Compiling error on Java I/O

Question

My first time to write a very simple Java progam. Any one could help me on this comipling error? Thanks in advance!
Compiling ERROR:
================
C:\java\class>javac hw01.java
hw01.java:43: cannot resolve symbol
symbol : variable in
location: class hw01
while((line = in.readLine()) != null ) {
^
1 error
SOURCE CODE:
============
*     Program name: hw01.java
*     Author:
*     Description: Simple I/O and computation
*     Date: 12/08/2002
*     compile: javac hw01.java
*     usage: java hw01 <infile> <utfile>
*     <infile> - input file
*     operator operand1 operand2
*          ex. + 1 1
* <outfile> - output file
* operand1 operator operand2 = result
*          ex. 1 + 1 = 2
import java.io.*;
import java.util.*;
public class hw01 {
     // Open input file and output file
     public static void main(String[] args) throws IOException {
          if (args.length == 2) {
               // Open File for Reading
               File inFile = new File(args[0]);
               FileReader in = new FileReader(inFile);
               // Open File for Writing
               File outFile = new File(args[1]);
               FileWriter out = new FileWriter(outFile);
          } else {
               System.out.println("java command <arg1> <arg2>");
          // Get operation, operand1 and operand2 for each line
          String line = null;
          while((line = in.readLine()) != null ) {
               //String op; String op1; String op2; String result;
               // Get operation and operands
               //stringTokenizer t = new StringTokenizer(line);
               //op = t.nextToken().charAt(0);
               //op1 = Integer.valueOf(t.nextToken()).intValue();
               //op2 = Integer.valueOf(t.nextToken()).intValue();
               // Compute math operation
               //if( op == '+' ) {
               //     result = op1 + op2;
               // } else if( op == '-' ) {
               //     result = op1 - op2;
               //} else if( op == '*' ) {
               //     result = op1 * op2;
               //} else if( op == '/' ) {
               //     result = op1 / op2;
               // Print out the result
               //system.out.println(op1 + op + op2 + "=" + result);
          // Close infile
          // in.close();
          // System.out.println("");
          // Close outFile
          // out.close();

Answer 1

The compiling error is fixed. The revised working source code hw01.java is provided below. Can someone help the remining question below?
PROBLEM/Question:
=================
The output only goes to the console. How code should be changed to allow output to a specified file from command line.
SOURCE FILE (without Compiling error):
=====================================
*     Program name: hw01.java
*     Author:
*     Description: Simple I/O and computation
*     Date: 12/08/2002
*     compile: javac hw01.java
*     usage: java hw01 <infile> <utfile>
* example: java hw01 hw1data.txt hw1out.txt
*     <infile> - input file
*     operator operand1 operand2
*          ex. + 1 1
* <outfile> - output file
* operand1 operator operand2 = result
*          ex. 1 + 1 = 2
import java.io.*;
import java.util.*;
public class hw01 {
     // Open input file and output file
     public static void main(String[] args) throws IOException {
          FileReader in = null;
          FileWriter out = null;
          BufferedReader br = null;
          System.out.println("input File Name = " + args[0]);
          System.out.println("output File Name = " + args[1]);
          if (args.length == 2) {
               // Open File for Reading
               File inFile = new File(args[0]);
               in = new FileReader(inFile);
               br = new BufferedReader(in);
               // Open File for Writing
               File outFile = new File(args[1]);
               out = new FileWriter(outFile);
          } else {
               System.out.println("java command <arg1> <arg2>");
          // Get operation and operands for each line
          String line = null;
     char op;
          int op1, op2;
          int result = 0;
          while((line = br.readLine()) != null ) {
               // Get operation and operands
               StringTokenizer t = new StringTokenizer(line);
               op = t.nextToken().charAt(0);
               op1 = Integer.valueOf(t.nextToken()).intValue();
               op2 = Integer.valueOf(t.nextToken()).intValue();
               // Compute math operation and print result
               if( op == '+' ) {
                    result = op1 + op2;
                    System.out.println(op1 + " + " + op2 + " = " + result);
               } else if( op == '-' ) {
                    result = op1 - op2;
                    System.out.println(op1 + " - " + op2 + " = " + result);
               } else if( op == '*' ) {
                    result = op1 * op2;
                    System.out.println(op1 + " * " + op2 + " = " + result);
               } else if( op == '/' ) {
                    result = op1 / op2;
                    System.out.println(op1 + " / " + op2 + " = " + result);
          // Close infile
          in.close();
          // Close outFile
          out.close();
}