大话设计模式笔记 代理模式

package proxy;

/*
 * Subject Class,the common interface of RealSubject and Proxy,
 */
public abstract class Subject {
    public abstract void Request();
}

package proxy;

//represent the real entity
public class RealSubject extends Subject {

    @Override
    public void Request() {
        System.out.println("thr real Request");
    }
    
}

package proxy;

/*
 * 保存一个引用使得代理可以访问实体，并提供一个与Subject的接口相同的接口
 * 这样代理可以用来替代实体
 */
public class Proxy extends Subject {

    RealSubject realSubject;

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

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