1 |
/* |
2 |
* 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 |
*/ |
5 |
|
6 |
package java.util; |
7 |
|
8 |
import java.io.Serializable; |
9 |
import java.util.function.Consumer; |
10 |
import java.util.function.Predicate; |
11 |
import java.util.function.UnaryOperator; |
12 |
|
13 |
/** |
14 |
* Resizable-array implementation of the {@link Deque} interface. Array |
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 |
* {@link Stack} when used as a stack, and faster than {@link LinkedList} |
20 |
* when used as a queue. |
21 |
* |
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 {@link #iterator() iterator} |
32 |
* method are <em>fail-fast</em>: If the deque is modified at any time after |
33 |
* the iterator is created, in any way except through the iterator's own |
34 |
* {@code remove} method, the iterator will generally throw a {@link |
35 |
* ConcurrentModificationException}. Thus, in the face of concurrent |
36 |
* modification, the iterator fails quickly and cleanly, rather than risking |
37 |
* arbitrary, non-deterministic behavior at an undetermined time in the |
38 |
* future. |
39 |
* |
40 |
* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
41 |
* as it is, generally speaking, impossible to make any hard guarantees in the |
42 |
* presence of unsynchronized concurrent modification. Fail-fast iterators |
43 |
* throw {@code ConcurrentModificationException} on a best-effort basis. |
44 |
* Therefore, it would be wrong to write a program that depended on this |
45 |
* exception for its correctness: <i>the fail-fast behavior of iterators |
46 |
* should be used only to detect bugs.</i> |
47 |
* |
48 |
* <p>This class and its iterator implement all of the |
49 |
* <em>optional</em> methods of the {@link Collection} and {@link |
50 |
* Iterator} interfaces. |
51 |
* |
52 |
* <p>This class is a member of the |
53 |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
54 |
* Java Collections Framework</a>. |
55 |
* |
56 |
* @author Josh Bloch and Doug Lea |
57 |
* @param <E> the type of elements held in this deque |
58 |
* @since 1.6 |
59 |
*/ |
60 |
public class ArrayDeque<E> extends AbstractCollection<E> |
61 |
implements Deque<E>, Cloneable, Serializable |
62 |
{ |
63 |
/** |
64 |
* The array in which the elements of the deque are stored. |
65 |
* We guarantee that all array cells not holding deque elements |
66 |
* are always null. |
67 |
*/ |
68 |
transient Object[] elements; |
69 |
|
70 |
/** |
71 |
* The index of the element at the head of the deque (which is the |
72 |
* element that would be removed by remove() or pop()); or an |
73 |
* arbitrary number 0 <= head < elements.length if the deque is empty. |
74 |
*/ |
75 |
transient int head; |
76 |
|
77 |
/** Number of elements in this collection. */ |
78 |
transient int size; |
79 |
|
80 |
/** |
81 |
* The maximum size of array to allocate. |
82 |
* Some VMs reserve some header words in an array. |
83 |
* Attempts to allocate larger arrays may result in |
84 |
* OutOfMemoryError: Requested array size exceeds VM limit |
85 |
*/ |
86 |
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
87 |
|
88 |
/** |
89 |
* Increases the capacity of this deque by at least the given amount. |
90 |
* |
91 |
* @param needed the required minimum extra capacity; must be positive |
92 |
*/ |
93 |
private void grow(int needed) { |
94 |
// overflow-conscious code |
95 |
// checkInvariants(); |
96 |
int oldCapacity = elements.length; |
97 |
int newCapacity; |
98 |
// Double size if small; else grow by 50% |
99 |
int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1); |
100 |
if (jump < needed |
101 |
|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0) |
102 |
newCapacity = newCapacity(needed, jump); |
103 |
elements = Arrays.copyOf(elements, newCapacity); |
104 |
if (oldCapacity - head < size) { |
105 |
// wrap around; slide first leg forward to end of array |
106 |
int newSpace = newCapacity - oldCapacity; |
107 |
System.arraycopy(elements, head, |
108 |
elements, head + newSpace, |
109 |
oldCapacity - head); |
110 |
Arrays.fill(elements, head, head + newSpace, null); |
111 |
head += newSpace; |
112 |
} |
113 |
// checkInvariants(); |
114 |
} |
115 |
|
116 |
/** Capacity calculation for edge conditions, especially overflow. */ |
117 |
private int newCapacity(int needed, int jump) { |
118 |
int oldCapacity = elements.length; |
119 |
int minCapacity; |
120 |
if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) { |
121 |
if (minCapacity < 0) |
122 |
throw new IllegalStateException("Sorry, deque too big"); |
123 |
return Integer.MAX_VALUE; |
124 |
} |
125 |
if (needed > jump) |
126 |
return minCapacity; |
127 |
return (oldCapacity + jump - MAX_ARRAY_SIZE < 0) |
128 |
? oldCapacity + jump |
129 |
: MAX_ARRAY_SIZE; |
130 |
} |
131 |
|
132 |
/** |
133 |
* Increases the internal storage of this collection, if necessary, |
134 |
* to ensure that it can hold at least the given number of elements. |
135 |
* |
136 |
* @param minCapacity the desired minimum capacity |
137 |
* @since TBD |
138 |
*/ |
139 |
/* public */ void ensureCapacity(int minCapacity) { |
140 |
if (minCapacity > elements.length) |
141 |
grow(minCapacity - elements.length); |
142 |
// checkInvariants(); |
143 |
} |
144 |
|
145 |
/** |
146 |
* Minimizes the internal storage of this collection. |
147 |
* |
148 |
* @since TBD |
149 |
*/ |
150 |
/* public */ void trimToSize() { |
151 |
if (size < elements.length) { |
152 |
elements = toArray(); |
153 |
head = 0; |
154 |
} |
155 |
// checkInvariants(); |
156 |
} |
157 |
|
158 |
/** |
159 |
* Constructs an empty array deque with an initial capacity |
160 |
* sufficient to hold 16 elements. |
161 |
*/ |
162 |
public ArrayDeque() { |
163 |
elements = new Object[16]; |
164 |
} |
165 |
|
166 |
/** |
167 |
* Constructs an empty array deque with an initial capacity |
168 |
* sufficient to hold the specified number of elements. |
169 |
* |
170 |
* @param numElements lower bound on initial capacity of the deque |
171 |
*/ |
172 |
public ArrayDeque(int numElements) { |
173 |
elements = new Object[numElements]; |
174 |
} |
175 |
|
176 |
/** |
177 |
* Constructs a deque containing the elements of the specified |
178 |
* collection, in the order they are returned by the collection's |
179 |
* iterator. (The first element returned by the collection's |
180 |
* iterator becomes the first element, or <i>front</i> of the |
181 |
* deque.) |
182 |
* |
183 |
* @param c the collection whose elements are to be placed into the deque |
184 |
* @throws NullPointerException if the specified collection is null |
185 |
*/ |
186 |
public ArrayDeque(Collection<? extends E> c) { |
187 |
Object[] elements = c.toArray(); |
188 |
// defend against c.toArray (incorrectly) not returning Object[] |
189 |
// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652) |
190 |
size = elements.length; |
191 |
if (elements.getClass() != Object[].class) |
192 |
elements = Arrays.copyOf(elements, size, Object[].class); |
193 |
for (Object obj : elements) |
194 |
Objects.requireNonNull(obj); |
195 |
this.elements = elements; |
196 |
} |
197 |
|
198 |
/** |
199 |
* Increments i, mod modulus. |
200 |
* Precondition and postcondition: 0 <= i < modulus. |
201 |
*/ |
202 |
static final int inc(int i, int modulus) { |
203 |
if (++i >= modulus) i = 0; |
204 |
return i; |
205 |
} |
206 |
|
207 |
/** |
208 |
* Decrements i, mod modulus. |
209 |
* Precondition and postcondition: 0 <= i < modulus. |
210 |
*/ |
211 |
static final int dec(int i, int modulus) { |
212 |
if (--i < 0) i = modulus - 1; |
213 |
return i; |
214 |
} |
215 |
|
216 |
/** |
217 |
* Adds i and j, mod modulus. |
218 |
* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus. |
219 |
*/ |
220 |
static final int add(int i, int j, int modulus) { |
221 |
if ((i += j) - modulus >= 0) i -= modulus; |
222 |
return i; |
223 |
} |
224 |
|
225 |
/** |
226 |
* Returns the array index of the last element. |
227 |
* May return invalid index -1 if there are no elements. |
228 |
*/ |
229 |
final int tail() { |
230 |
return add(head, size - 1, elements.length); |
231 |
} |
232 |
|
233 |
/** |
234 |
* Returns element at array index i. |
235 |
*/ |
236 |
@SuppressWarnings("unchecked") |
237 |
private E elementAt(int i) { |
238 |
return (E) elements[i]; |
239 |
} |
240 |
|
241 |
/** |
242 |
* A version of elementAt that checks for null elements. |
243 |
* This check doesn't catch all possible comodifications, |
244 |
* but does catch ones that corrupt traversal. |
245 |
*/ |
246 |
E checkedElementAt(Object[] elements, int i) { |
247 |
@SuppressWarnings("unchecked") E e = (E) elements[i]; |
248 |
if (e == null) |
249 |
throw new ConcurrentModificationException(); |
250 |
return e; |
251 |
} |
252 |
|
253 |
// The main insertion and extraction methods are addFirst, |
254 |
// addLast, pollFirst, pollLast. The other methods are defined in |
255 |
// terms of these. |
256 |
|
257 |
/** |
258 |
* Inserts the specified element at the front of this deque. |
259 |
* |
260 |
* @param e the element to add |
261 |
* @throws NullPointerException if the specified element is null |
262 |
*/ |
263 |
public void addFirst(E e) { |
264 |
// checkInvariants(); |
265 |
Objects.requireNonNull(e); |
266 |
Object[] elements; |
267 |
int capacity, h; |
268 |
final int s; |
269 |
if ((s = size) == (capacity = (elements = this.elements).length)) { |
270 |
grow(1); |
271 |
capacity = (elements = this.elements).length; |
272 |
} |
273 |
if ((h = head - 1) < 0) h = capacity - 1; |
274 |
elements[head = h] = e; |
275 |
size = s + 1; |
276 |
// checkInvariants(); |
277 |
} |
278 |
|
279 |
/** |
280 |
* Inserts the specified element at the end of this deque. |
281 |
* |
282 |
* <p>This method is equivalent to {@link #add}. |
283 |
* |
284 |
* @param e the element to add |
285 |
* @throws NullPointerException if the specified element is null |
286 |
*/ |
287 |
public void addLast(E e) { |
288 |
// checkInvariants(); |
289 |
Objects.requireNonNull(e); |
290 |
Object[] elements; |
291 |
int capacity; |
292 |
final int s; |
293 |
if ((s = size) == (capacity = (elements = this.elements).length)) { |
294 |
grow(1); |
295 |
capacity = (elements = this.elements).length; |
296 |
} |
297 |
elements[add(head, s, capacity)] = e; |
298 |
size = s + 1; |
299 |
// checkInvariants(); |
300 |
} |
301 |
|
302 |
/** |
303 |
* Adds all of the elements in the specified collection at the end |
304 |
* of this deque, as if by calling {@link #addLast} on each one, |
305 |
* in the order that they are returned by the collection's |
306 |
* iterator. |
307 |
* |
308 |
* @param c the elements to be inserted into this deque |
309 |
* @return {@code true} if this deque changed as a result of the call |
310 |
* @throws NullPointerException if the specified collection or any |
311 |
* of its elements are null |
312 |
*/ |
313 |
public boolean addAll(Collection<? extends E> c) { |
314 |
final int s = size, needed = c.size() - (elements.length - s); |
315 |
if (needed > 0) |
316 |
grow(needed); |
317 |
c.forEach((e) -> addLast(e)); |
318 |
// checkInvariants(); |
319 |
return size > s; |
320 |
} |
321 |
|
322 |
/** |
323 |
* Inserts the specified element at the front of this deque. |
324 |
* |
325 |
* @param e the element to add |
326 |
* @return {@code true} (as specified by {@link Deque#offerFirst}) |
327 |
* @throws NullPointerException if the specified element is null |
328 |
*/ |
329 |
public boolean offerFirst(E e) { |
330 |
addFirst(e); |
331 |
return true; |
332 |
} |
333 |
|
334 |
/** |
335 |
* Inserts the specified element at the end of this deque. |
336 |
* |
337 |
* @param e the element to add |
338 |
* @return {@code true} (as specified by {@link Deque#offerLast}) |
339 |
* @throws NullPointerException if the specified element is null |
340 |
*/ |
341 |
public boolean offerLast(E e) { |
342 |
addLast(e); |
343 |
return true; |
344 |
} |
345 |
|
346 |
/** |
347 |
* @throws NoSuchElementException {@inheritDoc} |
348 |
*/ |
349 |
public E removeFirst() { |
350 |
// checkInvariants(); |
351 |
E e = pollFirst(); |
352 |
if (e == null) |
353 |
throw new NoSuchElementException(); |
354 |
return e; |
355 |
} |
356 |
|
357 |
/** |
358 |
* @throws NoSuchElementException {@inheritDoc} |
359 |
*/ |
360 |
public E removeLast() { |
361 |
// checkInvariants(); |
362 |
E e = pollLast(); |
363 |
if (e == null) |
364 |
throw new NoSuchElementException(); |
365 |
return e; |
366 |
} |
367 |
|
368 |
public E pollFirst() { |
369 |
// checkInvariants(); |
370 |
int s, h; |
371 |
if ((s = size) == 0) |
372 |
return null; |
373 |
final Object[] elements = this.elements; |
374 |
@SuppressWarnings("unchecked") E e = (E) elements[h = head]; |
375 |
elements[h] = null; |
376 |
if (++h >= elements.length) h = 0; |
377 |
head = h; |
378 |
size = s - 1; |
379 |
return e; |
380 |
} |
381 |
|
382 |
public E pollLast() { |
383 |
// checkInvariants(); |
384 |
final int s, tail; |
385 |
if ((s = size) == 0) |
386 |
return null; |
387 |
final Object[] elements = this.elements; |
388 |
@SuppressWarnings("unchecked") |
389 |
E e = (E) elements[tail = add(head, s - 1, elements.length)]; |
390 |
elements[tail] = null; |
391 |
size = s - 1; |
392 |
return e; |
393 |
} |
394 |
|
395 |
/** |
396 |
* @throws NoSuchElementException {@inheritDoc} |
397 |
*/ |
398 |
public E getFirst() { |
399 |
// checkInvariants(); |
400 |
if (size == 0) throw new NoSuchElementException(); |
401 |
return elementAt(head); |
402 |
} |
403 |
|
404 |
/** |
405 |
* @throws NoSuchElementException {@inheritDoc} |
406 |
*/ |
407 |
public E getLast() { |
408 |
// checkInvariants(); |
409 |
if (size == 0) throw new NoSuchElementException(); |
410 |
return elementAt(tail()); |
411 |
} |
412 |
|
413 |
public E peekFirst() { |
414 |
// checkInvariants(); |
415 |
return (size == 0) ? null : elementAt(head); |
416 |
} |
417 |
|
418 |
public E peekLast() { |
419 |
// checkInvariants(); |
420 |
return (size == 0) ? null : elementAt(tail()); |
421 |
} |
422 |
|
423 |
/** |
424 |
* Removes the first occurrence of the specified element in this |
425 |
* deque (when traversing the deque from head to tail). |
426 |
* If the deque does not contain the element, it is unchanged. |
427 |
* More formally, removes the first element {@code e} such that |
428 |
* {@code o.equals(e)} (if such an element exists). |
429 |
* Returns {@code true} if this deque contained the specified element |
430 |
* (or equivalently, if this deque changed as a result of the call). |
431 |
* |
432 |
* @param o element to be removed from this deque, if present |
433 |
* @return {@code true} if the deque contained the specified element |
434 |
*/ |
435 |
public boolean removeFirstOccurrence(Object o) { |
436 |
if (o != null) { |
437 |
final Object[] elements = this.elements; |
438 |
final int capacity = elements.length; |
439 |
int from, end, to, leftover; |
440 |
leftover = (end = (from = head) + size) |
441 |
- (to = (capacity - end >= 0) ? end : capacity); |
442 |
for (;; from = 0, to = leftover, leftover = 0) { |
443 |
for (int i = from; i < to; i++) |
444 |
if (o.equals(elements[i])) { |
445 |
delete(i); |
446 |
return true; |
447 |
} |
448 |
if (leftover == 0) break; |
449 |
} |
450 |
} |
451 |
return false; |
452 |
} |
453 |
|
454 |
/** |
455 |
* Removes the last occurrence of the specified element in this |
456 |
* deque (when traversing the deque from head to tail). |
457 |
* If the deque does not contain the element, it is unchanged. |
458 |
* More formally, removes the last element {@code e} such that |
459 |
* {@code o.equals(e)} (if such an element exists). |
460 |
* Returns {@code true} if this deque contained the specified element |
461 |
* (or equivalently, if this deque changed as a result of the call). |
462 |
* |
463 |
* @param o element to be removed from this deque, if present |
464 |
* @return {@code true} if the deque contained the specified element |
465 |
*/ |
466 |
public boolean removeLastOccurrence(Object o) { |
467 |
if (o != null) { |
468 |
final Object[] elements = this.elements; |
469 |
final int capacity = elements.length; |
470 |
int from, to, end, leftover; |
471 |
leftover = (to = ((end = (from = tail()) - size) >= -1) ? end : -1) - end; |
472 |
for (;; from = capacity - 1, to = capacity - 1 - leftover, leftover = 0) { |
473 |
for (int i = from; i > to; i--) |
474 |
if (o.equals(elements[i])) { |
475 |
delete(i); |
476 |
return true; |
477 |
} |
478 |
if (leftover == 0) break; |
479 |
} |
480 |
} |
481 |
return false; |
482 |
} |
483 |
|
484 |
// *** Queue methods *** |
485 |
|
486 |
/** |
487 |
* Inserts the specified element at the end of this deque. |
488 |
* |
489 |
* <p>This method is equivalent to {@link #addLast}. |
490 |
* |
491 |
* @param e the element to add |
492 |
* @return {@code true} (as specified by {@link Collection#add}) |
493 |
* @throws NullPointerException if the specified element is null |
494 |
*/ |
495 |
public boolean add(E e) { |
496 |
addLast(e); |
497 |
return true; |
498 |
} |
499 |
|
500 |
/** |
501 |
* Inserts the specified element at the end of this deque. |
502 |
* |
503 |
* <p>This method is equivalent to {@link #offerLast}. |
504 |
* |
505 |
* @param e the element to add |
506 |
* @return {@code true} (as specified by {@link Queue#offer}) |
507 |
* @throws NullPointerException if the specified element is null |
508 |
*/ |
509 |
public boolean offer(E e) { |
510 |
return offerLast(e); |
511 |
} |
512 |
|
513 |
/** |
514 |
* Retrieves and removes the head of the queue represented by this deque. |
515 |
* |
516 |
* This method differs from {@link #poll poll} only in that it throws an |
517 |
* exception if this deque is empty. |
518 |
* |
519 |
* <p>This method is equivalent to {@link #removeFirst}. |
520 |
* |
521 |
* @return the head of the queue represented by this deque |
522 |
* @throws NoSuchElementException {@inheritDoc} |
523 |
*/ |
524 |
public E remove() { |
525 |
return removeFirst(); |
526 |
} |
527 |
|
528 |
/** |
529 |
* Retrieves and removes the head of the queue represented by this deque |
530 |
* (in other words, the first element of this deque), or returns |
531 |
* {@code null} if this deque is empty. |
532 |
* |
533 |
* <p>This method is equivalent to {@link #pollFirst}. |
534 |
* |
535 |
* @return the head of the queue represented by this deque, or |
536 |
* {@code null} if this deque is empty |
537 |
*/ |
538 |
public E poll() { |
539 |
return pollFirst(); |
540 |
} |
541 |
|
542 |
/** |
543 |
* Retrieves, but does not remove, the head of the queue represented by |
544 |
* this deque. This method differs from {@link #peek peek} only in |
545 |
* that it throws an exception if this deque is empty. |
546 |
* |
547 |
* <p>This method is equivalent to {@link #getFirst}. |
548 |
* |
549 |
* @return the head of the queue represented by this deque |
550 |
* @throws NoSuchElementException {@inheritDoc} |
551 |
*/ |
552 |
public E element() { |
553 |
return getFirst(); |
554 |
} |
555 |
|
556 |
/** |
557 |
* Retrieves, but does not remove, the head of the queue represented by |
558 |
* this deque, or returns {@code null} if this deque is empty. |
559 |
* |
560 |
* <p>This method is equivalent to {@link #peekFirst}. |
561 |
* |
562 |
* @return the head of the queue represented by this deque, or |
563 |
* {@code null} if this deque is empty |
564 |
*/ |
565 |
public E peek() { |
566 |
return peekFirst(); |
567 |
} |
568 |
|
569 |
// *** Stack methods *** |
570 |
|
571 |
/** |
572 |
* Pushes an element onto the stack represented by this deque. In other |
573 |
* words, inserts the element at the front of this deque. |
574 |
* |
575 |
* <p>This method is equivalent to {@link #addFirst}. |
576 |
* |
577 |
* @param e the element to push |
578 |
* @throws NullPointerException if the specified element is null |
579 |
*/ |
580 |
public void push(E e) { |
581 |
addFirst(e); |
582 |
} |
583 |
|
584 |
/** |
585 |
* Pops an element from the stack represented by this deque. In other |
586 |
* words, removes and returns the first element of this deque. |
587 |
* |
588 |
* <p>This method is equivalent to {@link #removeFirst()}. |
589 |
* |
590 |
* @return the element at the front of this deque (which is the top |
591 |
* of the stack represented by this deque) |
592 |
* @throws NoSuchElementException {@inheritDoc} |
593 |
*/ |
594 |
public E pop() { |
595 |
return removeFirst(); |
596 |
} |
597 |
|
598 |
/** |
599 |
* Removes the element at the specified position in the elements array. |
600 |
* This can result in forward or backwards motion of array elements. |
601 |
* We optimize for least element motion. |
602 |
* |
603 |
* <p>This method is called delete rather than remove to emphasize |
604 |
* that its semantics differ from those of {@link List#remove(int)}. |
605 |
* |
606 |
* @return true if elements moved backwards |
607 |
*/ |
608 |
boolean delete(int i) { |
609 |
// checkInvariants(); |
610 |
final Object[] elements = this.elements; |
611 |
final int capacity = elements.length; |
612 |
final int h = head; |
613 |
int front; // number of elements before to-be-deleted elt |
614 |
if ((front = i - h) < 0) front += capacity; |
615 |
final int back = size - front - 1; // number of elements after |
616 |
if (front < back) { |
617 |
// move front elements forwards |
618 |
if (h <= i) { |
619 |
System.arraycopy(elements, h, elements, h + 1, front); |
620 |
} else { // Wrap around |
621 |
System.arraycopy(elements, 0, elements, 1, i); |
622 |
elements[0] = elements[capacity - 1]; |
623 |
System.arraycopy(elements, h, elements, h + 1, front - (i + 1)); |
624 |
} |
625 |
elements[h] = null; |
626 |
if ((head = (h + 1)) >= capacity) head = 0; |
627 |
size--; |
628 |
// checkInvariants(); |
629 |
return false; |
630 |
} else { |
631 |
// move back elements backwards |
632 |
int tail = tail(); |
633 |
if (i <= tail) { |
634 |
System.arraycopy(elements, i + 1, elements, i, back); |
635 |
} else { // Wrap around |
636 |
int firstLeg = capacity - (i + 1); |
637 |
System.arraycopy(elements, i + 1, elements, i, firstLeg); |
638 |
elements[capacity - 1] = elements[0]; |
639 |
System.arraycopy(elements, 1, elements, 0, back - firstLeg - 1); |
640 |
} |
641 |
elements[tail] = null; |
642 |
size--; |
643 |
// checkInvariants(); |
644 |
return true; |
645 |
} |
646 |
} |
647 |
|
648 |
// *** Collection Methods *** |
649 |
|
650 |
/** |
651 |
* Returns the number of elements in this deque. |
652 |
* |
653 |
* @return the number of elements in this deque |
654 |
*/ |
655 |
public int size() { |
656 |
return size; |
657 |
} |
658 |
|
659 |
/** |
660 |
* Returns {@code true} if this deque contains no elements. |
661 |
* |
662 |
* @return {@code true} if this deque contains no elements |
663 |
*/ |
664 |
public boolean isEmpty() { |
665 |
return size == 0; |
666 |
} |
667 |
|
668 |
/** |
669 |
* Returns an iterator over the elements in this deque. The elements |
670 |
* will be ordered from first (head) to last (tail). This is the same |
671 |
* order that elements would be dequeued (via successive calls to |
672 |
* {@link #remove} or popped (via successive calls to {@link #pop}). |
673 |
* |
674 |
* @return an iterator over the elements in this deque |
675 |
*/ |
676 |
public Iterator<E> iterator() { |
677 |
return new DeqIterator(); |
678 |
} |
679 |
|
680 |
public Iterator<E> descendingIterator() { |
681 |
return new DescendingIterator(); |
682 |
} |
683 |
|
684 |
private class DeqIterator implements Iterator<E> { |
685 |
/** Index of element to be returned by subsequent call to next. */ |
686 |
int cursor; |
687 |
|
688 |
/** Number of elements yet to be returned. */ |
689 |
int remaining = size; |
690 |
|
691 |
/** |
692 |
* Index of element returned by most recent call to next. |
693 |
* Reset to -1 if element is deleted by a call to remove. |
694 |
*/ |
695 |
int lastRet = -1; |
696 |
|
697 |
DeqIterator() { cursor = head; } |
698 |
|
699 |
public final boolean hasNext() { |
700 |
return remaining > 0; |
701 |
} |
702 |
|
703 |
public E next() { |
704 |
if (remaining == 0) |
705 |
throw new NoSuchElementException(); |
706 |
final Object[] elements = ArrayDeque.this.elements; |
707 |
E e = checkedElementAt(elements, cursor); |
708 |
lastRet = cursor; |
709 |
if (++cursor >= elements.length) cursor = 0; |
710 |
remaining--; |
711 |
return e; |
712 |
} |
713 |
|
714 |
void postDelete(boolean leftShifted) { |
715 |
if (leftShifted) |
716 |
if (--cursor < 0) cursor = elements.length - 1; |
717 |
} |
718 |
|
719 |
public final void remove() { |
720 |
if (lastRet < 0) |
721 |
throw new IllegalStateException(); |
722 |
postDelete(delete(lastRet)); |
723 |
lastRet = -1; |
724 |
} |
725 |
|
726 |
public void forEachRemaining(Consumer<? super E> action) { |
727 |
int k; |
728 |
if ((k = remaining) > 0) { |
729 |
remaining = 0; |
730 |
ArrayDeque.forEachRemaining(action, elements, cursor, k); |
731 |
if ((lastRet = cursor + k - 1) >= elements.length) |
732 |
lastRet -= elements.length; |
733 |
} |
734 |
} |
735 |
} |
736 |
|
737 |
private class DescendingIterator extends DeqIterator { |
738 |
DescendingIterator() { cursor = tail(); } |
739 |
|
740 |
public final E next() { |
741 |
if (remaining == 0) |
742 |
throw new NoSuchElementException(); |
743 |
final Object[] elements = ArrayDeque.this.elements; |
744 |
E e = checkedElementAt(elements, cursor); |
745 |
lastRet = cursor; |
746 |
if (--cursor < 0) cursor = elements.length - 1; |
747 |
remaining--; |
748 |
return e; |
749 |
} |
750 |
|
751 |
void postDelete(boolean leftShifted) { |
752 |
if (!leftShifted) |
753 |
if (++cursor >= elements.length) cursor = 0; |
754 |
} |
755 |
|
756 |
public final void forEachRemaining(Consumer<? super E> action) { |
757 |
int k; |
758 |
if ((k = remaining) > 0) { |
759 |
remaining = 0; |
760 |
forEachRemainingDescending(action, elements, cursor, k); |
761 |
if ((lastRet = cursor - (k - 1)) < 0) |
762 |
lastRet += elements.length; |
763 |
} |
764 |
} |
765 |
} |
766 |
|
767 |
/** |
768 |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
769 |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
770 |
* deque. |
771 |
* |
772 |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
773 |
* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
774 |
* {@link Spliterator#NONNULL}. Overriding implementations should document |
775 |
* the reporting of additional characteristic values. |
776 |
* |
777 |
* @return a {@code Spliterator} over the elements in this deque |
778 |
* @since 1.8 |
779 |
*/ |
780 |
public Spliterator<E> spliterator() { |
781 |
return new ArrayDequeSpliterator(); |
782 |
} |
783 |
|
784 |
final class ArrayDequeSpliterator implements Spliterator<E> { |
785 |
private int cursor; |
786 |
private int remaining; // -1 until late-binding first use |
787 |
|
788 |
/** Constructs late-binding spliterator over all elements. */ |
789 |
ArrayDequeSpliterator() { |
790 |
this.remaining = -1; |
791 |
} |
792 |
|
793 |
/** Constructs spliterator over the given slice. */ |
794 |
ArrayDequeSpliterator(int cursor, int count) { |
795 |
this.cursor = cursor; |
796 |
this.remaining = count; |
797 |
} |
798 |
|
799 |
/** Ensures late-binding initialization; then returns remaining. */ |
800 |
private int remaining() { |
801 |
if (remaining < 0) { |
802 |
cursor = head; |
803 |
remaining = size; |
804 |
} |
805 |
return remaining; |
806 |
} |
807 |
|
808 |
public ArrayDequeSpliterator trySplit() { |
809 |
final int mid; |
810 |
if ((mid = remaining() >> 1) > 0) { |
811 |
int oldCursor = cursor; |
812 |
cursor = add(cursor, mid, elements.length); |
813 |
remaining -= mid; |
814 |
return new ArrayDequeSpliterator(oldCursor, mid); |
815 |
} |
816 |
return null; |
817 |
} |
818 |
|
819 |
public void forEachRemaining(Consumer<? super E> action) { |
820 |
int k = remaining(); // side effect! |
821 |
remaining = 0; |
822 |
ArrayDeque.forEachRemaining(action, elements, cursor, k); |
823 |
} |
824 |
|
825 |
public boolean tryAdvance(Consumer<? super E> action) { |
826 |
Objects.requireNonNull(action); |
827 |
if (remaining() == 0) |
828 |
return false; |
829 |
action.accept(checkedElementAt(elements, cursor)); |
830 |
if (++cursor >= elements.length) cursor = 0; |
831 |
remaining--; |
832 |
return true; |
833 |
} |
834 |
|
835 |
public long estimateSize() { |
836 |
return remaining(); |
837 |
} |
838 |
|
839 |
public int characteristics() { |
840 |
return Spliterator.NONNULL |
841 |
| Spliterator.ORDERED |
842 |
| Spliterator.SIZED |
843 |
| Spliterator.SUBSIZED; |
844 |
} |
845 |
} |
846 |
|
847 |
@SuppressWarnings("unchecked") |
848 |
public void forEach(Consumer<? super E> action) { |
849 |
Objects.requireNonNull(action); |
850 |
final Object[] elements = this.elements; |
851 |
final int capacity = elements.length; |
852 |
int from, end, to, leftover; |
853 |
leftover = (end = (from = head) + size) |
854 |
- (to = (capacity - end >= 0) ? end : capacity); |
855 |
for (;; from = 0, to = leftover, leftover = 0) { |
856 |
for (int i = from; i < to; i++) |
857 |
action.accept((E) elements[i]); |
858 |
if (leftover == 0) break; |
859 |
} |
860 |
// checkInvariants(); |
861 |
} |
862 |
|
863 |
/** |
864 |
* A variant of forEach that also checks for concurrent |
865 |
* modification, for use in iterators. |
866 |
*/ |
867 |
static <E> void forEachRemaining( |
868 |
Consumer<? super E> action, Object[] elements, int from, int size) { |
869 |
Objects.requireNonNull(action); |
870 |
final int capacity = elements.length; |
871 |
int end, to, leftover; |
872 |
leftover = (end = from + size) |
873 |
- (to = (capacity - end >= 0) ? end : capacity); |
874 |
for (;; from = 0, to = leftover, leftover = 0) { |
875 |
for (int i = from; i < to; i++) { |
876 |
@SuppressWarnings("unchecked") E e = (E) elements[i]; |
877 |
if (e == null) |
878 |
throw new ConcurrentModificationException(); |
879 |
action.accept(e); |
880 |
} |
881 |
if (leftover == 0) break; |
882 |
} |
883 |
} |
884 |
|
885 |
static <E> void forEachRemainingDescending( |
886 |
Consumer<? super E> action, Object[] elements, int from, int size) { |
887 |
Objects.requireNonNull(action); |
888 |
final int capacity = elements.length; |
889 |
int end, to, leftover; |
890 |
leftover = (to = ((end = from - size) >= -1) ? end : -1) - end; |
891 |
for (;; from = capacity - 1, to = capacity - 1 - leftover, leftover = 0) { |
892 |
for (int i = from; i > to; i--) { |
893 |
@SuppressWarnings("unchecked") E e = (E) elements[i]; |
894 |
if (e == null) |
895 |
throw new ConcurrentModificationException(); |
896 |
action.accept(e); |
897 |
} |
898 |
if (leftover == 0) break; |
899 |
} |
900 |
} |
901 |
|
902 |
/** |
903 |
* Replaces each element of this deque with the result of applying the |
904 |
* operator to that element, as specified by {@link List#replaceAll}. |
905 |
* |
906 |
* @param operator the operator to apply to each element |
907 |
* @since TBD |
908 |
*/ |
909 |
/* public */ void replaceAll(UnaryOperator<E> operator) { |
910 |
Objects.requireNonNull(operator); |
911 |
final Object[] elements = this.elements; |
912 |
final int capacity = elements.length; |
913 |
int from, end, to, leftover; |
914 |
leftover = (end = (from = head) + size) |
915 |
- (to = (capacity - end >= 0) ? end : capacity); |
916 |
for (;; from = 0, to = leftover, leftover = 0) { |
917 |
for (int i = from; i < to; i++) |
918 |
elements[i] = operator.apply(elementAt(i)); |
919 |
if (leftover == 0) break; |
920 |
} |
921 |
// checkInvariants(); |
922 |
} |
923 |
|
924 |
/** |
925 |
* @throws NullPointerException {@inheritDoc} |
926 |
*/ |
927 |
public boolean removeIf(Predicate<? super E> filter) { |
928 |
Objects.requireNonNull(filter); |
929 |
return bulkRemove(filter); |
930 |
} |
931 |
|
932 |
/** |
933 |
* @throws NullPointerException {@inheritDoc} |
934 |
*/ |
935 |
public boolean removeAll(Collection<?> c) { |
936 |
Objects.requireNonNull(c); |
937 |
return bulkRemove(e -> c.contains(e)); |
938 |
} |
939 |
|
940 |
/** |
941 |
* @throws NullPointerException {@inheritDoc} |
942 |
*/ |
943 |
public boolean retainAll(Collection<?> c) { |
944 |
Objects.requireNonNull(c); |
945 |
return bulkRemove(e -> !c.contains(e)); |
946 |
} |
947 |
|
948 |
/** Implementation of bulk remove methods. */ |
949 |
private boolean bulkRemove(Predicate<? super E> filter) { |
950 |
// checkInvariants(); |
951 |
final Object[] elements = this.elements; |
952 |
final int capacity = elements.length; |
953 |
int i = head, j = i, remaining = size, deleted = 0; |
954 |
try { |
955 |
for (; remaining > 0; remaining--) { |
956 |
@SuppressWarnings("unchecked") E e = (E) elements[i]; |
957 |
if (filter.test(e)) |
958 |
deleted++; |
959 |
else { |
960 |
if (j != i) |
961 |
elements[j] = e; |
962 |
if (++j >= capacity) j = 0; |
963 |
} |
964 |
if (++i >= capacity) i = 0; |
965 |
} |
966 |
return deleted > 0; |
967 |
} catch (Throwable ex) { |
968 |
if (deleted > 0) |
969 |
for (; remaining > 0; remaining--) { |
970 |
elements[j] = elements[i]; |
971 |
if (++i >= capacity) i = 0; |
972 |
if (++j >= capacity) j = 0; |
973 |
} |
974 |
throw ex; |
975 |
} finally { |
976 |
size -= deleted; |
977 |
clearSlice(elements, j, deleted); |
978 |
// checkInvariants(); |
979 |
} |
980 |
} |
981 |
|
982 |
/** |
983 |
* Returns {@code true} if this deque contains the specified element. |
984 |
* More formally, returns {@code true} if and only if this deque contains |
985 |
* at least one element {@code e} such that {@code o.equals(e)}. |
986 |
* |
987 |
* @param o object to be checked for containment in this deque |
988 |
* @return {@code true} if this deque contains the specified element |
989 |
*/ |
990 |
public boolean contains(Object o) { |
991 |
if (o != null) { |
992 |
final Object[] elements = this.elements; |
993 |
final int capacity = elements.length; |
994 |
int from, end, to, leftover; |
995 |
leftover = (end = (from = head) + size) |
996 |
- (to = (capacity - end >= 0) ? end : capacity); |
997 |
for (;; from = 0, to = leftover, leftover = 0) { |
998 |
for (int i = from; i < to; i++) |
999 |
if (o.equals(elements[i])) |
1000 |
return true; |
1001 |
if (leftover == 0) break; |
1002 |
} |
1003 |
} |
1004 |
return false; |
1005 |
} |
1006 |
|
1007 |
/** |
1008 |
* Removes a single instance of the specified element from this deque. |
1009 |
* If the deque does not contain the element, it is unchanged. |
1010 |
* More formally, removes the first element {@code e} such that |
1011 |
* {@code o.equals(e)} (if such an element exists). |
1012 |
* Returns {@code true} if this deque contained the specified element |
1013 |
* (or equivalently, if this deque changed as a result of the call). |
1014 |
* |
1015 |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
1016 |
* |
1017 |
* @param o element to be removed from this deque, if present |
1018 |
* @return {@code true} if this deque contained the specified element |
1019 |
*/ |
1020 |
public boolean remove(Object o) { |
1021 |
return removeFirstOccurrence(o); |
1022 |
} |
1023 |
|
1024 |
/** |
1025 |
* Removes all of the elements from this deque. |
1026 |
* The deque will be empty after this call returns. |
1027 |
*/ |
1028 |
public void clear() { |
1029 |
clearSlice(elements, head, size); |
1030 |
size = head = 0; |
1031 |
// checkInvariants(); |
1032 |
} |
1033 |
|
1034 |
/** |
1035 |
* Nulls out size elements, starting at head. |
1036 |
*/ |
1037 |
private static void clearSlice(Object[] elements, int head, int size) { |
1038 |
final int capacity = elements.length, end = head + size; |
1039 |
final int leg = (capacity - end >= 0) ? end : capacity; |
1040 |
Arrays.fill(elements, head, leg, null); |
1041 |
if (leg != end) |
1042 |
Arrays.fill(elements, 0, end - capacity, null); |
1043 |
} |
1044 |
|
1045 |
/** |
1046 |
* Returns an array containing all of the elements in this deque |
1047 |
* in proper sequence (from first to last element). |
1048 |
* |
1049 |
* <p>The returned array will be "safe" in that no references to it are |
1050 |
* maintained by this deque. (In other words, this method must allocate |
1051 |
* a new array). The caller is thus free to modify the returned array. |
1052 |
* |
1053 |
* <p>This method acts as bridge between array-based and collection-based |
1054 |
* APIs. |
1055 |
* |
1056 |
* @return an array containing all of the elements in this deque |
1057 |
*/ |
1058 |
public Object[] toArray() { |
1059 |
return toArray(Object[].class); |
1060 |
} |
1061 |
|
1062 |
private <T> T[] toArray(Class<T[]> klazz) { |
1063 |
final Object[] elements = this.elements; |
1064 |
final int capacity = elements.length; |
1065 |
final int head = this.head, end = head + size; |
1066 |
final T[] a; |
1067 |
if (end >= 0) { |
1068 |
a = Arrays.copyOfRange(elements, head, end, klazz); |
1069 |
} else { |
1070 |
// integer overflow! |
1071 |
a = Arrays.copyOfRange(elements, 0, size, klazz); |
1072 |
System.arraycopy(elements, head, a, 0, capacity - head); |
1073 |
} |
1074 |
if (end - capacity > 0) |
1075 |
System.arraycopy(elements, 0, a, capacity - head, end - capacity); |
1076 |
return a; |
1077 |
} |
1078 |
|
1079 |
/** |
1080 |
* Returns an array containing all of the elements in this deque in |
1081 |
* proper sequence (from first to last element); the runtime type of the |
1082 |
* returned array is that of the specified array. If the deque fits in |
1083 |
* the specified array, it is returned therein. Otherwise, a new array |
1084 |
* is allocated with the runtime type of the specified array and the |
1085 |
* size of this deque. |
1086 |
* |
1087 |
* <p>If this deque fits in the specified array with room to spare |
1088 |
* (i.e., the array has more elements than this deque), the element in |
1089 |
* the array immediately following the end of the deque is set to |
1090 |
* {@code null}. |
1091 |
* |
1092 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
1093 |
* array-based and collection-based APIs. Further, this method allows |
1094 |
* precise control over the runtime type of the output array, and may, |
1095 |
* under certain circumstances, be used to save allocation costs. |
1096 |
* |
1097 |
* <p>Suppose {@code x} is a deque known to contain only strings. |
1098 |
* The following code can be used to dump the deque into a newly |
1099 |
* allocated array of {@code String}: |
1100 |
* |
1101 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
1102 |
* |
1103 |
* Note that {@code toArray(new Object[0])} is identical in function to |
1104 |
* {@code toArray()}. |
1105 |
* |
1106 |
* @param a the array into which the elements of the deque are to |
1107 |
* be stored, if it is big enough; otherwise, a new array of the |
1108 |
* same runtime type is allocated for this purpose |
1109 |
* @return an array containing all of the elements in this deque |
1110 |
* @throws ArrayStoreException if the runtime type of the specified array |
1111 |
* is not a supertype of the runtime type of every element in |
1112 |
* this deque |
1113 |
* @throws NullPointerException if the specified array is null |
1114 |
*/ |
1115 |
@SuppressWarnings("unchecked") |
1116 |
public <T> T[] toArray(T[] a) { |
1117 |
final int size = this.size; |
1118 |
if (size > a.length) |
1119 |
return toArray((Class<T[]>) a.getClass()); |
1120 |
final Object[] elements = this.elements; |
1121 |
final int capacity = elements.length; |
1122 |
final int head = this.head, end = head + size; |
1123 |
final int front = (capacity - end >= 0) ? size : capacity - head; |
1124 |
System.arraycopy(elements, head, a, 0, front); |
1125 |
if (front != size) |
1126 |
System.arraycopy(elements, 0, a, capacity - head, end - capacity); |
1127 |
if (size < a.length) |
1128 |
a[size] = null; |
1129 |
return a; |
1130 |
} |
1131 |
|
1132 |
// *** Object methods *** |
1133 |
|
1134 |
/** |
1135 |
* Returns a copy of this deque. |
1136 |
* |
1137 |
* @return a copy of this deque |
1138 |
*/ |
1139 |
public ArrayDeque<E> clone() { |
1140 |
try { |
1141 |
@SuppressWarnings("unchecked") |
1142 |
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
1143 |
result.elements = Arrays.copyOf(elements, elements.length); |
1144 |
return result; |
1145 |
} catch (CloneNotSupportedException e) { |
1146 |
throw new AssertionError(); |
1147 |
} |
1148 |
} |
1149 |
|
1150 |
private static final long serialVersionUID = 2340985798034038923L; |
1151 |
|
1152 |
/** |
1153 |
* Saves this deque to a stream (that is, serializes it). |
1154 |
* |
1155 |
* @param s the stream |
1156 |
* @throws java.io.IOException if an I/O error occurs |
1157 |
* @serialData The current size ({@code int}) of the deque, |
1158 |
* followed by all of its elements (each an object reference) in |
1159 |
* first-to-last order. |
1160 |
*/ |
1161 |
private void writeObject(java.io.ObjectOutputStream s) |
1162 |
throws java.io.IOException { |
1163 |
s.defaultWriteObject(); |
1164 |
|
1165 |
// Write out size |
1166 |
s.writeInt(size); |
1167 |
|
1168 |
// Write out elements in order. |
1169 |
final Object[] elements = this.elements; |
1170 |
final int capacity = elements.length; |
1171 |
int from, end, to, leftover; |
1172 |
leftover = (end = (from = head) + size) |
1173 |
- (to = (capacity - end >= 0) ? end : capacity); |
1174 |
for (;; from = 0, to = leftover, leftover = 0) { |
1175 |
for (int i = from; i < to; i++) |
1176 |
s.writeObject(elements[i]); |
1177 |
if (leftover == 0) break; |
1178 |
} |
1179 |
} |
1180 |
|
1181 |
/** |
1182 |
* Reconstitutes this deque from a stream (that is, deserializes it). |
1183 |
* @param s the stream |
1184 |
* @throws ClassNotFoundException if the class of a serialized object |
1185 |
* could not be found |
1186 |
* @throws java.io.IOException if an I/O error occurs |
1187 |
*/ |
1188 |
private void readObject(java.io.ObjectInputStream s) |
1189 |
throws java.io.IOException, ClassNotFoundException { |
1190 |
s.defaultReadObject(); |
1191 |
|
1192 |
// Read in size and allocate array |
1193 |
elements = new Object[size = s.readInt()]; |
1194 |
|
1195 |
// Read in all elements in the proper order. |
1196 |
for (int i = 0; i < size; i++) |
1197 |
elements[i] = s.readObject(); |
1198 |
} |
1199 |
|
1200 |
/** debugging */ |
1201 |
void checkInvariants() { |
1202 |
try { |
1203 |
int capacity = elements.length; |
1204 |
// assert size >= 0 && size <= capacity; |
1205 |
// assert head >= 0; |
1206 |
// assert capacity == 0 || head < capacity; |
1207 |
// assert size == 0 || elements[head] != null; |
1208 |
// assert size == 0 || elements[tail()] != null; |
1209 |
// assert size == capacity || elements[dec(head, capacity)] == null; |
1210 |
// assert size == capacity || elements[inc(tail(), capacity)] == null; |
1211 |
} catch (Throwable t) { |
1212 |
System.err.printf("head=%d size=%d capacity=%d%n", |
1213 |
head, size, elements.length); |
1214 |
System.err.printf("elements=%s%n", |
1215 |
Arrays.toString(elements)); |
1216 |
throw t; |
1217 |
} |
1218 |
} |
1219 |
|
1220 |
} |