how to make a calculator using switch case in java

1/* Create Switch cases */
2Scanner sc= new Scanner(System.in);
3int firstNum= sc.nextInt();
4int secondNum= sc.nextInt();
5System.out.println("Enter an operator (+, -, *, /):");
6char operator= sc.next().chartAt(0);
7double result=0;
8switch(operator){
9  case "+":
10    result+= firstNum+ secondNum;
11    break;
12  case "-":
13    result+= firstNum-secondNum;
14    break;
15  case "*":
16    result+= firstNum*secondNum;
17    break;
18  case "/":
19    result+= firstNum/secondNum;
20    break;
21}