Painting JFrame Difficulty

Question

In my code I am trying to paint by JFrame but it is not painting correctly. I tell the frame to paint in the beginning where I create it however it is the normal grey color once it is created. I think it may have to do with the fact that I am repainting it, if so how can I make sure it is repainted yellow? Could someone try to figure out why my code is not painting the JFrame Yellow? Thank you!

public class EvolutionColor {

    public static void main(String args[]) {
        JFrame frame = new JFrame("Bouncing Ball");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        BallPanel bp = new BallPanel();
        frame.add(bp);
        frame.setSize(600, 600); // set frame size
        frame.setVisible(true); // display frame
        frame.setBackground(Color.YELLOW);
    }

    class BallPanel extends JPanel implements ActionListener {

        private int delay = 10;
        protected Timer timer;

        private int x = 0;        // x position
        private int y = 0;        // y position
        private int radius = 15;  // ball radius

        private int dx = 2;       // increment amount (x coord)
        private int dy = 2;       // increment amount (y coord)

        public BallPanel() {
            timer = new Timer(delay, this);
            timer.start();       // start the timer
        }

        public void actionPerformed(ActionEvent e) {
            repaint();
        }

        public void paintComponent(Graphics g) {
            super.paintComponent(g); // call superclass's paintComponent 
            g.setColor(Color.red);

// check for boundaries
            if (x < radius) {
                dx = Math.abs(dx);
            }
            if (x > getWidth() - radius) {
                dx = -Math.abs(dx);
            }
            if (y < radius) {
                dy = Math.abs(dy);
            }
            if (y > getHeight() - radius) {
                dy = -Math.abs(dy);
            }

// adjust ball position
            x += dx;
            y += dy;
            g.fillOval(x - radius, y - radius, radius * 2, radius * 2);
        }


}

Answer 1

Don't set the JFrame to yellow, set the BallPanel object to yellow.