/** The next entry */
        protected Entry next;

        /** The previous entry */
        protected Entry previous;

        Entry(final E element, final Entry next, final Entry previous) {
            this.element = element;
            this.next = next;
            this.previous = previous;
        }

        /**
         * Returns the element.
         *

   */
  private void removeNode(Node<K, V> node) {
    if (node.previous != null) {
      node.previous.next = node.next;
    } else { // node was head
      head = node.next;
    }
    if (node.next != null) {
      node.next.previous = node.previous;
    } else { // node was tail
      tail = node.previous;
    }
    if (node.previousSibling == null && node.nextSibling == null) {
      /*

    }

    /**
     * Checks if a previous page exists.
     *
     * @return true if a previous page exists, false otherwise.
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets the flag for the existence of a previous page.
     *
     * @param existPrePage true if a previous page exists.
     */

    }

    /**
     * Checks if a previous page exists.
     * @return true if a previous page exists, false otherwise.
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     * @param existPrePage true if a previous page exists, false otherwise.
     */

      protected @Nullable Integer computeNext(Integer previous) {
        return (previous == last) ? null : previous * 2;
      }
    };
  }

  private static class EmptyAbstractSequentialIterator<T> extends AbstractSequentialIterator<T> {

    EmptyAbstractSequentialIterator() {
      super(null);
    }

    @Override
    protected T computeNext(T previous) {
      throw new AssertionFailedError();
    }

    }

    /**
     * Checks if a previous page exists.
     *
     * @return true if previous page exists, false otherwise
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets whether a previous page exists.
     *
     * @param existPrePage true if previous page exists, false otherwise
     */

 * whose next element can always be derived from the previous element. Null elements are not
 * supported, nor is the {@link #remove()} method.
 *
 * <p>Example:
 *
 * {@snippet :
 * Iterator<Integer> powersOfTwo =
 *     new AbstractSequentialIterator<Integer>(1) {
 *       protected Integer computeNext(Integer previous) {
 *         return (previous == 1 << 30) ? null : previous * 2;
 *       }
 *     };
 * }
 *

    }

    /**
     * Checks if a previous page exists.
     *
     * @return true if a previous page exists, false otherwise
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets the flag indicating if a previous page exists.
     *
     * @param existPrePage true if a previous page exists, false otherwise
     */

    }

    /**
     * Checks if a previous page exists for pagination.
     *
     * @return true if a previous page exists, false otherwise
     */
    public boolean isExistPrePage() {
        return existPrePage;
    }

    /**
     * Sets the flag indicating whether a previous page exists.
     *
     * @param existPrePage true if a previous page exists, false otherwise
     */

  /** Sets the next entry in the access queue. */
  void setNextInAccessQueue(ReferenceEntry<K, V> next);

  /** Returns the previous entry in the access queue. */
  ReferenceEntry<K, V> getPreviousInAccessQueue();

  /** Sets the previous entry in the access queue. */
  void setPreviousInAccessQueue(ReferenceEntry<K, V> previous);

  /*
   * Implemented by entries that use write order. Write entries are maintained in a doubly-linked