need help converting from infix to postfix notation

[miatech]

guys, I have an expression like: 1 + 2 * 3, and I need to convert to postfix notation: 1 2 3 * +

This is my code, but for some reason I'm not displaying the operators, any help appreciated

package postfixstack;

import java.io.*;
import java.util.*;

public class Main {
    
    static Stack<String> optor = new Stack();
    static Stack<Integer> oprand = new Stack();
    
    static String strOut = "";
    
    public static void main(String[] args) throws FileNotFoundException
    {       
        
        File inFile = new File("datafile.txt");
        
        Scanner in = new Scanner(inFile);
        
        while(in.hasNext())
        {
            String next = in.next();
            do
            {
                if(optor.isOperator(next))
                {
                    //process operator
                    processOptor(next);
                }                
                else
                {
                    oprand.push(Integer.parseInt(next));
                    strOut += next+" ";
                    
                }
                next = in.next();
            }while(!next.equals("$"));                 
        }
        
        System.out.println(strOut);
        
    }
    
    //processing operators
    public static void processOptor(String op)
    {
        do
        {
            if(optor.isEmpty())
            {
                optor.push(op);
                return;
            }
            if(optor.priority(op) > optor.priority(optor.top()))
            {
                optor.push(op);
                return;
            }
            if(optor.priority(op) == optor.priority(optor.top()))
            {
                if(optor.associativity(optor.priority(op)).equals("right"))
                {
                    optor.push(op);
                    return;
                }
            }
            System.out.println("here!");
            strOut += optor.top()+" ";
            optor.pop();            
            
        }while(true);
    }
    
}

[Norm]

Also posted at: need help converting from infix to postfix notation