根据生日计算年龄

 /**
     * 根据生日计算年龄
     * 如：2011-02-13 换算之后是 8岁1个月24天
     * @param birth
     * @return String
     */
    public static String getAge(Date birthDay){
        Calendar birthday = Calendar.getInstance();
        birthday.setTime(birthDay);
        Calendar now = Calendar.getInstance();
        int day = now.get(Calendar.DAY_OF_MONTH) - birthday.get(Calendar.DAY_OF_MONTH);
        int month = now.get(Calendar.MONTH) - birthday.get(Calendar.MONTH);
        int year = now.get(Calendar.YEAR) - birthday.get(Calendar.YEAR);
        //按照减法原理，先day相减，不够向month借；然后month相减，不够向year借；最后year相减。
        if(day<0){
            month -= 1;
            now.add(Calendar.MONTH, -1);
　　　　　　//得到上一个月，用来得到上个月的天数。
            day = day + now.getActualMaximum(Calendar.DAY_OF_MONTH);
        }
        if(month<0){
            month = (month+12)%12;
            year--;
        }
        return year+"岁"+month+"月"+day+"天";
    }