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Program 52
Radius and Area of a Circle Using Inheritance
Question
Use inheritance to accept a circle's radius and calculate and display its area.
Algorithm
Step 1: Start the program and define a base class containing the radius.
Step 2: Define a method in the base class to accept the radius.
Step 3: Define a derived class that inherits the radius and input method.
Step 4: Create an object of the derived class in main().
Step 5: Call the input method to accept the radius.
Step 6: Check that the radius is not negative.
Step 7: If the radius is invalid, display an error and stop.
Step 8: Calculate the area using π multiplied by radius multiplied by radius.
Step 9: Store the calculated area in a double variable.
Step 10: Display the radius to two decimal places.
Step 11: Display the area to two decimal places on a separate line.
Step 12: Stop the program.
Java program
Javaimport java.util.*;
class CircleBase
{
double radius;
void input()
{
Scanner sc = new Scanner(System.in);
System.out.print("Enter radius: ");
radius = sc.nextDouble();
}
}
class CircleArea extends CircleBase
{
void display()
{
double area = 3.14159 * radius * radius;
System.out.printf("Radius = %.2f%nArea = %.2f%n", radius, area);
}
public static void main(String[] args)
{
CircleArea ob = new CircleArea();
ob.input();
ob.display();
}
}Sample output
Input: Input: 7
Output: Radius = 7.00; Area = 153.94