code: public static String requireNonBlank(final String str, final String argumentName) {
          requireNonNull(str, argumentName);
          if (isBlank(str)) {
              throw new IllegalArgumentException(String.format(NOT_EMPTY_MSG_FORMAT, argumentName));
          }
          return str;
      }
docs: Checks that the specified {@code str} {@code blank}, throws {@link IllegalArgumentException} with a customized error message if it is.
  
  @param str          the value to be checked.
  @param argumentName the name of the argument to be used in the error message.
  @return the {@code str}.
  @throws java.lang.NullPointerException     if {@code str} is null.
  @throws java.lang.IllegalArgumentException if {@code str} is blank.
  @see #requireNonNull(Object, String)
  @see #isBlank(String)