int prev = m_pos-1; if((prev >= 0) && (prev < m_nl.getLength()))
if (0 == m_pos)
    public Node previousNode()                             throws DOMException    {      int prev = m_pos-1;      if((prev >= 0) && (prev < m_nl.getLength()))        {        m_pos--;        return m_nl.item(prev);      }      else        return null;    }