How would I begin to turn this into a basic calculator, able to change like the equation (from multiplication to addition)?

import java.util.Scanner;

class Main {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

int i;

try {

String d = sc.nextLine();

i = Integer.parseInt(d);

}

catch(NumberFormatException e) {

System.out.println("Thats not an int");

}

}

}