I'm trying to use multithreading in my game. However, I can't seem to get rid of the sleep.

If I don't it's a blank screen, as there is no time for the computer to actually render the triangleMob as it can't access getArrayList(), in my main class I have a TriangleMob arraylist. If I delay it, then it can access the previousMob and it renders. If I don't, then it's blank screen.

Can I get rid of the delay? Also, is this a bad way to multithread?

Surely, this should be fast. I need multithreading so can you please not suggest not using it.

public class TriangleMob extends Thread implements Runnable {

        private static int count=0;

        private int objectDisplayList;
        private static ArrayList<TriangleMob> previousMob = new ArrayList<TriangleMob>();
        private static ArrayList<TriangleMob> currentMob = new ArrayList<TriangleMob>();
        private static ArrayList<TriangleMob> laterMob = new ArrayList<TriangleMob>();

        private Vector3f position = new Vector3f(0f,0f,0f);
        private Vector3f movement = new Vector3f(0f,0f,0f);



        public TriangleMob()
        {

                // Create the display list
                CreateDisplayList();

                count++;
        }

        public TriangleMob(Vector3f position)
        {

                // Create the display list
                CreateDisplayList();

                this.position = position;
                count++;
        }

        private void CreateDisplayList()
        {
                objectDisplayList = glGenLists(1);
                glNewList(objectDisplayList, GL_COMPILE);
                {
                        double topPoint = 0.75;
                        glBegin(GL_TRIANGLES);
                        glColor4f(1, 1, 0, 1f);
                        glVertex3d(0, topPoint, -5);
                        glColor4f(0, 0, 1, 1f);
                        glVertex3d(-1, -0.75, -4);
                        glColor4f(0, 0, 1, 1f);
                        glVertex3d(1, -.75, -4);

                        glColor4f(1, 1, 0, 1f);
                        glVertex3d(0, topPoint, -5);
                        glColor4f(0, 0, 1, 1f);
                        glVertex3d(1, -0.75, -4);
                        glColor4f(0, 0, 1, 1f);
                        glVertex3d(1, -0.75, -6);

                        glColor4f(1, 1, 0, 1f);
                        glVertex3d(0, topPoint, -5);
                        glColor4f(0, 0, 1, 1f);
                        glVertex3d(1, -0.75, -6);
                        glColor4f(0, 0, 1, 1f);
                        glVertex3d(-1, -.75, -6);

                        glColor4f(1, 1, 0, 1f);
                        glVertex3d(0, topPoint, -5);
                        glColor4f(0, 0, 1, 1f);
                        glVertex3d(-1, -0.75, -6);
                        glColor4f(0, 0, 1, 1f);
                        glVertex3d(-1, -.75, -4);

                        glEnd();
                        glColor4f(1, 1, 1, 1);
                }
                glEndList();
        }

        public static int getCount() {
                return count;
        }

        public Vector3f getMovement() {
            return movement;
        }

        public Vector3f getPosition() {
            return position;
        }

        public synchronized int getObjectList() {
            return objectDisplayList;
        }

        public synchronized static ArrayList<TriangleMob> getArrayList(){
            if(previousMob != null) {
                return previousMob;
            }

            previousMob.add(new TriangleMob());

            return previousMob;
        }

        public synchronized  void move(Vector3f movement) {

                // If you want to move in all 3 axis
                position.x += movement.x;
                position.y += movement.y;
                position.z += movement.z;

        }

        public synchronized void render() {
            glPushMatrix();

            glTranslatef(-position.x, -position.y, -position.z);

            glCallList(objectDisplayList);

            glPopMatrix();
        }


        public synchronized static void setTriangleMob(ArrayList<TriangleMob> triangleMobSet) {
            laterMob = triangleMobSet;  
        }


        private synchronized void setPreTriangleMob(ArrayList<TriangleMob> currentMob2) {
            previousMob = currentMob2;
        }

        public void run(){
            while(true) {
                if(laterMob == null) {
                    currentMob = laterMob;
                    System.out.println("Copying");
                }


                for(int i=0; i<currentMob.size(); i++) {
                    currentMob.get(i).move(new Vector3f(0.1f,0.01f,0.01f));
                }

                setPreTriangleMob(currentMob);

                try {
                    sleep(1L);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    }