My current idea is to showcase how kotlinlang improves implementation of and, in some cases, obsoletes some of Effective Java’s recommendations

I'd highlight, nullability, extension functions and data classes

+ sealed classes

For examples, I'd pull them from the codebase if possible. Find an existing class, show them it as a data class. Find a heavily used static utility method, show it to them as an extension function, etc

if you’re pushed for time - data classes and nullability

backend developer here, probably more important than everything is java compatibility. If you can show them they can start using kotlin in the java projects you are already running it might give them more security to try in terms of feature, nullability, data classes and first class functions (if they use functions in java)

With a small time, I'd go with Nullability + Extension functions

Thanks everyone. This is a good list. There is also a possibility that I can, week after week, get 10 more mins to talk about kotlin again so that I will be able to cover all of the suggestions in this thread, albeit over a couple weeks, so keep ’em coming!

And if they use Lombok, this will be very useful for them. I say if a team is using StringUtils, Guava or Lombok, they’ve already admitted Java could use some syntax help, so Kotlin is a very good option. https://blog.frankel.ch/comparing-lombok-and-kotlin/

Thanks, that’s helpful. We do indeed use Lombok!

Yep. Replace the Lombok annotation processor with the Kotlin compiler and reap the other benefits of Kotlin…