Write a Java program that demonstrates the use of an abstract class and abstract methods with
inheritance and polymorphism. Follow these guidelines:
1. Create an abstract class named Shape that contains:
o An abstract method calculateArea() that returns a double value representing the area
of the shape.
o A concrete method displayArea() that prints the area by calling the
calculateArea() method.
2. Create two subclasses, Circle and Rectangle, that each extend Shape:
o Circle:
Has a private field radius.
Includes a constructor to initialize the radius.
Implements the calculateArea() method using the formula for the area of a
circle: π×radius2\pi \times \text{radius}^2π×radius2.
o Rectangle:
Has private fields length and width.
Includes a constructor to initialize length and width.
Implements the calculateArea() method using the formula for the area of a
rectangle: length×width\text{length} \times \text{width}length×width.
3. In the main method, prompt the user to select a shape type:
o Ask the user to enter 1 for Circle or 2 for Rectangle.
o Based on the user's choice:
If the user selects Circle, ask for the radius and create a Circle object.
If the user selects Rectangle, ask for the length and width and create a
Rectangle object.
o After creating the appropriate object, call displayArea() on it to print the calculated
area.
4. Use Scanner for user input, and handle invalid choices by displaying an error message.
