BlueJ is a Java development environment that is being developed and maintained at the University of Kent at Canterbury, UK, and La Trobe University, Melbourne, explicitly as an environment for teaching introductory object-oriented programming. It is better suited to introductory teaching than other environments for a variety of reasons:
The user interface is much simpler. Beginning students can typically use the BlueJ environment in a competent manner after 20 minutes of introduction. From then on, instruction can concentrate on the important concepts at hand - object orientation and Java - and no time needs to be wasted talking about environments, file systems, class paths, DOS commands or DLL conflicts.
The environment supports important teaching tools not available in other environments. One of them is visualization of class structure. BlueJ automatically displays a UML-like diagram representing the classes and relationships in a project. Visualizing these important concepts is a great help to both teachers and students. It is hard to grasp the concept of an object when all you ever see on the screen is lines of code! The diagram notation is a simple subset of UML, again tailored to the needs of beginning students. This makes it easy to understand, but also allows migration to full UML in later courses.
One of the most important strengths of the BlueJ environment is the user's ability to create directly objects of any class, and then to interact with their methods. This creates the opportunity for direct experimentation with objects, for little overhead in the environment. Students can almost 'feel' what it means to create an object, call a method, pass a parameter or receive a return value. They can try out a method immediately after it has been written, without the need to write test drivers. This facility is an invaluable aid in understanding the underlying concepts and language details.
BlueJ is a full Java environment. It is not a cut down, simplified version of Java for teaching. It runs on top of Sun Microsystems' Java Development Kit, and makes use of the standard compiler and virtual machine. This ensures that it always conforms to the official and most up-to-date Java specification.
The authors of this book have several years of teaching experience with the BlueJ environment (and many more years without it before that). We both have experienced how the use of BlueJ has increased the involvement, understanding and activity of students in our courses. One of the authors is also a developer of the BlueJ system.
Sumber:
https://www.bluej.org/objects-first/description.html