code: public void destroy()
      {   
          for (int i=_fields.size();i-->0;)
          {
              Field field=(Field)_fields.get(i);
              if (field!=null)
                  field.destroy();
          }
          _fields=null;
          _index=null;
          _dateBuffer=null;
          _calendar=null;
          _dateReceive=null;
      }
docs: Destroy the header.
  Help the garbage collector by null everything that we can.