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root/jsr166/jsr166/src/main/java/util/ArrayDeque.java
Revision: 1.106
Committed: Sat Nov 5 00:25:44 2016 UTC (7 years, 6 months ago) by jsr166
Branch: MAIN
Changes since 1.105: +268 -273 lines
Log Message:
switch back to head/tail instead of head/size

File Contents

# User Rev Content
1 dl 1.1 /*
2 dl 1.47 * Written by Josh Bloch of Google Inc. and released to the public domain,
3     * as explained at http://creativecommons.org/publicdomain/zero/1.0/.
4 dl 1.1 */
5    
6     package java.util;
7 jsr166 1.61
8 dl 1.47 import java.io.Serializable;
9     import java.util.function.Consumer;
10 jsr166 1.75 import java.util.function.Predicate;
11     import java.util.function.UnaryOperator;
12 dl 1.1
13     /**
14     * Resizable-array implementation of the {@link Deque} interface. Array
15     * deques have no capacity restrictions; they grow as necessary to support
16     * usage. They are not thread-safe; in the absence of external
17     * synchronization, they do not support concurrent access by multiple threads.
18     * Null elements are prohibited. This class is likely to be faster than
19 dl 1.2 * {@link Stack} when used as a stack, and faster than {@link LinkedList}
20 dl 1.1 * when used as a queue.
21     *
22 jsr166 1.43 * <p>Most {@code ArrayDeque} operations run in amortized constant time.
23 jsr166 1.51 * 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 dl 1.41 *
31 jsr166 1.51 * <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 jsr166 1.7 * ConcurrentModificationException}. Thus, in the face of concurrent
36     * modification, the iterator fails quickly and cleanly, rather than risking
37     * arbitrary, non-deterministic behavior at an undetermined time in the
38     * future.
39 dl 1.1 *
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 jsr166 1.43 * throw {@code ConcurrentModificationException} on a best-effort basis.
44 dl 1.1 * Therefore, it would be wrong to write a program that depended on this
45     * exception for its correctness: <i>the fail-fast behavior of iterators
46     * should be used only to detect bugs.</i>
47     *
48     * <p>This class and its iterator implement all of the
49 jsr166 1.9 * <em>optional</em> methods of the {@link Collection} and {@link
50     * Iterator} interfaces.
51     *
52     * <p>This class is a member of the
53 jsr166 1.29 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
54 jsr166 1.9 * Java Collections Framework</a>.
55 dl 1.1 *
56     * @author Josh Bloch and Doug Lea
57 jsr166 1.74 * @param <E> the type of elements held in this deque
58 dl 1.1 * @since 1.6
59     */
60     public class ArrayDeque<E> extends AbstractCollection<E>
61 dl 1.47 implements Deque<E>, Cloneable, Serializable
62 dl 1.1 {
63 jsr166 1.106 /*
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 dl 1.1 /**
75 dl 1.4 * The array in which the elements of the deque are stored.
76 jsr166 1.75 * We guarantee that all array cells not holding deque elements
77     * are always null.
78 dl 1.1 */
79 jsr166 1.75 transient Object[] elements;
80 dl 1.1
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 jsr166 1.106 * arbitrary number 0 <= head < elements.length equal to tail if
85     * the deque is empty.
86 dl 1.1 */
87 dl 1.41 transient int head;
88 dl 1.1
89 jsr166 1.106 /**
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     transient int tail;
94 jsr166 1.75
95 dl 1.1 /**
96 jsr166 1.75 * 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 dl 1.1 */
101 jsr166 1.75 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
102 dl 1.1
103     /**
104 jsr166 1.75 * 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 dl 1.1 */
108 jsr166 1.106 private void grow(int needed) {
109 jsr166 1.75 // overflow-conscious code
110 jsr166 1.91 final int oldCapacity = elements.length;
111 jsr166 1.75 int newCapacity;
112 jsr166 1.106 // Double capacity if small; else grow by 50%
113 jsr166 1.75 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 jsr166 1.106 // Exceptionally, here tail == head needs to be disambiguated
119     if (tail < head || (tail == head && elements[head] != null)) {
120 jsr166 1.75 // 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 dl 1.1
131 jsr166 1.75 /** Capacity calculation for edge conditions, especially overflow. */
132     private int newCapacity(int needed, int jump) {
133 jsr166 1.91 final int oldCapacity = elements.length, minCapacity;
134 jsr166 1.75 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     if (needed > jump)
140     return minCapacity;
141     return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
142     ? oldCapacity + jump
143     : MAX_ARRAY_SIZE;
144     }
145 dl 1.1
146     /**
147 jsr166 1.75 * Increases the internal storage of this collection, if necessary,
148     * to ensure that it can hold at least the given number of elements.
149 dl 1.1 *
150 jsr166 1.75 * @param minCapacity the desired minimum capacity
151 jsr166 1.80 * @since TBD
152 dl 1.1 */
153 jsr166 1.80 /* public */ void ensureCapacity(int minCapacity) {
154 jsr166 1.106 int needed;
155     if ((needed = (minCapacity + 1 - elements.length)) > 0)
156     grow(needed);
157 jsr166 1.75 // checkInvariants();
158 dl 1.1 }
159    
160     /**
161 jsr166 1.75 * Minimizes the internal storage of this collection.
162 jsr166 1.80 *
163     * @since TBD
164 dl 1.1 */
165 jsr166 1.80 /* public */ void trimToSize() {
166 jsr166 1.106 int size;
167     if ((size = size()) + 1 < elements.length) {
168     elements = toArray(new Object[size + 1]);
169 jsr166 1.75 head = 0;
170 jsr166 1.106 tail = size;
171 jsr166 1.75 }
172     // checkInvariants();
173 dl 1.1 }
174    
175     /**
176 dl 1.4 * Constructs an empty array deque with an initial capacity
177 dl 1.1 * sufficient to hold 16 elements.
178     */
179     public ArrayDeque() {
180 jsr166 1.34 elements = new Object[16];
181 dl 1.1 }
182    
183     /**
184     * Constructs an empty array deque with an initial capacity
185     * sufficient to hold the specified number of elements.
186     *
187 jsr166 1.75 * @param numElements lower bound on initial capacity of the deque
188 dl 1.1 */
189     public ArrayDeque(int numElements) {
190 jsr166 1.106 elements = new Object[Math.max(1, numElements + 1)];
191 dl 1.1 }
192    
193     /**
194     * Constructs a deque containing the elements of the specified
195     * collection, in the order they are returned by the collection's
196     * iterator. (The first element returned by the collection's
197     * iterator becomes the first element, or <i>front</i> of the
198     * deque.)
199     *
200     * @param c the collection whose elements are to be placed into the deque
201     * @throws NullPointerException if the specified collection is null
202     */
203     public ArrayDeque(Collection<? extends E> c) {
204 jsr166 1.106 elements = new Object[c.size() + 1];
205     addAll(c);
206 jsr166 1.75 }
207    
208     /**
209 jsr166 1.79 * Increments i, mod modulus.
210     * Precondition and postcondition: 0 <= i < modulus.
211 jsr166 1.75 */
212 jsr166 1.79 static final int inc(int i, int modulus) {
213 jsr166 1.89 if (++i >= modulus) i = 0;
214 jsr166 1.79 return i;
215 jsr166 1.75 }
216    
217     /**
218 jsr166 1.79 * Decrements i, mod modulus.
219     * Precondition and postcondition: 0 <= i < modulus.
220 jsr166 1.75 */
221 jsr166 1.79 static final int dec(int i, int modulus) {
222 jsr166 1.89 if (--i < 0) i = modulus - 1;
223 jsr166 1.75 return i;
224     }
225    
226     /**
227 jsr166 1.79 * Adds i and j, mod modulus.
228     * Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
229 jsr166 1.75 */
230 jsr166 1.79 static final int add(int i, int j, int modulus) {
231     if ((i += j) - modulus >= 0) i -= modulus;
232 jsr166 1.75 return i;
233     }
234    
235     /**
236 jsr166 1.106 * 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 jsr166 1.79 * Returns the array index of the last element.
248     * May return invalid index -1 if there are no elements.
249 jsr166 1.75 */
250 jsr166 1.106 final int last() {
251     return dec(tail, elements.length);
252 jsr166 1.75 }
253    
254     /**
255     * Returns element at array index i.
256 jsr166 1.106 * This is a slight abuse of generics, accepted by javac.
257 jsr166 1.75 */
258     @SuppressWarnings("unchecked")
259 jsr166 1.106 static final <E> E elementAt(Object[] es, int i) {
260     return (E) es[i];
261 jsr166 1.75 }
262    
263     /**
264     * A version of elementAt that checks for null elements.
265     * This check doesn't catch all possible comodifications,
266 jsr166 1.106 * but does catch ones that corrupt traversal.
267 jsr166 1.75 */
268 jsr166 1.96 static final <E> E nonNullElementAt(Object[] es, int i) {
269     @SuppressWarnings("unchecked") E e = (E) es[i];
270 jsr166 1.75 if (e == null)
271     throw new ConcurrentModificationException();
272     return e;
273 dl 1.1 }
274    
275     // The main insertion and extraction methods are addFirst,
276     // addLast, pollFirst, pollLast. The other methods are defined in
277     // terms of these.
278    
279     /**
280 dl 1.5 * Inserts the specified element at the front of this deque.
281 dl 1.1 *
282 jsr166 1.9 * @param e the element to add
283     * @throws NullPointerException if the specified element is null
284 dl 1.1 */
285     public void addFirst(E e) {
286 jsr166 1.106 if (e == null)
287     throw new NullPointerException();
288     final Object[] es = elements;
289     es[head = dec(head, es.length)] = e;
290     if (head == tail)
291     grow(1);
292 jsr166 1.83 // checkInvariants();
293 dl 1.1 }
294    
295     /**
296 dl 1.6 * Inserts the specified element at the end of this deque.
297 jsr166 1.14 *
298     * <p>This method is equivalent to {@link #add}.
299 dl 1.1 *
300 jsr166 1.9 * @param e the element to add
301     * @throws NullPointerException if the specified element is null
302 dl 1.1 */
303     public void addLast(E e) {
304 jsr166 1.106 if (e == null)
305     throw new NullPointerException();
306     final Object[] es = elements;
307     es[tail] = e;
308     if (head == (tail = inc(tail, es.length)))
309     grow(1);
310 jsr166 1.83 // checkInvariants();
311 jsr166 1.75 }
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
317     * iterator.
318     *
319     * @param c the elements to be inserted into this deque
320     * @return {@code true} if this deque changed as a result of the call
321     * @throws NullPointerException if the specified collection or any
322     * of its elements are null
323     */
324     public boolean addAll(Collection<? extends E> c) {
325 jsr166 1.106 final int s = size(), needed;
326     if ((needed = s + c.size() - elements.length + 1) > 0)
327 jsr166 1.87 grow(needed);
328     c.forEach((e) -> addLast(e));
329 jsr166 1.75 // checkInvariants();
330 jsr166 1.106 return size() > s;
331 dl 1.1 }
332    
333     /**
334 dl 1.5 * Inserts the specified element at the front of this deque.
335 dl 1.1 *
336 jsr166 1.9 * @param e the element to add
337 jsr166 1.40 * @return {@code true} (as specified by {@link Deque#offerFirst})
338 jsr166 1.9 * @throws NullPointerException if the specified element is null
339 dl 1.1 */
340     public boolean offerFirst(E e) {
341     addFirst(e);
342     return true;
343     }
344    
345     /**
346 dl 1.6 * Inserts the specified element at the end of this deque.
347 dl 1.1 *
348 jsr166 1.9 * @param e the element to add
349 jsr166 1.40 * @return {@code true} (as specified by {@link Deque#offerLast})
350 jsr166 1.9 * @throws NullPointerException if the specified element is null
351 dl 1.1 */
352     public boolean offerLast(E e) {
353     addLast(e);
354     return true;
355     }
356    
357     /**
358 jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
359 dl 1.1 */
360     public E removeFirst() {
361 jsr166 1.84 E e = pollFirst();
362     if (e == null)
363 dl 1.1 throw new NoSuchElementException();
364 jsr166 1.106 // checkInvariants();
365 jsr166 1.84 return e;
366 dl 1.1 }
367    
368     /**
369 jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
370 dl 1.1 */
371     public E removeLast() {
372 jsr166 1.84 E e = pollLast();
373     if (e == null)
374 dl 1.1 throw new NoSuchElementException();
375 jsr166 1.106 // checkInvariants();
376 jsr166 1.84 return e;
377 dl 1.1 }
378    
379 jsr166 1.9 public E pollFirst() {
380 jsr166 1.106 final Object[] es;
381     final int h;
382     E e = elementAt(es = elements, h = head);
383     if (e != null) {
384     es[h] = null;
385     head = inc(h, es.length);
386     }
387 jsr166 1.75 // checkInvariants();
388     return e;
389 dl 1.1 }
390    
391 jsr166 1.9 public E pollLast() {
392 jsr166 1.106 final Object[] es;
393     final int t;
394     E e = elementAt(es = elements, t = dec(tail, es.length));
395     if (e != null)
396     es[tail = t] = null;
397 jsr166 1.75 // checkInvariants();
398     return e;
399 dl 1.1 }
400    
401     /**
402 jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
403 dl 1.1 */
404     public E getFirst() {
405 jsr166 1.106 E e = elementAt(elements, head);
406     if (e == null)
407     throw new NoSuchElementException();
408 jsr166 1.75 // checkInvariants();
409 jsr166 1.106 return e;
410 dl 1.1 }
411    
412     /**
413 jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
414 dl 1.1 */
415     public E getLast() {
416 jsr166 1.106 final Object[] es = elements;
417     E e = elementAt(es, dec(tail, es.length));
418     if (e == null)
419     throw new NoSuchElementException();
420 jsr166 1.75 // checkInvariants();
421 jsr166 1.106 return e;
422 dl 1.1 }
423    
424 jsr166 1.9 public E peekFirst() {
425 jsr166 1.75 // checkInvariants();
426 jsr166 1.106 return elementAt(elements, head);
427 jsr166 1.9 }
428    
429     public E peekLast() {
430 jsr166 1.75 // checkInvariants();
431 jsr166 1.106 final Object[] es;
432     return elementAt(es = elements, dec(tail, es.length));
433 jsr166 1.9 }
434    
435 dl 1.1 /**
436     * Removes the first occurrence of the specified element in this
437 jsr166 1.9 * deque (when traversing the deque from head to tail).
438     * If the deque does not contain the element, it is unchanged.
439 jsr166 1.40 * More formally, removes the first element {@code e} such that
440     * {@code o.equals(e)} (if such an element exists).
441     * Returns {@code true} if this deque contained the specified element
442 jsr166 1.12 * (or equivalently, if this deque changed as a result of the call).
443 dl 1.1 *
444 dl 1.5 * @param o element to be removed from this deque, if present
445 jsr166 1.40 * @return {@code true} if the deque contained the specified element
446 dl 1.1 */
447 dl 1.5 public boolean removeFirstOccurrence(Object o) {
448 jsr166 1.58 if (o != null) {
449 jsr166 1.99 final Object[] es = elements;
450 jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
451     ; i = 0, to = end) {
452 jsr166 1.92 for (; i < to; i++)
453 jsr166 1.99 if (o.equals(es[i])) {
454 jsr166 1.89 delete(i);
455     return true;
456     }
457 jsr166 1.106 if (to == end) break;
458 dl 1.1 }
459     }
460     return false;
461     }
462    
463     /**
464     * Removes the last occurrence of the specified element in this
465 jsr166 1.9 * deque (when traversing the deque from head to tail).
466     * If the deque does not contain the element, it is unchanged.
467 jsr166 1.40 * More formally, removes the last element {@code e} such that
468     * {@code o.equals(e)} (if such an element exists).
469     * Returns {@code true} if this deque contained the specified element
470 jsr166 1.12 * (or equivalently, if this deque changed as a result of the call).
471 dl 1.1 *
472 dl 1.5 * @param o element to be removed from this deque, if present
473 jsr166 1.40 * @return {@code true} if the deque contained the specified element
474 dl 1.1 */
475 dl 1.5 public boolean removeLastOccurrence(Object o) {
476 jsr166 1.59 if (o != null) {
477 jsr166 1.99 final Object[] es = elements;
478 jsr166 1.106 for (int i = last(), end = head - 1, to = (i >= end) ? end : -1;
479     ; i = es.length - 1, to = end) {
480 jsr166 1.92 for (; i > to; i--)
481 jsr166 1.99 if (o.equals(es[i])) {
482 jsr166 1.89 delete(i);
483     return true;
484     }
485 jsr166 1.106 if (to == end) break;
486 dl 1.1 }
487     }
488     return false;
489     }
490    
491     // *** Queue methods ***
492    
493     /**
494 dl 1.6 * Inserts the specified element at the end of this deque.
495 dl 1.1 *
496     * <p>This method is equivalent to {@link #addLast}.
497     *
498 jsr166 1.9 * @param e the element to add
499 jsr166 1.40 * @return {@code true} (as specified by {@link Collection#add})
500 jsr166 1.9 * @throws NullPointerException if the specified element is null
501 dl 1.1 */
502     public boolean add(E e) {
503     addLast(e);
504     return true;
505     }
506    
507     /**
508 jsr166 1.9 * Inserts the specified element at the end of this deque.
509 dl 1.1 *
510 jsr166 1.9 * <p>This method is equivalent to {@link #offerLast}.
511 dl 1.1 *
512 jsr166 1.9 * @param e the element to add
513 jsr166 1.40 * @return {@code true} (as specified by {@link Queue#offer})
514 jsr166 1.9 * @throws NullPointerException if the specified element is null
515 dl 1.1 */
516 jsr166 1.9 public boolean offer(E e) {
517     return offerLast(e);
518 dl 1.1 }
519    
520     /**
521     * Retrieves and removes the head of the queue represented by this deque.
522 jsr166 1.15 *
523     * This method differs from {@link #poll poll} only in that it throws an
524 jsr166 1.9 * exception if this deque is empty.
525 dl 1.1 *
526     * <p>This method is equivalent to {@link #removeFirst}.
527     *
528     * @return the head of the queue represented by this deque
529 jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
530 dl 1.1 */
531     public E remove() {
532     return removeFirst();
533     }
534    
535     /**
536 jsr166 1.9 * Retrieves and removes the head of the queue represented by this deque
537     * (in other words, the first element of this deque), or returns
538 jsr166 1.40 * {@code null} if this deque is empty.
539 dl 1.1 *
540 jsr166 1.9 * <p>This method is equivalent to {@link #pollFirst}.
541 dl 1.1 *
542     * @return the head of the queue represented by this deque, or
543 jsr166 1.40 * {@code null} if this deque is empty
544 dl 1.1 */
545 jsr166 1.9 public E poll() {
546     return pollFirst();
547 dl 1.1 }
548    
549     /**
550     * Retrieves, but does not remove, the head of the queue represented by
551 jsr166 1.15 * this deque. This method differs from {@link #peek peek} only in
552     * that it throws an exception if this deque is empty.
553 dl 1.1 *
554 jsr166 1.8 * <p>This method is equivalent to {@link #getFirst}.
555 dl 1.1 *
556     * @return the head of the queue represented by this deque
557 jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
558 dl 1.1 */
559     public E element() {
560     return getFirst();
561     }
562    
563 jsr166 1.9 /**
564     * Retrieves, but does not remove, the head of the queue represented by
565 jsr166 1.40 * this deque, or returns {@code null} if this deque is empty.
566 jsr166 1.9 *
567     * <p>This method is equivalent to {@link #peekFirst}.
568     *
569     * @return the head of the queue represented by this deque, or
570 jsr166 1.40 * {@code null} if this deque is empty
571 jsr166 1.9 */
572     public E peek() {
573     return peekFirst();
574     }
575    
576 dl 1.1 // *** Stack methods ***
577    
578     /**
579     * Pushes an element onto the stack represented by this deque. In other
580 dl 1.5 * words, inserts the element at the front of this deque.
581 dl 1.1 *
582     * <p>This method is equivalent to {@link #addFirst}.
583     *
584     * @param e the element to push
585 jsr166 1.9 * @throws NullPointerException if the specified element is null
586 dl 1.1 */
587     public void push(E e) {
588     addFirst(e);
589     }
590    
591     /**
592     * Pops an element from the stack represented by this deque. In other
593 dl 1.2 * words, removes and returns the first element of this deque.
594 dl 1.1 *
595     * <p>This method is equivalent to {@link #removeFirst()}.
596     *
597     * @return the element at the front of this deque (which is the top
598 jsr166 1.9 * of the stack represented by this deque)
599     * @throws NoSuchElementException {@inheritDoc}
600 dl 1.1 */
601     public E pop() {
602     return removeFirst();
603     }
604    
605     /**
606 jsr166 1.75 * Removes the element at the specified position in the elements array.
607     * This can result in forward or backwards motion of array elements.
608     * We optimize for least element motion.
609 dl 1.1 *
610 dl 1.5 * <p>This method is called delete rather than remove to emphasize
611 jsr166 1.9 * that its semantics differ from those of {@link List#remove(int)}.
612 dl 1.5 *
613 jsr166 1.106 * @return true if elements near tail moved backwards
614 dl 1.1 */
615 jsr166 1.71 boolean delete(int i) {
616 jsr166 1.75 // checkInvariants();
617 jsr166 1.99 final Object[] es = elements;
618     final int capacity = es.length;
619 jsr166 1.30 final int h = head;
620 jsr166 1.106 // number of elements before to-be-deleted elt
621     final int front = sub(i, h, capacity);
622     final int back = size() - front - 1; // number of elements after
623 jsr166 1.30 if (front < back) {
624 jsr166 1.75 // move front elements forwards
625 jsr166 1.30 if (h <= i) {
626 jsr166 1.99 System.arraycopy(es, h, es, h + 1, front);
627 jsr166 1.30 } else { // Wrap around
628 jsr166 1.99 System.arraycopy(es, 0, es, 1, i);
629     es[0] = es[capacity - 1];
630     System.arraycopy(es, h, es, h + 1, front - (i + 1));
631 jsr166 1.30 }
632 jsr166 1.99 es[h] = null;
633 jsr166 1.106 head = inc(h, capacity);
634 jsr166 1.75 // checkInvariants();
635 jsr166 1.30 return false;
636     } else {
637 jsr166 1.75 // move back elements backwards
638 jsr166 1.106 tail = dec(tail, capacity);
639 jsr166 1.75 if (i <= tail) {
640 jsr166 1.99 System.arraycopy(es, i + 1, es, i, back);
641 jsr166 1.30 } else { // Wrap around
642 jsr166 1.75 int firstLeg = capacity - (i + 1);
643 jsr166 1.99 System.arraycopy(es, i + 1, es, i, firstLeg);
644     es[capacity - 1] = es[0];
645     System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
646 jsr166 1.30 }
647 jsr166 1.99 es[tail] = null;
648 jsr166 1.75 // checkInvariants();
649 jsr166 1.30 return true;
650     }
651 dl 1.23 }
652    
653 dl 1.1 // *** Collection Methods ***
654    
655     /**
656     * Returns the number of elements in this deque.
657     *
658     * @return the number of elements in this deque
659     */
660     public int size() {
661 jsr166 1.106 return sub(tail, head, elements.length);
662 dl 1.1 }
663    
664     /**
665 jsr166 1.40 * Returns {@code true} if this deque contains no elements.
666 dl 1.1 *
667 jsr166 1.40 * @return {@code true} if this deque contains no elements
668 dl 1.1 */
669     public boolean isEmpty() {
670 jsr166 1.106 return head == tail;
671 dl 1.1 }
672    
673     /**
674     * Returns an iterator over the elements in this deque. The elements
675     * will be ordered from first (head) to last (tail). This is the same
676     * order that elements would be dequeued (via successive calls to
677     * {@link #remove} or popped (via successive calls to {@link #pop}).
678 dl 1.5 *
679 jsr166 1.18 * @return an iterator over the elements in this deque
680 dl 1.1 */
681     public Iterator<E> iterator() {
682     return new DeqIterator();
683     }
684    
685 dl 1.16 public Iterator<E> descendingIterator() {
686     return new DescendingIterator();
687     }
688    
689 dl 1.1 private class DeqIterator implements Iterator<E> {
690 jsr166 1.75 /** Index of element to be returned by subsequent call to next. */
691     int cursor;
692 dl 1.1
693 jsr166 1.75 /** Number of elements yet to be returned. */
694 jsr166 1.106 int remaining = size();
695 dl 1.1
696     /**
697     * Index of element returned by most recent call to next.
698     * Reset to -1 if element is deleted by a call to remove.
699     */
700 jsr166 1.75 int lastRet = -1;
701 dl 1.1
702 jsr166 1.75 DeqIterator() { cursor = head; }
703    
704     public final boolean hasNext() {
705     return remaining > 0;
706     }
707    
708 jsr166 1.81 public E next() {
709 jsr166 1.91 if (remaining <= 0)
710 dl 1.1 throw new NoSuchElementException();
711 jsr166 1.99 final Object[] es = elements;
712     E e = nonNullElementAt(es, cursor);
713 dl 1.1 lastRet = cursor;
714 jsr166 1.106 cursor = inc(cursor, es.length);
715 jsr166 1.75 remaining--;
716     return e;
717 dl 1.1 }
718    
719 jsr166 1.81 void postDelete(boolean leftShifted) {
720     if (leftShifted)
721 jsr166 1.106 cursor = dec(cursor, elements.length);
722 jsr166 1.81 }
723    
724 jsr166 1.75 public final void remove() {
725 dl 1.1 if (lastRet < 0)
726     throw new IllegalStateException();
727 jsr166 1.81 postDelete(delete(lastRet));
728 dl 1.1 lastRet = -1;
729     }
730 jsr166 1.68
731 jsr166 1.81 public void forEachRemaining(Consumer<? super E> action) {
732 jsr166 1.98 Objects.requireNonNull(action);
733 jsr166 1.106 int r;
734     if ((r = remaining) <= 0)
735     return;
736     remaining = 0;
737     final Object[] es = elements;
738     if (es[cursor] == null || sub(tail, cursor, es.length) != r)
739     throw new ConcurrentModificationException();
740     for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
741     ; i = 0, to = end) {
742     for (; i < to; i++)
743     action.accept(elementAt(es, i));
744     if (to == end) {
745     if (end != tail)
746     throw new ConcurrentModificationException();
747     lastRet = dec(end, es.length);
748     break;
749     }
750 jsr166 1.89 }
751 jsr166 1.68 }
752 dl 1.1 }
753    
754 jsr166 1.75 private class DescendingIterator extends DeqIterator {
755 jsr166 1.106 DescendingIterator() { cursor = last(); }
756 jsr166 1.75
757 jsr166 1.81 public final E next() {
758 jsr166 1.91 if (remaining <= 0)
759 jsr166 1.81 throw new NoSuchElementException();
760 jsr166 1.99 final Object[] es = elements;
761     E e = nonNullElementAt(es, cursor);
762 jsr166 1.81 lastRet = cursor;
763 jsr166 1.106 cursor = dec(cursor, es.length);
764 jsr166 1.81 remaining--;
765     return e;
766 jsr166 1.75 }
767    
768 jsr166 1.81 void postDelete(boolean leftShifted) {
769     if (!leftShifted)
770 jsr166 1.106 cursor = inc(cursor, elements.length);
771 jsr166 1.81 }
772    
773     public final void forEachRemaining(Consumer<? super E> action) {
774 jsr166 1.98 Objects.requireNonNull(action);
775 jsr166 1.106 int r;
776     if ((r = remaining) <= 0)
777     return;
778     remaining = 0;
779     final Object[] es = elements;
780     if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
781     throw new ConcurrentModificationException();
782     for (int i = cursor, end = head - 1, to = (i >= end) ? end : -1;
783     ; i = es.length - 1, to = end) {
784     for (; i > to; i--)
785     action.accept(elementAt(es, i));
786     if (to == end) {
787     if (end != head - 1)
788     throw new ConcurrentModificationException();
789     lastRet = head;
790     break;
791 jsr166 1.98 }
792 jsr166 1.89 }
793 jsr166 1.75 }
794     }
795    
796 jsr166 1.52 /**
797 jsr166 1.75 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
798     * and <em>fail-fast</em> {@link Spliterator} over the elements in this
799     * deque.
800     *
801     * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
802     * {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
803     * {@link Spliterator#NONNULL}. Overriding implementations should document
804     * the reporting of additional characteristic values.
805     *
806     * @return a {@code Spliterator} over the elements in this deque
807     * @since 1.8
808 jsr166 1.52 */
809 jsr166 1.75 public Spliterator<E> spliterator() {
810 jsr166 1.106 return new DeqSpliterator();
811 jsr166 1.75 }
812    
813 jsr166 1.106 final class DeqSpliterator implements Spliterator<E> {
814     private int fence; // -1 until first use
815     private int cursor; // current index, modified on traverse/split
816 jsr166 1.75
817 jsr166 1.76 /** Constructs late-binding spliterator over all elements. */
818 jsr166 1.106 DeqSpliterator() {
819     this.fence = -1;
820 jsr166 1.76 }
821    
822 jsr166 1.106 /** Constructs spliterator over the given range. */
823     DeqSpliterator(int origin, int fence) {
824     this.cursor = origin;
825     this.fence = fence;
826 jsr166 1.75 }
827    
828 jsr166 1.106 /** Ensures late-binding initialization; then returns fence. */
829     private int getFence() { // force initialization
830     int t;
831     if ((t = fence) < 0) {
832     t = fence = tail;
833 jsr166 1.76 cursor = head;
834     }
835 jsr166 1.106 return t;
836 jsr166 1.76 }
837    
838 jsr166 1.106 public DeqSpliterator trySplit() {
839     final Object[] es = elements;
840     final int i, n;
841     return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
842     ? null
843     : new DeqSpliterator(i, cursor = add(i, n, es.length));
844 jsr166 1.75 }
845 dl 1.16
846 jsr166 1.75 public void forEachRemaining(Consumer<? super E> action) {
847 jsr166 1.106 if (action == null)
848     throw new NullPointerException();
849     final int end = getFence(), cursor = this.cursor;
850     final Object[] es = elements;
851     if (cursor != end) {
852     this.cursor = end;
853     // null check at both ends of range is sufficient
854     if (es[cursor] == null || es[dec(end, es.length)] == null)
855     throw new ConcurrentModificationException();
856     for (int i = cursor, to = (i <= end) ? end : es.length;
857     ; i = 0, to = end) {
858     for (; i < to; i++)
859     action.accept(elementAt(es, i));
860     if (to == end) break;
861     }
862     }
863 dl 1.16 }
864    
865 jsr166 1.75 public boolean tryAdvance(Consumer<? super E> action) {
866 jsr166 1.106 if (action == null)
867     throw new NullPointerException();
868     int t, i;
869     if ((t = fence) < 0) t = getFence();
870     if (t == (i = cursor))
871 jsr166 1.75 return false;
872 jsr166 1.106 final Object[] es;
873     action.accept(nonNullElementAt(es = elements, i));
874     cursor = inc(i, es.length);
875 jsr166 1.75 return true;
876     }
877    
878     public long estimateSize() {
879 jsr166 1.106 return sub(getFence(), cursor, elements.length);
880 jsr166 1.75 }
881    
882     public int characteristics() {
883     return Spliterator.NONNULL
884     | Spliterator.ORDERED
885     | Spliterator.SIZED
886     | Spliterator.SUBSIZED;
887 dl 1.16 }
888 jsr166 1.75 }
889 dl 1.16
890 jsr166 1.75 public void forEach(Consumer<? super E> action) {
891     Objects.requireNonNull(action);
892 jsr166 1.99 final Object[] es = elements;
893 jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
894     ; i = 0, to = end) {
895 jsr166 1.92 for (; i < to; i++)
896 jsr166 1.106 action.accept(elementAt(es, i));
897     if (to == end) {
898     if (end != tail) throw new ConcurrentModificationException();
899     break;
900     }
901 jsr166 1.89 }
902 jsr166 1.75 // checkInvariants();
903     }
904    
905     /**
906     * Replaces each element of this deque with the result of applying the
907     * operator to that element, as specified by {@link List#replaceAll}.
908     *
909     * @param operator the operator to apply to each element
910 jsr166 1.80 * @since TBD
911 jsr166 1.75 */
912 jsr166 1.80 /* public */ void replaceAll(UnaryOperator<E> operator) {
913 jsr166 1.75 Objects.requireNonNull(operator);
914 jsr166 1.99 final Object[] es = elements;
915 jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
916     ; i = 0, to = end) {
917 jsr166 1.92 for (; i < to; i++)
918 jsr166 1.106 es[i] = operator.apply(elementAt(es, i));
919     if (to == end) {
920     if (end != tail) throw new ConcurrentModificationException();
921     break;
922     }
923 jsr166 1.89 }
924 jsr166 1.75 // checkInvariants();
925     }
926    
927     /**
928     * @throws NullPointerException {@inheritDoc}
929     */
930     public boolean removeIf(Predicate<? super E> filter) {
931     Objects.requireNonNull(filter);
932     return bulkRemove(filter);
933     }
934    
935     /**
936     * @throws NullPointerException {@inheritDoc}
937     */
938     public boolean removeAll(Collection<?> c) {
939     Objects.requireNonNull(c);
940     return bulkRemove(e -> c.contains(e));
941     }
942    
943     /**
944     * @throws NullPointerException {@inheritDoc}
945     */
946     public boolean retainAll(Collection<?> c) {
947     Objects.requireNonNull(c);
948     return bulkRemove(e -> !c.contains(e));
949     }
950    
951     /** Implementation of bulk remove methods. */
952     private boolean bulkRemove(Predicate<? super E> filter) {
953     // checkInvariants();
954 jsr166 1.99 final Object[] es = elements;
955 jsr166 1.106 // Optimize for initial run of survivors
956     for (int i = head, end = tail, to = (i <= end) ? end : es.length;
957     ; i = 0, to = end) {
958 jsr166 1.104 for (; i < to; i++)
959 jsr166 1.106 if (filter.test(elementAt(es, i)))
960     return bulkRemoveModified(filter, i, to);
961     if (to == end) {
962     if (end != tail) throw new ConcurrentModificationException();
963     break;
964     }
965 jsr166 1.104 }
966 jsr166 1.106 return false;
967 jsr166 1.104 }
968    
969     /**
970     * Helper for bulkRemove, in case of at least one deletion.
971     * @param i valid index of first element to be deleted
972     */
973 jsr166 1.106 private boolean bulkRemoveModified(
974     Predicate<? super E> filter, int i, int to) {
975 jsr166 1.104 final Object[] es = elements;
976 jsr166 1.99 final int capacity = es.length;
977 jsr166 1.106 // a two-finger algorithm, with hare i reading, tortoise j writing
978 jsr166 1.104 int j = i++;
979 jsr166 1.106 final int end = tail;
980 jsr166 1.75 try {
981 jsr166 1.106 for (;; j = 0) { // j rejoins i on second leg
982 jsr166 1.104 E e;
983     // In this loop, i and j are on the same leg, with i > j
984     for (; i < to; i++)
985 jsr166 1.106 if (!filter.test(e = elementAt(es, i)))
986 jsr166 1.104 es[j++] = e;
987 jsr166 1.106 if (to == end) break;
988 jsr166 1.104 // In this loop, j is on the first leg, i on the second
989 jsr166 1.106 for (i = 0, to = end; i < to && j < capacity; i++)
990     if (!filter.test(e = elementAt(es, i)))
991 jsr166 1.104 es[j++] = e;
992 jsr166 1.106 if (i >= to) {
993     if (j == capacity) j = 0; // "corner" case
994     break;
995     }
996 jsr166 1.104 }
997 jsr166 1.106 return true;
998 jsr166 1.104 } catch (Throwable ex) {
999     // copy remaining elements
1000 jsr166 1.106 for (; i != end; i = inc(i, capacity), j = inc(j, capacity))
1001 jsr166 1.104 es[j] = es[i];
1002 jsr166 1.106 throw ex;
1003     } finally {
1004     if (end != tail) throw new ConcurrentModificationException();
1005     circularClear(es, tail = j, end);
1006 jsr166 1.104 // checkInvariants();
1007 dl 1.16 }
1008     }
1009    
1010 dl 1.1 /**
1011 jsr166 1.40 * Returns {@code true} if this deque contains the specified element.
1012     * More formally, returns {@code true} if and only if this deque contains
1013     * at least one element {@code e} such that {@code o.equals(e)}.
1014 dl 1.1 *
1015     * @param o object to be checked for containment in this deque
1016 jsr166 1.40 * @return {@code true} if this deque contains the specified element
1017 dl 1.1 */
1018     public boolean contains(Object o) {
1019 jsr166 1.58 if (o != null) {
1020 jsr166 1.99 final Object[] es = elements;
1021 jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1022     ; i = 0, to = end) {
1023 jsr166 1.92 for (; i < to; i++)
1024 jsr166 1.99 if (o.equals(es[i]))
1025 jsr166 1.89 return true;
1026 jsr166 1.106 if (to == end) break;
1027 jsr166 1.89 }
1028 dl 1.1 }
1029     return false;
1030     }
1031    
1032     /**
1033     * Removes a single instance of the specified element from this deque.
1034 jsr166 1.9 * If the deque does not contain the element, it is unchanged.
1035 jsr166 1.40 * More formally, removes the first element {@code e} such that
1036     * {@code o.equals(e)} (if such an element exists).
1037     * Returns {@code true} if this deque contained the specified element
1038 jsr166 1.12 * (or equivalently, if this deque changed as a result of the call).
1039 jsr166 1.9 *
1040 jsr166 1.46 * <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1041 dl 1.1 *
1042 jsr166 1.9 * @param o element to be removed from this deque, if present
1043 jsr166 1.40 * @return {@code true} if this deque contained the specified element
1044 dl 1.1 */
1045 jsr166 1.9 public boolean remove(Object o) {
1046     return removeFirstOccurrence(o);
1047 dl 1.1 }
1048    
1049     /**
1050     * Removes all of the elements from this deque.
1051 jsr166 1.7 * The deque will be empty after this call returns.
1052 dl 1.1 */
1053     public void clear() {
1054 jsr166 1.106 circularClear(elements, head, tail);
1055     head = tail = 0;
1056 jsr166 1.75 // checkInvariants();
1057 dl 1.1 }
1058    
1059     /**
1060 jsr166 1.106 * Nulls out slots starting at array index i, upto index end.
1061 jsr166 1.89 */
1062 jsr166 1.106 private static void circularClear(Object[] es, int i, int end) {
1063     for (int to = (i <= end) ? end : es.length;
1064     ; i = 0, to = end) {
1065     Arrays.fill(es, i, to, null);
1066     if (to == end) break;
1067 jsr166 1.99 }
1068 jsr166 1.89 }
1069    
1070     /**
1071 dl 1.5 * Returns an array containing all of the elements in this deque
1072 jsr166 1.10 * in proper sequence (from first to last element).
1073 dl 1.1 *
1074 jsr166 1.10 * <p>The returned array will be "safe" in that no references to it are
1075     * maintained by this deque. (In other words, this method must allocate
1076     * a new array). The caller is thus free to modify the returned array.
1077 jsr166 1.13 *
1078 jsr166 1.11 * <p>This method acts as bridge between array-based and collection-based
1079     * APIs.
1080     *
1081 dl 1.5 * @return an array containing all of the elements in this deque
1082 dl 1.1 */
1083     public Object[] toArray() {
1084 jsr166 1.86 return toArray(Object[].class);
1085     }
1086    
1087     private <T> T[] toArray(Class<T[]> klazz) {
1088 jsr166 1.99 final Object[] es = elements;
1089 jsr166 1.86 final T[] a;
1090 jsr166 1.106 final int size = size(), head = this.head, end;
1091     final int len = Math.min(size, es.length - head);
1092 jsr166 1.102 if ((end = head + size) >= 0) {
1093 jsr166 1.99 a = Arrays.copyOfRange(es, head, end, klazz);
1094 jsr166 1.86 } else {
1095     // integer overflow!
1096 jsr166 1.99 a = Arrays.copyOfRange(es, 0, size, klazz);
1097 jsr166 1.102 System.arraycopy(es, head, a, 0, len);
1098 jsr166 1.86 }
1099 jsr166 1.106 if (tail < head)
1100     System.arraycopy(es, 0, a, len, tail);
1101 jsr166 1.50 return a;
1102 dl 1.1 }
1103    
1104     /**
1105 jsr166 1.10 * Returns an array containing all of the elements in this deque in
1106     * proper sequence (from first to last element); the runtime type of the
1107     * returned array is that of the specified array. If the deque fits in
1108     * the specified array, it is returned therein. Otherwise, a new array
1109     * is allocated with the runtime type of the specified array and the
1110     * size of this deque.
1111     *
1112     * <p>If this deque fits in the specified array with room to spare
1113     * (i.e., the array has more elements than this deque), the element in
1114     * the array immediately following the end of the deque is set to
1115 jsr166 1.40 * {@code null}.
1116 jsr166 1.10 *
1117     * <p>Like the {@link #toArray()} method, this method acts as bridge between
1118     * array-based and collection-based APIs. Further, this method allows
1119     * precise control over the runtime type of the output array, and may,
1120     * under certain circumstances, be used to save allocation costs.
1121     *
1122 jsr166 1.40 * <p>Suppose {@code x} is a deque known to contain only strings.
1123 jsr166 1.10 * The following code can be used to dump the deque into a newly
1124 jsr166 1.40 * allocated array of {@code String}:
1125 jsr166 1.10 *
1126 jsr166 1.63 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1127 jsr166 1.10 *
1128 jsr166 1.40 * Note that {@code toArray(new Object[0])} is identical in function to
1129     * {@code toArray()}.
1130 dl 1.1 *
1131     * @param a the array into which the elements of the deque are to
1132 jsr166 1.9 * be stored, if it is big enough; otherwise, a new array of the
1133     * same runtime type is allocated for this purpose
1134 jsr166 1.10 * @return an array containing all of the elements in this deque
1135     * @throws ArrayStoreException if the runtime type of the specified array
1136     * is not a supertype of the runtime type of every element in
1137     * this deque
1138     * @throws NullPointerException if the specified array is null
1139 dl 1.1 */
1140 jsr166 1.34 @SuppressWarnings("unchecked")
1141 dl 1.1 public <T> T[] toArray(T[] a) {
1142 jsr166 1.99 final int size;
1143 jsr166 1.106 if ((size = size()) > a.length)
1144 jsr166 1.86 return toArray((Class<T[]>) a.getClass());
1145 jsr166 1.99 final Object[] es = elements;
1146 jsr166 1.106 for (int i = head, j = 0, len = Math.min(size, es.length - i);
1147     ; i = 0, len = tail) {
1148 jsr166 1.101 System.arraycopy(es, i, a, j, len);
1149 jsr166 1.106 if ((j += len) == size) break;
1150 jsr166 1.101 }
1151 jsr166 1.86 if (size < a.length)
1152     a[size] = null;
1153 dl 1.1 return a;
1154     }
1155    
1156     // *** Object methods ***
1157    
1158     /**
1159     * Returns a copy of this deque.
1160     *
1161     * @return a copy of this deque
1162     */
1163     public ArrayDeque<E> clone() {
1164 dl 1.5 try {
1165 jsr166 1.34 @SuppressWarnings("unchecked")
1166 dl 1.1 ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1167 jsr166 1.28 result.elements = Arrays.copyOf(elements, elements.length);
1168 dl 1.1 return result;
1169 dl 1.5 } catch (CloneNotSupportedException e) {
1170 dl 1.1 throw new AssertionError();
1171     }
1172     }
1173    
1174     private static final long serialVersionUID = 2340985798034038923L;
1175    
1176     /**
1177 jsr166 1.38 * Saves this deque to a stream (that is, serializes it).
1178 dl 1.1 *
1179 jsr166 1.56 * @param s the stream
1180 jsr166 1.57 * @throws java.io.IOException if an I/O error occurs
1181 jsr166 1.40 * @serialData The current size ({@code int}) of the deque,
1182 dl 1.1 * followed by all of its elements (each an object reference) in
1183     * first-to-last order.
1184     */
1185 jsr166 1.32 private void writeObject(java.io.ObjectOutputStream s)
1186     throws java.io.IOException {
1187 dl 1.1 s.defaultWriteObject();
1188    
1189     // Write out size
1190 jsr166 1.106 s.writeInt(size());
1191 dl 1.1
1192     // Write out elements in order.
1193 jsr166 1.99 final Object[] es = elements;
1194 jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1195     ; i = 0, to = end) {
1196 jsr166 1.92 for (; i < to; i++)
1197 jsr166 1.99 s.writeObject(es[i]);
1198 jsr166 1.106 if (to == end) break;
1199 jsr166 1.89 }
1200 dl 1.1 }
1201    
1202     /**
1203 jsr166 1.38 * Reconstitutes this deque from a stream (that is, deserializes it).
1204 jsr166 1.56 * @param s the stream
1205 jsr166 1.57 * @throws ClassNotFoundException if the class of a serialized object
1206     * could not be found
1207     * @throws java.io.IOException if an I/O error occurs
1208 dl 1.1 */
1209 jsr166 1.32 private void readObject(java.io.ObjectInputStream s)
1210     throws java.io.IOException, ClassNotFoundException {
1211 dl 1.1 s.defaultReadObject();
1212    
1213     // Read in size and allocate array
1214 jsr166 1.106 int size = s.readInt();
1215     elements = new Object[size + 1];
1216     this.tail = size;
1217 dl 1.1
1218     // Read in all elements in the proper order.
1219     for (int i = 0; i < size; i++)
1220 jsr166 1.34 elements[i] = s.readObject();
1221 dl 1.1 }
1222 dl 1.41
1223 jsr166 1.75 /** debugging */
1224 jsr166 1.89 void checkInvariants() {
1225 jsr166 1.75 try {
1226     int capacity = elements.length;
1227 jsr166 1.106 // assert head >= 0 && head < capacity;
1228     // assert tail >= 0 && tail < capacity;
1229     // assert capacity > 0;
1230     // assert size() < capacity;
1231     // assert head == tail || elements[head] != null;
1232     // assert elements[tail] == null;
1233     // assert head == tail || elements[dec(tail, capacity)] != null;
1234 jsr166 1.75 } catch (Throwable t) {
1235 jsr166 1.106 System.err.printf("head=%d tail=%d capacity=%d%n",
1236     head, tail, elements.length);
1237 jsr166 1.75 System.err.printf("elements=%s%n",
1238     Arrays.toString(elements));
1239     throw t;
1240 dl 1.41 }
1241     }
1242    
1243 dl 1.1 }