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How to Streamline the Customer Experience with Monads in Kotlin

 At my company, we see a lot of SDKs and Swagger-generated clients that could throw exceptions at any time. This could be a fault in our logic, or it could be a fault with some 3rd party SDKs that have no rhyme or reason to how their exception handling works. But either way, when our customers want to fetch a Git commit history for a service, they do not want to be greeted with an error message.

We've seen GitHub go down during a customer demo and 3rd party integrations throwing other unexpected exceptions. Overall, it was a very discouraging experience for our customers that we had no control over.

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What Is Applicative? Basic Theory for Java Developers

Applicative is just another concept similar in meaning and history to Functors and Monads. I have covered these two in my previous articles, and I think it is finally time to start closing this little series about the most commonly known functional abstractions. Besides explaining some details and theory, I will implement a simple Applicative. I will also use Optional, hopefully one last time, to show what advantages Applicatives give us.

The source code for this article is available in GitHub repository.

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What Is a Functor? Basic Theory for Java Developers

In general, a Functor is a concept originating from mathematics, to be exact from a part of mathematics called category theory. In my very first article, I described in detail a similar concept known as Monad. Here I want to continue that thread, so I will try to give you some more insight into Functors — what they are, how they work, and what the theory behind them is. I will also implement a simple functor to better understand how they work and why using them may be a clearer solution.

The source code for this article is available in GitHub repository.

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What Is a Monad? Basic Theory for a Java Developer

As you can guess from the title, the main topic of this article will be monads. I will try to dive deep in their structure and inner workings. With some help of Java Optional, I will try to describe all of this in a more detailed way. At the end of this article, I will implement a log monad — a type of a writer monad —and then describe the role of each major code fragment and provide a simple example of its usage.

Why Learn How Monads Work?

First of all, it is always good to have a basic understanding of how things that we use work. If you are a Java developer, you probably use monads without even knowing about it. It may surprise you, but two of the most commonly known Java 8 features are monad implementations, namely Stream and Optional. In addition, functional programming becomes more and more popular nowadays so it is possible that we will have more similar monadic structures. Then, this knowledge will be even more very valuable.

Let’s start with describing what a monad is – more or less accurately. In my opinion, the matter here is fairly straightforward.