class Graph {

    public Edge edge(int u, int v) {
        final int d = degrees[u];
        for (int j = 0; j < d; ++j) {
            Edge e = edges[u][j];
            if (e.other(u) == v)
                return e;
        }
        throw new IllegalArgumentException(u + ", " + v + " are not adjacent");
    }

      Graph(int expSize);
      Graph(Graph org);

}