PoundstoKilogramsGUI.java

      import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class PoundstoKilogramsGUI
{
   private int WIDTH = 300;
   private int HEIGHT = 75;

   private JFrame frame;
   private JPanel panel;
   private JLabel inputLabel, outputLabel, resultLabel;
   private JTextField pounds;

   public PoundstoKilogramsGUI(String title, String label1, String label2)
   {
      frame = new JFrame (title);
      frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

      inputLabel = new JLabel (label1);
      outputLabel = new JLabel (label2);
      resultLabel = new JLabel ("---");

      pounds = new JTextField (5);
      pounds.addActionListener (new TempListener());

      panel = new JPanel();
      panel.setPreferredSize (new Dimension(WIDTH, HEIGHT));
      panel.setBackground (Color.yellow);
      panel.add (inputLabel);
      panel.add (pounds);
      panel.add (outputLabel);
      panel.add (resultLabel);

      frame.getContentPane().add (panel);
   }
   public void display()
   {
      frame.pack();
      frame.setVisible(true); // book has old version
   }

   private class TempListener implements ActionListener
   {
      public void actionPerformed (ActionEvent event)
      {
         Double poundsTemp, kilogramsTemp;

         String text = pounds.getText();

         poundsTemp = Double.parseDouble(text);
         kilogramsTemp = poundsTemp / 2.2 ;

         resultLabel.setText (Double.toString (kilogramsTemp));
      }
   }
}