ViewVC Help

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

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

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.21 by dl, Fri Sep 16 23:17:05 2005 UTC vs.
Revision 1.138 by jsr166, Fri Aug 30 18:05:38 2019 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	>	// OPENJDK import jdk.internal.access.SharedSecrets;
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.base/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 + 1];
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());
211	<	addAll(c);
210	>	this(c.size());
211	>	copyElements(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,
#	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	>	copyElements(c);
328	>	// checkInvariants();
329	>	return size() > s;
330	>	}
331	>
332	>	private void copyElements(Collection<? extends E> c) {
333	>	c.forEach(this::addLast);
334		}
335
336		/**
337		* Inserts the specified element at the front of this deque.
338		*
339		* @param e the element to add
340	<	* @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
340	>	* @return {@code true} (as specified by {@link Deque#offerFirst})
341		* @throws NullPointerException if the specified element is null
342		*/
343		public boolean offerFirst(E e) {
#	Line 233 | Line 349 | public class ArrayDeque<E> extends Abstr
349		* Inserts the specified element at the end of this deque.
350		*
351		* @param e the element to add
352	<	* @return <tt>true</tt> (as specified by {@link Deque#offerLast})
352	>	* @return {@code true} (as specified by {@link Deque#offerLast})
353		* @throws NullPointerException if the specified element is null
354		*/
355		public boolean offerLast(E e) {
#	Line 245 | Line 361 | public class ArrayDeque<E> extends Abstr
361		* @throws NoSuchElementException {@inheritDoc}
362		*/
363		public E removeFirst() {
364	<	E x = pollFirst();
365	<	if (x == null)
364	>	E e = pollFirst();
365	>	if (e == null)
366		throw new NoSuchElementException();
367	<	return x;
367	>	// checkInvariants();
368	>	return e;
369		}
370
371		/**
372		* @throws NoSuchElementException {@inheritDoc}
373		*/
374		public E removeLast() {
375	<	E x = pollLast();
376	<	if (x == null)
375	>	E e = pollLast();
376	>	if (e == null)
377		throw new NoSuchElementException();
378	<	return x;
378	>	// checkInvariants();
379	>	return e;
380		}
381
382		public E pollFirst() {
383	<	int h = head;
384	<	E result = elements[h]; // Element is null if deque empty
385	<	if (result == null)
386	<	return null;
387	<	elements[h] = null;     // Must null out slot
388	<	head = (h + 1) & (elements.length - 1);
389	<	return result;
383	>	final Object[] es;
384	>	final int h;
385	>	E e = elementAt(es = elements, h = head);
386	>	if (e != null) {
387	>	es[h] = null;
388	>	head = inc(h, es.length);
389	>	}
390	>	// checkInvariants();
391	>	return e;
392		}
393
394		public E pollLast() {
395	<	int t = (tail - 1) & (elements.length - 1);
396	<	E result = elements[t];
397	<	if (result == null)
398	<	return null;
399	<	elements[t] = null;
400	<	tail = t;
401	<	return result;
395	>	final Object[] es;
396	>	final int t;
397	>	E e = elementAt(es = elements, t = dec(tail, es.length));
398	>	if (e != null)
399	>	es[tail = t] = null;
400	>	// checkInvariants();
401	>	return e;
402		}
403
404		/**
405		* @throws NoSuchElementException {@inheritDoc}
406		*/
407		public E getFirst() {
408	<	E x = elements[head];
409	<	if (x == null)
408	>	E e = elementAt(elements, head);
409	>	if (e == null)
410		throw new NoSuchElementException();
411	<	return x;
411	>	// checkInvariants();
412	>	return e;
413		}
414
415		/**
416		* @throws NoSuchElementException {@inheritDoc}
417		*/
418		public E getLast() {
419	<	E x = elements[(tail - 1) & (elements.length - 1)];
420	<	if (x == null)
419	>	final Object[] es = elements;
420	>	E e = elementAt(es, dec(tail, es.length));
421	>	if (e == null)
422		throw new NoSuchElementException();
423	<	return x;
423	>	// checkInvariants();
424	>	return e;
425		}
426
427		public E peekFirst() {
428	<	return elements[head]; // elements[head] is null if deque empty
428	>	// checkInvariants();
429	>	return elementAt(elements, head);
430		}
431
432		public E peekLast() {
433	<	return elements[(tail - 1) & (elements.length - 1)];
433	>	// checkInvariants();
434	>	final Object[] es;
435	>	return elementAt(es = elements, dec(tail, es.length));
436		}
437
438		/**
439		* Removes the first occurrence of the specified element in this
440		* deque (when traversing the deque from head to tail).
441		* If the deque does not contain the element, it is unchanged.
442	<	* More formally, removes the first element <tt>e</tt> such that
443	<	* <tt>o.equals(e)</tt> (if such an element exists).
444	<	* Returns <tt>true</tt> if this deque contained the specified element
442	>	* More formally, removes the first element {@code e} such that
443	>	* {@code o.equals(e)} (if such an element exists).
444	>	* Returns {@code true} if this deque contained the specified element
445		* (or equivalently, if this deque changed as a result of the call).
446		*
447		* @param o element to be removed from this deque, if present
448	<	* @return <tt>true</tt> if the deque contained the specified element
448	>	* @return {@code true} if the deque contained the specified element
449		*/
450		public boolean removeFirstOccurrence(Object o) {
451	<	if (o == null)
452	<	return false;
453	<	int mask = elements.length - 1;
454	<	int i = head;
455	<	E x;
456	<	while ( (x = elements[i]) != null) {
457	<	if (o.equals(x)) {
458	<	delete(i);
459	<	return true;
451	>	if (o != null) {
452	>	final Object[] es = elements;
453	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
454	>	; i = 0, to = end) {
455	>	for (; i < to; i++)
456	>	if (o.equals(es[i])) {
457	>	delete(i);
458	>	return true;
459	>	}
460	>	if (to == end) break;
461		}
335	–	i = (i + 1) & mask;
462		}
463		return false;
464		}
#	Line 341 | Line 467 | public class ArrayDeque<E> extends Abstr
467		* Removes the last occurrence of the specified element in this
468		* deque (when traversing the deque from head to tail).
469		* If the deque does not contain the element, it is unchanged.
470	<	* More formally, removes the last element <tt>e</tt> such that
471	<	* <tt>o.equals(e)</tt> (if such an element exists).
472	<	* Returns <tt>true</tt> if this deque contained the specified element
470	>	* More formally, removes the last element {@code e} such that
471	>	* {@code o.equals(e)} (if such an element exists).
472	>	* Returns {@code true} if this deque contained the specified element
473		* (or equivalently, if this deque changed as a result of the call).
474		*
475		* @param o element to be removed from this deque, if present
476	<	* @return <tt>true</tt> if the deque contained the specified element
476	>	* @return {@code true} if the deque contained the specified element
477		*/
478		public boolean removeLastOccurrence(Object o) {
479	<	if (o == null)
480	<	return false;
481	<	int mask = elements.length - 1;
482	<	int i = (tail - 1) & mask;
483	<	E x;
484	<	while ( (x = elements[i]) != null) {
485	<	if (o.equals(x)) {
486	<	delete(i);
487	<	return true;
479	>	if (o != null) {
480	>	final Object[] es = elements;
481	>	for (int i = tail, end = head, to = (i >= end) ? end : 0;
482	>	; i = es.length, to = end) {
483	>	for (i--; i > to - 1; i--)
484	>	if (o.equals(es[i])) {
485	>	delete(i);
486	>	return true;
487	>	}
488	>	if (to == end) break;
489		}
363	–	i = (i - 1) & mask;
490		}
491		return false;
492		}
#	Line 373 | Line 499 | public class ArrayDeque<E> extends Abstr
499		* <p>This method is equivalent to {@link #addLast}.
500		*
501		* @param e the element to add
502	<	* @return <tt>true</tt> (as specified by {@link Collection#add})
502	>	* @return {@code true} (as specified by {@link Collection#add})
503		* @throws NullPointerException if the specified element is null
504		*/
505		public boolean add(E e) {
#	Line 387 | Line 513 | public class ArrayDeque<E> extends Abstr
513		* <p>This method is equivalent to {@link #offerLast}.
514		*
515		* @param e the element to add
516	<	* @return <tt>true</tt> (as specified by {@link Queue#offer})
516	>	* @return {@code true} (as specified by {@link Queue#offer})
517		* @throws NullPointerException if the specified element is null
518		*/
519		public boolean offer(E e) {
#	Line 397 | Line 523 | public class ArrayDeque<E> extends Abstr
523		/**
524		* Retrieves and removes the head of the queue represented by this deque.
525		*
526	<	* This method differs from {@link #poll poll} only in that it throws an
527	<	* exception if this deque is empty.
526	>	* This method differs from {@link #poll() poll()} only in that it
527	>	* throws an exception if this deque is empty.
528		*
529		* <p>This method is equivalent to {@link #removeFirst}.
530		*
#	Line 412 | Line 538 | public class ArrayDeque<E> extends Abstr
538		/**
539		* Retrieves and removes the head of the queue represented by this deque
540		* (in other words, the first element of this deque), or returns
541	<	* <tt>null</tt> if this deque is empty.
541	>	* {@code null} if this deque is empty.
542		*
543		* <p>This method is equivalent to {@link #pollFirst}.
544		*
545		* @return the head of the queue represented by this deque, or
546	<	*         <tt>null</tt> if this deque is empty
546	>	*         {@code null} if this deque is empty
547		*/
548		public E poll() {
549		return pollFirst();
#	Line 439 | Line 565 | public class ArrayDeque<E> extends Abstr
565
566		/**
567		* Retrieves, but does not remove, the head of the queue represented by
568	<	* this deque, or returns <tt>null</tt> if this deque is empty.
568	>	* this deque, or returns {@code null} if this deque is empty.
569		*
570		* <p>This method is equivalent to {@link #peekFirst}.
571		*
572		* @return the head of the queue represented by this deque, or
573	<	*         <tt>null</tt> if this deque is empty
573	>	*         {@code null} if this deque is empty
574		*/
575		public E peek() {
576		return peekFirst();
#	Line 480 | Line 606 | public class ArrayDeque<E> extends Abstr
606		}
607
608		/**
609	<	* Removes the element at the specified position in the elements array,
610	<	* adjusting head and tail as necessary.  This can result in motion of
611	<	* elements backwards or forwards in the array.
609	>	* Removes the element at the specified position in the elements array.
610	>	* This can result in forward or backwards motion of array elements.
611	>	* We optimize for least element motion.
612		*
613		* <p>This method is called delete rather than remove to emphasize
614		* that its semantics differ from those of {@link List#remove(int)}.
615		*
616	<	* @return true if elements moved backwards
616	>	* @return true if elements near tail moved backwards
617		*/
618	<	private boolean delete(int i) {
619	<	int mask = elements.length - 1;
620	<	int front = (i - head) & mask;
621	<	int back  = (tail - i) & mask;
622	<
623	<	// Invariant: head <= i < tail mod circularity
624	<	if (front >= ((tail - head) & mask))
625	<	throw new ConcurrentModificationException();
626	<
627	<	// Optimize for least element motion
628	<	if (front < back) {
629	<	if (head <= i) {
630	<	System.arraycopy(elements, head, elements, head + 1, front);
631	<	} else { // Wrap around
632	<	elements[0] = elements[mask];
633	<	System.arraycopy(elements, 0, elements, 1, i);
634	<	System.arraycopy(elements, head, elements, head + 1, mask - head);
635	<	}
636	<	elements[head] = null;
637	<	head = (head + 1) & mask;
618	>	boolean delete(int i) {
619	>	// checkInvariants();
620	>	final Object[] es = elements;
621	>	final int capacity = es.length;
622	>	final int h, t;
623	>	// number of elements before to-be-deleted elt
624	>	final int front = sub(i, h = head, capacity);
625	>	// number of elements after to-be-deleted elt
626	>	final int back = sub(t = tail, i, capacity) - 1;
627	>	if (front < back) {
628	>	// move front elements forwards
629	>	if (h <= i) {
630	>	System.arraycopy(es, h, es, h + 1, front);
631	>	} else { // Wrap around
632	>	System.arraycopy(es, 0, es, 1, i);
633	>	es[0] = es[capacity - 1];
634	>	System.arraycopy(es, h, es, h + 1, front - (i + 1));
635	>	}
636	>	es[h] = null;
637	>	head = inc(h, capacity);
638	>	// checkInvariants();
639		return false;
640	<	} else {
641	<	int t = tail;
642	<	tail = (tail - 1) & mask;
643	<	if (i < t) { // Copy the null tail as well
644	<	System.arraycopy(elements, i + 1, elements, i, back);
645	<	} else {     // Wrap around
646	<	elements[mask] = elements[0];
647	<	System.arraycopy(elements, i + 1, elements, i, mask - i);
648	<	System.arraycopy(elements, 1, elements, 0, t);
649	<	}
640	>	} else {
641	>	// move back elements backwards
642	>	tail = dec(t, capacity);
643	>	if (i <= tail) {
644	>	System.arraycopy(es, i + 1, es, i, back);
645	>	} else { // Wrap around
646	>	System.arraycopy(es, i + 1, es, i, capacity - (i + 1));
647	>	es[capacity - 1] = es[0];
648	>	System.arraycopy(es, 1, es, 0, t - 1);
649	>	}
650	>	es[tail] = null;
651	>	// checkInvariants();
652		return true;
653	<	}
653	>	}
654		}
655
656		// *** Collection Methods ***
#	Line 532 | Line 661 | public class ArrayDeque<E> extends Abstr
661		* @return the number of elements in this deque
662		*/
663		public int size() {
664	<	return (tail - head) & (elements.length - 1);
664	>	return sub(tail, head, elements.length);
665		}
666
667		/**
668	<	* Returns <tt>true</tt> if this deque contains no elements.
668	>	* Returns {@code true} if this deque contains no elements.
669		*
670	<	* @return <tt>true</tt> if this deque contains no elements
670	>	* @return {@code true} if this deque contains no elements
671		*/
672		public boolean isEmpty() {
673		return head == tail;
#	Line 561 | Line 690 | public class ArrayDeque<E> extends Abstr
690		}
691
692		private class DeqIterator implements Iterator<E> {
693	<	/**
694	<	* Index of element to be returned by subsequent call to next.
566	<	*/
567	<	private int cursor = head;
693	>	/** Index of element to be returned by subsequent call to next. */
694	>	int cursor;
695
696	<	/**
697	<	* Tail recorded at construction (also in remove), to stop
571	<	* iterator and also to check for comodification.
572	<	*/
573	<	private int fence = tail;
696	>	/** Number of elements yet to be returned. */
697	>	int remaining = size();
698
699		/**
700		* Index of element returned by most recent call to next.
701		* Reset to -1 if element is deleted by a call to remove.
702		*/
703	<	private int lastRet = -1;
703	>	int lastRet = -1;
704	>
705	>	DeqIterator() { cursor = head; }
706
707	<	public boolean hasNext() {
708	<	return cursor != fence;
707	>	public final boolean hasNext() {
708	>	return remaining > 0;
709		}
710
711		public E next() {
712	<	E result;
587	<	if (cursor == fence)
712	>	if (remaining <= 0)
713		throw new NoSuchElementException();
714	<	// This check doesn't catch all possible comodifications,
715	<	// but does catch the ones that corrupt traversal
716	<	if (tail != fence || (result = elements[cursor]) == null)
717	<	throw new ConcurrentModificationException();
718	<	lastRet = cursor;
594	<	cursor = (cursor + 1) & (elements.length - 1);
595	<	return result;
714	>	final Object[] es = elements;
715	>	E e = nonNullElementAt(es, cursor);
716	>	cursor = inc(lastRet = cursor, es.length);
717	>	remaining--;
718	>	return e;
719		}
720
721	<	public void remove() {
721	>	void postDelete(boolean leftShifted) {
722	>	if (leftShifted)
723	>	cursor = dec(cursor, elements.length);
724	>	}
725	>
726	>	public final void remove() {
727		if (lastRet < 0)
728		throw new IllegalStateException();
729	<	if (delete(lastRet)) // if left-shifted, undo increment in next()
602	<	cursor = (cursor - 1) & (elements.length - 1);
729	>	postDelete(delete(lastRet));
730		lastRet = -1;
731	<	fence = tail;
731	>	}
732	>
733	>	public void forEachRemaining(Consumer<? super E> action) {
734	>	Objects.requireNonNull(action);
735	>	int r;
736	>	if ((r = remaining) <= 0)
737	>	return;
738	>	remaining = 0;
739	>	final Object[] es = elements;
740	>	if (es[cursor] == null || sub(tail, cursor, es.length) != r)
741	>	throw new ConcurrentModificationException();
742	>	for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
743	>	; i = 0, to = end) {
744	>	for (; i < to; i++)
745	>	action.accept(elementAt(es, i));
746	>	if (to == end) {
747	>	if (end != tail)
748	>	throw new ConcurrentModificationException();
749	>	lastRet = dec(end, es.length);
750	>	break;
751	>	}
752	>	}
753		}
754		}
755
756	+	private class DescendingIterator extends DeqIterator {
757	+	DescendingIterator() { cursor = dec(tail, elements.length); }
758
759	<	private class DescendingIterator implements Iterator<E> {
760	<	/*
761	<	* This class is nearly a mirror-image of DeqIterator, using
762	<	* (tail-1) instead of head for initial cursor, (head-1)
763	<	* instead of tail for fence, and elements.length instead of -1
764	<	* for sentinel. It shares the same structure, but not many
765	<	* actual lines of code.
766	<	*/
767	<	private int cursor = (tail - 1) & (elements.length - 1);
618	<	private int fence =  (head - 1) & (elements.length - 1);
619	<	private int lastRet = elements.length;
759	>	public final E next() {
760	>	if (remaining <= 0)
761	>	throw new NoSuchElementException();
762	>	final Object[] es = elements;
763	>	E e = nonNullElementAt(es, cursor);
764	>	cursor = dec(lastRet = cursor, es.length);
765	>	remaining--;
766	>	return e;
767	>	}
768
769	<	public boolean hasNext() {
770	<	return cursor != fence;
769	>	void postDelete(boolean leftShifted) {
770	>	if (!leftShifted)
771	>	cursor = inc(cursor, elements.length);
772		}
773
774	<	public E next() {
775	<	E result;
776	<	if (cursor == fence)
777	<	throw new NoSuchElementException();
778	<	if (((head - 1) & (elements.length - 1)) != fence ||
779	<	(result = elements[cursor]) == null)
774	>	public final void forEachRemaining(Consumer<? super E> action) {
775	>	Objects.requireNonNull(action);
776	>	int r;
777	>	if ((r = remaining) <= 0)
778	>	return;
779	>	remaining = 0;
780	>	final Object[] es = elements;
781	>	if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
782		throw new ConcurrentModificationException();
783	<	lastRet = cursor;
784	<	cursor = (cursor - 1) & (elements.length - 1);
785	<	return result;
783	>	for (int i = cursor, end = head, to = (i >= end) ? end : 0;
784	>	; i = es.length - 1, to = end) {
785	>	// hotspot generates faster code than for: i >= to !
786	>	for (; i > to - 1; i--)
787	>	action.accept(elementAt(es, i));
788	>	if (to == end) {
789	>	if (end != head)
790	>	throw new ConcurrentModificationException();
791	>	lastRet = end;
792	>	break;
793	>	}
794	>	}
795		}
796	+	}
797
798	<	public void remove() {
799	<	if (lastRet >= elements.length)
800	<	throw new IllegalStateException();
801	<	if (!delete(lastRet))
802	<	cursor = (cursor + 1) & (elements.length - 1);
803	<	lastRet = elements.length;
804	<	fence = (head - 1) & (elements.length - 1);
798	>	/**
799	>	* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
800	>	* and <em>fail-fast</em> {@link Spliterator} over the elements in this
801	>	* deque.
802	>	*
803	>	* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
804	>	* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
805	>	* {@link Spliterator#NONNULL}.  Overriding implementations should document
806	>	* the reporting of additional characteristic values.
807	>	*
808	>	* @return a {@code Spliterator} over the elements in this deque
809	>	* @since 1.8
810	>	*/
811	>	public Spliterator<E> spliterator() {
812	>	return new DeqSpliterator();
813	>	}
814	>
815	>	final class DeqSpliterator implements Spliterator<E> {
816	>	private int fence;      // -1 until first use
817	>	private int cursor;     // current index, modified on traverse/split
818	>
819	>	/** Constructs late-binding spliterator over all elements. */
820	>	DeqSpliterator() {
821	>	this.fence = -1;
822	>	}
823	>
824	>	/** Constructs spliterator over the given range. */
825	>	DeqSpliterator(int origin, int fence) {
826	>	// assert 0 <= origin && origin < elements.length;
827	>	// assert 0 <= fence && fence < elements.length;
828	>	this.cursor = origin;
829	>	this.fence = fence;
830	>	}
831	>
832	>	/** Ensures late-binding initialization; then returns fence. */
833	>	private int getFence() { // force initialization
834	>	int t;
835	>	if ((t = fence) < 0) {
836	>	t = fence = tail;
837	>	cursor = head;
838	>	}
839	>	return t;
840	>	}
841	>
842	>	public DeqSpliterator trySplit() {
843	>	final Object[] es = elements;
844	>	final int i, n;
845	>	return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
846	>	? null
847	>	: new DeqSpliterator(i, cursor = inc(i, n, es.length));
848	>	}
849	>
850	>	public void forEachRemaining(Consumer<? super E> action) {
851	>	if (action == null)
852	>	throw new NullPointerException();
853	>	final int end = getFence(), cursor = this.cursor;
854	>	final Object[] es = elements;
855	>	if (cursor != end) {
856	>	this.cursor = end;
857	>	// null check at both ends of range is sufficient
858	>	if (es[cursor] == null || es[dec(end, es.length)] == null)
859	>	throw new ConcurrentModificationException();
860	>	for (int i = cursor, to = (i <= end) ? end : es.length;
861	>	; i = 0, to = end) {
862	>	for (; i < to; i++)
863	>	action.accept(elementAt(es, i));
864	>	if (to == end) break;
865	>	}
866	>	}
867	>	}
868	>
869	>	public boolean tryAdvance(Consumer<? super E> action) {
870	>	Objects.requireNonNull(action);
871	>	final Object[] es = elements;
872	>	if (fence < 0) { fence = tail; cursor = head; } // late-binding
873	>	final int i;
874	>	if ((i = cursor) == fence)
875	>	return false;
876	>	E e = nonNullElementAt(es, i);
877	>	cursor = inc(i, es.length);
878	>	action.accept(e);
879	>	return true;
880	>	}
881	>
882	>	public long estimateSize() {
883	>	return sub(getFence(), cursor, elements.length);
884	>	}
885	>
886	>	public int characteristics() {
887	>	return Spliterator.NONNULL
888	>	| Spliterator.ORDERED
889	>	| Spliterator.SIZED
890	>	| Spliterator.SUBSIZED;
891	>	}
892	>	}
893	>
894	>	/**
895	>	* @throws NullPointerException {@inheritDoc}
896	>	*/
897	>	public void forEach(Consumer<? super E> action) {
898	>	Objects.requireNonNull(action);
899	>	final Object[] es = elements;
900	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
901	>	; i = 0, to = end) {
902	>	for (; i < to; i++)
903	>	action.accept(elementAt(es, i));
904	>	if (to == end) {
905	>	if (end != tail) throw new ConcurrentModificationException();
906	>	break;
907	>	}
908		}
909	+	// checkInvariants();
910		}
911
912		/**
913	<	* Returns <tt>true</tt> if this deque contains the specified element.
914	<	* More formally, returns <tt>true</tt> if and only if this deque contains
915	<	* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
913	>	* Replaces each element of this deque with the result of applying the
914	>	* operator to that element, as specified by {@link List#replaceAll}.
915	>	*
916	>	* @param operator the operator to apply to each element
917	>	* @since TBD
918	>	*/
919	>	/* public */ void replaceAll(java.util.function.UnaryOperator<E> operator) {
920	>	Objects.requireNonNull(operator);
921	>	final Object[] es = elements;
922	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
923	>	; i = 0, to = end) {
924	>	for (; i < to; i++)
925	>	es[i] = operator.apply(elementAt(es, i));
926	>	if (to == end) {
927	>	if (end != tail) throw new ConcurrentModificationException();
928	>	break;
929	>	}
930	>	}
931	>	// checkInvariants();
932	>	}
933	>
934	>	/**
935	>	* @throws NullPointerException {@inheritDoc}
936	>	*/
937	>	public boolean removeIf(Predicate<? super E> filter) {
938	>	Objects.requireNonNull(filter);
939	>	return bulkRemove(filter);
940	>	}
941	>
942	>	/**
943	>	* @throws NullPointerException {@inheritDoc}
944	>	*/
945	>	public boolean removeAll(Collection<?> c) {
946	>	Objects.requireNonNull(c);
947	>	return bulkRemove(e -> c.contains(e));
948	>	}
949	>
950	>	/**
951	>	* @throws NullPointerException {@inheritDoc}
952	>	*/
953	>	public boolean retainAll(Collection<?> c) {
954	>	Objects.requireNonNull(c);
955	>	return bulkRemove(e -> !c.contains(e));
956	>	}
957	>
958	>	/** Implementation of bulk remove methods. */
959	>	private boolean bulkRemove(Predicate<? super E> filter) {
960	>	// checkInvariants();
961	>	final Object[] es = elements;
962	>	// Optimize for initial run of survivors
963	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
964	>	; i = 0, to = end) {
965	>	for (; i < to; i++)
966	>	if (filter.test(elementAt(es, i)))
967	>	return bulkRemoveModified(filter, i);
968	>	if (to == end) {
969	>	if (end != tail) throw new ConcurrentModificationException();
970	>	break;
971	>	}
972	>	}
973	>	return false;
974	>	}
975	>
976	>	// A tiny bit set implementation
977	>
978	>	private static long[] nBits(int n) {
979	>	return new long[((n - 1) >> 6) + 1];
980	>	}
981	>	private static void setBit(long[] bits, int i) {
982	>	bits[i >> 6] |= 1L << i;
983	>	}
984	>	private static boolean isClear(long[] bits, int i) {
985	>	return (bits[i >> 6] & (1L << i)) == 0;
986	>	}
987	>
988	>	/**
989	>	* Helper for bulkRemove, in case of at least one deletion.
990	>	* Tolerate predicates that reentrantly access the collection for
991	>	* read (but writers still get CME), so traverse once to find
992	>	* elements to delete, a second pass to physically expunge.
993	>	*
994	>	* @param beg valid index of first element to be deleted
995	>	*/
996	>	private boolean bulkRemoveModified(
997	>	Predicate<? super E> filter, final int beg) {
998	>	final Object[] es = elements;
999	>	final int capacity = es.length;
1000	>	final int end = tail;
1001	>	final long[] deathRow = nBits(sub(end, beg, capacity));
1002	>	deathRow[0] = 1L;   // set bit 0
1003	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1004	>	; i = 0, to = end, k -= capacity) {
1005	>	for (; i < to; i++)
1006	>	if (filter.test(elementAt(es, i)))
1007	>	setBit(deathRow, i - k);
1008	>	if (to == end) break;
1009	>	}
1010	>	// a two-finger traversal, with hare i reading, tortoise w writing
1011	>	int w = beg;
1012	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1013	>	; w = 0) { // w rejoins i on second leg
1014	>	// In this loop, i and w are on the same leg, with i > w
1015	>	for (; i < to; i++)
1016	>	if (isClear(deathRow, i - k))
1017	>	es[w++] = es[i];
1018	>	if (to == end) break;
1019	>	// In this loop, w is on the first leg, i on the second
1020	>	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1021	>	if (isClear(deathRow, i - k))
1022	>	es[w++] = es[i];
1023	>	if (i >= to) {
1024	>	if (w == capacity) w = 0; // "corner" case
1025	>	break;
1026	>	}
1027	>	}
1028	>	if (end != tail) throw new ConcurrentModificationException();
1029	>	circularClear(es, tail = w, end);
1030	>	// checkInvariants();
1031	>	return true;
1032	>	}
1033	>
1034	>	/**
1035	>	* Returns {@code true} if this deque contains the specified element.
1036	>	* More formally, returns {@code true} if and only if this deque contains
1037	>	* at least one element {@code e} such that {@code o.equals(e)}.
1038		*
1039		* @param o object to be checked for containment in this deque
1040	<	* @return <tt>true</tt> if this deque contains the specified element
1040	>	* @return {@code true} if this deque contains the specified element
1041		*/
1042		public boolean contains(Object o) {
1043	<	if (o == null)
1044	<	return false;
1045	<	int mask = elements.length - 1;
1046	<	int i = head;
1047	<	E x;
1048	<	while ( (x = elements[i]) != null) {
1049	<	if (o.equals(x))
1050	<	return true;
1051	<	i = (i + 1) & mask;
1043	>	if (o != null) {
1044	>	final Object[] es = elements;
1045	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1046	>	; i = 0, to = end) {
1047	>	for (; i < to; i++)
1048	>	if (o.equals(es[i]))
1049	>	return true;
1050	>	if (to == end) break;
1051	>	}
1052		}
1053		return false;
1054		}
#	Line 669 | Line 1056 | public class ArrayDeque<E> extends Abstr
1056		/**
1057		* Removes a single instance of the specified element from this deque.
1058		* If the deque does not contain the element, it is unchanged.
1059	<	* More formally, removes the first element <tt>e</tt> such that
1060	<	* <tt>o.equals(e)</tt> (if such an element exists).
1061	<	* Returns <tt>true</tt> if this deque contained the specified element
1059	>	* More formally, removes the first element {@code e} such that
1060	>	* {@code o.equals(e)} (if such an element exists).
1061	>	* Returns {@code true} if this deque contained the specified element
1062		* (or equivalently, if this deque changed as a result of the call).
1063		*
1064	<	* <p>This method is equivalent to {@link #removeFirstOccurrence}.
1064	>	* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1065		*
1066		* @param o element to be removed from this deque, if present
1067	<	* @return <tt>true</tt> if this deque contained the specified element
1067	>	* @return {@code true} if this deque contained the specified element
1068		*/
1069		public boolean remove(Object o) {
1070		return removeFirstOccurrence(o);
#	Line 688 | Line 1075 | public class ArrayDeque<E> extends Abstr
1075		* The deque will be empty after this call returns.
1076		*/
1077		public void clear() {
1078	<	int h = head;
1079	<	int t = tail;
1080	<	if (h != t) { // clear all cells
1081	<	head = tail = 0;
1082	<	int i = h;
1083	<	int mask = elements.length - 1;
1084	<	do {
1085	<	elements[i] = null;
1086	<	i = (i + 1) & mask;
1087	<	} while (i != t);
1078	>	circularClear(elements, head, tail);
1079	>	head = tail = 0;
1080	>	// checkInvariants();
1081	>	}
1082	>
1083	>	/**
1084	>	* Nulls out slots starting at array index i, upto index end.
1085	>	* Condition i == end means "empty" - nothing to do.
1086	>	*/
1087	>	private static void circularClear(Object[] es, int i, int end) {
1088	>	// assert 0 <= i && i < es.length;
1089	>	// assert 0 <= end && end < es.length;
1090	>	for (int to = (i <= end) ? end : es.length;
1091	>	; i = 0, to = end) {
1092	>	for (; i < to; i++) es[i] = null;
1093	>	if (to == end) break;
1094		}
1095		}
1096
#	Line 715 | Line 1108 | public class ArrayDeque<E> extends Abstr
1108		* @return an array containing all of the elements in this deque
1109		*/
1110		public Object[] toArray() {
1111	<	return copyElements(new Object[size()]);
1111	>	return toArray(Object[].class);
1112	>	}
1113	>
1114	>	private <T> T[] toArray(Class<T[]> klazz) {
1115	>	final Object[] es = elements;
1116	>	final T[] a;
1117	>	final int head = this.head, tail = this.tail, end;
1118	>	if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) {
1119	>	// Uses null extension feature of copyOfRange
1120	>	a = Arrays.copyOfRange(es, head, end, klazz);
1121	>	} else {
1122	>	// integer overflow!
1123	>	a = Arrays.copyOfRange(es, 0, end - head, klazz);
1124	>	System.arraycopy(es, head, a, 0, es.length - head);
1125	>	}
1126	>	if (end != tail)
1127	>	System.arraycopy(es, 0, a, es.length - head, tail);
1128	>	return a;
1129		}
1130
1131		/**
#	Line 729 | Line 1139 | public class ArrayDeque<E> extends Abstr
1139		* <p>If this deque fits in the specified array with room to spare
1140		* (i.e., the array has more elements than this deque), the element in
1141		* the array immediately following the end of the deque is set to
1142	<	* <tt>null</tt>.
1142	>	* {@code null}.
1143		*
1144		* <p>Like the {@link #toArray()} method, this method acts as bridge between
1145		* array-based and collection-based APIs.  Further, this method allows
1146		* precise control over the runtime type of the output array, and may,
1147		* under certain circumstances, be used to save allocation costs.
1148		*
1149	<	* <p>Suppose <tt>x</tt> is a deque known to contain only strings.
1149	>	* <p>Suppose {@code x} is a deque known to contain only strings.
1150		* The following code can be used to dump the deque into a newly
1151	<	* allocated array of <tt>String</tt>:
1151	>	* allocated array of {@code String}:
1152		*
1153	<	* <pre>
744	<	*     String[] y = x.toArray(new String[0]);</pre>
1153	>	* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1154		*
1155	<	* Note that <tt>toArray(new Object[0])</tt> is identical in function to
1156	<	* <tt>toArray()</tt>.
1155	>	* Note that {@code toArray(new Object[0])} is identical in function to
1156	>	* {@code toArray()}.
1157		*
1158		* @param a the array into which the elements of the deque are to
1159		*          be stored, if it is big enough; otherwise, a new array of the
#	Line 755 | Line 1164 | public class ArrayDeque<E> extends Abstr
1164		*         this deque
1165		* @throws NullPointerException if the specified array is null
1166		*/
1167	+	@SuppressWarnings("unchecked")
1168		public <T> T[] toArray(T[] a) {
1169	<	int size = size();
1170	<	if (a.length < size)
1171	<	a = (T[])java.lang.reflect.Array.newInstance(
1172	<	a.getClass().getComponentType(), size);
1173	<	copyElements(a);
1174	<	if (a.length > size)
1169	>	final int size;
1170	>	if ((size = size()) > a.length)
1171	>	return toArray((Class<T[]>) a.getClass());
1172	>	final Object[] es = elements;
1173	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1174	>	; i = 0, len = tail) {
1175	>	System.arraycopy(es, i, a, j, len);
1176	>	if ((j += len) == size) break;
1177	>	}
1178	>	if (size < a.length)
1179		a[size] = null;
1180		return a;
1181		}
#	Line 775 | Line 1189 | public class ArrayDeque<E> extends Abstr
1189		*/
1190		public ArrayDeque<E> clone() {
1191		try {
1192	+	@SuppressWarnings("unchecked")
1193		ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1194	<	// These two lines are currently faster than cloning the array:
780	<	result.elements = (E[]) new Object[elements.length];
781	<	System.arraycopy(elements, 0, result.elements, 0, elements.length);
1194	>	result.elements = Arrays.copyOf(elements, elements.length);
1195		return result;
783	–
1196		} catch (CloneNotSupportedException e) {
1197		throw new AssertionError();
1198		}
1199		}
1200
1201	<	/**
790	<	* Appease the serialization gods.
791	<	*/
1201	>	// OPENJDK @java.io.Serial
1202		private static final long serialVersionUID = 2340985798034038923L;
1203
1204		/**
1205	<	* Serialize this deque.
1205	>	* Saves this deque to a stream (that is, serializes it).
1206		*
1207	<	* @serialData The current size (<tt>int</tt>) of the deque,
1207	>	* @param s the stream
1208	>	* @throws java.io.IOException if an I/O error occurs
1209	>	* @serialData The current size ({@code int}) of the deque,
1210		* followed by all of its elements (each an object reference) in
1211		* first-to-last order.
1212		*/
1213	<	private void writeObject(ObjectOutputStream s) throws IOException {
1213	>	// OPENJDK @java.io.Serial
1214	>	private void writeObject(java.io.ObjectOutputStream s)
1215	>	throws java.io.IOException {
1216		s.defaultWriteObject();
1217
1218		// Write out size
1219		s.writeInt(size());
1220
1221		// Write out elements in order.
1222	<	int mask = elements.length - 1;
1223	<	for (int i = head; i != tail; i = (i + 1) & mask)
1224	<	s.writeObject(elements[i]);
1222	>	final Object[] es = elements;
1223	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1224	>	; i = 0, to = end) {
1225	>	for (; i < to; i++)
1226	>	s.writeObject(es[i]);
1227	>	if (to == end) break;
1228	>	}
1229		}
1230
1231		/**
1232	<	* Deserialize this deque.
1233	<	*/
1234	<	private void readObject(ObjectInputStream s)
1235	<	throws IOException, ClassNotFoundException {
1232	>	* Reconstitutes this deque from a stream (that is, deserializes it).
1233	>	* @param s the stream
1234	>	* @throws ClassNotFoundException if the class of a serialized object
1235	>	*         could not be found
1236	>	* @throws java.io.IOException if an I/O error occurs
1237	>	*/
1238	>	// OPENJDK @java.io.Serial
1239	>	private void readObject(java.io.ObjectInputStream s)
1240	>	throws java.io.IOException, ClassNotFoundException {
1241		s.defaultReadObject();
1242
1243		// Read in size and allocate array
1244		int size = s.readInt();
1245	<	allocateElements(size);
1246	<	head = 0;
1247	<	tail = size;
1245	>	jsr166.Platform.checkArray(s, Object[].class, size + 1);
1246	>	elements = new Object[size + 1];
1247	>	this.tail = size;
1248
1249		// Read in all elements in the proper order.
1250		for (int i = 0; i < size; i++)
1251	<	elements[i] = (E)s.readObject();
1251	>	elements[i] = s.readObject();
1252	>	}
1253
1254	+	/** debugging */
1255	+	void checkInvariants() {
1256	+	// Use head and tail fields with empty slot at tail strategy.
1257	+	// head == tail disambiguates to "empty".
1258	+	try {
1259	+	int capacity = elements.length;
1260	+	// assert 0 <= head && head < capacity;
1261	+	// assert 0 <= tail && tail < capacity;
1262	+	// assert capacity > 0;
1263	+	// assert size() < capacity;
1264	+	// assert head == tail || elements[head] != null;
1265	+	// assert elements[tail] == null;
1266	+	// assert head == tail || elements[dec(tail, capacity)] != null;
1267	+	} catch (Throwable t) {
1268	+	System.err.printf("head=%d tail=%d capacity=%d%n",
1269	+	head, tail, elements.length);
1270	+	System.err.printf("elements=%s%n",
1271	+	Arrays.toString(elements));
1272	+	throw t;
1273	+	}
1274		}
1275	+
1276		}

Diff Legend

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