GamePanel.java

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import java.awt.*;
import  javax.swing.JOptionPane;

class Score extends Rectangle{

    static int GAME_WIDTH;
    static int GAME_HEIGHT;
    int player1;
    int player2;


    Score(int GAME_WIDTH, int GAME_HEIGHT){
        Score.GAME_WIDTH = GAME_WIDTH;
        Score.GAME_HEIGHT = GAME_HEIGHT;
    }
    public void draw(Graphics g) {
        g.setColor(Color.white);
        g.setFont(new Font("Consolas", Font.PLAIN, 60));

        g.drawLine(GAME_WIDTH / 2, 0, GAME_WIDTH / 2, GAME_HEIGHT);

        g.drawString(String.valueOf(player1 / 10) + String.valueOf(player1 % 10), (GAME_WIDTH / 2) - 85, 50);
        g.drawString(String.valueOf(player2 / 10) + String.valueOf(player2 % 10), (GAME_WIDTH / 2) + 20, 50);
    }

    public int getPlayer1() {
        return player1;
    }

    public int getPlayer2() {
        return player2;
    }
}
public class GamePanel extends JPanel implements Runnable{

    static final int GAME_WIDTH = 1000;
    static final int GAME_HEIGHT = (int)(GAME_WIDTH * (0.5555));
    static final Dimension SCREEN_SIZE = new Dimension(GAME_WIDTH,GAME_HEIGHT);
    static final int BALL_DIAMETER = 20;
    static final int PADDLE_WIDTH = 25;
    static final int PADDLE_HEIGHT = 100;
    Thread gameThread;
    Image image;
    Graphics graphics;
    Random random;
    Paddle paddle1;
    Paddle paddle2;
    Ball ball;
    Score score;

    GamePanel(){
        newPaddles();
        newBall();
        score = new Score(GAME_WIDTH,GAME_HEIGHT);
        this.setFocusable(true);
        this.addKeyListener(new AL());
        this.setPreferredSize(SCREEN_SIZE);

        gameThread = new Thread(this);
        gameThread.start();
    }

    public void newBall() {
        random = new Random();
        ball = new Ball((GAME_WIDTH/2)-(BALL_DIAMETER/2),random.nextInt(GAME_HEIGHT-BALL_DIAMETER),BALL_DIAMETER,BALL_DIAMETER);
    }
    public void newPaddles() {
        paddle1 = new Paddle(0,(GAME_HEIGHT/2)-(PADDLE_HEIGHT/2),PADDLE_WIDTH,PADDLE_HEIGHT,1);
        paddle2 = new Paddle(GAME_WIDTH-PADDLE_WIDTH,(GAME_HEIGHT/2)-(PADDLE_HEIGHT/2),PADDLE_WIDTH,PADDLE_HEIGHT,2);
    }
    public void paint(Graphics g) {
        image = createImage(getWidth(),getHeight());
        graphics = image.getGraphics();
        draw(graphics);
        g.drawImage(image,0,0,this);
    }
    public void draw(Graphics g) {
        paddle1.draw(g);
        paddle2.draw(g);
        ball.draw(g);
        score.draw(g);
        Toolkit.getDefaultToolkit().sync(); // I forgot to add this line of code in the video, it helps with the animation

    }
    public void move() {
        paddle1.move();
        paddle2.move();
        ball.move();
    }
    public void checkCollision() {

        //bounce ball off top & bottom window edges
        if(ball.y <=0) {
            ball.setYDirection(-ball.yVelocity);
        }
        if(ball.y >= GAME_HEIGHT-BALL_DIAMETER) {
            ball.setYDirection(-ball.yVelocity);
        }
        //bounce ball off paddles
        if(ball.intersects(paddle1)) {
            ball.xVelocity = Math.abs(ball.xVelocity);
            ball.xVelocity++; //optional for more difficulty
            if(ball.yVelocity>0)
                ball.yVelocity++; //optional for more difficulty
            else
                ball.yVelocity--;
            ball.setXDirection(ball.xVelocity);
            ball.setYDirection(ball.yVelocity);
        }
        if(ball.intersects(paddle2)) {
            ball.xVelocity = Math.abs(ball.xVelocity);
            ball.xVelocity++; //optional for more difficulty
            if(ball.yVelocity>0)
                ball.yVelocity++; //optional for more difficulty
            else
                ball.yVelocity--;
            ball.setXDirection(-ball.xVelocity);
            ball.setYDirection(ball.yVelocity);
        }
        //stops paddles at window edges
        if(paddle1.y<=0)
            paddle1.y=0;
        if(paddle1.y >= (GAME_HEIGHT-PADDLE_HEIGHT))
            paddle1.y = GAME_HEIGHT-PADDLE_HEIGHT;
        if(paddle2.y<=0)
            paddle2.y=0;
        if(paddle2.y >= (GAME_HEIGHT-PADDLE_HEIGHT))
            paddle2.y = GAME_HEIGHT-PADDLE_HEIGHT;
        //give a player 1 point and creates new paddles & ball
        if(ball.x <=0) {
            score.player2++;
            newPaddles();
            newBall();
            System.out.println("Player 2: "+score.player2);
        }
        if(ball.x >= GAME_WIDTH-BALL_DIAMETER) {
            score.player1++;
            newPaddles();
            newBall();
            System.out.println("Player 1: "+score.player1);
        }
    }
    public void run() {
        //game loop
        long lastTime = System.nanoTime();
        double amountOfTicks =60.0;
        double ns = 1000000000 / amountOfTicks;
        double delta = 0;
        label:
        while(true) {
            long now = System.nanoTime();
            delta += (now -lastTime)/ns;
            lastTime = now;
            if(delta >=1) {
                move();
                checkCollision();
                repaint();
                delta--;
                if(score.player1 == 3 || score.player2 ==3){
                    if (score.player1==3) {
                        JOptionPane.showMessageDialog(null,"Player 1 wins", "Game Finished",JOptionPane.INFORMATION_MESSAGE);
                        break label;
                    }
                    else
                        JOptionPane.showMessageDialog(null,"Player 2 wins", "Game Finished",JOptionPane.INFORMATION_MESSAGE);
                    break label;
                }
            }
        }
    }
    public class AL extends KeyAdapter{
        public void keyPressed(KeyEvent e) {
            paddle1.keyPressed(e);
            paddle2.keyPressed(e);
        }
        public void keyReleased(KeyEvent e) {
            paddle1.keyReleased(e);
            paddle2.keyReleased(e);
        }
    }
}