public void createLinks() {//the adjacency list must be created at this point, then the links are created based on the adjacency list.
        for (int j = 0; j < graph_nodes.getLength(); j++) {
            //List gr_node=(List)graph_nodes.get(j);
            int lenght = ((GraphNode) (graph_nodes.get(j))).getNode_graphs().getLength();
            for (int i = 0; i < lenght; i++) {
                (graph_nodes.get(j)).addLink((graph_nodes.get(j)).getNode_graphs().get(i), 12);//12= peso o precio que se agarra del xml.
            }
        }
    }