docs: public static synchronized Schema getXJCLSchema() {
          if (schema == null) {
              final URL url = ValidatorHelper.class.getResource(SCHEMA_LOCATION);
              try {
                  schema = AccessController.doPrivileged(
                                                         new PrivilegedExceptionAction<Schema>() {
                                                             @Override
                                                             public Schema run() throws SAXException {
                                                                 return sf.newSchema(url);
                                                             }
                                                         });
              } catch (PrivilegedActionException e) {
                  throw new RuntimeException(e.getCause());
              }
  
          }
          return schema;
      }