private synchronized @Nonnull Set<String> getAcceptedGroups() {
if (acceptedGroups == null) {
final List<GroupSelector> selectors = getGroupList();
acceptedGroups = new HashSet<String>(selectors.size());
for (GroupSelector selector : selectors) {
// merge equal entries
acceptedGroups.add(selector.getSelectedGroupId());
}
}
return acceptedGroups;
}