1  import java.awt.event.ActionEvent;

  2  import java.awt.event.ActionListener;

  3  import javax.swing.JButton;

  4  import javax.swing.JFrame;

  5  import javax.swing.JLabel;

  6  import javax.swing.JPanel;

  7  import javax.swing.JScrollPane;

  8  import javax.swing.JTextArea;

  9  import javax.swing.JTextField;

 10  

 11  /**

 12     A frame that shows the growth of an investment with variable interest.

 13  */

 14  public class InvestmentFrame extends JFrame

 15  {

 16     private static final int FRAME_WIDTH = 400;

 17     private static final int FRAME_HEIGHT = 250;

 18     

 19     private static final int AREA_ROWS = 10;

 20     private static final int AREA_COLUMNS = 30;

 21     private static final double DEFAULT_RATE = 5;

 22     private static final double INITIAL_BALANCE = 1000;   

 23       

 24     private JLabel rateLabel;

 25     private JTextField rateField;

 26     private JButton button;

 27     private JTextArea resultArea;

 28     private JPanel panel;

 29     private BankAccount account;

 30   

 31     public InvestmentFrame()

 32     {  

 33        account = new BankAccount(INITIAL_BALANCE);

 34        resultArea = new JTextArea(AREA_ROWS, AREA_COLUMNS);

 35        resultArea.setEditable(false);

 36              

 37        // Use helper methods 

 38        createTextField();

 39        createButton();

 40        createPanel();

 41  

 42        setSize(FRAME_WIDTH, FRAME_HEIGHT);

 43     }

 44  

 45     private void createTextField()

 46     {

 47        rateLabel = new JLabel("Interest Rate: ");

 48  

 49        final int FIELD_WIDTH = 10;

 50        rateField = new JTextField(FIELD_WIDTH);

 51        rateField.setText("" + DEFAULT_RATE);

 52     }

 53     

 54     private void createButton()

 55     {

 56        button = new JButton("Add Interest");

 57        

 58        class AddInterestListener implements ActionListener

 59        {

 60           public void actionPerformed(ActionEvent event)

 61           {

 62              double rate = Double.parseDouble(rateField.getText());

 63              double interest = account.getBalance() * rate / 100;

 64              account.deposit(interest);

 65              resultArea.append(account.getBalance() + "\n");

 66           }            

 67        }

 68        

 69        ActionListener listener = new AddInterestListener();

 70        button.addActionListener(listener);

 71     }

 72  

 73     private void createPanel()

 74     {

 75        panel = new JPanel();

 76        panel.add(rateLabel);

 77        panel.add(rateField);

 78        panel.add(button);

 79        JScrollPane scrollPane = new JScrollPane(resultArea);

 80        panel.add(scrollPane);      

 81        add(panel);

 82     }

 83   }