java根据身份证计算年龄

可以通过以下代码来计算身份证对应的年龄：

public static int calculateAge(String idCard) {
    Calendar cal = Calendar.getInstance();
    int yearNow = cal.get(Calendar.YEAR);
    int monthNow = cal.get(Calendar.MONTH) + 1;
    int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH);
    int yearBirth, monthBirth, dayOfMonthBirth;
    if (idCard.length() == 18) {
        yearBirth = Integer.parseInt(idCard.substring(6, 10));
        monthBirth = Integer.parseInt(idCard.substring(10, 12));
        dayOfMonthBirth = Integer.parseInt(idCard.substring(12, 14));
    } else if (idCard.length() == 15) {
        yearBirth = Integer.parseInt(idCard.substring(6, 8)) + 1900;
        monthBirth = Integer.parseInt(idCard.substring(8, 10));
        dayOfMonthBirth = Integer.parseInt(idCard.substring(10, 12));
    } else {
        return -1; // 身份证号码不合法
    }
    int age = yearNow - yearBirth;
    if (monthNow < monthBirth || (monthNow == monthBirth && dayOfMonthNow < dayOfMonthBirth)) {
        age--;
    }
    return age;
}

其中，idCard 为身份证号码，返回值为身份证对应的年龄。注意，这里假设传入的身份证号码是合法的，如果身份证号码不合法，返回值为 -1。