java常用设计模式之迭代器模式

------------------------------ 迭代器模式(Iterator) -------------------------------
(1)
基本概念:
迭代器模式属于行为型模式，其意图是提供一种方法顺序访问一个聚合对象中得各个元素，而又不需要暴露该对象的

内部表示。
至少可以历遍first,next,previous,last,isOver,或是历遍选择符合某种条件的子元素.
(2)
结构:
由一个接口与一个实现类组成.
接口:
主要是定义各历遍的方法.
实现类:
需要一个计算点private int current=0 ; 以及一个容器Vector,来存在原来的进行历遍的一团东西;再对接口方法进行实现.(3)
实例:???????
Iterator接口：
package iterator;
public interface Iterator{
/*
Item:即是集合中的各对象的类型.若为String,即把所有的ITEM改为String,若为其它自定义的类,则改为各自定义的类的接口,或类. --->important.?
*/
??? public Item first();
??? public Item next();
??? public boolean isDone();
??? public Item currentItem();
}Controller类实现了Iterator接口。
package iterator;
import java.util.Vector;
public class Controller implements Iterator{
??? private int current =0;
??? Vector channel;
??? public Controller(Vector v){
?????? channel = v;
??? }
??? public Item first(){
?????? current = 0;
?????? return (Item)channel.get(current);
??? }
??? public Item next(){
?????? current ++;
?????? return (Item)channel.get(current);
??? }
??? public Item currentItem(){
?????? return (Item)channel.get(current);
??? }
??? public boolean isDone(){
?????? return current>= channel.size()-1;
??? }
}Television接口：
package iterator;
import java.util.Vector;
public interface Television{
??? public Iterator createIterator();
}
HaierTV类实现了Television接口。
package iterator;
import java.util.Vector;
public class HaierTV implements Television{???? ---对象
??? private Vector channel;
??? public HaierTV(){
?????? channel = new Vector();
?????? channel.addElement(new Item("channel 1")); --各元素，用VECTOR存放
?????? channel.addElement(new Item("channel 2"));
?????? channel.addElement(new Item("channel 3"));
?????? channel.addElement(new Item("channel 4"));
?????? channel.addElement(new Item("channel 5"));
?????? channel.addElement(new Item("channel 6"));
?????? channel.addElement(new Item("channel 7"));
??? }
??? public Iterator createIterator(){
?????? return new Controller(channel);????????? --把这个VECTOR放到迭代器中构造方法中去
??? }
}
Client客户端：
package iterator;
public class Client{
??? public static void main(String[] args){
?????? Television tv = new HaierTV();
?????? Iterator it =tv.createIterator();
?????? System.out.println(it.first().getName());
?????? while(!it.isDone()){
?????????? System.out.println(it.next().getName());
?????? }
??? }
}
Item类的接口：?????????????
package iterator;
public class Item{
??? private String name;
??? public Item(String aName){
?????? name = aName;
??? }
??? public String getName(){
?????? return name;
??? }
}转自：http://shenzhenchufa.blog.51cto.com/730213/161581