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

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.37 by jsr166, Tue Dec 6 04:37:55 2011 UTC vs.
Revision 1.99 by jsr166, Sun Oct 30 16:32:40 2016 UTC

#	Line 5 | Line 5
5
6		package java.util;
7
8	+	import java.io.Serializable;
9	+	import java.util.function.Consumer;
10	+	import java.util.function.Predicate;
11	+	import java.util.function.UnaryOperator;
12	+
13		/**
14		* Resizable-array implementation of the {@link Deque} interface.  Array
15		* deques have no capacity restrictions; they grow as necessary to support
#	Line 14 | Line 19 | package java.util;
19		* {@link Stack} when used as a stack, and faster than {@link LinkedList}
20		* when used as a queue.
21		*
22	<	* <p>Most <tt>ArrayDeque</tt> 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.
22	>	* <p>Most {@code ArrayDeque} operations run in amortized constant 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 <tt>iterator</tt> 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 <tt>remove</tt>
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 33 | Line 40 | package java.util;
40		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
41		* as it is, generally speaking, impossible to make any hard guarantees in the
42		* presence of unsynchronized concurrent modification.  Fail-fast iterators
43	<	* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
43	>	* throw {@code ConcurrentModificationException} on a best-effort basis.
44		* Therefore, it would be wrong to write a program that depended on this
45		* exception for its correctness: <i>the fail-fast behavior of iterators
46		* should be used only to detect bugs.</i>
#	Line 47 | Line 54 | package java.util;
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
51	–	* @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
60	<	* full, except transiently within an addX method where it is
61	<	* resized (see doubleCapacity) immediately upon becoming full,
62	<	* thus avoiding head and tail wrapping around to equal each
63	<	* other.  We also guarantee that all array cells not holding
64	<	* deque elements are always null.
65	>	* We guarantee that all array cells not holding deque elements
66	>	* are always null.
67		*/
68	<	private transient Object[] elements;
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	<	private transient int head;
75	>	transient int head;
76
77	<	/**
78	<	* The index at which the next element would be added to the tail
77	<	* of the deque (via addLast(E), add(E), or push(E)).
78	<	*/
79	<	private transient int tail;
77	>	/** Number of elements in this collection. */
78	>	transient int size;
79
80		/**
81	<	* The minimum capacity that we'll use for a newly created deque.
82	<	* Must be a power of 2.
83	<	*/
84	<	private static final int MIN_INITIAL_CAPACITY = 8;
85	<
86	<	// ******  Array allocation and resizing utilities ******
87	<
88	<	/**
89	<	* Allocate empty array to hold the given number of elements.
90	<	*
91	<	* @param numElements  the number of elements to hold
92	<	*/
93	<	private void allocateElements(int numElements) {
94	<	int initialCapacity = MIN_INITIAL_CAPACITY;
95	<	// Find the best power of two to hold elements.
96	<	// Tests "<=" because arrays aren't kept full.
97	<	if (numElements >= initialCapacity) {
98	<	initialCapacity = numElements;
99	<	initialCapacity |= (initialCapacity >>>  1);
100	<	initialCapacity |= (initialCapacity >>>  2);
101	<	initialCapacity |= (initialCapacity >>>  4);
102	<	initialCapacity |= (initialCapacity >>>  8);
103	<	initialCapacity |= (initialCapacity >>> 16);
104	<	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 void 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	>	// checkInvariants();
114	>	}
115
116	<	if (initialCapacity < 0)   // Too many elements, must back off
117	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
116	>	/** Capacity calculation for edge conditions, especially overflow. */
117	>	private int newCapacity(int needed, int jump) {
118	>	final int oldCapacity = elements.length, minCapacity;
119	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
120	>	if (minCapacity < 0)
121	>	throw new IllegalStateException("Sorry, deque too big");
122	>	return Integer.MAX_VALUE;
123		}
124	<	elements = new Object[initialCapacity];
124	>	if (needed > jump)
125	>	return minCapacity;
126	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
127	>	? oldCapacity + jump
128	>	: MAX_ARRAY_SIZE;
129		}
130
131		/**
132	<	* Double the capacity of this deque.  Call only when full, i.e.,
133	<	* when head and tail have wrapped around to become equal.
132	>	* Increases the internal storage of this collection, if necessary,
133	>	* to ensure that it can hold at least the given number of elements.
134	>	*
135	>	* @param minCapacity the desired minimum capacity
136	>	* @since TBD
137		*/
138	<	private void doubleCapacity() {
139	<	assert head == tail;
140	<	int p = head;
141	<	int n = elements.length;
121	<	int r = n - p; // number of elements to the right of p
122	<	int newCapacity = n << 1;
123	<	if (newCapacity < 0)
124	<	throw new IllegalStateException("Sorry, deque too big");
125	<	Object[] a = new Object[newCapacity];
126	<	System.arraycopy(elements, p, a, 0, r);
127	<	System.arraycopy(elements, 0, a, r, p);
128	<	elements = a;
129	<	head = 0;
130	<	tail = n;
138	>	/* public */ void ensureCapacity(int minCapacity) {
139	>	if (minCapacity > elements.length)
140	>	grow(minCapacity - elements.length);
141	>	// checkInvariants();
142		}
143
144		/**
145	<	* Copies the elements from our element array into the specified array,
135	<	* in order (from first to last element in the deque).  It is assumed
136	<	* that the array is large enough to hold all elements in the deque.
145	>	* Minimizes the internal storage of this collection.
146		*
147	<	* @return its argument
147	>	* @since TBD
148		*/
149	<	private <T> T[] copyElements(T[] a) {
150	<	if (head < tail) {
151	<	System.arraycopy(elements, head, a, 0, size());
152	<	} else if (head > tail) {
144	<	int headPortionLen = elements.length - head;
145	<	System.arraycopy(elements, head, a, 0, headPortionLen);
146	<	System.arraycopy(elements, 0, a, headPortionLen, tail);
149	>	/* public */ void trimToSize() {
150	>	if (size < elements.length) {
151	>	elements = toArray();
152	>	head = 0;
153		}
154	<	return a;
154	>	// checkInvariants();
155		}
156
157		/**
#	Line 160 | Line 166 | public class ArrayDeque<E> extends Abstr
166		* Constructs an empty array deque with an initial capacity
167		* sufficient to hold the specified number of elements.
168		*
169	<	* @param numElements  lower bound on initial capacity of the deque
169	>	* @param numElements lower bound on initial capacity of the deque
170		*/
171		public ArrayDeque(int numElements) {
172	<	allocateElements(numElements);
172	>	elements = new Object[numElements];
173		}
174
175		/**
#	Line 177 | Line 183 | public class ArrayDeque<E> extends Abstr
183		* @throws NullPointerException if the specified collection is null
184		*/
185		public ArrayDeque(Collection<? extends E> c) {
186	<	allocateElements(c.size());
187	<	addAll(c);
186	>	Object[] es = c.toArray();
187	>	// defend against c.toArray (incorrectly) not returning Object[]
188	>	// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
189	>	if (es.getClass() != Object[].class)
190	>	es = Arrays.copyOf(es, es.length, Object[].class);
191	>	for (Object obj : es)
192	>	Objects.requireNonNull(obj);
193	>	this.elements = es;
194	>	this.size = es.length;
195	>	}
196	>
197	>	/**
198	>	* Increments i, mod modulus.
199	>	* Precondition and postcondition: 0 <= i < modulus.
200	>	*/
201	>	static final int inc(int i, int modulus) {
202	>	if (++i >= modulus) i = 0;
203	>	return i;
204	>	}
205	>
206	>	/**
207	>	* Decrements i, mod modulus.
208	>	* Precondition and postcondition: 0 <= i < modulus.
209	>	*/
210	>	static final int dec(int i, int modulus) {
211	>	if (--i < 0) i = modulus - 1;
212	>	return i;
213	>	}
214	>
215	>	/**
216	>	* Adds i and j, mod modulus.
217	>	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
218	>	*/
219	>	static final int add(int i, int j, int modulus) {
220	>	if ((i += j) - modulus >= 0) i -= modulus;
221	>	return i;
222	>	}
223	>
224	>	/**
225	>	* Returns the array index of the last element.
226	>	* May return invalid index -1 if there are no elements.
227	>	*/
228	>	final int tail() {
229	>	return add(head, size - 1, elements.length);
230	>	}
231	>
232	>	/**
233	>	* Returns element at array index i.
234	>	*/
235	>	@SuppressWarnings("unchecked")
236	>	private E elementAt(int i) {
237	>	return (E) elements[i];
238	>	}
239	>
240	>	/**
241	>	* A version of elementAt that checks for null elements.
242	>	* This check doesn't catch all possible comodifications,
243	>	* but does catch ones that corrupt traversal.  It's a little
244	>	* surprising that javac allows this abuse of generics.
245	>	*/
246	>	static final <E> E nonNullElementAt(Object[] es, int i) {
247	>	@SuppressWarnings("unchecked") E e = (E) es[i];
248	>	if (e == null)
249	>	throw new ConcurrentModificationException();
250	>	return e;
251		}
252
253		// The main insertion and extraction methods are addFirst,
#	Line 192 | Line 261 | public class ArrayDeque<E> extends Abstr
261		* @throws NullPointerException if the specified element is null
262		*/
263		public void addFirst(E e) {
264	<	if (e == null)
265	<	throw new NullPointerException();
266	<	elements[head = (head - 1) & (elements.length - 1)] = e;
267	<	if (head == tail)
268	<	doubleCapacity();
264	>	// checkInvariants();
265	>	Objects.requireNonNull(e);
266	>	Object[] es;
267	>	int capacity, h;
268	>	final int s;
269	>	if ((s = size) == (capacity = (es = elements).length)) {
270	>	grow(1);
271	>	capacity = (es = elements).length;
272	>	}
273	>	if ((h = head - 1) < 0) h = capacity - 1;
274	>	es[head = h] = e;
275	>	size = s + 1;
276	>	// checkInvariants();
277		}
278
279		/**
#	Line 208 | Line 285 | public class ArrayDeque<E> extends Abstr
285		* @throws NullPointerException if the specified element is null
286		*/
287		public void addLast(E e) {
288	<	if (e == null)
289	<	throw new NullPointerException();
290	<	elements[tail] = e;
291	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
292	<	doubleCapacity();
288	>	// checkInvariants();
289	>	Objects.requireNonNull(e);
290	>	Object[] es;
291	>	int capacity;
292	>	final int s;
293	>	if ((s = size) == (capacity = (es = elements).length)) {
294	>	grow(1);
295	>	capacity = (es = elements).length;
296	>	}
297	>	es[add(head, s, capacity)] = e;
298	>	size = s + 1;
299	>	// checkInvariants();
300	>	}
301	>
302	>	/**
303	>	* Adds all of the elements in the specified collection at the end
304	>	* of this deque, as if by calling {@link #addLast} on each one,
305	>	* in the order that they are returned by the collection's
306	>	* iterator.
307	>	*
308	>	* @param c the elements to be inserted into this deque
309	>	* @return {@code true} if this deque changed as a result of the call
310	>	* @throws NullPointerException if the specified collection or any
311	>	*         of its elements are null
312	>	*/
313	>	public boolean addAll(Collection<? extends E> c) {
314	>	final int s = size, needed = c.size() - (elements.length - s);
315	>	if (needed > 0)
316	>	grow(needed);
317	>	c.forEach((e) -> addLast(e));
318	>	// checkInvariants();
319	>	return size > s;
320		}
321
322		/**
323		* Inserts the specified element at the front of this deque.
324		*
325		* @param e the element to add
326	<	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
326	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
327		* @throws NullPointerException if the specified element is null
328		*/
329		public boolean offerFirst(E e) {
#	Line 231 | Line 335 | public class ArrayDeque<E> extends Abstr
335		* Inserts the specified element at the end of this deque.
336		*
337		* @param e the element to add
338	<	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
338	>	* @return {@code true} (as specified by {@link Deque#offerLast})
339		* @throws NullPointerException if the specified element is null
340		*/
341		public boolean offerLast(E e) {
#	Line 243 | Line 347 | public class ArrayDeque<E> extends Abstr
347		* @throws NoSuchElementException {@inheritDoc}
348		*/
349		public E removeFirst() {
350	<	E x = pollFirst();
351	<	if (x == null)
350	>	// checkInvariants();
351	>	E e = pollFirst();
352	>	if (e == null)
353		throw new NoSuchElementException();
354	<	return x;
354	>	return e;
355		}
356
357		/**
358		* @throws NoSuchElementException {@inheritDoc}
359		*/
360		public E removeLast() {
361	<	E x = pollLast();
362	<	if (x == null)
361	>	// checkInvariants();
362	>	E e = pollLast();
363	>	if (e == null)
364		throw new NoSuchElementException();
365	<	return x;
365	>	return e;
366		}
367
368		public E pollFirst() {
369	<	int h = head;
370	<	@SuppressWarnings("unchecked")
371	<	E result = (E) elements[h];
266	<	// Element is null if deque empty
267	<	if (result == null)
369	>	// checkInvariants();
370	>	int s, h;
371	>	if ((s = size) <= 0)
372		return null;
373	<	elements[h] = null;     // Must null out slot
374	<	head = (h + 1) & (elements.length - 1);
375	<	return result;
373	>	final Object[] es = elements;
374	>	@SuppressWarnings("unchecked") E e = (E) es[h = head];
375	>	es[h] = null;
376	>	if (++h >= es.length) h = 0;
377	>	head = h;
378	>	size = s - 1;
379	>	return e;
380		}
381
382		public E pollLast() {
383	<	int t = (tail - 1) & (elements.length - 1);
384	<	@SuppressWarnings("unchecked")
385	<	E result = (E) elements[t];
278	<	if (result == null)
383	>	// checkInvariants();
384	>	final int s, tail;
385	>	if ((s = size) <= 0)
386		return null;
387	<	elements[t] = null;
388	<	tail = t;
389	<	return result;
387	>	final Object[] es = elements;
388	>	@SuppressWarnings("unchecked")
389	>	E e = (E) es[tail = add(head, s - 1, es.length)];
390	>	es[tail] = null;
391	>	size = s - 1;
392	>	return e;
393		}
394
395		/**
396		* @throws NoSuchElementException {@inheritDoc}
397		*/
398		public E getFirst() {
399	<	@SuppressWarnings("unchecked")
400	<	E result = (E) elements[head];
401	<	if (result == null)
292	<	throw new NoSuchElementException();
293	<	return result;
399	>	// checkInvariants();
400	>	if (size <= 0) throw new NoSuchElementException();
401	>	return elementAt(head);
402		}
403
404		/**
405		* @throws NoSuchElementException {@inheritDoc}
406		*/
407	+	@SuppressWarnings("unchecked")
408		public E getLast() {
409	<	@SuppressWarnings("unchecked")
410	<	E result = (E) elements[(tail - 1) & (elements.length - 1)];
411	<	if (result == null)
412	<	throw new NoSuchElementException();
413	<	return result;
409	>	// checkInvariants();
410	>	final int s;
411	>	if ((s = size) <= 0) throw new NoSuchElementException();
412	>	final Object[] es = elements;
413	>	return (E) es[add(head, s - 1, es.length)];
414		}
415
307	–	@SuppressWarnings("unchecked")
416		public E peekFirst() {
417	<	// elements[head] is null if deque empty
418	<	return (E) elements[head];
417	>	// checkInvariants();
418	>	return (size <= 0) ? null : elementAt(head);
419		}
420
421		@SuppressWarnings("unchecked")
422		public E peekLast() {
423	<	return (E) elements[(tail - 1) & (elements.length - 1)];
423	>	// checkInvariants();
424	>	final int s;
425	>	if ((s = size) <= 0) return null;
426	>	final Object[] es = elements;
427	>	return (E) es[add(head, s - 1, es.length)];
428		}
429
430		/**
431		* Removes the first occurrence of the specified element in this
432		* deque (when traversing the deque from head to tail).
433		* If the deque does not contain the element, it is unchanged.
434	<	* More formally, removes the first element <tt>e</tt> such that
435	<	* <tt>o.equals(e)</tt> (if such an element exists).
436	<	* Returns <tt>true</tt> if this deque contained the specified element
434	>	* More formally, removes the first element {@code e} such that
435	>	* {@code o.equals(e)} (if such an element exists).
436	>	* Returns {@code true} if this deque contained the specified element
437		* (or equivalently, if this deque changed as a result of the call).
438		*
439		* @param o element to be removed from this deque, if present
440	<	* @return <tt>true</tt> if the deque contained the specified element
440	>	* @return {@code true} if the deque contained the specified element
441		*/
442		public boolean removeFirstOccurrence(Object o) {
443	<	if (o == null)
444	<	return false;
445	<	int mask = elements.length - 1;
446	<	int i = head;
447	<	Object x;
448	<	while ( (x = elements[i]) != null) {
449	<	if (o.equals(x)) {
450	<	delete(i);
451	<	return true;
443	>	if (o != null) {
444	>	final Object[] es = elements;
445	>	int i, end, to, todo;
446	>	todo = (end = (i = head) + size)
447	>	- (to = (es.length - end >= 0) ? end : es.length);
448	>	for (;; to = todo, i = 0, todo = 0) {
449	>	for (; i < to; i++)
450	>	if (o.equals(es[i])) {
451	>	delete(i);
452	>	return true;
453	>	}
454	>	if (todo == 0) break;
455		}
341	–	i = (i + 1) & mask;
456		}
457		return false;
458		}
#	Line 347 | Line 461 | public class ArrayDeque<E> extends Abstr
461		* Removes the last occurrence of the specified element in this
462		* deque (when traversing the deque from head to tail).
463		* If the deque does not contain the element, it is unchanged.
464	<	* More formally, removes the last element <tt>e</tt> such that
465	<	* <tt>o.equals(e)</tt> (if such an element exists).
466	<	* Returns <tt>true</tt> if this deque contained the specified element
464	>	* More formally, removes the last element {@code e} such that
465	>	* {@code o.equals(e)} (if such an element exists).
466	>	* Returns {@code true} if this deque contained the specified element
467		* (or equivalently, if this deque changed as a result of the call).
468		*
469		* @param o element to be removed from this deque, if present
470	<	* @return <tt>true</tt> if the deque contained the specified element
470	>	* @return {@code true} if the deque contained the specified element
471		*/
472		public boolean removeLastOccurrence(Object o) {
473	<	if (o == null)
474	<	return false;
475	<	int mask = elements.length - 1;
476	<	int i = (tail - 1) & mask;
477	<	Object x;
478	<	while ( (x = elements[i]) != null) {
479	<	if (o.equals(x)) {
480	<	delete(i);
481	<	return true;
473	>	if (o != null) {
474	>	final Object[] es = elements;
475	>	int i, to, end, todo;
476	>	todo = (to = ((end = (i = tail()) - size) >= -1) ? end : -1) - end;
477	>	for (;; to = (i = es.length - 1) - todo, todo = 0) {
478	>	for (; i > to; i--)
479	>	if (o.equals(es[i])) {
480	>	delete(i);
481	>	return true;
482	>	}
483	>	if (todo == 0) break;
484		}
369	–	i = (i - 1) & mask;
485		}
486		return false;
487		}
#	Line 379 | Line 494 | public class ArrayDeque<E> extends Abstr
494		* <p>This method is equivalent to {@link #addLast}.
495		*
496		* @param e the element to add
497	<	* @return <tt>true</tt> (as specified by {@link Collection#add})
497	>	* @return {@code true} (as specified by {@link Collection#add})
498		* @throws NullPointerException if the specified element is null
499		*/
500		public boolean add(E e) {
#	Line 393 | Line 508 | public class ArrayDeque<E> extends Abstr
508		* <p>This method is equivalent to {@link #offerLast}.
509		*
510		* @param e the element to add
511	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
511	>	* @return {@code true} (as specified by {@link Queue#offer})
512		* @throws NullPointerException if the specified element is null
513		*/
514		public boolean offer(E e) {
#	Line 418 | Line 533 | public class ArrayDeque<E> extends Abstr
533		/**
534		* Retrieves and removes the head of the queue represented by this deque
535		* (in other words, the first element of this deque), or returns
536	<	* <tt>null</tt> if this deque is empty.
536	>	* {@code null} if this deque is empty.
537		*
538		* <p>This method is equivalent to {@link #pollFirst}.
539		*
540		* @return the head of the queue represented by this deque, or
541	<	*         <tt>null</tt> if this deque is empty
541	>	*         {@code null} if this deque is empty
542		*/
543		public E poll() {
544		return pollFirst();
#	Line 445 | Line 560 | public class ArrayDeque<E> extends Abstr
560
561		/**
562		* Retrieves, but does not remove, the head of the queue represented by
563	<	* this deque, or returns <tt>null</tt> if this deque is empty.
563	>	* this deque, or returns {@code null} if this deque is empty.
564		*
565		* <p>This method is equivalent to {@link #peekFirst}.
566		*
567		* @return the head of the queue represented by this deque, or
568	<	*         <tt>null</tt> if this deque is empty
568	>	*         {@code null} if this deque is empty
569		*/
570		public E peek() {
571		return peekFirst();
#	Line 485 | Line 600 | public class ArrayDeque<E> extends Abstr
600		return removeFirst();
601		}
602
488	–	private void checkInvariants() {
489	–	assert elements[tail] == null;
490	–	assert head == tail ? elements[head] == null :
491	–	(elements[head] != null &&
492	–	elements[(tail - 1) & (elements.length - 1)] != null);
493	–	assert elements[(head - 1) & (elements.length - 1)] == null;
494	–	}
495	–
603		/**
604	<	* Removes the element at the specified position in the elements array,
605	<	* adjusting head and tail as necessary.  This can result in motion of
606	<	* elements backwards or forwards in the array.
604	>	* Removes the element at the specified position in the elements array.
605	>	* This can result in forward or backwards motion of array elements.
606	>	* We optimize for least element motion.
607		*
608		* <p>This method is called delete rather than remove to emphasize
609		* that its semantics differ from those of {@link List#remove(int)}.
610		*
611		* @return true if elements moved backwards
612		*/
613	<	private boolean delete(int i) {
614	<	checkInvariants();
615	<	final Object[] elements = this.elements;
616	<	final int mask = elements.length - 1;
613	>	boolean delete(int i) {
614	>	// checkInvariants();
615	>	final Object[] es = elements;
616	>	final int capacity = es.length;
617		final int h = head;
618	<	final int t = tail;
619	<	final int front = (i - h) & mask;
620	<	final int back  = (t - i) & mask;
514	<
515	<	// Invariant: head <= i < tail mod circularity
516	<	if (front >= ((t - h) & mask))
517	<	throw new ConcurrentModificationException();
518	<
519	<	// Optimize for least element motion
618	>	int front;              // number of elements before to-be-deleted elt
619	>	if ((front = i - h) < 0) front += capacity;
620	>	final int back = size - front - 1; // number of elements after
621		if (front < back) {
622	+	// move front elements forwards
623		if (h <= i) {
624	<	System.arraycopy(elements, h, elements, h + 1, front);
624	>	System.arraycopy(es, h, es, h + 1, front);
625		} else { // Wrap around
626	<	System.arraycopy(elements, 0, elements, 1, i);
627	<	elements[0] = elements[mask];
628	<	System.arraycopy(elements, h, elements, h + 1, mask - h);
626	>	System.arraycopy(es, 0, es, 1, i);
627	>	es[0] = es[capacity - 1];
628	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
629		}
630	<	elements[h] = null;
631	<	head = (h + 1) & mask;
630	>	es[h] = null;
631	>	if ((head = (h + 1)) >= capacity) head = 0;
632	>	size--;
633	>	// checkInvariants();
634		return false;
635		} else {
636	<	if (i < t) { // Copy the null tail as well
637	<	System.arraycopy(elements, i + 1, elements, i, back);
638	<	tail = t - 1;
636	>	// move back elements backwards
637	>	int tail = tail();
638	>	if (i <= tail) {
639	>	System.arraycopy(es, i + 1, es, i, back);
640		} else { // Wrap around
641	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
642	<	elements[mask] = elements[0];
643	<	System.arraycopy(elements, 1, elements, 0, t);
644	<	tail = (t - 1) & mask;
641	>	int firstLeg = capacity - (i + 1);
642	>	System.arraycopy(es, i + 1, es, i, firstLeg);
643	>	es[capacity - 1] = es[0];
644	>	System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
645		}
646	+	es[tail] = null;
647	+	size--;
648	+	// checkInvariants();
649		return true;
650		}
651		}
#	Line 550 | Line 658 | public class ArrayDeque<E> extends Abstr
658		* @return the number of elements in this deque
659		*/
660		public int size() {
661	<	return (tail - head) & (elements.length - 1);
661	>	return size;
662		}
663
664		/**
665	<	* Returns <tt>true</tt> if this deque contains no elements.
665	>	* Returns {@code true} if this deque contains no elements.
666		*
667	<	* @return <tt>true</tt> if this deque contains no elements
667	>	* @return {@code true} if this deque contains no elements
668		*/
669		public boolean isEmpty() {
670	<	return head == tail;
670	>	return size == 0;
671		}
672
673		/**
#	Line 579 | Line 687 | public class ArrayDeque<E> extends Abstr
687		}
688
689		private class DeqIterator implements Iterator<E> {
690	<	/**
691	<	* Index of element to be returned by subsequent call to next.
584	<	*/
585	<	private int cursor = head;
690	>	/** Index of element to be returned by subsequent call to next. */
691	>	int cursor;
692
693	<	/**
694	<	* Tail recorded at construction (also in remove), to stop
589	<	* iterator and also to check for comodification.
590	<	*/
591	<	private int fence = tail;
693	>	/** Number of elements yet to be returned. */
694	>	int remaining = size;
695
696		/**
697		* Index of element returned by most recent call to next.
698		* Reset to -1 if element is deleted by a call to remove.
699		*/
700	<	private int lastRet = -1;
700	>	int lastRet = -1;
701
702	<	public boolean hasNext() {
703	<	return cursor != fence;
702	>	DeqIterator() { cursor = head; }
703	>
704	>	public final boolean hasNext() {
705	>	return remaining > 0;
706		}
707
708		public E next() {
709	<	if (cursor == fence)
709	>	if (remaining <= 0)
710		throw new NoSuchElementException();
711	<	@SuppressWarnings("unchecked")
712	<	E result = (E) elements[cursor];
608	<	// This check doesn't catch all possible comodifications,
609	<	// but does catch the ones that corrupt traversal
610	<	if (tail != fence || result == null)
611	<	throw new ConcurrentModificationException();
711	>	final Object[] es = elements;
712	>	E e = nonNullElementAt(es, cursor);
713		lastRet = cursor;
714	<	cursor = (cursor + 1) & (elements.length - 1);
715	<	return result;
714	>	if (++cursor >= es.length) cursor = 0;
715	>	remaining--;
716	>	return e;
717	>	}
718	>
719	>	void postDelete(boolean leftShifted) {
720	>	if (leftShifted)
721	>	if (--cursor < 0) cursor = elements.length - 1;
722		}
723
724	<	public void remove() {
724	>	public final void remove() {
725		if (lastRet < 0)
726		throw new IllegalStateException();
727	<	if (delete(lastRet)) { // if left-shifted, undo increment in next()
621	<	cursor = (cursor - 1) & (elements.length - 1);
622	<	fence = tail;
623	<	}
727	>	postDelete(delete(lastRet));
728		lastRet = -1;
729		}
626	–	}
730
731	<	private class DescendingIterator implements Iterator<E> {
732	<	/*
733	<	* This class is nearly a mirror-image of DeqIterator, using
734	<	* tail instead of head for initial cursor, and head instead of
735	<	* tail for fence.
736	<	*/
737	<	private int cursor = tail;
738	<	private int fence = head;
739	<	private int lastRet = -1;
637	<
638	<	public boolean hasNext() {
639	<	return cursor != fence;
731	>	public void forEachRemaining(Consumer<? super E> action) {
732	>	Objects.requireNonNull(action);
733	>	final int k;
734	>	if ((k = remaining) > 0) {
735	>	remaining = 0;
736	>	ArrayDeque.forEachRemaining(action, elements, cursor, k);
737	>	if ((lastRet = cursor + k - 1) >= elements.length)
738	>	lastRet -= elements.length;
739	>	}
740		}
741	+	}
742
743	<	public E next() {
744	<	if (cursor == fence)
743	>	private class DescendingIterator extends DeqIterator {
744	>	DescendingIterator() { cursor = tail(); }
745	>
746	>	public final E next() {
747	>	if (remaining <= 0)
748		throw new NoSuchElementException();
749	<	cursor = (cursor - 1) & (elements.length - 1);
750	<	@SuppressWarnings("unchecked")
647	<	E result = (E) elements[cursor];
648	<	if (head != fence || result == null)
649	<	throw new ConcurrentModificationException();
749	>	final Object[] es = elements;
750	>	E e = nonNullElementAt(es, cursor);
751		lastRet = cursor;
752	<	return result;
752	>	if (--cursor < 0) cursor = es.length - 1;
753	>	remaining--;
754	>	return e;
755		}
756
757	<	public void remove() {
758	<	if (lastRet < 0)
759	<	throw new IllegalStateException();
760	<	if (!delete(lastRet)) {
761	<	cursor = (cursor + 1) & (elements.length - 1);
762	<	fence = head;
757	>	void postDelete(boolean leftShifted) {
758	>	if (!leftShifted)
759	>	if (++cursor >= elements.length) cursor = 0;
760	>	}
761	>
762	>	public final void forEachRemaining(Consumer<? super E> action) {
763	>	Objects.requireNonNull(action);
764	>	final int k;
765	>	if ((k = remaining) > 0) {
766	>	remaining = 0;
767	>	final Object[] es = elements;
768	>	int i, end, to, todo;
769	>	todo = (to = ((end = (i = cursor) - k) >= -1) ? end : -1) - end;
770	>	for (;; to = (i = es.length - 1) - todo, todo = 0) {
771	>	for (; i > to; i--)
772	>	action.accept(nonNullElementAt(es, i));
773	>	if (todo == 0) break;
774	>	}
775	>	if ((lastRet = cursor - (k - 1)) < 0)
776	>	lastRet += es.length;
777		}
661	–	lastRet = -1;
778		}
779		}
780
781		/**
782	<	* Returns <tt>true</tt> if this deque contains the specified element.
783	<	* More formally, returns <tt>true</tt> if and only if this deque contains
784	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
782	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
783	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
784	>	* deque.
785	>	*
786	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
787	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
788	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
789	>	* the reporting of additional characteristic values.
790	>	*
791	>	* @return a {@code Spliterator} over the elements in this deque
792	>	* @since 1.8
793	>	*/
794	>	public Spliterator<E> spliterator() {
795	>	return new ArrayDequeSpliterator();
796	>	}
797	>
798	>	final class ArrayDequeSpliterator implements Spliterator<E> {
799	>	private int cursor;
800	>	private int remaining; // -1 until late-binding first use
801	>
802	>	/** Constructs late-binding spliterator over all elements. */
803	>	ArrayDequeSpliterator() {
804	>	this.remaining = -1;
805	>	}
806	>
807	>	/** Constructs spliterator over the given slice. */
808	>	ArrayDequeSpliterator(int cursor, int count) {
809	>	this.cursor = cursor;
810	>	this.remaining = count;
811	>	}
812	>
813	>	/** Ensures late-binding initialization; then returns remaining. */
814	>	private int remaining() {
815	>	if (remaining < 0) {
816	>	cursor = head;
817	>	remaining = size;
818	>	}
819	>	return remaining;
820	>	}
821	>
822	>	public ArrayDequeSpliterator trySplit() {
823	>	final int mid;
824	>	if ((mid = remaining() >> 1) > 0) {
825	>	int oldCursor = cursor;
826	>	cursor = add(cursor, mid, elements.length);
827	>	remaining -= mid;
828	>	return new ArrayDequeSpliterator(oldCursor, mid);
829	>	}
830	>	return null;
831	>	}
832	>
833	>	public void forEachRemaining(Consumer<? super E> action) {
834	>	Objects.requireNonNull(action);
835	>	final int k = remaining(); // side effect!
836	>	remaining = 0;
837	>	ArrayDeque.forEachRemaining(action, elements, cursor, k);
838	>	}
839	>
840	>	public boolean tryAdvance(Consumer<? super E> action) {
841	>	Objects.requireNonNull(action);
842	>	final int k;
843	>	if ((k = remaining()) <= 0)
844	>	return false;
845	>	action.accept(nonNullElementAt(elements, cursor));
846	>	if (++cursor >= elements.length) cursor = 0;
847	>	remaining = k - 1;
848	>	return true;
849	>	}
850	>
851	>	public long estimateSize() {
852	>	return remaining();
853	>	}
854	>
855	>	public int characteristics() {
856	>	return Spliterator.NONNULL
857	>	| Spliterator.ORDERED
858	>	| Spliterator.SIZED
859	>	| Spliterator.SUBSIZED;
860	>	}
861	>	}
862	>
863	>	@SuppressWarnings("unchecked")
864	>	public void forEach(Consumer<? super E> action) {
865	>	Objects.requireNonNull(action);
866	>	final Object[] es = elements;
867	>	int i, end, to, todo;
868	>	todo = (end = (i = head) + size)
869	>	- (to = (es.length - end >= 0) ? end : es.length);
870	>	for (;; to = todo, i = 0, todo = 0) {
871	>	for (; i < to; i++)
872	>	action.accept((E) es[i]);
873	>	if (todo == 0) break;
874	>	}
875	>	// checkInvariants();
876	>	}
877	>
878	>	/**
879	>	* Calls action on remaining elements, starting at index i and
880	>	* traversing in ascending order.  A variant of forEach that also
881	>	* checks for concurrent modification, for use in iterators.
882	>	*/
883	>	static <E> void forEachRemaining(
884	>	Consumer<? super E> action, Object[] es, int i, int remaining) {
885	>	int end, to, todo;
886	>	todo = (end = i + remaining)
887	>	- (to = (es.length - end >= 0) ? end : es.length);
888	>	for (;; to = todo, i = 0, todo = 0) {
889	>	for (; i < to; i++)
890	>	action.accept(nonNullElementAt(es, i));
891	>	if (todo == 0) break;
892	>	}
893	>	}
894	>
895	>	/**
896	>	* Replaces each element of this deque with the result of applying the
897	>	* operator to that element, as specified by {@link List#replaceAll}.
898	>	*
899	>	* @param operator the operator to apply to each element
900	>	* @since TBD
901	>	*/
902	>	@SuppressWarnings("unchecked")
903	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
904	>	Objects.requireNonNull(operator);
905	>	final Object[] es = elements;
906	>	int i, end, to, todo;
907	>	todo = (end = (i = head) + size)
908	>	- (to = (es.length - end >= 0) ? end : es.length);
909	>	for (;; to = todo, i = 0, todo = 0) {
910	>	for (; i < to; i++)
911	>	es[i] = operator.apply((E) es[i]);
912	>	if (todo == 0) break;
913	>	}
914	>	// checkInvariants();
915	>	}
916	>
917	>	/**
918	>	* @throws NullPointerException {@inheritDoc}
919	>	*/
920	>	public boolean removeIf(Predicate<? super E> filter) {
921	>	Objects.requireNonNull(filter);
922	>	return bulkRemove(filter);
923	>	}
924	>
925	>	/**
926	>	* @throws NullPointerException {@inheritDoc}
927	>	*/
928	>	public boolean removeAll(Collection<?> c) {
929	>	Objects.requireNonNull(c);
930	>	return bulkRemove(e -> c.contains(e));
931	>	}
932	>
933	>	/**
934	>	* @throws NullPointerException {@inheritDoc}
935	>	*/
936	>	public boolean retainAll(Collection<?> c) {
937	>	Objects.requireNonNull(c);
938	>	return bulkRemove(e -> !c.contains(e));
939	>	}
940	>
941	>	/** Implementation of bulk remove methods. */
942	>	private boolean bulkRemove(Predicate<? super E> filter) {
943	>	// checkInvariants();
944	>	final Object[] es = elements;
945	>	final int capacity = es.length;
946	>	int i = head, j = i, remaining = size, deleted = 0;
947	>	try {
948	>	for (; remaining > 0; remaining--) {
949	>	@SuppressWarnings("unchecked") E e = (E) es[i];
950	>	if (filter.test(e))
951	>	deleted++;
952	>	else {
953	>	if (j != i)
954	>	es[j] = e;
955	>	if (++j >= capacity) j = 0;
956	>	}
957	>	if (++i >= capacity) i = 0;
958	>	}
959	>	return deleted > 0;
960	>	} catch (Throwable ex) {
961	>	if (deleted > 0)
962	>	for (; remaining > 0; remaining--) {
963	>	es[j] = es[i];
964	>	if (++i >= capacity) i = 0;
965	>	if (++j >= capacity) j = 0;
966	>	}
967	>	throw ex;
968	>	} finally {
969	>	size -= deleted;
970	>	clearSlice(es, j, deleted);
971	>	// checkInvariants();
972	>	}
973	>	}
974	>
975	>	/**
976	>	* Returns {@code true} if this deque contains the specified element.
977	>	* More formally, returns {@code true} if and only if this deque contains
978	>	* at least one element {@code e} such that {@code o.equals(e)}.
979		*
980		* @param o object to be checked for containment in this deque
981	<	* @return <tt>true</tt> if this deque contains the specified element
981	>	* @return {@code true} if this deque contains the specified element
982		*/
983		public boolean contains(Object o) {
984	<	if (o == null)
985	<	return false;
986	<	int mask = elements.length - 1;
987	<	int i = head;
988	<	Object x;
989	<	while ( (x = elements[i]) != null) {
990	<	if (o.equals(x))
991	<	return true;
992	<	i = (i + 1) & mask;
984	>	if (o != null) {
985	>	final Object[] es = elements;
986	>	int i, end, to, todo;
987	>	todo = (end = (i = head) + size)
988	>	- (to = (es.length - end >= 0) ? end : es.length);
989	>	for (;; to = todo, i = 0, todo = 0) {
990	>	for (; i < to; i++)
991	>	if (o.equals(es[i]))
992	>	return true;
993	>	if (todo == 0) break;
994	>	}
995		}
996		return false;
997		}
#	Line 687 | Line 999 | public class ArrayDeque<E> extends Abstr
999		/**
1000		* Removes a single instance of the specified element from this deque.
1001		* If the deque does not contain the element, it is unchanged.
1002	<	* More formally, removes the first element <tt>e</tt> such that
1003	<	* <tt>o.equals(e)</tt> (if such an element exists).
1004	<	* Returns <tt>true</tt> if this deque contained the specified element
1002	>	* More formally, removes the first element {@code e} such that
1003	>	* {@code o.equals(e)} (if such an element exists).
1004	>	* Returns {@code true} if this deque contained the specified element
1005		* (or equivalently, if this deque changed as a result of the call).
1006		*
1007	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1007	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1008		*
1009		* @param o element to be removed from this deque, if present
1010	<	* @return <tt>true</tt> if this deque contained the specified element
1010	>	* @return {@code true} if this deque contained the specified element
1011		*/
1012		public boolean remove(Object o) {
1013		return removeFirstOccurrence(o);
#	Line 706 | Line 1018 | public class ArrayDeque<E> extends Abstr
1018		* The deque will be empty after this call returns.
1019		*/
1020		public void clear() {
1021	<	int h = head;
1022	<	int t = tail;
1023	<	if (h != t) { // clear all cells
1024	<	head = tail = 0;
1025	<	int i = h;
1026	<	int mask = elements.length - 1;
1027	<	do {
1028	<	elements[i] = null;
1029	<	i = (i + 1) & mask;
1030	<	} while (i != t);
1021	>	clearSlice(elements, head, size);
1022	>	size = head = 0;
1023	>	// checkInvariants();
1024	>	}
1025	>
1026	>	/**
1027	>	* Nulls out count elements, starting at array index i.
1028	>	*/
1029	>	private static void clearSlice(Object[] es, int i, int count) {
1030	>	int end, to, todo;
1031	>	todo = (end = i + count)
1032	>	- (to = (es.length - end >= 0) ? end : es.length);
1033	>	for (;; to = todo, i = 0, todo = 0) {
1034	>	Arrays.fill(es, i, to, null);
1035	>	if (todo == 0) break;
1036		}
1037		}
1038
#	Line 733 | Line 1050 | public class ArrayDeque<E> extends Abstr
1050		* @return an array containing all of the elements in this deque
1051		*/
1052		public Object[] toArray() {
1053	<	return copyElements(new Object[size()]);
1053	>	return toArray(Object[].class);
1054	>	}
1055	>
1056	>	private <T> T[] toArray(Class<T[]> klazz) {
1057	>	final Object[] es = elements;
1058	>	final int capacity = es.length;
1059	>	final int head = this.head, end = head + size;
1060	>	final T[] a;
1061	>	if (end >= 0) {
1062	>	a = Arrays.copyOfRange(es, head, end, klazz);
1063	>	} else {
1064	>	// integer overflow!
1065	>	a = Arrays.copyOfRange(es, 0, size, klazz);
1066	>	System.arraycopy(es, head, a, 0, capacity - head);
1067	>	}
1068	>	if (end - capacity > 0)
1069	>	System.arraycopy(es, 0, a, capacity - head, end - capacity);
1070	>	return a;
1071		}
1072
1073		/**
#	Line 747 | Line 1081 | public class ArrayDeque<E> extends Abstr
1081		* <p>If this deque fits in the specified array with room to spare
1082		* (i.e., the array has more elements than this deque), the element in
1083		* the array immediately following the end of the deque is set to
1084	<	* <tt>null</tt>.
1084	>	* {@code null}.
1085		*
1086		* <p>Like the {@link #toArray()} method, this method acts as bridge between
1087		* array-based and collection-based APIs.  Further, this method allows
1088		* precise control over the runtime type of the output array, and may,
1089		* under certain circumstances, be used to save allocation costs.
1090		*
1091	<	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
1091	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1092		* The following code can be used to dump the deque into a newly
1093	<	* allocated array of <tt>String</tt>:
1093	>	* allocated array of {@code String}:
1094		*
1095	<	*  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1095	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1096		*
1097	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
1098	<	* <tt>toArray()</tt>.
1097	>	* Note that {@code toArray(new Object[0])} is identical in function to
1098	>	* {@code toArray()}.
1099		*
1100		* @param a the array into which the elements of the deque are to
1101		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 774 | Line 1108 | public class ArrayDeque<E> extends Abstr
1108		*/
1109		@SuppressWarnings("unchecked")
1110		public <T> T[] toArray(T[] a) {
1111	<	int size = size();
1112	<	if (a.length < size)
1113	<	a = (T[])java.lang.reflect.Array.newInstance(
1114	<	a.getClass().getComponentType(), size);
1115	<	copyElements(a);
1116	<	if (a.length > size)
1111	>	final int size;
1112	>	if ((size = this.size) > a.length)
1113	>	return toArray((Class<T[]>) a.getClass());
1114	>	final Object[] es = elements;
1115	>	final int head = this.head, end = head + size;
1116	>	final int front = (es.length - end >= 0) ? size : es.length - head;
1117	>	System.arraycopy(es, head, a, 0, front);
1118	>	if (front < size)
1119	>	System.arraycopy(es, 0, a, front, size - front);
1120	>	if (size < a.length)
1121		a[size] = null;
1122		return a;
1123		}
#	Line 802 | Line 1140 | public class ArrayDeque<E> extends Abstr
1140		}
1141		}
1142
805	–	/**
806	–	* Appease the serialization gods.
807	–	*/
1143		private static final long serialVersionUID = 2340985798034038923L;
1144
1145		/**
1146	<	* Serialize this deque.
1146	>	* Saves this deque to a stream (that is, serializes it).
1147		*
1148	<	* @serialData The current size (<tt>int</tt>) of the deque,
1148	>	* @param s the stream
1149	>	* @throws java.io.IOException if an I/O error occurs
1150	>	* @serialData The current size ({@code int}) of the deque,
1151		* followed by all of its elements (each an object reference) in
1152		* first-to-last order.
1153		*/
#	Line 819 | Line 1156 | public class ArrayDeque<E> extends Abstr
1156		s.defaultWriteObject();
1157
1158		// Write out size
1159	<	s.writeInt(size());
1159	>	s.writeInt(size);
1160
1161		// Write out elements in order.
1162	<	int mask = elements.length - 1;
1163	<	for (int i = head; i != tail; i = (i + 1) & mask)
1164	<	s.writeObject(elements[i]);
1162	>	final Object[] es = elements;
1163	>	int i, end, to, todo;
1164	>	todo = (end = (i = head) + size)
1165	>	- (to = (es.length - end >= 0) ? end : es.length);
1166	>	for (;; to = todo, i = 0, todo = 0) {
1167	>	for (; i < to; i++)
1168	>	s.writeObject(es[i]);
1169	>	if (todo == 0) break;
1170	>	}
1171		}
1172
1173		/**
1174	<	* Deserialize this deque.
1174	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1175	>	* @param s the stream
1176	>	* @throws ClassNotFoundException if the class of a serialized object
1177	>	*         could not be found
1178	>	* @throws java.io.IOException if an I/O error occurs
1179		*/
1180		private void readObject(java.io.ObjectInputStream s)
1181		throws java.io.IOException, ClassNotFoundException {
1182		s.defaultReadObject();
1183
1184		// Read in size and allocate array
1185	<	int size = s.readInt();
839	<	allocateElements(size);
840	<	head = 0;
841	<	tail = size;
1185	>	elements = new Object[size = s.readInt()];
1186
1187		// Read in all elements in the proper order.
1188		for (int i = 0; i < size; i++)
1189		elements[i] = s.readObject();
1190		}
1191	+
1192	+	/** debugging */
1193	+	void checkInvariants() {
1194	+	try {
1195	+	int capacity = elements.length;
1196	+	// assert size >= 0 && size <= capacity;
1197	+	// assert head >= 0;
1198	+	// assert capacity == 0 || head < capacity;
1199	+	// assert size == 0 || elements[head] != null;
1200	+	// assert size == 0 || elements[tail()] != null;
1201	+	// assert size == capacity || elements[dec(head, capacity)] == null;
1202	+	// assert size == capacity || elements[inc(tail(), capacity)] == null;
1203	+	} catch (Throwable t) {
1204	+	System.err.printf("head=%d size=%d capacity=%d%n",
1205	+	head, size, elements.length);
1206	+	System.err.printf("elements=%s%n",
1207	+	Arrays.toString(elements));
1208	+	throw t;
1209	+	}
1210	+	}
1211	+
1212		}

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