ArrayList vs mutablelist Kotlin
The only difference between the two is communicating your intent.
When you write val a = mutableListOf(),
you're saying "I want a mutable list, and I don't particularly
care about the implementation". When you write, instead, val a = ArrayList(),
you're saying "I specifically want an ArrayList".
In practice, in the current implementation of Kotlin compiling to the JVM,
calling mutableListOf will produce an ArrayList,
and there's no difference in behaviour: once the list is built,
everything will behave the same.
abdullah