// imports allow you to use code already written by others.  It is good to explore and learn libraries.  The names around the dots often give you a hint to the originator of the code.
import java.util.Scanner; //library for user input
import java.lang.Math; //library for random numbers


public class Menu {
    // Instance Variables
    public final String DEFAULT = "\u001B[0m";  // Default Terminal Color
    public final String[][] COLORS = { // 2D Array of ANSI Terminal Colors
        {"Default",DEFAULT},
        {"Red", "\u001B[31m"}, 
        {"Green", "\u001B[32m"}, 
        {"Yellow", "\u001B[33m"}, 
        {"Blue", "\u001B[34m"}, 
        {"Purple", "\u001B[35m"}, 
        {"Cyan", "\u001B[36m"}, 
        {"White", "\u001B[37m"}, 
    };
    // 2D column location for data
    public final int NAME = 0;
    public final int ANSI = 1;  // ANSI is the "standard" for terminal codes

    // Constructor on this Object takes control of menu events and actions
    public Menu() {
        Scanner sc = new Scanner(System.in);  // using Java Scanner Object
        
        this.print();  // print Menu
        boolean quit = false;
        while (!quit) {
            try {  // scan for Input
                int choice = sc.nextInt();  // using method from Java Scanner Object
                System.out.print("" + choice + ": ");
                quit = this.action(choice);  // take action
            } catch (Exception e) {
                sc.nextLine(); // error: clear buffer
                System.out.println(e + ": Not a number, try again.");
            }
        }
        sc.close();
    }

    // Print the menu options to Terminal
    private void print() {
        //System.out.println commands below is used to present a Menu to the user. 
        System.out.println("-------------------------");
        System.out.println("Select A Function");
        System.out.println("-------------------------");
        System.out.println("1 - Subtraction");
        System.out.println("2 - Addition");
        System.out.println("3 - Multiplication");
        System.out.println("4 - Division");
        System.out.println("0 - Quit");
        System.out.println("-------------------------\n");
    }

    // Private method to perform action and return true if action is to quit/exit
    private boolean action(int selection) {
        boolean quit = false;

        switch (selection) {  // Switch or Switch/Case is Control Flow statement and is used to evaluate the user selection
            case 0:  
                System.out.print("See you later!");
                quit = true;
                break;
            case 1:
                Scanner sc = new Scanner(System.in);
                System.out.println("Simple Subtraction ---");
                System.out.println("Please select first number: ");
                int choice1 = sc.nextInt(); //

                System.out.println("Please select second number: ");
                int choice2 = sc.nextInt();

                System.out.print("Your answer is: " + (choice1 - choice2));
                sc.close();

                break;
            case 2:
                Scanner asc = new Scanner(System.in);
                System.out.println("Simple Addition ---");
                System.out.println("Please select first number: ");
                int add1 = asc.nextInt(); //

                System.out.println("Please select second number: ");
                int add2 = asc.nextInt();

                System.out.print("Your answer is: " + (add1 + add2));
                asc.close();

                break;
            case 3:
                Scanner msc = new Scanner(System.in);
                System.out.println("Simple Multiplication ---");
                System.out.println("Please select first number: ");
                int time1 = msc.nextInt(); //

                System.out.println("Please select second number: ");
                int time2 = msc.nextInt();

                System.out.print("Your answer is: " + (time1 * time2));
                msc.close();

                break;
            case 4:
                Scanner dsc = new Scanner(System.in);
                System.out.println("Simple Division ---");
                System.out.println("Please select first number: ");
                int div1 = dsc.nextInt(); //

                System.out.println("Please select second number: ");
                int div2 = dsc.nextInt();

                System.out.print("Your answer is: " + (div1 / div2));
                dsc.close();

                break;
                    
            default:
                //Prints error message from console
                System.out.print("Unexpected choice, try again.");
        }
        System.out.println(DEFAULT);  // make sure to reset color and provide new line
        return quit;
    }

    // Static driver/tester method
    static public void main(String[] args)  {  
        new Menu(); // starting Menu object
    }

}
Menu.main(null);

-------------------------
Select A Function
-------------------------
1 - Subtraction
2 - Addition
3 - Multiplication
4 - Division
0 - Quit
-------------------------

3: Simple Multiplication ---
Please select first number: 
Please select second number: 
Your answer is: 125
0: See you later!