Help with networked pong game

I am having a couple of problems with my code. First, whenever I try to remove the JOptionPane from line 79 in my code, I get a NullPointerException from the line this.dbGraphics = this.dbImage.getGraphics(); a couple of lines down from the JOptionPane. Does anyone know why? Another problems is that I tried to convert this applet into a application program, and whenever I did so, I lost all of the score/info from the top of the screen. It's still there, but not all of it is visible for some reason. Why is that? Also, the main purpose of this project is to create a networked pong game. I want to create two other classes, hostpong and clientpong where the host holds all of the game logic, sends its paddle and ball location to the client, the client simply draws everything, and sends its paddle location back to the host (using udp datagram packets). Is this the best way to implement this? I will take any help, advice, code that you are willing to provide. Thank you for any help you may give!

*Need help resolving NullPointException, turning applet into proper application (w/out errors), networking.

Code:

import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.Image; import java.awt.event.KeyEvent; import java.awt.event.KeyListener; import java.util.Random; import java.io.*; import java.awt.*; import java.util.*; import java.applet.*; import javax.swing.*; import java.awt.event.*; import javax.swing.event.*; import javax.swing.JApplet; public class SinglePlayer extends JFrame implements KeyListener { // just a random variable to randomize some things static Random rand = new Random(System.currentTimeMillis()); // the width & height for our applet public static int width = 500, height = 500; // will the user be playing against the computer or a person //public boolean twoPlayers = false; // is the game paused boolean paused = true; // what is the top boundary int top = 20; // information to be displayed static String info = "TECHNO PONG"; static String pause1 = "blue player use a/z"; static String pause2 = "red player use k/m"; static String pause3 = "p to pause"; // font to display normal info Font defFont = new Font("arial", 0, 12); // double buffering stuff Image dbImage; Graphics dbGraphics; // the ball Ball ball = new Ball(this, width/2, height/2, 2, 2, top, height); // the paddles Paddle leftPaddle = new Paddle(Paddle.TYPE_LEFT, 5, height/2, top, height, 'a', 'z'); Paddle rightPaddle = new Paddle(Paddle.TYPE_RIGHT, width-Paddle.width-5, height/2, top, height, 'k', 'm'); // scores int leftScore=0; int rightScore=0; // font used to display score Font scoreFont = new Font("Arial", 0, 18); /** * Initialize method, it will start up pong * and keep it going. */ public SinglePlayer() { init(); setSize(width, height); setVisible(true); setResizable(false); } public void init() { // ask the user if they want to play against the computer int option = JOptionPane.showConfirmDialog(this, "placeholder", "Competition", JOptionPane.OK_OPTION); // set the size and background color this.setSize(width, height); this.getContentPane().setBackground(Color.black); // create the double buffering images/graphics this.dbImage = this.createImage(width, height); this.dbGraphics = this.dbImage.getGraphics(); // give ability to catch keyboard input this.addKeyListener(this); // a new thread that keeps on updating our applet new Thread() { public void run() { while(true) { // do if paused if(!paused) { // update and paint our game often updatePong(); paint(getGraphics()); pause(5); } else { // paint our game only, we are paused paint(getGraphics()); pause(100); } } } }.start(); } /* updates the game */ public void updatePong() { updateBall(); updatePaddles(); } /* update our ball */ public void updateBall() { checkBallWithPaddle(ball, leftPaddle); checkBallWithPaddle(ball, rightPaddle); ball.update(); } /* check to see if the given ball collided with the given paddle */ public void checkBallWithPaddle(Ball ball, Paddle paddle) { // make some temp variables for easy referencing int bx = ball.xLoc, by = ball.yLoc, bs = ball.size; int px = paddle.xLoc, py = paddle.yLoc; int pw = Paddle.width, ph = Paddle.height, sec = ph/5; boolean ballCollided=false; if(paddle.myType == Paddle.TYPE_LEFT) { if(isWithin(px, px+pw, bx, 0) && isWithin(py, py+ph, by, bs)) { ballCollided = true; ball.xLoc = px+pw; } } else { if(isWithin(px, px+pw, bx+bs, 0) && isWithin(py, py+ph, by, bs)) { ballCollided = true; ball.xLoc = px-bs; } } if(ballCollided) { // bounce the ball ball.bounceX(); // randomize the bounce a little int change = rand.nextInt(4); int change2 = rand.nextInt(2)-1; // depending on where the ball hit the paddle // change the velocity a little if(by<=py+sec) ball.yVel -= change; else if(by<=py+(2*sec)) ball.yVel -= (change/2); else if(by >= py+(3*sec)) ball.yVel += (change/2); else if(by >= py+(4*sec)) ball.yVel += change; else ball.yVel += change2*change; } } // check if the targed is within the given range with size buffer public static boolean isWithin(int min, int max, int target, int size) { if(min > max) { int temp = min; min = max; max = temp; } if(target+size>=min && target<=max) return true; return false; } public void updatePaddles() { leftPaddle.update(); // pick which update to do, user or ai if(PongGui.twoplayers) rightPaddle.update(); else rightPaddle.aiUpdate(ball); } /* paint function */ public void paint(Graphics g) { super.paint(dbGraphics); drawBall(); drawPaddles(); drawScore(); drawBoard(); drawInfo(); if(paused) drawPause(); // update our screen update(g); } public void drawBall() { dbGraphics.setColor(Color.white); dbGraphics.fillOval(ball.xLoc, ball.yLoc, ball.size, ball.size); } public void drawPaddles() { dbGraphics.setColor(Color.blue); dbGraphics.fillRect(leftPaddle.xLoc, leftPaddle.yLoc, Paddle.width, Paddle.height); dbGraphics.setColor(Color.red); dbGraphics.fillRect(rightPaddle.xLoc, rightPaddle.yLoc, Paddle.width, Paddle.height); } public void drawScore() { dbGraphics.setFont(scoreFont); dbGraphics.setColor(Color.blue); dbGraphics.drawString(""+leftScore, 10, top-1); dbGraphics.setColor(Color.red); dbGraphics.drawString(""+rightScore, width-50, top-1); } public void drawBoard() { dbGraphics.setColor(Color.white); dbGraphics.drawLine(0, top, width, top); } public void drawInfo() { dbGraphics.setColor(Color.white); dbGraphics.setFont(scoreFont); dbGraphics.drawString(info, (width/2)-50, top-5); } public void drawPause() { dbGraphics.setFont(defFont); int x = width/2; int y = top+30; dbGraphics.setColor(Color.blue); dbGraphics.drawString(pause1, x-48, y-15); dbGraphics.setColor(Color.red); dbGraphics.drawString(pause2, x-48, y); dbGraphics.setColor(Color.white); dbGraphics.drawString(pause3, x-28, y+15); } public void update(Graphics g) { if(g == null) return; g.drawImage(this.dbImage, 0,0, this); } // gets called whena key is pressed public void keyPressed(KeyEvent e) { //send the key press to each of the paddles leftPaddle.handleKey(e.getKeyChar(), true); rightPaddle.handleKey(e.getKeyChar(), true); } // gets call when a key is released public void keyReleased(KeyEvent e) { // pause the game if need be if(e.getKeyChar() == 'p') paused = !paused; // send the signal to each of the paddles leftPaddle.handleKey(e.getKeyChar(), false); rightPaddle.handleKey(e.getKeyChar(), false); } // the ball went out public void ballOut(boolean outAtRight) { // on the left side if(ball.xLoc < 10) rightScore++; else// on the right side leftScore++; // reset the ball ball.reset(); // pause the game paused = true; } // do nothing on type public void keyTyped(KeyEvent e) {;} // makes the program sleep for a little bit public static void pause(long millis) { try{Thread.sleep(millis);} catch(Exception e) {;} } public static void main(String[] args) { new SinglePlayer(); } }