// If users use this when they shouldn't, we hope that NewApi will catch subsequent Optional calls
  @IgnoreJRERequirement
  public java.util.Optional<T> toJavaUtil() {
    return java.util.Optional.ofNullable(orNull());
  }

  Optional() {}

  /**
   * Returns {@code true} if this holder contains a (non-null) instance.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> no differences.
   */

  }

  @SuppressWarnings("OptionalOfRedundantMethod") // Unit tests for Optional
  public void testOrNull_present() {
    assertEquals("a", Optional.of("a").orNull());
  }

  public void testOrNull_absent() {
    assertThat(Optional.absent().orNull()).isNull();
  }

  public void testAsSet_present() {
    Set<String> expected = Collections.singleton("a");
    assertEquals(expected, Optional.of("a").asSet());