code: public void l7dlog(Priority priority, String key, Object[] params, Throwable t) {
          if (repository.isDisabled(priority.level)) {
              return;
          }
          if (priority.isGreaterOrEqual(this.getEffectiveLevel())) {
              String pattern = getResourceBundleString(key);
              String msg;
              if (pattern == null)
                  msg = key;
              else
                  msg = java.text.MessageFormat.format(pattern, params);
              forcedLog(FQCN, priority, msg, t);
          }
      }
docs: Log a localized and parameterized message. First, the user supplied <code>key</code> is searched in the resource bundle. Next, the
  resulting pattern is formatted using {@link java.text.MessageFormat#format(String,Object[])} method with the user supplied object
  array <code>params</code>.
  
  @since 0.8.4