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

class ThreeButtons2 extends JFrame 
{
  private JPanel centerPanel;

  void centerPanelColorRed()
    { centerPanel.setBackground(Color.RED); }

  void centerPanelColorGreen()
    { centerPanel.setBackground(Color.GREEN); }

  void centerPanelColorBlue()
    { centerPanel.setBackground(Color.BLUE); }

  public ThreeButtons2()
  {
    Container c = getContentPane();
    c.setLayout(new BorderLayout());

    centerPanel = new JPanel();

    c.add("Center",centerPanel);

    JButton b1 = new JButton("Red");
    JButton b2 = new JButton("Green");
    JButton b3 = new JButton("Blue");

    b1.addActionListener
    (
      new ActionListener()
      {
        public void actionPerformed(ActionEvent e)
          { centerPanelColorRed(); }
      }
    );

    b2.addActionListener
    (
      new ActionListener()
      {
        public void actionPerformed(ActionEvent e)
          { centerPanelColorGreen(); }
      }
    );

    b3.addActionListener
    (
      new ActionListener()
      {
        public void actionPerformed(ActionEvent e)
          { centerPanelColorBlue(); }
      }
    );

    JPanel bp = new JPanel();
    bp.add(b1);
    bp.add(b2);
    bp.add(b3);

    c.add("South", bp);

    setSize(400,400);
    setVisible(true);
  }

  public static void main( String[] arg )
  {
    ThreeButtons2 app = new ThreeButtons2();
    app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }

}