code: private static ConcurrentHashMap<Class, List<ParamValidator>> getValidatorsMap() {
  
          // use <ConcurrentHashMap> in case validators are added while initializing parameters through <getValidator> method.
          ConcurrentHashMap<Class, List<ParamValidator>> map = new ConcurrentHashMap();
          addValidators(map, ParamValidator.class,    new ParamValidator(true),   new ParamValidator(false)); // default validator
          addValidators(map, FileValidator.class,     new FileValidator(true),    new FileValidator(false));
          addValidators(map, URLValidator.class,      new URLValidator(true),     new URLValidator(false));
          addValidators(map, HEXValidator.class,      new HEXValidator(true),     new HEXValidator(false));
  
          return map;
      }
docs: build a map of all Validator implementations by their class type and required value