code: @Override
      public boolean incrementToken() throws IOException {
          if (!input.incrementToken()) {
              return false;
          }
  
          final String t = myTermAttribute.toString();
  
          if (t != null && t.length() != 0) {
              try {
                  myTermAttribute.setEmpty().append(ISO639Converter.convert(t));
              } catch (final IllegalArgumentException details) {
                  if (LOGGER.isWarnEnabled()) {
                      LOGGER.warn(details.getMessage(), details);
                  }
              }
          }
  
          return true;
      }
docs: Increments and processes tokens in the ISO-639 code stream.
  
  @return True if a value is still available for processing in the token stream; otherwise, false