【Java 工具类】通过出生日期获取年龄

public static int getAge(Date birthDay) {
        if (birthDay == null) {
            return 0;
        }
        Calendar cal = Calendar.getInstance();
        if (cal.before(birthDay)) {
            return 0;
        }
        int yearNow = cal.get(Calendar.YEAR);
        int monthNow = cal.get(Calendar.MONTH);
        int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH);
        cal.setTime(birthDay);

        int yearBirth = cal.get(Calendar.YEAR);
        int monthBirth = cal.get(Calendar.MONTH);
        int dayOfMonthBirth = cal.get(Calendar.DAY_OF_MONTH);

        int age = yearNow - yearBirth;

        boolean lowAge = monthBirth == monthNow && dayOfMonthBirth < dayOfMonthNow;

        if (monthNow > monthBirth || lowAge) {
            age--;
        }
        return age;
    }