Importing Graph Class/help implement a weighted graph class

Question

Is there a way to import a graph structure into my java program so that I do not need to write my own graph class?
If not, does anyone have a graph class that I can use? I've been trying to implement this program for the past few days..
I'm having trouble implementing a weighted graph class. This is what I have so far:
import java.util.ArrayList;
import java.util.Queue;
import java.util.*;
public class Graph<T>
     private ArrayList<Vertex> vertices;
     int size = -1;
     public Graph() throws BadInputException
          ReadFile source = new ReadFile("inputgraph.txt");
          size = source.getNumberOfWebpages();
          System.out.println(size);
          vertices = new ArrayList<Vertex>();
     public int bfs(int start, int end) //breadth first search
          Queue<Integer> queue = new LinkedList<Integer>();
          if(start == -1 || end == -1)
               return -1;
          if(start == end)
               return 0;
          int[] d = new int[size];
          System.out.println(size + "vertices size");
          for(int i = 0; i < d.length; i++)
               d[i] = -1;
          System.out.println(start + " START GRAPH");
          d[start] = 0;
          queue.add(start);
          while(!queue.isEmpty())
               int r = queue.remove();
               if(r == end)
                    return d[r];
               for(EdgeNode ptr = vertices.get(r).head; ptr != null; ptr = ptr.next)
                    int neighbor = ptr.dest;
                    if(d[neighbor] == -1)
                         queue.add(neighbor);
                         d[neighbor] = d[r] + 1;
                         if(neighbor == end)
                              return d[neighbor];
          return d[end];
     public boolean addEdge(int start, int end)
          Vertex v = new Vertex();
          v = vertices.get(start);
          EdgeNode temp = v.head;
          EdgeNode newnode = new EdgeNode(end, temp);
          v.head = newnode;
          return true;
     public void setRank(int vertex, double rank) //set the weights
          vertices.get(vertex).pageRank = rank;
     public double getRank(int vertex)
          return vertices.get(vertex).pageRank;
If anyone could help. It would be greatly appreciated
Edited by: brones on May 3, 2008 12:33 PM

Answer 1

brones wrote:
along with the rest of my code, I'm not sure how to implement it as a weighted graphA single list is not the proper way of representing a graph. An easy way to implement a graph is to "map" keys, the source-vertex, to values, which is a collection of edges that run from your source-vertex to your destination-vertex. Here's a little demo:
import java.util.*;
public class TestGraph {
    public static void main(String[] args) {
        WeightedGraph<String, Integer> graph = new WeightedGraph<String, Integer>();
        graph.add("New York", "Washington", 230);
        graph.add("New York", "Boston", 215);
        graph.add("Washington", "Pittsburgh", 250);
        graph.add("Pittsburgh", "Washington", 250);
        graph.add("Pittsburgh", "New York", 370);
        graph.add("New York", "Pittsburgh", 370);
        System.out.println("New York's edges:\n"+graph.getEdgesFrom("New York"));
        System.out.println("\nThe entire graph:\n"+graph);
class WeightedGraph<V extends Comparable<V>, W extends Number> {
    private Map<V, List<Edge<V, W>>> adjacencyMap;
    public WeightedGraph() {
        adjacencyMap = new TreeMap<V, List<Edge<V, W>>>();
    public void add(V from, V to, W weight) {
        ensureExistenceOf(from);
        ensureExistenceOf(to);
        getEdgesFrom(from).add(new Edge<V, W>(to, weight));
    private void ensureExistenceOf(V vertex) {
        if(!adjacencyMap.containsKey(vertex)) {
            adjacencyMap.put(vertex, new ArrayList<Edge<V, W>>());
    public List<Edge<V, W>> getEdgesFrom(V from) {
        return adjacencyMap.get(from);
    // other methods
    public String toString() {
        if(adjacencyMap.isEmpty()) return "<empty graph>";
        StringBuilder b = new StringBuilder();
        for(V vertex: adjacencyMap.keySet()) {
            b.append(vertex+" -> "+getEdgesFrom(vertex)+"\n");
        return b.toString();
class Edge<V, W extends Number> {
    private V toVertex;
    private W weight;
    public Edge(V toVertex, W weight) {
        this.toVertex = toVertex;
        this.weight = weight;
    // other methods
    public String toString() {
        return "{"+weight+" : "+toVertex+"}";
}Note that I didn't comment it, so you will need to study it a bit before you can use it. If you have further question, feel free to ask them. However, if I feel that you did not take the time to study this example, I won't feel compelled to assist you any further (sorry to be so blunt).
Good luck.