ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

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

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.1 by dl, Tue Dec 28 12:14:07 2004 UTC vs.
Revision 1.88 by jsr166, Mon Oct 24 16:01:25 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 12 | Line 16 | import java.io.*;
16		* usage.  They are not thread-safe; in the absence of external
17		* synchronization, they do not support concurrent access by multiple threads.
18		* Null elements are prohibited.  This class is likely to be faster than
19	<	* {@link Stack} when used as as a stack, and faster than {@link LinkedList}
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 remove method, the
34	<	* iterator will generally throw a {@link ConcurrentModificationException}.
35	<	* Thus, in the face of concurrent modification, the iterator fails quickly
36	<	* and cleanly, rather than risking arbitrary, non-deterministic behavior at
37	<	* an undetermined time in the future.
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
38	>	* future.
39		*
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
49	–	* @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 in 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
58	<	* full, except transiently within an addX method where it is
59	<	* resized (see doubleCapacity) immediately upon becoming full,
60	<	* thus avoiding head and tail wrapping around to equal each
61	<	* other.  We also guarantee that all array cells not holding
62	<	* deque elements are always null.
64	>	* The array in which the elements of the deque are stored.
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.
70	<	*/
71	<	private transient int head;
72	<
73	<	/**
74	<	* The index at which the next element would be added to the tail
75	<	* of the deque (via addLast(E), add(E), or push(E)).
76	<	*/
77	<	private transient int tail;
78	<
79	<	/**
80	<	* The minimum capacity that we'll use for a newly created deque.
81	<	* 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	>	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	>	int oldCapacity = elements.length;
119	>	int 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;
119	<	int r = n - p; // number of elements to the right of p
120	<	int newCapacity = n << 1;
121	<	if (newCapacity < 0)
122	<	throw new IllegalStateException("Sorry, deque too big");
123	<	Object[] a = new Object[newCapacity];
124	<	System.arraycopy(elements, p, a, 0, r);
125	<	System.arraycopy(elements, 0, a, r, p);
126	<	elements = (E[])a;
127	<	head = 0;
128	<	tail = n;
139	>	/* public */ void ensureCapacity(int minCapacity) {
140	>	if (minCapacity > elements.length)
141	>	grow(minCapacity - elements.length);
142	>	// checkInvariants();
143		}
144
145		/**
146	<	* Copy the elements from our element array into the specified array,
133	<	* in order (from first to last element in the deque).  It is assumed
134	<	* 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) {
142	<	int headPortionLen = elements.length - head;
143	<	System.arraycopy(elements, head, a, 0, headPortionLen);
144	<	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		/**
159	<	* Constructs an empty array deque with the an initial capacity
159	>	* Constructs an empty array deque with an initial capacity
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 175 | 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[] elements = c.toArray();
188	>	// defend against c.toArray (incorrectly) not returning Object[]
189	>	// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
190	>	size = elements.length;
191	>	if (elements.getClass() != Object[].class)
192	>	elements = Arrays.copyOf(elements, size, Object[].class);
193	>	for (Object obj : elements)
194	>	Objects.requireNonNull(obj);
195	>	this.elements = elements;
196		}
197
198	<	// The main insertion and extraction methods are addFirst,
199	<	// addLast, pollFirst, pollLast. The other methods are defined in
200	<	// terms of these.
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	<	* Inserts the specified element to the front this deque.
209	<	*
189	<	* @param e the element to insert
190	<	* @throws NullPointerException if <tt>e</tt> is null
208	>	* Decrements i, mod modulus.
209	>	* Precondition and postcondition: 0 <= i < modulus.
210		*/
211	<	public void addFirst(E e) {
212	<	if (e == null)
213	<	throw new NullPointerException();
195	<	elements[head = (head - 1) & (elements.length - 1)] = e;
196	<	if (head == tail)
197	<	doubleCapacity();
211	>	static final int dec(int i, int modulus) {
212	>	if (--i < 0) i += modulus;
213	>	return i;
214		}
215
216		/**
217	<	* Inserts the specified element to the end this deque.
218	<	* This method is equivalent to {@link Collection#add} and
203	<	* {@link #push}.
204	<	*
205	<	* @param e the element to insert
206	<	* @throws NullPointerException if <tt>e</tt> is null
217	>	* Adds i and j, mod modulus.
218	>	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
219		*/
220	<	public void addLast(E e) {
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.
245	>	*/
246	>	E checkedElementAt(Object[] elements, int i) {
247	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
248		if (e == null)
249	<	throw new NullPointerException();
250	<	elements[tail] = e;
212	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
213	<	doubleCapacity();
249	>	throw new ConcurrentModificationException();
250	>	return e;
251		}
252
253	+	// The main insertion and extraction methods are addFirst,
254	+	// addLast, pollFirst, pollLast. The other methods are defined in
255	+	// terms of these.
256	+
257		/**
258	<	* Retrieves and removes the first element of this deque, or
218	<	* <tt>null</tt> if this deque is empty.
258	>	* Inserts the specified element at the front of this deque.
259		*
260	<	* @return the first element of this deque, or <tt>null</tt> if
261	<	*     this deque is empty
260	>	* @param e the element to add
261	>	* @throws NullPointerException if the specified element is null
262		*/
263	<	public E pollFirst() {
264	<	int h = head;
265	<	E result = elements[h]; // Element is null if deque empty
266	<	if (result == null)
267	<	return null;
268	<	elements[h] = null;     // Must null out slot
269	<	head = (h + 1) & (elements.length - 1);
270	<	return result;
263	>	public void addFirst(E e) {
264	>	// checkInvariants();
265	>	Objects.requireNonNull(e);
266	>	final Object[] elements;
267	>	final int capacity, s;
268	>	if ((s = size) == (capacity = (elements = this.elements).length))
269	>	addFirstSlowPath(e);
270	>	else
271	>	elements[head = dec(head, capacity)] = e;
272	>	size = s + 1;
273	>	// checkInvariants();
274	>	}
275	>
276	>	private void addFirstSlowPath(E e) {
277	>	grow(1);
278	>	final Object[] elements = this.elements;
279	>	elements[head = dec(head, elements.length)] = e;
280		}
281
282		/**
283	<	* Retrieves and removes the last element of this deque, or
284	<	* <tt>null</tt> if this deque is empty.
283	>	* Inserts the specified element at the end of this deque.
284	>	*
285	>	* <p>This method is equivalent to {@link #add}.
286		*
287	<	* @return the last element of this deque, or <tt>null</tt> if
288	<	*     this deque is empty
287	>	* @param e the element to add
288	>	* @throws NullPointerException if the specified element is null
289		*/
290	<	public E pollLast() {
291	<	int t = (tail - 1) & (elements.length - 1);
292	<	E result = elements[t];
293	<	if (result == null)
294	<	return null;
295	<	elements[t] = null;
296	<	tail = t;
297	<	return result;
290	>	public void addLast(E e) {
291	>	// checkInvariants();
292	>	Objects.requireNonNull(e);
293	>	final Object[] elements;
294	>	final int capacity, s;
295	>	if ((s = size) == (capacity = (elements = this.elements).length))
296	>	addLastSlowPath(e);
297	>	else
298	>	elements[add(head, s, capacity)] = e;
299	>	size = s + 1;
300	>	// checkInvariants();
301	>	}
302	>
303	>	private void addLastSlowPath(E e) {
304	>	grow(1);
305	>	final Object[] elements = this.elements;
306	>	elements[add(head, size, elements.length)] = e;
307		}
308
309		/**
310	<	* Inserts the specified element to the front this deque.
311	<	*
312	<	* @param e the element to insert
313	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
314	<	* @throws NullPointerException if <tt>e</tt> is null
310	>	* Adds all of the elements in the specified collection at the end
311	>	* of this deque, as if by calling {@link #addLast} on each one,
312	>	* in the order that they are returned by the collection's
313	>	* iterator.
314	>	*
315	>	* @param c the elements to be inserted into this deque
316	>	* @return {@code true} if this deque changed as a result of the call
317	>	* @throws NullPointerException if the specified collection or any
318	>	*         of its elements are null
319	>	*/
320	>	public boolean addAll(Collection<? extends E> c) {
321	>	final int s = size, needed = c.size() - (elements.length - s);
322	>	if (needed > 0)
323	>	grow(needed);
324	>	c.forEach((e) -> addLast(e));
325	>	// checkInvariants();
326	>	return size > s;
327	>	}
328	>
329	>	/**
330	>	* Inserts the specified element at the front of this deque.
331	>	*
332	>	* @param e the element to add
333	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
334	>	* @throws NullPointerException if the specified element is null
335		*/
336		public boolean offerFirst(E e) {
337		addFirst(e);
#	Line 260 | Line 339 | public class ArrayDeque<E> extends Abstr
339		}
340
341		/**
342	<	* Inserts the specified element to the end this deque.
342	>	* Inserts the specified element at the end of this deque.
343		*
344	<	* @param e the element to insert
345	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
346	<	* @throws NullPointerException if <tt>e</tt> is null
344	>	* @param e the element to add
345	>	* @return {@code true} (as specified by {@link Deque#offerLast})
346	>	* @throws NullPointerException if the specified element is null
347		*/
348		public boolean offerLast(E e) {
349		addLast(e);
#	Line 272 | Line 351 | public class ArrayDeque<E> extends Abstr
351		}
352
353		/**
354	<	* Retrieves and removes the first element of this deque.  This method
276	<	* differs from the <tt>pollFirst</tt> method in that it throws an
277	<	* exception if this deque is empty.
278	<	*
279	<	* @return the first element of this deque
280	<	* @throws NoSuchElementException if this deque is empty
354	>	* @throws NoSuchElementException {@inheritDoc}
355		*/
356		public E removeFirst() {
357	<	E x = pollFirst();
358	<	if (x == null)
357	>	// checkInvariants();
358	>	E e = pollFirst();
359	>	if (e == null)
360		throw new NoSuchElementException();
361	<	return x;
361	>	return e;
362		}
363
364		/**
365	<	* Retrieves and removes the last element of this deque.  This method
291	<	* differs from the <tt>pollLast</tt> method in that it throws an
292	<	* exception if this deque is empty.
293	<	*
294	<	* @return the last element of this deque
295	<	* @throws NoSuchElementException if this deque is empty
365	>	* @throws NoSuchElementException {@inheritDoc}
366		*/
367		public E removeLast() {
368	<	E x = pollLast();
369	<	if (x == null)
368	>	// checkInvariants();
369	>	E e = pollLast();
370	>	if (e == null)
371		throw new NoSuchElementException();
372	<	return x;
372	>	return e;
373		}
374
375	<	/**
376	<	* Retrieves, but does not remove, the first element of this deque,
377	<	* returning <tt>null</tt> if this deque is empty.
378	<	*
379	<	* @return the first element of this deque, or <tt>null</tt> if
380	<	*     this deque is empty
381	<	*/
382	<	public E peekFirst() {
383	<	return elements[head]; // elements[head] is null if deque empty
375	>	public E pollFirst() {
376	>	// checkInvariants();
377	>	final int s, h;
378	>	if ((s = size) == 0)
379	>	return null;
380	>	final Object[] elements = this.elements;
381	>	@SuppressWarnings("unchecked") E e = (E) elements[h = head];
382	>	elements[h] = null;
383	>	head = inc(h, elements.length);
384	>	size = s - 1;
385	>	return e;
386		}
387
388	<	/**
389	<	* Retrieves, but does not remove, the last element of this deque,
390	<	* returning <tt>null</tt> if this deque is empty.
391	<	*
392	<	* @return the last element of this deque, or <tt>null</tt> if this deque
393	<	*     is empty
394	<	*/
395	<	public E peekLast() {
396	<	return elements[(tail - 1) & (elements.length - 1)];
388	>	public E pollLast() {
389	>	// checkInvariants();
390	>	final int s, tail;
391	>	if ((s = size) == 0)
392	>	return null;
393	>	final Object[] elements = this.elements;
394	>	@SuppressWarnings("unchecked")
395	>	E e = (E) elements[tail = add(head, s - 1, elements.length)];
396	>	elements[tail] = null;
397	>	size = s - 1;
398	>	return e;
399		}
400
401		/**
402	<	* Retrieves, but does not remove, the first element of this
328	<	* deque.  This method differs from the <tt>peek</tt> method only
329	<	* in that it throws an exception if this deque is empty.
330	<	*
331	<	* @return the first element of this deque
332	<	* @throws NoSuchElementException if this deque is empty
402	>	* @throws NoSuchElementException {@inheritDoc}
403		*/
404		public E getFirst() {
405	<	E x = elements[head];
406	<	if (x == null)
407	<	throw new NoSuchElementException();
338	<	return x;
405	>	// checkInvariants();
406	>	if (size == 0) throw new NoSuchElementException();
407	>	return elementAt(head);
408		}
409
410		/**
411	<	* Retrieves, but does not remove, the last element of this
343	<	* deque.  This method differs from the <tt>peek</tt> method only
344	<	* in that it throws an exception if this deque is empty.
345	<	*
346	<	* @return the last element of this deque
347	<	* @throws NoSuchElementException if this deque is empty
411	>	* @throws NoSuchElementException {@inheritDoc}
412		*/
413		public E getLast() {
414	<	E x = elements[(tail - 1) & (elements.length - 1)];
415	<	if (x == null)
416	<	throw new NoSuchElementException();
417	<	return x;
414	>	// checkInvariants();
415	>	if (size == 0) throw new NoSuchElementException();
416	>	return elementAt(tail());
417	>	}
418	>
419	>	public E peekFirst() {
420	>	// checkInvariants();
421	>	return (size == 0) ? null : elementAt(head);
422	>	}
423	>
424	>	public E peekLast() {
425	>	// checkInvariants();
426	>	return (size == 0) ? null : elementAt(tail());
427		}
428
429		/**
430		* Removes the first occurrence of the specified element in this
431	<	* deque (when traversing the deque from head to tail).  If the deque
432	<	* does not contain the element, it is unchanged.
433	<	*
434	<	* @param e element to be removed from this deque, if present
435	<	* @return <tt>true</tt> if the deque contained the specified element
436	<	*/
437	<	public boolean removeFirstOccurrence(Object e) {
438	<	if (e == null)
439	<	return false;
440	<	int mask = elements.length - 1;
441	<	int i = head;
442	<	E x;
443	<	while ( (x = elements[i]) != null) {
444	<	if (e.equals(x)) {
445	<	delete(i);
446	<	return true;
431	>	* deque (when traversing the deque from head to tail).
432	>	* If the deque does not contain the element, it is unchanged.
433	>	* More formally, removes the first element {@code e} such that
434	>	* {@code o.equals(e)} (if such an element exists).
435	>	* Returns {@code true} if this deque contained the specified element
436	>	* (or equivalently, if this deque changed as a result of the call).
437	>	*
438	>	* @param o element to be removed from this deque, if present
439	>	* @return {@code true} if the deque contained the specified element
440	>	*/
441	>	public boolean removeFirstOccurrence(Object o) {
442	>	// checkInvariants();
443	>	if (o != null) {
444	>	final Object[] elements = this.elements;
445	>	final int capacity = elements.length;
446	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) {
447	>	if (o.equals(elements[i])) {
448	>	delete(i);
449	>	return true;
450	>	}
451		}
375	–	i = (i + 1) & mask;
452		}
453		return false;
454		}
455
456		/**
457		* Removes the last occurrence of the specified element in this
458	<	* deque (when traversing the deque from head to tail).  If the deque
459	<	* does not contain the element, it is unchanged.
460	<	*
461	<	* @param e element to be removed from this deque, if present
462	<	* @return <tt>true</tt> if the deque contained the specified element
463	<	*/
464	<	public boolean removeLastOccurrence(Object e) {
465	<	if (e == null)
466	<	return false;
467	<	int mask = elements.length - 1;
468	<	int i = (tail - 1) & mask;
469	<	E x;
470	<	while ( (x = elements[i]) != null) {
471	<	if (e.equals(x)) {
472	<	delete(i);
473	<	return true;
458	>	* deque (when traversing the deque from head to tail).
459	>	* If the deque does not contain the element, it is unchanged.
460	>	* More formally, removes the last element {@code e} such that
461	>	* {@code o.equals(e)} (if such an element exists).
462	>	* Returns {@code true} if this deque contained the specified element
463	>	* (or equivalently, if this deque changed as a result of the call).
464	>	*
465	>	* @param o element to be removed from this deque, if present
466	>	* @return {@code true} if the deque contained the specified element
467	>	*/
468	>	public boolean removeLastOccurrence(Object o) {
469	>	if (o != null) {
470	>	final Object[] elements = this.elements;
471	>	final int capacity = elements.length;
472	>	for (int k = size, i = add(head, k - 1, capacity);
473	>	--k >= 0; i = dec(i, capacity)) {
474	>	if (o.equals(elements[i])) {
475	>	delete(i);
476	>	return true;
477	>	}
478		}
399	–	i = (i - 1) & mask;
479		}
480		return false;
481		}
#	Line 404 | Line 483 | public class ArrayDeque<E> extends Abstr
483		// *** Queue methods ***
484
485		/**
486	<	* Inserts the specified element to the end of this deque.
408	<	*
409	<	* <p>This method is equivalent to {@link #offerLast}.
410	<	*
411	<	* @param e the element to insert
412	<	* @return <tt>true</tt> (as per the spec for {@link Queue#offer})
413	<	* @throws NullPointerException if <tt>e</tt> is null
414	<	*/
415	<	public boolean offer(E e) {
416	<	return offerLast(e);
417	<	}
418	<
419	<	/**
420	<	* Inserts the specified element to the end of this deque.
486	>	* Inserts the specified element at the end of this deque.
487		*
488		* <p>This method is equivalent to {@link #addLast}.
489		*
490	<	* @param e the element to insert
491	<	* @return <tt>true</tt> (as per the spec for {@link Collection#add})
492	<	* @throws NullPointerException if <tt>e</tt> is null
490	>	* @param e the element to add
491	>	* @return {@code true} (as specified by {@link Collection#add})
492	>	* @throws NullPointerException if the specified element is null
493		*/
494		public boolean add(E e) {
495		addLast(e);
#	Line 431 | Line 497 | public class ArrayDeque<E> extends Abstr
497		}
498
499		/**
500	<	* Retrieves and removes the head of the queue represented by
435	<	* this deque, or <tt>null</tt> if this deque is empty.  In other words,
436	<	* retrieves and removes the first element of this deque, or <tt>null</tt>
437	<	* if this deque is empty.
500	>	* Inserts the specified element at the end of this deque.
501		*
502	<	* <p>This method is equivalent to {@link #pollFirst}.
502	>	* <p>This method is equivalent to {@link #offerLast}.
503		*
504	<	* @return the first element of this deque, or <tt>null</tt> if
505	<	*     this deque is empty
504	>	* @param e the element to add
505	>	* @return {@code true} (as specified by {@link Queue#offer})
506	>	* @throws NullPointerException if the specified element is null
507		*/
508	<	public E poll() {
509	<	return pollFirst();
508	>	public boolean offer(E e) {
509	>	return offerLast(e);
510		}
511
512		/**
513		* Retrieves and removes the head of the queue represented by this deque.
514	<	* This method differs from the <tt>poll</tt> method in that it throws an
514	>	*
515	>	* This method differs from {@link #poll poll} only in that it throws an
516		* exception if this deque is empty.
517		*
518		* <p>This method is equivalent to {@link #removeFirst}.
519		*
520		* @return the head of the queue represented by this deque
521	<	* @throws NoSuchElementException if this deque is empty
521	>	* @throws NoSuchElementException {@inheritDoc}
522		*/
523		public E remove() {
524		return removeFirst();
525		}
526
527		/**
528	<	* Retrieves, but does not remove, the head of the queue represented by
529	<	* this deque, returning <tt>null</tt> if this deque is empty.
528	>	* Retrieves and removes the head of the queue represented by this deque
529	>	* (in other words, the first element of this deque), or returns
530	>	* {@code null} if this deque is empty.
531		*
532	<	* <p>This method is equivalent to {@link #peekFirst}
532	>	* <p>This method is equivalent to {@link #pollFirst}.
533		*
534		* @return the head of the queue represented by this deque, or
535	<	*     <tt>null</tt> if this deque is empty
535	>	*         {@code null} if this deque is empty
536		*/
537	<	public E peek() {
538	<	return peekFirst();
537	>	public E poll() {
538	>	return pollFirst();
539		}
540
541		/**
542		* Retrieves, but does not remove, the head of the queue represented by
543	<	* this deque.  This method differs from the <tt>peek</tt> method only in
543	>	* this deque.  This method differs from {@link #peek peek} only in
544		* that it throws an exception if this deque is empty.
545		*
546	<	* <p>This method is equivalent to {@link #getFirst}
546	>	* <p>This method is equivalent to {@link #getFirst}.
547		*
548		* @return the head of the queue represented by this deque
549	<	* @throws NoSuchElementException if this deque is empty
549	>	* @throws NoSuchElementException {@inheritDoc}
550		*/
551		public E element() {
552		return getFirst();
553		}
554
555	+	/**
556	+	* Retrieves, but does not remove, the head of the queue represented by
557	+	* this deque, or returns {@code null} if this deque is empty.
558	+	*
559	+	* <p>This method is equivalent to {@link #peekFirst}.
560	+	*
561	+	* @return the head of the queue represented by this deque, or
562	+	*         {@code null} if this deque is empty
563	+	*/
564	+	public E peek() {
565	+	return peekFirst();
566	+	}
567	+
568		// *** Stack methods ***
569
570		/**
571		* Pushes an element onto the stack represented by this deque.  In other
572	<	* words, inserts the element to the front this deque.
572	>	* words, inserts the element at the front of this deque.
573		*
574		* <p>This method is equivalent to {@link #addFirst}.
575		*
576		* @param e the element to push
577	<	* @throws NullPointerException if <tt>e</tt> is null
577	>	* @throws NullPointerException if the specified element is null
578		*/
579		public void push(E e) {
580		addFirst(e);
#	Line 503 | Line 582 | public class ArrayDeque<E> extends Abstr
582
583		/**
584		* Pops an element from the stack represented by this deque.  In other
585	<	* words, removes and returns the the first element of this deque.
585	>	* words, removes and returns the first element of this deque.
586		*
587		* <p>This method is equivalent to {@link #removeFirst()}.
588		*
589		* @return the element at the front of this deque (which is the top
590	<	*     of the stack represented by this deque)
591	<	* @throws NoSuchElementException if this deque is empty
590	>	*         of the stack represented by this deque)
591	>	* @throws NoSuchElementException {@inheritDoc}
592		*/
593		public E pop() {
594		return removeFirst();
595		}
596
597		/**
598	<	* Remove the element at the specified position in the elements array,
599	<	* adjusting head, tail, and size as necessary.  This can result in
600	<	* motion of elements backwards or forwards in the array.
601	<	*
602	<	* <p>This method is called delete rather than remove to emphasize the
603	<	* that that its semantics differ from those of List.remove(int).
604	<	*
598	>	* Removes the element at the specified position in the elements array.
599	>	* This can result in forward or backwards motion of array elements.
600	>	* We optimize for least element motion.
601	>	*
602	>	* <p>This method is called delete rather than remove to emphasize
603	>	* that its semantics differ from those of {@link List#remove(int)}.
604	>	*
605		* @return true if elements moved backwards
606		*/
607	<	private boolean delete(int i) {
608	<	// Case 1: Deque doesn't wrap
609	<	// Case 2: Deque does wrap and removed element is in the head portion
610	<	if ((head < tail || tail == 0) || i >= head) {
611	<	System.arraycopy(elements, head, elements, head + 1, i - head);
612	<	elements[head] = null;
613	<	head = (head + 1) & (elements.length - 1);
607	>	boolean delete(int i) {
608	>	// checkInvariants();
609	>	final Object[] elements = this.elements;
610	>	final int capacity = elements.length;
611	>	final int h = head;
612	>	int front;              // number of elements before to-be-deleted elt
613	>	if ((front = i - h) < 0) front += capacity;
614	>	final int back = size - front - 1; // number of elements after
615	>	if (front < back) {
616	>	// move front elements forwards
617	>	if (h <= i) {
618	>	System.arraycopy(elements, h, elements, h + 1, front);
619	>	} else { // Wrap around
620	>	System.arraycopy(elements, 0, elements, 1, i);
621	>	elements[0] = elements[capacity - 1];
622	>	System.arraycopy(elements, h, elements, h + 1, front - (i + 1));
623	>	}
624	>	elements[h] = null;
625	>	head = inc(h, capacity);
626	>	size--;
627	>	// checkInvariants();
628		return false;
629	+	} else {
630	+	// move back elements backwards
631	+	int tail = tail();
632	+	if (i <= tail) {
633	+	System.arraycopy(elements, i + 1, elements, i, back);
634	+	} else { // Wrap around
635	+	int firstLeg = capacity - (i + 1);
636	+	System.arraycopy(elements, i + 1, elements, i, firstLeg);
637	+	elements[capacity - 1] = elements[0];
638	+	System.arraycopy(elements, 1, elements, 0, back - firstLeg - 1);
639	+	}
640	+	elements[tail] = null;
641	+	size--;
642	+	// checkInvariants();
643	+	return true;
644		}
537	–
538	–	// Case 3: Deque wraps and removed element is in the tail portion
539	–	tail--;
540	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
541	–	elements[tail] = null;
542	–	return true;
645		}
646
647		// *** Collection Methods ***
#	Line 550 | Line 652 | public class ArrayDeque<E> extends Abstr
652		* @return the number of elements in this deque
653		*/
654		public int size() {
655	<	return (tail - head) & (elements.length - 1);
655	>	return size;
656		}
657
658		/**
659	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
659	>	* Returns {@code true} if this deque contains no elements.
660		*
661	<	* @return <tt>true</tt> if this collection contains no elements.
661	>	* @return {@code true} if this deque contains no elements
662		*/
663		public boolean isEmpty() {
664	<	return head == tail;
664	>	return size == 0;
665		}
666
667		/**
#	Line 567 | Line 669 | public class ArrayDeque<E> extends Abstr
669		* will be ordered from first (head) to last (tail).  This is the same
670		* order that elements would be dequeued (via successive calls to
671		* {@link #remove} or popped (via successive calls to {@link #pop}).
672	<	*
673	<	* @return an <tt>Iterator</tt> over the elements in this deque
672	>	*
673	>	* @return an iterator over the elements in this deque
674		*/
675		public Iterator<E> iterator() {
676		return new DeqIterator();
677		}
678
679	+	public Iterator<E> descendingIterator() {
680	+	return new DescendingIterator();
681	+	}
682	+
683		private class DeqIterator implements Iterator<E> {
684	<	/**
685	<	* Index of element to be returned by subsequent call to next.
580	<	*/
581	<	private int cursor = head;
684	>	/** Index of element to be returned by subsequent call to next. */
685	>	int cursor;
686
687	<	/**
688	<	* Tail recorded at construction (also in remove), to stop
585	<	* iterator and also to check for comodification.
586	<	*/
587	<	private int fence = tail;
687	>	/** Number of elements yet to be returned. */
688	>	int remaining = size;
689
690		/**
691		* Index of element returned by most recent call to next.
692		* Reset to -1 if element is deleted by a call to remove.
693		*/
694	<	private int lastRet = -1;
694	>	int lastRet = -1;
695	>
696	>	DeqIterator() { cursor = head; }
697
698	<	public boolean hasNext() {
699	<	return cursor != fence;
698	>	public final boolean hasNext() {
699	>	return remaining > 0;
700		}
701
702		public E next() {
703	<	E result;
601	<	if (cursor == fence)
703	>	if (remaining == 0)
704		throw new NoSuchElementException();
705	<	// This check doesn't catch all possible comodifications,
604	<	// but does catch the ones that corrupt traversal
605	<	if (tail != fence || (result = elements[cursor]) == null)
606	<	throw new ConcurrentModificationException();
705	>	E e = checkedElementAt(elements, cursor);
706		lastRet = cursor;
707	<	cursor = (cursor + 1) & (elements.length - 1);
708	<	return result;
707	>	cursor = inc(cursor, elements.length);
708	>	remaining--;
709	>	return e;
710	>	}
711	>
712	>	void postDelete(boolean leftShifted) {
713	>	if (leftShifted)
714	>	cursor = dec(cursor, elements.length); // undo inc in next
715		}
716
717	<	public void remove() {
717	>	public final void remove() {
718		if (lastRet < 0)
719		throw new IllegalStateException();
720	<	if (delete(lastRet))
616	<	cursor--;
720	>	postDelete(delete(lastRet));
721		lastRet = -1;
618	–	fence = tail;
722		}
723	+
724	+	public void forEachRemaining(Consumer<? super E> action) {
725	+	Objects.requireNonNull(action);
726	+	final Object[] elements = ArrayDeque.this.elements;
727	+	final int capacity = elements.length;
728	+	int k = remaining;
729	+	remaining = 0;
730	+	for (int i = cursor; --k >= 0; i = inc(i, capacity))
731	+	action.accept(checkedElementAt(elements, i));
732	+	}
733	+	}
734	+
735	+	private class DescendingIterator extends DeqIterator {
736	+	DescendingIterator() { cursor = tail(); }
737	+
738	+	public final E next() {
739	+	if (remaining == 0)
740	+	throw new NoSuchElementException();
741	+	E e = checkedElementAt(elements, cursor);
742	+	lastRet = cursor;
743	+	cursor = dec(cursor, elements.length);
744	+	remaining--;
745	+	return e;
746	+	}
747	+
748	+	void postDelete(boolean leftShifted) {
749	+	if (!leftShifted)
750	+	cursor = inc(cursor, elements.length); // undo dec in next
751	+	}
752	+
753	+	public final void forEachRemaining(Consumer<? super E> action) {
754	+	Objects.requireNonNull(action);
755	+	final Object[] elements = ArrayDeque.this.elements;
756	+	final int capacity = elements.length;
757	+	int k = remaining;
758	+	remaining = 0;
759	+	for (int i = cursor; --k >= 0; i = dec(i, capacity))
760	+	action.accept(checkedElementAt(elements, i));
761	+	}
762	+	}
763	+
764	+	/**
765	+	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
766	+	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
767	+	* deque.
768	+	*
769	+	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
770	+	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
771	+	* {@link Spliterator#NONNULL}.  Overriding implementations should document
772	+	* the reporting of additional characteristic values.
773	+	*
774	+	* @return a {@code Spliterator} over the elements in this deque
775	+	* @since 1.8
776	+	*/
777	+	public Spliterator<E> spliterator() {
778	+	return new ArrayDequeSpliterator();
779	+	}
780	+
781	+	final class ArrayDequeSpliterator implements Spliterator<E> {
782	+	private int cursor;
783	+	private int remaining; // -1 until late-binding first use
784	+
785	+	/** Constructs late-binding spliterator over all elements. */
786	+	ArrayDequeSpliterator() {
787	+	this.remaining = -1;
788	+	}
789	+
790	+	/** Constructs spliterator over the given slice. */
791	+	ArrayDequeSpliterator(int cursor, int count) {
792	+	this.cursor = cursor;
793	+	this.remaining = count;
794	+	}
795	+
796	+	/** Ensures late-binding initialization; then returns remaining. */
797	+	private int remaining() {
798	+	if (remaining < 0) {
799	+	cursor = head;
800	+	remaining = size;
801	+	}
802	+	return remaining;
803	+	}
804	+
805	+	public ArrayDequeSpliterator trySplit() {
806	+	final int mid;
807	+	if ((mid = remaining() >> 1) > 0) {
808	+	int oldCursor = cursor;
809	+	cursor = add(cursor, mid, elements.length);
810	+	remaining -= mid;
811	+	return new ArrayDequeSpliterator(oldCursor, mid);
812	+	}
813	+	return null;
814	+	}
815	+
816	+	public void forEachRemaining(Consumer<? super E> action) {
817	+	Objects.requireNonNull(action);
818	+	final Object[] elements = ArrayDeque.this.elements;
819	+	final int capacity = elements.length;
820	+	int k = remaining();
821	+	remaining = 0;
822	+	for (int i = cursor; --k >= 0; i = inc(i, capacity))
823	+	action.accept(checkedElementAt(elements, i));
824	+	}
825	+
826	+	public boolean tryAdvance(Consumer<? super E> action) {
827	+	Objects.requireNonNull(action);
828	+	if (remaining() == 0)
829	+	return false;
830	+	action.accept(checkedElementAt(elements, cursor));
831	+	cursor = inc(cursor, elements.length);
832	+	remaining--;
833	+	return true;
834	+	}
835	+
836	+	public long estimateSize() {
837	+	return remaining();
838	+	}
839	+
840	+	public int characteristics() {
841	+	return Spliterator.NONNULL
842	+	| Spliterator.ORDERED
843	+	| Spliterator.SIZED
844	+	| Spliterator.SUBSIZED;
845	+	}
846	+	}
847	+
848	+	public void forEach(Consumer<? super E> action) {
849	+	// checkInvariants();
850	+	Objects.requireNonNull(action);
851	+	final Object[] elements = this.elements;
852	+	final int capacity = elements.length;
853	+	for (int k = size, i = head; --k >= 0; i = inc(i, capacity))
854	+	action.accept(elementAt(i));
855	+	// checkInvariants();
856		}
857
858		/**
859	<	* Returns <tt>true</tt> if this deque contains the specified
860	<	* element.  More formally, returns <tt>true</tt> if and only if this
861	<	* deque contains at least one element <tt>e</tt> such that
862	<	* <tt>e.equals(o)</tt>.
859	>	* Replaces each element of this deque with the result of applying the
860	>	* operator to that element, as specified by {@link List#replaceAll}.
861	>	*
862	>	* @param operator the operator to apply to each element
863	>	* @since TBD
864	>	*/
865	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
866	>	Objects.requireNonNull(operator);
867	>	final Object[] elements = this.elements;
868	>	final int capacity = elements.length;
869	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity))
870	>	elements[i] = operator.apply(elementAt(i));
871	>	// checkInvariants();
872	>	}
873	>
874	>	/**
875	>	* @throws NullPointerException {@inheritDoc}
876	>	*/
877	>	public boolean removeIf(Predicate<? super E> filter) {
878	>	Objects.requireNonNull(filter);
879	>	return bulkRemove(filter);
880	>	}
881	>
882	>	/**
883	>	* @throws NullPointerException {@inheritDoc}
884	>	*/
885	>	public boolean removeAll(Collection<?> c) {
886	>	Objects.requireNonNull(c);
887	>	return bulkRemove(e -> c.contains(e));
888	>	}
889	>
890	>	/**
891	>	* @throws NullPointerException {@inheritDoc}
892	>	*/
893	>	public boolean retainAll(Collection<?> c) {
894	>	Objects.requireNonNull(c);
895	>	return bulkRemove(e -> !c.contains(e));
896	>	}
897	>
898	>	/** Implementation of bulk remove methods. */
899	>	private boolean bulkRemove(Predicate<? super E> filter) {
900	>	// checkInvariants();
901	>	final Object[] elements = this.elements;
902	>	final int capacity = elements.length;
903	>	int i = head, j = i, remaining = size, deleted = 0;
904	>	try {
905	>	for (; remaining > 0; remaining--, i = inc(i, capacity)) {
906	>	@SuppressWarnings("unchecked") E e = (E) elements[i];
907	>	if (filter.test(e))
908	>	deleted++;
909	>	else {
910	>	if (j != i)
911	>	elements[j] = e;
912	>	j = inc(j, capacity);
913	>	}
914	>	}
915	>	return deleted > 0;
916	>	} catch (Throwable ex) {
917	>	if (deleted > 0)
918	>	for (; remaining > 0;
919	>	remaining--, i = inc(i, capacity), j = inc(j, capacity))
920	>	elements[j] = elements[i];
921	>	throw ex;
922	>	} finally {
923	>	size -= deleted;
924	>	for (; --deleted >= 0; j = inc(j, capacity))
925	>	elements[j] = null;
926	>	// checkInvariants();
927	>	}
928	>	}
929	>
930	>	/**
931	>	* Returns {@code true} if this deque contains the specified element.
932	>	* More formally, returns {@code true} if and only if this deque contains
933	>	* at least one element {@code e} such that {@code o.equals(e)}.
934		*
935		* @param o object to be checked for containment in this deque
936	<	* @return <tt>true</tt> if this deque contains the specified element
936	>	* @return {@code true} if this deque contains the specified element
937		*/
938		public boolean contains(Object o) {
939	<	if (o == null)
940	<	return false;
941	<	int mask = elements.length - 1;
942	<	int i = head;
943	<	E x;
944	<	while ( (x = elements[i]) != null) {
638	<	if (o.equals(x))
639	<	return true;
640	<	i = (i + 1) & mask;
939	>	if (o != null) {
940	>	final Object[] elements = this.elements;
941	>	final int capacity = elements.length;
942	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity))
943	>	if (o.equals(elements[i]))
944	>	return true;
945		}
946		return false;
947		}
948
949		/**
950		* Removes a single instance of the specified element from this deque.
951	<	* This method is equivalent to {@link #removeFirstOccurrence}.
951	>	* If the deque does not contain the element, it is unchanged.
952	>	* More formally, removes the first element {@code e} such that
953	>	* {@code o.equals(e)} (if such an element exists).
954	>	* Returns {@code true} if this deque contained the specified element
955	>	* (or equivalently, if this deque changed as a result of the call).
956		*
957	<	* @param e element to be removed from this deque, if present
958	<	* @return <tt>true</tt> if this deque contained the specified element
957	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
958	>	*
959	>	* @param o element to be removed from this deque, if present
960	>	* @return {@code true} if this deque contained the specified element
961		*/
962	<	public boolean remove(Object e) {
963	<	return removeFirstOccurrence(e);
962	>	public boolean remove(Object o) {
963	>	return removeFirstOccurrence(o);
964		}
965
966		/**
967		* Removes all of the elements from this deque.
968	+	* The deque will be empty after this call returns.
969		*/
970		public void clear() {
971	<	int h = head;
972	<	int t = tail;
973	<	if (h != t) { // clear all cells
974	<	head = tail = 0;
975	<	int i = h;
976	<	int mask = elements.length - 1;
977	<	do {
667	<	elements[i] = null;
668	<	i = (i + 1) & mask;
669	<	} while(i != t);
971	>	final Object[] elements = this.elements;
972	>	final int capacity = elements.length, tail = head + size;
973	>	if (capacity - tail >= 0)
974	>	Arrays.fill(elements, head, tail, null);
975	>	else {
976	>	Arrays.fill(elements, head, capacity, null);
977	>	Arrays.fill(elements, 0, tail - capacity, null);
978		}
979	+	size = head = 0;
980	+	// checkInvariants();
981		}
982
983		/**
984	<	* Returns an array containing all of the elements in this list
985	<	* in the correct order.
984	>	* Returns an array containing all of the elements in this deque
985	>	* in proper sequence (from first to last element).
986	>	*
987	>	* <p>The returned array will be "safe" in that no references to it are
988	>	* maintained by this deque.  (In other words, this method must allocate
989	>	* a new array).  The caller is thus free to modify the returned array.
990	>	*
991	>	* <p>This method acts as bridge between array-based and collection-based
992	>	* APIs.
993		*
994	<	* @return an array containing all of the elements in this list
678	<	*         in the correct order
994	>	* @return an array containing all of the elements in this deque
995		*/
996		public Object[] toArray() {
997	<	return copyElements(new Object[size()]);
997	>	return toArray(Object[].class);
998	>	}
999	>
1000	>	private <T> T[] toArray(Class<T[]> klazz) {
1001	>	final Object[] elements = this.elements;
1002	>	final int capacity = elements.length;
1003	>	final int head = this.head, tail = head + size;
1004	>	final T[] a;
1005	>	if (tail >= 0) {
1006	>	a = Arrays.copyOfRange(elements, head, tail, klazz);
1007	>	} else {
1008	>	// integer overflow!
1009	>	a = Arrays.copyOfRange(elements, 0, size, klazz);
1010	>	System.arraycopy(elements, head, a, 0, capacity - head);
1011	>	}
1012	>	if (tail - capacity > 0)
1013	>	System.arraycopy(elements, 0, a, capacity - head, tail - capacity);
1014	>	return a;
1015		}
1016
1017		/**
1018	<	* Returns an array containing all of the elements in this deque in the
1019	<	* correct order; the runtime type of the returned array is that of the
1020	<	* specified array.  If the deque fits in the specified array, it is
1021	<	* returned therein.  Otherwise, a new array is allocated with the runtime
1022	<	* type of the specified array and the size of this deque.
1018	>	* Returns an array containing all of the elements in this deque in
1019	>	* proper sequence (from first to last element); the runtime type of the
1020	>	* returned array is that of the specified array.  If the deque fits in
1021	>	* the specified array, it is returned therein.  Otherwise, a new array
1022	>	* is allocated with the runtime type of the specified array and the
1023	>	* size of this deque.
1024	>	*
1025	>	* <p>If this deque fits in the specified array with room to spare
1026	>	* (i.e., the array has more elements than this deque), the element in
1027	>	* the array immediately following the end of the deque is set to
1028	>	* {@code null}.
1029	>	*
1030	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
1031	>	* array-based and collection-based APIs.  Further, this method allows
1032	>	* precise control over the runtime type of the output array, and may,
1033	>	* under certain circumstances, be used to save allocation costs.
1034	>	*
1035	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1036	>	* The following code can be used to dump the deque into a newly
1037	>	* allocated array of {@code String}:
1038		*
1039	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
1040	<	* the array has more elements than the deque), the element in the array
1041	<	* immediately following the end of the collection is set to <tt>null</tt>.
1039	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1040	>	*
1041	>	* Note that {@code toArray(new Object[0])} is identical in function to
1042	>	* {@code toArray()}.
1043		*
1044		* @param a the array into which the elements of the deque are to
1045	<	*          be stored, if it is big enough; otherwise, a new array of the
1046	<	*          same runtime type is allocated for this purpose
1047	<	* @return an array containing the elements of the deque
1048	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
1049	<	*         of the runtime type of every element in this deque
1045	>	*          be stored, if it is big enough; otherwise, a new array of the
1046	>	*          same runtime type is allocated for this purpose
1047	>	* @return an array containing all of the elements in this deque
1048	>	* @throws ArrayStoreException if the runtime type of the specified array
1049	>	*         is not a supertype of the runtime type of every element in
1050	>	*         this deque
1051	>	* @throws NullPointerException if the specified array is null
1052		*/
1053	+	@SuppressWarnings("unchecked")
1054		public <T> T[] toArray(T[] a) {
1055	<	int size = size();
1056	<	if (a.length < size)
1057	<	a = (T[])java.lang.reflect.Array.newInstance(
1058	<	a.getClass().getComponentType(), size);
1059	<	copyElements(a);
1060	<	if (a.length > size)
1055	>	final int size = this.size;
1056	>	if (size > a.length)
1057	>	return toArray((Class<T[]>) a.getClass());
1058	>	final Object[] elements = this.elements;
1059	>	final int capacity = elements.length;
1060	>	final int head = this.head, tail = head + size;
1061	>	if (capacity - tail >= 0)
1062	>	System.arraycopy(elements, head, a, 0, size);
1063	>	else {
1064	>	System.arraycopy(elements, head, a, 0, capacity - head);
1065	>	System.arraycopy(elements, 0, a, capacity - head, tail - capacity);
1066	>	}
1067	>	if (size < a.length)
1068		a[size] = null;
1069		return a;
1070		}
#	Line 718 | Line 1077 | public class ArrayDeque<E> extends Abstr
1077		* @return a copy of this deque
1078		*/
1079		public ArrayDeque<E> clone() {
1080	<	try {
1080	>	try {
1081	>	@SuppressWarnings("unchecked")
1082		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1083	<	// These two lines are currently faster than cloning the array:
724	<	result.elements = (E[]) new Object[elements.length];
725	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
1083	>	result.elements = Arrays.copyOf(elements, elements.length);
1084		return result;
1085	<
728	<	} catch (CloneNotSupportedException e) {
1085	>	} catch (CloneNotSupportedException e) {
1086		throw new AssertionError();
1087		}
1088		}
1089
733	–	/**
734	–	* Appease the serialization gods.
735	–	*/
1090		private static final long serialVersionUID = 2340985798034038923L;
1091
1092		/**
1093	<	* Serialize this deque.
1093	>	* Saves this deque to a stream (that is, serializes it).
1094		*
1095	<	* @serialData The current size (<tt>int</tt>) of the deque,
1095	>	* @param s the stream
1096	>	* @throws java.io.IOException if an I/O error occurs
1097	>	* @serialData The current size ({@code int}) of the deque,
1098		* followed by all of its elements (each an object reference) in
1099		* first-to-last order.
1100		*/
1101	<	private void writeObject(ObjectOutputStream s) throws IOException {
1101	>	private void writeObject(java.io.ObjectOutputStream s)
1102	>	throws java.io.IOException {
1103		s.defaultWriteObject();
1104
1105		// Write out size
749	–	int size = size();
1106		s.writeInt(size);
1107
1108		// Write out elements in order.
1109	<	int i = head;
1110	<	int mask = elements.length - 1;
1111	<	for (int j = 0; j < size; j++) {
1109	>	final Object[] elements = this.elements;
1110	>	final int capacity = elements.length;
1111	>	for (int k = size, i = head; --k >= 0; i = inc(i, capacity))
1112		s.writeObject(elements[i]);
757	–	i = (i + 1) & mask;
758	–	}
1113		}
1114
1115		/**
1116	<	* Deserialize this deque.
1116	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1117	>	* @param s the stream
1118	>	* @throws ClassNotFoundException if the class of a serialized object
1119	>	*         could not be found
1120	>	* @throws java.io.IOException if an I/O error occurs
1121		*/
1122	<	private void readObject(ObjectInputStream s)
1123	<	throws IOException, ClassNotFoundException {
1122	>	private void readObject(java.io.ObjectInputStream s)
1123	>	throws java.io.IOException, ClassNotFoundException {
1124		s.defaultReadObject();
1125
1126		// Read in size and allocate array
1127	<	int size = s.readInt();
770	<	allocateElements(size);
771	<	head = 0;
772	<	tail = size;
1127	>	elements = new Object[size = s.readInt()];
1128
1129		// Read in all elements in the proper order.
1130		for (int i = 0; i < size; i++)
1131	<	elements[i] = (E)s.readObject();
1131	>	elements[i] = s.readObject();
1132	>	}
1133
1134	+	/** debugging */
1135	+	private void checkInvariants() {
1136	+	try {
1137	+	int capacity = elements.length;
1138	+	assert size >= 0 && size <= capacity;
1139	+	assert head >= 0 && ((capacity == 0 && head == 0 && size == 0)
1140	+	|| head < capacity);
1141	+	assert size == 0
1142	+	|| (elements[head] != null && elements[tail()] != null);
1143	+	assert size == capacity
1144	+	|| (elements[dec(head, capacity)] == null
1145	+	&& elements[inc(tail(), capacity)] == null);
1146	+	} catch (Throwable t) {
1147	+	System.err.printf("head=%d size=%d capacity=%d%n",
1148	+	head, size, elements.length);
1149	+	System.err.printf("elements=%s%n",
1150	+	Arrays.toString(elements));
1151	+	throw t;
1152	+	}
1153		}
1154	+
1155		}

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines