code: public Graph generateRandomMMapGraph(String graphName, int size, float dens) {
  		
  		Graph graph = null;
  		String dir = "graphs/MMap/" + graphName;
  		
  		SerializationUtils.deleteMMapGraph(dir);
  		graph = new Graph(new MMapGraphStructure(dir));
  		
  		Random rand = new Random();
  		
  		for (int i = 0; i < size; i++)
  			graph.addNode(new Node(i));
  		
  		for (int i = 0; i < size; i++) {
  			for (int j = i+1; j < size; j++) {
  				
  				if (rand.nextFloat() < dens) {
  					int randomCost = Math.abs(rand.nextInt(50)) + 1;
  					Edge e = new Edge(i, j, randomCost);
  					e.setBidirectional(rand.nextBoolean());
  					
  					graph.addEdge(e);
  				}
  			
  			}
  		}
  
  		return graph;
  	}
docs: Create a new Graph which has the given graphName, size and dens.
  @param graphName the graph's name.
  @param size the graph's size.
  @param dens the graph's dens.
  @return the graph generated.