Convert ListMultimap to list of keys with duplicates?

Question

So I have a ListMultimap<Integer, String> that I want to convert to a List<Integer> that contains duplicates of the same Integer if there was >1 value associated with a Integer key in the ListMultimap. For instance, if:

ListMultimap<Integer, String> myMap = {2 -> "foo", 3 -> ("bar1, bar2")}

I want my resultant List<Integer> to look like: [2, 3, 3]. What is the easiest way to do this?

Thanks.

Answer 1

Assuming this is Guava, this is just the one line

Lists.newArrayList(multimap.keys())

or, if you have an ImmutableListMultimap,

multimap.keys().asList()

(Note here that Multimap.keys() is a Multiset<Integer>, which iterates over elements exactly in the way you want -- that is, it will have one occurrence of each key for each value associated with that key.)