Java: how to represent graphs?

I'm implementing some algorithms to teach myself about graphs and how to work with them. What would you recommend is the best way to do that in Java? I was thinking something like this:

public class Vertex {

    private ArrayList<Vertex> outnodes; //Adjacency list. if I wanted to support edge weight, this would be a hash map.

    //methods to manipulate outnodes
}

public class Graph {
    private ArrayList<Vertex> nodes;
    //algorithms on graphs
}

But I basically just made this up. Is there a better way?

Also, I want it to be able to support variations on vanilla graphs like digraphs, weighted edges, multigraphs, etc.