迭代器模式

迭代器模式的定义：提供一种顺序访问一个聚合对象中各个元素的方法，但是又不会暴露该对象的内部表示。这个内部表示我的理解就是指向集合的指针，因为一般来讲遍历一个集合必须要像游标遍历结果集一样，迭代器模式就是让外界调用集合的createIterator方法来创建一个接口，这个接口暴露的方法和具体集合无关，然后通过这个接口的实现类和具体聚合对象之间的引用，把这个迭代器和具体聚合对象联系起来。

package com.jerry.design.iterator;import java.util.ArrayList;import java.util.List;// 测试类public class Test {public static void main(String[] args) {String[] s = {"测试一","测试二","测试三","测试四"};Aggregate a = new ConcreteAggregate(s);Iterator it = a.createIterator();it.first();while(it.hasNext()){System.out.println(it.current());it.next();}}}interface Iterator{ public void first(); public void next(); public boolean hasNext(); public Object current();}class ConcreteIterator implements Iterator{private int index = -1;private ConcreteAggregate aggregate;public ConcreteIterator(ConcreteAggregate aggregate) {super();this.aggregate = aggregate;}@Overridepublic void first() {index = 0;}@Overridepublic void next() {if(index<aggregate.size()){index++;}}@Overridepublic boolean hasNext() {int temp = index;if(temp<aggregate.size()){return true;}return false;}@Overridepublic Object current() {return aggregate.get(index);}}interface Aggregate{ public abstract  Iterator createIterator();}class ConcreteAggregate implements Aggregate{private String[] s = null;public ConcreteAggregate(String[] s) {super();this.s = s;}@Overridepublic Iterator createIterator() {return new ConcreteIterator(this);}public Object get(int index){if(index<s.length){return s[index];}else{return null;}}public int size(){return s.length;}}