public Boardable[] canBoard(Boardable batch[]) {
    final Batch <Boardable> CB = new Batch <Boardable> () ;
    if (mainEntrance() != null) CB.add(mainEntrance()) ;
    if (docking != null) CB.add(docking) ;
    int i = 2 ; for (Mobile m : inside()) if (m instanceof Boardable) {
      CB.add((Boardable) m) ;
    }
    return CB.toArray(Boardable.class) ;
  }