jshell - The java REPL

Checkout features in the new java REPL(read eval print loop).

Concurrency with Akka Actors

Implementing concurrent programs with Actor model in Java, Scala and Kotlin.

Java & Scala concurrency comparison

Scala is easier than java come take a look.

Page object pattern

Within your web app's UI there are areas that your tests interact with. A Page Object simply models these as objects within the test code. This reduces the amount of duplicated code and means that if the UI changes, the fix need only be applied in one place.

Event Sourcing with scala, play framework and eventuate (Part 2 - Persisting Actor States)

This is the basic idea behind event sourcing - instead of storing current application state, the full history of changes is stored as immutable facts and current state is derived from these facts.