Java 根据出生日期计算年龄

1.把出生日期字符串转换为日期格式。

public static  Date parse(String strDate) throws ParseException {
	    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
	    return sdf.parse(strDate);
	}

2.计算年龄

public static  int getAge(Date birthDay) throws Exception {
	    Calendar cal = Calendar.getInstance();
	    if (cal.before(birthDay)) { //出生日期晚于当前时间，无法计算
	        throw new IllegalArgumentException(
	                "The birthDay is before Now.It's unbelievable!");
	    }
	    int yearNow = cal.get(Calendar.YEAR);  //当前年份
	    int monthNow = cal.get(Calendar.MONTH);  //当前月份
	    int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH); //当前日期
	    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;   //计算整岁数
            if (monthNow <= monthBirth) {
	        if (monthNow == monthBirth) {
	            if (dayOfMonthNow < dayOfMonthBirth) age--;//当前日期在生日之前，年龄减一
	        }else{
	            age--;//当前月份在生日之前，年龄减一

} } return age; }

3.执行方法

public static void main(String[] args) {
		try {
	      int  age = getAge(parse("1990-09-27"));           //由出生日期获得年龄***
	      System.out.println("age:"+age);
	    } catch (Exception e) {
	        e.printStackTrace();
	    }
	}