Can you re-make a method abstract in the inheritance tree?

Question

EDIT:

To be clear: The fact that the design is quite ugly is not the point. The point is, that the design is there and I am in the situation to have to add another sub-c

Answer 1

Yes, You have to redefine the bar(...) as abstract method. Then you have to declare public class FlyingMotorizedVehicle as a abstract class as well

public abstract class FlyingMotorizedVehicle extends MotorizedVehicle {

    @Override
    SomethingElse doOtherStuff(...) {
        return new SomethingElse();
    }

    abstract Foo bar(...);

}