前言：【】——————————by xingoo
模式意图
提供一个方法按顺序遍历一个集合内的元素，而又不需要暴露该对象的内部表示。
应用场景
1 访问一个聚合的对象，而不需要暴露对象的内部表示
2 支持对聚合对象的多种遍历
3 对遍历不同的对象，提供统一的接口。
模式结构
Iterator 定义访问的接口
/** * 抽象的迭代，有判断结束和下一个，获取当前元素等函数 * @author xingoo * */interface Iterator{ void first(); void next(); boolean isDone(); Object currentItem();}
ConcreteIterator 具体的迭代器，跟踪聚合内的元素
/** * 具体的迭代类 * @author xingoo * */class ConcreteIterator implements Iterator{ private ConreteAggregate agg; private int index = 0; private int size = 0; public ConcreteIterator(ConreteAggregate agg) { this.agg = agg; size = agg.size(); index = 0; } public void first() { index = 0; } public void next() { if(index < size){ index++; } } public boolean isDone() { return (index >= size); } public Object currentItem() { return agg.getElement(index); } }
Aggregate 提供聚合的接口
/** * 聚合的类 * @author xingoo * */abstract class Aggregate{ public Iterator createIterator(){ return null; }}
ConcreteAggregate 具体的聚合
/** * 具体的聚合对象，拥有大小，创建迭代子等函数 * @author xingoo * */class ConreteAggregate extends Aggregate{ private Object[] obj = { "test1","test2","test3","test4"}; public Iterator createIterator(){ return new ConcreteIterator(this); } public Object getElement(int index){ if(index < obj.length){ return obj[index]; }else{ return null; } } public int size(){ return obj.length; }} 全部代码
1 package com.xingoo.Iterator; 2 /** 3 * 聚合的类 4 * @author xingoo 5 * 6 */ 7 abstract class Aggregate{ 8 public Iterator createIterator(){ 9 return null;10 }11 }12 /**13 * 抽象的迭代，有判断结束和下一个，获取当前元素等函数14 * @author xingoo15 *16 */17 interface Iterator{18 void first();19 void next();20 boolean isDone();21 Object currentItem();22 }23 /**24 * 具体的聚合对象，拥有大小，创建迭代子等函数25 * @author xingoo26 *27 */28 class ConreteAggregate extends Aggregate{29 private Object[] obj = { "test1","test2","test3","test4"};30 public Iterator createIterator(){31 return new ConcreteIterator(this);32 }33 public Object getElement(int index){34 if(index < obj.length){35 return obj[index];36 }else{37 return null;38 }39 }40 public int size(){41 return obj.length;42 }43 }44 /**45 * 具体的迭代类46 * @author xingoo47 *48 */49 class ConcreteIterator implements Iterator{50 private ConreteAggregate agg;51 private int index = 0;52 private int size = 0;53 54 public ConcreteIterator(ConreteAggregate agg) {55 this.agg = agg;56 size = agg.size();57 index = 0;58 }59 60 public void first() {61 index = 0;62 }63 64 public void next() {65 if(index < size){66 index++;67 }68 }69 70 public boolean isDone() {71 return (index >= size);72 }73 74 public Object currentItem() {75 return agg.getElement(index);76 }77 78 }79 /**80 * 客户端 使用方法81 * @author xingoo82 *83 */84 public class Client {85 private Iterator it;86 private Aggregate agg = new ConreteAggregate();87 public void operation(){88 it = agg.createIterator();89 while(!it.isDone()){90 System.out.println(it.currentItem().toString());91 it.next();92 }93 }94 public static void main(String[] args) {95 Client client = new Client();96 client.operation();97 }98 } 运行结果
test1test2test3test4