//threading
final ExecutorService executorService;
if(nuOfThreads > 0){
log.info("setup executor-service with " + nuOfThreads + " threads");
executorService = Executors.newFixedThreadPool(nuOfThreads);
algorithmListeners.add(new PrioritizedVRAListener(Priority.LOW, new AlgorithmEndsListener() {
@Override
public void informAlgorithmEnds(VehicleRoutingProblem problem,Collection<VehicleRoutingProblemSolution> solutions) {
log.info("shutdown executor-service");
executorService.shutdown();