Complies but shows null expection on console

okay i'm trying to stop the console displaying a null expection but i'm not sure why its doing it i was wondering if you guys could help me

Code java:

package  miniass3;
public class AirLock {
 
        private boolean lockState = false;
 
        public AirLock(boolean newLock){
                lockState = newLock;
        }
 
		public boolean isLockState() {
                return lockState;
        }
 
        public void setLockState(boolean lockState) {
                this.lockState = lockState;
        }
 
}

Code java:

package miniass3;
public class AirlockDoor implements Runnable {
 
        private AirLock lockOperator;
        private String doorName;
 
        public AirlockDoor(String name, AirLock airLock){
                doorName = name;
 
        }
 
        public AirlockDoor() { }
 
        public void run() {    
                while (true){
                        if(lockOperator.isLockState() == false){
                                System.out.println("False");
                        }
                }
        }
 
        public synchronized  void  requestToOpen() {
 
                System.out.println(doorName +  " requests to be opened");
        }
     }

Code java:

package uk.ac.aber.dcs.airlock;
 
 
import miniass3.AirLock;
import miniass3.AirlockDoor;
 
public class AstronautSimulator {
 
        public static void main(String [] args){
                simulate();
        }
 
        private static void simulate() {
                // Create an AirLock object
                // STEP 1: CREATE AN EMPTY VERSION OF THE AirlockDoor CLASS
                AirlockDoor[] doors = new AirlockDoor[2];
 
                // For this prototype this can be an empty (no method)
                // class. It is a common object used in the Door class
                // that contains the single lock-key that protects the
                // imaginary airlock room from having two doors open at
                // the same time
                // STEP 2: CREATE THIS CLASS
                AirLock MainAirLock = new AirLock(false);
 
                // Give the doors a name (for debugging purposes) and
                // a common airlock object used to store the "key" used
                // by a critical section of code in the Door class
 
 
                doors[0] = new AirlockDoor("Door 1", MainAirLock);
                doors[1] = new AirlockDoor("Door 2", MainAirLock);
 
                // AirlockDoor implements Runnable and so make sure
                // we tie the objects to Thread objects
 
                Runnable threadJob = new AirlockDoor();
 
        // STEP 3: CREATE TWO THREADS FOR THE TWO DOORS AND START THEM
                // ENTER CODE HERE
 
                Thread doorController1 = new Thread(threadJob);
                Thread doorController2 = new Thread(threadJob);
 
                doorController1.setName("DoorLock");
               doorController2.setName("DoorLock");
 
                doorController1.start();
               doorController2.start();
 
                // Loop infinitely which try's to open the airlock doors
                while (true){
                        // random() returns a value in range 0.0..<1.0 multiplied by 10 and mod doors.length
                        // to return either 0 or 1 in order to randomly decide which door to request
                        int doorNum = (int)((Math.random() * 10) % doors.length);
 
                        // STEP 4: MAKE A REQUEST TO OPEN THE DOOR AND THEN ADD A DELAY BEFORE
                        // TRYING TO OPEN ANOTHER DOOR
                        // ENTER CODE HERE
 
                        doors[doorNum].requestToOpen();
 
 
                        try{
                                Thread.sleep(800);
                        }
                        catch(InterruptedException ex){
                                ex.printStackTrace();
                        }
 
 
 
                }
        }
}