import java.awt.*;					// Graphics stuff
import java.awt.event.*;			// ActionListener and Timer
import javax.swing.*;				// JFrame, JPanel
import java.util.Random;			// Random number generator used by each BouncingBall

public class BouncingBalls
{
	public static void main(String[] args)
	{
		JFrame frame=new JFrame();
		frame.setSize(540,540);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		GraphicsPanel gp=new GraphicsPanel();
		frame.add(gp);
		frame.setVisible(true);
	}
	
	public static class GraphicsPanel extends JPanel implements ActionListener	// here is where the action is
	{
		private BouncingBall[] balls;					// We will create an array of BouncingBalls to move around the screen
		private int number;								// this stores the number of BouncingBalls to deal with, change this value to increase or decrease number of balls on the screen
		private Random generator;						// used to initialize ball location, motion and color
		
		public GraphicsPanel()
		{
			number=25;									// we'll use 25
			generator=new Random();						
			balls=new BouncingBall[number];				// instantiate the array
			for(int i=0;i<number;i++)					// instantiate each BouncingBall
				balls[i]=new BouncingBall(500,500,generator);	
			Timer t=new Timer(30,this);					// create a Timer whose ActionListener will be this class
			t.start();									// start the Timer
		}
		
		public void actionPerformed(ActionEvent e)		// Timer generated an ActionEvent, move the balls
		{
			for(int i=0;i<number;i++)
				balls[i].move();						// tell each ball to move itself
			repaint();									// and then redraw the Graphics object
		}
		
		public void paintComponent(Graphics g)
		{
			super.paintComponent(g);					// start with a new image
			g.setColor(Color.white);
			g.fillRect(0,0,540,540);					// fill the background as white
			for(int i=0;i<number;i++)
				balls[i].draw(g);						// then have each ball draw itself
		}
	}
}