public Set<User> list(Group aGroup) {
Set<User> result = new TreeSet<User>();
for (User user : users) {
if (user.getGroups().contains(aGroup)) {
public Set<User> list(Group aGroup) {
Set<User> result = new TreeSet<User>();
for (User user : users) {
if (user.getGroups().contains(aGroup)) {