单选题

main程序输出: interface Alpha { &n...

Question

main程序输出:

interface Alpha {
    void f()
}
class Beta implements Alpha {
    public void f() {
        System.out.println("Beta.f()")
    }
    public void g() {
        System.out.println("Beta.g()")
    }
}
public class Main {
    public static void main(String[] args) {
        Alpha a = new Beta()
        a.f()
        System.out.println(a.getClass().getName())
        try {
            Beta b = (Beta)a
            b.g()
        } catch (Exception e) {
            System.out.println("Error")
        }
    }
}

A. Alpha

Error

B. Beta.f()

Beta

Beta.g()

C. Alpha

Beta.g()

D. Beta.f()

Beta

Error