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一、概述

       迭代器模式（Iterator），提供一个方法顺序访问一个聚合对象中的各个元素，而又不暴露该对象的内部表示 。

二、UML图示

三、代码实现

1、迭代器抽象类

public abstract class Iterator {    public abstract Object first();    public abstract Object next();    public abstract boolean isDone();    public abstract Object currentItem();}

2、聚集抽象类

public abstract class Aggregate {    public abstract Iterator createIterator();}

3、具体迭代器

public class ConcreteIterator extends Iterator {    private ConcreteAggregate concreteAggregate;    private int current = 0;    public ConcreteIterator(ConcreteAggregate concreteAggregate) {        this.concreteAggregate = concreteAggregate;    }    @Override    public Object first() {        return concreteAggregate.getObject(0);    }    @Override    public Object next() {        Object o = null;        current++;        if(current < concreteAggregate.count()){            o = concreteAggregate.getObject(current);        }        return o;    }    @Override    public boolean isDone() {        return current >= concreteAggregate.count()?true:false;    }    @Override    public Object currentItem() {        return concreteAggregate.getObject(current);    }}

4、具体聚集类

public class ConcreteAggregate extends Aggregate {    private List

5、测试类

public class Test {    public static void main(String[] args) {        ConcreteAggregate concreteAggregate = new ConcreteAggregate();        concreteAggregate.createIterator();        concreteAggregate.setObject(0,"张三");        concreteAggregate.setObject(1,"李四");        concreteAggregate.setObject(2,"王五");        Iterator iterator = new ConcreteIterator(concreteAggregate);        Object o = iterator.first();        while (!iterator.isDone()){            System.out.println(iterator.currentItem()+"：请买车票！");            iterator.next();        }    }}输出：张三：请买车票！李四：请买车票！王五：请买车票！

注：参考文献《大话设计模式》程杰著。