Error RE: add method in GUI application

Question

I'm trying to put three circles (red, yellow, green) in a sub panel called "trafficLight." Unfortunately, I keep getting the following error message that prevents me from compiling the program:
*.\TrafficPanel.java:36: cannot find symbol*
symbol  : method add(Circle)
location: class javax.swing.JPanel
*          trafficLight.add(red);*
I believe I have all the import statements necessary, and the program will compile with the trafficLight.add(particular color - red, yellow or green) removed. In other words, if I leave the add(trafficLight); method, the program will compile, and I will see the sub panel trafficLight, just no circles. The class code with the add methods is below followed by my other classes.
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class TrafficPanel extends JPanel
     private final int PRIMARY_PANEL_WIDTH = 1000;
     private final int PRIMARY_PANEL_HEIGHT = 700;
     private final int TRAFFICLIGHT_PANEL_WIDTH = 400;
     private final int TRAFFICLIGHT_PANEL_HEIGHT = 660;
     private final int DIAMETER = 30;
     private final int Xr = 10;
     private final int Yr = 10;
     private final int Xy = 10;
     private final int Yy = 200;
     private final int Xg = 10;
     private final int Yg = 400;
     private JPanel trafficLight;
     private Circle red, yellow, green;
     public TrafficPanel()
          setBackground(Color.gray);
          setPreferredSize(new Dimension(PRIMARY_PANEL_WIDTH, PRIMARY_PANEL_HEIGHT));
          trafficLight = new JPanel();
          trafficLight.setBackground(Color.black);
          trafficLight.setPreferredSize(new Dimension(TRAFFICLIGHT_PANEL_WIDTH, TRAFFICLIGHT_PANEL_HEIGHT));
          red = new Circle(Xr, Yr, DIAMETER, DIAMETER, Color.gray);
          yellow = new Circle(Xy, Yy, DIAMETER, DIAMETER, Color.gray);
          green = new Circle(Xg, Yg, DIAMETER, DIAMETER, Color.gray);
          trafficLight.add(red);
          trafficLight.add(yellow);        // PROBLEM AREA. I DON'T KNOW WHY??
          trafficLight.add(green);
          add(trafficLight);
     public void paintComponent(Graphics page)
          super.paintComponent(page);
          red.draw(page);
          yellow.draw(page);
          green.draw(page);
import javax.swing.*;
import java.awt.*;
public class Circle
     private int X, Y, Width, Height;
     private Color color;
     public Circle(int x, int y, int width, int height, Color c )
          X = x;
          Y = y;
          Width = width;
          Height = height;
          color = c;
     public void draw(Graphics page)
          page.setColor(color);
          page.fillOval(X, Y, Width, Height);
     public void setColor(Color c)
          color = c;
import javax.swing.*;
public class TrafficLight
     public static void main(String[] args)
          JFrame frame = new JFrame("Traffic Light");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          TrafficPanel primary = new TrafficPanel();
          frame.getContentPane().add(primary);
          frame.pack();
          frame.setVisible(true);
}

Answer 1

Still having trouble getting the circles to appear on the sub panel "light." They are showing up on the primary panel and being covered by the sub panel. Here's the code. Please give me a strong hint, at least. This is not a school assignment; I'm just trying to learn this for school next fall.
import javax.swing.*;
import java.awt.*;
public class TrafficLight extends JPanel
     Circle red, yellow, green;
     public static void main(String[] args)
          final int DIAMETER = 30;
           final int Xr = 500;
          final int Yr = 10;
          final int Xy = 500;
          final int Yy = 200;
          final int Xg = 500;
           final int Yg = 400;
          JFrame frame = new JFrame("Traffic Light");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          TrafficPanel primary = new TrafficPanel();
          Circle red = new Circle(Xr, Yr, DIAMETER, DIAMETER, Color.red);
          Circle yellow = new Circle(Xr, Yr, DIAMETER, DIAMETER, Color.yellow);
          Circle green = new Circle(Xr, Yr, DIAMETER, DIAMETER, Color.red);
          frame.getContentPane().add(primary);
          frame.pack();
          frame.setVisible(true);
     public void paintComponent(Graphics page)
          super.paintComponent(page);
          red.draw(page);
          yellow.draw(page);
          green.draw(page);
import javax.swing.*;
import java.awt.*;
public class TrafficPanel extends JPanel
     private final int PRIMARY_PANEL_WIDTH = 1000;
     private final int PRIMARY_PANEL_HEIGHT = 700;
     private final int TRAFFICPANEL_PANEL_WIDTH = 400;
     private final int TRAFFICPANEL_PANEL_HEIGHT = 660;
     private JPanel light;
     public TrafficPanel()
          setBackground(Color.green);
          setPreferredSize(new Dimension(PRIMARY_PANEL_WIDTH, PRIMARY_PANEL_HEIGHT));
          light = new JPanel();
          light.setBackground(Color.black);
          light.setPreferredSize(new Dimension(TRAFFICPANEL_PANEL_WIDTH, TRAFFICPANEL_PANEL_HEIGHT));
          add(light);
import javax.swing.*;
import java.awt.*;
public class Circle
     private int X, Y, Width, Height;
     private Color color;
     public Circle(int x, int y, int width, int height, Color c )
          X = x;
          Y = y;
          Width = width;
          Height = height;
          color = c;
     public void draw(Graphics page)
          page.setColor(color);
          page.fillOval(X, Y, Width, Height);
     public void setColor(Color c)
          color = c;
}