interface A{
    void say();
}

class BImpl implements A{

    public void say() {
        System.out.println("Hello");
    }
}

class CProxy implements A{
    private Aspect aspect;
    
    private A a;
    
    public void setAspect(Aspect aspect) {
        this.aspect = aspect;
    }
    public CProxy(A a) {
        this.a = a;
    }
    public void say() {
        aspect.start();
        a.say();
        aspect.end();
    }
}
class Aspect{
    public void start() {
        System.out.println("start()");
    }
    public void end() {
        System.out.println("end");
    }
}
class Test{
    public static void main(String[] args) {
        A bimpl = new BImpl();
        A cproxy = new CProxy(bimpl);
        Aspect aspect = new Aspect();
        //cproxy.setAspect(aspect)
    }
}