Sunday, 1 April 2018

Handling nulls with Optional

Let's imagine following situation:
We have some 3rd party code (or legacy one that you can't change at the moment) that fetches objects representing people based on some parameter. This could look as following:


Our task is to retrieve city in which specific person lives for further processing. We don't have any guarantee over data consistency, so we need to handle it on our own.

Task seems to be simple, how can we achieve this?
One solution could look something like: As you can see above it's quite ugly. Multiple nested if statements don't look nice. What is more, returning null is not a good practice.

What can we do to get rid of the ifs and indicate that city might not be present?

We can use Optional type: map methods take care of handling null and we're returning Optional to indicate that value might not be there.
Instead of returning Optional we could consider null object

The whole project (with the tests checking the solution) can be found on github
In the next post we'll take a look at error handling.

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