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。

实验要求：

1. 提交源代码，不要提交类图；

2. 注意编程规范。

package test25;

public class Apple implements Product {
    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}


package test25;

public class Book implements Product{
    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}


package test25;

import java.util.ArrayList;
import java.util.Iterator;

public class BuyBasket{

    private ArrayList list = new ArrayList();

    public void accept(Visitor visitor){
        Iterator iterator = list.iterator();
        while (iterator.hasNext()){
            ((Product)iterator.next()).accept(visitor);
        }
    }

    public void addProduce(Product product){
        list.add(product);
    }

    public void removeProduce(Product product){
        list.remove(product);
    }

}



package test25;

public class Client {

    public static void main(String[] args) {
        Product b1 = new Book();
        Product b2 = new Book();
        Product a1 = new Apple();
        Visitor visitor;

        BuyBasket basket = new BuyBasket();
        basket.addProduce(b1);
        basket.addProduce(b2);
        basket.addProduce(a1);

        visitor = new Packager();
        visitor.setName("张三");
        basket.accept(visitor);
    }

}


package test25;

public class Customer extends Visitor{
    @Override
    public void visit(Apple apple) {
        System.out.println("顾客"+name+"选苹果");
    }

    @Override
    public void visit(Book book) {
        System.out.println("顾客"+name+"买书");
    }
}


package test25;

public class Packager extends Visitor{
    @Override
    public void visit(Apple apple) {
        System.out.println("打包员"+name+"打包苹果");
    }

    @Override
    public void visit(Book book) {
        System.out.println("打包员"+name+"打包书籍");
    }
}


package test25;

public interface Product {

    void accept(Visitor visitor);

}


package test25;

public class Saler extends Visitor{
    @Override
    public void visit(Apple apple) {
        System.out.println("收银员"+
                name+"给苹果过称，计算价格");
    }

    @Override
    public void visit(Book book) {
        System.out.println("收银员"+name+"直接计算书的价格");
    }
}


package test25;

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);

}