Future-Stream

// The executor in charge of executing the different crawls in its thread pool
ExecutorService executor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());

// Start all the crawl tasks in a separate Thread and get the results of each tasks in a Future
List<Future<List<MyDto>>> tasksResults = myList.stream()
    .map(item -> {
      // Create an instance of a Class that implements Callable<List<MyDto>> {
      return executor.submit(instanceOfCallable);
    }).collect(Collectors.toList());

// For each Futur from Threads
tasksResults.stream().forEach(futureResult -> {
  try {
    List<MyDto> myDtos = futureResult.get();

    if ( myDtos.size() > 0 ) {
      // Do Stuff here
    }
  }
  catch ( InterruptedException | ExecutionException e ) {
    e.printStackTrace();
  }
});