### Question:
LongUtils { public static boolean hasNCommonItems(LongSortedSet a, LongSortedSet b, int n) { Preconditions.checkArgument(n >= 0, "common item count must be nonnegative"); return n == 0 || countCommonItems(a, b, n) >= n; } private  LongUtils(); static Long2DoubleSortedMap frozenMap(Map<Long,Double> map); static LongSortedSet frozenSet(Collection<Long> longs); static LongSortedArraySet packedSet(Collection<Long> longs); static LongSortedArraySet packedSet(long... longs); static LongComparator keyValueComparator(final Long2DoubleFunction vals); static Long2DoubleMap flyweightMap(LongSet keys, LongToDoubleFunction valueFunc); static LongCollection asLongCollection(final Collection<Long> longs); static Long2DoubleMap asLong2DoubleMap(final Map<Long,Double> map); @Deprecated static Long2DoubleMap asLong2DoubleFunction(final Map<Long,Double> map); static LongList asLongList(List<Long> longs); static Long2DoubleMap constantDoubleMap(Set<Long> keys, double value); static LongSet asLongSet(@Nullable final Set<Long> longs); static LongSet asLongSet(@Nullable final Collection<Long> longs); static Long2IntMap itemRanks(LongList results); static LongSortedSet setDifference(LongSet items, LongSet exclude); static int intersectSize(LongSortedSet a, LongSortedSet b); static int intersectSize(LongSet a, LongSet b); static boolean hasNCommonItems(LongSortedSet a, LongSortedSet b, int n); static int unionSize(LongSortedSet a, LongSortedSet b); static LongSortedSet setUnion(LongSet a, LongSet b); static LongSortedSet setUnion(LongSortedSet a, LongSortedSet b); static LongSortedSet setIntersect(LongSet a, LongSet b); static LongSortedSet setIntersect(LongSortedSet a, LongSortedSet b); static LongSet randomSubset(LongSet set, int num, Random random); static LongSortedSet randomSubset(LongSet set, int num, LongSet exclude,
                                             Random rng); static Collector<T,?,Long2ObjectMap<List<E>>> mapCollector(ToLongFunction<T> kf, Function<T, E> vf);  }### Answer:
@Test public void testHasNCommonSingleton() { assertThat(hasNCommonItems(LongSortedSets.singleton(52), LongSortedSets.singleton(52), 1), equalTo(true)); assertThat(hasNCommonItems(LongSortedSets.singleton(52), LongSortedSets.singleton(42), 1), equalTo(false)); assertThat(hasNCommonItems(LongSortedSets.singleton(42), LongSortedSets.singleton(52), 1), equalTo(false)); assertThat(hasNCommonItems(LongSortedSets.singleton(52), LongSortedSets.singleton(52), 2), equalTo(false)); }