JAVA根据身份证计算年龄的实现代码

birthDate = idCard.substring(6,10)+"-"+idCard.substring(10,12)+"-"+idCard.substring(12,14)
public static int getAgefromBirthTime(String birthTimeString){
 // 先截取到字符串中的年、月、日
 String strs[] = birthTimeString.trim().split("-");
 int selectYear = Integer.parseInt(strs[0]);
 int selectMonth = Integer.parseInt(strs[1]);
 int selectDay = Integer.parseInt(strs[2]);
 // 得到当前时间的年、月、日
 Calendar cal = Calendar.getInstance();
 int yearNow = cal.get(Calendar.YEAR);
 int monthNow = cal.get(Calendar.MONTH) + 1;
 int dayNow = cal.get(Calendar.DATE);
 // 用当前年月日减去生日年月日
 int yearMinus = yearNow - selectYear;
 int monthMinus = monthNow - selectMonth;
 int dayMinus = dayNow - selectDay;
 int age = yearMinus;
 if (yearMinus < 0) {// 选了未来的年份
  age = 0;
 } else if (yearMinus == 0) {// 同年的，要么为1，要么为0
  if (monthMinus < 0) {// 选了未来的月份
   age = 0;
  } else if (monthMinus == 0) {// 同月份的
   if (dayMinus < 0) {// 选了未来的日期
    age = 0;
   } else if (dayMinus >= 0) {
    age = 1;
   }
  } else if (monthMinus > 0) {
   age = 1;
  }
 } else if (yearMinus > 0) {
  if (monthMinus < 0) {// 当前月>生日月
  } else if (monthMinus == 0) {// 同月份的，再根据日期计算年龄
   if (dayMinus < 0) {
   } else if (dayMinus >= 0) {
    age = age + 1;
   }
  } else if (monthMinus > 0) {
   age = age + 1;
  }
 }
 return age;
}

public static int getAge(Date birthDay) throws Exception { 
  Calendar cal = Calendar.getInstance(); 
  if (cal.before(birthDay)) { 
   throw new IllegalArgumentException( 
    "The birthDay is before Now.It's unbelievable!"); 
  } 
  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--; 
   } 
  } 
  System.out.println("age:"+age); 
  return age; 
 }