var listOfLists : List<List<Int>> = mutableListOf()
If I want to add some elements to the inner list, what should I do? The inner list seems to be immutable be default.
Same thing happens with Map. In Java, I can do this:
Map<String, List<String>> map = ......
map.computeIfAbsent(key, key -> new ArrayList<>()).add("a string").
How can I achieve the same with Kotlin?