How to draw in a JPanel and refresh it?

Question

Hey guys,
i want to draw a map, consisting of a lot of colored rectangles, in a JPanel.
it is part of project i am working on. a robot is discovering a track and i want to draw this track step by step, the informations are sent via bluetooth.
i am not sure how to draw it step by step and how to refresh it?
i am able to draw a static graphic with the abstract class Graphics and the method paintComponent of the class JPanel.
How do I add one or more rectangles to the existing graphic?
thanks for your help!

Answer 1

i would like to realize the standard approach.
but i am not quite sure how.
i tried to realize it like this, but there is an error, if the i uncomment the two lines and i do not understand why!
import java.awt.image.*;
import java.awt.*;
import javax.swing.*;
public class TrackWindow extends JFrame {   
     public TrackWindow() {
          super("Mapping");
          this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          this.setAlwaysOnTop(true);
          this.setLocationByPlatform(true);
          this.setSize(500, 500);
          this.add(new TrackPanel());
          this.setVisible(true);
     public static void main(String[] args) {
          new TrackWindow();
     public class TrackPanel extends JPanel {
          public BufferedImage track = null;
          public TrackPanel() {
               track = (BufferedImage)this.createImage(200, 200);
               //Graphics2D g2 = track.createGraphics();
               //g2.fillRect(0, 0, 15, 15);
          public void paintComponent(Graphics g) {
}could you please help me a little.
Thank you!