PacMan and His Many Friends (Ghosts)

Question

Well, my friend and I are working very diligently on a Pacman game and had it working perfectly... with just PacMan. We have never really explored or used threads, and have only used buffering sporadically.
So we decided to use Threads on this project of ours, since we wanted the Ghosts each to move at their own speed, and PacMan at his own, of course. So we wrote up our Ghost class... which reads something like this:
import java.lang.Thread;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;
import javax.swing.JApplet;
import java.awt.Image;
public class Ghost extends Thread{
     //Data Fields
     private Graphics g,G;
     private Image Buffer;
     private JApplet app;
     private int gX,gY,gridSize,speed;
     private char direction;
     private Point destination,homePoint;
     private int state;
     private String strat;
     private Color color;
     private boolean staticRoute,running;
     private Sleeper s;
     Ghost(){}
     Ghost(JApplet app,Graphics G,int x,int y,String s, Color c, int gridSize, int speed){
          this.app=app;
          Buffer = app.createImage(app.getWidth(),app.getHeight());
          Graphics g=Buffer.getGraphics();
          this.G=G;
          gX=x;
          gY=y;
          homePoint = new Point(x,y);
          strat=s;
          color=c;
          this.gridSize=gridSize;
          this.speed=speed;
          this.s = new Sleeper();
          this.g=g;
          running=true;
          calcDestination();
     public int getX(){ return gX; }
     public int getY(){ return gY; }
     public String getStrat(){ return strat; }
     public int getState(){ return state; }
     public Color getColor(){ return color; }
     public void run(){
          while(running){
               if(destination.equals(new Point(gX,gY)))
                    staticRoute=false;
               calcDestination();
               if(direction=='R')
                    PacMan.drawLevel(g,gX-1,gY);
               else if(direction=='L')
                    PacMan.drawLevel(g,gX+1,gY);
               draw();
               s.sleep(speed);
               G.drawImage(Buffer,0,0,app);
     public void stopRun(){
          running=false;
     public void die(){
          destination = new Point((int)homePoint.getX(),(int)homePoint.getY());
          staticRoute=true;
     public void draw(){
          g.setColor(color);
          g.fillOval(((gX+1)*gridSize-(gridSize*2))+2,((gY+1)*gridSize-(gridSize*2))+2,(gridSize*3)-4,(gridSize*3)-4);
     public void calcDestination(){ //Doesn't work as it will in final version, just makes it go back and forth along the bottom or top... trying to get two ghosts going at once
          if(!staticRoute){
               if(strat.equals("Test")){
                    if(gX==2 && gY==42){
                         destination = new Point(30,42);
                         direction='R';
                    else{
                         destination = new Point(2,42);
                         direction='L';
                    staticRoute=true;
               if(strat.equals("Test2")){
                    if(gX==2 && gY==2){
                         destination = new Point(30,2);
                         direction='R';
                    else{
                         destination = new Point(2,2);
                         direction='L';
                    staticRoute=true;
          calcPoint();
     public void calcPoint(){  //Excuse the utter stupidity of this method.  It is merely for testing and will be better implemented later.
          if(gY==(int)destination.getY() && (int)destination.getX()>gX)
               gX++;
          else
               gX--;
}Let me explain part of the development behind this...
First off we started with just PacMan.java. I wrote it pretty much on my own and made it so it would read a series of numbers from a textfile to generate a level. It also contained the speed and how much pelets were worth, but that's not relevant. It worked fine, all of it.
Then the next step was having a yellow 'circle' move around in that field in the way we wanted it to. That also worked.
The third step was implementing the warps, which could be represented and generated from the text field itself. This worked and was implemented quite well. However, we did not use Threads up until now.
The fourth and current step was the Ghost implementation. This isn't going as planned. We use two Graphics objects in our PacMan class (which extends JApplet) and simply drew everything in one step to the 'invisible' one, then at the end of the paint method, draw it all over to the 'visible' graphics object. That worked fine in the previous steps, as mentioned above. However, we ran into a problem with the different speeds of the Ghosts. We passed in the 'invisible' Graphics object and had the Ghosts draw themselves to that via the run method. That worked fine if the speed was the same, but when it was different it created problems. Another problem was that since we passed in the SAME Graphics object, if one of the two Ghost instances changed the color, then it could affect the color of what was being drawn in the main PacMan class. (Usually during the inital display of the level. We'd have red-colored dots.)
I know this all sounds very... overwhelming.. and trust me, it is for us too. I'm just not sure how to go about solving this problem. If you look at the code closely, I have two Graphics objects for each Ghost. One is the main one from the app, and the other is the one it draws itself to so it prevents Color conflicts. Then at the end of the 'run' method we try drawing the individual Ghost Graphics object to the bigger one... and it all just jumbles up.
I guess to cut to the chase, what I'm asking for is advice on how to have multiple Ghost Threads running and drawing constantly without conflicts with color or too much lag. (I noticed when we set all the speeds to the same thing then it worked, but it was very choppy) One guess of mine would be to put PacMan on his own Thread, but my brain is so fried I'm not quite sure where to begin. Any guidance/references would be appriciated.

Answer 1

Personally I think you've got the wrong approach.
Instead of creating a Thread for every ghost, you should keep yourself to the one you've got in the PackMan class.
Tough what you need to do is make the whole game frames based.
You've got a speed variable that you should use to add/increase the X/Y location each frame, something like:
Ghost[X].newTick();Where newTick() should be something like:
public void newTick(); {
     x += speed;
     y += speed;
}and instead of drawing inside the Ghost class you should draw in the PackMan class, no collision with double usage of the Graphics objects.
Well, I hope you've got the general idea, post a message if you would like a practical example.
GL HF