Java8 Stream分组

//根据排课id分组
Map<Integer, List<Schedule4Homework>> idSchedule4HomeworksMap = schedule4Homeworks.stream().collect(Collectors.groupingBy(Schedule4Homework::getScheduleId));
//List转Map
Map<KeyType, ValueType> resultMap = list.stream().collect(Collectors.toMap(DTO::getKey, DTO::getValue));

 

//根据时间排序（reversed方法表示倒序）
memberCards.sort(Comparator.comparing(MemberCard::getProfileCreated).reversed());

 

//分组并获取前几个
 List<StoreSituation> collect = storeSituationsReturn.stream().sorted(Comparator.comparing(StoreSituation::getGmtCreate).reversed()).limit(storeSituationQuery.getRows()).collect(Collectors.toList());

 

//获取对象集合中某个字段的集合
List<Integer> ids = list.stream().map(p -> p.getId()).collect(Collectors.toList());

 

//去重
ids = ids.stream().distinct().collect(Collectors.toList());