public String getUserInput(String prompt) {
     String inputLine = null;
     System.out.print(prompt + "  ");
     try {
       BufferedReader is = new BufferedReader(
	 new InputStreamReader(System.in));
       inputLine = is.readLine();
       if (inputLine.length() == 0 )  return null; 
     } catch (IOException e) {
       System.out.println("IOException: " + e);
     }
     return inputLine.toLowerCase();
  }