java内部接口

public class Sample{    public interface A(){    public void functionA();    }        public interface B(){    public void functionB();    }        public void functionA(){        //...    }    public void functionB(){        //...    }}public class Test{    public static main(String[] args){        Sample.A a = ???        a.functionA();        Sample.B b = ???        b.functionB();    }}

是这么用吗？查不到。。。不清楚。。。