java 迭代器模式实例详解

package iterator;

/**
 * 
* @ClassName: Item 
* @Description: 订单项
* @author minjun
*
 */
public class Item {

 /**商品名称*/
 private String name;
 
 /**价格*/
 private double price;
 
 /**描述*/
 private String desc;
 
 /**数量*/
 private int count;

 public Item(String name, double price, String desc, int count) {
 this.name = name;
 this.price = price;
 this.desc = desc;
 this.count = count;
 }

 public String getName() {
 return name;
 }

 public void setName(String name) {
 this.name = name;
 }

 public double getPrice() {
 return price;
 }

 public void setPrice(double price) {
 this.price = price;
 }

 public String getDesc() {
 return desc;
 }

 public void setDesc(String desc) {
 this.desc = desc;
 }

 public int getCount() {
 return count;
 }

 public void setCount(int count) {
 this.count = count;
 }

 @Override
 public String toString() {
 return "Item [name=" + name + ", price=" + price + ", desc=" + desc
  + ", count=" + count + "]";
 }
}

package iterator;

import org.junit.Test;

public class TestCase {

 @Test
 public void test() {
 Order o = 
  new TBOrder();//淘宝的订单
//  new JDOrder();//京东的订单
 printOrder(o);//打印订单

 }

 /**打印订单 */
 private void printOrder(Order o) {
 for (Item item : o) {
  System.out.println(item);
 }
 }
}

/*
 * %W% %E%
 *
 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.lang;

import java.util.Iterator;

/** Implementing this interface allows an object to be the target of
 * the "foreach" statement.
 * @since 1.5
 */
public interface Iterable<T> {

  /**
   * Returns an iterator over a set of elements of type T.
   * 
   * @return an Iterator.
   */
  Iterator<T> iterator();
}

package iterator;

public interface Order extends Iterable<Item>{

}

package iterator;

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

/**
 * 
 * @ClassName: JDOrder
 * @Description: 京东订单
 * @author minjun
 * 
 */
public class JDOrder implements Order {

 /** 京东用集合装订单项 */
 private List<Item> list = new ArrayList<Item>();

 public JDOrder() {
 add("iphone6", 5000.00, "一部手机", 2);
 add("mbp", 16000.00, "一台电脑", 1);
 add("西门子洗衣机", 3000.00, "一台洗衣机", 3);
 }

 /** 添加订单条目 */
 public void add(String name, double price, String desc, int count) {
 list.add(new Item(name, price, desc, count));
 }

 @Override
 public Iterator<Item> iterator() {
 return new MyIterator();
 }

 private class MyIterator implements Iterator<Item> {

 private Iterator<Item> it = list.iterator();

 @Override
 public boolean hasNext() {
  return it.hasNext();
 }

 @Override
 public Item next() {
  return it.next();
 }

 @Override
 public void remove() {
  throw new UnsupportedOperationException("目前不支持删除操作");
 }

 }
}

package iterator;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * 
* @ClassName: TBOrder 
* @Description: 淘宝订单 
* @author minjun
*
 */
public class TBOrder implements Order{
 
 private int size=3;

 private Item[] orders=new Item[size];
 
 private int index=0;
 
 public TBOrder(){
 add("天猫1", 1111, "天猫活动1", 1);
 add("天猫2", 1111, "天猫活动1", 1);
 add("天猫3", 1111, "天猫活动1", 1);
 add("天猫4", 1111, "天猫活动1", 1);
 add("天猫5", 1111, "天猫活动1", 1);
 add("天猫6", 1111, "天猫活动1", 1);
 add("天猫7", 1111, "天猫活动1", 1);
 add("天猫8", 1111, "天猫活动1", 1);
 }
 
 /**添加订单条目*/
 public void add(String name, double price, String desc, int count) {
 
 //如果超过数组大小，就扩容
 if(index>=size-1){
  resize();
 }
  
 orders[index++]=new Item(name, price, desc, count);
 }
 
 /**扩容*/
 private void resize() {
 size=size<<1;//移位运算符--相当于size=size*2
 Item[] newItems=new Item[size];
 //将原始数组内容拷贝到新数组中去
 for(int i=0;i<orders.length;i++){
  newItems[i]=orders[i];
 }
 orders=newItems;
 }

 @Override
 public Iterator<Item> iterator() {
 return new MyIterator();
 }
 
 private class MyIterator implements Iterator<Item>{
 
 private int curr=0;

 @Override
 public boolean hasNext() {
  return orders[curr]!=null;
 }

 @Override
 public Item next() {
  if(hasNext()){
  return orders[curr++];
  }else{
  throw new NoSuchElementException("没有这个元素");
  }
 }

 @Override
 public void remove() {
  throw new UnsupportedOperationException("目前不支持删除操作");
 }
 
 }

}