* Registers this extractor with the ExtractorFactory.
     * @param keyList The list of keys to register this extractor under.
     */
    public void register(final List<String> keyList) {
        if (keyList == null || keyList.isEmpty()) {
            throw new IllegalArgumentException("keyList must not be null or empty.");
        }
        getExtractorFactory().addExtractor(keyList, this);
    }

    /**

     *
     * @return the first element
     */
    public E getFirst() {
        if (isEmpty()) {
            throw new NoSuchElementException();
        }
        return getFirstEntry().element;
    }

    /**
     * Returns the last element.
     *
     * @return the last element
     */
    public E getLast() {
        if (isEmpty()) {
            throw new NoSuchElementException();
        }

        // Assert - Verify URL components
        assertEquals("smb", url1.getProtocol());
        assertEquals("host", url1.getHost());
        assertEquals(445, url1.getPort());
        assertEquals("/share", url1.getPath());

        assertEquals("smb", url2.getProtocol());
        assertEquals("host", url2.getHost());
        assertEquals(1234, url2.getPort());
        assertEquals("/share/file.txt", url2.getPath());

     *
     * @param keyList the list of keys to associate with the extractor
     * @param extractor the extractor to add
     * @throws CrawlerSystemException if the key list is null or empty, or if the extractor is null
     */
    public void addExtractor(final List<String> keyList, final Extractor extractor) {
        if (keyList == null || keyList.isEmpty()) {

                .actionGet()
                .getHits()
                .getTotalHits()
                .value() > 0);
        assertTrue(fesenClient.prepareSearch("fess_crawler.filter")
                .setQuery(QueryBuilders.termQuery("sessionId", sessionId2))
                .setSize(0)
                .execute()
                .actionGet()
                .getHits()
                .getTotalHits()

            // Test with mock
            when(mockReferralData.getLink()).thenReturn(link);
            assertEquals(link, mockReferralData.getLink());
            verify(mockReferralData, times(1)).getLink();

            // Test with concrete implementation
            concreteImplementation.setLink(link);
            assertEquals(link, concreteImplementation.getLink());
        }

        @Test

                .execute()
                .actionGet()
                .getHits()
                .getTotalHits()
                .value() > 0);
        assertTrue(fesenClient.prepareSearch("fess_crawler.queue")
                .setQuery(QueryBuilders.termQuery("sessionId", "id2"))
                .execute()
                .actionGet()
                .getHits()
                .getTotalHits()
                .value() > 0);

Set<String> caseInsensitiveSet = new CaseInsensitiveSet<>();

// Java 21 Sequenced Collections support
SequencedCollection<String> sequenced = CollectionsUtil.newLinkedHashSet();
String first = CollectionsUtil.getFirst(sequenced);
String last = CollectionsUtil.getLast(sequenced);
SequencedCollection<String> reversed = CollectionsUtil.reversed(sequenced);

// Specialized collections

        ftpInfo = new FtpClient.FtpInfo(value, Constants.UTF_8);
        assertEquals(value, ftpInfo.toUrl());
        assertEquals("123.123.123.123:9999", ftpInfo.getCacheKey());
        assertEquals("123.123.123.123", ftpInfo.getHost());
        assertEquals(9999, ftpInfo.getPort());
        assertEquals("/", ftpInfo.getParent());
        assertNull(ftpInfo.getName());

        value = "ftp://123.123.123.123/test.txt";

   *
   * @throws NullPointerException if the last element is null; if this is a possibility, use {@link
   *     Iterables#getLast} instead.
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> last() {
    // Iterables#getLast was inlined here so we don't have to throw/catch a NSEE

    // TODO(kevinb): Support a concurrently modified collection?