Pong Game - Overflow Error

I can't figure out this problem that I'm having in my Pong game. It's compiling fine, except when I run it, it gives me an overflow error.

Here's the code:

// Pong
import javax.swing.JFrame;
import java.awt.Color;
import java.awt.Graphics;
 public class Pong extends JFrame {
private static final int WIDTH = 400;
private static final int HEIGHT = 400;
 
[Code] .....

Here's the error:

java.lang.StackOverflowError
at sun.awt.AppContext.get(AppContext.java:604)
at com.sun.java.swing.SwingUtilities3.getDelegateRepa intManager(SwingUtilities3.java:120)
at javax.swing.RepaintManager.getDelegate(RepaintMana ger.java:1625)
at javax.swing.RepaintManager.addDirtyRegion(RepaintM anager.java:445)

The error keeps going for a lot of more lines.

The line that gets highlighted is the first bracket of the Pong constructor.