BlockingQueue<Future<T>> futureQueue = Queues.newLinkedBlockingQueue();
    long timeoutNanos = unit.toNanos(timeout);

    // For efficiency, especially in executors with limited
    // parallelism, check to see if previously submitted tasks are
    // done before submitting more of them. This interleaving
    // plus the exception mechanics account for messiness of main
    // loop.

    try {

            int parallelism = DEFAULT_BUILDER_PARALLELISM;
            try {
                String str = request.getUserProperties().getProperty(BUILDER_PARALLELISM);
                if (str == null) {
                    str = request.getSystemProperties().getProperty(BUILDER_PARALLELISM);
                }
                if (str != null) {
                    parallelism = Integer.parseInt(str);
                }

   *
   * <p>To avoid having this type, we could use {@code FlatMapSpliterator} directly. The main
   * advantages to having the type are the ability to use its constructor reference below and the
   * parallelism with the primitive version. In short, it makes its caller ({@code flatMap})
   * simpler.
   *
   * @param <InElementT> the element type of the input spliterator