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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.13 by jsr166, Wed May 18 00:46:42 2005 UTC vs.
Revision 1.53 by dl, Wed Mar 13 12:38:56 2013 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	>	import java.io.Serializable;
8	>	import java.util.function.Consumer;
9	>	import java.util.stream.Stream;
10	>	import java.util.stream.Streams;
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 <tt>remove</tt>
33	<	* method, the iterator will generally throw a {@link
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
#	Line 34 | Line 39 | import java.io.*;
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>
#	Line 44 | Line 49 | import java.io.*;
49		* Iterator} interfaces.
50		*
51		* <p>This class is a member of the
52	<	* <a href="{@docRoot}/../guide/collections/index.html">
52	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
53		* Java Collections Framework</a>.
54		*
55		* @author  Josh Bloch and Doug Lea
#	Line 64 | 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 88 | 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
99		*/
#	Line 108 | 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 126 | 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		/**
135	–	* Copies the elements from our element array into the specified array,
136	–	* in order (from first to last element in the deque).  It is assumed
137	–	* that the array is large enough to hold all elements in the deque.
138	–	*
139	–	* @return its argument
140	–	*/
141	–	private <T> T[] copyElements(T[] a) {
142	–	if (head < tail) {
143	–	System.arraycopy(elements, head, a, 0, size());
144	–	} else if (head > tail) {
145	–	int headPortionLen = elements.length - head;
146	–	System.arraycopy(elements, head, a, 0, headPortionLen);
147	–	System.arraycopy(elements, 0, a, headPortionLen, tail);
148	–	}
149	–	return a;
150	–	}
151	–
152	–	/**
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 202 | Line 189 | public class ArrayDeque<E> extends Abstr
189
190		/**
191		* Inserts the specified element at the end of this deque.
192	<	* This method is equivalent to {@link #add} and {@link #push}.
192	>	*
193	>	* <p>This method is equivalent to {@link #add}.
194		*
195		* @param e the element to add
196		* @throws NullPointerException if the specified element is null
#	Line 219 | Line 207 | public class ArrayDeque<E> extends Abstr
207		* Inserts the specified element at the front of this deque.
208		*
209		* @param e the element to add
210	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
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) {
#	Line 231 | Line 219 | public class ArrayDeque<E> extends Abstr
219		* Inserts the specified element at the end of this deque.
220		*
221		* @param e the element to add
222	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
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) {
#	Line 261 | Line 249 | public class ArrayDeque<E> extends Abstr
249
250		public E pollFirst() {
251		int h = head;
252	<	E result = elements[h]; // Element is null if deque empty
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
#	Line 271 | Line 261 | public class ArrayDeque<E> extends Abstr
261
262		public E pollLast() {
263		int t = (tail - 1) & (elements.length - 1);
264	<	E result = elements[t];
264	>	@SuppressWarnings("unchecked")
265	>	E result = (E) elements[t];
266		if (result == null)
267		return null;
268		elements[t] = null;
#	Line 283 | Line 274 | public class ArrayDeque<E> extends Abstr
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		* @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	<	return elements[head]; // elements[head] is null if deque empty
297	>	// elements[head] is null if deque empty
298	>	return (E) elements[head];
299		}
300
301	+	@SuppressWarnings("unchecked")
302		public E peekLast() {
303	<	return elements[(tail - 1) & (elements.length - 1)];
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).
309		* If the deque does not contain the element, it is unchanged.
310	<	* More formally, removes the first element <tt>e</tt> such that
311	<	* <tt>o.equals(e)</tt> (if such an element exists).
312	<	* Returns <tt>true</tt> if this deque contained the specified element
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;
323	>	Object x;
324		while ( (x = elements[i]) != null) {
325		if (o.equals(x)) {
326		delete(i);
#	Line 339 | Line 335 | public class ArrayDeque<E> extends Abstr
335		* Removes the last occurrence of the specified element in this
336		* deque (when traversing the deque from head to tail).
337		* If the deque does not contain the element, it is unchanged.
338	<	* More formally, removes the last element <tt>e</tt> such that
339	<	* <tt>o.equals(e)</tt> (if such an element exists).
340	<	* Returns <tt>true</tt> if this deque contained the specified element
338	>	* More formally, removes the last element {@code e} such that
339	>	* {@code o.equals(e)} (if such an element exists).
340	>	* Returns {@code true} if this deque contained the specified element
341		* (or equivalently, if this deque changed as a result of the call).
342		*
343		* @param o element to be removed from this deque, if present
344	<	* @return <tt>true</tt> if the deque contained the specified element
344	>	* @return {@code true} if the deque contained the specified element
345		*/
346		public boolean removeLastOccurrence(Object o) {
347		if (o == null)
348		return false;
349		int mask = elements.length - 1;
350		int i = (tail - 1) & mask;
351	<	E x;
351	>	Object x;
352		while ( (x = elements[i]) != null) {
353		if (o.equals(x)) {
354		delete(i);
#	Line 371 | Line 367 | public class ArrayDeque<E> extends Abstr
367		* <p>This method is equivalent to {@link #addLast}.
368		*
369		* @param e the element to add
370	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
370	>	* @return {@code true} (as specified by {@link Collection#add})
371		* @throws NullPointerException if the specified element is null
372		*/
373		public boolean add(E e) {
#	Line 385 | Line 381 | public class ArrayDeque<E> extends Abstr
381		* <p>This method is equivalent to {@link #offerLast}.
382		*
383		* @param e the element to add
384	<	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
384	>	* @return {@code true} (as specified by {@link Queue#offer})
385		* @throws NullPointerException if the specified element is null
386		*/
387		public boolean offer(E e) {
#	Line 394 | Line 390 | public class ArrayDeque<E> extends Abstr
390
391		/**
392		* Retrieves and removes the head of the queue represented by this deque.
393	<	* This method differs from {@link #poll} only in that it throws an
393	>	*
394	>	* This method differs from {@link #poll poll} only in that it throws an
395		* exception if this deque is empty.
396		*
397		* <p>This method is equivalent to {@link #removeFirst}.
#	Line 409 | Line 406 | public class ArrayDeque<E> extends Abstr
406		/**
407		* Retrieves and removes the head of the queue represented by this deque
408		* (in other words, the first element of this deque), or returns
409	<	* <tt>null</tt> if this deque is empty.
409	>	* {@code null} if this deque is empty.
410		*
411		* <p>This method is equivalent to {@link #pollFirst}.
412		*
413		* @return the head of the queue represented by this deque, or
414	<	*         <tt>null</tt> if this deque is empty
414	>	*         {@code null} if this deque is empty
415		*/
416		public E poll() {
417		return pollFirst();
#	Line 422 | Line 419 | public class ArrayDeque<E> extends Abstr
419
420		/**
421		* Retrieves, but does not remove, the head of the queue represented by
422	<	* this deque.  This method differs from {@link #peek} only in that it
423	<	* throws an exception if this deque is empty.
422	>	* this deque.  This method differs from {@link #peek peek} only in
423	>	* that it throws an exception if this deque is empty.
424		*
425		* <p>This method is equivalent to {@link #getFirst}.
426		*
#	Line 436 | Line 433 | public class ArrayDeque<E> extends Abstr
433
434		/**
435		* Retrieves, but does not remove, the head of the queue represented by
436	<	* this deque, or returns <tt>null</tt> if this deque is empty.
436	>	* this deque, or returns {@code null} if this deque is empty.
437		*
438		* <p>This method is equivalent to {@link #peekFirst}.
439		*
440		* @return the head of the queue represented by this deque, or
441	<	*         <tt>null</tt> if this deque is empty
441	>	*         {@code null} if this deque is empty
442		*/
443		public E peek() {
444		return peekFirst();
#	Line 476 | Line 473 | public class ArrayDeque<E> extends Abstr
473		return removeFirst();
474		}
475
476	+	private void checkInvariants() {
477	+	assert elements[tail] == null;
478	+	assert head == tail ? elements[head] == null :
479	+	(elements[head] != null &&
480	+	elements[(tail - 1) & (elements.length - 1)] != null);
481	+	assert elements[(head - 1) & (elements.length - 1)] == null;
482	+	}
483	+
484		/**
485		* Removes the element at the specified position in the elements array,
486		* adjusting head and tail as necessary.  This can result in motion of
#	Line 487 | Line 492 | public class ArrayDeque<E> extends Abstr
492		* @return true if elements moved backwards
493		*/
494		private boolean delete(int i) {
495	<	int mask = elements.length - 1;
496	<
497	<	// Invariant: head <= i < tail mod circularity
498	<	if (((i - head) & mask) >= ((tail - head) & mask))
499	<	throw new ConcurrentModificationException();
500	<
501	<	// Case 1: Deque doesn't wrap
502	<	// Case 2: Deque does wrap and removed element is in the head portion
503	<	if (i >= head) {
504	<	System.arraycopy(elements, head, elements, head + 1, i - head);
505	<	elements[head] = null;
506	<	head = (head + 1) & mask;
495	>	checkInvariants();
496	>	final Object[] elements = this.elements;
497	>	final int mask = elements.length - 1;
498	>	final int h = head;
499	>	final int t = tail;
500	>	final int front = (i - h) & mask;
501	>	final int back  = (t - i) & mask;
502	>
503	>	// Invariant: head <= i < tail mod circularity
504	>	if (front >= ((t - h) & mask))
505	>	throw new ConcurrentModificationException();
506	>
507	>	// Optimize for least element motion
508	>	if (front < back) {
509	>	if (h <= i) {
510	>	System.arraycopy(elements, h, elements, h + 1, front);
511	>	} else { // Wrap around
512	>	System.arraycopy(elements, 0, elements, 1, i);
513	>	elements[0] = elements[mask];
514	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
515	>	}
516	>	elements[h] = null;
517	>	head = (h + 1) & mask;
518		return false;
519	+	} else {
520	+	if (i < t) { // Copy the null tail as well
521	+	System.arraycopy(elements, i + 1, elements, i, back);
522	+	tail = t - 1;
523	+	} else { // Wrap around
524	+	System.arraycopy(elements, i + 1, elements, i, mask - i);
525	+	elements[mask] = elements[0];
526	+	System.arraycopy(elements, 1, elements, 0, t);
527	+	tail = (t - 1) & mask;
528	+	}
529	+	return true;
530		}
504	–
505	–	// Case 3: Deque wraps and removed element is in the tail portion
506	–	tail--;
507	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
508	–	elements[tail] = null;
509	–	return true;
531		}
532
533		// *** Collection Methods ***
#	Line 521 | Line 542 | public class ArrayDeque<E> extends Abstr
542		}
543
544		/**
545	<	* Returns <tt>true</tt> if this deque contains no elements.
545	>	* Returns {@code true} if this deque contains no elements.
546		*
547	<	* @return <tt>true</tt> if this deque contains no elements
547	>	* @return {@code true} if this deque contains no elements
548		*/
549		public boolean isEmpty() {
550		return head == tail;
#	Line 535 | Line 556 | public class ArrayDeque<E> extends Abstr
556		* order that elements would be dequeued (via successive calls to
557		* {@link #remove} or popped (via successive calls to {@link #pop}).
558		*
559	<	* @return an <tt>Iterator</tt> over the elements in this deque
559	>	* @return an iterator over the elements in this deque
560		*/
561		public Iterator<E> iterator() {
562		return new DeqIterator();
563		}
564
565	+	public Iterator<E> descendingIterator() {
566	+	return new DescendingIterator();
567	+	}
568	+
569		private class DeqIterator implements Iterator<E> {
570		/**
571		* Index of element to be returned by subsequent call to next.
#	Line 564 | Line 589 | public class ArrayDeque<E> extends Abstr
589		}
590
591		public E next() {
567	–	E result;
592		if (cursor == fence)
593		throw new NoSuchElementException();
594	+	@SuppressWarnings("unchecked")
595	+	E result = (E) elements[cursor];
596		// This check doesn't catch all possible comodifications,
597		// but does catch the ones that corrupt traversal
598	<	if (tail != fence || (result = elements[cursor]) == null)
598	>	if (tail != fence || result == null)
599		throw new ConcurrentModificationException();
600		lastRet = cursor;
601		cursor = (cursor + 1) & (elements.length - 1);
#	Line 579 | Line 605 | public class ArrayDeque<E> extends Abstr
605		public void remove() {
606		if (lastRet < 0)
607		throw new IllegalStateException();
608	<	if (delete(lastRet))
609	<	cursor--;
608	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
609	>	cursor = (cursor - 1) & (elements.length - 1);
610	>	fence = tail;
611	>	}
612		lastRet = -1;
585	–	fence = tail;
613		}
614		}
615
616		/**
617	<	* Returns <tt>true</tt> if this deque contains the specified element.
618	<	* More formally, returns <tt>true</tt> if and only if this deque contains
619	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
617	>	* This class is nearly a mirror-image of DeqIterator, using tail
618	>	* instead of head for initial cursor, and head instead of tail
619	>	* for fence.
620	>	*/
621	>	private class DescendingIterator implements Iterator<E> {
622	>	private int cursor = tail;
623	>	private int fence = head;
624	>	private int lastRet = -1;
625	>
626	>	public boolean hasNext() {
627	>	return cursor != fence;
628	>	}
629	>
630	>	public E next() {
631	>	if (cursor == fence)
632	>	throw new NoSuchElementException();
633	>	cursor = (cursor - 1) & (elements.length - 1);
634	>	@SuppressWarnings("unchecked")
635	>	E result = (E) elements[cursor];
636	>	if (head != fence || result == null)
637	>	throw new ConcurrentModificationException();
638	>	lastRet = cursor;
639	>	return result;
640	>	}
641	>
642	>	public void remove() {
643	>	if (lastRet < 0)
644	>	throw new IllegalStateException();
645	>	if (!delete(lastRet)) {
646	>	cursor = (cursor + 1) & (elements.length - 1);
647	>	fence = head;
648	>	}
649	>	lastRet = -1;
650	>	}
651	>	}
652	>
653	>	/**
654	>	* Returns {@code true} if this deque contains the specified element.
655	>	* More formally, returns {@code true} if and only if this deque contains
656	>	* at least one element {@code e} such that {@code o.equals(e)}.
657		*
658		* @param o object to be checked for containment in this deque
659	<	* @return <tt>true</tt> if this deque contains the specified element
659	>	* @return {@code true} if this deque contains the specified element
660		*/
661		public boolean contains(Object o) {
662		if (o == null)
663		return false;
664		int mask = elements.length - 1;
665		int i = head;
666	<	E x;
666	>	Object x;
667		while ( (x = elements[i]) != null) {
668		if (o.equals(x))
669		return true;
#	Line 611 | Line 675 | public class ArrayDeque<E> extends Abstr
675		/**
676		* Removes a single instance of the specified element from this deque.
677		* If the deque does not contain the element, it is unchanged.
678	<	* More formally, removes the first element <tt>e</tt> such that
679	<	* <tt>o.equals(e)</tt> (if such an element exists).
680	<	* Returns <tt>true</tt> if this deque contained the specified element
678	>	* More formally, removes the first element {@code e} such that
679	>	* {@code o.equals(e)} (if such an element exists).
680	>	* Returns {@code true} if this deque contained the specified element
681		* (or equivalently, if this deque changed as a result of the call).
682		*
683	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
683	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
684		*
685		* @param o element to be removed from this deque, if present
686	<	* @return <tt>true</tt> if this deque contained the specified element
686	>	* @return {@code true} if this deque contained the specified element
687		*/
688		public boolean remove(Object o) {
689		return removeFirstOccurrence(o);
#	Line 657 | Line 721 | public class ArrayDeque<E> extends Abstr
721		* @return an array containing all of the elements in this deque
722		*/
723		public Object[] toArray() {
724	<	return copyElements(new Object[size()]);
724	>	final int head = this.head;
725	>	final int tail = this.tail;
726	>	boolean wrap = (tail < head);
727	>	int end = wrap ? tail + elements.length : tail;
728	>	Object[] a = Arrays.copyOfRange(elements, head, end);
729	>	if (wrap)
730	>	System.arraycopy(elements, 0, a, elements.length - head, tail);
731	>	return a;
732		}
733
734		/**
#	Line 671 | Line 742 | public class ArrayDeque<E> extends Abstr
742		* <p>If this deque fits in the specified array with room to spare
743		* (i.e., the array has more elements than this deque), the element in
744		* the array immediately following the end of the deque is set to
745	<	* <tt>null</tt>.
745	>	* {@code null}.
746		*
747		* <p>Like the {@link #toArray()} method, this method acts as bridge between
748		* array-based and collection-based APIs.  Further, this method allows
749		* precise control over the runtime type of the output array, and may,
750		* under certain circumstances, be used to save allocation costs.
751		*
752	<	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
752	>	* <p>Suppose {@code x} is a deque known to contain only strings.
753		* The following code can be used to dump the deque into a newly
754	<	* allocated array of <tt>String</tt>:
754	>	* allocated array of {@code String}:
755		*
756	<	* <pre>
686	<	*     String[] y = x.toArray(new String[0]);</pre>
756	>	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
757		*
758	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
759	<	* <tt>toArray()</tt>.
758	>	* Note that {@code toArray(new Object[0])} is identical in function to
759	>	* {@code toArray()}.
760		*
761		* @param a the array into which the elements of the deque are to
762		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 697 | Line 767 | public class ArrayDeque<E> extends Abstr
767		*         this deque
768		* @throws NullPointerException if the specified array is null
769		*/
770	+	@SuppressWarnings("unchecked")
771		public <T> T[] toArray(T[] a) {
772	<	int size = size();
773	<	if (a.length < size)
774	<	a = (T[])java.lang.reflect.Array.newInstance(
775	<	a.getClass().getComponentType(), size);
776	<	copyElements(a);
777	<	if (a.length > size)
778	<	a[size] = null;
772	>	final int head = this.head;
773	>	final int tail = this.tail;
774	>	boolean wrap = (tail < head);
775	>	int size = (tail - head) + (wrap ? elements.length : 0);
776	>	int firstLeg = size - (wrap ? tail : 0);
777	>	int len = a.length;
778	>	if (size > len) {
779	>	a = (T[]) Arrays.copyOfRange(elements, head, head + size,
780	>	a.getClass());
781	>	} else {
782	>	System.arraycopy(elements, head, a, 0, firstLeg);
783	>	if (size < len)
784	>	a[size] = null;
785	>	}
786	>	if (wrap)
787	>	System.arraycopy(elements, 0, a, firstLeg, tail);
788		return a;
789		}
790
#	Line 717 | Line 797 | public class ArrayDeque<E> extends Abstr
797		*/
798		public ArrayDeque<E> clone() {
799		try {
800	+	@SuppressWarnings("unchecked")
801		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
802	<	// These two lines are currently faster than cloning the array:
722	<	result.elements = (E[]) new Object[elements.length];
723	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
802	>	result.elements = Arrays.copyOf(elements, elements.length);
803		return result;
725	–
804		} catch (CloneNotSupportedException e) {
805		throw new AssertionError();
806		}
807		}
808
731	–	/**
732	–	* Appease the serialization gods.
733	–	*/
809		private static final long serialVersionUID = 2340985798034038923L;
810
811		/**
812	<	* Serialize this deque.
812	>	* Saves this deque to a stream (that is, serializes it).
813		*
814	<	* @serialData The current size (<tt>int</tt>) of the deque,
814	>	* @serialData The current size ({@code int}) of the deque,
815		* followed by all of its elements (each an object reference) in
816		* first-to-last order.
817		*/
818	<	private void writeObject(ObjectOutputStream s) throws IOException {
818	>	private void writeObject(java.io.ObjectOutputStream s)
819	>	throws java.io.IOException {
820		s.defaultWriteObject();
821
822		// Write out size
823	<	int size = size();
748	<	s.writeInt(size);
823	>	s.writeInt(size());
824
825		// Write out elements in order.
751	–	int i = head;
826		int mask = elements.length - 1;
827	<	for (int j = 0; j < size; j++) {
827	>	for (int i = head; i != tail; i = (i + 1) & mask)
828		s.writeObject(elements[i]);
755	–	i = (i + 1) & mask;
756	–	}
829		}
830
831		/**
832	<	* Deserialize this deque.
832	>	* Reconstitutes this deque from a stream (that is, deserializes it).
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 771 | 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 forEach(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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