MapBuilder { public static <K, V> MapBuilder<K, V> newHashMap() { return create(map -> new HashMap<>(map), HashMap::new); }  static MapBuilder<K, V> newHashMap(); static MapBuilder<K, V> newLinkedHashMap(); static MapBuilder<K, V> newUnmodifableMap(final Provider<Map<K, V>> provider); static MapBuilder<K, V> newTreeMap(); MapBuilder<K, V> put(final K key, final V value); MapBuilder<K, V> putAll(final Map<K, V> map); MapBuilder<K, V> remove(final K key); boolean containsKey(final K k); Map<K, V> get();  }
@Test void newHashMap() { final MapBuilder<String, String> mapBuilder = MapBuilder.newHashMap(); Assertions.assertNotNull(mapBuilder); Assertions.assertTrue(mapBuilder.get() instanceof HashMap); }