Main.java

package com.studevs.example.test.core;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		System.out.print("Please type your name: ");
		String name = scanner.nextLine();

		try {

			System.out.println("Hello " + name + ", please follow to rules to use the calculator.");
			System.out.println("To add two number input like, 12 + 2.4");
			System.out.println("To subtract two number input like, 12 - 2.4");
			System.out.println("To multiply two number input like, 12 * 2.4");
			System.out.println("To divide first number by second number input like, 12 / 2.4");
			System.out.println("Be casefult to give space between first number, operator and second number!");
			System.out.println("Use EXIT or exit to terminate the program!\n\n\n");
			
			while (true) {

				String firstNumer = scanner.next();
				
				if (firstNumer.trim().toUpperCase().equals("EXIT")) {
					System.out.println("Thank you " + name + " to use this calculator!");
					break;
				}
				
				String operator = scanner.next();
				String secondNumber = scanner.next();
				
				switch (operator) {
				case "+": {

					System.out.println(Double.valueOf(firstNumer) + Double.valueOf(secondNumber));
					break;
				}
				case "-": {

					System.out.println(Double.valueOf(firstNumer) - Double.valueOf(secondNumber));
					break;
				}
				case "*": {

					System.out.println(Double.valueOf(firstNumer) * Double.valueOf(secondNumber));
					break;
				}
				case "/": {

					System.out.println(Double.valueOf(firstNumer) / Double.valueOf(secondNumber));
					break;
				}
				default:
					
					System.out.println("Invalid input type!");
					break;
				}
				
				System.out.println("Try again.");
			}
		} catch (Exception e) {

			System.out.println("You have done a serious mistake!");
		}
	}
}