Painting the slider icon of JSlider

Extending the BasicSliderUI delegate is not without peril, but it does allow arbitrary control over the rendering, as suggested in the example below.

slider.setUI(new MySliderUI(slider));
...
private static class MySliderUI extends BasicSliderUI {

    private static float[] fracs = {0.0f, 0.2f, 0.4f, 0.6f, 0.8f, 1.0f};
    private LinearGradientPaint p;

    public MySliderUI(JSlider slider) {
        super(slider);
    }

    @Override
    public void paintTrack(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        Rectangle t = trackRect;
        Point2D start = new Point2D.Float(t.x, t.y);
        Point2D end = new Point2D.Float(t.width, t.height);
        Color[] colors = {Color.magenta, Color.blue, Color.cyan,
            Color.green, Color.yellow, Color.red};
        p = new LinearGradientPaint(start, end, fracs, colors);
        g2d.setPaint(p);
        g2d.fillRect(t.x, t.y, t.width, t.height);
    }

    @Override
    public void paintThumb(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        Rectangle t = thumbRect;
        g2d.setColor(Color.black);
        int tw2 = t.width / 2;
        g2d.drawLine(t.x, t.y, t.x + t.width - 1, t.y);
        g2d.drawLine(t.x, t.y, t.x + tw2, t.y + t.height);
        g2d.drawLine(t.x + t.width - 1, t.y, t.x + tw2, t.y + t.height);
    }
}