How can I apply an Optional in which I want to call a method?

Question

I have this piece of code:

final ResultDO response = transformJsonToResponseDO(rawDataResponse, ResultDO.class);
return Optional.ofNullable(response)
 .map(results -> createPOIs(Collections.singletonList(response), providerResponse))
 .orElse(Collections.emptyList());

The important part is that: response is an object of type ResultDO. Within an Optional I want to call that method createPois(). Methot createPois wants a list of ResultDO, but there I will always have it only element because of that I wrapped in a Collections.singletonList().

As I wrote it, is it the right way, with that .map() ?

I don't want to use if(response != null) ...

Maybe it is worth to mention that createPois() return a list of some other types. A list of Points.

• Andrew: Why not use an if statement here?

Answer 1

This looks mostly correct. IMO, should not use response in the map function, but results. I.e.

final ResultDO response = transformJsonToResponseDO(rawDataResponse, ResultDO.class);
return Optional.ofNullable(response)
 .map(results -> createPOIs(Collections.singletonList(results), providerResponse))
 .orElse(Collections.emptyList());

Even though they are the same in this case, typically this is how you are supposed to use Optional when you're not wrapping in #ofNullable.

Furthermore, this lets you put it all on one line:

return Optional.ofNullable(transformJsonToResponseDO(rawDataResponse, ResultDO.class))
 .map(results -> createPOIs(Collections.singletonList(results), providerResponse))
 .orElse(Collections.emptyList());