import javax.swing.*;
import java.util.*;
import java.awt.*;
import java.io.*;

public class Roller {
	private Circle circle;
	private Color color;
	private JFrame w;
	Random random;
	
	public Roller() {
		int   r = 20;
		Point p = new Point(100, 100);
		circle = new Circle(r, p);
		
		color = Color.RED;
				
		w = new JFrame("Rolling around");
		w.setSize(250, 250);
		w.setVisible(true);
		w.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE  );

		random = new Random();
	}
	
	public void roll() {
		erase();
		
		Point here = circle.getCenter();
		int x = here.x;
		int y = here.y;
		
		int deltax = random.nextInt(31) - 15;
		int deltay = random.nextInt(31) - 15;
		
		Point there = new Point( x + deltax, y + deltay );
		
		circle.setCenter(there);

		paint();
		
		pause();
	}
	
	public static void pause() {
		try {
			(new Thread()).sleep(500);
		}
		catch (Exception e) {
			return;
		}
	}
	
	public void erase() {
		Graphics g = w.getGraphics();
		
		Color background = w.getBackground();
		g.setColor( background );
		
		g.fillOval(
			circle.getCenter().x, circle.getCenter().y,
			circle.getRadius(), circle.getRadius() );
	}
	
	public void paint() {
		Graphics g = w.getGraphics();

		g.setColor( this.color );
		
		g.fillOval(
			circle.getCenter().x, circle.getCenter().y,
			circle.getRadius(), circle.getRadius()
			);		
	}
	
	public static void main(String[] args) throws IOException {
		
		Roller ball = new Roller( );
		
		System.out.println("Hit enter when ready");
		System.in.read();
		
		while ( true)  {
			ball.roll();
		}
		
		
	}
}