* first.or(supplier)}.
   *
   * <p><b>Java 9 users:</b> use {@link Objects#requireNonNullElse} instead. For lazy evaluation of
   * the fallback, use {@link Objects#requireNonNullElseGet Objects.requireNonNullElseGet(first, ()
   * -> second)}}.
   *
   * @return {@code first} if it is non-null; otherwise {@code second} if it is non-null
   * @throws NullPointerException if both {@code first} and {@code second} are null

   * first.or(supplier)}.
   *
   * <p><b>Java 9 users:</b> use {@link Objects#requireNonNullElse} instead. For lazy evaluation of
   * the fallback, use {@link Objects#requireNonNullElseGet Objects.requireNonNullElseGet(first, ()
   * -> second)}}.
   *
   * @return {@code first} if it is non-null; otherwise {@code second} if it is non-null
   * @throws NullPointerException if both {@code first} and {@code second} are null