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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.11 by jsr166, Tue May 17 06:36:47 2005 UTC vs.
Revision 1.23 by dl, Sat Sep 17 12:50:34 2005 UTC

# Line 4 | Line 4
4   */
5  
6   package java.util;
7 + import java.util.*; // for javadoc (till 6280605 is fixed)
8   import java.io.*;
9  
10   /**
# Line 202 | Line 203 | public class ArrayDeque<E> extends Abstr
203  
204      /**
205       * Inserts the specified element at the end of this deque.
206 <     * This method is equivalent to {@link #add} and {@link #push}.
206 >     *
207 >     * <p>This method is equivalent to {@link #add}.
208       *
209       * @param e the element to add
210       * @throws NullPointerException if the specified element is null
# Line 219 | Line 221 | public class ArrayDeque<E> extends Abstr
221       * Inserts the specified element at the front of this deque.
222       *
223       * @param e the element to add
224 <     * @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst})
224 >     * @return <tt>true</tt> (as specified by {@link Deque#offerFirst})
225       * @throws NullPointerException if the specified element is null
226       */
227      public boolean offerFirst(E e) {
# Line 231 | Line 233 | public class ArrayDeque<E> extends Abstr
233       * Inserts the specified element at the end of this deque.
234       *
235       * @param e the element to add
236 <     * @return <tt>true</tt> (as per the spec for {@link Deque#offerLast})
236 >     * @return <tt>true</tt> (as specified by {@link Deque#offerLast})
237       * @throws NullPointerException if the specified element is null
238       */
239      public boolean offerLast(E e) {
# Line 313 | Line 315 | public class ArrayDeque<E> extends Abstr
315       * If the deque does not contain the element, it is unchanged.
316       * More formally, removes the first element <tt>e</tt> such that
317       * <tt>o.equals(e)</tt> (if such an element exists).
318 <     * Returns true if this deque contained the specified element (or
319 <     * equivalently, if this deque changed as a result of the call).
318 >     * Returns <tt>true</tt> if this deque contained the specified element
319 >     * (or equivalently, if this deque changed as a result of the call).
320       *
321       * @param o element to be removed from this deque, if present
322       * @return <tt>true</tt> if the deque contained the specified element
# Line 341 | Line 343 | public class ArrayDeque<E> extends Abstr
343       * If the deque does not contain the element, it is unchanged.
344       * More formally, removes the last element <tt>e</tt> such that
345       * <tt>o.equals(e)</tt> (if such an element exists).
346 <     * Returns true if this deque contained the specified element (or
347 <     * equivalently, if this deque changed as a result of the call).
346 >     * Returns <tt>true</tt> if this deque contained the specified element
347 >     * (or equivalently, if this deque changed as a result of the call).
348       *
349       * @param o element to be removed from this deque, if present
350       * @return <tt>true</tt> if the deque contained the specified element
# Line 371 | Line 373 | public class ArrayDeque<E> extends Abstr
373       * <p>This method is equivalent to {@link #addLast}.
374       *
375       * @param e the element to add
376 <     * @return <tt>true</tt> (as per the spec for {@link Collection#add})
376 >     * @return <tt>true</tt> (as specified by {@link Collection#add})
377       * @throws NullPointerException if the specified element is null
378       */
379      public boolean add(E e) {
# Line 385 | Line 387 | public class ArrayDeque<E> extends Abstr
387       * <p>This method is equivalent to {@link #offerLast}.
388       *
389       * @param e the element to add
390 <     * @return <tt>true</tt> (as per the spec for {@link Queue#offer})
390 >     * @return <tt>true</tt> (as specified by {@link Queue#offer})
391       * @throws NullPointerException if the specified element is null
392       */
393      public boolean offer(E e) {
# Line 394 | Line 396 | public class ArrayDeque<E> extends Abstr
396  
397      /**
398       * Retrieves and removes the head of the queue represented by this deque.
399 <     * This method differs from {@link #poll} only in that it throws an
399 >     *
400 >     * This method differs from {@link #poll poll} only in that it throws an
401       * exception if this deque is empty.
402       *
403       * <p>This method is equivalent to {@link #removeFirst}.
# Line 422 | Line 425 | public class ArrayDeque<E> extends Abstr
425  
426      /**
427       * Retrieves, but does not remove, the head of the queue represented by
428 <     * this deque.  This method differs from {@link #peek} only in that it
429 <     * throws an exception if this deque is empty.
428 >     * this deque.  This method differs from {@link #peek peek} only in
429 >     * that it throws an exception if this deque is empty.
430       *
431       * <p>This method is equivalent to {@link #getFirst}.
432       *
# Line 487 | Line 490 | public class ArrayDeque<E> extends Abstr
490       * @return true if elements moved backwards
491       */
492      private boolean delete(int i) {
493 +        final E[] elements = this.elements;
494 +        final int mask = elements.length - 1;
495 +        final int h = head;
496 +        final int t = tail;
497 +        final int front = (i - h) & mask;
498 +        final int back  = (t - i) & mask;
499 +
500 +        // Invariant: head <= i < tail mod circularity
501 +        if (front >= ((t - h) & mask))
502 +            throw new ConcurrentModificationException();
503 +
504 +        // Optimize for least element motion
505 +        if (front < back) {
506 +            if (h <= i) {
507 +                System.arraycopy(elements, h, elements, h + 1, front);
508 +            } else { // Wrap around
509 +                System.arraycopy(elements, 0, elements, 1, i);
510 +                elements[0] = elements[mask];
511 +                System.arraycopy(elements, h, elements, h + 1, mask - h);
512 +            }
513 +            elements[h] = null;
514 +            head = (h + 1) & mask;
515 +            return false;
516 +        } else {
517 +            if (i < t) { // Copy the null tail as well
518 +                System.arraycopy(elements, i + 1, elements, i, back);
519 +                tail = t - 1;
520 +            } else { // Wrap around
521 +                System.arraycopy(elements, i + 1, elements, i, mask - i);
522 +                elements[mask] = elements[0];
523 +                System.arraycopy(elements, 1, elements, 0, t);
524 +                tail = (t - 1) & mask;
525 +            }
526 +            return true;
527 +        }
528 +    }
529 +
530 +    private boolean xdelete(int i) {
531          int mask = elements.length - 1;
532 +        int front = (i - head) & mask;
533 +        int back  = (tail - i) & mask;
534  
535          // Invariant: head <= i < tail mod circularity
536 <        if (((i - head) & mask) >= ((tail - head) & mask))
536 >        if (front >= ((tail - head) & mask))
537              throw new ConcurrentModificationException();
538  
539 <        // Case 1: Deque doesn't wrap
540 <        // Case 2: Deque does wrap and removed element is in the head portion
541 <        if (i >= head) {
542 <            System.arraycopy(elements, head, elements, head + 1, i - head);
543 <            elements[head] = null;
544 <            head = (head + 1) & mask;
539 >        // Optimize for least element motion
540 >        if (front < back) {
541 >            if (head <= i) {
542 >                System.arraycopy(elements, head, elements, head + 1, front);
543 >            } else { // Wrap around
544 >                System.arraycopy(elements, 0, elements, 1, i);
545 >                elements[0] = elements[mask];
546 >                System.arraycopy(elements, head, elements, head + 1, mask - head);
547 >            }
548 >            elements[head] = null;
549 >            head = (head + 1) & mask;
550              return false;
551 <        }
552 <
553 <        // Case 3: Deque wraps and removed element is in the tail portion
554 <        tail--;
555 <        System.arraycopy(elements, i + 1, elements, i, tail - i);
556 <        elements[tail] = null;
557 <        return true;
551 >        } else {
552 >            int t = tail;
553 >            tail = (tail - 1) & mask;
554 >            if (i < t) { // Copy the null tail as well
555 >                System.arraycopy(elements, i + 1, elements, i, back);
556 >            } else {     // Wrap around
557 >                System.arraycopy(elements, i + 1, elements, i, mask - i);
558 >                elements[mask] = elements[0];
559 >                System.arraycopy(elements, 1, elements, 0, t);
560 >            }
561 >            return true;
562 >        }
563      }
564  
565      // *** Collection Methods ***
# Line 535 | Line 588 | public class ArrayDeque<E> extends Abstr
588       * order that elements would be dequeued (via successive calls to
589       * {@link #remove} or popped (via successive calls to {@link #pop}).
590       *
591 <     * @return an <tt>Iterator</tt> over the elements in this deque
591 >     * @return an iterator over the elements in this deque
592       */
593      public Iterator<E> iterator() {
594          return new DeqIterator();
595      }
596  
597 +    public Iterator<E> descendingIterator() {
598 +        return new DescendingIterator();
599 +    }
600 +
601      private class DeqIterator implements Iterator<E> {
602          /**
603           * Index of element to be returned by subsequent call to next.
# Line 579 | Line 636 | public class ArrayDeque<E> extends Abstr
636          public void remove() {
637              if (lastRet < 0)
638                  throw new IllegalStateException();
639 <            if (delete(lastRet))
640 <                cursor--;
639 >            if (delete(lastRet)) // if left-shifted, undo increment in next()
640 >                cursor = (cursor - 1) & (elements.length - 1);
641              lastRet = -1;
642              fence = tail;
643          }
644      }
645  
646 +
647 +    private class DescendingIterator implements Iterator<E> {
648 +        /*
649 +         * This class is nearly a mirror-image of DeqIterator, using
650 +         * (tail-1) instead of head for initial cursor, (head-1)
651 +         * instead of tail for fence, and elements.length instead of -1
652 +         * for sentinel. It shares the same structure, but not many
653 +         * actual lines of code.
654 +         */
655 +        private int cursor = (tail - 1) & (elements.length - 1);
656 +        private int fence =  (head - 1) & (elements.length - 1);
657 +        private int lastRet = elements.length;
658 +
659 +        public boolean hasNext() {
660 +            return cursor != fence;
661 +        }
662 +
663 +        public E next() {
664 +            E result;
665 +            if (cursor == fence)
666 +                throw new NoSuchElementException();
667 +            if (((head - 1) & (elements.length - 1)) != fence ||
668 +                (result = elements[cursor]) == null)
669 +                throw new ConcurrentModificationException();
670 +            lastRet = cursor;
671 +            cursor = (cursor - 1) & (elements.length - 1);
672 +            return result;
673 +        }
674 +
675 +        public void remove() {
676 +            if (lastRet >= elements.length)
677 +                throw new IllegalStateException();
678 +            if (!delete(lastRet))
679 +                cursor = (cursor + 1) & (elements.length - 1);
680 +            lastRet = elements.length;
681 +            fence = (head - 1) & (elements.length - 1);
682 +        }
683 +    }
684 +
685      /**
686       * Returns <tt>true</tt> if this deque contains the specified element.
687       * More formally, returns <tt>true</tt> if and only if this deque contains
# Line 613 | Line 709 | public class ArrayDeque<E> extends Abstr
709       * If the deque does not contain the element, it is unchanged.
710       * More formally, removes the first element <tt>e</tt> such that
711       * <tt>o.equals(e)</tt> (if such an element exists).
712 <     * Returns true if this deque contained the specified element (or
713 <     * equivalently, if this deque changed as a result of the call).
712 >     * Returns <tt>true</tt> if this deque contained the specified element
713 >     * (or equivalently, if this deque changed as a result of the call).
714       *
715       * <p>This method is equivalent to {@link #removeFirstOccurrence}.
716       *
# Line 650 | Line 746 | public class ArrayDeque<E> extends Abstr
746       * <p>The returned array will be "safe" in that no references to it are
747       * maintained by this deque.  (In other words, this method must allocate
748       * a new array).  The caller is thus free to modify the returned array.
749 <     *
749 >     *
750       * <p>This method acts as bridge between array-based and collection-based
751       * APIs.
752       *
# Line 744 | Line 840 | public class ArrayDeque<E> extends Abstr
840          s.defaultWriteObject();
841  
842          // Write out size
843 <        int size = size();
748 <        s.writeInt(size);
843 >        s.writeInt(size());
844  
845          // Write out elements in order.
751 –        int i = head;
846          int mask = elements.length - 1;
847 <        for (int j = 0; j < size; j++) {
847 >        for (int i = head; i != tail; i = (i + 1) & mask)
848              s.writeObject(elements[i]);
755 –            i = (i + 1) & mask;
756 –        }
849      }
850  
851      /**

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