### Question:
ServiceUtils { public static String join(List<String> strings) { String result = ""; boolean first = true; for (final String s : strings) { if (!first) { result += ", "; } result += s; first = false; } return result; }  static Date parseIso8601Date(String dateString); static String formatIso8601Date(Date date); static Date parseRfc822Date(String dateString); static String formatRfc822Date(Date date); static boolean isMultipartUploadETag(String eTag); static byte[] toByteArray(String s); static String removeQuotes(String s); static URL convertRequestToUrl(Request<?> request); static URL convertRequestToUrl(Request<?> request,
            boolean removeLeadingSlashInResourcePath); static String join(List<String> strings); static void downloadObjectToFile(S3Object s3Object,
            File destinationFile, boolean performIntegrityCheck,
            boolean appendData); static S3Object retryableDownloadS3ObjectToFile(File file,
            RetryableS3DownloadTask retryableS3DownloadTask, boolean appendData); static boolean skipMd5CheckPerResponse(ObjectMetadata metadata); static boolean skipMd5CheckPerResponse(ObjectMetadata metadata, S3ClientOptions clientOptions); static boolean skipMd5CheckPerRequest(AmazonWebServiceRequest request); static boolean skipMd5CheckPerRequest(AmazonWebServiceRequest request, S3ClientOptions clientOptions); static final boolean APPEND_MODE; static final boolean OVERWRITE_MODE; }### Answer:
@Test public void testJoin() { final ServiceUtils utils = new ServiceUtils(); final List<String> list = new ArrayList<String>(); final String one = "1"; list.add(one); assertEquals("1", ServiceUtils.join(list)); final String two = "2"; list.add(two); assertEquals("1, 2", ServiceUtils.join(list)); final String three = "3"; list.add(three); assertEquals("1, 2, 3", ServiceUtils.join(list)); }