Java 根據出生日期計算年齡

1.把出生日期字符串轉換為日期格式。

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

2.計算年齡

public static  int getAge(Date birthDay) throws Exception {
	    Calendar cal = Calendar.getInstance();	
	    if (cal.before(birthDay)) { //出生日期晚於當前時間，無法計算
	        throw new IllegalArgumentException(
	                "The birthDay is before Now.It's unbelievable!");
	    }
	    int yearNow = cal.get(Calendar.YEAR);  //當前年份
	    int monthNow = cal.get(Calendar.MONTH);  //當前月份
	    int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH); //當前日期
	    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;   //計算整歲數
            if (monthNow <= monthBirth) {
	        if (monthNow == monthBirth) {
	            if (dayOfMonthNow < dayOfMonthBirth) age--;//當前日期在生日之前，年齡減一
	        }else{
	            age--;//當前月份在生日之前，年齡減一

} } return age; }

3.執行方法

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