Java 根据年月日精确计算年龄

 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.Date;  

 /**
  * Created by qing on 2017/3/28.
  */
 public class AgeUtils {
     // 根据年月日计算年龄,birthTimeString:"1994-11-14"
     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;// 先大致赋值
         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;
     }  

     // 根据时间戳计算年龄
     public static int getAgeFromBirthTime(long birthTimeLong) {
         Date date = new Date(birthTimeLong * 1000l);
         SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
         String birthTimeString = format.format(date);
         return getAgeFromBirthTime(birthTimeString);
     }
 }  

精确到月：

/**
 * Created by admin on 2017/12/15.
 */

public String getAgeFromBirthTime(Date birthDay) {
     Calendar cal = Calendar.getInstance();
     // 得到当前时间的年、月、日
     int yearNow = cal.get(Calendar.YEAR);
     int monthNow = cal.get(Calendar.MONTH)+1;
     int dayNow = cal.get(Calendar.DATE);
     // 先截取到传入中的年、月、日
     cal.setTime(birthDay);
     int selectYear = cal.get(Calendar.YEAR);
     int selectMonth = cal.get(Calendar.MONTH) + 1;
     int selectDay = cal.get(Calendar.DAY_OF_MONTH);
     // 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;
     String  ageToMonth= "1月";

     if (yearMinus > 0){
          ageToMonth = String.valueOf(yearMinus)+"岁";
     } else if (monthMinus > 0) {
          ageToMonth = String.valueOf(monthMinus)+"月";
     }
     return ageToMonth;
}

　　

 public static void main(String[] args) {
         String dataOfBirth = "2017-10-28";
         String age = getAgeFromBirthTime(dataOfBirth);
         System.out.println("age:" + age);
     }

鸡肋：

 public class TestAge {
     public static void main(String[] args) {
 //        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
         try {
             //此处是获得的年龄
             int age = getAge(parse("2015-12-5 00:00:00"));           //由出生日期获得年龄***
             System.out.println(age);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     //出生日期字符串转化成Date对象
     public static Date parse(String strDate) throws ParseException {
         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
         return sdf.parse(strDate);
     }

     //由出生日期获得年龄
     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--;
             }
         }
         return age;
     }