I find the answer
PajekNetReader<Graph<Number, Number>, Number, Number> pnr =
new PajekNetReader<Graph<Number, Number>, Number,Number>(
vertexFactory, edgeFactory);
final Graph<Number,Number> graph = new SparseMultigraph<Number, Number>();
pnr.load(br, graph);
final AggregateLayout<Number,Number> layout =
new AggregateLayout<Number,Number>(new FRLayout<Number,Number>(graph));
vv = new VisualizationViewer<Number,Number>(layout);
vv.setBackground( Color.white );
vv.getRenderContext().setVertexLabelTransformer(pnr.getVertexLabeller());