JAVA: Interface com 2 Botões

package interfacesgraficas;

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

public class InterfacesGraficas {
    JFrame frame;
    JLabel label;

    public static void main(String[] args) {
        InterfacesGraficas gui = new InterfacesGraficas();
        gui.go();
    }
        public void go(){
            frame = new JFrame();
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            JButton labelButton = new JButton("clique aqui");
            labelButton.addActionListener(new LabelListener());

            JButton colorButton = new JButton("Mudar circulo");
            colorButton.addActionListener(new ColorListener());

            label = new JLabel("Eu sou um texto");

            MyDrawPanel drawPanel = new MyDrawPanel();

            frame.getContentPane().add(BorderLayout.SOUTH, colorButton);
            frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
            frame.getContentPane().add(BorderLayout.EAST, labelButton);
            frame.getContentPane().add(BorderLayout.WEST, label);

            frame.setSize(300, 300);
            frame.setVisible(true);
        }
        class LabelListener implements ActionListener{

        @Override
        public void actionPerformed(ActionEvent e) {
            label.setText("Olá");
        }
        }
        class ColorListener implements ActionListener{

        @Override
        public void actionPerformed(ActionEvent e) {
            frame.repaint();
        }

        }

    }

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package interfacesgraficas;

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

public class MyDrawPanel extends JPanel{
    @Override
    public void paintComponent(Graphics g){
        /* Exemplo pg261
        g.setColor(Color.orange);
        g.fillRect(20,50,100,100);
        */

        /* Exemplo de uma imagem
        Image image = new ImageIcon("C:\\Users\\fabio\\Documents\\NetBeansProjects\\mavenproject2\\InterfacesGraficas\\src\\interfacesgraficas\\pilha.jpg").getImage();
        g.drawImage(image, 3,4, this);
        */
        /* Exemplo de um circulo que muda de cor */
        Graphics2D g2d = (Graphics2D) g;
        int red = (int) (Math.random() * 255);
        int green = (int) (Math.random() * 255);
        int blue = (int) (Math.random() * 255);

        Color startColor = new Color(red, green, blue);

        red = (int) (Math.random() * 255);
        green = (int) (Math.random() * 255);
        blue = (int) (Math.random() * 255);

        Color endColor = new Color(red, green, blue);
        GradientPaint gradient = new GradientPaint(70, 70, startColor,150,150, endColor);
        g2d.setPaint(gradient);
        g2d.fillOval(70, 70, 100, 100);
    }
}