### Question:
CollectionUtils { public static <T> List<T> minus(Collection<T> first, Collection<T> second) { ArrayList<T> result = new ArrayList<>(first); result.removeAll(second); result.trimToSize(); return result; }  static T singleValue(Collection<T> values); static List<T> join(Collection<T> first, Collection<T> second); static List<T> minus(Collection<T> first, Collection<T> second); static Set<T> joinToSet(Collection<T> first, Collection<T> second); @SafeVarargs static Set<T> setOf(T... t);  }### Answer:
@Test void testMinus() { assertEquals( asList(2, 4, 4, 5), minus(asList(1, 1, 2, 3, 4, 4, 5), asList(1, 3, 3, 56)) ); }