将身份证号转换为年龄

/**
 * 将身份证号转换为年龄
 * @param idCard 身份证号
 * @return 年龄字符串
 */
public static int idCard2Age(String idCard) {
   if (idCard == null) {
      return null;
   }
   if (idCard.length() == 15) {
      idCard = idCard.substring(0, 6) + "19" + idCard.substring(6, 15);
   }
   Calendar now = Calendar.getInstance();
   int year = now.get(Calendar.YEAR);
   int month = (now.get(Calendar.MONTH) + 1);
   int day = now.get(Calendar.DAY_OF_MONTH);
   int age = year - Integer.parseInt(idCard.substring(6, 10)) - 1;
   if (Integer.parseInt(idCard.substring(10, 12)) < month
         || Integer.parseInt(idCard.substring(10, 12)) == month
         && Integer.parseInt(idCard.substring(12, 14)) <= day) {
      age++;
   }
   return age;
}