### Question:
CollectionUtil { public static boolean isEmpty(final Collection<?> col) { return col == null || col.isEmpty(); } private  CollectionUtil(); static boolean isEmpty(final Collection<?> col); static boolean isNotEmpty(final Collection<?> col); static boolean hasOneItem(final Collection<?> col); static boolean isNotEmpty(final Object[] array); static int size(final Collection<?> col); static boolean contains(final Collection<?> collection, final Object item); static boolean containsAny(final Collection<?> collection, final Object... items); static boolean noneEmpty(final Collection<?>... collections); static boolean sameContent(final Collection<?> c1, final Collection<?> c2);  }### Answer:
@Test public void testIsEmpty() { assertTrue("null", CollectionUtil.isEmpty(null)); final HashSet<Integer> col = new HashSet<>(); assertTrue("empty set", CollectionUtil.isEmpty(col)); col.add(1); assertFalse("not empty set", CollectionUtil.isEmpty(col)); col.add(2); assertFalse("not empty set", CollectionUtil.isEmpty(col)); }