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public class KFZ {
    String kennzeichen;
    int ps;

    @Override
    public String toString() {
        return kennzeichen + ", " + ps;
    }
}

public class PKW extends KFZ {

}

public class Program {
    public static void main(String[] args) {
        KFZ kfz = new KFZ();
        kfz.kennzeichen = "Kraftfahrzeug";
        kfz.ps = 25;

        PKW pkw = new PKW();
        pkw.kennzeichen = "Personenkraftwagen";
        pkw.ps = 35;

        System.out.println(kfz);
        System.out.println(pkw);
    }
}