public String toString()
	{
		if(isEmpty())
			return "Empty graph";
		else 
		{
			String nodes="Nodes = {";
			String edges="Edges = {";
			Iterator<String> itSource=mapNodes.keySet().iterator();
			while(itSource.hasNext())
			{
				String idSource=itSource.next();
				nodes+=idSource+", ";
				HashMap<String,Double> adiac=mapNodes.get(idSource).getAdiacs();
				Iterator<String> itDest=adiac.keySet().iterator();
				while(itDest.hasNext())
				{
					String idDest=itDest.next();
					if(idSource.compareTo(idDest)<0)
						edges+="("+idSource+","+idDest+","+adiac.get(idDest)+"); ";
				}
			}
			if(nodes.length()!=9)
				nodes=nodes.substring(0,nodes.length()-2);
			nodes+="}\n";
			if(edges.length()!=9)
				edges=edges.substring(0,edges.length()-2);
			edges+="}\n";
			return nodes+edges;
		}
        }