Java 8 streaming and sql like join [closed]

Question

I have 2 csv files so defined 2 objects i.e. Person and Address. Person can have multiple addresses objects. I need to join and perform aggregation on data. This is similar to having 2 separate tables in database and performing join. What would be right approach to achieve this? Any options in steaming/Lambda? If not any framework you can recommend?

Thanks, Kam

Answer 1

I don't think there is an equivalent of join in standard library. The closest you can do is something like

Map<String, Person> pMap = persons.stream
                                  .collect(Collectors.groupingBy(Person::getId);
List<Pair<Person,Address>> joined = addresses.stream
                                      .map (a -> new Pair(pMap.get(a.personId()), a));

etc.

(Note, that I made up a class Pair here, because there is (still) no such thing as a tuple in java).