java根据出生日期计算年龄

    public static  int getUserAge(Date birthDay) throws Exception {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date birthDayAge = sdf.parse(sdf.format(birthDay));
        Calendar cal = Calendar.getInstance();
        if (cal.before(birthDayAge)) { //出生日期晚于当前时间，无法计算
            throw new IllegalArgumentException(
                    "日期填写错误！！");
        }
        int yearNow = cal.get(Calendar.YEAR);  //当前年份
        int monthNow = cal.get(Calendar.MONTH);  //当前月份
        int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH); //当前日期
        cal.setTime(birthDayAge);
        int yearBirth = cal.get(Calendar.YEAR);
        int monthBirth = cal.get(Calendar.MONTH);
        int dayOfMonthBirth = cal.get(Calendar.DAY_OF_MONTH);
        int age = yearNow - yearBirth;   //计算整岁数
        if (monthNow <= monthBirth) {
            if (monthNow == monthBirth) {
                if (dayOfMonthNow < dayOfMonthBirth) {
                    age--;//当前日期在生日之前，年龄减一
                }
            }else{
                age--;//当前月份在生日之前，年龄减一
            } } return age;
    }

    public static void main(String[] args) {
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Date parse = sdf.parse("2019-12-30 18:34:05");
            int age = getUserAge(parse); //由出生日期获得年龄***
            System.out.println("age:"+age);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }