Simpel Socket Server fejl

Exception in thread "FrozenComServerControl" java.lang.NullPointerException - Det er den fejl der har drevet mig til vanvid den sidste time...

Er i gang med at lave en simpel socket baseret chat, IRC agtigt hvor serveren sender clients streng ud til alle connectede clienter.

Fejlen sker da jeg vil have fat i en ArrayList der indeholder samtlige client tråde.

Fejlen ligger i:

 package frozenchat;
 
 import java.net.*;
 import java.io.*;
 
 public class FrozenComServerThread extends FrozenComServerControl {
     private Socket socket = null;
     private PrintWriter out = null;
     private BufferedReader in = null;
 
     public FrozenComServerThread(Socket socket) throws IOException {
         super("FrozenComServerThread");
         this.socket = socket;
         try {
             this.out = new PrintWriter(this.socket.getOutputStream(), true);
             this.in = new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
         } catch(IOException e) {
             System.err.println("Couldn't get I/O rights to server: localhost");
             System.exit(1);
         }
         
     }
 
     public void write(String aString) {
         this.out.println(aString);
     }
 
     public void run() {
         try {
             String inputString, outputString;
             this.write("Welcome User!");
 
             while((inputString = this.in.readLine()) != null) {
                 if(inputString.equals("Bye!"))
                 {
                     this.write("Bye!");
                     break;
                 }
                 for(int i = 0, length = super.allClients.size(); i < length; i++) // <------------ DET ER HER DEN BROKKER SIG!
                     super.allClients.get(i).write(inputString);
             }
 
             out.close();
             in.close();
             socket.close();
         } catch(IOException e) {
             e.printStackTrace();
         }
     }
 }

Og:

 package frozenchat;
 import java.net.*;
 import java.io.*;
 import java.util.*;
 
 public class FrozenComServerControl extends Thread {
     public ArrayList<FrozenComServerThread> allClients = null;
 
     public FrozenComServerControl() throws IOException {
         ServerSocket serverSocket = null;
         this.allClients = new ArrayList<FrozenComServerThread>();
         boolean listening = true;
         try {
             serverSocket = new ServerSocket(4444);
         } catch(IOException e) {
             System.err.println("Couldn't listen to port: 4444");
             System.exit(1);
         }
 
         while(listening)
         {
             FrozenComServerThread aThread = new FrozenComServerThread(serverSocket.accept());
             aThread.start();
             this.allClients.add(aThread);
             
         }
 
         serverSocket.close();
     }
 
     public FrozenComServerControl(String aString) {
         super("FrozenComServerControl");
     }
 }

Sig endelig til hvis i har brug for flere filer at se på.