code: public Object next()
      {
          _current1.reset();
          if (_last1.key() == null)
              findFirst(_dstack);
          else
          {
              findNext(_dstack);
              if (_current1.key() == null)
                  _eof = true;
          }
  
          if (_current1.key() != null)
              _last1.setLocation(_current1);
  
          return _current1.key();
      }
docs: Return the next element in the collection.