private final Map<String, List<Person>> people = new HashMap<String, List<Person>>();
private final Map<Person, Address> addresses = new HashMap<Person, Address>();
public Person addPerson(final String firstName, final String lastName) {
final Person person = new PersonImpl();
person.setFirstName(firstName);
person.setLastName(lastName);
if (people.containsKey(firstName)) {
people.get(firstName).add(person);
} else {
people.put(firstName, new ArrayList(Arrays.asList(person)));