代理模式

结构图

Subject

public interface Subject {

    void request();
}

RealSubject

public class RealSubject implements Subject{

    @Override
    public void request() {
        System.out.println("真实的请求");
    }
}

Proxy

public class Proxy implements Subject {

    RealSubject realSubject = null;

    @Override
    public void request() {
        if (realSubject == null) {
            realSubject = new RealSubject();
        }
        realSubject.request();
    }
}

Main

public class Main {

    public static void main(String[] args) {
        Proxy proxy = new Proxy();
        proxy.request();
    }
}