下載一個圖片ban.jpg 別人的寫法： public?void?doGet(HttpServletRequest?request,?HttpServletResponse?response) throws?ServletException,?IOException?{ response.setContentType("text/html;charset=utf-8"); response.setCharacterEncoding("utf-8"); response.setHeader("Content-Disposition",?"attachment;?filename=ban.jpg"); String?path=this.getServletContext().getRealPath("/image/ban.jpg"); FileInputStream?fis=new?FileInputStream(path); byte?buff[]=new?byte[1024]; int?len=0; OutputStream?os=response.getOutputStream(); while((len=fis.read(buff))>0){ os.write(buff,?0,?len);} os.close(); fis.close(); } 請問為何不這樣寫： public?void?doGet(HttpServletRequest?request,?HttpServletResponse?response) throws?ServletException,?IOException?{ response.setContentType("text/html;charset=utf-8"); response.setCharacterEncoding("utf-8"); response.setHeader("Content-Disposition",?"attachment;?filename=ban.jpg"); String?path=this.getServletContext().getRealPath("/image/ban.jpg"); FileInputStream?fis=new?FileInputStream(path); byte?buff[]=new?byte[1024]; int?len=0; OutputStream?os=response.getOutputStream(); while((len=fis.read(buff))>0){ fis.read(buff);//這個地方 os.write(buff,?0,?len); } os.close(); fis.close(); }為何不寫這句？fis.read(buff);