code: public void write_attribute_asynch(final DeviceProxy deviceProxy,
  	    final DeviceAttribute[] attribs, final CallBack cb) throws DevFailed {
          final int id = write_attribute_asynch(deviceProxy, attribs);
          ApiUtil.set_async_reply_model(id, CALLBACK);
          ApiUtil.set_async_reply_cb(id, cb);
  
          // if push callback, start a thread to do it
          if (ApiUtil.get_asynch_cb_sub_model() == PUSH_CALLBACK) {
              final AsyncCallObject aco = ApiUtil.get_async_object(id);
              new CallbackThread(aco).start();
          }
      }
docs: ==========================================================================