I translated this article into Japanese in InfoQ.
I haven't known Javaslang library for now.
What is Javaslang?
Javaslang's website is below:
Javaslang brings functional programming to Java.
This library is inspired by Scala. It mainly focuses on Collection library.
How to use?
I try to use Javaslang version 2.0.5.
Differ from Java 8, Javaslang has its own List and Stream interface.
Number sum = List.of(1, 2, 3).sum(); System.out.println(sum); // 6
And it has Option which correspond to Java 8's Optional, Tuple, Pattern Matching and so on.
For more infomation, visit Javaslang website.