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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.69 by jsr166, Fri Sep 18 02:06:44 2015 UTC vs.
Revision 1.123 by jsr166, Sat Nov 26 14:16:18 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.  Having only
72	+	* one hot inner loop body instead of two or three eases human
73	+	* maintenance and encourages VM loop inlining into the caller.
74	+	*/
75	+
76		/**
77		* The array in which the elements of the deque are stored.
78	<	* The capacity of the deque is the length of this array, which is
79	<	* 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.
78	>	* All array cells not holding deque elements are always null.
79	>	* The array always has at least one null slot (at tail).
80		*/
81	<	transient Object[] elements; // non-private to simplify nested class access
81	>	transient Object[] elements;
82
83		/**
84		* The index of the element at the head of the deque (which is the
85		* element that would be removed by remove() or pop()); or an
86	<	* arbitrary number equal to tail if the deque is empty.
86	>	* arbitrary number 0 <= head < elements.length equal to tail if
87	>	* the deque is empty.
88		*/
89		transient int head;
90
91		/**
92		* The index at which the next element would be added to the tail
93	<	* of the deque (via addLast(E), add(E), or push(E)).
93	>	* of the deque (via addLast(E), add(E), or push(E));
94	>	* elements[tail] is always null.
95		*/
96		transient int tail;
97
98		/**
99	<	* The minimum capacity that we'll use for a newly created deque.
100	<	* Must be a power of 2.
99	>	* The maximum size of array to allocate.
100	>	* Some VMs reserve some header words in an array.
101	>	* Attempts to allocate larger arrays may result in
102	>	* OutOfMemoryError: Requested array size exceeds VM limit
103		*/
104	<	private static final int MIN_INITIAL_CAPACITY = 8;
104	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
105
106	<	// ******  Array allocation and resizing utilities ******
106	>	/**
107	>	* Increases the capacity of this deque by at least the given amount.
108	>	*
109	>	* @param needed the required minimum extra capacity; must be positive
110	>	*/
111	>	private void grow(int needed) {
112	>	// overflow-conscious code
113	>	final int oldCapacity = elements.length;
114	>	int newCapacity;
115	>	// Double capacity if small; else grow by 50%
116	>	int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
117	>	if (jump < needed
118	>	|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
119	>	newCapacity = newCapacity(needed, jump);
120	>	elements = Arrays.copyOf(elements, newCapacity);
121	>	// Exceptionally, here tail == head needs to be disambiguated
122	>	if (tail < head || (tail == head && elements[head] != null)) {
123	>	// wrap around; slide first leg forward to end of array
124	>	int newSpace = newCapacity - oldCapacity;
125	>	System.arraycopy(elements, head,
126	>	elements, head + newSpace,
127	>	oldCapacity - head);
128	>	Arrays.fill(elements, head, head + newSpace, null);
129	>	head += newSpace;
130	>	}
131	>	// checkInvariants();
132	>	}
133	>
134	>	/** Capacity calculation for edge conditions, especially overflow. */
135	>	private int newCapacity(int needed, int jump) {
136	>	final int oldCapacity = elements.length, minCapacity;
137	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
138	>	if (minCapacity < 0)
139	>	throw new IllegalStateException("Sorry, deque too big");
140	>	return Integer.MAX_VALUE;
141	>	}
142	>	if (needed > jump)
143	>	return minCapacity;
144	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
145	>	? oldCapacity + jump
146	>	: MAX_ARRAY_SIZE;
147	>	}
148
149		/**
150	<	* Allocates empty array to hold the given number of elements.
151	<	*
152	<	* @param numElements  the number of elements to hold
153	<	*/
154	<	private void allocateElements(int numElements) {
155	<	int initialCapacity = MIN_INITIAL_CAPACITY;
156	<	// Find the best power of two to hold elements.
157	<	// Tests "<=" because arrays aren't kept full.
158	<	if (numElements >= initialCapacity) {
159	<	initialCapacity = numElements;
160	<	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];
150	>	* Increases the internal storage of this collection, if necessary,
151	>	* to ensure that it can hold at least the given number of elements.
152	>	*
153	>	* @param minCapacity the desired minimum capacity
154	>	* @since TBD
155	>	*/
156	>	/* public */ void ensureCapacity(int minCapacity) {
157	>	int needed;
158	>	if ((needed = (minCapacity + 1 - elements.length)) > 0)
159	>	grow(needed);
160	>	// checkInvariants();
161		}
162
163		/**
164	<	* Doubles the capacity of this deque.  Call only when full, i.e.,
165	<	* when head and tail have wrapped around to become equal.
166	<	*/
167	<	private void doubleCapacity() {
168	<	assert head == tail;
169	<	int p = head;
170	<	int n = elements.length;
171	<	int r = n - p; // number of elements to the right of p
172	<	int newCapacity = n << 1;
173	<	if (newCapacity < 0)
174	<	throw new IllegalStateException("Sorry, deque too big");
175	<	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;
164	>	* Minimizes the internal storage of this collection.
165	>	*
166	>	* @since TBD
167	>	*/
168	>	/* public */ void trimToSize() {
169	>	int size;
170	>	if ((size = size()) + 1 < elements.length) {
171	>	elements = toArray(new Object[size + 1]);
172	>	head = 0;
173	>	tail = size;
174	>	}
175	>	// checkInvariants();
176		}
177
178		/**
#	Line 147 | Line 187 | public class ArrayDeque<E> extends Abstr
187		* Constructs an empty array deque with an initial capacity
188		* sufficient to hold the specified number of elements.
189		*
190	<	* @param numElements  lower bound on initial capacity of the deque
190	>	* @param numElements lower bound on initial capacity of the deque
191		*/
192		public ArrayDeque(int numElements) {
193	<	allocateElements(numElements);
193	>	elements =
194	>	new Object[(numElements < 1) ? 1 :
195	>	(numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE :
196	>	numElements + 1];
197		}
198
199		/**
#	Line 164 | Line 207 | public class ArrayDeque<E> extends Abstr
207		* @throws NullPointerException if the specified collection is null
208		*/
209		public ArrayDeque(Collection<? extends E> c) {
210	<	allocateElements(c.size());
210	>	this(c.size());
211		addAll(c);
212		}
213
214	+	/**
215	+	* Increments i, mod modulus.
216	+	* Precondition and postcondition: 0 <= i < modulus.
217	+	*/
218	+	static final int inc(int i, int modulus) {
219	+	if (++i >= modulus) i = 0;
220	+	return i;
221	+	}
222	+
223	+	/**
224	+	* Decrements i, mod modulus.
225	+	* Precondition and postcondition: 0 <= i < modulus.
226	+	*/
227	+	static final int dec(int i, int modulus) {
228	+	if (--i < 0) i = modulus - 1;
229	+	return i;
230	+	}
231	+
232	+	/**
233	+	* Circularly adds the given distance to index i, mod modulus.
234	+	* Precondition: 0 <= i < modulus, 0 <= distance <= modulus.
235	+	* @return index 0 <= i < modulus
236	+	*/
237	+	static final int add(int i, int distance, int modulus) {
238	+	if ((i += distance) - modulus >= 0) distance -= modulus;
239	+	return i;
240	+	}
241	+
242	+	/**
243	+	* Subtracts j from i, mod modulus.
244	+	* Index i must be logically ahead of index j.
245	+	* Precondition: 0 <= i < modulus, 0 <= j < modulus.
246	+	* @return the "circular distance" from j to i; corner case i == j
247	+	* is diambiguated to "empty", returning 0.
248	+	*/
249	+	static final int sub(int i, int j, int modulus) {
250	+	if ((i -= j) < 0) i += modulus;
251	+	return i;
252	+	}
253	+
254	+	/**
255	+	* Returns element at array index i.
256	+	* This is a slight abuse of generics, accepted by javac.
257	+	*/
258	+	@SuppressWarnings("unchecked")
259	+	static final <E> E elementAt(Object[] es, int i) {
260	+	return (E) es[i];
261	+	}
262	+
263	+	/**
264	+	* A version of elementAt that checks for null elements.
265	+	* This check doesn't catch all possible comodifications,
266	+	* but does catch ones that corrupt traversal.
267	+	*/
268	+	static final <E> E nonNullElementAt(Object[] es, int i) {
269	+	@SuppressWarnings("unchecked") E e = (E) es[i];
270	+	if (e == null)
271	+	throw new ConcurrentModificationException();
272	+	return e;
273	+	}
274	+
275		// The main insertion and extraction methods are addFirst,
276		// addLast, pollFirst, pollLast. The other methods are defined in
277		// terms of these.
#	Line 181 | Line 285 | public class ArrayDeque<E> extends Abstr
285		public void addFirst(E e) {
286		if (e == null)
287		throw new NullPointerException();
288	<	elements[head = (head - 1) & (elements.length - 1)] = e;
288	>	final Object[] es = elements;
289	>	es[head = dec(head, es.length)] = e;
290		if (head == tail)
291	<	doubleCapacity();
291	>	grow(1);
292	>	// checkInvariants();
293		}
294
295		/**
#	Line 197 | Line 303 | public class ArrayDeque<E> extends Abstr
303		public void addLast(E e) {
304		if (e == null)
305		throw new NullPointerException();
306	<	elements[tail] = e;
307	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
308	<	doubleCapacity();
306	>	final Object[] es = elements;
307	>	es[tail] = e;
308	>	if (head == (tail = inc(tail, es.length)))
309	>	grow(1);
310	>	// checkInvariants();
311	>	}
312	>
313	>	/**
314	>	* Adds all of the elements in the specified collection at the end
315	>	* of this deque, as if by calling {@link #addLast} on each one,
316	>	* in the order that they are returned by the collection's
317	>	* iterator.
318	>	*
319	>	* @param c the elements to be inserted into this deque
320	>	* @return {@code true} if this deque changed as a result of the call
321	>	* @throws NullPointerException if the specified collection or any
322	>	*         of its elements are null
323	>	*/
324	>	public boolean addAll(Collection<? extends E> c) {
325	>	final int s, needed;
326	>	if ((needed = (s = size()) + c.size() + 1 - elements.length) > 0)
327	>	grow(needed);
328	>	c.forEach(this::addLast);
329	>	// checkInvariants();
330	>	return size() > s;
331		}
332
333		/**
#	Line 230 | Line 358 | public class ArrayDeque<E> extends Abstr
358		* @throws NoSuchElementException {@inheritDoc}
359		*/
360		public E removeFirst() {
361	<	E x = pollFirst();
362	<	if (x == null)
361	>	E e = pollFirst();
362	>	if (e == null)
363		throw new NoSuchElementException();
364	<	return x;
364	>	// checkInvariants();
365	>	return e;
366		}
367
368		/**
369		* @throws NoSuchElementException {@inheritDoc}
370		*/
371		public E removeLast() {
372	<	E x = pollLast();
373	<	if (x == null)
372	>	E e = pollLast();
373	>	if (e == null)
374		throw new NoSuchElementException();
375	<	return x;
375	>	// checkInvariants();
376	>	return e;
377		}
378
379		public E pollFirst() {
380	<	final Object[] elements = this.elements;
381	<	final int h = head;
382	<	@SuppressWarnings("unchecked")
383	<	E result = (E) elements[h];
384	<	// Element is null if deque empty
385	<	if (result != null) {
256	<	elements[h] = null; // Must null out slot
257	<	head = (h + 1) & (elements.length - 1);
380	>	final Object[] es;
381	>	final int h;
382	>	E e = elementAt(es = elements, h = head);
383	>	if (e != null) {
384	>	es[h] = null;
385	>	head = inc(h, es.length);
386		}
387	<	return result;
387	>	// checkInvariants();
388	>	return e;
389		}
390
391		public E pollLast() {
392	<	final Object[] elements = this.elements;
393	<	final int t = (tail - 1) & (elements.length - 1);
394	<	@SuppressWarnings("unchecked")
395	<	E result = (E) elements[t];
396	<	if (result != null) {
397	<	elements[t] = null;
398	<	tail = t;
270	<	}
271	<	return result;
392	>	final Object[] es;
393	>	final int t;
394	>	E e = elementAt(es = elements, t = dec(tail, es.length));
395	>	if (e != null)
396	>	es[tail = t] = null;
397	>	// checkInvariants();
398	>	return e;
399		}
400
401		/**
402		* @throws NoSuchElementException {@inheritDoc}
403		*/
404		public E getFirst() {
405	<	@SuppressWarnings("unchecked")
406	<	E result = (E) elements[head];
280	<	if (result == null)
405	>	E e = elementAt(elements, head);
406	>	if (e == null)
407		throw new NoSuchElementException();
408	<	return result;
408	>	// checkInvariants();
409	>	return e;
410		}
411
412		/**
413		* @throws NoSuchElementException {@inheritDoc}
414		*/
415		public E getLast() {
416	<	@SuppressWarnings("unchecked")
417	<	E result = (E) elements[(tail - 1) & (elements.length - 1)];
418	<	if (result == null)
416	>	final Object[] es = elements;
417	>	E e = elementAt(es, dec(tail, es.length));
418	>	if (e == null)
419		throw new NoSuchElementException();
420	<	return result;
420	>	// checkInvariants();
421	>	return e;
422		}
423
296	–	@SuppressWarnings("unchecked")
424		public E peekFirst() {
425	<	// elements[head] is null if deque empty
426	<	return (E) elements[head];
425	>	// checkInvariants();
426	>	return elementAt(elements, head);
427		}
428
302	–	@SuppressWarnings("unchecked")
429		public E peekLast() {
430	<	return (E) elements[(tail - 1) & (elements.length - 1)];
430	>	// checkInvariants();
431	>	final Object[] es;
432	>	return elementAt(es = elements, dec(tail, es.length));
433		}
434
435		/**
#	Line 318 | Line 446 | public class ArrayDeque<E> extends Abstr
446		*/
447		public boolean removeFirstOccurrence(Object o) {
448		if (o != null) {
449	<	int mask = elements.length - 1;
450	<	int i = head;
451	<	for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
452	<	if (o.equals(x)) {
453	<	delete(i);
454	<	return true;
455	<	}
449	>	final Object[] es = elements;
450	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
451	>	; i = 0, to = end) {
452	>	for (; i < to; i++)
453	>	if (o.equals(es[i])) {
454	>	delete(i);
455	>	return true;
456	>	}
457	>	if (to == end) break;
458		}
459		}
460		return false;
#	Line 344 | Line 474 | public class ArrayDeque<E> extends Abstr
474		*/
475		public boolean removeLastOccurrence(Object o) {
476		if (o != null) {
477	<	int mask = elements.length - 1;
478	<	int i = (tail - 1) & mask;
479	<	for (Object x; (x = elements[i]) != null; i = (i - 1) & mask) {
480	<	if (o.equals(x)) {
481	<	delete(i);
482	<	return true;
483	<	}
477	>	final Object[] es = elements;
478	>	for (int i = tail, end = head, to = (i >= end) ? end : 0;
479	>	; i = es.length, to = end) {
480	>	for (i--; i > to - 1; i--)
481	>	if (o.equals(es[i])) {
482	>	delete(i);
483	>	return true;
484	>	}
485	>	if (to == end) break;
486		}
487		}
488		return false;
#	Line 470 | Line 602 | public class ArrayDeque<E> extends Abstr
602		return removeFirst();
603		}
604
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	–
605		/**
606	<	* Removes the element at the specified position in the elements array,
607	<	* adjusting head and tail as necessary.  This can result in motion of
608	<	* elements backwards or forwards in the array.
606	>	* Removes the element at the specified position in the elements array.
607	>	* This can result in forward or backwards motion of array elements.
608	>	* We optimize for least element motion.
609		*
610		* <p>This method is called delete rather than remove to emphasize
611		* that its semantics differ from those of {@link List#remove(int)}.
612		*
613	<	* @return true if elements moved backwards
613	>	* @return true if elements near tail moved backwards
614		*/
615	<	private boolean delete(int i) {
616	<	checkInvariants();
617	<	final Object[] elements = this.elements;
618	<	final int mask = elements.length - 1;
619	<	final int h = head;
620	<	final int t = tail;
621	<	final int front = (i - h) & mask;
622	<	final int back  = (t - i) & mask;
623	<
500	<	// Invariant: head <= i < tail mod circularity
501	<	if (front >= ((t - h) & mask))
502	<	throw new ConcurrentModificationException();
503	<
504	<	// Optimize for least element motion
615	>	boolean delete(int i) {
616	>	// checkInvariants();
617	>	final Object[] es = elements;
618	>	final int capacity = es.length;
619	>	final int h, t;
620	>	// number of elements before to-be-deleted elt
621	>	final int front = sub(i, h = head, capacity);
622	>	// number of elements after to-be-deleted elt
623	>	final int back = sub(t = tail, i, capacity) - 1;
624		if (front < back) {
625	+	// move front elements forwards
626		if (h <= i) {
627	<	System.arraycopy(elements, h, elements, h + 1, front);
627	>	System.arraycopy(es, h, es, h + 1, front);
628		} else { // Wrap around
629	<	System.arraycopy(elements, 0, elements, 1, i);
630	<	elements[0] = elements[mask];
631	<	System.arraycopy(elements, h, elements, h + 1, mask - h);
629	>	System.arraycopy(es, 0, es, 1, i);
630	>	es[0] = es[capacity - 1];
631	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
632		}
633	<	elements[h] = null;
634	<	head = (h + 1) & mask;
633	>	es[h] = null;
634	>	head = inc(h, capacity);
635	>	// checkInvariants();
636		return false;
637		} else {
638	<	if (i < t) { // Copy the null tail as well
639	<	System.arraycopy(elements, i + 1, elements, i, back);
640	<	tail = t - 1;
638	>	// move back elements backwards
639	>	tail = dec(t, capacity);
640	>	if (i <= tail) {
641	>	System.arraycopy(es, i + 1, es, i, back);
642		} else { // Wrap around
643	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
644	<	elements[mask] = elements[0];
645	<	System.arraycopy(elements, 1, elements, 0, t);
524	<	tail = (t - 1) & mask;
643	>	System.arraycopy(es, i + 1, es, i, capacity - (i + 1));
644	>	es[capacity - 1] = es[0];
645	>	System.arraycopy(es, 1, es, 0, t - 1);
646		}
647	+	es[tail] = null;
648	+	// checkInvariants();
649		return true;
650		}
651		}
#	Line 535 | Line 658 | public class ArrayDeque<E> extends Abstr
658		* @return the number of elements in this deque
659		*/
660		public int size() {
661	<	return (tail - head) & (elements.length - 1);
661	>	return sub(tail, head, elements.length);
662		}
663
664		/**
#	Line 564 | Line 687 | public class ArrayDeque<E> extends Abstr
687		}
688
689		private class DeqIterator implements Iterator<E> {
690	<	/**
691	<	* Index of element to be returned by subsequent call to next.
569	<	*/
570	<	private int cursor = head;
690	>	/** Index of element to be returned by subsequent call to next. */
691	>	int cursor;
692
693	<	/**
694	<	* Tail recorded at construction (also in remove), to stop
574	<	* iterator and also to check for comodification.
575	<	*/
576	<	private int fence = tail;
693	>	/** Number of elements yet to be returned. */
694	>	int remaining = size();
695
696		/**
697		* Index of element returned by most recent call to next.
698		* Reset to -1 if element is deleted by a call to remove.
699		*/
700	<	private int lastRet = -1;
700	>	int lastRet = -1;
701
702	<	public boolean hasNext() {
703	<	return cursor != fence;
702	>	DeqIterator() { cursor = head; }
703	>
704	>	public final boolean hasNext() {
705	>	return remaining > 0;
706		}
707
708		public E next() {
709	<	if (cursor == fence)
709	>	if (remaining <= 0)
710		throw new NoSuchElementException();
711	<	@SuppressWarnings("unchecked")
712	<	E result = (E) elements[cursor];
713	<	// This check doesn't catch all possible comodifications,
714	<	// but does catch the ones that corrupt traversal
715	<	if (tail != fence || result == null)
596	<	throw new ConcurrentModificationException();
597	<	lastRet = cursor;
598	<	cursor = (cursor + 1) & (elements.length - 1);
599	<	return result;
711	>	final Object[] es = elements;
712	>	E e = nonNullElementAt(es, cursor);
713	>	cursor = inc(lastRet = cursor, es.length);
714	>	remaining--;
715	>	return e;
716		}
717
718	<	public void remove() {
718	>	void postDelete(boolean leftShifted) {
719	>	if (leftShifted)
720	>	cursor = dec(cursor, elements.length);
721	>	}
722	>
723	>	public final void remove() {
724		if (lastRet < 0)
725		throw new IllegalStateException();
726	<	if (delete(lastRet)) { // if left-shifted, undo increment in next()
606	<	cursor = (cursor - 1) & (elements.length - 1);
607	<	fence = tail;
608	<	}
726	>	postDelete(delete(lastRet));
727		lastRet = -1;
728		}
729
730		public void forEachRemaining(Consumer<? super E> action) {
731		Objects.requireNonNull(action);
732	<	Object[] a = elements;
733	<	int m = a.length - 1, f = fence, i = cursor;
734	<	cursor = f;
735	<	while (i != f) {
736	<	@SuppressWarnings("unchecked") E e = (E)a[i];
737	<	i = (i + 1) & m;
738	<	if (e == null)
739	<	throw new ConcurrentModificationException();
740	<	action.accept(e);
732	>	int r;
733	>	if ((r = remaining) <= 0)
734	>	return;
735	>	remaining = 0;
736	>	final Object[] es = elements;
737	>	if (es[cursor] == null || sub(tail, cursor, es.length) != r)
738	>	throw new ConcurrentModificationException();
739	>	for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
740	>	; i = 0, to = end) {
741	>	for (; i < to; i++)
742	>	action.accept(elementAt(es, i));
743	>	if (to == end) {
744	>	if (end != tail)
745	>	throw new ConcurrentModificationException();
746	>	lastRet = dec(end, es.length);
747	>	break;
748	>	}
749	>	}
750	>	}
751	>	}
752	>
753	>	private class DescendingIterator extends DeqIterator {
754	>	DescendingIterator() { cursor = dec(tail, elements.length); }
755	>
756	>	public final E next() {
757	>	if (remaining <= 0)
758	>	throw new NoSuchElementException();
759	>	final Object[] es = elements;
760	>	E e = nonNullElementAt(es, cursor);
761	>	cursor = dec(lastRet = cursor, es.length);
762	>	remaining--;
763	>	return e;
764	>	}
765	>
766	>	void postDelete(boolean leftShifted) {
767	>	if (!leftShifted)
768	>	cursor = inc(cursor, elements.length);
769	>	}
770	>
771	>	public final void forEachRemaining(Consumer<? super E> action) {
772	>	Objects.requireNonNull(action);
773	>	int r;
774	>	if ((r = remaining) <= 0)
775	>	return;
776	>	remaining = 0;
777	>	final Object[] es = elements;
778	>	if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
779	>	throw new ConcurrentModificationException();
780	>	for (int i = cursor, end = head, to = (i >= end) ? end : 0;
781	>	; i = es.length - 1, to = end) {
782	>	// hotspot generates faster code than for: i >= to !
783	>	for (; i > to - 1; i--)
784	>	action.accept(elementAt(es, i));
785	>	if (to == end) {
786	>	if (end != head)
787	>	throw new ConcurrentModificationException();
788	>	lastRet = end;
789	>	break;
790	>	}
791		}
792		}
793		}
794
795		/**
796	<	* This class is nearly a mirror-image of DeqIterator, using tail
797	<	* instead of head for initial cursor, and head instead of tail
798	<	* for fence.
796	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
797	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
798	>	* deque.
799	>	*
800	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
801	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
802	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
803	>	* the reporting of additional characteristic values.
804	>	*
805	>	* @return a {@code Spliterator} over the elements in this deque
806	>	* @since 1.8
807		*/
808	<	private class DescendingIterator implements Iterator<E> {
809	<	private int cursor = tail;
810	<	private int fence = head;
811	<	private int lastRet = -1;
808	>	public Spliterator<E> spliterator() {
809	>	return new DeqSpliterator();
810	>	}
811	>
812	>	final class DeqSpliterator implements Spliterator<E> {
813	>	private int fence;      // -1 until first use
814	>	private int cursor;     // current index, modified on traverse/split
815
816	<	public boolean hasNext() {
817	<	return cursor != fence;
816	>	/** Constructs late-binding spliterator over all elements. */
817	>	DeqSpliterator() {
818	>	this.fence = -1;
819		}
820
821	<	public E next() {
822	<	if (cursor == fence)
823	<	throw new NoSuchElementException();
824	<	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;
821	>	/** Constructs spliterator over the given range. */
822	>	DeqSpliterator(int origin, int fence) {
823	>	this.cursor = origin;
824	>	this.fence = fence;
825		}
826
827	<	public void remove() {
828	<	if (lastRet < 0)
829	<	throw new IllegalStateException();
830	<	if (!delete(lastRet)) {
831	<	cursor = (cursor + 1) & (elements.length - 1);
832	<	fence = head;
827	>	/** Ensures late-binding initialization; then returns fence. */
828	>	private int getFence() { // force initialization
829	>	int t;
830	>	if ((t = fence) < 0) {
831	>	t = fence = tail;
832	>	cursor = head;
833		}
834	<	lastRet = -1;
834	>	return t;
835	>	}
836	>
837	>	public DeqSpliterator trySplit() {
838	>	final Object[] es = elements;
839	>	final int i, n;
840	>	return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
841	>	? null
842	>	: new DeqSpliterator(i, cursor = add(i, n, es.length));
843		}
844	+
845	+	public void forEachRemaining(Consumer<? super E> action) {
846	+	if (action == null)
847	+	throw new NullPointerException();
848	+	final int end = getFence(), cursor = this.cursor;
849	+	final Object[] es = elements;
850	+	if (cursor != end) {
851	+	this.cursor = end;
852	+	// null check at both ends of range is sufficient
853	+	if (es[cursor] == null || es[dec(end, es.length)] == null)
854	+	throw new ConcurrentModificationException();
855	+	for (int i = cursor, to = (i <= end) ? end : es.length;
856	+	; i = 0, to = end) {
857	+	for (; i < to; i++)
858	+	action.accept(elementAt(es, i));
859	+	if (to == end) break;
860	+	}
861	+	}
862	+	}
863	+
864	+	public boolean tryAdvance(Consumer<? super E> action) {
865	+	Objects.requireNonNull(action);
866	+	final Object[] es = elements;
867	+	if (fence < 0) { fence = tail; cursor = head; } // late-binding
868	+	final int i;
869	+	if ((i = cursor) == fence)
870	+	return false;
871	+	E e = nonNullElementAt(es, i);
872	+	cursor = inc(i, es.length);
873	+	action.accept(e);
874	+	return true;
875	+	}
876	+
877	+	public long estimateSize() {
878	+	return sub(getFence(), cursor, elements.length);
879	+	}
880	+
881	+	public int characteristics() {
882	+	return Spliterator.NONNULL
883	+	| Spliterator.ORDERED
884	+	| Spliterator.SIZED
885	+	| Spliterator.SUBSIZED;
886	+	}
887	+	}
888	+
889	+	public void forEach(Consumer<? super E> action) {
890	+	Objects.requireNonNull(action);
891	+	final Object[] es = elements;
892	+	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
893	+	; i = 0, to = end) {
894	+	for (; i < to; i++)
895	+	action.accept(elementAt(es, i));
896	+	if (to == end) {
897	+	if (end != tail) throw new ConcurrentModificationException();
898	+	break;
899	+	}
900	+	}
901	+	// checkInvariants();
902	+	}
903	+
904	+	/**
905	+	* Replaces each element of this deque with the result of applying the
906	+	* operator to that element, as specified by {@link List#replaceAll}.
907	+	*
908	+	* @param operator the operator to apply to each element
909	+	* @since TBD
910	+	*/
911	+	/* public */ void replaceAll(UnaryOperator<E> operator) {
912	+	Objects.requireNonNull(operator);
913	+	final Object[] es = elements;
914	+	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
915	+	; i = 0, to = end) {
916	+	for (; i < to; i++)
917	+	es[i] = operator.apply(elementAt(es, i));
918	+	if (to == end) {
919	+	if (end != tail) throw new ConcurrentModificationException();
920	+	break;
921	+	}
922	+	}
923	+	// checkInvariants();
924	+	}
925	+
926	+	/**
927	+	* @throws NullPointerException {@inheritDoc}
928	+	*/
929	+	public boolean removeIf(Predicate<? super E> filter) {
930	+	Objects.requireNonNull(filter);
931	+	return bulkRemove(filter);
932	+	}
933	+
934	+	/**
935	+	* @throws NullPointerException {@inheritDoc}
936	+	*/
937	+	public boolean removeAll(Collection<?> c) {
938	+	Objects.requireNonNull(c);
939	+	return bulkRemove(e -> c.contains(e));
940	+	}
941	+
942	+	/**
943	+	* @throws NullPointerException {@inheritDoc}
944	+	*/
945	+	public boolean retainAll(Collection<?> c) {
946	+	Objects.requireNonNull(c);
947	+	return bulkRemove(e -> !c.contains(e));
948	+	}
949	+
950	+	/** Implementation of bulk remove methods. */
951	+	private boolean bulkRemove(Predicate<? super E> filter) {
952	+	// checkInvariants();
953	+	final Object[] es = elements;
954	+	// Optimize for initial run of survivors
955	+	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
956	+	; i = 0, to = end) {
957	+	for (; i < to; i++)
958	+	if (filter.test(elementAt(es, i)))
959	+	return bulkRemoveModified(filter, i);
960	+	if (to == end) {
961	+	if (end != tail) throw new ConcurrentModificationException();
962	+	break;
963	+	}
964	+	}
965	+	return false;
966	+	}
967	+
968	+	// A tiny bit set implementation
969	+
970	+	private static long[] nBits(int n) {
971	+	return new long[((n - 1) >> 6) + 1];
972	+	}
973	+	private static void setBit(long[] bits, int i) {
974	+	bits[i >> 6] |= 1L << i;
975	+	}
976	+	private static boolean isClear(long[] bits, int i) {
977	+	return (bits[i >> 6] & (1L << i)) == 0;
978	+	}
979	+
980	+	/**
981	+	* Helper for bulkRemove, in case of at least one deletion.
982	+	* Tolerate predicates that reentrantly access the collection for
983	+	* read (but writers still get CME), so traverse once to find
984	+	* elements to delete, a second pass to physically expunge.
985	+	*
986	+	* @param beg valid index of first element to be deleted
987	+	*/
988	+	private boolean bulkRemoveModified(
989	+	Predicate<? super E> filter, final int beg) {
990	+	final Object[] es = elements;
991	+	final int capacity = es.length;
992	+	final int end = tail;
993	+	final long[] deathRow = nBits(sub(end, beg, capacity));
994	+	deathRow[0] = 1L;   // set bit 0
995	+	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
996	+	; i = 0, to = end, k -= capacity) {
997	+	for (; i < to; i++)
998	+	if (filter.test(elementAt(es, i)))
999	+	setBit(deathRow, i - k);
1000	+	if (to == end) break;
1001	+	}
1002	+	// a two-finger traversal, with hare i reading, tortoise w writing
1003	+	int w = beg;
1004	+	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1005	+	; w = 0) { // w rejoins i on second leg
1006	+	// In this loop, i and w are on the same leg, with i > w
1007	+	for (; i < to; i++)
1008	+	if (isClear(deathRow, i - k))
1009	+	es[w++] = es[i];
1010	+	if (to == end) break;
1011	+	// In this loop, w is on the first leg, i on the second
1012	+	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1013	+	if (isClear(deathRow, i - k))
1014	+	es[w++] = es[i];
1015	+	if (i >= to) {
1016	+	if (w == capacity) w = 0; // "corner" case
1017	+	break;
1018	+	}
1019	+	}
1020	+	if (end != tail) throw new ConcurrentModificationException();
1021	+	circularClear(es, tail = w, end);
1022	+	// checkInvariants();
1023	+	return true;
1024		}
1025
1026		/**
#	Line 671 | Line 1033 | public class ArrayDeque<E> extends Abstr
1033		*/
1034		public boolean contains(Object o) {
1035		if (o != null) {
1036	<	int mask = elements.length - 1;
1037	<	int i = head;
1038	<	for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) {
1039	<	if (o.equals(x))
1040	<	return true;
1036	>	final Object[] es = elements;
1037	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1038	>	; i = 0, to = end) {
1039	>	for (; i < to; i++)
1040	>	if (o.equals(es[i]))
1041	>	return true;
1042	>	if (to == end) break;
1043		}
1044		}
1045		return false;
#	Line 703 | Line 1067 | public class ArrayDeque<E> extends Abstr
1067		* The deque will be empty after this call returns.
1068		*/
1069		public void clear() {
1070	<	int h = head;
1071	<	int t = tail;
1072	<	if (h != t) { // clear all cells
1073	<	head = tail = 0;
1074	<	int i = h;
1075	<	int mask = elements.length - 1;
1076	<	do {
1077	<	elements[i] = null;
1078	<	i = (i + 1) & mask;
1079	<	} while (i != t);
1070	>	circularClear(elements, head, tail);
1071	>	head = tail = 0;
1072	>	// checkInvariants();
1073	>	}
1074	>
1075	>	/**
1076	>	* Nulls out slots starting at array index i, upto index end.
1077	>	*/
1078	>	private static void circularClear(Object[] es, int i, int end) {
1079	>	for (int to = (i <= end) ? end : es.length;
1080	>	; i = 0, to = end) {
1081	>	Arrays.fill(es, i, to, null);
1082	>	if (to == end) break;
1083		}
1084		}
1085
#	Line 730 | Line 1097 | public class ArrayDeque<E> extends Abstr
1097		* @return an array containing all of the elements in this deque
1098		*/
1099		public Object[] toArray() {
1100	<	final int head = this.head;
1101	<	final int tail = this.tail;
1102	<	boolean wrap = (tail < head);
1103	<	int end = wrap ? tail + elements.length : tail;
1104	<	Object[] a = Arrays.copyOfRange(elements, head, end);
1105	<	if (wrap)
1106	<	System.arraycopy(elements, 0, a, elements.length - head, tail);
1100	>	return toArray(Object[].class);
1101	>	}
1102	>
1103	>	private <T> T[] toArray(Class<T[]> klazz) {
1104	>	final Object[] es = elements;
1105	>	final T[] a;
1106	>	final int head = this.head, tail = this.tail, end;
1107	>	if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) {
1108	>	// Uses null extension feature of copyOfRange
1109	>	a = Arrays.copyOfRange(es, head, end, klazz);
1110	>	} else {
1111	>	// integer overflow!
1112	>	a = Arrays.copyOfRange(es, 0, end - head, klazz);
1113	>	System.arraycopy(es, head, a, 0, es.length - head);
1114	>	}
1115	>	if (end != tail)
1116	>	System.arraycopy(es, 0, a, es.length - head, tail);
1117		return a;
1118		}
1119
#	Line 778 | Line 1155 | public class ArrayDeque<E> extends Abstr
1155		*/
1156		@SuppressWarnings("unchecked")
1157		public <T> T[] toArray(T[] a) {
1158	<	final int head = this.head;
1159	<	final int tail = this.tail;
1160	<	boolean wrap = (tail < head);
1161	<	int size = (tail - head) + (wrap ? elements.length : 0);
1162	<	int firstLeg = size - (wrap ? tail : 0);
1163	<	int len = a.length;
1164	<	if (size > len) {
1165	<	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;
1158	>	final int size;
1159	>	if ((size = size()) > a.length)
1160	>	return toArray((Class<T[]>) a.getClass());
1161	>	final Object[] es = elements;
1162	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1163	>	; i = 0, len = tail) {
1164	>	System.arraycopy(es, i, a, j, len);
1165	>	if ((j += len) == size) break;
1166		}
1167	<	if (wrap)
1168	<	System.arraycopy(elements, 0, a, firstLeg, tail);
1167	>	if (size < a.length)
1168	>	a[size] = null;
1169		return a;
1170		}
1171
#	Line 834 | Line 1206 | public class ArrayDeque<E> extends Abstr
1206		s.writeInt(size());
1207
1208		// Write out elements in order.
1209	<	int mask = elements.length - 1;
1210	<	for (int i = head; i != tail; i = (i + 1) & mask)
1211	<	s.writeObject(elements[i]);
1209	>	final Object[] es = elements;
1210	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1211	>	; i = 0, to = end) {
1212	>	for (; i < to; i++)
1213	>	s.writeObject(es[i]);
1214	>	if (to == end) break;
1215	>	}
1216		}
1217
1218		/**
#	Line 852 | Line 1228 | public class ArrayDeque<E> extends Abstr
1228
1229		// Read in size and allocate array
1230		int size = s.readInt();
1231	<	allocateElements(size);
1232	<	head = 0;
857	<	tail = size;
1231	>	elements = new Object[size + 1];
1232	>	this.tail = size;
1233
1234		// Read in all elements in the proper order.
1235		for (int i = 0; i < size; i++)
1236		elements[i] = s.readObject();
1237		}
1238
1239	<	/**
1240	<	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1241	<	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
1242	<	* deque.
1243	<	*
1244	<	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1245	<	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
1246	<	* {@link Spliterator#NONNULL}.  Overriding implementations should document
1247	<	* the reporting of additional characteristic values.
1248	<	*
1249	<	* @return a {@code Spliterator} over the elements in this deque
1250	<	* @since 1.8
1251	<	*/
1252	<	public Spliterator<E> spliterator() {
1253	<	return new DeqSpliterator<>(this, -1, -1);
1254	<	}
1255	<
1256	<	static final class DeqSpliterator<E> implements Spliterator<E> {
1257	<	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;
1239	>	/** debugging */
1240	>	void checkInvariants() {
1241	>	// Use head and tail fields with empty slot at tail strategy.
1242	>	// head == tail disambiguates to "empty".
1243	>	try {
1244	>	int capacity = elements.length;
1245	>	// assert head >= 0 && head < capacity;
1246	>	// assert tail >= 0 && tail < capacity;
1247	>	// assert capacity > 0;
1248	>	// assert size() < capacity;
1249	>	// assert head == tail || elements[head] != null;
1250	>	// assert elements[tail] == null;
1251	>	// assert head == tail || elements[dec(tail, capacity)] != null;
1252	>	} catch (Throwable t) {
1253	>	System.err.printf("head=%d tail=%d capacity=%d%n",
1254	>	head, tail, elements.length);
1255	>	System.err.printf("elements=%s%n",
1256	>	Arrays.toString(elements));
1257	>	throw t;
1258		}
1259		}
1260

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