java计算年龄

 public static int getAgeByCardId(String card) throws Exception {
        Integer len = card.length();
        if (len == CHINA_ID_MIN_LENGTH) {
            card = conver15CardTo18(card);
        }
        String birthDate = card.substring(6, 14);
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");  
        Date date = sdf.parse(birthDate);  
        return calcAge(date);
    }



 /**
     * 由出生日期获得年龄  精确到天
     * @param birthDay
     * @return
     * @throws Exception
     */
    public static int calcAge(Date birthDay) throws Exception {  
        Calendar cal = Calendar.getInstance();  
        if (cal.before(birthDay)) {  
            throw new IllegalArgumentException("出生日期不能晚于当前日期");  
        }  
        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;  
  
        if (monthNow <= monthBirth) {  
            if (monthNow == monthBirth) {  
                if (dayOfMonthNow < dayOfMonthBirth) age--;  
            }else{  
                age--;  
            }  
        }  
        return age;  
    }

 /**
     * 根据身份编号获取年龄
     * 
     * @param idCard
     *            身份编号
     * @return 年龄
     */
    public static int getAgeByIdCard(String idCard) {
        int iAge = 0;
        if (idCard.length() == CHINA_ID_MIN_LENGTH) {
            idCard = conver15CardTo18(idCard);
        }
        String year = idCard.substring(6, 10);
        Calendar cal = Calendar.getInstance();
        int iCurrYear = cal.get(Calendar.YEAR);
        iAge = iCurrYear - Integer.valueOf(year);
        return iAge;
    }