code: public static <T> CompletableFuture<T> newIncompleteFuture(Executor executor) {
          if (JAVA8)
              return new ManagedCompletableFuture<T>(new CompletableFuture<T>(), executor, null);
          else
              return new ManagedCompletableFuture<T>(executor, null);
      }
docs: Construct a new incomplete CompletableFuture that is backed by the specified executor.
  
  @param executor the default asynchronous execution facility for the new CompletableFuture.
  @return incomplete completable future where the specified executor is the default asynchronous execution facility.