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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.24 by dl, Sat Sep 17 13:21:19 2005 UTC vs.
Revision 1.110 by jsr166, Sat Nov 5 17:45:44 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.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}/../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
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.
72	+	*/
73	+
74		/**
75		* The array in which the elements of 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
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.
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;
82	<
83	<	/**
84	<	* The minimum capacity that we'll use for a newly created deque.
85	<	* Must be a power of 2.
86	<	*/
87	<	private static final int MIN_INITIAL_CAPACITY = 8;
88	<
89	<	// ******  Array allocation and resizing utilities ******
93	>	transient int tail;
94
95		/**
96	<	* Allocate empty array to hold the given number of elements.
97	<	*
98	<	* @param numElements  the number of elements to hold
99	<	*/
100	<	private void allocateElements(int numElements) {
101	<	int initialCapacity = MIN_INITIAL_CAPACITY;
102	<	// Find the best power of two to hold elements.
103	<	// Tests "<=" because arrays aren't kept full.
104	<	if (numElements >= initialCapacity) {
105	<	initialCapacity = numElements;
106	<	initialCapacity |= (initialCapacity >>>  1);
107	<	initialCapacity |= (initialCapacity >>>  2);
108	<	initialCapacity |= (initialCapacity >>>  4);
109	<	initialCapacity |= (initialCapacity >>>  8);
110	<	initialCapacity |= (initialCapacity >>> 16);
111	<	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
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;
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	<	* 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.
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);
148	<	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		/**
#	Line 155 | Line 177 | public class ArrayDeque<E> extends Abstr
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 179 | 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.
#	Line 196 | Line 277 | public class ArrayDeque<E> extends Abstr
277		public void addFirst(E e) {
278		if (e == null)
279		throw new NullPointerException();
280	<	elements[head = (head - 1) & (elements.length - 1)] = e;
280	>	final Object[] es = elements;
281	>	es[head = dec(head, es.length)] = e;
282		if (head == tail)
283	<	doubleCapacity();
283	>	grow(1);
284	>	// checkInvariants();
285		}
286
287		/**
#	Line 212 | Line 295 | public class ArrayDeque<E> extends Abstr
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	>	* 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	>	* @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 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		* Inserts the specified element at the front of this deque.
327		*
328		* @param e the element to add
329	<	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
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) {
#	Line 233 | Line 338 | public class ArrayDeque<E> extends Abstr
338		* Inserts the specified element at the end of this deque.
339		*
340		* @param e the element to add
341	<	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
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) {
#	Line 245 | Line 350 | public class ArrayDeque<E> extends Abstr
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		* @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		public E pollFirst() {
372	<	int h = head;
373	<	E result = elements[h]; // Element is null if deque empty
374	<	if (result == null)
375	<	return null;
376	<	elements[h] = null;     // Must null out slot
377	<	head = (h + 1) & (elements.length - 1);
378	<	return result;
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		public E pollLast() {
384	<	int t = (tail - 1) & (elements.length - 1);
385	<	E result = elements[t];
386	<	if (result == null)
387	<	return null;
388	<	elements[t] = null;
389	<	tail = t;
390	<	return result;
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		* @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		* @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	<	return elements[head]; // elements[head] is null if deque empty
417	>	// checkInvariants();
418	>	return elementAt(elements, head);
419		}
420
421		public E peekLast() {
422	<	return elements[(tail - 1) & (elements.length - 1)];
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).
430		* If the deque does not contain the element, it is unchanged.
431	<	* More formally, removes the first element <tt>e</tt> such that
432	<	* <tt>o.equals(e)</tt> (if such an element exists).
433	<	* Returns <tt>true</tt> if this deque contained the specified element
431	>	* More formally, removes the first element {@code e} such that
432	>	* {@code o.equals(e)} (if such an element exists).
433	>	* Returns {@code true} if this deque contained the specified element
434		* (or equivalently, if this deque changed as a result of the call).
435		*
436		* @param o element to be removed from this deque, if present
437	<	* @return <tt>true</tt> if the deque contained the specified element
437	>	* @return {@code true} if the deque contained the specified element
438		*/
439		public boolean removeFirstOccurrence(Object o) {
440	<	if (o == null)
441	<	return false;
442	<	int mask = elements.length - 1;
443	<	int i = head;
444	<	E x;
445	<	while ( (x = elements[i]) != null) {
446	<	if (o.equals(x)) {
447	<	delete(i);
448	<	return true;
440	>	if (o != null) {
441	>	final Object[] es = elements;
442	>	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		}
335	–	i = (i + 1) & mask;
451		}
452		return false;
453		}
#	Line 341 | Line 456 | public class ArrayDeque<E> extends Abstr
456		* Removes the last occurrence of the specified element in this
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 <tt>e</tt> such that
460	<	* <tt>o.equals(e)</tt> (if such an element exists).
461	<	* Returns <tt>true</tt> if this deque contained the specified element
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 <tt>true</tt> if the deque contained the specified element
465	>	* @return {@code true} if the deque contained the specified element
466		*/
467		public boolean removeLastOccurrence(Object o) {
468	<	if (o == null)
469	<	return false;
470	<	int mask = elements.length - 1;
471	<	int i = (tail - 1) & mask;
472	<	E x;
473	<	while ( (x = elements[i]) != null) {
474	<	if (o.equals(x)) {
475	<	delete(i);
476	<	return true;
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		}
363	–	i = (i - 1) & mask;
479		}
480		return false;
481		}
#	Line 373 | Line 488 | public class ArrayDeque<E> extends Abstr
488		* <p>This method is equivalent to {@link #addLast}.
489		*
490		* @param e the element to add
491	<	* @return <tt>true</tt> (as specified by {@link Collection#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) {
#	Line 387 | Line 502 | public class ArrayDeque<E> extends Abstr
502		* <p>This method is equivalent to {@link #offerLast}.
503		*
504		* @param e the element to add
505	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
505	>	* @return {@code true} (as specified by {@link Queue#offer})
506		* @throws NullPointerException if the specified element is null
507		*/
508		public boolean offer(E e) {
#	Line 412 | Line 527 | public class ArrayDeque<E> extends Abstr
527		/**
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	<	* <tt>null</tt> if this deque is empty.
530	>	* {@code null} if this deque is empty.
531		*
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 poll() {
538		return pollFirst();
#	Line 439 | Line 554 | public class ArrayDeque<E> extends Abstr
554
555		/**
556		* Retrieves, but does not remove, the head of the queue represented by
557	<	* this deque, or returns <tt>null</tt> if this deque is empty.
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	<	*         <tt>null</tt> if this deque is empty
562	>	*         {@code null} if this deque is empty
563		*/
564		public E peek() {
565		return peekFirst();
#	Line 480 | Line 595 | public class ArrayDeque<E> extends Abstr
595		}
596
597		/**
598	<	* Removes the element at the specified position in the elements array,
599	<	* adjusting head and tail as necessary.  This can result in motion of
600	<	* elements backwards or forwards in the array.
598	>	* Removes the element at the specified position in the elements array.
599	>	* This can result in forward or backwards motion of array elements.
600	>	* We optimize for least element motion.
601		*
602		* <p>This method is called delete rather than remove to emphasize
603		* that its semantics differ from those of {@link List#remove(int)}.
604		*
605	<	* @return true if elements moved backwards
605	>	* @return true if elements near tail moved backwards
606		*/
607	<	private boolean delete(int i) {
608	<	final E[] elements = this.elements;
609	<	final int mask = elements.length - 1;
610	<	final int h = head;
611	<	final int t = tail;
612	<	final int front = (i - h) & mask;
613	<	final int back  = (t - i) & mask;
614	<
615	<	// Invariant: head <= i < tail mod circularity
616	<	if (front >= ((t - h) & mask))
617	<	throw new ConcurrentModificationException();
618	<
619	<	// Optimize for least element motion
620	<	if (front < back) {
621	<	if (h <= i) {
622	<	System.arraycopy(elements, h, elements, h + 1, front);
623	<	} else { // Wrap around
624	<	System.arraycopy(elements, 0, elements, 1, i);
625	<	elements[0] = elements[mask];
626	<	System.arraycopy(elements, h, elements, h + 1, mask - h);
627	<	}
628	<	elements[h] = null;
629	<	head = (h + 1) & mask;
630	<	return false;
631	<	} else {
632	<	if (i < t) { // Copy the null tail as well
633	<	System.arraycopy(elements, i + 1, elements, i, back);
634	<	tail = t - 1;
635	<	} else { // Wrap around
636	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
637	<	elements[mask] = elements[0];
638	<	System.arraycopy(elements, 1, elements, 0, t);
639	<	tail = (t - 1) & mask;
640	<	}
641	<	return true;
642	<	}
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	>	}
643		}
644
645		// *** Collection Methods ***
#	Line 535 | 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 deque contains no elements.
657	>	* Returns {@code true} if this deque contains no elements.
658		*
659	<	* @return <tt>true</tt> if this deque contains no elements
659	>	* @return {@code true} if this deque contains no elements
660		*/
661		public boolean isEmpty() {
662		return head == tail;
#	Line 564 | Line 679 | public class ArrayDeque<E> extends Abstr
679		}
680
681		private class DeqIterator implements Iterator<E> {
682	<	/**
683	<	* Index of element to be returned by subsequent call to next.
569	<	*/
570	<	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
574	<	* iterator and also to check for comodification.
575	<	*/
576	<	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	>	DeqIterator() { cursor = head; }
695
696	<	public boolean hasNext() {
697	<	return cursor != fence;
696	>	public final boolean hasNext() {
697	>	return remaining > 0;
698		}
699
700		public E next() {
701	<	E result;
590	<	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
594	<	if (tail != fence || (result = elements[cursor]) == null)
595	<	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	<	public void remove() {
711	>	void postDelete(boolean leftShifted) {
712	>	if (leftShifted)
713	>	cursor = dec(cursor, elements.length);
714	>	}
715	>
716	>	public final void remove() {
717		if (lastRet < 0)
718		throw new IllegalStateException();
719	<	if (delete(lastRet)) // if left-shifted, undo increment in next()
605	<	cursor = (cursor - 1) & (elements.length - 1);
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	<	private class DescendingIterator implements Iterator<E> {
750	<	/*
751	<	* This class is nearly a mirror-image of DeqIterator, using
752	<	* (tail-1) instead of head for initial cursor, (head-1)
753	<	* instead of tail for fence, and elements.length instead of -1
754	<	* for sentinel. It shares the same structure, but not many
755	<	* actual lines of code.
756	<	*/
757	<	private int cursor = (tail - 1) & (elements.length - 1);
758	<	private int fence =  (head - 1) & (elements.length - 1);
622	<	private int lastRet = elements.length;
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	<	public boolean hasNext() {
761	<	return cursor != fence;
760	>	void postDelete(boolean leftShifted) {
761	>	if (!leftShifted)
762	>	cursor = inc(cursor, elements.length);
763		}
764
765	<	public E next() {
766	<	E result;
767	<	if (cursor == fence)
768	<	throw new NoSuchElementException();
769	<	if (((head - 1) & (elements.length - 1)) != fence ||
770	<	(result = elements[cursor]) == null)
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	<	lastRet = cursor;
775	<	cursor = (cursor - 1) & (elements.length - 1);
776	<	return result;
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 = head;
783	>	break;
784	>	}
785	>	}
786		}
787	+	}
788
789	<	public void remove() {
790	<	if (lastRet >= elements.length)
791	<	throw new IllegalStateException();
792	<	if (!delete(lastRet))
793	<	cursor = (cursor + 1) & (elements.length - 1);
794	<	lastRet = elements.length;
795	<	fence = (head - 1) & (elements.length - 1);
789	>	/**
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, to);
954	>	if (to == end) {
955	>	if (end != tail) throw new ConcurrentModificationException();
956	>	break;
957	>	}
958	>	}
959	>	return false;
960	>	}
961	>
962	>	/**
963	>	* Helper for bulkRemove, in case of at least one deletion.
964	>	* @param i valid index of first element to be deleted
965	>	*/
966	>	private boolean bulkRemoveModified(
967	>	Predicate<? super E> filter, int i, int to) {
968	>	final Object[] es = elements;
969	>	final int capacity = es.length;
970	>	// a two-finger algorithm, with hare i reading, tortoise j writing
971	>	int j = i++;
972	>	final int end = tail;
973	>	try {
974	>	for (;; j = 0) {    // j rejoins i on second leg
975	>	E e;
976	>	// In this loop, i and j are on the same leg, with i > j
977	>	for (; i < to; i++)
978	>	if (!filter.test(e = elementAt(es, i)))
979	>	es[j++] = e;
980	>	if (to == end) break;
981	>	// In this loop, j is on the first leg, i on the second
982	>	for (i = 0, to = end; i < to && j < capacity; i++)
983	>	if (!filter.test(e = elementAt(es, i)))
984	>	es[j++] = e;
985	>	if (i >= to) {
986	>	if (j == capacity) j = 0; // "corner" case
987	>	break;
988	>	}
989	>	}
990	>	return true;
991	>	} catch (Throwable ex) {
992	>	// copy remaining elements
993	>	for (; i != end; i = inc(i, capacity), j = inc(j, capacity))
994	>	es[j] = es[i];
995	>	throw ex;
996	>	} finally {
997	>	if (end != tail) throw new ConcurrentModificationException();
998	>	circularClear(es, tail = j, end);
999	>	// checkInvariants();
1000		}
1001		}
1002
1003		/**
1004	<	* Returns <tt>true</tt> if this deque contains the specified element.
1005	<	* More formally, returns <tt>true</tt> if and only if this deque contains
1006	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
1004	>	* Returns {@code true} if this deque contains the specified element.
1005	>	* More formally, returns {@code true} if and only if this deque contains
1006	>	* at least one element {@code e} such that {@code o.equals(e)}.
1007		*
1008		* @param o object to be checked for containment in this deque
1009	<	* @return <tt>true</tt> if this deque contains the specified element
1009	>	* @return {@code true} if this deque contains the specified element
1010		*/
1011		public boolean contains(Object o) {
1012	<	if (o == null)
1013	<	return false;
1014	<	int mask = elements.length - 1;
1015	<	int i = head;
1016	<	E x;
1017	<	while ( (x = elements[i]) != null) {
1018	<	if (o.equals(x))
1019	<	return true;
1020	<	i = (i + 1) & mask;
1012	>	if (o != null) {
1013	>	final Object[] es = elements;
1014	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1015	>	; i = 0, to = end) {
1016	>	for (; i < to; i++)
1017	>	if (o.equals(es[i]))
1018	>	return true;
1019	>	if (to == end) break;
1020	>	}
1021		}
1022		return false;
1023		}
#	Line 672 | Line 1025 | public class ArrayDeque<E> extends Abstr
1025		/**
1026		* Removes a single instance of the specified element from this deque.
1027		* If the deque does not contain the element, it is unchanged.
1028	<	* More formally, removes the first element <tt>e</tt> such that
1029	<	* <tt>o.equals(e)</tt> (if such an element exists).
1030	<	* Returns <tt>true</tt> if this deque contained the specified element
1028	>	* More formally, removes the first element {@code e} such that
1029	>	* {@code o.equals(e)} (if such an element exists).
1030	>	* Returns {@code true} if this deque contained the specified element
1031		* (or equivalently, if this deque changed as a result of the call).
1032		*
1033	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1033	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1034		*
1035		* @param o element to be removed from this deque, if present
1036	<	* @return <tt>true</tt> if this deque contained the specified element
1036	>	* @return {@code true} if this deque contained the specified element
1037		*/
1038		public boolean remove(Object o) {
1039		return removeFirstOccurrence(o);
#	Line 691 | Line 1044 | public class ArrayDeque<E> extends Abstr
1044		* The deque will be empty after this call returns.
1045		*/
1046		public void clear() {
1047	<	int h = head;
1048	<	int t = tail;
1049	<	if (h != t) { // clear all cells
1050	<	head = tail = 0;
1051	<	int i = h;
1052	<	int mask = elements.length - 1;
1053	<	do {
1054	<	elements[i] = null;
1055	<	i = (i + 1) & mask;
1056	<	} while (i != t);
1047	>	circularClear(elements, head, tail);
1048	>	head = tail = 0;
1049	>	// checkInvariants();
1050	>	}
1051	>
1052	>	/**
1053	>	* Nulls out slots starting at array index i, upto index end.
1054	>	*/
1055	>	private static void circularClear(Object[] es, int i, int end) {
1056	>	for (int to = (i <= end) ? end : es.length;
1057	>	; i = 0, to = end) {
1058	>	Arrays.fill(es, i, to, null);
1059	>	if (to == end) break;
1060		}
1061		}
1062
#	Line 718 | Line 1074 | public class ArrayDeque<E> extends Abstr
1074		* @return an array containing all of the elements in this deque
1075		*/
1076		public Object[] toArray() {
1077	<	return copyElements(new Object[size()]);
1077	>	return toArray(Object[].class);
1078	>	}
1079	>
1080	>	private <T> T[] toArray(Class<T[]> klazz) {
1081	>	final Object[] es = elements;
1082	>	final T[] a;
1083	>	final int size = size(), head = this.head, end;
1084	>	final int len = Math.min(size, es.length - head);
1085	>	if ((end = head + size) >= 0) {
1086	>	a = Arrays.copyOfRange(es, head, end, klazz);
1087	>	} else {
1088	>	// integer overflow!
1089	>	a = Arrays.copyOfRange(es, 0, size, klazz);
1090	>	System.arraycopy(es, head, a, 0, len);
1091	>	}
1092	>	if (tail < head)
1093	>	System.arraycopy(es, 0, a, len, tail);
1094	>	return a;
1095		}
1096
1097		/**
#	Line 732 | Line 1105 | public class ArrayDeque<E> extends Abstr
1105		* <p>If this deque fits in the specified array with room to spare
1106		* (i.e., the array has more elements than this deque), the element in
1107		* the array immediately following the end of the deque is set to
1108	<	* <tt>null</tt>.
1108	>	* {@code null}.
1109		*
1110		* <p>Like the {@link #toArray()} method, this method acts as bridge between
1111		* array-based and collection-based APIs.  Further, this method allows
1112		* precise control over the runtime type of the output array, and may,
1113		* under certain circumstances, be used to save allocation costs.
1114		*
1115	<	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
1115	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1116		* The following code can be used to dump the deque into a newly
1117	<	* allocated array of <tt>String</tt>:
1117	>	* allocated array of {@code String}:
1118		*
1119	<	* <pre>
747	<	*     String[] y = x.toArray(new String[0]);</pre>
1119	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1120		*
1121	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
1122	<	* <tt>toArray()</tt>.
1121	>	* Note that {@code toArray(new Object[0])} is identical in function to
1122	>	* {@code toArray()}.
1123		*
1124		* @param a the array into which the elements of the deque are to
1125		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 758 | Line 1130 | public class ArrayDeque<E> extends Abstr
1130		*         this deque
1131		* @throws NullPointerException if the specified array is null
1132		*/
1133	+	@SuppressWarnings("unchecked")
1134		public <T> T[] toArray(T[] a) {
1135	<	int size = size();
1136	<	if (a.length < size)
1137	<	a = (T[])java.lang.reflect.Array.newInstance(
1138	<	a.getClass().getComponentType(), size);
1139	<	copyElements(a);
1140	<	if (a.length > size)
1135	>	final int size;
1136	>	if ((size = size()) > a.length)
1137	>	return toArray((Class<T[]>) a.getClass());
1138	>	final Object[] es = elements;
1139	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1140	>	; i = 0, len = tail) {
1141	>	System.arraycopy(es, i, a, j, len);
1142	>	if ((j += len) == size) break;
1143	>	}
1144	>	if (size < a.length)
1145		a[size] = null;
1146		return a;
1147		}
#	Line 778 | Line 1155 | public class ArrayDeque<E> extends Abstr
1155		*/
1156		public ArrayDeque<E> clone() {
1157		try {
1158	+	@SuppressWarnings("unchecked")
1159		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1160	<	// These two lines are currently faster than cloning the array:
783	<	result.elements = (E[]) new Object[elements.length];
784	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
1160	>	result.elements = Arrays.copyOf(elements, elements.length);
1161		return result;
786	–
1162		} catch (CloneNotSupportedException e) {
1163		throw new AssertionError();
1164		}
1165		}
1166
792	–	/**
793	–	* Appease the serialization gods.
794	–	*/
1167		private static final long serialVersionUID = 2340985798034038923L;
1168
1169		/**
1170	<	* Serialize this deque.
1170	>	* Saves this deque to a stream (that is, serializes it).
1171		*
1172	<	* @serialData The current size (<tt>int</tt>) of the deque,
1172	>	* @param s the stream
1173	>	* @throws java.io.IOException if an I/O error occurs
1174	>	* @serialData The current size ({@code int}) of the deque,
1175		* followed by all of its elements (each an object reference) in
1176		* first-to-last order.
1177		*/
1178	<	private void writeObject(ObjectOutputStream s) throws IOException {
1178	>	private void writeObject(java.io.ObjectOutputStream s)
1179	>	throws java.io.IOException {
1180		s.defaultWriteObject();
1181
1182		// Write out size
1183		s.writeInt(size());
1184
1185		// Write out elements in order.
1186	<	int mask = elements.length - 1;
1187	<	for (int i = head; i != tail; i = (i + 1) & mask)
1188	<	s.writeObject(elements[i]);
1186	>	final Object[] es = elements;
1187	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1188	>	; i = 0, to = end) {
1189	>	for (; i < to; i++)
1190	>	s.writeObject(es[i]);
1191	>	if (to == end) break;
1192	>	}
1193		}
1194
1195		/**
1196	<	* Deserialize this deque.
1196	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1197	>	* @param s the stream
1198	>	* @throws ClassNotFoundException if the class of a serialized object
1199	>	*         could not be found
1200	>	* @throws java.io.IOException if an I/O error occurs
1201		*/
1202	<	private void readObject(ObjectInputStream s)
1203	<	throws IOException, ClassNotFoundException {
1202	>	private void readObject(java.io.ObjectInputStream s)
1203	>	throws java.io.IOException, ClassNotFoundException {
1204		s.defaultReadObject();
1205
1206		// Read in size and allocate array
1207		int size = s.readInt();
1208	<	allocateElements(size);
1209	<	head = 0;
827	<	tail = size;
1208	>	elements = new Object[size + 1];
1209	>	this.tail = size;
1210
1211		// Read in all elements in the proper order.
1212		for (int i = 0; i < size; i++)
1213	<	elements[i] = (E)s.readObject();
1213	>	elements[i] = s.readObject();
1214	>	}
1215
1216	+	/** debugging */
1217	+	void checkInvariants() {
1218	+	try {
1219	+	int capacity = elements.length;
1220	+	// assert head >= 0 && head < capacity;
1221	+	// assert tail >= 0 && tail < capacity;
1222	+	// assert capacity > 0;
1223	+	// assert size() < capacity;
1224	+	// assert head == tail || elements[head] != null;
1225	+	// assert elements[tail] == null;
1226	+	// assert head == tail || elements[dec(tail, capacity)] != null;
1227	+	} catch (Throwable t) {
1228	+	System.err.printf("head=%d tail=%d capacity=%d%n",
1229	+	head, tail, elements.length);
1230	+	System.err.printf("elements=%s%n",
1231	+	Arrays.toString(elements));
1232	+	throw t;
1233	+	}
1234		}
1235	+
1236		}

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