public static Date getDayOfWeek(int dayOfWeek,int weekOffset){
        if(dayOfWeek>Calendar.SATURDAY || dayOfWeek<Calendar.SUNDAY){
            return null;
        }
        Calendar date=Calendar.getInstance(Locale.CHINA);
        //將每周第一天設為星期一，默認是星期天
        date.setFirstDayOfWeek(Calendar.MONDAY);
        
 
//周數減一，即上周
        date.add(Calendar.WEEK_OF_MONTH,weekOffset);
        //日子設為周幾
        date.set(Calendar.DAY_OF_WEEK, dayOfWeek);
        //時分秒全部置0
        date.set(Calendar.HOUR_OF_DAY, 0);
        date.set(Calendar.MINUTE, 0);
        date.set(Calendar.SECOND, 0);
        date.set(Calendar.MILLISECOND, 
 
0);
        return date.getTime();
    }

java獲取上周任意一天的日期