TreeSet<Derived> set = Sets.newTreeSet();
    assertTrue(set.isEmpty());
    set.add(new Derived("foo"));
    set.add(new Derived("bar"));
    assertThat(set).containsExactly(new Derived("bar"), new Derived("foo")).inOrder();
  }

  public void testNewTreeSetEmptyNonGeneric() {
    TreeSet<LegacyComparable> set = Sets.newTreeSet();
    assertTrue(set.isEmpty());
    set.add(new LegacyComparable("foo"));

    public void test_robotsTxtUrlSet() {
        Set<String> urlSet = crawlerContext.getRobotsTxtUrlSet();
        assertNotNull(urlSet);
        assertTrue(urlSet instanceof LruHashSet);
        assertTrue(urlSet.isEmpty());

        // Add URLs to default set
        urlSet.add("http://example.com/robots.txt");
        urlSet.add("http://test.com/robots.txt");
        assertEquals(2, crawlerContext.getRobotsTxtUrlSet().size());

    if (address.size == 4) return inet4AddressToAscii(address) // An IPv4-mapped IPv6 address.
    throw AssertionError("Invalid IPv6 address: '$host'")
  }

  val result = idnToAscii(host) ?: return null
  if (result.isEmpty()) return null
  if (result.containsInvalidHostnameAsciiCodes()) return null
  if (result.containsInvalidLabelLengths()) return null

  return result
}

internal fun idnToAscii(host: String): String? {

                        }
                    }
                }

                wordsList.add(word);
                readingList.add(l.toArray(new String[l.size()]));
            }
            if (wordsList.isEmpty()) {
                return null;
            }
            return new SuggestItem(wordsList.toArray(new String[wordsList.size()]), readingList.toArray(new String[readingList.size()][]),

  }

  internal fun check(
    hostname: String,
    cleanedPeerCertificatesFn: () -> List<X509Certificate>,
  ) {
    val pins = findMatchingPins(hostname)
    if (pins.isEmpty()) return

    val peerCertificates = cleanedPeerCertificatesFn()

    for (peerCertificate in peerCertificates) {
      // Lazily compute the hashes for each certificate.
      var sha1: ByteString? = null

  fun idleLatch(): CountDownLatch {
    taskRunner.withLock {
      // If the queue is already idle, that's easy.
      if (activeTask == null && futureTasks.isEmpty()) {
        return CountDownLatch(0)
      }

      // If there's an existing AwaitIdleTask, use it. This is necessary when the executor is
      // shutdown but still busy as we can't enqueue in that case.

                }
                break;
            case WitnessAsyncNotifyMessage.WitnessNotificationMessage.WITNESS_IP_CHANGE:
                if (message.getIpAddresses() != null && !message.getIpAddresses().isEmpty()) {
                    notification.setNewNodeAddress(message.getIpAddresses().get(0));
                }
                break;
            }

     */
    public void addExtractor(final List<String> keyList, final Extractor extractor) {
        if (keyList == null || keyList.isEmpty()) {
            throw new CrawlerSystemException("The key list is empty.");
        }
        keyList.stream().distinct().forEach(key -> addExtractor(key, extractor));
    }

    /**

  }

  public void testLineReading() throws IOException {
    File temp = createTempFile();
    assertNull(Files.readFirstLine(temp, UTF_8));
    assertTrue(Files.readLines(temp, UTF_8).isEmpty());

    PrintWriter w = new PrintWriter(Files.newWriter(temp, UTF_8));
    w.println("hello");
    w.println("");
    w.println(" world  ");
    w.println("");
    w.close();

                return (T) ((List<?>) value).stream().filter(s -> s != null).map(Object::toString).toArray(n -> new String[n]);
            }

            if (((List<?>) value).isEmpty()) {
                return null;
            }

            return convertObj(((List<?>) value).get(0), clazz);
        }
        if (value instanceof String[]) {