Java reduce a collection of string to a map of occurence

Consider the a list as id1_f, id2_d, id3_f, id1_g, how can I use stream to get a reduced map in format of <String, Integer>of statistics like:

id1 2
id2 1
id3 1

Note: the key is part before _. Can reduce function help here?

This will get the job done:

Map<String, Long> map = Stream.of("id1_f", "id2_d", "id3_f", "id1_g")
  .collect(
    Collectors.groupingBy(v -> v.split("_")[0],
    Collectors.counting())
  );