Java 计算年龄

    public static String getAgeTxt(String birthTime,String beginTime,int level){
        if(StringUtils.isBlank(birthTime)||StringUtils.isBlank(beginTime)){
            System.out.println("参数中有空值！");
        }
        
        int year = 0,month=0,day=0,hour=0;
        
        Date birthDate = getDateByString(birthTime,"yyyy-MM-dd HH:mm:ss");
        Date beginDate = getDateByString(beginTime,"yyyy-MM-dd HH:mm:ss");
        Calendar cBirthDate = Calendar.getInstance();
        Calendar cBeginDate = Calendar.getInstance();
        cBirthDate.setTime(birthDate);
        cBeginDate.setTime(beginDate);
        
        if(cBeginDate.get(Calendar.YEAR) < cBirthDate.get(Calendar.YEAR)){
            return "出生日期大于当前时间";
        }
        
        //计算出生小时
        if(cBeginDate.get(Calendar.HOUR_OF_DAY) < cBirthDate.get(Calendar.HOUR_OF_DAY)){
            hour = cBeginDate.get(Calendar.HOUR_OF_DAY)+24 - cBirthDate.get(Calendar.HOUR_OF_DAY);
            day = day-1;
        }else{
            hour = cBeginDate.get(Calendar.HOUR_OF_DAY) - cBirthDate.get(Calendar.HOUR_OF_DAY);
        }
        
        //计算出生日
        if(cBeginDate.get(Calendar.DAY_OF_MONTH)<cBirthDate.get(Calendar.DAY_OF_MONTH)){
            day = day + cBeginDate.get(Calendar.DAY_OF_MONTH)+ cBirthDate.getActualMaximum(Calendar.DAY_OF_MONTH)-cBirthDate.get(Calendar.DAY_OF_MONTH);
            month = month-1;
        }else {
            day = day + cBeginDate.get(Calendar.DAY_OF_MONTH)-cBirthDate.get(Calendar.DAY_OF_MONTH);
        }
        
        //计算出生月
        if(cBeginDate.get(Calendar.MONTH) < cBirthDate.get(Calendar.MONTH)){
            month = month + cBeginDate.get(Calendar.MONTH)+12 - cBirthDate.get(Calendar.MONTH);
            year = year -1;
        }else{
            month = month + cBeginDate.get(Calendar.MONTH) - cBirthDate.get(Calendar.MONTH);
        }
        
        //计算出生年
        year = year + cBeginDate.get(Calendar.YEAR) - cBirthDate.get(Calendar.YEAR);
        
        if(year >7){
            return year+"岁";
        }else if (year >0 && year <7){
            if(month>0 && month <10){
                return year+"岁零"+month+"月";
            }else if(month >=10 ){
                return year+"岁"+month+"月";
            }else {
                if(day>0){
                    return year+"岁零"+day+"天";
                }else{
                    return year+"岁";
                }
            }
        }else {
            if(month >0){
                if( day >0 && day <10){
                    return month+"个月零"+day+"天";
                }else if(day >=10){
                    return month+"个月"+day+"天";
                }else{
                    return month+"个月";
                }
            }else{
                if(day >0){
                    if( hour >0 && hour <10){
                        return day+"天零"+hour+"小时";
                    }else if(hour >=10){
                        return day+"天"+hour+"小时";
                    }else{
                        return day+"天";
                    }
                }else{
                    if(hour>0){
                        return hour+"小时";
                    }else{
                        return "出生不足一小时";
                    }
                }
            }
        }
    }

 其中比较重要的几点

1、Calendar.getActualMaximum()计算对应的范围内最大值

2、计算年龄应该是从小到大计算年龄，这样方便计算后面的年龄（利用减法的原理）；