This example demonstrates how to set a clipping area using a shape. The example sets an oval for the clipping area and then draws and image. Only those pixels of the image that fall within the oval are displayed. 
    // See e575 The Quintessential Drawing Program
    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D)g;
    
        // Create an oval shape that's as large as the component
        float fx = 0;
        float fy = 0;
        float fw = getSize().width-1;
        float fh = getSize().height-1;
        Shape shape = new java.awt.geom.Ellipse2D.Float(fx, fy, fw, fh);
    
        // Set the clipping area
        g2d.setClip(shape);
    
        // Draw an image
        int x = 0;
        int y = 0;
        g2d.drawImage(image, x, y, this);
    }