I can not figure out how to add a way to get the following program to
display the total value of the inventory or a re-stocking fee. Any help
would be greatly appreciated.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
class Testing
{
 java.util.List dvds = new java.util.ArrayList();

 JTextField tfTitle = new JTextField(15);
 JTextField tfProductNumber = new JTextField();
 JTextField tfPrice = new JTextField();
 JTextField tfQuantity = new JTextField();
 DefaultListModel dlm = new DefaultListModel();
 JList list = new JList(dlm);
 public void buildGUI()
 {
   JButton btn = new JButton("Add");
   JPanel p1 = new JPanel(new BorderLayout());
   JPanel p = new JPanel(new GridLayout(4,2));
   p.add(new JLabel("DVD Title: "));
   p.add(tfTitle);
   p.add(new JLabel("Product Number: "));
   p.add(tfProductNumber);
   p.add(new JLabel("Price per Unit: "));
   p.add(tfPrice);
   p.add(new JLabel("Quantity on Hand: "));
   p.add(tfQuantity);
   p1.add(p,BorderLayout.NORTH);
   JPanel p2 = new JPanel();
   p2.add(btn);
   p1.add(p2,BorderLayout.CENTER);
   JFrame f = new JFrame();
   f.getContentPane().add(p1,BorderLayout.NORTH);
   JScrollPane sp = new JScrollPane(list);
   f.getContentPane().add(sp,BorderLayout.CENTER);
   f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   f.pack();
   f.setLocationRelativeTo(null);
   f.setVisible(true);
   btn.addActionListener(new ActionListener(){
     public void actionPerformed(ActionEvent ae){
       dvds.add(new DVD(tfTitle.getText(),tfProductNumber.getText(),
                               Double.parseDouble(tfPrice.getText()),

Integer.parseInt(tfQuantity.getText())));
       setList();
       clearTextFields();
     }
   });
   list.addListSelectionListener(new ListSelectionListener(){
     public void valueChanged(ListSelectionEvent lse){
       if(lse.getValueIsAdjusting() == false)
       {
         DVD dvd = (DVD)dvds.get(list.getSelectedIndex());
         tfTitle.setText(dvd.title);
         tfProductNumber.setText(dvd.productNumber);
         tfPrice.setText(""+dvd.price);
         tfQuantity.setText(""+dvd.quantity);
       }
     }
   });
 }
 public void setList()
 {
   dlm.clear();
   for(int x = 0, y = dvds.size(); x < y; x++)
   {
     dlm.addElement((DVD)dvds.get(x));
   }
 }
 public void clearTextFields()
 {
   tfTitle.setText("");
   tfProductNumber.setText("");
   tfPrice.setText("");
   tfQuantity.setText("");
   tfTitle.requestFocusInWindow();
 }
 public static void main(String[] args)
 {
   EventQueue.invokeLater(new Runnable(){
     public void run(){
       new Testing().buildGUI();
     }
   });
 }
}
class DVD
{
 String title;
 String productNumber;
 double price;
 int quantity;
 public DVD(String t,String pn, double p, int q)
 {
   title = t; productNumber = pn; price = p; quantity = q;
 }
 public String toString(){return title;}
}