Stream流分组，统计，求和

我不是女神ヾ 2022-06-13 12:14 510阅读 0赞

public class Test {
    
        public static void main(String[] args) {
            List<OrdersDO> list = new ArrayList<>();//查询昨天一天的所有交易
            OrdersDO o1 = new OrdersDO();
            o1.setAppId(1L);
            o1.setTradeAmount(100L);
            o1.setStatus(1);
            list.add(o1);
            OrdersDO o2 = new OrdersDO();
            o2.setAppId(5L);
            o2.setTradeAmount(300L);
            o2.setStatus(2);
            list.add(o2);
            OrdersDO o3 = new OrdersDO();
            o3.setAppId(1L);
            o3.setTradeAmount(100L);
            o3.setStatus(3);
            list.add(o3);
            OrdersDO o4 = new OrdersDO();
            o4.setAppId(5L);
            o4.setTradeAmount(300L);
            o4.setStatus(4);
            list.add(o4);
            OrdersDO o5 = new OrdersDO();
            o5.setAppId(5L);
            o5.setTradeAmount(300L);
            o5.setStatus(4);
            list.add(o5);
            //统计每个应用实际支付总额
            Map<Long, Long> tradeAmountMap = list.stream().filter(o->o.getStatus()==2)
                    .collect(Collectors.groupingBy(OrdersDO::getAppId,
                            Collectors.summingLong(OrdersDO::getTradeAmount)));
            System.out.println(tradeAmountMap);
    
            //统计每个应用取消总额
            Map<Long, Long> cancelAmountMap = list.stream()
                    .collect(Collectors.groupingBy(OrdersDO::getAppId,
                            Collectors.summingLong(OrdersDO::getTradeAmount)));
            System.out.println(cancelAmountMap);
    
            //统计每个应用下交易笔数
            Map<Long, Long> appTradeNum = list.stream().collect(Collectors.groupingBy(OrdersDO::getAppId, Collectors.counting()));
            System.out.println(appTradeNum);
    
            //统计每个应用每种状态下交易笔数
            Map<Long, Map<Integer, Long>> tradeNumMap = list.stream().
                    collect(Collectors.groupingBy(OrdersDO::getAppId,
                            Collectors.groupingBy(OrdersDO::getStatus,
                                    Collectors.counting())));
            System.out.println(tradeNumMap);
    
            //每个应用下交易笔数按数量排序
            Map<Long,Long> finalMap = new LinkedHashMap<>();
            appTradeNum.entrySet().stream().sorted(Map.Entry.<Long, Long>comparingByValue().reversed()).forEachOrdered(e->finalMap.put(e.getKey(),e.getValue()));
            System.out.println(finalMap);
        }
    }