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

/***************************************************
 *Simple demonstration of putting buttons in a panel.
 ***************************************************/
public class PanelDemo extends JFrame implements ActionListener
{
    public static final int WIDTH = 300;
    public static final int HEIGHT = 200;

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

    public PanelDemo()
    {
        setSize(WIDTH, HEIGHT);
        addWindowListener(new WindowDestroyer()); 
        setTitle("Panel Demonstration"); 
        Container contentPane = getContentPane();
        contentPane.setBackground(Color.blue);
        contentPane.setLayout(new BorderLayout());
   
        JPanel buttonPanel = new JPanel();
        buttonPanel.setBackground(Color.white);

        buttonPanel.setLayout(new FlowLayout());

        JButton stopButton = new JButton("Red");
        stopButton.setBackground(Color.red); 
        stopButton.addActionListener(this);
        buttonPanel.add(stopButton);

        JButton goButton = new JButton("Green");
        goButton.setBackground(Color.green);
        goButton.addActionListener(this); 
        buttonPanel.add(goButton);

        contentPane.add(buttonPanel, BorderLayout.SOUTH);
    }

    public void actionPerformed(ActionEvent e) 
    {
       Container contentPane = getContentPane();

       if (e.getActionCommand().equals("Red"))
            contentPane.setBackground(Color.red);
        else if (e.getActionCommand().equals("Green"))
           contentPane.setBackground(Color.green);
        else
            System.out.println("Error in button interface.");
    }
}