ArrayList相关问题



/**
 *用户类
 */


public class User {
    private int id;
    private String name;
    public User(){
        
    }
    public User(int id, String name) {
        super();
        this.id = id;
        this.name = name;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    
}







/**
 *订单类
 */
public class OrderForm {

    private int id;
    private String Goods;//以json格式存储订单中所包含的商品信息
                       //[{"goods_id":1,"good_name":"白糖","good_type":"食物"}]
    private String addTime;
    private int userId;
    
    public OrderForm(){
        
    }
    
    public OrderForm(int id, String goods, String addTime, int userId) {
        super();
        this.id = id;
        Goods = goods;
        this.addTime = addTime;
        this.userId = userId;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getGoods() {
        return Goods;
    }

    public void setGoods(String goods) {
        Goods = goods;
    }

    public String getAddTime() {
        return addTime;
    }

    public void setAddTime(String addTime) {
        this.addTime = addTime;
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }
       
}







/**
  *订单商品类（订单中包含的商品）
  */
public class OrderFormGoods {
    private int id;
    private String good_name;
    private String type;
        
    public OrderFormGoods(){
        
    }
    
    public OrderFormGoods(int id, String good_name, String type) {
        super();
        this.id = id;
        this.good_name = good_name;
        this.type = type;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getGood_name() {
        return good_name;
    }
    public void setGood_name(String good_name) {
        this.good_name = good_name;
    }
    public String getType() {
        return type;
    }
    public void setType(String type) {
        this.type = type;
    }
        
}







/**
 *评价类
 */
public class Evaluate {
    private int id;
    private String eva_info;// 评价内容
    private int orderFormId;// 订单id
    private int goodId;// 商品id
    private int userId;

    public Evaluate() {

    }

    public Evaluate(int id, String eva_info, int orderFormId, int goodId ,int userId) {
        super();
        this.id = id;
        this.eva_info = eva_info;
        this.orderFormId = orderFormId;
        this.goodId = goodId;
        this.userId = userId;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getEva_info() {
        return eva_info;
    }

    public void setEva_info(String eva_info) {
        this.eva_info = eva_info;
    }

    public int getOrderFormId() {
        return orderFormId;
    }

    public void setOrderFormId(int orderFormId) {
        this.orderFormId = orderFormId;
    }

    public int getGoodId() {
        return goodId;
    }

    public void setGoodId(int goodId) {
        this.goodId = goodId;
    }
    public int getUserId() {
        return userId;
    }
    public void setUserId(int userId) {
        this.userId = userId;
    }
}




   




 1 public class Demo {
 2 
 3     /**
 4      * @return 订单中有评价的商品
 5      */
 6     public static List<OrderFormGoods> fun(){
 7         
 8      System.out.println("=============开始添加临时数据!!!==============");
 9      
10      List<User>user_list = new ArrayList<>();
11      user_list.add(new User(1,"盖伦"));
12      user_list.add(new User(2,"鲁迅"));
13      
14      List<OrderForm>orderForm_list = new ArrayList<>();
15      orderForm_list.add(new OrderForm(1,"["
16              + "{'id':34,'good_name':'饮血剑','type':'武器'},"
17              + "{'id':56,'good_name':'血瓶','type':'消耗品'},"
18              + "{'id':1,'good_name':'多兰之盾','type':'防御'}"
19              + " ]","2015-9-18",1));
20      orderForm_list.add(new OrderForm(2,"["
21              + "{'id':55,'good_name':'+30 冰河裂谷剑','type':'武器'},"
22              + "{'id':12,'good_name':'魔剑·阿波菲斯','type':'武器'}"
23              + "]","2015-1-1",1));
24      orderForm_list.add(new OrderForm(3,"["
25              + "{'id':32,'good_name':'里鬼剑术','type':'技能'}"
26              + "]","2011-3-18",1));
27      orderForm_list.add(new OrderForm(4,"["
28              + "{'id':80,'good_name':'流星·刺','type':'技能'},"
29              + "{'id':79,'good_name':'流星·跃','type':'技能'},"
30              + "{'id':78,'good_name':'流星·升','type':'技能'},"
31              + "{'id':99,'good_name':'流星·落','type':'技能'},"
32              + "{'id':565,'good_name':'+13 深海熔岩肩甲','type':'护甲'}"
33              + "]","1998-9-18",2));
34      
35       List<Evaluate>eva_list = new ArrayList<>();
36       eva_list.add(new Evaluate(1,"不够结实，断掉了",1,34,1));
37       eva_list.add(new Evaluate(45,"不错",1,56,1));
38       eva_list.add(new Evaluate(33,"不好",1,1,1));
39       eva_list.add(new Evaluate(31,"霸气",2,55,1));
40       eva_list.add(new Evaluate(65,"装逼神器",2,12,1));
41       eva_list.add(new Evaluate(56,"技能很帅，秒天秒地",3,32,1));
42       eva_list.add(new Evaluate(44,"霸气",4,80,2));
43       eva_list.add(new Evaluate(70,"很不错的技能",4,79,2));
44       eva_list.add(new Evaluate(71,"流星技能很帅",4,78,2));
45       eva_list.add(new Evaluate(72,"还不错",4,99,2));
46       //eva_list.add(new Evaluate(73,"防御力很好",4,565,2));
47         
48       System.out.println("==============数据添加完毕!!!==============");    
49     
50        List<OrderFormGoods> ofg_list = new ArrayList<OrderFormGoods>();
51       int user_id=1;
52 
53       for (OrderForm of : orderForm_list) {
54             if(of.getUserId()==user_id){ 
55                 List<OrderFormGoods>orderFormGoods_list = JSON.parseArray(of.getGoods(),OrderFormGoods.class);//把json格式的字符串转换成集合
56                 //OrderFormGoods orderFormGood = new OrderFormGoods();    
57                 for (OrderFormGoods ofg : orderFormGoods_list) {//遍历用户id为1的订单中所包含的商品
58                     OrderFormGoods orderFormGood = new OrderFormGoods();//创建实例对象    
59                       for (Evaluate evaluate : eva_list) {  //遍历评价
60                         if(evaluate.getGoodId()==ofg.getId()&&evaluate.getUserId()==user_id){//判断用户订单中的商品是否有评论
61                             orderFormGood.setId(ofg.getId());
62                             orderFormGood.setGood_name(ofg.getGood_name());
63                             orderFormGood.setType(ofg.getType());
64                             ofg_list.add(OrderFormGood);  //如果有评价，把商品添加到集合
65                         }
66                     }
67                 }
68             }
69     }
70       
71         return ofg_list; 
72         
73     }
74     
75     public static void main(String[] args) {
76         List<OrderFormGoods>list = fun();
77         for (OrderFormGoods orderFormGoods : list) {
78             System.out.println(orderFormGoods.getGood_name());
79         }
80     }
81 }





     这些示例代码是把项目订单评价这一部分简单抽象出来的，可以输出某一用户评价过的商品，代码的主人留下了一个bug，当某一订单存在多个商品，这三个商品全部会显示成最后一个。


     这个bug被指给我，发现造成这个问题的原因是ArrayList（50行）的值被覆盖，代码出错在56行。创建实例的操作写在for循环前面，也就是说每次遍历(59行)时，都会覆盖前一次添加到集合里的值，因为实例对象只有一个。




        

	      

	    

	  

	  

	    
      
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          原文地址：https://www.cnblogs.com/sflik/p/4820485.html