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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.53 by dl, Wed Mar 13 12:38:56 2013 UTC vs.
Revision 1.113 by jsr166, Sun Nov 13 02:10:09 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 53 | 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
57	–	* @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
66	<	* full, except transiently within an addX method where it is
67	<	* resized (see doubleCapacity) immediately upon becoming full,
68	<	* thus avoiding head and tail wrapping around to equal each
69	<	* other.  We also guarantee that all array cells not holding
70	<	* 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 85 | 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);
107	<	initialCapacity |= (initialCapacity >>>  2);
108	<	initialCapacity |= (initialCapacity >>>  4);
109	<	initialCapacity |= (initialCapacity >>>  8);
110	<	initialCapacity |= (initialCapacity >>> 16);
111	<	initialCapacity++;
112	<
113	<	if (initialCapacity < 0)   // Too many elements, must back off
114	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
115	<	}
116	<	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];
132	<	System.arraycopy(elements, p, a, 0, r);
133	<	System.arraycopy(elements, 0, a, r, p);
134	<	elements = a;
135	<	head = 0;
136	<	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 148 | 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 165 | 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 182 | 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 198 | 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 231 | 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;
270	<	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];
279	<	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
295	–	@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
301	–	@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 316 | 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		}
329	–	i = (i + 1) & mask;
451		}
452		return false;
453		}
#	Line 344 | 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		}
357	–	i = (i - 1) & mask;
479		}
480		return false;
481		}
#	Line 473 | Line 594 | public class ArrayDeque<E> extends Abstr
594		return removeFirst();
595		}
596
476	–	private void checkInvariants() {
477	–	assert elements[tail] == null;
478	–	assert head == tail ? elements[head] == null :
479	–	(elements[head] != null &&
480	–	elements[(tail - 1) & (elements.length - 1)] != null);
481	–	assert elements[(head - 1) & (elements.length - 1)] == null;
482	–	}
483	–
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;
502	<
503	<	// Invariant: head <= i < tail mod circularity
504	<	if (front >= ((t - h) & mask))
505	<	throw new ConcurrentModificationException();
506	<
507	<	// Optimize for least element motion
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 538 | 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 567 | 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.
572	<	*/
573	<	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
577	<	* iterator and also to check for comodification.
578	<	*/
579	<	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];
596	<	// This check doesn't catch all possible comodifications,
597	<	// but does catch the ones that corrupt traversal
598	<	if (tail != fence || result == null)
599	<	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	>	void postDelete(boolean leftShifted) {
712	>	if (leftShifted)
713	>	cursor = dec(cursor, elements.length);
714		}
715
716	<	public void remove() {
716	>	public final void remove() {
717		if (lastRet < 0)
718		throw new IllegalStateException();
719	<	if (delete(lastRet)) { // if left-shifted, undo increment in next()
609	<	cursor = (cursor - 1) & (elements.length - 1);
610	<	fence = tail;
611	<	}
719	>	postDelete(delete(lastRet));
720		lastRet = -1;
721		}
722	+
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	+	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	+	final Object[] es = elements;
753	+	E e = nonNullElementAt(es, cursor);
754	+	lastRet = cursor;
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 = end;
783	+	break;
784	+	}
785	+	}
786	+	}
787		}
788
789		/**
790	<	* This class is nearly a mirror-image of DeqIterator, using tail
791	<	* instead of head for initial cursor, and head instead of tail
792	<	* for fence.
793	<	*/
794	<	private class DescendingIterator implements Iterator<E> {
795	<	private int cursor = tail;
796	<	private int fence = head;
797	<	private int lastRet = -1;
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	<	public boolean hasNext() {
811	<	return cursor != fence;
810	>	/** Constructs late-binding spliterator over all elements. */
811	>	DeqSpliterator() {
812	>	this.fence = -1;
813		}
814
815	<	public E next() {
816	<	if (cursor == fence)
817	<	throw new NoSuchElementException();
818	<	cursor = (cursor - 1) & (elements.length - 1);
634	<	@SuppressWarnings("unchecked")
635	<	E result = (E) elements[cursor];
636	<	if (head != fence || result == null)
637	<	throw new ConcurrentModificationException();
638	<	lastRet = cursor;
639	<	return result;
815	>	/** Constructs spliterator over the given range. */
816	>	DeqSpliterator(int origin, int fence) {
817	>	this.cursor = origin;
818	>	this.fence = fence;
819		}
820
821	<	public void remove() {
822	<	if (lastRet < 0)
823	<	throw new IllegalStateException();
824	<	if (!delete(lastRet)) {
825	<	cursor = (cursor + 1) & (elements.length - 1);
826	<	fence = head;
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	>	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);
954	>	if (to == end) {
955	>	if (end != tail) throw new ConcurrentModificationException();
956	>	break;
957	>	}
958	>	}
959	>	return false;
960	>	}
961	>
962	>	// A tiny bit set implementation
963	>
964	>	private static long[] nBits(int n) {
965	>	return new long[((n - 1) >> 6) + 1];
966	>	}
967	>	private static void setBit(long[] bits, int i) {
968	>	bits[i >> 6] |= 1L << i;
969	>	}
970	>	private static boolean isClear(long[] bits, int i) {
971	>	return (bits[i >> 6] & (1L << i)) == 0;
972	>	}
973	>
974	>	/**
975	>	* Helper for bulkRemove, in case of at least one deletion.
976	>	* Tolerate predicates that reentrantly access the collection for
977	>	* read (but writers still get CME), so traverse once to find
978	>	* elements to delete, a second pass to physically expunge.
979	>	*
980	>	* @param beg valid index of first element to be deleted
981	>	*/
982	>	private boolean bulkRemoveModified(
983	>	Predicate<? super E> filter, final int beg) {
984	>	final Object[] es = elements;
985	>	final int capacity = es.length;
986	>	final int end = tail;
987	>	final long[] deathRow = nBits(sub(end, beg, capacity));
988	>	deathRow[0] = 1L;   // set bit 0
989	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
990	>	; i = 0, to = end, k -= capacity) {
991	>	for (; i < to; i++)
992	>	if (filter.test(elementAt(es, i)))
993	>	setBit(deathRow, i - k);
994	>	if (to == end) break;
995	>	}
996	>	// a two-finger traversal, with hare i reading, tortoise w writing
997	>	int w = beg;
998	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
999	>	; w = 0) { // w rejoins i on second leg
1000	>	// In this loop, i and w are on the same leg, with i > w
1001	>	for (; i < to; i++)
1002	>	if (isClear(deathRow, i - k))
1003	>	es[w++] = es[i];
1004	>	if (to == end) break;
1005	>	// In this loop, w is on the first leg, i on the second
1006	>	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1007	>	if (isClear(deathRow, i - k))
1008	>	es[w++] = es[i];
1009	>	if (i >= to) {
1010	>	if (w == capacity) w = 0; // "corner" case
1011	>	break;
1012		}
649	–	lastRet = -1;
1013		}
1014	+	if (end != tail) throw new ConcurrentModificationException();
1015	+	circularClear(es, tail = w, end);
1016	+	// checkInvariants();
1017	+	return true;
1018		}
1019
1020		/**
#	Line 659 | Line 1026 | public class ArrayDeque<E> extends Abstr
1026		* @return {@code true} if this deque contains the specified element
1027		*/
1028		public boolean contains(Object o) {
1029	<	if (o == null)
1030	<	return false;
1031	<	int mask = elements.length - 1;
1032	<	int i = head;
1033	<	Object x;
1034	<	while ( (x = elements[i]) != null) {
1035	<	if (o.equals(x))
1036	<	return true;
1037	<	i = (i + 1) & mask;
1029	>	if (o != null) {
1030	>	final Object[] es = elements;
1031	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1032	>	; i = 0, to = end) {
1033	>	for (; i < to; i++)
1034	>	if (o.equals(es[i]))
1035	>	return true;
1036	>	if (to == end) break;
1037	>	}
1038		}
1039		return false;
1040		}
#	Line 694 | Line 1061 | public class ArrayDeque<E> extends Abstr
1061		* The deque will be empty after this call returns.
1062		*/
1063		public void clear() {
1064	<	int h = head;
1065	<	int t = tail;
1066	<	if (h != t) { // clear all cells
1067	<	head = tail = 0;
1068	<	int i = h;
1069	<	int mask = elements.length - 1;
1070	<	do {
1071	<	elements[i] = null;
1072	<	i = (i + 1) & mask;
1073	<	} while (i != t);
1064	>	circularClear(elements, head, tail);
1065	>	head = tail = 0;
1066	>	// checkInvariants();
1067	>	}
1068	>
1069	>	/**
1070	>	* Nulls out slots starting at array index i, upto index end.
1071	>	*/
1072	>	private static void circularClear(Object[] es, int i, int end) {
1073	>	for (int to = (i <= end) ? end : es.length;
1074	>	; i = 0, to = end) {
1075	>	Arrays.fill(es, i, to, null);
1076	>	if (to == end) break;
1077		}
1078		}
1079
#	Line 721 | Line 1091 | public class ArrayDeque<E> extends Abstr
1091		* @return an array containing all of the elements in this deque
1092		*/
1093		public Object[] toArray() {
1094	<	final int head = this.head;
1095	<	final int tail = this.tail;
1096	<	boolean wrap = (tail < head);
1097	<	int end = wrap ? tail + elements.length : tail;
1098	<	Object[] a = Arrays.copyOfRange(elements, head, end);
1099	<	if (wrap)
1100	<	System.arraycopy(elements, 0, a, elements.length - head, tail);
1094	>	return toArray(Object[].class);
1095	>	}
1096	>
1097	>	private <T> T[] toArray(Class<T[]> klazz) {
1098	>	final Object[] es = elements;
1099	>	final T[] a;
1100	>	final int size = size(), head = this.head, end;
1101	>	final int len = Math.min(size, es.length - head);
1102	>	if ((end = head + size) >= 0) {
1103	>	a = Arrays.copyOfRange(es, head, end, klazz);
1104	>	} else {
1105	>	// integer overflow!
1106	>	a = Arrays.copyOfRange(es, 0, size, klazz);
1107	>	System.arraycopy(es, head, a, 0, len);
1108	>	}
1109	>	if (tail < head)
1110	>	System.arraycopy(es, 0, a, len, tail);
1111		return a;
1112		}
1113
#	Line 753 | Line 1133 | public class ArrayDeque<E> extends Abstr
1133		* The following code can be used to dump the deque into a newly
1134		* allocated array of {@code String}:
1135		*
1136	<	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1136	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1137		*
1138		* Note that {@code toArray(new Object[0])} is identical in function to
1139		* {@code toArray()}.
#	Line 769 | Line 1149 | public class ArrayDeque<E> extends Abstr
1149		*/
1150		@SuppressWarnings("unchecked")
1151		public <T> T[] toArray(T[] a) {
1152	<	final int head = this.head;
1153	<	final int tail = this.tail;
1154	<	boolean wrap = (tail < head);
1155	<	int size = (tail - head) + (wrap ? elements.length : 0);
1156	<	int firstLeg = size - (wrap ? tail : 0);
1157	<	int len = a.length;
1158	<	if (size > len) {
1159	<	a = (T[]) Arrays.copyOfRange(elements, head, head + size,
780	<	a.getClass());
781	<	} else {
782	<	System.arraycopy(elements, head, a, 0, firstLeg);
783	<	if (size < len)
784	<	a[size] = null;
1152	>	final int size;
1153	>	if ((size = size()) > a.length)
1154	>	return toArray((Class<T[]>) a.getClass());
1155	>	final Object[] es = elements;
1156	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1157	>	; i = 0, len = tail) {
1158	>	System.arraycopy(es, i, a, j, len);
1159	>	if ((j += len) == size) break;
1160		}
1161	<	if (wrap)
1162	<	System.arraycopy(elements, 0, a, firstLeg, tail);
1161	>	if (size < a.length)
1162	>	a[size] = null;
1163		return a;
1164		}
1165
#	Line 811 | Line 1186 | public class ArrayDeque<E> extends Abstr
1186		/**
1187		* Saves this deque to a stream (that is, serializes it).
1188		*
1189	+	* @param s the stream
1190	+	* @throws java.io.IOException if an I/O error occurs
1191		* @serialData The current size ({@code int}) of the deque,
1192		* followed by all of its elements (each an object reference) in
1193		* first-to-last order.
#	Line 823 | Line 1200 | public class ArrayDeque<E> extends Abstr
1200		s.writeInt(size());
1201
1202		// Write out elements in order.
1203	<	int mask = elements.length - 1;
1204	<	for (int i = head; i != tail; i = (i + 1) & mask)
1205	<	s.writeObject(elements[i]);
1203	>	final Object[] es = elements;
1204	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1205	>	; i = 0, to = end) {
1206	>	for (; i < to; i++)
1207	>	s.writeObject(es[i]);
1208	>	if (to == end) break;
1209	>	}
1210		}
1211
1212		/**
1213		* Reconstitutes this deque from a stream (that is, deserializes it).
1214	+	* @param s the stream
1215	+	* @throws ClassNotFoundException if the class of a serialized object
1216	+	*         could not be found
1217	+	* @throws java.io.IOException if an I/O error occurs
1218		*/
1219		private void readObject(java.io.ObjectInputStream s)
1220		throws java.io.IOException, ClassNotFoundException {
#	Line 837 | Line 1222 | public class ArrayDeque<E> extends Abstr
1222
1223		// Read in size and allocate array
1224		int size = s.readInt();
1225	<	allocateElements(size);
1226	<	head = 0;
842	<	tail = size;
1225	>	elements = new Object[size + 1];
1226	>	this.tail = size;
1227
1228		// Read in all elements in the proper order.
1229		for (int i = 0; i < size; i++)
1230		elements[i] = s.readObject();
1231		}
1232
1233	<	public Spliterator<E> spliterator() {
1234	<	return new DeqSpliterator<E>(this, -1, -1);
1235	<	}
1236	<
1237	<	static final class DeqSpliterator<E> implements Spliterator<E> {
1238	<	private final ArrayDeque<E> deq;
1239	<	private int fence;  // -1 until first use
1240	<	private int index;  // current index, modified on traverse/split
1241	<
1242	<	/** Creates new spliterator covering the given array and range */
1243	<	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
1244	<	this.deq = deq;
1245	<	this.index = origin;
1246	<	this.fence = fence;
1247	<	}
1248	<
1249	<	private int getFence() { // force initialization
866	<	int t;
867	<	if ((t = fence) < 0) {
868	<	t = fence = deq.tail;
869	<	index = deq.head;
870	<	}
871	<	return t;
872	<	}
873	<
874	<	public Spliterator<E> trySplit() {
875	<	int t = getFence(), h = index, n = deq.elements.length;
876	<	if (h != t && ((h + 1) & (n - 1)) != t) {
877	<	if (h > t)
878	<	t += n;
879	<	int m = ((h + t) >>> 1) & (n - 1);
880	<	return new DeqSpliterator<>(deq, h, index = m);
881	<	}
882	<	return null;
883	<	}
884	<
885	<	public void forEach(Consumer<? super E> consumer) {
886	<	if (consumer == null)
887	<	throw new NullPointerException();
888	<	Object[] a = deq.elements;
889	<	int m = a.length - 1, f = getFence(), i = index;
890	<	index = f;
891	<	while (i != f) {
892	<	@SuppressWarnings("unchecked") E e = (E)a[i];
893	<	i = (i + 1) & m;
894	<	if (e == null)
895	<	throw new ConcurrentModificationException();
896	<	consumer.accept(e);
897	<	}
898	<	}
899	<
900	<	public boolean tryAdvance(Consumer<? super E> consumer) {
901	<	if (consumer == null)
902	<	throw new NullPointerException();
903	<	Object[] a = deq.elements;
904	<	int m = a.length - 1, f = getFence(), i = index;
905	<	if (i != fence) {
906	<	@SuppressWarnings("unchecked") E e = (E)a[i];
907	<	index = (i + 1) & m;
908	<	if (e == null)
909	<	throw new ConcurrentModificationException();
910	<	consumer.accept(e);
911	<	return true;
912	<	}
913	<	return false;
914	<	}
915	<
916	<	public long estimateSize() {
917	<	int n = getFence() - index;
918	<	if (n < 0)
919	<	n += deq.elements.length;
920	<	return (long) n;
921	<	}
922	<
923	<	@Override
924	<	public int characteristics() {
925	<	return Spliterator.ORDERED | Spliterator.SIZED |
926	<	Spliterator.NONNULL | Spliterator.SUBSIZED;
1233	>	/** debugging */
1234	>	void checkInvariants() {
1235	>	try {
1236	>	int capacity = elements.length;
1237	>	// assert head >= 0 && head < capacity;
1238	>	// assert tail >= 0 && tail < capacity;
1239	>	// assert capacity > 0;
1240	>	// assert size() < capacity;
1241	>	// assert head == tail || elements[head] != null;
1242	>	// assert elements[tail] == null;
1243	>	// assert head == tail || elements[dec(tail, capacity)] != null;
1244	>	} catch (Throwable t) {
1245	>	System.err.printf("head=%d tail=%d capacity=%d%n",
1246	>	head, tail, elements.length);
1247	>	System.err.printf("elements=%s%n",
1248	>	Arrays.toString(elements));
1249	>	throw t;
1250		}
1251		}
1252

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