多线程处理集合

@Override
   public TotalPaymentPpdSettlementDTO querySettlementTotalFee(Integer channelTye, Long startDate, Long endDate ) {

      TotalPaymentPpdSettlementDTO paymentDto = new TotalPaymentPpdSettlementDTO(BigDecimal.ZERO,BigDecimal.ZERO,BigDecimal.ZERO,BigDecimal.ZERO,
            BigDecimal.ZERO,BigDecimal.ZERO,BigDecimal.ZERO,BigDecimal.ZERO);
      List<PaymentPpdSettlement> paymentPpdSettlements = paymentPpdSettlementMapperExt.queryByChannelTypeAndPayDate(channelTye, startDate, endDate);
      if(CollectionUtils.isEmpty(paymentPpdSettlements)){
         return null;
      }

      //每个线程处理集合的大小
      Integer perSize = 5;
      //获取数据的总数
      int length = paymentPpdSettlements.size();
      //获取线程池  单例实现的
      SettlementTreadPool executorService = SettlementTreadPool.getInstance();
      //要多少个线程去处理
      int threadNum = length % perSize == 0 ? length / perSize : (length / perSize + 1);
      //使用countDownLatch 做倒计数threadFactory
      CountDownLatch countDownLatch = new CountDownLatch(threadNum);

      for (int i = 0; i < threadNum; i++) {
         List<PaymentPpdSettlement> paymentPpdSettlementsThread =
               (i+1) * perSize < paymentPpdSettlements.size() ?
                     paymentPpdSettlements.subList(i * perSize, (i + 1) * perSize) :
                     paymentPpdSettlements.subList(i * perSize,paymentPpdSettlements.size());

         executorService.execute(()->{

            //提交给线程池去异步处理
            for (PaymentPpdSettlement paymentSettlement: paymentPpdSettlementsThread) {
               setSettlementDTOFee(paymentDto,paymentSettlement);
            }
            //countDownLatch 每执行一个线程 就进行一个countDownLatch -1
               countDownLatch.countDown();
         });

      }
      //阻塞 主线程 直到倒计时为 0 时 才会释放
      try {
         countDownLatch.await();
      } catch (InterruptedException e) {
         e.printStackTrace();
      }


//    for (PaymentPpdSettlement paymentPpdSettlement : paymentPpdSettlements) {
//       setSettlementDTOFee(paymentDto,paymentPpdSettlement);
//    }
      return paymentDto;
   }