code: public static Date getFirstDayOfLastWeek(Date date) {
          Calendar c = Calendar.getInstance();
          c.setTimeInMillis(date.getTime() - 604800000L);
          c.set(Calendar.HOUR_OF_DAY, 0);
          c.set(Calendar.MINUTE, 0);
          c.set(Calendar.SECOND, 0);
          Date lastWeekDate = c.getTime();
  
          c = new GregorianCalendar();
          c.setFirstDayOfWeek(Calendar.MONDAY);
          c.setTime(new Date(lastWeekDate.getTime()));
          c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek()); // Monday
          return c.getTime();
      }
docs: 取得指定日期所在周的前一周的第一天
  
  @param date
  
  @return
  
  @author yang_yun