java stream Collectors.groupingBy()多个字段 [英] java stream Collectors.groupingBy() multiple fields

问题描述

Stream<Map.Entry<String, Long>> duplicates = notificationServiceOrderItemDto.getService()
    .getServiceCharacteristics()
    .stream()
    .collect(
        Collectors.groupingBy(
            ServiceCharacteristicDto::getName, Collectors.counting()
        )
     )
     .entrySet()
     .stream()
     .filter(e -> e.getValue() > 1);

Optional<String> dupName = duplicates.map(Map.Entry::getKey).findFirst();

工作完美.但是我很想找到不仅包含名称，而且包含名称+值+键的重复项

works perfect. But I wold like to find duplicates not just with name but also name + value + key

这意味着如果名称+值+键相同，则表示重复.

That means if name + value + key is the same this is duplicate.

我正在寻找Collectors.groupingBy()

I am looking Collectors.groupingBy()

http://www.technicalkeeda.com/java -8-tutorials/java-8-stream-grouping

但我找不到正确的解决方案

but I can not find correct solution

推荐答案

代替

.collect(Collectors.groupingBy(ServiceCharacteristicDto::getName, Collectors.counting()))

你可以写

.collect(Collectors.groupingBy(s->s.getName()+'-'+s.getValue()+'-'+s.getKey(), Collectors.counting()))

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