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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.12 by jsr166, Tue May 17 16:14:34 2005 UTC vs.
Revision 1.105 by jsr166, Tue Nov 1 21:42:45 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 44 | 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
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 Object[] grow(int needed) {
94	>	// overflow-conscious code
95	>	// checkInvariants();
96	>	final int oldCapacity = elements.length;
97	>	int newCapacity;
98	>	// Double size if small; else grow by 50%
99	>	int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
100	>	if (jump < needed
101	>	|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
102	>	newCapacity = newCapacity(needed, jump);
103	>	elements = Arrays.copyOf(elements, newCapacity);
104	>	if (oldCapacity - head < size) {
105	>	// wrap around; slide first leg forward to end of array
106	>	int newSpace = newCapacity - oldCapacity;
107	>	System.arraycopy(elements, head,
108	>	elements, head + newSpace,
109	>	oldCapacity - head);
110	>	Arrays.fill(elements, head, head + newSpace, null);
111	>	head += newSpace;
112	>	}
113	>	return elements;
114	>	// checkInvariants();
115	>	}
116
117	<	if (initialCapacity < 0)   // Too many elements, must back off
118	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
117	>	/** Capacity calculation for edge conditions, especially overflow. */
118	>	private int newCapacity(int needed, int jump) {
119	>	final int oldCapacity = elements.length, minCapacity;
120	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
121	>	if (minCapacity < 0)
122	>	throw new IllegalStateException("Sorry, deque too big");
123	>	return Integer.MAX_VALUE;
124		}
125	<	elements = (E[]) new Object[initialCapacity];
125	>	if (needed > jump)
126	>	return minCapacity;
127	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
128	>	? oldCapacity + jump
129	>	: MAX_ARRAY_SIZE;
130		}
131
132		/**
133	<	* Double the capacity of this deque.  Call only when full, i.e.,
134	<	* when head and tail have wrapped around to become equal.
133	>	* Increases the internal storage of this collection, if necessary,
134	>	* to ensure that it can hold at least the given number of elements.
135	>	*
136	>	* @param minCapacity the desired minimum capacity
137	>	* @since TBD
138		*/
139	<	private void doubleCapacity() {
140	<	assert head == tail;
141	<	int p = head;
142	<	int n = elements.length;
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;
139	>	/* public */ void ensureCapacity(int minCapacity) {
140	>	if (minCapacity > elements.length)
141	>	grow(minCapacity - elements.length);
142	>	// checkInvariants();
143		}
144
145		/**
146	<	* Copies the elements from our element array into the specified array,
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.
146	>	* Minimizes the internal storage of this collection.
147		*
148	<	* @return its argument
148	>	* @since TBD
149		*/
150	<	private <T> T[] copyElements(T[] a) {
151	<	if (head < tail) {
152	<	System.arraycopy(elements, head, a, 0, size());
153	<	} else if (head > tail) {
145	<	int headPortionLen = elements.length - head;
146	<	System.arraycopy(elements, head, a, 0, headPortionLen);
147	<	System.arraycopy(elements, 0, a, headPortionLen, tail);
150	>	/* public */ void trimToSize() {
151	>	if (size < elements.length) {
152	>	elements = toArray();
153	>	head = 0;
154		}
155	<	return a;
155	>	// checkInvariants();
156		}
157
158		/**
#	Line 154 | Line 160 | public class ArrayDeque<E> extends Abstr
160		* sufficient to hold 16 elements.
161		*/
162		public ArrayDeque() {
163	<	elements = (E[]) new Object[16];
163	>	elements = new Object[16];
164		}
165
166		/**
167		* Constructs an empty array deque with an initial capacity
168		* sufficient to hold the specified number of elements.
169		*
170	<	* @param numElements  lower bound on initial capacity of the deque
170	>	* @param numElements lower bound on initial capacity of the deque
171		*/
172		public ArrayDeque(int numElements) {
173	<	allocateElements(numElements);
173	>	elements = new Object[numElements];
174		}
175
176		/**
#	Line 178 | Line 184 | public class ArrayDeque<E> extends Abstr
184		* @throws NullPointerException if the specified collection is null
185		*/
186		public ArrayDeque(Collection<? extends E> c) {
187	<	allocateElements(c.size());
188	<	addAll(c);
187	>	Object[] es = c.toArray();
188	>	// defend against c.toArray (incorrectly) not returning Object[]
189	>	// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
190	>	if (es.getClass() != Object[].class)
191	>	es = Arrays.copyOf(es, es.length, Object[].class);
192	>	for (Object obj : es)
193	>	Objects.requireNonNull(obj);
194	>	this.elements = es;
195	>	this.size = es.length;
196	>	}
197	>
198	>	/**
199	>	* Increments i, mod modulus.
200	>	* Precondition and postcondition: 0 <= i < modulus.
201	>	*/
202	>	static final int inc(int i, int modulus) {
203	>	if (++i >= modulus) i = 0;
204	>	return i;
205	>	}
206	>
207	>	/**
208	>	* Decrements i, mod modulus.
209	>	* Precondition and postcondition: 0 <= i < modulus.
210	>	*/
211	>	static final int dec(int i, int modulus) {
212	>	if (--i < 0) i = modulus - 1;
213	>	return i;
214	>	}
215	>
216	>	/**
217	>	* Adds i and j, mod modulus.
218	>	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
219	>	*/
220	>	static final int add(int i, int j, int modulus) {
221	>	if ((i += j) - modulus >= 0) i -= modulus;
222	>	return i;
223	>	}
224	>
225	>	/**
226	>	* Returns the array index of the last element.
227	>	* May return invalid index -1 if there are no elements.
228	>	*/
229	>	final int tail() {
230	>	return add(head, size - 1, elements.length);
231	>	}
232	>
233	>	/**
234	>	* Returns element at array index i.
235	>	*/
236	>	@SuppressWarnings("unchecked")
237	>	private E elementAt(int i) {
238	>	return (E) elements[i];
239	>	}
240	>
241	>	/**
242	>	* A version of elementAt that checks for null elements.
243	>	* This check doesn't catch all possible comodifications,
244	>	* but does catch ones that corrupt traversal.  It's a little
245	>	* surprising that javac allows this abuse of generics.
246	>	*/
247	>	static final <E> E nonNullElementAt(Object[] es, int i) {
248	>	@SuppressWarnings("unchecked") E e = (E) es[i];
249	>	if (e == null)
250	>	throw new ConcurrentModificationException();
251	>	return e;
252		}
253
254		// The main insertion and extraction methods are addFirst,
#	Line 193 | Line 262 | public class ArrayDeque<E> extends Abstr
262		* @throws NullPointerException if the specified element is null
263		*/
264		public void addFirst(E e) {
265	<	if (e == null)
266	<	throw new NullPointerException();
267	<	elements[head = (head - 1) & (elements.length - 1)] = e;
268	<	if (head == tail)
269	<	doubleCapacity();
265	>	// checkInvariants();
266	>	Objects.requireNonNull(e);
267	>	Object[] es;
268	>	int capacity, h;
269	>	final int s;
270	>	if ((s = size) == (capacity = (es = elements).length))
271	>	capacity = (es = grow(1)).length;
272	>	if ((h = head - 1) < 0) h = capacity - 1;
273	>	es[head = h] = e;
274	>	size = s + 1;
275	>	// checkInvariants();
276		}
277
278		/**
279		* Inserts the specified element at the end of this deque.
280	<	* This method is equivalent to {@link #add} and {@link #push}.
280	>	*
281	>	* <p>This method is equivalent to {@link #add}.
282		*
283		* @param e the element to add
284		* @throws NullPointerException if the specified element is null
285		*/
286		public void addLast(E e) {
287	<	if (e == null)
288	<	throw new NullPointerException();
289	<	elements[tail] = e;
290	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
291	<	doubleCapacity();
287	>	// checkInvariants();
288	>	Objects.requireNonNull(e);
289	>	Object[] es;
290	>	int capacity;
291	>	final int s;
292	>	if ((s = size) == (capacity = (es = elements).length))
293	>	capacity = (es = grow(1)).length;
294	>	es[add(head, s, capacity)] = e;
295	>	size = s + 1;
296	>	// checkInvariants();
297	>	}
298	>
299	>	/**
300	>	* Adds all of the elements in the specified collection at the end
301	>	* of this deque, as if by calling {@link #addLast} on each one,
302	>	* in the order that they are returned by the collection's
303	>	* iterator.
304	>	*
305	>	* @param c the elements to be inserted into this deque
306	>	* @return {@code true} if this deque changed as a result of the call
307	>	* @throws NullPointerException if the specified collection or any
308	>	*         of its elements are null
309	>	*/
310	>	public boolean addAll(Collection<? extends E> c) {
311	>	final int s = size, needed = c.size() - (elements.length - s);
312	>	if (needed > 0)
313	>	grow(needed);
314	>	c.forEach((e) -> addLast(e));
315	>	// checkInvariants();
316	>	return size > s;
317		}
318
319		/**
320		* Inserts the specified element at the front of this deque.
321		*
322		* @param e the element to add
323	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
323	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
324		* @throws NullPointerException if the specified element is null
325		*/
326		public boolean offerFirst(E e) {
#	Line 231 | Line 332 | public class ArrayDeque<E> extends Abstr
332		* Inserts the specified element at the end of this deque.
333		*
334		* @param e the element to add
335	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
335	>	* @return {@code true} (as specified by {@link Deque#offerLast})
336		* @throws NullPointerException if the specified element is null
337		*/
338		public boolean offerLast(E e) {
#	Line 243 | Line 344 | public class ArrayDeque<E> extends Abstr
344		* @throws NoSuchElementException {@inheritDoc}
345		*/
346		public E removeFirst() {
347	<	E x = pollFirst();
348	<	if (x == null)
347	>	// checkInvariants();
348	>	E e = pollFirst();
349	>	if (e == null)
350		throw new NoSuchElementException();
351	<	return x;
351	>	return e;
352		}
353
354		/**
355		* @throws NoSuchElementException {@inheritDoc}
356		*/
357		public E removeLast() {
358	<	E x = pollLast();
359	<	if (x == null)
358	>	// checkInvariants();
359	>	E e = pollLast();
360	>	if (e == null)
361		throw new NoSuchElementException();
362	<	return x;
362	>	return e;
363		}
364
365		public E pollFirst() {
366	<	int h = head;
367	<	E result = elements[h]; // Element is null if deque empty
368	<	if (result == null)
366	>	// checkInvariants();
367	>	int s, h;
368	>	if ((s = size) <= 0)
369		return null;
370	<	elements[h] = null;     // Must null out slot
371	<	head = (h + 1) & (elements.length - 1);
372	<	return result;
370	>	final Object[] es = elements;
371	>	@SuppressWarnings("unchecked") E e = (E) es[h = head];
372	>	es[h] = null;
373	>	if (++h >= es.length) h = 0;
374	>	head = h;
375	>	size = s - 1;
376	>	return e;
377		}
378
379		public E pollLast() {
380	<	int t = (tail - 1) & (elements.length - 1);
381	<	E result = elements[t];
382	<	if (result == null)
380	>	// checkInvariants();
381	>	final int s, tail;
382	>	if ((s = size) <= 0)
383		return null;
384	<	elements[t] = null;
385	<	tail = t;
386	<	return result;
384	>	final Object[] es = elements;
385	>	@SuppressWarnings("unchecked")
386	>	E e = (E) es[tail = add(head, s - 1, es.length)];
387	>	es[tail] = null;
388	>	size = s - 1;
389	>	return e;
390		}
391
392		/**
393		* @throws NoSuchElementException {@inheritDoc}
394		*/
395		public E getFirst() {
396	<	E x = elements[head];
397	<	if (x == null)
398	<	throw new NoSuchElementException();
289	<	return x;
396	>	// checkInvariants();
397	>	if (size <= 0) throw new NoSuchElementException();
398	>	return elementAt(head);
399		}
400
401		/**
402		* @throws NoSuchElementException {@inheritDoc}
403		*/
404	+	@SuppressWarnings("unchecked")
405		public E getLast() {
406	<	E x = elements[(tail - 1) & (elements.length - 1)];
407	<	if (x == null)
408	<	throw new NoSuchElementException();
409	<	return x;
406	>	// checkInvariants();
407	>	final int s;
408	>	if ((s = size) <= 0) throw new NoSuchElementException();
409	>	final Object[] es = elements;
410	>	return (E) es[add(head, s - 1, es.length)];
411		}
412
413		public E peekFirst() {
414	<	return elements[head]; // elements[head] is null if deque empty
414	>	// checkInvariants();
415	>	return (size <= 0) ? null : elementAt(head);
416		}
417
418	+	@SuppressWarnings("unchecked")
419		public E peekLast() {
420	<	return elements[(tail - 1) & (elements.length - 1)];
420	>	// checkInvariants();
421	>	final int s;
422	>	if ((s = size) <= 0) return null;
423	>	final Object[] es = elements;
424	>	return (E) es[add(head, s - 1, es.length)];
425		}
426
427		/**
428		* Removes the first occurrence of the specified element in this
429		* deque (when traversing the deque from head to tail).
430		* If the deque does not contain the element, it is unchanged.
431	<	* More formally, removes the first element <tt>e</tt> such that
432	<	* <tt>o.equals(e)</tt> (if such an element exists).
433	<	* Returns <tt>true</tt> if this deque contained the specified element
431	>	* More formally, removes the first element {@code e} such that
432	>	* {@code o.equals(e)} (if such an element exists).
433	>	* Returns {@code true} if this deque contained the specified element
434		* (or equivalently, if this deque changed as a result of the call).
435		*
436		* @param o element to be removed from this deque, if present
437	<	* @return <tt>true</tt> if the deque contained the specified element
437	>	* @return {@code true} if the deque contained the specified element
438		*/
439		public boolean removeFirstOccurrence(Object o) {
440	<	if (o == null)
441	<	return false;
442	<	int mask = elements.length - 1;
443	<	int i = head;
444	<	E x;
445	<	while ( (x = elements[i]) != null) {
446	<	if (o.equals(x)) {
447	<	delete(i);
448	<	return true;
440	>	if (o != null) {
441	>	final Object[] es = elements;
442	>	int i, end, to, todo;
443	>	todo = (end = (i = head) + size)
444	>	- (to = (es.length - end >= 0) ? end : es.length);
445	>	for (;; to = todo, todo = 0, i = 0) {
446	>	for (; i < to; i++)
447	>	if (o.equals(es[i])) {
448	>	delete(i);
449	>	return true;
450	>	}
451	>	if (todo == 0) break;
452		}
333	–	i = (i + 1) & mask;
453		}
454		return false;
455		}
#	Line 339 | Line 458 | public class ArrayDeque<E> extends Abstr
458		* Removes the last occurrence of the specified element in this
459		* deque (when traversing the deque from head to tail).
460		* If the deque does not contain the element, it is unchanged.
461	<	* More formally, removes the last element <tt>e</tt> such that
462	<	* <tt>o.equals(e)</tt> (if such an element exists).
463	<	* Returns <tt>true</tt> if this deque contained the specified element
461	>	* More formally, removes the last element {@code e} such that
462	>	* {@code o.equals(e)} (if such an element exists).
463	>	* Returns {@code true} if this deque contained the specified element
464		* (or equivalently, if this deque changed as a result of the call).
465		*
466		* @param o element to be removed from this deque, if present
467	<	* @return <tt>true</tt> if the deque contained the specified element
467	>	* @return {@code true} if the deque contained the specified element
468		*/
469		public boolean removeLastOccurrence(Object o) {
470	<	if (o == null)
471	<	return false;
472	<	int mask = elements.length - 1;
473	<	int i = (tail - 1) & mask;
474	<	E x;
475	<	while ( (x = elements[i]) != null) {
476	<	if (o.equals(x)) {
477	<	delete(i);
478	<	return true;
470	>	if (o != null) {
471	>	final Object[] es = elements;
472	>	int i, to, end, todo;
473	>	todo = (to = ((end = (i = tail()) - size) >= -1) ? end : -1) - end;
474	>	for (;; to = (i = es.length - 1) - todo, todo = 0) {
475	>	for (; i > to; i--)
476	>	if (o.equals(es[i])) {
477	>	delete(i);
478	>	return true;
479	>	}
480	>	if (todo == 0) break;
481		}
361	–	i = (i - 1) & mask;
482		}
483		return false;
484		}
#	Line 371 | Line 491 | public class ArrayDeque<E> extends Abstr
491		* <p>This method is equivalent to {@link #addLast}.
492		*
493		* @param e the element to add
494	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
494	>	* @return {@code true} (as specified by {@link Collection#add})
495		* @throws NullPointerException if the specified element is null
496		*/
497		public boolean add(E e) {
#	Line 385 | Line 505 | public class ArrayDeque<E> extends Abstr
505		* <p>This method is equivalent to {@link #offerLast}.
506		*
507		* @param e the element to add
508	<	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
508	>	* @return {@code true} (as specified by {@link Queue#offer})
509		* @throws NullPointerException if the specified element is null
510		*/
511		public boolean offer(E e) {
#	Line 394 | Line 514 | public class ArrayDeque<E> extends Abstr
514
515		/**
516		* Retrieves and removes the head of the queue represented by this deque.
517	<	* This method differs from {@link #poll} only in that it throws an
517	>	*
518	>	* This method differs from {@link #poll poll} only in that it throws an
519		* exception if this deque is empty.
520		*
521		* <p>This method is equivalent to {@link #removeFirst}.
#	Line 409 | Line 530 | public class ArrayDeque<E> extends Abstr
530		/**
531		* Retrieves and removes the head of the queue represented by this deque
532		* (in other words, the first element of this deque), or returns
533	<	* <tt>null</tt> if this deque is empty.
533	>	* {@code null} if this deque is empty.
534		*
535		* <p>This method is equivalent to {@link #pollFirst}.
536		*
537		* @return the head of the queue represented by this deque, or
538	<	*         <tt>null</tt> if this deque is empty
538	>	*         {@code null} if this deque is empty
539		*/
540		public E poll() {
541		return pollFirst();
#	Line 422 | Line 543 | public class ArrayDeque<E> extends Abstr
543
544		/**
545		* Retrieves, but does not remove, the head of the queue represented by
546	<	* this deque.  This method differs from {@link #peek} only in that it
547	<	* throws an exception if this deque is empty.
546	>	* this deque.  This method differs from {@link #peek peek} only in
547	>	* that it throws an exception if this deque is empty.
548		*
549		* <p>This method is equivalent to {@link #getFirst}.
550		*
#	Line 436 | Line 557 | public class ArrayDeque<E> extends Abstr
557
558		/**
559		* Retrieves, but does not remove, the head of the queue represented by
560	<	* this deque, or returns <tt>null</tt> if this deque is empty.
560	>	* this deque, or returns {@code null} if this deque is empty.
561		*
562		* <p>This method is equivalent to {@link #peekFirst}.
563		*
564		* @return the head of the queue represented by this deque, or
565	<	*         <tt>null</tt> if this deque is empty
565	>	*         {@code null} if this deque is empty
566		*/
567		public E peek() {
568		return peekFirst();
#	Line 477 | Line 598 | public class ArrayDeque<E> extends Abstr
598		}
599
600		/**
601	<	* Removes the element at the specified position in the elements array,
602	<	* adjusting head and tail as necessary.  This can result in motion of
603	<	* elements backwards or forwards in the array.
601	>	* Removes the element at the specified position in the elements array.
602	>	* This can result in forward or backwards motion of array elements.
603	>	* We optimize for least element motion.
604		*
605		* <p>This method is called delete rather than remove to emphasize
606		* that its semantics differ from those of {@link List#remove(int)}.
607		*
608		* @return true if elements moved backwards
609		*/
610	<	private boolean delete(int i) {
611	<	int mask = elements.length - 1;
612	<
613	<	// Invariant: head <= i < tail mod circularity
614	<	if (((i - head) & mask) >= ((tail - head) & mask))
615	<	throw new ConcurrentModificationException();
616	<
617	<	// Case 1: Deque doesn't wrap
618	<	// Case 2: Deque does wrap and removed element is in the head portion
619	<	if (i >= head) {
620	<	System.arraycopy(elements, head, elements, head + 1, i - head);
621	<	elements[head] = null;
622	<	head = (head + 1) & mask;
610	>	boolean delete(int i) {
611	>	// checkInvariants();
612	>	final Object[] es = elements;
613	>	final int capacity = es.length;
614	>	final int h = head;
615	>	int front;              // number of elements before to-be-deleted elt
616	>	if ((front = i - h) < 0) front += capacity;
617	>	final int back = size - front - 1; // number of elements after
618	>	if (front < back) {
619	>	// move front elements forwards
620	>	if (h <= i) {
621	>	System.arraycopy(es, h, es, h + 1, front);
622	>	} else { // Wrap around
623	>	System.arraycopy(es, 0, es, 1, i);
624	>	es[0] = es[capacity - 1];
625	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
626	>	}
627	>	es[h] = null;
628	>	if ((head = (h + 1)) >= capacity) head = 0;
629	>	size--;
630	>	// checkInvariants();
631		return false;
632	+	} else {
633	+	// move back elements backwards
634	+	int tail = tail();
635	+	if (i <= tail) {
636	+	System.arraycopy(es, i + 1, es, i, back);
637	+	} else { // Wrap around
638	+	int firstLeg = capacity - (i + 1);
639	+	System.arraycopy(es, i + 1, es, i, firstLeg);
640	+	es[capacity - 1] = es[0];
641	+	System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
642	+	}
643	+	es[tail] = null;
644	+	size--;
645	+	// checkInvariants();
646	+	return true;
647		}
504	–
505	–	// Case 3: Deque wraps and removed element is in the tail portion
506	–	tail--;
507	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
508	–	elements[tail] = null;
509	–	return true;
648		}
649
650		// *** Collection Methods ***
#	Line 517 | Line 655 | public class ArrayDeque<E> extends Abstr
655		* @return the number of elements in this deque
656		*/
657		public int size() {
658	<	return (tail - head) & (elements.length - 1);
658	>	return size;
659		}
660
661		/**
662	<	* Returns <tt>true</tt> if this deque contains no elements.
662	>	* Returns {@code true} if this deque contains no elements.
663		*
664	<	* @return <tt>true</tt> if this deque contains no elements
664	>	* @return {@code true} if this deque contains no elements
665		*/
666		public boolean isEmpty() {
667	<	return head == tail;
667	>	return size == 0;
668		}
669
670		/**
#	Line 535 | Line 673 | public class ArrayDeque<E> extends Abstr
673		* order that elements would be dequeued (via successive calls to
674		* {@link #remove} or popped (via successive calls to {@link #pop}).
675		*
676	<	* @return an <tt>Iterator</tt> over the elements in this deque
676	>	* @return an iterator over the elements in this deque
677		*/
678		public Iterator<E> iterator() {
679		return new DeqIterator();
680		}
681
682	+	public Iterator<E> descendingIterator() {
683	+	return new DescendingIterator();
684	+	}
685	+
686		private class DeqIterator implements Iterator<E> {
687	<	/**
688	<	* Index of element to be returned by subsequent call to next.
547	<	*/
548	<	private int cursor = head;
687	>	/** Index of element to be returned by subsequent call to next. */
688	>	int cursor;
689
690	<	/**
691	<	* Tail recorded at construction (also in remove), to stop
552	<	* iterator and also to check for comodification.
553	<	*/
554	<	private int fence = tail;
690	>	/** Number of elements yet to be returned. */
691	>	int remaining = size;
692
693		/**
694		* Index of element returned by most recent call to next.
695		* Reset to -1 if element is deleted by a call to remove.
696		*/
697	<	private int lastRet = -1;
697	>	int lastRet = -1;
698	>
699	>	DeqIterator() { cursor = head; }
700
701	<	public boolean hasNext() {
702	<	return cursor != fence;
701	>	public final boolean hasNext() {
702	>	return remaining > 0;
703		}
704
705		public E next() {
706	<	E result;
568	<	if (cursor == fence)
706	>	if (remaining <= 0)
707		throw new NoSuchElementException();
708	<	// This check doesn't catch all possible comodifications,
709	<	// but does catch the ones that corrupt traversal
572	<	if (tail != fence || (result = elements[cursor]) == null)
573	<	throw new ConcurrentModificationException();
708	>	final Object[] es = elements;
709	>	E e = nonNullElementAt(es, cursor);
710		lastRet = cursor;
711	<	cursor = (cursor + 1) & (elements.length - 1);
712	<	return result;
711	>	if (++cursor >= es.length) cursor = 0;
712	>	remaining--;
713	>	return e;
714	>	}
715	>
716	>	void postDelete(boolean leftShifted) {
717	>	if (leftShifted)
718	>	if (--cursor < 0) cursor = elements.length - 1;
719		}
720
721	<	public void remove() {
721	>	public final void remove() {
722		if (lastRet < 0)
723		throw new IllegalStateException();
724	<	if (delete(lastRet))
583	<	cursor--;
724	>	postDelete(delete(lastRet));
725		lastRet = -1;
585	–	fence = tail;
726		}
727	+
728	+	public void forEachRemaining(Consumer<? super E> action) {
729	+	Objects.requireNonNull(action);
730	+	final int k;
731	+	if ((k = remaining) > 0) {
732	+	remaining = 0;
733	+	ArrayDeque.forEachRemaining(action, elements, cursor, k);
734	+	if ((lastRet = cursor + k - 1) >= elements.length)
735	+	lastRet -= elements.length;
736	+	}
737	+	}
738	+	}
739	+
740	+	private class DescendingIterator extends DeqIterator {
741	+	DescendingIterator() { cursor = tail(); }
742	+
743	+	public final E next() {
744	+	if (remaining <= 0)
745	+	throw new NoSuchElementException();
746	+	final Object[] es = elements;
747	+	E e = nonNullElementAt(es, cursor);
748	+	lastRet = cursor;
749	+	if (--cursor < 0) cursor = es.length - 1;
750	+	remaining--;
751	+	return e;
752	+	}
753	+
754	+	void postDelete(boolean leftShifted) {
755	+	if (!leftShifted)
756	+	if (++cursor >= elements.length) cursor = 0;
757	+	}
758	+
759	+	public final void forEachRemaining(Consumer<? super E> action) {
760	+	Objects.requireNonNull(action);
761	+	final int k;
762	+	if ((k = remaining) > 0) {
763	+	remaining = 0;
764	+	final Object[] es = elements;
765	+	int i, end, to, todo;
766	+	todo = (to = ((end = (i = cursor) - k) >= -1) ? end : -1) - end;
767	+	for (;; to = (i = es.length - 1) - todo, todo = 0) {
768	+	for (; i > to; i--)
769	+	action.accept(nonNullElementAt(es, i));
770	+	if (todo == 0) break;
771	+	}
772	+	if ((lastRet = cursor - (k - 1)) < 0)
773	+	lastRet += es.length;
774	+	}
775	+	}
776	+	}
777	+
778	+	/**
779	+	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
780	+	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
781	+	* deque.
782	+	*
783	+	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
784	+	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
785	+	* {@link Spliterator#NONNULL}.  Overriding implementations should document
786	+	* the reporting of additional characteristic values.
787	+	*
788	+	* @return a {@code Spliterator} over the elements in this deque
789	+	* @since 1.8
790	+	*/
791	+	public Spliterator<E> spliterator() {
792	+	return new ArrayDequeSpliterator();
793	+	}
794	+
795	+	final class ArrayDequeSpliterator implements Spliterator<E> {
796	+	private int cursor;
797	+	private int remaining; // -1 until late-binding first use
798	+
799	+	/** Constructs late-binding spliterator over all elements. */
800	+	ArrayDequeSpliterator() {
801	+	this.remaining = -1;
802	+	}
803	+
804	+	/** Constructs spliterator over the given slice. */
805	+	ArrayDequeSpliterator(int cursor, int count) {
806	+	this.cursor = cursor;
807	+	this.remaining = count;
808	+	}
809	+
810	+	/** Ensures late-binding initialization; then returns remaining. */
811	+	private int remaining() {
812	+	if (remaining < 0) {
813	+	cursor = head;
814	+	remaining = size;
815	+	}
816	+	return remaining;
817	+	}
818	+
819	+	public ArrayDequeSpliterator trySplit() {
820	+	final int mid;
821	+	if ((mid = remaining() >> 1) > 0) {
822	+	int oldCursor = cursor;
823	+	cursor = add(cursor, mid, elements.length);
824	+	remaining -= mid;
825	+	return new ArrayDequeSpliterator(oldCursor, mid);
826	+	}
827	+	return null;
828	+	}
829	+
830	+	public void forEachRemaining(Consumer<? super E> action) {
831	+	Objects.requireNonNull(action);
832	+	final int k = remaining(); // side effect!
833	+	remaining = 0;
834	+	ArrayDeque.forEachRemaining(action, elements, cursor, k);
835	+	}
836	+
837	+	public boolean tryAdvance(Consumer<? super E> action) {
838	+	Objects.requireNonNull(action);
839	+	final int k;
840	+	if ((k = remaining()) <= 0)
841	+	return false;
842	+	action.accept(nonNullElementAt(elements, cursor));
843	+	if (++cursor >= elements.length) cursor = 0;
844	+	remaining = k - 1;
845	+	return true;
846	+	}
847	+
848	+	public long estimateSize() {
849	+	return remaining();
850	+	}
851	+
852	+	public int characteristics() {
853	+	return Spliterator.NONNULL
854	+	| Spliterator.ORDERED
855	+	| Spliterator.SIZED
856	+	| Spliterator.SUBSIZED;
857	+	}
858	+	}
859	+
860	+	@SuppressWarnings("unchecked")
861	+	public void forEach(Consumer<? super E> action) {
862	+	Objects.requireNonNull(action);
863	+	final Object[] es = elements;
864	+	int i, end, to, todo;
865	+	todo = (end = (i = head) + size)
866	+	- (to = (es.length - end >= 0) ? end : es.length);
867	+	for (;; to = todo, todo = 0, i = 0) {
868	+	for (; i < to; i++)
869	+	action.accept((E) es[i]);
870	+	if (todo == 0) break;
871	+	}
872	+	// checkInvariants();
873		}
874
875		/**
876	<	* Returns <tt>true</tt> if this deque contains the specified element.
877	<	* More formally, returns <tt>true</tt> if and only if this deque contains
878	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
876	>	* Calls action on remaining elements, starting at index i and
877	>	* traversing in ascending order.  A variant of forEach that also
878	>	* checks for concurrent modification, for use in iterators.
879	>	*/
880	>	static <E> void forEachRemaining(
881	>	Consumer<? super E> action, Object[] es, int i, int remaining) {
882	>	int end, to, todo;
883	>	todo = (end = i + remaining)
884	>	- (to = (es.length - end >= 0) ? end : es.length);
885	>	for (;; to = todo, todo = 0, i = 0) {
886	>	for (; i < to; i++)
887	>	action.accept(nonNullElementAt(es, i));
888	>	if (todo == 0) break;
889	>	}
890	>	}
891	>
892	>	/**
893	>	* Replaces each element of this deque with the result of applying the
894	>	* operator to that element, as specified by {@link List#replaceAll}.
895	>	*
896	>	* @param operator the operator to apply to each element
897	>	* @since TBD
898	>	*/
899	>	@SuppressWarnings("unchecked")
900	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
901	>	Objects.requireNonNull(operator);
902	>	final Object[] es = elements;
903	>	int i, end, to, todo;
904	>	todo = (end = (i = head) + size)
905	>	- (to = (es.length - end >= 0) ? end : es.length);
906	>	for (;; to = todo, todo = 0, i = 0) {
907	>	for (; i < to; i++)
908	>	es[i] = operator.apply((E) es[i]);
909	>	if (todo == 0) break;
910	>	}
911	>	// checkInvariants();
912	>	}
913	>
914	>	/**
915	>	* @throws NullPointerException {@inheritDoc}
916	>	*/
917	>	public boolean removeIf(Predicate<? super E> filter) {
918	>	Objects.requireNonNull(filter);
919	>	return bulkRemove(filter);
920	>	}
921	>
922	>	/**
923	>	* @throws NullPointerException {@inheritDoc}
924	>	*/
925	>	public boolean removeAll(Collection<?> c) {
926	>	Objects.requireNonNull(c);
927	>	return bulkRemove(e -> c.contains(e));
928	>	}
929	>
930	>	/**
931	>	* @throws NullPointerException {@inheritDoc}
932	>	*/
933	>	public boolean retainAll(Collection<?> c) {
934	>	Objects.requireNonNull(c);
935	>	return bulkRemove(e -> !c.contains(e));
936	>	}
937	>
938	>	/** Implementation of bulk remove methods. */
939	>	@SuppressWarnings("unchecked")
940	>	private boolean bulkRemove(Predicate<? super E> filter) {
941	>	// checkInvariants();
942	>	final Object[] es = elements;
943	>	int i, end, to, todo;
944	>	todo = (end = (i = head) + size)
945	>	- (to = (es.length - end >= 0) ? end : es.length);
946	>	// Optimize for initial run of non-removed elements
947	>	findFirstRemoved:
948	>	for (;; to = todo, todo = 0, i = 0) {
949	>	for (; i < to; i++)
950	>	if (filter.test((E) es[i]))
951	>	break findFirstRemoved;
952	>	if (todo == 0) return false;
953	>	}
954	>	bulkRemoveModified(filter, i, to, todo);
955	>	return true;
956	>	}
957	>
958	>	/**
959	>	* Helper for bulkRemove, in case of at least one deletion.
960	>	* @param i valid index of first element to be deleted
961	>	*/
962	>	@SuppressWarnings("unchecked")
963	>	private void bulkRemoveModified(
964	>	Predicate<? super E> filter, int i, int to, int todo) {
965	>	final Object[] es = elements;
966	>	final int capacity = es.length;
967	>	// a two-finger algorithm, with hare i and tortoise j
968	>	int j = i++;
969	>	try {
970	>	for (;;) {
971	>	E e;
972	>	// In this loop, i and j are on the same leg, with i > j
973	>	for (; i < to; i++)
974	>	if (!filter.test(e = (E) es[i]))
975	>	es[j++] = e;
976	>	if (todo == 0) break;
977	>	// In this loop, j is on the first leg, i on the second
978	>	for (to = todo, todo = 0, i = 0; i < to && j < capacity; i++)
979	>	if (!filter.test(e = (E) es[i]))
980	>	es[j++] = e;
981	>	if (i >= to) break;
982	>	j = 0;          // j rejoins i on second leg
983	>	}
984	>	bulkRemoveClear(es, j, i);
985	>	// checkInvariants();
986	>	} catch (Throwable ex) {
987	>	// copy remaining elements
988	>	for (int remaining = (to - i) + todo; --remaining >= 0;) {
989	>	es[j] = es[i];
990	>	if (++i >= capacity) i = 0;
991	>	if (++j >= capacity) j = 0;
992	>	}
993	>	bulkRemoveClear(es, j, i);
994	>	// checkInvariants();
995	>	throw ex;
996	>	}
997	>	}
998	>
999	>	/**
1000	>	* Nulls out all elements from index j upto index i.
1001	>	*/
1002	>	private void bulkRemoveClear(Object[] es, int j, int i) {
1003	>	int deleted;
1004	>	if ((deleted = i - j) <= 0) deleted += es.length;
1005	>	size -= deleted;
1006	>	circularClear(es, j, deleted);
1007	>	}
1008	>
1009	>	/**
1010	>	* Returns {@code true} if this deque contains the specified element.
1011	>	* More formally, returns {@code true} if and only if this deque contains
1012	>	* at least one element {@code e} such that {@code o.equals(e)}.
1013		*
1014		* @param o object to be checked for containment in this deque
1015	<	* @return <tt>true</tt> if this deque contains the specified element
1015	>	* @return {@code true} if this deque contains the specified element
1016		*/
1017		public boolean contains(Object o) {
1018	<	if (o == null)
1019	<	return false;
1020	<	int mask = elements.length - 1;
1021	<	int i = head;
1022	<	E x;
1023	<	while ( (x = elements[i]) != null) {
1024	<	if (o.equals(x))
1025	<	return true;
1026	<	i = (i + 1) & mask;
1018	>	if (o != null) {
1019	>	final Object[] es = elements;
1020	>	int i, end, to, todo;
1021	>	todo = (end = (i = head) + size)
1022	>	- (to = (es.length - end >= 0) ? end : es.length);
1023	>	for (;; to = todo, todo = 0, i = 0) {
1024	>	for (; i < to; i++)
1025	>	if (o.equals(es[i]))
1026	>	return true;
1027	>	if (todo == 0) break;
1028	>	}
1029		}
1030		return false;
1031		}
#	Line 611 | Line 1033 | public class ArrayDeque<E> extends Abstr
1033		/**
1034		* Removes a single instance of the specified element from this deque.
1035		* If the deque does not contain the element, it is unchanged.
1036	<	* More formally, removes the first element <tt>e</tt> such that
1037	<	* <tt>o.equals(e)</tt> (if such an element exists).
1038	<	* Returns <tt>true</tt> if this deque contained the specified element
1036	>	* More formally, removes the first element {@code e} such that
1037	>	* {@code o.equals(e)} (if such an element exists).
1038	>	* Returns {@code true} if this deque contained the specified element
1039		* (or equivalently, if this deque changed as a result of the call).
1040		*
1041	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1041	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1042		*
1043		* @param o element to be removed from this deque, if present
1044	<	* @return <tt>true</tt> if this deque contained the specified element
1044	>	* @return {@code true} if this deque contained the specified element
1045		*/
1046		public boolean remove(Object o) {
1047		return removeFirstOccurrence(o);
#	Line 630 | Line 1052 | public class ArrayDeque<E> extends Abstr
1052		* The deque will be empty after this call returns.
1053		*/
1054		public void clear() {
1055	<	int h = head;
1056	<	int t = tail;
1057	<	if (h != t) { // clear all cells
1058	<	head = tail = 0;
1059	<	int i = h;
1060	<	int mask = elements.length - 1;
1061	<	do {
1062	<	elements[i] = null;
1063	<	i = (i + 1) & mask;
1064	<	} while (i != t);
1055	>	circularClear(elements, head, size);
1056	>	size = head = 0;
1057	>	// checkInvariants();
1058	>	}
1059	>
1060	>	/**
1061	>	* Nulls out count elements, starting at array index from.
1062	>	* Special case (from == es.length) is treated the same as (from == 0).
1063	>	*/
1064	>	private static void circularClear(Object[] es, int from, int count) {
1065	>	int end, to, todo;
1066	>	todo = (end = from + count)
1067	>	- (to = (es.length - end >= 0) ? end : es.length);
1068	>	for (;; to = todo, todo = 0, from = 0) {
1069	>	Arrays.fill(es, from, to, null);
1070	>	if (todo == 0) break;
1071		}
1072		}
1073
#	Line 650 | Line 1078 | public class ArrayDeque<E> extends Abstr
1078		* <p>The returned array will be "safe" in that no references to it are
1079		* maintained by this deque.  (In other words, this method must allocate
1080		* a new array).  The caller is thus free to modify the returned array.
1081	<	*
1081	>	*
1082		* <p>This method acts as bridge between array-based and collection-based
1083		* APIs.
1084		*
1085		* @return an array containing all of the elements in this deque
1086		*/
1087		public Object[] toArray() {
1088	<	return copyElements(new Object[size()]);
1088	>	return toArray(Object[].class);
1089	>	}
1090	>
1091	>	private <T> T[] toArray(Class<T[]> klazz) {
1092	>	final Object[] es = elements;
1093	>	final T[] a;
1094	>	final int head, len, end, todo;
1095	>	todo = size - (len = Math.min(size, es.length - (head = this.head)));
1096	>	if ((end = head + size) >= 0) {
1097	>	a = Arrays.copyOfRange(es, head, end, klazz);
1098	>	} else {
1099	>	// integer overflow!
1100	>	a = Arrays.copyOfRange(es, 0, size, klazz);
1101	>	System.arraycopy(es, head, a, 0, len);
1102	>	}
1103	>	if (todo > 0)
1104	>	System.arraycopy(es, 0, a, len, todo);
1105	>	return a;
1106		}
1107
1108		/**
#	Line 671 | Line 1116 | public class ArrayDeque<E> extends Abstr
1116		* <p>If this deque fits in the specified array with room to spare
1117		* (i.e., the array has more elements than this deque), the element in
1118		* the array immediately following the end of the deque is set to
1119	<	* <tt>null</tt>.
1119	>	* {@code null}.
1120		*
1121		* <p>Like the {@link #toArray()} method, this method acts as bridge between
1122		* array-based and collection-based APIs.  Further, this method allows
1123		* precise control over the runtime type of the output array, and may,
1124		* under certain circumstances, be used to save allocation costs.
1125		*
1126	<	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
1126	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1127		* The following code can be used to dump the deque into a newly
1128	<	* allocated array of <tt>String</tt>:
1128	>	* allocated array of {@code String}:
1129		*
1130	<	* <pre>
686	<	*     String[] y = x.toArray(new String[0]);</pre>
1130	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1131		*
1132	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
1133	<	* <tt>toArray()</tt>.
1132	>	* Note that {@code toArray(new Object[0])} is identical in function to
1133	>	* {@code toArray()}.
1134		*
1135		* @param a the array into which the elements of the deque are to
1136		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 697 | Line 1141 | public class ArrayDeque<E> extends Abstr
1141		*         this deque
1142		* @throws NullPointerException if the specified array is null
1143		*/
1144	+	@SuppressWarnings("unchecked")
1145		public <T> T[] toArray(T[] a) {
1146	<	int size = size();
1147	<	if (a.length < size)
1148	<	a = (T[])java.lang.reflect.Array.newInstance(
1149	<	a.getClass().getComponentType(), size);
1150	<	copyElements(a);
1151	<	if (a.length > size)
1146	>	final int size;
1147	>	if ((size = this.size) > a.length)
1148	>	return toArray((Class<T[]>) a.getClass());
1149	>	final Object[] es = elements;
1150	>	int i, j, len, todo;
1151	>	todo = size - (len = Math.min(size, es.length - (i = head)));
1152	>	for (j = 0;; j += len, len = todo, todo = 0, i = 0) {
1153	>	System.arraycopy(es, i, a, j, len);
1154	>	if (todo == 0) break;
1155	>	}
1156	>	if (size < a.length)
1157		a[size] = null;
1158		return a;
1159		}
#	Line 717 | Line 1167 | public class ArrayDeque<E> extends Abstr
1167		*/
1168		public ArrayDeque<E> clone() {
1169		try {
1170	+	@SuppressWarnings("unchecked")
1171		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1172	<	// These two lines are currently faster than cloning the array:
722	<	result.elements = (E[]) new Object[elements.length];
723	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
1172	>	result.elements = Arrays.copyOf(elements, elements.length);
1173		return result;
725	–
1174		} catch (CloneNotSupportedException e) {
1175		throw new AssertionError();
1176		}
1177		}
1178
731	–	/**
732	–	* Appease the serialization gods.
733	–	*/
1179		private static final long serialVersionUID = 2340985798034038923L;
1180
1181		/**
1182	<	* Serialize this deque.
1182	>	* Saves this deque to a stream (that is, serializes it).
1183		*
1184	<	* @serialData The current size (<tt>int</tt>) of the deque,
1184	>	* @param s the stream
1185	>	* @throws java.io.IOException if an I/O error occurs
1186	>	* @serialData The current size ({@code int}) of the deque,
1187		* followed by all of its elements (each an object reference) in
1188		* first-to-last order.
1189		*/
1190	<	private void writeObject(ObjectOutputStream s) throws IOException {
1190	>	private void writeObject(java.io.ObjectOutputStream s)
1191	>	throws java.io.IOException {
1192		s.defaultWriteObject();
1193
1194		// Write out size
747	–	int size = size();
1195		s.writeInt(size);
1196
1197		// Write out elements in order.
1198	<	int i = head;
1199	<	int mask = elements.length - 1;
1200	<	for (int j = 0; j < size; j++) {
1201	<	s.writeObject(elements[i]);
1202	<	i = (i + 1) & mask;
1198	>	final Object[] es = elements;
1199	>	int i, end, to, todo;
1200	>	todo = (end = (i = head) + size)
1201	>	- (to = (es.length - end >= 0) ? end : es.length);
1202	>	for (;; to = todo, todo = 0, i = 0) {
1203	>	for (; i < to; i++)
1204	>	s.writeObject(es[i]);
1205	>	if (todo == 0) break;
1206		}
1207		}
1208
1209		/**
1210	<	* Deserialize this deque.
1210	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1211	>	* @param s the stream
1212	>	* @throws ClassNotFoundException if the class of a serialized object
1213	>	*         could not be found
1214	>	* @throws java.io.IOException if an I/O error occurs
1215		*/
1216	<	private void readObject(ObjectInputStream s)
1217	<	throws IOException, ClassNotFoundException {
1216	>	private void readObject(java.io.ObjectInputStream s)
1217	>	throws java.io.IOException, ClassNotFoundException {
1218		s.defaultReadObject();
1219
1220		// Read in size and allocate array
1221	<	int size = s.readInt();
768	<	allocateElements(size);
769	<	head = 0;
770	<	tail = size;
1221	>	elements = new Object[size = s.readInt()];
1222
1223		// Read in all elements in the proper order.
1224		for (int i = 0; i < size; i++)
1225	<	elements[i] = (E)s.readObject();
1225	>	elements[i] = s.readObject();
1226	>	}
1227
1228	+	/** debugging */
1229	+	void checkInvariants() {
1230	+	try {
1231	+	int capacity = elements.length;
1232	+	// assert size >= 0 && size <= capacity;
1233	+	// assert head >= 0;
1234	+	// assert capacity == 0 || head < capacity;
1235	+	// assert size == 0 || elements[head] != null;
1236	+	// assert size == 0 || elements[tail()] != null;
1237	+	// assert size == capacity || elements[dec(head, capacity)] == null;
1238	+	// assert size == capacity || elements[inc(tail(), capacity)] == null;
1239	+	} catch (Throwable t) {
1240	+	System.err.printf("head=%d size=%d capacity=%d%n",
1241	+	head, size, elements.length);
1242	+	System.err.printf("elements=%s%n",
1243	+	Arrays.toString(elements));
1244	+	throw t;
1245	+	}
1246		}
1247	+
1248		}

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