Missing Scroll Pane

Question

Could someone please tell me why in the following code the Scroll Pane does not appear? The code refers to two other classes I didn't include here although I've added comments to explain how they're used.
Thanks very much.
public class VPA extends JPanel implements ListSelectionListener {
static DB2Connect vpaDB2connect = null;
JPanel contentPanel;
JPanel subPanel;
JList listOfData;
DataList dataList;
VPAsql vpaSQL;
public VPA() {
vpaDB2connect = new DB2Connect(); // a DB2 database connection
vpaDB2connect.makeConnection();
subPanel = new JPanel();
subPanel.setLayout(new BoxLayout(subPanel,BoxLayout.Y_AXIS));
subPanel.add(Box.createRigidArea(new Dimension(0,5)));
dataList = new DataList(vpaDB2connect); //returns a list of data
listOfData = dataList.getList(); // listOfData is a JList
listOfData.addListSelectionListener(this);
JScrollPane scrollPane = new JScrollPane(listOfData);
scrollPane.setPreferredSize(new Dimension(250,80));
scrollPane.setMinimumSize(new Dimension(250,80));
scrollPane.setAlignmentX(LEFT_ALIGNMENT);
subPanel.add(listOfData);
subPanel.add(scrollPane);
contentPanel = new JPanel();
contentPanel.add(subPanel,BorderLayout.CENTER);
public void valueChanged(ListSelectionEvent e) {}
public static void main(String[] args) {                
VPA vpa = new VPA();
JFrame frame = new JFrame("VPA");
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
frame.setContentPane(vpa.contentPanel);
frame.pack();
frame.setVisible(true);
}

Answer 1

The suggested solution about adding the following line
to my code does not make any difference.
frame.setContentPane(vpa);
I'm still looking for an answer on why the Scroll Pane
is not being displayed. If you havent fixed the prob then why did you give Duke Dollars to someone? anyway i don't see the probem Try this out:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class VPA extends JPanel
  JPanel contentPanel;
  JPanel subPanel;
  JList listOfData;
  public VPA()
    String[] list = {"one", "two", "three", "four", "five", "Six", "seven", "eight", "nine", "ten"};
    listOfData = new JList(list);
    subPanel = new JPanel();
    subPanel.setLayout(new BoxLayout(subPanel,BoxLayout.Y_AXIS));
    subPanel.add(Box.createRigidArea(new Dimension(0,5)));
    JScrollPane scrollPane = new JScrollPane(listOfData);
    scrollPane.setPreferredSize(new Dimension(250,80));
    scrollPane.setMinimumSize(new Dimension(250,80));
    scrollPane.setAlignmentX(LEFT_ALIGNMENT);
    subPanel.setBackground(Color.yellow);// to see where subPanel is in the layout
    subPanel.add(new JTextField());
    subPanel.add(scrollPane);
    contentPanel = new JPanel();
    contentPanel.setBackground(Color.orange);// to see where the contentPanel is in the layout
    contentPanel.add(subPanel,BorderLayout.CENTER);
  public static void main(String[] args)
    VPA vpa = new VPA();
    JFrame frame = new JFrame("VPA");
    frame.addWindowListener(new WindowAdapter() {
    public void windowClosing(WindowEvent e) {
    System.exit(0);
   frame.setContentPane(vpa.contentPanel);
   frame.pack();
   frame.setVisible(true);