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root/jsr166/jsr166/src/main/java/util/ArrayDeque.java

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.45 by dl, Fri Feb 1 01:02:25 2013 UTC vs.
Revision 1.105 by jsr166, Tue Nov 1 21:42:45 2016 UTC

#	Line 1 | Line 1
1		/*
2	<	* Written by Doug Lea with assistance from members of JCP JSR-166
3	<	* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/publicdomain/zero/1.0/
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;
10	<	import java.util.stream.Streams;
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 20 | Line 20 | import java.util.function.Consumer;
20		* when used as a queue.
21		*
22		* <p>Most {@code ArrayDeque} operations run in amortized constant time.
23	<	* Exceptions include {@link #remove(Object) remove}, {@link
24	<	* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
25	<	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
26	<	* iterator.remove()}, and the bulk operations, all of which run in linear
27	<	* time.
23	>	* Exceptions include
24	>	* {@link #remove(Object) remove},
25	>	* {@link #removeFirstOccurrence removeFirstOccurrence},
26	>	* {@link #removeLastOccurrence removeLastOccurrence},
27	>	* {@link #contains contains},
28	>	* {@link #iterator iterator.remove()},
29	>	* and the bulk operations, all of which run in linear time.
30		*
31	<	* <p>The iterators returned by this class's {@code iterator} method are
32	<	* <i>fail-fast</i>: If the deque is modified at any time after the iterator
33	<	* is created, in any way except through the iterator's own {@code remove}
34	<	* method, the iterator will generally throw a {@link
31	>	* <p>The iterators returned by this class's {@link #iterator() iterator}
32	>	* method are <em>fail-fast</em>: If the deque is modified at any time after
33	>	* the iterator is created, in any way except through the iterator's own
34	>	* {@code remove} method, the iterator will generally throw a {@link
35		* ConcurrentModificationException}.  Thus, in the face of concurrent
36		* modification, the iterator fails quickly and cleanly, rather than risking
37		* arbitrary, non-deterministic behavior at an undetermined time in the
#	Line 52 | Line 54 | import java.util.function.Consumer;
54		* Java Collections Framework</a>.
55		*
56		* @author  Josh Bloch and Doug Lea
57	+	* @param <E> the type of elements held in this deque
58		* @since   1.6
56	–	* @param <E> the type of elements held in this collection
59		*/
60		public class ArrayDeque<E> extends AbstractCollection<E>
61	<	implements Deque<E>, Cloneable, java.io.Serializable
61	>	implements Deque<E>, Cloneable, Serializable
62		{
63		/**
64		* The array in which the elements of the deque are stored.
65	<	* The capacity of the deque is the length of this array, which is
66	<	* 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.
65	>	* We guarantee that all array cells not holding deque elements
66	>	* are always null.
67		*/
68	<	transient Object[] elements; // non-private to simplify nested class access
68	>	transient Object[] elements;
69
70		/**
71		* The index of the element at the head of the deque (which is the
72		* element that would be removed by remove() or pop()); or an
73	<	* arbitrary number equal to tail if the deque is empty.
73	>	* arbitrary number 0 <= head < elements.length if the deque is empty.
74		*/
75		transient int head;
76
77	<	/**
78	<	* The index at which the next element would be added to the tail
82	<	* of the deque (via addLast(E), add(E), or push(E)).
83	<	*/
84	<	transient int tail;
85	<
86	<	/**
87	<	* The minimum capacity that we'll use for a newly created deque.
88	<	* Must be a power of 2.
89	<	*/
90	<	private static final int MIN_INITIAL_CAPACITY = 8;
91	<
92	<	// ******  Array allocation and resizing utilities ******
77	>	/** Number of elements in this collection. */
78	>	transient int size;
79
80		/**
81	<	* Allocates empty array to hold the given number of elements.
82	<	*
83	<	* @param numElements  the number of elements to hold
84	<	*/
85	<	private void allocateElements(int numElements) {
86	<	int initialCapacity = MIN_INITIAL_CAPACITY;
87	<	// Find the best power of two to hold elements.
88	<	// Tests "<=" because arrays aren't kept full.
89	<	if (numElements >= initialCapacity) {
90	<	initialCapacity = numElements;
91	<	initialCapacity |= (initialCapacity >>>  1);
92	<	initialCapacity |= (initialCapacity >>>  2);
93	<	initialCapacity |= (initialCapacity >>>  4);
94	<	initialCapacity |= (initialCapacity >>>  8);
95	<	initialCapacity |= (initialCapacity >>> 16);
96	<	initialCapacity++;
81	>	* The maximum size of array to allocate.
82	>	* Some VMs reserve some header words in an array.
83	>	* Attempts to allocate larger arrays may result in
84	>	* OutOfMemoryError: Requested array size exceeds VM limit
85	>	*/
86	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
87	>
88	>	/**
89	>	* Increases the capacity of this deque by at least the given amount.
90	>	*
91	>	* @param needed the required minimum extra capacity; must be positive
92	>	*/
93	>	private Object[] grow(int needed) {
94	>	// overflow-conscious code
95	>	// checkInvariants();
96	>	final int oldCapacity = elements.length;
97	>	int newCapacity;
98	>	// Double size if small; else grow by 50%
99	>	int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
100	>	if (jump < needed
101	>	|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
102	>	newCapacity = newCapacity(needed, jump);
103	>	elements = Arrays.copyOf(elements, newCapacity);
104	>	if (oldCapacity - head < size) {
105	>	// wrap around; slide first leg forward to end of array
106	>	int newSpace = newCapacity - oldCapacity;
107	>	System.arraycopy(elements, head,
108	>	elements, head + newSpace,
109	>	oldCapacity - head);
110	>	Arrays.fill(elements, head, head + newSpace, null);
111	>	head += newSpace;
112	>	}
113	>	return elements;
114	>	// checkInvariants();
115	>	}
116
117	<	if (initialCapacity < 0)   // Too many elements, must back off
118	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
117	>	/** Capacity calculation for edge conditions, especially overflow. */
118	>	private int newCapacity(int needed, int jump) {
119	>	final int oldCapacity = elements.length, minCapacity;
120	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
121	>	if (minCapacity < 0)
122	>	throw new IllegalStateException("Sorry, deque too big");
123	>	return Integer.MAX_VALUE;
124		}
125	<	elements = new Object[initialCapacity];
125	>	if (needed > jump)
126	>	return minCapacity;
127	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
128	>	? oldCapacity + jump
129	>	: MAX_ARRAY_SIZE;
130		}
131
132		/**
133	<	* Doubles the capacity of this deque.  Call only when full, i.e.,
134	<	* when head and tail have wrapped around to become equal.
133	>	* Increases the internal storage of this collection, if necessary,
134	>	* to ensure that it can hold at least the given number of elements.
135	>	*
136	>	* @param minCapacity the desired minimum capacity
137	>	* @since TBD
138		*/
139	<	private void doubleCapacity() {
140	<	assert head == tail;
141	<	int p = head;
142	<	int n = elements.length;
126	<	int r = n - p; // number of elements to the right of p
127	<	int newCapacity = n << 1;
128	<	if (newCapacity < 0)
129	<	throw new IllegalStateException("Sorry, deque too big");
130	<	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;
139	>	/* public */ void ensureCapacity(int minCapacity) {
140	>	if (minCapacity > elements.length)
141	>	grow(minCapacity - elements.length);
142	>	// checkInvariants();
143		}
144
145		/**
146	<	* Copies the elements from our element array into the specified array,
140	<	* in order (from first to last element in the deque).  It is assumed
141	<	* that the array is large enough to hold all elements in the deque.
146	>	* Minimizes the internal storage of this collection.
147		*
148	<	* @return its argument
148	>	* @since TBD
149		*/
150	<	private <T> T[] copyElements(T[] a) {
151	<	if (head < tail) {
152	<	System.arraycopy(elements, head, a, 0, size());
153	<	} else if (head > tail) {
149	<	int headPortionLen = elements.length - head;
150	<	System.arraycopy(elements, head, a, 0, headPortionLen);
151	<	System.arraycopy(elements, 0, a, headPortionLen, tail);
150	>	/* public */ void trimToSize() {
151	>	if (size < elements.length) {
152	>	elements = toArray();
153	>	head = 0;
154		}
155	<	return a;
155	>	// checkInvariants();
156		}
157
158		/**
#	Line 165 | Line 167 | public class ArrayDeque<E> extends Abstr
167		* Constructs an empty array deque with an initial capacity
168		* sufficient to hold the specified number of elements.
169		*
170	<	* @param numElements  lower bound on initial capacity of the deque
170	>	* @param numElements lower bound on initial capacity of the deque
171		*/
172		public ArrayDeque(int numElements) {
173	<	allocateElements(numElements);
173	>	elements = new Object[numElements];
174		}
175
176		/**
#	Line 182 | Line 184 | public class ArrayDeque<E> extends Abstr
184		* @throws NullPointerException if the specified collection is null
185		*/
186		public ArrayDeque(Collection<? extends E> c) {
187	<	allocateElements(c.size());
188	<	addAll(c);
187	>	Object[] es = c.toArray();
188	>	// defend against c.toArray (incorrectly) not returning Object[]
189	>	// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
190	>	if (es.getClass() != Object[].class)
191	>	es = Arrays.copyOf(es, es.length, Object[].class);
192	>	for (Object obj : es)
193	>	Objects.requireNonNull(obj);
194	>	this.elements = es;
195	>	this.size = es.length;
196	>	}
197	>
198	>	/**
199	>	* Increments i, mod modulus.
200	>	* Precondition and postcondition: 0 <= i < modulus.
201	>	*/
202	>	static final int inc(int i, int modulus) {
203	>	if (++i >= modulus) i = 0;
204	>	return i;
205	>	}
206	>
207	>	/**
208	>	* Decrements i, mod modulus.
209	>	* Precondition and postcondition: 0 <= i < modulus.
210	>	*/
211	>	static final int dec(int i, int modulus) {
212	>	if (--i < 0) i = modulus - 1;
213	>	return i;
214	>	}
215	>
216	>	/**
217	>	* Adds i and j, mod modulus.
218	>	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
219	>	*/
220	>	static final int add(int i, int j, int modulus) {
221	>	if ((i += j) - modulus >= 0) i -= modulus;
222	>	return i;
223	>	}
224	>
225	>	/**
226	>	* Returns the array index of the last element.
227	>	* May return invalid index -1 if there are no elements.
228	>	*/
229	>	final int tail() {
230	>	return add(head, size - 1, elements.length);
231	>	}
232	>
233	>	/**
234	>	* Returns element at array index i.
235	>	*/
236	>	@SuppressWarnings("unchecked")
237	>	private E elementAt(int i) {
238	>	return (E) elements[i];
239	>	}
240	>
241	>	/**
242	>	* A version of elementAt that checks for null elements.
243	>	* This check doesn't catch all possible comodifications,
244	>	* but does catch ones that corrupt traversal.  It's a little
245	>	* surprising that javac allows this abuse of generics.
246	>	*/
247	>	static final <E> E nonNullElementAt(Object[] es, int i) {
248	>	@SuppressWarnings("unchecked") E e = (E) es[i];
249	>	if (e == null)
250	>	throw new ConcurrentModificationException();
251	>	return e;
252		}
253
254		// The main insertion and extraction methods are addFirst,
#	Line 197 | Line 262 | public class ArrayDeque<E> extends Abstr
262		* @throws NullPointerException if the specified element is null
263		*/
264		public void addFirst(E e) {
265	<	if (e == null)
266	<	throw new NullPointerException();
267	<	elements[head = (head - 1) & (elements.length - 1)] = e;
268	<	if (head == tail)
269	<	doubleCapacity();
265	>	// checkInvariants();
266	>	Objects.requireNonNull(e);
267	>	Object[] es;
268	>	int capacity, h;
269	>	final int s;
270	>	if ((s = size) == (capacity = (es = elements).length))
271	>	capacity = (es = grow(1)).length;
272	>	if ((h = head - 1) < 0) h = capacity - 1;
273	>	es[head = h] = e;
274	>	size = s + 1;
275	>	// checkInvariants();
276		}
277
278		/**
#	Line 213 | Line 284 | public class ArrayDeque<E> extends Abstr
284		* @throws NullPointerException if the specified element is null
285		*/
286		public void addLast(E e) {
287	<	if (e == null)
288	<	throw new NullPointerException();
289	<	elements[tail] = e;
290	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
291	<	doubleCapacity();
287	>	// checkInvariants();
288	>	Objects.requireNonNull(e);
289	>	Object[] es;
290	>	int capacity;
291	>	final int s;
292	>	if ((s = size) == (capacity = (es = elements).length))
293	>	capacity = (es = grow(1)).length;
294	>	es[add(head, s, capacity)] = e;
295	>	size = s + 1;
296	>	// checkInvariants();
297	>	}
298	>
299	>	/**
300	>	* Adds all of the elements in the specified collection at the end
301	>	* of this deque, as if by calling {@link #addLast} on each one,
302	>	* in the order that they are returned by the collection's
303	>	* iterator.
304	>	*
305	>	* @param c the elements to be inserted into this deque
306	>	* @return {@code true} if this deque changed as a result of the call
307	>	* @throws NullPointerException if the specified collection or any
308	>	*         of its elements are null
309	>	*/
310	>	public boolean addAll(Collection<? extends E> c) {
311	>	final int s = size, needed = c.size() - (elements.length - s);
312	>	if (needed > 0)
313	>	grow(needed);
314	>	c.forEach((e) -> addLast(e));
315	>	// checkInvariants();
316	>	return size > s;
317		}
318
319		/**
#	Line 248 | Line 344 | public class ArrayDeque<E> extends Abstr
344		* @throws NoSuchElementException {@inheritDoc}
345		*/
346		public E removeFirst() {
347	<	E x = pollFirst();
348	<	if (x == null)
347	>	// checkInvariants();
348	>	E e = pollFirst();
349	>	if (e == null)
350		throw new NoSuchElementException();
351	<	return x;
351	>	return e;
352		}
353
354		/**
355		* @throws NoSuchElementException {@inheritDoc}
356		*/
357		public E removeLast() {
358	<	E x = pollLast();
359	<	if (x == null)
358	>	// checkInvariants();
359	>	E e = pollLast();
360	>	if (e == null)
361		throw new NoSuchElementException();
362	<	return x;
362	>	return e;
363		}
364
365		public E pollFirst() {
366	<	int h = head;
367	<	@SuppressWarnings("unchecked")
368	<	E result = (E) elements[h];
271	<	// Element is null if deque empty
272	<	if (result == null)
366	>	// checkInvariants();
367	>	int s, h;
368	>	if ((s = size) <= 0)
369		return null;
370	<	elements[h] = null;     // Must null out slot
371	<	head = (h + 1) & (elements.length - 1);
372	<	return result;
370	>	final Object[] es = elements;
371	>	@SuppressWarnings("unchecked") E e = (E) es[h = head];
372	>	es[h] = null;
373	>	if (++h >= es.length) h = 0;
374	>	head = h;
375	>	size = s - 1;
376	>	return e;
377		}
378
379		public E pollLast() {
380	<	int t = (tail - 1) & (elements.length - 1);
381	<	@SuppressWarnings("unchecked")
382	<	E result = (E) elements[t];
283	<	if (result == null)
380	>	// checkInvariants();
381	>	final int s, tail;
382	>	if ((s = size) <= 0)
383		return null;
384	<	elements[t] = null;
385	<	tail = t;
386	<	return result;
384	>	final Object[] es = elements;
385	>	@SuppressWarnings("unchecked")
386	>	E e = (E) es[tail = add(head, s - 1, es.length)];
387	>	es[tail] = null;
388	>	size = s - 1;
389	>	return e;
390		}
391
392		/**
393		* @throws NoSuchElementException {@inheritDoc}
394		*/
395		public E getFirst() {
396	<	@SuppressWarnings("unchecked")
397	<	E result = (E) elements[head];
398	<	if (result == null)
297	<	throw new NoSuchElementException();
298	<	return result;
396	>	// checkInvariants();
397	>	if (size <= 0) throw new NoSuchElementException();
398	>	return elementAt(head);
399		}
400
401		/**
402		* @throws NoSuchElementException {@inheritDoc}
403		*/
404	+	@SuppressWarnings("unchecked")
405		public E getLast() {
406	<	@SuppressWarnings("unchecked")
407	<	E result = (E) elements[(tail - 1) & (elements.length - 1)];
408	<	if (result == null)
409	<	throw new NoSuchElementException();
410	<	return result;
406	>	// checkInvariants();
407	>	final int s;
408	>	if ((s = size) <= 0) throw new NoSuchElementException();
409	>	final Object[] es = elements;
410	>	return (E) es[add(head, s - 1, es.length)];
411		}
412
312	–	@SuppressWarnings("unchecked")
413		public E peekFirst() {
414	<	// elements[head] is null if deque empty
415	<	return (E) elements[head];
414	>	// checkInvariants();
415	>	return (size <= 0) ? null : elementAt(head);
416		}
417
418		@SuppressWarnings("unchecked")
419		public E peekLast() {
420	<	return (E) elements[(tail - 1) & (elements.length - 1)];
420	>	// checkInvariants();
421	>	final int s;
422	>	if ((s = size) <= 0) return null;
423	>	final Object[] es = elements;
424	>	return (E) es[add(head, s - 1, es.length)];
425		}
426
427		/**
#	Line 333 | Line 437 | public class ArrayDeque<E> extends Abstr
437		* @return {@code true} if the deque contained the specified element
438		*/
439		public boolean removeFirstOccurrence(Object o) {
440	<	if (o == null)
441	<	return false;
442	<	int mask = elements.length - 1;
443	<	int i = head;
444	<	Object x;
445	<	while ( (x = elements[i]) != null) {
446	<	if (o.equals(x)) {
447	<	delete(i);
448	<	return true;
440	>	if (o != null) {
441	>	final Object[] es = elements;
442	>	int i, end, to, todo;
443	>	todo = (end = (i = head) + size)
444	>	- (to = (es.length - end >= 0) ? end : es.length);
445	>	for (;; to = todo, todo = 0, i = 0) {
446	>	for (; i < to; i++)
447	>	if (o.equals(es[i])) {
448	>	delete(i);
449	>	return true;
450	>	}
451	>	if (todo == 0) break;
452		}
346	–	i = (i + 1) & mask;
453		}
454		return false;
455		}
#	Line 361 | Line 467 | public class ArrayDeque<E> extends Abstr
467		* @return {@code true} if the deque contained the specified element
468		*/
469		public boolean removeLastOccurrence(Object o) {
470	<	if (o == null)
471	<	return false;
472	<	int mask = elements.length - 1;
473	<	int i = (tail - 1) & mask;
474	<	Object x;
475	<	while ( (x = elements[i]) != null) {
476	<	if (o.equals(x)) {
477	<	delete(i);
478	<	return true;
470	>	if (o != null) {
471	>	final Object[] es = elements;
472	>	int i, to, end, todo;
473	>	todo = (to = ((end = (i = tail()) - size) >= -1) ? end : -1) - end;
474	>	for (;; to = (i = es.length - 1) - todo, todo = 0) {
475	>	for (; i > to; i--)
476	>	if (o.equals(es[i])) {
477	>	delete(i);
478	>	return true;
479	>	}
480	>	if (todo == 0) break;
481		}
374	–	i = (i - 1) & mask;
482		}
483		return false;
484		}
#	Line 490 | Line 597 | public class ArrayDeque<E> extends Abstr
597		return removeFirst();
598		}
599
493	–	private void checkInvariants() {
494	–	assert elements[tail] == null;
495	–	assert head == tail ? elements[head] == null :
496	–	(elements[head] != null &&
497	–	elements[(tail - 1) & (elements.length - 1)] != null);
498	–	assert elements[(head - 1) & (elements.length - 1)] == null;
499	–	}
500	–
600		/**
601	<	* Removes the element at the specified position in the elements array,
602	<	* adjusting head and tail as necessary.  This can result in motion of
603	<	* elements backwards or forwards in the array.
601	>	* Removes the element at the specified position in the elements array.
602	>	* This can result in forward or backwards motion of array elements.
603	>	* We optimize for least element motion.
604		*
605		* <p>This method is called delete rather than remove to emphasize
606		* that its semantics differ from those of {@link List#remove(int)}.
607		*
608		* @return true if elements moved backwards
609		*/
610	<	private boolean delete(int i) {
611	<	checkInvariants();
612	<	final Object[] elements = this.elements;
613	<	final int mask = elements.length - 1;
610	>	boolean delete(int i) {
611	>	// checkInvariants();
612	>	final Object[] es = elements;
613	>	final int capacity = es.length;
614		final int h = head;
615	<	final int t = tail;
616	<	final int front = (i - h) & mask;
617	<	final int back  = (t - i) & mask;
519	<
520	<	// Invariant: head <= i < tail mod circularity
521	<	if (front >= ((t - h) & mask))
522	<	throw new ConcurrentModificationException();
523	<
524	<	// Optimize for least element motion
615	>	int front;              // number of elements before to-be-deleted elt
616	>	if ((front = i - h) < 0) front += capacity;
617	>	final int back = size - front - 1; // number of elements after
618		if (front < back) {
619	+	// move front elements forwards
620		if (h <= i) {
621	<	System.arraycopy(elements, h, elements, h + 1, front);
621	>	System.arraycopy(es, h, es, h + 1, front);
622		} else { // Wrap around
623	<	System.arraycopy(elements, 0, elements, 1, i);
624	<	elements[0] = elements[mask];
625	<	System.arraycopy(elements, h, elements, h + 1, mask - h);
623	>	System.arraycopy(es, 0, es, 1, i);
624	>	es[0] = es[capacity - 1];
625	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
626		}
627	<	elements[h] = null;
628	<	head = (h + 1) & mask;
627	>	es[h] = null;
628	>	if ((head = (h + 1)) >= capacity) head = 0;
629	>	size--;
630	>	// checkInvariants();
631		return false;
632		} else {
633	<	if (i < t) { // Copy the null tail as well
634	<	System.arraycopy(elements, i + 1, elements, i, back);
635	<	tail = t - 1;
633	>	// move back elements backwards
634	>	int tail = tail();
635	>	if (i <= tail) {
636	>	System.arraycopy(es, i + 1, es, i, back);
637		} else { // Wrap around
638	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
639	<	elements[mask] = elements[0];
640	<	System.arraycopy(elements, 1, elements, 0, t);
641	<	tail = (t - 1) & mask;
638	>	int firstLeg = capacity - (i + 1);
639	>	System.arraycopy(es, i + 1, es, i, firstLeg);
640	>	es[capacity - 1] = es[0];
641	>	System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
642		}
643	+	es[tail] = null;
644	+	size--;
645	+	// checkInvariants();
646		return true;
647		}
648		}
#	Line 555 | Line 655 | public class ArrayDeque<E> extends Abstr
655		* @return the number of elements in this deque
656		*/
657		public int size() {
658	<	return (tail - head) & (elements.length - 1);
658	>	return size;
659		}
660
661		/**
#	Line 564 | Line 664 | public class ArrayDeque<E> extends Abstr
664		* @return {@code true} if this deque contains no elements
665		*/
666		public boolean isEmpty() {
667	<	return head == tail;
667	>	return size == 0;
668		}
669
670		/**
#	Line 584 | Line 684 | public class ArrayDeque<E> extends Abstr
684		}
685
686		private class DeqIterator implements Iterator<E> {
687	<	/**
688	<	* Index of element to be returned by subsequent call to next.
589	<	*/
590	<	private int cursor = head;
687	>	/** Index of element to be returned by subsequent call to next. */
688	>	int cursor;
689
690	<	/**
691	<	* Tail recorded at construction (also in remove), to stop
594	<	* iterator and also to check for comodification.
595	<	*/
596	<	private int fence = tail;
690	>	/** Number of elements yet to be returned. */
691	>	int remaining = size;
692
693		/**
694		* Index of element returned by most recent call to next.
695		* Reset to -1 if element is deleted by a call to remove.
696		*/
697	<	private int lastRet = -1;
697	>	int lastRet = -1;
698	>
699	>	DeqIterator() { cursor = head; }
700
701	<	public boolean hasNext() {
702	<	return cursor != fence;
701	>	public final boolean hasNext() {
702	>	return remaining > 0;
703		}
704
705		public E next() {
706	<	if (cursor == fence)
706	>	if (remaining <= 0)
707		throw new NoSuchElementException();
708	<	@SuppressWarnings("unchecked")
709	<	E result = (E) elements[cursor];
613	<	// This check doesn't catch all possible comodifications,
614	<	// but does catch the ones that corrupt traversal
615	<	if (tail != fence || result == null)
616	<	throw new ConcurrentModificationException();
708	>	final Object[] es = elements;
709	>	E e = nonNullElementAt(es, cursor);
710		lastRet = cursor;
711	<	cursor = (cursor + 1) & (elements.length - 1);
712	<	return result;
711	>	if (++cursor >= es.length) cursor = 0;
712	>	remaining--;
713	>	return e;
714	>	}
715	>
716	>	void postDelete(boolean leftShifted) {
717	>	if (leftShifted)
718	>	if (--cursor < 0) cursor = elements.length - 1;
719		}
720
721	<	public void remove() {
721	>	public final void remove() {
722		if (lastRet < 0)
723		throw new IllegalStateException();
724	<	if (delete(lastRet)) { // if left-shifted, undo increment in next()
626	<	cursor = (cursor - 1) & (elements.length - 1);
627	<	fence = tail;
628	<	}
724	>	postDelete(delete(lastRet));
725		lastRet = -1;
726		}
631	–	}
632	–
633	–	private class DescendingIterator implements Iterator<E> {
634	–	/*
635	–	* This class is nearly a mirror-image of DeqIterator, using
636	–	* tail instead of head for initial cursor, and head instead of
637	–	* tail for fence.
638	–	*/
639	–	private int cursor = tail;
640	–	private int fence = head;
641	–	private int lastRet = -1;
727
728	<	public boolean hasNext() {
729	<	return cursor != fence;
728	>	public void forEachRemaining(Consumer<? super E> action) {
729	>	Objects.requireNonNull(action);
730	>	final int k;
731	>	if ((k = remaining) > 0) {
732	>	remaining = 0;
733	>	ArrayDeque.forEachRemaining(action, elements, cursor, k);
734	>	if ((lastRet = cursor + k - 1) >= elements.length)
735	>	lastRet -= elements.length;
736	>	}
737		}
738	+	}
739
740	<	public E next() {
741	<	if (cursor == fence)
740	>	private class DescendingIterator extends DeqIterator {
741	>	DescendingIterator() { cursor = tail(); }
742	>
743	>	public final E next() {
744	>	if (remaining <= 0)
745		throw new NoSuchElementException();
746	<	cursor = (cursor - 1) & (elements.length - 1);
747	<	@SuppressWarnings("unchecked")
652	<	E result = (E) elements[cursor];
653	<	if (head != fence || result == null)
654	<	throw new ConcurrentModificationException();
746	>	final Object[] es = elements;
747	>	E e = nonNullElementAt(es, cursor);
748		lastRet = cursor;
749	<	return result;
749	>	if (--cursor < 0) cursor = es.length - 1;
750	>	remaining--;
751	>	return e;
752		}
753
754	<	public void remove() {
755	<	if (lastRet < 0)
756	<	throw new IllegalStateException();
757	<	if (!delete(lastRet)) {
758	<	cursor = (cursor + 1) & (elements.length - 1);
759	<	fence = head;
754	>	void postDelete(boolean leftShifted) {
755	>	if (!leftShifted)
756	>	if (++cursor >= elements.length) cursor = 0;
757	>	}
758	>
759	>	public final void forEachRemaining(Consumer<? super E> action) {
760	>	Objects.requireNonNull(action);
761	>	final int k;
762	>	if ((k = remaining) > 0) {
763	>	remaining = 0;
764	>	final Object[] es = elements;
765	>	int i, end, to, todo;
766	>	todo = (to = ((end = (i = cursor) - k) >= -1) ? end : -1) - end;
767	>	for (;; to = (i = es.length - 1) - todo, todo = 0) {
768	>	for (; i > to; i--)
769	>	action.accept(nonNullElementAt(es, i));
770	>	if (todo == 0) break;
771	>	}
772	>	if ((lastRet = cursor - (k - 1)) < 0)
773	>	lastRet += es.length;
774		}
666	–	lastRet = -1;
775		}
776		}
777
778		/**
779	+	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
780	+	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
781	+	* deque.
782	+	*
783	+	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
784	+	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
785	+	* {@link Spliterator#NONNULL}.  Overriding implementations should document
786	+	* the reporting of additional characteristic values.
787	+	*
788	+	* @return a {@code Spliterator} over the elements in this deque
789	+	* @since 1.8
790	+	*/
791	+	public Spliterator<E> spliterator() {
792	+	return new ArrayDequeSpliterator();
793	+	}
794	+
795	+	final class ArrayDequeSpliterator implements Spliterator<E> {
796	+	private int cursor;
797	+	private int remaining; // -1 until late-binding first use
798	+
799	+	/** Constructs late-binding spliterator over all elements. */
800	+	ArrayDequeSpliterator() {
801	+	this.remaining = -1;
802	+	}
803	+
804	+	/** Constructs spliterator over the given slice. */
805	+	ArrayDequeSpliterator(int cursor, int count) {
806	+	this.cursor = cursor;
807	+	this.remaining = count;
808	+	}
809	+
810	+	/** Ensures late-binding initialization; then returns remaining. */
811	+	private int remaining() {
812	+	if (remaining < 0) {
813	+	cursor = head;
814	+	remaining = size;
815	+	}
816	+	return remaining;
817	+	}
818	+
819	+	public ArrayDequeSpliterator trySplit() {
820	+	final int mid;
821	+	if ((mid = remaining() >> 1) > 0) {
822	+	int oldCursor = cursor;
823	+	cursor = add(cursor, mid, elements.length);
824	+	remaining -= mid;
825	+	return new ArrayDequeSpliterator(oldCursor, mid);
826	+	}
827	+	return null;
828	+	}
829	+
830	+	public void forEachRemaining(Consumer<? super E> action) {
831	+	Objects.requireNonNull(action);
832	+	final int k = remaining(); // side effect!
833	+	remaining = 0;
834	+	ArrayDeque.forEachRemaining(action, elements, cursor, k);
835	+	}
836	+
837	+	public boolean tryAdvance(Consumer<? super E> action) {
838	+	Objects.requireNonNull(action);
839	+	final int k;
840	+	if ((k = remaining()) <= 0)
841	+	return false;
842	+	action.accept(nonNullElementAt(elements, cursor));
843	+	if (++cursor >= elements.length) cursor = 0;
844	+	remaining = k - 1;
845	+	return true;
846	+	}
847	+
848	+	public long estimateSize() {
849	+	return remaining();
850	+	}
851	+
852	+	public int characteristics() {
853	+	return Spliterator.NONNULL
854	+	| Spliterator.ORDERED
855	+	| Spliterator.SIZED
856	+	| Spliterator.SUBSIZED;
857	+	}
858	+	}
859	+
860	+	@SuppressWarnings("unchecked")
861	+	public void forEach(Consumer<? super E> action) {
862	+	Objects.requireNonNull(action);
863	+	final Object[] es = elements;
864	+	int i, end, to, todo;
865	+	todo = (end = (i = head) + size)
866	+	- (to = (es.length - end >= 0) ? end : es.length);
867	+	for (;; to = todo, todo = 0, i = 0) {
868	+	for (; i < to; i++)
869	+	action.accept((E) es[i]);
870	+	if (todo == 0) break;
871	+	}
872	+	// checkInvariants();
873	+	}
874	+
875	+	/**
876	+	* Calls action on remaining elements, starting at index i and
877	+	* traversing in ascending order.  A variant of forEach that also
878	+	* checks for concurrent modification, for use in iterators.
879	+	*/
880	+	static <E> void forEachRemaining(
881	+	Consumer<? super E> action, Object[] es, int i, int remaining) {
882	+	int end, to, todo;
883	+	todo = (end = i + remaining)
884	+	- (to = (es.length - end >= 0) ? end : es.length);
885	+	for (;; to = todo, todo = 0, i = 0) {
886	+	for (; i < to; i++)
887	+	action.accept(nonNullElementAt(es, i));
888	+	if (todo == 0) break;
889	+	}
890	+	}
891	+
892	+	/**
893	+	* Replaces each element of this deque with the result of applying the
894	+	* operator to that element, as specified by {@link List#replaceAll}.
895	+	*
896	+	* @param operator the operator to apply to each element
897	+	* @since TBD
898	+	*/
899	+	@SuppressWarnings("unchecked")
900	+	/* public */ void replaceAll(UnaryOperator<E> operator) {
901	+	Objects.requireNonNull(operator);
902	+	final Object[] es = elements;
903	+	int i, end, to, todo;
904	+	todo = (end = (i = head) + size)
905	+	- (to = (es.length - end >= 0) ? end : es.length);
906	+	for (;; to = todo, todo = 0, i = 0) {
907	+	for (; i < to; i++)
908	+	es[i] = operator.apply((E) es[i]);
909	+	if (todo == 0) break;
910	+	}
911	+	// checkInvariants();
912	+	}
913	+
914	+	/**
915	+	* @throws NullPointerException {@inheritDoc}
916	+	*/
917	+	public boolean removeIf(Predicate<? super E> filter) {
918	+	Objects.requireNonNull(filter);
919	+	return bulkRemove(filter);
920	+	}
921	+
922	+	/**
923	+	* @throws NullPointerException {@inheritDoc}
924	+	*/
925	+	public boolean removeAll(Collection<?> c) {
926	+	Objects.requireNonNull(c);
927	+	return bulkRemove(e -> c.contains(e));
928	+	}
929	+
930	+	/**
931	+	* @throws NullPointerException {@inheritDoc}
932	+	*/
933	+	public boolean retainAll(Collection<?> c) {
934	+	Objects.requireNonNull(c);
935	+	return bulkRemove(e -> !c.contains(e));
936	+	}
937	+
938	+	/** Implementation of bulk remove methods. */
939	+	@SuppressWarnings("unchecked")
940	+	private boolean bulkRemove(Predicate<? super E> filter) {
941	+	// checkInvariants();
942	+	final Object[] es = elements;
943	+	int i, end, to, todo;
944	+	todo = (end = (i = head) + size)
945	+	- (to = (es.length - end >= 0) ? end : es.length);
946	+	// Optimize for initial run of non-removed elements
947	+	findFirstRemoved:
948	+	for (;; to = todo, todo = 0, i = 0) {
949	+	for (; i < to; i++)
950	+	if (filter.test((E) es[i]))
951	+	break findFirstRemoved;
952	+	if (todo == 0) return false;
953	+	}
954	+	bulkRemoveModified(filter, i, to, todo);
955	+	return true;
956	+	}
957	+
958	+	/**
959	+	* Helper for bulkRemove, in case of at least one deletion.
960	+	* @param i valid index of first element to be deleted
961	+	*/
962	+	@SuppressWarnings("unchecked")
963	+	private void bulkRemoveModified(
964	+	Predicate<? super E> filter, int i, int to, int todo) {
965	+	final Object[] es = elements;
966	+	final int capacity = es.length;
967	+	// a two-finger algorithm, with hare i and tortoise j
968	+	int j = i++;
969	+	try {
970	+	for (;;) {
971	+	E e;
972	+	// In this loop, i and j are on the same leg, with i > j
973	+	for (; i < to; i++)
974	+	if (!filter.test(e = (E) es[i]))
975	+	es[j++] = e;
976	+	if (todo == 0) break;
977	+	// In this loop, j is on the first leg, i on the second
978	+	for (to = todo, todo = 0, i = 0; i < to && j < capacity; i++)
979	+	if (!filter.test(e = (E) es[i]))
980	+	es[j++] = e;
981	+	if (i >= to) break;
982	+	j = 0;          // j rejoins i on second leg
983	+	}
984	+	bulkRemoveClear(es, j, i);
985	+	// checkInvariants();
986	+	} catch (Throwable ex) {
987	+	// copy remaining elements
988	+	for (int remaining = (to - i) + todo; --remaining >= 0;) {
989	+	es[j] = es[i];
990	+	if (++i >= capacity) i = 0;
991	+	if (++j >= capacity) j = 0;
992	+	}
993	+	bulkRemoveClear(es, j, i);
994	+	// checkInvariants();
995	+	throw ex;
996	+	}
997	+	}
998	+
999	+	/**
1000	+	* Nulls out all elements from index j upto index i.
1001	+	*/
1002	+	private void bulkRemoveClear(Object[] es, int j, int i) {
1003	+	int deleted;
1004	+	if ((deleted = i - j) <= 0) deleted += es.length;
1005	+	size -= deleted;
1006	+	circularClear(es, j, deleted);
1007	+	}
1008	+
1009	+	/**
1010		* Returns {@code true} if this deque contains the specified element.
1011		* More formally, returns {@code true} if and only if this deque contains
1012		* at least one element {@code e} such that {@code o.equals(e)}.
#	Line 676 | Line 1015 | public class ArrayDeque<E> extends Abstr
1015		* @return {@code true} if this deque contains the specified element
1016		*/
1017		public boolean contains(Object o) {
1018	<	if (o == null)
1019	<	return false;
1020	<	int mask = elements.length - 1;
1021	<	int i = head;
1022	<	Object x;
1023	<	while ( (x = elements[i]) != null) {
1024	<	if (o.equals(x))
1025	<	return true;
1026	<	i = (i + 1) & mask;
1018	>	if (o != null) {
1019	>	final Object[] es = elements;
1020	>	int i, end, to, todo;
1021	>	todo = (end = (i = head) + size)
1022	>	- (to = (es.length - end >= 0) ? end : es.length);
1023	>	for (;; to = todo, todo = 0, i = 0) {
1024	>	for (; i < to; i++)
1025	>	if (o.equals(es[i]))
1026	>	return true;
1027	>	if (todo == 0) break;
1028	>	}
1029		}
1030		return false;
1031		}
#	Line 697 | Line 1038 | public class ArrayDeque<E> extends Abstr
1038		* Returns {@code true} if this deque contained the specified element
1039		* (or equivalently, if this deque changed as a result of the call).
1040		*
1041	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1041	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1042		*
1043		* @param o element to be removed from this deque, if present
1044		* @return {@code true} if this deque contained the specified element
#	Line 711 | Line 1052 | public class ArrayDeque<E> extends Abstr
1052		* The deque will be empty after this call returns.
1053		*/
1054		public void clear() {
1055	<	int h = head;
1056	<	int t = tail;
1057	<	if (h != t) { // clear all cells
1058	<	head = tail = 0;
1059	<	int i = h;
1060	<	int mask = elements.length - 1;
1061	<	do {
1062	<	elements[i] = null;
1063	<	i = (i + 1) & mask;
1064	<	} while (i != t);
1055	>	circularClear(elements, head, size);
1056	>	size = head = 0;
1057	>	// checkInvariants();
1058	>	}
1059	>
1060	>	/**
1061	>	* Nulls out count elements, starting at array index from.
1062	>	* Special case (from == es.length) is treated the same as (from == 0).
1063	>	*/
1064	>	private static void circularClear(Object[] es, int from, int count) {
1065	>	int end, to, todo;
1066	>	todo = (end = from + count)
1067	>	- (to = (es.length - end >= 0) ? end : es.length);
1068	>	for (;; to = todo, todo = 0, from = 0) {
1069	>	Arrays.fill(es, from, to, null);
1070	>	if (todo == 0) break;
1071		}
1072		}
1073
#	Line 738 | Line 1085 | public class ArrayDeque<E> extends Abstr
1085		* @return an array containing all of the elements in this deque
1086		*/
1087		public Object[] toArray() {
1088	<	return copyElements(new Object[size()]);
1088	>	return toArray(Object[].class);
1089	>	}
1090	>
1091	>	private <T> T[] toArray(Class<T[]> klazz) {
1092	>	final Object[] es = elements;
1093	>	final T[] a;
1094	>	final int head, len, end, todo;
1095	>	todo = size - (len = Math.min(size, es.length - (head = this.head)));
1096	>	if ((end = head + size) >= 0) {
1097	>	a = Arrays.copyOfRange(es, head, end, klazz);
1098	>	} else {
1099	>	// integer overflow!
1100	>	a = Arrays.copyOfRange(es, 0, size, klazz);
1101	>	System.arraycopy(es, head, a, 0, len);
1102	>	}
1103	>	if (todo > 0)
1104	>	System.arraycopy(es, 0, a, len, todo);
1105	>	return a;
1106		}
1107
1108		/**
#	Line 763 | Line 1127 | public class ArrayDeque<E> extends Abstr
1127		* The following code can be used to dump the deque into a newly
1128		* allocated array of {@code String}:
1129		*
1130	<	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1130	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1131		*
1132		* Note that {@code toArray(new Object[0])} is identical in function to
1133		* {@code toArray()}.
#	Line 779 | Line 1143 | public class ArrayDeque<E> extends Abstr
1143		*/
1144		@SuppressWarnings("unchecked")
1145		public <T> T[] toArray(T[] a) {
1146	<	int size = size();
1147	<	if (a.length < size)
1148	<	a = (T[])java.lang.reflect.Array.newInstance(
1149	<	a.getClass().getComponentType(), size);
1150	<	copyElements(a);
1151	<	if (a.length > size)
1146	>	final int size;
1147	>	if ((size = this.size) > a.length)
1148	>	return toArray((Class<T[]>) a.getClass());
1149	>	final Object[] es = elements;
1150	>	int i, j, len, todo;
1151	>	todo = size - (len = Math.min(size, es.length - (i = head)));
1152	>	for (j = 0;; j += len, len = todo, todo = 0, i = 0) {
1153	>	System.arraycopy(es, i, a, j, len);
1154	>	if (todo == 0) break;
1155	>	}
1156	>	if (size < a.length)
1157		a[size] = null;
1158		return a;
1159		}
#	Line 812 | Line 1181 | public class ArrayDeque<E> extends Abstr
1181		/**
1182		* Saves this deque to a stream (that is, serializes it).
1183		*
1184	+	* @param s the stream
1185	+	* @throws java.io.IOException if an I/O error occurs
1186		* @serialData The current size ({@code int}) of the deque,
1187		* followed by all of its elements (each an object reference) in
1188		* first-to-last order.
#	Line 821 | Line 1192 | public class ArrayDeque<E> extends Abstr
1192		s.defaultWriteObject();
1193
1194		// Write out size
1195	<	s.writeInt(size());
1195	>	s.writeInt(size);
1196
1197		// Write out elements in order.
1198	<	int mask = elements.length - 1;
1199	<	for (int i = head; i != tail; i = (i + 1) & mask)
1200	<	s.writeObject(elements[i]);
1198	>	final Object[] es = elements;
1199	>	int i, end, to, todo;
1200	>	todo = (end = (i = head) + size)
1201	>	- (to = (es.length - end >= 0) ? end : es.length);
1202	>	for (;; to = todo, todo = 0, i = 0) {
1203	>	for (; i < to; i++)
1204	>	s.writeObject(es[i]);
1205	>	if (todo == 0) break;
1206	>	}
1207		}
1208
1209		/**
1210		* Reconstitutes this deque from a stream (that is, deserializes it).
1211	+	* @param s the stream
1212	+	* @throws ClassNotFoundException if the class of a serialized object
1213	+	*         could not be found
1214	+	* @throws java.io.IOException if an I/O error occurs
1215		*/
1216		private void readObject(java.io.ObjectInputStream s)
1217		throws java.io.IOException, ClassNotFoundException {
1218		s.defaultReadObject();
1219
1220		// Read in size and allocate array
1221	<	int size = s.readInt();
841	<	allocateElements(size);
842	<	head = 0;
843	<	tail = size;
1221	>	elements = new Object[size = s.readInt()];
1222
1223		// Read in all elements in the proper order.
1224		for (int i = 0; i < size; i++)
1225		elements[i] = s.readObject();
1226		}
1227
1228	<	public Stream<E> stream() {
1229	<	int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED;
1230	<	return Streams.stream
1231	<	(() -> new DeqSpliterator<E>(this, head, tail), flags);
1232	<	}
1233	<	public Stream<E> parallelStream() {
1234	<	int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED;
1235	<	return Streams.parallelStream
1236	<	(() -> new DeqSpliterator<E>(this, head, tail), flags);
1237	<	}
1238	<
1239	<
1240	<	static final class DeqSpliterator<E> implements Spliterator<E> {
1241	<	private final ArrayDeque<E> deq;
1242	<	private final int fence;  // initially tail
1243	<	private int index;        // current index, modified on traverse/split
1244	<
867	<	/** Create new spliterator covering the given array and range */
868	<	DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) {
869	<	this.deq = deq; this.index = origin; this.fence = fence;
870	<	}
871	<
872	<	public DeqSpliterator<E> trySplit() {
873	<	int n = deq.elements.length;
874	<	int h = index, t = fence;
875	<	if (h != t && ((h + 1) & (n - 1)) != t) {
876	<	if (h > t)
877	<	t += n;
878	<	int m = ((h + t) >>> 1) & (n - 1);
879	<	return new DeqSpliterator<E>(deq, h, index = m);
880	<	}
881	<	return null;
882	<	}
883	<
884	<	public void forEach(Consumer<? super E> block) {
885	<	if (block == null)
886	<	throw new NullPointerException();
887	<	Object[] a = deq.elements;
888	<	int m = a.length - 1, f = fence, i = index;
889	<	index = f;
890	<	while (i != f) {
891	<	@SuppressWarnings("unchecked") E e = (E)a[i];
892	<	i = (i + 1) & m;
893	<	if (e == null)
894	<	throw new ConcurrentModificationException();
895	<	block.accept(e);
896	<	}
897	<	}
898	<
899	<	public boolean tryAdvance(Consumer<? super E> block) {
900	<	if (block == null)
901	<	throw new NullPointerException();
902	<	Object[] a = deq.elements;
903	<	int m = a.length - 1, i = index;
904	<	if (i != fence) {
905	<	@SuppressWarnings("unchecked") E e = (E)a[i];
906	<	index = (i + 1) & m;
907	<	if (e == null)
908	<	throw new ConcurrentModificationException();
909	<	block.accept(e);
910	<	return true;
911	<	}
912	<	return false;
913	<	}
914	<
915	<	// Other spliterator methods
916	<	public long estimateSize() {
917	<	int n = fence - index;
918	<	if (n < 0)
919	<	n += deq.elements.length;
920	<	return (long)n;
1228	>	/** debugging */
1229	>	void checkInvariants() {
1230	>	try {
1231	>	int capacity = elements.length;
1232	>	// assert size >= 0 && size <= capacity;
1233	>	// assert head >= 0;
1234	>	// assert capacity == 0 || head < capacity;
1235	>	// assert size == 0 || elements[head] != null;
1236	>	// assert size == 0 || elements[tail()] != null;
1237	>	// assert size == capacity || elements[dec(head, capacity)] == null;
1238	>	// assert size == capacity || elements[inc(tail(), capacity)] == null;
1239	>	} catch (Throwable t) {
1240	>	System.err.printf("head=%d size=%d capacity=%d%n",
1241	>	head, size, elements.length);
1242	>	System.err.printf("elements=%s%n",
1243	>	Arrays.toString(elements));
1244	>	throw t;
1245		}
922	–	public boolean hasExactSize() { return true; }
923	–	public boolean hasExactSplits() { return true; }
1246		}
1247
1248		}

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