code: public void debugf(String format, Object param1) {
          if (isEnabled(Level.DEBUG)) {
              doLogf(Level.DEBUG, FQCN, format, new Object[] { param1 }, null);
          }
      }
docs: Issue a formatted log message with a level of DEBUG.
  
  @param format the format string as per {@link String#format(String, Object...)} or resource bundle key therefor
  @param param1 the sole parameter