### Question:
B2Collections { public static <T> Set<T> unmodifiableSet(T[] elements) { final Set<T> set = new HashSet<>(elements.length); set.addAll(Arrays.asList(elements)); return Collections.unmodifiableSet(set); }  static Set<T> unmodifiableSet(T[] elements); static Map<K,V> unmodifiableMap(Map<K,V> orig); static Map<K, V> mapOf(); static Map<K, V> mapOf(K k1, V v1); static Map<K, V> mapOf(K k1, V v1,
                                        K k2, V v2); static Map<K, V> mapOf(K k1, V v1,
                                        K k2, V v2,
                                        K k3, V v3); @SafeVarargs static List<T> listOf(T... orig);  }### Answer:
@Test public void testUnmodifiableSet() { final Set<String> set = B2Collections.unmodifiableSet(new String[] {"a", "b"}); assertEquals(2, set.size()); assertTrue(set.contains("a")); assertTrue(set.contains("b")); thrown.expect(UnsupportedOperationException.class); set.add("mutation"); }