@Override
                                                     public boolean checkInput(String inputString) {
                                                       try {
                                                         parser.apply(inputString);
                                                         return true;
                                                       }
                                                       catch (NumberFormatException nfe) {
                                                         return false;
                                                       }
                                                     }
@Override
                                                     public boolean checkInput(String inputString)