@SuppressWarnings("unchecked")
  private void fetch(Object o) {
    Iterator<Car> cars;

    if (o instanceof Collection) {
      cars = ((Collection<Car>) o).iterator();
    } else if (o instanceof Stream) {
      cars = ((Stream<Car>) o).iterator();
    } else {
      cars = (Iterator<Car>) o;
    }

    while (cars.hasNext()) {
      cars.next();
    }
  }
This test shows up how fast different json array response processing implementations are.
benchmark/src/main/java/feign/benchmark/DecoderIteratorsBenchmark.java