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

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

    /******************************************************
     *Creates and displays a window of the class ButtonDemo.
     ******************************************************/
    public static void main(String[] args)
    {
        ButtonDemo buttonGui = new ButtonDemo();
        buttonGui.setVisible(true);
    }

    public ButtonDemo()
    {
        setSize(WIDTH, HEIGHT);

        addWindowListener(new WindowDestroyer()); 
        setTitle("Button Demo"); 
        Container contentPane = getContentPane();
        contentPane.setBackground(Color.blue);
 
        contentPane.setLayout(new FlowLayout());

        JButton stopButton = new JButton("Red");
        stopButton.addActionListener(this);
        contentPane.add(stopButton);

        JButton goButton = new JButton("Green");
        goButton.addActionListener(this); 
        contentPane.add(goButton);
    }

    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.");
    }
}