private void expandCluster(HashSet<Point> cluster, HashSet<Point> neighbourPts) {
            Queue<Point> neighbourList = new LinkedList<Point>(neighbourPts);
            while(!neighbourList.isEmpty()) {
                Point p = neighbourList.remove();
                if(!p.visited) {
                    p.visited = true;
                    pointsClustered++;
                    HashSet<Point> neighbourPts_ = p.getNeighbours();
                    if(neighbourPts_.size()+1 >= minpts) { // Add 1 because p is also a part of the cluster
                        neighbourList.addAll(neighbourPts_);
                    }
                }
                
                if(!p.inCluster) {
                    cluster.add(p);
                    p.inCluster = true;
                }
               
            }
        }