PongGame.java

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

public class PongGame extends Applet implements Runnable {

    Thread th;
    boolean rbup = false;
    boolean rbdown = false;
    boolean lbup = false;
    boolean lbdown = false;
    final int TOP = 20;
    final int BOTTOM = 280;
    int rbpx, rbpy, lbpx, lbpy;
    int ballX, ballY, balldx, balldy;
    int rpoints, lpoints;
    Image buf;
    Graphics buffergr;
    public static final int frameWidth = 500;
    public static final int frameHeight = 350;

    public void start() {
        th = new Thread(this);
        th.start();
    }

    public void stop() {
        th = null;
    }

    public void run() {
        while (th != null) {
            controlBars();
            ballUpdate();
            repaint();
            try {
                Thread.sleep(30);
            } catch (InterruptedException e) {
                System.err.println("Sleep catch:" + e);
            }
        }
    }

    public void init() {
        setBackground(new Color(26, 26, 26));
        setSize(500, 350);
        ballX = 70;
        ballY = 70;
        balldx = 7;
        balldy = 3;
        rbpx = 450;
        rbpy = 50;
        lbpx = 50;
        lbpy = 50;
        addKeyListener(new keypadControl());
        addMouseListener(new mouseControl());
    }

    public void paint(Graphics g) {

        g.clearRect(0, 0, frameWidth, frameHeight);

        //Draw Ball
        g.fillOval(ballX - 10, ballY - 10, 20, 20);
        g.setColor(new Color(30,164,16));

        //Draw Bars
        g.fillRect(rbpx - 4, rbpy, 8, 30);
        g.fillRect(lbpx - 4, lbpy, 8, 30);

        g.setColor(new Color(255, 82, 82));
        g.drawString("" + lpoints, 80, 310);
        g.drawString("" + rpoints, 340, 310);
    }

    public void update(Graphics g) {
        if (buf == null) {
            buf = createImage(frameWidth, frameHeight);
            buffergr = buf.getGraphics();
        }
        paint(buffergr);
        g.drawImage(buf, 0, 0, null);
    }

    private class keypadControl extends KeyAdapter {

        public void keyPressed(KeyEvent e) {
            switch (e.getKeyCode()) {
                case KeyEvent.VK_Q:
                    lbup = true;
                    break;
                case KeyEvent.VK_A:
                    lbdown = true;
                    break;
                case KeyEvent.VK_W:
                    rbup = true;
                    break;
                case KeyEvent.VK_S:
                    rbdown = true;
                    break;
            }
        }

        public void keyReleased(KeyEvent e) {
            switch (e.getKeyCode()) {
                case KeyEvent.VK_Q:
                    lbup = false;
                    break;
                case KeyEvent.VK_A:
                    lbdown = false;
                    break;
                case KeyEvent.VK_W:
                    rbup = false;
                    break;
                case KeyEvent.VK_S:
                    rbdown = false;
                    break;
            }
        }
    }

    private class mouseControl extends MouseAdapter {

        public void mouseClicked(MouseEvent e) {
            requestFocus();
        }
    }

    void controlBars() {
        if (rbup) {
            if (rbpy > TOP + 4) {
                rbpy -= 4;
            }
        }
        if (rbdown) {
            if (rbpy + 30 < BOTTOM - 4) {
                rbpy += 4;
            }
        }
        if (lbup) {
            if (lbpy > TOP + 4) {
                lbpy -= 4;
            }
        }
        if (lbdown) {
            if (lbpy + 30 < BOTTOM - 4) {
                lbpy += 4;
            }
        }
    }

    void ballUpdate() {
        ballX += balldx;
        ballY += balldy;
        if (ballX < 20) {
            rpoints++;
            ballX = 430;
            ballY = (int) (70 + 20 * Math.random());
            balldx = -7;
            balldy = 4;
        }
        if (ballX > PongGame.frameWidth - 20) {
            lpoints++;
            ballX = 70;
            ballY = (int) (70 + 20 * Math.random());
            balldx = 7;
            balldy = 4;
        }
        if (ballY - 10 < TOP) {
            balldy = -balldy;
        }
        if (ballY + 10 > BOTTOM) {
            balldy = -balldy;
        }
        if ((Math.abs(rbpx - ballX) < 14) && (ballY > rbpy - 10) && (ballY < rbpy + 40)) {
            balldx = -balldx;
        }
        if ((Math.abs(lbpx - ballX) < 14) && (ballY > lbpy - 10) && (ballY < lbpy + 40)) {
            balldx = -balldx;
        }

    }
}