Bouncing Ball game using java

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package bouncingball;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JPanel;


/**
 *
 * @author project
 */
public class BouncingBall extends JPanel{
    static final int BOX_WIDTH=300;
    static final int BOX_HEIGHT=400;
    Ball ball=new Ball(this);
    Bat bat=new Bat(this);
  
   
BouncingBall(){
  
    this.setPreferredSize(new Dimension(BOX_WIDTH, BOX_HEIGHT));
  
    addKeyListener(new KeyListener() {

            @Override
            public void keyTyped(KeyEvent e) {
              //  throw new UnsupportedOperationException("Not supported yet.");
            }

            @Override
            public void keyPressed(KeyEvent e) {
              //  throw new UnsupportedOperationException("Not supported yet.");
                bat.keyPressed(e);
            }

            @Override
            public void keyReleased(KeyEvent e) {
                //throw new UnsupportedOperationException("Not supported yet.");
                bat.keyReleased(e);
            }
        });setFocusable(true);
}
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        Graphics2D g2d=(Graphics2D)g;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);       
        g2d.setColor(Color.black);
        g2d.fillRect(0, 0, BOX_WIDTH, BOX_HEIGHT);
         g2d.setColor(Color.white);
        g2d.drawString("Developed By Aravind Sankaran", BOX_WIDTH/5, BOX_HEIGHT/getHeight()+15);
        ball.paint(g2d);
        bat.paint(g2d);
    }
void move(){
    ball.move();
    bat.move();
}
      public static void main(String[] args) {
        // TODO code application logic here
        BouncingBall bBall=new BouncingBall();
        
        JFrame frame=new JFrame("Ball Game");
       
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(BOX_WIDTH, BOX_HEIGHT);
        frame.add(bBall);
        frame.setResizable(false);
        frame.setVisible(true);
       
       while(true){
           bBall.move();
           bBall.repaint();
            try {
                Thread.sleep(8);
               
            } catch (InterruptedException ex) {
                Logger.getLogger(BouncingBall.class.getName()).log(Level.SEVERE, null, ex);
            }
       }
    }
}

class Ball{
    int x=0;
    int y=0;
    int xa=1;
    int ya=1;
    private BouncingBall bBall;
    public  Ball(BouncingBall bBall){
      this.bBall=bBall; 
    }
    void move(){
        if(x+xa<0){
            xa=1;
        }
        if(x+xa>bBall.getWidth()-30){
            xa=-1;
        }
        if(y+ya<0){
            ya=1;
        }
        if(y+ya>bBall.getHeight()-40){
            ya=-1;
        }
        x=x+xa;
        y=y+ya;
    }
   public void paint(Graphics g){
      //super.paint(g);
       Graphics2D g2d=(Graphics2D)g;
       g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
       g2d.setColor(Color.red);
       g2d.fillOval(x, y, 30, 30);
    
    }
}

class Bat{
    int x=0;
    int xa=0;
    private BouncingBall bBall;
    public  Bat(BouncingBall bBall){
      this.bBall=bBall; 
    }
    void paint(Graphics g){
         Graphics2D g2d=(Graphics2D)g;
       g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
       g2d.setColor(Color.white);
       g2d.fillRect(x, bBall.getHeight()-12, 70, 20);
    }
    void move(){
        if(x+xa>0 && x+xa<bBall.getWidth()-60){
            x=x+xa;          
        }
    }
    void keyPressed(KeyEvent e) {
        if(e.getKeyCode()==KeyEvent.VK_LEFT){
            xa=-1;
        }
        if(e.getKeyCode()==KeyEvent.VK_RIGHT){
            xa=1;
        }
    }
    public void keyReleased(KeyEvent e) {
        xa=0;
    }
}