자바 시간차이 문자열 변환

  public String getDifferenceTime(String uploadTime){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date date = null;
        try {
            date = sdf.parse(uploadTime);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        long uploadMills = date.getTime();

        long nowMills = System.currentTimeMillis();
        long difference = (long) ((nowMills - uploadMills)/1000.0);
        String returnValue;

        if(difference <=60){
            returnValue = difference+"초전";
        }else if(difference <= 60*60){
            returnValue = (difference/60)+"분전";
        }else if(difference <= 60*60*24){
            returnValue = (difference/(60*60))+"시간전";
        }else if(difference <= 60*60*24*7){
            returnValue = (difference/(60*60*24))+"일전";
        }else if(difference <= 60*60*24*7*52){
            returnValue = (difference/(60*60*24*7))+"주전";
        }else{
            returnValue = (difference/(60*60*24*7*52))+"년전";
        }

        return returnValue;
    }