CollectionUtil { public static <T> String join(final Collection<T> collection, String joiner) { return smartJoin(collection, Object::toString, joiner); }  static int clear(final Collection collection); static List<String> toStringList(final Collection<T> collection); static String smartJoin(final Collection<T> collection,
        final Generator<T, String> stringGenerator, final String joiner); @SafeVarargs static C arrayToCollection(
        final Supplier<C> creator, final T... array); @Deprecated static Collection<String> toStringCollection(final String stringList); static String join(final Collection<T> collection, String joiner); static boolean containsIgnoreCase(final Collection<? extends String> collection,
        final String string);  }
@Test void join() { final Collection<Integer> collection = Arrays.asList(3, 8, 6); String joined = CollectionUtil.join(collection, ", "); Assertions.assertEquals("3, 8, 6", joined); }