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)));