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BlueJ is a unique integrated development environment
(IDE) for teaching Java and object oriented programming,
characterized by the ability of the user to
interactively create objects and call their methods.
The feature that distinguishes it from all other IDEs is that
the user can interactively create objects and call the
methods of the created objects. In other words, the BlueJ user
can play the role of an object in the running program. In fact,
the BlueJ user is essentially a "super-object" because he or she
has powers that other objects do not have. For example, the BlueJ
user can inspect any other object, even if its instance
variables have been declared private.
There are many advantages in being able to create objects and
call methods interactively:
- There is no need for a
main method
The user can directly start the program by creating an
initial object and if necessary calling one of its methods.
In other IDEs it is necessary to write a special method
called main whose only purpose is to start the
program running.
- Testing can be performed interactively
The user can directly call methods with different
arguments in order to ensure that they are working as
expected. In other IDEs it is necessary to write additional
methods or even classes just in order to test the code. This
creates more potential for error (is it the code that is
incorrect or the test?) and the temptation to skimp on
testing. Interactive testing is completely natural and can be
performed directly each method is completed.
- It allows the complexity of input/output to be deferred
Learning Java is almost always made unnecessarily complex
by the problems of input/output. Java's I/O mechanism is
extremely general, and it relies heavily on inheritance,
exceptions and other sophisticated concepts. However input is
necessary to avoid every program simply performing a
"hardwired" calculation of some sort, and so students are
inevitably asked to use something that they cannot
initially understand. However with BlueJ, input is completely
natural - whenever a method is called the user is prompted
for the arguments for that method call and can enter any
values. Essentially BlueJ performs the role of a black box
input device, but it is much easier for students to
comprehend because it is clear that BlueJ's prompt is
logically part of the IDE, rather than their program.
- It encourages OO thinking and programming
A program written in BlueJ consists only of the
classes directly relevant to the problem at hand. This means
that there is a direct relationship between the problem and
the computational model used for its solution. There need not
be any of the overhead normally associated with small OO
programs.
- BlueJ programs are standard Java
A program developed in BlueJ is standard Java. It can be
run separately from BlueJ simply by creating a
main method that creates an object and calls a
method. This has the additional positive effect that students
are unlikely to code an entire program in the
main method, but realize that the only purpose
of main is to start the real program
running.
The BlueJ program is itself a Java program, and so it
is necessary to have Java installed on your computer in order to
run BlueJ.
In CITS1200 we will be using a new version of BlueJ that support the JUnit4
unit test system.
First download the installation files for Java and BlueJ. You can
use the links below. I suggest that you bring in a USB thumb drive
and plug it into one of our machines in the computer lab, and download
the files directly onto that.
 Note that because of some distribution restrictions on some of the
software available on our download site (http://software.csse.uwa.edu.au/Lab_Software_2010/), we can only permit downloads
from machines that are on the UWA network. If you attempt to download
from home you will get a "permission denied" message.
Once you have copied these files onto your home computer you should
first install Java by simply double clicking on the .exe file
and following the instructions.
Once Java is installed, installation of BlueJ on Windows is simply
a matter of of double-clicking on
BlueJ-windows-9901junit4-4.exe
If you have problems with BlueJ, then the best way to try to
resolve these is by going to the BlueJ Web site and looking at
the frequently asked
questions (FAQ).
For problems with UWA BlueJ version see the contact details on
the UWAJavaTools page.
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