Help. Problem creating a visual graph.

Question

I am creating a push down automata. Im getting a compile error when getting 2 nodes out of a vector and placing them in the parameters of an edge which is being placed in a separate vector. Here is some code to help explain:
public class Graph {
    Vector nodes;
    Vector edges;
    public Graph()
        nodes = new Vector();
        edges = new Vector();
        nodes.add(new Node(20, 20, '1')); //0
        nodes.add(new Node(200, 20,'2')); //1
        nodes.add(new Node(100, 100,'3')); //2
        edges.add(new Edge('a', nodes.get(0), nodes.get(1)));    //PROBLEM HERE
public class Node {
     Vector edges = new Vector();
     int x, y;
     char nLabel;
     boolean wasVisited;
    public Node(int x, int y, char label)
       nLabel = label;
       this.x = x;
       this.y = y;
       wasVisited=false;
public class Edge {
    char label;
    Node nodeOne;
    Node nodeTwo;
    public Edge(char lab, Node one, Node two)
        label = lab;
        nodeOne = one;
        nodeTwo = two;
    }in the graph class is where my error occurs, when im adding an edge to my edge vector.
I'm sure it has to be something pretty simple that im missing....or maybe something im just oblivious to.
thank you for the help.

Answer 1

Ok you have two options:
1) Use generics (recommended)
2) Casting
Declare the vectors as Vector<Node> and get information from [1] to learn about generics (very powerful feature and REALLY simple).
Or when you call the Edge constructor, do this:
edges.add(new Edge('a', (Node)nodes.get(0), (Node)nodes.get(1)));[1] http://java.sun.com/j2se/1.5/pdf/generics-tutorial.pdf
HTH : )