Painting JComponent Onto JPanel

I am attempting to make some Java2D shapes by wrapping them in subclasses of JComponent and giving them functionality. Unfortunately after defining paintComponent and adding it to the JPanel the shape is not showing up. As in my last thread the code is mostly irrelevant but the perhaps worth a skim. The only methods truely relevant are the paintComponent method in my shape and Sandbox constructor.

Java Code:

public class Sandbox extends JPanel
{
private Timer timer;
private Circle c;
public Sandbox()
{
c = new Circle();
add(c);
setPreferredSize(new Dimension(400, 300));

[Code] ....