    01: import java.awt.*;
    02: import java.awt.event.*;
    03: import javax.swing.*;
    04: import javax.swing.event.*;
    05:
    06: /**
    07:    A program that tests the invoice classes.
    08: */
    09: public class InvoiceTest
    10: {
    11:    public static void main(String[] args)
    12:    {
    13:       final Invoice invoice = new Invoice();
    14:       final InvoiceFormatter formatter = new SimpleFormatter();
    15:
    16:       // this text area will contain the formatted invoice
    17:       final JTextArea textArea = new JTextArea(20, 40);
    18:
    19:       // when the invoice changes, update the text area
    20:       ChangeListener listener = new
    21:          ChangeListener()
    22:          {
    23:             public void stateChanged(ChangeEvent event)
    24:             {
    25:                textArea.setText(invoice.format(formatter));
    26:             }
    27:          };
    28:       invoice.addChangeListener(listener);
    29:
    30:       // add line items to a combo box
    31:       final JComboBox combo = new JComboBox();
    32:       Product hammer = new Product("Hammer", 19.95);
    33:       Product nails = new Product("Assorted nails", 9.95);
    34:       combo.addItem(hammer);
    35:       Bundle bundle = new Bundle();
    36:       bundle.add(hammer);
    37:       bundle.add(nails);
    38:       combo.addItem(new DiscountedItem(bundle, 10));
    39:
    40:       // make a button for adding the currently selected
    41:       // item to the invoice
    42:       JButton addButton = new JButton("Add");
    43:       addButton.addActionListener(new
    44:          ActionListener()
    45:          {
    46:             public void actionPerformed(ActionEvent event)
    47:             {
    48:                LineItem item = (LineItem) combo.getSelectedItem();
    49:                invoice.addItem(item);
    50:             }
    51:          });
    52:
    53:       // put the combo box and the add button into a panel
    54:       JPanel panel = new JPanel();
    55:       panel.add(combo);
    56:       panel.add(addButton);
    57:
    58:       // add the text area and panel to the content pane
    59:       JFrame frame = new JFrame();
    60:       Container contentPane = frame.getContentPane();
    61:       contentPane.add(new JScrollPane(textArea),
    62:          BorderLayout.CENTER);
    63:       contentPane.add(panel, BorderLayout.SOUTH);
    64:       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    65:       frame.pack();
    66:       frame.show();
    67:    }
    68: }