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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.50 by jsr166, Wed Feb 20 12:32:01 2013 UTC vs.
Revision 1.110 by jsr166, Sat Nov 5 17:45:44 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;
11	<	import java.util.stream.Streams;
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 19 | Line 20 | import java.util.stream.Streams;
20		* when used as a queue.
21		*
22		* <p>Most {@code ArrayDeque} operations run in amortized constant time.
23	<	* Exceptions include {@link #remove(Object) remove}, {@link
24	<	* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
25	<	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
26	<	* iterator.remove()}, and the bulk operations, all of which run in linear
27	<	* time.
23	>	* Exceptions include
24	>	* {@link #remove(Object) remove},
25	>	* {@link #removeFirstOccurrence removeFirstOccurrence},
26	>	* {@link #removeLastOccurrence removeLastOccurrence},
27	>	* {@link #contains contains},
28	>	* {@link #iterator iterator.remove()},
29	>	* and the bulk operations, all of which run in linear time.
30		*
31	<	* <p>The iterators returned by this class's {@code iterator} method are
32	<	* <i>fail-fast</i>: If the deque is modified at any time after the iterator
33	<	* is created, in any way except through the iterator's own {@code remove}
34	<	* method, the iterator will generally throw a {@link
31	>	* <p>The iterators returned by this class's {@link #iterator() iterator}
32	>	* method are <em>fail-fast</em>: If the deque is modified at any time after
33	>	* the iterator is created, in any way except through the iterator's own
34	>	* {@code remove} method, the iterator will generally throw a {@link
35		* ConcurrentModificationException}.  Thus, in the face of concurrent
36		* modification, the iterator fails quickly and cleanly, rather than risking
37		* arbitrary, non-deterministic behavior at an undetermined time in the
#	Line 51 | Line 54 | import java.util.stream.Streams;
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
55	–	* @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	+	* VMs excel at optimizing simple array loops where indices are
65	+	* incrementing or decrementing over a valid slice, e.g.
66	+	*
67	+	* for (int i = start; i < end; i++) ... elements[i]
68	+	*
69	+	* Because in a circular array, elements are in general stored in
70	+	* two disjoint such slices, we help the VM by writing unusual
71	+	* nested loops for all traversals over the elements.
72	+	*/
73	+
74		/**
75		* The array in which the elements of the deque are stored.
76	<	* The capacity of the deque is the length of this array, which is
77	<	* always a power of two. The array is never allowed to become
64	<	* full, except transiently within an addX method where it is
65	<	* resized (see doubleCapacity) immediately upon becoming full,
66	<	* thus avoiding head and tail wrapping around to equal each
67	<	* other.  We also guarantee that all array cells not holding
68	<	* deque elements are always null.
76	>	* We guarantee that all array cells not holding deque elements
77	>	* are always null.
78		*/
79	<	transient Object[] elements; // non-private to simplify nested class access
79	>	transient Object[] elements;
80
81		/**
82		* The index of the element at the head of the deque (which is the
83		* element that would be removed by remove() or pop()); or an
84	<	* arbitrary number equal to tail if the deque is empty.
84	>	* arbitrary number 0 <= head < elements.length equal to tail if
85	>	* the deque is empty.
86		*/
87		transient int head;
88
#	Line 83 | Line 93 | public class ArrayDeque<E> extends Abstr
93		transient int tail;
94
95		/**
96	<	* The minimum capacity that we'll use for a newly created deque.
97	<	* Must be a power of 2.
96	>	* The maximum size of array to allocate.
97	>	* Some VMs reserve some header words in an array.
98	>	* Attempts to allocate larger arrays may result in
99	>	* OutOfMemoryError: Requested array size exceeds VM limit
100		*/
101	<	private static final int MIN_INITIAL_CAPACITY = 8;
101	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
102
103	<	// ******  Array allocation and resizing utilities ******
103	>	/**
104	>	* Increases the capacity of this deque by at least the given amount.
105	>	*
106	>	* @param needed the required minimum extra capacity; must be positive
107	>	*/
108	>	private void grow(int needed) {
109	>	// overflow-conscious code
110	>	final int oldCapacity = elements.length;
111	>	int newCapacity;
112	>	// Double capacity if small; else grow by 50%
113	>	int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
114	>	if (jump < needed
115	>	|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
116	>	newCapacity = newCapacity(needed, jump);
117	>	elements = Arrays.copyOf(elements, newCapacity);
118	>	// Exceptionally, here tail == head needs to be disambiguated
119	>	if (tail < head || (tail == head && elements[head] != null)) {
120	>	// wrap around; slide first leg forward to end of array
121	>	int newSpace = newCapacity - oldCapacity;
122	>	System.arraycopy(elements, head,
123	>	elements, head + newSpace,
124	>	oldCapacity - head);
125	>	Arrays.fill(elements, head, head + newSpace, null);
126	>	head += newSpace;
127	>	}
128	>	// checkInvariants();
129	>	}
130	>
131	>	/** Capacity calculation for edge conditions, especially overflow. */
132	>	private int newCapacity(int needed, int jump) {
133	>	final int oldCapacity = elements.length, minCapacity;
134	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
135	>	if (minCapacity < 0)
136	>	throw new IllegalStateException("Sorry, deque too big");
137	>	return Integer.MAX_VALUE;
138	>	}
139	>	if (needed > jump)
140	>	return minCapacity;
141	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
142	>	? oldCapacity + jump
143	>	: MAX_ARRAY_SIZE;
144	>	}
145
146		/**
147	<	* Allocates empty array to hold the given number of elements.
148	<	*
149	<	* @param numElements  the number of elements to hold
150	<	*/
151	<	private void allocateElements(int numElements) {
152	<	int initialCapacity = MIN_INITIAL_CAPACITY;
153	<	// Find the best power of two to hold elements.
154	<	// Tests "<=" because arrays aren't kept full.
155	<	if (numElements >= initialCapacity) {
156	<	initialCapacity = numElements;
157	<	initialCapacity |= (initialCapacity >>>  1);
105	<	initialCapacity |= (initialCapacity >>>  2);
106	<	initialCapacity |= (initialCapacity >>>  4);
107	<	initialCapacity |= (initialCapacity >>>  8);
108	<	initialCapacity |= (initialCapacity >>> 16);
109	<	initialCapacity++;
110	<
111	<	if (initialCapacity < 0)   // Too many elements, must back off
112	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
113	<	}
114	<	elements = new Object[initialCapacity];
147	>	* Increases the internal storage of this collection, if necessary,
148	>	* to ensure that it can hold at least the given number of elements.
149	>	*
150	>	* @param minCapacity the desired minimum capacity
151	>	* @since TBD
152	>	*/
153	>	/* public */ void ensureCapacity(int minCapacity) {
154	>	int needed;
155	>	if ((needed = (minCapacity + 1 - elements.length)) > 0)
156	>	grow(needed);
157	>	// checkInvariants();
158		}
159
160		/**
161	<	* Doubles the capacity of this deque.  Call only when full, i.e.,
162	<	* when head and tail have wrapped around to become equal.
163	<	*/
164	<	private void doubleCapacity() {
165	<	assert head == tail;
166	<	int p = head;
167	<	int n = elements.length;
168	<	int r = n - p; // number of elements to the right of p
169	<	int newCapacity = n << 1;
170	<	if (newCapacity < 0)
171	<	throw new IllegalStateException("Sorry, deque too big");
172	<	Object[] a = new Object[newCapacity];
130	<	System.arraycopy(elements, p, a, 0, r);
131	<	System.arraycopy(elements, 0, a, r, p);
132	<	elements = a;
133	<	head = 0;
134	<	tail = n;
161	>	* Minimizes the internal storage of this collection.
162	>	*
163	>	* @since TBD
164	>	*/
165	>	/* public */ void trimToSize() {
166	>	int size;
167	>	if ((size = size()) + 1 < elements.length) {
168	>	elements = toArray(new Object[size + 1]);
169	>	head = 0;
170	>	tail = size;
171	>	}
172	>	// checkInvariants();
173		}
174
175		/**
#	Line 146 | Line 184 | public class ArrayDeque<E> extends Abstr
184		* Constructs an empty array deque with an initial capacity
185		* sufficient to hold the specified number of elements.
186		*
187	<	* @param numElements  lower bound on initial capacity of the deque
187	>	* @param numElements lower bound on initial capacity of the deque
188		*/
189		public ArrayDeque(int numElements) {
190	<	allocateElements(numElements);
190	>	elements = new Object[Math.max(1, numElements + 1)];
191		}
192
193		/**
#	Line 163 | Line 201 | public class ArrayDeque<E> extends Abstr
201		* @throws NullPointerException if the specified collection is null
202		*/
203		public ArrayDeque(Collection<? extends E> c) {
204	<	allocateElements(c.size());
204	>	elements = new Object[c.size() + 1];
205		addAll(c);
206		}
207
208	+	/**
209	+	* Increments i, mod modulus.
210	+	* Precondition and postcondition: 0 <= i < modulus.
211	+	*/
212	+	static final int inc(int i, int modulus) {
213	+	if (++i >= modulus) i = 0;
214	+	return i;
215	+	}
216	+
217	+	/**
218	+	* Decrements i, mod modulus.
219	+	* Precondition and postcondition: 0 <= i < modulus.
220	+	*/
221	+	static final int dec(int i, int modulus) {
222	+	if (--i < 0) i = modulus - 1;
223	+	return i;
224	+	}
225	+
226	+	/**
227	+	* Adds i and j, mod modulus.
228	+	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
229	+	*/
230	+	static final int add(int i, int j, int modulus) {
231	+	if ((i += j) - modulus >= 0) i -= modulus;
232	+	return i;
233	+	}
234	+
235	+	/**
236	+	* Subtracts j from i, mod modulus.
237	+	* Index i must be logically ahead of j.
238	+	* Returns the "circular distance" from j to i.
239	+	* Precondition and postcondition: 0 <= i < modulus, 0 <= j < modulus.
240	+	*/
241	+	static final int sub(int i, int j, int modulus) {
242	+	if ((i -= j) < 0) i += modulus;
243	+	return i;
244	+	}
245	+
246	+	/**
247	+	* Returns element at array index i.
248	+	* This is a slight abuse of generics, accepted by javac.
249	+	*/
250	+	@SuppressWarnings("unchecked")
251	+	static final <E> E elementAt(Object[] es, int i) {
252	+	return (E) es[i];
253	+	}
254	+
255	+	/**
256	+	* A version of elementAt that checks for null elements.
257	+	* This check doesn't catch all possible comodifications,
258	+	* but does catch ones that corrupt traversal.
259	+	*/
260	+	static final <E> E nonNullElementAt(Object[] es, int i) {
261	+	@SuppressWarnings("unchecked") E e = (E) es[i];
262	+	if (e == null)
263	+	throw new ConcurrentModificationException();
264	+	return e;
265	+	}
266	+
267		// The main insertion and extraction methods are addFirst,
268		// addLast, pollFirst, pollLast. The other methods are defined in
269		// terms of these.
#	Line 180 | Line 277 | public class ArrayDeque<E> extends Abstr
277		public void addFirst(E e) {
278		if (e == null)
279		throw new NullPointerException();
280	<	elements[head = (head - 1) & (elements.length - 1)] = e;
280	>	final Object[] es = elements;
281	>	es[head = dec(head, es.length)] = e;
282		if (head == tail)
283	<	doubleCapacity();
283	>	grow(1);
284	>	// checkInvariants();
285		}
286
287		/**
#	Line 196 | Line 295 | public class ArrayDeque<E> extends Abstr
295		public void addLast(E e) {
296		if (e == null)
297		throw new NullPointerException();
298	<	elements[tail] = e;
299	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
300	<	doubleCapacity();
298	>	final Object[] es = elements;
299	>	es[tail] = e;
300	>	if (head == (tail = inc(tail, es.length)))
301	>	grow(1);
302	>	// checkInvariants();
303	>	}
304	>
305	>	/**
306	>	* Adds all of the elements in the specified collection at the end
307	>	* of this deque, as if by calling {@link #addLast} on each one,
308	>	* in the order that they are returned by the collection's
309	>	* iterator.
310	>	*
311	>	* @param c the elements to be inserted into this deque
312	>	* @return {@code true} if this deque changed as a result of the call
313	>	* @throws NullPointerException if the specified collection or any
314	>	*         of its elements are null
315	>	*/
316	>	public boolean addAll(Collection<? extends E> c) {
317	>	final int s = size(), needed;
318	>	if ((needed = s + c.size() - elements.length + 1) > 0)
319	>	grow(needed);
320	>	c.forEach((e) -> addLast(e));
321	>	// checkInvariants();
322	>	return size() > s;
323		}
324
325		/**
#	Line 229 | Line 350 | public class ArrayDeque<E> extends Abstr
350		* @throws NoSuchElementException {@inheritDoc}
351		*/
352		public E removeFirst() {
353	<	E x = pollFirst();
354	<	if (x == null)
353	>	E e = pollFirst();
354	>	if (e == null)
355		throw new NoSuchElementException();
356	<	return x;
356	>	// checkInvariants();
357	>	return e;
358		}
359
360		/**
361		* @throws NoSuchElementException {@inheritDoc}
362		*/
363		public E removeLast() {
364	<	E x = pollLast();
365	<	if (x == null)
364	>	E e = pollLast();
365	>	if (e == null)
366		throw new NoSuchElementException();
367	<	return x;
367	>	// checkInvariants();
368	>	return e;
369		}
370
371		public E pollFirst() {
372	<	int h = head;
373	<	@SuppressWarnings("unchecked")
374	<	E result = (E) elements[h];
375	<	// Element is null if deque empty
376	<	if (result == null)
377	<	return null;
378	<	elements[h] = null;     // Must null out slot
379	<	head = (h + 1) & (elements.length - 1);
380	<	return result;
372	>	final Object[] es;
373	>	final int h;
374	>	E e = elementAt(es = elements, h = head);
375	>	if (e != null) {
376	>	es[h] = null;
377	>	head = inc(h, es.length);
378	>	}
379	>	// checkInvariants();
380	>	return e;
381		}
382
383		public E pollLast() {
384	<	int t = (tail - 1) & (elements.length - 1);
385	<	@SuppressWarnings("unchecked")
386	<	E result = (E) elements[t];
387	<	if (result == null)
388	<	return null;
389	<	elements[t] = null;
390	<	tail = t;
268	<	return result;
384	>	final Object[] es;
385	>	final int t;
386	>	E e = elementAt(es = elements, t = dec(tail, es.length));
387	>	if (e != null)
388	>	es[tail = t] = null;
389	>	// checkInvariants();
390	>	return e;
391		}
392
393		/**
394		* @throws NoSuchElementException {@inheritDoc}
395		*/
396		public E getFirst() {
397	<	@SuppressWarnings("unchecked")
398	<	E result = (E) elements[head];
277	<	if (result == null)
397	>	E e = elementAt(elements, head);
398	>	if (e == null)
399		throw new NoSuchElementException();
400	<	return result;
400	>	// checkInvariants();
401	>	return e;
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)
408	>	final Object[] es = elements;
409	>	E e = elementAt(es, dec(tail, es.length));
410	>	if (e == null)
411		throw new NoSuchElementException();
412	<	return result;
412	>	// checkInvariants();
413	>	return e;
414		}
415
293	–	@SuppressWarnings("unchecked")
416		public E peekFirst() {
417	<	// elements[head] is null if deque empty
418	<	return (E) elements[head];
417	>	// checkInvariants();
418	>	return elementAt(elements, head);
419		}
420
299	–	@SuppressWarnings("unchecked")
421		public E peekLast() {
422	<	return (E) elements[(tail - 1) & (elements.length - 1)];
422	>	// checkInvariants();
423	>	final Object[] es;
424	>	return elementAt(es = elements, dec(tail, es.length));
425		}
426
427		/**
#	Line 314 | Line 437 | public class ArrayDeque<E> extends Abstr
437		* @return {@code true} if the deque contained the specified element
438		*/
439		public boolean removeFirstOccurrence(Object o) {
440	<	if (o == null)
441	<	return false;
442	<	int mask = elements.length - 1;
443	<	int i = head;
444	<	Object x;
445	<	while ( (x = elements[i]) != null) {
446	<	if (o.equals(x)) {
447	<	delete(i);
448	<	return true;
440	>	if (o != null) {
441	>	final Object[] es = elements;
442	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
443	>	; i = 0, to = end) {
444	>	for (; i < to; i++)
445	>	if (o.equals(es[i])) {
446	>	delete(i);
447	>	return true;
448	>	}
449	>	if (to == end) break;
450		}
327	–	i = (i + 1) & mask;
451		}
452		return false;
453		}
#	Line 342 | Line 465 | public class ArrayDeque<E> extends Abstr
465		* @return {@code true} if the deque contained the specified element
466		*/
467		public boolean removeLastOccurrence(Object o) {
468	<	if (o == null)
469	<	return false;
470	<	int mask = elements.length - 1;
471	<	int i = (tail - 1) & mask;
472	<	Object x;
473	<	while ( (x = elements[i]) != null) {
474	<	if (o.equals(x)) {
475	<	delete(i);
476	<	return true;
468	>	if (o != null) {
469	>	final Object[] es = elements;
470	>	for (int i = tail, end = head, to = (i >= end) ? end : 0;
471	>	; i = es.length, to = end) {
472	>	for (i--; i > to - 1; i--)
473	>	if (o.equals(es[i])) {
474	>	delete(i);
475	>	return true;
476	>	}
477	>	if (to == end) break;
478		}
355	–	i = (i - 1) & mask;
479		}
480		return false;
481		}
#	Line 471 | Line 594 | public class ArrayDeque<E> extends Abstr
594		return removeFirst();
595		}
596
474	–	private void checkInvariants() {
475	–	assert elements[tail] == null;
476	–	assert head == tail ? elements[head] == null :
477	–	(elements[head] != null &&
478	–	elements[(tail - 1) & (elements.length - 1)] != null);
479	–	assert elements[(head - 1) & (elements.length - 1)] == null;
480	–	}
481	–
597		/**
598	<	* Removes the element at the specified position in the elements array,
599	<	* adjusting head and tail as necessary.  This can result in motion of
600	<	* elements backwards or forwards in the array.
598	>	* Removes the element at the specified position in the elements array.
599	>	* This can result in forward or backwards motion of array elements.
600	>	* We optimize for least element motion.
601		*
602		* <p>This method is called delete rather than remove to emphasize
603		* that its semantics differ from those of {@link List#remove(int)}.
604		*
605	<	* @return true if elements moved backwards
605	>	* @return true if elements near tail moved backwards
606		*/
607	<	private boolean delete(int i) {
608	<	checkInvariants();
609	<	final Object[] elements = this.elements;
610	<	final int mask = elements.length - 1;
607	>	boolean delete(int i) {
608	>	// checkInvariants();
609	>	final Object[] es = elements;
610	>	final int capacity = es.length;
611		final int h = head;
612	<	final int t = tail;
613	<	final int front = (i - h) & mask;
614	<	final int back  = (t - i) & mask;
500	<
501	<	// Invariant: head <= i < tail mod circularity
502	<	if (front >= ((t - h) & mask))
503	<	throw new ConcurrentModificationException();
504	<
505	<	// Optimize for least element motion
612	>	// number of elements before to-be-deleted elt
613	>	final int front = sub(i, h, capacity);
614	>	final int back = size() - front - 1; // number of elements after
615		if (front < back) {
616	+	// move front elements forwards
617		if (h <= i) {
618	<	System.arraycopy(elements, h, elements, h + 1, front);
618	>	System.arraycopy(es, h, es, h + 1, front);
619		} else { // Wrap around
620	<	System.arraycopy(elements, 0, elements, 1, i);
621	<	elements[0] = elements[mask];
622	<	System.arraycopy(elements, h, elements, h + 1, mask - h);
620	>	System.arraycopy(es, 0, es, 1, i);
621	>	es[0] = es[capacity - 1];
622	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
623		}
624	<	elements[h] = null;
625	<	head = (h + 1) & mask;
624	>	es[h] = null;
625	>	head = inc(h, capacity);
626	>	// checkInvariants();
627		return false;
628		} else {
629	<	if (i < t) { // Copy the null tail as well
630	<	System.arraycopy(elements, i + 1, elements, i, back);
631	<	tail = t - 1;
629	>	// move back elements backwards
630	>	tail = dec(tail, capacity);
631	>	if (i <= tail) {
632	>	System.arraycopy(es, i + 1, es, i, back);
633		} else { // Wrap around
634	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
635	<	elements[mask] = elements[0];
636	<	System.arraycopy(elements, 1, elements, 0, t);
637	<	tail = (t - 1) & mask;
634	>	int firstLeg = capacity - (i + 1);
635	>	System.arraycopy(es, i + 1, es, i, firstLeg);
636	>	es[capacity - 1] = es[0];
637	>	System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
638		}
639	+	es[tail] = null;
640	+	// checkInvariants();
641		return true;
642		}
643		}
#	Line 536 | Line 650 | public class ArrayDeque<E> extends Abstr
650		* @return the number of elements in this deque
651		*/
652		public int size() {
653	<	return (tail - head) & (elements.length - 1);
653	>	return sub(tail, head, elements.length);
654		}
655
656		/**
#	Line 565 | Line 679 | public class ArrayDeque<E> extends Abstr
679		}
680
681		private class DeqIterator implements Iterator<E> {
682	<	/**
683	<	* Index of element to be returned by subsequent call to next.
570	<	*/
571	<	private int cursor = head;
682	>	/** Index of element to be returned by subsequent call to next. */
683	>	int cursor;
684
685	<	/**
686	<	* Tail recorded at construction (also in remove), to stop
575	<	* iterator and also to check for comodification.
576	<	*/
577	<	private int fence = tail;
685	>	/** Number of elements yet to be returned. */
686	>	int remaining = size();
687
688		/**
689		* Index of element returned by most recent call to next.
690		* Reset to -1 if element is deleted by a call to remove.
691		*/
692	<	private int lastRet = -1;
692	>	int lastRet = -1;
693
694	<	public boolean hasNext() {
695	<	return cursor != fence;
694	>	DeqIterator() { cursor = head; }
695	>
696	>	public final boolean hasNext() {
697	>	return remaining > 0;
698		}
699
700		public E next() {
701	<	if (cursor == fence)
701	>	if (remaining <= 0)
702		throw new NoSuchElementException();
703	<	@SuppressWarnings("unchecked")
704	<	E result = (E) elements[cursor];
594	<	// This check doesn't catch all possible comodifications,
595	<	// but does catch the ones that corrupt traversal
596	<	if (tail != fence || result == null)
597	<	throw new ConcurrentModificationException();
703	>	final Object[] es = elements;
704	>	E e = nonNullElementAt(es, cursor);
705		lastRet = cursor;
706	<	cursor = (cursor + 1) & (elements.length - 1);
707	<	return result;
706	>	cursor = inc(cursor, es.length);
707	>	remaining--;
708	>	return e;
709		}
710
711	<	public void remove() {
711	>	void postDelete(boolean leftShifted) {
712	>	if (leftShifted)
713	>	cursor = dec(cursor, elements.length);
714	>	}
715	>
716	>	public final void remove() {
717		if (lastRet < 0)
718		throw new IllegalStateException();
719	<	if (delete(lastRet)) { // if left-shifted, undo increment in next()
607	<	cursor = (cursor - 1) & (elements.length - 1);
608	<	fence = tail;
609	<	}
719	>	postDelete(delete(lastRet));
720		lastRet = -1;
721		}
612	–	}
613	–
614	–	private class DescendingIterator implements Iterator<E> {
615	–	/*
616	–	* This class is nearly a mirror-image of DeqIterator, using
617	–	* tail instead of head for initial cursor, and head instead of
618	–	* tail for fence.
619	–	*/
620	–	private int cursor = tail;
621	–	private int fence = head;
622	–	private int lastRet = -1;
722
723	<	public boolean hasNext() {
724	<	return cursor != fence;
723	>	public void forEachRemaining(Consumer<? super E> action) {
724	>	Objects.requireNonNull(action);
725	>	int r;
726	>	if ((r = remaining) <= 0)
727	>	return;
728	>	remaining = 0;
729	>	final Object[] es = elements;
730	>	if (es[cursor] == null || sub(tail, cursor, es.length) != r)
731	>	throw new ConcurrentModificationException();
732	>	for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
733	>	; i = 0, to = end) {
734	>	for (; i < to; i++)
735	>	action.accept(elementAt(es, i));
736	>	if (to == end) {
737	>	if (end != tail)
738	>	throw new ConcurrentModificationException();
739	>	lastRet = dec(end, es.length);
740	>	break;
741	>	}
742	>	}
743		}
744	+	}
745
746	<	public E next() {
747	<	if (cursor == fence)
746	>	private class DescendingIterator extends DeqIterator {
747	>	DescendingIterator() { cursor = dec(tail, elements.length); }
748	>
749	>	public final E next() {
750	>	if (remaining <= 0)
751		throw new NoSuchElementException();
752	<	cursor = (cursor - 1) & (elements.length - 1);
753	<	@SuppressWarnings("unchecked")
633	<	E result = (E) elements[cursor];
634	<	if (head != fence || result == null)
635	<	throw new ConcurrentModificationException();
752	>	final Object[] es = elements;
753	>	E e = nonNullElementAt(es, cursor);
754		lastRet = cursor;
755	<	return result;
755	>	cursor = dec(cursor, es.length);
756	>	remaining--;
757	>	return e;
758	>	}
759	>
760	>	void postDelete(boolean leftShifted) {
761	>	if (!leftShifted)
762	>	cursor = inc(cursor, elements.length);
763	>	}
764	>
765	>	public final void forEachRemaining(Consumer<? super E> action) {
766	>	Objects.requireNonNull(action);
767	>	int r;
768	>	if ((r = remaining) <= 0)
769	>	return;
770	>	remaining = 0;
771	>	final Object[] es = elements;
772	>	if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
773	>	throw new ConcurrentModificationException();
774	>	for (int i = cursor, end = head, to = (i >= end) ? end : 0;
775	>	; i = es.length - 1, to = end) {
776	>	// hotspot generates faster code than for: i >= to !
777	>	for (; i > to - 1; i--)
778	>	action.accept(elementAt(es, i));
779	>	if (to == end) {
780	>	if (end != head)
781	>	throw new ConcurrentModificationException();
782	>	lastRet = head;
783	>	break;
784	>	}
785	>	}
786		}
787	+	}
788
789	<	public void remove() {
790	<	if (lastRet < 0)
791	<	throw new IllegalStateException();
792	<	if (!delete(lastRet)) {
793	<	cursor = (cursor + 1) & (elements.length - 1);
794	<	fence = head;
789	>	/**
790	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
791	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
792	>	* deque.
793	>	*
794	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
795	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
796	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
797	>	* the reporting of additional characteristic values.
798	>	*
799	>	* @return a {@code Spliterator} over the elements in this deque
800	>	* @since 1.8
801	>	*/
802	>	public Spliterator<E> spliterator() {
803	>	return new DeqSpliterator();
804	>	}
805	>
806	>	final class DeqSpliterator implements Spliterator<E> {
807	>	private int fence;      // -1 until first use
808	>	private int cursor;     // current index, modified on traverse/split
809	>
810	>	/** Constructs late-binding spliterator over all elements. */
811	>	DeqSpliterator() {
812	>	this.fence = -1;
813	>	}
814	>
815	>	/** Constructs spliterator over the given range. */
816	>	DeqSpliterator(int origin, int fence) {
817	>	this.cursor = origin;
818	>	this.fence = fence;
819	>	}
820	>
821	>	/** Ensures late-binding initialization; then returns fence. */
822	>	private int getFence() { // force initialization
823	>	int t;
824	>	if ((t = fence) < 0) {
825	>	t = fence = tail;
826	>	cursor = head;
827		}
828	<	lastRet = -1;
828	>	return t;
829	>	}
830	>
831	>	public DeqSpliterator trySplit() {
832	>	final Object[] es = elements;
833	>	final int i, n;
834	>	return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
835	>	? null
836	>	: new DeqSpliterator(i, cursor = add(i, n, es.length));
837	>	}
838	>
839	>	public void forEachRemaining(Consumer<? super E> action) {
840	>	if (action == null)
841	>	throw new NullPointerException();
842	>	final int end = getFence(), cursor = this.cursor;
843	>	final Object[] es = elements;
844	>	if (cursor != end) {
845	>	this.cursor = end;
846	>	// null check at both ends of range is sufficient
847	>	if (es[cursor] == null || es[dec(end, es.length)] == null)
848	>	throw new ConcurrentModificationException();
849	>	for (int i = cursor, to = (i <= end) ? end : es.length;
850	>	; i = 0, to = end) {
851	>	for (; i < to; i++)
852	>	action.accept(elementAt(es, i));
853	>	if (to == end) break;
854	>	}
855	>	}
856	>	}
857	>
858	>	public boolean tryAdvance(Consumer<? super E> action) {
859	>	if (action == null)
860	>	throw new NullPointerException();
861	>	int t, i;
862	>	if ((t = fence) < 0) t = getFence();
863	>	if (t == (i = cursor))
864	>	return false;
865	>	final Object[] es;
866	>	action.accept(nonNullElementAt(es = elements, i));
867	>	cursor = inc(i, es.length);
868	>	return true;
869	>	}
870	>
871	>	public long estimateSize() {
872	>	return sub(getFence(), cursor, elements.length);
873	>	}
874	>
875	>	public int characteristics() {
876	>	return Spliterator.NONNULL
877	>	| Spliterator.ORDERED
878	>	| Spliterator.SIZED
879	>	| Spliterator.SUBSIZED;
880	>	}
881	>	}
882	>
883	>	public void forEach(Consumer<? super E> action) {
884	>	Objects.requireNonNull(action);
885	>	final Object[] es = elements;
886	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
887	>	; i = 0, to = end) {
888	>	for (; i < to; i++)
889	>	action.accept(elementAt(es, i));
890	>	if (to == end) {
891	>	if (end != tail) throw new ConcurrentModificationException();
892	>	break;
893	>	}
894	>	}
895	>	// checkInvariants();
896	>	}
897	>
898	>	/**
899	>	* Replaces each element of this deque with the result of applying the
900	>	* operator to that element, as specified by {@link List#replaceAll}.
901	>	*
902	>	* @param operator the operator to apply to each element
903	>	* @since TBD
904	>	*/
905	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
906	>	Objects.requireNonNull(operator);
907	>	final Object[] es = elements;
908	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
909	>	; i = 0, to = end) {
910	>	for (; i < to; i++)
911	>	es[i] = operator.apply(elementAt(es, i));
912	>	if (to == end) {
913	>	if (end != tail) throw new ConcurrentModificationException();
914	>	break;
915	>	}
916	>	}
917	>	// checkInvariants();
918	>	}
919	>
920	>	/**
921	>	* @throws NullPointerException {@inheritDoc}
922	>	*/
923	>	public boolean removeIf(Predicate<? super E> filter) {
924	>	Objects.requireNonNull(filter);
925	>	return bulkRemove(filter);
926	>	}
927	>
928	>	/**
929	>	* @throws NullPointerException {@inheritDoc}
930	>	*/
931	>	public boolean removeAll(Collection<?> c) {
932	>	Objects.requireNonNull(c);
933	>	return bulkRemove(e -> c.contains(e));
934	>	}
935	>
936	>	/**
937	>	* @throws NullPointerException {@inheritDoc}
938	>	*/
939	>	public boolean retainAll(Collection<?> c) {
940	>	Objects.requireNonNull(c);
941	>	return bulkRemove(e -> !c.contains(e));
942	>	}
943	>
944	>	/** Implementation of bulk remove methods. */
945	>	private boolean bulkRemove(Predicate<? super E> filter) {
946	>	// checkInvariants();
947	>	final Object[] es = elements;
948	>	// Optimize for initial run of survivors
949	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
950	>	; i = 0, to = end) {
951	>	for (; i < to; i++)
952	>	if (filter.test(elementAt(es, i)))
953	>	return bulkRemoveModified(filter, i, to);
954	>	if (to == end) {
955	>	if (end != tail) throw new ConcurrentModificationException();
956	>	break;
957	>	}
958	>	}
959	>	return false;
960	>	}
961	>
962	>	/**
963	>	* Helper for bulkRemove, in case of at least one deletion.
964	>	* @param i valid index of first element to be deleted
965	>	*/
966	>	private boolean bulkRemoveModified(
967	>	Predicate<? super E> filter, int i, int to) {
968	>	final Object[] es = elements;
969	>	final int capacity = es.length;
970	>	// a two-finger algorithm, with hare i reading, tortoise j writing
971	>	int j = i++;
972	>	final int end = tail;
973	>	try {
974	>	for (;; j = 0) {    // j rejoins i on second leg
975	>	E e;
976	>	// In this loop, i and j are on the same leg, with i > j
977	>	for (; i < to; i++)
978	>	if (!filter.test(e = elementAt(es, i)))
979	>	es[j++] = e;
980	>	if (to == end) break;
981	>	// In this loop, j is on the first leg, i on the second
982	>	for (i = 0, to = end; i < to && j < capacity; i++)
983	>	if (!filter.test(e = elementAt(es, i)))
984	>	es[j++] = e;
985	>	if (i >= to) {
986	>	if (j == capacity) j = 0; // "corner" case
987	>	break;
988	>	}
989	>	}
990	>	return true;
991	>	} catch (Throwable ex) {
992	>	// copy remaining elements
993	>	for (; i != end; i = inc(i, capacity), j = inc(j, capacity))
994	>	es[j] = es[i];
995	>	throw ex;
996	>	} finally {
997	>	if (end != tail) throw new ConcurrentModificationException();
998	>	circularClear(es, tail = j, end);
999	>	// checkInvariants();
1000		}
1001		}
1002
#	Line 657 | Line 1009 | public class ArrayDeque<E> extends Abstr
1009		* @return {@code true} if this deque contains the specified element
1010		*/
1011		public boolean contains(Object o) {
1012	<	if (o == null)
1013	<	return false;
1014	<	int mask = elements.length - 1;
1015	<	int i = head;
1016	<	Object x;
1017	<	while ( (x = elements[i]) != null) {
1018	<	if (o.equals(x))
1019	<	return true;
1020	<	i = (i + 1) & mask;
1012	>	if (o != null) {
1013	>	final Object[] es = elements;
1014	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1015	>	; i = 0, to = end) {
1016	>	for (; i < to; i++)
1017	>	if (o.equals(es[i]))
1018	>	return true;
1019	>	if (to == end) break;
1020	>	}
1021		}
1022		return false;
1023		}
#	Line 692 | Line 1044 | public class ArrayDeque<E> extends Abstr
1044		* The deque will be empty after this call returns.
1045		*/
1046		public void clear() {
1047	<	int h = head;
1048	<	int t = tail;
1049	<	if (h != t) { // clear all cells
1050	<	head = tail = 0;
1051	<	int i = h;
1052	<	int mask = elements.length - 1;
1053	<	do {
1054	<	elements[i] = null;
1055	<	i = (i + 1) & mask;
1056	<	} while (i != t);
1047	>	circularClear(elements, head, tail);
1048	>	head = tail = 0;
1049	>	// checkInvariants();
1050	>	}
1051	>
1052	>	/**
1053	>	* Nulls out slots starting at array index i, upto index end.
1054	>	*/
1055	>	private static void circularClear(Object[] es, int i, int end) {
1056	>	for (int to = (i <= end) ? end : es.length;
1057	>	; i = 0, to = end) {
1058	>	Arrays.fill(es, i, to, null);
1059	>	if (to == end) break;
1060		}
1061		}
1062
#	Line 719 | Line 1074 | public class ArrayDeque<E> extends Abstr
1074		* @return an array containing all of the elements in this deque
1075		*/
1076		public Object[] toArray() {
1077	<	final int head = this.head;
1078	<	final int tail = this.tail;
1079	<	boolean wrap = (tail < head);
1080	<	int end = wrap ? tail + elements.length : tail;
1081	<	Object[] a = Arrays.copyOfRange(elements, head, end);
1082	<	if (wrap)
1083	<	System.arraycopy(elements, 0, a, elements.length - head, tail);
1077	>	return toArray(Object[].class);
1078	>	}
1079	>
1080	>	private <T> T[] toArray(Class<T[]> klazz) {
1081	>	final Object[] es = elements;
1082	>	final T[] a;
1083	>	final int size = size(), head = this.head, end;
1084	>	final int len = Math.min(size, es.length - head);
1085	>	if ((end = head + size) >= 0) {
1086	>	a = Arrays.copyOfRange(es, head, end, klazz);
1087	>	} else {
1088	>	// integer overflow!
1089	>	a = Arrays.copyOfRange(es, 0, size, klazz);
1090	>	System.arraycopy(es, head, a, 0, len);
1091	>	}
1092	>	if (tail < head)
1093	>	System.arraycopy(es, 0, a, len, tail);
1094		return a;
1095		}
1096
#	Line 751 | Line 1116 | public class ArrayDeque<E> extends Abstr
1116		* The following code can be used to dump the deque into a newly
1117		* allocated array of {@code String}:
1118		*
1119	<	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1119	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1120		*
1121		* Note that {@code toArray(new Object[0])} is identical in function to
1122		* {@code toArray()}.
#	Line 767 | Line 1132 | public class ArrayDeque<E> extends Abstr
1132		*/
1133		@SuppressWarnings("unchecked")
1134		public <T> T[] toArray(T[] a) {
1135	<	final int head = this.head;
1136	<	final int tail = this.tail;
1137	<	boolean wrap = (tail < head);
1138	<	int size = (tail - head) + (wrap ? elements.length : 0);
1139	<	int firstLeg = size - (wrap ? tail : 0);
1140	<	int len = a.length;
1141	<	if (size > len) {
1142	<	a = (T[]) Arrays.copyOfRange(elements, head, head + size,
778	<	a.getClass());
779	<	} else {
780	<	System.arraycopy(elements, head, a, 0, firstLeg);
781	<	if (size < len)
782	<	a[size] = null;
1135	>	final int size;
1136	>	if ((size = size()) > a.length)
1137	>	return toArray((Class<T[]>) a.getClass());
1138	>	final Object[] es = elements;
1139	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1140	>	; i = 0, len = tail) {
1141	>	System.arraycopy(es, i, a, j, len);
1142	>	if ((j += len) == size) break;
1143		}
1144	<	if (wrap)
1145	<	System.arraycopy(elements, 0, a, firstLeg, tail);
1144	>	if (size < a.length)
1145	>	a[size] = null;
1146		return a;
1147		}
1148
#	Line 809 | Line 1169 | public class ArrayDeque<E> extends Abstr
1169		/**
1170		* Saves this deque to a stream (that is, serializes it).
1171		*
1172	+	* @param s the stream
1173	+	* @throws java.io.IOException if an I/O error occurs
1174		* @serialData The current size ({@code int}) of the deque,
1175		* followed by all of its elements (each an object reference) in
1176		* first-to-last order.
#	Line 821 | Line 1183 | public class ArrayDeque<E> extends Abstr
1183		s.writeInt(size());
1184
1185		// Write out elements in order.
1186	<	int mask = elements.length - 1;
1187	<	for (int i = head; i != tail; i = (i + 1) & mask)
1188	<	s.writeObject(elements[i]);
1186	>	final Object[] es = elements;
1187	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1188	>	; i = 0, to = end) {
1189	>	for (; i < to; i++)
1190	>	s.writeObject(es[i]);
1191	>	if (to == end) break;
1192	>	}
1193		}
1194
1195		/**
1196		* Reconstitutes this deque from a stream (that is, deserializes it).
1197	+	* @param s the stream
1198	+	* @throws ClassNotFoundException if the class of a serialized object
1199	+	*         could not be found
1200	+	* @throws java.io.IOException if an I/O error occurs
1201		*/
1202		private void readObject(java.io.ObjectInputStream s)
1203		throws java.io.IOException, ClassNotFoundException {
#	Line 835 | Line 1205 | public class ArrayDeque<E> extends Abstr
1205
1206		// Read in size and allocate array
1207		int size = s.readInt();
1208	<	allocateElements(size);
1209	<	head = 0;
840	<	tail = size;
1208	>	elements = new Object[size + 1];
1209	>	this.tail = size;
1210
1211		// Read in all elements in the proper order.
1212		for (int i = 0; i < size; i++)
1213		elements[i] = s.readObject();
1214		}
1215
1216	<	Spliterator<E> spliterator() {
1217	<	return new DeqSpliterator<E>(this, -1, -1);
1218	<	}
1219	<
1220	<	public Stream<E> stream() {
1221	<	return Streams.stream(spliterator());
1222	<	}
1223	<
1224	<	public Stream<E> parallelStream() {
1225	<	return Streams.parallelStream(spliterator());
1226	<	}
1227	<
1228	<	static final class DeqSpliterator<E> implements Spliterator<E> {
1229	<	private final ArrayDeque<E> deq;
1230	<	private int fence;  // -1 until first use
1231	<	private int index;  // current index, modified on traverse/split
1232	<
864	<	/** Creates new spliterator covering the given array and range */
865	<	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
866	<	this.deq = deq;
867	<	this.index = origin;
868	<	this.fence = fence;
869	<	}
870	<
871	<	private int getFence() { // force initialization
872	<	int t;
873	<	if ((t = fence) < 0) {
874	<	t = fence = deq.tail;
875	<	index = deq.head;
876	<	}
877	<	return t;
878	<	}
879	<
880	<	public DeqSpliterator<E> trySplit() {
881	<	int t = getFence(), h = index, n = deq.elements.length;
882	<	if (h != t && ((h + 1) & (n - 1)) != t) {
883	<	if (h > t)
884	<	t += n;
885	<	int m = ((h + t) >>> 1) & (n - 1);
886	<	return new DeqSpliterator<>(deq, h, index = m);
887	<	}
888	<	return null;
889	<	}
890	<
891	<	public void forEach(Consumer<? super E> consumer) {
892	<	if (consumer == null)
893	<	throw new NullPointerException();
894	<	Object[] a = deq.elements;
895	<	int m = a.length - 1, f = getFence(), i = index;
896	<	index = f;
897	<	while (i != f) {
898	<	@SuppressWarnings("unchecked") E e = (E)a[i];
899	<	i = (i + 1) & m;
900	<	if (e == null)
901	<	throw new ConcurrentModificationException();
902	<	consumer.accept(e);
903	<	}
904	<	}
905	<
906	<	public boolean tryAdvance(Consumer<? super E> consumer) {
907	<	if (consumer == null)
908	<	throw new NullPointerException();
909	<	Object[] a = deq.elements;
910	<	int m = a.length - 1, f = getFence(), i = index;
911	<	if (i != fence) {
912	<	@SuppressWarnings("unchecked") E e = (E)a[i];
913	<	index = (i + 1) & m;
914	<	if (e == null)
915	<	throw new ConcurrentModificationException();
916	<	consumer.accept(e);
917	<	return true;
918	<	}
919	<	return false;
920	<	}
921	<
922	<	public long estimateSize() {
923	<	int n = getFence() - index;
924	<	if (n < 0)
925	<	n += deq.elements.length;
926	<	return (long) n;
927	<	}
928	<
929	<	@Override
930	<	public int characteristics() {
931	<	return Spliterator.ORDERED | Spliterator.SIZED |
932	<	Spliterator.NONNULL | Spliterator.SUBSIZED;
1216	>	/** debugging */
1217	>	void checkInvariants() {
1218	>	try {
1219	>	int capacity = elements.length;
1220	>	// assert head >= 0 && head < capacity;
1221	>	// assert tail >= 0 && tail < capacity;
1222	>	// assert capacity > 0;
1223	>	// assert size() < capacity;
1224	>	// assert head == tail || elements[head] != null;
1225	>	// assert elements[tail] == null;
1226	>	// assert head == tail || elements[dec(tail, capacity)] != null;
1227	>	} catch (Throwable t) {
1228	>	System.err.printf("head=%d tail=%d capacity=%d%n",
1229	>	head, tail, elements.length);
1230	>	System.err.printf("elements=%s%n",
1231	>	Arrays.toString(elements));
1232	>	throw t;
1233		}
1234		}
1235

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