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

Brother, study Interfaces too.

If you want some class, such as Vehicle to only provide function prototypes, then you should always use Interface.

And make your FlyingMotorizedVehicle as abstract class.

• Abstract class can have both types of functions, either prototype only (abstrac functions) or fully implemented functions.
• Interfaces have only function prototypes, they can't contain function implementations, Interfaces are required to be implemented.

For further study, you can find many useful links, including this one.

=============================CODE-EXAMPLE=======================================

For Vehicle

public interface Vehicle {

    Something doStuff(...);   
    SomethingElse doOtherStuff(...);
    Foo bar(...);

}

For FlyingMotorizedVehicle

public abstract class FlyingMotorizedVehicle extends MotorizedVehicle {

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

===============================================================================

Happy OOP-ing!