Simple (Left to Right) Calculator Java

import java.util.Scanner;


public class Calc24 {
	    public static void main(String[] args) {
	        try (Scanner scanner = new Scanner(System.in)) {
	            System.out.println("Enter an expression of the form 3 m 5");
	            int n1 = scanner.nextInt();
	            String operation = scanner.next();
	            int n2 = scanner.nextInt();

	            switch (operation)  {
	            case "a":
	                System.out.println("Your answer is " + (n1 + n2));
	                break;

	            case "s":
	                System.out.println("Your answer is " + (n1 - n2));
	                break;

	            case "d":
	                System.out.println("Your answer is " + (n1 / n2));
	                break;

	            case "m":
	                System.out.println("Your asnwer is " + (n1 * n2));
	                break;

	            default:
	                System.out.println("Je ne sais pas");

	            }
	        }
	    }
	}