return GetCheckedTypeValidatorHolder.BEST_VALIDATOR;
  }

  @VisibleForTesting
  static GetCheckedTypeValidator weakSetValidator() {
    return GetCheckedTypeValidatorHolder.WeakSetValidator.INSTANCE;
  }

  @J2ObjCIncompatible // ClassValue
  @VisibleForTesting
  static GetCheckedTypeValidator classValueValidator() {

  private static GetCheckedTypeValidator bestGetCheckedTypeValidator() {
    return GetCheckedTypeValidatorHolder.BEST_VALIDATOR;
  }

  @VisibleForTesting
  static GetCheckedTypeValidator weakSetValidator() {
    return GetCheckedTypeValidatorHolder.WeakSetValidator.INSTANCE;
  }

  /**
   * Provides a check of whether an exception type is valid for use with {@link
   * FuturesGetChecked#getChecked(Future, Class)}, possibly using caching.