retrieve data from hashtable

Hi all,

I am currently developing a java application that allows the user to
wake up computers using Wake On Lan. The program reads in a CSV file
whic has the computer names and there MAC Address. Once the file has
been read it then populates a HashTable to add the records. What I
would like to happen is when the user selects a computer name from the
JList on the application it searches through the hashtable to find its
MAC address. However whether I use the variable used for the computer
name or hard code the computer name into the program it keeps on
returning null and am not sure why this is happening.

Below is the code that I am using:

public class WakeOnLan {
    Hashtable macTable = null;
    String ipStr;
    String macStr;
    String mac;
// String Computer;

    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) {
             System.out.println("strLine is: " + strLine );
             StringTokenizer st = new StringTokenizer(strLine, ",");

             String Computer = st.nextToken();
             mac = st.nextToken();
             System.out.println("Computer TOKENIZED: " + Computer);
             System.out.println("Mac Token: " + mac);
             macTable = new Hashtable();
             macTable.put(Computer, mac);
             System.out.println("Inside the HashMap: " + macTable);
             // WOL();
                // Print the content on the console
            //Close the input stream
            }

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

        }
        WOL();
        }

    public void WOL() {

        final int PORT = 9;
        String ipStr = "255.255.255.255";
        String choice = (String)
mainScreen.lstComputerNames.getSelectedValue();
        System.out.println( choice );
        // will be -1 if there aare none or muliple selections.
        int which = mainScreen.lstComputerNames.getSelectedIndex();
        System.out.println( which );

        // detecting multiple selections
        System.out.println( "--multiples--" );

        Object[] choices = mainScreen.lstComputerNames.getSelectedValues();

// macStr = "00:07:E9:93:18:EB";
        for ( Object aChoice : choices )
        {
        macTable.get(aChoice);
        System.out.println("The selection for wake on lan is: " +
aChoice);
        System.out.println("The mac address is: " + mac);
        System.out.println("Retrieving data from the hash table: " +
macTable.get("CBO_TEST"));
        try {
            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);
            System.exit(1);
        }
    }
    }

    private static byte[] getMacBytes(String macStr) throws
IllegalArgumentException {
        byte[] bytes = new byte[6];
        String[] hex = macStr.split("(\\:|\\-)");
        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;
    }
}

Any help in this matter would be highly apprieciated.

Thank you