最近在写项目的时候遇到了一个需要根据出生日期计算年龄的问题，今天特意将代码记下来已被后期使用。

 1   //根据出生日期计算年龄
 2     public  int getAgeByBirth(String birthDayStr) {
 3         SimpleDateFormat sdf =   new SimpleDateFormat( "yy-MM-dd" );
 4         Date birthDay= null;
 5         try {
 6             birthDay = sdf.parse(birthDayStr);
 7         } catch (ParseException e) {
 8             e.printStackTrace();
 9         }
10         // String str = sdf.format(parse( " 2005-06-09 00:00:00 " );
11 
12 
13         int age = 0;
14         Calendar cal = Calendar.getInstance();
15         if (cal.before(birthDay)) { //出生日期晚于当前时间，无法计算
16             throw new IllegalArgumentException(
17                     "The birthDay is before Now.It's unbelievable!");
18         }
19         int yearNow = cal.get(Calendar.YEAR);  //当前年份
20         int monthNow = cal.get(Calendar.MONTH);  //当前月份
21         int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH); //当前日期
22         cal.setTime(birthDay);
23         int yearBirth = cal.get(Calendar.YEAR);
24         int monthBirth = cal.get(Calendar.MONTH);
25         int dayOfMonthBirth = cal.get(Calendar.DAY_OF_MONTH);
26         age = yearNow - yearBirth;   //计算整岁数
27         if (monthNow <= monthBirth) {
28             if (monthNow == monthBirth) {
29                 if (dayOfMonthNow < dayOfMonthBirth) age--;//当前日期在生日之前，年龄减一
30             } else {
31                 age--;//当前月份在生日之前，年龄减一
32             }
33         }
34         return age;
35     }

在调用的时候注意：

//根据修改过的出生日期从新计算被保险人的年龄
tSaveLPInsuredSchema.setAge(String.valueOf(getAgeByBirth(mLPInsuredSchema.getBirthDay())));