code: public static BoxRetentionPolicy.Info createFinitePolicy(BoxAPIConnection api, String name, int length,
                                                               String action, RetentionPolicyParams optionalParams) {
          return createRetentionPolicy(api, name, TYPE_FINITE, length, action, optionalParams);
      }
docs: Used to create a new finite retention policy with optional parameters.
  @param api the API connection to be used by the created user.
  @param name the name of the retention policy.
  @param length the duration in days that the retention policy will be active for after being assigned to content.
  @param action the disposition action can be "permanently_delete" or "remove_retention".
  @param optionalParams the optional parameters.
  @return the created retention policy's info.