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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.56 by jsr166, Thu Jul 18 17:48:28 2013 UTC vs.
Revision 1.81 by jsr166, Sat Oct 22 18:16:56 2016 UTC

#	Line 4 | Line 4
4		*/
5
6		package java.util;
7	+
8		import java.io.Serializable;
9		import java.util.function.Consumer;
10	<	import java.util.stream.Stream;
10	>	import java.util.function.Predicate;
11	>	import java.util.function.UnaryOperator;
12
13		/**
14		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 52 | Line 54 | import java.util.stream.Stream;
54		* Java Collections Framework</a>.
55		*
56		* @author  Josh Bloch and Doug Lea
57	+	* @param <E> the type of elements held in this deque
58		* @since   1.6
56	–	* @param <E> the type of elements held in this collection
59		*/
60		public class ArrayDeque<E> extends AbstractCollection<E>
61		implements Deque<E>, Cloneable, Serializable
62		{
63		/**
64		* The array in which the elements of the deque are stored.
65	<	* The capacity of the deque is the length of this array, which is
66	<	* always a power of two. The array is never allowed to become
65	<	* full, except transiently within an addX method where it is
66	<	* resized (see doubleCapacity) immediately upon becoming full,
67	<	* thus avoiding head and tail wrapping around to equal each
68	<	* other.  We also guarantee that all array cells not holding
69	<	* deque elements are always null.
65	>	* We guarantee that all array cells not holding deque elements
66	>	* are always null.
67		*/
68	<	transient Object[] elements; // non-private to simplify nested class access
68	>	transient Object[] elements;
69
70		/**
71		* The index of the element at the head of the deque (which is the
72		* element that would be removed by remove() or pop()); or an
73	<	* arbitrary number equal to tail if the deque is empty.
73	>	* arbitrary number 0 <= head < elements.length if the deque is empty.
74		*/
75		transient int head;
76
77	+	/** Number of elements in this collection. */
78	+	transient int size;
79	+
80		/**
81	<	* The index at which the next element would be added to the tail
82	<	* of the deque (via addLast(E), add(E), or push(E)).
81	>	* The maximum size of array to allocate.
82	>	* Some VMs reserve some header words in an array.
83	>	* Attempts to allocate larger arrays may result in
84	>	* OutOfMemoryError: Requested array size exceeds VM limit
85		*/
86	<	transient int tail;
86	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
87
88		/**
89	<	* The minimum capacity that we'll use for a newly created deque.
90	<	* Must be a power of 2.
89	>	* Increases the capacity of this deque by at least the given amount.
90	>	*
91	>	* @param needed the required minimum extra capacity; must be positive
92		*/
93	<	private static final int MIN_INITIAL_CAPACITY = 8;
93	>	private void grow(int needed) {
94	>	// overflow-conscious code
95	>	// checkInvariants();
96	>	int oldCapacity = elements.length;
97	>	int newCapacity;
98	>	// Double size if small; else grow by 50%
99	>	int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
100	>	if (jump < needed
101	>	|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
102	>	newCapacity = newCapacity(needed, jump);
103	>	elements = Arrays.copyOf(elements, newCapacity);
104	>	if (oldCapacity - head < size) {
105	>	// wrap around; slide first leg forward to end of array
106	>	int newSpace = newCapacity - oldCapacity;
107	>	System.arraycopy(elements, head,
108	>	elements, head + newSpace,
109	>	oldCapacity - head);
110	>	Arrays.fill(elements, head, head + newSpace, null);
111	>	head += newSpace;
112	>	}
113	>	// checkInvariants();
114	>	}
115
116	<	// ******  Array allocation and resizing utilities ******
116	>	/** Capacity calculation for edge conditions, especially overflow. */
117	>	private int newCapacity(int needed, int jump) {
118	>	int oldCapacity = elements.length;
119	>	int minCapacity;
120	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
121	>	if (minCapacity < 0)
122	>	throw new IllegalStateException("Sorry, deque too big");
123	>	return Integer.MAX_VALUE;
124	>	}
125	>	if (needed > jump)
126	>	return minCapacity;
127	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
128	>	? oldCapacity + jump
129	>	: MAX_ARRAY_SIZE;
130	>	}
131
132		/**
133	<	* Allocates empty array to hold the given number of elements.
133	>	* Increases the internal storage of this collection, if necessary,
134	>	* to ensure that it can hold at least the given number of elements.
135		*
136	<	* @param numElements  the number of elements to hold
136	>	* @param minCapacity the desired minimum capacity
137	>	* @since TBD
138		*/
139	<	private void allocateElements(int numElements) {
140	<	int initialCapacity = MIN_INITIAL_CAPACITY;
141	<	// Find the best power of two to hold elements.
142	<	// Tests "<=" because arrays aren't kept full.
103	<	if (numElements >= initialCapacity) {
104	<	initialCapacity = numElements;
105	<	initialCapacity |= (initialCapacity >>>  1);
106	<	initialCapacity |= (initialCapacity >>>  2);
107	<	initialCapacity |= (initialCapacity >>>  4);
108	<	initialCapacity |= (initialCapacity >>>  8);
109	<	initialCapacity |= (initialCapacity >>> 16);
110	<	initialCapacity++;
111	<
112	<	if (initialCapacity < 0)   // Too many elements, must back off
113	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
114	<	}
115	<	elements = new Object[initialCapacity];
139	>	/* public */ void ensureCapacity(int minCapacity) {
140	>	if (minCapacity > elements.length)
141	>	grow(minCapacity - elements.length);
142	>	// checkInvariants();
143		}
144
145		/**
146	<	* Doubles the capacity of this deque.  Call only when full, i.e.,
147	<	* when head and tail have wrapped around to become equal.
146	>	* Minimizes the internal storage of this collection.
147	>	*
148	>	* @since TBD
149		*/
150	<	private void doubleCapacity() {
151	<	assert head == tail;
152	<	int p = head;
153	<	int n = elements.length;
154	<	int r = n - p; // number of elements to the right of p
155	<	int newCapacity = n << 1;
128	<	if (newCapacity < 0)
129	<	throw new IllegalStateException("Sorry, deque too big");
130	<	Object[] a = new Object[newCapacity];
131	<	System.arraycopy(elements, p, a, 0, r);
132	<	System.arraycopy(elements, 0, a, r, p);
133	<	elements = a;
134	<	head = 0;
135	<	tail = n;
150	>	/* public */ void trimToSize() {
151	>	if (size < elements.length) {
152	>	elements = toArray();
153	>	head = 0;
154	>	}
155	>	// checkInvariants();
156		}
157
158		/**
#	Line 147 | Line 167 | public class ArrayDeque<E> extends Abstr
167		* Constructs an empty array deque with an initial capacity
168		* sufficient to hold the specified number of elements.
169		*
170	<	* @param numElements  lower bound on initial capacity of the deque
170	>	* @param numElements lower bound on initial capacity of the deque
171		*/
172		public ArrayDeque(int numElements) {
173	<	allocateElements(numElements);
173	>	elements = new Object[numElements];
174		}
175
176		/**
#	Line 164 | Line 184 | public class ArrayDeque<E> extends Abstr
184		* @throws NullPointerException if the specified collection is null
185		*/
186		public ArrayDeque(Collection<? extends E> c) {
187	<	allocateElements(c.size());
188	<	addAll(c);
187	>	Object[] elements = c.toArray();
188	>	// defend against c.toArray (incorrectly) not returning Object[]
189	>	// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
190	>	if (elements.getClass() != Object[].class)
191	>	elements = Arrays.copyOf(elements, size, Object[].class);
192	>	for (Object obj : elements)
193	>	Objects.requireNonNull(obj);
194	>	size = elements.length;
195	>	this.elements = elements;
196	>	}
197	>
198	>	/**
199	>	* Increments i, mod modulus.
200	>	* Precondition and postcondition: 0 <= i < modulus.
201	>	*/
202	>	static final int inc(int i, int modulus) {
203	>	if (++i == modulus) i = 0;
204	>	return i;
205	>	}
206	>
207	>	/**
208	>	* Decrements i, mod modulus.
209	>	* Precondition and postcondition: 0 <= i < modulus.
210	>	*/
211	>	static final int dec(int i, int modulus) {
212	>	if (--i < 0) i += modulus;
213	>	return i;
214	>	}
215	>
216	>	/**
217	>	* Adds i and j, mod modulus.
218	>	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
219	>	*/
220	>	static final int add(int i, int j, int modulus) {
221	>	if ((i += j) - modulus >= 0) i -= modulus;
222	>	return i;
223	>	}
224	>
225	>	/**
226	>	* Returns the array index of the last element.
227	>	* May return invalid index -1 if there are no elements.
228	>	*/
229	>	final int tail() {
230	>	return add(head, size - 1, elements.length);
231	>	}
232	>
233	>	/**
234	>	* Returns element at array index i.
235	>	*/
236	>	@SuppressWarnings("unchecked")
237	>	final E elementAt(int i) {
238	>	return (E) elements[i];
239	>	}
240	>
241	>	/**
242	>	* A version of elementAt that checks for null elements.
243	>	* This check doesn't catch all possible comodifications,
244	>	* but does catch ones that corrupt traversal.
245	>	*/
246	>	E checkedElementAt(Object[] elements, int i) {
247	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
248	>	if (e == null)
249	>	throw new ConcurrentModificationException();
250	>	return e;
251		}
252
253		// The main insertion and extraction methods are addFirst,
#	Line 179 | Line 261 | public class ArrayDeque<E> extends Abstr
261		* @throws NullPointerException if the specified element is null
262		*/
263		public void addFirst(E e) {
264	<	if (e == null)
265	<	throw new NullPointerException();
266	<	elements[head = (head - 1) & (elements.length - 1)] = e;
267	<	if (head == tail)
268	<	doubleCapacity();
264	>	// checkInvariants();
265	>	Objects.requireNonNull(e);
266	>	Object[] elements;
267	>	int capacity, s = size;
268	>	while (s == (capacity = (elements = this.elements).length))
269	>	grow(1);
270	>	elements[head = dec(head, capacity)] = e;
271	>	size = s + 1;
272		}
273
274		/**
#	Line 195 | Line 280 | public class ArrayDeque<E> extends Abstr
280		* @throws NullPointerException if the specified element is null
281		*/
282		public void addLast(E e) {
283	<	if (e == null)
284	<	throw new NullPointerException();
285	<	elements[tail] = e;
286	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
287	<	doubleCapacity();
283	>	// checkInvariants();
284	>	Objects.requireNonNull(e);
285	>	Object[] elements;
286	>	int capacity, s = size;
287	>	while (s == (capacity = (elements = this.elements).length))
288	>	grow(1);
289	>	elements[add(head, s, capacity)] = e;
290	>	size = s + 1;
291	>	}
292	>
293	>	/**
294	>	* Adds all of the elements in the specified collection at the end
295	>	* of this deque, as if by calling {@link #addLast} on each one,
296	>	* in the order that they are returned by the collection's
297	>	* iterator.
298	>	*
299	>	* @param c the elements to be inserted into this deque
300	>	* @return {@code true} if this deque changed as a result of the call
301	>	* @throws NullPointerException if the specified collection or any
302	>	*         of its elements are null
303	>	*/
304	>	@Override
305	>	public boolean addAll(Collection<? extends E> c) {
306	>	// checkInvariants();
307	>	Object[] a, elements;
308	>	int newcomers, capacity, s = size;
309	>	if ((newcomers = (a = c.toArray()).length) == 0)
310	>	return false;
311	>	while ((capacity = (elements = this.elements).length) - s < newcomers)
312	>	grow(newcomers - (capacity - s));
313	>	int i = add(head, s, capacity);
314	>	for (Object x : a) {
315	>	Objects.requireNonNull(x);
316	>	elements[i] = x;
317	>	i = inc(i, capacity);
318	>	size++;
319	>	}
320	>	return true;
321		}
322
323		/**
#	Line 230 | Line 348 | public class ArrayDeque<E> extends Abstr
348		* @throws NoSuchElementException {@inheritDoc}
349		*/
350		public E removeFirst() {
351	+	// checkInvariants();
352		E x = pollFirst();
353		if (x == null)
354		throw new NoSuchElementException();
#	Line 240 | Line 359 | public class ArrayDeque<E> extends Abstr
359		* @throws NoSuchElementException {@inheritDoc}
360		*/
361		public E removeLast() {
362	+	// checkInvariants();
363		E x = pollLast();
364		if (x == null)
365		throw new NoSuchElementException();
#	Line 247 | Line 367 | public class ArrayDeque<E> extends Abstr
367		}
368
369		public E pollFirst() {
370	<	int h = head;
371	<	@SuppressWarnings("unchecked")
372	<	E result = (E) elements[h];
253	<	// Element is null if deque empty
254	<	if (result == null)
370	>	// checkInvariants();
371	>	final int s, h;
372	>	if ((s = size) == 0)
373		return null;
374	<	elements[h] = null;     // Must null out slot
375	<	head = (h + 1) & (elements.length - 1);
376	<	return result;
374	>	final Object[] elements = this.elements;
375	>	@SuppressWarnings("unchecked") E e = (E) elements[h = head];
376	>	elements[h] = null;
377	>	head = inc(h, elements.length);
378	>	size = s - 1;
379	>	return e;
380		}
381
382		public E pollLast() {
383	<	int t = (tail - 1) & (elements.length - 1);
384	<	@SuppressWarnings("unchecked")
385	<	E result = (E) elements[t];
265	<	if (result == null)
383	>	// checkInvariants();
384	>	final int s, tail;
385	>	if ((s = size) == 0)
386		return null;
387	<	elements[t] = null;
388	<	tail = t;
389	<	return result;
387	>	final Object[] elements = this.elements;
388	>	@SuppressWarnings("unchecked")
389	>	E e = (E) elements[tail = add(head, s - 1, elements.length)];
390	>	elements[tail] = null;
391	>	size = s - 1;
392	>	return e;
393		}
394
395		/**
396		* @throws NoSuchElementException {@inheritDoc}
397		*/
398		public E getFirst() {
399	<	@SuppressWarnings("unchecked")
400	<	E result = (E) elements[head];
401	<	if (result == null)
279	<	throw new NoSuchElementException();
280	<	return result;
399	>	// checkInvariants();
400	>	if (size == 0) throw new NoSuchElementException();
401	>	return elementAt(head);
402		}
403
404		/**
405		* @throws NoSuchElementException {@inheritDoc}
406		*/
407		public E getLast() {
408	<	@SuppressWarnings("unchecked")
409	<	E result = (E) elements[(tail - 1) & (elements.length - 1)];
410	<	if (result == null)
290	<	throw new NoSuchElementException();
291	<	return result;
408	>	// checkInvariants();
409	>	if (size == 0) throw new NoSuchElementException();
410	>	return elementAt(tail());
411		}
412
294	–	@SuppressWarnings("unchecked")
413		public E peekFirst() {
414	<	// elements[head] is null if deque empty
415	<	return (E) elements[head];
414	>	// checkInvariants();
415	>	return (size == 0) ? null : elementAt(head);
416		}
417
300	–	@SuppressWarnings("unchecked")
418		public E peekLast() {
419	<	return (E) elements[(tail - 1) & (elements.length - 1)];
419	>	// checkInvariants();
420	>	return (size == 0) ? null : elementAt(tail());
421		}
422
423		/**
#	Line 315 | Line 433 | public class ArrayDeque<E> extends Abstr
433		* @return {@code true} if the deque contained the specified element
434		*/
435		public boolean removeFirstOccurrence(Object o) {
436	<	if (o == null)
437	<	return false;
438	<	int mask = elements.length - 1;
439	<	int i = head;
440	<	Object x;
441	<	while ( (x = elements[i]) != null) {
442	<	if (o.equals(x)) {
443	<	delete(i);
444	<	return true;
436	>	// checkInvariants();
437	>	if (o != null) {
438	>	final Object[] elements = this.elements;
439	>	final int capacity = elements.length;
440	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) {
441	>	if (o.equals(elements[i])) {
442	>	delete(i);
443	>	return true;
444	>	}
445		}
328	–	i = (i + 1) & mask;
446		}
447		return false;
448		}
#	Line 343 | Line 460 | public class ArrayDeque<E> extends Abstr
460		* @return {@code true} if the deque contained the specified element
461		*/
462		public boolean removeLastOccurrence(Object o) {
463	<	if (o == null)
464	<	return false;
465	<	int mask = elements.length - 1;
466	<	int i = (tail - 1) & mask;
467	<	Object x;
468	<	while ( (x = elements[i]) != null) {
469	<	if (o.equals(x)) {
470	<	delete(i);
471	<	return true;
463	>	if (o != null) {
464	>	final Object[] elements = this.elements;
465	>	final int capacity = elements.length;
466	>	for (int k = size, i = add(head, k - 1, capacity);
467	>	--k >= 0; i = dec(i, capacity)) {
468	>	if (o.equals(elements[i])) {
469	>	delete(i);
470	>	return true;
471	>	}
472		}
356	–	i = (i - 1) & mask;
473		}
474		return false;
475		}
#	Line 472 | Line 588 | public class ArrayDeque<E> extends Abstr
588		return removeFirst();
589		}
590
475	–	private void checkInvariants() {
476	–	assert elements[tail] == null;
477	–	assert head == tail ? elements[head] == null :
478	–	(elements[head] != null &&
479	–	elements[(tail - 1) & (elements.length - 1)] != null);
480	–	assert elements[(head - 1) & (elements.length - 1)] == null;
481	–	}
482	–
591		/**
592	<	* Removes the element at the specified position in the elements array,
593	<	* adjusting head and tail as necessary.  This can result in motion of
594	<	* elements backwards or forwards in the array.
592	>	* Removes the element at the specified position in the elements array.
593	>	* This can result in forward or backwards motion of array elements.
594	>	* We optimize for least element motion.
595		*
596		* <p>This method is called delete rather than remove to emphasize
597		* that its semantics differ from those of {@link List#remove(int)}.
598		*
599		* @return true if elements moved backwards
600		*/
601	<	private boolean delete(int i) {
602	<	checkInvariants();
601	>	boolean delete(int i) {
602	>	// checkInvariants();
603		final Object[] elements = this.elements;
604	<	final int mask = elements.length - 1;
604	>	final int capacity = elements.length;
605		final int h = head;
606	<	final int t = tail;
607	<	final int front = (i - h) & mask;
608	<	final int back  = (t - i) & mask;
501	<
502	<	// Invariant: head <= i < tail mod circularity
503	<	if (front >= ((t - h) & mask))
504	<	throw new ConcurrentModificationException();
505	<
506	<	// Optimize for least element motion
606	>	int front;              // number of elements before to-be-deleted elt
607	>	if ((front = i - h) < 0) front += capacity;
608	>	final int back = size - front - 1; // number of elements after
609		if (front < back) {
610	+	// move front elements forwards
611		if (h <= i) {
612		System.arraycopy(elements, h, elements, h + 1, front);
613		} else { // Wrap around
614		System.arraycopy(elements, 0, elements, 1, i);
615	<	elements[0] = elements[mask];
616	<	System.arraycopy(elements, h, elements, h + 1, mask - h);
615	>	elements[0] = elements[capacity - 1];
616	>	System.arraycopy(elements, h, elements, h + 1, front - (i + 1));
617		}
618		elements[h] = null;
619	<	head = (h + 1) & mask;
619	>	head = inc(h, capacity);
620	>	size--;
621	>	// checkInvariants();
622		return false;
623		} else {
624	<	if (i < t) { // Copy the null tail as well
624	>	// move back elements backwards
625	>	int tail = tail();
626	>	if (i <= tail) {
627		System.arraycopy(elements, i + 1, elements, i, back);
521	–	tail = t - 1;
628		} else { // Wrap around
629	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
630	<	elements[mask] = elements[0];
631	<	System.arraycopy(elements, 1, elements, 0, t);
632	<	tail = (t - 1) & mask;
629	>	int firstLeg = capacity - (i + 1);
630	>	System.arraycopy(elements, i + 1, elements, i, firstLeg);
631	>	elements[capacity - 1] = elements[0];
632	>	System.arraycopy(elements, 1, elements, 0, back - firstLeg - 1);
633		}
634	+	elements[tail] = null;
635	+	size--;
636	+	// checkInvariants();
637		return true;
638		}
639		}
#	Line 537 | Line 646 | public class ArrayDeque<E> extends Abstr
646		* @return the number of elements in this deque
647		*/
648		public int size() {
649	<	return (tail - head) & (elements.length - 1);
649	>	return size;
650		}
651
652		/**
#	Line 546 | Line 655 | public class ArrayDeque<E> extends Abstr
655		* @return {@code true} if this deque contains no elements
656		*/
657		public boolean isEmpty() {
658	<	return head == tail;
658	>	return size == 0;
659		}
660
661		/**
#	Line 566 | Line 675 | public class ArrayDeque<E> extends Abstr
675		}
676
677		private class DeqIterator implements Iterator<E> {
678	<	/**
679	<	* Index of element to be returned by subsequent call to next.
571	<	*/
572	<	private int cursor = head;
678	>	/** Index of element to be returned by subsequent call to next. */
679	>	int cursor;
680
681	<	/**
682	<	* Tail recorded at construction (also in remove), to stop
576	<	* iterator and also to check for comodification.
577	<	*/
578	<	private int fence = tail;
681	>	/** Number of elements yet to be returned. */
682	>	int remaining = size;
683
684		/**
685		* Index of element returned by most recent call to next.
686		* Reset to -1 if element is deleted by a call to remove.
687		*/
688	<	private int lastRet = -1;
688	>	int lastRet = -1;
689	>
690	>	DeqIterator() { cursor = head; }
691
692	<	public boolean hasNext() {
693	<	return cursor != fence;
692	>	public final boolean hasNext() {
693	>	return remaining > 0;
694		}
695
696		public E next() {
697	<	if (cursor == fence)
697	>	if (remaining == 0)
698		throw new NoSuchElementException();
699	<	@SuppressWarnings("unchecked")
594	<	E result = (E) elements[cursor];
595	<	// This check doesn't catch all possible comodifications,
596	<	// but does catch the ones that corrupt traversal
597	<	if (tail != fence || result == null)
598	<	throw new ConcurrentModificationException();
699	>	E e = checkedElementAt(elements, cursor);
700		lastRet = cursor;
701	<	cursor = (cursor + 1) & (elements.length - 1);
702	<	return result;
701	>	cursor = inc(cursor, elements.length);
702	>	remaining--;
703	>	return e;
704		}
705
706	<	public void remove() {
706	>	void postDelete(boolean leftShifted) {
707	>	if (leftShifted)
708	>	cursor = dec(cursor, elements.length); // undo inc in next
709	>	}
710	>
711	>	public final void remove() {
712		if (lastRet < 0)
713		throw new IllegalStateException();
714	<	if (delete(lastRet)) { // if left-shifted, undo increment in next()
608	<	cursor = (cursor - 1) & (elements.length - 1);
609	<	fence = tail;
610	<	}
714	>	postDelete(delete(lastRet));
715		lastRet = -1;
716		}
717	+
718	+	public void forEachRemaining(Consumer<? super E> action) {
719	+	Objects.requireNonNull(action);
720	+	final Object[] elements = ArrayDeque.this.elements;
721	+	final int capacity = elements.length;
722	+	int k = remaining;
723	+	remaining = 0;
724	+	for (int i = cursor; --k >= 0; i = inc(i, capacity))
725	+	action.accept(checkedElementAt(elements, i));
726	+	}
727	+	}
728	+
729	+	private class DescendingIterator extends DeqIterator {
730	+	DescendingIterator() { cursor = tail(); }
731	+
732	+	public final E next() {
733	+	if (remaining == 0)
734	+	throw new NoSuchElementException();
735	+	E e = checkedElementAt(elements, cursor);
736	+	lastRet = cursor;
737	+	cursor = dec(cursor, elements.length);
738	+	remaining--;
739	+	return e;
740	+	}
741	+
742	+	void postDelete(boolean leftShifted) {
743	+	if (!leftShifted)
744	+	cursor = inc(cursor, elements.length); // undo dec in next
745	+	}
746	+
747	+	public final void forEachRemaining(Consumer<? super E> action) {
748	+	Objects.requireNonNull(action);
749	+	final Object[] elements = ArrayDeque.this.elements;
750	+	final int capacity = elements.length;
751	+	int k = remaining;
752	+	remaining = 0;
753	+	for (int i = cursor; --k >= 0; i = dec(i, capacity))
754	+	action.accept(checkedElementAt(elements, i));
755	+	}
756		}
757
758		/**
759	<	* This class is nearly a mirror-image of DeqIterator, using tail
760	<	* instead of head for initial cursor, and head instead of tail
761	<	* for fence.
762	<	*/
763	<	private class DescendingIterator implements Iterator<E> {
764	<	private int cursor = tail;
765	<	private int fence = head;
766	<	private int lastRet = -1;
759	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
760	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
761	>	* deque.
762	>	*
763	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
764	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
765	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
766	>	* the reporting of additional characteristic values.
767	>	*
768	>	* @return a {@code Spliterator} over the elements in this deque
769	>	* @since 1.8
770	>	*/
771	>	public Spliterator<E> spliterator() {
772	>	return new ArrayDequeSpliterator();
773	>	}
774	>
775	>	final class ArrayDequeSpliterator implements Spliterator<E> {
776	>	private int cursor;
777	>	private int remaining; // -1 until late-binding first use
778
779	<	public boolean hasNext() {
780	<	return cursor != fence;
779	>	/** Constructs late-binding spliterator over all elements. */
780	>	ArrayDequeSpliterator() {
781	>	this.remaining = -1;
782		}
783
784	<	public E next() {
785	<	if (cursor == fence)
786	<	throw new NoSuchElementException();
787	<	cursor = (cursor - 1) & (elements.length - 1);
633	<	@SuppressWarnings("unchecked")
634	<	E result = (E) elements[cursor];
635	<	if (head != fence || result == null)
636	<	throw new ConcurrentModificationException();
637	<	lastRet = cursor;
638	<	return result;
784	>	/** Constructs spliterator over the given slice. */
785	>	ArrayDequeSpliterator(int cursor, int count) {
786	>	this.cursor = cursor;
787	>	this.remaining = count;
788		}
789
790	<	public void remove() {
791	<	if (lastRet < 0)
792	<	throw new IllegalStateException();
793	<	if (!delete(lastRet)) {
794	<	cursor = (cursor + 1) & (elements.length - 1);
646	<	fence = head;
790	>	/** Ensures late-binding initialization; then returns remaining. */
791	>	private int remaining() {
792	>	if (remaining < 0) {
793	>	cursor = head;
794	>	remaining = size;
795		}
796	<	lastRet = -1;
796	>	return remaining;
797	>	}
798	>
799	>	public ArrayDequeSpliterator trySplit() {
800	>	final int mid;
801	>	if ((mid = remaining() >> 1) > 0) {
802	>	int oldCursor = cursor;
803	>	cursor = add(cursor, mid, elements.length);
804	>	remaining -= mid;
805	>	return new ArrayDequeSpliterator(oldCursor, mid);
806	>	}
807	>	return null;
808	>	}
809	>
810	>	public void forEachRemaining(Consumer<? super E> action) {
811	>	Objects.requireNonNull(action);
812	>	final Object[] elements = ArrayDeque.this.elements;
813	>	final int capacity = elements.length;
814	>	int k = remaining();
815	>	remaining = 0;
816	>	for (int i = cursor; --k >= 0; i = inc(i, capacity))
817	>	action.accept(checkedElementAt(elements, i));
818	>	}
819	>
820	>	public boolean tryAdvance(Consumer<? super E> action) {
821	>	Objects.requireNonNull(action);
822	>	if (remaining() == 0)
823	>	return false;
824	>	action.accept(checkedElementAt(elements, cursor));
825	>	cursor = inc(cursor, elements.length);
826	>	remaining--;
827	>	return true;
828	>	}
829	>
830	>	public long estimateSize() {
831	>	return remaining();
832	>	}
833	>
834	>	public int characteristics() {
835	>	return Spliterator.NONNULL
836	>	| Spliterator.ORDERED
837	>	| Spliterator.SIZED
838	>	| Spliterator.SUBSIZED;
839	>	}
840	>	}
841	>
842	>	@Override
843	>	public void forEach(Consumer<? super E> action) {
844	>	// checkInvariants();
845	>	Objects.requireNonNull(action);
846	>	final Object[] elements = this.elements;
847	>	final int capacity = elements.length;
848	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity))
849	>	action.accept(elementAt(i));
850	>	// checkInvariants();
851	>	}
852	>
853	>	/**
854	>	* Replaces each element of this deque with the result of applying the
855	>	* operator to that element, as specified by {@link List#replaceAll}.
856	>	*
857	>	* @param operator the operator to apply to each element
858	>	* @since TBD
859	>	*/
860	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
861	>	Objects.requireNonNull(operator);
862	>	final Object[] elements = this.elements;
863	>	final int capacity = elements.length;
864	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity))
865	>	elements[i] = operator.apply(elementAt(i));
866	>	// checkInvariants();
867	>	}
868	>
869	>	/**
870	>	* @throws NullPointerException {@inheritDoc}
871	>	*/
872	>	@Override
873	>	public boolean removeIf(Predicate<? super E> filter) {
874	>	Objects.requireNonNull(filter);
875	>	return bulkRemove(filter);
876	>	}
877	>
878	>	/**
879	>	* @throws NullPointerException {@inheritDoc}
880	>	*/
881	>	@Override
882	>	public boolean removeAll(Collection<?> c) {
883	>	Objects.requireNonNull(c);
884	>	return bulkRemove(e -> c.contains(e));
885	>	}
886	>
887	>	/**
888	>	* @throws NullPointerException {@inheritDoc}
889	>	*/
890	>	@Override
891	>	public boolean retainAll(Collection<?> c) {
892	>	Objects.requireNonNull(c);
893	>	return bulkRemove(e -> !c.contains(e));
894	>	}
895	>
896	>	/** Implementation of bulk remove methods. */
897	>	private boolean bulkRemove(Predicate<? super E> filter) {
898	>	// checkInvariants();
899	>	final Object[] elements = this.elements;
900	>	final int capacity = elements.length;
901	>	int i = head, j = i, remaining = size, deleted = 0;
902	>	try {
903	>	for (; remaining > 0; remaining--, i = inc(i, capacity)) {
904	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
905	>	if (filter.test(e))
906	>	deleted++;
907	>	else {
908	>	if (j != i)
909	>	elements[j] = e;
910	>	j = inc(j, capacity);
911	>	}
912	>	}
913	>	return deleted > 0;
914	>	} catch (Throwable ex) {
915	>	if (deleted > 0)
916	>	for (; remaining > 0;
917	>	remaining--, i = inc(i, capacity), j = inc(j, capacity))
918	>	elements[j] = elements[i];
919	>	throw ex;
920	>	} finally {
921	>	size -= deleted;
922	>	for (; --deleted >= 0; j = inc(j, capacity))
923	>	elements[j] = null;
924	>	// checkInvariants();
925		}
926		}
927
#	Line 658 | Line 934 | public class ArrayDeque<E> extends Abstr
934		* @return {@code true} if this deque contains the specified element
935		*/
936		public boolean contains(Object o) {
937	<	if (o == null)
938	<	return false;
939	<	int mask = elements.length - 1;
940	<	int i = head;
941	<	Object x;
942	<	while ( (x = elements[i]) != null) {
667	<	if (o.equals(x))
668	<	return true;
669	<	i = (i + 1) & mask;
937	>	if (o != null) {
938	>	final Object[] elements = this.elements;
939	>	final int capacity = elements.length;
940	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity))
941	>	if (o.equals(elements[i]))
942	>	return true;
943		}
944		return false;
945		}
#	Line 693 | Line 966 | public class ArrayDeque<E> extends Abstr
966		* The deque will be empty after this call returns.
967		*/
968		public void clear() {
969	<	int h = head;
970	<	int t = tail;
971	<	if (h != t) { // clear all cells
972	<	head = tail = 0;
973	<	int i = h;
974	<	int mask = elements.length - 1;
975	<	do {
976	<	elements[i] = null;
977	<	i = (i + 1) & mask;
705	<	} while (i != t);
969	>	final Object[] elements = this.elements;
970	>	final int capacity = elements.length;
971	>	final int h = this.head;
972	>	final int s = size;
973	>	if (capacity - h >= s)
974	>	Arrays.fill(elements, h, h + s, null);
975	>	else {
976	>	Arrays.fill(elements, h, capacity, null);
977	>	Arrays.fill(elements, 0, s - capacity + h, null);
978		}
979	+	size = head = 0;
980	+	// checkInvariants();
981		}
982
983		/**
#	Line 721 | Line 995 | public class ArrayDeque<E> extends Abstr
995		*/
996		public Object[] toArray() {
997		final int head = this.head;
998	<	final int tail = this.tail;
999	<	boolean wrap = (tail < head);
1000	<	int end = wrap ? tail + elements.length : tail;
1001	<	Object[] a = Arrays.copyOfRange(elements, head, end);
728	<	if (wrap)
729	<	System.arraycopy(elements, 0, a, elements.length - head, tail);
998	>	final int firstLeg;
999	>	Object[] a = Arrays.copyOfRange(elements, head, head + size);
1000	>	if ((firstLeg = elements.length - head) < size)
1001	>	System.arraycopy(elements, 0, a, firstLeg, size - firstLeg);
1002		return a;
1003		}
1004
#	Line 752 | Line 1024 | public class ArrayDeque<E> extends Abstr
1024		* The following code can be used to dump the deque into a newly
1025		* allocated array of {@code String}:
1026		*
1027	<	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1027	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1028		*
1029		* Note that {@code toArray(new Object[0])} is identical in function to
1030		* {@code toArray()}.
#	Line 768 | Line 1040 | public class ArrayDeque<E> extends Abstr
1040		*/
1041		@SuppressWarnings("unchecked")
1042		public <T> T[] toArray(T[] a) {
1043	+	final Object[] elements = this.elements;
1044		final int head = this.head;
1045	<	final int tail = this.tail;
1046	<	boolean wrap = (tail < head);
1047	<	int size = (tail - head) + (wrap ? elements.length : 0);
775	<	int firstLeg = size - (wrap ? tail : 0);
776	<	int len = a.length;
777	<	if (size > len) {
1045	>	final int firstLeg;
1046	>	boolean wrap = (firstLeg = elements.length - head) < size;
1047	>	if (size > a.length) {
1048		a = (T[]) Arrays.copyOfRange(elements, head, head + size,
1049		a.getClass());
1050		} else {
1051	<	System.arraycopy(elements, head, a, 0, firstLeg);
1052	<	if (size < len)
1051	>	System.arraycopy(elements, head, a, 0, wrap ? firstLeg : size);
1052	>	if (size < a.length)
1053		a[size] = null;
1054		}
1055		if (wrap)
1056	<	System.arraycopy(elements, 0, a, firstLeg, tail);
1056	>	System.arraycopy(elements, 0, a, firstLeg, size - firstLeg);
1057		return a;
1058		}
1059
#	Line 811 | Line 1081 | public class ArrayDeque<E> extends Abstr
1081		* Saves this deque to a stream (that is, serializes it).
1082		*
1083		* @param s the stream
1084	+	* @throws java.io.IOException if an I/O error occurs
1085		* @serialData The current size ({@code int}) of the deque,
1086		* followed by all of its elements (each an object reference) in
1087		* first-to-last order.
#	Line 820 | Line 1091 | public class ArrayDeque<E> extends Abstr
1091		s.defaultWriteObject();
1092
1093		// Write out size
1094	<	s.writeInt(size());
1094	>	s.writeInt(size);
1095
1096		// Write out elements in order.
1097	<	int mask = elements.length - 1;
1098	<	for (int i = head; i != tail; i = (i + 1) & mask)
1097	>	final Object[] elements = this.elements;
1098	>	final int capacity = elements.length;
1099	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity))
1100		s.writeObject(elements[i]);
1101		}
1102
1103		/**
1104		* Reconstitutes this deque from a stream (that is, deserializes it).
1105		* @param s the stream
1106	+	* @throws ClassNotFoundException if the class of a serialized object
1107	+	*         could not be found
1108	+	* @throws java.io.IOException if an I/O error occurs
1109		*/
1110		private void readObject(java.io.ObjectInputStream s)
1111		throws java.io.IOException, ClassNotFoundException {
1112		s.defaultReadObject();
1113
1114		// Read in size and allocate array
1115	<	int size = s.readInt();
841	<	allocateElements(size);
842	<	head = 0;
843	<	tail = size;
1115	>	elements = new Object[size = s.readInt()];
1116
1117		// Read in all elements in the proper order.
1118		for (int i = 0; i < size; i++)
1119		elements[i] = s.readObject();
1120		}
1121
1122	<	public Spliterator<E> spliterator() {
1123	<	return new DeqSpliterator<E>(this, -1, -1);
1124	<	}
1125	<
1126	<	static final class DeqSpliterator<E> implements Spliterator<E> {
1127	<	private final ArrayDeque<E> deq;
1128	<	private int fence;  // -1 until first use
1129	<	private int index;  // current index, modified on traverse/split
1130	<
1131	<	/** Creates new spliterator covering the given array and range */
1132	<	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
1133	<	this.deq = deq;
1134	<	this.index = origin;
1135	<	this.fence = fence;
1136	<	}
1137	<
1138	<	private int getFence() { // force initialization
1139	<	int t;
868	<	if ((t = fence) < 0) {
869	<	t = fence = deq.tail;
870	<	index = deq.head;
871	<	}
872	<	return t;
873	<	}
874	<
875	<	public Spliterator<E> trySplit() {
876	<	int t = getFence(), h = index, n = deq.elements.length;
877	<	if (h != t && ((h + 1) & (n - 1)) != t) {
878	<	if (h > t)
879	<	t += n;
880	<	int m = ((h + t) >>> 1) & (n - 1);
881	<	return new DeqSpliterator<>(deq, h, index = m);
882	<	}
883	<	return null;
884	<	}
885	<
886	<	public void forEachRemaining(Consumer<? super E> consumer) {
887	<	if (consumer == null)
888	<	throw new NullPointerException();
889	<	Object[] a = deq.elements;
890	<	int m = a.length - 1, f = getFence(), i = index;
891	<	index = f;
892	<	while (i != f) {
893	<	@SuppressWarnings("unchecked") E e = (E)a[i];
894	<	i = (i + 1) & m;
895	<	if (e == null)
896	<	throw new ConcurrentModificationException();
897	<	consumer.accept(e);
898	<	}
899	<	}
900	<
901	<	public boolean tryAdvance(Consumer<? super E> consumer) {
902	<	if (consumer == null)
903	<	throw new NullPointerException();
904	<	Object[] a = deq.elements;
905	<	int m = a.length - 1, f = getFence(), i = index;
906	<	if (i != fence) {
907	<	@SuppressWarnings("unchecked") E e = (E)a[i];
908	<	index = (i + 1) & m;
909	<	if (e == null)
910	<	throw new ConcurrentModificationException();
911	<	consumer.accept(e);
912	<	return true;
913	<	}
914	<	return false;
915	<	}
916	<
917	<	public long estimateSize() {
918	<	int n = getFence() - index;
919	<	if (n < 0)
920	<	n += deq.elements.length;
921	<	return (long) n;
922	<	}
923	<
924	<	@Override
925	<	public int characteristics() {
926	<	return Spliterator.ORDERED | Spliterator.SIZED |
927	<	Spliterator.NONNULL | Spliterator.SUBSIZED;
1122	>	/** debugging */
1123	>	private void checkInvariants() {
1124	>	try {
1125	>	int capacity = elements.length;
1126	>	assert size >= 0 && size <= capacity;
1127	>	assert head >= 0 && ((capacity == 0 && head == 0 && size == 0)
1128	>	|| head < capacity);
1129	>	assert size == 0
1130	>	|| (elements[head] != null && elements[tail()] != null);
1131	>	assert size == capacity
1132	>	|| (elements[dec(head, capacity)] == null
1133	>	&& elements[inc(tail(), capacity)] == null);
1134	>	} catch (Throwable t) {
1135	>	System.err.printf("head=%d size=%d capacity=%d%n",
1136	>	head, size, elements.length);
1137	>	System.err.printf("elements=%s%n",
1138	>	Arrays.toString(elements));
1139	>	throw t;
1140		}
1141		}
1142

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