	>	return result;
642	>	}
643	>
644	>	public void remove() {
645	>	if (lastRet < 0)
646	>	throw new IllegalStateException();
647	>	if (!delete(lastRet)) {
648	>	cursor = (cursor + 1) & (elements.length - 1);
649	>	fence = head;
650	>	}
651		lastRet = -1;
618	–	fence = tail;
652		}
653		}
654
655		/**
656	<	* Returns <tt>true</tt> if this deque contains the specified
657	<	* element.  More formally, returns <tt>true</tt> if and only if this
658	<	* deque contains at least one element <tt>e</tt> such that
626	<	* <tt>e.equals(o)</tt>.
656	>	* Returns <tt>true</tt> if this deque contains the specified element.
657	>	* More formally, returns <tt>true</tt> if and only if this deque contains
658	>	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
659		*
660		* @param o object to be checked for containment in this deque
661		* @return <tt>true</tt> if this deque contains the specified element
#	Line 644 | Line 676 | public class ArrayDeque<E> extends Abstr
676
677		/**
678		* Removes a single instance of the specified element from this deque.
679	<	* This method is equivalent to {@link #removeFirstOccurrence}.
679	>	* If the deque does not contain the element, it is unchanged.
680	>	* More formally, removes the first element <tt>e</tt> such that
681	>	* <tt>o.equals(e)</tt> (if such an element exists).
682	>	* Returns <tt>true</tt> if this deque contained the specified element
683	>	* (or equivalently, if this deque changed as a result of the call).
684	>	*
685	>	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
686		*
687	<	* @param e element to be removed from this deque, if present
687	>	* @param o element to be removed from this deque, if present
688		* @return <tt>true</tt> if this deque contained the specified element
689		*/
690	<	public boolean remove(Object e) {
691	<	return removeFirstOccurrence(e);
690	>	public boolean remove(Object o) {
691	>	return removeFirstOccurrence(o);
692		}
693
694		/**
695		* Removes all of the elements from this deque.
696	+	* The deque will be empty after this call returns.
697		*/
698		public void clear() {
699		int h = head;
#	Line 666 | Line 705 | public class ArrayDeque<E> extends Abstr
705		do {
706		elements[i] = null;
707		i = (i + 1) & mask;
708	<	} while(i != t);
708	>	} while (i != t);
709		}
710		}
711
712		/**
713	<	* Returns an array containing all of the elements in this list
714	<	* in the correct order.
713	>	* Returns an array containing all of the elements in this deque
714	>	* in proper sequence (from first to last element).
715	>	*
716	>	* <p>The returned array will be "safe" in that no references to it are
717	>	* maintained by this deque.  (In other words, this method must allocate
718	>	* a new array).  The caller is thus free to modify the returned array.
719	>	*
720	>	* <p>This method acts as bridge between array-based and collection-based
721	>	* APIs.
722		*
723	<	* @return an array containing all of the elements in this list
678	<	*         in the correct order
723	>	* @return an array containing all of the elements in this deque
724		*/
725		public Object[] toArray() {
726	<	return copyElements(new Object[size()]);
726	>	return copyElements(new Object[size()]);
727		}
728
729		/**
730	<	* Returns an array containing all of the elements in this deque in the
731	<	* correct order; the runtime type of the returned array is that of the
732	<	* specified array.  If the deque fits in the specified array, it is
733	<	* returned therein.  Otherwise, a new array is allocated with the runtime
734	<	* type of the specified array and the size of this deque.
730	>	* Returns an array containing all of the elements in this deque in
731	>	* proper sequence (from first to last element); the runtime type of the
732	>	* returned array is that of the specified array.  If the deque fits in
733	>	* the specified array, it is returned therein.  Otherwise, a new array
734	>	* is allocated with the runtime type of the specified array and the
735	>	* size of this deque.
736		*
737	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
738	<	* the array has more elements than the deque), the element in the array
739	<	* immediately following the end of the collection is set to <tt>null</tt>.
737	>	* <p>If this deque fits in the specified array with room to spare
738	>	* (i.e., the array has more elements than this deque), the element in
739	>	* the array immediately following the end of the deque is set to
740	>	* <tt>null</tt>.
741	>	*
742	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
743	>	* array-based and collection-based APIs.  Further, this method allows
744	>	* precise control over the runtime type of the output array, and may,
745	>	* under certain circumstances, be used to save allocation costs.
746	>	*
747	>	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
748	>	* The following code can be used to dump the deque into a newly
749	>	* allocated array of <tt>String</tt>:
750	>	*
751	>	* <pre>
752	>	*     String[] y = x.toArray(new String[0]);</pre>
753	>	*
754	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
755	>	* <tt>toArray()</tt>.
756		*
757		* @param a the array into which the elements of the deque are to
758	<	*          be stored, if it is big enough; otherwise, a new array of the
759	<	*          same runtime type is allocated for this purpose
760	<	* @return an array containing the elements of the deque
761	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
762	<	*         of the runtime type of every element in this deque
758	>	*          be stored, if it is big enough; otherwise, a new array of the
759	>	*          same runtime type is allocated for this purpose
760	>	* @return an array containing all of the elements in this deque
761	>	* @throws ArrayStoreException if the runtime type of the specified array
762	>	*         is not a supertype of the runtime type of every element in
763	>	*         this deque
764	>	* @throws NullPointerException if the specified array is null
765		*/
766		public <T> T[] toArray(T[] a) {
767		int size = size();
768		if (a.length < size)
769		a = (T[])java.lang.reflect.Array.newInstance(
770		a.getClass().getComponentType(), size);
771	<	copyElements(a);
771	>	copyElements(a);
772		if (a.length > size)
773		a[size] = null;
774		return a;
#	Line 718 | Line 782 | public class ArrayDeque<E> extends Abstr
782		* @return a copy of this deque
783		*/
784		public ArrayDeque<E> clone() {
785	<	try {
785	>	try {
786		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
787	<	// 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);
787	>	result.elements = Arrays.copyOf(elements, elements.length);
788		return result;
789
790	<	} catch (CloneNotSupportedException e) {
790	>	} catch (CloneNotSupportedException e) {
791		throw new AssertionError();
792		}
793		}
#	Line 742 | Line 804 | public class ArrayDeque<E> extends Abstr
804		* followed by all of its elements (each an object reference) in
805		* first-to-last order.
806		*/
807	<	private void writeObject(ObjectOutputStream s) throws IOException {
807	>	private void writeObject(java.io.ObjectOutputStream s)
808	>	throws java.io.IOException {
809		s.defaultWriteObject();
810
811		// Write out size
812	<	int size = size();
750	<	s.writeInt(size);
812	>	s.writeInt(size());
813
814		// Write out elements in order.
753	–	int i = head;
815		int mask = elements.length - 1;
816	<	for (int j = 0; j < size; j++) {
816	>	for (int i = head; i != tail; i = (i + 1) & mask)
817		s.writeObject(elements[i]);
757	–	i = (i + 1) & mask;
758	–	}
818		}
819
820		/**
821		* Deserialize this deque.
822		*/
823	<	private void readObject(ObjectInputStream s)
824	<	throws IOException, ClassNotFoundException {
823	>	private void readObject(java.io.ObjectInputStream s)
824	>	throws java.io.IOException, ClassNotFoundException {
825		s.defaultReadObject();
826
827		// Read in size and allocate array
#	Line 774 | Line 833 | public class ArrayDeque<E> extends Abstr
833		// Read in all elements in the proper order.
834		for (int i = 0; i < size; i++)
835		elements[i] = (E)s.readObject();
777	–
836		}
837		}

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