TwoButtons

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

public class TwoButtons extends JFrame implements ActionListener
{
    JButton redButton ;
    JButton grnButton ;
    JButton bluButton ;
    JButton gryButton ;

    public TwoButtons(String title)
    {
        super( title );

        redButton = new JButton("Red");
        grnButton = new JButton("Green");
        bluButton = new JButton("Blue");
        gryButton = new JButton("Gray");

        redButton.setActionCommand( "red" );
        grnButton.setActionCommand( "green" );
        bluButton.setActionCommand( "blue" );
        gryButton.setActionCommand( "gray" );

        redButton.addActionListener( this );
        grnButton.addActionListener( this );
        bluButton.addActionListener( this );
        gryButton.addActionListener( this );

        setLayout( new FlowLayout() );
        add( redButton );
        add( grnButton );
        add( bluButton );
        add( gryButton );

        setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    }

    public void actionPerformed( ActionEvent evt)
    {
        if ( evt.getActionCommand().equals( "red" ) )
            getContentPane().setBackground(  Color.red  );
        else if ( evt.getActionCommand().equals( "green" ) )
            getContentPane().setBackground( Color.green );
        else if ( evt.getActionCommand().equals( "blue" ) )
            getContentPane().setBackground( Color.blue );
        else
            getContentPane().setBackground( Color.gray );

        repaint();
    }

    public static void main ( String[] args )
    {
        TwoButtons demo  = new TwoButtons( "Click a Button" ) ;

        demo.setSize( 200, 150 );
        demo.setVisible( true );
    }
}