public void add(final T id) {
        if (id == null) {
            throw new IllegalArgumentException("CriteriaSet does not allow adding null - use setMatchNull if required");
        }
        matchAll = false;
        set.add(id);
    }
Utility class to match on sets of id's with concepts like match anything and specific id's.
stroom-util-shared/src/main/java/stroom/util/shared/Selection.java