I have to write a program in java that will calculate a postfix expression......I

[DaQuan]

need help.? Heres what I have so far:

import java.util.Stack;

public class Postfix{
public static double evaluate (String exp){
Stack<Double> s = new Stack<Double>();
String[] token = exp.split("\s+");
for(int i=0; i<token.length; i++){
if(isOperator(token));
double op2 = s.pop();
double op1 = s.pop();
op = token;
if (op.equals("+"))
s.push(op1+op2);
else if (op.equals("-"))
s.push(op1-op2);
else if (op.equals("*"))
s.push(op1*op2);
else if (op.equals("/"))
s.push(op1/op2);

if(isOperator(token)){
Double num = Double.valueOf(token);
s.push(token);
}
return s.pop();
} }
}