code: private String buildMessage(String firstMessageLine, int exceptionLine) {
      if (additionalLines.size() == 0) {
        return firstMessageLine;
      }
      StringBuffer message = new StringBuffer();
      if (firstMessageLine != null) {
        message.append(firstMessageLine);
      }
  
      int linesToProcess = (exceptionLine == -1?additionalLines.size(): exceptionLine);
  
      for (int i = 0; i < linesToProcess; i++) {
        message.append(newLine);
        message.append(additionalLines.get(i));
      }
      return message.toString();
    }
docs: Combine all message lines occuring in the additionalLines list, adding
  a newline character between each line
  <p>
  the event will already have a message - combine this message
  with the message lines in the additionalLines list
  (all entries prior to the exceptionLine index)
  
  @param firstMessageLine primary message line
  @param exceptionLine index of first exception line
  @return message