Screen.java

package game.pong;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

public class Screen extends JPanel implements ActionListener, KeyListener{

    private static final long serialVersionUID = -2269658144317723282L;

    Player player = new Player();
    Ball ball = new Ball();
    Computer computer = new Computer(this);

    public Screen(){
        Timer time = new Timer(20, this);
        time.start();

        this.addKeyListener(this);
        this.setFocusable(true);
    }

    private void update(){
        player.update();
        ball.update();
        computer.update();

        ball.hasCollided(player);
    }

    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.fillRect(0, 0, Game.WIDTH, Game.HEIGHT);
        g.setColor(Color.WHITE);
        g.drawString("" + player.score, 30, 30);
        g.drawString("" + computer.score, 560, 30);
        player.paint(g);
        ball.paint(g);
        computer.paint(g);
    }

    public Ball getBall() {
        return ball;
    }

    public void actionPerformed(ActionEvent e) {
        update();
        repaint();
    }

    public void keyPressed(KeyEvent e) {
        if(e.getKeyCode() == KeyEvent.VK_W || e.getKeyCode() == KeyEvent.VK_UP){
            player.setVelocity(-3);
        }else if(e.getKeyCode() == KeyEvent.VK_S || e.getKeyCode() == KeyEvent.VK_DOWN){
            player.setVelocity(3);
        }

        if(e.getKeyCode() == KeyEvent.VK_W || e.getKeyCode() == KeyEvent.VK_UP && player.getY() < 0){
            player.setVelocity(0);
        }else if(e.getKeyCode() == KeyEvent.VK_S || e.getKeyCode() == KeyEvent.VK_DOWN  && player.getY() > 311){
            player.setVelocity(0);
        }
    }

    public void keyReleased(KeyEvent e) {
        int keyCode = e.getKeyCode();

        if(keyCode == KeyEvent.VK_W || keyCode == KeyEvent.VK_S || keyCode == KeyEvent.VK_UP || keyCode == KeyEvent.VK_DOWN){
            player.setVelocity(0);
        }
    }

    public void keyTyped(KeyEvent e) {

    }
}