java求n小时候的时间

Calendar c = Calendar.getInstance();    Date date = new Date();    c.setTime(date);//    c.add(Calendar.DAY_OF_MONTH, -2);    c.add(Calendar.HOUR_OF_DAY, -48);    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");    String searchDate = sdf.format(c.getTime());System.out.println(searchDate);