Flowable to perform task and return List of String Rx Java ReactiveX

Question

Perform task and finally return the value using Flowable rxjva3. I have below code

public Maybe<List<String>> uploadObject(Publisher<CompletedFileUpload> images) {
        Storage storage = StorageOptions.getDefaultInstance().getService();
        var returnValue = Flowable.fromPublisher(images)
                .collect((List<String> returnImages, CompletedFileUpload image) -> {
                    BlobId blobId = BlobId.of(googleUploadObjectConfiguration.bucketName(), image.getName());
                    BlobInfo blobInfo = BlobInfo.newBuilder(blobId).build();
                    Blob updatedImage = storage.create(blobInfo, image.getBytes());
                    returnImages.add(updatedImage.getName());
                })
                .flatMapMaybe(returnImages -> Maybe.just(returnImages));
    }

Basically, it iterates and uploads the image to google storage. Then the return media URL should return to the list of String. Tried the below code however, the return type is Maybe<U>. What is the proper way of performing this?

Update 1

Flowable.fromPublisher(images).collect(ArrayList::new, (returnImages, image) -> {
            BlobId blobId = BlobId.of(googleUploadObjectConfiguration.bucketName(), image.getName());
            BlobInfo blobInfo = BlobInfo.newBuilder(blobId).build();
            Blob updatedImage = storage.create(blobInfo, image.getBytes());
            returnImages.add(updatedImage.getName());
            LOG.info(
                    String.format("File %s uploaded to bucket %s as %s", image.getName(),
                            googleUploadObjectConfiguration.bucketName(), image.getName())
            );
        }).flatMapMaybe((returnImages)-> List.of(returnImages));

This is also not correct, the return type should be Maybe<List<String>>

Answer 1

From the comments, use the two argument collect and then use toMaybe. You may have to reinforce the collection type as shown below:

Flowable.fromPublisher(images)
.<List<String>>collect(ArrayList::new, (returnImages, image) -> {
    BlobId blobId = BlobId.of(googleUploadObjectConfiguration.bucketName(), image.getName());
    BlobInfo blobInfo = BlobInfo.newBuilder(blobId).build();
    Blob updatedImage = storage.create(blobInfo, image.getBytes());
    returnImages.add(updatedImage.getName());
    LOG.info(
        String.format("File %s uploaded to bucket %s as %s", image.getName(),
                            googleUploadObjectConfiguration.bucketName(), image.getName())
            );
}).toMaybe();