访问者模式——HeadFirst设计模式学习笔记

 1 abstract class Element {  
 2     public abstract void accept(IVisitor visitor);  
 3     public abstract void doSomething();  
 4 }  
 5   
 6 interface IVisitor {  
 7     public void visit(Element e);  
 8 }  
 9   
10 class ConcreteElement extends Element {  
11     public void doSomething(){  
12         System.out.println("这是元素");  
13     }  
14       
15     public void accept(IVisitor visitor) {  
16         visitor.visit(this);  
17     }  
18 }  
19 
20 class Visitor implements IVisitor {  
21   
22     public void visit(Element e) {  
23         e.doSomething();  
24     }  
25 }  
26   
27 
28 public class Client {  
29     public static void main(String[] args){  
30         List<Element> list = ObjectStruture.getList();  
31         for(Element e: list){  
32             e.accept(new Visitor());  
33         }  
34     }  
35 }