nV = 1;
        }

        checkVertices(nV);

        int nE = nVertices;
        if (nEdges <= nV) {
            nE = 2 * nE;
        }

        checkEdges(nE);
    }

    private void checkVertices() {
        checkVertices(DEFAULT_VERTICES);
    }

    private void checkVertices(int nVertices) {
        if (vertices == null) {