code: public static String getCategory(String eventSrcName) {
          if (eventSrcName == null) {
              return null;
          }
  
          int end = eventSrcName.lastIndexOf('.');
          eventSrcName = eventSrcName.substring(0, end);
  
          if (CHECKSTYLE_PACKAGE.equals(eventSrcName)) {
              return "misc";
          } else if (!eventSrcName.startsWith(CHECKSTYLE_PACKAGE)) {
              return "extension";
          }
  
          return eventSrcName.substring(eventSrcName.lastIndexOf('.') + 1);
      }
docs: Get the rule category from an audit event source name.
  
  @param eventSrcName the audit event source name
  @return the rule category, which is the last package name or "misc" or "extension"