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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 1.113 by jsr166, Sun Nov 13 02:10:09 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	+	* VMs excel at optimizing simple array loops where indices are
65	+	* incrementing or decrementing over a valid slice, e.g.
66	+	*
67	+	* for (int i = start; i < end; i++) ... elements[i]
68	+	*
69	+	* Because in a circular array, elements are in general stored in
70	+	* two disjoint such slices, we help the VM by writing unusual
71	+	* nested loops for all traversals over the elements.
72	+	*/
73	+
74		/**
75	<	* The array in which the elements of in the deque are stored.
76	<	* The capacity of the deque is the length of this array, which is
77	<	* 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.
75	>	* The array in which the elements of the deque are stored.
76	>	* We guarantee that all array cells not holding deque elements
77	>	* are always null.
78		*/
79	<	private transient E[] elements;
79	>	transient Object[] elements;
80
81		/**
82		* The index of the element at the head of the deque (which is the
83		* element that would be removed by remove() or pop()); or an
84	<	* arbitrary number equal to tail if the deque is empty.
84	>	* arbitrary number 0 <= head < elements.length equal to tail if
85	>	* the deque is empty.
86		*/
87	<	private transient int head;
87	>	transient int head;
88
89		/**
90		* The index at which the next element would be added to the tail
91		* of the deque (via addLast(E), add(E), or push(E)).
92		*/
93	<	private transient int tail;
93	>	transient int tail;
94
95		/**
96	<	* The minimum capacity that we'll use for a newly created deque.
97	<	* Must be a power of 2.
98	<	*/
99	<	private static final int MIN_INITIAL_CAPACITY = 8;
100	<
101	<	// ******  Array allocation and resizing utilities ******
102	<
103	<	/**
104	<	* Allocate empty array to hold the given number of elements.
105	<	*
106	<	* @param numElements  the number of elements to hold.
107	<	*/
108	<	private void allocateElements(int numElements) {
109	<	int initialCapacity = MIN_INITIAL_CAPACITY;
110	<	// Find the best power of two to hold elements.
111	<	// Tests "<=" because arrays aren't kept full.
112	<	if (numElements >= initialCapacity) {
113	<	initialCapacity = numElements;
114	<	initialCapacity |= (initialCapacity >>>  1);
115	<	initialCapacity |= (initialCapacity >>>  2);
116	<	initialCapacity |= (initialCapacity >>>  4);
117	<	initialCapacity |= (initialCapacity >>>  8);
118	<	initialCapacity |= (initialCapacity >>> 16);
119	<	initialCapacity++;
96	>	* The maximum size of array to allocate.
97	>	* Some VMs reserve some header words in an array.
98	>	* Attempts to allocate larger arrays may result in
99	>	* OutOfMemoryError: Requested array size exceeds VM limit
100	>	*/
101	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
102	>
103	>	/**
104	>	* Increases the capacity of this deque by at least the given amount.
105	>	*
106	>	* @param needed the required minimum extra capacity; must be positive
107	>	*/
108	>	private void grow(int needed) {
109	>	// overflow-conscious code
110	>	final int oldCapacity = elements.length;
111	>	int newCapacity;
112	>	// Double capacity if small; else grow by 50%
113	>	int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
114	>	if (jump < needed
115	>	|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
116	>	newCapacity = newCapacity(needed, jump);
117	>	elements = Arrays.copyOf(elements, newCapacity);
118	>	// Exceptionally, here tail == head needs to be disambiguated
119	>	if (tail < head || (tail == head && elements[head] != null)) {
120	>	// wrap around; slide first leg forward to end of array
121	>	int newSpace = newCapacity - oldCapacity;
122	>	System.arraycopy(elements, head,
123	>	elements, head + newSpace,
124	>	oldCapacity - head);
125	>	Arrays.fill(elements, head, head + newSpace, null);
126	>	head += newSpace;
127	>	}
128	>	// checkInvariants();
129	>	}
130
131	<	if (initialCapacity < 0)   // Too many elements, must back off
132	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
131	>	/** Capacity calculation for edge conditions, especially overflow. */
132	>	private int newCapacity(int needed, int jump) {
133	>	final int oldCapacity = elements.length, minCapacity;
134	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
135	>	if (minCapacity < 0)
136	>	throw new IllegalStateException("Sorry, deque too big");
137	>	return Integer.MAX_VALUE;
138		}
139	<	elements = (E[]) new Object[initialCapacity];
139	>	if (needed > jump)
140	>	return minCapacity;
141	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
142	>	? oldCapacity + jump
143	>	: MAX_ARRAY_SIZE;
144		}
145
146		/**
147	<	* Double the capacity of this deque.  Call only when full, i.e.,
148	<	* when head and tail have wrapped around to become equal.
147	>	* Increases the internal storage of this collection, if necessary,
148	>	* to ensure that it can hold at least the given number of elements.
149	>	*
150	>	* @param minCapacity the desired minimum capacity
151	>	* @since TBD
152		*/
153	<	private void doubleCapacity() {
154	<	assert head == tail;
155	<	int p = head;
156	<	int n = elements.length;
157	<	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;
153	>	/* public */ void ensureCapacity(int minCapacity) {
154	>	int needed;
155	>	if ((needed = (minCapacity + 1 - elements.length)) > 0)
156	>	grow(needed);
157	>	// checkInvariants();
158		}
159
160		/**
161	<	* 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.
161	>	* Minimizes the internal storage of this collection.
162		*
163	<	* @return its argument
163	>	* @since TBD
164		*/
165	<	private <T> T[] copyElements(T[] a) {
166	<	if (head < tail) {
167	<	System.arraycopy(elements, head, a, 0, size());
168	<	} else if (head > tail) {
169	<	int headPortionLen = elements.length - head;
170	<	System.arraycopy(elements, head, a, 0, headPortionLen);
144	<	System.arraycopy(elements, 0, a, headPortionLen, tail);
165	>	/* public */ void trimToSize() {
166	>	int size;
167	>	if ((size = size()) + 1 < elements.length) {
168	>	elements = toArray(new Object[size + 1]);
169	>	head = 0;
170	>	tail = size;
171		}
172	<	return a;
172	>	// checkInvariants();
173		}
174
175		/**
176	<	* Constructs an empty array deque with the an initial capacity
176	>	* Constructs an empty array deque with an initial capacity
177		* sufficient to hold 16 elements.
178		*/
179		public ArrayDeque() {
180	<	elements = (E[]) new Object[16];
180	>	elements = new Object[16];
181		}
182
183		/**
184		* Constructs an empty array deque with an initial capacity
185		* sufficient to hold the specified number of elements.
186		*
187	<	* @param numElements  lower bound on initial capacity of the deque
187	>	* @param numElements lower bound on initial capacity of the deque
188		*/
189		public ArrayDeque(int numElements) {
190	<	allocateElements(numElements);
190	>	elements = new Object[Math.max(1, numElements + 1)];
191		}
192
193		/**
#	Line 175 | Line 201 | public class ArrayDeque<E> extends Abstr
201		* @throws NullPointerException if the specified collection is null
202		*/
203		public ArrayDeque(Collection<? extends E> c) {
204	<	allocateElements(c.size());
204	>	elements = new Object[c.size() + 1];
205		addAll(c);
206		}
207
208	+	/**
209	+	* Increments i, mod modulus.
210	+	* Precondition and postcondition: 0 <= i < modulus.
211	+	*/
212	+	static final int inc(int i, int modulus) {
213	+	if (++i >= modulus) i = 0;
214	+	return i;
215	+	}
216	+
217	+	/**
218	+	* Decrements i, mod modulus.
219	+	* Precondition and postcondition: 0 <= i < modulus.
220	+	*/
221	+	static final int dec(int i, int modulus) {
222	+	if (--i < 0) i = modulus - 1;
223	+	return i;
224	+	}
225	+
226	+	/**
227	+	* Adds i and j, mod modulus.
228	+	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
229	+	*/
230	+	static final int add(int i, int j, int modulus) {
231	+	if ((i += j) - modulus >= 0) i -= modulus;
232	+	return i;
233	+	}
234	+
235	+	/**
236	+	* Subtracts j from i, mod modulus.
237	+	* Index i must be logically ahead of j.
238	+	* Returns the "circular distance" from j to i.
239	+	* Precondition and postcondition: 0 <= i < modulus, 0 <= j < modulus.
240	+	*/
241	+	static final int sub(int i, int j, int modulus) {
242	+	if ((i -= j) < 0) i += modulus;
243	+	return i;
244	+	}
245	+
246	+	/**
247	+	* Returns element at array index i.
248	+	* This is a slight abuse of generics, accepted by javac.
249	+	*/
250	+	@SuppressWarnings("unchecked")
251	+	static final <E> E elementAt(Object[] es, int i) {
252	+	return (E) es[i];
253	+	}
254	+
255	+	/**
256	+	* A version of elementAt that checks for null elements.
257	+	* This check doesn't catch all possible comodifications,
258	+	* but does catch ones that corrupt traversal.
259	+	*/
260	+	static final <E> E nonNullElementAt(Object[] es, int i) {
261	+	@SuppressWarnings("unchecked") E e = (E) es[i];
262	+	if (e == null)
263	+	throw new ConcurrentModificationException();
264	+	return e;
265	+	}
266	+
267		// The main insertion and extraction methods are addFirst,
268		// addLast, pollFirst, pollLast. The other methods are defined in
269		// terms of these.
270
271		/**
272	<	* Inserts the specified element to the front this deque.
272	>	* Inserts the specified element at the front of this deque.
273		*
274	<	* @param e the element to insert
275	<	* @throws NullPointerException if <tt>e</tt> is null
274	>	* @param e the element to add
275	>	* @throws NullPointerException if the specified element is null
276		*/
277		public void addFirst(E e) {
278		if (e == null)
279		throw new NullPointerException();
280	<	elements[head = (head - 1) & (elements.length - 1)] = e;
281	<	if (head == tail)
282	<	doubleCapacity();
280	>	final Object[] es = elements;
281	>	es[head = dec(head, es.length)] = e;
282	>	if (head == tail)
283	>	grow(1);
284	>	// checkInvariants();
285		}
286
287		/**
288	<	* Inserts the specified element to the end this deque.
202	<	* This method is equivalent to {@link Collection#add} and
203	<	* {@link #push}.
288	>	* Inserts the specified element at the end of this deque.
289		*
290	<	* @param e the element to insert
291	<	* @throws NullPointerException if <tt>e</tt> is null
290	>	* <p>This method is equivalent to {@link #add}.
291	>	*
292	>	* @param e the element to add
293	>	* @throws NullPointerException if the specified element is null
294		*/
295		public void addLast(E e) {
296		if (e == null)
297		throw new NullPointerException();
298	<	elements[tail] = e;
299	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
300	<	doubleCapacity();
298	>	final Object[] es = elements;
299	>	es[tail] = e;
300	>	if (head == (tail = inc(tail, es.length)))
301	>	grow(1);
302	>	// checkInvariants();
303		}
304
305		/**
306	<	* Retrieves and removes the first element of this deque, or
307	<	* <tt>null</tt> if this deque is empty.
306	>	* Adds all of the elements in the specified collection at the end
307	>	* of this deque, as if by calling {@link #addLast} on each one,
308	>	* in the order that they are returned by the collection's
309	>	* iterator.
310		*
311	<	* @return the first element of this deque, or <tt>null</tt> if
312	<	*     this deque is empty
311	>	* @param c the elements to be inserted into this deque
312	>	* @return {@code true} if this deque changed as a result of the call
313	>	* @throws NullPointerException if the specified collection or any
314	>	*         of its elements are null
315		*/
316	<	public E pollFirst() {
317	<	int h = head;
318	<	E result = elements[h]; // Element is null if deque empty
319	<	if (result == null)
320	<	return null;
321	<	elements[h] = null;     // Must null out slot
322	<	head = (h + 1) & (elements.length - 1);
230	<	return result;
316	>	public boolean addAll(Collection<? extends E> c) {
317	>	final int s = size(), needed;
318	>	if ((needed = s + c.size() - elements.length + 1) > 0)
319	>	grow(needed);
320	>	c.forEach(e -> addLast(e));
321	>	// checkInvariants();
322	>	return size() > s;
323		}
324
325		/**
326	<	* Retrieves and removes the last element of this deque, or
235	<	* <tt>null</tt> if this deque is empty.
326	>	* Inserts the specified element at the front of this deque.
327		*
328	<	* @return the last element of this deque, or <tt>null</tt> if
329	<	*     this deque is empty
330	<	*/
240	<	public E pollLast() {
241	<	int t = (tail - 1) & (elements.length - 1);
242	<	E result = elements[t];
243	<	if (result == null)
244	<	return null;
245	<	elements[t] = null;
246	<	tail = t;
247	<	return result;
248	<	}
249	<
250	<	/**
251	<	* Inserts the specified element to the front this deque.
252	<	*
253	<	* @param e the element to insert
254	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
255	<	* @throws NullPointerException if <tt>e</tt> is null
328	>	* @param e the element to add
329	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
330	>	* @throws NullPointerException if the specified element is null
331		*/
332		public boolean offerFirst(E e) {
333		addFirst(e);
#	Line 260 | Line 335 | public class ArrayDeque<E> extends Abstr
335		}
336
337		/**
338	<	* Inserts the specified element to the end this deque.
338	>	* Inserts the specified element at the end of this deque.
339		*
340	<	* @param e the element to insert
341	<	* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
342	<	* @throws NullPointerException if <tt>e</tt> is null
340	>	* @param e the element to add
341	>	* @return {@code true} (as specified by {@link Deque#offerLast})
342	>	* @throws NullPointerException if the specified element is null
343		*/
344		public boolean offerLast(E e) {
345		addLast(e);
#	Line 272 | Line 347 | public class ArrayDeque<E> extends Abstr
347		}
348
349		/**
350	<	* 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
350	>	* @throws NoSuchElementException {@inheritDoc}
351		*/
352		public E removeFirst() {
353	<	E x = pollFirst();
354	<	if (x == null)
353	>	E e = pollFirst();
354	>	if (e == null)
355		throw new NoSuchElementException();
356	<	return x;
356	>	// checkInvariants();
357	>	return e;
358		}
359
360		/**
361	<	* 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
361	>	* @throws NoSuchElementException {@inheritDoc}
362		*/
363		public E removeLast() {
364	<	E x = pollLast();
365	<	if (x == null)
364	>	E e = pollLast();
365	>	if (e == null)
366		throw new NoSuchElementException();
367	<	return x;
367	>	// checkInvariants();
368	>	return e;
369		}
370
371	<	/**
372	<	* Retrieves, but does not remove, the first element of this deque,
373	<	* returning <tt>null</tt> if this deque is empty.
374	<	*
375	<	* @return the first element of this deque, or <tt>null</tt> if
376	<	*     this deque is empty
377	<	*/
378	<	public E peekFirst() {
379	<	return elements[head]; // elements[head] is null if deque empty
371	>	public E pollFirst() {
372	>	final Object[] es;
373	>	final int h;
374	>	E e = elementAt(es = elements, h = head);
375	>	if (e != null) {
376	>	es[h] = null;
377	>	head = inc(h, es.length);
378	>	}
379	>	// checkInvariants();
380	>	return e;
381		}
382
383	<	/**
384	<	* Retrieves, but does not remove, the last element of this deque,
385	<	* returning <tt>null</tt> if this deque is empty.
386	<	*
387	<	* @return the last element of this deque, or <tt>null</tt> if this deque
388	<	*     is empty
389	<	*/
390	<	public E peekLast() {
323	<	return elements[(tail - 1) & (elements.length - 1)];
383	>	public E pollLast() {
384	>	final Object[] es;
385	>	final int t;
386	>	E e = elementAt(es = elements, t = dec(tail, es.length));
387	>	if (e != null)
388	>	es[tail = t] = null;
389	>	// checkInvariants();
390	>	return e;
391		}
392
393		/**
394	<	* 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
394	>	* @throws NoSuchElementException {@inheritDoc}
395		*/
396		public E getFirst() {
397	<	E x = elements[head];
398	<	if (x == null)
397	>	E e = elementAt(elements, head);
398	>	if (e == null)
399		throw new NoSuchElementException();
400	<	return x;
400	>	// checkInvariants();
401	>	return e;
402		}
403
404		/**
405	<	* 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
405	>	* @throws NoSuchElementException {@inheritDoc}
406		*/
407		public E getLast() {
408	<	E x = elements[(tail - 1) & (elements.length - 1)];
409	<	if (x == null)
408	>	final Object[] es = elements;
409	>	E e = elementAt(es, dec(tail, es.length));
410	>	if (e == null)
411		throw new NoSuchElementException();
412	<	return x;
412	>	// checkInvariants();
413	>	return e;
414	>	}
415	>
416	>	public E peekFirst() {
417	>	// checkInvariants();
418	>	return elementAt(elements, head);
419	>	}
420	>
421	>	public E peekLast() {
422	>	// checkInvariants();
423	>	final Object[] es;
424	>	return elementAt(es = elements, dec(tail, es.length));
425		}
426
427		/**
428		* Removes the first occurrence of the specified element in this
429	<	* deque (when traversing the deque from head to tail).  If the deque
430	<	* does not contain the element, it is unchanged.
431	<	*
432	<	* @param e element to be removed from this deque, if present
433	<	* @return <tt>true</tt> if the deque contained the specified element
434	<	*/
435	<	public boolean removeFirstOccurrence(Object e) {
436	<	if (e == null)
437	<	return false;
438	<	int mask = elements.length - 1;
439	<	int i = head;
440	<	E x;
441	<	while ( (x = elements[i]) != null) {
442	<	if (e.equals(x)) {
443	<	delete(i);
444	<	return true;
429	>	* deque (when traversing the deque from head to tail).
430	>	* If the deque does not contain the element, it is unchanged.
431	>	* More formally, removes the first element {@code e} such that
432	>	* {@code o.equals(e)} (if such an element exists).
433	>	* Returns {@code true} if this deque contained the specified element
434	>	* (or equivalently, if this deque changed as a result of the call).
435	>	*
436	>	* @param o element to be removed from this deque, if present
437	>	* @return {@code true} if the deque contained the specified element
438	>	*/
439	>	public boolean removeFirstOccurrence(Object o) {
440	>	if (o != null) {
441	>	final Object[] es = elements;
442	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
443	>	; i = 0, to = end) {
444	>	for (; i < to; i++)
445	>	if (o.equals(es[i])) {
446	>	delete(i);
447	>	return true;
448	>	}
449	>	if (to == end) break;
450		}
375	–	i = (i + 1) & mask;
451		}
452		return false;
453		}
454
455		/**
456		* Removes the last occurrence of the specified element in this
457	<	* deque (when traversing the deque from head to tail).  If the deque
458	<	* does not contain the element, it is unchanged.
459	<	*
460	<	* @param e element to be removed from this deque, if present
461	<	* @return <tt>true</tt> if the deque contained the specified element
462	<	*/
463	<	public boolean removeLastOccurrence(Object e) {
464	<	if (e == null)
465	<	return false;
466	<	int mask = elements.length - 1;
467	<	int i = (tail - 1) & mask;
468	<	E x;
469	<	while ( (x = elements[i]) != null) {
470	<	if (e.equals(x)) {
471	<	delete(i);
472	<	return true;
457	>	* deque (when traversing the deque from head to tail).
458	>	* If the deque does not contain the element, it is unchanged.
459	>	* More formally, removes the last element {@code e} such that
460	>	* {@code o.equals(e)} (if such an element exists).
461	>	* Returns {@code true} if this deque contained the specified element
462	>	* (or equivalently, if this deque changed as a result of the call).
463	>	*
464	>	* @param o element to be removed from this deque, if present
465	>	* @return {@code true} if the deque contained the specified element
466	>	*/
467	>	public boolean removeLastOccurrence(Object o) {
468	>	if (o != null) {
469	>	final Object[] es = elements;
470	>	for (int i = tail, end = head, to = (i >= end) ? end : 0;
471	>	; i = es.length, to = end) {
472	>	for (i--; i > to - 1; i--)
473	>	if (o.equals(es[i])) {
474	>	delete(i);
475	>	return true;
476	>	}
477	>	if (to == end) break;
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	<	*
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);
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 near tail moved backwards
606	>	*/
607	>	boolean delete(int i) {
608	>	// checkInvariants();
609	>	final Object[] es = elements;
610	>	final int capacity = es.length;
611	>	final int h = head;
612	>	// number of elements before to-be-deleted elt
613	>	final int front = sub(i, h, 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(es, h, es, h + 1, front);
619	>	} else { // Wrap around
620	>	System.arraycopy(es, 0, es, 1, i);
621	>	es[0] = es[capacity - 1];
622	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
623	>	}
624	>	es[h] = null;
625	>	head = inc(h, capacity);
626	>	// checkInvariants();
627		return false;
628	+	} else {
629	+	// move back elements backwards
630	+	tail = dec(tail, capacity);
631	+	if (i <= tail) {
632	+	System.arraycopy(es, i + 1, es, i, back);
633	+	} else { // Wrap around
634	+	int firstLeg = capacity - (i + 1);
635	+	System.arraycopy(es, i + 1, es, i, firstLeg);
636	+	es[capacity - 1] = es[0];
637	+	System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
638	+	}
639	+	es[tail] = null;
640	+	// checkInvariants();
641	+	return true;
642		}
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;
643		}
644
645		// *** Collection Methods ***
#	Line 550 | Line 650 | public class ArrayDeque<E> extends Abstr
650		* @return the number of elements in this deque
651		*/
652		public int size() {
653	<	return (tail - head) & (elements.length - 1);
653	>	return sub(tail, head, elements.length);
654		}
655
656		/**
657	<	* Returns <tt>true</tt> if this collection contains no elements.<p>
657	>	* Returns {@code true} if this deque contains no elements.
658		*
659	<	* @return <tt>true</tt> if this collection contains no elements.
659	>	* @return {@code true} if this deque contains no elements
660		*/
661		public boolean isEmpty() {
662		return head == tail;
#	Line 567 | Line 667 | public class ArrayDeque<E> extends Abstr
667		* will be ordered from first (head) to last (tail).  This is the same
668		* order that elements would be dequeued (via successive calls to
669		* {@link #remove} or popped (via successive calls to {@link #pop}).
670	<	*
671	<	* @return an <tt>Iterator</tt> over the elements in this deque
670	>	*
671	>	* @return an iterator over the elements in this deque
672		*/
673		public Iterator<E> iterator() {
674		return new DeqIterator();
675		}
676
677	+	public Iterator<E> descendingIterator() {
678	+	return new DescendingIterator();
679	+	}
680	+
681		private class DeqIterator implements Iterator<E> {
682	<	/**
683	<	* Index of element to be returned by subsequent call to next.
580	<	*/
581	<	private int cursor = head;
682	>	/** Index of element to be returned by subsequent call to next. */
683	>	int cursor;
684
685	<	/**
686	<	* Tail recorded at construction (also in remove), to stop
585	<	* iterator and also to check for comodification.
586	<	*/
587	<	private int fence = tail;
685	>	/** Number of elements yet to be returned. */
686	>	int remaining = size();
687
688		/**
689		* Index of element returned by most recent call to next.
690		* Reset to -1 if element is deleted by a call to remove.
691		*/
692	<	private int lastRet = -1;
692	>	int lastRet = -1;
693
694	<	public boolean hasNext() {
695	<	return cursor != fence;
694	>	DeqIterator() { cursor = head; }
695	>
696	>	public final boolean hasNext() {
697	>	return remaining > 0;
698		}
699
700		public E next() {
701	<	E result;
601	<	if (cursor == fence)
701	>	if (remaining <= 0)
702		throw new NoSuchElementException();
703	<	// This check doesn't catch all possible comodifications,
704	<	// but does catch the ones that corrupt traversal
605	<	if (tail != fence || (result = elements[cursor]) == null)
606	<	throw new ConcurrentModificationException();
703	>	final Object[] es = elements;
704	>	E e = nonNullElementAt(es, cursor);
705		lastRet = cursor;
706	<	cursor = (cursor + 1) & (elements.length - 1);
707	<	return result;
706	>	cursor = inc(cursor, es.length);
707	>	remaining--;
708	>	return e;
709	>	}
710	>
711	>	void postDelete(boolean leftShifted) {
712	>	if (leftShifted)
713	>	cursor = dec(cursor, elements.length);
714		}
715
716	<	public void remove() {
716	>	public final void remove() {
717		if (lastRet < 0)
718		throw new IllegalStateException();
719	<	if (delete(lastRet))
616	<	cursor--;
719	>	postDelete(delete(lastRet));
720		lastRet = -1;
721	<	fence = tail;
721	>	}
722	>
723	>	public void forEachRemaining(Consumer<? super E> action) {
724	>	Objects.requireNonNull(action);
725	>	int r;
726	>	if ((r = remaining) <= 0)
727	>	return;
728	>	remaining = 0;
729	>	final Object[] es = elements;
730	>	if (es[cursor] == null || sub(tail, cursor, es.length) != r)
731	>	throw new ConcurrentModificationException();
732	>	for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
733	>	; i = 0, to = end) {
734	>	for (; i < to; i++)
735	>	action.accept(elementAt(es, i));
736	>	if (to == end) {
737	>	if (end != tail)
738	>	throw new ConcurrentModificationException();
739	>	lastRet = dec(end, es.length);
740	>	break;
741	>	}
742	>	}
743	>	}
744	>	}
745	>
746	>	private class DescendingIterator extends DeqIterator {
747	>	DescendingIterator() { cursor = dec(tail, elements.length); }
748	>
749	>	public final E next() {
750	>	if (remaining <= 0)
751	>	throw new NoSuchElementException();
752	>	final Object[] es = elements;
753	>	E e = nonNullElementAt(es, cursor);
754	>	lastRet = cursor;
755	>	cursor = dec(cursor, es.length);
756	>	remaining--;
757	>	return e;
758	>	}
759	>
760	>	void postDelete(boolean leftShifted) {
761	>	if (!leftShifted)
762	>	cursor = inc(cursor, elements.length);
763	>	}
764	>
765	>	public final void forEachRemaining(Consumer<? super E> action) {
766	>	Objects.requireNonNull(action);
767	>	int r;
768	>	if ((r = remaining) <= 0)
769	>	return;
770	>	remaining = 0;
771	>	final Object[] es = elements;
772	>	if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
773	>	throw new ConcurrentModificationException();
774	>	for (int i = cursor, end = head, to = (i >= end) ? end : 0;
775	>	; i = es.length - 1, to = end) {
776	>	// hotspot generates faster code than for: i >= to !
777	>	for (; i > to - 1; i--)
778	>	action.accept(elementAt(es, i));
779	>	if (to == end) {
780	>	if (end != head)
781	>	throw new ConcurrentModificationException();
782	>	lastRet = end;
783	>	break;
784	>	}
785	>	}
786		}
787		}
788
789		/**
790	<	* Returns <tt>true</tt> if this deque contains the specified
791	<	* element.  More formally, returns <tt>true</tt> if and only if this
792	<	* deque contains at least one element <tt>e</tt> such that
793	<	* <tt>e.equals(o)</tt>.
790	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
791	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
792	>	* deque.
793	>	*
794	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
795	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
796	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
797	>	* the reporting of additional characteristic values.
798	>	*
799	>	* @return a {@code Spliterator} over the elements in this deque
800	>	* @since 1.8
801	>	*/
802	>	public Spliterator<E> spliterator() {
803	>	return new DeqSpliterator();
804	>	}
805	>
806	>	final class DeqSpliterator implements Spliterator<E> {
807	>	private int fence;      // -1 until first use
808	>	private int cursor;     // current index, modified on traverse/split
809	>
810	>	/** Constructs late-binding spliterator over all elements. */
811	>	DeqSpliterator() {
812	>	this.fence = -1;
813	>	}
814	>
815	>	/** Constructs spliterator over the given range. */
816	>	DeqSpliterator(int origin, int fence) {
817	>	this.cursor = origin;
818	>	this.fence = fence;
819	>	}
820	>
821	>	/** Ensures late-binding initialization; then returns fence. */
822	>	private int getFence() { // force initialization
823	>	int t;
824	>	if ((t = fence) < 0) {
825	>	t = fence = tail;
826	>	cursor = head;
827	>	}
828	>	return t;
829	>	}
830	>
831	>	public DeqSpliterator trySplit() {
832	>	final Object[] es = elements;
833	>	final int i, n;
834	>	return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
835	>	? null
836	>	: new DeqSpliterator(i, cursor = add(i, n, es.length));
837	>	}
838	>
839	>	public void forEachRemaining(Consumer<? super E> action) {
840	>	if (action == null)
841	>	throw new NullPointerException();
842	>	final int end = getFence(), cursor = this.cursor;
843	>	final Object[] es = elements;
844	>	if (cursor != end) {
845	>	this.cursor = end;
846	>	// null check at both ends of range is sufficient
847	>	if (es[cursor] == null || es[dec(end, es.length)] == null)
848	>	throw new ConcurrentModificationException();
849	>	for (int i = cursor, to = (i <= end) ? end : es.length;
850	>	; i = 0, to = end) {
851	>	for (; i < to; i++)
852	>	action.accept(elementAt(es, i));
853	>	if (to == end) break;
854	>	}
855	>	}
856	>	}
857	>
858	>	public boolean tryAdvance(Consumer<? super E> action) {
859	>	if (action == null)
860	>	throw new NullPointerException();
861	>	int t, i;
862	>	if ((t = fence) < 0) t = getFence();
863	>	if (t == (i = cursor))
864	>	return false;
865	>	final Object[] es;
866	>	action.accept(nonNullElementAt(es = elements, i));
867	>	cursor = inc(i, es.length);
868	>	return true;
869	>	}
870	>
871	>	public long estimateSize() {
872	>	return sub(getFence(), cursor, elements.length);
873	>	}
874	>
875	>	public int characteristics() {
876	>	return Spliterator.NONNULL
877	>	| Spliterator.ORDERED
878	>	| Spliterator.SIZED
879	>	| Spliterator.SUBSIZED;
880	>	}
881	>	}
882	>
883	>	public void forEach(Consumer<? super E> action) {
884	>	Objects.requireNonNull(action);
885	>	final Object[] es = elements;
886	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
887	>	; i = 0, to = end) {
888	>	for (; i < to; i++)
889	>	action.accept(elementAt(es, i));
890	>	if (to == end) {
891	>	if (end != tail) throw new ConcurrentModificationException();
892	>	break;
893	>	}
894	>	}
895	>	// checkInvariants();
896	>	}
897	>
898	>	/**
899	>	* Replaces each element of this deque with the result of applying the
900	>	* operator to that element, as specified by {@link List#replaceAll}.
901	>	*
902	>	* @param operator the operator to apply to each element
903	>	* @since TBD
904	>	*/
905	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
906	>	Objects.requireNonNull(operator);
907	>	final Object[] es = elements;
908	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
909	>	; i = 0, to = end) {
910	>	for (; i < to; i++)
911	>	es[i] = operator.apply(elementAt(es, i));
912	>	if (to == end) {
913	>	if (end != tail) throw new ConcurrentModificationException();
914	>	break;
915	>	}
916	>	}
917	>	// checkInvariants();
918	>	}
919	>
920	>	/**
921	>	* @throws NullPointerException {@inheritDoc}
922	>	*/
923	>	public boolean removeIf(Predicate<? super E> filter) {
924	>	Objects.requireNonNull(filter);
925	>	return bulkRemove(filter);
926	>	}
927	>
928	>	/**
929	>	* @throws NullPointerException {@inheritDoc}
930	>	*/
931	>	public boolean removeAll(Collection<?> c) {
932	>	Objects.requireNonNull(c);
933	>	return bulkRemove(e -> c.contains(e));
934	>	}
935	>
936	>	/**
937	>	* @throws NullPointerException {@inheritDoc}
938	>	*/
939	>	public boolean retainAll(Collection<?> c) {
940	>	Objects.requireNonNull(c);
941	>	return bulkRemove(e -> !c.contains(e));
942	>	}
943	>
944	>	/** Implementation of bulk remove methods. */
945	>	private boolean bulkRemove(Predicate<? super E> filter) {
946	>	// checkInvariants();
947	>	final Object[] es = elements;
948	>	// Optimize for initial run of survivors
949	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
950	>	; i = 0, to = end) {
951	>	for (; i < to; i++)
952	>	if (filter.test(elementAt(es, i)))
953	>	return bulkRemoveModified(filter, i);
954	>	if (to == end) {
955	>	if (end != tail) throw new ConcurrentModificationException();
956	>	break;
957	>	}
958	>	}
959	>	return false;
960	>	}
961	>
962	>	// A tiny bit set implementation
963	>
964	>	private static long[] nBits(int n) {
965	>	return new long[((n - 1) >> 6) + 1];
966	>	}
967	>	private static void setBit(long[] bits, int i) {
968	>	bits[i >> 6] |= 1L << i;
969	>	}
970	>	private static boolean isClear(long[] bits, int i) {
971	>	return (bits[i >> 6] & (1L << i)) == 0;
972	>	}
973	>
974	>	/**
975	>	* Helper for bulkRemove, in case of at least one deletion.
976	>	* Tolerate predicates that reentrantly access the collection for
977	>	* read (but writers still get CME), so traverse once to find
978	>	* elements to delete, a second pass to physically expunge.
979	>	*
980	>	* @param beg valid index of first element to be deleted
981	>	*/
982	>	private boolean bulkRemoveModified(
983	>	Predicate<? super E> filter, final int beg) {
984	>	final Object[] es = elements;
985	>	final int capacity = es.length;
986	>	final int end = tail;
987	>	final long[] deathRow = nBits(sub(end, beg, capacity));
988	>	deathRow[0] = 1L;   // set bit 0
989	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
990	>	; i = 0, to = end, k -= capacity) {
991	>	for (; i < to; i++)
992	>	if (filter.test(elementAt(es, i)))
993	>	setBit(deathRow, i - k);
994	>	if (to == end) break;
995	>	}
996	>	// a two-finger traversal, with hare i reading, tortoise w writing
997	>	int w = beg;
998	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
999	>	; w = 0) { // w rejoins i on second leg
1000	>	// In this loop, i and w are on the same leg, with i > w
1001	>	for (; i < to; i++)
1002	>	if (isClear(deathRow, i - k))
1003	>	es[w++] = es[i];
1004	>	if (to == end) break;
1005	>	// In this loop, w is on the first leg, i on the second
1006	>	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1007	>	if (isClear(deathRow, i - k))
1008	>	es[w++] = es[i];
1009	>	if (i >= to) {
1010	>	if (w == capacity) w = 0; // "corner" case
1011	>	break;
1012	>	}
1013	>	}
1014	>	if (end != tail) throw new ConcurrentModificationException();
1015	>	circularClear(es, tail = w, end);
1016	>	// checkInvariants();
1017	>	return true;
1018	>	}
1019	>
1020	>	/**
1021	>	* Returns {@code true} if this deque contains the specified element.
1022	>	* More formally, returns {@code true} if and only if this deque contains
1023	>	* at least one element {@code e} such that {@code o.equals(e)}.
1024		*
1025		* @param o object to be checked for containment in this deque
1026	<	* @return <tt>true</tt> if this deque contains the specified element
1026	>	* @return {@code true} if this deque contains the specified element
1027		*/
1028		public boolean contains(Object o) {
1029	<	if (o == null)
1030	<	return false;
1031	<	int mask = elements.length - 1;
1032	<	int i = head;
1033	<	E x;
1034	<	while ( (x = elements[i]) != null) {
1035	<	if (o.equals(x))
1036	<	return true;
1037	<	i = (i + 1) & mask;
1029	>	if (o != null) {
1030	>	final Object[] es = elements;
1031	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1032	>	; i = 0, to = end) {
1033	>	for (; i < to; i++)
1034	>	if (o.equals(es[i]))
1035	>	return true;
1036	>	if (to == end) break;
1037	>	}
1038		}
1039		return false;
1040		}
1041
1042		/**
1043		* Removes a single instance of the specified element from this deque.
1044	<	* This method is equivalent to {@link #removeFirstOccurrence}.
1044	>	* If the deque does not contain the element, it is unchanged.
1045	>	* More formally, removes the first element {@code e} such that
1046	>	* {@code o.equals(e)} (if such an element exists).
1047	>	* Returns {@code true} if this deque contained the specified element
1048	>	* (or equivalently, if this deque changed as a result of the call).
1049		*
1050	<	* @param e element to be removed from this deque, if present
1051	<	* @return <tt>true</tt> if this deque contained the specified element
1050	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1051	>	*
1052	>	* @param o element to be removed from this deque, if present
1053	>	* @return {@code true} if this deque contained the specified element
1054		*/
1055	<	public boolean remove(Object e) {
1056	<	return removeFirstOccurrence(e);
1055	>	public boolean remove(Object o) {
1056	>	return removeFirstOccurrence(o);
1057		}
1058
1059		/**
1060		* Removes all of the elements from this deque.
1061	+	* The deque will be empty after this call returns.
1062		*/
1063		public void clear() {
1064	<	int h = head;
1065	<	int t = tail;
1066	<	if (h != t) { // clear all cells
1067	<	head = tail = 0;
1068	<	int i = h;
1069	<	int mask = elements.length - 1;
1070	<	do {
1071	<	elements[i] = null;
1072	<	i = (i + 1) & mask;
1073	<	} while(i != t);
1064	>	circularClear(elements, head, tail);
1065	>	head = tail = 0;
1066	>	// checkInvariants();
1067	>	}
1068	>
1069	>	/**
1070	>	* Nulls out slots starting at array index i, upto index end.
1071	>	*/
1072	>	private static void circularClear(Object[] es, int i, int end) {
1073	>	for (int to = (i <= end) ? end : es.length;
1074	>	; i = 0, to = end) {
1075	>	Arrays.fill(es, i, to, null);
1076	>	if (to == end) break;
1077		}
1078		}
1079
1080		/**
1081	<	* Returns an array containing all of the elements in this list
1082	<	* in the correct order.
1081	>	* Returns an array containing all of the elements in this deque
1082	>	* in proper sequence (from first to last element).
1083		*
1084	<	* @return an array containing all of the elements in this list
1085	<	*         in the correct order
1084	>	* <p>The returned array will be "safe" in that no references to it are
1085	>	* maintained by this deque.  (In other words, this method must allocate
1086	>	* a new array).  The caller is thus free to modify the returned array.
1087	>	*
1088	>	* <p>This method acts as bridge between array-based and collection-based
1089	>	* APIs.
1090	>	*
1091	>	* @return an array containing all of the elements in this deque
1092		*/
1093		public Object[] toArray() {
1094	<	return copyElements(new Object[size()]);
1094	>	return toArray(Object[].class);
1095	>	}
1096	>
1097	>	private <T> T[] toArray(Class<T[]> klazz) {
1098	>	final Object[] es = elements;
1099	>	final T[] a;
1100	>	final int size = size(), head = this.head, end;
1101	>	final int len = Math.min(size, es.length - head);
1102	>	if ((end = head + size) >= 0) {
1103	>	a = Arrays.copyOfRange(es, head, end, klazz);
1104	>	} else {
1105	>	// integer overflow!
1106	>	a = Arrays.copyOfRange(es, 0, size, klazz);
1107	>	System.arraycopy(es, head, a, 0, len);
1108	>	}
1109	>	if (tail < head)
1110	>	System.arraycopy(es, 0, a, len, tail);
1111	>	return a;
1112		}
1113
1114		/**
1115	<	* Returns an array containing all of the elements in this deque in the
1116	<	* correct order; the runtime type of the returned array is that of the
1117	<	* specified array.  If the deque fits in the specified array, it is
1118	<	* returned therein.  Otherwise, a new array is allocated with the runtime
1119	<	* type of the specified array and the size of this deque.
1115	>	* Returns an array containing all of the elements in this deque in
1116	>	* proper sequence (from first to last element); the runtime type of the
1117	>	* returned array is that of the specified array.  If the deque fits in
1118	>	* the specified array, it is returned therein.  Otherwise, a new array
1119	>	* is allocated with the runtime type of the specified array and the
1120	>	* size of this deque.
1121	>	*
1122	>	* <p>If this deque fits in the specified array with room to spare
1123	>	* (i.e., the array has more elements than this deque), the element in
1124	>	* the array immediately following the end of the deque is set to
1125	>	* {@code null}.
1126	>	*
1127	>	* <p>Like the {@link #toArray()} method, this method acts as bridge between
1128	>	* array-based and collection-based APIs.  Further, this method allows
1129	>	* precise control over the runtime type of the output array, and may,
1130	>	* under certain circumstances, be used to save allocation costs.
1131	>	*
1132	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1133	>	* The following code can be used to dump the deque into a newly
1134	>	* allocated array of {@code String}:
1135	>	*
1136	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1137		*
1138	<	* <p>If the deque fits in the specified array with room to spare (i.e.,
1139	<	* the array has more elements than the deque), the element in the array
693	<	* immediately following the end of the collection is set to <tt>null</tt>.
1138	>	* Note that {@code toArray(new Object[0])} is identical in function to
1139	>	* {@code toArray()}.
1140		*
1141		* @param a the array into which the elements of the deque are to
1142	<	*          be stored, if it is big enough; otherwise, a new array of the
1143	<	*          same runtime type is allocated for this purpose
1144	<	* @return an array containing the elements of the deque
1145	<	* @throws ArrayStoreException if the runtime type of a is not a supertype
1146	<	*         of the runtime type of every element in this deque
1142	>	*          be stored, if it is big enough; otherwise, a new array of the
1143	>	*          same runtime type is allocated for this purpose
1144	>	* @return an array containing all of the elements in this deque
1145	>	* @throws ArrayStoreException if the runtime type of the specified array
1146	>	*         is not a supertype of the runtime type of every element in
1147	>	*         this deque
1148	>	* @throws NullPointerException if the specified array is null
1149		*/
1150	+	@SuppressWarnings("unchecked")
1151		public <T> T[] toArray(T[] a) {
1152	<	int size = size();
1153	<	if (a.length < size)
1154	<	a = (T[])java.lang.reflect.Array.newInstance(
1155	<	a.getClass().getComponentType(), size);
1156	<	copyElements(a);
1157	<	if (a.length > size)
1152	>	final int size;
1153	>	if ((size = size()) > a.length)
1154	>	return toArray((Class<T[]>) a.getClass());
1155	>	final Object[] es = elements;
1156	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1157	>	; i = 0, len = tail) {
1158	>	System.arraycopy(es, i, a, j, len);
1159	>	if ((j += len) == size) break;
1160	>	}
1161	>	if (size < a.length)
1162		a[size] = null;
1163		return a;
1164		}
#	Line 718 | Line 1171 | public class ArrayDeque<E> extends Abstr
1171		* @return a copy of this deque
1172		*/
1173		public ArrayDeque<E> clone() {
1174	<	try {
1174	>	try {
1175	>	@SuppressWarnings("unchecked")
1176		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1177	<	// 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);
1177	>	result.elements = Arrays.copyOf(elements, elements.length);
1178		return result;
1179	<
728	<	} catch (CloneNotSupportedException e) {
1179	>	} catch (CloneNotSupportedException e) {
1180		throw new AssertionError();
1181		}
1182		}
1183
733	–	/**
734	–	* Appease the serialization gods.
735	–	*/
1184		private static final long serialVersionUID = 2340985798034038923L;
1185
1186		/**
1187	<	* Serialize this deque.
1187	>	* Saves this deque to a stream (that is, serializes it).
1188		*
1189	<	* @serialData The current size (<tt>int</tt>) of the deque,
1189	>	* @param s the stream
1190	>	* @throws java.io.IOException if an I/O error occurs
1191	>	* @serialData The current size ({@code int}) of the deque,
1192		* followed by all of its elements (each an object reference) in
1193		* first-to-last order.
1194		*/
1195	<	private void writeObject(ObjectOutputStream s) throws IOException {
1195	>	private void writeObject(java.io.ObjectOutputStream s)
1196	>	throws java.io.IOException {
1197		s.defaultWriteObject();
1198
1199		// Write out size
1200	<	int size = size();
750	<	s.writeInt(size);
1200	>	s.writeInt(size());
1201
1202		// Write out elements in order.
1203	<	int i = head;
1204	<	int mask = elements.length - 1;
1205	<	for (int j = 0; j < size; j++) {
1206	<	s.writeObject(elements[i]);
1207	<	i = (i + 1) & mask;
1203	>	final Object[] es = elements;
1204	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1205	>	; i = 0, to = end) {
1206	>	for (; i < to; i++)
1207	>	s.writeObject(es[i]);
1208	>	if (to == end) break;
1209		}
1210		}
1211
1212		/**
1213	<	* Deserialize this deque.
1213	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1214	>	* @param s the stream
1215	>	* @throws ClassNotFoundException if the class of a serialized object
1216	>	*         could not be found
1217	>	* @throws java.io.IOException if an I/O error occurs
1218		*/
1219	<	private void readObject(ObjectInputStream s)
1220	<	throws IOException, ClassNotFoundException {
1219	>	private void readObject(java.io.ObjectInputStream s)
1220	>	throws java.io.IOException, ClassNotFoundException {
1221		s.defaultReadObject();
1222
1223		// Read in size and allocate array
1224		int size = s.readInt();
1225	<	allocateElements(size);
1226	<	head = 0;
772	<	tail = size;
1225	>	elements = new Object[size + 1];
1226	>	this.tail = size;
1227
1228		// Read in all elements in the proper order.
1229		for (int i = 0; i < size; i++)
1230	<	elements[i] = (E)s.readObject();
1230	>	elements[i] = s.readObject();
1231	>	}
1232
1233	+	/** debugging */
1234	+	void checkInvariants() {
1235	+	try {
1236	+	int capacity = elements.length;
1237	+	// assert head >= 0 && head < capacity;
1238	+	// assert tail >= 0 && tail < capacity;
1239	+	// assert capacity > 0;
1240	+	// assert size() < capacity;
1241	+	// assert head == tail || elements[head] != null;
1242	+	// assert elements[tail] == null;
1243	+	// assert head == tail || elements[dec(tail, capacity)] != null;
1244	+	} catch (Throwable t) {
1245	+	System.err.printf("head=%d tail=%d capacity=%d%n",
1246	+	head, tail, elements.length);
1247	+	System.err.printf("elements=%s%n",
1248	+	Arrays.toString(elements));
1249	+	throw t;
1250	+	}
1251		}
1252	+
1253		}

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