public void addFirmwareUpdateCallback(OneSheeldFirmwareUpdateCallback firmwareUpdateCallback){
  if (firmwareUpdateCallback != null && !firmwareUpdateCallbacks.contains(firmwareUpdateCallback))   firmwareUpdateCallbacks.add(firmwareUpdateCallback);
}

public void addFirmwareUpdateCallback ( OneSheeldFirmwareUpdateCallback firmwareUpdateCallback ) { if ( firmwareUpdateCallback != null && ! firmwareUpdateCallbacks . contains ( firmwareUpdateCallback ) ) firmwareUpdateCallbacks . add ( firmwareUpdateCallback ) ; }
add a firmware update callback .
