Java to Kotlin

Chapter 23. Continuing the Journey

We’ve arrived at the end of the book. Thank you for coming on the journey. Your authors are privileged to have worked with, and learned from, many great developers, and now you are on that list. Even if you skipped a couple of chapters, or zoned out in the middle of the odd refactoring, it’s been good to have someone to talk to. We can’t pair on improving Travelator anymore, but what have we learned from our travels?

When O’Reilly asked us if we would like to write a book on Kotlin, we had to think about what we wanted to write and about what enough people might want to read. We knew that we had been on a journey adopting the language and that we are comfortable at the destination, but we also knew that our starting point was not that of the typical Java developer. We saw that most existing books taught Kotlin as if it were just another syntax for Java, one that could achieve more with less typing but didn’t require a change in approach. That wasn’t our experience; we found that Kotlin’s sweet spot required more functional thinking than Java. Books on functional programming in Kotlin, though, seem to ask the reader to leave behind all that they know about programming with objects and join a new cult. We weren’t comfortable with this either. Classes and objects are a humane way of expressing behavior, especially compared to many functional idioms. Why remove tools from our box when there is plenty of room? Can’t we just have more tools and pick ...