18 |
|
* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time. |
19 |
|
* Exceptions include {@link #remove(Object) remove}, {@link |
20 |
|
* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence |
21 |
< |
* removeLastOccurrence}, {@link #contains contains }, {@link #iterator |
21 |
> |
* removeLastOccurrence}, {@link #contains contains}, {@link #iterator |
22 |
|
* iterator.remove()}, and the bulk operations, all of which run in linear |
23 |
|
* time. |
24 |
|
* |
40 |
|
* should be used only to detect bugs.</i> |
41 |
|
* |
42 |
|
* <p>This class and its iterator implement all of the |
43 |
< |
* optional methods of the {@link Collection} and {@link |
44 |
< |
* Iterator} interfaces. This class is a member of the <a |
45 |
< |
* href="{@docRoot}/../guide/collections/index.html"> Java Collections |
46 |
< |
* Framework</a>. |
43 |
> |
* <em>optional</em> methods of the {@link Collection} and {@link |
44 |
> |
* Iterator} interfaces. |
45 |
> |
* |
46 |
> |
* <p>This class is a member of the |
47 |
> |
* <a href="{@docRoot}/../guide/collections/index.html"> |
48 |
> |
* Java Collections Framework</a>. |
49 |
|
* |
50 |
|
* @author Josh Bloch and Doug Lea |
51 |
|
* @since 1.6 |
90 |
|
/** |
91 |
|
* Allocate empty array to hold the given number of elements. |
92 |
|
* |
93 |
< |
* @param numElements the number of elements to hold. |
93 |
> |
* @param numElements the number of elements to hold |
94 |
|
*/ |
95 |
|
private void allocateElements(int numElements) { |
96 |
|
int initialCapacity = MIN_INITIAL_CAPACITY; |
189 |
|
/** |
190 |
|
* Inserts the specified element at the front of this deque. |
191 |
|
* |
192 |
< |
* @param e the element to insert |
193 |
< |
* @throws NullPointerException if <tt>e</tt> is null |
192 |
> |
* @param e the element to add |
193 |
> |
* @throws NullPointerException if the specified element is null |
194 |
|
*/ |
195 |
|
public void addFirst(E e) { |
196 |
|
if (e == null) |
202 |
|
|
203 |
|
/** |
204 |
|
* Inserts the specified element at the end of this deque. |
205 |
< |
* This method is equivalent to {@link Collection#add} and |
204 |
< |
* {@link #push}. |
205 |
> |
* This method is equivalent to {@link #add} and {@link #push}. |
206 |
|
* |
207 |
< |
* @param e the element to insert |
208 |
< |
* @throws NullPointerException if <tt>e</tt> is null |
207 |
> |
* @param e the element to add |
208 |
> |
* @throws NullPointerException if the specified element is null |
209 |
|
*/ |
210 |
|
public void addLast(E e) { |
211 |
|
if (e == null) |
216 |
|
} |
217 |
|
|
218 |
|
/** |
218 |
– |
* Retrieves and removes the first element of this deque, or |
219 |
– |
* <tt>null</tt> if this deque is empty. |
220 |
– |
* |
221 |
– |
* @return the first element of this deque, or <tt>null</tt> if |
222 |
– |
* this deque is empty |
223 |
– |
*/ |
224 |
– |
public E pollFirst() { |
225 |
– |
int h = head; |
226 |
– |
E result = elements[h]; // Element is null if deque empty |
227 |
– |
if (result == null) |
228 |
– |
return null; |
229 |
– |
elements[h] = null; // Must null out slot |
230 |
– |
head = (h + 1) & (elements.length - 1); |
231 |
– |
return result; |
232 |
– |
} |
233 |
– |
|
234 |
– |
/** |
235 |
– |
* Retrieves and removes the last element of this deque, or |
236 |
– |
* <tt>null</tt> if this deque is empty. |
237 |
– |
* |
238 |
– |
* @return the last element of this deque, or <tt>null</tt> if |
239 |
– |
* this deque is empty |
240 |
– |
*/ |
241 |
– |
public E pollLast() { |
242 |
– |
int t = (tail - 1) & (elements.length - 1); |
243 |
– |
E result = elements[t]; |
244 |
– |
if (result == null) |
245 |
– |
return null; |
246 |
– |
elements[t] = null; |
247 |
– |
tail = t; |
248 |
– |
return result; |
249 |
– |
} |
250 |
– |
|
251 |
– |
/** |
219 |
|
* Inserts the specified element at the front of this deque. |
220 |
|
* |
221 |
< |
* @param e the element to insert |
221 |
> |
* @param e the element to add |
222 |
|
* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
223 |
< |
* @throws NullPointerException if <tt>e</tt> is null |
223 |
> |
* @throws NullPointerException if the specified element is null |
224 |
|
*/ |
225 |
|
public boolean offerFirst(E e) { |
226 |
|
addFirst(e); |
230 |
|
/** |
231 |
|
* Inserts the specified element at the end of this deque. |
232 |
|
* |
233 |
< |
* @param e the element to insert |
233 |
> |
* @param e the element to add |
234 |
|
* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
235 |
< |
* @throws NullPointerException if <tt>e</tt> is null |
235 |
> |
* @throws NullPointerException if the specified element is null |
236 |
|
*/ |
237 |
|
public boolean offerLast(E e) { |
238 |
|
addLast(e); |
240 |
|
} |
241 |
|
|
242 |
|
/** |
243 |
< |
* Retrieves and removes the first element of this deque. This method |
277 |
< |
* differs from the {@link #pollFirst} method only in that it throws an |
278 |
< |
* exception if this deque is empty. |
279 |
< |
* |
280 |
< |
* @return the first element of this deque |
281 |
< |
* @throws NoSuchElementException if this deque is empty |
243 |
> |
* @throws NoSuchElementException {@inheritDoc} |
244 |
|
*/ |
245 |
|
public E removeFirst() { |
246 |
|
E x = pollFirst(); |
250 |
|
} |
251 |
|
|
252 |
|
/** |
253 |
< |
* Retrieves and removes the last element of this deque. This method |
292 |
< |
* differs from the {@link #pollLast} method only in that it throws an |
293 |
< |
* exception if this deque is empty. |
294 |
< |
* |
295 |
< |
* @return the last element of this deque |
296 |
< |
* @throws NoSuchElementException if this deque is empty |
253 |
> |
* @throws NoSuchElementException {@inheritDoc} |
254 |
|
*/ |
255 |
|
public E removeLast() { |
256 |
|
E x = pollLast(); |
259 |
|
return x; |
260 |
|
} |
261 |
|
|
262 |
< |
/** |
263 |
< |
* Retrieves, but does not remove, the first element of this deque, |
264 |
< |
* returning <tt>null</tt> if this deque is empty. |
265 |
< |
* |
266 |
< |
* @return the first element of this deque, or <tt>null</tt> if |
267 |
< |
* this deque is empty |
268 |
< |
*/ |
269 |
< |
public E peekFirst() { |
313 |
< |
return elements[head]; // elements[head] is null if deque empty |
262 |
> |
public E pollFirst() { |
263 |
> |
int h = head; |
264 |
> |
E result = elements[h]; // Element is null if deque empty |
265 |
> |
if (result == null) |
266 |
> |
return null; |
267 |
> |
elements[h] = null; // Must null out slot |
268 |
> |
head = (h + 1) & (elements.length - 1); |
269 |
> |
return result; |
270 |
|
} |
271 |
|
|
272 |
< |
/** |
273 |
< |
* Retrieves, but does not remove, the last element of this deque, |
274 |
< |
* returning <tt>null</tt> if this deque is empty. |
275 |
< |
* |
276 |
< |
* @return the last element of this deque, or <tt>null</tt> if this deque |
277 |
< |
* is empty |
278 |
< |
*/ |
279 |
< |
public E peekLast() { |
324 |
< |
return elements[(tail - 1) & (elements.length - 1)]; |
272 |
> |
public E pollLast() { |
273 |
> |
int t = (tail - 1) & (elements.length - 1); |
274 |
> |
E result = elements[t]; |
275 |
> |
if (result == null) |
276 |
> |
return null; |
277 |
> |
elements[t] = null; |
278 |
> |
tail = t; |
279 |
> |
return result; |
280 |
|
} |
281 |
|
|
282 |
|
/** |
283 |
< |
* Retrieves, but does not remove, the first element of this |
329 |
< |
* deque. This method differs from the {@link #peekFirst} method only |
330 |
< |
* in that it throws an exception if this deque is empty. |
331 |
< |
* |
332 |
< |
* @return the first element of this deque |
333 |
< |
* @throws NoSuchElementException if this deque is empty |
283 |
> |
* @throws NoSuchElementException {@inheritDoc} |
284 |
|
*/ |
285 |
|
public E getFirst() { |
286 |
|
E x = elements[head]; |
290 |
|
} |
291 |
|
|
292 |
|
/** |
293 |
< |
* Retrieves, but does not remove, the last element of this |
344 |
< |
* deque. This method differs from the {@link #peekLast} method only |
345 |
< |
* in that it throws an exception if this deque is empty. |
346 |
< |
* |
347 |
< |
* @return the last element of this deque |
348 |
< |
* @throws NoSuchElementException if this deque is empty |
293 |
> |
* @throws NoSuchElementException {@inheritDoc} |
294 |
|
*/ |
295 |
|
public E getLast() { |
296 |
|
E x = elements[(tail - 1) & (elements.length - 1)]; |
299 |
|
return x; |
300 |
|
} |
301 |
|
|
302 |
+ |
public E peekFirst() { |
303 |
+ |
return elements[head]; // elements[head] is null if deque empty |
304 |
+ |
} |
305 |
+ |
|
306 |
+ |
public E peekLast() { |
307 |
+ |
return elements[(tail - 1) & (elements.length - 1)]; |
308 |
+ |
} |
309 |
+ |
|
310 |
|
/** |
311 |
|
* Removes the first occurrence of the specified element in this |
312 |
< |
* deque (when traversing the deque from head to tail). More |
313 |
< |
* formally, removes the first element e such that (o==null ? |
314 |
< |
* e==null : o.equals(e)). If the deque does not contain the |
315 |
< |
* element, it is unchanged. |
312 |
> |
* deque (when traversing the deque from head to tail). |
313 |
> |
* If the deque does not contain the element, it is unchanged. |
314 |
> |
* More formally, removes the first element <tt>e</tt> such that |
315 |
> |
* <tt>o.equals(e)</tt> (if such an element exists). |
316 |
> |
* Returns true if this deque contained the specified element (or |
317 |
> |
* equivalently, if this deque changed as a result of the call). |
318 |
|
* |
319 |
|
* @param o element to be removed from this deque, if present |
320 |
|
* @return <tt>true</tt> if the deque contained the specified element |
337 |
|
|
338 |
|
/** |
339 |
|
* Removes the last occurrence of the specified element in this |
340 |
< |
* deque (when traversing the deque from head to tail). More |
341 |
< |
* formally, removes the last element e such that (o==null ? |
342 |
< |
* e==null : o.equals(e)). If the deque |
343 |
< |
* does not contain the element, it is unchanged. |
340 |
> |
* deque (when traversing the deque from head to tail). |
341 |
> |
* If the deque does not contain the element, it is unchanged. |
342 |
> |
* More formally, removes the last element <tt>e</tt> such that |
343 |
> |
* <tt>o.equals(e)</tt> (if such an element exists). |
344 |
> |
* Returns true if this deque contained the specified element (or |
345 |
> |
* equivalently, if this deque changed as a result of the call). |
346 |
|
* |
347 |
|
* @param o element to be removed from this deque, if present |
348 |
|
* @return <tt>true</tt> if the deque contained the specified element |
368 |
|
/** |
369 |
|
* Inserts the specified element at the end of this deque. |
370 |
|
* |
414 |
– |
* <p>This method is equivalent to {@link #offerLast}. |
415 |
– |
* |
416 |
– |
* @param e the element to insert |
417 |
– |
* @return <tt>true</tt> (as per the spec for {@link Queue#offer}) |
418 |
– |
* @throws NullPointerException if <tt>e</tt> is null |
419 |
– |
*/ |
420 |
– |
public boolean offer(E e) { |
421 |
– |
return offerLast(e); |
422 |
– |
} |
423 |
– |
|
424 |
– |
/** |
425 |
– |
* Inserts the specified element at the end of this deque. |
426 |
– |
* |
371 |
|
* <p>This method is equivalent to {@link #addLast}. |
372 |
|
* |
373 |
< |
* @param e the element to insert |
373 |
> |
* @param e the element to add |
374 |
|
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
375 |
< |
* @throws NullPointerException if <tt>e</tt> is null |
375 |
> |
* @throws NullPointerException if the specified element is null |
376 |
|
*/ |
377 |
|
public boolean add(E e) { |
378 |
|
addLast(e); |
380 |
|
} |
381 |
|
|
382 |
|
/** |
383 |
< |
* Retrieves and removes the head of the queue represented by |
440 |
< |
* this deque, or <tt>null</tt> if this deque is empty. In other words, |
441 |
< |
* retrieves and removes the first element of this deque, or <tt>null</tt> |
442 |
< |
* if this deque is empty. |
383 |
> |
* Inserts the specified element at the end of this deque. |
384 |
|
* |
385 |
< |
* <p>This method is equivalent to {@link #pollFirst}. |
385 |
> |
* <p>This method is equivalent to {@link #offerLast}. |
386 |
|
* |
387 |
< |
* @return the first element of this deque, or <tt>null</tt> if |
388 |
< |
* this deque is empty |
387 |
> |
* @param e the element to add |
388 |
> |
* @return <tt>true</tt> (as per the spec for {@link Queue#offer}) |
389 |
> |
* @throws NullPointerException if the specified element is null |
390 |
|
*/ |
391 |
< |
public E poll() { |
392 |
< |
return pollFirst(); |
391 |
> |
public boolean offer(E e) { |
392 |
> |
return offerLast(e); |
393 |
|
} |
394 |
|
|
395 |
|
/** |
396 |
|
* Retrieves and removes the head of the queue represented by this deque. |
397 |
< |
* This method differs from the {@link #poll} method only in that it |
398 |
< |
* throws an exception if this deque is empty. |
397 |
> |
* This method differs from {@link #poll} only in that it throws an |
398 |
> |
* exception if this deque is empty. |
399 |
|
* |
400 |
|
* <p>This method is equivalent to {@link #removeFirst}. |
401 |
|
* |
402 |
|
* @return the head of the queue represented by this deque |
403 |
< |
* @throws NoSuchElementException if this deque is empty |
403 |
> |
* @throws NoSuchElementException {@inheritDoc} |
404 |
|
*/ |
405 |
|
public E remove() { |
406 |
|
return removeFirst(); |
407 |
|
} |
408 |
|
|
409 |
|
/** |
410 |
< |
* Retrieves, but does not remove, the head of the queue represented by |
411 |
< |
* this deque, returning <tt>null</tt> if this deque is empty. |
410 |
> |
* Retrieves and removes the head of the queue represented by this deque |
411 |
> |
* (in other words, the first element of this deque), or returns |
412 |
> |
* <tt>null</tt> if this deque is empty. |
413 |
|
* |
414 |
< |
* <p>This method is equivalent to {@link #peekFirst}. |
414 |
> |
* <p>This method is equivalent to {@link #pollFirst}. |
415 |
|
* |
416 |
|
* @return the head of the queue represented by this deque, or |
417 |
< |
* <tt>null</tt> if this deque is empty |
417 |
> |
* <tt>null</tt> if this deque is empty |
418 |
|
*/ |
419 |
< |
public E peek() { |
420 |
< |
return peekFirst(); |
419 |
> |
public E poll() { |
420 |
> |
return pollFirst(); |
421 |
|
} |
422 |
|
|
423 |
|
/** |
424 |
|
* Retrieves, but does not remove, the head of the queue represented by |
425 |
< |
* this deque. This method differs from the {@link #peek} method only in |
426 |
< |
* that it throws an exception if this deque is empty. |
425 |
> |
* this deque. This method differs from {@link #peek} only in that it |
426 |
> |
* throws an exception if this deque is empty. |
427 |
|
* |
428 |
|
* <p>This method is equivalent to {@link #getFirst}. |
429 |
|
* |
430 |
|
* @return the head of the queue represented by this deque |
431 |
< |
* @throws NoSuchElementException if this deque is empty |
431 |
> |
* @throws NoSuchElementException {@inheritDoc} |
432 |
|
*/ |
433 |
|
public E element() { |
434 |
|
return getFirst(); |
435 |
|
} |
436 |
|
|
437 |
+ |
/** |
438 |
+ |
* Retrieves, but does not remove, the head of the queue represented by |
439 |
+ |
* this deque, or returns <tt>null</tt> if this deque is empty. |
440 |
+ |
* |
441 |
+ |
* <p>This method is equivalent to {@link #peekFirst}. |
442 |
+ |
* |
443 |
+ |
* @return the head of the queue represented by this deque, or |
444 |
+ |
* <tt>null</tt> if this deque is empty |
445 |
+ |
*/ |
446 |
+ |
public E peek() { |
447 |
+ |
return peekFirst(); |
448 |
+ |
} |
449 |
+ |
|
450 |
|
// *** Stack methods *** |
451 |
|
|
452 |
|
/** |
456 |
|
* <p>This method is equivalent to {@link #addFirst}. |
457 |
|
* |
458 |
|
* @param e the element to push |
459 |
< |
* @throws NullPointerException if <tt>e</tt> is null |
459 |
> |
* @throws NullPointerException if the specified element is null |
460 |
|
*/ |
461 |
|
public void push(E e) { |
462 |
|
addFirst(e); |
469 |
|
* <p>This method is equivalent to {@link #removeFirst()}. |
470 |
|
* |
471 |
|
* @return the element at the front of this deque (which is the top |
472 |
< |
* of the stack represented by this deque) |
473 |
< |
* @throws NoSuchElementException if this deque is empty |
472 |
> |
* of the stack represented by this deque) |
473 |
> |
* @throws NoSuchElementException {@inheritDoc} |
474 |
|
*/ |
475 |
|
public E pop() { |
476 |
|
return removeFirst(); |
478 |
|
|
479 |
|
/** |
480 |
|
* Removes the element at the specified position in the elements array, |
481 |
< |
* adjusting head, tail, and size as necessary. This can result in |
482 |
< |
* motion of elements backwards or forwards in the array. |
481 |
> |
* adjusting head and tail as necessary. This can result in motion of |
482 |
> |
* elements backwards or forwards in the array. |
483 |
|
* |
484 |
|
* <p>This method is called delete rather than remove to emphasize |
485 |
< |
* that its semantics differ from those of List.remove(int). |
485 |
> |
* that its semantics differ from those of {@link List#remove(int)}. |
486 |
|
* |
487 |
|
* @return true if elements moved backwards |
488 |
|
*/ |
489 |
|
private boolean delete(int i) { |
490 |
+ |
int mask = elements.length - 1; |
491 |
+ |
|
492 |
+ |
// Invariant: head <= i < tail mod circularity |
493 |
+ |
if (((i - head) & mask) >= ((tail - head) & mask)) |
494 |
+ |
throw new ConcurrentModificationException(); |
495 |
+ |
|
496 |
|
// Case 1: Deque doesn't wrap |
497 |
|
// Case 2: Deque does wrap and removed element is in the head portion |
498 |
< |
if ((head < tail || tail == 0) || i >= head) { |
498 |
> |
if (i >= head) { |
499 |
|
System.arraycopy(elements, head, elements, head + 1, i - head); |
500 |
|
elements[head] = null; |
501 |
< |
head = (head + 1) & (elements.length - 1); |
501 |
> |
head = (head + 1) & mask; |
502 |
|
return false; |
503 |
|
} |
504 |
|
|
521 |
|
} |
522 |
|
|
523 |
|
/** |
524 |
< |
* Returns <tt>true</tt> if this deque contains no elements.<p> |
524 |
> |
* Returns <tt>true</tt> if this deque contains no elements. |
525 |
|
* |
526 |
< |
* @return <tt>true</tt> if this deque contains no elements. |
526 |
> |
* @return <tt>true</tt> if this deque contains no elements |
527 |
|
*/ |
528 |
|
public boolean isEmpty() { |
529 |
|
return head == tail; |
587 |
|
} |
588 |
|
|
589 |
|
/** |
590 |
< |
* Returns <tt>true</tt> if this deque contains the specified |
591 |
< |
* element. More formally, returns <tt>true</tt> if and only if this |
592 |
< |
* deque contains at least one element <tt>e</tt> such that |
631 |
< |
* <tt>e.equals(o)</tt>. |
590 |
> |
* Returns <tt>true</tt> if this deque contains the specified element. |
591 |
> |
* More formally, returns <tt>true</tt> if and only if this deque contains |
592 |
> |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
593 |
|
* |
594 |
|
* @param o object to be checked for containment in this deque |
595 |
|
* @return <tt>true</tt> if this deque contains the specified element |
610 |
|
|
611 |
|
/** |
612 |
|
* Removes a single instance of the specified element from this deque. |
613 |
< |
* This method is equivalent to {@link #removeFirstOccurrence}. |
613 |
> |
* If the deque does not contain the element, it is unchanged. |
614 |
> |
* More formally, removes the first element <tt>e</tt> such that |
615 |
> |
* <tt>o.equals(e)</tt> (if such an element exists). |
616 |
> |
* Returns true if this deque contained the specified element (or |
617 |
> |
* equivalently, if this deque changed as a result of the call). |
618 |
> |
* |
619 |
> |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
620 |
|
* |
621 |
< |
* @param e element to be removed from this deque, if present |
621 |
> |
* @param o element to be removed from this deque, if present |
622 |
|
* @return <tt>true</tt> if this deque contained the specified element |
623 |
|
*/ |
624 |
< |
public boolean remove(Object e) { |
625 |
< |
return removeFirstOccurrence(e); |
624 |
> |
public boolean remove(Object o) { |
625 |
> |
return removeFirstOccurrence(o); |
626 |
|
} |
627 |
|
|
628 |
|
/** |
639 |
|
do { |
640 |
|
elements[i] = null; |
641 |
|
i = (i + 1) & mask; |
642 |
< |
} while(i != t); |
642 |
> |
} while (i != t); |
643 |
|
} |
644 |
|
} |
645 |
|
|
648 |
|
* in the correct order. |
649 |
|
* |
650 |
|
* @return an array containing all of the elements in this deque |
651 |
< |
* in the correct order |
651 |
> |
* in the correct order |
652 |
|
*/ |
653 |
|
public Object[] toArray() { |
654 |
|
return copyElements(new Object[size()]); |
666 |
|
* immediately following the end of the collection is set to <tt>null</tt>. |
667 |
|
* |
668 |
|
* @param a the array into which the elements of the deque are to |
669 |
< |
* be stored, if it is big enough; otherwise, a new array of the |
670 |
< |
* same runtime type is allocated for this purpose |
669 |
> |
* be stored, if it is big enough; otherwise, a new array of the |
670 |
> |
* same runtime type is allocated for this purpose |
671 |
|
* @return an array containing the elements of the deque |
672 |
|
* @throws ArrayStoreException if the runtime type of a is not a supertype |
673 |
|
* of the runtime type of every element in this deque |