双层for循环的3种方案

最新推荐文章于 2024-05-12 23:27:33 发布

原创最新推荐文章于 2024-05-12 23:27:33 发布 · 3.7k 阅读

1 ·

CC 4.0 BY-SA版权

文章标签：

#java #java集合

java 同时被 2 个专栏收录

2 篇文章

订阅专栏

java集合

1 篇文章

订阅专栏

怎么写出最优的循环代码

第一种

    for (TradeMachineRef tradeMachineRef : tradeOrderMachineList) {
        tradeMachineRef.setId(null);
    }

    int updateMachineSize = 0;
    for (TradeMachineRef tmRef : tradeMachineRefs) {
        for (TradeMachineRef tradeMachineRef : tradeOrderMachineList) {
            if (null == tradeMachineRef.getId() && tradeMachineRef.getMachineTypeCode().equals(tmRef.getMachineTypeCode())) {
                tradeMachineRef.setId(tmRef.getId());
                tradeMachineRef.setOrderNo(orderNo);
                updateMachineSize ++ ;
                break;
            }
        }
    }

    if (updateMachineSize != tradeOrderMachineList.size()) {
        throw new TradeBusinessException(TradeExceptionEnum.CHECK_FAILURE);
    }

第二种

	Map<String,List<TradeMachineRef>> machineMap = new HashMap<>();
    // 遍历数据库的设备集合
    for (TradeMachineRef tradeMachineRef : tradeMachineRefs) {
        List<TradeMachineRef> tmrList = machineMap.get(tradeMachineRef.getMachineTypeCode());
        if (CollectionUtils.isEmpty(tmrList)){
            tmrList = new ArrayList<>();
        }
        tmrList.add(tradeMachineRef);
        machineMap.put(tradeMachineRef.getMachineTypeCode(), tmrList);
    }

    // 遍历参数: 设备集合
    for (TradeMachineRef tradeMachineRef : tradeOrderMachineList) {
        List<TradeMachineRef> tmrList = machineMap.get(tradeMachineRef.getMachineTypeCode());
        if (CollectionUtils.isNotEmpty(tmrList)) {
            TradeMachineRef tmr = tmrList.get(0);
            tradeMachineRef.setId(tmr.getId());
            tradeMachineRef.setOrderNo(orderNo);

            tmrList.remove(tmr);
            machineMap.put(tradeMachineRef.getMachineTypeCode(), tmrList);
        } else {
            throw new TradeBusinessException(TradeExceptionEnum.CHECK_FAILURE, "订单设备类型编码不一致");
        }
    }

第三种

machineMap = tradeMachineRefs.stream()
            .filter((TradeMachineRef dto) -> dto.getId() != null).collect(Collectors.groupingBy(TradeMachineRef::getMachineTypeCode));

// 遍历参数: 设备集合
    for (TradeMachineRef tradeMachineRef : tradeOrderMachineList) {
        List<TradeMachineRef> tmrList = machineMap.get(tradeMachineRef.getMachineTypeCode());
        if (CollectionUtils.isNotEmpty(tmrList)) {
            TradeMachineRef tmr = tmrList.get(0);
            tradeMachineRef.setId(tmr.getId());
            tradeMachineRef.setOrderNo(orderNo);

            tmrList.remove(tmr);
            machineMap.put(tradeMachineRef.getMachineTypeCode(), tmrList);
        } else {
            throw new TradeBusinessException(TradeExceptionEnum.CHECK_FAILURE, "订单设备类型编码不一致");
        }
    }