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

public class SimpleGui3C implements ActionListener {

  JFrame frame;

  public static void main(String[] args) {
    
    SimpleGui3C gui = new SimpleGui3C();
    gui.go();
  }

  public void go() {

    frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JButton button = new JButton("Change colors");
    button.addActionListener(this);

    MyDrawPanel drawPanel = new MyDrawPanel();

    frame.getContentPane().add(BorderLayout.SOUTH, button);
    frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
    frame.setSize(300,300);
    frame.setVisible(true);
  }

  public void actionPerformed(ActionEvent event) {
    
    frame.repaint();
  }
}