class Lastebil extends Bil implements LagerLyd, FrakterTungLast {

    public Lastebil(String regNr) {
        super(regNr);
    }

    @Override
    public String hentInfo() {
        return "Jeg er en lastebil, regNr: " + regNr;
    }

    @Override
    public void lagLyd() {
        System.out.println("BROOM!");
    }

    @Override
    public void fraktTungt() {
        System.out.println("Frakter tungt");
    }

    public void pluss(int n) throws Exception{
        if (n<0)
            throw new IllegalArgumentException();
    }
}