public void add(final T id) {
        if (id == null) {
            throw new IllegalArgumentException("CriteriaSet does not allow adding null - use setMatchNull if required");
        }
        set.add(id);
    }
By default the criteria will match anything. NULL matchAll implies match
anything when nothing is in the set or we are to not matchNull. By
setting match all it will match all regardless.
stroom-legacy/stroom-legacy-model_6_1/src/main/java/stroom/legacy/model_6_1/CriteriaSet.java