Thread: infix to prefix

hey guys i m having a problem with infix and prefix
here is the code

import java.util.StringTokenizer;
import static java.lang.Math.pow;
import java.util.Stack;
 
public class Calculator {
 
       static int precedence(char op) {
              switch(op) {
              case '+' :
              case '-' : 
                       return 5;
              case '*' :
              case '/' :
                       return 10;
              default :
                       throw new IllegalArgumentException("λαθος εκφραση");
               }
         }
       public static String infixToPostfix(String infix) {
              StringTokenizer tokenizer = new StringTokenizer (infix);
              String postfix = "";
              Stack opStack = new Stack ();
 
              while (tokenizer.hasMoreTokens()) {
                     String token = tokenizer.nextToken();
                     char c = token.charAt(0);
                     if (Character.isDigit(c)){
                            postfix +=(token + " ");
                     }
                     else {
                             while (!opStack.empty()){
                                    char top = ((Character)opStack.peek()).charValue();
                                    if (precedence(top) >= precedence(c)) {
                                            postfix += (top + " ");
                                            opStack.pop();
                                     }
                                     else {
                                            break;
                                           }
                                     }
                                     opStack.push(new Character (c));
                          }
                      }
 
               while (!opStack.empty()) {
                      char top = ((Character)opStack.pop()).charValue();
                      postfix += (top + " ");
                }
                return postfix;
        }
 
     public static int evalPostfix(String postfix) {
              StringTokenizer tokenizer = new StringTokenizer(postfix);
              Stack valStack = new Stack();
 
              while(tokenizer.hasMoreTokens()) {
                     String token = tokenizer.nextToken();
                     char c = token.charAt(0);
                     if (Character.isDigit(c)) {
                            valStack.push(new Integer(token));
                      }
                      else {
                              int rightVal = ((Integer)valStack.pop()).intValue();
                              int leftVal = ((Integer)valStack.pop()).intValue();
                              int rslt;
 
                              switch(c) {
                              case '+' : rslt = leftVal + rightVal;break;
                              case '-' : rslt = leftVal - rightVal;break;
                              case '*' : rslt = leftVal * rightVal;break;
                              case '/' : rslt = leftVal / rightVal;break;
                              case '^' : rslt = pow(leftVal,rightVal);break;
                              default:
                                     throw new IllegalArgumentException("λαθος εκφραση");
                                }
                               valStack.push(new Integer(rslt));
                            }
                     }
                 int rslt = ((Integer)valStack.pop()).intValue();
                 if (!valStack.empty()){
                          throw new IllegalArgumentException("λαθος εκφαρση");
                  }
                      return rslt;
          }
      public static void main(String[] args)  {
             String infix = args[0];
             String postfix = infixToPostfix(infix); 
             System.out.println("postfix"+postfix);
             int value = evalPostfix(postfix);
             System.out.println("value: " + value);
         }
}

it says in line 72
possible loss of precision
required: int
found: double
the pow only takes int values?not doubles?how do i fix it?