CollectionUtils { public static boolean isEmpty(Object[] array) { return array == null || array.length == 0; }  static boolean isEmpty(Object[] array); static boolean isEmpty(Map<?, ?> map); static boolean isEmpty(Collection<?> collection); static Set<T> intersect(Set<T> a, Set<T> b); static Set<T> union(Set<T> a, Set<T> b); static boolean hasIntersection(Set<T> a, Set<T> b); @SafeVarargs static Set<T> newHashSet(T... values);  }
@Test void testIsEmpty() { assertTrue(CollectionUtils.isEmpty(Collections.emptyMap())); assertTrue(CollectionUtils.isEmpty(Collections.emptyList())); assertTrue(CollectionUtils.isEmpty(new HashMap<>())); Set<Object> map = null; assertTrue(CollectionUtils.isEmpty(map)); }