Inheritance in Java

Explanation

This Java program demonstrates the fundamental concept of Single Inheritance. In inheritance, one class (the subclass) acquires the properties and behaviors of another class (the superclass).

1. The Base Class (Shape): We start by defining a class named Shape. This class acts as a template containing two attributes: length and breadth. These represent the common properties that many geometric shapes share.
2. The Derived Class (Rectangle): We then define a class named Rectangle. By using the keyword extends, we tell Java that Rectangle is a specialized type of Shape. Because of inheritance, the Rectangle class automatically "inherits" the length and breadth variables from the Shape class without having to redefine them.
3. Specific Functionality: Inside the Rectangle class, we add a new variable area and a method calculateArea(). This method uses the inherited attributes to compute the area.
4. Execution Logic: In the main method, we create an instance (object) of the Rectangle class. Even though we didn't define length or breadth inside the Rectangle class block, we can access them through the Rectangle object r. We assign values to these attributes, call the calculation method, and print the final result to the console.

Algorithm

1. Start.
2. Define a superclass named Shape with integer members length and breadth.
3. Define a subclass named Rectangle that extends the Shape class.
4. Declare a member area and a method calculateArea() within the Rectangle class.
5. In the main method:
   • Create an object r of the Rectangle class.
   • Assign integer values to r.length and r.breadth (inherited from Shape).
   • Invoke the r.calculateArea() method to multiply length and breadth.
   • Store the result in the area variable.
6. Display the results using a formatted print statement.
7. End.