import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;

public class ClipTest extends JPanel {
    Rectangle2D r;
    Ellipse2D e;
    
    public static void main(String[] args) { 
	JFrame f = new JFrame("ClipTest");
	f.setContentPane(new ClipTest());
	f.setSize(500, 300);
	f.setVisible(true);
	f.addWindowListener(new WindowAdapter() {
		public void windowClosing(WindowEvent e) {
		    System.exit(0);
		}
	    });
    }
    
    public void paintComponent(Graphics g) {
	super.paintComponent(g);
	Graphics2D g2 = (Graphics2D)g;
	
	//Create a ellipse in the center of this 
	//JPanel and a rectangle in the upper left corner.
	//Next two line can not be placed in the constructor since the the panel
	//report 0x0 sixe there.
	e = new Ellipse2D.Float(getWidth()/4f, getHeight()/4f, 
				getWidth()/2f, getHeight()/2f);
	r = new Rectangle2D.Float(0, 0, getWidth()/2, getHeight()/2);
	
	//Set the clipping area to the ellipse. 
	g2.setClip(e);
	g2.setColor(Color.cyan);
	//The next line seems to paint the whole JPanel, but only 
	//the ellipse gets painted sinve we have restricted the clipping area.
	g2.fillRect(0, 0, getWidth(), getHeight());
	
	//Set the clipping area to the intersection
	//of the ellipse and the rectangle.
	g2.clip(r);
	g2.setColor(Color.magenta);
	//Paint the new clipping area in another color.
	g2.fillRect(0, 0, getWidth(), getHeight());
    }
    
}