code: public static<T extends ParamValidator> T getValidator(Class<T> clazz, boolean required) {
  
          List<ParamValidator> validators = validatorsMap.get(clazz);
          if (validators != null) {
  
              if (required) {
                  return (T)validators.get(0);
              }
  
              return (T)validators.get(1);
          }
  
          return null;
      }
docs: return the relevant Validator by the given class type and required indication