I see that [`#filter`](<https://kotlinlang.org/api...

# getting-started

[arnab]

I see that [#filter](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/filter.html) is defined on Map, but I am not able to figure out how to use it. Anyone care to share an example?

I have a deeply nested TreeMap instance (TreeMap<String, Map<String, Map<*, *>>>) and I want to filter/find the first (which is the only in the domain) top-level key that has a certain characteristics associated with something deeper in the value. I have this following non-functional code which solves it right now:

val indexToAliasMappingType = LinkedTreeMap<String, Map<String, Map<*, *>>>()
        val indexToAliasMappings = Gson().fromJson(response.jsonString, indexToAliasMappingType.javaClass)

        var currentIndexName = ""
        for ((index, aliasMappings) in indexToAliasMappings) {
            val hasCurrentAlias = aliasMappings.get("aliases")?.containsKey(alias)
            if (hasCurrentAlias != null && hasCurrentAlias) {
                currentIndexName = index
            }
        }

        return currentIndexName