The decision which method to use basically has two phases: first the overload resolution, then the method dispatch. Overload resolution happens at compile-time, method dispatch at runtime.
In this example the overload resolution decides that the overload someMethod(A param) should be used because that's the only overload of someMethod defined in class A (and the static type of ac is A).
At runtime it is decided which implementation of someMethod(A param) to use, but since there is only one implementation (C.someMethod(C) does not override someMethod(A) as C is more specific than A), A.someMethod(A) is chosen.
