* 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 count, used in parameter comment. <br>

                (et, vl) -> ((FileAuthentication) et).setFileConfigId(DfTypeUtil.toString(vl)), "fileConfigId");
        setupEpg(_epgMap, et -> ((FileAuthentication) et).getHostname(),
                (et, vl) -> ((FileAuthentication) et).setHostname(DfTypeUtil.toString(vl)), "hostname");
        setupEpg(_epgMap, et -> ((FileAuthentication) et).getParameters(),

                        } else {
                            postcard.addTo(fessConfig.getMailFromAddress());
                            postcard.dryrun();
                        }
                        postcard.setHostname(systemHelper.getHostname());
                        postcard.setClustername(ping.getClusterName());
                        postcard.setClusterstatus(ping.getClusterStatus());
                    });

                    } else {
                        postcard.addTo(fessConfig.getMailFromAddress());
                        postcard.dryrun();
                    }
                    postcard.setHostname(systemHelper.getHostname());
                    postcard.setLevel(level);
                    postcard.setCount(String.valueOf(levelEvents.size()));

                    connector.setProperty("SSLEnabled", "true");
                    final SSLHostConfig sslHostConfig = new SSLHostConfig();
                    sslHostConfig.setHostName("_default_");
                    final SSLHostConfigCertificate certificate =
                            new SSLHostConfigCertificate(sslHostConfig, SSLHostConfigCertificate.Type.UNDEFINED);

            }

            String hostname = fessConfig.getMailHostname();
            if (StringUtil.isBlank(hostname)) {
                hostname = ComponentUtil.getSystemHelper().getHostname();
            }
            dataMap.put("hostname", hostname);

            logger.debug("\ninfoMap: {}\ndataMap: {}", infoMap, dataMap);

    }

    @Test
    @DisplayName("getHostName should return valid hostname or address")
    void testGetHostNameContract() {
        // Given
        String expectedHostName = "server.example.com";
        when(mockAddress.getHostName()).thenReturn(expectedHostName);

        // When
        String hostName = mockAddress.getHostName();

        // Then

    }

    @Test
    void getHostNameDelegatesToWrappedInetAddress() {
        InetAddress dummy = mock(InetAddress.class);
        when(dummy.getHostName()).thenReturn("host.example.com");
        UniAddress ua = new UniAddress(dummy);
        assertEquals("host.example.com", ua.getHostName(), "should forward hostName to underlying InetAddress");
    }

    @Test
    void getHostAddressDelegatesToWrappedInetAddress() {

     *
     * @return the hostname associated with the address
     */
    @Override
    public String getHostName() {
        if (this.addr instanceof NbtAddress) {
            return ((NbtAddress) this.addr).getHostName();
        }
        return ((InetAddress) this.addr).getHostName();
    }

    /**
     * Return the IP address as text such as "192.168.1.15".
     *
     * @return the ip address

        // Test getHostName when hostname is known
        mockName = new Name(mockConfig, "KNOWNHOST", 0x20, null);
        NbtAddress nbtAddress = new NbtAddress(mockName, testAddressInt, false, NbtAddress.H_NODE);
        assertEquals("KNOWNHOST", nbtAddress.getHostName());
    }

    @Test
    void testGetHostName_UnknownHost() {
        // Test getHostName when hostname is unknown, should return IP address