java groupingBy 分组并统计数量

分组并统计每组的数量

Map<Long, Long> collect = memberList.stream().collect(Collectors.groupingBy(
                DsiBasPartyMember::getStatus, Collectors.counting()));

分组并统计每组某个属性的总和

Map<Long, Long> maps = logs.stream()
                .collect(Collectors.groupingBy(DsiMemberScoreLog::getSource, 
                        summingLong(DsiMemberScoreLog::getScoreNum)));