Hello Members,

I am trying to add weights to a Graph that is implemented using JGrapht. I keep getting a

NullPointerException, which I am unable to understand as all other edges seems to be added fine. I would be grateful for any help.

The code so far:

```
import org.jgrapht.*;
import org.jgrapht.alg.*;
import org.jgrapht.graph.*;
import java.util.List;
public class Graph {
public static void main(String args[]) {
SimpleWeightedGraph<String, DefaultWeightedEdge> graph = new SimpleWeightedGraph<String, DefaultWeightedEdge>(DefaultWeightedEdge.class);
graph.addVertex("47");
graph.addVertex("28");
graph.addVertex("29");
graph.addVertex("26");
graph.addVertex("79");
DefaultWeightedEdge e1 = graph.addEdge("47", "28");
graph.setEdgeWeight(e1, 5);
DefaultWeightedEdge e2 = graph.addEdge("28", "29");
graph.setEdgeWeight(e2, 3);
DefaultWeightedEdge e3 = graph.addEdge("26", "79");
graph.setEdgeWeight(e3, 6);
DefaultWeightedEdge e4 = graph.addEdge("28", "26");
graph.setEdgeWeight(e4, 2);
DefaultWeightedEdge e5 = graph.addEdge("79", "26");
graph.setEdgeWeight(e5, 4);
DefaultWeightedEdge e6 = graph.addEdge("28", "79");
graph.setEdgeWeight(e6, 9);
DefaultWeightedEdge e7 = graph.addEdge("26", "47");
graph.setEdgeWeight(e7, 7);
DefaultWeightedEdge e8 = graph.addEdge("29", "28");
graph.setEdgeWeight(e8, 2);
DefaultWeightedEdge e9 = graph.addEdge("47", "29");
graph.setEdgeWeight(e9, 10);
DefaultWeightedEdge e10 = graph.addEdge("29", "79");
graph.setEdgeWeight(e10, 1);
System.out.println("Shortest path from 47 to 79:");
List shortest_path = DijkstraShortestPath.findPathBetween(graph, "47", "79");
System.out.println(shortest_path);
}
}
```

The run-time exception:

```
java.lang.NullPointerException
at org.jgrapht.graph.AbstractBaseGraph.setEdgeWeight(Unknown Source)
at Graph.main(Graph.java:32)
```