根據出生日期自動計算年齡

public static int getAgeByBirth(Date birthDay) throws ParseException {
        int age = 0;
        Calendar cal = Calendar.getInstance();
        if (cal.before(birthDay)) { //出生日期晚於當前時間，無法計算
            throw new IllegalArgumentException(
                    "The birthDay is before Now.It's unbelievable!");
        }
        int yearNow = cal.get(Calendar.YEAR);  //當前年份
        int monthNow = cal.get(Calendar.MONTH);  //當前月份
        int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH); //當前日期
        cal.setTime(birthDay);
        int yearBirth = cal.get(Calendar.YEAR);
        int monthBirth = cal.get(Calendar.MONTH);
        int dayOfMonthBirth = cal.get(Calendar.DAY_OF_MONTH);
        age = yearNow - yearBirth;   //計算整歲數
        if (monthNow <= monthBirth) {
            if (monthNow == monthBirth) {
                if (dayOfMonthNow < dayOfMonthBirth) age--;//當前日期在生日之前，年齡減一
            } else {
                age--;//當前月份在生日之前，年齡減一
            }
        }
        return age;
    }
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作者：SunnyLjs 
來源：CSDN 
原文：https://blog.csdn.net/sunnyljs/article/details/80934685 
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