### Question:
UuidUtil { public static String insertHyphens(String uuidWithoutHyphens) { return uuidWithoutHyphens.replaceFirst("(\\p{XDigit}{8})(\\p{XDigit}{4})(\\p{XDigit}{4})(\\p{XDigit}{4})(\\p{XDigit}+)", "$1-$2-$3-$4-$5"); } private  UuidUtil(); static String insertHyphens(String uuidWithoutHyphens); static String stripHyphens(String uuid); static boolean isValidUUID(String uuid);  }### Answer:
@Test public void insertHyphensTest() { Assert.assertEquals("9aa395cb-8e91-4e77-aeaf-1a41d85bffa8", UuidUtil.insertHyphens("9aa395cb8e914e77aeaf1a41d85bffa8")); }