Difference between Observable.create() and Observable.fromCallable()

Question

Suppose we are getting a generic Object from SharedPrefs using .create():

return Observable.create(subscriber -> {
             


        

Answer 1

Observable.create let's you emit multiple items while fromCallable emits only a single item.

You should use the latter as it is more expressive about the intent of having a single element sequence and has a slighly lower overhead.

Drawback is that you can't have an async single element source with it whereas create let's you delay the call to onNext to a later point in time.