Sealed classes are one of the new Java 17 features. It has been on preview before, however with the latest Java 17 it is part of a LTS release for the first time.
Kotlin also supports sealed classes and improved those in Kotlin 1.5 with additional details.

In this live coding session, Lothar compares Java and Kotlin sealed classes. He uses Java and Kotlin code that smells.
He improves the Kotlin and Java code with sealed classes (and interfaces) live on stage in an IDE and talks the audience through the code refactoring step by step.

#slideless