private static String intToOperator(int i){
        if(i != 0 && i != 1 && i != 2){
            //System.out.println("incorrect value for int to operator"); used for testing
        }
        switch (i){
            case 0: return "+";
            case 1: return "-";
            case 2: return "*";
            case 3: return "/";
            default: System.out.println("incorrect value for int to operator");
                     break;
        }
        return "";
    }