LeetCode 150 Evaluate Reverse Polish Notation

Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are

+

,

-

,

*

,

/

. Each operand may be an integer or another expression.Some examples:

["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
  ["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6

public class Solution {
	public int evalRPN(String[] tokens) {
		int num1, num2, temp;
		Stack<Integer> sk = new Stack<Integer>();
		for (String str : tokens) {
			if (str.equals("+")) {
				num1 = sk.pop();
				num2 = sk.pop();
				temp = num2 + num1;
			} else if (str.equals("-")) {
				num1 = sk.pop();
				num2 = sk.pop();
				temp = num2 - num1;
			} else if (str.equals("/")) {
				num1 = sk.pop();
				num2 = sk.pop();
				temp = num2 / num1;
			} else if (str.equals("*")) {
				num1 = sk.pop();
				num2 = sk.pop();
				temp = num2 * num1;
			} else
				temp = Integer.parseInt(str);
			sk.push(temp);
		}
		return sk.pop();
	}
}