java获取字符串格式日期向前或向后n天的日期

private void setTilteMessage(){  
        BaseDao dao = new BaseDao();  
        String titleData = dao.getLatestData();  
        dao.closeDB();  
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");  
        try {  
            Date date = sdf.parse(titleData);  
            Calendar   calendar   =   new   GregorianCalendar();   
            calendar.setTime(date);   
            calendar.add(calendar.DATE,1);//把日期往后增加一天.整数往后推,负数往前移动   
            date=calendar.getTime();   //这个时间就是日期往后推一天的结果   
            String putDate = sdf.format(date); //增加一天后的日期  
              
        } catch (ParseException e) {  
            e.printStackTrace();  
        }  
    }