public String sap(String nounA, String nounB) {
        if (!isNoun(nounA)) {
            throw new IllegalArgumentException(nounA
                    + " is not a WordNet noun.");
        }
        if (!isNoun(nounB)) {
            throw new IllegalArgumentException(nounB
                    + " is not a WordNet noun.");
        }
        Iterable<Integer> v = tableNoun.get(nounA);
        Iterable<Integer> w = tableNoun.get(nounB);
        int ancestor = sap.ancestor(v, w);
        if (ancestor == -1) {
            return "";
        } else {
            return tableID.get(ancestor);
        }
    }