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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.19 by dl, Fri Sep 16 11:15:41 2005 UTC vs.
Revision 1.98 by jsr166, Sat Oct 29 22:47:55 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.util.*; // for javadoc (till 6280605 is fixed)
8	<	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 16 | 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 35 | 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 45 | Line 50 | import java.io.*;
50		* Iterator} interfaces.
51		*
52		* <p>This class is a member of the
53	<	* <a href="{@docRoot}/../guide/collections/index.html">
53	>	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
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
53	–	* @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
62	<	* full, except transiently within an addX method where it is
63	<	* resized (see doubleCapacity) immediately upon becoming full,
64	<	* thus avoiding head and tail wrapping around to equal each
65	<	* other.  We also guarantee that all array cells not holding
66	<	* 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.
74	<	*/
75	<	private transient int head;
76	<
77	<	/**
78	<	* The index at which the next element would be added to the tail
79	<	* of the deque (via addLast(E), add(E), or push(E)).
80	<	*/
81	<	private transient int tail;
82	<
83	<	/**
84	<	* The minimum capacity that we'll use for a newly created deque.
85	<	* Must be a power of 2.
73	>	* arbitrary number 0 <= head < elements.length if the deque is empty.
74		*/
75	<	private static final int MIN_INITIAL_CAPACITY = 8;
75	>	transient int head;
76
77	<	// ******  Array allocation and resizing utilities ******
77	>	/** Number of elements in this collection. */
78	>	transient int size;
79
80		/**
81	<	* Allocate empty array to hold the given number of elements.
82	<	*
83	<	* @param numElements  the number of elements to hold
84	<	*/
85	<	private void allocateElements(int numElements) {
86	<	int initialCapacity = MIN_INITIAL_CAPACITY;
87	<	// Find the best power of two to hold elements.
88	<	// Tests "<=" because arrays aren't kept full.
89	<	if (numElements >= initialCapacity) {
90	<	initialCapacity = numElements;
91	<	initialCapacity |= (initialCapacity >>>  1);
92	<	initialCapacity |= (initialCapacity >>>  2);
93	<	initialCapacity |= (initialCapacity >>>  4);
94	<	initialCapacity |= (initialCapacity >>>  8);
95	<	initialCapacity |= (initialCapacity >>> 16);
96	<	initialCapacity++;
81	>	* The maximum size of array to allocate.
82	>	* Some VMs reserve some header words in an array.
83	>	* Attempts to allocate larger arrays may result in
84	>	* OutOfMemoryError: Requested array size exceeds VM limit
85	>	*/
86	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
87	>
88	>	/**
89	>	* Increases the capacity of this deque by at least the given amount.
90	>	*
91	>	* @param needed the required minimum extra capacity; must be positive
92	>	*/
93	>	private 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;
123	<	int r = n - p; // number of elements to the right of p
124	<	int newCapacity = n << 1;
125	<	if (newCapacity < 0)
126	<	throw new IllegalStateException("Sorry, deque too big");
127	<	Object[] a = new Object[newCapacity];
128	<	System.arraycopy(elements, p, a, 0, r);
129	<	System.arraycopy(elements, 0, a, r, p);
130	<	elements = (E[])a;
131	<	head = 0;
132	<	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,
137	<	* in order (from first to last element in the deque).  It is assumed
138	<	* 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) {
146	<	int headPortionLen = elements.length - head;
147	<	System.arraycopy(elements, head, a, 0, headPortionLen);
148	<	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 155 | 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 179 | 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 194 | 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 210 | 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 233 | 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 245 | 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	<	E result = elements[h]; // Element is null if deque empty
371	<	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[] elements = this.elements;
374	>	@SuppressWarnings("unchecked") E e = (E) elements[h = head];
375	>	elements[h] = null;
376	>	if (++h >= elements.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	<	E result = elements[t];
385	<	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[] elements = this.elements;
388	>	@SuppressWarnings("unchecked")
389	>	E e = (E) elements[tail = add(head, s - 1, elements.length)];
390	>	elements[tail] = null;
391	>	size = s - 1;
392	>	return e;
393		}
394
395		/**
396		* @throws NoSuchElementException {@inheritDoc}
397		*/
398		public E getFirst() {
399	<	E x = elements[head];
400	<	if (x == null)
401	<	throw new NoSuchElementException();
291	<	return x;
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	<	E x = elements[(tail - 1) & (elements.length - 1)];
410	<	if (x == null)
411	<	throw new NoSuchElementException();
412	<	return x;
409	>	// checkInvariants();
410	>	final int s;
411	>	if ((s = size) <= 0) throw new NoSuchElementException();
412	>	final Object[] elements = this.elements;
413	>	return (E) elements[add(head, s - 1, elements.length)];
414		}
415
416		public E peekFirst() {
417	<	return elements[head]; // elements[head] is null if deque empty
417	>	// checkInvariants();
418	>	return (size <= 0) ? null : elementAt(head);
419		}
420
421	+	@SuppressWarnings("unchecked")
422		public E peekLast() {
423	<	return elements[(tail - 1) & (elements.length - 1)];
423	>	// checkInvariants();
424	>	final int s;
425	>	if ((s = size) <= 0) return null;
426	>	final Object[] elements = this.elements;
427	>	return (E) elements[add(head, s - 1, elements.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	<	E 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[] elements = this.elements;
445	>	final int capacity = elements.length;
446	>	int i, end, to, todo;
447	>	todo = (end = (i = head) + size)
448	>	- (to = (capacity - end >= 0) ? end : capacity);
449	>	for (;; to = todo, i = 0, todo = 0) {
450	>	for (; i < to; i++)
451	>	if (o.equals(elements[i])) {
452	>	delete(i);
453	>	return true;
454	>	}
455	>	if (todo == 0) break;
456		}
335	–	i = (i + 1) & mask;
457		}
458		return false;
459		}
#	Line 341 | Line 462 | public class ArrayDeque<E> extends Abstr
462		* Removes the last occurrence of the specified element in this
463		* deque (when traversing the deque from head to tail).
464		* If the deque does not contain the element, it is unchanged.
465	<	* More formally, removes the last element <tt>e</tt> such that
466	<	* <tt>o.equals(e)</tt> (if such an element exists).
467	<	* Returns <tt>true</tt> if this deque contained the specified element
465	>	* More formally, removes the last element {@code e} such that
466	>	* {@code o.equals(e)} (if such an element exists).
467	>	* Returns {@code true} if this deque contained the specified element
468		* (or equivalently, if this deque changed as a result of the call).
469		*
470		* @param o element to be removed from this deque, if present
471	<	* @return <tt>true</tt> if the deque contained the specified element
471	>	* @return {@code true} if the deque contained the specified element
472		*/
473		public boolean removeLastOccurrence(Object o) {
474	<	if (o == null)
475	<	return false;
476	<	int mask = elements.length - 1;
477	<	int i = (tail - 1) & mask;
478	<	E x;
479	<	while ( (x = elements[i]) != null) {
480	<	if (o.equals(x)) {
481	<	delete(i);
482	<	return true;
474	>	if (o != null) {
475	>	final Object[] elements = this.elements;
476	>	final int capacity = elements.length;
477	>	int i, to, end, todo;
478	>	todo = (to = ((end = (i = tail()) - size) >= -1) ? end : -1) - end;
479	>	for (;; to = (i = capacity - 1) - todo, todo = 0) {
480	>	for (; i > to; i--)
481	>	if (o.equals(elements[i])) {
482	>	delete(i);
483	>	return true;
484	>	}
485	>	if (todo == 0) break;
486		}
363	–	i = (i - 1) & mask;
487		}
488		return false;
489		}
#	Line 373 | Line 496 | public class ArrayDeque<E> extends Abstr
496		* <p>This method is equivalent to {@link #addLast}.
497		*
498		* @param e the element to add
499	<	* @return <tt>true</tt> (as specified by {@link Collection#add})
499	>	* @return {@code true} (as specified by {@link Collection#add})
500		* @throws NullPointerException if the specified element is null
501		*/
502		public boolean add(E e) {
#	Line 387 | Line 510 | public class ArrayDeque<E> extends Abstr
510		* <p>This method is equivalent to {@link #offerLast}.
511		*
512		* @param e the element to add
513	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
513	>	* @return {@code true} (as specified by {@link Queue#offer})
514		* @throws NullPointerException if the specified element is null
515		*/
516		public boolean offer(E e) {
#	Line 412 | Line 535 | public class ArrayDeque<E> extends Abstr
535		/**
536		* Retrieves and removes the head of the queue represented by this deque
537		* (in other words, the first element of this deque), or returns
538	<	* <tt>null</tt> if this deque is empty.
538	>	* {@code null} if this deque is empty.
539		*
540		* <p>This method is equivalent to {@link #pollFirst}.
541		*
542		* @return the head of the queue represented by this deque, or
543	<	*         <tt>null</tt> if this deque is empty
543	>	*         {@code null} if this deque is empty
544		*/
545		public E poll() {
546		return pollFirst();
#	Line 439 | Line 562 | public class ArrayDeque<E> extends Abstr
562
563		/**
564		* Retrieves, but does not remove, the head of the queue represented by
565	<	* this deque, or returns <tt>null</tt> if this deque is empty.
565	>	* this deque, or returns {@code null} if this deque is empty.
566		*
567		* <p>This method is equivalent to {@link #peekFirst}.
568		*
569		* @return the head of the queue represented by this deque, or
570	<	*         <tt>null</tt> if this deque is empty
570	>	*         {@code null} if this deque is empty
571		*/
572		public E peek() {
573		return peekFirst();
#	Line 480 | Line 603 | public class ArrayDeque<E> extends Abstr
603		}
604
605		/**
606	<	* Removes the element at the specified position in the elements array,
607	<	* adjusting head and tail as necessary.  This can result in motion of
608	<	* elements backwards or forwards in the array.
606	>	* Removes the element at the specified position in the elements array.
607	>	* This can result in forward or backwards motion of array elements.
608	>	* We optimize for least element motion.
609		*
610		* <p>This method is called delete rather than remove to emphasize
611		* that its semantics differ from those of {@link List#remove(int)}.
612		*
613		* @return true if elements moved backwards
614		*/
615	<	private boolean delete(int i) {
616	<	int mask = elements.length - 1;
617	<
618	<	// Invariant: head <= i < tail mod circularity
619	<	if (((i - head) & mask) >= ((tail - head) & mask))
620	<	throw new ConcurrentModificationException();
621	<
622	<	// Case 1: Deque doesn't wrap
623	<	// Case 2: Deque does wrap and removed element is in the head portion
624	<	if (i >= head) {
625	<	System.arraycopy(elements, head, elements, head + 1, i - head);
626	<	elements[head] = null;
627	<	head = (head + 1) & mask;
615	>	boolean delete(int i) {
616	>	// checkInvariants();
617	>	final Object[] elements = this.elements;
618	>	final int capacity = elements.length;
619	>	final int h = head;
620	>	int front;              // number of elements before to-be-deleted elt
621	>	if ((front = i - h) < 0) front += capacity;
622	>	final int back = size - front - 1; // number of elements after
623	>	if (front < back) {
624	>	// move front elements forwards
625	>	if (h <= i) {
626	>	System.arraycopy(elements, h, elements, h + 1, front);
627	>	} else { // Wrap around
628	>	System.arraycopy(elements, 0, elements, 1, i);
629	>	elements[0] = elements[capacity - 1];
630	>	System.arraycopy(elements, h, elements, h + 1, front - (i + 1));
631	>	}
632	>	elements[h] = null;
633	>	if ((head = (h + 1)) >= capacity) head = 0;
634	>	size--;
635	>	// checkInvariants();
636		return false;
637	+	} else {
638	+	// move back elements backwards
639	+	int tail = tail();
640	+	if (i <= tail) {
641	+	System.arraycopy(elements, i + 1, elements, i, back);
642	+	} else { // Wrap around
643	+	int firstLeg = capacity - (i + 1);
644	+	System.arraycopy(elements, i + 1, elements, i, firstLeg);
645	+	elements[capacity - 1] = elements[0];
646	+	System.arraycopy(elements, 1, elements, 0, back - firstLeg - 1);
647	+	}
648	+	elements[tail] = null;
649	+	size--;
650	+	// checkInvariants();
651	+	return true;
652		}
507	–
508	–	// Case 3: Deque wraps and removed element is in the tail portion
509	–	tail--;
510	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
511	–	elements[tail] = null;
512	–	return true;
653		}
654
655		// *** Collection Methods ***
#	Line 520 | Line 660 | public class ArrayDeque<E> extends Abstr
660		* @return the number of elements in this deque
661		*/
662		public int size() {
663	<	return (tail - head) & (elements.length - 1);
663	>	return size;
664		}
665
666		/**
667	<	* Returns <tt>true</tt> if this deque contains no elements.
667	>	* Returns {@code true} if this deque contains no elements.
668		*
669	<	* @return <tt>true</tt> if this deque contains no elements
669	>	* @return {@code true} if this deque contains no elements
670		*/
671		public boolean isEmpty() {
672	<	return head == tail;
672	>	return size == 0;
673		}
674
675		/**
#	Line 549 | Line 689 | public class ArrayDeque<E> extends Abstr
689		}
690
691		private class DeqIterator implements Iterator<E> {
692	<	/**
693	<	* Index of element to be returned by subsequent call to next.
554	<	*/
555	<	private int cursor = head;
692	>	/** Index of element to be returned by subsequent call to next. */
693	>	int cursor;
694
695	<	/**
696	<	* Tail recorded at construction (also in remove), to stop
559	<	* iterator and also to check for comodification.
560	<	*/
561	<	private int fence = tail;
695	>	/** Number of elements yet to be returned. */
696	>	int remaining = size;
697
698		/**
699		* Index of element returned by most recent call to next.
700		* Reset to -1 if element is deleted by a call to remove.
701		*/
702	<	private int lastRet = -1;
702	>	int lastRet = -1;
703	>
704	>	DeqIterator() { cursor = head; }
705
706	<	public boolean hasNext() {
707	<	return cursor != fence;
706	>	public final boolean hasNext() {
707	>	return remaining > 0;
708		}
709
710		public E next() {
711	<	E result;
575	<	if (cursor == fence)
711	>	if (remaining <= 0)
712		throw new NoSuchElementException();
713	<	// This check doesn't catch all possible comodifications,
714	<	// but does catch the ones that corrupt traversal
579	<	if (tail != fence || (result = elements[cursor]) == null)
580	<	throw new ConcurrentModificationException();
713	>	final Object[] elements = ArrayDeque.this.elements;
714	>	E e = nonNullElementAt(elements, cursor);
715		lastRet = cursor;
716	<	cursor = (cursor + 1) & (elements.length - 1);
717	<	return result;
716	>	if (++cursor >= elements.length) cursor = 0;
717	>	remaining--;
718	>	return e;
719	>	}
720	>
721	>	void postDelete(boolean leftShifted) {
722	>	if (leftShifted)
723	>	if (--cursor < 0) cursor = elements.length - 1;
724		}
725
726	<	public void remove() {
726	>	public final void remove() {
727		if (lastRet < 0)
728		throw new IllegalStateException();
729	<	if (delete(lastRet)) // if left-shifted, undo increment in next()
590	<	cursor = (cursor - 1) & (elements.length - 1);
729	>	postDelete(delete(lastRet));
730		lastRet = -1;
731	<	fence = tail;
731	>	}
732	>
733	>	public void forEachRemaining(Consumer<? super E> action) {
734	>	Objects.requireNonNull(action);
735	>	final int k;
736	>	if ((k = remaining) > 0) {
737	>	remaining = 0;
738	>	ArrayDeque.forEachRemaining(action, elements, cursor, k);
739	>	if ((lastRet = cursor + k - 1) >= elements.length)
740	>	lastRet -= elements.length;
741	>	}
742		}
743		}
744
745	+	private class DescendingIterator extends DeqIterator {
746	+	DescendingIterator() { cursor = tail(); }
747
748	<	private class DescendingIterator implements Iterator<E> {
749	<	/*
750	<	* This class is nearly a mirror-image of DeqIterator, using
751	<	* (tail-1) instead of head for initial cursor, (head-1)
752	<	* instead of tail for fence, and elements.length instead of -1
753	<	* for sentinel. It shares the same structure, but not many
754	<	* actual lines of code.
755	<	*/
756	<	private int cursor = (tail - 1) & (elements.length - 1);
757	<	private int fence =  (head - 1) & (elements.length - 1);
607	<	private int lastRet = elements.length;
748	>	public final E next() {
749	>	if (remaining <= 0)
750	>	throw new NoSuchElementException();
751	>	final Object[] elements = ArrayDeque.this.elements;
752	>	E e = nonNullElementAt(elements, cursor);
753	>	lastRet = cursor;
754	>	if (--cursor < 0) cursor = elements.length - 1;
755	>	remaining--;
756	>	return e;
757	>	}
758
759	<	public boolean hasNext() {
760	<	return cursor != fence;
759	>	void postDelete(boolean leftShifted) {
760	>	if (!leftShifted)
761	>	if (++cursor >= elements.length) cursor = 0;
762		}
763
764	<	public E next() {
765	<	E result;
766	<	if (cursor == fence)
767	<	throw new NoSuchElementException();
768	<	if (((head - 1) & (elements.length - 1)) != fence ||
769	<	(result = elements[cursor]) == null)
770	<	throw new ConcurrentModificationException();
771	<	lastRet = cursor;
772	<	cursor = (cursor - 1) & (elements.length - 1);
773	<	return result;
764	>	public final void forEachRemaining(Consumer<? super E> action) {
765	>	Objects.requireNonNull(action);
766	>	final int k;
767	>	if ((k = remaining) > 0) {
768	>	remaining = 0;
769	>	final Object[] elements = ArrayDeque.this.elements;
770	>	int i, end, to, todo;
771	>	todo = (to = ((end = (i = cursor) - k) >= -1) ? end : -1) - end;
772	>	for (;; to = (i = elements.length - 1) - todo, todo = 0) {
773	>	for (; i > to; i--)
774	>	action.accept(nonNullElementAt(elements, i));
775	>	if (todo == 0) break;
776	>	}
777	>	if ((lastRet = cursor - (k - 1)) < 0)
778	>	lastRet += elements.length;
779	>	}
780		}
781	+	}
782
783	<	public void remove() {
784	<	if (lastRet >= elements.length)
785	<	throw new IllegalStateException();
786	<	if (!delete(lastRet))
787	<	cursor = (cursor + 1) & (elements.length - 1);
788	<	lastRet = elements.length;
789	<	fence = (head - 1) & (elements.length - 1);
783	>	/**
784	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
785	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
786	>	* deque.
787	>	*
788	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
789	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
790	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
791	>	* the reporting of additional characteristic values.
792	>	*
793	>	* @return a {@code Spliterator} over the elements in this deque
794	>	* @since 1.8
795	>	*/
796	>	public Spliterator<E> spliterator() {
797	>	return new ArrayDequeSpliterator();
798	>	}
799	>
800	>	final class ArrayDequeSpliterator implements Spliterator<E> {
801	>	private int cursor;
802	>	private int remaining; // -1 until late-binding first use
803	>
804	>	/** Constructs late-binding spliterator over all elements. */
805	>	ArrayDequeSpliterator() {
806	>	this.remaining = -1;
807	>	}
808	>
809	>	/** Constructs spliterator over the given slice. */
810	>	ArrayDequeSpliterator(int cursor, int count) {
811	>	this.cursor = cursor;
812	>	this.remaining = count;
813	>	}
814	>
815	>	/** Ensures late-binding initialization; then returns remaining. */
816	>	private int remaining() {
817	>	if (remaining < 0) {
818	>	cursor = head;
819	>	remaining = size;
820	>	}
821	>	return remaining;
822	>	}
823	>
824	>	public ArrayDequeSpliterator trySplit() {
825	>	final int mid;
826	>	if ((mid = remaining() >> 1) > 0) {
827	>	int oldCursor = cursor;
828	>	cursor = add(cursor, mid, elements.length);
829	>	remaining -= mid;
830	>	return new ArrayDequeSpliterator(oldCursor, mid);
831	>	}
832	>	return null;
833	>	}
834	>
835	>	public void forEachRemaining(Consumer<? super E> action) {
836	>	Objects.requireNonNull(action);
837	>	final int k = remaining(); // side effect!
838	>	remaining = 0;
839	>	ArrayDeque.forEachRemaining(action, elements, cursor, k);
840	>	}
841	>
842	>	public boolean tryAdvance(Consumer<? super E> action) {
843	>	Objects.requireNonNull(action);
844	>	final int k;
845	>	if ((k = remaining()) <= 0)
846	>	return false;
847	>	action.accept(nonNullElementAt(elements, cursor));
848	>	if (++cursor >= elements.length) cursor = 0;
849	>	remaining = k - 1;
850	>	return true;
851	>	}
852	>
853	>	public long estimateSize() {
854	>	return remaining();
855	>	}
856	>
857	>	public int characteristics() {
858	>	return Spliterator.NONNULL
859	>	| Spliterator.ORDERED
860	>	| Spliterator.SIZED
861	>	| Spliterator.SUBSIZED;
862	>	}
863	>	}
864	>
865	>	@SuppressWarnings("unchecked")
866	>	public void forEach(Consumer<? super E> action) {
867	>	Objects.requireNonNull(action);
868	>	final Object[] elements = this.elements;
869	>	final int capacity = elements.length;
870	>	int i, end, to, todo;
871	>	todo = (end = (i = head) + size)
872	>	- (to = (capacity - end >= 0) ? end : capacity);
873	>	for (;; to = todo, i = 0, todo = 0) {
874	>	for (; i < to; i++)
875	>	action.accept((E) elements[i]);
876	>	if (todo == 0) break;
877	>	}
878	>	// checkInvariants();
879	>	}
880	>
881	>	/**
882	>	* Calls action on remaining elements, starting at index i and
883	>	* traversing in ascending order.  A variant of forEach that also
884	>	* checks for concurrent modification, for use in iterators.
885	>	*/
886	>	static <E> void forEachRemaining(
887	>	Consumer<? super E> action, Object[] es, int i, int remaining) {
888	>	final int capacity = es.length;
889	>	int end, to, todo;
890	>	todo = (end = i + remaining)
891	>	- (to = (capacity - end >= 0) ? end : capacity);
892	>	for (;; to = todo, i = 0, todo = 0) {
893	>	for (; i < to; i++)
894	>	action.accept(nonNullElementAt(es, i));
895	>	if (todo == 0) break;
896	>	}
897	>	}
898	>
899	>	/**
900	>	* Replaces each element of this deque with the result of applying the
901	>	* operator to that element, as specified by {@link List#replaceAll}.
902	>	*
903	>	* @param operator the operator to apply to each element
904	>	* @since TBD
905	>	*/
906	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
907	>	Objects.requireNonNull(operator);
908	>	final Object[] elements = this.elements;
909	>	final int capacity = elements.length;
910	>	int i, end, to, todo;
911	>	todo = (end = (i = head) + size)
912	>	- (to = (capacity - end >= 0) ? end : capacity);
913	>	for (;; to = todo, i = 0, todo = 0) {
914	>	for (; i < to; i++)
915	>	elements[i] = operator.apply(elementAt(i));
916	>	if (todo == 0) break;
917	>	}
918	>	// checkInvariants();
919	>	}
920	>
921	>	/**
922	>	* @throws NullPointerException {@inheritDoc}
923	>	*/
924	>	public boolean removeIf(Predicate<? super E> filter) {
925	>	Objects.requireNonNull(filter);
926	>	return bulkRemove(filter);
927	>	}
928	>
929	>	/**
930	>	* @throws NullPointerException {@inheritDoc}
931	>	*/
932	>	public boolean removeAll(Collection<?> c) {
933	>	Objects.requireNonNull(c);
934	>	return bulkRemove(e -> c.contains(e));
935	>	}
936	>
937	>	/**
938	>	* @throws NullPointerException {@inheritDoc}
939	>	*/
940	>	public boolean retainAll(Collection<?> c) {
941	>	Objects.requireNonNull(c);
942	>	return bulkRemove(e -> !c.contains(e));
943	>	}
944	>
945	>	/** Implementation of bulk remove methods. */
946	>	private boolean bulkRemove(Predicate<? super E> filter) {
947	>	// checkInvariants();
948	>	final Object[] elements = this.elements;
949	>	final int capacity = elements.length;
950	>	int i = head, j = i, remaining = size, deleted = 0;
951	>	try {
952	>	for (; remaining > 0; remaining--) {
953	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
954	>	if (filter.test(e))
955	>	deleted++;
956	>	else {
957	>	if (j != i)
958	>	elements[j] = e;
959	>	if (++j >= capacity) j = 0;
960	>	}
961	>	if (++i >= capacity) i = 0;
962	>	}
963	>	return deleted > 0;
964	>	} catch (Throwable ex) {
965	>	if (deleted > 0)
966	>	for (; remaining > 0; remaining--) {
967	>	elements[j] = elements[i];
968	>	if (++i >= capacity) i = 0;
969	>	if (++j >= capacity) j = 0;
970	>	}
971	>	throw ex;
972	>	} finally {
973	>	size -= deleted;
974	>	clearSlice(elements, j, deleted);
975	>	// checkInvariants();
976		}
977		}
978
979		/**
980	<	* Returns <tt>true</tt> if this deque contains the specified element.
981	<	* More formally, returns <tt>true</tt> if and only if this deque contains
982	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
980	>	* Returns {@code true} if this deque contains the specified element.
981	>	* More formally, returns {@code true} if and only if this deque contains
982	>	* at least one element {@code e} such that {@code o.equals(e)}.
983		*
984		* @param o object to be checked for containment in this deque
985	<	* @return <tt>true</tt> if this deque contains the specified element
985	>	* @return {@code true} if this deque contains the specified element
986		*/
987		public boolean contains(Object o) {
988	<	if (o == null)
989	<	return false;
990	<	int mask = elements.length - 1;
991	<	int i = head;
992	<	E x;
993	<	while ( (x = elements[i]) != null) {
994	<	if (o.equals(x))
995	<	return true;
996	<	i = (i + 1) & mask;
988	>	if (o != null) {
989	>	final Object[] elements = this.elements;
990	>	final int capacity = elements.length;
991	>	int i, end, to, todo;
992	>	todo = (end = (i = head) + size)
993	>	- (to = (capacity - end >= 0) ? end : capacity);
994	>	for (;; to = todo, i = 0, todo = 0) {
995	>	for (; i < to; i++)
996	>	if (o.equals(elements[i]))
997	>	return true;
998	>	if (todo == 0) break;
999	>	}
1000		}
1001		return false;
1002		}
#	Line 657 | Line 1004 | public class ArrayDeque<E> extends Abstr
1004		/**
1005		* Removes a single instance of the specified element from this deque.
1006		* If the deque does not contain the element, it is unchanged.
1007	<	* More formally, removes the first element <tt>e</tt> such that
1008	<	* <tt>o.equals(e)</tt> (if such an element exists).
1009	<	* Returns <tt>true</tt> if this deque contained the specified element
1007	>	* More formally, removes the first element {@code e} such that
1008	>	* {@code o.equals(e)} (if such an element exists).
1009	>	* Returns {@code true} if this deque contained the specified element
1010		* (or equivalently, if this deque changed as a result of the call).
1011		*
1012	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1012	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1013		*
1014		* @param o element to be removed from this deque, if present
1015	<	* @return <tt>true</tt> if this deque contained the specified element
1015	>	* @return {@code true} if this deque contained the specified element
1016		*/
1017		public boolean remove(Object o) {
1018		return removeFirstOccurrence(o);
#	Line 676 | Line 1023 | public class ArrayDeque<E> extends Abstr
1023		* The deque will be empty after this call returns.
1024		*/
1025		public void clear() {
1026	<	int h = head;
1027	<	int t = tail;
1028	<	if (h != t) { // clear all cells
1029	<	head = tail = 0;
1030	<	int i = h;
1031	<	int mask = elements.length - 1;
1032	<	do {
1033	<	elements[i] = null;
1034	<	i = (i + 1) & mask;
1035	<	} while (i != t);
1036	<	}
1026	>	clearSlice(elements, head, size);
1027	>	size = head = 0;
1028	>	// checkInvariants();
1029	>	}
1030	>
1031	>	/**
1032	>	* Nulls out count elements, starting at array index from.
1033	>	*/
1034	>	private static void clearSlice(Object[] es, int from, int count) {
1035	>	final int capacity = es.length, end = from + count;
1036	>	final int leg = (capacity - end >= 0) ? end : capacity;
1037	>	Arrays.fill(es, from, leg, null);
1038	>	if (leg != end)
1039	>	Arrays.fill(es, 0, end - capacity, null);
1040		}
1041
1042		/**
#	Line 703 | Line 1053 | public class ArrayDeque<E> extends Abstr
1053		* @return an array containing all of the elements in this deque
1054		*/
1055		public Object[] toArray() {
1056	<	return copyElements(new Object[size()]);
1056	>	return toArray(Object[].class);
1057	>	}
1058	>
1059	>	private <T> T[] toArray(Class<T[]> klazz) {
1060	>	final Object[] elements = this.elements;
1061	>	final int capacity = elements.length;
1062	>	final int head = this.head, end = head + size;
1063	>	final T[] a;
1064	>	if (end >= 0) {
1065	>	a = Arrays.copyOfRange(elements, head, end, klazz);
1066	>	} else {
1067	>	// integer overflow!
1068	>	a = Arrays.copyOfRange(elements, 0, size, klazz);
1069	>	System.arraycopy(elements, head, a, 0, capacity - head);
1070	>	}
1071	>	if (end - capacity > 0)
1072	>	System.arraycopy(elements, 0, a, capacity - head, end - capacity);
1073	>	return a;
1074		}
1075
1076		/**
#	Line 717 | Line 1084 | public class ArrayDeque<E> extends Abstr
1084		* <p>If this deque fits in the specified array with room to spare
1085		* (i.e., the array has more elements than this deque), the element in
1086		* the array immediately following the end of the deque is set to
1087	<	* <tt>null</tt>.
1087	>	* {@code null}.
1088		*
1089		* <p>Like the {@link #toArray()} method, this method acts as bridge between
1090		* array-based and collection-based APIs.  Further, this method allows
1091		* precise control over the runtime type of the output array, and may,
1092		* under certain circumstances, be used to save allocation costs.
1093		*
1094	<	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
1094	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1095		* The following code can be used to dump the deque into a newly
1096	<	* allocated array of <tt>String</tt>:
1096	>	* allocated array of {@code String}:
1097		*
1098	<	* <pre>
732	<	*     String[] y = x.toArray(new String[0]);</pre>
1098	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1099		*
1100	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
1101	<	* <tt>toArray()</tt>.
1100	>	* Note that {@code toArray(new Object[0])} is identical in function to
1101	>	* {@code toArray()}.
1102		*
1103		* @param a the array into which the elements of the deque are to
1104		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 743 | Line 1109 | public class ArrayDeque<E> extends Abstr
1109		*         this deque
1110		* @throws NullPointerException if the specified array is null
1111		*/
1112	+	@SuppressWarnings("unchecked")
1113		public <T> T[] toArray(T[] a) {
1114	<	int size = size();
1115	<	if (a.length < size)
1116	<	a = (T[])java.lang.reflect.Array.newInstance(
1117	<	a.getClass().getComponentType(), size);
1118	<	copyElements(a);
1119	<	if (a.length > size)
1114	>	final int size = this.size;
1115	>	if (size > a.length)
1116	>	return toArray((Class<T[]>) a.getClass());
1117	>	final Object[] elements = this.elements;
1118	>	final int capacity = elements.length;
1119	>	final int head = this.head, end = head + size;
1120	>	final int front = (capacity - end >= 0) ? size : capacity - head;
1121	>	System.arraycopy(elements, head, a, 0, front);
1122	>	if (front != size)
1123	>	System.arraycopy(elements, 0, a, capacity - head, end - capacity);
1124	>	if (size < a.length)
1125		a[size] = null;
1126		return a;
1127		}
#	Line 763 | Line 1135 | public class ArrayDeque<E> extends Abstr
1135		*/
1136		public ArrayDeque<E> clone() {
1137		try {
1138	+	@SuppressWarnings("unchecked")
1139		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1140	<	// These two lines are currently faster than cloning the array:
768	<	result.elements = (E[]) new Object[elements.length];
769	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
1140	>	result.elements = Arrays.copyOf(elements, elements.length);
1141		return result;
771	–
1142		} catch (CloneNotSupportedException e) {
1143		throw new AssertionError();
1144		}
1145		}
1146
777	–	/**
778	–	* Appease the serialization gods.
779	–	*/
1147		private static final long serialVersionUID = 2340985798034038923L;
1148
1149		/**
1150	<	* Serialize this deque.
1150	>	* Saves this deque to a stream (that is, serializes it).
1151		*
1152	<	* @serialData The current size (<tt>int</tt>) of the deque,
1152	>	* @param s the stream
1153	>	* @throws java.io.IOException if an I/O error occurs
1154	>	* @serialData The current size ({@code int}) of the deque,
1155		* followed by all of its elements (each an object reference) in
1156		* first-to-last order.
1157		*/
1158	<	private void writeObject(ObjectOutputStream s) throws IOException {
1158	>	private void writeObject(java.io.ObjectOutputStream s)
1159	>	throws java.io.IOException {
1160		s.defaultWriteObject();
1161
1162		// Write out size
1163	<	s.writeInt(size());
1163	>	s.writeInt(size);
1164
1165		// Write out elements in order.
1166	<	int mask = elements.length - 1;
1167	<	for (int i = head; i != tail; i = (i + 1) & mask)
1168	<	s.writeObject(elements[i]);
1166	>	final Object[] elements = this.elements;
1167	>	final int capacity = elements.length;
1168	>	int i, end, to, todo;
1169	>	todo = (end = (i = head) + size)
1170	>	- (to = (capacity - end >= 0) ? end : capacity);
1171	>	for (;; to = todo, i = 0, todo = 0) {
1172	>	for (; i < to; i++)
1173	>	s.writeObject(elements[i]);
1174	>	if (todo == 0) break;
1175	>	}
1176		}
1177
1178		/**
1179	<	* Deserialize this deque.
1179	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1180	>	* @param s the stream
1181	>	* @throws ClassNotFoundException if the class of a serialized object
1182	>	*         could not be found
1183	>	* @throws java.io.IOException if an I/O error occurs
1184		*/
1185	<	private void readObject(ObjectInputStream s)
1186	<	throws IOException, ClassNotFoundException {
1185	>	private void readObject(java.io.ObjectInputStream s)
1186	>	throws java.io.IOException, ClassNotFoundException {
1187		s.defaultReadObject();
1188
1189		// Read in size and allocate array
1190	<	int size = s.readInt();
810	<	allocateElements(size);
811	<	head = 0;
812	<	tail = size;
1190	>	elements = new Object[size = s.readInt()];
1191
1192		// Read in all elements in the proper order.
1193		for (int i = 0; i < size; i++)
1194	<	elements[i] = (E)s.readObject();
1194	>	elements[i] = s.readObject();
1195	>	}
1196
1197	+	/** debugging */
1198	+	void checkInvariants() {
1199	+	try {
1200	+	int capacity = elements.length;
1201	+	// assert size >= 0 && size <= capacity;
1202	+	// assert head >= 0;
1203	+	// assert capacity == 0 || head < capacity;
1204	+	// assert size == 0 || elements[head] != null;
1205	+	// assert size == 0 || elements[tail()] != null;
1206	+	// assert size == capacity || elements[dec(head, capacity)] == null;
1207	+	// assert size == capacity || elements[inc(tail(), capacity)] == null;
1208	+	} catch (Throwable t) {
1209	+	System.err.printf("head=%d size=%d capacity=%d%n",
1210	+	head, size, elements.length);
1211	+	System.err.printf("elements=%s%n",
1212	+	Arrays.toString(elements));
1213	+	throw t;
1214	+	}
1215		}
1216	+
1217		}

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