Geometry

import java.util.Scanner;

public class Geometry {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        int choice;

        do {
            displayMenu(); // Call display menu
            System.out.print("Enter choice (1-3): ");
            choice = in.nextInt();
            selectOption(choice, in);
        } while ((choice < 1) || (choice > 3));
        System.out.println("Thanks for using the Geometry Calculator - Goodbye!");
    }

    /**
     * This will display the welcome message and your choice for the
     * three options (circle, triangle, or rectangle).
     */
    public static void displayMenu() {
        System.out.println("Welcome to the Geometry Calculator Application");
        System.out.println("1. Calculate the Area of a Circle");
        System.out.println("2. Calculate the Area of a Rectangle");
        System.out.println("3. Calculate the Area of a Triangle");
    }

    /**
     * This will prompt the user to put in the circle's radius,
     * then calculate the area.
     *
     * @param s Scanner object
     * @return the area
     */
    public static double getCircleArea(Scanner s) {
        System.out.print("What is the circle's radius? ");
        double radius = s.nextDouble();
        while (radius <=0) {
            System.out.println("Invalid radius entered.");
            System.out.print("What is the circle's radius? ");
            radius = s.nextDouble();
        }
        return Math.PI * Math.pow(radius, 2);
    }

    /**
     * This will prompt the user to put in the rectangle's length
     * and width. Afterwards calculating the area.
     *
     * @param s Scanner object
     * @return the area
     */
    public static double getRectangleArea(Scanner s) {
        System.out.print("What is the rectangle's length? ");
        double length = s.nextDouble();
        while (length <= 0) {
            System.out.println("Invalid length!");
            System.out.print("What is the rectangle's length? ");
            length = s.nextDouble();
        }

        System.out.print("What is the rectangle's width? ");
        double width = s.nextDouble();
        while (width <= 0) {
            System.out.println("Invalid width!");
            System.out.print("What is the rectangle's width? ");
            width = s.nextDouble();
        }

        return length * width;
    }

    /**
     * This will prompt the user to put in the triangle's
     * base and height, then calculating the area.
     *
     * @param s Scanner object
     * @return the area
     */
    public static double getTriangleArea(Scanner s) {
        System.out.print("What is the triangle's base? ");
        double base = s.nextDouble();
        while (base <= 0) {
            System.out.println("Invalid base!");
            System.out.print("What is the rectangle's base? ");
            base = s.nextDouble();
        }
        System.out.print("What is the triangle's height? ");
        double height = s.nextDouble();
        while (height <= 0) {
            System.out.println("Invalid height!");
            System.out.print("What is the rectangle's height? ");
            height = s.nextDouble();
        }
        return (base * height) / 2;
    }

    /**
     * This will prompt the user to put in the triangle's
     * base and height, then calculating the area.
     *
     */
    public static void printArea(double someArea) {

        System.out.printf("The area is %.2f\n", someArea);

    }

    /**
     * This will input the user's choice.
     *
     * @param choice the value of the option
     * @param s Scanner object
     */
    public static void selectOption(int choice, Scanner s) {
        if (choice == 1) {
            double areaOfCircle = getCircleArea(s);
            printArea(areaOfCircle);
        } else if (choice == 2) {
            double areaOfRectangle = getRectangleArea(s); // assign the return value of the method
            printArea(areaOfRectangle); // then use that return value as parameter to another method
        } else if (choice == 3) {
            double areaOfTriangle = getTriangleArea(s);
            printArea(areaOfTriangle);
        } else {
            System.out.println("Invalid choice made!");
        }
    }
}