code: public static <T> FastFuture<T> fromCompletableFuture(final CompletableFuture<T> cf) {
          final FastFuture<T> f = new FastFuture<>();
          cf.thenAccept(i -> f.set(i));
          cf.exceptionally(t -> {
  
              f.completedExceptionally(t);
              return f.join();
          });
          return f;
      }
docs: Internal conversion method to convert CompletableFutures to FastFuture.