Ensure this "Optional" could never be null and remove this null-check

Question

I am using Spring boot and analysing my code with sonarqube, on the below line

Optional<Animal> animal = animalRepository.findById(animalId);
if (animal == null) {
            throw new DeviceNotValidException("Failed to found animal detail",  new String[] { animalId});
        }

i am getting this error

Ensure this "Optional" could never be null and remove this null-check. `

As per my understanding, "Optional is generally used as a return type for methods that might not always have a result to return."

I want to make sure that i dont get a null pointer exception even if "findById()" returns null, so i have used "Optional" here.

Is there anything that I can do to improve my code so that the error disappears?

I read this Checking whether an Optional object isn't Empty and null but it did not help.

Answer 1

An optional's application is to reduce null-values.

Checking if the supplied optional is null isn't enough for the compiler to be sure its value isn't.

To check for an Optional's value use either optional.isEmpty(); or optional.isPresent();.

In your case: check for the repository's response as follows:

Optional<Animal> animal = animalRepository.findById(animalId);
if (animal.isEmpty()) {
            throw new DeviceNotValidException("...");
}

Or even simpler:

Animal animal = animalRepository.findById(animalId)
                      .orElseThrow(() -> new DeviceNotValidException("...");

The last approach ensures animal not being null.