4 |
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*/ |
5 |
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6 |
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package java.util; |
7 |
– |
import java.util.*; // for javadoc (till 6280605 is fixed) |
7 |
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import java.io.*; |
8 |
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|
9 |
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/** |
44 |
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* Iterator} interfaces. |
45 |
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* |
46 |
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* <p>This class is a member of the |
47 |
< |
* <a href="{@docRoot}/../guide/collections/index.html"> |
47 |
> |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
48 |
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* Java Collections Framework</a>. |
49 |
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* |
50 |
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* @author Josh Bloch and Doug Lea |
478 |
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return removeFirst(); |
479 |
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} |
480 |
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|
481 |
+ |
private void checkInvariants() { |
482 |
+ |
assert elements[tail] == null; |
483 |
+ |
assert head == tail ? elements[head] == null : |
484 |
+ |
(elements[head] != null && |
485 |
+ |
elements[(tail - 1) & (elements.length - 1)] != null); |
486 |
+ |
assert elements[(head - 1) & (elements.length - 1)] == null; |
487 |
+ |
} |
488 |
+ |
|
489 |
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/** |
490 |
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* Removes the element at the specified position in the elements array, |
491 |
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* adjusting head and tail as necessary. This can result in motion of |
497 |
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* @return true if elements moved backwards |
498 |
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*/ |
499 |
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private boolean delete(int i) { |
500 |
+ |
checkInvariants(); |
501 |
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final E[] elements = this.elements; |
502 |
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final int mask = elements.length - 1; |
503 |
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final int h = head; |
594 |
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} |
595 |
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|
596 |
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public E next() { |
589 |
– |
E result; |
597 |
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if (cursor == fence) |
598 |
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throw new NoSuchElementException(); |
599 |
+ |
E result = elements[cursor]; |
600 |
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// This check doesn't catch all possible comodifications, |
601 |
|
// but does catch the ones that corrupt traversal |
602 |
< |
if (tail != fence || (result = elements[cursor]) == null) |
602 |
> |
if (tail != fence || result == null) |
603 |
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throw new ConcurrentModificationException(); |
604 |
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lastRet = cursor; |
605 |
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cursor = (cursor + 1) & (elements.length - 1); |
609 |
|
public void remove() { |
610 |
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if (lastRet < 0) |
611 |
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throw new IllegalStateException(); |
612 |
< |
if (delete(lastRet)) // if left-shifted, undo increment in next() |
612 |
> |
if (delete(lastRet)) { // if left-shifted, undo increment in next() |
613 |
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cursor = (cursor - 1) & (elements.length - 1); |
614 |
+ |
fence = tail; |
615 |
+ |
} |
616 |
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lastRet = -1; |
607 |
– |
fence = tail; |
617 |
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} |
618 |
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} |
619 |
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|
611 |
– |
|
620 |
|
private class DescendingIterator implements Iterator<E> { |
621 |
|
/* |
622 |
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* This class is nearly a mirror-image of DeqIterator, using |
623 |
< |
* (tail-1) instead of head for initial cursor, (head-1) |
624 |
< |
* instead of tail for fence, and elements.length instead of -1 |
617 |
< |
* for sentinel. It shares the same structure, but not many |
618 |
< |
* actual lines of code. |
623 |
> |
* tail instead of head for initial cursor, and head instead of |
624 |
> |
* tail for fence. |
625 |
|
*/ |
626 |
< |
private int cursor = (tail - 1) & (elements.length - 1); |
627 |
< |
private int fence = (head - 1) & (elements.length - 1); |
628 |
< |
private int lastRet = elements.length; |
626 |
> |
private int cursor = tail; |
627 |
> |
private int fence = head; |
628 |
> |
private int lastRet = -1; |
629 |
|
|
630 |
|
public boolean hasNext() { |
631 |
|
return cursor != fence; |
632 |
|
} |
633 |
|
|
634 |
|
public E next() { |
629 |
– |
E result; |
635 |
|
if (cursor == fence) |
636 |
|
throw new NoSuchElementException(); |
637 |
< |
if (((head - 1) & (elements.length - 1)) != fence || |
638 |
< |
(result = elements[cursor]) == null) |
637 |
> |
cursor = (cursor - 1) & (elements.length - 1); |
638 |
> |
E result = elements[cursor]; |
639 |
> |
if (head != fence || result == null) |
640 |
|
throw new ConcurrentModificationException(); |
641 |
|
lastRet = cursor; |
636 |
– |
cursor = (cursor - 1) & (elements.length - 1); |
642 |
|
return result; |
643 |
|
} |
644 |
|
|
645 |
|
public void remove() { |
646 |
< |
if (lastRet >= elements.length) |
646 |
> |
if (lastRet < 0) |
647 |
|
throw new IllegalStateException(); |
648 |
< |
if (!delete(lastRet)) |
648 |
> |
if (!delete(lastRet)) { |
649 |
|
cursor = (cursor + 1) & (elements.length - 1); |
650 |
< |
lastRet = elements.length; |
651 |
< |
fence = (head - 1) & (elements.length - 1); |
650 |
> |
fence = head; |
651 |
> |
} |
652 |
> |
lastRet = -1; |
653 |
|
} |
654 |
|
} |
655 |
|
|
785 |
|
public ArrayDeque<E> clone() { |
786 |
|
try { |
787 |
|
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
788 |
< |
// These two lines are currently faster than cloning the array: |
783 |
< |
result.elements = (E[]) new Object[elements.length]; |
784 |
< |
System.arraycopy(elements, 0, result.elements, 0, elements.length); |
788 |
> |
result.elements = Arrays.copyOf(elements, elements.length); |
789 |
|
return result; |
790 |
|
|
791 |
|
} catch (CloneNotSupportedException e) { |
833 |
|
// Read in all elements in the proper order. |
834 |
|
for (int i = 0; i < size; i++) |
835 |
|
elements[i] = (E)s.readObject(); |
832 |
– |
|
836 |
|
} |
837 |
|
} |