1.根据集合中对象的某个属性求2个集合交集和差集
List newUsersList = new ArrayList<>();
List oldUsersList = new ArrayList<>();
//根据userId求集合的交集（返回结果为newUsersList集合中的元素）
List intersection = newUsersList.stream().filter(m -> oldUsersList.stream().map(d -> d.getUserId()).collect(Collectors.toList()).contains(m.getUserId())).collect(Collectors.toList());
//根据userId求2个集合的差集
List newReduce = newUsersList.stream().filter(m -> !intersection.stream().map(d -> d.getUserId()).collect(Collectors.toList()).contains(m.getUserId())).collect(Collectors.toList());
2.日期集合排序
public static List getSortdate(List dateList) {
dateList.sort((a1, a2) -> {
return a1.compareTo(a2);
});
return dateList;
}
3.mysql运维命令
select * from information_schema.processlist where db="test_db"; --查询进程
kill 1248580; --杀掉进程
show OPEN TABLES where In_use > 0; -- 查询正在使用中的表
