Simple Calculator

import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.Collections;
import java.util.Scanner;

public class SimpleCalculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        ArrayDeque<String> stack = new ArrayDeque<>();
        String[] symbols = scanner.nextLine().split("\\s+");
        //Arrays.stream(scanner.nextLine().split(" ")).forEach(stack::push);
        Collections.addAll(stack,symbols);

        while (stack.size() > 1){
            int firstNum = Integer.parseInt(stack.pop());
            String operator = stack.pop();
            int secondNum = Integer.parseInt(stack.pop());

            switch (operator){
                case "+":
                    stack.push(String.valueOf(firstNum + secondNum));
                    break;
                case "-":
                    stack.push(String.valueOf(firstNum - secondNum));
                    break;
            }
            System.out.println(stack.pop());
        }
    }
}