chali

private Map<Integer, ? extends Address> getAddressIndex(Optional<SubjectData> currentSubjectData) {
    return currentSubjectData
        .map((SubjectData subjectData) ->
            subjectData.getAddresses().stream()
                .filter((Address address) -> address.getEsoId() != null)
                .collect(toMap(Address::getEsoId, identity()))
        ).orElse(emptyMap());
}