I'm curious why does Kotlin create a class implementation instead of default methods when creating a...

# getting-started

[Jan]

I'm curious why does Kotlin create a class implementation instead of default methods when creating an interface with methods that have a body? (I now you can change that)

[Tim Oltjenbruns]

probably so it can support earlier versions of Java that don’t have default methods

[Joffrey]

It was not possible to do so with bytecode < JVM 8, so they had to do it another way.
When compiling to bytecode 8+, you can now choose to use default methods (it might even be the default now).

(remember the initial target was Android)

[Jan]

Ah okay thanks!

[ephemient]

Android was not the initial target, I don't know why people think that.

[Casey Brooks]

remember the initial target was Android

Not exactly. Kotlin existed for like, 7 years before Google adopted it for Android. Jetbrains created it initially for their own use, which at the time was on Java 6. Kotlin has always been a much bigger thing than just Android

[ephemient]

https://wiki.jvmlangsummit.com/index.php?title=Kotlin first public announcement

[ephemient]

https://blog.jetbrains.com/kotlin/2011/07/hello-world-2/ a bit of a retrospective around the time of 1.0

Ten years of Java development led us to feeling that our productivity at JetBrains could be improved significantly by using a modern JVM language alongside Java.

[ephemient]

exactly, the connection with Android only came as the community started using it later, with Google picking it up after that

[Joffrey]

Fair enough, that was not quite correct. They did have to maintain compat with JDK < 8 even until recently because of Android though, while the rest could more easily upgrade to more recent JDKs

[Jan]

Do you need another compiler argument when using the compiler option -Xjvm-default=all?
Because I get a "Inheritance from an interface with 'JvmDefault'...' error

[gildor]

because of Android though, while the rest could more easily upgrade to more recent JDKs

It's not exactly correct either.
Even server java was not completely java 8+, there is a bunch of older big projects which still using java 6, you can check any Java survey for the last 5 years.
I agree, Android is a big factor later, but Android app a lot easier to migrate on Java 8 bytecode than a big enterprise server app, it supported for at least 4 years on d8