class DateUtil {

    public static Date getMondayBefore4Week() {
        Calendar cd = Calendar.getInstance();
        // 获得今天是一周的第几天，星期日是第一天，星期二是第二天......
        int dayOfWeek = cd.get(Calendar.DAY_OF_WEEK) - 1; // 因为按中国礼拜一作为第一天所以这里减1
        Date date;
        if (dayOfWeek == 1) {
            date = addDays(cd.getTime(), -28);
        } else {
            date = addDays(cd.getTime(), -27 - dayOfWeek);
        }
        return getStartOfDate(date);
    }

}