Demeter Law

Just Look at The Example Below The difference between the two if Condition

Do Not Do This

 private final List<Carriage> carriages [...]
 private int percentReservedBarrier = 70;
 public void reserveSeats(ReservationRequest request) {
   for (Carriage carriage : carriages) {
     if (carriage.getSeats().getPercentReserved() < 
                                  percentReservedBarrier) {
     request.reserveSeatsIn(carriage);
     return;
    }
  }
 request.cannotFindSeats();
}

Do This Instead

public void reserveSeats(ReservationRequest request) {
 for (Carriage carriage : carriages) {
  if 
  (carriage.hasSeatsAvailableWithin(percentReservedBarrier)) 
  {
   request.reserveSeatsIn(carriage);
   return;
  }
 }
 request.cannotFindSeats();
}