Animal.java

abstract class Animal<F extends Food> { abstract void eats(F f);}
abstract class Food {}
class Veg extends Food {}
class Meat extends Food {}
class Grass extends Veg {}
class Carrot extends Veg {}
class Cow extends Animal<Veg> { void eats(Veg f) {}}

class Main {
    public static void main(String[] args) {
        Cow cow = new Cow();
        cow.eats(new Meat());
    }
}

Money.java

abstract class Money<A extends Money<A>> {  abstract A add(A m); }
class Fiat extends Money<Fiat> {
    @Override
    Fiat add(Fiat m) {
        return m;
    }
}
class Metal extends Money<Metal> {
    @Override
    Metal add(Metal m) {
        return m;
    }
}
class Main {

    public static void main(String[] args) {
        Fiat f = new Fiat();
        Fiat f2 = new Fiat();
        Fiat ff = f.add(f2);
        System.out.println(add(f2, ff));
    }

    static <T extends Money<T>> T add(T a, T b) {
        return a.add(b);
    }

}