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• Polymorphism: Polymorphism allows objects of different classes to be treated as objects of
a common superclass. In object-oriented programming, polymorphism allows objects to be
treated as instances of their parent class rather than their actual class. This means that a single
function or method can operate on different types of objects, making the code more flexible
and reusable.
Example: As a family car, it’s equipped with extra seats and space for luggage, making it
suitable for personal trips. When used as a taxi, it features a fare meter and a taxi sign for
transporting passengers. As a pool car for students, it includes extra safety seats and a schedule
to manage shared transportation. Despite these different uses, the car remains fundamentally
the same, demonstrating how one object can fulfil multiple roles.
i + INTRODUCING BLUEJ
Previously, we used simple text editors such as Notepad to develop Java programs. With the
advancement in technology, there are different types of Integrated Development Environment
(IDE) available free of cost. Some of the IDEs are Netbeans, Eclipse, and BlueJ. In this chapter, we
are using BlueJ.
BlueJ is an IDE designed for beginners. It has a built-in editor, debugger,
and viewer. An editor gives us an area where we can write programs,
and a debugger allows us to find errors in the programs. On the other
hand, the viewer shows the output of the program.
BlueJ is a freely downloadable application. We can download it from
https://www.bluej.org/. After downloading the application, we need to
install it on our computer.
i + INTERFACE OF BLUEJ
After installing the BlueJ IDE, double-click on the BlueJ application shortcut icon on the Desktop.
The BlueJ application window appears.
Title Bar
Menu Bar
New Class
Button
Compile
Button
Project Icon
Object Bench
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iPlus (Ver. 2.1)-VIII

