Lamda expressions were introduced in Java 8 and have been around for a while. They are in my opinion one of the better features of Java 8, allowing for a more functional approach to writing code, and thus enabling most of the java 8 features. So let’s take a closer look at lambda’s and see what they are, how to reason about them, and why they are a good addition.

This is a blog post that tries to give a pragmatic explanation about what a monad is, and what problem it tries to solve. This post is written by Ties van de Ven and Justus Brugman.

When I tried to learn about functional programming, I found myself lost in new words and jargon, I did not know about. Suddenly my vocabulary needed to be extended with terms like Monads, Monoids, Composable, Functors and so on. When trying to understand these terms, it became clear that I found it hard to understand what a monad is.

Since about a month I’m developing some microservices using Javalin, a small, simple and lightweight web-framework that started as a fork from SparkJava. By now it’s a ground-up rewrite, influenced by the Javascript framework koa.js. Don’t let the stuff like Either scare you, we use the Arrow library to make our life a bit more easy :)

When requesting user input from a form, it’s evident that we need to validate our input. Javalin has its own way of doing so (from the docs):