I need to
Modify the Inventory Program by adding a button to the GUI that allows the user to move to the first item, the previous item, the next item, and the last item in the inventory. If the first item is displayed and the user clicks on the Previous button, the last item should display. If the last item is displayed and the user clicks on the Next button, the first item
should display.
Add a company logo to the GUI using Java graphics classes.

This is what I have so far.

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
 
    public void actionPerformed(ActionEvent e)
    {
        int index = ((JComboBox)e.getSource()).getSelectedIndex();
        populateFields(index);
    }
 
    public static void main(String[] args) 
    {
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
  
    /**
     * 
     */
    public void initCD() {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
        //Sort elements in array in alphabetical order by product name
//        product[0].sortItems(product);
    final JButton firstBtn = new JButton("First"); // first button
final JButton prevBtn = new JButton("Previous"); // previous button
final JButton nextBtn = new JButton("Next"); // next button
final JButton lastBtn = new JButton("Last"); // last button
final JLabel label; // logo
final JTextArea textArea; // text area for product list
final JPanel buttonJPanel; // panel to hold buttons
//JLabel constructor for logo
Icon logo = new ImageIcon("C:/logo.jpg"); // load logo
label = new JLabel(logo); // create logo label
label.setToolTipText("Company Logo"); // create tooltip


    }
    
    
        
    private void showGUI() {
        JLabel l;
        JButton b;
        fields = new JTextField[9];
        JComboBox combo = new JComboBox();
        for(int j = 0; j < product.length; j++)
            combo.addItem(product[j].getName());
        combo.addActionListener(this);
        JFrame f = new JFrame("InventoryGUI");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        cp.add(b = new JButton("OK"), c);
        cp.add(b = new JButton("First"),c); // set up panel
        cp.add(b = new JButton("Prev"),c);
        cp.add(b = new JButton("Next"),c);
        cp.add(b = new JButton("Last"),c);
        b.setMnemonic('o');
        f.pack();
        f.addWindowListener(new WindowAdapter()

        {
            public void windowClosing(WindowEvent evt) 
            {
                System.exit(0);
            }
        });
        f.setVisible(true);
        
    }
 
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    }
}
 
class CD {
      
    int itemNumber;
    String name;
    int units;
    double price;
    String itemCode; 
  
    public CD(int n, String name, double price, int units, String itemCo) {
        itemNumber = n;
        this.name = name;
        this.price = price;
        this.units = units;
        itemCode = itemCo;
    }

    public int getNumberCode() { return itemNumber; }
    public String getName() { return name; }
    public int getUnits() { return units; }
    public double getPrice() { return price; }
    public double getSum() { return units*price; }
    public String getCode() { return itemCode; }
 
    public double totalAllInventory(CD[] cds) {
        double total = 0;
        for(int j = 0; j < cds.length; j++)
            total += cds[j].getSum();
        return total;
    }
}

public class InventoryI {
        
    String productnumber;
 
    String name;
 
    int numberofunits;
 
    double priceperunit;
        
        String itemcode; 
        

    // Create a new instance of Inventory
    // main constructor for the class
    public InventoryI(String Item_Number, String Item_Name, int Items_in_Stock,
            double Item_Price, String Item_Code) {
        productnumber = Item_Number;
        name = Item_Name;
        numberofunits = Items_in_Stock;
        priceperunit = Item_Price;
                itemcode = Item_Code;
    }        
 
    public void setItemName(String Item_Name) {
    // sets the items name

        name = Item_Name;
    }
 
    public void setItemCode(String Item_Code) {
    // sets the items name

        itemcode = Item_Code;
    }
        public void setItemNumber(String Item_Number) { // Sets the Product =Number
    // for the item
 
        productnumber = Item_Number;
    }
 
    public void setItemsInStock(int Items_in_Stock) { // sets the =number of
    // units in stock
 
        numberofunits = Items_in_Stock;
    }
 
    public void setItemPrice(double Item_Price) { // sets the price of =the
    // item
        priceperunit = Item_Price;
    }
       
        public String getItemName() { // returns the Product Name of this item
        return name;
    }
 
     public String getItemCode() { // returns the Product Name of this item
        return itemcode;
        }
         
        public String getItemNumber() { // returns the Product Number of the =item
 
        return productnumber;
    }
 
    public int getItemsInStock() { // returns how many units are in stock
        return numberofunits;
    }
 
    public double getItemPrice() { // returns the price of the item
        return priceperunit;
    }
 
    public double getInventoryIValue() { // returns the total value of =the stock
    // for this item
        return priceperunit * numberofunits;
    }
        
    public static double getTotalValueOfAllInventory(InventoryI [] inv) {
    
            double tot = 0.0;
        
        for(int i = 0; i < inv.length; i++)   
                
            tot += inv[i].getInventoryIValue();
        
        return tot;
        
    }
    
    public static InventoryI[] sort(InventoryI [] inventory)
    {
        InventoryI temp[] = new InventoryI[1];
         
        //sorting the array using Bubble Sort
        for(int j = 0; j < inventory.length - 1; j++)
        {
         
            for(int k = 0; k < inventory.length - 1; k++)
            {
         
                if(inventory[k].getItemName().compareToIgnoreCase(inventory[k+1].getItemName()) > 0)
                {
         
                    temp[0] = inventory[k];
                    inventory[k] = inventory[k+1];
                    inventory[k+1] = temp[0];
         
                }//end if
         
            }//end for loop
         
        }//end for loop

        
        return inventory;
    }
    
    public String toString()
    {
        StringBuffer sb = new StringBuffer();
        
                
        sb.append("CD Title:      \t").append(name).append("\n");
                                    sb.append("Item Code:      \t").append(itemcode).append("\n");
        sb.append("Item #:           \t").append(productnumber).append("\n");
        sb.append("Number in stock:\t").append(numberofunits).append("\n");
        sb.append("Price:          \t").append(String.format("$%.2f%n", priceperunit));
        sb.append("Inventory Value:\t").append(String.format("$%.2f%n", this.getInventoryIValue()));
 
        return sb.toString();
    }
    
    
}

I forgot to say that my code compiles and runs showing the buttons but the buttons do nothing.

You actually define the buttons twice, once in the initCD() method and then again in showGUI(), but you do not add any ActionListeners (or Actions, both are valid) to be executed when the buttons are pressed.
How To Use Actions

here is the code with changes,

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain extends Frame implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
    JButton b;
    
    public void actionPerformed(ActionEvent e)
    {
        int index = ((JComboBox)e.getSource()).getSelectedIndex();
        populateFields(index);
    }
  
    public static void main(String[] args) 
    {
        
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
  
    /**
     * 
     */
    public void initCD() {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
        //Sort elements in array in alphabetical order by product name
    // product[0].sortItems(product);
       b = new JButton("First"); // first button
       b.addActionListener(this);
       b = new JButton("Previous"); // previous button
       b.addActionListener(this);
       b = new JButton("Next"); // next button
       b.addActionListener(this);
       b = new JButton("Last"); // last button
       
    }
    
      // inner class for button event handling
   private class ButtonHandler implements ActionListener
   {

      // handle button event
      public void actionPerformed( ActionEvent event )

      {
 

//           System.out.println(event.getActionCommand());
 

         // See which button was pressed
         if (event.getActionCommand()== "Next"){

 
        }

       else if (event.getActionCommand()== "Prev"){

       
        }
         else if (event.getActionCommand()== "Last"){

         
         }
           else if (event.getActionCommand()== "First"){
             

           }
 

       } // end method actionPerformed

   } // end private inner class ButtonHandler
        
    private void showGUI() {
        JLabel l;
        JButton b;
        fields = new JTextField[9];
        JComboBox combo = new JComboBox();
        for(int j = 0; j < product.length; j++)
            combo.addItem(product[j].getName());
        combo.addActionListener(this);
        JFrame f = new JFrame("InventoryGUI");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        cp.add(b = new JButton("OK"), c); 
        cp.add(b = new JButton("First"),c);             
        cp.add(b = new JButton("Prev"),c);             
        cp.add(b = new JButton("Next"),c);
        cp.add(b = new JButton("Last"),c);
        b.setMnemonic('o');
        f.pack();
        f.addWindowListener(new WindowAdapter()

        {
            public void windowClosing(WindowEvent evt) 
            {
                System.exit(0);
            }
        });
        f.setVisible(true);
        
    }
 
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    }
}
 
class CD {
      
    int itemNumber;
    String name;
    int units;
    double price;
    String itemCode; 
    String command;
    public CD(int n, String name, double price, int units, String itemCo) {
        itemNumber = n;
        this.name = name;
        this.price = price;
        this.units = units;
        itemCode = itemCo;
    }

    public int getNumberCode() { return itemNumber; }
    public String getName() { return name; }
    public int getUnits() { return units; }
    public double getPrice() { return price; }
    public double getSum() { return units*price; }
    public String getCode() { return itemCode; }
    public String getActionnCommand() {return command; }
    public double totalAllInventory(CD[] cds) {
        double total = 0;
        for(int j = 0; j < cds.length; j++)
            total += cds[j].getSum();
        return total;
    }
}

public class InventoryI {
        
    String productnumber;
 
    String name;
 
    int numberofunits;
 
    double priceperunit;
        
        String itemcode; 
        
        String command; 
        

    // Create a new instance of Inventory
    // main constructor for the class
    public InventoryI(String Item_Number, String Item_Name, int Items_in_Stock,
            double Item_Price, String Item_Code) {
        productnumber = Item_Number;
        name = Item_Name;
        numberofunits = Items_in_Stock;
        priceperunit = Item_Price;
                itemcode = Item_Code;
    }        
 
    public void setItemName(String Item_Name) {
    // sets the items name

        name = Item_Name;
    }
 
    public void setItemCode(String Item_Code) {
    // sets the items name

        itemcode = Item_Code;
    }
        public void setItemNumber(String Item_Number) { // Sets the Product =Number
    // for the item
 
        productnumber = Item_Number;
    }
 
    public void setItemsInStock(int Items_in_Stock) { // sets the =number of
    // units in stock
 
        numberofunits = Items_in_Stock;
    }
 
    public void setItemPrice(double Item_Price) { // sets the price of =the
    // item
        priceperunit = Item_Price;
    }
       
        public String getItemName() { // returns the Product Name of this item
        return name;
    }
 
     public String getItemCode() { // returns the Product Name of this item
        return itemcode;
        }
         
        public String getItemNumber() { // returns the Product Number of the =item
 
        return productnumber;
    }
 
    public int getItemsInStock() { // returns how many units are in stock
        return numberofunits;
    }
 
    public double getItemPrice() { // returns the price of the item
        return priceperunit;
    }
 
    public double getInventoryIValue() { // returns the total value of =the stock
    // for this item
        return priceperunit * numberofunits;
    }
        
    public static double getTotalValueOfAllInventory(InventoryI [] inv) {
    
            double tot = 0.0;
        
        for(int i = 0; i < inv.length; i++)   
                
            tot += inv[i].getInventoryIValue();
        
        return tot;
        
    }
    
    public static InventoryI[] sort(InventoryI [] inventory)
    {
        InventoryI temp[] = new InventoryI[1];
         
        //sorting the array using Bubble Sort
        for(int j = 0; j < inventory.length - 1; j++)
        {
         
            for(int k = 0; k < inventory.length - 1; k++)
            {
         
                if(inventory[k].getItemName().compareToIgnoreCase(inventory[k+1].getItemName()) > 0)
                {
         
                    temp[0] = inventory[k];
                    inventory[k] = inventory[k+1];
                    inventory[k+1] = temp[0];
         
                }//end if
         
            }//end for loop
         
        }//end for loop

        
        return inventory;
                
    }
    
    public String toString()
    {
        StringBuffer sb = new StringBuffer();
        
                
        sb.append("CD Title:      \t").append(name).append("\n");
                sb.append("Item Code:      \t").append(itemcode).append("\n");
        sb.append("Item #:           \t").append(productnumber).append("\n");
        sb.append("Number in stock:\t").append(numberofunits).append("\n");
        sb.append("Price:          \t").append(String.format("$%.2f%n", priceperunit));
        sb.append("Inventory Value:\t").append(String.format("$%.2f%n", this.getInventoryIValue()));
 
        return sb.toString();
                
                
    }
    
    
}
b = new JButton("First"); // first button
       b.addActionListener(this);
       b = new JButton("Previous"); // previous button
       b.addActionListener(this);
       b = new JButton("Next"); // next button
       b.addActionListener(this);

Still does not do anything. You are assigning "b" instances of new buttons (replacing the previous each time I might add), but the buttons that are getting added to the panel are being created in showGUI(). You need to add the action listener to the button that is being added to the panel. Also, your current action listener implementation is picking up the combo box index. Each button will need to have its own action to perform.

Ok, I changes it so the action listener is added to the buttons that are being added to the panel annd still nothing. by the way, i want to thank you for all your help and advice, they are much appreciated.

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain extends Frame implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
    JButton b;
    
    public void actionPerformed(ActionEvent e)
    {
        int index = ((JComboBox)e.getSource()).getSelectedIndex();
        populateFields(index);
    }
     // inner class for button event handling
   private class ButtonHandler implements ActionListener
   {

      // handle button event
      public void actionPerformed( ActionEvent event )

      {
 

          System.out.println(event.getActionCommand());
 

         // See which button was pressed
         if (event.getActionCommand()== "Next"){

 
        }

       else if (event.getActionCommand()== "Prev"){

       
        }
         else if (event.getActionCommand()== "Last"){

         
         }
           else if (event.getActionCommand()== "First"){
             

           }
 

       } // end method actionPerformed

   } // end private inner class ButtonHandler
    public static void main(String[] args) 
    {
        
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
  
    /**
     * 
     */
    public void initCD() {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
        //Sort elements in array in alphabetical order by product name
    // product[0].sortItems(product);
       b = new JButton("First"); // first button      
       b = new JButton("Previous"); // previous button
       b = new JButton("Next"); // next button
       b = new JButton("Last"); // last button
    
       
    }
    
     
        
    private void showGUI() {
        JLabel l;
        JButton b;
        fields = new JTextField[9];
        JComboBox combo = new JComboBox();
        for(int j = 0; j < product.length; j++)
            combo.addItem(product[j].getName());
       
        JFrame f = new JFrame("InventoryGUI");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        cp.add(b = new JButton("OK"), c);
        b.addActionListener(this);
        cp.add(b = new JButton("First"),c); 
        b.addActionListener(this);
        cp.add(b = new JButton("Prev"),c);
        b.addActionListener(this);
        cp.add(b = new JButton("Next"),c);
        b.addActionListener(this);
        cp.add(b = new JButton("Last"),c);
        b.addActionListener(this);
        b.setMnemonic('o');
        f.pack();
        f.addWindowListener(new WindowAdapter()

        {
            public void windowClosing(WindowEvent evt) 
            {
                System.exit(0);
            }
        });
        f.setVisible(true);
        
    }
 
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    }
}
 
class CD {
      
    int itemNumber;
    String name;
    int units;
    double price;
    String itemCode; 
    String command;
    public CD(int n, String name, double price, int units, String itemCo) {
        itemNumber = n;
        this.name = name;
        this.price = price;
        this.units = units;
        itemCode = itemCo;
    }

    public int getNumberCode() { return itemNumber; }
    public String getName() { return name; }
    public int getUnits() { return units; }
    public double getPrice() { return price; }
    public double getSum() { return units*price; }
    public String getCode() { return itemCode; }
    public String getActionnCommand() {return command; }
    public double totalAllInventory(CD[] cds) {
        double total = 0;
        for(int j = 0; j < cds.length; j++)
            total += cds[j].getSum();
        return total;
    }
}

public class InventoryI {
        
    String productnumber;
 
    String name;
 
    int numberofunits;
 
    double priceperunit;
        
        String itemcode; 
        
        String command; 
        

    // Create a new instance of Inventory
    // main constructor for the class
    public InventoryI(String Item_Number, String Item_Name, int Items_in_Stock,
            double Item_Price, String Item_Code) {
        productnumber = Item_Number;
        name = Item_Name;
        numberofunits = Items_in_Stock;
        priceperunit = Item_Price;
                itemcode = Item_Code;
    }        
 
    public void setItemName(String Item_Name) {
    // sets the items name

        name = Item_Name;
    }
 
    public void setItemCode(String Item_Code) {
    // sets the items name

        itemcode = Item_Code;
    }
        public void setItemNumber(String Item_Number) { // Sets the Product =Number
    // for the item
 
        productnumber = Item_Number;
    }
 
    public void setItemsInStock(int Items_in_Stock) { // sets the =number of
    // units in stock
 
        numberofunits = Items_in_Stock;
    }
 
    public void setItemPrice(double Item_Price) { // sets the price of =the
    // item
        priceperunit = Item_Price;
    }
       
        public String getItemName() { // returns the Product Name of this item
        return name;
    }
 
     public String getItemCode() { // returns the Product Name of this item
        return itemcode;
        }
         
        public String getItemNumber() { // returns the Product Number of the =item
 
        return productnumber;
    }
 
    public int getItemsInStock() { // returns how many units are in stock
        return numberofunits;
    }
 
    public double getItemPrice() { // returns the price of the item
        return priceperunit;
    }
 
    public double getInventoryIValue() { // returns the total value of =the stock
    // for this item
        return priceperunit * numberofunits;
    }
        
    public static double getTotalValueOfAllInventory(InventoryI [] inv) {
    
            double tot = 0.0;
        
        for(int i = 0; i < inv.length; i++)   
                
            tot += inv[i].getInventoryIValue();
        
        return tot;
        
    }
    
    public static InventoryI[] sort(InventoryI [] inventory)
    {
        InventoryI temp[] = new InventoryI[1];
         
        //sorting the array using Bubble Sort
        for(int j = 0; j < inventory.length - 1; j++)
        {
         
            for(int k = 0; k < inventory.length - 1; k++)
            {
         
                if(inventory[k].getItemName().compareToIgnoreCase(inventory[k+1].getItemName()) > 0)
                {
         
                    temp[0] = inventory[k];
                    inventory[k] = inventory[k+1];
                    inventory[k+1] = temp[0];
         
                }//end if
         
            }//end for loop
         
        }//end for loop

        
        return inventory;
                
    }
    
    public String toString()
    {
        StringBuffer sb = new StringBuffer();
        
                
        sb.append("CD Title:      \t").append(name).append("\n");
                sb.append("Item Code:      \t").append(itemcode).append("\n");
        sb.append("Item #:           \t").append(productnumber).append("\n");
        sb.append("Number in stock:\t").append(numberofunits).append("\n");
        sb.append("Price:          \t").append(String.format("$%.2f%n", priceperunit));
        sb.append("Inventory Value:\t").append(String.format("$%.2f%n", this.getInventoryIValue()));
 
        return sb.toString();
                
                
    }
    
    
}

To be fair this program is in mess you should organize it little, good thing is you willing to work on it.
Bellow are some uptades for you, check the red marked parts.

PS: Can you please next time put each java file is separated code tags? Thanx

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain extends Frame implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
    JButton jbtOk, jbtFirst, jbtPrev, jbtNext, jbtLast;
    
    public static void main(String[] args) 
    {        
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
    
    /* DOESN'T DO ANYTHING
     public void actionPerformed(ActionEvent e)
    {
        int index = ((JComboBox)e.getSource()).getSelectedIndex();
        populateFields(index);
    }
     // inner class for button event handling
   private class ButtonHandler implements ActionListener
   {
      // handle button event
      public void actionPerformed( ActionEvent event )
      {
          System.out.println(event.getActionCommand());
         // See which button was pressed
         if (event.getActionCommand()== "Next"){ 
        }

       else if (event.getActionCommand()== "Prev"){
       
        }
         else if (event.getActionCommand()== "Last"){
         
         }
           else if (event.getActionCommand()== "First"){             

           }
       } // end method actionPerformed

   } // end private inner class ButtonHandler*/
    
    public void actionPerformed(ActionEvent ae)
    {
    	if(ae.getSource() == jbtOk)
    	{
    		// add OK button functionality
    		System.out.println("OK pressed");
    	}
    	if(ae.getSource() == jbtFirst)
    	{
    		// add First button functionality
    		System.out.println("FIRST pressed");
    	}
    	if(ae.getSource() == jbtPrev)
    	{
    		// add Previous button functionality
    		System.out.println("PREVIOUS pressed");
    	}
    	if(ae.getSource() == jbtNext)
    	{
    		// add Next button functionality
    		System.out.println("NEXT pressed");
    	}
    	if(ae.getSource() == jbtLast)
    	{
    		// add Last button functionality
    		System.out.println("LAST pressed");
    	}
    }
    
    public void initCD() 
    {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
        //Sort elements in array in alphabetical order by product name
   		// product[0].sortItems(product);
   		
       /* WHAT IS THIS FOR ? ? ?
       b = new JButton("First"); // first button      
       b = new JButton("Previous"); // previous button
       b = new JButton("Next"); // next button
       b = new JButton("Last"); // last button */      
    }
    
     
        
    private void showGUI() 
    {
        JLabel l;
        /* ONE BUTTON DOESN'T DO FOR ALL ! ! !
           ALSO THIS IS SECOND DECLARATION OF THE BUTTON, ONE ON THE START
         JButton b;*/
        fields = new JTextField[9];
        JComboBox combo = new JComboBox();
        for(int j = 0; j < product.length; j++)
            combo.addItem(product[j].getName());
       
        JFrame f = new JFrame("InventoryGUI");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        jbtOk = new JButton("OK");
        jbtOk.addActionListener(this);
        jbtFirst = new JButton("First");
        jbtFirst.addActionListener(this);
        jbtPrev = new JButton("Previous");
        jbtPrev.addActionListener(this);
        jbtNext = new JButton("Next");
        jbtNext.addActionListener(this);
        jbtLast = new JButton("Last");
        jbtLast.addActionListener(this);
        
        cp.add(jbtOk, c);
        cp.add(jbtFirst, c);
        cp.add(jbtPrev, c);
        cp.add(jbtNext, c);
        cp.add(jbtLast, c);
        /* INTERESTING SHORTCUT BUT YOU OVERWRITING YOUR BUTTON b
         	THAT IS ONE OF THE REASONS WHY NOTHING IS WORKING FOR YOU ! ! !
        cp.add(b = new JButton("OK"), c);
        b.addActionListener(this);
        cp.add(b = new JButton("First"),c); 
        b.addActionListener(this);
        cp.add(b = new JButton("Prev"),c);
        b.addActionListener(this);
        cp.add(b = new JButton("Next"),c);
        b.addActionListener(this);
        cp.add(b = new JButton("Last"),c);
        b.addActionListener(this);*/
        
        /* ASIGN MNEMONIC TO WHICH OF THE BUTTONS ? ? ?
         b.setMnemonic('o');*/
        f.pack();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        /* ABOVE IS SIMPLER SOLUTION
         f.addWindowListener(new WindowAdapter()

        {
            public void windowClosing(WindowEvent evt) 
            {
                System.exit(0);
            }
        });*/
        f.setVisible(true);
        
    }
 
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    }
}

Thank you for the help, I was up all night last night and got my buttons to print out that they were pushed but I still can not get them to function so that if the list is at the first item and I push previous button the list will show the last item and so on. I have been trying to get my code to do that for the last 32 hours, I even fell asleep with my fingers on the keyboard and woke up from dreaming about java coding. lol lol. if you can point me in the right direction it would be much appreciated, dont get me wrong I'm not asking you to do it for me I'm just asking for a little help.
once again I want to thank you for your help.

It looks to me like you have written the whole thing in one go and now you're trying to back pedal.

What you should have done is to hit compile and run and check at each stage if it's correct!

If you keep a pointer to the current record int currentIndex; then moving within your array is trivial. You just increment the index as needed and populate the fields based on that index.

I'm sorry I am still new to this and do not understand the language yet, so I did not understand what you mean?

What Ezzaral is sugesting is create a variable which will hold value/position of currently selected item. On the start it will be zero as you wish to display first value from your array. When you press Next this value get increased by one. When you press Previous get decreased. Last it will change to length of your array minus one. If First selected the value will set to zero.
When this done you should thing what you want to happens when you reach last position of array. Do you want to start automaticaly from first array variable or you want to disable next move. Then apply same for first position in the array

i want to thank both of you for helping me.

ok, this is what I have done but the buttons still do not change the inventory to the next, previous, or the others.

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain extends Frame implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
    JButton jbtOk, jbtFirst, jbtPrev, jbtNext, jbtLast;
        static int dispProd = 0; // variable for actionEvents
    // main method begins execution of java application
 
    static JTextArea textArea;
 
    public static void main(String[] args) 
    {
           int i; // varialbe for looping
        double total = 0; // variable for total inventory
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
  
      public void actionPerformed(ActionEvent ae)
    {
        if(ae.getSource() == jbtOk)
        {
            // add OK button functionality
            System.out.println("OK pressed");
        }
        if(ae.getSource() == jbtFirst)
        {
            // add First button functionality
            System.out.println("FIRST pressed");
        }
        if(ae.getSource() == jbtPrev)
        {
            // add Previous button functionality
            System.out.println("PREVIOUS pressed");
        }
        if(ae.getSource() == jbtNext)
        {
            // add Next button functionality
            System.out.println("NEXT pressed");
        }
        if(ae.getSource() == jbtLast)
        {
            // add Last button functionality
            System.out.println("LAST pressed");
        }
    }
    
    public void initCD() {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
      //Sort elements in array in alphabetical order by product name
           // product[0].sortItems(product);
      
    
       
    }
private void showGUI() {
        JLabel l;
        JButton b;
        fields = new JTextField[9];
        JComboBox combo = new JComboBox();
        for(int j = 0; j < product.length; j++)
        combo.addItem(product[j].getName());
        combo.addActionListener(this);
        JFrame f = new JFrame("InventoryGUI");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        jbtOk = new JButton("OK");
        jbtOk.addActionListener(this);
        jbtFirst = new JButton("First");
        jbtFirst.addActionListener(this);
        jbtPrev = new JButton("Previous");
        jbtPrev.addActionListener(this);
        jbtNext = new JButton("Next");
        jbtNext.addActionListener(this);
        jbtLast = new JButton("Last");
        jbtLast.addActionListener(this);
        
        cp.add(jbtOk, c);
        cp.add(jbtFirst, c);
        cp.add(jbtPrev, c);
        cp.add(jbtNext, c);
        cp.add(jbtLast, c);
        f.pack();
       f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
           // assign actionListener and actionEvent for each button
        jbtFirst.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = 0;
                
 
            } // end firstBtn actionEvent
 
        }); // end firstBtn actionListener
 
 
        jbtPrev.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd--;
                if (dispProd < 0)
                {
                    dispProd = 0;
                }
                 dispProd = (product.length+dispProd-1) % product.length;
               
            } // end prevBtn actionEvent
        }); // end prevBtn actionListener
 
        jbtLast.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = product.length - 1;
                
 
            } // end lastBtn actionEvent
 
        }); // end lastBtn actionListener
 
        jbtNext.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd++;
                if (dispProd >= product.length)
                {
                    dispProd = product.length - 1;
                }
               
            } // end nextBtn actionEvent
        }); // end nextBtn actionListener
    }
 
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    }
}

It is still working, you just do not see output on command line don't you? Or you do not know where this is comming from? Why you not getting action from "your" ActionListeners?
Well answer is very simple. You have 2 ActionListeners. One is top level which I created

public void actionPerformed(ActionEvent ae)
    {
        if(ae.getSource() == jbtOk)
        {
            // add OK button functionality
            System.out.println("OK pressed");
        }
        if(ae.getSource() == jbtFirst)
        {
            // add First button functionality
            System.out.println("FIRST pressed");
        }
        if(ae.getSource() == jbtPrev)
        {
            // add Previous button functionality
            System.out.println("PREVIOUS pressed");
        }
        if(ae.getSource() == jbtNext)
        {
            // add Next button functionality
            System.out.println("NEXT pressed");
        }
        if(ae.getSource() == jbtLast)
        {
            // add Last button functionality
            System.out.println("LAST pressed");
        }
    }

and then there are yours anonymous inner class listeners like this one

jbtFirst.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = 0;
                
 
            } // end firstBtn actionEvent
 
        }); // end firstBtn actionListener

So all action events by buttons get catch by my event handle as it is top level instead of yours. Simply comment out content of my actionPerformed() method /* */, just content not whole or you get error for JComboBox to which you assign event but not handle anywhere

combo.addActionListener(this);

and do not forget to call a method for updating content of the fields, the one in red

jbtNext.addActionListener(new ActionListener() 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd++;
                if (dispProd >= product.length)
                {                	
                    dispProd = product.length - 1;
                }
                populateFields(dispProd);
            } // end nextBtn actionEvent
        }); // end nextBtn actionListener

PS: You may complitely remove my event handler once you implement anonymous inner class event handler for that combo box.

the next button needs to navagate to the next item when pushed and the previous button needs to navagate to the previous item and so on. The buttons just print out that they have been pushed and thats it. I am having a hard time understanding.

Just delete event handle created by me, create event handler for JComboBox and call following method

populateFields(dispProd);

to update your fields...

I did what you suggested and now I get these errors:

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: javax.swing.JButton cannot be cast to javax.swing.JComboBox
at inventoryi.InventoryMain.actionPerformed(InventoryI.java:48)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.java:6038)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3260)
at java.awt.Component.processEvent(Component.java:5803)
at java.awt.Container.processEvent(Container.java:2058)
at java.awt.Component.dispatchEventImpl(Component.java:4410)
at java.awt.Container.dispatchEventImpl(Container.java:2116)
at java.awt.Component.dispatchEvent(Component.java:4240)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
at java.awt.Container.dispatchEventImpl(Container.java:2102)
at java.awt.Window.dispatchEventImpl(Window.java:2429)
at java.awt.Component.dispatchEvent(Component.java:4240)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)


This is my code that I get errors

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain extends Frame implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
    JButton jbtOk, jbtFirst, jbtPrev, jbtNext, jbtLast;
    JLabel label; // logo   
    JPanel buttonJPanel; // panel to hold buttons
    String nameText;
    private int index; 
    int i; // varialbe for looping
    double total = 0; // variable for total inventory   
    static int dispProd = 0; // variable for actionEvents   
    static JTextArea textArea;
 
     public void actionPerformed(ActionEvent e)
    {
        int index = ((JComboBox)e.getSource()).getSelectedIndex();
        populateFields(dispProd);
    }
    
    public static void main(String[] args) 
    {
           
       
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
  
   
    
    public void initCD() {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
      //Sort elements in array in alphabetical order by product name
           // product[0].sortItems(product);
      
    
    }
    
     
        
    private void showGUI() {
        JLabel l;
        JButton b;
        fields = new JTextField[9];
        JComboBox combo = new JComboBox();
        for(int j = 0; j < product.length; j++)
        combo.addItem(product[j].getName());
        combo.addActionListener(this);
          Icon logo = new ImageIcon("C:/logo.jpg"); // load logo
        label = new JLabel(logo); // create logo label
        label.setToolTipText("Company Logo"); // create tooltip
            textArea = new JTextArea(product[3] + "\n"); // create textArea for
                                                        // product display
        JFrame f = new JFrame("CD Inventory");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        
        jbtOk = new JButton("OK");
        jbtOk.addActionListener(this);
        jbtFirst = new JButton("First");
        jbtFirst.addActionListener(this);
        jbtPrev = new JButton("Previous");
        jbtPrev.addActionListener(this);
        jbtNext = new JButton("Next");
        jbtNext.addActionListener(this);
        jbtLast = new JButton("Last");
        jbtLast.addActionListener(this);
        
        cp.add(jbtOk, c);
        cp.add(jbtFirst, c);
        cp.add(jbtPrev, c);
        cp.add(jbtNext, c);
        cp.add(jbtLast, c);
        f.pack();
       f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
           
// assign actionListener and actionEvent for each button
        jbtFirst.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = 0;
                
 
            } // end firstBtn actionEvent
 
        }); // end firstBtn actionListener
 
 
        jbtPrev.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd--;
                if (dispProd < 0)
                {
                    dispProd = product.length - 1;
                }
                 dispProd = (product.length+dispProd-1) % product.length;
               
            } // end prevBtn actionEvent
        }); // end prevBtn actionListener
 
        jbtLast.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = product.length - 1;
                
           
            } // end lastBtn actionEvent
 
        }); // end lastBtn actionListener
 
        jbtNext.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd++;
                if (dispProd >= product.length - 1)
                {
                    dispProd = 0;
                }
               
            } // end nextBtn actionEvent
        }); // end nextBtn actionListener
    }
 
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    }
class CD {
      
    int itemNumber;
    String name;
    int units;
    double price;
    String itemCode; 
    String command;
    public CD(int n, String name, double price, int units, String itemCo) {
        itemNumber = n;
        this.name = name;
        this.price = price;
        this.units = units;
        itemCode = itemCo;
    }

    public int getNumberCode() { return itemNumber; }
    public String getName() { return name; }
    public int getUnits() { return units; }
    public double getPrice() { return price; }
    public double getSum() { return units*price; }
    public String getCode() { return itemCode; }
    public String getActionnCommand() {return command; }
    public double totalAllInventory(CD[] cds) {
        double total = 0;
        for(int j = 0; j < cds.length; j++)
            total += cds[j].getSum();
        return total;
    }
}

public class InventoryI {
        
    String productnumber;
 
    String name;
 
    String Text;
        
        int numberofunits;
 
    double priceperunit;
        
        String itemcode; 
        
        String command; 
        

    // Create a new instance of Inventory
    // main constructor for the class
    public InventoryI(String Item_Number, String Item_Name, int Items_in_Stock,
            double Item_Price, String Item_Code) {
        productnumber = Item_Number;
        name = Item_Name;
        numberofunits = Items_in_Stock;
        priceperunit = Item_Price;
                itemcode = Item_Code;
    }        
 
    public void setItemName(String Item_Name) {
    // sets the items name

        name = Item_Name;
    }
 
    public void setItemCode(String Item_Code) {
    // sets the items name

        itemcode = Item_Code;
    }
        public void setItemNumber(String Item_Number) { // Sets the Product =Number
    // for the item
 
        productnumber = Item_Number;
    }
 
    public void setItemsInStock(int Items_in_Stock) { // sets the =number of
    // units in stock
 
        numberofunits = Items_in_Stock;
    }
 
    public void setItemPrice(double Item_Price) { // sets the price of =the
    // item
        priceperunit = Item_Price;
    }
       
        public String getItemName() { // returns the Product Name of this item
        return name;
    }
 
     public String getItemCode() { // returns the Product Name of this item
        return itemcode;
        }
         
        public String getItemNumber() { // returns the Product Number of the =item
 
        return productnumber;
    }
 
    public int getItemsInStock() { // returns how many units are in stock
        return numberofunits;
    }
 
    public double getItemPrice() { // returns the price of the item
        return priceperunit;
    }
 
    public double getInventoryIValue() { // returns the total value of =the stock
    // for this item
        return priceperunit * numberofunits;
    }
        
    public static double getTotalValueOfAllInventory(InventoryI [] inv) {
    
            double tot = 0.0;
        
        for(int i = 0; i < inv.length; i++)   
                
            tot += inv[i].getInventoryIValue();
        
        return tot;
        
    }
    
    public static InventoryI[] sort(InventoryI [] inventory)
    {
        InventoryI temp[] = new InventoryI[1];
         
        //sorting the array using Bubble Sort
        for(int j = 0; j < inventory.length - 1; j++)
        {
         
            for(int k = 0; k < inventory.length - 1; k++)
            {
         
                if(inventory[k].getItemName().compareToIgnoreCase(inventory[k+1].getItemName()) > 0)
                {
         
                    temp[0] = inventory[k];
                    inventory[k] = inventory[k+1];
                    inventory[k+1] = temp[0];
         
                }//end if
         
            }//end for loop
         
        }//end for loop

        
        return inventory;
                
    }
    
    public String toString()
    {
        StringBuffer sb = new StringBuffer();
        
                
        sb.append("CD Title:      \t").append(name).append("\n");
                sb.append("Item Code:      \t").append(itemcode).append("\n");
        sb.append("Item #:           \t").append(productnumber).append("\n");
        sb.append("Number in stock:\t").append(numberofunits).append("\n");
        sb.append("Price:          \t").append(String.format("$%.2f%n", priceperunit));
        sb.append("Inventory Value:\t").append(String.format("$%.2f%n", this.getInventoryIValue()));
 
        return sb.toString();
                
                
    }
    
    
}

I don't think this is best way to implement event handler for JComboBox

public void actionPerformed(ActionEvent e)
    {
        int index = ((JComboBox)e.getSource()).getSelectedIndex();
        populateFields(dispProd);
    }

aslo I moved your declaration of JComboBox from ShowGUI() on the start with other variables only initialization is left there. You OK button doesn't do anything as you did not create anonymous event handler for it, like other buttons, and has no action declared in top level event handler with JComboBox

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain extends Frame implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
    JButton jbtOk, jbtFirst, jbtPrev, jbtNext, jbtLast;
    JLabel label; // logo   
    JPanel buttonJPanel; // panel to hold buttons
    String nameText;
    JComboBox combo;  // New place to declare combo box
    private int index; 
    int i; // varialbe for looping
    double total = 0; // variable for total inventory   
    static int dispProd = 0; // variable for actionEvents   
    static JTextArea textArea;     
    
    public static void main(String[] args) 
    {
           
       
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
  
   
    
    public void initCD() {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
      //Sort elements in array in alphabetical order by product name
           // product[0].sortItems(product);
      
    
    }
    
    private void showGUI() {
        JLabel l;
        JButton b;
        fields = new JTextField[9];
        combo = new JComboBox(); // combo box initialization left sa was
        for(int j = 0; j < product.length; j++)
        combo.addItem(product[j].getName());
        combo.addActionListener(this);
          Icon logo = new ImageIcon("C:/logo.jpg"); // load logo
        label = new JLabel(logo); // create logo label
        label.setToolTipText("Company Logo"); // create tooltip
            textArea = new JTextArea(product[3] + "\n"); // create textArea for
                                                        // product display
        JFrame f = new JFrame("CD Inventory");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        
        jbtOk = new JButton("OK");
        jbtOk.addActionListener(this);
        jbtFirst = new JButton("First");
        jbtFirst.addActionListener(this);
        jbtPrev = new JButton("Previous");
        jbtPrev.addActionListener(this);
        jbtNext = new JButton("Next");
        jbtNext.addActionListener(this);
        jbtLast = new JButton("Last");
        jbtLast.addActionListener(this);
        
        cp.add(jbtOk, c);
        cp.add(jbtFirst, c);
        cp.add(jbtPrev, c);
        cp.add(jbtNext, c);
        cp.add(jbtLast, c);
        f.pack();
       f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
           
// assign actionListener and actionEvent for each button
        jbtFirst.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = 0;
                populateFields(dispProd);  // missing method call for update
            } // end firstBtn actionEvent
 
        }); // end firstBtn actionListener
 
 
        jbtPrev.addActionListener(new ActionListener() 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd--;
                if (dispProd < 0)
                {
                    dispProd = product.length - 1;
                }
                 //WHAT IS THIS FOR??
                 //dispProd = (product.length+dispProd-1) % product.length;

                 populateFields(dispProd);  // missing method call for update
            } // end prevBtn actionEvent
        }); // end prevBtn actionListener
 
        jbtLast.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = product.length - 1;
                populateFields(dispProd);  // missing method call for update
            } // end lastBtn actionEvent
 
        }); // end lastBtn actionListener
 
        jbtNext.addActionListener(new ActionListener() 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd++;
                if (dispProd >= product.length - 1)
                {
                    dispProd = 0;
                }
                populateFields(dispProd);  // Missing method call for update
            } // end nextBtn actionEvent
        }); // end nextBtn actionListener
    }

    // event handler for combo box
    public void actionPerformed(ActionEvent e)
    {        
        if(e.getSource() == combo)
        {
               //System message, I do not know what you wish to do with combo box
            System.out.println("Selected option: " + combo.getSelectedIndex() );
        }
    }
 
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    
    }
}

I finaly got my buttons to work and now I have added 3 more buttons which are not working and I added them the same way the other buttons that are working were added. the code compiles and runs with no errors but the 3 new buttons are not working the way I need them to. I think that its the action listener that is not workinng right.
here is what I have so far:

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain extends Frame implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
    JButton jbtAdd, jbtFirst, jbtPrev, jbtNext, jbtLast, jbtDelete, jbtModify;
    JLabel label; // logo   
    JPanel buttonJPanel; // panel to hold buttons
    String nameText;
    JComboBox combo;
    private int index; 
    int i; // varialbe for looping
    double total = 0; // variable for total inventory   
    static int dispProd = 0; // variable for actionEvents   
    static JTextArea textArea;
    static int addProd = 0;
    static int deleteProd = 0;
    static int modifyProd = 0;
    public static void main(String[] args) 
    {
           
       
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
  
   
    
    public void initCD() {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
      //Sort elements in array in alphabetical order by product name
           // product[0].sortItems(product);
      
    
    }
    
     
        
    private void showGUI() {
        JLabel l;
        JButton b;
        fields = new JTextField[9];
        combo = new JComboBox();
        for(int j = 0; j < product.length; j++)
        combo.addItem(product[j].getName());
        combo.addActionListener(this);
          Icon logo = new ImageIcon("C:/logo.jpg"); // load logo
        label = new JLabel(logo); // create logo label
        label.setToolTipText("Company Logo"); // create tooltip
            textArea = new JTextArea(product[3] + "\n"); // create textArea for
                                                        // product display
        JFrame f = new JFrame("CD Inventory");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        
        jbtAdd = new JButton("Add");
        jbtAdd.addActionListener(this);
        jbtFirst = new JButton("First");
        jbtFirst.addActionListener(this);
        jbtPrev = new JButton("Previous");
        jbtPrev.addActionListener(this);
        jbtNext = new JButton("Next");
        jbtNext.addActionListener(this);
        jbtLast = new JButton("Last");
        jbtLast.addActionListener(this);
        jbtDelete = new JButton("Delete");
        jbtDelete.addActionListener(this);
        jbtModify = new JButton("Modify");
        jbtModify.addActionListener(this);
        
        cp.add(jbtAdd, c);
        cp.add(jbtFirst, c);
        cp.add(jbtPrev, c);
        cp.add(jbtNext, c);
        cp.add(jbtLast, c);
        cp.add(jbtDelete, c);
        cp.add(jbtModify, c);
        f.pack();
       f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
           
// assign actionListener and actionEvent for each button
        jbtAdd.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                addProd = 0;
                populateFields(dispProd);
                
            } // end addBtn actionEvent
            
        }); // end addBtn actionListener
        jbtFirst.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = 0;
                populateFields(dispProd);
 
            } // end firstBtn actionEvent
 
        }); // end firstBtn actionListener
 
 
        jbtPrev.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd--;
                if (dispProd < 0)
                {
                    dispProd = product.length - 1;
                }
                populateFields(dispProd); 
               
            } // end prevBtn actionEvent
        }); // end prevBtn actionListener
 
        jbtLast.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = product.length - 1;
               populateFields(dispProd); 
           
            } // end lastBtn actionEvent
 
        }); // end lastBtn actionListener
 
        jbtNext.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd++;
                if (dispProd >= product.length - 1)
                {
                    dispProd = 0;
                }
               populateFields(dispProd);
            } // end nextBtn actionEvent
        }); // end nextBtn actionListener
       
         jbtDelete.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                
            deleteProd = 0;
            
            } // end deleteBtn actionEvent
         }); // end deleteBtn actionListener
         
         jbtModify.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                
            modifyProd = 0;
            populateFields(dispProd);
            
            } // end modifyBtn actionEvent
         }); // end modifyBtn actionListener
    }
    // event handler for combo box
    public void actionPerformed(ActionEvent e)
    {        
        if(e.getSource() == combo)
        {
               
            System.out.println("Selected option: " + combo.getSelectedIndex() );
        }
    }
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    }
}
public class InventoryI {
        
    String productnumber;
 
    String name;
 
    String Text;
        
        int numberofunits;
 
    double priceperunit;
        
        String itemcode; 
        
        String command; 
        

    // Create a new instance of Inventory
    // main constructor for the class
    public InventoryI(String Item_Number, String Item_Name, int Items_in_Stock,
            double Item_Price, String Item_Code) {
        productnumber = Item_Number;
        name = Item_Name;
        numberofunits = Items_in_Stock;
        priceperunit = Item_Price;
                itemcode = Item_Code;
    }        
 
    public void setItemName(String Item_Name) {
    // sets the items name

        name = Item_Name;
    }
 
    public void setItemCode(String Item_Code) {
    // sets the items name

        itemcode = Item_Code;
    }
        public void setItemNumber(String Item_Number) { // Sets the Product =Number
    // for the item
 
        productnumber = Item_Number;
    }
 
    public void setItemsInStock(int Items_in_Stock) { // sets the =number of
    // units in stock
 
        numberofunits = Items_in_Stock;
    }
 
    public void setItemPrice(double Item_Price) { // sets the price of =the
    // item
        priceperunit = Item_Price;
    }
       
        public String getItemName() { // returns the Product Name of this item
        return name;
    }
 
     public String getItemCode() { // returns the Product Name of this item
        return itemcode;
        }
         
        public String getItemNumber() { // returns the Product Number of the =item
 
        return productnumber;
    }
 
    public int getItemsInStock() { // returns how many units are in stock
        return numberofunits;
    }
 
    public double getItemPrice() { // returns the price of the item
        return priceperunit;
    }
 
    public double getInventoryIValue() { // returns the total value of =the stock
    // for this item
        return priceperunit * numberofunits;
    }
        
    public static double getTotalValueOfAllInventory(InventoryI [] inv) {
    
            double tot = 0.0;
        
        for(int i = 0; i < inv.length; i++)   
                
            tot += inv[i].getInventoryIValue();
        
        return tot;
        
    }
    
    public static InventoryI[] sort(InventoryI [] inventory)
    {
        InventoryI temp[] = new InventoryI[1];
         
        //sorting the array using Bubble Sort
        for(int j = 0; j < inventory.length - 1; j++)
        {
         
            for(int k = 0; k < inventory.length - 1; k++)
            {
         
                if(inventory[k].getItemName().compareToIgnoreCase(inventory[k+1].getItemName()) > 0)
                {
         
                    temp[0] = inventory[k];
                    inventory[k] = inventory[k+1];
                    inventory[k+1] = temp[0];
         
                }//end if
         
            }//end for loop
         
        }//end for loop

        
        return inventory;
                
    }
    
    public String toString()
    {
        StringBuffer sb = new StringBuffer();
        
                
        sb.append("CD Title:      \t").append(name).append("\n");
                sb.append("Item Code:      \t").append(itemcode).append("\n");
        sb.append("Item #:           \t").append(productnumber).append("\n");
        sb.append("Number in stock:\t").append(numberofunits).append("\n");
        sb.append("Price:          \t").append(String.format("$%.2f%n", priceperunit));
        sb.append("Inventory Value:\t").append(String.format("$%.2f%n", this.getInventoryIValue()));
 
        return sb.toString();
                
                
    }
    
    
}

See comments bolded in the code:

I finaly got my buttons to work and now I have added 3 more buttons which are not working and I added them the same way the other buttons that are working were added. the code compiles and runs with no errors but the 3 new buttons are not working the way I need them to. I think that its the action listener that is not workinng right.
here is what I have so far:

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat; // used to format currency
import javax.swing.*;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
class InventoryMain extends Frame implements ActionListener
{
    CD[] product;
    JTextField[] fields;
    NumberFormat nf;
    JButton jbtAdd, jbtFirst, jbtPrev, jbtNext, jbtLast, jbtDelete, jbtModify;
    JLabel label; // logo   
    JPanel buttonJPanel; // panel to hold buttons
    String nameText;
    JComboBox combo;
    private int index; 
    int i; // varialbe for looping
    double total = 0; // variable for total inventory   
    static int dispProd = 0; // variable for actionEvents   
    static JTextArea textArea;
    static int addProd = 0;
    static int deleteProd = 0;
    static int modifyProd = 0;
    public static void main(String[] args) 
    {
           
       
        try 
        {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
        InventoryMain test = new InventoryMain();
        test.initCD();
        test.showGUI();
        test.populateFields(0);
    }
  
   
    
    public void initCD() {
        //Create an array    
        product = new CD[10];
     
        //fill in the classes
        product[0] = new CD( 1, "Crowbar" , 20.00, 10, "00722");
        product[1] = new CD( 2, "Pantera" , 20.00, 10, "00263");
        product[2] = new CD( 3, "Ozzy" , 15.00, 10, "00142");
        product[3] = new CD( 4, "Soulfly" , 18.00, 10, "00553");
        product[4] = new CD( 5, "Down", 24.00, 10, "00789");
        product[5] = new CD( 6, "God Forbid" , 10.00, 10, "00712");
        product[6] = new CD( 7, "Black Label Society" , 16.00, 10, "00458" );
        product[7] = new CD( 8, "Saint Vitus" , 15.00, 10, "00889");
        product[8] = new CD( 9, "Clearlight" , 15.00, 10, "00897");
        product[9] = new CD( 10, "Testament" , 15.00, 10, "00656");        
    
      //Sort elements in array in alphabetical order by product name
           // product[0].sortItems(product);
      
    
    }
    
     
        
    private void showGUI() {
        JLabel l;
        JButton b;
        fields = new JTextField[9];
        combo = new JComboBox();
        for(int j = 0; j < product.length; j++)
        combo.addItem(product[j].getName());
        combo.addActionListener(this);
          Icon logo = new ImageIcon("C:/logo.jpg"); // load logo
        label = new JLabel(logo); // create logo label
        label.setToolTipText("Company Logo"); // create tooltip
            textArea = new JTextArea(product[3] + "\n"); // create textArea for
                                                        // product display
        JFrame f = new JFrame("CD Inventory");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor("control"));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);    l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);       l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of This Item: $", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of All Merchandise in Inventory: $",
                               SwingConstants.CENTER), c);   l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Item Code:", SwingConstants.CENTER), c);   l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Product Restocking Fee: $", SwingConstants.CENTER), c);  l.setDisplayedMnemonic('h');
        cp.add(combo, c);
        c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);         fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);         fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);         fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);         fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);         fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);         fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);         fields[7].setFocusAccelerator('h');
        cp.add(fields[8] = new JTextField(), c);         fields[8].setFocusAccelerator('i');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
        
        jbtAdd = new JButton("Add");
        [B]jbtAdd.addActionListener(this);  // None of these statements are needed. You are essentially adding your combobox listener to these buttons.[/B]
        jbtFirst = new JButton("First");
        [B]jbtFirst.addActionListener(this);[/B]
        jbtPrev = new JButton("Previous");
        [B]jbtPrev.addActionListener(this);[/B]
        jbtNext = new JButton("Next");
        [B]jbtNext.addActionListener(this);[/B]
        jbtLast = new JButton("Last");
        [B]jbtLast.addActionListener(this);[/B]
        jbtDelete = new JButton("Delete");
       [B] jbtDelete.addActionListener(this);[/B]
        jbtModify = new JButton("Modify");
        [B]jbtModify.addActionListener(this);[/B]
        
        cp.add(jbtAdd, c);
        cp.add(jbtFirst, c);
        cp.add(jbtPrev, c);
        cp.add(jbtNext, c);
        cp.add(jbtLast, c);
        cp.add(jbtDelete, c);
        cp.add(jbtModify, c);
        f.pack();
       f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
           
// assign actionListener and actionEvent for each button
        jbtAdd.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                [B]addProd = 0;  // this isn't really doing anything at all
                // you need to add a new object to your array here
[/B]                 populateFields(dispProd);
                
            } // end addBtn actionEvent
            
        }); // end addBtn actionListener
        jbtFirst.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = 0;
                populateFields(dispProd);
 
            } // end firstBtn actionEvent
 
        }); // end firstBtn actionListener
 
 
        jbtPrev.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd--;
                if (dispProd < 0)
                {
                    dispProd = product.length - 1;
                }
                populateFields(dispProd); 
               
            } // end prevBtn actionEvent
        }); // end prevBtn actionListener
 
        jbtLast.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = product.length - 1;
               populateFields(dispProd); 
           
            } // end lastBtn actionEvent
 
        }); // end lastBtn actionListener
 
        jbtNext.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd++;
                [B]if (dispProd >= product.length - 1) // should just be >, not >=. You are missing the last item in the array with >= (since that is the index of the last item and is a valid entry)[/B]
                {
                    dispProd = 0;
                }
               populateFields(dispProd);
            } // end nextBtn actionEvent
        }); // end nextBtn actionListener
       
         jbtDelete.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                
[B]             deleteProd = 0; [/B][B]// this isn't doing anything either
            // you need to remove an object from the array
[/B]             
            } // end deleteBtn actionEvent
         }); // end deleteBtn actionListener
         
         jbtModify.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                
            [B]modifyProd = 0;  // again nothing here
            // needs to update the values on the object that is in this position
[/B]             populateFields(dispProd);
            
            } // end modifyBtn actionEvent
         }); // end modifyBtn actionListener
    }
    // event handler for combo box
    public void actionPerformed(ActionEvent e)
    {        
        if(e.getSource() == combo)
        {
               
            System.out.println("Selected option: " + combo.getSelectedIndex() );
        }
    }
    private void populateFields(int index) {
        CD cd = product[index];
        fields[0].setText(Long.toString(cd.getNumberCode()));
        fields[1].setText(cd.getName());
        fields[2].setText(Long.toString(cd.getUnits()));
        fields[3].setText(Double.toString(cd.getPrice()));
        fields[4].setText(Double.toString(cd.getSum()));
        fields[5].setText(Double.toString(cd.totalAllInventory(product)));
        fields[6].setText(cd.getCode());
        fields[7].setText(Double.toString(cd.getSum()*.05));        
    }
}
public class InventoryI {
        
    String productnumber;
 
    String name;
 
    String Text;
        
        int numberofunits;
 
    double priceperunit;
        
        String itemcode; 
        
        String command; 
        

    // Create a new instance of Inventory
    // main constructor for the class
    public InventoryI(String Item_Number, String Item_Name, int Items_in_Stock,
            double Item_Price, String Item_Code) {
        productnumber = Item_Number;
        name = Item_Name;
        numberofunits = Items_in_Stock;
        priceperunit = Item_Price;
                itemcode = Item_Code;
    }        
 
    public void setItemName(String Item_Name) {
    // sets the items name

        name = Item_Name;
    }
 
    public void setItemCode(String Item_Code) {
    // sets the items name

        itemcode = Item_Code;
    }
        public void setItemNumber(String Item_Number) { // Sets the Product =Number
    // for the item
 
        productnumber = Item_Number;
    }
 
    public void setItemsInStock(int Items_in_Stock) { // sets the =number of
    // units in stock
 
        numberofunits = Items_in_Stock;
    }
 
    public void setItemPrice(double Item_Price) { // sets the price of =the
    // item
        priceperunit = Item_Price;
    }
       
        public String getItemName() { // returns the Product Name of this item
        return name;
    }
 
     public String getItemCode() { // returns the Product Name of this item
        return itemcode;
        }
         
        public String getItemNumber() { // returns the Product Number of the =item
 
        return productnumber;
    }
 
    public int getItemsInStock() { // returns how many units are in stock
        return numberofunits;
    }
 
    public double getItemPrice() { // returns the price of the item
        return priceperunit;
    }
 
    public double getInventoryIValue() { // returns the total value of =the stock
    // for this item
        return priceperunit * numberofunits;
    }
        
    public static double getTotalValueOfAllInventory(InventoryI [] inv) {
    
            double tot = 0.0;
        
        for(int i = 0; i < inv.length; i++)   
                
            tot += inv[i].getInventoryIValue();
        
        return tot;
        
    }
    
    public static InventoryI[] sort(InventoryI [] inventory)
    {
        InventoryI temp[] = new InventoryI[1];
         
        //sorting the array using Bubble Sort
        for(int j = 0; j < inventory.length - 1; j++)
        {
         
            for(int k = 0; k < inventory.length - 1; k++)
            {
         
                if(inventory[k].getItemName().compareToIgnoreCase(inventory[k+1].getItemName()) > 0)
                {
         
                    temp[0] = inventory[k];
                    inventory[k] = inventory[k+1];
                    inventory[k+1] = temp[0];
         
                }//end if
         
            }//end for loop
         
        }//end for loop

        
        return inventory;
                
    }
    
    public String toString()
    {
        StringBuffer sb = new StringBuffer();
        
                
        sb.append("CD Title:      \t").append(name).append("\n");
                sb.append("Item Code:      \t").append(itemcode).append("\n");
        sb.append("Item #:           \t").append(productnumber).append("\n");
        sb.append("Number in stock:\t").append(numberofunits).append("\n");
        sb.append("Price:          \t").append(String.format("$%.2f%n", priceperunit));
        sb.append("Inventory Value:\t").append(String.format("$%.2f%n", this.getInventoryIValue()));
 
        return sb.toString();
                
                
    }
    
    
}

Well spotted adding of Action Listeners is my mistake, I did not take it out when I edited code last time.I'm used to top level event handling insted of dkdeleon68 anonymous...

Well spotted adding of Action Listeners is my mistake, I did not take it out when I edited code last time.I'm used to top level event handling insted of dkdeleon68 anonymous...

Well, he can do it either way: with the single listener that checks the source of the ActionEvent and operates accordingly, or with a separate listener for each component - but having both is probably causing the confusion right now. It's probably best to pick one way and stick with it at this point :)

Thank you for the help, I will do what you suggested. I still have a save and a search button to add but I am just doing them a few at at time so I can understand what I'm doing wrong. again, thank you for all the help.

still not working right.
here is the part of code that I changed:

// assign actionListener and actionEvent for each button
        jbtAdd.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                [B]dispProd = (product.length - 0);[/B]
                populateFields(dispProd);
                
            } // end addBtn actionEvent
            
        }); // end addBtn actionListener
        jbtFirst.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = 0;
                populateFields(dispProd);
 
            } // end firstBtn actionEvent
 
        }); // end firstBtn actionListener
 
 
        jbtPrev.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd--;
                if (dispProd < 0)
                {
                    dispProd = product.length - 1;
                }
                populateFields(dispProd); 
               
            } // end prevBtn actionEvent
        }); // end prevBtn actionListener
 
        jbtLast.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd = product.length - 1;
               populateFields(dispProd); 
           
            } // end lastBtn actionEvent
 
        }); // end lastBtn actionListener
 
        jbtNext.addActionListener(new ActionListener()
 
        {
            public void actionPerformed(ActionEvent ae)
            {
                dispProd++;
                if (dispProd > product.length - 1)
                {
                    dispProd = 0;
                }
               populateFields(dispProd);
            } // end nextBtn actionEvent
        }); // end nextBtn actionListener
       
         jbtDelete.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                
            dispProd = 0;
            
            } // end deleteBtn actionEvent
         }); // end deleteBtn actionListener
         
         jbtModify.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                
           [B] for(int j = 0; j < product.length; j++)[/B]
            populateFields(dispProd);
            
            } // end modifyBtn actionEvent
         }); // end modifyBtn actionListener
    }

dkdeleon68 you better pay more attention in classes...
Ofcourse it will do nothing, because in this case you are supposed to read value/values from your JTextField and update selected CD with new data. However what you do is just updating view, notging more. Same will go for your delete function.
WHAT TO DO ! ! !
Create method which will handle delete process and update process

I have been paying attention, its just that I am not getting feedback from my instructor. I have learned more from you guys in the past couple of days than I have learned this hole class. thank you very much it is very appreciated.

Ok, think about the operations that need to be performed to add, modify, and delete:
Add: Create a new product object and place it in your array. Since your array is currently full, you will have to make it larger.
Modify: The easiest. Just replace the values of the current product object with the values from your fields.
Delete: Remove an object from your array. There are a couple of ways to handle this, but probably easiest to shift all objects in positions higher than current index down and make the empty position at the end = null. Deleting things in this way will leave nulls in your array, which your navigation operations will probably need to check for and skip over.

I don't know if your classes have gotten to collections yet, but the things you are doing are easier to implement with a List. Look at the javadocs for ArrayList (or Vector would work too) and this tutorial is a very basic example of using it: http://www.anyexample.com/programming/java/java_arraylist_example.xml

Comments
This one is a realy difficult case ;)
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