项目中需要根据用户填写的出生日期获得用户的年龄，一般直接写成一个方法，然后调用方法进行计算比较省事。

下面介绍一种根据出生日期计算年龄的方法：

package com.hyhl.util;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Calendar;import java.util.Date;public class AgeUtil {     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;          }                  public static void main(String args[]) {              try {                int  age = getAge(parse("2991-10-21"));                System.out.println("age=="+age);            } catch (ParseException e) {                e.printStackTrace();            } catch (Exception e) {                e.printStackTrace();            }                         }}

直接方法即可

package com.hyhl.util;

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

public class AgeUtil {

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;      }          public static void main(String args[]) {      try {int  age = getAge(parse("2991-10-21"));System.out.println("age=="+age);} catch (ParseException e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();}             }}