Erick,
Whenever you encounter method chaining, beit in a Stream or elsewhere, it is always a good idea to take a step back and reflect on the code. Walk through it one step at the time. What does each method take as a parameter? What does it return? Is that what the next method is expecting? etc.
Also, to avoid confusion: this
thread is titled "OCA Preparation" and has been created in the corresponding subforum but please do know that neither Streams nor Optionals are on the OCA exam (but they do appear on the OCP one).