public class A {


public static void main(String[] args) {
C c = new C();
B b = c.s();
b.f();


}


}


interface B{
public void f();
}


class C{
private class D implements B{
public void f() {
System.out.println("這是一個內部類");
}
}
public B s(){
return new D();
}

}