Java中List根据对象的属性值进行数据库group by功能的操作

  1 public class test {
  2     public static void main(String[] args) {
  3
  4         List<Bill> list = new test().setObject();
  5
  6         Set<String> set = new HashSet();
  7
  8         for (Bill bills : list) {
  9             set.add(bills.getTradeTime().substring(0, 8));
 10         }
 11
 12         List list1 = new ArrayList();
 13         int paySuccess = 0;
 14         int dfSuccess = 0;
 15         int fee = 0;
 16         int count = 0;
 17         //遍历set集合中的日期
 18         for (String a : set) {
 19             for (Bill bill : list) {
 20                 if (a.equals(bill.getTradeTime().substring(0, 8))) {
 21                     paySuccess += bill.getMoney();
 22                     fee += bill.getFee();
 23                     count++;
 24                     if ("承兑或交易成功".equals(bill.getType()))
 25                         dfSuccess += bill.getMoney();
 26                 }
 27             }
 28             Object[] objects = new Object[10];
 29             objects[0] = new BigDecimal(paySuccess);
 30             objects[1] = new BigDecimal(dfSuccess);
 31             objects[2] = new BigDecimal(fee);
 32             objects[3] = new BigDecimal(paySuccess-fee);
 33             objects[4] = a;
 34             list1.add(objects);
 35             System.out.println("支付成功金额：" + objects[0] + "\t" + "承兑或交易成功: " + objects[1] + "\t" + objects[4] + "\t" + "手续费：" + objects[2] + "\t" + "商户结算" +
 36                     "金额：" + objects[3] + "\t" + "交易笔数：" + count + "\t日期：" + a);
 37             paySuccess = 0;
 38             dfSuccess = 0;
 39             fee = 0;
 40             count = 0;
 41         }
 42         String date = null;
 43         System.out.println(date == null || date.isEmpty());
 44     }
 45
 46     public List<Bill> setObject() {
 47         List<Bill> list = new ArrayList<Bill>();
 48         Bill bill = new Bill();
 49         bill.setTradeTime("201605050203");
 50         bill.setMoney(2);
 51         bill.setPayType("支付成功");
 52         bill.setType("承兑或交易成功");
 53         bill.setFee(1);
 54         list.add(bill);
 55
 56         bill = new Bill();
 57         bill.setTradeTime("201605060203");
 58         bill.setMoney(3);
 59         bill.setType("");
 60         bill.setPayType("支付成功");
 61         bill.setFee(1);
 62         list.add(bill);
 63
 64         bill = new Bill();
 65         bill.setMoney(4);
 66         bill.setTradeTime("201605050203");
 67         bill.setPayType("支付成功");
 68         bill.setType("承兑或交易成功");
 69         bill.setFee(1);
 70         list.add(bill);
 71
 72         bill = new Bill();
 73         bill.setType("");
 74         bill.setPayType("支付成功");
 75         bill.setTradeTime("201605060203");
 76         bill.setMoney(4);
 77         bill.setFee(1);
 78         list.add(bill);
 79         return list;
 80     }
 81 }
 82
 83 class Bill {
 84     int money;
 85     String type;
 86     String tradeTime;
 87     String payType;
 88     int fee;
 89
 90     public String getPayType() {
 91         return payType;
 92     }
 93
 94     public void setPayType(String payType) {
 95         this.payType = payType;
 96     }
 97
 98     public int getMoney() {
 99         return money;
100     }
101
102     public void setMoney(int money) {
103         this.money = money;
104     }
105
106     public String getType() {
107         return type;
108     }
109
110     public void setType(String type) {
111         this.type = type;
112     }
113
114     public String getTradeTime() {
115         return tradeTime;
116     }
117
118     public void setTradeTime(String tradeTime) {
119         this.tradeTime = tradeTime;
120     }
121
122     public int getFee() {
123         return fee;
124     }
125
126     public void setFee(int fee) {
127         this.fee = fee;
128     }
129
130     @Override
131     public String toString() {
132         return "Bill{" +
133                 "money=" + money +
134                 ", type=‘" + type + ‘\‘‘ +
135                 ", tradeTime=‘" + tradeTime + ‘\‘‘ +
136                 ", payType=‘" + payType + ‘\‘‘ +
137                 ‘}‘;
138     }
139 }

我的思路是先用set集合对对象的某个属性中不重复的值进行筛选，然后进行计算

如果有更好的方法请在下面留言！