流文件读写有关问题，求解答

              int buffsize=1024;                                                           

    			FileInputStream fis= null;                                                                                                                                                                                   

    			BufferedInputStream bis = null;                                                                          

    			try                                                                                                      

    			{                                                                                                        

	    		synchronized (socket.getOutputStream())                                                                

	    	    	{