获得指定日期的前几天日期

/**
   * 获得指定日期的前几天日期
   *
   * @param specifiedDay 指定日期
   * @param pattern      需要返回的日期格式，如yyyy-MM-dd
   * @param before       前几天
   * @return String
   */
public static String getSpecifiedDayBefore(String pattern, String specifiedDay, int before) {
   Calendar c = Calendar.getInstance();
   Date date;
   String dayBefore = "";
   try {
       date = new SimpleDateFormat(pattern).parse(specifiedDay);
       c.setTime(date);
       int day = c.get(Calendar.DATE);
       c.set(Calendar.DATE, day - before);
       dayBefore = new SimpleDateFormat(pattern).format(c.getTime());
   } catch (Exception e) {
      //todo
   } finally {
       return dayBefore;
   }
}