### Question:
NetUtils { public static String normalizeHostName(String name) { try { return InetAddress.getByName(name).getHostAddress(); } catch (UnknownHostException e) { return name; } }  static SocketFactory getSocketFactory(Configuration conf,
      Class<?> clazz); static SocketFactory getDefaultSocketFactory(Configuration conf); static SocketFactory getSocketFactoryFromProperty(
      Configuration conf, String propValue); static InetSocketAddress createSocketAddr(String target); static InetSocketAddress createSocketAddr(String target,
                                                   int defaultPort); static InetSocketAddress createSocketAddr(String target,
                                                   int defaultPort,
                                                   String configName); static InetSocketAddress createSocketAddrForHost(String host, int port); static URI getCanonicalUri(URI uri, int defaultPort); static void addStaticResolution(String host, String resolvedName); static String getStaticResolution(String host); static List <String[]> getAllStaticResolutions(); static InetSocketAddress getConnectAddress(Server server); static InetSocketAddress getConnectAddress(InetSocketAddress addr); static SocketInputWrapper getInputStream(Socket socket); static SocketInputWrapper getInputStream(Socket socket, long timeout); static OutputStream getOutputStream(Socket socket); static OutputStream getOutputStream(Socket socket, long timeout); static void connect(Socket socket,
      SocketAddress address,
      int timeout); static void connect(Socket socket, 
                             SocketAddress endpoint,
                             SocketAddress localAddr,
                             int timeout); static String normalizeHostName(String name); static List<String> normalizeHostNames(Collection<String> names); static void verifyHostnames(String[] names); static String getHostNameOfIP(String ipPort); static String getHostname(); static String getHostPortString(InetSocketAddress addr); static InetAddress getLocalInetAddress(String host); static boolean isLocalAddress(InetAddress addr); static IOException wrapException(final String destHost,
                                          final int destPort,
                                          final String localHost,
                                          final int localPort,
                                          final IOException exception); static boolean isValidSubnet(String subnet); static List<InetAddress> getIPs(String subnet,
      boolean returnSubinterfaces); static final String UNKNOWN_HOST; static final String HADOOP_WIKI; }### Answer:
@Test public void testNormalizeHostName() { List<String> hosts = Arrays.asList(new String[] {"127.0.0.1", "localhost", "3w.org", "UnknownHost"}); List<String> normalizedHosts = NetUtils.normalizeHostNames(hosts); assertEquals(normalizedHosts.get(0), hosts.get(0)); assertFalse(normalizedHosts.get(1).equals(hosts.get(1))); assertEquals(normalizedHosts.get(1), hosts.get(0)); assertFalse(normalizedHosts.get(2).equals(hosts.get(2))); assertEquals(normalizedHosts.get(3), hosts.get(3)); }