public void findAllPairsShortestPath() throws IOException {
		
		PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(outputFileName)));
		PrintWriter log = new PrintWriter(new BufferedWriter(new FileWriter(logFileName)));
		
		for(Map.Entry<Character,Position> s : nodes.entrySet()) {
			for(Map.Entry<Character,Position> e : nodes.entrySet()) {
				if(s.getKey() < e.getKey()) {
					log.println("from '"+s.getKey()+"' to '"+e.getKey()+"'");
					log.println("-----------------------------------------------");
					findShortestPath(s.getValue(),e.getValue(),out,log);
					log.println("-----------------------------------------------");
				}
			}
		}
		//System.out.println(graph);
		out.close();
		log.close();
	}