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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.10 by jsr166, Tue May 17 04:09:23 2005 UTC vs.
Revision 1.21 by dl, Fri Sep 16 23:17:05 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 488 | Line 491 | public class ArrayDeque<E> extends Abstr
491       */
492      private boolean delete(int i) {
493          int mask = elements.length - 1;
494 +        int front = (i - head) & mask;
495 +        int back  = (tail - i) & mask;
496  
497          // Invariant: head <= i < tail mod circularity
498 <        if (((i - head) & mask) >= ((tail - head) & mask))
498 >        if (front >= ((tail - head) & mask))
499              throw new ConcurrentModificationException();
500  
501 <        // Case 1: Deque doesn't wrap
502 <        // Case 2: Deque does wrap and removed element is in the head portion
503 <        if (i >= head) {
504 <            System.arraycopy(elements, head, elements, head + 1, i - head);
505 <            elements[head] = null;
506 <            head = (head + 1) & mask;
501 >        // Optimize for least element motion
502 >        if (front < back) {
503 >            if (head <= i) {
504 >                System.arraycopy(elements, head, elements, head + 1, front);
505 >            } else { // Wrap around
506 >                elements[0] = elements[mask];
507 >                System.arraycopy(elements, 0, elements, 1, i);
508 >                System.arraycopy(elements, head, elements, head + 1, mask - head);
509 >            }
510 >            elements[head] = null;
511 >            head = (head + 1) & mask;
512              return false;
513 <        }
514 <
515 <        // Case 3: Deque wraps and removed element is in the tail portion
516 <        tail--;
517 <        System.arraycopy(elements, i + 1, elements, i, tail - i);
518 <        elements[tail] = null;
519 <        return true;
513 >        } else {
514 >            int t = tail;
515 >            tail = (tail - 1) & mask;
516 >            if (i < t) { // Copy the null tail as well
517 >                System.arraycopy(elements, i + 1, elements, i, back);
518 >            } else {     // Wrap around
519 >                elements[mask] = elements[0];
520 >                System.arraycopy(elements, i + 1, elements, i, mask - i);
521 >                System.arraycopy(elements, 1, elements, 0, t);
522 >            }
523 >            return true;
524 >        }
525      }
526  
527      // *** Collection Methods ***
# Line 535 | Line 550 | public class ArrayDeque<E> extends Abstr
550       * order that elements would be dequeued (via successive calls to
551       * {@link #remove} or popped (via successive calls to {@link #pop}).
552       *
553 <     * @return an <tt>Iterator</tt> over the elements in this deque
553 >     * @return an iterator over the elements in this deque
554       */
555      public Iterator<E> iterator() {
556          return new DeqIterator();
557      }
558  
559 +    public Iterator<E> descendingIterator() {
560 +        return new DescendingIterator();
561 +    }
562 +
563      private class DeqIterator implements Iterator<E> {
564          /**
565           * Index of element to be returned by subsequent call to next.
# Line 579 | Line 598 | public class ArrayDeque<E> extends Abstr
598          public void remove() {
599              if (lastRet < 0)
600                  throw new IllegalStateException();
601 <            if (delete(lastRet))
602 <                cursor--;
601 >            if (delete(lastRet)) // if left-shifted, undo increment in next()
602 >                cursor = (cursor - 1) & (elements.length - 1);
603              lastRet = -1;
604              fence = tail;
605          }
606      }
607  
608 +
609 +    private class DescendingIterator implements Iterator<E> {
610 +        /*
611 +         * This class is nearly a mirror-image of DeqIterator, using
612 +         * (tail-1) instead of head for initial cursor, (head-1)
613 +         * instead of tail for fence, and elements.length instead of -1
614 +         * for sentinel. It shares the same structure, but not many
615 +         * actual lines of code.
616 +         */
617 +        private int cursor = (tail - 1) & (elements.length - 1);
618 +        private int fence =  (head - 1) & (elements.length - 1);
619 +        private int lastRet = elements.length;
620 +
621 +        public boolean hasNext() {
622 +            return cursor != fence;
623 +        }
624 +
625 +        public E next() {
626 +            E result;
627 +            if (cursor == fence)
628 +                throw new NoSuchElementException();
629 +            if (((head - 1) & (elements.length - 1)) != fence ||
630 +                (result = elements[cursor]) == null)
631 +                throw new ConcurrentModificationException();
632 +            lastRet = cursor;
633 +            cursor = (cursor - 1) & (elements.length - 1);
634 +            return result;
635 +        }
636 +
637 +        public void remove() {
638 +            if (lastRet >= elements.length)
639 +                throw new IllegalStateException();
640 +            if (!delete(lastRet))
641 +                cursor = (cursor + 1) & (elements.length - 1);
642 +            lastRet = elements.length;
643 +            fence = (head - 1) & (elements.length - 1);
644 +        }
645 +    }
646 +
647      /**
648       * Returns <tt>true</tt> if this deque contains the specified element.
649       * More formally, returns <tt>true</tt> if and only if this deque contains
# Line 613 | Line 671 | public class ArrayDeque<E> extends Abstr
671       * If the deque does not contain the element, it is unchanged.
672       * More formally, removes the first element <tt>e</tt> such that
673       * <tt>o.equals(e)</tt> (if such an element exists).
674 <     * Returns true if this deque contained the specified element (or
675 <     * equivalently, if this deque changed as a result of the call).
674 >     * Returns <tt>true</tt> if this deque contained the specified element
675 >     * (or equivalently, if this deque changed as a result of the call).
676       *
677       * <p>This method is equivalent to {@link #removeFirstOccurrence}.
678       *
# Line 650 | Line 708 | public class ArrayDeque<E> extends Abstr
708       * <p>The returned array will be "safe" in that no references to it are
709       * maintained by this deque.  (In other words, this method must allocate
710       * a new array).  The caller is thus free to modify the returned array.
711 <     *
711 >     *
712 >     * <p>This method acts as bridge between array-based and collection-based
713 >     * APIs.
714 >     *
715       * @return an array containing all of the elements in this deque
716       */
717      public Object[] toArray() {
# Line 741 | Line 802 | public class ArrayDeque<E> extends Abstr
802          s.defaultWriteObject();
803  
804          // Write out size
805 <        int size = size();
745 <        s.writeInt(size);
805 >        s.writeInt(size());
806  
807          // Write out elements in order.
748 –        int i = head;
808          int mask = elements.length - 1;
809 <        for (int j = 0; j < size; j++) {
809 >        for (int i = head; i != tail; i = (i + 1) & mask)
810              s.writeObject(elements[i]);
752 –            i = (i + 1) & mask;
753 –        }
811      }
812  
813      /**

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