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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 1.25 by jsr166, Sat Sep 17 17:22:17 2005 UTC

#	Line 4 | Line 4
4		*/
5
6		package java.util;
7	+	import java.util.*; // for javadoc (till 6280605 is fixed)
8		import java.io.*;
9
10		/**
#	Line 18 | Line 19 | import java.io.*;
19		* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time.
20		* Exceptions include {@link #remove(Object) remove}, {@link
21		* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
22	<	* removeLastOccurrence}, {@link #contains contains }, {@link #iterator
22	>	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
23		* iterator.remove()}, and the bulk operations, all of which run in linear
24		* time.
25		*
26		* <p>The iterators returned by this class's <tt>iterator</tt> method are
27		* <i>fail-fast</i>: If the deque is modified at any time after the iterator
28	<	* is created, in any way except through the iterator's own remove method, the
29	<	* iterator will generally throw a {@link ConcurrentModificationException}.
30	<	* Thus, in the face of concurrent modification, the iterator fails quickly
31	<	* and cleanly, rather than risking arbitrary, non-deterministic behavior at
32	<	* an undetermined time in the future.
28	>	* is created, in any way except through the iterator's own <tt>remove</tt>
29	>	* method, the iterator will generally throw a {@link
30	>	* ConcurrentModificationException}.  Thus, in the face of concurrent
31	>	* modification, the iterator fails quickly and cleanly, rather than risking
32	>	* arbitrary, non-deterministic behavior at an undetermined time in the
33	>	* future.
34		*
35		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
36		* as it is, generally speaking, impossible to make any hard guarantees in the
#	Line 39 | Line 41 | import java.io.*;
41		* should be used only to detect bugs.</i>
42		*
43		* <p>This class and its iterator implement all of the
44	<	* optional methods of the {@link Collection} and {@link
45	<	* Iterator} interfaces.  This class is a member of the <a
46	<	* href="{@docRoot}/../guide/collections/index.html"> Java Collections
47	<	* Framework</a>.
44	>	* <em>optional</em> methods of the {@link Collection} and {@link
45	>	* Iterator} interfaces.
46	>	*
47	>	* <p>This class is a member of the
48	>	* <a href="{@docRoot}/../guide/collections/index.html">
49	>	* Java Collections Framework</a>.
50		*
51		* @author  Josh Bloch and Doug Lea
52		* @since   1.6
#	Line 87 | Line 91 | public class ArrayDeque<E> extends Abstr
91		/**
92		* Allocate empty array to hold the given number of elements.
93		*
94	<	* @param numElements  the number of elements to hold.
94	>	* @param numElements  the number of elements to hold
95		*/
96		private void allocateElements(int numElements) {
97		int initialCapacity = MIN_INITIAL_CAPACITY;
#	Line 129 | Line 133 | public class ArrayDeque<E> extends Abstr
133		}
134
135		/**
136	<	* Copy the elements from our element array into the specified array,
136	>	* Copies the elements from our element array into the specified array,
137		* in order (from first to last element in the deque).  It is assumed
138		* that the array is large enough to hold all elements in the deque.
139		*
#	Line 186 | Line 190 | public class ArrayDeque<E> extends Abstr
190		/**
191		* Inserts the specified element at the front of this deque.
192		*
193	<	* @param e the element to insert
194	<	* @throws NullPointerException if <tt>e</tt> is null
193	>	* @param e the element to add
194	>	* @throws NullPointerException if the specified element is null
195		*/
196		public void addFirst(E e) {
197		if (e == null)
#	Line 198 | Line 202 | public class ArrayDeque<E> extends Abstr
202		}
203
204		/**
205	<	* Inserts the specified element to the end of this deque.
206	<	* This method is equivalent to {@link Collection#add} and
207	<	* {@link #push}.
205	>	* Inserts the specified element at the end of this deque.
206	>	*
207	>	* <p>This method is equivalent to {@link #add}.
208		*
209	<	* @param e the element to insert
210	<	* @throws NullPointerException if <tt>e</tt> is null
209	>	* @param e the element to add
210	>	* @throws NullPointerException if the specified element is null
211		*/
212		public void addLast(E e) {
213		if (e == null)
#	Line 214 | Line 218 | public class ArrayDeque<E> extends Abstr
218		}
219
220		/**
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	–	/**
221		* Inserts the specified element at the front of this deque.
222		*
223	<	* @param e the element to insert
224	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
225	<	* @throws NullPointerException if <tt>e</tt> is null
223	>	* @param e the element to add
224	>	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
225	>	* @throws NullPointerException if the specified element is null
226		*/
227		public boolean offerFirst(E e) {
228		addFirst(e);
#	Line 260 | Line 230 | public class ArrayDeque<E> extends Abstr
230		}
231
232		/**
233	<	* Inserts the specified element to the end of this deque.
233	>	* Inserts the specified element at the end of this deque.
234		*
235	<	* @param e the element to insert
236	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
237	<	* @throws NullPointerException if <tt>e</tt> is null
235	>	* @param e the element to add
236	>	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
237	>	* @throws NullPointerException if the specified element is null
238		*/
239		public boolean offerLast(E e) {
240		addLast(e);
#	Line 272 | Line 242 | public class ArrayDeque<E> extends Abstr
242		}
243
244		/**
245	<	* 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
245	>	* @throws NoSuchElementException {@inheritDoc}
246		*/
247		public E removeFirst() {
248		E x = pollFirst();
#	Line 287 | Line 252 | public class ArrayDeque<E> extends Abstr
252		}
253
254		/**
255	<	* 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
255	>	* @throws NoSuchElementException {@inheritDoc}
256		*/
257		public E removeLast() {
258		E x = pollLast();
#	Line 301 | Line 261 | public class ArrayDeque<E> extends Abstr
261		return x;
262		}
263
264	<	/**
265	<	* Retrieves, but does not remove, the first element of this deque,
266	<	* returning <tt>null</tt> if this deque is empty.
267	<	*
268	<	* @return the first element of this deque, or <tt>null</tt> if
269	<	*     this deque is empty
270	<	*/
271	<	public E peekFirst() {
312	<	return elements[head]; // elements[head] is null if deque empty
264	>	public E pollFirst() {
265	>	int h = head;
266	>	E result = elements[h]; // Element is null if deque empty
267	>	if (result == null)
268	>	return null;
269	>	elements[h] = null;     // Must null out slot
270	>	head = (h + 1) & (elements.length - 1);
271	>	return result;
272		}
273
274	<	/**
275	<	* Retrieves, but does not remove, the last element of this deque,
276	<	* returning <tt>null</tt> if this deque is empty.
277	<	*
278	<	* @return the last element of this deque, or <tt>null</tt> if this deque
279	<	*     is empty
280	<	*/
281	<	public E peekLast() {
323	<	return elements[(tail - 1) & (elements.length - 1)];
274	>	public E pollLast() {
275	>	int t = (tail - 1) & (elements.length - 1);
276	>	E result = elements[t];
277	>	if (result == null)
278	>	return null;
279	>	elements[t] = null;
280	>	tail = t;
281	>	return result;
282		}
283
284		/**
285	<	* 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
285	>	* @throws NoSuchElementException {@inheritDoc}
286		*/
287		public E getFirst() {
288		E x = elements[head];
#	Line 339 | Line 292 | public class ArrayDeque<E> extends Abstr
292		}
293
294		/**
295	<	* 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
295	>	* @throws NoSuchElementException {@inheritDoc}
296		*/
297		public E getLast() {
298		E x = elements[(tail - 1) & (elements.length - 1)];
#	Line 353 | Line 301 | public class ArrayDeque<E> extends Abstr
301		return x;
302		}
303
304	+	public E peekFirst() {
305	+	return elements[head]; // elements[head] is null if deque empty
306	+	}
307	+
308	+	public E peekLast() {
309	+	return elements[(tail - 1) & (elements.length - 1)];
310	+	}
311	+
312		/**
313		* Removes the first occurrence of the specified element in this
314	<	* deque (when traversing the deque from head to tail).  More
315	<	* formally, removes the first element e such that (o==null ?
316	<	* e==null : o.equals(e)). If the deque does not contain the
317	<	* element, it is unchanged.
314	>	* deque (when traversing the deque from head to tail).
315	>	* If the deque does not contain the element, it is unchanged.
316	>	* More formally, removes the first element <tt>e</tt> such that
317	>	* <tt>o.equals(e)</tt> (if such an element exists).
318	>	* Returns <tt>true</tt> if this deque contained the specified element
319	>	* (or equivalently, if this deque changed as a result of the call).
320		*
321		* @param o element to be removed from this deque, if present
322		* @return <tt>true</tt> if the deque contained the specified element
#	Line 381 | Line 339 | public class ArrayDeque<E> extends Abstr
339
340		/**
341		* Removes the last occurrence of the specified element in this
342	<	* deque (when traversing the deque from head to tail). More
343	<	* formally, removes the last element e such that (o==null ?
344	<	* e==null : o.equals(e)). If the deque
345	<	* does not contain the element, it is unchanged.
342	>	* deque (when traversing the deque from head to tail).
343	>	* If the deque does not contain the element, it is unchanged.
344	>	* More formally, removes the last element <tt>e</tt> such that
345	>	* <tt>o.equals(e)</tt> (if such an element exists).
346	>	* Returns <tt>true</tt> if this deque contained the specified element
347	>	* (or equivalently, if this deque changed as a result of the call).
348		*
349		* @param o element to be removed from this deque, if present
350		* @return <tt>true</tt> if the deque contained the specified element
#	Line 408 | Line 368 | public class ArrayDeque<E> extends Abstr
368		// *** Queue methods ***
369
370		/**
371	<	* 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.
371	>	* Inserts the specified element at the end of this deque.
372		*
373		* <p>This method is equivalent to {@link #addLast}.
374		*
375	<	* @param e the element to insert
376	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
377	<	* @throws NullPointerException if <tt>e</tt> is null
375	>	* @param e the element to add
376	>	* @return <tt>true</tt> (as specified by {@link Collection#add})
377	>	* @throws NullPointerException if the specified element is null
378		*/
379		public boolean add(E e) {
380		addLast(e);
#	Line 435 | Line 382 | public class ArrayDeque<E> extends Abstr
382		}
383
384		/**
385	<	* 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.
385	>	* Inserts the specified element at the end of this deque.
386		*
387	<	* <p>This method is equivalent to {@link #pollFirst}.
387	>	* <p>This method is equivalent to {@link #offerLast}.
388		*
389	<	* @return the first element of this deque, or <tt>null</tt> if
390	<	*     this deque is empty
389	>	* @param e the element to add
390	>	* @return <tt>true</tt> (as specified by {@link Queue#offer})
391	>	* @throws NullPointerException if the specified element is null
392		*/
393	<	public E poll() {
394	<	return pollFirst();
393	>	public boolean offer(E e) {
394	>	return offerLast(e);
395		}
396
397		/**
398		* Retrieves and removes the head of the queue represented by this deque.
399	<	* This method differs from the <tt>poll</tt> method in that it throws an
399	>	*
400	>	* This method differs from {@link #poll poll} only in that it throws an
401		* exception if this deque is empty.
402		*
403		* <p>This method is equivalent to {@link #removeFirst}.
404		*
405		* @return the head of the queue represented by this deque
406	<	* @throws NoSuchElementException if this deque is empty
406	>	* @throws NoSuchElementException {@inheritDoc}
407		*/
408		public E remove() {
409		return removeFirst();
410		}
411
412		/**
413	<	* Retrieves, but does not remove, the head of the queue represented by
414	<	* this deque, returning <tt>null</tt> if this deque is empty.
413	>	* Retrieves and removes the head of the queue represented by this deque
414	>	* (in other words, the first element of this deque), or returns
415	>	* <tt>null</tt> if this deque is empty.
416		*
417	<	* <p>This method is equivalent to {@link #peekFirst}
417	>	* <p>This method is equivalent to {@link #pollFirst}.
418		*
419		* @return the head of the queue represented by this deque, or
420	<	*     <tt>null</tt> if this deque is empty
420	>	*         <tt>null</tt> if this deque is empty
421		*/
422	<	public E peek() {
423	<	return peekFirst();
422	>	public E poll() {
423	>	return pollFirst();
424		}
425
426		/**
427		* Retrieves, but does not remove, the head of the queue represented by
428	<	* this deque.  This method differs from the <tt>peek</tt> method only in
428	>	* this deque.  This method differs from {@link #peek peek} only in
429		* that it throws an exception if this deque is empty.
430		*
431	<	* <p>This method is equivalent to {@link #getFirst}
431	>	* <p>This method is equivalent to {@link #getFirst}.
432		*
433		* @return the head of the queue represented by this deque
434	<	* @throws NoSuchElementException if this deque is empty
434	>	* @throws NoSuchElementException {@inheritDoc}
435		*/
436		public E element() {
437		return getFirst();
438		}
439
440	+	/**
441	+	* Retrieves, but does not remove, the head of the queue represented by
442	+	* this deque, or returns <tt>null</tt> if this deque is empty.
443	+	*
444	+	* <p>This method is equivalent to {@link #peekFirst}.
445	+	*
446	+	* @return the head of the queue represented by this deque, or
447	+	*         <tt>null</tt> if this deque is empty
448	+	*/
449	+	public E peek() {
450	+	return peekFirst();
451	+	}
452	+
453		// *** Stack methods ***
454
455		/**
#	Line 499 | Line 459 | public class ArrayDeque<E> extends Abstr
459		* <p>This method is equivalent to {@link #addFirst}.
460		*
461		* @param e the element to push
462	<	* @throws NullPointerException if <tt>e</tt> is null
462	>	* @throws NullPointerException if the specified element is null
463		*/
464		public void push(E e) {
465		addFirst(e);
#	Line 512 | Line 472 | public class ArrayDeque<E> extends Abstr
472		* <p>This method is equivalent to {@link #removeFirst()}.
473		*
474		* @return the element at the front of this deque (which is the top
475	<	*     of the stack represented by this deque)
476	<	* @throws NoSuchElementException if this deque is empty
475	>	*         of the stack represented by this deque)
476	>	* @throws NoSuchElementException {@inheritDoc}
477		*/
478		public E pop() {
479		return removeFirst();
480		}
481
482	+	private void checkInvariants() {
483	+	assert elements[tail] == null;
484	+	assert head == tail ? elements[head] == null :
485	+	(elements[head] != null &&
486	+	elements[(tail - 1) & (elements.length - 1)] != null);
487	+	assert elements[(head - 1) & (elements.length - 1)] == null;
488	+	}
489	+
490		/**
491	<	* Remove the element at the specified position in the elements array,
492	<	* adjusting head, tail, and size as necessary.  This can result in
493	<	* motion of elements backwards or forwards in the array.
491	>	* Removes the element at the specified position in the elements array,
492	>	* adjusting head and tail as necessary.  This can result in motion of
493	>	* elements backwards or forwards in the array.
494		*
495		* <p>This method is called delete rather than remove to emphasize
496	<	* that its semantics differ from those of List.remove(int).
496	>	* that its semantics differ from those of {@link List#remove(int)}.
497		*
498		* @return true if elements moved backwards
499		*/
500		private boolean delete(int i) {
501	<	// Case 1: Deque doesn't wrap
502	<	// Case 2: Deque does wrap and removed element is in the head portion
503	<	if ((head < tail || tail == 0) || i >= head) {
504	<	System.arraycopy(elements, head, elements, head + 1, i - head);
505	<	elements[head] = null;
506	<	head = (head + 1) & (elements.length - 1);
507	<	return false;
508	<	}
509	<
510	<	// Case 3: Deque wraps and removed element is in the tail portion
511	<	tail--;
512	<	System.arraycopy(elements, i + 1, elements, i, tail - i);
513	<	elements[tail] = null;
514	<	return true;
501	>	checkInvariants();
502	>	final E[] elements = this.elements;
503	>	final int mask = elements.length - 1;
504	>	final int h = head;
505	>	final int t = tail;
506	>	final int front = (i - h) & mask;
507	>	final int back  = (t - i) & mask;
508	>
509	>	// Invariant: head <= i < tail mod circularity
510	>	if (front >= ((t - h) & mask))
511	>	throw new ConcurrentModificationException();
512	>
513	>	// Optimize for least element motion
514	>	if (front < back) {
515	>	if (h <= i) {
516	>	System.arraycopy(elements, h, elements, h + 1, front);
517	>	} else { // Wrap around
518	>	System.arraycopy(elements, 0, elements, 1, i);
519	>	elements[0] = elements[mask];
520	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
521	>	}
522	>	elements[h] = null;
523	>	head = (h + 1) & mask;
524	>	return false;
525	>	} else {
526	>	if (i < t) { // Copy the null tail as well
527	>	System.arraycopy(elements, i + 1, elements, i, back);
528	>	tail = t - 1;
529	>	} else { // Wrap around
530	>	System.arraycopy(elements, i + 1, elements, i, mask - i);
531	>	elements[mask] = elements[0];
532	>	System.arraycopy(elements, 1, elements, 0, t);
533	>	tail = (t - 1) & mask;
534	>	}
535	>	return true;
536	>	}
537		}
538
539		// *** Collection Methods ***
#	Line 558 | Line 548 | public class ArrayDeque<E> extends Abstr
548		}
549
550		/**
551	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
551	>	* Returns <tt>true</tt> if this deque contains no elements.
552		*
553	<	* @return <tt>true</tt> if this collection contains no elements.
553	>	* @return <tt>true</tt> if this deque contains no elements
554		*/
555		public boolean isEmpty() {
556		return head == tail;
#	Line 572 | Line 562 | public class ArrayDeque<E> extends Abstr
562		* order that elements would be dequeued (via successive calls to
563		* {@link #remove} or popped (via successive calls to {@link #pop}).
564		*
565	<	* @return an <tt>Iterator</tt> over the elements in this deque
565	>	* @return an iterator over the elements in this deque
566		*/
567		public Iterator<E> iterator() {
568		return new DeqIterator();
569		}
570
571	+	public Iterator<E> descendingIterator() {
572	+	return new DescendingIterator();
573	+	}
574	+
575		private class DeqIterator implements Iterator<E> {
576		/**
577		* Index of element to be returned by subsequent call to next.
#	Line 616 | Line 610 | public class ArrayDeque<E> extends Abstr
610		public void remove() {
611		if (lastRet < 0)
612		throw new IllegalStateException();
613	<	if (delete(lastRet))
614	<	cursor--;
613	>	if (delete(lastRet)) // if left-shifted, undo increment in next()
614	>	cursor = (cursor - 1) & (elements.length - 1);
615		lastRet = -1;
616		fence = tail;
617		}
618		}
619
620	+	private class DescendingIterator implements Iterator<E> {
621	+	/*
622	+	* This class is nearly a mirror-image of DeqIterator, using
623	+	* (tail-1) instead of head for initial cursor, (head-1)
624	+	* instead of tail for fence, and elements.length instead of -1
625	+	* for sentinel. It shares the same structure, but not many
626	+	* actual lines of code.
627	+	*/
628	+	private int cursor = (tail - 1) & (elements.length - 1);
629	+	private int fence =  (head - 1) & (elements.length - 1);
630	+	private int lastRet = elements.length;
631	+
632	+	public boolean hasNext() {
633	+	return cursor != fence;
634	+	}
635	+
636	+	public E next() {
637	+	E result;
638	+	if (cursor == fence)
639	+	throw new NoSuchElementException();
640	+	if (((head - 1) & (elements.length - 1)) != fence ||
641	+	(result = elements[cursor]) == null)
642	+	throw new ConcurrentModificationException();
643	+	lastRet = cursor;
644	+	cursor = (cursor - 1) & (elements.length - 1);
645	+	return result;
646	+	}
647	+
648	+	public void remove() {
649	+	if (lastRet >= elements.length)
650	+	throw new IllegalStateException();
651	+	if (!delete(lastRet))
652	+	cursor = (cursor + 1) & (elements.length - 1);
653	+	lastRet = elements.length;
654	+	fence = (head - 1) & (elements.length - 1);
655	+	}
656	+	}
657	+
658		/**
659	<	* Returns <tt>true</tt> if this deque contains the specified
660	<	* element.  More formally, returns <tt>true</tt> if and only if this
661	<	* deque contains at least one element <tt>e</tt> such that
630	<	* <tt>e.equals(o)</tt>.
659	>	* Returns <tt>true</tt> if this deque contains the specified element.
660	>	* More formally, returns <tt>true</tt> if and only if this deque contains
661	>	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
662		*
663		* @param o object to be checked for containment in this deque
664		* @return <tt>true</tt> if this deque contains the specified element
#	Line 648 | Line 679 | public class ArrayDeque<E> extends Abstr
679
680		/**
681		* Removes a single instance of the specified element from this deque.
682	<	* This method is equivalent to {@link #removeFirstOccurrence}.
682	>	* If the deque does not contain the element, it is unchanged.
683	>	* More formally, removes the first element <tt>e</tt> such that
684	>	* <tt>o.equals(e)</tt> (if such an element exists).
685	>	* Returns <tt>true</tt> if this deque contained the specified element
686	>	* (or equivalently, if this deque changed as a result of the call).
687		*
688	<	* @param e element to be removed from this deque, if present
688	>	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
689	>	*
690	>	* @param o element to be removed from this deque, if present
691		* @return <tt>true</tt> if this deque contained the specified element
692		*/
693	<	public boolean remove(Object e) {
694	<	return removeFirstOccurrence(e);
693	>	public boolean remove(Object o) {
694	>	return removeFirstOccurrence(o);
695		}
696
697		/**
698		* Removes all of the elements from this deque.
699	+	* The deque will be empty after this call returns.
700		*/
701		public void clear() {
702		int h = head;
#	Line 670 | Line 708 | public class ArrayDeque<E> extends Abstr
708		do {
709		elements[i] = null;
710		i = (i + 1) & mask;
711	<	} while(i != t);
711	>	} while (i != t);
712		}
713		}
714
715		/**
716		* Returns an array containing all of the elements in this deque
717	<	* in the correct order.
717	>	* in proper sequence (from first to last element).
718	>	*
719	>	* <p>The returned array will be "safe" in that no references to it are
720	>	* maintained by this deque.  (In other words, this method must allocate
721	>	* a new array).  The caller is thus free to modify the returned array.
722	>	*
723	>	* <p>This method acts as bridge between array-based and collection-based
724	>	* APIs.
725		*
726		* @return an array containing all of the elements in this deque
682	–	*         in the correct order
727		*/
728		public Object[] toArray() {
729		return copyElements(new Object[size()]);
730		}
731
732		/**
733	<	* Returns an array containing all of the elements in this deque in the
734	<	* correct order; the runtime type of the returned array is that of the
735	<	* specified array.  If the deque fits in the specified array, it is
736	<	* returned therein.  Otherwise, a new array is allocated with the runtime
737	<	* type of the specified array and the size of this deque.
738	<	*
739	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
740	<	* the array has more elements than the deque), the element in the array
741	<	* immediately following the end of the collection is set to <tt>null</tt>.
733	>	* Returns an array containing all of the elements in this deque in
734	>	* proper sequence (from first to last element); the runtime type of the
735	>	* returned array is that of the specified array.  If the deque fits in
736	>	* the specified array, it is returned therein.  Otherwise, a new array
737	>	* is allocated with the runtime type of the specified array and the
738	>	* size of this deque.
739	>	*
740	>	* <p>If this deque fits in the specified array with room to spare
741	>	* (i.e., the array has more elements than this deque), the element in
742	>	* the array immediately following the end of the deque is set to
743	>	* <tt>null</tt>.
744	>	*
745	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
746	>	* array-based and collection-based APIs.  Further, this method allows
747	>	* precise control over the runtime type of the output array, and may,
748	>	* under certain circumstances, be used to save allocation costs.
749	>	*
750	>	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
751	>	* The following code can be used to dump the deque into a newly
752	>	* allocated array of <tt>String</tt>:
753	>	*
754	>	* <pre>
755	>	*     String[] y = x.toArray(new String[0]);</pre>
756	>	*
757	>	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
758	>	* <tt>toArray()</tt>.
759		*
760		* @param a the array into which the elements of the deque are to
761	<	*          be stored, if it is big enough; otherwise, a new array of the
762	<	*          same runtime type is allocated for this purpose
763	<	* @return an array containing the elements of the deque
764	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
765	<	*         of the runtime type of every element in this deque
761	>	*          be stored, if it is big enough; otherwise, a new array of the
762	>	*          same runtime type is allocated for this purpose
763	>	* @return an array containing all of the elements in this deque
764	>	* @throws ArrayStoreException if the runtime type of the specified array
765	>	*         is not a supertype of the runtime type of every element in
766	>	*         this deque
767	>	* @throws NullPointerException if the specified array is null
768		*/
769		public <T> T[] toArray(T[] a) {
770		int size = size();
#	Line 750 | Line 813 | public class ArrayDeque<E> extends Abstr
813		s.defaultWriteObject();
814
815		// Write out size
816	<	int size = size();
754	<	s.writeInt(size);
816	>	s.writeInt(size());
817
818		// Write out elements in order.
757	–	int i = head;
819		int mask = elements.length - 1;
820	<	for (int j = 0; j < size; j++) {
820	>	for (int i = head; i != tail; i = (i + 1) & mask)
821		s.writeObject(elements[i]);
761	–	i = (i + 1) & mask;
762	–	}
822		}
823
824		/**
#	Line 778 | Line 837 | public class ArrayDeque<E> extends Abstr
837		// Read in all elements in the proper order.
838		for (int i = 0; i < size; i++)
839		elements[i] = (E)s.readObject();
781	–
840		}
841		}

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