java1.8Stream流

取出list的里面userId的那一列

List<String> userList = list.stream().map(userInfo ->userInfo.getDnUserId()) .collect(Collectors.toList())

将list按照DataItem分组

Map<String,List<DeviceDataVo>> map=list.stream().collect(Collectors.groupingBy(DeviceDataVo::getDataItem,
        Collectors.mapping(a->a,Collectors.toList())));

将list按照年龄从小到大排序

List<User> collect2 = list.stream().sorted((s1, s2) -> s1.getAge() - s2.getAge()).collect(Collectors.toList());
collect2.forEach(x->{
    System.out.print(x.getAge());
});

取出年龄的最大值

Optional<User> collect1 = list.stream().collect(Collectors.maxBy((s1, s2) -> s1.getAge() - s2.getAge()));

summingInt、summingLong、summingDouble取出总和

averageInt、averageLong、averageDouble取出平均值

Counting是计数 distinct去重

遍历map集合

   for (Map.Entry<String,List<DeviceDataVo>>

entry:map.entrySet()){
    List<DeviceDataVo> dataList=entry.getValue();

}

将xData的内容去重

xData=xData.stream().distinct().collect(Collectors.toList());

取出符合条件的数据

List<DeviceDataVo> inDatas=dataList.stream().filter(x->x.getKey().equals(in)).collect(Collectors.toList());

判断两个list是否有交集

boolean flag = Collections.disjoint(list1, list2);//无交集是true,有交集是false