访问者模式

合集 - 设计模式(26)

1.面向对象程序设计中类与类的关系2024-12-292.单一职责原则2024-12-293.建造者模式2024-12-294.抽象工厂模式2024-12-295.工厂方法模式2024-12-296.女娲造人2024-12-297.原型模式2024-12-298.组合模式2024-12-299.装饰模式2024-12-2910.单例模式2024-12-2911.适配器模式2024-12-2912.桥接模式2024-12-2913.外观模式2024-12-2914.享元模式2024-12-2915.代理模式2024-12-2916.职责链模式2024-12-2917.命令模式2024-12-2918.解释器模式2024-12-2919.迭代器模式2024-12-2920.中介者模式2024-12-2921.备忘录模式2024-12-2922.观察者模式2024-12-2923.状态模式2024-12-2924.策略模式2024-12-2925.模板方法模式2024-12-29

26.访问者模式2024-12-29

收起

实验 25：访问者模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容：

1、理解访问者模式的动机，掌握该模式的结构；

2、能够利用访问者模式法解决实际问题。

[实验任务一]：打包员

在我们课堂上的“购物车”的例子中，增加一个新的访问者：打包员，负责对购物车中货物装包。

类图

 

源代码

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public interface Product {     void accept(Visitor visitor); } public class Apple implements Product{       @Override     public void accept(Visitor visitor) {         // TODO Auto-generated method stub         visitor.visit(this);     }       } public class Book implements Product{       @Override     public void accept(Visitor visitor) {         // TODO Auto-generated method stub         visitor.visit(this);     }   } public class BuyBasket {     private ArrayList list=new ArrayList();           public void accept(Visitor visitor) {         Iterator i=list.iterator();                   while(i.hasNext()) {             ((Product)i.next()).accept(visitor);         }     }     public void addProduct(Product product) {         list.add(product);     }     public void removeProduct(Product product) {         list.remove(product);     } } public class Customer extends Visitor{       @Override     public void visit(Apple apple) {         // TODO Auto-generated method stub         System.out.println("顾客"+name+"选苹果。");     }       @Override     public void visit(Book book) {         // TODO Auto-generated method stub         System.out.println("顾客"+name+"买书。");     }       } public class Packer extends Visitor{       @Override     public void visit(Apple apple) {         // TODO Auto-generated method stub         System.out.println("打包员"+name+"给苹果打包。");     }       @Override     public void visit(Book book) {         // TODO Auto-generated method stub         System.out.println("打包员"+name+"给书打包。");     }   } public class Saler extends Visitor{       @Override     public void visit(Apple apple) {         // TODO Auto-generated method stub         System.out.println("收银员"+name+"给苹果过秤，然后计算其价格");     }       @Override     public void visit(Book book) {         // TODO Auto-generated method stub         System.out.println("收银员"+name+"直接计算书的价格。");     }   } public abstract class Visitor {     protected String name;     public void setName(String name) {         this.name=name;     }     public abstract void visit(Apple apple);     public abstract void visit(Book book); } public class Client {       public static void main(String[] args) {         // TODO Auto-generated method stub         Product b1=new Book();         Product b2=new Book();         Product a1=new Apple();         Visitor visitor;                   BuyBasket basket=new BuyBasket();         basket.addProduct(b1);         basket.addProduct(b2);         basket.addProduct(a1);                   visitor=new Customer();         visitor.setName("张三");         basket.accept(visitor);         System.out.println("----------------------------");         visitor=new Packer();         visitor.setName("李四");         basket.accept(visitor);         System.out.println("----------------------------");         visitor=new Saler();         visitor.setName("王五");         basket.accept(visitor);     }   }