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