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

这里采用别人使用异常来做判断，这个我个人觉得很厉害。

public int evalRPN(String[] tokens){
        Stack<Integer> stack = new Stack<Integer>();
        for(int i = 0; i<tokens.length;i++){
            try{
                int num = Integer.parseInt(tokens[i]);
                stack.add(num);
            }catch(Exception e){
                int b = stack.pop();
                int a = stack.pop();
                stack.add(get(a,b,tokens[i]));
            }
            
        }
        return stack.pop();
    }
    private int get(int a, int b,String op){
        switch(op){
        case "+":
            return a + b;
        case "-":
            return a - b;
        case "*":
            return a * b;
        case "/":
            return a / b;
        default:
            return 0;
        }
                
    }