Functional Utils

Description

This library aims to provide a set of utilities to help with functional programming in Java.

It is inspired by the functional programming libraries in other languages, such as Scala, Haskell, and Clojure and aims to be a zero-dependencies library.

It is also inspired by libraries such as Vavr or Cyclops. But these have issues such as:

1. They do not seem to be maintained anymore.
2. They are not zero-dependencies libraries.
3. They have a big learning curve.

It is a small library, and it will never compete the big ones, but it can be useful for those that would like to remain lean.

Features

1. Either monad which represents a value that can be either of two types.
2. Try monad which represents an operation that can either succeed or fail.
3. EitherT monad transformer which allows to encapsulate an Either monad inside a CompletableFuture. This allows chaining and composing asynchronous computations that may fail, using functional programming principles.
4. TryT monad transformer which allows to encapsulate a Try monad inside a CompletableFuture. This allows chaining and composing asynchronous computations that may fail, using functional programming principles.
5. Validated monad which represents a value that can be either of two types, but it accumulates errors.
6. Resource which represents a resource that needs to be managed and closed after use for safe resource management.
7. For Comprehension which allows to chain and compose monads in a more readable way than using nested flatMaps.
8. Lazy monad which represents a value that is computed lazily and memoized.
9. SeqList monad which represents a persistent and immutable list.
10. Option monad which represents a value that may or may not be present which is an enhancement over the Java Optional.
11. Reader monad which represents a computation that depends on a configuration.
12. Writer monad which represents a computation that produces a log.
13. IO monad which represents a computation that performs side effects which is lazy.

Installation guide

To add the library to your project, you need to add the jitpack repository to your build file.

<repositories>
  <repository>
    <id>jitpack.io</id>
    <url>https://jitpack.io</url>
  </repository>
</repositories>

Then, you can add the dependency to your project.

<dependency>
  <groupId>com.github.VassilisSoum</groupId>
  <artifactId>FunctionalUtils</artifactId>
  <version>2.8.0</version>
</dependency>

Articles to read

1. Introducing TryT monad with some examples TryT article
2. Explaining SeqList monad with some examples SeqList article
3. Explaining the Lazy monad with some examples Lazy monad article
4. Explaining the Option monad with some examples Optional monad article
5. Explaining the Either monad with some examples Either monad article

TODO

1. Persistent List monad implementation equivalent to ArrayList but different from the Java collections to be truly immutable and performant using structural sharing.
2. Persistent HashMap/HashSet monad implementation but different from the Java collections to be truly immutable and performant using structural sharing.