/**
* Creates a new edge and adds it to the specified graph similarly to the
* {@link Graph#addEdge(Object, Object)} method.
*
* @param g the graph for which the edge to be added
* @param sourceVertex source vertex of the edge
* @param targetVertex target vertex of the edge
* @param weight weight of the edge
* @param <V> the graph vertex type
* @param <E> the graph edge type
*
* @return The newly created edge if added to the graph, otherwise <code>
* null</code>.
*
* @see Graph#addEdge(Object, Object)
*/
public static E addEdge <V, E>(Graph <V, E> g, V sourceVertex, V targetVertex, double weight)
{
EdgeFactory <V, E> ef = g.getEdgeFactory();
E e = ef.createEdge(sourceVertex, targetVertex);
// we first create the edge and set the weight to make sure that
// listeners will see the correct weight upon addEdge.
g.setEdgeWeight(e, weight);
return(g.addEdge(sourceVertex, targetVertex, e) ? e : default(E));
}