优化下段代码 Map<String, List<StkTransferOrderDtl>> collect = stkTransferOrderDtls.stream().collect(Collectors.groupingBy(StkTransferOrderDtl::getProjId)); collect.forEach((projId,stkTransferOrderDtlList)->{ List<String> bigClassCodes = stkTransferOrderDtlList.stream().map(p->{ return p.getMatCode().substring(0,2); }).distinct().collect(Collectors.toList()); for (String bigClassCode : bigClassCodes) {}

可以尝试将两个Stream合并成一个来提高效率，代码如下：

Map<String, List<String>> collect = stkTransferOrderDtls.stream()
        .collect(Collectors.groupingBy(StkTransferOrderDtl::getProjId,
                Collectors.mapping(p -> p.getMatCode().substring(0, 2),
                        Collectors.collectingAndThen(Collectors.toSet(), ArrayList::new))));

collect.forEach((projId, bigClassCodes) -> {
    for (String bigClassCode : bigClassCodes) {
        // do something
    }
});

这里使用了`Collectors.mapping()`和`Collectors.collectingAndThen()`方法来进行分组和去重操作，同时将结果转换为ArrayList，以便后续的遍历操作。

相关问题

优化这段代码 Map<String, List<MonitorRuleMetricDO>> collect = conditionMetrics.stream().collect(Collectors.groupingBy(MonitorRuleMetricDO::getMetricName));

Map<String, List<MonitorRuleMetricDO>> collect = conditionMetrics.stream()
.collect(Collectors.groupingBy(
MonitorRuleMetricDO::getMetricName));

将Map<String, List<DictResponseVO>> collect = dictTree.stream().collect(Collectors.groupingBy(DictResponseVO::getCode));的结果修改为Map<String, Map<String, List<DictResponseVO>>>

可以使用Collectors.groupingBy嵌套来完成这个转换，代码如下：

Map<String, Map<String, List<DictResponseVO>>> collect = dictTree.stream()
        .collect(Collectors.groupingBy(DictResponseVO::getCode, Collectors.groupingBy(DictResponseVO::getType)));

这样就可以按照code和type两个属性进行分组，得到一个嵌套的Map。其中外层Map的key是code，value是内层Map；内层Map的key是type，value是对应的DictResponseVO列表。