Graph and Dijkstra infinite loop?

Question

So I creating a minecraft plugin where I am in need of a graph to create a navigation system. I researched a bit and found out that I should be able to use Dijkstra, but I have a problem. When searching for the shortest path I am sometimes getting an infinite loop(not always, it usally works the first 2-3 runs but after that it goes into the loop).

When the player wants to get to a destination I search for the closest vertex and use computePaths with that vertex as parameter. When I then run the getShortestPathTo it sometimes gets stuck in an infinite loop and I run out of memory(which makes sence since im adding the same vertexes to the list). Can you see why it is getting stuck? As far as I knew Dijkstra should be able to handle going from A node to B node and from B node to A node right?

Below is my code:

public class Dijkstra {
    public static void computePaths(Vertex source) {
    source.minDistance = 0.;
    PriorityQueue<Vertex> vertexQueue = new PriorityQueue<Vertex>();
    vertexQueue.add(source);

    while (!vertexQueue.isEmpty()) {
        Vertex u = vertexQueue.poll();

        // Visit each edge exiting u
        for (Edge e : u.adjacencies) {
            Vertex v = e.target;
            double weight = e.weight;
            double distanceThroughU = u.minDistance + weight;
            if (distanceThroughU < v.minDistance) {
                vertexQueue.remove(v);
                v.minDistance = distanceThroughU;
                v.previous = u;
                vertexQueue.add(v);
            }
        }
    }
}

public static List<Vertex> getShortestPathTo(Vertex target) {
    List<Vertex> path = new ArrayList<Vertex>();
    for (Vertex vertex = target; vertex != null; vertex = vertex.previous) {
        path.add(vertex);
    }
    Collections.reverse(path);
    return path;
}
}

and the vertex class:

public class Vertex implements Comparable<Vertex>
{
    public final String name;
    public Edge[] adjacencies;
    public double minDistance = Double.POSITIVE_INFINITY;
    public Vertex previous;
    public Location location;
    public Vertex(String argName) { name = argName; }
    public Vertex(String argName,Location l) { name = argName; location = l;}
    public String toString() { return name; }
    public int compareTo(Vertex other)
    {
        return Double.compare(minDistance, other.minDistance);
    }

}

When first the plugin is enabled I load all the vertexes from a config file looking something like this(It is the test one i am using)

I am adding vertexes and edges here(not sure if relevent but thought it might be?):

public void loadAllVertex() {
    ConfigurationSection section = nodeConfig.config.getConfigurationSection("nodes");
    for (String key: section.getKeys(false)) {
        String locationString = nodeConfig.getString("nodes." + key + ".location");
        if (locationString == null)
            return;
        String[] locationSplit = locationString.split(",");
        if (locationSplit.length <=1) {
            log.log(Level.SEVERE, "Location is not specified correctly in nodes.yml");
            return;
        }
        Location l = new Location(Bukkit.getWorlds().get(0),Integer.parseInt(locationSplit[0]),Integer.parseInt(locationSplit[1]),Integer.parseInt(locationSplit[2]));
        Vertex tmpVertex = new Vertex(key, l);
        allNodes.add(tmpVertex);

    }

    for (Vertex v : allNodes) {
        String path = "nodes." + v.name + ".connectedTo";
        List<String> connectedTo = nodeConfig.getStringList(path,true);
        List<Edge> edges = new ArrayList<>();

        for (String sideNodeName : connectedTo) {
            Vertex vertexCon = GraphUtils.getVertexByName(allNodes, sideNodeName);
            if (vertexCon == null) {
                log.warning("The '" + sideNodeName + "' node is not defined");
                return;
            }
            //A.adjacencies = new Edge[]{ new Edge(M, 8) };
            edges.add(new Edge(vertexCon,vertexCon.location.distance(v.location)));
        }
        Edge[] arrayEdges = new Edge[edges.size()];
        arrayEdges = edges.toArray(arrayEdges);
        v.adjacencies = arrayEdges;
    }

}

Answer 1

Think i found the error, so I never had any loops the first time I ran the compute path and findshortestpath so I finally figured out that I could not be resetting things correctly(should have been obvious I know) - I didn't update the vertexes afterwards. So I added a method to reset the mindistance and previous attributes and this seems to have done the trick.