public class CompletableFutureTests {

    public static final int END_EXCLUSIVE = 1000000;
    public static final Random random = new Random();

    @Test
    public void __1() throws ExecutionException, InterruptedException {

        final long d = System.currentTimeMillis();

        final Optional<CompletableFuture<BigDecimal>> reduce = IntStream
                .range(0, END_EXCLUSIVE)
                .mapToObj((t) -> supplyAsync(() -> new BigDecimal(random.nextInt())))
                .parallel()
                .reduce((left, right) -> left.thenCombine(right, (l, r) -> l.add(r)));

        final BigDecimal x = reduce.get().get();
        final long l1 = System.currentTimeMillis();
        System.out.println(x);
        System.out.println(l1 - d);
    }

    @Test
    public void __2() throws ExecutionException, InterruptedException {

        final long d = System.currentTimeMillis();

        final Optional<CompletableFuture<Stream<Integer>>> reduce = IntStream
                .range(0, END_EXCLUSIVE)
                .mapToObj((t) -> supplyAsync(() -> ...))
                .parallel()
                .reduce((left, right) -> left.thenCombine(right, (l, r) -> ... ));


        final List<Integer> collect = reduce.get().get().collect(Collectors.toList());

        System.out.println(collect.size());

    }
}