code: public void clear()
      {
          _version++;
          if (_version>1000)
          {
              _version=0;
              for (int i=_fields.size();i-->0;)
              {
                  Field field=(Field)_fields.get(i);
                  if (field!=null)
                      field.clear();
              }
          }
      }
docs: Clear the header.