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

class MyDrawPanel extends JPanel {

  public void paintComponent(Graphics g) {

    g.fillRect(0, 0, this.getWidth(), this.getHeight());

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

    Color randomColor = new Color(red, green, blue);
    g.setColor(randomColor);
    g.fillOval(70, 70, 100, 100);
  }
}