A modern programming language that makes developers happier.

kotlinlang

I'm not understanding inline classes... What do they do? I only have a small amount of knowledge of the JVM and stack/heap stuff. etc. I am trying to improve my knowledge in that sector of things.

It’s for performance. It’s not a good idea to have small one-property objects in memory everywhere. Primitive types take up much less memory

Inline classes give you the best of both worlds. It’s a normal object until it’s compiled, where it's replaced with the primitive property

And it's sort of a way of sub-typing.
Eg an email and an address can be represented by a String.
But they should never be assigned to each other.
Inline classes help here. Create an inline class `Email` ,with a String, and one called `Address` , with a String. Both are now kinda like sub-types of String, through their boxing and un-boxing. They are both like Strings, but one cannot assign one to the other.

<https://medium.com/@riggaroo/lessons-learnt-with-kotlin-using-inline-classes-9c3d424650d1#:~:text=An%20inline%20class%20is%20a,into%20where%20it%20was%20called>.