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

public class VisibilityDemoExercise extends JFrame
                            implements ActionListener
{
    public static final int WIDTH = 300;
    public static final int HEIGHT = 200;

    private JLabel upLabel;
    private JLabel downLabel;
    private JButton upButton;
    private JButton downButton;

    public VisibilityDemoExercise()
    {
        setSize(WIDTH, HEIGHT);
        addWindowListener(new WindowDestroyer());
        setTitle("Visibility Demonstration");
        Container contentPane = getContentPane();
        contentPane.setLayout(new BorderLayout());
        contentPane.setBackground(Color.white);

        upLabel = new JLabel("Here I am up here!");
        contentPane.add(upLabel, BorderLayout.NORTH);
        upLabel.setVisible(false);
        downLabel = new JLabel("Here I am down here!");
        contentPane.add(downLabel, BorderLayout.SOUTH);
        downLabel.setVisible(false);

        JPanel buttonPanel = new JPanel();
        buttonPanel.setBackground(Color.white);
        buttonPanel.setLayout(new FlowLayout());
        upButton = new JButton("Up");
        upButton.addActionListener(this);
        buttonPanel.add(upButton);
        downButton = new JButton("Down");
        downButton.addActionListener(this);
        buttonPanel.add(downButton);
        contentPane.add(buttonPanel, BorderLayout.CENTER);
    }

    public void actionPerformed(ActionEvent e)
    {
       if (e.getActionCommand().equals("Up"))
	   {
	       upLabel.setVisible(true);
	       downLabel.setVisible(false);
	       upButton.setVisible(false);
	       downButton.setVisible(true);
	       validate();
	   }
	   else if (e.getActionCommand().equals("Down"))
	   {
	       downLabel.setVisible(true);
	       upLabel.setVisible(false);
	       downButton.setVisible(false);
	       upButton.setVisible(true);
	       validate();
	   }
	   else
	       System.out.println(
                 "Error in VisibilityDemoExercise interface.");
    }

    public static void main(String[] args)
    {
        VisibilityDemoExercise demoGui = new VisibilityDemoExercise();
        demoGui.setVisible(true);
    }
}