Images disappearing / being painted over

Question

Hi,
Not especially familiar with images and am having issues with images being painted over when ever I move or adjust the size of my GUI. I built a majority of the GUI using the Form Designer included with Netbeans.
Would really appreciate any advice, happy to include more detail if required.
Cheers,
Tim
GUIView
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Vector;
import javax.imageio.ImageIO;
* GUIView.java
* Created on 22 April 2007, 21:25
* The GUIView class is responsible to display a graphical interface.
* This class interacts with the user and the GUIControl class allowing the user to operate the system.
* @author  Tim
public class GUIView extends JFrame implements ActionListener {
// Declare method variables
    private JTextField prodIDInput0;
    private JLabel prodIDLabel0;
    private JLabel prodIDLabel1;
    private JLabel prodIDLabel2;
    private JLabel prodNameLabel0;
    private JLabel prodNameLabel1;
    private JTextField amtRcvdInput0;
    private JLabel amtRcvdLabel0;
    private JButton cancelButton0;
    private JMenu fileMenu0;
    private JMenuItem exportXMLMenuItem;
    private JMenuItem exitMenuItem;
    private JButton findButton0;
    private JLabel itemPrice0;
    private JScrollPane jScrollPane1;
    private JMenuBar menuBar0;
    private JButton paymentButton0;
    private JLabel prodDescLabel0;
    private JLabel prodDescLabel1;
    private JPanel prodImagePanel0;
    private JPanel prodPanel0;
    private JLabel qtyLabel0;
    private JTextField qtyInput0;
    private JLabel totalPrice0;
    private JLabel totalPrice1;
    private JList transList0;
    private JPanel transPanel0;
    private Vector listData;
    private BufferedImage img;
    private GUIControl guiCtl0;
    /** Creates new form GUIView */
    public GUIView (GUIControl guiCtl0) {
        // reference guiCtl object
        this.guiCtl0 = guiCtl0;
    /** initilise gui object */
    public void initGui () {
        // initialise the GUI
        initComponents ();
        // paint image
        paintImage ("images/transparent.gif");
        // show the GUI
        setVisible (true);
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
    private void initComponents () {
        // Instantiate GUI objects
        prodIDLabel0 = new JLabel ();
        prodIDLabel1 = new JLabel ();
        prodNameLabel0 = new JLabel ();
        prodNameLabel1 = new JLabel ();
        prodDescLabel0 = new JLabel ();
        prodDescLabel1 = new JLabel ();
        prodImagePanel0 = new JPanel ();
        itemPrice0 = new JLabel ();
        totalPrice0 = new JLabel ();
        totalPrice1 = new JLabel ();
        prodPanel0 = new JPanel ();
        prodIDLabel2 = new JLabel ();
        prodIDInput0 = new JTextField ();
        qtyInput0 = new JTextField ();
        qtyLabel0 = new JLabel ();
        findButton0 = new JButton ();
        transPanel0 = new JPanel ();
        paymentButton0 = new JButton ();
        cancelButton0 = new JButton ();
        amtRcvdInput0 = new JTextField ();
        amtRcvdLabel0 = new JLabel ();
        jScrollPane1 = new JScrollPane ();
        transList0 = new JList ();
        menuBar0 = new JMenuBar ();
        fileMenu0 = new JMenu ();
        listData = new Vector ();
        // default close operation is to terminate the application
        setDefaultCloseOperation (WindowConstants.EXIT_ON_CLOSE);
        // title of the window
        setTitle ("Supermarket Management System");
        // centre the GUI on the screen
        Rectangle rect = GraphicsEnvironment.getLocalGraphicsEnvironment ().getMaximumWindowBounds ();
        rect.grow (-185,-100);
        setBounds (rect);
        // sets the minimum size the wonw can be shrunk to
        setMinimumSize (new java.awt.Dimension (880, 480));
        // sets the name of the frame
        setName ("mainFrame");
        // setup label to show Product ID:
        prodIDLabel0.setFont (new java.awt.Font ("Tahoma", 1, 14));
        prodIDLabel0.setText ("Product ID:");
        // setup label to show the id of the latest product object
        prodIDLabel1.setFont (new java.awt.Font ("Tahoma", 0, 14));
        prodIDLabel1.setText ("");
        prodIDLabel1.setToolTipText ("Product ID");
        // setup label to show Name:
        prodNameLabel0.setFont (new java.awt.Font ("Tahoma", 1, 14));
        prodNameLabel0.setText ("Name:");
        // setup label to show the name of the latest product object
        prodNameLabel1.setFont (new java.awt.Font ("Tahoma", 0, 14));
        prodNameLabel1.setText ("");
        prodNameLabel1.setToolTipText ("Product Name");
        // setup label to show Description:
        prodDescLabel0.setFont (new java.awt.Font ("Tahoma", 1, 14));
        prodDescLabel0.setText ("Description:");
        // setup label to show the description of the latest product object
        prodDescLabel1.setFont (new java.awt.Font ("Tahoma", 0, 14));
        prodDescLabel1.setText ("");
        prodDescLabel1.setToolTipText ("Product Description");
        // align the prodDescLabel1 to TOP
        prodDescLabel1.setVerticalAlignment (SwingConstants.TOP);
        // setup panel to display image
        prodImagePanel0.setBackground (new java.awt.Color (255, 255, 255));
        prodImagePanel0.setBorder (javax.swing.BorderFactory.createEtchedBorder (javax.swing.border.EtchedBorder.RAISED));
        org.jdesktop.layout.GroupLayout prodImagePanel0Layout = new org.jdesktop.layout.GroupLayout (prodImagePanel0);
        prodImagePanel0.setLayout (prodImagePanel0Layout);
        // specify how much the panel expands on the horizontal axis
        prodImagePanel0Layout.setHorizontalGroup (
                prodImagePanel0Layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (0, 304, Short.MAX_VALUE)
        // specify how much the panel expands on the vertical axis
        prodImagePanel0Layout.setVerticalGroup (
                prodImagePanel0Layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (0, 255, Short.MAX_VALUE)
        // setup item price label
        itemPrice0.setFont (new java.awt.Font ("Tahoma", 1, 14));
        itemPrice0.setText ("");
        itemPrice0.setToolTipText ("Transaction Item Price information");
        // setup label to display Total Price:
        totalPrice0.setFont (new java.awt.Font ("Tahoma", 1, 18));
        totalPrice0.setText ("Total Price:");
        // setup label to display current transaction total price
        totalPrice1.setFont (new java.awt.Font ("Tahoma", 0, 18));
        totalPrice1.setText ("$0.00");
        totalPrice1.setToolTipText ("Total cost of transaction");
        // setup JPanel to contain product look up components
        prodPanel0.setBorder (BorderFactory.createTitledBorder ("Enter Product"));
        // setup label to display Product ID:
        prodIDLabel2.setText ("Product ID:");
        // setup label to display Quantity:
        qtyLabel0.setText ("Quantity:");
        // setup button and display FIND as the text
        findButton0.setFont (new java.awt.Font ("Tahoma", 0, 14));
        findButton0.setText ("FIND");
        findButton0.setToolTipText ("Click to find product");
        findButton0.addActionListener (this);
        // create new GroupLayout for prodPanel0
        org.jdesktop.layout.GroupLayout prodPanel0Layout = new org.jdesktop.layout.GroupLayout (prodPanel0);
        prodPanel0.setLayout (prodPanel0Layout);
        // set horizontal group
        prodPanel0Layout.setHorizontalGroup (
                prodPanel0Layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (prodPanel0Layout.createSequentialGroup ()
                .add (15, 15, 15)
                .add (prodIDLabel2)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                // add prodIDInput0 JTextField to form
                .add (prodIDInput0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 126, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add (22, 22, 22)
                .add (qtyLabel0)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                // addd qtyInput0 JTextField to form
                .add (qtyInput0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 39, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add (22, 22, 22)
                .add (findButton0)
                .addContainerGap (org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        // set vertical group
        prodPanel0Layout.setVerticalGroup (
                prodPanel0Layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (prodPanel0Layout.createSequentialGroup ()
                .addContainerGap ()
                .add (prodPanel0Layout.createParallelGroup (org.jdesktop.layout.GroupLayout.BASELINE)
                .add (prodIDLabel2)
                // add prodIDInput0 JTextField to form
                .add (prodIDInput0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add (qtyLabel0)
                // add qtyInput0 JTextField to form
                .add (qtyInput0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add (findButton0))
                .addContainerGap (org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        // setup JPanel to contain finialise payment components
        transPanel0.setBorder (BorderFactory.createTitledBorder ("Finalise Transaction"));
        // setup button and display PAYMENT as the text
        paymentButton0.setFont (new java.awt.Font ("Tahoma", 0, 14));
        paymentButton0.setText ("PAYMENT");
        paymentButton0.setToolTipText ("Click to finalise transaction");
        // setup button and display CANCEL as the text
        cancelButton0.setFont (new java.awt.Font ("Tahoma", 0, 14));
        cancelButton0.setText ("CANCEL");
        cancelButton0.setToolTipText ("Cancel the current transaction");
        cancelButton0.addActionListener (this);
        // setup label to display Amount received:
        amtRcvdLabel0.setText ("Amount received:");
        // create new GroupLayout for TransPanel0
        org.jdesktop.layout.GroupLayout transPanel0Layout = new org.jdesktop.layout.GroupLayout (transPanel0);
        transPanel0.setLayout (transPanel0Layout);
        // set horizontal group
        transPanel0Layout.setHorizontalGroup (
                transPanel0Layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (org.jdesktop.layout.GroupLayout.TRAILING, transPanel0Layout.createSequentialGroup ()
                .addContainerGap (org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .add (amtRcvdLabel0)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                // add amtRcvdInput0 JTextField to form
                .add (amtRcvdInput0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 58, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add (22, 22, 22)
                .add (paymentButton0)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (cancelButton0)
                .addContainerGap ())
        // set vertical group
        transPanel0Layout.setVerticalGroup (
                transPanel0Layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (transPanel0Layout.createSequentialGroup ()
                .addContainerGap ()
                .add (transPanel0Layout.createParallelGroup (org.jdesktop.layout.GroupLayout.BASELINE)
                .add (cancelButton0)
                .add (paymentButton0)
                // add amtRcvdInput0 JTextField to form
                .add (amtRcvdInput0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add (amtRcvdLabel0))
                .addContainerGap (org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        // setup JScrollPanel to display transaction items
        transList0.setFont (new java.awt.Font ("Tahoma", 0, 14));
        transList0.setListData (listData);
        transList0.setToolTipText ("Items entered in the current transaction");
        // specify scrollbars
        jScrollPane1.setViewportView (transList0);
        // setup the file menu
        fileMenu0.setText ("File");
        // add Export XML menu item to file menu
        exportXMLMenuItem = new JMenuItem ("Export to XML");
        exportXMLMenuItem.setToolTipText ("Export current product list to product.xml");
        fileMenu0.add (exportXMLMenuItem);
        // add menu seperator
        fileMenu0.addSeparator ();
        // add Exit menu item to file menu
        exitMenuItem = new JMenuItem ("Exit");
        exitMenuItem.setToolTipText ("Exit application");
        fileMenu0.add (exitMenuItem);
        // add the file menu to the menu bar
        menuBar0.add (fileMenu0);
        // set the menu bar to be menuBar0
        setJMenuBar (menuBar0);
        // layout remaining components onto JFrame
        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout (getContentPane ());
        getContentPane ().setLayout (layout);
        // set horizontal group
        layout.setHorizontalGroup (
                layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (layout.createSequentialGroup ()
                .addContainerGap ()
                .add (layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (layout.createSequentialGroup ()
                .add (prodIDLabel0)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (prodIDLabel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 78, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (prodNameLabel0)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (prodNameLabel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 164, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                .add (layout.createSequentialGroup ()
                .add (prodDescLabel0)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (prodDescLabel1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 725, Short.MAX_VALUE))
                .add (layout.createSequentialGroup ()
                .add (prodImagePanel0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (jScrollPane1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 499, Short.MAX_VALUE))
                .add (layout.createSequentialGroup ()
                .add (itemPrice0)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED, 441, Short.MAX_VALUE)
                .add (totalPrice0)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (totalPrice1))
                .add (layout.createSequentialGroup ()
                .add (prodPanel0, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (transPanel0, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))
                .addContainerGap ())
        // set vertical group
        layout.setVerticalGroup (
                layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (layout.createSequentialGroup ()
                .addContainerGap ()
                .add (layout.createParallelGroup (org.jdesktop.layout.GroupLayout.BASELINE)
                .add (prodIDLabel1)
                .add (prodNameLabel1)
                .add (prodNameLabel0)
                .add (prodIDLabel0))
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (layout.createParallelGroup (org.jdesktop.layout.GroupLayout.BASELINE)
                .add (prodDescLabel0)
                .add (prodDescLabel1))
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (jScrollPane1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 259, Short.MAX_VALUE)
                .add (prodImagePanel0, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (itemPrice0)
                .add (layout.createParallelGroup (org.jdesktop.layout.GroupLayout.BASELINE)
                .add (totalPrice1)
                .add (totalPrice0)))
                .addPreferredGap (org.jdesktop.layout.LayoutStyle.RELATED)
                .add (layout.createParallelGroup (org.jdesktop.layout.GroupLayout.LEADING)
                .add (prodPanel0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add (transPanel0, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                .addContainerGap ())
        // resize the frame to the minimum size needed to satisfy the preferred size of each of the components in the layout
        pack ();
    /** actionPerformed()
     *  handles events from components.
    public void actionPerformed (ActionEvent e) {
        if ( e.getSource () == findButton0 )
            guiCtl0.findButtonAction (prodIDInput0.getText (), qtyInput0.getText ());
        if ( e.getSource () == cancelButton0 )
            guiCtl0.cancelButtonAction ();
    /** showWelcomeMsg()
     *  Shows a welcome dialogue message to the user.
    public void showWelcomeMsg (){
        // Create a new dialogue box
        JOptionPane welcomeMsg = new JOptionPane ();
        // Show welcome dialogue box
        welcomeMsg.showMessageDialog (null, "Welcome to the Supermarket Management System.  Click OK to begin.", "Welcome", welcomeMsg.INFORMATION_MESSAGE);
    /** showMsg()
     *  Shows a message to the user.
    public void showErrorMsg (String s){
        // Create a new dialogue box
        JOptionPane errorMsg = new JOptionPane ();
        // Show welcome dialogue box
        errorMsg.showMessageDialog (null, s, "Message", errorMsg.ERROR_MESSAGE);
    /** set prodIDInput0 text field */
    public void setProdIDInput0 (String s){
        prodIDInput0.setText (s);
    /** set qtyInput0 text field */
    public void setQtyInput0 (String s){
        qtyInput0.setText (s);
    /** set ProdDescLabel1 label */
    public void setProdDescLabel1 (String s) {
        prodDescLabel1.setText (s);
    /** set prodIDLabel1 label */
    public void setProdIDLabel1 (String s) {
        prodIDLabel1.setText (s);
    /** set prodNameLabel1 label */
    public void setProdNameLabel1 (String s) {
        prodNameLabel1.setText (s);
    /** set totalPrice1 label */
    public void setTotalPrice1 (String s) {
        totalPrice1.setText (s);
    /** populate transList0 with latest trans info */
    public void setTransList0 (Vector v){
        transList0.setListData (v);
    /** set itemPrice0 label */
    public void setItemPrice0 (String s) {
        itemPrice0.setText (s);
    /** draw prod images onto gui */
    public void paintImage (String imagePath) {
        // get Graphics
        Graphics g = prodImagePanel0.getGraphics ();
        // draw image into prodImagePanel0
        img = null;
        try {
            img = ImageIO.read (new File (imagePath));
        } catch (IOException e) {
            System.err.println ("Caught IOException: "
                    + e.getMessage ());
        // draw the image on screen
        g.drawImage (img, 2, 2, prodImagePanel0);
    /** Change image */
    public void updateImage (String imagePath){
        // draw image into prodImagePanel0
        img = null;
        try {
            img = ImageIO.read (new File (imagePath));
        } catch (IOException e) {
            System.err.println ("Caught IOException: "
                    + e.getMessage ());
GUIControl
import javax.swing.*;
import java.text.*;
* GUIControl.java
* The GUIControl class is responsible to perform actions requested from the GUIView class.
* It also liaises with the TransControl and ProdControl objects to generate output to the
* gui and handle input from the gui.
* @author Tim
public class GUIControl {
    // Declare object variables
    private GUIView gui;
    private ProdControl prodCtl0;
    private TransControl transCtl0;
    /** Creates a new instance of GUIControl */
    public GUIControl (ProdControl prodCtl0, TransControl transCtl0) {
        // make reference to prodCtl0, transCtl0 and gui objects
        this.prodCtl0 = prodCtl0;
        this.transCtl0 = transCtl0;
    /** Set gui view object */
    public void setGui (GUIView gui) {
        this.gui = gui;
    /** show the welcome dialouge */
    public void showWelcome (){
        // Call the showWelcomeMsg() method from gui to dispay welcome dialogue.
        gui.showWelcomeMsg ();
    /** find product */
    public Product findProd (int prodId){
        Product foundProd = prodCtl0.getProdByID (prodId);
        return foundProd;
    /** add product to transaction */
    public String addProdToTrans (int prodId, double transQuantity){
        // declare method variables
        String status = "Product not added";
        Product curProd0;
        // find prodduct by ID
        curProd0 = prodCtl0.getProdByID (prodId);
        //  1. if product exists then add a new transaction item to the transaction list.
        if (curProd0 != null) {
            // 2. check quantity is a whole number for UPC Products
            if (curProd0 instanceof UPCProd) {
                // check if the result is a whole number
                boolean isWhole = (Math.rint (transQuantity) == transQuantity);
                // 3. if isWhole is false change status message.
                if (isWhole == false) {
                    // return status as Product cannot be found.
                    status = "You must enter the quantity as a whole number for UPC products.";
                    return status;
                } else {
                    // 4. check there is enough stock in the store
                    if (transQuantity > curProd0.getQuantity ()) {
                        // return status as there is not enough stock.
                        status = "There is currently not enough stock to fulfill this transaction.  Please reduce the quantity." ;
                        return status;
                    } else {
                    }  // end if 4.
                }  // end if 3.
            } else {
            }  // end if 2.
            // add curProd as new transItem
            transCtl0.addTransItem (curProd0, transQuantity);
            // return status as null to notify that the Product was added.
            status = null;
            return status;
        } else {
            // return status as Product cannot be found.
            status = "Product " + prodId + " cannot be found.";
            return status;
        }  // end if 1.
    }  // end addProdToTrans method
    /** action Find button */
    public void findButtonAction (String prodId0, String quantity0){
        // status msg
        String status;
        // check prodId0 is not null
        if (prodId0.equals ("")) {
            // set status message to error and display error msg
            status = "Please enter a valid Product ID.";
            gui.showErrorMsg (status);
            // check quantity0 is not null
        } else if (quantity0.equals ("")) {
            // set status message to error and display error msg
            status = "Please enter a valid quantity.";
            gui.showErrorMsg (status);
        } else {
            // parse String values into int and double
            int prodId1 = Integer.parseInt (prodId0);
            double quantity1 = Double.parseDouble (quantity0);
            // reset prodIDInput0 and qtyInput0 text fields in the gui
            gui.setProdIDInput0 ("");
            gui.setQtyInput0 ("");
            // add trans item and return result as a string
            status = addProdToTrans (prodId1, quantity1);
            if (status == null) {
                updateProdTransView ();
            } else {
                // display msg to the user
                gui.showErrorMsg (status);
            } // end if
        } // end if
    } // end findButtonAction method
    /** update product and transaction view on gui */
    public void updateProdTransView (){
        // get the last trans item added
        TransItem lastTransItem0 = transCtl0.getLastTransItem ();
        // find the product
        Product p = findProd (lastTransItem0.getId ());
        // update product info displayed in the gui
        gui.setProdIDLabel1 (Integer.toString (p.getId ()));
        gui.setProdNameLabel1 (p.getName ());
        gui.setProdDescLabel1 (p.getDescription ());
        // paint prod image
        gui.paintImage (p.getImage ());
        // update transaction info displayed in the gui
        gui.setTransList0 (transCtl0.getTransItems ());
        gui.setItemPrice0 (transCtl0.transItemPriceInfo (lastTransItem0));
        // update total transaction cost displayed in the gui
        gui.setTotalPrice1 ("$" + transCtl0.transTotal ());
    } // end updateProdTransView method
    /** action Cancel button */
    public void cancelButtonAction (){
        // cleat transaction items from transaction array list
        transCtl0.clearTrans ();
        // reset gui components
        gui.setProdIDLabel1 ("");
        gui.setProdNameLabel1 ("");
        gui.setProdDescLabel1 ("");
        gui.setTransList0 (transCtl0.getTransItems ());
        gui.setItemPrice0 ("");
        gui.setTotalPrice1 ("$0.00");
        gui.paintImage ("images/transparent.gif");
}

Answer 1

happy to include more detail if required.You've included too much detail.
If you need further help then you need to create a [url http://homepage1.nifty.com/algafield/sscce.html]Short, Self Contained, Compilable and Executable, Example Program (SSCCE) that demonstrates the incorrect behaviour, because I can't guess exactly what you are doing based on the information provided.
Don't forget to use the [url http://forum.java.sun.com/help.jspa?sec=formatting]Code Formatting Tags so the posted code retains its original formatting.
And don't post code generated by NetBeans. It uses the GroupLayout which is not a standard layout manager until JDK6 and a lot of people don't use JDK6 yet so we won't be able to execute you code to see whats happening.