访问者模式 Visitor Pattern

 1 package headfirst.visitor;
 2 
 3 abstract class Acceptor {
 4     public abstract void accept(IVisitor visitor);
 5     public abstract void execute()throws Exception;
 6 }
 7 
 8 class AcceptorInstance extends Acceptor{
 9     private IVisitor visitor;
10 
11     @Override
12     public void accept(IVisitor visitor) {
13         this.visitor = visitor;
14         visitor.visit(this);
15     }
16 
17     @Override
18     public void execute() throws Exception {
19         System.out.println(String.format("接受者：欢迎[%s]来做客！", visitor.getDescription()));
20     }
21 }
22 
23 interface IVisitor{
24     
25     String getDescription();
26     void visit(Acceptor acceptor);
27     
28 }
29 
30 class Visitor implements IVisitor{
31     
32     private final static String name = "jonex";
33 
34     @Override
35     public String getDescription() {
36         return name;
37     }
38 
39     @Override
40     public void visit(Acceptor acceptor) {
41         try {
42             acceptor.execute();
43         } catch (Exception e) {
44             e.printStackTrace();
45         }
46     }
47 }
48 
49 public class VisitorPattern{
50     public static void main(String[] args) {
51         Acceptor acceptor = new AcceptorInstance();
52         acceptor.accept(new Visitor());
53     }
54 }