安卓获取几天之前的日期

  /**
    * 获得几天之前的日期
    *
    * @param day
    * @return
    */
   public static String getXday(int day) {
       SimpleDateFormat sdf = new SimpleDateFormat(DATE_PATTERN_1);
       Calendar c = Calendar.getInstance();
       c.add(Calendar.DATE, -day);
       Date monday = c.getTime();
       String preMonday = sdf.format(monday);
       return preMonday;
   }