BlueJ

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BlueJ running on Mac OS X

BlueJ is an interactive Java development environment, developed mainly for educational purposes, but also suitable for small-scale development.

BlueJ was developed to support the learning and teaching of object-oriented programming, and its design differs from other development environments as a result. The main screen graphically shows the class structure of an application under development (in a UML-like diagram), and objects can be interactively created and tested. This interaction facility, combined with a clean, simple user interface, allows easy experimentation with objects under development. Object-oriented concepts (classes, objects, communication through method calls) are represented visually and in its interaction design in the interface.

The visual interaction features of BlueJ were designed to allow one to delay the introduction of certain programming concepts considered difficult or problematic by educators. These include:

Syntax such as public static void main(String [] args) - which requires unnecessarily introducing the keywords public and static, as well as method arguments and arrays. BlueJ allows arbitrary classes to be instantiated and arbitrary methods to be invoked interactively.
Program input/output. In BlueJ both the parameter values for and the return values from method calls can be entered/inspected directly, so there is no need for students to deal with terminal I/O or write graphical user interfaces when they are still struggling with the basic concepts of programming.
Object orientation - the concepts of classes and objects are presented in a visual manner. Both have distinct visual representations, and it is easy to demonstrate that code is associated directly with a class, that an object has a class type, and that the class type of an object directly determines its available methods and fields as well as its behavior.

The program is a fully functional development tool, commonly used by schools, universities, and other low-budget groups.

[edit] History

The development of BlueJ was started in 1999 by Michael Kölling and John Rosenberg at Monash University in Melbourne, Australia, as a successor to the Blue system. Blue was an integrated system with its own programming language and environment. BlueJ implements the Blue environment design for the Java Programming Language.

BlueJ is currently being maintained by a joint team at the University of Kent at Canterbury, England - where Kölling now lectures, and Deakin University in Melbourne, Australia.