### Question:
AttachmentUtil { public static String createContentID(String ns) throws UnsupportedEncodingException { String cid = "cxf.apache.org"; if (ns != null && !ns.isEmpty()) { try { URI uri = new URI(ns); String host = uri.getHost(); if (host != null) { cid = host; } else { cid = ns; } } catch (Exception e) { cid = ns; } } return ATT_UUID + '-' + Integer.toString(COUNTER.incrementAndGet()) + '@' + URLEncoder.encode(cid, StandardCharsets.UTF_8.name()); } private  AttachmentUtil(); static CommandMap getCommandMap(); static boolean isMtomEnabled(Message message); static void setStreamedAttachmentProperties(Message message, CachedOutputStream bos); static String createContentID(String ns); static String getUniqueBoundaryValue(); static Map<String, DataHandler> getDHMap(final Collection<Attachment> attachments); static String cleanContentId(String id); static Attachment createAttachment(InputStream stream, Map<String, List<String>> headers); static InputStream decode(InputStream in, String encoding); static boolean isTypeSupported(String contentType, List<String> types); static Attachment createMtomAttachment(boolean isXop, String mimeType, String elementNS,
                                                 byte[] data, int offset, int length, int threshold); static Attachment createMtomAttachmentFromDH(
        boolean isXop, DataHandler handler, String elementNS, int threshold); static DataSource getAttachmentDataSource(String contentId, Collection<Attachment> atts); static final String BODY_ATTACHMENT_ID; }### Answer:
@Test public void testCreateContentID() throws Exception { assertNotEquals(AttachmentUtil.createContentID(null), AttachmentUtil.createContentID(null)); }