package clist;

class NullNode extends ANode
{
  /**
   * Singleton pattern
   */
  public final static NullNode Singleton = new NullNode();

  private NullNode()
  {
  }

  Object getDat(CLList parent)
  {
    throw new java.util.NoSuchElementException("Null Node has no data");
  }

  void setDat(Object dat, CLList parent)
  {
    throw new java.util.NoSuchElementException("Null Node has no data");
  }

  CLList getClockwiseTail(CLList parent)
  {
    throw new java.util.NoSuchElementException("Null Node has no clockwise tail");
  }

  CLList getCounterwiseTail(CLList parent)
  {
    throw new java.util.NoSuchElementException("Null Node has no counter clockwise tail.");
  }

  void insertClockwise(Object dat, CLList parent)
  {
    new DatNode(dat, parent, parent);
  }

  void insertCounterwise(Object dat, CLList parent)
  {
    new DatNode(dat, parent, parent);
  }

  Object removeClockwise(CLList parent)
  {
    throw new java.util.NoSuchElementException("Null Node has no data");
  }

  Object removeCounterwise(CLList parent)
  {
    throw new java.util.NoSuchElementException("Null Node has no data");
  }

  Object execClockwise(ICLVisitor algo, CLList start, Object input, CLList parent)
  {
    return algo.nullCase(parent, start, input);
  }

  Object execCounterwise(ICLVisitor algo, CLList start, Object input, CLList parent)
  {
    return algo.nullCase(parent, start, input);
  }

  void setClockwiseParent(CLList cllist)
  {
    // do nothing.
  }

  void setCounterwiseParent(CLList cllist)
  {
    // do nothing.
  }
}