試題詳解

 10. interface Foo{} 

11. class Alpha implements Foo{} 

12. class Beta extends Alpha{}

 13. class Delta extends Beta{ 

14. public static void main(String[] args){

 15. Beta x = new Beta()； 

16. //insert code here 

17. }

 18. } 

Which code, inserted at line 16, will cause a java.lang.ClassCastException?
(A) Alpha a = x；
(B) Foo f = (Delta)x；
(C) Foo f = (Alpha)x；
(D) Beta b = (Beta)(Alpha)x；