Java 分组函数 groupBy

4.1: 分组去重，多字段构成key, 返回 Map<String, List<Talk>> 类型数据
2 　　　　Map<String, List<Talk>> talkMap = talkList.stream().collect(Collectors.groupingBy(talk -> talk.getGradeId() + "" + talk.getSubjectId() + ""
3         + talk.getUnitId()));

标签：Map,Java,Collectors,groupingBy,分组,groupBy,talk,函数
来源： https://www.cnblogs.com/libinshenbg/p/15637379.html