public static void main(String[] args) {
   TransportSystem transportSystem = new TransportSystem();

   if (readFile(transportSystem, "WashingtonDCMetro.txt")) {
         int selection = -1;
         String line;
         String lineID;
         String name;
         double distance;
         Scanner keyboard = new Scanner(System.in);
         int t = 0;
         while (selection != 0) {
            System.out.println("Enter your selection");
            System.out.println("(1) display the string representation of the transport system; \n"
                     + "(2) addLine; \n"
                     + "(3) removeLine; \n"
                     + "(4) getLineLength; \n"
                     + "(5) getLengthAllLines; \n"
                     + "(6) getLongestLine; \n"
                     + "(7) getTransferStationMax; \n"
                     + "(8) getTransferLinesForStation \n"
                     + "(0) exit");
            System.out.print("-->");
            selection = keyboard.nextInt();
            switch(selection){
               case 1:
                     System.out.println(transportSystem.toString() + "\n");
                     break;
               case 2:
                     System.out.print("Enter LineID: ");
                     lineID = keyboard.next();
                     TransportLine transportLine = new TransportLine(lineID);

Prime Numbers Objectives: * Practice with arithmetic operator...