I need to get only a list of keys from a hash map.
Here is how I do it:
data is hashmap type.
val flatten = data.flatMap { it.entries }
val keys = flatten.map { it.key }
As you can see on the rows above first, the data is flattened, and then with help of the map method I create a list only of keys.
But it looks like that flatten.map { it.key } work slow.
My question is, is there any other way to fetch a list of keys from Hashmap, or how can I improve the performance of the code above?