LocalDateTime相关

https://www.cnblogs.com/huanshilang/p/12013386.html
https://www.cnblogs.com/xr210/p/13626494.html

本月第一天0时0分
LocalDateTime.of(LocalDate.from(LocalDateTime.now().with(TemporalAdjusters.firstDayOfMonth())), LocalTime.MIN);
本月最后一天23：59：59
LocalDateTime.of(LocalDate.from(LocalDateTime.now().with(TemporalAdjusters.lastDayOfMonth())), LocalTime.MAX);

其中TemporalAdjusters也是java8才有的接口