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())                                                                
	    	    	{