1、集合A判断是否包含集合B里面的元素，并且把包含元素放到一个新集合里面

List<TagBean> tagBean = tagBeans.stream().filter(adminMo.getTagList()::contains).collect(toList());

2、把subListByChildId里面的subId作为key,本身对象ChannelSubMo作为value

List<ChannelSubMo> subListByChildId;
Map<String, ChannelSubMo> subMoMap =  subListByChildId.stream().collect(Collectors.toMap(ChannelSubMo::getSubId, channelSubMo -> channelSubMo));

3、把集合里面对象的某个字段转成List

List<String> ageList = list.stream().map(Person::getAge).collect(Collectors.toList());

4、根据集合对象里面的某个字段分组

List<SvOrderInputVo> excelVos;
Map<Integer,List<SvOrderInputVo>>  map = excelVos.stream().collect(Collectors.groupingBy(SvOrderInputVo::getSvOrderThirdStatus));

5、根据map里面的key获取value值，把value值去重并放到一个新的集合里面

Map<Integer,List<SvOrderInputVo>>  map;
List<String> svOrderIdList = map.get(svOrderThirdStatus).stream().map(SvOrderInputVo::getSvOrderId).distinct().collect(Collectors.toList());

6、key是分配客户的数量（根据thisWeekNum分组），value是分配客户数量的顾问id集合（需要去重）

List<DacMatchAgentWeightMo> totalList;
Map<Integer, Long> weekMap = totalList.stream().filter(mo -> saleArea.equals(mo.getSaleArea())).collect(Collectors.groupingBy(DacMatchAgentWeightMo::getThisWeekNum, Collectors.mapping(DacMatchAgentWeightMo::getAgentId, Collectors.toList())));

7、判断map里面key>0的数据并把value加和

Map<Integer, List<String>> map;
List<String> alreadyMatchList = map.entrySet().stream().filter(entry -> entry.getKey() > 0).flatMap(entry -> entry.getValue().stream()).collect(Collectors.toList());

8、循环map里面的key,把key和value(也就是list.size)相乘，然后把所有的值sum起来

Map<Integer, List<String>> map;
int totalWeekNum = map.entrySet().stream().mapToInt(entry -> entry.getKey() * entry.getValue().size()).sum();

9、低于某个值的数据加和

Map<Integer, Long> weekMap;
long lessAverageNumWeek = weekMap.values().stream().filter(value -> value < 3).mapToLong(value -> value).sum();