### Question:
ListUtils { public static <T> List<T> defaultIfNull(final List<T> list, final List<T> defaultList) { return list == null ? defaultList : list; } private  ListUtils(); static List<T> emptyIfNull(final List<T> list); static List<T> defaultIfNull(final List<T> list, final List<T> defaultList); static List<E> intersection(final List<? extends E> list1, final List<? extends E> list2); static List<E> subtract(final List<E> list1, final List<? extends E> list2); static List<E> sum(final List<? extends E> list1, final List<? extends E> list2); static List<E> union(final List<? extends E> list1, final List<? extends E> list2); static List<E> select(final Collection<? extends E> inputCollection,
            final Predicate<? super E> predicate); static List<E> selectRejected(final Collection<? extends E> inputCollection,
            final Predicate<? super E> predicate); static boolean isEqualList(final Collection<?> list1, final Collection<?> list2); static int hashCodeForList(final Collection<?> list); static List<E> retainAll(final Collection<E> collection, final Collection<?> retain); static List<E> removeAll(final Collection<E> collection, final Collection<?> remove); static List<E> synchronizedList(final List<E> list); static List<E> unmodifiableList(final List<? extends E> list); static List<E> predicatedList(final List<E> list, final Predicate<E> predicate); static List<E> transformedList(final List<E> list,
                                              final Transformer<? super E, ? extends E> transformer); static List<E> lazyList(final List<E> list, final Factory<? extends E> factory); static List<E> fixedSizeList(final List<E> list); static int indexOf(final List<E> list, final Predicate<E> predicate); static List<E> longestCommonSubsequence(final List<E> a, final List<E> b); static List<E> longestCommonSubsequence(final List<E> a, final List<E> b,
                                                       final Equator<? super E> equator); static String longestCommonSubsequence(final CharSequence a, final CharSequence b); static List<List<T>> partition(final List<T> list, final int size);  }### Answer:
@Test public void testDefaultIfNull() { assertTrue(ListUtils.defaultIfNull(null, Collections.emptyList()).isEmpty()); final List<Long> list = new ArrayList<Long>(); assertSame(list, ListUtils.defaultIfNull(list, Collections.<Long>emptyList())); }