某公司java面试题

题目：根据程序信息写出程序的输出结果：

class A{public String show(D d){return ("AD");}public String show(A a){return ("AA");}} class B extends A{public String show(B b){return ("BB");}public String show(A a){return ("BA");}} class C extends B{} class D extends B{} public class Test{    public static void main(String[] args) {        A a = new A();        B b = new B();        C c = new C();        D d = new D();        System.out.println(a.show(b)+"-"+a.show(c)+"-"+a.show(d)+"-"+b.show(a)+"-"+b.show(c)+"-"+b.show(d));    }}

运行结果：

AA-AA-AD-BA-BB-AD