Edge edge23 = factory.newEdge(node2, node3);
Edge edge35 = factory.newEdge(node3, node5);
Edge edge34 = factory.newEdge(node3, node4);
Edge edge15 = factory.newEdge(node1, node5);
Edge edge36 = factory.newEdge(node3, node6);
graph.addEdge(edge23);
graph.addEdge(edge35);
graph.addEdge(edge34);
graph.addEdge(edge15);
graph.addEdge(edge36);