abstract class Definition and Implementation

In this problem, you will create a program that defines an abstract class Shape, implements the area() method in concrete classes Circle and Rectangle, and displays the area of each shape to standard output.

Learning Objective: Understand the role of abstract classes and methods, and learn to implement them in concrete classes

Overview

Abstract classes cannot be directly instantiated. Abstract methods force implementation in subclasses.

Specifications

• Define abstract class Shape with abstract double area() and concrete method describe()
• Circle and Rectangle extend Shape and implement area()
• describe() displays shape name and area

Output Format

Circle: area = 78.54
Rectangle: area = 24.00