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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.30 by jsr166, Sun May 18 23:47:55 2008 UTC vs.
Revision 1.91 by jsr166, Tue Oct 25 16:51:17 2016 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Josh Bloch of Google Inc. and released to the public domain,
3	<	* as explained at http://creativecommons.org/licenses/publicdomain.
3	>	* as explained at http://creativecommons.org/publicdomain/zero/1.0/.
4		*/
5
6		package java.util;
7	<	import java.io.*;
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 15 | Line 19 | import java.io.*;
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 34 | Line 40 | import java.io.*;
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 48 | Line 54 | import java.io.*;
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
52	–	* @param <E> the type of elements held in this collection
59		*/
60		public class ArrayDeque<E> extends AbstractCollection<E>
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
61	<	* full, except transiently within an addX method where it is
62	<	* resized (see doubleCapacity) immediately upon becoming full,
63	<	* thus avoiding head and tail wrapping around to equal each
64	<	* other.  We also guarantee that all array cells not holding
65	<	* deque elements are always null.
65	>	* We guarantee that all array cells not holding deque elements
66	>	* are always null.
67		*/
68	<	private transient E[] 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
78	<	* of the deque (via addLast(E), add(E), or push(E)).
79	<	*/
80	<	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 = (E[]) 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;
122	<	int r = n - p; // number of elements to the right of p
123	<	int newCapacity = n << 1;
124	<	if (newCapacity < 0)
125	<	throw new IllegalStateException("Sorry, deque too big");
126	<	Object[] a = new Object[newCapacity];
127	<	System.arraycopy(elements, p, a, 0, r);
128	<	System.arraycopy(elements, 0, a, r, p);
129	<	elements = (E[])a;
130	<	head = 0;
131	<	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,
136	<	* in order (from first to last element in the deque).  It is assumed
137	<	* 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) {
145	<	int headPortionLen = elements.length - head;
146	<	System.arraycopy(elements, head, a, 0, headPortionLen);
147	<	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 154 | Line 159 | public class ArrayDeque<E> extends Abstr
159		* sufficient to hold 16 elements.
160		*/
161		public ArrayDeque() {
162	<	elements = (E[]) new Object[16];
162	>	elements = new Object[16];
163		}
164
165		/**
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 178 | 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[] elements = c.toArray();
187	>	// defend against c.toArray (incorrectly) not returning Object[]
188	>	// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
189	>	size = elements.length;
190	>	if (elements.getClass() != Object[].class)
191	>	elements = Arrays.copyOf(elements, size, Object[].class);
192	>	for (Object obj : elements)
193	>	Objects.requireNonNull(obj);
194	>	this.elements = elements;
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.
244	>	*/
245	>	E checkedElementAt(Object[] elements, int i) {
246	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
247	>	if (e == null)
248	>	throw new ConcurrentModificationException();
249	>	return e;
250		}
251
252		// The main insertion and extraction methods are addFirst,
#	Line 193 | Line 260 | public class ArrayDeque<E> extends Abstr
260		* @throws NullPointerException if the specified element is null
261		*/
262		public void addFirst(E e) {
263	<	if (e == null)
264	<	throw new NullPointerException();
265	<	elements[head = (head - 1) & (elements.length - 1)] = e;
266	<	if (head == tail)
267	<	doubleCapacity();
263	>	// checkInvariants();
264	>	Objects.requireNonNull(e);
265	>	Object[] elements;
266	>	int capacity, h;
267	>	final int s;
268	>	if ((s = size) == (capacity = (elements = this.elements).length)) {
269	>	grow(1);
270	>	capacity = (elements = this.elements).length;
271	>	}
272	>	if ((h = head - 1) < 0) h = capacity - 1;
273	>	elements[head = h] = e;
274	>	size = s + 1;
275	>	// checkInvariants();
276		}
277
278		/**
#	Line 209 | 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[] elements;
290	>	int capacity;
291	>	final int s;
292	>	if ((s = size) == (capacity = (elements = this.elements).length)) {
293	>	grow(1);
294	>	capacity = (elements = this.elements).length;
295	>	}
296	>	elements[add(head, s, capacity)] = e;
297	>	size = s + 1;
298	>	// checkInvariants();
299	>	}
300	>
301	>	/**
302	>	* Adds all of the elements in the specified collection at the end
303	>	* of this deque, as if by calling {@link #addLast} on each one,
304	>	* in the order that they are returned by the collection's
305	>	* iterator.
306	>	*
307	>	* @param c the elements to be inserted into this deque
308	>	* @return {@code true} if this deque changed as a result of the call
309	>	* @throws NullPointerException if the specified collection or any
310	>	*         of its elements are null
311	>	*/
312	>	public boolean addAll(Collection<? extends E> c) {
313	>	final int s = size, needed = c.size() - (elements.length - s);
314	>	if (needed > 0)
315	>	grow(needed);
316	>	c.forEach((e) -> addLast(e));
317	>	// checkInvariants();
318	>	return size > s;
319		}
320
321		/**
322		* Inserts the specified element at the front of this deque.
323		*
324		* @param e the element to add
325	<	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
325	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
326		* @throws NullPointerException if the specified element is null
327		*/
328		public boolean offerFirst(E e) {
#	Line 232 | Line 334 | public class ArrayDeque<E> extends Abstr
334		* Inserts the specified element at the end of this deque.
335		*
336		* @param e the element to add
337	<	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
337	>	* @return {@code true} (as specified by {@link Deque#offerLast})
338		* @throws NullPointerException if the specified element is null
339		*/
340		public boolean offerLast(E e) {
#	Line 244 | Line 346 | public class ArrayDeque<E> extends Abstr
346		* @throws NoSuchElementException {@inheritDoc}
347		*/
348		public E removeFirst() {
349	<	E x = pollFirst();
350	<	if (x == null)
349	>	// checkInvariants();
350	>	E e = pollFirst();
351	>	if (e == null)
352		throw new NoSuchElementException();
353	<	return x;
353	>	return e;
354		}
355
356		/**
357		* @throws NoSuchElementException {@inheritDoc}
358		*/
359		public E removeLast() {
360	<	E x = pollLast();
361	<	if (x == null)
360	>	// checkInvariants();
361	>	E e = pollLast();
362	>	if (e == null)
363		throw new NoSuchElementException();
364	<	return x;
364	>	return e;
365		}
366
367		public E pollFirst() {
368	<	int h = head;
369	<	E result = elements[h]; // Element is null if deque empty
370	<	if (result == null)
368	>	// checkInvariants();
369	>	int s, h;
370	>	if ((s = size) <= 0)
371		return null;
372	<	elements[h] = null;     // Must null out slot
373	<	head = (h + 1) & (elements.length - 1);
374	<	return result;
372	>	final Object[] elements = this.elements;
373	>	@SuppressWarnings("unchecked") E e = (E) elements[h = head];
374	>	elements[h] = null;
375	>	if (++h >= elements.length) h = 0;
376	>	head = h;
377	>	size = s - 1;
378	>	return e;
379		}
380
381		public E pollLast() {
382	<	int t = (tail - 1) & (elements.length - 1);
383	<	E result = elements[t];
384	<	if (result == null)
382	>	// checkInvariants();
383	>	final int s, tail;
384	>	if ((s = size) <= 0)
385		return null;
386	<	elements[t] = null;
387	<	tail = t;
388	<	return result;
386	>	final Object[] elements = this.elements;
387	>	@SuppressWarnings("unchecked")
388	>	E e = (E) elements[tail = add(head, s - 1, elements.length)];
389	>	elements[tail] = null;
390	>	size = s - 1;
391	>	return e;
392		}
393
394		/**
395		* @throws NoSuchElementException {@inheritDoc}
396		*/
397		public E getFirst() {
398	<	E x = elements[head];
399	<	if (x == null)
400	<	throw new NoSuchElementException();
290	<	return x;
398	>	// checkInvariants();
399	>	if (size <= 0) throw new NoSuchElementException();
400	>	return elementAt(head);
401		}
402
403		/**
404		* @throws NoSuchElementException {@inheritDoc}
405		*/
406	+	@SuppressWarnings("unchecked")
407		public E getLast() {
408	<	E x = elements[(tail - 1) & (elements.length - 1)];
409	<	if (x == null)
410	<	throw new NoSuchElementException();
411	<	return x;
408	>	// checkInvariants();
409	>	final int s;
410	>	if ((s = size) <= 0) throw new NoSuchElementException();
411	>	final Object[] elements = this.elements;
412	>	return (E) elements[add(head, s - 1, elements.length)];
413		}
414
415		public E peekFirst() {
416	<	return elements[head]; // elements[head] is null if deque empty
416	>	// checkInvariants();
417	>	return (size <= 0) ? null : elementAt(head);
418		}
419
420	+	@SuppressWarnings("unchecked")
421		public E peekLast() {
422	<	return elements[(tail - 1) & (elements.length - 1)];
422	>	// checkInvariants();
423	>	final int s;
424	>	if ((s = size) <= 0) return null;
425	>	final Object[] elements = this.elements;
426	>	return (E) elements[add(head, s - 1, elements.length)];
427		}
428
429		/**
430		* Removes the first occurrence of the specified element in this
431		* deque (when traversing the deque from head to tail).
432		* If the deque does not contain the element, it is unchanged.
433	<	* More formally, removes the first element <tt>e</tt> such that
434	<	* <tt>o.equals(e)</tt> (if such an element exists).
435	<	* Returns <tt>true</tt> if this deque contained the specified element
433	>	* More formally, removes the first element {@code e} such that
434	>	* {@code o.equals(e)} (if such an element exists).
435	>	* Returns {@code true} if this deque contained the specified element
436		* (or equivalently, if this deque changed as a result of the call).
437		*
438		* @param o element to be removed from this deque, if present
439	<	* @return <tt>true</tt> if the deque contained the specified element
439	>	* @return {@code true} if the deque contained the specified element
440		*/
441		public boolean removeFirstOccurrence(Object o) {
442	<	if (o == null)
443	<	return false;
444	<	int mask = elements.length - 1;
445	<	int i = head;
446	<	E x;
447	<	while ( (x = elements[i]) != null) {
448	<	if (o.equals(x)) {
449	<	delete(i);
450	<	return true;
442	>	if (o != null) {
443	>	final Object[] elements = this.elements;
444	>	final int capacity = elements.length;
445	>	int from, end, to, todo;
446	>	todo = (end = (from = head) + size)
447	>	- (to = (capacity - end >= 0) ? end : capacity);
448	>	for (;; from = 0, to = todo, todo = 0) {
449	>	for (int i = from; i < to; i++)
450	>	if (o.equals(elements[i])) {
451	>	delete(i);
452	>	return true;
453	>	}
454	>	if (todo == 0) break;
455		}
334	–	i = (i + 1) & mask;
456		}
457		return false;
458		}
#	Line 340 | 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	<	E 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[] elements = this.elements;
475	>	final int capacity = elements.length;
476	>	int from, to, end, todo;
477	>	todo = (to = ((end = (from = tail()) - size) >= -1) ? end : -1) - end;
478	>	for (;; from = capacity - 1, to = capacity - 1 - todo, todo = 0) {
479	>	for (int i = from; i > to; i--)
480	>	if (o.equals(elements[i])) {
481	>	delete(i);
482	>	return true;
483	>	}
484	>	if (todo == 0) break;
485		}
362	–	i = (i - 1) & mask;
486		}
487		return false;
488		}
#	Line 372 | Line 495 | public class ArrayDeque<E> extends Abstr
495		* <p>This method is equivalent to {@link #addLast}.
496		*
497		* @param e the element to add
498	<	* @return <tt>true</tt> (as specified by {@link Collection#add})
498	>	* @return {@code true} (as specified by {@link Collection#add})
499		* @throws NullPointerException if the specified element is null
500		*/
501		public boolean add(E e) {
#	Line 386 | Line 509 | public class ArrayDeque<E> extends Abstr
509		* <p>This method is equivalent to {@link #offerLast}.
510		*
511		* @param e the element to add
512	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
512	>	* @return {@code true} (as specified by {@link Queue#offer})
513		* @throws NullPointerException if the specified element is null
514		*/
515		public boolean offer(E e) {
#	Line 411 | Line 534 | public class ArrayDeque<E> extends Abstr
534		/**
535		* Retrieves and removes the head of the queue represented by this deque
536		* (in other words, the first element of this deque), or returns
537	<	* <tt>null</tt> if this deque is empty.
537	>	* {@code null} if this deque is empty.
538		*
539		* <p>This method is equivalent to {@link #pollFirst}.
540		*
541		* @return the head of the queue represented by this deque, or
542	<	*         <tt>null</tt> if this deque is empty
542	>	*         {@code null} if this deque is empty
543		*/
544		public E poll() {
545		return pollFirst();
#	Line 438 | Line 561 | public class ArrayDeque<E> extends Abstr
561
562		/**
563		* Retrieves, but does not remove, the head of the queue represented by
564	<	* this deque, or returns <tt>null</tt> if this deque is empty.
564	>	* this deque, or returns {@code null} if this deque is empty.
565		*
566		* <p>This method is equivalent to {@link #peekFirst}.
567		*
568		* @return the head of the queue represented by this deque, or
569	<	*         <tt>null</tt> if this deque is empty
569	>	*         {@code null} if this deque is empty
570		*/
571		public E peek() {
572		return peekFirst();
#	Line 478 | Line 601 | public class ArrayDeque<E> extends Abstr
601		return removeFirst();
602		}
603
481	–	private void checkInvariants() {
482	–	assert elements[tail] == null;
483	–	assert head == tail ? elements[head] == null :
484	–	(elements[head] != null &&
485	–	elements[(tail - 1) & (elements.length - 1)] != null);
486	–	assert elements[(head - 1) & (elements.length - 1)] == null;
487	–	}
488	–
604		/**
605	<	* Removes the element at the specified position in the elements array,
606	<	* adjusting head and tail as necessary.  This can result in motion of
607	<	* elements backwards or forwards in the array.
605	>	* Removes the element at the specified position in the elements array.
606	>	* This can result in forward or backwards motion of array elements.
607	>	* We optimize for least element motion.
608		*
609		* <p>This method is called delete rather than remove to emphasize
610		* that its semantics differ from those of {@link List#remove(int)}.
611		*
612		* @return true if elements moved backwards
613		*/
614	<	private boolean delete(int i) {
615	<	checkInvariants();
616	<	final E[] elements = this.elements;
617	<	final int mask = elements.length - 1;
614	>	boolean delete(int i) {
615	>	// checkInvariants();
616	>	final Object[] elements = this.elements;
617	>	final int capacity = elements.length;
618		final int h = head;
619	<	final int t = tail;
620	<	final int front = (i - h) & mask;
621	<	final int back  = (t - i) & mask;
507	<
508	<	// Invariant: head <= i < tail mod circularity
509	<	if (front >= ((t - h) & mask))
510	<	throw new ConcurrentModificationException();
511	<
512	<	// Optimize for least element motion
619	>	int front;              // number of elements before to-be-deleted elt
620	>	if ((front = i - h) < 0) front += capacity;
621	>	final int back = size - front - 1; // number of elements after
622		if (front < back) {
623	+	// move front elements forwards
624		if (h <= i) {
625		System.arraycopy(elements, h, elements, h + 1, front);
626		} else { // Wrap around
627		System.arraycopy(elements, 0, elements, 1, i);
628	<	elements[0] = elements[mask];
629	<	System.arraycopy(elements, h, elements, h + 1, mask - h);
628	>	elements[0] = elements[capacity - 1];
629	>	System.arraycopy(elements, h, elements, h + 1, front - (i + 1));
630		}
631		elements[h] = null;
632	<	head = (h + 1) & mask;
632	>	if ((head = (h + 1)) >= capacity) head = 0;
633	>	size--;
634	>	// checkInvariants();
635		return false;
636		} else {
637	<	if (i < t) { // Copy the null tail as well
637	>	// move back elements backwards
638	>	int tail = tail();
639	>	if (i <= tail) {
640		System.arraycopy(elements, i + 1, elements, i, back);
527	–	tail = t - 1;
641		} else { // Wrap around
642	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
643	<	elements[mask] = elements[0];
644	<	System.arraycopy(elements, 1, elements, 0, t);
645	<	tail = (t - 1) & mask;
642	>	int firstLeg = capacity - (i + 1);
643	>	System.arraycopy(elements, i + 1, elements, i, firstLeg);
644	>	elements[capacity - 1] = elements[0];
645	>	System.arraycopy(elements, 1, elements, 0, back - firstLeg - 1);
646		}
647	+	elements[tail] = null;
648	+	size--;
649	+	// checkInvariants();
650		return true;
651		}
652		}
#	Line 543 | Line 659 | public class ArrayDeque<E> extends Abstr
659		* @return the number of elements in this deque
660		*/
661		public int size() {
662	<	return (tail - head) & (elements.length - 1);
662	>	return size;
663		}
664
665		/**
666	<	* Returns <tt>true</tt> if this deque contains no elements.
666	>	* Returns {@code true} if this deque contains no elements.
667		*
668	<	* @return <tt>true</tt> if this deque contains no elements
668	>	* @return {@code true} if this deque contains no elements
669		*/
670		public boolean isEmpty() {
671	<	return head == tail;
671	>	return size == 0;
672		}
673
674		/**
#	Line 572 | Line 688 | public class ArrayDeque<E> extends Abstr
688		}
689
690		private class DeqIterator implements Iterator<E> {
691	<	/**
692	<	* Index of element to be returned by subsequent call to next.
577	<	*/
578	<	private int cursor = head;
691	>	/** Index of element to be returned by subsequent call to next. */
692	>	int cursor;
693
694	<	/**
695	<	* Tail recorded at construction (also in remove), to stop
582	<	* iterator and also to check for comodification.
583	<	*/
584	<	private int fence = tail;
694	>	/** Number of elements yet to be returned. */
695	>	int remaining = size;
696
697		/**
698		* Index of element returned by most recent call to next.
699		* Reset to -1 if element is deleted by a call to remove.
700		*/
701	<	private int lastRet = -1;
701	>	int lastRet = -1;
702	>
703	>	DeqIterator() { cursor = head; }
704
705	<	public boolean hasNext() {
706	<	return cursor != fence;
705	>	public final boolean hasNext() {
706	>	return remaining > 0;
707		}
708
709		public E next() {
710	<	if (cursor == fence)
710	>	if (remaining <= 0)
711		throw new NoSuchElementException();
712	<	E result = elements[cursor];
713	<	// This check doesn't catch all possible comodifications,
601	<	// but does catch the ones that corrupt traversal
602	<	if (tail != fence || result == null)
603	<	throw new ConcurrentModificationException();
712	>	final Object[] elements = ArrayDeque.this.elements;
713	>	E e = checkedElementAt(elements, cursor);
714		lastRet = cursor;
715	<	cursor = (cursor + 1) & (elements.length - 1);
716	<	return result;
715	>	if (++cursor >= elements.length) cursor = 0;
716	>	remaining--;
717	>	return e;
718	>	}
719	>
720	>	void postDelete(boolean leftShifted) {
721	>	if (leftShifted)
722	>	if (--cursor < 0) cursor = elements.length - 1;
723		}
724
725	<	public void remove() {
725	>	public final void remove() {
726		if (lastRet < 0)
727		throw new IllegalStateException();
728	<	if (delete(lastRet)) { // if left-shifted, undo increment in next()
613	<	cursor = (cursor - 1) & (elements.length - 1);
614	<	fence = tail;
615	<	}
728	>	postDelete(delete(lastRet));
729		lastRet = -1;
730		}
618	–	}
731
732	<	private class DescendingIterator implements Iterator<E> {
733	<	/*
734	<	* This class is nearly a mirror-image of DeqIterator, using
735	<	* tail instead of head for initial cursor, and head instead of
736	<	* tail for fence.
737	<	*/
738	<	private int cursor = tail;
739	<	private int fence = head;
628	<	private int lastRet = -1;
629	<
630	<	public boolean hasNext() {
631	<	return cursor != fence;
732	>	public void forEachRemaining(Consumer<? super E> 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	<	E result = elements[cursor];
639	<	if (head != fence || result == null)
640	<	throw new ConcurrentModificationException();
749	>	final Object[] elements = ArrayDeque.this.elements;
750	>	E e = checkedElementAt(elements, cursor);
751		lastRet = cursor;
752	<	return result;
752	>	if (--cursor < 0) cursor = elements.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	>	final int k;
764	>	if ((k = remaining) > 0) {
765	>	remaining = 0;
766	>	forEachRemainingDescending(action, elements, cursor, k);
767	>	if ((lastRet = cursor - (k - 1)) < 0)
768	>	lastRet += elements.length;
769		}
652	–	lastRet = -1;
770		}
771		}
772
773		/**
774	<	* Returns <tt>true</tt> if this deque contains the specified element.
775	<	* More formally, returns <tt>true</tt> if and only if this deque contains
776	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
774	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
775	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
776	>	* deque.
777	>	*
778	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
779	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
780	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
781	>	* the reporting of additional characteristic values.
782	>	*
783	>	* @return a {@code Spliterator} over the elements in this deque
784	>	* @since 1.8
785	>	*/
786	>	public Spliterator<E> spliterator() {
787	>	return new ArrayDequeSpliterator();
788	>	}
789	>
790	>	final class ArrayDequeSpliterator implements Spliterator<E> {
791	>	private int cursor;
792	>	private int remaining; // -1 until late-binding first use
793	>
794	>	/** Constructs late-binding spliterator over all elements. */
795	>	ArrayDequeSpliterator() {
796	>	this.remaining = -1;
797	>	}
798	>
799	>	/** Constructs spliterator over the given slice. */
800	>	ArrayDequeSpliterator(int cursor, int count) {
801	>	this.cursor = cursor;
802	>	this.remaining = count;
803	>	}
804	>
805	>	/** Ensures late-binding initialization; then returns remaining. */
806	>	private int remaining() {
807	>	if (remaining < 0) {
808	>	cursor = head;
809	>	remaining = size;
810	>	}
811	>	return remaining;
812	>	}
813	>
814	>	public ArrayDequeSpliterator trySplit() {
815	>	final int mid;
816	>	if ((mid = remaining() >> 1) > 0) {
817	>	int oldCursor = cursor;
818	>	cursor = add(cursor, mid, elements.length);
819	>	remaining -= mid;
820	>	return new ArrayDequeSpliterator(oldCursor, mid);
821	>	}
822	>	return null;
823	>	}
824	>
825	>	public void forEachRemaining(Consumer<? super E> action) {
826	>	final int k = remaining(); // side effect!
827	>	remaining = 0;
828	>	ArrayDeque.forEachRemaining(action, elements, cursor, k);
829	>	}
830	>
831	>	public boolean tryAdvance(Consumer<? super E> action) {
832	>	Objects.requireNonNull(action);
833	>	final int k;
834	>	if ((k = remaining()) <= 0)
835	>	return false;
836	>	action.accept(checkedElementAt(elements, cursor));
837	>	if (++cursor >= elements.length) cursor = 0;
838	>	remaining = k - 1;
839	>	return true;
840	>	}
841	>
842	>	public long estimateSize() {
843	>	return remaining();
844	>	}
845	>
846	>	public int characteristics() {
847	>	return Spliterator.NONNULL
848	>	| Spliterator.ORDERED
849	>	| Spliterator.SIZED
850	>	| Spliterator.SUBSIZED;
851	>	}
852	>	}
853	>
854	>	@SuppressWarnings("unchecked")
855	>	public void forEach(Consumer<? super E> action) {
856	>	Objects.requireNonNull(action);
857	>	final Object[] elements = this.elements;
858	>	final int capacity = elements.length;
859	>	int from, end, to, todo;
860	>	todo = (end = (from = head) + size)
861	>	- (to = (capacity - end >= 0) ? end : capacity);
862	>	for (;; from = 0, to = todo, todo = 0) {
863	>	for (int i = from; i < to; i++)
864	>	action.accept((E) elements[i]);
865	>	if (todo == 0) break;
866	>	}
867	>	// checkInvariants();
868	>	}
869	>
870	>	/**
871	>	* A variant of forEach that also checks for concurrent
872	>	* modification, for use in iterators.
873	>	*/
874	>	static <E> void forEachRemaining(
875	>	Consumer<? super E> action, Object[] elements, int from, int remaining) {
876	>	Objects.requireNonNull(action);
877	>	final int capacity = elements.length;
878	>	int end, to, todo;
879	>	todo = (end = from + remaining)
880	>	- (to = (capacity - end >= 0) ? end : capacity);
881	>	for (;; from = 0, to = todo, todo = 0) {
882	>	for (int i = from; i < to; i++) {
883	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
884	>	if (e == null)
885	>	throw new ConcurrentModificationException();
886	>	action.accept(e);
887	>	}
888	>	if (todo == 0) break;
889	>	}
890	>	}
891	>
892	>	static <E> void forEachRemainingDescending(
893	>	Consumer<? super E> action, Object[] elements, int from, int remaining) {
894	>	Objects.requireNonNull(action);
895	>	final int capacity = elements.length;
896	>	int end, to, todo;
897	>	todo = (to = ((end = from - remaining) >= -1) ? end : -1) - end;
898	>	for (;; from = capacity - 1, to = capacity - 1 - todo, todo = 0) {
899	>	for (int i = from; i > to; i--) {
900	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
901	>	if (e == null)
902	>	throw new ConcurrentModificationException();
903	>	action.accept(e);
904	>	}
905	>	if (todo == 0) break;
906	>	}
907	>	}
908	>
909	>	/**
910	>	* Replaces each element of this deque with the result of applying the
911	>	* operator to that element, as specified by {@link List#replaceAll}.
912	>	*
913	>	* @param operator the operator to apply to each element
914	>	* @since TBD
915	>	*/
916	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
917	>	Objects.requireNonNull(operator);
918	>	final Object[] elements = this.elements;
919	>	final int capacity = elements.length;
920	>	int from, end, to, todo;
921	>	todo = (end = (from = head) + size)
922	>	- (to = (capacity - end >= 0) ? end : capacity);
923	>	for (;; from = 0, to = todo, todo = 0) {
924	>	for (int i = from; i < to; i++)
925	>	elements[i] = operator.apply(elementAt(i));
926	>	if (todo == 0) break;
927	>	}
928	>	// checkInvariants();
929	>	}
930	>
931	>	/**
932	>	* @throws NullPointerException {@inheritDoc}
933	>	*/
934	>	public boolean removeIf(Predicate<? super E> filter) {
935	>	Objects.requireNonNull(filter);
936	>	return bulkRemove(filter);
937	>	}
938	>
939	>	/**
940	>	* @throws NullPointerException {@inheritDoc}
941	>	*/
942	>	public boolean removeAll(Collection<?> c) {
943	>	Objects.requireNonNull(c);
944	>	return bulkRemove(e -> c.contains(e));
945	>	}
946	>
947	>	/**
948	>	* @throws NullPointerException {@inheritDoc}
949	>	*/
950	>	public boolean retainAll(Collection<?> c) {
951	>	Objects.requireNonNull(c);
952	>	return bulkRemove(e -> !c.contains(e));
953	>	}
954	>
955	>	/** Implementation of bulk remove methods. */
956	>	private boolean bulkRemove(Predicate<? super E> filter) {
957	>	// checkInvariants();
958	>	final Object[] elements = this.elements;
959	>	final int capacity = elements.length;
960	>	int i = head, j = i, remaining = size, deleted = 0;
961	>	try {
962	>	for (; remaining > 0; remaining--) {
963	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
964	>	if (filter.test(e))
965	>	deleted++;
966	>	else {
967	>	if (j != i)
968	>	elements[j] = e;
969	>	if (++j >= capacity) j = 0;
970	>	}
971	>	if (++i >= capacity) i = 0;
972	>	}
973	>	return deleted > 0;
974	>	} catch (Throwable ex) {
975	>	if (deleted > 0)
976	>	for (; remaining > 0; remaining--) {
977	>	elements[j] = elements[i];
978	>	if (++i >= capacity) i = 0;
979	>	if (++j >= capacity) j = 0;
980	>	}
981	>	throw ex;
982	>	} finally {
983	>	size -= deleted;
984	>	clearSlice(elements, j, deleted);
985	>	// checkInvariants();
986	>	}
987	>	}
988	>
989	>	/**
990	>	* Returns {@code true} if this deque contains the specified element.
991	>	* More formally, returns {@code true} if and only if this deque contains
992	>	* at least one element {@code e} such that {@code o.equals(e)}.
993		*
994		* @param o object to be checked for containment in this deque
995	<	* @return <tt>true</tt> if this deque contains the specified element
995	>	* @return {@code true} if this deque contains the specified element
996		*/
997		public boolean contains(Object o) {
998	<	if (o == null)
999	<	return false;
1000	<	int mask = elements.length - 1;
1001	<	int i = head;
1002	<	E x;
1003	<	while ( (x = elements[i]) != null) {
1004	<	if (o.equals(x))
1005	<	return true;
1006	<	i = (i + 1) & mask;
998	>	if (o != null) {
999	>	final Object[] elements = this.elements;
1000	>	final int capacity = elements.length;
1001	>	int from, end, to, todo;
1002	>	todo = (end = (from = head) + size)
1003	>	- (to = (capacity - end >= 0) ? end : capacity);
1004	>	for (;; from = 0, to = todo, todo = 0) {
1005	>	for (int i = from; i < to; i++)
1006	>	if (o.equals(elements[i]))
1007	>	return true;
1008	>	if (todo == 0) break;
1009	>	}
1010		}
1011		return false;
1012		}
#	Line 678 | Line 1014 | public class ArrayDeque<E> extends Abstr
1014		/**
1015		* Removes a single instance of the specified element from this deque.
1016		* If the deque does not contain the element, it is unchanged.
1017	<	* More formally, removes the first element <tt>e</tt> such that
1018	<	* <tt>o.equals(e)</tt> (if such an element exists).
1019	<	* Returns <tt>true</tt> if this deque contained the specified element
1017	>	* More formally, removes the first element {@code e} such that
1018	>	* {@code o.equals(e)} (if such an element exists).
1019	>	* Returns {@code true} if this deque contained the specified element
1020		* (or equivalently, if this deque changed as a result of the call).
1021		*
1022	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1022	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1023		*
1024		* @param o element to be removed from this deque, if present
1025	<	* @return <tt>true</tt> if this deque contained the specified element
1025	>	* @return {@code true} if this deque contained the specified element
1026		*/
1027		public boolean remove(Object o) {
1028		return removeFirstOccurrence(o);
#	Line 697 | Line 1033 | public class ArrayDeque<E> extends Abstr
1033		* The deque will be empty after this call returns.
1034		*/
1035		public void clear() {
1036	<	int h = head;
1037	<	int t = tail;
1038	<	if (h != t) { // clear all cells
1039	<	head = tail = 0;
1040	<	int i = h;
1041	<	int mask = elements.length - 1;
1042	<	do {
1043	<	elements[i] = null;
1044	<	i = (i + 1) & mask;
1045	<	} while (i != t);
1046	<	}
1036	>	clearSlice(elements, head, size);
1037	>	size = head = 0;
1038	>	// checkInvariants();
1039	>	}
1040	>
1041	>	/**
1042	>	* Nulls out count elements, starting at array index from.
1043	>	*/
1044	>	private static void clearSlice(Object[] elements, int from, int count) {
1045	>	final int capacity = elements.length, end = from + count;
1046	>	final int leg = (capacity - end >= 0) ? end : capacity;
1047	>	Arrays.fill(elements, from, leg, null);
1048	>	if (leg != end)
1049	>	Arrays.fill(elements, 0, end - capacity, null);
1050		}
1051
1052		/**
#	Line 724 | Line 1063 | public class ArrayDeque<E> extends Abstr
1063		* @return an array containing all of the elements in this deque
1064		*/
1065		public Object[] toArray() {
1066	<	return copyElements(new Object[size()]);
1066	>	return toArray(Object[].class);
1067	>	}
1068	>
1069	>	private <T> T[] toArray(Class<T[]> klazz) {
1070	>	final Object[] elements = this.elements;
1071	>	final int capacity = elements.length;
1072	>	final int head = this.head, end = head + size;
1073	>	final T[] a;
1074	>	if (end >= 0) {
1075	>	a = Arrays.copyOfRange(elements, head, end, klazz);
1076	>	} else {
1077	>	// integer overflow!
1078	>	a = Arrays.copyOfRange(elements, 0, size, klazz);
1079	>	System.arraycopy(elements, head, a, 0, capacity - head);
1080	>	}
1081	>	if (end - capacity > 0)
1082	>	System.arraycopy(elements, 0, a, capacity - head, end - capacity);
1083	>	return a;
1084		}
1085
1086		/**
#	Line 738 | Line 1094 | public class ArrayDeque<E> extends Abstr
1094		* <p>If this deque fits in the specified array with room to spare
1095		* (i.e., the array has more elements than this deque), the element in
1096		* the array immediately following the end of the deque is set to
1097	<	* <tt>null</tt>.
1097	>	* {@code null}.
1098		*
1099		* <p>Like the {@link #toArray()} method, this method acts as bridge between
1100		* array-based and collection-based APIs.  Further, this method allows
1101		* precise control over the runtime type of the output array, and may,
1102		* under certain circumstances, be used to save allocation costs.
1103		*
1104	<	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
1104	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1105		* The following code can be used to dump the deque into a newly
1106	<	* allocated array of <tt>String</tt>:
1106	>	* allocated array of {@code String}:
1107		*
1108	<	* <pre>
753	<	*     String[] y = x.toArray(new String[0]);</pre>
1108	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1109		*
1110	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
1111	<	* <tt>toArray()</tt>.
1110	>	* Note that {@code toArray(new Object[0])} is identical in function to
1111	>	* {@code toArray()}.
1112		*
1113		* @param a the array into which the elements of the deque are to
1114		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 764 | Line 1119 | public class ArrayDeque<E> extends Abstr
1119		*         this deque
1120		* @throws NullPointerException if the specified array is null
1121		*/
1122	+	@SuppressWarnings("unchecked")
1123		public <T> T[] toArray(T[] a) {
1124	<	int size = size();
1125	<	if (a.length < size)
1126	<	a = (T[])java.lang.reflect.Array.newInstance(
1127	<	a.getClass().getComponentType(), size);
1128	<	copyElements(a);
1129	<	if (a.length > size)
1124	>	final int size = this.size;
1125	>	if (size > a.length)
1126	>	return toArray((Class<T[]>) a.getClass());
1127	>	final Object[] elements = this.elements;
1128	>	final int capacity = elements.length;
1129	>	final int head = this.head, end = head + size;
1130	>	final int front = (capacity - end >= 0) ? size : capacity - head;
1131	>	System.arraycopy(elements, head, a, 0, front);
1132	>	if (front != size)
1133	>	System.arraycopy(elements, 0, a, capacity - head, end - capacity);
1134	>	if (size < a.length)
1135		a[size] = null;
1136		return a;
1137		}
#	Line 784 | Line 1145 | public class ArrayDeque<E> extends Abstr
1145		*/
1146		public ArrayDeque<E> clone() {
1147		try {
1148	+	@SuppressWarnings("unchecked")
1149		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1150		result.elements = Arrays.copyOf(elements, elements.length);
1151		return result;
790	–
1152		} catch (CloneNotSupportedException e) {
1153		throw new AssertionError();
1154		}
1155		}
1156
796	–	/**
797	–	* Appease the serialization gods.
798	–	*/
1157		private static final long serialVersionUID = 2340985798034038923L;
1158
1159		/**
1160	<	* Serialize this deque.
1160	>	* Saves this deque to a stream (that is, serializes it).
1161		*
1162	<	* @serialData The current size (<tt>int</tt>) of the deque,
1162	>	* @param s the stream
1163	>	* @throws java.io.IOException if an I/O error occurs
1164	>	* @serialData The current size ({@code int}) of the deque,
1165		* followed by all of its elements (each an object reference) in
1166		* first-to-last order.
1167		*/
1168	<	private void writeObject(ObjectOutputStream s) throws IOException {
1168	>	private void writeObject(java.io.ObjectOutputStream s)
1169	>	throws java.io.IOException {
1170		s.defaultWriteObject();
1171
1172		// Write out size
1173	<	s.writeInt(size());
1173	>	s.writeInt(size);
1174
1175		// Write out elements in order.
1176	<	int mask = elements.length - 1;
1177	<	for (int i = head; i != tail; i = (i + 1) & mask)
1178	<	s.writeObject(elements[i]);
1176	>	final Object[] elements = this.elements;
1177	>	final int capacity = elements.length;
1178	>	int from, end, to, todo;
1179	>	todo = (end = (from = head) + size)
1180	>	- (to = (capacity - end >= 0) ? end : capacity);
1181	>	for (;; from = 0, to = todo, todo = 0) {
1182	>	for (int i = from; i < to; i++)
1183	>	s.writeObject(elements[i]);
1184	>	if (todo == 0) break;
1185	>	}
1186		}
1187
1188		/**
1189	<	* Deserialize this deque.
1189	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1190	>	* @param s the stream
1191	>	* @throws ClassNotFoundException if the class of a serialized object
1192	>	*         could not be found
1193	>	* @throws java.io.IOException if an I/O error occurs
1194		*/
1195	<	private void readObject(ObjectInputStream s)
1196	<	throws IOException, ClassNotFoundException {
1195	>	private void readObject(java.io.ObjectInputStream s)
1196	>	throws java.io.IOException, ClassNotFoundException {
1197		s.defaultReadObject();
1198
1199		// Read in size and allocate array
1200	<	int size = s.readInt();
829	<	allocateElements(size);
830	<	head = 0;
831	<	tail = size;
1200	>	elements = new Object[size = s.readInt()];
1201
1202		// Read in all elements in the proper order.
1203		for (int i = 0; i < size; i++)
1204	<	elements[i] = (E)s.readObject();
1204	>	elements[i] = s.readObject();
1205		}
1206	+
1207	+	/** debugging */
1208	+	void checkInvariants() {
1209	+	try {
1210	+	int capacity = elements.length;
1211	+	// assert size >= 0 && size <= capacity;
1212	+	// assert head >= 0;
1213	+	// assert capacity == 0 || head < capacity;
1214	+	// assert size == 0 || elements[head] != null;
1215	+	// assert size == 0 || elements[tail()] != null;
1216	+	// assert size == capacity || elements[dec(head, capacity)] == null;
1217	+	// assert size == capacity || elements[inc(tail(), capacity)] == null;
1218	+	} catch (Throwable t) {
1219	+	System.err.printf("head=%d size=%d capacity=%d%n",
1220	+	head, size, elements.length);
1221	+	System.err.printf("elements=%s%n",
1222	+	Arrays.toString(elements));
1223	+	throw t;
1224	+	}
1225	+	}
1226	+
1227		}

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