Klasse A und B

package polymorphie;

public class A {

    int val = 0;

        A(){

            this(42);
    }

        A(int v){

            val = v;

        }

    public String toString() {

        return String.valueOf(val);

    }

    public static void main(String[] args) {

    }

}


package polymorphie;

public class B extends A{

    B(){

        super();
        val = 9;

    }

    public String toString(int val) {

    return String.valueOf(val);

    }

    public static void main(String[] args) {

        A a1 = new A();
        A a2 = new A(3);
        A a3 = new A();
        B b1 = new B();


        System.out.println(a1);
        System.out.println(a2);
        System.out.println(a3);
        System.out.println(b1);
    }

}