java 中怎麼根據當前時間得到上週一和上週五的日期

/**
     * 獲取上週五時間
     */
    public Date lastFirday() {

　　//作用防止週日得到本週日期
        Calendar calendar = Calendar.getInstance();
        while (calendar.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY) {
            calendar.add(Calendar.DAY_OF_WEEK, -1);
        }
        int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK) - 1;
        int offset = 7 - dayOfWeek;
        calendar.add(Calendar.DATE, offset - 9);

        return DateTimeUtil.getFirstDayOfWeek(calendar.getTime(), 6);//這是從上週日開始數的到本週五為6

    }

/**
     * 獲取上週一時間
     */
    public Date lastMonday() {
        Calendar calendar = Calendar.getInstance();
        while (calendar.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY) {
            calendar.add(Calendar.DAY_OF_WEEK, -1);
        }
        int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK) - 1;
        int offset = 1 - dayOfWeek;
        calendar.add(Calendar.DATE, offset - 7);
        return DateTimeUtil.getFirstDayOfWeek(calendar.getTime(), 2);
    }

/**
  * 得到某一天的該星期的第一日 00:00:00
  * 
  * @param date
  * @param firstDayOfWeek
  *            一個星期的第一天為星期幾
  * 
  * @return
  */
 public static Date getFirstDayOfWeek(Date date, int firstDayOfWeek) {
  Calendar cal = Calendar.getInstance();
  if (date != null)
   cal.setTime(date);
  cal.setFirstDayOfWeek(firstDayOfWeek);//設定一星期的第一天是哪一天
  cal.set(Calendar.DAY_OF_WEEK, firstDayOfWeek);//指示一個星期中的某天
  cal.set(Calendar.HOUR_OF_DAY, 0);//指示一天中的小時。HOUR_OF_DAY