evaluate reverse polish notation

public int (String[] tokens) {
    Stack<String> operator = new Stack<String>();
    Stack<Integer> operand = new Stack<Integer>();
    for (String str : tokens) {
        int val = 0;
        switch (str) {
            case "*":
                val = operand.pop() * operand.pop();
                operand.push(val);
                break;
            case "+":
                val = operand.pop() + operand.pop();
                operand.push(val);
                break;
            case "-":
                int min = operand.pop();
                val = operand.pop() - min;
                operand.push(val);
                break;
            case "/":
                int div = operand.pop();
                val = operand.pop() / div;
                operand.push(val);
                break;
            default:
                val = Integer.parseInt(str);
                operand.push(val);
        }
    }
    return operand.pop();
}