Variable is null

Hi all, I am currently developing a java application that will enable
the user to be able to wake computers remotely using the feature
called Wake On Lan. This works by reading in a CSV file that has been
exported from DHCP. However DHCP doesn't export the data very well and
therefore needs a lot of corrective code within the program to ignore
errors within the file or try and fix errors.

However since I have put this code in the program it no longer sends
the wake on lan packet and have discovered the the variable called hex
down the bottom of the page is null. The code that I am using is
below:

package remoteshutdown;

import java.awt.Dimension;
import java.awt.Point;
import java.io.*;
import java.net.*;
import java.util.*;

public class WakeOnLan {
    String[] macStr;
// String mac;
// String Computer;
    Hashtable<String, String> macTable = new Hashtable<String,
String>();

    public static final int PORT = 9;

    public void readFile() {
        try {
            // Open the file that is the first
            // command line parameter
            FileInputStream fstream = new FileInputStream("C:\
\Documents and Settings\\All Users\\Application Data\\Remote Shutdown\
\DHCP Export.csv");
            // Get the object of DataInputStream
            DataInputStream in = new DataInputStream(fstream);
            BufferedReader br = new BufferedReader(new
InputStreamReader(fstream));
            String strLine;
            //Read File Line By Line
            while ((strLine = br.readLine()) != null) {
             strLine.toUpperCase();
// try {
             System.out.println("strLine is: " + strLine );
             StringTokenizer st = new StringTokenizer(strLine, ",.");

             String Computer = st.nextToken();

             boolean network = strLine.indexOf("ETC") < 0;
             if (network = false) {
             System.out.println("The string doesn't contain ETC");
             }
             else {
             System.out.println("The string does contain ETC");
             }

             if(strLine.contains("."))
             {
             int firstIndex = strLine.indexOf(".");
             int lastIndex = strLine.lastIndexOf(".");
             if (firstIndex == lastIndex) {
             st.nextToken();
             }
             else {
         st.nextToken();
             st.nextToken();
             }
             }
             String mac = st.nextToken();
             System.out.println("\t\tComputer : " + Computer+" for
"+mac);

             macTable.put((String)Computer, (String)mac);
// }
// catch (Exception e)
// {
// System.err.println("MAJOR ERROR: " + e.toString());
// }
                // Print the content on the console
            //Close the input stream
            }
           System.out.println("CLOSING IN");
            in.close();

        } catch (Exception e) { //Catch exception if any
            System.err.println("Error: " + e.toString());
        }
        WOL();
    }

    public void WOL() {
     Object[] choices =
mainScreen.lstComputerNames.getSelectedValues();
     for (Object aChoice : choices) {

     String wakeComputer = (String)macTable.get(aChoice);

     System.out.println("wakeComputer is:" + wakeComputer);
     int stringLength = wakeComputer.getBytes().length;

     if (stringLength < 12) {
     wakeComputer = "00" + wakeComputer;
         String originalMac = wakeComputer.substring(0,2) + ":" +
wakeComputer.substring(2,4) + ":" + wakeComputer.substring(4,6) + ":"
+ wakeComputer.substring(6,8) + ":" + wakeComputer.substring(8, 10) +
":" + wakeComputer.substring(10,12);
     System.out.println("original mac: " + originalMac);

            String macStr = originalMac; //"00:30:4F:1C:95:dF";
            System.out.println("String length is less than 12 is
true");
            System.out.println("macStr is: " + macStr);
     }
     else {
     String originalMac = wakeComputer.substring(0,2) + ":" +
wakeComputer.substring(2,4) + ":" + wakeComputer.substring(4,6) + ":"
+ wakeComputer.substring(6,8) + ":" + wakeComputer.substring(8, 10) +
":" + wakeComputer.substring(10,12);
     System.out.println("original mac: " + originalMac);
            String macStr = originalMac; //"00:30:4F:1C:95:dF";
            System.out.println("String length is less than 12 is
false");
            System.out.println("macStr is: " + macStr);
     }

     String ipStr = "255.255.255.255"; //broadcast address

        try {
// wait(5000);
            byte[] macBytes = getMacBytes(macStr);
            byte[] bytes = new byte[6 + 16 * macBytes.length];
            for (int i = 0; i < 6; i++) {
                bytes[i] = (byte) 0xff;
            }
            for (int i = 6; i < bytes.length; i += macBytes.length) {
                System.arraycopy(macBytes, 0, bytes, i,
macBytes.length);
            }

            InetAddress address = InetAddress.getByName(ipStr);
            DatagramPacket packet = new DatagramPacket(bytes,
bytes.length, address, PORT);
            DatagramSocket socket = new DatagramSocket();
            socket.send(packet);
            socket.close();

            System.out.println("Wake-on-LAN packet sent.");
        }
        catch (Exception e) {
            System.out.println("Failed to send Wake-on-LAN packet: " +
e.toString());
            System.exit(1);
        }
     }

    }

    private static byte[] getMacBytes(String[] macStr) throws
IllegalArgumentException {
        byte[] bytes = new byte[6];
        String[] hex = macStr;
        System.out.println("hex is: " + hex);
// System.out.println("macStr 2 is: " + macStr);
// if (hex.length != 6) {
// throw new IllegalArgumentException("Invalid MAC
address.");
// }
        try {
            for (int i = 0; i < 6; i++) {
                bytes[i] = (byte) Integer.parseInt(hex[i], 16);
            }
        }
        catch (NumberFormatException e) {
            throw new IllegalArgumentException("Invalid hex digit in
MAC address.");
        }
        return bytes;
    }

}

If anyone could help me in this matter it would be highly appreciated.
Thank you