if (this.getClass().getName() == Digraph.class.getName()) {
if (this.getClass().getName().equals (Digraph.class.getName())) {
        public String toString ()    {        StringBuffer sb = new StringBuffer(25);        sb.append("{").append(getPrefix());        if (id != null) {            sb.append("#").append(id);        }        sb.append(" ").append(getVertexCount()).append(" vertices");        if (this.getClass().getName() == Digraph.class.getName()) {            sb.append("}");        }        return sb.toString();    }