时间的问题

Question

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  Date birthday = sdf.parse("2004-09-09");
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(birthday);
calendar.add(Calendar.DAY_OF_YEAR,Integer.parseInt("2"*30);
            System.out.println(calendar.getTime());
我怎么从calendar得到“2004-11-09”这样的字符串呀 谢谢