NotFoundCustomer.java

public interface Customer {
    double getEarnedDiscount();

    void addToOrdersHistory(Order order);
}

// Null Customer's implementation
public class NotFoundCustomer implements Customer {
    private final double DEFAULT_DISCOUNT = 1.0;

    @Override
    public double getEarnedDiscount() {
        return DEFAULT_DISCOUNT;
    }

    // Refused bequest???
    @Override
    public void addToOrdersHistory(Order order) {

    }
}