leetcode 150 evaluate reverse polish notation

class  {
    public int evalRPN(String[] tokens) {
        Stack<Integer> s = new Stack<>();
        for (String t: tokens){
            if ("+".equals(t)){
                int b = s.pop();
                int a = s.pop();
                int ans = a + b;
                s.push(ans);
            }
            else if ("-".equals(t)){
                int b = s.pop();
                int a = s.pop();
                int ans = a - b;
                s.push(ans);

            }
            else if ("*".equals(t)){
                int b = s.pop();
                int a = s.pop();
                int ans = a * b;
                s.push(ans);
            }
            else if ("/".equals(t)){
                int b = s.pop();
                int a = s.pop();
                int ans = a / b;
                s.push(ans);
            }
            else{
                int num = Integer.parseInt(t);
                s.push(num);
            }
        }
        return s.peek();
    }
}