Java程序辅导

CP4044 – Programming for Systems and Networks 
 
Mel Ralph, 21/11/2007, Assig2.doc  Page 1  
Assignment 2 
 
The basic task is to develop a simple file transfer program in Java. 
 
This will be a basic Internet client that uses the methods of the URL class.  Remember that it 
is possible to obtain a file from a public FTP archive via a WWW browser using a URL such 
as ftp://ftp.scit.wlv.ac.uk/pub.  (Try this using a normal WWW browser).  Using the methods 
from the Java class java.net.URL, write a program that will allow a command line user to 
explore an FTP archive (i.e. display the files and directories in the archive and get files) using 
simple commands such as CD dirname (change directory), DIR (list directory) and GET 
filename (get a file and save it locally) entered interactively by the user.  The functionality is, 
in part, inspired by the Linux/Windows command line tool ftp. 
 
Basic solution (Grade D) 
 
The program will allow the user to perform the basic exploration of a remote archive using the 
simple commands described above.  No particular attempt has been made to interpret and 
display directory listings in any particular fashion.  When a file is transferred it is simply saved 
in the local directory in which the program has been started. 
 
The following are suggestions for improving on the basic solution, with indicative grades: 
 
Grade C 
 
The program allows access to non-public archives.  (The URL syntax is 
ftp://username:password@host).  The program will not crash.  Error conditions will be 
interpreted and suitable messages given to the user. 
 
Grade B 
 
The GET command will support an extra optional parameter that allows a local filename to be 
specified.  The command LCD dirname will be implemented to allow the local directory to be 
changed.  Checks will be made to determine whether files requested for download will over-
write local files and the user is offered a choice if this is detected. 
 
Grade A  
 
A high standard of command line user interface is expected.  Information on download size 
and time will be logged and displayed.  Remote site directory listings will be in a standard 
form for most different types of site.  For extra credit, implement a facility allowing the user to 
specify multiple files to be transferred using a standard “wild-card” notation.   
 
For extra credit investigate adding a file uploading command (i.e. PUT). 
 
Submitting the Assignment 
 
The deadline for this assignment is Friday, 11th January (week 13). 
 
You should submit a printed copy of the program documentation with a floppy disk or CD 
securely attached containing the program source code and executable files. 
 
The program must be written in Java.  Source code generation tools should not be used.  In 
assessing your program, credit will be awarded for the observation of good programming 
practice in both O-O design and implementation. 
 
The documentation should include a commented listing of the source code (printed in a non-
proportional font).  You should also submit a log clearly demonstrating the capabilities of your 
program.   
CP4044 – Programming for Systems and Networks 
 
Mel Ralph, 21/11/2007, Assig2.doc  Page 2  
Include a critical evaluation of the program, commenting on the program behaviour 
(particularly execution time).  Reference any sources used other than the lecture and 
workshop notes. 
 
You may be required to demonstrate your program.