### Question:
Utils { public static boolean isNullOrEmpty(String url) { return url == null || url.isEmpty(); } private  Utils(); static String generateParameterHash(String path, String func, List<String> args); static String generateDirectoryHash(String rootDir, String chaincodeDir, String hash); static byte[] generateTarGz(File sourceDirectory, String pathPrefix); static byte[] readFile(File input); static String generateUUID(); static Timestamp generateTimestamp(); static void deleteFileOrDirectory(File file); static byte[] hash(byte[] input, Digest digest); static String combinePaths(String first, String... other); static byte[] readFileFromClasspath(String fileName); static Properties parseGrpcUrl(String url); static Exception checkGrpcUrl(String url); static boolean isNullOrEmpty(String url); static String logString(final String string); static byte[] generateNonce(); static String toHexString(ByteString byteString); static String toHexString(byte[] bytes);  }### Answer:
@Test public void testIsNullOrEmpty() { Assert.assertTrue(Utils.isNullOrEmpty(null)); Assert.assertTrue(Utils.isNullOrEmpty("")); Assert.assertFalse(Utils.isNullOrEmpty("xyzzy")); Assert.assertFalse(Utils.isNullOrEmpty(" ")); }