java獲取上周任意一天的日期

/**
     * 獲取上周周幾的日期,默認一周從周一開始
     * @param dayOfWeek
     * @param weekOffset
     * @return
     */
    public static Date getDayOfWeek(int dayOfWeek,int weekOffset){
        return getDayOfWeek(Calendar.MONDAY,dayOfWeek,weekOffset);
    }

    /**
     * 獲取上(下)周周幾的日期
     * @param firstDayOfWeek {@link Calendar}
     * 值范圍 <code>SUNDAY</code>,
     * <code>MONDAY</code>, <code>TUESDAY</code>, <code>WEDNESDAY</code>,
     * <code>THURSDAY</code>, <code>FRIDAY</code>, and <code>SATURDAY</code>
     * @param dayOfWeek {@link Calendar}
     * @param weekOffset  周偏移，上周為-1，本周為0，下周為1，以此類推
     * @return
     */
    public static Date getDayOfWeek(int firstDayOfWeek,int dayOfWeek,int weekOffset){
        if(dayOfWeek>Calendar.SATURDAY || dayOfWeek<Calendar.SUNDAY){
            return null;
        }
        if(firstDayOfWeek>Calendar.SATURDAY || firstDayOfWeek < Calendar.SUNDAY){
            return null;
        }
        Calendar date=Calendar.getInstance(Locale.CHINA);
        date.setFirstDayOfWeek(firstDayOfWeek);
        //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();
    }