java-拼串计算日期时间差

/**
     * 组织时间差
     * @tags @return
     * @exception
     * @author wanghc
     * @date 2015-7-22 下午6:49:26
     * @return String
     */
    private String setDateDifferenceStr(Date startTime,Date endTime){
        StringBuffer sb = new StringBuffer();
        if(ParamValidator.validatorParamsIsEmpty(startTime,endTime)){
            sb.append("00:00:00");
            return sb.toString();
        }
        Long l = endTime.getTime() - startTime.getTime();
        long ss=l/(1000); //共计秒数
        int MM = (int)ss/60;   //共计分钟数
        int hh=(int)ss/3600;  //共计小时数
        //int dd=(int)hh/24;   //共计天数
        if((hh%24) >=0 && (hh%24) < 10){
            sb.append("0"+(hh%24));
        }else{
            sb.append(hh%24);
           }
        if((MM%60) >=0 && (MM%60) < 10){
            sb.append(":0"+(MM%60));
        }else{
            sb.append(":"+(MM%60));
        　 }
        if((ss%60) >=0 && (ss%60) < 10){
            sb.append(":0"+(ss%60));
        }else{
            sb.append(":"+(ss%60));
        }
        return sb.toString();
    }