150. Evaluate Reverse Polish Notation

class Solution {
    public int evalRPN(String[] tokens) {
        LinkedList<Integer> stack = new LinkedList<>();
        int a, b;
        for (String s : tokens) {
            switch (s) {
                case "+":
                    stack.addLast(stack.removeLast() + stack.removeLast());
                    break;
                case "-":
                    a = stack.removeLast();
                    b = stack.removeLast();
                    stack.addLast(b - a);
                    break;
                case "*":
                    stack.addLast(stack.removeLast() * stack.removeLast());
                    break;
                case "/":
                    a = stack.removeLast();
                    b = stack.removeLast();
                    stack.addLast(b / a);
                    break;
                default:
                    stack.addLast(Integer.parseInt(s));
                    break;
            }
        }
        return stack.removeLast();
    }
}