exercice 3

class Exercice3{
    public static void main(String[] args) {
        A x = new A();
        B y = new B();
        C z = new C();
        y.b = 2;
        z.c = 3;
    }
    abstract class  A{
        int a;
    }
    class  B extends A{
        int b;
        public B(int b){
            this.b= b;
        }
    }
    class C extends A {
        final double c = 1;
    }

    abstract class D extends  A{
        double d;
        int operation(int a){
            return (a*2);
        }
        abstract int calcul(int b){

        }
        abstract void afficher();
    }

}