When you are already familiar with it or work in a Java shop, there are better options if you are starting from scratch, but if you already have 50 guys that know Java it's a pretty big ask for all of them to switch.
Most organizations that use Java tend to be pretty conservative with their technology picks and nowadays with newer Java versions the only real gap with Kotlin is null-safety which is supposed to also come to Java at some point.
There is also an organization culture component most of the time, one our engineers actually proposed to use Kotlin for one of the new projects but it got rejected because "We are a Java shop"
> Most organizations that use Java tend to be pretty conservative with their technology picks
That part i s true.
> with newer Java versions the only real gap with Kotlin is null-safety
But that part isn't. Kotlin has:
- Structured Concurrency: Coming to Java sometime in the future, but it's been in preview for very long now.
- Standalone functions that don't have to live in classes
- Properties
- Property delegation
- Data classes: more powerful than records. Can be used for large DTOs that you can modify with copy(). Java needs something like Lombok to make records more useful.
- Extension methods
- Context parameters
- Operator overloading
- Implementation delegation
- Inline functions (which can receive returning closures and reified types)
- Block syntax (supports `it` for unnamed arguments)
- Sequence abstractions: more powerful and more efficient than Java streams due to the inlining and block syntax.
This is just a partial list, but Kotlin clearly has a lot of things that Java doesn't. If you only personally care about NPEs that's fine, but that's not the only thing.
I think the two languages mean slightly different things here. In any case, Java's model is so much more simpler that I don't think they are honestly comparable. In kotlin's case you have to be very on top of your game to have a chance of correctly using it - there is concurrency, parallelism, exception handling all combined into a single abstraction in a non-native way - so your stack traces will be useless/swallowed etc on incorrect usage. Of course the usual caveat applies, just use java's abstraction if you need that.
> Standalone function
Don't really see the benefit, if anything it creates place for style disagreements. A SomethingUtil class was just fine (and findable).
> Properties
Difficult topic with both cons and pros.
> Data classes
Exactly because they are "more powerful" they are strictly worse. A design element is just as much about what it is as it isn't. Copy is good though.
> Delegation
Used a couple of times, but it's not the full blown thing (see manifold)
> Extension method
I will be honest, I really dislike these. They can occasionally help a bit with some DSL, but for the most part they just make code very hard to read. I much prefer a normal static method instead.
> Context parameters
One of the few useful syntactic sugar.
> Operator overloading
Argued to death already :)
> Inline function
Feels more like a hack to support some of these extra features than something you would want to use yourself
> Block syntax
For the rare DSL usecase it's useful. Everywhere else I really dislike it and the accompanying coding style. These .also and similar implicit receiver thingies are just straight up evil.
All in all, there are a few things that are very elegant in kotlin, but I feel they went the c++ c# way of over abstracting just to have a long feature list.
