public List<Integer> fetchVehicleIds(String datasetId) throws ApiException {

    VehiclesApi vehiclesApi = new VehiclesApi();

    List<Integer> vehicleIds;
    vehicleIds = vehiclesApi.vehiclesGetIds(datasetId).getVehicleIds();

    return vehicleIds;
}

 public List<VehicleResponse> fetchVehicleDetails(String datasetId, List<Integer> vehicleIds) throws InterruptedException, ApiException {

    CountDownLatch latch = new CountDownLatch(vehicleIds.size());
    List<VehicleResponse> vehiclesList = new ArrayList<>();

    for (Integer vehicleId: vehicleIds) {
        populateEachVehicleDetail(datasetId, vehicleId, vehiclesList, latch);
    }

    latch.await();

    return vehiclesList;
}

private void populateEachVehicleDetail(String datasetId, Integer vehicleId, List<VehicleResponse> vehiclesList, CountDownLatch latch) throws ApiException {

    ApiCallback<VehicleResponse> vehicleResponseApiCallback = new ApiCallback<VehicleResponse>() {
        @Override
        synchronized public void onSuccess(VehicleResponse result, int statusCode, Map<String, List<String>> responseHeaders) {
            vehiclesList.add(result);
            latch.countDown();
        }
    };

    VehiclesApi vehiclesApi = new VehiclesApi();
    vehiclesApi.vehiclesGetVehicleAsync(datasetId,vehicleId,vehicleResponseApiCallback);

}