Question

Write a Java program such that it consists of 2 classes:

1. a class that serves as the driver (contains main())

2. a class that contains multiple private methods that compute and display

a. area of a triangle (need base and height)

b area of a circle (use named constant for PI) (need radius)

c. area of rectangle (width and length)

d. area of a square (side)

e. surface area of a solid cylinder (height and radius of base)

N.B. You will also need an accessor public method (interface) that is called from the driver. This method should:

a. Display a menu of options to the user. (Suggest use switch statement)

b. Accept input from the user (keyboard) representing parameter values needed.

c. Invoke other [private] methods in the class to perform the necessary area computations

Add comments throughout your code as you deem appropriate.

Answer 1

import java.util.Scanner;

class Geometry {

    static Scanner in = new Scanner(System.in);
    static double PI = 3.14;

// public interface method which asks user for choice and calls private method
    public void performUserOperation() {
        // Show menu
        System.out.println("1. Compute Area of triangle");
        System.out.println("2. Compute Area of Circle");
        System.out.println("3. Compute Area of Rectangle");
        System.out.println("4. Compute Area of Square");
        System.out.println("5. Compute Surface Area of Cylinder");
        System.out.println("Enter choice: ");
        int choice = in.nextInt();

        switch (choice) {
        case 1:
            System.out.print("Enter triangle base: ");
            double base = in.nextDouble();
            System.out.print("Enter triangle height: ");
            double height = in.nextDouble();
            System.out.println("Area: " + triangleArea(base, height));
            break;

        case 2:
            System.out.print("Enter circle radius: ");
            double radius = in.nextDouble();
            System.out.println("Area: " + circleArea(radius));
            break;

        case 3:
            System.out.print("Enter Rectangle width: ");
            double width = in.nextDouble();
            System.out.print("Enter Rectangle height: ");
            height = in.nextDouble();
            System.out.println("Area: " + rectangleArea(width, height));
            break;

        case 4:
            System.out.print("Enter Square side: ");
            double side = in.nextDouble();
            System.out.println("Area: " + squareArea(side));
            break;

        case 5:
            System.out.print("Enter cylinder base radius: ");
            radius = in.nextDouble();
            System.out.print("Enter cylinder height: ");
            height = in.nextDouble();
            System.out.println("Area: " + cylindersurfaceArea(radius, height));
            break;

        default:
            break;
        }
    }

    private double cylindersurfaceArea(double radius, double height) {
        return 2 * PI * radius * (radius + height);
    }

    private double squareArea(double side) {
        return side * side;
    }

    private double rectangleArea(double width, double height) {
        return width * height;
    }

    private double circleArea(double radius) {
        return PI * radius * radius;
    }

    private double triangleArea(double base, double height) {
        return 0.5 * base * height;
    }
}

// driver class
public class GeometryHelper {

    public static void main(String[] args) {
        Geometry geometry = new Geometry();
        
        geometry.performUserOperation();
    }

}

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