8.2

class Solution {
  public static int numberOfConnectedComponents(Graph g) {
    Collection<Vertex> unexplored = g.getAllVertices();

    for (int count = 0;;count++)
    {
      Iterator<Vertex> uIt = unexplored.iterator();

      if (!uIt.hasNext())
      {
        return count;
      }

      Vertex v = uIt.next();
      Iterator<Vertex> it = new GraphIterator(g, v);
      List<Vertex> explored = new ArrayList<>();

      while (it.hasNext())
      {
        explored.add(it.next());
      }

      unexplored.removeAll(explored);
    }
  }
}