https://www.pluralsight.com/courses/kotlin-java-developers

Java is a popular language, but it remains relatively verbose. In this course, Kotlin for Java Developers, you'll learn the fundamentals of Kotlin - a modern, pragmatic language designed to improve productivity and readability.  First, you'll explore the basic building blocks of Kotlin - variables, their types and how their declaration differs from Java.  Next, you'll learn how to write concise and expressive code with fundamental branching and looping statements and expressions, as well as how to write idiomatic Kotlin functions.  Finally, you'll learn the basics of creating Object-Oriented Kotling code.  When you’re finished with this course, you’ll have the skills and knowledge of Kotlin fundamentals needed to write idiomatic Kotlin code.