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

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.3 by dl, Tue Mar 8 17:52:02 2005 UTC vs.
Revision 1.47 by dl, Sun Feb 17 23:36:16 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.
21	>	* <p>Most {@code ArrayDeque} 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
24	>	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
25		* iterator.remove()}, and the bulk operations, all of which run in linear
26		* time.
27		*
28	<	* <p>The iterators returned by this class's <tt>iterator</tt> method are
28	>	* <p>The iterators returned by this class's {@code iterator} method are
29		* <i>fail-fast</i>: If the deque is modified at any time after the iterator
30	<	* is created, in any way except through the iterator's own remove method, the
31	<	* iterator will generally throw a {@link ConcurrentModificationException}.
32	<	* Thus, in the face of concurrent modification, the iterator fails quickly
33	<	* and cleanly, rather than risking arbitrary, non-deterministic behavior at
34	<	* an undetermined time in the future.
30	>	* is created, in any way except through the iterator's own {@code remove}
31	>	* method, the iterator will generally throw a {@link
32	>	* ConcurrentModificationException}.  Thus, in the face of concurrent
33	>	* modification, the iterator fails quickly and cleanly, rather than risking
34	>	* arbitrary, non-deterministic behavior at an undetermined time in the
35	>	* future.
36		*
37		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
38		* as it is, generally speaking, impossible to make any hard guarantees in the
39		* presence of unsynchronized concurrent modification.  Fail-fast iterators
40	<	* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
40	>	* throw {@code ConcurrentModificationException} on a best-effort basis.
41		* Therefore, it would be wrong to write a program that depended on this
42		* exception for its correctness: <i>the fail-fast behavior of iterators
43		* should be used only to detect bugs.</i>
44		*
45		* <p>This class and its iterator implement all of the
46	<	* optional methods of the {@link Collection} and {@link
47	<	* Iterator} interfaces.  This class is a member of the <a
48	<	* href="{@docRoot}/../guide/collections/index.html"> Java Collections
49	<	* Framework</a>.
46	>	* <em>optional</em> methods of the {@link Collection} and {@link
47	>	* Iterator} interfaces.
48	>	*
49	>	* <p>This class is a member of the
50	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
51	>	* Java Collections Framework</a>.
52		*
53		* @author  Josh Bloch and Doug Lea
54		* @since   1.6
#	Line 52 | Line 58 | public class ArrayDeque<E> extends Abstr
58		implements Deque<E>, Cloneable, Serializable
59		{
60		/**
61	<	* The array in which the elements of in the deque are stored.
61	>	* The array in which the elements of the deque are stored.
62		* The capacity of the deque is the length of this array, which is
63		* always a power of two. The array is never allowed to become
64		* full, except transiently within an addX method where it is
#	Line 61 | Line 67 | public class ArrayDeque<E> extends Abstr
67		* other.  We also guarantee that all array cells not holding
68		* deque elements are always null.
69		*/
70	<	private transient E[] elements;
70	>	transient Object[] elements; // non-private to simplify nested class access
71
72		/**
73		* The index of the element at the head of the deque (which is the
74		* element that would be removed by remove() or pop()); or an
75		* arbitrary number equal to tail if the deque is empty.
76		*/
77	<	private transient int head;
77	>	transient int head;
78
79		/**
80		* The index at which the next element would be added to the tail
81		* of the deque (via addLast(E), add(E), or push(E)).
82		*/
83	<	private transient int tail;
83	>	transient int tail;
84
85		/**
86		* The minimum capacity that we'll use for a newly created deque.
#	Line 85 | Line 91 | public class ArrayDeque<E> extends Abstr
91		// ******  Array allocation and resizing utilities ******
92
93		/**
94	<	* Allocate empty array to hold the given number of elements.
94	>	* Allocates empty array to hold the given number of elements.
95		*
96	<	* @param numElements  the number of elements to hold.
96	>	* @param numElements  the number of elements to hold
97		*/
98	<	private void allocateElements(int numElements) {
98	>	private void allocateElements(int numElements) {
99		int initialCapacity = MIN_INITIAL_CAPACITY;
100		// Find the best power of two to hold elements.
101		// Tests "<=" because arrays aren't kept full.
#	Line 105 | Line 111 | public class ArrayDeque<E> extends Abstr
111		if (initialCapacity < 0)   // Too many elements, must back off
112		initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
113		}
114	<	elements = (E[]) new Object[initialCapacity];
114	>	elements = new Object[initialCapacity];
115		}
116
117		/**
118	<	* Double the capacity of this deque.  Call only when full, i.e.,
118	>	* Doubles the capacity of this deque.  Call only when full, i.e.,
119		* when head and tail have wrapped around to become equal.
120		*/
121		private void doubleCapacity() {
122	<	assert head == tail;
122	>	assert head == tail;
123		int p = head;
124		int n = elements.length;
125		int r = n - p; // number of elements to the right of p
#	Line 123 | Line 129 | public class ArrayDeque<E> extends Abstr
129		Object[] a = new Object[newCapacity];
130		System.arraycopy(elements, p, a, 0, r);
131		System.arraycopy(elements, 0, a, r, p);
132	<	elements = (E[])a;
132	>	elements = a;
133		head = 0;
134		tail = n;
135		}
136
137		/**
138	<	* Copy the elements from our element array into the specified array,
138	>	* Copies the elements from our element array into the specified array,
139		* in order (from first to last element in the deque).  It is assumed
140		* that the array is large enough to hold all elements in the deque.
141		*
#	Line 147 | Line 153 | public class ArrayDeque<E> extends Abstr
153		}
154
155		/**
156	<	* Constructs an empty array deque with the an initial capacity
156	>	* Constructs an empty array deque with an initial capacity
157		* sufficient to hold 16 elements.
158		*/
159		public ArrayDeque() {
160	<	elements = (E[]) new Object[16];
160	>	elements = new Object[16];
161		}
162
163		/**
#	Line 184 | Line 190 | public class ArrayDeque<E> extends Abstr
190		// terms of these.
191
192		/**
193	<	* Inserts the specified element to the front this deque.
193	>	* Inserts the specified element at the front of this deque.
194		*
195	<	* @param e the element to insert
196	<	* @throws NullPointerException if <tt>e</tt> is null
195	>	* @param e the element to add
196	>	* @throws NullPointerException if the specified element is null
197		*/
198		public void addFirst(E e) {
199		if (e == null)
200		throw new NullPointerException();
201		elements[head = (head - 1) & (elements.length - 1)] = e;
202	<	if (head == tail)
202	>	if (head == tail)
203		doubleCapacity();
204		}
205
206		/**
207	<	* Inserts the specified element to the end this deque.
208	<	* This method is equivalent to {@link Collection#add} and
209	<	* {@link #push}.
207	>	* Inserts the specified element at the end of this deque.
208	>	*
209	>	* <p>This method is equivalent to {@link #add}.
210		*
211	<	* @param e the element to insert
212	<	* @throws NullPointerException if <tt>e</tt> is null
211	>	* @param e the element to add
212	>	* @throws NullPointerException if the specified element is null
213		*/
214		public void addLast(E e) {
215		if (e == null)
#	Line 214 | Line 220 | public class ArrayDeque<E> extends Abstr
220		}
221
222		/**
223	<	* Retrieves and removes the first element of this deque, or
218	<	* <tt>null</tt> if this deque is empty.
223	>	* Inserts the specified element at the front of this deque.
224		*
225	<	* @return the first element of this deque, or <tt>null</tt> if
226	<	*     this deque is empty
227	<	*/
223	<	public E pollFirst() {
224	<	int h = head;
225	<	E result = elements[h]; // Element is null if deque empty
226	<	if (result == null)
227	<	return null;
228	<	elements[h] = null;     // Must null out slot
229	<	head = (h + 1) & (elements.length - 1);
230	<	return result;
231	<	}
232	<
233	<	/**
234	<	* Retrieves and removes the last element of this deque, or
235	<	* <tt>null</tt> if this deque is empty.
236	<	*
237	<	* @return the last element of this deque, or <tt>null</tt> if
238	<	*     this deque is empty
239	<	*/
240	<	public E pollLast() {
241	<	int t = (tail - 1) & (elements.length - 1);
242	<	E result = elements[t];
243	<	if (result == null)
244	<	return null;
245	<	elements[t] = null;
246	<	tail = t;
247	<	return result;
248	<	}
249	<
250	<	/**
251	<	* Inserts the specified element to the front this deque.
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
225	>	* @param e the element to add
226	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
227	>	* @throws NullPointerException if the specified element is null
228		*/
229		public boolean offerFirst(E e) {
230		addFirst(e);
#	Line 260 | Line 232 | public class ArrayDeque<E> extends Abstr
232		}
233
234		/**
235	<	* Inserts the specified element to the end this deque.
235	>	* Inserts the specified element at the end of this deque.
236		*
237	<	* @param e the element to insert
238	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
239	<	* @throws NullPointerException if <tt>e</tt> is null
237	>	* @param e the element to add
238	>	* @return {@code true} (as specified by {@link Deque#offerLast})
239	>	* @throws NullPointerException if the specified element is null
240		*/
241		public boolean offerLast(E e) {
242		addLast(e);
#	Line 272 | Line 244 | public class ArrayDeque<E> extends Abstr
244		}
245
246		/**
247	<	* 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
247	>	* @throws NoSuchElementException {@inheritDoc}
248		*/
249		public E removeFirst() {
250		E x = pollFirst();
#	Line 287 | Line 254 | public class ArrayDeque<E> extends Abstr
254		}
255
256		/**
257	<	* 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
257	>	* @throws NoSuchElementException {@inheritDoc}
258		*/
259		public E removeLast() {
260		E x = pollLast();
#	Line 301 | Line 263 | public class ArrayDeque<E> extends Abstr
263		return x;
264		}
265
266	<	/**
267	<	* Retrieves, but does not remove, the first element of this deque,
268	<	* returning <tt>null</tt> if this deque is empty.
269	<	*
270	<	* @return the first element of this deque, or <tt>null</tt> if
271	<	*     this deque is empty
272	<	*/
273	<	public E peekFirst() {
274	<	return elements[head]; // elements[head] is null if deque empty
266	>	public E pollFirst() {
267	>	int h = head;
268	>	@SuppressWarnings("unchecked")
269	>	E result = (E) elements[h];
270	>	// Element is null if deque empty
271	>	if (result == null)
272	>	return null;
273	>	elements[h] = null;     // Must null out slot
274	>	head = (h + 1) & (elements.length - 1);
275	>	return result;
276		}
277
278	<	/**
279	<	* Retrieves, but does not remove, the last element of this deque,
280	<	* returning <tt>null</tt> if this deque is empty.
281	<	*
282	<	* @return the last element of this deque, or <tt>null</tt> if this deque
283	<	*     is empty
284	<	*/
285	<	public E peekLast() {
286	<	return elements[(tail - 1) & (elements.length - 1)];
278	>	public E pollLast() {
279	>	int t = (tail - 1) & (elements.length - 1);
280	>	@SuppressWarnings("unchecked")
281	>	E result = (E) elements[t];
282	>	if (result == null)
283	>	return null;
284	>	elements[t] = null;
285	>	tail = t;
286	>	return result;
287		}
288
289		/**
290	<	* 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
290	>	* @throws NoSuchElementException {@inheritDoc}
291		*/
292		public E getFirst() {
293	<	E x = elements[head];
294	<	if (x == null)
293	>	@SuppressWarnings("unchecked")
294	>	E result = (E) elements[head];
295	>	if (result == null)
296		throw new NoSuchElementException();
297	<	return x;
297	>	return result;
298		}
299
300		/**
301	<	* 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
301	>	* @throws NoSuchElementException {@inheritDoc}
302		*/
303		public E getLast() {
304	<	E x = elements[(tail - 1) & (elements.length - 1)];
305	<	if (x == null)
304	>	@SuppressWarnings("unchecked")
305	>	E result = (E) elements[(tail - 1) & (elements.length - 1)];
306	>	if (result == null)
307		throw new NoSuchElementException();
308	<	return x;
308	>	return result;
309	>	}
310	>
311	>	@SuppressWarnings("unchecked")
312	>	public E peekFirst() {
313	>	// elements[head] is null if deque empty
314	>	return (E) elements[head];
315	>	}
316	>
317	>	@SuppressWarnings("unchecked")
318	>	public E peekLast() {
319	>	return (E) elements[(tail - 1) & (elements.length - 1)];
320		}
321
322		/**
323		* Removes the first occurrence of the specified element in this
324	<	* deque (when traversing the deque from head to tail).  If the deque
325	<	* does not contain the element, it is unchanged.
324	>	* deque (when traversing the deque from head to tail).
325	>	* If the deque does not contain the element, it is unchanged.
326	>	* More formally, removes the first element {@code e} such that
327	>	* {@code o.equals(e)} (if such an element exists).
328	>	* Returns {@code true} if this deque contained the specified element
329	>	* (or equivalently, if this deque changed as a result of the call).
330		*
331	<	* @param e element to be removed from this deque, if present
332	<	* @return <tt>true</tt> if the deque contained the specified element
331	>	* @param o element to be removed from this deque, if present
332	>	* @return {@code true} if the deque contained the specified element
333		*/
334	<	public boolean removeFirstOccurrence(Object e) {
335	<	if (e == null)
334	>	public boolean removeFirstOccurrence(Object o) {
335	>	if (o == null)
336		return false;
337		int mask = elements.length - 1;
338		int i = head;
339	<	E x;
339	>	Object x;
340		while ( (x = elements[i]) != null) {
341	<	if (e.equals(x)) {
341	>	if (o.equals(x)) {
342		delete(i);
343		return true;
344		}
#	Line 379 | Line 349 | public class ArrayDeque<E> extends Abstr
349
350		/**
351		* Removes the last occurrence of the specified element in this
352	<	* deque (when traversing the deque from head to tail).  If the deque
353	<	* does not contain the element, it is unchanged.
352	>	* deque (when traversing the deque from head to tail).
353	>	* If the deque does not contain the element, it is unchanged.
354	>	* More formally, removes the last element {@code e} such that
355	>	* {@code o.equals(e)} (if such an element exists).
356	>	* Returns {@code true} if this deque contained the specified element
357	>	* (or equivalently, if this deque changed as a result of the call).
358		*
359	<	* @param e element to be removed from this deque, if present
360	<	* @return <tt>true</tt> if the deque contained the specified element
359	>	* @param o element to be removed from this deque, if present
360	>	* @return {@code true} if the deque contained the specified element
361		*/
362	<	public boolean removeLastOccurrence(Object e) {
363	<	if (e == null)
362	>	public boolean removeLastOccurrence(Object o) {
363	>	if (o == null)
364		return false;
365		int mask = elements.length - 1;
366		int i = (tail - 1) & mask;
367	<	E x;
367	>	Object x;
368		while ( (x = elements[i]) != null) {
369	<	if (e.equals(x)) {
369	>	if (o.equals(x)) {
370		delete(i);
371		return true;
372		}
#	Line 404 | Line 378 | public class ArrayDeque<E> extends Abstr
378		// *** Queue methods ***
379
380		/**
381	<	* 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.
381	>	* Inserts the specified element at the end of this deque.
382		*
383		* <p>This method is equivalent to {@link #addLast}.
384		*
385	<	* @param e the element to insert
386	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
387	<	* @throws NullPointerException if <tt>e</tt> is null
385	>	* @param e the element to add
386	>	* @return {@code true} (as specified by {@link Collection#add})
387	>	* @throws NullPointerException if the specified element is null
388		*/
389		public boolean add(E e) {
390		addLast(e);
#	Line 431 | Line 392 | public class ArrayDeque<E> extends Abstr
392		}
393
394		/**
395	<	* 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.
395	>	* Inserts the specified element at the end of this deque.
396		*
397	<	* <p>This method is equivalent to {@link #pollFirst}.
397	>	* <p>This method is equivalent to {@link #offerLast}.
398		*
399	<	* @return the first element of this deque, or <tt>null</tt> if
400	<	*     this deque is empty
399	>	* @param e the element to add
400	>	* @return {@code true} (as specified by {@link Queue#offer})
401	>	* @throws NullPointerException if the specified element is null
402		*/
403	<	public E poll() {
404	<	return pollFirst();
403	>	public boolean offer(E e) {
404	>	return offerLast(e);
405		}
406
407		/**
408		* Retrieves and removes the head of the queue represented by this deque.
409	<	* This method differs from the <tt>poll</tt> method in that it throws an
409	>	*
410	>	* This method differs from {@link #poll poll} only in that it throws an
411		* exception if this deque is empty.
412		*
413		* <p>This method is equivalent to {@link #removeFirst}.
414		*
415		* @return the head of the queue represented by this deque
416	<	* @throws NoSuchElementException if this deque is empty
416	>	* @throws NoSuchElementException {@inheritDoc}
417		*/
418		public E remove() {
419		return removeFirst();
420		}
421
422		/**
423	<	* Retrieves, but does not remove, the head of the queue represented by
424	<	* this deque, returning <tt>null</tt> if this deque is empty.
423	>	* Retrieves and removes the head of the queue represented by this deque
424	>	* (in other words, the first element of this deque), or returns
425	>	* {@code null} if this deque is empty.
426		*
427	<	* <p>This method is equivalent to {@link #peekFirst}
427	>	* <p>This method is equivalent to {@link #pollFirst}.
428		*
429		* @return the head of the queue represented by this deque, or
430	<	*     <tt>null</tt> if this deque is empty
430	>	*         {@code null} if this deque is empty
431		*/
432	<	public E peek() {
433	<	return peekFirst();
432	>	public E poll() {
433	>	return pollFirst();
434		}
435
436		/**
437		* Retrieves, but does not remove, the head of the queue represented by
438	<	* this deque.  This method differs from the <tt>peek</tt> method only in
438	>	* this deque.  This method differs from {@link #peek peek} only in
439		* that it throws an exception if this deque is empty.
440		*
441	<	* <p>This method is equivalent to {@link #getFirst}
441	>	* <p>This method is equivalent to {@link #getFirst}.
442		*
443		* @return the head of the queue represented by this deque
444	<	* @throws NoSuchElementException if this deque is empty
444	>	* @throws NoSuchElementException {@inheritDoc}
445		*/
446		public E element() {
447		return getFirst();
448		}
449
450	+	/**
451	+	* Retrieves, but does not remove, the head of the queue represented by
452	+	* this deque, or returns {@code null} if this deque is empty.
453	+	*
454	+	* <p>This method is equivalent to {@link #peekFirst}.
455	+	*
456	+	* @return the head of the queue represented by this deque, or
457	+	*         {@code null} if this deque is empty
458	+	*/
459	+	public E peek() {
460	+	return peekFirst();
461	+	}
462	+
463		// *** Stack methods ***
464
465		/**
466		* Pushes an element onto the stack represented by this deque.  In other
467	<	* words, inserts the element to the front this deque.
467	>	* words, inserts the element at the front of this deque.
468		*
469		* <p>This method is equivalent to {@link #addFirst}.
470		*
471		* @param e the element to push
472	<	* @throws NullPointerException if <tt>e</tt> is null
472	>	* @throws NullPointerException if the specified element is null
473		*/
474		public void push(E e) {
475		addFirst(e);
#	Line 508 | Line 482 | public class ArrayDeque<E> extends Abstr
482		* <p>This method is equivalent to {@link #removeFirst()}.
483		*
484		* @return the element at the front of this deque (which is the top
485	<	*     of the stack represented by this deque)
486	<	* @throws NoSuchElementException if this deque is empty
485	>	*         of the stack represented by this deque)
486	>	* @throws NoSuchElementException {@inheritDoc}
487		*/
488		public E pop() {
489		return removeFirst();
490		}
491
492	+	private void checkInvariants() {
493	+	assert elements[tail] == null;
494	+	assert head == tail ? elements[head] == null :
495	+	(elements[head] != null &&
496	+	elements[(tail - 1) & (elements.length - 1)] != null);
497	+	assert elements[(head - 1) & (elements.length - 1)] == null;
498	+	}
499	+
500		/**
501	<	* Remove the element at the specified position in the elements array,
502	<	* adjusting head, tail, and size as necessary.  This can result in
503	<	* motion of elements backwards or forwards in the array.
504	<	*
505	<	* <p>This method is called delete rather than remove to emphasize
506	<	* that its semantics differ from those of List.remove(int).
507	<	*
501	>	* Removes the element at the specified position in the elements array,
502	>	* adjusting head and tail as necessary.  This can result in motion of
503	>	* elements backwards or forwards in the array.
504	>	*
505	>	* <p>This method is called delete rather than remove to emphasize
506	>	* that its semantics differ from those of {@link List#remove(int)}.
507	>	*
508		* @return true if elements moved backwards
509		*/
510		private boolean delete(int i) {
511	<	// Case 1: Deque doesn't wrap
512	<	// Case 2: Deque does wrap and removed element is in the head portion
513	<	if ((head < tail || tail == 0) || i >= head) {
514	<	System.arraycopy(elements, head, elements, head + 1, i - head);
515	<	elements[head] = null;
516	<	head = (head + 1) & (elements.length - 1);
511	>	checkInvariants();
512	>	final Object[] elements = this.elements;
513	>	final int mask = elements.length - 1;
514	>	final int h = head;
515	>	final int t = tail;
516	>	final int front = (i - h) & mask;
517	>	final int back  = (t - i) & mask;
518	>
519	>	// Invariant: head <= i < tail mod circularity
520	>	if (front >= ((t - h) & mask))
521	>	throw new ConcurrentModificationException();
522	>
523	>	// Optimize for least element motion
524	>	if (front < back) {
525	>	if (h <= i) {
526	>	System.arraycopy(elements, h, elements, h + 1, front);
527	>	} else { // Wrap around
528	>	System.arraycopy(elements, 0, elements, 1, i);
529	>	elements[0] = elements[mask];
530	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
531	>	}
532	>	elements[h] = null;
533	>	head = (h + 1) & mask;
534		return false;
535	+	} else {
536	+	if (i < t) { // Copy the null tail as well
537	+	System.arraycopy(elements, i + 1, elements, i, back);
538	+	tail = t - 1;
539	+	} else { // Wrap around
540	+	System.arraycopy(elements, i + 1, elements, i, mask - i);
541	+	elements[mask] = elements[0];
542	+	System.arraycopy(elements, 1, elements, 0, t);
543	+	tail = (t - 1) & mask;
544	+	}
545	+	return true;
546		}
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;
547		}
548
549		// *** Collection Methods ***
#	Line 554 | Line 558 | public class ArrayDeque<E> extends Abstr
558		}
559
560		/**
561	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
561	>	* Returns {@code true} if this deque contains no elements.
562		*
563	<	* @return <tt>true</tt> if this collection contains no elements.
563	>	* @return {@code true} if this deque contains no elements
564		*/
565		public boolean isEmpty() {
566		return head == tail;
#	Line 567 | Line 571 | public class ArrayDeque<E> extends Abstr
571		* will be ordered from first (head) to last (tail).  This is the same
572		* order that elements would be dequeued (via successive calls to
573		* {@link #remove} or popped (via successive calls to {@link #pop}).
574	<	*
575	<	* @return an <tt>Iterator</tt> over the elements in this deque
574	>	*
575	>	* @return an iterator over the elements in this deque
576		*/
577		public Iterator<E> iterator() {
578		return new DeqIterator();
579		}
580
581	+	public Iterator<E> descendingIterator() {
582	+	return new DescendingIterator();
583	+	}
584	+
585		private class DeqIterator implements Iterator<E> {
586		/**
587		* Index of element to be returned by subsequent call to next.
#	Line 597 | Line 605 | public class ArrayDeque<E> extends Abstr
605		}
606
607		public E next() {
600	–	E result;
608		if (cursor == fence)
609		throw new NoSuchElementException();
610	+	@SuppressWarnings("unchecked")
611	+	E result = (E) elements[cursor];
612		// This check doesn't catch all possible comodifications,
613		// but does catch the ones that corrupt traversal
614	<	if (tail != fence || (result = elements[cursor]) == null)
614	>	if (tail != fence || result == null)
615		throw new ConcurrentModificationException();
616		lastRet = cursor;
617		cursor = (cursor + 1) & (elements.length - 1);
#	Line 612 | Line 621 | public class ArrayDeque<E> extends Abstr
621		public void remove() {
622		if (lastRet < 0)
623		throw new IllegalStateException();
624	<	if (delete(lastRet))
625	<	cursor--;
624	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
625	>	cursor = (cursor - 1) & (elements.length - 1);
626	>	fence = tail;
627	>	}
628	>	lastRet = -1;
629	>	}
630	>	}
631	>
632	>	private class DescendingIterator implements Iterator<E> {
633	>	/*
634	>	* This class is nearly a mirror-image of DeqIterator, using
635	>	* tail instead of head for initial cursor, and head instead of
636	>	* tail for fence.
637	>	*/
638	>	private int cursor = tail;
639	>	private int fence = head;
640	>	private int lastRet = -1;
641	>
642	>	public boolean hasNext() {
643	>	return cursor != fence;
644	>	}
645	>
646	>	public E next() {
647	>	if (cursor == fence)
648	>	throw new NoSuchElementException();
649	>	cursor = (cursor - 1) & (elements.length - 1);
650	>	@SuppressWarnings("unchecked")
651	>	E result = (E) elements[cursor];
652	>	if (head != fence || result == null)
653	>	throw new ConcurrentModificationException();
654	>	lastRet = cursor;
655	>	return result;
656	>	}
657	>
658	>	public void remove() {
659	>	if (lastRet < 0)
660	>	throw new IllegalStateException();
661	>	if (!delete(lastRet)) {
662	>	cursor = (cursor + 1) & (elements.length - 1);
663	>	fence = head;
664	>	}
665		lastRet = -1;
618	–	fence = tail;
666		}
667		}
668
669		/**
670	<	* Returns <tt>true</tt> if this deque contains the specified
671	<	* element.  More formally, returns <tt>true</tt> if and only if this
672	<	* deque contains at least one element <tt>e</tt> such that
626	<	* <tt>e.equals(o)</tt>.
670	>	* Returns {@code true} if this deque contains the specified element.
671	>	* More formally, returns {@code true} if and only if this deque contains
672	>	* at least one element {@code e} such that {@code o.equals(e)}.
673		*
674		* @param o object to be checked for containment in this deque
675	<	* @return <tt>true</tt> if this deque contains the specified element
675	>	* @return {@code true} if this deque contains the specified element
676		*/
677		public boolean contains(Object o) {
678		if (o == null)
679		return false;
680		int mask = elements.length - 1;
681		int i = head;
682	<	E x;
682	>	Object x;
683		while ( (x = elements[i]) != null) {
684		if (o.equals(x))
685		return true;
#	Line 644 | Line 690 | public class ArrayDeque<E> extends Abstr
690
691		/**
692		* Removes a single instance of the specified element from this deque.
693	<	* This method is equivalent to {@link #removeFirstOccurrence}.
693	>	* If the deque does not contain the element, it is unchanged.
694	>	* More formally, removes the first element {@code e} such that
695	>	* {@code o.equals(e)} (if such an element exists).
696	>	* Returns {@code true} if this deque contained the specified element
697	>	* (or equivalently, if this deque changed as a result of the call).
698		*
699	<	* @param e element to be removed from this deque, if present
700	<	* @return <tt>true</tt> if this deque contained the specified element
699	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
700	>	*
701	>	* @param o element to be removed from this deque, if present
702	>	* @return {@code true} if this deque contained the specified element
703		*/
704	<	public boolean remove(Object e) {
705	<	return removeFirstOccurrence(e);
704	>	public boolean remove(Object o) {
705	>	return removeFirstOccurrence(o);
706		}
707
708		/**
709		* Removes all of the elements from this deque.
710	+	* The deque will be empty after this call returns.
711		*/
712		public void clear() {
713		int h = head;
#	Line 666 | Line 719 | public class ArrayDeque<E> extends Abstr
719		do {
720		elements[i] = null;
721		i = (i + 1) & mask;
722	<	} while(i != t);
722	>	} while (i != t);
723		}
724		}
725
726		/**
727	<	* Returns an array containing all of the elements in this list
728	<	* in the correct order.
727	>	* Returns an array containing all of the elements in this deque
728	>	* in proper sequence (from first to last element).
729	>	*
730	>	* <p>The returned array will be "safe" in that no references to it are
731	>	* maintained by this deque.  (In other words, this method must allocate
732	>	* a new array).  The caller is thus free to modify the returned array.
733	>	*
734	>	* <p>This method acts as bridge between array-based and collection-based
735	>	* APIs.
736		*
737	<	* @return an array containing all of the elements in this list
678	<	*         in the correct order
737	>	* @return an array containing all of the elements in this deque
738		*/
739		public Object[] toArray() {
740	<	return copyElements(new Object[size()]);
740	>	return copyElements(new Object[size()]);
741		}
742
743		/**
744	<	* Returns an array containing all of the elements in this deque in the
745	<	* correct order; the runtime type of the returned array is that of the
746	<	* specified array.  If the deque fits in the specified array, it is
747	<	* returned therein.  Otherwise, a new array is allocated with the runtime
748	<	* type of the specified array and the size of this deque.
744	>	* Returns an array containing all of the elements in this deque in
745	>	* proper sequence (from first to last element); the runtime type of the
746	>	* returned array is that of the specified array.  If the deque fits in
747	>	* the specified array, it is returned therein.  Otherwise, a new array
748	>	* is allocated with the runtime type of the specified array and the
749	>	* size of this deque.
750		*
751	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
752	<	* the array has more elements than the deque), the element in the array
753	<	* immediately following the end of the collection is set to <tt>null</tt>.
751	>	* <p>If this deque fits in the specified array with room to spare
752	>	* (i.e., the array has more elements than this deque), the element in
753	>	* the array immediately following the end of the deque is set to
754	>	* {@code null}.
755	>	*
756	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
757	>	* array-based and collection-based APIs.  Further, this method allows
758	>	* precise control over the runtime type of the output array, and may,
759	>	* under certain circumstances, be used to save allocation costs.
760	>	*
761	>	* <p>Suppose {@code x} is a deque known to contain only strings.
762	>	* The following code can be used to dump the deque into a newly
763	>	* allocated array of {@code String}:
764	>	*
765	>	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
766	>	*
767	>	* Note that {@code toArray(new Object[0])} is identical in function to
768	>	* {@code toArray()}.
769		*
770		* @param a the array into which the elements of the deque are to
771	<	*          be stored, if it is big enough; otherwise, a new array of the
772	<	*          same runtime type is allocated for this purpose
773	<	* @return an array containing the elements of the deque
774	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
775	<	*         of the runtime type of every element in this deque
771	>	*          be stored, if it is big enough; otherwise, a new array of the
772	>	*          same runtime type is allocated for this purpose
773	>	* @return an array containing all of the elements in this deque
774	>	* @throws ArrayStoreException if the runtime type of the specified array
775	>	*         is not a supertype of the runtime type of every element in
776	>	*         this deque
777	>	* @throws NullPointerException if the specified array is null
778		*/
779	+	@SuppressWarnings("unchecked")
780		public <T> T[] toArray(T[] a) {
781		int size = size();
782		if (a.length < size)
783		a = (T[])java.lang.reflect.Array.newInstance(
784		a.getClass().getComponentType(), size);
785	<	copyElements(a);
785	>	copyElements(a);
786		if (a.length > size)
787		a[size] = null;
788		return a;
#	Line 718 | Line 796 | public class ArrayDeque<E> extends Abstr
796		* @return a copy of this deque
797		*/
798		public ArrayDeque<E> clone() {
799	<	try {
799	>	try {
800	>	@SuppressWarnings("unchecked")
801		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
802	<	// 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);
802	>	result.elements = Arrays.copyOf(elements, elements.length);
803		return result;
804	<
728	<	} catch (CloneNotSupportedException e) {
804	>	} catch (CloneNotSupportedException e) {
805		throw new AssertionError();
806		}
807		}
808
733	–	/**
734	–	* Appease the serialization gods.
735	–	*/
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();
750	<	s.writeInt(size);
823	>	s.writeInt(size());
824
825		// Write out elements in order.
753	–	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]);
757	–	i = (i + 1) & mask;
758	–	}
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 773 | 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	+	Spliterator<E> spliterator() {
850	+	return new DeqSpliterator<E>(this, -1, -1);
851		}
852	+
853	+	public Stream<E> stream() {
854	+	return Streams.stream(spliterator());
855	+	}
856	+
857	+	public Stream<E> parallelStream() {
858	+	return Streams.parallelStream(spliterator());
859	+	}
860	+
861	+	static final class DeqSpliterator<E> implements Spliterator<E> {
862	+	private final ArrayDeque<E> deq;
863	+	private int fence;  // -1 until first use
864	+	private int index;  // current index, modified on traverse/split
865	+
866	+	/** Create new spliterator covering the given array and range */
867	+	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
868	+	this.deq = deq;
869	+	this.index = origin;
870	+	this.fence = fence;
871	+	}
872	+
873	+	private int getFence() { // force initialization
874	+	int t;
875	+	if ((t = fence) < 0) {
876	+	t = fence = deq.tail;
877	+	index = deq.head;
878	+	}
879	+	return t;
880	+	}
881	+
882	+	public DeqSpliterator<E> trySplit() {
883	+	int t = getFence(), h = index, n = deq.elements.length;
884	+	if (h != t && ((h + 1) & (n - 1)) != t) {
885	+	if (h > t)
886	+	t += n;
887	+	int m = ((h + t) >>> 1) & (n - 1);
888	+	return new DeqSpliterator<>(deq, h, index = m);
889	+	}
890	+	return null;
891	+	}
892	+
893	+	public void forEach(Consumer<? super E> consumer) {
894	+	if (consumer == null)
895	+	throw new NullPointerException();
896	+	Object[] a = deq.elements;
897	+	int m = a.length - 1, f = getFence(), i = index;
898	+	index = f;
899	+	while (i != f) {
900	+	@SuppressWarnings("unchecked") E e = (E)a[i];
901	+	i = (i + 1) & m;
902	+	if (e == null)
903	+	throw new ConcurrentModificationException();
904	+	consumer.accept(e);
905	+	}
906	+	}
907	+
908	+	public boolean tryAdvance(Consumer<? super E> consumer) {
909	+	if (consumer == null)
910	+	throw new NullPointerException();
911	+	Object[] a = deq.elements;
912	+	int m = a.length - 1, f = getFence(), i = index;
913	+	if (i != fence) {
914	+	@SuppressWarnings("unchecked") E e = (E)a[i];
915	+	index = (i + 1) & m;
916	+	if (e == null)
917	+	throw new ConcurrentModificationException();
918	+	consumer.accept(e);
919	+	return true;
920	+	}
921	+	return false;
922	+	}
923	+
924	+	public long estimateSize() {
925	+	int n = getFence() - index;
926	+	if (n < 0)
927	+	n += deq.elements.length;
928	+	return (long) n;
929	+	}
930	+
931	+	@Override
932	+	public int characteristics() {
933	+	return Spliterator.ORDERED | Spliterator.SIZED |
934	+	Spliterator.NONNULL | Spliterator.SUBSIZED;
935	+	}
936	+	}
937	+
938		}

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