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 Visitor;
public interface Product {
void accept(Visitor visitor);
}
package Visitor;
public class Apple implements Product {
@Override
public void accept(Visitor visitor) {
visitor.visit(this);
}
}
package Visitor;
public class Book implements Product {
@Override
public void accept(Visitor visitor) {
visitor.visit(this);
}
}
package Visitor;
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);
}
package Visitor;
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 Visitor;
public class Packer extends Visitor {
@Override
public void visit(Apple apple) {
System.out.println("打包员" + name + "给苹果打包");
}
@Override
public void visit(Book book) {
System.out.println("打包员" + name + "给书打包");
}
}
package Visitor;
public class Saler extends Visitor {
@Override
public void visit(Apple apple) {
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) {
System.out.println("收银员" + name + "直接计算书的价格");
}
}
package Visitor;
import java.util.ArrayList;
import java.util.List;
public class BuyBasket {
private List<Product> products = new ArrayList();
public void accept(Visitor visitor) {
for (Product product : products) {
product.accept(visitor);
}
}
public void addProduct(Product p) {
products.add(p);
}
public void removeProduct(Product p) {
products.remove(p);
}
}
package Visitor;
public class Client {
public static void main(String[] args) {
BuyBasket buyBasket = new BuyBasket();
buyBasket.addProduct(new Apple());
buyBasket.addProduct(new Book());
Visitor saler = new Saler();
saler.setName("张三");
System.out.println("----收银员----");
buyBasket.accept(saler);
Visitor packer = new Packer();
packer.setName("李四");
System.out.println("----打包员----");
buyBasket.accept(packer);
Visitor customer = new Customer();
customer.setName("王五");
System.out.println("----顾客----");
buyBasket.accept(customer);
}
}