LocalDateTime获取月第一天最后一天和年的第一天和最后一天

LocalDate now        
        //月第一天
        LocalDate first = now.with(TemporalAdjusters.firstDayOfMonth());
        //月最后一天
        LocalDate last = now.with(TemporalAdjusters.lastDayOfMonth());

//年第一天
localDate.with(TemporalAdjusters.firstDayOfYear());
//年最后一天
localDate.with(TemporalAdjusters.lastDayOfYear();