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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.17 by dl, Thu Sep 15 16:55:24 2005 UTC vs.
Revision 1.131 by jsr166, Wed Aug 23 22:41:49 2017 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Josh Bloch of Google Inc. and released to the public domain,
3	<	* as explained at http://creativecommons.org/licenses/publicdomain.
3	>	* as explained at http://creativecommons.org/publicdomain/zero/1.0/.
4		*/
5
6		package java.util;
7	<	import java.util.*; // for javadoc (till 6280605 is fixed)
8	<	import java.io.*;
7	>
8	>	import java.io.Serializable;
9	>	import java.util.function.Consumer;
10	>	import java.util.function.Predicate;
11	>	import java.util.function.UnaryOperator;
12
13		/**
14		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 16 | Line 19 | import java.io.*;
19		* {@link Stack} when used as a stack, and faster than {@link LinkedList}
20		* when used as a queue.
21		*
22	<	* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time.
23	<	* Exceptions include {@link #remove(Object) remove}, {@link
24	<	* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence
25	<	* removeLastOccurrence}, {@link #contains contains}, {@link #iterator
26	<	* iterator.remove()}, and the bulk operations, all of which run in linear
27	<	* time.
22	>	* <p>Most {@code ArrayDeque} operations run in amortized constant time.
23	>	* Exceptions include
24	>	* {@link #remove(Object) remove},
25	>	* {@link #removeFirstOccurrence removeFirstOccurrence},
26	>	* {@link #removeLastOccurrence removeLastOccurrence},
27	>	* {@link #contains contains},
28	>	* {@link #iterator iterator.remove()},
29	>	* and the bulk operations, all of which run in linear time.
30		*
31	<	* <p>The iterators returned by this class's <tt>iterator</tt> method are
32	<	* <i>fail-fast</i>: If the deque is modified at any time after the iterator
33	<	* is created, in any way except through the iterator's own <tt>remove</tt>
34	<	* method, the iterator will generally throw a {@link
31	>	* <p>The iterators returned by this class's {@link #iterator() iterator}
32	>	* method are <em>fail-fast</em>: If the deque is modified at any time after
33	>	* the iterator is created, in any way except through the iterator's own
34	>	* {@code remove} method, the iterator will generally throw a {@link
35		* ConcurrentModificationException}.  Thus, in the face of concurrent
36		* modification, the iterator fails quickly and cleanly, rather than risking
37		* arbitrary, non-deterministic behavior at an undetermined time in the
#	Line 35 | Line 40 | import java.io.*;
40		* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
41		* as it is, generally speaking, impossible to make any hard guarantees in the
42		* presence of unsynchronized concurrent modification.  Fail-fast iterators
43	<	* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
43	>	* throw {@code ConcurrentModificationException} on a best-effort basis.
44		* Therefore, it would be wrong to write a program that depended on this
45		* exception for its correctness: <i>the fail-fast behavior of iterators
46		* should be used only to detect bugs.</i>
#	Line 45 | Line 50 | import java.io.*;
50		* Iterator} interfaces.
51		*
52		* <p>This class is a member of the
53	<	* <a href="{@docRoot}/../guide/collections/index.html">
53	>	* <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
54		* Java Collections Framework</a>.
55		*
56		* @author  Josh Bloch and Doug Lea
57	+	* @param <E> the type of elements held in this deque
58		* @since   1.6
53	–	* @param <E> the type of elements held in this collection
59		*/
60		public class ArrayDeque<E> extends AbstractCollection<E>
61		implements Deque<E>, Cloneable, Serializable
62		{
63	+	/*
64	+	* 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.  Having only
72	+	* one hot inner loop body instead of two or three eases human
73	+	* maintenance and encourages VM loop inlining into the caller.
74	+	*/
75	+
76		/**
77		* The array in which the elements of the deque are stored.
78	<	* The capacity of the deque is the length of this array, which is
79	<	* always a power of two. The array is never allowed to become
62	<	* full, except transiently within an addX method where it is
63	<	* resized (see doubleCapacity) immediately upon becoming full,
64	<	* thus avoiding head and tail wrapping around to equal each
65	<	* other.  We also guarantee that all array cells not holding
66	<	* deque elements are always null.
78	>	* All array cells not holding deque elements are always null.
79	>	* The array always has at least one null slot (at tail).
80		*/
81	<	private transient E[] elements;
81	>	transient Object[] elements;
82
83		/**
84		* The index of the element at the head of the deque (which is the
85		* element that would be removed by remove() or pop()); or an
86	<	* arbitrary number equal to tail if the deque is empty.
86	>	* arbitrary number 0 <= head < elements.length equal to tail if
87	>	* the deque is empty.
88		*/
89	<	private transient int head;
89	>	transient int head;
90
91		/**
92		* The index at which the next element would be added to the tail
93	<	* of the deque (via addLast(E), add(E), or push(E)).
94	<	*/
81	<	private transient int tail;
82	<
83	<	/**
84	<	* The minimum capacity that we'll use for a newly created deque.
85	<	* Must be a power of 2.
93	>	* of the deque (via addLast(E), add(E), or push(E));
94	>	* elements[tail] is always null.
95		*/
96	<	private static final int MIN_INITIAL_CAPACITY = 8;
88	<
89	<	// ******  Array allocation and resizing utilities ******
96	>	transient int tail;
97
98		/**
99	<	* Allocate empty array to hold the given number of elements.
100	<	*
101	<	* @param numElements  the number of elements to hold
102	<	*/
103	<	private void allocateElements(int numElements) {
104	<	int initialCapacity = MIN_INITIAL_CAPACITY;
105	<	// Find the best power of two to hold elements.
106	<	// Tests "<=" because arrays aren't kept full.
107	<	if (numElements >= initialCapacity) {
108	<	initialCapacity = numElements;
109	<	initialCapacity |= (initialCapacity >>>  1);
110	<	initialCapacity |= (initialCapacity >>>  2);
111	<	initialCapacity |= (initialCapacity >>>  4);
112	<	initialCapacity |= (initialCapacity >>>  8);
113	<	initialCapacity |= (initialCapacity >>> 16);
114	<	initialCapacity++;
99	>	* The maximum size of array to allocate.
100	>	* Some VMs reserve some header words in an array.
101	>	* Attempts to allocate larger arrays may result in
102	>	* OutOfMemoryError: Requested array size exceeds VM limit
103	>	*/
104	>	private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
105	>
106	>	/**
107	>	* Increases the capacity of this deque by at least the given amount.
108	>	*
109	>	* @param needed the required minimum extra capacity; must be positive
110	>	*/
111	>	private void grow(int needed) {
112	>	// overflow-conscious code
113	>	final int oldCapacity = elements.length;
114	>	int newCapacity;
115	>	// Double capacity if small; else grow by 50%
116	>	int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
117	>	if (jump < needed
118	>	|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
119	>	newCapacity = newCapacity(needed, jump);
120	>	final Object[] es = elements = Arrays.copyOf(elements, newCapacity);
121	>	// Exceptionally, here tail == head needs to be disambiguated
122	>	if (tail < head || (tail == head && es[head] != null)) {
123	>	// wrap around; slide first leg forward to end of array
124	>	int newSpace = newCapacity - oldCapacity;
125	>	System.arraycopy(es, head,
126	>	es, head + newSpace,
127	>	oldCapacity - head);
128	>	for (int i = head, to = (head += newSpace); i < to; i++)
129	>	es[i] = null;
130	>	}
131	>	// checkInvariants();
132	>	}
133
134	<	if (initialCapacity < 0)   // Too many elements, must back off
135	<	initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements
134	>	/** Capacity calculation for edge conditions, especially overflow. */
135	>	private int newCapacity(int needed, int jump) {
136	>	final int oldCapacity = elements.length, minCapacity;
137	>	if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
138	>	if (minCapacity < 0)
139	>	throw new IllegalStateException("Sorry, deque too big");
140	>	return Integer.MAX_VALUE;
141		}
142	<	elements = (E[]) new Object[initialCapacity];
142	>	if (needed > jump)
143	>	return minCapacity;
144	>	return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
145	>	? oldCapacity + jump
146	>	: MAX_ARRAY_SIZE;
147		}
148
149		/**
150	<	* Double the capacity of this deque.  Call only when full, i.e.,
151	<	* when head and tail have wrapped around to become equal.
150	>	* Increases the internal storage of this collection, if necessary,
151	>	* to ensure that it can hold at least the given number of elements.
152	>	*
153	>	* @param minCapacity the desired minimum capacity
154	>	* @since TBD
155		*/
156	<	private void doubleCapacity() {
157	<	assert head == tail;
158	<	int p = head;
159	<	int n = elements.length;
160	<	int r = n - p; // number of elements to the right of p
124	<	int newCapacity = n << 1;
125	<	if (newCapacity < 0)
126	<	throw new IllegalStateException("Sorry, deque too big");
127	<	Object[] a = new Object[newCapacity];
128	<	System.arraycopy(elements, p, a, 0, r);
129	<	System.arraycopy(elements, 0, a, r, p);
130	<	elements = (E[])a;
131	<	head = 0;
132	<	tail = n;
156	>	/* public */ void ensureCapacity(int minCapacity) {
157	>	int needed;
158	>	if ((needed = (minCapacity + 1 - elements.length)) > 0)
159	>	grow(needed);
160	>	// checkInvariants();
161		}
162
163		/**
164	<	* Copies the elements from our element array into the specified array,
137	<	* in order (from first to last element in the deque).  It is assumed
138	<	* that the array is large enough to hold all elements in the deque.
164	>	* Minimizes the internal storage of this collection.
165		*
166	<	* @return its argument
166	>	* @since TBD
167		*/
168	<	private <T> T[] copyElements(T[] a) {
169	<	if (head < tail) {
170	<	System.arraycopy(elements, head, a, 0, size());
171	<	} else if (head > tail) {
172	<	int headPortionLen = elements.length - head;
173	<	System.arraycopy(elements, head, a, 0, headPortionLen);
148	<	System.arraycopy(elements, 0, a, headPortionLen, tail);
168	>	/* public */ void trimToSize() {
169	>	int size;
170	>	if ((size = size()) + 1 < elements.length) {
171	>	elements = toArray(new Object[size + 1]);
172	>	head = 0;
173	>	tail = size;
174		}
175	<	return a;
175	>	// checkInvariants();
176		}
177
178		/**
#	Line 155 | Line 180 | public class ArrayDeque<E> extends Abstr
180		* sufficient to hold 16 elements.
181		*/
182		public ArrayDeque() {
183	<	elements = (E[]) new Object[16];
183	>	elements = new Object[16];
184		}
185
186		/**
187		* Constructs an empty array deque with an initial capacity
188		* sufficient to hold the specified number of elements.
189		*
190	<	* @param numElements  lower bound on initial capacity of the deque
190	>	* @param numElements lower bound on initial capacity of the deque
191		*/
192		public ArrayDeque(int numElements) {
193	<	allocateElements(numElements);
193	>	elements =
194	>	new Object[(numElements < 1) ? 1 :
195	>	(numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE :
196	>	numElements + 1];
197		}
198
199		/**
#	Line 179 | Line 207 | public class ArrayDeque<E> extends Abstr
207		* @throws NullPointerException if the specified collection is null
208		*/
209		public ArrayDeque(Collection<? extends E> c) {
210	<	allocateElements(c.size());
210	>	this(c.size());
211		addAll(c);
212		}
213
214	+	/**
215	+	* Circularly increments i, mod modulus.
216	+	* Precondition and postcondition: 0 <= i < modulus.
217	+	*/
218	+	static final int inc(int i, int modulus) {
219	+	if (++i >= modulus) i = 0;
220	+	return i;
221	+	}
222	+
223	+	/**
224	+	* Circularly decrements i, mod modulus.
225	+	* Precondition and postcondition: 0 <= i < modulus.
226	+	*/
227	+	static final int dec(int i, int modulus) {
228	+	if (--i < 0) i = modulus - 1;
229	+	return i;
230	+	}
231	+
232	+	/**
233	+	* Circularly adds the given distance to index i, mod modulus.
234	+	* Precondition: 0 <= i < modulus, 0 <= distance <= modulus.
235	+	* @return index 0 <= i < modulus
236	+	*/
237	+	static final int inc(int i, int distance, int modulus) {
238	+	if ((i += distance) - modulus >= 0) i -= modulus;
239	+	return i;
240	+	}
241	+
242	+	/**
243	+	* Subtracts j from i, mod modulus.
244	+	* Index i must be logically ahead of index j.
245	+	* Precondition: 0 <= i < modulus, 0 <= j < modulus.
246	+	* @return the "circular distance" from j to i; corner case i == j
247	+	* is disambiguated to "empty", returning 0.
248	+	*/
249	+	static final int sub(int i, int j, int modulus) {
250	+	if ((i -= j) < 0) i += modulus;
251	+	return i;
252	+	}
253	+
254	+	/**
255	+	* Returns element at array index i.
256	+	* This is a slight abuse of generics, accepted by javac.
257	+	*/
258	+	@SuppressWarnings("unchecked")
259	+	static final <E> E elementAt(Object[] es, int i) {
260	+	return (E) es[i];
261	+	}
262	+
263	+	/**
264	+	* A version of elementAt that checks for null elements.
265	+	* This check doesn't catch all possible comodifications,
266	+	* but does catch ones that corrupt traversal.
267	+	*/
268	+	static final <E> E nonNullElementAt(Object[] es, int i) {
269	+	@SuppressWarnings("unchecked") E e = (E) es[i];
270	+	if (e == null)
271	+	throw new ConcurrentModificationException();
272	+	return e;
273	+	}
274	+
275		// The main insertion and extraction methods are addFirst,
276		// addLast, pollFirst, pollLast. The other methods are defined in
277		// terms of these.
#	Line 196 | Line 285 | public class ArrayDeque<E> extends Abstr
285		public void addFirst(E e) {
286		if (e == null)
287		throw new NullPointerException();
288	<	elements[head = (head - 1) & (elements.length - 1)] = e;
288	>	final Object[] es = elements;
289	>	es[head = dec(head, es.length)] = e;
290		if (head == tail)
291	<	doubleCapacity();
291	>	grow(1);
292	>	// checkInvariants();
293		}
294
295		/**
#	Line 212 | Line 303 | public class ArrayDeque<E> extends Abstr
303		public void addLast(E e) {
304		if (e == null)
305		throw new NullPointerException();
306	<	elements[tail] = e;
307	<	if ( (tail = (tail + 1) & (elements.length - 1)) == head)
308	<	doubleCapacity();
306	>	final Object[] es = elements;
307	>	es[tail] = e;
308	>	if (head == (tail = inc(tail, es.length)))
309	>	grow(1);
310	>	// checkInvariants();
311	>	}
312	>
313	>	/**
314	>	* Adds all of the elements in the specified collection at the end
315	>	* of this deque, as if by calling {@link #addLast} on each one,
316	>	* in the order that they are returned by the collection's iterator.
317	>	*
318	>	* @param c the elements to be inserted into this deque
319	>	* @return {@code true} if this deque changed as a result of the call
320	>	* @throws NullPointerException if the specified collection or any
321	>	*         of its elements are null
322	>	*/
323	>	public boolean addAll(Collection<? extends E> c) {
324	>	final int s, needed;
325	>	if ((needed = (s = size()) + c.size() + 1 - elements.length) > 0)
326	>	grow(needed);
327	>	c.forEach(this::addLast);
328	>	// checkInvariants();
329	>	return size() > s;
330		}
331
332		/**
333		* Inserts the specified element at the front of this deque.
334		*
335		* @param e the element to add
336	<	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
336	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
337		* @throws NullPointerException if the specified element is null
338		*/
339		public boolean offerFirst(E e) {
#	Line 233 | Line 345 | public class ArrayDeque<E> extends Abstr
345		* Inserts the specified element at the end of this deque.
346		*
347		* @param e the element to add
348	<	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
348	>	* @return {@code true} (as specified by {@link Deque#offerLast})
349		* @throws NullPointerException if the specified element is null
350		*/
351		public boolean offerLast(E e) {
#	Line 245 | Line 357 | public class ArrayDeque<E> extends Abstr
357		* @throws NoSuchElementException {@inheritDoc}
358		*/
359		public E removeFirst() {
360	<	E x = pollFirst();
361	<	if (x == null)
360	>	E e = pollFirst();
361	>	if (e == null)
362		throw new NoSuchElementException();
363	<	return x;
363	>	// checkInvariants();
364	>	return e;
365		}
366
367		/**
368		* @throws NoSuchElementException {@inheritDoc}
369		*/
370		public E removeLast() {
371	<	E x = pollLast();
372	<	if (x == null)
371	>	E e = pollLast();
372	>	if (e == null)
373		throw new NoSuchElementException();
374	<	return x;
374	>	// checkInvariants();
375	>	return e;
376		}
377
378		public E pollFirst() {
379	<	int h = head;
380	<	E result = elements[h]; // Element is null if deque empty
381	<	if (result == null)
382	<	return null;
383	<	elements[h] = null;     // Must null out slot
384	<	head = (h + 1) & (elements.length - 1);
385	<	return result;
379	>	final Object[] es;
380	>	final int h;
381	>	E e = elementAt(es = elements, h = head);
382	>	if (e != null) {
383	>	es[h] = null;
384	>	head = inc(h, es.length);
385	>	}
386	>	// checkInvariants();
387	>	return e;
388		}
389
390		public E pollLast() {
391	<	int t = (tail - 1) & (elements.length - 1);
392	<	E result = elements[t];
393	<	if (result == null)
394	<	return null;
395	<	elements[t] = null;
396	<	tail = t;
397	<	return result;
391	>	final Object[] es;
392	>	final int t;
393	>	E e = elementAt(es = elements, t = dec(tail, es.length));
394	>	if (e != null)
395	>	es[tail = t] = null;
396	>	// checkInvariants();
397	>	return e;
398		}
399
400		/**
401		* @throws NoSuchElementException {@inheritDoc}
402		*/
403		public E getFirst() {
404	<	E x = elements[head];
405	<	if (x == null)
404	>	E e = elementAt(elements, head);
405	>	if (e == null)
406		throw new NoSuchElementException();
407	<	return x;
407	>	// checkInvariants();
408	>	return e;
409		}
410
411		/**
412		* @throws NoSuchElementException {@inheritDoc}
413		*/
414		public E getLast() {
415	<	E x = elements[(tail - 1) & (elements.length - 1)];
416	<	if (x == null)
415	>	final Object[] es = elements;
416	>	E e = elementAt(es, dec(tail, es.length));
417	>	if (e == null)
418		throw new NoSuchElementException();
419	<	return x;
419	>	// checkInvariants();
420	>	return e;
421		}
422
423		public E peekFirst() {
424	<	return elements[head]; // elements[head] is null if deque empty
424	>	// checkInvariants();
425	>	return elementAt(elements, head);
426		}
427
428		public E peekLast() {
429	<	return elements[(tail - 1) & (elements.length - 1)];
429	>	// checkInvariants();
430	>	final Object[] es;
431	>	return elementAt(es = elements, dec(tail, es.length));
432		}
433
434		/**
435		* Removes the first occurrence of the specified element in this
436		* deque (when traversing the deque from head to tail).
437		* If the deque does not contain the element, it is unchanged.
438	<	* More formally, removes the first element <tt>e</tt> such that
439	<	* <tt>o.equals(e)</tt> (if such an element exists).
440	<	* Returns <tt>true</tt> if this deque contained the specified element
438	>	* More formally, removes the first element {@code e} such that
439	>	* {@code o.equals(e)} (if such an element exists).
440	>	* Returns {@code true} if this deque contained the specified element
441		* (or equivalently, if this deque changed as a result of the call).
442		*
443		* @param o element to be removed from this deque, if present
444	<	* @return <tt>true</tt> if the deque contained the specified element
444	>	* @return {@code true} if the deque contained the specified element
445		*/
446		public boolean removeFirstOccurrence(Object o) {
447	<	if (o == null)
448	<	return false;
449	<	int mask = elements.length - 1;
450	<	int i = head;
451	<	E x;
452	<	while ( (x = elements[i]) != null) {
453	<	if (o.equals(x)) {
454	<	delete(i);
455	<	return true;
447	>	if (o != null) {
448	>	final Object[] es = elements;
449	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
450	>	; i = 0, to = end) {
451	>	for (; i < to; i++)
452	>	if (o.equals(es[i])) {
453	>	delete(i);
454	>	return true;
455	>	}
456	>	if (to == end) break;
457		}
335	–	i = (i + 1) & mask;
458		}
459		return false;
460		}
#	Line 341 | Line 463 | public class ArrayDeque<E> extends Abstr
463		* Removes the last occurrence of the specified element in this
464		* deque (when traversing the deque from head to tail).
465		* If the deque does not contain the element, it is unchanged.
466	<	* More formally, removes the last element <tt>e</tt> such that
467	<	* <tt>o.equals(e)</tt> (if such an element exists).
468	<	* Returns <tt>true</tt> if this deque contained the specified element
466	>	* More formally, removes the last element {@code e} such that
467	>	* {@code o.equals(e)} (if such an element exists).
468	>	* Returns {@code true} if this deque contained the specified element
469		* (or equivalently, if this deque changed as a result of the call).
470		*
471		* @param o element to be removed from this deque, if present
472	<	* @return <tt>true</tt> if the deque contained the specified element
472	>	* @return {@code true} if the deque contained the specified element
473		*/
474		public boolean removeLastOccurrence(Object o) {
475	<	if (o == null)
476	<	return false;
477	<	int mask = elements.length - 1;
478	<	int i = (tail - 1) & mask;
479	<	E x;
480	<	while ( (x = elements[i]) != null) {
481	<	if (o.equals(x)) {
482	<	delete(i);
483	<	return true;
475	>	if (o != null) {
476	>	final Object[] es = elements;
477	>	for (int i = tail, end = head, to = (i >= end) ? end : 0;
478	>	; i = es.length, to = end) {
479	>	for (i--; i > to - 1; i--)
480	>	if (o.equals(es[i])) {
481	>	delete(i);
482	>	return true;
483	>	}
484	>	if (to == end) break;
485		}
363	–	i = (i - 1) & mask;
486		}
487		return false;
488		}
#	Line 373 | Line 495 | public class ArrayDeque<E> extends Abstr
495		* <p>This method is equivalent to {@link #addLast}.
496		*
497		* @param e the element to add
498	<	* @return <tt>true</tt> (as specified by {@link Collection#add})
498	>	* @return {@code true} (as specified by {@link Collection#add})
499		* @throws NullPointerException if the specified element is null
500		*/
501		public boolean add(E e) {
#	Line 387 | Line 509 | public class ArrayDeque<E> extends Abstr
509		* <p>This method is equivalent to {@link #offerLast}.
510		*
511		* @param e the element to add
512	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
512	>	* @return {@code true} (as specified by {@link Queue#offer})
513		* @throws NullPointerException if the specified element is null
514		*/
515		public boolean offer(E e) {
#	Line 397 | Line 519 | public class ArrayDeque<E> extends Abstr
519		/**
520		* Retrieves and removes the head of the queue represented by this deque.
521		*
522	<	* This method differs from {@link #poll poll} only in that it throws an
523	<	* exception if this deque is empty.
522	>	* This method differs from {@link #poll() poll()} only in that it
523	>	* throws an exception if this deque is empty.
524		*
525		* <p>This method is equivalent to {@link #removeFirst}.
526		*
#	Line 412 | Line 534 | public class ArrayDeque<E> extends Abstr
534		/**
535		* Retrieves and removes the head of the queue represented by this deque
536		* (in other words, the first element of this deque), or returns
537	<	* <tt>null</tt> if this deque is empty.
537	>	* {@code null} if this deque is empty.
538		*
539		* <p>This method is equivalent to {@link #pollFirst}.
540		*
541		* @return the head of the queue represented by this deque, or
542	<	*         <tt>null</tt> if this deque is empty
542	>	*         {@code null} if this deque is empty
543		*/
544		public E poll() {
545		return pollFirst();
#	Line 439 | Line 561 | public class ArrayDeque<E> extends Abstr
561
562		/**
563		* Retrieves, but does not remove, the head of the queue represented by
564	<	* this deque, or returns <tt>null</tt> if this deque is empty.
564	>	* this deque, or returns {@code null} if this deque is empty.
565		*
566		* <p>This method is equivalent to {@link #peekFirst}.
567		*
568		* @return the head of the queue represented by this deque, or
569	<	*         <tt>null</tt> if this deque is empty
569	>	*         {@code null} if this deque is empty
570		*/
571		public E peek() {
572		return peekFirst();
#	Line 480 | Line 602 | public class ArrayDeque<E> extends Abstr
602		}
603
604		/**
605	<	* Removes the element at the specified position in the elements array,
606	<	* adjusting head and tail as necessary.  This can result in motion of
607	<	* elements backwards or forwards in the array.
605	>	* Removes the element at the specified position in the elements array.
606	>	* This can result in forward or backwards motion of array elements.
607	>	* We optimize for least element motion.
608		*
609		* <p>This method is called delete rather than remove to emphasize
610		* that its semantics differ from those of {@link List#remove(int)}.
611		*
612	<	* @return true if elements moved backwards
612	>	* @return true if elements near tail moved backwards
613		*/
614	<	private boolean delete(int i) {
615	<	int mask = elements.length - 1;
616	<
617	<	// Invariant: head <= i < tail mod circularity
618	<	if (((i - head) & mask) >= ((tail - head) & mask))
619	<	throw new ConcurrentModificationException();
620	<
621	<	// Case 1: Deque doesn't wrap
622	<	// Case 2: Deque does wrap and removed element is in the head portion
623	<	if (i >= head) {
624	<	System.arraycopy(elements, head, elements, head + 1, i - head);
625	<	elements[head] = null;
626	<	head = (head + 1) & mask;
614	>	boolean delete(int i) {
615	>	// checkInvariants();
616	>	final Object[] es = elements;
617	>	final int capacity = es.length;
618	>	final int h, t;
619	>	// number of elements before to-be-deleted elt
620	>	final int front = sub(i, h = head, capacity);
621	>	// number of elements after to-be-deleted elt
622	>	final int back = sub(t = tail, i, capacity) - 1;
623	>	if (front < back) {
624	>	// move front elements forwards
625	>	if (h <= i) {
626	>	System.arraycopy(es, h, es, h + 1, front);
627	>	} else { // Wrap around
628	>	System.arraycopy(es, 0, es, 1, i);
629	>	es[0] = es[capacity - 1];
630	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
631	>	}
632	>	es[h] = null;
633	>	head = inc(h, capacity);
634	>	// checkInvariants();
635		return false;
636	+	} else {
637	+	// move back elements backwards
638	+	tail = dec(t, capacity);
639	+	if (i <= tail) {
640	+	System.arraycopy(es, i + 1, es, i, back);
641	+	} else { // Wrap around
642	+	System.arraycopy(es, i + 1, es, i, capacity - (i + 1));
643	+	es[capacity - 1] = es[0];
644	+	System.arraycopy(es, 1, es, 0, t - 1);
645	+	}
646	+	es[tail] = null;
647	+	// checkInvariants();
648	+	return true;
649		}
507	–
508	–	// Case 3: Deque wraps and removed element is in the tail portion
509	–	tail--;
510	–	System.arraycopy(elements, i + 1, elements, i, tail - i);
511	–	elements[tail] = null;
512	–	return true;
650		}
651
652		// *** Collection Methods ***
#	Line 520 | Line 657 | public class ArrayDeque<E> extends Abstr
657		* @return the number of elements in this deque
658		*/
659		public int size() {
660	<	return (tail - head) & (elements.length - 1);
660	>	return sub(tail, head, elements.length);
661		}
662
663		/**
664	<	* Returns <tt>true</tt> if this deque contains no elements.
664	>	* Returns {@code true} if this deque contains no elements.
665		*
666	<	* @return <tt>true</tt> if this deque contains no elements
666	>	* @return {@code true} if this deque contains no elements
667		*/
668		public boolean isEmpty() {
669		return head == tail;
#	Line 538 | Line 675 | public class ArrayDeque<E> extends Abstr
675		* order that elements would be dequeued (via successive calls to
676		* {@link #remove} or popped (via successive calls to {@link #pop}).
677		*
678	<	* @return an <tt>Iterator</tt> over the elements in this deque
678	>	* @return an iterator over the elements in this deque
679		*/
680		public Iterator<E> iterator() {
681		return new DeqIterator();
682		}
683
547	–	/**
548	–	* Returns an iterator over the elements in this deque in reverse
549	–	* sequential order.  The elements will be returned in order from
550	–	* last (tail) to first (head).
551	–	*
552	–	* @return an iterator over the elements in this deque in reverse
553	–	* sequence
554	–	*/
684		public Iterator<E> descendingIterator() {
685		return new DescendingIterator();
686		}
687
688		private class DeqIterator implements Iterator<E> {
689	<	/**
690	<	* Index of element to be returned by subsequent call to next.
562	<	*/
563	<	private int cursor = head;
689	>	/** Index of element to be returned by subsequent call to next. */
690	>	int cursor;
691
692	<	/**
693	<	* Tail recorded at construction (also in remove), to stop
567	<	* iterator and also to check for comodification.
568	<	*/
569	<	private int fence = tail;
692	>	/** Number of elements yet to be returned. */
693	>	int remaining = size();
694
695		/**
696		* Index of element returned by most recent call to next.
697		* Reset to -1 if element is deleted by a call to remove.
698		*/
699	<	private int lastRet = -1;
699	>	int lastRet = -1;
700
701	<	public boolean hasNext() {
702	<	return cursor != fence;
701	>	DeqIterator() { cursor = head; }
702	>
703	>	public final boolean hasNext() {
704	>	return remaining > 0;
705		}
706
707		public E next() {
708	<	E result;
583	<	if (cursor == fence)
708	>	if (remaining <= 0)
709		throw new NoSuchElementException();
710	<	// This check doesn't catch all possible comodifications,
711	<	// but does catch the ones that corrupt traversal
712	<	if (tail != fence || (result = elements[cursor]) == null)
713	<	throw new ConcurrentModificationException();
714	<	lastRet = cursor;
715	<	cursor = (cursor + 1) & (elements.length - 1);
716	<	return result;
710	>	final Object[] es = elements;
711	>	E e = nonNullElementAt(es, cursor);
712	>	cursor = inc(lastRet = cursor, es.length);
713	>	remaining--;
714	>	return e;
715	>	}
716	>
717	>	void postDelete(boolean leftShifted) {
718	>	if (leftShifted)
719	>	cursor = dec(cursor, elements.length);
720		}
721
722	<	public void remove() {
722	>	public final void remove() {
723		if (lastRet < 0)
724		throw new IllegalStateException();
725	<	if (delete(lastRet)) // if left-shifted, undo increment in next()
598	<	cursor = (cursor - 1) & (elements.length - 1);
725	>	postDelete(delete(lastRet));
726		lastRet = -1;
727	<	fence = tail;
727	>	}
728	>
729	>	public void forEachRemaining(Consumer<? super E> action) {
730	>	Objects.requireNonNull(action);
731	>	int r;
732	>	if ((r = remaining) <= 0)
733	>	return;
734	>	remaining = 0;
735	>	final Object[] es = elements;
736	>	if (es[cursor] == null || sub(tail, cursor, es.length) != r)
737	>	throw new ConcurrentModificationException();
738	>	for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
739	>	; i = 0, to = end) {
740	>	for (; i < to; i++)
741	>	action.accept(elementAt(es, i));
742	>	if (to == end) {
743	>	if (end != tail)
744	>	throw new ConcurrentModificationException();
745	>	lastRet = dec(end, es.length);
746	>	break;
747	>	}
748	>	}
749		}
750		}
751
752	+	private class DescendingIterator extends DeqIterator {
753	+	DescendingIterator() { cursor = dec(tail, elements.length); }
754
755	<	private class DescendingIterator implements Iterator<E> {
756	<	/*
757	<	* This class is nearly a mirror-image of DeqIterator, using
758	<	* (tail-1) instead of head for initial cursor, (head-1)
759	<	* instead of tail for fence, and elements.length instead of -1
760	<	* for sentinel. It shares the same structure, but not many
761	<	* actual lines of code.
762	<	*/
763	<	private int cursor = (tail - 1) & (elements.length - 1);
614	<	private int fence =  (head - 1) & (elements.length - 1);
615	<	private int lastRet = elements.length;
755	>	public final E next() {
756	>	if (remaining <= 0)
757	>	throw new NoSuchElementException();
758	>	final Object[] es = elements;
759	>	E e = nonNullElementAt(es, cursor);
760	>	cursor = dec(lastRet = cursor, es.length);
761	>	remaining--;
762	>	return e;
763	>	}
764
765	<	public boolean hasNext() {
766	<	return cursor != fence;
765	>	void postDelete(boolean leftShifted) {
766	>	if (!leftShifted)
767	>	cursor = inc(cursor, elements.length);
768		}
769
770	<	public E next() {
771	<	E result;
772	<	if (cursor == fence)
773	<	throw new NoSuchElementException();
774	<	if (((head - 1) & (elements.length - 1)) != fence ||
775	<	(result = elements[cursor]) == null)
770	>	public final void forEachRemaining(Consumer<? super E> action) {
771	>	Objects.requireNonNull(action);
772	>	int r;
773	>	if ((r = remaining) <= 0)
774	>	return;
775	>	remaining = 0;
776	>	final Object[] es = elements;
777	>	if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
778		throw new ConcurrentModificationException();
779	<	lastRet = cursor;
780	<	cursor = (cursor - 1) & (elements.length - 1);
781	<	return result;
779	>	for (int i = cursor, end = head, to = (i >= end) ? end : 0;
780	>	; i = es.length - 1, to = end) {
781	>	// hotspot generates faster code than for: i >= to !
782	>	for (; i > to - 1; i--)
783	>	action.accept(elementAt(es, i));
784	>	if (to == end) {
785	>	if (end != head)
786	>	throw new ConcurrentModificationException();
787	>	lastRet = end;
788	>	break;
789	>	}
790	>	}
791		}
792	+	}
793
794	<	public void remove() {
795	<	if (lastRet >= elements.length)
796	<	throw new IllegalStateException();
797	<	if (!delete(lastRet))
798	<	cursor = (cursor + 1) & (elements.length - 1);
799	<	lastRet = elements.length;
800	<	fence = (head - 1) & (elements.length - 1);
794	>	/**
795	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
796	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
797	>	* deque.
798	>	*
799	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
800	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
801	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
802	>	* the reporting of additional characteristic values.
803	>	*
804	>	* @return a {@code Spliterator} over the elements in this deque
805	>	* @since 1.8
806	>	*/
807	>	public Spliterator<E> spliterator() {
808	>	return new DeqSpliterator();
809	>	}
810	>
811	>	final class DeqSpliterator implements Spliterator<E> {
812	>	private int fence;      // -1 until first use
813	>	private int cursor;     // current index, modified on traverse/split
814	>
815	>	/** Constructs late-binding spliterator over all elements. */
816	>	DeqSpliterator() {
817	>	this.fence = -1;
818	>	}
819	>
820	>	/** Constructs spliterator over the given range. */
821	>	DeqSpliterator(int origin, int fence) {
822	>	// assert 0 <= origin && origin < elements.length;
823	>	// assert 0 <= fence && fence < elements.length;
824	>	this.cursor = origin;
825	>	this.fence = fence;
826	>	}
827	>
828	>	/** Ensures late-binding initialization; then returns fence. */
829	>	private int getFence() { // force initialization
830	>	int t;
831	>	if ((t = fence) < 0) {
832	>	t = fence = tail;
833	>	cursor = head;
834	>	}
835	>	return t;
836	>	}
837	>
838	>	public DeqSpliterator trySplit() {
839	>	final Object[] es = elements;
840	>	final int i, n;
841	>	return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
842	>	? null
843	>	: new DeqSpliterator(i, cursor = inc(i, n, es.length));
844	>	}
845	>
846	>	public void forEachRemaining(Consumer<? super E> action) {
847	>	if (action == null)
848	>	throw new NullPointerException();
849	>	final int end = getFence(), cursor = this.cursor;
850	>	final Object[] es = elements;
851	>	if (cursor != end) {
852	>	this.cursor = end;
853	>	// null check at both ends of range is sufficient
854	>	if (es[cursor] == null || es[dec(end, es.length)] == null)
855	>	throw new ConcurrentModificationException();
856	>	for (int i = cursor, to = (i <= end) ? end : es.length;
857	>	; i = 0, to = end) {
858	>	for (; i < to; i++)
859	>	action.accept(elementAt(es, i));
860	>	if (to == end) break;
861	>	}
862	>	}
863	>	}
864	>
865	>	public boolean tryAdvance(Consumer<? super E> action) {
866	>	Objects.requireNonNull(action);
867	>	final Object[] es = elements;
868	>	if (fence < 0) { fence = tail; cursor = head; } // late-binding
869	>	final int i;
870	>	if ((i = cursor) == fence)
871	>	return false;
872	>	E e = nonNullElementAt(es, i);
873	>	cursor = inc(i, es.length);
874	>	action.accept(e);
875	>	return true;
876	>	}
877	>
878	>	public long estimateSize() {
879	>	return sub(getFence(), cursor, elements.length);
880	>	}
881	>
882	>	public int characteristics() {
883	>	return Spliterator.NONNULL
884	>	| Spliterator.ORDERED
885	>	| Spliterator.SIZED
886	>	| Spliterator.SUBSIZED;
887	>	}
888	>	}
889	>
890	>	/**
891	>	* @throws NullPointerException {@inheritDoc}
892	>	*/
893	>	public void forEach(Consumer<? super E> action) {
894	>	Objects.requireNonNull(action);
895	>	final Object[] es = elements;
896	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
897	>	; i = 0, to = end) {
898	>	for (; i < to; i++)
899	>	action.accept(elementAt(es, i));
900	>	if (to == end) {
901	>	if (end != tail) throw new ConcurrentModificationException();
902	>	break;
903	>	}
904		}
905	+	// checkInvariants();
906		}
907
908		/**
909	<	* Returns <tt>true</tt> if this deque contains the specified element.
910	<	* More formally, returns <tt>true</tt> if and only if this deque contains
911	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
909	>	* Replaces each element of this deque with the result of applying the
910	>	* operator to that element, as specified by {@link List#replaceAll}.
911	>	*
912	>	* @param operator the operator to apply to each element
913	>	* @since TBD
914	>	*/
915	>	/* public */ void replaceAll(UnaryOperator<E> operator) {
916	>	Objects.requireNonNull(operator);
917	>	final Object[] es = elements;
918	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
919	>	; i = 0, to = end) {
920	>	for (; i < to; i++)
921	>	es[i] = operator.apply(elementAt(es, i));
922	>	if (to == end) {
923	>	if (end != tail) throw new ConcurrentModificationException();
924	>	break;
925	>	}
926	>	}
927	>	// checkInvariants();
928	>	}
929	>
930	>	/**
931	>	* @throws NullPointerException {@inheritDoc}
932	>	*/
933	>	public boolean removeIf(Predicate<? super E> filter) {
934	>	Objects.requireNonNull(filter);
935	>	return bulkRemove(filter);
936	>	}
937	>
938	>	/**
939	>	* @throws NullPointerException {@inheritDoc}
940	>	*/
941	>	public boolean removeAll(Collection<?> c) {
942	>	Objects.requireNonNull(c);
943	>	return bulkRemove(e -> c.contains(e));
944	>	}
945	>
946	>	/**
947	>	* @throws NullPointerException {@inheritDoc}
948	>	*/
949	>	public boolean retainAll(Collection<?> c) {
950	>	Objects.requireNonNull(c);
951	>	return bulkRemove(e -> !c.contains(e));
952	>	}
953	>
954	>	/** Implementation of bulk remove methods. */
955	>	private boolean bulkRemove(Predicate<? super E> filter) {
956	>	// checkInvariants();
957	>	final Object[] es = elements;
958	>	// Optimize for initial run of survivors
959	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
960	>	; i = 0, to = end) {
961	>	for (; i < to; i++)
962	>	if (filter.test(elementAt(es, i)))
963	>	return bulkRemoveModified(filter, i);
964	>	if (to == end) {
965	>	if (end != tail) throw new ConcurrentModificationException();
966	>	break;
967	>	}
968	>	}
969	>	return false;
970	>	}
971	>
972	>	// A tiny bit set implementation
973	>
974	>	private static long[] nBits(int n) {
975	>	return new long[((n - 1) >> 6) + 1];
976	>	}
977	>	private static void setBit(long[] bits, int i) {
978	>	bits[i >> 6] |= 1L << i;
979	>	}
980	>	private static boolean isClear(long[] bits, int i) {
981	>	return (bits[i >> 6] & (1L << i)) == 0;
982	>	}
983	>
984	>	/**
985	>	* Helper for bulkRemove, in case of at least one deletion.
986	>	* Tolerate predicates that reentrantly access the collection for
987	>	* read (but writers still get CME), so traverse once to find
988	>	* elements to delete, a second pass to physically expunge.
989	>	*
990	>	* @param beg valid index of first element to be deleted
991	>	*/
992	>	private boolean bulkRemoveModified(
993	>	Predicate<? super E> filter, final int beg) {
994	>	final Object[] es = elements;
995	>	final int capacity = es.length;
996	>	final int end = tail;
997	>	final long[] deathRow = nBits(sub(end, beg, capacity));
998	>	deathRow[0] = 1L;   // set bit 0
999	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1000	>	; i = 0, to = end, k -= capacity) {
1001	>	for (; i < to; i++)
1002	>	if (filter.test(elementAt(es, i)))
1003	>	setBit(deathRow, i - k);
1004	>	if (to == end) break;
1005	>	}
1006	>	// a two-finger traversal, with hare i reading, tortoise w writing
1007	>	int w = beg;
1008	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1009	>	; w = 0) { // w rejoins i on second leg
1010	>	// In this loop, i and w are on the same leg, with i > w
1011	>	for (; i < to; i++)
1012	>	if (isClear(deathRow, i - k))
1013	>	es[w++] = es[i];
1014	>	if (to == end) break;
1015	>	// In this loop, w is on the first leg, i on the second
1016	>	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1017	>	if (isClear(deathRow, i - k))
1018	>	es[w++] = es[i];
1019	>	if (i >= to) {
1020	>	if (w == capacity) w = 0; // "corner" case
1021	>	break;
1022	>	}
1023	>	}
1024	>	if (end != tail) throw new ConcurrentModificationException();
1025	>	circularClear(es, tail = w, end);
1026	>	// checkInvariants();
1027	>	return true;
1028	>	}
1029	>
1030	>	/**
1031	>	* Returns {@code true} if this deque contains the specified element.
1032	>	* More formally, returns {@code true} if and only if this deque contains
1033	>	* at least one element {@code e} such that {@code o.equals(e)}.
1034		*
1035		* @param o object to be checked for containment in this deque
1036	<	* @return <tt>true</tt> if this deque contains the specified element
1036	>	* @return {@code true} if this deque contains the specified element
1037		*/
1038		public boolean contains(Object o) {
1039	<	if (o == null)
1040	<	return false;
1041	<	int mask = elements.length - 1;
1042	<	int i = head;
1043	<	E x;
1044	<	while ( (x = elements[i]) != null) {
1045	<	if (o.equals(x))
1046	<	return true;
1047	<	i = (i + 1) & mask;
1039	>	if (o != null) {
1040	>	final Object[] es = elements;
1041	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1042	>	; i = 0, to = end) {
1043	>	for (; i < to; i++)
1044	>	if (o.equals(es[i]))
1045	>	return true;
1046	>	if (to == end) break;
1047	>	}
1048		}
1049		return false;
1050		}
#	Line 665 | Line 1052 | public class ArrayDeque<E> extends Abstr
1052		/**
1053		* Removes a single instance of the specified element from this deque.
1054		* If the deque does not contain the element, it is unchanged.
1055	<	* More formally, removes the first element <tt>e</tt> such that
1056	<	* <tt>o.equals(e)</tt> (if such an element exists).
1057	<	* Returns <tt>true</tt> if this deque contained the specified element
1055	>	* More formally, removes the first element {@code e} such that
1056	>	* {@code o.equals(e)} (if such an element exists).
1057	>	* Returns {@code true} if this deque contained the specified element
1058		* (or equivalently, if this deque changed as a result of the call).
1059		*
1060	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1060	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1061		*
1062		* @param o element to be removed from this deque, if present
1063	<	* @return <tt>true</tt> if this deque contained the specified element
1063	>	* @return {@code true} if this deque contained the specified element
1064		*/
1065		public boolean remove(Object o) {
1066		return removeFirstOccurrence(o);
#	Line 684 | Line 1071 | public class ArrayDeque<E> extends Abstr
1071		* The deque will be empty after this call returns.
1072		*/
1073		public void clear() {
1074	<	int h = head;
1075	<	int t = tail;
1076	<	if (h != t) { // clear all cells
1077	<	head = tail = 0;
1078	<	int i = h;
1079	<	int mask = elements.length - 1;
1080	<	do {
1081	<	elements[i] = null;
1082	<	i = (i + 1) & mask;
1083	<	} while (i != t);
1074	>	circularClear(elements, head, tail);
1075	>	head = tail = 0;
1076	>	// checkInvariants();
1077	>	}
1078	>
1079	>	/**
1080	>	* Nulls out slots starting at array index i, upto index end.
1081	>	* Condition i == end means "empty" - nothing to do.
1082	>	*/
1083	>	private static void circularClear(Object[] es, int i, int end) {
1084	>	// assert 0 <= i && i < es.length;
1085	>	// assert 0 <= end && end < es.length;
1086	>	for (int to = (i <= end) ? end : es.length;
1087	>	; i = 0, to = end) {
1088	>	for (; i < to; i++) es[i] = null;
1089	>	if (to == end) break;
1090		}
1091		}
1092
#	Line 711 | Line 1104 | public class ArrayDeque<E> extends Abstr
1104		* @return an array containing all of the elements in this deque
1105		*/
1106		public Object[] toArray() {
1107	<	return copyElements(new Object[size()]);
1107	>	return toArray(Object[].class);
1108	>	}
1109	>
1110	>	private <T> T[] toArray(Class<T[]> klazz) {
1111	>	final Object[] es = elements;
1112	>	final T[] a;
1113	>	final int head = this.head, tail = this.tail, end;
1114	>	if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) {
1115	>	// Uses null extension feature of copyOfRange
1116	>	a = Arrays.copyOfRange(es, head, end, klazz);
1117	>	} else {
1118	>	// integer overflow!
1119	>	a = Arrays.copyOfRange(es, 0, end - head, klazz);
1120	>	System.arraycopy(es, head, a, 0, es.length - head);
1121	>	}
1122	>	if (end != tail)
1123	>	System.arraycopy(es, 0, a, es.length - head, tail);
1124	>	return a;
1125		}
1126
1127		/**
#	Line 725 | Line 1135 | public class ArrayDeque<E> extends Abstr
1135		* <p>If this deque fits in the specified array with room to spare
1136		* (i.e., the array has more elements than this deque), the element in
1137		* the array immediately following the end of the deque is set to
1138	<	* <tt>null</tt>.
1138	>	* {@code null}.
1139		*
1140		* <p>Like the {@link #toArray()} method, this method acts as bridge between
1141		* array-based and collection-based APIs.  Further, this method allows
1142		* precise control over the runtime type of the output array, and may,
1143		* under certain circumstances, be used to save allocation costs.
1144		*
1145	<	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
1145	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1146		* The following code can be used to dump the deque into a newly
1147	<	* allocated array of <tt>String</tt>:
1147	>	* allocated array of {@code String}:
1148		*
1149	<	* <pre>
740	<	*     String[] y = x.toArray(new String[0]);</pre>
1149	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1150		*
1151	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
1152	<	* <tt>toArray()</tt>.
1151	>	* Note that {@code toArray(new Object[0])} is identical in function to
1152	>	* {@code toArray()}.
1153		*
1154		* @param a the array into which the elements of the deque are to
1155		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 751 | Line 1160 | public class ArrayDeque<E> extends Abstr
1160		*         this deque
1161		* @throws NullPointerException if the specified array is null
1162		*/
1163	+	@SuppressWarnings("unchecked")
1164		public <T> T[] toArray(T[] a) {
1165	<	int size = size();
1166	<	if (a.length < size)
1167	<	a = (T[])java.lang.reflect.Array.newInstance(
1168	<	a.getClass().getComponentType(), size);
1169	<	copyElements(a);
1170	<	if (a.length > size)
1165	>	final int size;
1166	>	if ((size = size()) > a.length)
1167	>	return toArray((Class<T[]>) a.getClass());
1168	>	final Object[] es = elements;
1169	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1170	>	; i = 0, len = tail) {
1171	>	System.arraycopy(es, i, a, j, len);
1172	>	if ((j += len) == size) break;
1173	>	}
1174	>	if (size < a.length)
1175		a[size] = null;
1176		return a;
1177		}
#	Line 771 | Line 1185 | public class ArrayDeque<E> extends Abstr
1185		*/
1186		public ArrayDeque<E> clone() {
1187		try {
1188	+	@SuppressWarnings("unchecked")
1189		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1190	<	// These two lines are currently faster than cloning the array:
776	<	result.elements = (E[]) new Object[elements.length];
777	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
1190	>	result.elements = Arrays.copyOf(elements, elements.length);
1191		return result;
779	–
1192		} catch (CloneNotSupportedException e) {
1193		throw new AssertionError();
1194		}
1195		}
1196
785	–	/**
786	–	* Appease the serialization gods.
787	–	*/
1197		private static final long serialVersionUID = 2340985798034038923L;
1198
1199		/**
1200	<	* Serialize this deque.
1200	>	* Saves this deque to a stream (that is, serializes it).
1201		*
1202	<	* @serialData The current size (<tt>int</tt>) of the deque,
1202	>	* @param s the stream
1203	>	* @throws java.io.IOException if an I/O error occurs
1204	>	* @serialData The current size ({@code int}) of the deque,
1205		* followed by all of its elements (each an object reference) in
1206		* first-to-last order.
1207		*/
1208	<	private void writeObject(ObjectOutputStream s) throws IOException {
1208	>	private void writeObject(java.io.ObjectOutputStream s)
1209	>	throws java.io.IOException {
1210		s.defaultWriteObject();
1211
1212		// Write out size
1213	<	int size = size();
802	<	s.writeInt(size);
1213	>	s.writeInt(size());
1214
1215		// Write out elements in order.
1216	<	int i = head;
1217	<	int mask = elements.length - 1;
1218	<	for (int j = 0; j < size; j++) {
1219	<	s.writeObject(elements[i]);
1220	<	i = (i + 1) & mask;
1216	>	final Object[] es = elements;
1217	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1218	>	; i = 0, to = end) {
1219	>	for (; i < to; i++)
1220	>	s.writeObject(es[i]);
1221	>	if (to == end) break;
1222		}
1223		}
1224
1225		/**
1226	<	* Deserialize this deque.
1226	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1227	>	* @param s the stream
1228	>	* @throws ClassNotFoundException if the class of a serialized object
1229	>	*         could not be found
1230	>	* @throws java.io.IOException if an I/O error occurs
1231		*/
1232	<	private void readObject(ObjectInputStream s)
1233	<	throws IOException, ClassNotFoundException {
1232	>	private void readObject(java.io.ObjectInputStream s)
1233	>	throws java.io.IOException, ClassNotFoundException {
1234		s.defaultReadObject();
1235
1236		// Read in size and allocate array
1237		int size = s.readInt();
1238	<	allocateElements(size);
1239	<	head = 0;
824	<	tail = size;
1238	>	elements = new Object[size + 1];
1239	>	this.tail = size;
1240
1241		// Read in all elements in the proper order.
1242		for (int i = 0; i < size; i++)
1243	<	elements[i] = (E)s.readObject();
1243	>	elements[i] = s.readObject();
1244	>	}
1245
1246	+	/** debugging */
1247	+	void checkInvariants() {
1248	+	// Use head and tail fields with empty slot at tail strategy.
1249	+	// head == tail disambiguates to "empty".
1250	+	try {
1251	+	int capacity = elements.length;
1252	+	// assert 0 <= head && head < capacity;
1253	+	// assert 0 <= tail && tail < capacity;
1254	+	// assert capacity > 0;
1255	+	// assert size() < capacity;
1256	+	// assert head == tail || elements[head] != null;
1257	+	// assert elements[tail] == null;
1258	+	// assert head == tail || elements[dec(tail, capacity)] != null;
1259	+	} catch (Throwable t) {
1260	+	System.err.printf("head=%d tail=%d capacity=%d%n",
1261	+	head, tail, elements.length);
1262	+	System.err.printf("elements=%s%n",
1263	+	Arrays.toString(elements));
1264	+	throw t;
1265	+	}
1266		}
1267	+
1268		}

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