private boolean isNegative(final String input){
  requireNonNull(input);
  for (  final String negativeString : negativeStrings) {
    if (input.equalsIgnoreCase(negativeString)) {
      return true;
    }
  }
  return false;
}

private boolean isNegative ( final String input ) { requireNonNull ( input ) ; for ( final String negativeString : negativeStrings ) { if ( input . equalsIgnoreCase ( negativeString ) ) { return true ; } } return false ; }
checks if a user ' s input matches one of the negative strings .
