Practical 0 – Hello World

CS5001 Object-Oriented Modelling, Design and
Programming
Practical 0 – Hello World
School of Computer Science

MMS is the definitive source for deadlines and weightings.
This exercise permits you to practice using the School servers and our Module Management System (MMS) for submitting coursework and will introduce you to programming
in Java. It will also give you the opportunity to use and familiarise yourself with our
automated checking tools (which will be used for many assignments in future). Although
this exercise involves submitting an archive file containing your work to MMS, it is not
formally assessed and merely provides you with a chance to practice procedures that
you will need from now on.
You can discuss this practical, as well as watching a video of me doing the whole thing,
in the following thread: https://discourse.cs.st-andrews.ac.uk/t/practical-0-hello-world/
901/. This is a demo on Windows, but I’m willing to do a Linux one as well if there’s
demand.
Task 1: Basic Requirement
For this task you will be using a text editor to write a short program and the Java compiler
and Java runtime from a Terminal Window, to compile and run your program. You might
want to refer to the first exercise sheet here for some of the details. Try to complete the
following steps.
• Create a new folder with the name p0-hello .
• Open the p0-hello folder and similarly to above, create a new folder with the
name src .
• Open a terminal/command prompt window and navigate to the src directory
using the cd command.
1
• Create a new file in your src directory, called HelloWorld.java , and open it with
a text editor.
• Type in the HelloWorld program from the lectures. You can find the slides here.
• Once you have finished writing the program, save it.
• In the Terminal window, you can compile your program now by typing
javac HelloWorld.java
If the compile completed successfully, you should have generated a class file called
HelloWorld.class . This contains the bytecode for your program which you can
run on the Java virtual machine (JVM).
• Run your program using java HelloWorld
If all went well, you should see the output Hello World in the terminal window. At this
point, you should try running the automated checker on your solution. Details are given
in the section below: Running the Automated Checker. At this stage, only the build and
first comparison test should pass.
Task 2: Enhancements
Extend your basic HelloWorld program to allow command line arguments to be accepted
• Open HelloWorld.java with the text editor.
• Change the code so that instead of always printing “Hello World”, it prints “Hello”
plus the first command line argument the program receives e.g.
java HelloWorld Bob
will result in “Hello Bob” being displayed in the terminal window. If no argument
is given, it should still print “Hello World”.
Below are some examples of the expected output for some different command line
arguments:
java HelloWorld
Hello World
java HelloWorld Bob
Hello Bob
2
java HelloWorld Michael and friends
Hello Michael
java HelloWorld "Michael and friends"
Hello Michael and friends
Hint: what do you think the parameter String[] args represents in the main method?
Running the Automated Checker
When you submit a practical, it will be checked automatically using the automated
checker, stacscheck . You can try running this on your program before submitting it, to
ensure that nothing has broken accidentally.
You will always upload an archive file of your work to MMS, so you should archive
your work first before running stacscheck on it. Compress the whole of your p0-hello
directory to a .zip file.
In order to run stacscheck on your code, you should upload it somewhere in your
home directory on the lab computers. Then, access the terminal on the lab computers by
using ssh. You can complete these two steps using the following commands from the
terminal/command prompt:
sftp <yourusername>@<yourusername>.host.cs.st-andrews.ac.uk
ssh <yourusername>@<yourusername>.host.cs.st-andrews.ac.uk
Note that you’ll need to use your CompSci password here – the same one you use for
Discourse. If you’re not used to sftp , you might prefer a graphical FTP client such as
FileZilla.
Once you’ve uploaded your file and logged into the lab PCs via SSH, you can run the
automated checking system on your archive by navigating to the archive’s location and
running the following command:
stacscheck --archive p0-hello.zip /cs/studres/CS5001/Practicals/p0-hello/Tests
If you have uploaded the original p0-hello directory instead of an archive, then you
should instead navigate into it and run the following command:
3
stacscheck /cs/studres/CS5001/Practicals/p0-hello/Tests
If all goes well, then you should see output like this:
Testing CS5001 Practical 0 (Hello World)
- Looking for directory 'src': found in current directory
* BUILD TEST - basic/build : pass
* COMPARISON TEST - basic/Test01_HelloWorld/progRun-expected.out : pass
* COMPARISON TEST - basic/Test02_HelloWorld_Bob/progRun-expected.out : pass
* COMPARISON TEST - basic/Test03_HelloWorld_Michael_and_friends/progRun-expected.out : pass
* COMPARISON TEST - basic/Test04_HelloWorld_MichaelAndFriends/progRun-expected.out : pass
* INFO - basic/TestQ_CheckStyle/infoCheckStyle : pass
--- output ---
Starting audit...
Audit done.
If it is not going so well, here are some things to consider
• If the automated checker cannot be started, then you have most likely mis-typed
the commands to invoke the checker shown above.
• If the automated checker runs but fails at the build stage, then no other tests can
be conducted, so you will have to fix this issue first. Likely reasons for the build
failure include:
– executing the checker from some directory other than your assignment directory or specifying an incorrect path to the tests.
– your program cannot be compiled as required by the checker and as specified
above. Try to modify your program such that it can be compiled using the
simple command javac HelloWorld.java from within the p0-hello/src
directory.
• If the automated checker runs and the build succeeds, but all comparison tests
fail, it could be that your program cannot be run using the simple command
java HelloWorld from within the src directory in your submission. Make sure
you have written a main method in your HelloWorld class and for the enhancement tasks try to ensure your program uses the args command-line arguments
that are passed to your main method.
• The names of the comparison tests 1 to 4 indicate the command-line arguments
being passed to your program. Each test expects your program to produce a specific
output as outlined above. If one or more of the tests fail, then it may be that your
4
program has a bug or is simply not printing out exactly what is expected and shown
in the sample execution runs above. Maybe you have included some additional
debug messages in your output or additional new lines, these will also cause tests
to fail. Try to ensure your output matches the one shown above exactly when
executing your program from the command-line.
• You may see a warning about missing Javadoc strings. You should generally include
Javadoc strings to explain your code, as discussed in lectures. However, there’s no
need to worry about it for this practical.
• The final test TestQ_CheckStyle runs a program called Checkstyle over your
source code and uses a style adapted from our St Andrews coding style (informally known as the Kirby Style). You may receive a lot of output from the
style checker for your program. In order to address these, you can look at the
published guide at https://info.cs.st-andrews.ac.uk/student-handbook/learningteaching/programming-style.html#programming_style.
The style recommends the use of spaces as opposed to TABs for indentation. Try to
get used to doing this, because it’s great for when working with others!
• If nothing is working and you don’t know why, please don’t suffer in silence, ask us.
This is the first time you will have tried to use the automated checking system, so
there are bound to be some issues.
Deliverables – Software
Hand in an archive of your work via MMS to the P0 slot.
Marking
This exercise is not assessed so no marks will be given.
Lateness
This exercise is not assessed so no lateness penalties apply.
Good Academic Practice
The University policy on Good Academic Practice applies:
https://www.st-andrews.ac.uk/students/rules/academicpractice/
5