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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.8 by jsr166, Mon May 2 04:19:58 2005 UTC vs.
Revision 1.95 by jsr166, Sat Oct 29 19:10:27 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>
47		*
48		* <p>This class and its iterator implement all of the
49	<	* optional methods of the {@link Collection} and {@link
50	<	* Iterator} interfaces.  This class is a member of the <a
51	<	* href="{@docRoot}/../guide/collections/index.html"> Java Collections
52	<	* Framework</a>.
49	>	* <em>optional</em> methods of the {@link Collection} and {@link
50	>	* Iterator} interfaces.
51	>	*
52	>	* <p>This class is a member of the
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
50	–	* @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
59	<	* full, except transiently within an addX method where it is
60	<	* resized (see doubleCapacity) immediately upon becoming full,
61	<	* thus avoiding head and tail wrapping around to equal each
62	<	* other.  We also guarantee that all array cells not holding
63	<	* 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.
71	<	*/
72	<	private transient int head;
73	<
74	<	/**
75	<	* The index at which the next element would be added to the tail
76	<	* of the deque (via addLast(E), add(E), or push(E)).
77	<	*/
78	<	private transient int tail;
79	<
80	<	/**
81	<	* The minimum capacity that we'll use for a newly created deque.
82	<	* 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;
120	<	int r = n - p; // number of elements to the right of p
121	<	int newCapacity = n << 1;
122	<	if (newCapacity < 0)
123	<	throw new IllegalStateException("Sorry, deque too big");
124	<	Object[] a = new Object[newCapacity];
125	<	System.arraycopy(elements, p, a, 0, r);
126	<	System.arraycopy(elements, 0, a, r, p);
127	<	elements = (E[])a;
128	<	head = 0;
129	<	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,
134	<	* in order (from first to last element in the deque).  It is assumed
135	<	* 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) {
143	<	int headPortionLen = elements.length - head;
144	<	System.arraycopy(elements, head, a, 0, headPortionLen);
145	<	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 152 | 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 176 | 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[] elements, int i) {
247	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
248	>	if (e == null)
249	>	throw new ConcurrentModificationException();
250	>	return e;
251		}
252
253		// The main insertion and extraction methods are addFirst,
#	Line 187 | Line 257 | public class ArrayDeque<E> extends Abstr
257		/**
258		* Inserts the specified element at the front of this deque.
259		*
260	<	* @param e the element to insert
261	<	* @throws NullPointerException if <tt>e</tt> is null
260	>	* @param e the element to add
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		/**
280		* Inserts the specified element at the end of this deque.
203	–	* This method is equivalent to {@link Collection#add} and
204	–	* {@link #push}.
281		*
282	<	* @param e the element to insert
207	<	* @throws NullPointerException if <tt>e</tt> is null
208	<	*/
209	<	public void addLast(E e) {
210	<	if (e == null)
211	<	throw new NullPointerException();
212	<	elements[tail] = e;
213	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
214	<	doubleCapacity();
215	<	}
216	<
217	<	/**
218	<	* Retrieves and removes the first element of this deque, or
219	<	* <tt>null</tt> if this deque is empty.
282	>	* <p>This method is equivalent to {@link #add}.
283		*
284	<	* @return the first element of this deque, or <tt>null</tt> if
285	<	*     this deque is empty
284	>	* @param e the element to add
285	>	* @throws NullPointerException if the specified element is null
286		*/
287	<	public E pollFirst() {
288	<	int h = head;
289	<	E result = elements[h]; // Element is null if deque empty
290	<	if (result == null)
291	<	return null;
292	<	elements[h] = null;     // Must null out slot
293	<	head = (h + 1) & (elements.length - 1);
294	<	return result;
287	>	public void addLast(E e) {
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	<	* Retrieves and removes the last element of this deque, or
304	<	* <tt>null</tt> if this deque is empty.
305	<	*
306	<	* @return the last element of this deque, or <tt>null</tt> if
307	<	*     this deque is empty
308	<	*/
309	<	public E pollLast() {
310	<	int t = (tail - 1) & (elements.length - 1);
311	<	E result = elements[t];
312	<	if (result == null)
313	<	return null;
314	<	elements[t] = null;
315	<	tail = t;
316	<	return result;
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 insert
326	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
327	<	* @throws NullPointerException if <tt>e</tt> is null
325	>	* @param e the element to add
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) {
330		addFirst(e);
#	Line 263 | Line 334 | public class ArrayDeque<E> extends Abstr
334		/**
335		* Inserts the specified element at the end of this deque.
336		*
337	<	* @param e the element to insert
338	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
339	<	* @throws NullPointerException if <tt>e</tt> is null
337	>	* @param e the element to add
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) {
342		addLast(e);
#	Line 273 | Line 344 | public class ArrayDeque<E> extends Abstr
344		}
345
346		/**
347	<	* Retrieves and removes the first element of this deque.  This method
277	<	* differs from the {@link #pollFirst} method only in that it throws an
278	<	* exception if this deque is empty.
279	<	*
280	<	* @return the first element of this deque
281	<	* @throws NoSuchElementException if this deque is empty
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	<	* Retrieves and removes the last element of this deque.  This method
292	<	* differs from the {@link #pollLast} method only in that it throws an
293	<	* exception if this deque is empty.
294	<	*
295	<	* @return the last element of this deque
296	<	* @throws NoSuchElementException if this deque is empty
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	<	/**
369	<	* Retrieves, but does not remove, the first element of this deque,
370	<	* returning <tt>null</tt> if this deque is empty.
371	<	*
372	<	* @return the first element of this deque, or <tt>null</tt> if
373	<	*     this deque is empty
374	<	*/
375	<	public E peekFirst() {
376	<	return elements[head]; // elements[head] is null if deque empty
368	>	public E pollFirst() {
369	>	// checkInvariants();
370	>	int s, h;
371	>	if ((s = size) <= 0)
372	>	return null;
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	<	/**
383	<	* Retrieves, but does not remove, the last element of this deque,
384	<	* returning <tt>null</tt> if this deque is empty.
385	<	*
386	<	* @return the last element of this deque, or <tt>null</tt> if this deque
387	<	*     is empty
388	<	*/
389	<	public E peekLast() {
390	<	return elements[(tail - 1) & (elements.length - 1)];
382	>	public E pollLast() {
383	>	// checkInvariants();
384	>	final int s, tail;
385	>	if ((s = size) <= 0)
386	>	return null;
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	<	* Retrieves, but does not remove, the first element of this
329	<	* deque.  This method differs from the {@link #peekFirst} method only
330	<	* in that it throws an exception if this deque is empty.
331	<	*
332	<	* @return the first element of this deque
333	<	* @throws NoSuchElementException if this deque is empty
396	>	* @throws NoSuchElementException {@inheritDoc}
397		*/
398		public E getFirst() {
399	<	E x = elements[head];
400	<	if (x == null)
401	<	throw new NoSuchElementException();
339	<	return x;
399	>	// checkInvariants();
400	>	if (size <= 0) throw new NoSuchElementException();
401	>	return elementAt(head);
402		}
403
404		/**
405	<	* Retrieves, but does not remove, the last element of this
344	<	* deque.  This method differs from the {@link #peekLast} method only
345	<	* in that it throws an exception if this deque is empty.
346	<	*
347	<	* @return the last element of this deque
348	<	* @throws NoSuchElementException if this deque is empty
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	>	// checkInvariants();
418	>	return (size <= 0) ? null : elementAt(head);
419	>	}
420	>
421	>	@SuppressWarnings("unchecked")
422	>	public E peekLast() {
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).  More
433	<	* formally, removes the first element e such that (o==null ?
434	<	* e==null : o.equals(e)). If the deque does not contain the
435	<	* element, it is unchanged.
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 {@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		}
378	–	i = (i + 1) & mask;
457		}
458		return false;
459		}
460
461		/**
462		* Removes the last occurrence of the specified element in this
463	<	* deque (when traversing the deque from head to tail). More
464	<	* formally, removes the last element e such that (o==null ?
465	<	* e==null : o.equals(e)). If the deque
466	<	* does not contain the element, it is unchanged.
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 {@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		}
404	–	i = (i - 1) & mask;
487		}
488		return false;
489		}
#	Line 411 | Line 493 | public class ArrayDeque<E> extends Abstr
493		/**
494		* Inserts the specified element at the end of this deque.
495		*
414	–	* <p>This method is equivalent to {@link #offerLast}.
415	–	*
416	–	* @param e the element to insert
417	–	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
418	–	* @throws NullPointerException if <tt>e</tt> is null
419	–	*/
420	–	public boolean offer(E e) {
421	–	return offerLast(e);
422	–	}
423	–
424	–	/**
425	–	* Inserts the specified element at the end of this deque.
426	–	*
496		* <p>This method is equivalent to {@link #addLast}.
497		*
498	<	* @param e the element to insert
499	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
500	<	* @throws NullPointerException if <tt>e</tt> is null
498	>	* @param e the element to 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) {
503		addLast(e);
#	Line 436 | Line 505 | public class ArrayDeque<E> extends Abstr
505		}
506
507		/**
508	<	* Retrieves and removes the head of the queue represented by
440	<	* this deque, or <tt>null</tt> if this deque is empty.  In other words,
441	<	* retrieves and removes the first element of this deque, or <tt>null</tt>
442	<	* if this deque is empty.
508	>	* Inserts the specified element at the end of this deque.
509		*
510	<	* <p>This method is equivalent to {@link #pollFirst}.
510	>	* <p>This method is equivalent to {@link #offerLast}.
511		*
512	<	* @return the first element of this deque, or <tt>null</tt> if
513	<	*     this deque is empty
512	>	* @param e the element to add
513	>	* @return {@code true} (as specified by {@link Queue#offer})
514	>	* @throws NullPointerException if the specified element is null
515		*/
516	<	public E poll() {
517	<	return pollFirst();
516	>	public boolean offer(E e) {
517	>	return offerLast(e);
518		}
519
520		/**
521		* Retrieves and removes the head of the queue represented by this deque.
522	<	* This method differs from the {@link #poll} method only in that it
523	<	* throws an exception if this deque is empty.
522	>	*
523	>	* This method differs from {@link #poll poll} only in that it throws an
524	>	* exception if this deque is empty.
525		*
526		* <p>This method is equivalent to {@link #removeFirst}.
527		*
528		* @return the head of the queue represented by this deque
529	<	* @throws NoSuchElementException if this deque is empty
529	>	* @throws NoSuchElementException {@inheritDoc}
530		*/
531		public E remove() {
532		return removeFirst();
533		}
534
535		/**
536	<	* Retrieves, but does not remove, the head of the queue represented by
537	<	* this deque, returning <tt>null</tt> if this deque is empty.
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	>	* {@code null} if this deque is empty.
539		*
540	<	* <p>This method is equivalent to {@link #peekFirst}.
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 peek() {
546	<	return peekFirst();
545	>	public E poll() {
546	>	return pollFirst();
547		}
548
549		/**
550		* Retrieves, but does not remove, the head of the queue represented by
551	<	* this deque.  This method differs from the {@link #peek} method only in
551	>	* this deque.  This method differs from {@link #peek peek} only in
552		* that it throws an exception if this deque is empty.
553		*
554		* <p>This method is equivalent to {@link #getFirst}.
555		*
556		* @return the head of the queue represented by this deque
557	<	* @throws NoSuchElementException if this deque is empty
557	>	* @throws NoSuchElementException {@inheritDoc}
558		*/
559		public E element() {
560		return getFirst();
561		}
562
563	+	/**
564	+	* Retrieves, but does not remove, the head of the queue represented by
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	+	*         {@code null} if this deque is empty
571	+	*/
572	+	public E peek() {
573	+	return peekFirst();
574	+	}
575	+
576		// *** Stack methods ***
577
578		/**
#	Line 500 | Line 582 | public class ArrayDeque<E> extends Abstr
582		* <p>This method is equivalent to {@link #addFirst}.
583		*
584		* @param e the element to push
585	<	* @throws NullPointerException if <tt>e</tt> is null
585	>	* @throws NullPointerException if the specified element is null
586		*/
587		public void push(E e) {
588		addFirst(e);
#	Line 513 | Line 595 | public class ArrayDeque<E> extends Abstr
595		* <p>This method is equivalent to {@link #removeFirst()}.
596		*
597		* @return the element at the front of this deque (which is the top
598	<	*     of the stack represented by this deque)
599	<	* @throws NoSuchElementException if this deque is empty
598	>	*         of the stack represented by this deque)
599	>	* @throws NoSuchElementException {@inheritDoc}
600		*/
601		public E pop() {
602		return removeFirst();
603		}
604
605		/**
606	<	* Removes the element at the specified position in the elements array,
607	<	* adjusting head, tail, and size as necessary.  This can result in
608	<	* motion of 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 List.remove(int).
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	<	// Case 1: Deque doesn't wrap
617	<	// Case 2: Deque does wrap and removed element is in the head portion
618	<	if ((head < tail || tail == 0) || i >= head) {
619	<	System.arraycopy(elements, head, elements, head + 1, i - head);
620	<	elements[head] = null;
621	<	head = (head + 1) & (elements.length - 1);
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		}
542	–
543	–	// Case 3: Deque wraps and removed element is in the tail portion
544	–	tail--;
545	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
546	–	elements[tail] = null;
547	–	return true;
653		}
654
655		// *** Collection Methods ***
#	Line 555 | 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.<p>
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 573 | Line 678 | public class ArrayDeque<E> extends Abstr
678		* order that elements would be dequeued (via successive calls to
679		* {@link #remove} or popped (via successive calls to {@link #pop}).
680		*
681	<	* @return an <tt>Iterator</tt> over the elements in this deque
681	>	* @return an iterator over the elements in this deque
682		*/
683		public Iterator<E> iterator() {
684		return new DeqIterator();
685		}
686
687	+	public Iterator<E> descendingIterator() {
688	+	return new DescendingIterator();
689	+	}
690	+
691		private class DeqIterator implements Iterator<E> {
692	<	/**
693	<	* Index of element to be returned by subsequent call to next.
585	<	*/
586	<	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
590	<	* iterator and also to check for comodification.
591	<	*/
592	<	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;
606	<	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
610	<	if (tail != fence || (result = elements[cursor]) == null)
611	<	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))
621	<	cursor--;
729	>	postDelete(delete(lastRet));
730		lastRet = -1;
623	–	fence = tail;
731		}
732	+
733	+	public void forEachRemaining(Consumer<? super E> action) {
734	+	final int k;
735	+	if ((k = remaining) > 0) {
736	+	remaining = 0;
737	+	ArrayDeque.forEachRemaining(action, elements, cursor, k);
738	+	if ((lastRet = cursor + k - 1) >= elements.length)
739	+	lastRet -= elements.length;
740	+	}
741	+	}
742	+	}
743	+
744	+	private class DescendingIterator extends DeqIterator {
745	+	DescendingIterator() { cursor = tail(); }
746	+
747	+	public final E next() {
748	+	if (remaining <= 0)
749	+	throw new NoSuchElementException();
750	+	final Object[] elements = ArrayDeque.this.elements;
751	+	E e = nonNullElementAt(elements, cursor);
752	+	lastRet = cursor;
753	+	if (--cursor < 0) cursor = elements.length - 1;
754	+	remaining--;
755	+	return e;
756	+	}
757	+
758	+	void postDelete(boolean leftShifted) {
759	+	if (!leftShifted)
760	+	if (++cursor >= elements.length) cursor = 0;
761	+	}
762	+
763	+	public final void forEachRemaining(Consumer<? super E> action) {
764	+	final int k;
765	+	if ((k = remaining) > 0) {
766	+	remaining = 0;
767	+	forEachRemainingDescending(action, elements, cursor, k);
768	+	if ((lastRet = cursor - (k - 1)) < 0)
769	+	lastRet += elements.length;
770	+	}
771	+	}
772	+	}
773	+
774	+	/**
775	+	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
776	+	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
777	+	* deque.
778	+	*
779	+	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
780	+	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
781	+	* {@link Spliterator#NONNULL}.  Overriding implementations should document
782	+	* the reporting of additional characteristic values.
783	+	*
784	+	* @return a {@code Spliterator} over the elements in this deque
785	+	* @since 1.8
786	+	*/
787	+	public Spliterator<E> spliterator() {
788	+	return new ArrayDequeSpliterator();
789	+	}
790	+
791	+	final class ArrayDequeSpliterator implements Spliterator<E> {
792	+	private int cursor;
793	+	private int remaining; // -1 until late-binding first use
794	+
795	+	/** Constructs late-binding spliterator over all elements. */
796	+	ArrayDequeSpliterator() {
797	+	this.remaining = -1;
798	+	}
799	+
800	+	/** Constructs spliterator over the given slice. */
801	+	ArrayDequeSpliterator(int cursor, int count) {
802	+	this.cursor = cursor;
803	+	this.remaining = count;
804	+	}
805	+
806	+	/** Ensures late-binding initialization; then returns remaining. */
807	+	private int remaining() {
808	+	if (remaining < 0) {
809	+	cursor = head;
810	+	remaining = size;
811	+	}
812	+	return remaining;
813	+	}
814	+
815	+	public ArrayDequeSpliterator trySplit() {
816	+	final int mid;
817	+	if ((mid = remaining() >> 1) > 0) {
818	+	int oldCursor = cursor;
819	+	cursor = add(cursor, mid, elements.length);
820	+	remaining -= mid;
821	+	return new ArrayDequeSpliterator(oldCursor, mid);
822	+	}
823	+	return null;
824	+	}
825	+
826	+	public void forEachRemaining(Consumer<? super E> action) {
827	+	final int k = remaining(); // side effect!
828	+	remaining = 0;
829	+	ArrayDeque.forEachRemaining(action, elements, cursor, k);
830	+	}
831	+
832	+	public boolean tryAdvance(Consumer<? super E> action) {
833	+	Objects.requireNonNull(action);
834	+	final int k;
835	+	if ((k = remaining()) <= 0)
836	+	return false;
837	+	action.accept(nonNullElementAt(elements, cursor));
838	+	if (++cursor >= elements.length) cursor = 0;
839	+	remaining = k - 1;
840	+	return true;
841	+	}
842	+
843	+	public long estimateSize() {
844	+	return remaining();
845	+	}
846	+
847	+	public int characteristics() {
848	+	return Spliterator.NONNULL
849	+	| Spliterator.ORDERED
850	+	| Spliterator.SIZED
851	+	| Spliterator.SUBSIZED;
852	+	}
853	+	}
854	+
855	+	@SuppressWarnings("unchecked")
856	+	public void forEach(Consumer<? super E> action) {
857	+	Objects.requireNonNull(action);
858	+	final Object[] elements = this.elements;
859	+	final int capacity = elements.length;
860	+	int i, end, to, todo;
861	+	todo = (end = (i = head) + size)
862	+	- (to = (capacity - end >= 0) ? end : capacity);
863	+	for (;; to = todo, i = 0, todo = 0) {
864	+	for (; i < to; i++)
865	+	action.accept((E) elements[i]);
866	+	if (todo == 0) break;
867	+	}
868	+	// checkInvariants();
869		}
870
871		/**
872	<	* Returns <tt>true</tt> if this deque contains the specified
873	<	* element.  More formally, returns <tt>true</tt> if and only if this
874	<	* deque contains at least one element <tt>e</tt> such that
875	<	* <tt>e.equals(o)</tt>.
872	>	* Calls action on remaining elements, starting at index i and
873	>	* traversing in ascending order.  A variant of forEach that also
874	>	* checks for concurrent modification, for use in iterators.
875	>	*/
876	>	static <E> void forEachRemaining(
877	>	Consumer<? super E> action, Object[] elements, int i, int remaining) {
878	>	Objects.requireNonNull(action);
879	>	final int capacity = elements.length;
880	>	int end, to, todo;
881	>	todo = (end = i + remaining)
882	>	- (to = (capacity - end >= 0) ? end : capacity);
883	>	for (;; to = todo, i = 0, todo = 0) {
884	>	for (; i < to; i++)
885	>	action.accept(nonNullElementAt(elements, i));
886	>	if (todo == 0) break;
887	>	}
888	>	}
889	>
890	>	static <E> void forEachRemainingDescending(
891	>	Consumer<? super E> action, Object[] elements, int i, int remaining) {
892	>	Objects.requireNonNull(action);
893	>	final int capacity = elements.length;
894	>	int end, to, todo;
895	>	todo = (to = ((end = i - remaining) >= -1) ? end : -1) - end;
896	>	for (;; to = (i = capacity - 1) - todo, todo = 0) {
897	>	for (; i > to; i--)
898	>	action.accept(nonNullElementAt(elements, i));
899	>	if (todo == 0) break;
900	>	}
901	>	}
902	>
903	>	/**
904	>	* Replaces each element of this deque with the result of applying the
905	>	* operator to that element, as specified by {@link List#replaceAll}.
906	>	*
907	>	* @param operator the operator to apply to each element
908	>	* @since TBD
909	>	*/
910	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
911	>	Objects.requireNonNull(operator);
912	>	final Object[] elements = this.elements;
913	>	final int capacity = elements.length;
914	>	int i, end, to, todo;
915	>	todo = (end = (i = head) + size)
916	>	- (to = (capacity - end >= 0) ? end : capacity);
917	>	for (;; to = todo, i = 0, todo = 0) {
918	>	for (; i < to; i++)
919	>	elements[i] = operator.apply(elementAt(i));
920	>	if (todo == 0) break;
921	>	}
922	>	// checkInvariants();
923	>	}
924	>
925	>	/**
926	>	* @throws NullPointerException {@inheritDoc}
927	>	*/
928	>	public boolean removeIf(Predicate<? super E> filter) {
929	>	Objects.requireNonNull(filter);
930	>	return bulkRemove(filter);
931	>	}
932	>
933	>	/**
934	>	* @throws NullPointerException {@inheritDoc}
935	>	*/
936	>	public boolean removeAll(Collection<?> c) {
937	>	Objects.requireNonNull(c);
938	>	return bulkRemove(e -> c.contains(e));
939	>	}
940	>
941	>	/**
942	>	* @throws NullPointerException {@inheritDoc}
943	>	*/
944	>	public boolean retainAll(Collection<?> c) {
945	>	Objects.requireNonNull(c);
946	>	return bulkRemove(e -> !c.contains(e));
947	>	}
948	>
949	>	/** Implementation of bulk remove methods. */
950	>	private boolean bulkRemove(Predicate<? super E> filter) {
951	>	// checkInvariants();
952	>	final Object[] elements = this.elements;
953	>	final int capacity = elements.length;
954	>	int i = head, j = i, remaining = size, deleted = 0;
955	>	try {
956	>	for (; remaining > 0; remaining--) {
957	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
958	>	if (filter.test(e))
959	>	deleted++;
960	>	else {
961	>	if (j != i)
962	>	elements[j] = e;
963	>	if (++j >= capacity) j = 0;
964	>	}
965	>	if (++i >= capacity) i = 0;
966	>	}
967	>	return deleted > 0;
968	>	} catch (Throwable ex) {
969	>	if (deleted > 0)
970	>	for (; remaining > 0; remaining--) {
971	>	elements[j] = elements[i];
972	>	if (++i >= capacity) i = 0;
973	>	if (++j >= capacity) j = 0;
974	>	}
975	>	throw ex;
976	>	} finally {
977	>	size -= deleted;
978	>	clearSlice(elements, j, deleted);
979	>	// checkInvariants();
980	>	}
981	>	}
982	>
983	>	/**
984	>	* Returns {@code true} if this deque contains the specified element.
985	>	* More formally, returns {@code true} if and only if this deque contains
986	>	* at least one element {@code e} such that {@code o.equals(e)}.
987		*
988		* @param o object to be checked for containment in this deque
989	<	* @return <tt>true</tt> if this deque contains the specified element
989	>	* @return {@code true} if this deque contains the specified element
990		*/
991		public boolean contains(Object o) {
992	<	if (o == null)
993	<	return false;
994	<	int mask = elements.length - 1;
995	<	int i = head;
996	<	E x;
997	<	while ( (x = elements[i]) != null) {
998	<	if (o.equals(x))
999	<	return true;
1000	<	i = (i + 1) & mask;
992	>	if (o != null) {
993	>	final Object[] elements = this.elements;
994	>	final int capacity = elements.length;
995	>	int i, end, to, todo;
996	>	todo = (end = (i = head) + size)
997	>	- (to = (capacity - end >= 0) ? end : capacity);
998	>	for (;; to = todo, i = 0, todo = 0) {
999	>	for (; i < to; i++)
1000	>	if (o.equals(elements[i]))
1001	>	return true;
1002	>	if (todo == 0) break;
1003	>	}
1004		}
1005		return false;
1006		}
1007
1008		/**
1009		* Removes a single instance of the specified element from this deque.
1010	<	* This method is equivalent to {@link #removeFirstOccurrence}.
1010	>	* If the deque does not contain the element, it is unchanged.
1011	>	* More formally, removes the first element {@code e} such that
1012	>	* {@code o.equals(e)} (if such an element exists).
1013	>	* Returns {@code true} if this deque contained the specified element
1014	>	* (or equivalently, if this deque changed as a result of the call).
1015	>	*
1016	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1017		*
1018	<	* @param e element to be removed from this deque, if present
1019	<	* @return <tt>true</tt> if this deque contained the specified element
1018	>	* @param o element to be removed from this deque, if present
1019	>	* @return {@code true} if this deque contained the specified element
1020		*/
1021	<	public boolean remove(Object e) {
1022	<	return removeFirstOccurrence(e);
1021	>	public boolean remove(Object o) {
1022	>	return removeFirstOccurrence(o);
1023		}
1024
1025		/**
#	Line 663 | Line 1027 | public class ArrayDeque<E> extends Abstr
1027		* The deque will be empty after this call returns.
1028		*/
1029		public void clear() {
1030	<	int h = head;
1031	<	int t = tail;
1032	<	if (h != t) { // clear all cells
1033	<	head = tail = 0;
1034	<	int i = h;
1035	<	int mask = elements.length - 1;
1036	<	do {
1037	<	elements[i] = null;
1038	<	i = (i + 1) & mask;
1039	<	} while(i != t);
1040	<	}
1030	>	clearSlice(elements, head, size);
1031	>	size = head = 0;
1032	>	// checkInvariants();
1033	>	}
1034	>
1035	>	/**
1036	>	* Nulls out count elements, starting at array index from.
1037	>	*/
1038	>	private static void clearSlice(Object[] elements, int from, int count) {
1039	>	final int capacity = elements.length, end = from + count;
1040	>	final int leg = (capacity - end >= 0) ? end : capacity;
1041	>	Arrays.fill(elements, from, leg, null);
1042	>	if (leg != end)
1043	>	Arrays.fill(elements, 0, end - capacity, null);
1044		}
1045
1046		/**
1047		* Returns an array containing all of the elements in this deque
1048	<	* in the correct order.
1048	>	* in proper sequence (from first to last element).
1049	>	*
1050	>	* <p>The returned array will be "safe" in that no references to it are
1051	>	* maintained by this deque.  (In other words, this method must allocate
1052	>	* a new array).  The caller is thus free to modify the returned array.
1053	>	*
1054	>	* <p>This method acts as bridge between array-based and collection-based
1055	>	* APIs.
1056		*
1057		* @return an array containing all of the elements in this deque
684	–	*         in the correct order
1058		*/
1059		public Object[] toArray() {
1060	<	return copyElements(new Object[size()]);
1060	>	return toArray(Object[].class);
1061	>	}
1062	>
1063	>	private <T> T[] toArray(Class<T[]> klazz) {
1064	>	final Object[] elements = this.elements;
1065	>	final int capacity = elements.length;
1066	>	final int head = this.head, end = head + size;
1067	>	final T[] a;
1068	>	if (end >= 0) {
1069	>	a = Arrays.copyOfRange(elements, head, end, klazz);
1070	>	} else {
1071	>	// integer overflow!
1072	>	a = Arrays.copyOfRange(elements, 0, size, klazz);
1073	>	System.arraycopy(elements, head, a, 0, capacity - head);
1074	>	}
1075	>	if (end - capacity > 0)
1076	>	System.arraycopy(elements, 0, a, capacity - head, end - capacity);
1077	>	return a;
1078		}
1079
1080		/**
1081	<	* Returns an array containing all of the elements in this deque in the
1082	<	* correct order; the runtime type of the returned array is that of the
1083	<	* specified array.  If the deque fits in the specified array, it is
1084	<	* returned therein.  Otherwise, a new array is allocated with the runtime
1085	<	* type of the specified array and the size of this deque.
1081	>	* Returns an array containing all of the elements in this deque in
1082	>	* proper sequence (from first to last element); the runtime type of the
1083	>	* returned array is that of the specified array.  If the deque fits in
1084	>	* the specified array, it is returned therein.  Otherwise, a new array
1085	>	* is allocated with the runtime type of the specified array and the
1086	>	* size of this deque.
1087	>	*
1088	>	* <p>If this deque fits in the specified array with room to spare
1089	>	* (i.e., the array has more elements than this deque), the element in
1090	>	* the array immediately following the end of the deque is set to
1091	>	* {@code null}.
1092	>	*
1093	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
1094	>	* array-based and collection-based APIs.  Further, this method allows
1095	>	* precise control over the runtime type of the output array, and may,
1096	>	* under certain circumstances, be used to save allocation costs.
1097	>	*
1098	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1099	>	* The following code can be used to dump the deque into a newly
1100	>	* allocated array of {@code String}:
1101	>	*
1102	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1103		*
1104	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
1105	<	* the array has more elements than the deque), the element in the array
699	<	* immediately following the end of the collection is set to <tt>null</tt>.
1104	>	* Note that {@code toArray(new Object[0])} is identical in function to
1105	>	* {@code toArray()}.
1106		*
1107		* @param a the array into which the elements of the deque are to
1108	<	*          be stored, if it is big enough; otherwise, a new array of the
1109	<	*          same runtime type is allocated for this purpose
1110	<	* @return an array containing the elements of the deque
1111	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
1112	<	*         of the runtime type of every element in this deque
1108	>	*          be stored, if it is big enough; otherwise, a new array of the
1109	>	*          same runtime type is allocated for this purpose
1110	>	* @return an array containing all of the elements in this deque
1111	>	* @throws ArrayStoreException if the runtime type of the specified array
1112	>	*         is not a supertype of the runtime type of every element in
1113	>	*         this deque
1114	>	* @throws NullPointerException if the specified array is null
1115		*/
1116	+	@SuppressWarnings("unchecked")
1117		public <T> T[] toArray(T[] a) {
1118	<	int size = size();
1119	<	if (a.length < size)
1120	<	a = (T[])java.lang.reflect.Array.newInstance(
1121	<	a.getClass().getComponentType(), size);
1122	<	copyElements(a);
1123	<	if (a.length > size)
1118	>	final int size = this.size;
1119	>	if (size > a.length)
1120	>	return toArray((Class<T[]>) a.getClass());
1121	>	final Object[] elements = this.elements;
1122	>	final int capacity = elements.length;
1123	>	final int head = this.head, end = head + size;
1124	>	final int front = (capacity - end >= 0) ? size : capacity - head;
1125	>	System.arraycopy(elements, head, a, 0, front);
1126	>	if (front != size)
1127	>	System.arraycopy(elements, 0, a, capacity - head, end - capacity);
1128	>	if (size < a.length)
1129		a[size] = null;
1130		return a;
1131		}
#	Line 725 | Line 1139 | public class ArrayDeque<E> extends Abstr
1139		*/
1140		public ArrayDeque<E> clone() {
1141		try {
1142	+	@SuppressWarnings("unchecked")
1143		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1144	<	// These two lines are currently faster than cloning the array:
730	<	result.elements = (E[]) new Object[elements.length];
731	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
1144	>	result.elements = Arrays.copyOf(elements, elements.length);
1145		return result;
733	–
1146		} catch (CloneNotSupportedException e) {
1147		throw new AssertionError();
1148		}
1149		}
1150
739	–	/**
740	–	* Appease the serialization gods.
741	–	*/
1151		private static final long serialVersionUID = 2340985798034038923L;
1152
1153		/**
1154	<	* Serialize this deque.
1154	>	* Saves this deque to a stream (that is, serializes it).
1155		*
1156	<	* @serialData The current size (<tt>int</tt>) of the deque,
1156	>	* @param s the stream
1157	>	* @throws java.io.IOException if an I/O error occurs
1158	>	* @serialData The current size ({@code int}) of the deque,
1159		* followed by all of its elements (each an object reference) in
1160		* first-to-last order.
1161		*/
1162	<	private void writeObject(ObjectOutputStream s) throws IOException {
1162	>	private void writeObject(java.io.ObjectOutputStream s)
1163	>	throws java.io.IOException {
1164		s.defaultWriteObject();
1165
1166		// Write out size
755	–	int size = size();
1167		s.writeInt(size);
1168
1169		// Write out elements in order.
1170	<	int i = head;
1171	<	int mask = elements.length - 1;
1172	<	for (int j = 0; j < size; j++) {
1173	<	s.writeObject(elements[i]);
1174	<	i = (i + 1) & mask;
1170	>	final Object[] elements = this.elements;
1171	>	final int capacity = elements.length;
1172	>	int i, end, to, todo;
1173	>	todo = (end = (i = head) + size)
1174	>	- (to = (capacity - end >= 0) ? end : capacity);
1175	>	for (;; to = todo, i = 0, todo = 0) {
1176	>	for (; i < to; i++)
1177	>	s.writeObject(elements[i]);
1178	>	if (todo == 0) break;
1179		}
1180		}
1181
1182		/**
1183	<	* Deserialize this deque.
1183	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1184	>	* @param s the stream
1185	>	* @throws ClassNotFoundException if the class of a serialized object
1186	>	*         could not be found
1187	>	* @throws java.io.IOException if an I/O error occurs
1188		*/
1189	<	private void readObject(ObjectInputStream s)
1190	<	throws IOException, ClassNotFoundException {
1189	>	private void readObject(java.io.ObjectInputStream s)
1190	>	throws java.io.IOException, ClassNotFoundException {
1191		s.defaultReadObject();
1192
1193		// Read in size and allocate array
1194	<	int size = s.readInt();
776	<	allocateElements(size);
777	<	head = 0;
778	<	tail = size;
1194	>	elements = new Object[size = s.readInt()];
1195
1196		// Read in all elements in the proper order.
1197		for (int i = 0; i < size; i++)
1198	<	elements[i] = (E)s.readObject();
1198	>	elements[i] = s.readObject();
1199	>	}
1200
1201	+	/** debugging */
1202	+	void checkInvariants() {
1203	+	try {
1204	+	int capacity = elements.length;
1205	+	// assert size >= 0 && size <= capacity;
1206	+	// assert head >= 0;
1207	+	// assert capacity == 0 || head < capacity;
1208	+	// assert size == 0 || elements[head] != null;
1209	+	// assert size == 0 || elements[tail()] != null;
1210	+	// assert size == capacity || elements[dec(head, capacity)] == null;
1211	+	// assert size == capacity || elements[inc(tail(), capacity)] == null;
1212	+	} catch (Throwable t) {
1213	+	System.err.printf("head=%d size=%d capacity=%d%n",
1214	+	head, size, elements.length);
1215	+	System.err.printf("elements=%s%n",
1216	+	Arrays.toString(elements));
1217	+	throw t;
1218	+	}
1219		}
1220	+
1221		}

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