import java.awt.Component;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Frame;
import java.awt.Button;
import java.awt.Panel;
import java.awt.BorderLayout;
import java.awt.event.WindowEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import java.awt.event.*;
public class Ringid {
    
    public static void main(String args[]) {   
        final Frame  frame     = new Frame ("Ilustus ringid");
        final Button btnStart  = new Button("Start");
        final Panel  pnlTarget = new Panel ();
        
        frame.add(btnStart,  BorderLayout.NORTH );
        frame.add(pnlTarget, BorderLayout.CENTER);
        
        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
               System.exit(0);
            }
        });        
        
        btnStart.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {                
                Thread painter = new Thread(new Runnable() {
                    public void run() {
                        try {
                            while (true) {
                                Thread circle = new 
CircleThread(pnlTarget);
                                circle.start();
                                Thread.sleep(100);
                            }
                        } catch (InterruptedException e) {}           
                    }                     
                });
                
                painter.start();
                btnStart.setEnabled(false);
            }
        });
        
        frame.setSize(500, 500);
        frame.setVisible(true);        
    }  
}
//----------------------------------------------------------------------------
// class CircleThread
//----------------------------------------------------------------------------
class CircleThread extends Thread {
    
    private int       x;
    private int       y;
    private int       maxDiameter; 
   

    private Graphics  graphics;
    
    public CircleThread(Component target) {               
        Dimension size = target.getSize();
        
        x           = (int)(Math.random() * size.width );
        y           = (int)(Math.random() * size.height);        
        maxDiameter = Math.min(size.width, size.height);             
        graphics    = target.getGraphics();     
    }

    public void run() {        
        int      red      = (int) (Math.random() * 255);
        int      green    = (int) (Math.random() * 255);
        int      blue     = (int) (Math.random() * 255);                           
        long     pause    = (long)(Math.random() *  10);        
        Color    color    = new Color(red, green, blue); 
        
        graphics.setColor(color);
        
        try {                        
            for (int diameter = 1; diameter < maxDiameter; diameter += 2, x--, y--) {                             

                graphics.drawOval(x, y, diameter, diameter);
                Thread.sleep(pause);                 
            }                        
        } catch (InterruptedException e) {}
    }    
}