yyyy-mm-dd mm是分钟 困扰了我好久 操

 public static void main(String[] args) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd");
        SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd");
        String lotNoNowStr = sdf.format(new Date());
        String packNowStr = sdf2.format(new Date());
        System.out.println("批号：" + lotNoNowStr);
        System.out.println("包号：" + packNowStr);
    }

 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd");

mm是分钟,mm是分钟  困扰我好久