public double strength(int vertex) {
        SparseWeightedDirectedTypedEdgeSet<T> e = vertexToEdges.get(vertex);
        return (e == null) ? 0 : e.sum();        
    }
public double strength ( int vertex ) { SparseWeightedDirectedTypedEdgeSet < T > e = vertexToEdges . get ( vertex ) ; return ( e == null ) ? 0 : e . sum ( ) ; }
{@inheritDoc}