How do I double-buffer renders to a JPanel?

I'm trying to make a little breakout game with Java and Swing. The only issue so far is that drawing on the JPanel causes lots of flickering!

The relevant code:

JFrame frame = new JFrame("Breakout");
JPanel gameField = (JPanel) frame.getContentPane();

private void gameLoop() {
    while(running) {
        update();
        render((Graphics2D) gameField.getGraphics());
    }
}

private void render(Graphics2D g) {
    g.clearRect(0, 0, gameField.getWidth(), gameField.getHeight());
    for (GameObject o : objects) {
        o.draw(g);
    }
}

I've looked into manually double buffering (e.g. by making an offscreen Image, drawing on it, then doing g.drawImage(offscreen). Is there a better way?