How can I get the the unrecognized Token in an ANTLRErrorListener for a Lexer?

I have a lexer, generated with ANTLR. What I try to achive is to handle an error during lexing in case of an not recognized token.

How can I get only the character causing this error?

lexer.addErrorListener(new ANTLRErrorListener() {
  @Override
  public void syntaxError(Recognizer<?, ?> recognizer,  
                          Object offendingSymbol, int line,
                          int charPositionInLine, String msg,
                          RecognitionException e) {

  }

  // ....
}

The given message msg contains a message and the character, but I would like to have the character only to generated a better message for the users of my code.

You can get the offending character like this:

lexer.addErrorListener(new ANTLRErrorListener() {
    @Override
    public void syntaxError(Recognizer<?, ?> recognizer,
                            Object offendingSymbol, int line,
                            int charPositionInLine, String msg,
                            RecognitionException e) {

        int index = recognizer.getInputStream().index();
        String text = lexer.getInputStream().getText(Interval.of(index, index));

        throw new RuntimeException(String.format("Don't know how to handle '%s'", text));
    }

    // ...
});