import java.awt.*;
import java.applet.Applet;
import java.awt.event.*;

class Ball {
    int x = 7, xChange = 7;
    int y = 2, yChange = 2;
    int diameter = 10;
    Color color = Color.RED;
    
    Ball() {
        
    }
    
    Ball(int x, int y, int xChange, int yChange, int diameter, Color color) {
        this.x = x;
        this.y = y;
        this.xChange = xChange;
        this.yChange = yChange;
        this.diameter = diameter;
        this.color = color;
    }
    
}

class Bounds {
    int LeftX = 50, RightX = 150;
    int TopY = 50, BottomY = 150;
}

public class BallBox6  extends Applet implements Runnable, MouseListener {
    
    
    int numBalls = 5;
    Ball [] balls;
    
    
    Bounds box;
    
    // Next two lines allow for "friendly" animation
    Thread t = null;
    boolean threadSuspended = true;
    
    public void init() {
        box = new Bounds();
        balls = new Ball[numBalls];
        balls[0] = new Ball();
        balls[1] = new Ball(7, 2, 3, 5, 12, Color.GREEN);
        balls[2] = new Ball(7, 2, 4, -1, 8, Color.BLUE);
        balls[3] = new Ball(7, 2, 5, 2, 9, Color.CYAN);
        balls[4] = new Ball(7, 2, 3, -4, 11, Color.MAGENTA);
        
        addMouseListener(this);
        
    }
    
    private void eraseBall(Graphics g, Ball ball) {
        g.fillOval(ball.x + box.LeftX, ball.y + box.TopY, ball.diameter, ball.diameter);
    }
    
    private void moveAndDrawBall(Graphics g, Ball ball) {
        int margin = ball.diameter;
        int width = box.RightX - box.LeftX - margin;
        int height = box.BottomY - box.TopY - margin;
        if (ball.x <= 0) ball.xChange = -ball.xChange;
        if (ball.x >= width) ball.xChange = -ball.xChange;
        
        if (ball.y <= 0) ball.yChange = -ball.yChange;
        if (ball.y >= height) ball.yChange = -ball.yChange;
        ball.x = ball.x + ball.xChange;
        ball.y = ball.y + ball.yChange;
        g.setColor(ball.color);
        g.fillOval(ball.x + box.LeftX, ball.y + box.TopY, ball.diameter, ball.diameter);
        
    }
    
    
    public void paint(Graphics g) {
        if (!threadSuspended) {
        g.drawString("Click to Stop", box.LeftX, box.TopY - 10);
        } 
        else {
            g.drawString("Click to Start", box.LeftX, box.TopY - 10);
        }
        
        g.drawRect(box.LeftX, box.TopY, box.RightX - box.LeftX,
                box.BottomY - box.TopY);
        
        Color backgroundColor = getBackground();
        g.setColor(backgroundColor);
        
        for (int i = 0; i < numBalls; i++) {
            eraseBall(g, balls[i]);
        }
        
        for (int i = 0; i < numBalls; i++) {
            moveAndDrawBall(g, balls[i]);
        }
        
    }
    
    
            /*
             *  The following routines destroy(), start(), stop(), run() are needed
             *  to manage the thread which handles the animation.  You don't need to
             *  understand them (threads are in chapter 25).  If you wanted to put int
             *  a different animation you would change paint() and updateMyAnim();
             */
    // Executed when the applet is destroyed.
    public void destroy() {
        
    }
    
    // Executed after the applet is created; and also whenever
    // the browser returns to the page containing the applet.
    // This is boilerplate - don't change it!
    public void start() {
        
        if ( t == null ) {
            
            t = new Thread( this );
            
            threadSuspended = false;
            t.start();
        } else {
            if ( threadSuspended ) {
                threadSuspended = false;
                
                synchronized( this ) {
                    notify();
                }
            }
        }
        
    }
    
    // Executed whenever the browser leaves the page containing the applet.
    public void stop() {
        
        threadSuspended = true;
    }
    
    // Executed within the thread that this applet created.
    // more boilerplate.
    public void run() {
        
        try {
            while (true) {
                
                // Here's where the thread does some work
                // In BallBox all updating actually happens in paint so we
                // don't have this routine.
                // updateMyAnim();
                
                // Now the thread checks to see if it should suspend itself
                if ( threadSuspended ) {
                    synchronized( this ) {
                        while ( threadSuspended ) {
                            
                            wait();
                        }
                    }
                }
                
                // the call to repaint causes the window system to call our paint.
                repaint();
                
                t.sleep( 50 );  // interval given in milliseconds to sleep
                // larger number - slower animation
                // smaller number - faster animation
            }
        } catch (InterruptedException e) { }
        
    }
    
    //  Mouse listener routines to allow for starting / stopping of animation
    public void mouseClicked(MouseEvent event) {
        if (!threadSuspended) {
            stop();
            repaint();
        } else {
            start();
        }
        
    }
    
    public void mouseReleased(MouseEvent event) {
        
    }
    
    public void mousePressed(MouseEvent event) {
        
    }
    
    public void mouseEntered(MouseEvent event) {
        
    }
    
    public void mouseExited(MouseEvent event) {
        
    }
}