code: @Override
    public synchronized String format(final LogRecord record) {
      buffer.setLength(PREFIX.length());
      buffer.append(timestampFormatter.format(new Date(record.getMillis())));
      buffer.append(' ');
      buffer.append(levelNumberToCommonsLevelName(record.getLevel()));
      String[] parts = record.getSourceClassName().split("\\.");
      buffer.append(" [" + parts[parts.length-1] + "." + record.getSourceMethodName() + "]");
      buffer.append(SUFFIX);
      buffer.append(formatMessage(record)).append(lineSeparator);
      if (record.getThrown() != null) {
        final StringWriter trace = new StringWriter();
        record.getThrown().printStackTrace(new PrintWriter(trace));
        buffer.append(trace);
      }
  
      return buffer.toString();
    }
docs: Format the given log record and return the formatted string.
  
  @param record the log record to be formatted.
  @return a formatted log record