code: public static long monday(long time) {
          ZoneId zid = ZoneId.systemDefault();
          Instant instant = Instant.ofEpochMilli(time);
          LocalDate ld = instant.atZone(zid).toLocalDate();
          ld = ld.minusDays(ld.getDayOfWeek().getValue() - 1);
          return ld.atStartOfDay(zid).toInstant().toEpochMilli();
      }
docs: 获取时间点所在星期的周一
  
  @param time 指定时间
  
  @return 毫秒数