public class AsyncStreamExecutorProcessing {
    private final ServiceInvoker serviceInvoker;
    private final ExecutorService executorService = Executors.newFixedThreadPool(100);

    public AsyncStreamExecutorProcessing() {
        this.serviceInvoker = new ServiceInvoker();
    }

    public static void main(String[] args) {
        new AsyncStreamExecutorProcessing().start();
    }

    private void start() {
        List<String> ids = Arrays.asList(
            "C01", "C02", "C03", "C04", "C05", "C06", "C07", "C08", "C09", "C10",
            "C11", "C12", "C13", "C14", "C15", "C16", "C17", "C18", "C19", "C20");

        long startTime = System.nanoTime();
        List<CompletableFuture<Client>> futureRequests = ids.stream()
            .map(id -> CompletableFuture.supplyAsync(() -> serviceInvoker.invoke(id), executorService))
            .collect(toList());

        double totalPurchases = futureRequests.stream()
            .map(CompletableFuture::join)
            .collect(summingDouble(Client::getPurchases));

        long endTime = (System.nanoTime() - startTime) / 1_000_000;
        System.out.println("Async with executor | Total time: " + endTime + " ms");
        System.out.println("Total purchases: " + totalPurchases);

        executorService.shutdown();
    }
}