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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.43 by jsr166, Wed Jan 16 21:25:33 2013 UTC vs.
Revision 1.134 by jsr166, Sat Jun 30 22:35:55 2018 UTC

#	Line 1 | Line 1
1		/*
2	–	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3	–	*
4	–	* This code is free software; you can redistribute it and/or modify it
5	–	* under the terms of the GNU General Public License version 2 only, as
6	–	* published by the Free Software Foundation.  Oracle designates this
7	–	* particular file as subject to the "Classpath" exception as provided
8	–	* by Oracle in the LICENSE file that accompanied this code.
9	–	*
10	–	* This code is distributed in the hope that it will be useful, but WITHOUT
11	–	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12	–	* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
13	–	* version 2 for more details (a copy is included in the LICENSE file that
14	–	* accompanied this code).
15	–	*
16	–	* You should have received a copy of the GNU General Public License version
17	–	* 2 along with this work; if not, write to the Free Software Foundation,
18	–	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19	–	*
20	–	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21	–	* or visit www.oracle.com if you need additional information or have any
22	–	* questions.
23	–	*/
24	–
25	–	/*
26	–	* This file is available under and governed by the GNU General Public
27	–	* License version 2 only, as published by the Free Software Foundation.
28	–	* However, the following notice accompanied the original version of this
29	–	* file:
30	–	*
2		* Written by Josh Bloch of Google Inc. and released to the public domain,
3		* as explained at http://creativecommons.org/publicdomain/zero/1.0/.
4		*/
5
6		package java.util;
7	<	import java.util.Spliterator;
8	<	import java.util.stream.Stream;
9	<	import java.util.stream.Streams;
10	<	import java.util.function.Block;
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	>	import jdk.internal.misc.SharedSecrets;
13
14		/**
15		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 48 | Line 21 | import java.util.function.Block;
21		* when used as a queue.
22		*
23		* <p>Most {@code ArrayDeque} operations run in amortized constant time.
24	<	* Exceptions include {@link #remove(Object) remove}, {@link
25	<	* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
26	<	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
27	<	* iterator.remove()}, and the bulk operations, all of which run in linear
28	<	* time.
24	>	* Exceptions include
25	>	* {@link #remove(Object) remove},
26	>	* {@link #removeFirstOccurrence removeFirstOccurrence},
27	>	* {@link #removeLastOccurrence removeLastOccurrence},
28	>	* {@link #contains contains},
29	>	* {@link #iterator iterator.remove()},
30	>	* and the bulk operations, all of which run in linear time.
31		*
32	<	* <p>The iterators returned by this class's {@code iterator} method are
33	<	* <i>fail-fast</i>: If the deque is modified at any time after the iterator
34	<	* is created, in any way except through the iterator's own {@code remove}
35	<	* method, the iterator will generally throw a {@link
32	>	* <p>The iterators returned by this class's {@link #iterator() iterator}
33	>	* method are <em>fail-fast</em>: If the deque is modified at any time after
34	>	* the iterator is created, in any way except through the iterator's own
35	>	* {@code remove} method, the iterator will generally throw a {@link
36		* ConcurrentModificationException}.  Thus, in the face of concurrent
37		* modification, the iterator fails quickly and cleanly, rather than risking
38		* arbitrary, non-deterministic behavior at an undetermined time in the
#	Line 76 | Line 51 | import java.util.function.Block;
51		* Iterator} interfaces.
52		*
53		* <p>This class is a member of the
54	<	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
54	>	* <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
55		* Java Collections Framework</a>.
56		*
57		* @author  Josh Bloch and Doug Lea
58	+	* @param <E> the type of elements held in this deque
59		* @since   1.6
84	–	* @param <E> the type of elements held in this collection
60		*/
61		public class ArrayDeque<E> extends AbstractCollection<E>
62	<	implements Deque<E>, Cloneable, java.io.Serializable
62	>	implements Deque<E>, Cloneable, Serializable
63		{
64	+	/*
65	+	* VMs excel at optimizing simple array loops where indices are
66	+	* incrementing or decrementing over a valid slice, e.g.
67	+	*
68	+	* for (int i = start; i < end; i++) ... elements[i]
69	+	*
70	+	* Because in a circular array, elements are in general stored in
71	+	* two disjoint such slices, we help the VM by writing unusual
72	+	* nested loops for all traversals over the elements.  Having only
73	+	* one hot inner loop body instead of two or three eases human
74	+	* maintenance and encourages VM loop inlining into the caller.
75	+	*/
76	+
77		/**
78		* The array in which the elements of the deque are stored.
79	<	* The capacity of the deque is the length of this array, which is
80	<	* always a power of two. The array is never allowed to become
93	<	* full, except transiently within an addX method where it is
94	<	* resized (see doubleCapacity) immediately upon becoming full,
95	<	* thus avoiding head and tail wrapping around to equal each
96	<	* other.  We also guarantee that all array cells not holding
97	<	* deque elements are always null.
79	>	* All array cells not holding deque elements are always null.
80	>	* The array always has at least one null slot (at tail).
81		*/
82	<	transient Object[] elements; // non-private to simplify nested class access
82	>	transient Object[] elements;
83
84		/**
85		* The index of the element at the head of the deque (which is the
86		* element that would be removed by remove() or pop()); or an
87	<	* arbitrary number equal to tail if the deque is empty.
87	>	* arbitrary number 0 <= head < elements.length equal to tail if
88	>	* the deque is empty.
89		*/
90		transient int head;
91
92		/**
93		* The index at which the next element would be added to the tail
94	<	* of the deque (via addLast(E), add(E), or push(E)).
94	>	* of the deque (via addLast(E), add(E), or push(E));
95	>	* elements[tail] is always null.
96		*/
97		transient int tail;
98
99		/**
100	<	* The minimum capacity that we'll use for a newly created deque.
101	<	* Must be a power of 2.
100	>	* The maximum size of array to allocate.
101	>	* Some VMs reserve some header words in an array.
102	>	* Attempts to allocate larger arrays may result in
103	>	* OutOfMemoryError: Requested array size exceeds VM limit
104		*/
105	<	private static final int MIN_INITIAL_CAPACITY = 8;
119	<
120	<	// ******  Array allocation and resizing utilities ******
105	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
106
107		/**
108	<	* Allocates empty array to hold the given number of elements.
108	>	* Increases the capacity of this deque by at least the given amount.
109		*
110	<	* @param numElements  the number of elements to hold
110	>	* @param needed the required minimum extra capacity; must be positive
111		*/
112	<	private void allocateElements(int numElements) {
113	<	int initialCapacity = MIN_INITIAL_CAPACITY;
114	<	// Find the best power of two to hold elements.
115	<	// Tests "<=" because arrays aren't kept full.
116	<	if (numElements >= initialCapacity) {
117	<	initialCapacity = numElements;
118	<	initialCapacity |= (initialCapacity >>>  1);
119	<	initialCapacity |= (initialCapacity >>>  2);
120	<	initialCapacity |= (initialCapacity >>>  4);
121	<	initialCapacity |= (initialCapacity >>>  8);
122	<	initialCapacity |= (initialCapacity >>> 16);
123	<	initialCapacity++;
112	>	private void grow(int needed) {
113	>	// overflow-conscious code
114	>	final int oldCapacity = elements.length;
115	>	int newCapacity;
116	>	// Double capacity if small; else grow by 50%
117	>	int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
118	>	if (jump < needed
119	>	|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
120	>	newCapacity = newCapacity(needed, jump);
121	>	final Object[] es = elements = Arrays.copyOf(elements, newCapacity);
122	>	// Exceptionally, here tail == head needs to be disambiguated
123	>	if (tail < head || (tail == head && es[head] != null)) {
124	>	// wrap around; slide first leg forward to end of array
125	>	int newSpace = newCapacity - oldCapacity;
126	>	System.arraycopy(es, head,
127	>	es, head + newSpace,
128	>	oldCapacity - head);
129	>	for (int i = head, to = (head += newSpace); i < to; i++)
130	>	es[i] = null;
131	>	}
132	>	// checkInvariants();
133	>	}
134
135	<	if (initialCapacity < 0)   // Too many elements, must back off
136	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
135	>	/** Capacity calculation for edge conditions, especially overflow. */
136	>	private int newCapacity(int needed, int jump) {
137	>	final int oldCapacity = elements.length, minCapacity;
138	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
139	>	if (minCapacity < 0)
140	>	throw new IllegalStateException("Sorry, deque too big");
141	>	return Integer.MAX_VALUE;
142		}
143	<	elements = new Object[initialCapacity];
143	>	if (needed > jump)
144	>	return minCapacity;
145	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
146	>	? oldCapacity + jump
147	>	: MAX_ARRAY_SIZE;
148		}
149
150		/**
151	<	* Doubles the capacity of this deque.  Call only when full, i.e.,
152	<	* when head and tail have wrapped around to become equal.
151	>	* Increases the internal storage of this collection, if necessary,
152	>	* to ensure that it can hold at least the given number of elements.
153	>	*
154	>	* @param minCapacity the desired minimum capacity
155	>	* @since TBD
156		*/
157	<	private void doubleCapacity() {
158	<	assert head == tail;
159	<	int p = head;
160	<	int n = elements.length;
161	<	int r = n - p; // number of elements to the right of p
155	<	int newCapacity = n << 1;
156	<	if (newCapacity < 0)
157	<	throw new IllegalStateException("Sorry, deque too big");
158	<	Object[] a = new Object[newCapacity];
159	<	System.arraycopy(elements, p, a, 0, r);
160	<	System.arraycopy(elements, 0, a, r, p);
161	<	elements = a;
162	<	head = 0;
163	<	tail = n;
157	>	/* public */ void ensureCapacity(int minCapacity) {
158	>	int needed;
159	>	if ((needed = (minCapacity + 1 - elements.length)) > 0)
160	>	grow(needed);
161	>	// checkInvariants();
162		}
163
164		/**
165	<	* Copies the elements from our element array into the specified array,
168	<	* in order (from first to last element in the deque).  It is assumed
169	<	* that the array is large enough to hold all elements in the deque.
165	>	* Minimizes the internal storage of this collection.
166		*
167	<	* @return its argument
167	>	* @since TBD
168		*/
169	<	private <T> T[] copyElements(T[] a) {
170	<	if (head < tail) {
171	<	System.arraycopy(elements, head, a, 0, size());
172	<	} else if (head > tail) {
173	<	int headPortionLen = elements.length - head;
174	<	System.arraycopy(elements, head, a, 0, headPortionLen);
179	<	System.arraycopy(elements, 0, a, headPortionLen, tail);
169	>	/* public */ void trimToSize() {
170	>	int size;
171	>	if ((size = size()) + 1 < elements.length) {
172	>	elements = toArray(new Object[size + 1]);
173	>	head = 0;
174	>	tail = size;
175		}
176	<	return a;
176	>	// checkInvariants();
177		}
178
179		/**
#	Line 186 | Line 181 | public class ArrayDeque<E> extends Abstr
181		* sufficient to hold 16 elements.
182		*/
183		public ArrayDeque() {
184	<	elements = new Object[16];
184	>	elements = new Object[16 + 1];
185		}
186
187		/**
188		* Constructs an empty array deque with an initial capacity
189		* sufficient to hold the specified number of elements.
190		*
191	<	* @param numElements  lower bound on initial capacity of the deque
191	>	* @param numElements lower bound on initial capacity of the deque
192		*/
193		public ArrayDeque(int numElements) {
194	<	allocateElements(numElements);
194	>	elements =
195	>	new Object[(numElements < 1) ? 1 :
196	>	(numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE :
197	>	numElements + 1];
198		}
199
200		/**
#	Line 210 | Line 208 | public class ArrayDeque<E> extends Abstr
208		* @throws NullPointerException if the specified collection is null
209		*/
210		public ArrayDeque(Collection<? extends E> c) {
211	<	allocateElements(c.size());
212	<	addAll(c);
211	>	this(c.size());
212	>	copyElements(c);
213	>	}
214	>
215	>	/**
216	>	* Circularly increments i, mod modulus.
217	>	* Precondition and postcondition: 0 <= i < modulus.
218	>	*/
219	>	static final int inc(int i, int modulus) {
220	>	if (++i >= modulus) i = 0;
221	>	return i;
222	>	}
223	>
224	>	/**
225	>	* Circularly decrements i, mod modulus.
226	>	* Precondition and postcondition: 0 <= i < modulus.
227	>	*/
228	>	static final int dec(int i, int modulus) {
229	>	if (--i < 0) i = modulus - 1;
230	>	return i;
231	>	}
232	>
233	>	/**
234	>	* Circularly adds the given distance to index i, mod modulus.
235	>	* Precondition: 0 <= i < modulus, 0 <= distance <= modulus.
236	>	* @return index 0 <= i < modulus
237	>	*/
238	>	static final int inc(int i, int distance, int modulus) {
239	>	if ((i += distance) - modulus >= 0) i -= modulus;
240	>	return i;
241	>	}
242	>
243	>	/**
244	>	* Subtracts j from i, mod modulus.
245	>	* Index i must be logically ahead of index j.
246	>	* Precondition: 0 <= i < modulus, 0 <= j < modulus.
247	>	* @return the "circular distance" from j to i; corner case i == j
248	>	* is disambiguated to "empty", returning 0.
249	>	*/
250	>	static final int sub(int i, int j, int modulus) {
251	>	if ((i -= j) < 0) i += modulus;
252	>	return i;
253	>	}
254	>
255	>	/**
256	>	* Returns element at array index i.
257	>	* This is a slight abuse of generics, accepted by javac.
258	>	*/
259	>	@SuppressWarnings("unchecked")
260	>	static final <E> E elementAt(Object[] es, int i) {
261	>	return (E) es[i];
262	>	}
263	>
264	>	/**
265	>	* A version of elementAt that checks for null elements.
266	>	* This check doesn't catch all possible comodifications,
267	>	* but does catch ones that corrupt traversal.
268	>	*/
269	>	static final <E> E nonNullElementAt(Object[] es, int i) {
270	>	@SuppressWarnings("unchecked") E e = (E) es[i];
271	>	if (e == null)
272	>	throw new ConcurrentModificationException();
273	>	return e;
274		}
275
276		// The main insertion and extraction methods are addFirst,
#	Line 227 | Line 286 | public class ArrayDeque<E> extends Abstr
286		public void addFirst(E e) {
287		if (e == null)
288		throw new NullPointerException();
289	<	elements[head = (head - 1) & (elements.length - 1)] = e;
289	>	final Object[] es = elements;
290	>	es[head = dec(head, es.length)] = e;
291		if (head == tail)
292	<	doubleCapacity();
292	>	grow(1);
293	>	// checkInvariants();
294		}
295
296		/**
#	Line 243 | Line 304 | public class ArrayDeque<E> extends Abstr
304		public void addLast(E e) {
305		if (e == null)
306		throw new NullPointerException();
307	<	elements[tail] = e;
308	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
309	<	doubleCapacity();
307	>	final Object[] es = elements;
308	>	es[tail] = e;
309	>	if (head == (tail = inc(tail, es.length)))
310	>	grow(1);
311	>	// checkInvariants();
312	>	}
313	>
314	>	/**
315	>	* Adds all of the elements in the specified collection at the end
316	>	* of this deque, as if by calling {@link #addLast} on each one,
317	>	* in the order that they are returned by the collection's 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	>	copyElements(c);
329	>	// checkInvariants();
330	>	return size() > s;
331	>	}
332	>
333	>	private void copyElements(Collection<? extends E> c) {
334	>	c.forEach(this::addLast);
335		}
336
337		/**
#	Line 276 | Line 362 | public class ArrayDeque<E> extends Abstr
362		* @throws NoSuchElementException {@inheritDoc}
363		*/
364		public E removeFirst() {
365	<	E x = pollFirst();
366	<	if (x == null)
365	>	E e = pollFirst();
366	>	if (e == null)
367		throw new NoSuchElementException();
368	<	return x;
368	>	// checkInvariants();
369	>	return e;
370		}
371
372		/**
373		* @throws NoSuchElementException {@inheritDoc}
374		*/
375		public E removeLast() {
376	<	E x = pollLast();
377	<	if (x == null)
376	>	E e = pollLast();
377	>	if (e == null)
378		throw new NoSuchElementException();
379	<	return x;
379	>	// checkInvariants();
380	>	return e;
381		}
382
383		public E pollFirst() {
384	<	int h = head;
385	<	@SuppressWarnings("unchecked")
386	<	E result = (E) elements[h];
387	<	// Element is null if deque empty
388	<	if (result == null)
389	<	return null;
390	<	elements[h] = null;     // Must null out slot
391	<	head = (h + 1) & (elements.length - 1);
392	<	return result;
384	>	final Object[] es;
385	>	final int h;
386	>	E e = elementAt(es = elements, h = head);
387	>	if (e != null) {
388	>	es[h] = null;
389	>	head = inc(h, es.length);
390	>	}
391	>	// checkInvariants();
392	>	return e;
393		}
394
395		public E pollLast() {
396	<	int t = (tail - 1) & (elements.length - 1);
397	<	@SuppressWarnings("unchecked")
398	<	E result = (E) elements[t];
399	<	if (result == null)
400	<	return null;
401	<	elements[t] = null;
402	<	tail = t;
315	<	return result;
396	>	final Object[] es;
397	>	final int t;
398	>	E e = elementAt(es = elements, t = dec(tail, es.length));
399	>	if (e != null)
400	>	es[tail = t] = null;
401	>	// checkInvariants();
402	>	return e;
403		}
404
405		/**
406		* @throws NoSuchElementException {@inheritDoc}
407		*/
408		public E getFirst() {
409	<	@SuppressWarnings("unchecked")
410	<	E result = (E) elements[head];
324	<	if (result == null)
409	>	E e = elementAt(elements, head);
410	>	if (e == null)
411		throw new NoSuchElementException();
412	<	return result;
412	>	// checkInvariants();
413	>	return e;
414		}
415
416		/**
417		* @throws NoSuchElementException {@inheritDoc}
418		*/
419		public E getLast() {
420	<	@SuppressWarnings("unchecked")
421	<	E result = (E) elements[(tail - 1) & (elements.length - 1)];
422	<	if (result == null)
420	>	final Object[] es = elements;
421	>	E e = elementAt(es, dec(tail, es.length));
422	>	if (e == null)
423		throw new NoSuchElementException();
424	<	return result;
424	>	// checkInvariants();
425	>	return e;
426		}
427
340	–	@SuppressWarnings("unchecked")
428		public E peekFirst() {
429	<	// elements[head] is null if deque empty
430	<	return (E) elements[head];
429	>	// checkInvariants();
430	>	return elementAt(elements, head);
431		}
432
346	–	@SuppressWarnings("unchecked")
433		public E peekLast() {
434	<	return (E) elements[(tail - 1) & (elements.length - 1)];
434	>	// checkInvariants();
435	>	final Object[] es;
436	>	return elementAt(es = elements, dec(tail, es.length));
437		}
438
439		/**
#	Line 361 | Line 449 | public class ArrayDeque<E> extends Abstr
449		* @return {@code true} if the deque contained the specified element
450		*/
451		public boolean removeFirstOccurrence(Object o) {
452	<	if (o == null)
453	<	return false;
454	<	int mask = elements.length - 1;
455	<	int i = head;
456	<	Object x;
457	<	while ( (x = elements[i]) != null) {
458	<	if (o.equals(x)) {
459	<	delete(i);
460	<	return true;
452	>	if (o != null) {
453	>	final Object[] es = elements;
454	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
455	>	; i = 0, to = end) {
456	>	for (; i < to; i++)
457	>	if (o.equals(es[i])) {
458	>	delete(i);
459	>	return true;
460	>	}
461	>	if (to == end) break;
462		}
374	–	i = (i + 1) & mask;
463		}
464		return false;
465		}
#	Line 389 | Line 477 | public class ArrayDeque<E> extends Abstr
477		* @return {@code true} if the deque contained the specified element
478		*/
479		public boolean removeLastOccurrence(Object o) {
480	<	if (o == null)
481	<	return false;
482	<	int mask = elements.length - 1;
483	<	int i = (tail - 1) & mask;
484	<	Object x;
485	<	while ( (x = elements[i]) != null) {
486	<	if (o.equals(x)) {
487	<	delete(i);
488	<	return true;
480	>	if (o != null) {
481	>	final Object[] es = elements;
482	>	for (int i = tail, end = head, to = (i >= end) ? end : 0;
483	>	; i = es.length, to = end) {
484	>	for (i--; i > to - 1; i--)
485	>	if (o.equals(es[i])) {
486	>	delete(i);
487	>	return true;
488	>	}
489	>	if (to == end) break;
490		}
402	–	i = (i - 1) & mask;
491		}
492		return false;
493		}
#	Line 436 | Line 524 | public class ArrayDeque<E> extends Abstr
524		/**
525		* Retrieves and removes the head of the queue represented by this deque.
526		*
527	<	* This method differs from {@link #poll poll} only in that it throws an
528	<	* exception if this deque is empty.
527	>	* This method differs from {@link #poll() poll()} only in that it
528	>	* throws an exception if this deque is empty.
529		*
530		* <p>This method is equivalent to {@link #removeFirst}.
531		*
#	Line 518 | Line 606 | public class ArrayDeque<E> extends Abstr
606		return removeFirst();
607		}
608
521	–	private void checkInvariants() {
522	–	assert elements[tail] == null;
523	–	assert head == tail ? elements[head] == null :
524	–	(elements[head] != null &&
525	–	elements[(tail - 1) & (elements.length - 1)] != null);
526	–	assert elements[(head - 1) & (elements.length - 1)] == null;
527	–	}
528	–
609		/**
610	<	* Removes the element at the specified position in the elements array,
611	<	* adjusting head and tail as necessary.  This can result in motion of
612	<	* elements backwards or forwards in the array.
610	>	* Removes the element at the specified position in the elements array.
611	>	* This can result in forward or backwards motion of array elements.
612	>	* We optimize for least element motion.
613		*
614		* <p>This method is called delete rather than remove to emphasize
615		* that its semantics differ from those of {@link List#remove(int)}.
616		*
617	<	* @return true if elements moved backwards
617	>	* @return true if elements near tail moved backwards
618		*/
619	<	private boolean delete(int i) {
620	<	checkInvariants();
621	<	final Object[] elements = this.elements;
622	<	final int mask = elements.length - 1;
623	<	final int h = head;
624	<	final int t = tail;
625	<	final int front = (i - h) & mask;
626	<	final int back  = (t - i) & mask;
627	<
548	<	// Invariant: head <= i < tail mod circularity
549	<	if (front >= ((t - h) & mask))
550	<	throw new ConcurrentModificationException();
551	<
552	<	// Optimize for least element motion
619	>	boolean delete(int i) {
620	>	// checkInvariants();
621	>	final Object[] es = elements;
622	>	final int capacity = es.length;
623	>	final int h, t;
624	>	// number of elements before to-be-deleted elt
625	>	final int front = sub(i, h = head, capacity);
626	>	// number of elements after to-be-deleted elt
627	>	final int back = sub(t = tail, i, capacity) - 1;
628		if (front < back) {
629	+	// move front elements forwards
630		if (h <= i) {
631	<	System.arraycopy(elements, h, elements, h + 1, front);
631	>	System.arraycopy(es, h, es, h + 1, front);
632		} else { // Wrap around
633	<	System.arraycopy(elements, 0, elements, 1, i);
634	<	elements[0] = elements[mask];
635	<	System.arraycopy(elements, h, elements, h + 1, mask - h);
633	>	System.arraycopy(es, 0, es, 1, i);
634	>	es[0] = es[capacity - 1];
635	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
636		}
637	<	elements[h] = null;
638	<	head = (h + 1) & mask;
637	>	es[h] = null;
638	>	head = inc(h, capacity);
639	>	// checkInvariants();
640		return false;
641		} else {
642	<	if (i < t) { // Copy the null tail as well
643	<	System.arraycopy(elements, i + 1, elements, i, back);
644	<	tail = t - 1;
642	>	// move back elements backwards
643	>	tail = dec(t, capacity);
644	>	if (i <= tail) {
645	>	System.arraycopy(es, i + 1, es, i, back);
646		} else { // Wrap around
647	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
648	<	elements[mask] = elements[0];
649	<	System.arraycopy(elements, 1, elements, 0, t);
572	<	tail = (t - 1) & mask;
647	>	System.arraycopy(es, i + 1, es, i, capacity - (i + 1));
648	>	es[capacity - 1] = es[0];
649	>	System.arraycopy(es, 1, es, 0, t - 1);
650		}
651	+	es[tail] = null;
652	+	// checkInvariants();
653		return true;
654		}
655		}
#	Line 583 | Line 662 | public class ArrayDeque<E> extends Abstr
662		* @return the number of elements in this deque
663		*/
664		public int size() {
665	<	return (tail - head) & (elements.length - 1);
665	>	return sub(tail, head, elements.length);
666		}
667
668		/**
#	Line 612 | Line 691 | public class ArrayDeque<E> extends Abstr
691		}
692
693		private class DeqIterator implements Iterator<E> {
694	<	/**
695	<	* Index of element to be returned by subsequent call to next.
617	<	*/
618	<	private int cursor = head;
694	>	/** Index of element to be returned by subsequent call to next. */
695	>	int cursor;
696
697	<	/**
698	<	* Tail recorded at construction (also in remove), to stop
622	<	* iterator and also to check for comodification.
623	<	*/
624	<	private int fence = tail;
697	>	/** Number of elements yet to be returned. */
698	>	int remaining = size();
699
700		/**
701		* Index of element returned by most recent call to next.
702		* Reset to -1 if element is deleted by a call to remove.
703		*/
704	<	private int lastRet = -1;
704	>	int lastRet = -1;
705	>
706	>	DeqIterator() { cursor = head; }
707
708	<	public boolean hasNext() {
709	<	return cursor != fence;
708	>	public final boolean hasNext() {
709	>	return remaining > 0;
710		}
711
712		public E next() {
713	<	if (cursor == fence)
713	>	if (remaining <= 0)
714		throw new NoSuchElementException();
715	<	@SuppressWarnings("unchecked")
716	<	E result = (E) elements[cursor];
717	<	// This check doesn't catch all possible comodifications,
718	<	// but does catch the ones that corrupt traversal
719	<	if (tail != fence || result == null)
644	<	throw new ConcurrentModificationException();
645	<	lastRet = cursor;
646	<	cursor = (cursor + 1) & (elements.length - 1);
647	<	return result;
715	>	final Object[] es = elements;
716	>	E e = nonNullElementAt(es, cursor);
717	>	cursor = inc(lastRet = cursor, es.length);
718	>	remaining--;
719	>	return e;
720		}
721
722	<	public void remove() {
722	>	void postDelete(boolean leftShifted) {
723	>	if (leftShifted)
724	>	cursor = dec(cursor, elements.length);
725	>	}
726	>
727	>	public final void remove() {
728		if (lastRet < 0)
729		throw new IllegalStateException();
730	<	if (delete(lastRet)) { // if left-shifted, undo increment in next()
654	<	cursor = (cursor - 1) & (elements.length - 1);
655	<	fence = tail;
656	<	}
730	>	postDelete(delete(lastRet));
731		lastRet = -1;
732		}
659	–	}
660	–
661	–	private class DescendingIterator implements Iterator<E> {
662	–	/*
663	–	* This class is nearly a mirror-image of DeqIterator, using
664	–	* tail instead of head for initial cursor, and head instead of
665	–	* tail for fence.
666	–	*/
667	–	private int cursor = tail;
668	–	private int fence = head;
669	–	private int lastRet = -1;
733
734	<	public boolean hasNext() {
735	<	return cursor != fence;
734	>	public void forEachRemaining(Consumer<? super E> action) {
735	>	Objects.requireNonNull(action);
736	>	int r;
737	>	if ((r = remaining) <= 0)
738	>	return;
739	>	remaining = 0;
740	>	final Object[] es = elements;
741	>	if (es[cursor] == null || sub(tail, cursor, es.length) != r)
742	>	throw new ConcurrentModificationException();
743	>	for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
744	>	; i = 0, to = end) {
745	>	for (; i < to; i++)
746	>	action.accept(elementAt(es, i));
747	>	if (to == end) {
748	>	if (end != tail)
749	>	throw new ConcurrentModificationException();
750	>	lastRet = dec(end, es.length);
751	>	break;
752	>	}
753	>	}
754		}
755	+	}
756
757	<	public E next() {
758	<	if (cursor == fence)
757	>	private class DescendingIterator extends DeqIterator {
758	>	DescendingIterator() { cursor = dec(tail, elements.length); }
759	>
760	>	public final E next() {
761	>	if (remaining <= 0)
762		throw new NoSuchElementException();
763	<	cursor = (cursor - 1) & (elements.length - 1);
764	<	@SuppressWarnings("unchecked")
765	<	E result = (E) elements[cursor];
766	<	if (head != fence || result == null)
763	>	final Object[] es = elements;
764	>	E e = nonNullElementAt(es, cursor);
765	>	cursor = dec(lastRet = cursor, es.length);
766	>	remaining--;
767	>	return e;
768	>	}
769	>
770	>	void postDelete(boolean leftShifted) {
771	>	if (!leftShifted)
772	>	cursor = inc(cursor, elements.length);
773	>	}
774	>
775	>	public final void forEachRemaining(Consumer<? super E> action) {
776	>	Objects.requireNonNull(action);
777	>	int r;
778	>	if ((r = remaining) <= 0)
779	>	return;
780	>	remaining = 0;
781	>	final Object[] es = elements;
782	>	if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
783		throw new ConcurrentModificationException();
784	<	lastRet = cursor;
785	<	return result;
784	>	for (int i = cursor, end = head, to = (i >= end) ? end : 0;
785	>	; i = es.length - 1, to = end) {
786	>	// hotspot generates faster code than for: i >= to !
787	>	for (; i > to - 1; i--)
788	>	action.accept(elementAt(es, i));
789	>	if (to == end) {
790	>	if (end != head)
791	>	throw new ConcurrentModificationException();
792	>	lastRet = end;
793	>	break;
794	>	}
795	>	}
796		}
797	+	}
798
799	<	public void remove() {
800	<	if (lastRet < 0)
801	<	throw new IllegalStateException();
802	<	if (!delete(lastRet)) {
803	<	cursor = (cursor + 1) & (elements.length - 1);
804	<	fence = head;
799	>	/**
800	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
801	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
802	>	* deque.
803	>	*
804	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
805	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
806	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
807	>	* the reporting of additional characteristic values.
808	>	*
809	>	* @return a {@code Spliterator} over the elements in this deque
810	>	* @since 1.8
811	>	*/
812	>	public Spliterator<E> spliterator() {
813	>	return new DeqSpliterator();
814	>	}
815	>
816	>	final class DeqSpliterator implements Spliterator<E> {
817	>	private int fence;      // -1 until first use
818	>	private int cursor;     // current index, modified on traverse/split
819	>
820	>	/** Constructs late-binding spliterator over all elements. */
821	>	DeqSpliterator() {
822	>	this.fence = -1;
823	>	}
824	>
825	>	/** Constructs spliterator over the given range. */
826	>	DeqSpliterator(int origin, int fence) {
827	>	// assert 0 <= origin && origin < elements.length;
828	>	// assert 0 <= fence && fence < elements.length;
829	>	this.cursor = origin;
830	>	this.fence = fence;
831	>	}
832	>
833	>	/** Ensures late-binding initialization; then returns fence. */
834	>	private int getFence() { // force initialization
835	>	int t;
836	>	if ((t = fence) < 0) {
837	>	t = fence = tail;
838	>	cursor = head;
839		}
840	<	lastRet = -1;
840	>	return t;
841	>	}
842	>
843	>	public DeqSpliterator trySplit() {
844	>	final Object[] es = elements;
845	>	final int i, n;
846	>	return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
847	>	? null
848	>	: new DeqSpliterator(i, cursor = inc(i, n, es.length));
849		}
850	+
851	+	public void forEachRemaining(Consumer<? super E> action) {
852	+	if (action == null)
853	+	throw new NullPointerException();
854	+	final int end = getFence(), cursor = this.cursor;
855	+	final Object[] es = elements;
856	+	if (cursor != end) {
857	+	this.cursor = end;
858	+	// null check at both ends of range is sufficient
859	+	if (es[cursor] == null || es[dec(end, es.length)] == null)
860	+	throw new ConcurrentModificationException();
861	+	for (int i = cursor, to = (i <= end) ? end : es.length;
862	+	; i = 0, to = end) {
863	+	for (; i < to; i++)
864	+	action.accept(elementAt(es, i));
865	+	if (to == end) break;
866	+	}
867	+	}
868	+	}
869	+
870	+	public boolean tryAdvance(Consumer<? super E> action) {
871	+	Objects.requireNonNull(action);
872	+	final Object[] es = elements;
873	+	if (fence < 0) { fence = tail; cursor = head; } // late-binding
874	+	final int i;
875	+	if ((i = cursor) == fence)
876	+	return false;
877	+	E e = nonNullElementAt(es, i);
878	+	cursor = inc(i, es.length);
879	+	action.accept(e);
880	+	return true;
881	+	}
882	+
883	+	public long estimateSize() {
884	+	return sub(getFence(), cursor, elements.length);
885	+	}
886	+
887	+	public int characteristics() {
888	+	return Spliterator.NONNULL
889	+	| Spliterator.ORDERED
890	+	| Spliterator.SIZED
891	+	| Spliterator.SUBSIZED;
892	+	}
893	+	}
894	+
895	+	/**
896	+	* @throws NullPointerException {@inheritDoc}
897	+	*/
898	+	public void forEach(Consumer<? super E> action) {
899	+	Objects.requireNonNull(action);
900	+	final Object[] es = elements;
901	+	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
902	+	; i = 0, to = end) {
903	+	for (; i < to; i++)
904	+	action.accept(elementAt(es, i));
905	+	if (to == end) {
906	+	if (end != tail) throw new ConcurrentModificationException();
907	+	break;
908	+	}
909	+	}
910	+	// checkInvariants();
911	+	}
912	+
913	+	/**
914	+	* Replaces each element of this deque with the result of applying the
915	+	* operator to that element, as specified by {@link List#replaceAll}.
916	+	*
917	+	* @param operator the operator to apply to each element
918	+	* @since TBD
919	+	*/
920	+	/* public */ void replaceAll(UnaryOperator<E> operator) {
921	+	Objects.requireNonNull(operator);
922	+	final Object[] es = elements;
923	+	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
924	+	; i = 0, to = end) {
925	+	for (; i < to; i++)
926	+	es[i] = operator.apply(elementAt(es, i));
927	+	if (to == end) {
928	+	if (end != tail) throw new ConcurrentModificationException();
929	+	break;
930	+	}
931	+	}
932	+	// checkInvariants();
933	+	}
934	+
935	+	/**
936	+	* @throws NullPointerException {@inheritDoc}
937	+	*/
938	+	public boolean removeIf(Predicate<? super E> filter) {
939	+	Objects.requireNonNull(filter);
940	+	return bulkRemove(filter);
941	+	}
942	+
943	+	/**
944	+	* @throws NullPointerException {@inheritDoc}
945	+	*/
946	+	public boolean removeAll(Collection<?> c) {
947	+	Objects.requireNonNull(c);
948	+	return bulkRemove(e -> c.contains(e));
949	+	}
950	+
951	+	/**
952	+	* @throws NullPointerException {@inheritDoc}
953	+	*/
954	+	public boolean retainAll(Collection<?> c) {
955	+	Objects.requireNonNull(c);
956	+	return bulkRemove(e -> !c.contains(e));
957	+	}
958	+
959	+	/** Implementation of bulk remove methods. */
960	+	private boolean bulkRemove(Predicate<? super E> filter) {
961	+	// checkInvariants();
962	+	final Object[] es = elements;
963	+	// Optimize for initial run of survivors
964	+	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
965	+	; i = 0, to = end) {
966	+	for (; i < to; i++)
967	+	if (filter.test(elementAt(es, i)))
968	+	return bulkRemoveModified(filter, i);
969	+	if (to == end) {
970	+	if (end != tail) throw new ConcurrentModificationException();
971	+	break;
972	+	}
973	+	}
974	+	return false;
975	+	}
976	+
977	+	// A tiny bit set implementation
978	+
979	+	private static long[] nBits(int n) {
980	+	return new long[((n - 1) >> 6) + 1];
981	+	}
982	+	private static void setBit(long[] bits, int i) {
983	+	bits[i >> 6] |= 1L << i;
984	+	}
985	+	private static boolean isClear(long[] bits, int i) {
986	+	return (bits[i >> 6] & (1L << i)) == 0;
987	+	}
988	+
989	+	/**
990	+	* Helper for bulkRemove, in case of at least one deletion.
991	+	* Tolerate predicates that reentrantly access the collection for
992	+	* read (but writers still get CME), so traverse once to find
993	+	* elements to delete, a second pass to physically expunge.
994	+	*
995	+	* @param beg valid index of first element to be deleted
996	+	*/
997	+	private boolean bulkRemoveModified(
998	+	Predicate<? super E> filter, final int beg) {
999	+	final Object[] es = elements;
1000	+	final int capacity = es.length;
1001	+	final int end = tail;
1002	+	final long[] deathRow = nBits(sub(end, beg, capacity));
1003	+	deathRow[0] = 1L;   // set bit 0
1004	+	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1005	+	; i = 0, to = end, k -= capacity) {
1006	+	for (; i < to; i++)
1007	+	if (filter.test(elementAt(es, i)))
1008	+	setBit(deathRow, i - k);
1009	+	if (to == end) break;
1010	+	}
1011	+	// a two-finger traversal, with hare i reading, tortoise w writing
1012	+	int w = beg;
1013	+	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1014	+	; w = 0) { // w rejoins i on second leg
1015	+	// In this loop, i and w are on the same leg, with i > w
1016	+	for (; i < to; i++)
1017	+	if (isClear(deathRow, i - k))
1018	+	es[w++] = es[i];
1019	+	if (to == end) break;
1020	+	// In this loop, w is on the first leg, i on the second
1021	+	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1022	+	if (isClear(deathRow, i - k))
1023	+	es[w++] = es[i];
1024	+	if (i >= to) {
1025	+	if (w == capacity) w = 0; // "corner" case
1026	+	break;
1027	+	}
1028	+	}
1029	+	if (end != tail) throw new ConcurrentModificationException();
1030	+	circularClear(es, tail = w, end);
1031	+	// checkInvariants();
1032	+	return true;
1033		}
1034
1035		/**
#	Line 704 | Line 1041 | public class ArrayDeque<E> extends Abstr
1041		* @return {@code true} if this deque contains the specified element
1042		*/
1043		public boolean contains(Object o) {
1044	<	if (o == null)
1045	<	return false;
1046	<	int mask = elements.length - 1;
1047	<	int i = head;
1048	<	Object x;
1049	<	while ( (x = elements[i]) != null) {
1050	<	if (o.equals(x))
1051	<	return true;
1052	<	i = (i + 1) & mask;
1044	>	if (o != null) {
1045	>	final Object[] es = elements;
1046	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1047	>	; i = 0, to = end) {
1048	>	for (; i < to; i++)
1049	>	if (o.equals(es[i]))
1050	>	return true;
1051	>	if (to == end) break;
1052	>	}
1053		}
1054		return false;
1055		}
#	Line 725 | Line 1062 | public class ArrayDeque<E> extends Abstr
1062		* Returns {@code true} if this deque contained the specified element
1063		* (or equivalently, if this deque changed as a result of the call).
1064		*
1065	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1065	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1066		*
1067		* @param o element to be removed from this deque, if present
1068		* @return {@code true} if this deque contained the specified element
#	Line 739 | Line 1076 | public class ArrayDeque<E> extends Abstr
1076		* The deque will be empty after this call returns.
1077		*/
1078		public void clear() {
1079	<	int h = head;
1080	<	int t = tail;
1081	<	if (h != t) { // clear all cells
1082	<	head = tail = 0;
1083	<	int i = h;
1084	<	int mask = elements.length - 1;
1085	<	do {
1086	<	elements[i] = null;
1087	<	i = (i + 1) & mask;
1088	<	} while (i != t);
1079	>	circularClear(elements, head, tail);
1080	>	head = tail = 0;
1081	>	// checkInvariants();
1082	>	}
1083	>
1084	>	/**
1085	>	* Nulls out slots starting at array index i, upto index end.
1086	>	* Condition i == end means "empty" - nothing to do.
1087	>	*/
1088	>	private static void circularClear(Object[] es, int i, int end) {
1089	>	// assert 0 <= i && i < es.length;
1090	>	// assert 0 <= end && end < es.length;
1091	>	for (int to = (i <= end) ? end : es.length;
1092	>	; i = 0, to = end) {
1093	>	for (; i < to; i++) es[i] = null;
1094	>	if (to == end) break;
1095		}
1096		}
1097
#	Line 766 | Line 1109 | public class ArrayDeque<E> extends Abstr
1109		* @return an array containing all of the elements in this deque
1110		*/
1111		public Object[] toArray() {
1112	<	return copyElements(new Object[size()]);
1112	>	return toArray(Object[].class);
1113	>	}
1114	>
1115	>	private <T> T[] toArray(Class<T[]> klazz) {
1116	>	final Object[] es = elements;
1117	>	final T[] a;
1118	>	final int head = this.head, tail = this.tail, end;
1119	>	if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) {
1120	>	// Uses null extension feature of copyOfRange
1121	>	a = Arrays.copyOfRange(es, head, end, klazz);
1122	>	} else {
1123	>	// integer overflow!
1124	>	a = Arrays.copyOfRange(es, 0, end - head, klazz);
1125	>	System.arraycopy(es, head, a, 0, es.length - head);
1126	>	}
1127	>	if (end != tail)
1128	>	System.arraycopy(es, 0, a, es.length - head, tail);
1129	>	return a;
1130		}
1131
1132		/**
#	Line 791 | Line 1151 | public class ArrayDeque<E> extends Abstr
1151		* The following code can be used to dump the deque into a newly
1152		* allocated array of {@code String}:
1153		*
1154	<	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1154	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1155		*
1156		* Note that {@code toArray(new Object[0])} is identical in function to
1157		* {@code toArray()}.
#	Line 807 | Line 1167 | public class ArrayDeque<E> extends Abstr
1167		*/
1168		@SuppressWarnings("unchecked")
1169		public <T> T[] toArray(T[] a) {
1170	<	int size = size();
1171	<	if (a.length < size)
1172	<	a = (T[])java.lang.reflect.Array.newInstance(
1173	<	a.getClass().getComponentType(), size);
1174	<	copyElements(a);
1175	<	if (a.length > size)
1170	>	final int size;
1171	>	if ((size = size()) > a.length)
1172	>	return toArray((Class<T[]>) a.getClass());
1173	>	final Object[] es = elements;
1174	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1175	>	; i = 0, len = tail) {
1176	>	System.arraycopy(es, i, a, j, len);
1177	>	if ((j += len) == size) break;
1178	>	}
1179	>	if (size < a.length)
1180		a[size] = null;
1181		return a;
1182		}
#	Line 840 | Line 1204 | public class ArrayDeque<E> extends Abstr
1204		/**
1205		* Saves this deque to a stream (that is, serializes it).
1206		*
1207	+	* @param s the stream
1208	+	* @throws java.io.IOException if an I/O error occurs
1209		* @serialData The current size ({@code int}) of the deque,
1210		* followed by all of its elements (each an object reference) in
1211		* first-to-last order.
#	Line 852 | Line 1218 | public class ArrayDeque<E> extends Abstr
1218		s.writeInt(size());
1219
1220		// Write out elements in order.
1221	<	int mask = elements.length - 1;
1222	<	for (int i = head; i != tail; i = (i + 1) & mask)
1223	<	s.writeObject(elements[i]);
1221	>	final Object[] es = elements;
1222	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1223	>	; i = 0, to = end) {
1224	>	for (; i < to; i++)
1225	>	s.writeObject(es[i]);
1226	>	if (to == end) break;
1227	>	}
1228		}
1229
1230		/**
1231		* Reconstitutes this deque from a stream (that is, deserializes it).
1232	+	* @param s the stream
1233	+	* @throws ClassNotFoundException if the class of a serialized object
1234	+	*         could not be found
1235	+	* @throws java.io.IOException if an I/O error occurs
1236		*/
1237		private void readObject(java.io.ObjectInputStream s)
1238		throws java.io.IOException, ClassNotFoundException {
#	Line 866 | Line 1240 | public class ArrayDeque<E> extends Abstr
1240
1241		// Read in size and allocate array
1242		int size = s.readInt();
1243	<	allocateElements(size);
1244	<	head = 0;
1245	<	tail = size;
1243	>	SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size + 1);
1244	>	elements = new Object[size + 1];
1245	>	this.tail = size;
1246
1247		// Read in all elements in the proper order.
1248		for (int i = 0; i < size; i++)
1249		elements[i] = s.readObject();
1250		}
1251
1252	<	public Stream<E> stream() {
1253	<	int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED;
1254	<	return Streams.stream
1255	<	(() -> new DeqSpliterator<E>(this, head, tail), flags);
1256	<	}
1257	<	public Stream<E> parallelStream() {
1258	<	int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED;
1259	<	return Streams.parallelStream
1260	<	(() -> new DeqSpliterator<E>(this, head, tail), flags);
1261	<	}
1262	<
1263	<
1264	<	static final class DeqSpliterator<E> implements Spliterator<E>, Iterator<E> {
1265	<	private final ArrayDeque<E> deq;
1266	<	private final Object[] array;
1267	<	private final int fence;  // initially tail
1268	<	private int index;        // current index, modified on traverse/split
1269	<
1270	<	/** Create new spliterator covering the given array and range */
897	<	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
898	<	this.deq = deq; this.array = deq.elements;
899	<	this.index = origin; this.fence = fence;
900	<	}
901	<
902	<	public DeqSpliterator<E> trySplit() {
903	<	int n = array.length;
904	<	int h = index, t = fence;
905	<	if (h != t && ((h + 1) & (n - 1)) != t) {
906	<	if (h > t)
907	<	t += n;
908	<	int m = ((h + t) >>> 1) & (n - 1);
909	<	return new DeqSpliterator<E>(deq, h, index = m);
910	<	}
911	<	return null;
912	<	}
913	<
914	<	@SuppressWarnings("unchecked")
915	<	public void forEach(Block<? super E> block) {
916	<	if (block == null)
917	<	throw new NullPointerException();
918	<	Object[] a = array;
919	<	if (a != deq.elements)
920	<	throw new ConcurrentModificationException();
921	<	int m = a.length - 1, f = fence, i = index;
922	<	index = f;
923	<	while (i != f) {
924	<	Object e = a[i];
925	<	if (e == null)
926	<	throw new ConcurrentModificationException();
927	<	block.accept((E)e);
928	<	i = (i + 1) & m;
929	<	}
930	<	}
931	<
932	<	@SuppressWarnings("unchecked")
933	<	public boolean tryAdvance(Block<? super E> block) {
934	<	if (block == null)
935	<	throw new NullPointerException();
936	<	Object[] a = array;
937	<	if (a != deq.elements)
938	<	throw new ConcurrentModificationException();
939	<	int m = a.length - 1, i = index;
940	<	if (i != fence) {
941	<	Object e = a[i];
942	<	if (e == null)
943	<	throw new ConcurrentModificationException();
944	<	block.accept((E)e);
945	<	index = (i + 1) & m;
946	<	return true;
947	<	}
948	<	return false;
949	<	}
950	<
951	<	// Iterator support
952	<	public Iterator<E> iterator() {
953	<	return this;
954	<	}
955	<
956	<	public boolean hasNext() {
957	<	return index >= 0 && index != fence;
958	<	}
959	<
960	<	@SuppressWarnings("unchecked")
961	<	public E next() {
962	<	if (index < 0 || index == fence)
963	<	throw new NoSuchElementException();
964	<	Object[] a = array;
965	<	if (a != deq.elements)
966	<	throw new ConcurrentModificationException();
967	<	Object e = a[index];
968	<	if (e == null)
969	<	throw new ConcurrentModificationException();
970	<	index = (index + 1) & (a.length - 1);
971	<	return (E) e;
972	<	}
973	<
974	<	public void remove() { throw new UnsupportedOperationException(); }
975	<
976	<	// Other spliterator methods
977	<	public long estimateSize() {
978	<	int n = fence - index;
979	<	if (n < 0)
980	<	n += array.length;
981	<	return (long)n;
1252	>	/** debugging */
1253	>	void checkInvariants() {
1254	>	// Use head and tail fields with empty slot at tail strategy.
1255	>	// head == tail disambiguates to "empty".
1256	>	try {
1257	>	int capacity = elements.length;
1258	>	// assert 0 <= head && head < capacity;
1259	>	// assert 0 <= tail && tail < capacity;
1260	>	// assert capacity > 0;
1261	>	// assert size() < capacity;
1262	>	// assert head == tail || elements[head] != null;
1263	>	// assert elements[tail] == null;
1264	>	// assert head == tail || elements[dec(tail, capacity)] != null;
1265	>	} catch (Throwable t) {
1266	>	System.err.printf("head=%d tail=%d capacity=%d%n",
1267	>	head, tail, elements.length);
1268	>	System.err.printf("elements=%s%n",
1269	>	Arrays.toString(elements));
1270	>	throw t;
1271		}
983	–	public boolean hasExactSize() { return true; }
984	–	public boolean hasExactSplits() { return true; }
1272		}
1273
1274		}

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