十七、迭代器模式 Iterator

一、定义

二、结构图

三、代码示例

import java.util.ArrayList;
import java.util.List;

/**
* @use 测试迭代器模式
* @author lattice
*
*/
public class IteratorItest {

public static void main(String[] args) {
ConcreteAggregate a=new ConcreteAggregate();
a.pushItem("大鸟");
a.pushItem("小菜");
a.pushItem("小明");
a.pushItem("老外");
a.pushItem("格子");

Iterator i=new ConcreteIteractor(a);
Object item=i.First();
while(!i.isDone()){
System.out.println(i.CurrentItem()+"请买票。");
i.Next();
}
}

}
/**
* 迭代器抽象类
* @author lattice
*
*/
abstract class Iterator{
public abstract Object First();
public abstract Object Next();
public abstract boolean isDone();
public abstract Object CurrentItem();
}
/**
* 聚合抽象类
* @author lattice
*
*/
abstract class Aggregate{
public abstract Iterator createIterator();
}

/**
* 具体迭代器，继承Iterator
* @author lattice
*
*/
class ConcreteIteractor extends Iterator{
private ConcreteAggregate  aggregate;
int currentItem=0;

public ConcreteIteractor(ConcreteAggregate  aggregate){
this.aggregate = aggregate;
}
@Override
public Object First() {
return aggregate.getItem(0);
}
@Override
public Object Next() {
Object ret=null;
currentItem++;
if(currentItem<aggregate.getCount()){
ret=aggregate.getItem(currentItem);
}
return ret;
}

@Override
public boolean isDone() {
return currentItem>=aggregate.getCount()?true:false;
}

@Override
public Object CurrentItem() {
return aggregate.getItem(currentItem);
}

}
/**
* 具体聚集类，继承Aggregate
* @author lattice
*
*/
class ConcreteAggregate extends Aggregate{
private List<Object> item=new ArrayList<Object>();
@Override
public Iterator createIterator() {

return new ConcreteIteractor(this);
}
public int getCount(){
return item.size();
}
public void pushItem(Object obj){
this.item.add(obj);
}

public void setItem(int index,Object obj){
this.item.remove(index);
this.item.add(index, obj);
}
public Object getItem(int index){
return item.get(index);
}

}