JPCAP: Network Device Information Display

Question

hi i am using JPCAP to display network device information.. but, problem i am getting with following code is that it works only on first JComboBox value change and then, Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException occurs..
import java.awt.*;
import java.awt.TrayIcon.MessageType;
import java.awt.event.*;
import javax.swing.*;
import jpcap.*;
public class jpcap_example {
      * @param args
     public static void main(String[] args) {
          // TODO Auto-generated method stub
          JFrame frame1 = new JFrame("Network Device(s) Information");
          String device_names[];
          JComboBox device_select;
          JPanel panel1 = new JPanel(new BorderLayout());
          JPanel panel2 = new JPanel(new GridLayout(5, 1));
          final JLabel IPAddress = new JLabel("IP Address", JLabel.LEFT);
          final JLabel SubnetMask = new JLabel("Subnet Mask", JLabel.LEFT);
          final JLabel Broadcast = new JLabel("Broadcast Address", JLabel.LEFT);
          final JLabel MACAddress = new JLabel("MAC Address", JLabel.LEFT);
          final JLabel Localloop = new JLabel("IsLocal", JLabel.LEFT);
          final NetworkInterface devices[] = JpcapCaptor.getDeviceList();
          device_names = new String[devices.length];
          for (int i = 0; i < devices.length; i++)
               device_names[i] = devices.name;
          if (devices.length == 0)
               JOptionPane.showMessageDialog(frame1, "Should run this app as root to see all hidden devices..", "Fatal Error", JOptionPane.ERROR_MESSAGE);
          device_select = new JComboBox(device_names);
          device_select.setForeground(Color.BLUE);
          device_select.setMaximumRowCount(3);
          panel1.add(device_select, BorderLayout.NORTH);
          panel2.add(IPAddress);
          panel2.add(SubnetMask);
          panel2.add(Broadcast);
          panel2.add(MACAddress);
          panel2.add(Localloop);
          panel1.add(panel2, BorderLayout.WEST);
          frame1.add(panel1);
          frame1.setSize(new Dimension(640, 480));
          frame1.setVisible(true);
          frame1.addWindowListener(new WindowAdapter()
               @Override
               public void windowClosing(WindowEvent e) {
                    // TODO Auto-generated method stub
                    super.windowClosing(e);
                    System.exit(0);
          device_select.addActionListener(new ActionListener(){
               @Override
               public void actionPerformed(ActionEvent e) {
                    // TODO Auto-generated method stub
                    JComboBox temp = (JComboBox)e.getSource();
                    IPAddress.setText("IPAddress");
                    SubnetMask.setText("SubnetMask");
                    Broadcast.setText("BroadcastAddress");
                    MACAddress.setText("MAC Address");
                    Localloop.setText("IsLocal?");
                    for (int i = 0; i < devices[temp.getSelectedIndex()].addresses.length; i++)
                         IPAddress.setText(IPAddress.getText() + devices[temp.getSelectedIndex()].addresses[i].address.toString());
                         SubnetMask.setText(SubnetMask.getText() + devices[temp.getSelectedIndex()].addresses[i].subnet.toString());
                         Broadcast.setText(Broadcast.getText() + devices[temp.getSelectedIndex()].addresses[i].broadcast.toString());
                    MACAddress.setText(MACAddress.getText() + devices[temp.getSelectedIndex()].mac_address.toString());
                    Localloop.setText(Localloop.getText() + devices[temp.getSelectedIndex()].loopback);
can somebody please tell me where i am making mistake??                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

sorry, for late reply..
i changed code for displaying mac address correctly (thought it should correct the problem but, still same error).. here's the change..
for (int i = 0; i < devices[temp.getSelectedIndex()].mac_address.length; i++)
     int j = (int)devices[temp.getSelectedIndex()].mac_address;
     j &= 0xff;
     MACAddress.setText(MACAddress.getText() + " : "+ Integer.toHexString(j));
Localloop.setText(Localloop.getText() + devices[temp.getSelectedIndex()].loopback);
anyhow, it is showing exception in this line..Broadcast.setText(Broadcast.getText() + devices[temp.getSelectedIndex()].addresses[i].broadcast.toString());
i wonder what could be problem in that line .. ??
{for last value of i, it showed like fe80:0:0:.... in IP Address field; and ffff:ffff:ffff:ffff:0:0:0:0 in subnet mask .. before exception occured..
i suppose i know what it is but, still not sure.. what is it??}