Plotting the position of a robot.

Question

Hi, I am building a GUI that receives data from a serial port. Once the information has been handle, I divide the stream into pieces and display the numbers they contain into JTextFields. Each of these pieces indicate the x-y coordinates, of a moving robot, which I want to show inside of a panel.
I can do the basics: draw a filled circle, the background, etc, but I dont know how to pass those numbers into the method that creates the draw. Also, I don't want to delete the "n-1" filled circles, so that at the end, I can see the path the robot took from the first position to the final one.
Thanks I really appreciate your help!

Answer 1

First of all thanks for your prompt reply.
I have considered the option number one as well. As you can see in the following two classes, I call from InfoGpsGui the Dibujo class which makes the circle with variables "a" and "b". My problem is that I dont know how to implement that iteration that you mentioned, since I can't modify the parameters at the paintComponent method in Dibujo, so to be able to introduce these variables "a" and "b" from InfoGpsGui as it is receiving them from my serial port class.
I will appreciate any snippet or code that can give a hint on the matter.
// class Dibujo
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Arc2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.GeneralPath;
import java.awt.geom.Rectangle2D;
import javax.swing.JPanel;
public class Dibujo extends JPanel {
     public static float a, b;
     public Graphics2D comp2D;
     public void paintComponent(Graphics comp) {
          // Creates a Java 2D object
          comp2D = (Graphics2D)comp;
          // Defines the color of the rectangle that is going to be built
          // to make a background
          comp2D.setColor(Color.white);
          Rectangle2D.Float background = new Rectangle2D.Float(
                    0F, 0F, (float)getSize().width, (float)getSize().height);
          comp2D.fill(background);
//           Defines a color-filled circle inside of the background
          comp2D.setColor(Color.black);
        BasicStroke pen2 = new BasicStroke();
        comp2D.setStroke(pen2);
        Ellipse2D.Float e1 = new Ellipse2D.Float(a, b, 15, 15);
        comp2D.fill(e1);
// Class InfoGpsGui
import java.awt.Container;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import javax.swing.*;
public class InfoGpsGui extends JFrame{
     static JTextField alt, lon, pos;
     public static char[] letras = new char[5];
     public static byte [] otroBuffer;
     public static Dibujo map = new Dibujo();
     private static Graphics comp;
     public InfoGpsGui(){
          //Characteristics of the frame
          super("GPS Info");
          setSize(650, 450);
          setDefaultCloseOperation(EXIT_ON_CLOSE);
          //Outside-most frame, will contain the draw and info panels
          JPanel pane = new JPanel();
          pane.setLayout(new GridLayout(1, 0));
          //Left sided frame, contains the drawing
          JPanel draw = new JPanel();
          //Container content = getContentPane();
          draw.setLayout(new GridLayout(1,0));
        draw.add(map);
          pane.add(draw);
          //Right sided frame, contains the info from the GPS
          JPanel info = new JPanel();
          info.setLayout(new GridLayout(3, 2));
          JLabel altitudeLabel = new JLabel("Altitude: ");
          alt = new JTextField(letras[0]);
          JLabel positionLabel = new JLabel("Position: ");
          pos = new JTextField(letras[1]);
          JLabel longitudeLabel = new JLabel("Longitude: ");
          lon = new JTextField(letras[2]);
          //info.add(map);
          info.add(altitudeLabel);
          info.add(alt);
          info.add(positionLabel);
          info.add(pos);
          info.add(longitudeLabel);
          info.add(lon);
          pane.add(info);
          setContentPane(pane);
          setVisible(true);
     // Updates the values of the JTextFields in the GUI
     public static void updateValues(String c, String d, String e){
          alt.setText(c);
          pos.setText(d);
          lon.setText(e);
     public static void main(String[] args){
          InfoGpsGui berf = new InfoGpsGui();
          SerialEcho input = new SerialEcho("COM4", 9600);
//          Map prueba = new Map();
          while (true) { // Keeps open the link between the serial port and the GUI
               if (input.serialData) { // if there's data
                    otroBuffer = input.getData();
                    for (int i = 0; i < otroBuffer.length; i++) {
                         // System.out.print((char)otroBuffer);
                         letras = (char) otroBuffer; // Store data in letras
                    //System.out.println();
                    updateValues(Character.toString(letras[0]),Character.toString(letras[1]),
                              Character.toString(letras[2]));