* Even if empty string, treated as empty plainly. So "IF pmb != null" is false if empty.
     * @param hostname The parameter value of hostname. (NotNull)
     */
    public void setHostname(String hostname) {
        registerVariable("hostname", hostname);
    }

    /**
     * Set the value of clustername, used in parameter comment. <br>

  private val headers: Headers = Headers.EMPTY

  @Test fun testIPv4() {
    val socket =
      MockWebServerSocket(
        FakeSocket(
          localAddress = InetAddress.getByAddress("127.0.0.1", byteArrayOf(127, 0, 0, 1)),
          localPort = 80,
        ),
      )
    val request = RecordedRequest(DEFAULT_REQUEST_LINE_HTTP_1, headers, emptyList(), 0, ByteString.EMPTY, 0, 0, socket)

     *
     * @param u the URL string to extract host from
     * @return the host name, or empty string if URL is blank, or unknown hostname if parsing fails
     */
    default String getHost(final String u) {
        if (StringUtil.isBlank(u)) {
            return StringUtil.EMPTY; // empty
        }

        String url = u;
        final String originalUrl = url;

        int idx = url.indexOf("://");

    private void validateIdentity() {
        if (empty(groupId)) {
            throw new InvalidArtifactRTException(
                    groupId, artifactId, getVersion(), type, "The groupId cannot be empty.");
        }

        if (empty(artifactId)) {
            throw new InvalidArtifactRTException(
                    groupId, artifactId, getVersion(), type, "The artifactId cannot be empty.");
        }

        if (empty(type)) {

        // Test with empty source array
        dest = new byte[8];
        nextOffset = NtlmMessage.writeSecurityBuffer(dest, 0, new byte[0]);
        assertEquals(4, nextOffset, "Should return correct next offset for empty source.");
        assertEquals(0, NtlmMessage.readUShort(dest, 0), "Length should be 0 for empty source.");

     * Sets a converter for dates.
     *
     * @param pattern
     *            The date pattern. Must not be {@literal null} or an empty string.
     * @param propertyNames
     *            The property names to which this converter will be applied. Each element must not be {@literal null} or an empty string.
     * @return This instance itself
     * @see DateConverter
     */

     *
     * @return the application type string, or empty string if not set
     */
    public static String getAppType() {
        final String appType = System.getenv(FESS_APP_TYPE);
        if (StringUtil.isNotBlank(appType)) {
            return appType;
        }
        return StringUtil.EMPTY;
    }

    /**

     * If the input array is {@code null}, an empty stream is returned.
     *
     * @param <T> The type of elements in the stream.
     * @param values The elements to be included in the stream. Can be {@code null}.
     * @return A {@link StreamOf} instance containing the provided values, or an empty stream if {@code values} is {@code null}.
     */
    @SafeVarargs

   * otherwise returns an empty stream.
   */
  public static <T> Stream<T> stream(com.google.common.base.Optional<T> optional) {
    return optional.isPresent() ? Stream.of(optional.get()) : Stream.empty();
  }

  /**
   * If a value is present in {@code optional}, returns a stream containing only that element,
   * otherwise returns an empty stream.
   *

     *            The property name. Must not be {@literal null} or empty string
     * @return Whether the {@link PropertyDesc} exists
     */
    boolean hasPropertyDesc(String propertyName);

    /**
     * Returns the {@link PropertyDesc}.
     *
     * @param propertyName
     *            The property name. Must not be {@literal null} or empty string
     * @return {@link PropertyDesc}
     */