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。
源码：
java
Apple.java
package test25;
public class Apple implements Product {
@Override
public void accept(Visitor visitor) {
visitor.visit(this);
}
}
Book.java
package test25;
public class Book implements Product{
@Override
public void accept(Visitor visitor) {
visitor.visit(this);
}
}
BuyBasket.java
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);
}
}
Client.java
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);
}
}
Customer.java
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");
}
}
Packager.java
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");
}
}
Product.java
package test25;
public interface Product {
void accept(Visitor visitor);
}
Saler.java
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");
}
}
Visitor.java
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);
}