设计模式-迭代器

定义：提供一种方法顺序访问一个聚合对象中的各个元素，而又不暴露其内部的表示。

UML类图：

 1 interface Iterator {
 2     public Object next();
 3     public boolean hasNext();
 4 }
 5 class ConcreteIterator implements Iterator{
 6     private List list = new ArrayList();
 7     private int cursor =0;
 8     public ConcreteIterator(List list){
 9         this.list = list;
10     }
11     public boolean hasNext() {
12         if(cursor==list.size()){
13             return false;
14         }
15         return true;
16     }
17     public Object next() {
18         Object obj = null;
19         if(this.hasNext()){
20             obj = this.list.get(cursor++);
21         }
22         return obj;
23     }
24 }
25 interface Aggregate {
26     public void add(Object obj);
27     public void remove(Object obj);
28     public Iterator iterator();
29 }
30 class ConcreteAggregate implements Aggregate {
31     private List list = new ArrayList();
32     public void add(Object obj) {
33         list.add(obj);
34     }
35
36     public Iterator iterator() {
37         return new ConcreteIterator(list);
38     }
39
40     public void remove(Object obj) {
41         list.remove(obj);
42     }
43 }
44 public class Client {
45     public static void main(String[] args){
46         Aggregate ag = new ConcreteAggregate();
47         ag.add("小明");
48         ag.add("小红");
49         ag.add("小刚");
50         Iterator it = ag.iterator();
51         while(it.hasNext()){
52             String str = (String)it.next();
53             System.out.println(str);
54         }
55     }
56 }