【GOF23设计模式】迭代器模式

 1 package com.test.iterator;
 2 /**
 3  * 自定义的迭代器接口
 4  */
 5 public interface MyIterator {
 6     void first();   //将游标指向第一个元素    
 7     void next();    //将游标指向下一个元素
 8     boolean hasNext();  //判断是否存在下一个元素
 9 
10     boolean isFirst();
11     boolean isLast();
12 
13     Object getCurrentObj(); //获取当前游标指向的对象
14 }

 1 package com.test.iterator;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 /**
 7  * 自定义的聚合类
 8  */
 9 public class ConcreteMyAggregate {
10     private List<Object> list = new ArrayList<Object>();
11 
12     public void addObject(Object obj){
13         this.list.add(obj);
14     }
15     public void removeObject(Object obj){
16         this.list.remove(obj);
17     }
18 
19     public List<Object> getList() {
20         return list;
21     }
22     public void setList(List<Object> list) {
23         this.list = list;
24     }
25 
26     //获得迭代器
27     public MyIterator createIterator(){
28         return new ConcreteIterator();
29     }
30 
31     //使用内部类定义迭代器，可以直接使用外部类的属性
32     private class ConcreteIterator implements MyIterator{
33 
34         private int cursor; //定义游标用于记录遍历时的位置
35 
36         @Override
37         public void first() {
38             cursor = 0;
39         }
40 
41         @Override
42         public void next() {
43             if(cursor<list.size()){
44                 cursor++;
45             }
46         }
47 
48         @Override
49         public boolean hasNext() {
50             if(cursor<list.size()){
51                 return true;
52             }
53             return false;
54         }
55 
56         @Override
57         public boolean isFirst() {
58             return cursor==0?true:false;
59         }
60 
61         @Override
62         public boolean isLast() {
63             return cursor==(list.size()-1)?true:false;
64         }
65 
66         @Override
67         public Object getCurrentObj() {
68             return list.get(cursor);
69         }
70     }
71 }

 1 package com.test.iterator;
 2 
 3 public class Client {
 4     public static void main(String[] args) {
 5         ConcreteMyAggregate cma = new ConcreteMyAggregate();
 6         cma.addObject("aa");
 7         cma.addObject("bb");
 8         cma.addObject("cc");
 9 
10         MyIterator iter = cma.createIterator();
11         while(iter.hasNext()){
12             System.out.println(iter.getCurrentObj());
13             iter.next();
14         }
15     }
16 }