150. Evaluate Reverse Polish Notation

class Solution {
    public int evalRPN(String[] tokens) {
        Stack<Integer> numStack = new Stack<>();
        for (String token : tokens) {
            switch (token) {
                case "+": {
                    numStack.push(numStack.pop() + numStack.pop());
                    break;
                }
                case "-": {
                    int b = numStack.pop(), a = numStack.pop();
                    numStack.push(a - b);
                    break;
                }
                case "*": {
                    numStack.push(numStack.pop() * numStack.pop());
                    break;
                }
                case "/": {
                    int b = numStack.pop(), a = numStack.pop();
                    numStack.push(a / b);
                    break;
                }
                default:
                    numStack.push(Integer.parseInt(token));
            }
        }

        return numStack.pop();
    }
}

Reference

150. Evaluate Reverse Polish Notation
剑指 Offer II 036. 后缀表达式