Java从string实例化类

public interface SuperbInterface
public class A implements SuperbInterface
public class B extends A
public class C extends B

我想实例化C但我似乎得到了B,我做错了什么？

Class classz = Class.forName("C");
SuperbInterface superb = (SuperbInterface)classz.newInstance();

//Here when I debug it seems to be going to B.doWork() methods instead of C.doWork().
superb.doWork();