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

/*
 ***************************************************************
 * Silly Sample program which demonstrates the basic paint
 * mechanism for Swing components.
 ***************************************************************
 */
public class SwingPaintDemo {
    public static void main(String[] args) {
        JFrame f = new JFrame("Aim For the Center");
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        Container panel = new BullsEyePanel();
        panel.add(new JLabel("BullsEye!", SwingConstants.CENTER), BorderLayout.CENTER);
        f.getContentPane().add(panel, BorderLayout.CENTER);
        f.pack();
        f.show();
    }
}

/**
 * A Swing container that renders a bullseye background
 * where the area around the bullseye is transparent.
 */
class BullsEyePanel extends JPanel {

    public BullsEyePanel() {
        super();
        setOpaque(false); // we don't paint all our bits
        setLayout(new BorderLayout());
        setBorder(BorderFactory.createLineBorder(Color.black));
    }

    public Dimension getPreferredSize() {
        // Figure out what the layout manager needs and
        // then add 100 to the largest of the dimensions
        // in order to enforce a 'round' bullseye 
        Dimension layoutSize = super.getPreferredSize();
        int max = Math.max(layoutSize.width,layoutSize.height);
        return new Dimension(max+100,max+100);
    }

    protected void paintComponent(Graphics g) {
        Dimension size = getSize();
        int x = 0;
        int y = 0;
        int i = 0;
        while(x < size.width && y < size.height) {
            g.setColor(i%2==0? Color.red : Color.white);
            g.fillOval(x,y,size.width-(2*x),size.height-(2*y));
            x+=10; y+=10; i++;
        }
    }
}