public ActivityTransporter addExtra(String key,String value){
  if (extras == null)   extras=new ArrayList<>();
  extras.add(new ActivityExtra(key,value));
  return this;
}

public ActivityTransporter addExtra ( String key , String value ) { if ( extras == null ) extras = new ArrayList < > ( ) ; extras . add ( new ActivityExtra ( key , value ) ) ; return this ; }
it is only possible to send strings as extra .
