Method overloading using derived types as parameters in Java

Question

Let\'s say I have existing code which I want to extend but also to avoid changing it as much as possible.

Somewhere around this code there is a method that receives

Answer 1

Why not simply call the method with a parameter of the correct type?

Base b = null;
if (flag) {
    Derived d = new Derived()
    Engine.method(d); // so the correct method will be used for Derived
    b = d;
} else{
    b = new Base()
    Engine.method(b) 
}

You could also consider reusing the method(Base b):

public void method(Derived d) {
    method((Base)b);
    ...
}