LeetCode 2 Evaluate Reverse Polish Notation

public class Solution {
    public int evalRPN(String[] tokens) {
        Stack<integer> st = new Stack<integer>();
        for(String token : tokens){
            if(token.matches("-?[0-9]+")){
                st.push(Integer.parseInt(token));
            }else{
                int num2 = st.pop();
                int num1 = st.pop();
                if(token.equals("+")){
                    st.push(num1+num2);
                }else if(token.equals("-")){
                    st.push(num1-num2);
                }else if(token.equals("*")){
                    st.push(num1*num2);
                }else if(token.equals("/")){
                    st.push(num1/num2);
                }
            } 
        }
        return st.pop();
    }
}</integer></integer>