How to turn a Mutable Collection into an Immutable one

Question

I was writing a small piece of code in which I internally handle my data in a mutable map, which in turn has mutable lists.

I wanted to expose my data to the API use

Answer 1

Simply call toMap() on your MutableMap.

val myMap = mutableMapOf("x" to "y").toMap()

Done.

The same also works for lists.