@Nullable
  private static List<String> addErrorsIf(boolean condition, List<String> errors, String newErr) {
    if (condition) {
      return addError(errors, newErr);
    }

    return errors;
  }
Combines two {@literal List<String>s} together.
jobdispatcher/src/main/java/com/firebase/jobdispatcher/DefaultJobValidator.java