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）；