In this final chapter, we've built an app step by step. Although the app we wrote wasn't big, it gave us enough room to see Kotlin features in action. 

Most of the types we used were from the Java Standard Library or written in Java itself. This showed how good the interoperability with Java and existing Java types is. 

We've also seen how Kotlin works with a popular build tool such as Gradle, and how it has first-class support in IntelliJ IDE.

After this final chapter, where we showed how Kotlin is used in practice, you should have a good understanding of the language and its features.