code: public int getLength() {
          int count=0;
          for (int handle=m_firstChild;
               handle!=DTM.NULL;
               handle=m_parentDTM.getNextSibling(handle)) {
              ++count;
          }
          return count;
      }
docs: The number of nodes in the list. The range of valid child node indices
  is 0 to <code>length-1</code> inclusive.