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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.71 by jsr166, Sun Sep 20 02:53:40 2015 UTC vs.
Revision 1.109 by jsr166, Sat Nov 5 16:21:06 2016 UTC

#	Line 7 | Line 7 | package java.util;
7
8		import java.io.Serializable;
9		import java.util.function.Consumer;
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.function.Consumer;
54		* Java Collections Framework</a>.
55		*
56		* @author  Josh Bloch and Doug Lea
55	–	* @since   1.6
57		* @param <E> the type of elements held in this deque
58	+	* @since   1.6
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
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.
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 84 | 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);
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];
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];
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;
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 147 | 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 164 | 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 181 | 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 197 | 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 230 | 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	<	final Object[] elements = this.elements;
373	<	final int h = head;
374	<	@SuppressWarnings("unchecked")
375	<	E result = (E) elements[h];
376	<	// Element is null if deque empty
377	<	if (result != null) {
256	<	elements[h] = null; // Must null out slot
257	<	head = (h + 1) & (elements.length - 1);
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	<	return result;
379	>	// checkInvariants();
380	>	return e;
381		}
382
383		public E pollLast() {
384	<	final Object[] elements = this.elements;
385	<	final int t = (tail - 1) & (elements.length - 1);
386	<	@SuppressWarnings("unchecked")
387	<	E result = (E) elements[t];
388	<	if (result != null) {
389	<	elements[t] = null;
390	<	tail = t;
270	<	}
271	<	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];
280	<	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
296	–	@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
302	–	@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 318 | Line 438 | public class ArrayDeque<E> extends Abstr
438		*/
439		public boolean removeFirstOccurrence(Object o) {
440		if (o != null) {
441	<	int mask = elements.length - 1;
442	<	int i = head;
443	<	for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
444	<	if (o.equals(x)) {
445	<	delete(i);
446	<	return true;
447	<	}
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		}
451		}
452		return false;
#	Line 344 | Line 466 | public class ArrayDeque<E> extends Abstr
466		*/
467		public boolean removeLastOccurrence(Object o) {
468		if (o != null) {
469	<	int mask = elements.length - 1;
470	<	int i = (tail - 1) & mask;
471	<	for (Object x; (x = elements[i]) != null; i = (i - 1) & mask) {
472	<	if (o.equals(x)) {
473	<	delete(i);
474	<	return true;
475	<	}
469	>	final Object[] es = elements;
470	>	for (int i = tail, end = head, to = (i >= end) ? end : 0;
471	>	; i = es.length, to = end) {
472	>	while (--i >= to)
473	>	if (o.equals(es[i])) {
474	>	delete(i);
475	>	return true;
476	>	}
477	>	if (to == end) break;
478		}
479		}
480		return false;
#	Line 470 | Line 594 | public class ArrayDeque<E> extends Abstr
594		return removeFirst();
595		}
596
473	–	private void checkInvariants() {
474	–	assert elements[tail] == null;
475	–	assert head == tail ? elements[head] == null :
476	–	(elements[head] != null &&
477	–	elements[(tail - 1) & (elements.length - 1)] != null);
478	–	assert elements[(head - 1) & (elements.length - 1)] == null;
479	–	}
480	–
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		boolean delete(int i) {
608	<	checkInvariants();
609	<	final Object[] elements = this.elements;
610	<	final int mask = elements.length - 1;
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;
499	<
500	<	// Invariant: head <= i < tail mod circularity
501	<	if (front >= ((t - h) & mask))
502	<	throw new ConcurrentModificationException();
503	<
504	<	// 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 535 | 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 564 | 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.
569	<	*/
570	<	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
574	<	* iterator and also to check for comodification.
575	<	*/
576	<	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	>	DeqIterator() { cursor = head; }
695
696	<	public boolean hasNext() {
697	<	return cursor != fence;
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];
593	<	// This check doesn't catch all possible comodifications,
594	<	// but does catch the ones that corrupt traversal
595	<	if (tail != fence || result == null)
596	<	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()
606	<	cursor = (cursor - 1) & (elements.length - 1);
607	<	fence = tail;
608	<	}
719	>	postDelete(delete(lastRet));
720		lastRet = -1;
721		}
722
723		public void forEachRemaining(Consumer<? super E> action) {
724		Objects.requireNonNull(action);
725	<	Object[] a = elements;
726	<	int m = a.length - 1, f = fence, i = cursor;
727	<	cursor = f;
728	<	while (i != f) {
729	<	@SuppressWarnings("unchecked") E e = (E)a[i];
730	<	i = (i + 1) & m;
731	<	if (e == null)
732	<	throw new ConcurrentModificationException();
733	<	action.accept(e);
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	>	for (; i >= to; i--)
777	>	action.accept(elementAt(es, i));
778	>	if (to == end) {
779	>	if (end != head)
780	>	throw new ConcurrentModificationException();
781	>	lastRet = head;
782	>	break;
783	>	}
784		}
785		}
786		}
787
788		/**
789	<	* This class is nearly a mirror-image of DeqIterator, using tail
790	<	* instead of head for initial cursor, and head instead of tail
791	<	* for fence.
789	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
790	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
791	>	* deque.
792	>	*
793	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
794	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
795	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
796	>	* the reporting of additional characteristic values.
797	>	*
798	>	* @return a {@code Spliterator} over the elements in this deque
799	>	* @since 1.8
800		*/
801	<	private class DescendingIterator implements Iterator<E> {
802	<	private int cursor = tail;
803	<	private int fence = head;
804	<	private int lastRet = -1;
801	>	public Spliterator<E> spliterator() {
802	>	return new DeqSpliterator();
803	>	}
804	>
805	>	final class DeqSpliterator implements Spliterator<E> {
806	>	private int fence;      // -1 until first use
807	>	private int cursor;     // current index, modified on traverse/split
808
809	<	public boolean hasNext() {
810	<	return cursor != fence;
809	>	/** Constructs late-binding spliterator over all elements. */
810	>	DeqSpliterator() {
811	>	this.fence = -1;
812		}
813
814	<	public E next() {
815	<	if (cursor == fence)
816	<	throw new NoSuchElementException();
817	<	cursor = (cursor - 1) & (elements.length - 1);
645	<	@SuppressWarnings("unchecked")
646	<	E result = (E) elements[cursor];
647	<	if (head != fence || result == null)
648	<	throw new ConcurrentModificationException();
649	<	lastRet = cursor;
650	<	return result;
814	>	/** Constructs spliterator over the given range. */
815	>	DeqSpliterator(int origin, int fence) {
816	>	this.cursor = origin;
817	>	this.fence = fence;
818		}
819
820	<	public void remove() {
821	<	if (lastRet < 0)
822	<	throw new IllegalStateException();
823	<	if (!delete(lastRet)) {
824	<	cursor = (cursor + 1) & (elements.length - 1);
825	<	fence = head;
820	>	/** Ensures late-binding initialization; then returns fence. */
821	>	private int getFence() { // force initialization
822	>	int t;
823	>	if ((t = fence) < 0) {
824	>	t = fence = tail;
825	>	cursor = head;
826		}
827	<	lastRet = -1;
827	>	return t;
828	>	}
829	>
830	>	public DeqSpliterator trySplit() {
831	>	final Object[] es = elements;
832	>	final int i, n;
833	>	return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
834	>	? null
835	>	: new DeqSpliterator(i, cursor = add(i, n, es.length));
836	>	}
837	>
838	>	public void forEachRemaining(Consumer<? super E> action) {
839	>	if (action == null)
840	>	throw new NullPointerException();
841	>	final int end = getFence(), cursor = this.cursor;
842	>	final Object[] es = elements;
843	>	if (cursor != end) {
844	>	this.cursor = end;
845	>	// null check at both ends of range is sufficient
846	>	if (es[cursor] == null || es[dec(end, es.length)] == null)
847	>	throw new ConcurrentModificationException();
848	>	for (int i = cursor, to = (i <= end) ? end : es.length;
849	>	; i = 0, to = end) {
850	>	for (; i < to; i++)
851	>	action.accept(elementAt(es, i));
852	>	if (to == end) break;
853	>	}
854	>	}
855	>	}
856	>
857	>	public boolean tryAdvance(Consumer<? super E> action) {
858	>	if (action == null)
859	>	throw new NullPointerException();
860	>	int t, i;
861	>	if ((t = fence) < 0) t = getFence();
862	>	if (t == (i = cursor))
863	>	return false;
864	>	final Object[] es;
865	>	action.accept(nonNullElementAt(es = elements, i));
866	>	cursor = inc(i, es.length);
867	>	return true;
868	>	}
869	>
870	>	public long estimateSize() {
871	>	return sub(getFence(), cursor, elements.length);
872	>	}
873	>
874	>	public int characteristics() {
875	>	return Spliterator.NONNULL
876	>	| Spliterator.ORDERED
877	>	| Spliterator.SIZED
878	>	| Spliterator.SUBSIZED;
879	>	}
880	>	}
881	>
882	>	public void forEach(Consumer<? super E> action) {
883	>	Objects.requireNonNull(action);
884	>	final Object[] es = elements;
885	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
886	>	; i = 0, to = end) {
887	>	for (; i < to; i++)
888	>	action.accept(elementAt(es, i));
889	>	if (to == end) {
890	>	if (end != tail) throw new ConcurrentModificationException();
891	>	break;
892	>	}
893	>	}
894	>	// checkInvariants();
895	>	}
896	>
897	>	/**
898	>	* Replaces each element of this deque with the result of applying the
899	>	* operator to that element, as specified by {@link List#replaceAll}.
900	>	*
901	>	* @param operator the operator to apply to each element
902	>	* @since TBD
903	>	*/
904	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
905	>	Objects.requireNonNull(operator);
906	>	final Object[] es = elements;
907	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
908	>	; i = 0, to = end) {
909	>	for (; i < to; i++)
910	>	es[i] = operator.apply(elementAt(es, i));
911	>	if (to == end) {
912	>	if (end != tail) throw new ConcurrentModificationException();
913	>	break;
914	>	}
915	>	}
916	>	// checkInvariants();
917	>	}
918	>
919	>	/**
920	>	* @throws NullPointerException {@inheritDoc}
921	>	*/
922	>	public boolean removeIf(Predicate<? super E> filter) {
923	>	Objects.requireNonNull(filter);
924	>	return bulkRemove(filter);
925	>	}
926	>
927	>	/**
928	>	* @throws NullPointerException {@inheritDoc}
929	>	*/
930	>	public boolean removeAll(Collection<?> c) {
931	>	Objects.requireNonNull(c);
932	>	return bulkRemove(e -> c.contains(e));
933	>	}
934	>
935	>	/**
936	>	* @throws NullPointerException {@inheritDoc}
937	>	*/
938	>	public boolean retainAll(Collection<?> c) {
939	>	Objects.requireNonNull(c);
940	>	return bulkRemove(e -> !c.contains(e));
941	>	}
942	>
943	>	/** Implementation of bulk remove methods. */
944	>	private boolean bulkRemove(Predicate<? super E> filter) {
945	>	// checkInvariants();
946	>	final Object[] es = elements;
947	>	// Optimize for initial run of survivors
948	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
949	>	; i = 0, to = end) {
950	>	for (; i < to; i++)
951	>	if (filter.test(elementAt(es, i)))
952	>	return bulkRemoveModified(filter, i, to);
953	>	if (to == end) {
954	>	if (end != tail) throw new ConcurrentModificationException();
955	>	break;
956	>	}
957	>	}
958	>	return false;
959	>	}
960	>
961	>	/**
962	>	* Helper for bulkRemove, in case of at least one deletion.
963	>	* @param i valid index of first element to be deleted
964	>	*/
965	>	private boolean bulkRemoveModified(
966	>	Predicate<? super E> filter, int i, int to) {
967	>	final Object[] es = elements;
968	>	final int capacity = es.length;
969	>	// a two-finger algorithm, with hare i reading, tortoise j writing
970	>	int j = i++;
971	>	final int end = tail;
972	>	try {
973	>	for (;; j = 0) {    // j rejoins i on second leg
974	>	E e;
975	>	// In this loop, i and j are on the same leg, with i > j
976	>	for (; i < to; i++)
977	>	if (!filter.test(e = elementAt(es, i)))
978	>	es[j++] = e;
979	>	if (to == end) break;
980	>	// In this loop, j is on the first leg, i on the second
981	>	for (i = 0, to = end; i < to && j < capacity; i++)
982	>	if (!filter.test(e = elementAt(es, i)))
983	>	es[j++] = e;
984	>	if (i >= to) {
985	>	if (j == capacity) j = 0; // "corner" case
986	>	break;
987	>	}
988	>	}
989	>	return true;
990	>	} catch (Throwable ex) {
991	>	// copy remaining elements
992	>	for (; i != end; i = inc(i, capacity), j = inc(j, capacity))
993	>	es[j] = es[i];
994	>	throw ex;
995	>	} finally {
996	>	if (end != tail) throw new ConcurrentModificationException();
997	>	circularClear(es, tail = j, end);
998	>	// checkInvariants();
999		}
1000		}
1001
#	Line 671 | Line 1009 | public class ArrayDeque<E> extends Abstr
1009		*/
1010		public boolean contains(Object o) {
1011		if (o != null) {
1012	<	int mask = elements.length - 1;
1013	<	int i = head;
1014	<	for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
1015	<	if (o.equals(x))
1016	<	return true;
1012	>	final Object[] es = elements;
1013	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1014	>	; i = 0, to = end) {
1015	>	for (; i < to; i++)
1016	>	if (o.equals(es[i]))
1017	>	return true;
1018	>	if (to == end) break;
1019		}
1020		}
1021		return false;
#	Line 703 | Line 1043 | public class ArrayDeque<E> extends Abstr
1043		* The deque will be empty after this call returns.
1044		*/
1045		public void clear() {
1046	<	int h = head;
1047	<	int t = tail;
1048	<	if (h != t) { // clear all cells
1049	<	head = tail = 0;
1050	<	int i = h;
1051	<	int mask = elements.length - 1;
1052	<	do {
1053	<	elements[i] = null;
1054	<	i = (i + 1) & mask;
1055	<	} while (i != t);
1046	>	circularClear(elements, head, tail);
1047	>	head = tail = 0;
1048	>	// checkInvariants();
1049	>	}
1050	>
1051	>	/**
1052	>	* Nulls out slots starting at array index i, upto index end.
1053	>	*/
1054	>	private static void circularClear(Object[] es, int i, int end) {
1055	>	for (int to = (i <= end) ? end : es.length;
1056	>	; i = 0, to = end) {
1057	>	Arrays.fill(es, i, to, null);
1058	>	if (to == end) break;
1059		}
1060		}
1061
#	Line 730 | Line 1073 | public class ArrayDeque<E> extends Abstr
1073		* @return an array containing all of the elements in this deque
1074		*/
1075		public Object[] toArray() {
1076	<	final int head = this.head;
1077	<	final int tail = this.tail;
1078	<	boolean wrap = (tail < head);
1079	<	int end = wrap ? tail + elements.length : tail;
1080	<	Object[] a = Arrays.copyOfRange(elements, head, end);
1081	<	if (wrap)
1082	<	System.arraycopy(elements, 0, a, elements.length - head, tail);
1076	>	return toArray(Object[].class);
1077	>	}
1078	>
1079	>	private <T> T[] toArray(Class<T[]> klazz) {
1080	>	final Object[] es = elements;
1081	>	final T[] a;
1082	>	final int size = size(), head = this.head, end;
1083	>	final int len = Math.min(size, es.length - head);
1084	>	if ((end = head + size) >= 0) {
1085	>	a = Arrays.copyOfRange(es, head, end, klazz);
1086	>	} else {
1087	>	// integer overflow!
1088	>	a = Arrays.copyOfRange(es, 0, size, klazz);
1089	>	System.arraycopy(es, head, a, 0, len);
1090	>	}
1091	>	if (tail < head)
1092	>	System.arraycopy(es, 0, a, len, tail);
1093		return a;
1094		}
1095
#	Line 778 | Line 1131 | public class ArrayDeque<E> extends Abstr
1131		*/
1132		@SuppressWarnings("unchecked")
1133		public <T> T[] toArray(T[] a) {
1134	<	final int head = this.head;
1135	<	final int tail = this.tail;
1136	<	boolean wrap = (tail < head);
1137	<	int size = (tail - head) + (wrap ? elements.length : 0);
1138	<	int firstLeg = size - (wrap ? tail : 0);
1139	<	int len = a.length;
1140	<	if (size > len) {
1141	<	a = (T[]) Arrays.copyOfRange(elements, head, head + size,
789	<	a.getClass());
790	<	} else {
791	<	System.arraycopy(elements, head, a, 0, firstLeg);
792	<	if (size < len)
793	<	a[size] = null;
1134	>	final int size;
1135	>	if ((size = size()) > a.length)
1136	>	return toArray((Class<T[]>) a.getClass());
1137	>	final Object[] es = elements;
1138	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1139	>	; i = 0, len = tail) {
1140	>	System.arraycopy(es, i, a, j, len);
1141	>	if ((j += len) == size) break;
1142		}
1143	<	if (wrap)
1144	<	System.arraycopy(elements, 0, a, firstLeg, tail);
1143	>	if (size < a.length)
1144	>	a[size] = null;
1145		return a;
1146		}
1147
#	Line 834 | Line 1182 | public class ArrayDeque<E> extends Abstr
1182		s.writeInt(size());
1183
1184		// Write out elements in order.
1185	<	int mask = elements.length - 1;
1186	<	for (int i = head; i != tail; i = (i + 1) & mask)
1187	<	s.writeObject(elements[i]);
1185	>	final Object[] es = elements;
1186	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1187	>	; i = 0, to = end) {
1188	>	for (; i < to; i++)
1189	>	s.writeObject(es[i]);
1190	>	if (to == end) break;
1191	>	}
1192		}
1193
1194		/**
#	Line 852 | Line 1204 | public class ArrayDeque<E> extends Abstr
1204
1205		// Read in size and allocate array
1206		int size = s.readInt();
1207	<	allocateElements(size);
1208	<	head = 0;
857	<	tail = size;
1207	>	elements = new Object[size + 1];
1208	>	this.tail = size;
1209
1210		// Read in all elements in the proper order.
1211		for (int i = 0; i < size; i++)
1212		elements[i] = s.readObject();
1213		}
1214
1215	<	/**
1216	<	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1217	<	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
1218	<	* deque.
1219	<	*
1220	<	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1221	<	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
1222	<	* {@link Spliterator#NONNULL}.  Overriding implementations should document
1223	<	* the reporting of additional characteristic values.
1224	<	*
1225	<	* @return a {@code Spliterator} over the elements in this deque
1226	<	* @since 1.8
1227	<	*/
1228	<	public Spliterator<E> spliterator() {
1229	<	return new DeqSpliterator<>(this, -1, -1);
1230	<	}
1231	<
881	<	static final class DeqSpliterator<E> implements Spliterator<E> {
882	<	private final ArrayDeque<E> deq;
883	<	private int fence;  // -1 until first use
884	<	private int index;  // current index, modified on traverse/split
885	<
886	<	/** Creates new spliterator covering the given array and range */
887	<	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
888	<	this.deq = deq;
889	<	this.index = origin;
890	<	this.fence = fence;
891	<	}
892	<
893	<	private int getFence() { // force initialization
894	<	int t;
895	<	if ((t = fence) < 0) {
896	<	t = fence = deq.tail;
897	<	index = deq.head;
898	<	}
899	<	return t;
900	<	}
901	<
902	<	public Spliterator<E> trySplit() {
903	<	int t = getFence(), h = index, n = deq.elements.length;
904	<	if (h != t && ((h + 1) & (n - 1)) != t) {
905	<	if (h > t)
906	<	t += n;
907	<	int m = ((h + t) >>> 1) & (n - 1);
908	<	return new DeqSpliterator<>(deq, h, index = m);
909	<	}
910	<	return null;
911	<	}
912	<
913	<	public void forEachRemaining(Consumer<? super E> consumer) {
914	<	if (consumer == null)
915	<	throw new NullPointerException();
916	<	Object[] a = deq.elements;
917	<	int m = a.length - 1, f = getFence(), i = index;
918	<	index = f;
919	<	while (i != f) {
920	<	@SuppressWarnings("unchecked") E e = (E)a[i];
921	<	i = (i + 1) & m;
922	<	if (e == null)
923	<	throw new ConcurrentModificationException();
924	<	consumer.accept(e);
925	<	}
926	<	}
927	<
928	<	public boolean tryAdvance(Consumer<? super E> consumer) {
929	<	if (consumer == null)
930	<	throw new NullPointerException();
931	<	Object[] a = deq.elements;
932	<	int m = a.length - 1, f = getFence(), i = index;
933	<	if (i != f) {
934	<	@SuppressWarnings("unchecked") E e = (E)a[i];
935	<	index = (i + 1) & m;
936	<	if (e == null)
937	<	throw new ConcurrentModificationException();
938	<	consumer.accept(e);
939	<	return true;
940	<	}
941	<	return false;
942	<	}
943	<
944	<	public long estimateSize() {
945	<	int n = getFence() - index;
946	<	if (n < 0)
947	<	n += deq.elements.length;
948	<	return (long) n;
949	<	}
950	<
951	<	@Override
952	<	public int characteristics() {
953	<	return Spliterator.ORDERED | Spliterator.SIZED |
954	<	Spliterator.NONNULL | Spliterator.SUBSIZED;
1215	>	/** debugging */
1216	>	void checkInvariants() {
1217	>	try {
1218	>	int capacity = elements.length;
1219	>	// assert head >= 0 && head < capacity;
1220	>	// assert tail >= 0 && tail < capacity;
1221	>	// assert capacity > 0;
1222	>	// assert size() < capacity;
1223	>	// assert head == tail || elements[head] != null;
1224	>	// assert elements[tail] == null;
1225	>	// assert head == tail || elements[dec(tail, capacity)] != null;
1226	>	} catch (Throwable t) {
1227	>	System.err.printf("head=%d tail=%d capacity=%d%n",
1228	>	head, tail, elements.length);
1229	>	System.err.printf("elements=%s%n",
1230	>	Arrays.toString(elements));
1231	>	throw t;
1232		}
1233		}
1234

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