ImmutableMapFactory { public static <K, V> ImmutableMap<K, V> createFromKeys( Collection<K> keys, Supplier<V> valueSupplier) { return keys.stream() .collect(ImmutableMap.toImmutableMap( key -> key, key -> valueSupplier.get())); }  static ImmutableMap<L, W> create(
            Map<K, V> baseMap,
            BiFunction<? super K, ? super V, ? extends L> keyCreator,
            BiFunction<? super K, ? super V, ? extends W> valueCreator); static ImmutableMap<L, W> create(
            Map<K, V> baseMap,
            Function<? super K, ? extends L> keyMapper,
            Function<? super V, ? extends W> valueMapper); static ImmutableMap<L, W> createAndReduceCollisions(
            Map<K, V> baseMap,
            Function<? super K, ? extends L> keyMapper,
            Function<? super V, ? extends W> valueMapper,
            W valueIdentity,
            BinaryOperator<W> collidingKeysAccumulator); static ImmutableMap<L, V> createWithNewKeys(
            Map<K, V> baseMap,
            Function<? super K, ? extends L> keyMapper); static ImmutableMap<K, W> createWithNewValues(
            Map<K, V> baseMap,
            Function<? super V, ? extends W> valueMapper); static ImmutableMap<K, W> createWithNewValues(
            Map<K, V> baseMap,
            BiFunction<? super K, ? super V, ? extends W> valueMapper); static ImmutableMap<K, V> createFromKeys(
            Collection<K> keys,
            Supplier<V> valueSupplier); static ImmutableMap<K, V> createFromKeys(
            Collection<K> keys,
            Function<K, V> valueCreator); static ImmutableMap<K, V> zip(
            List<K> keys,
            List<V> values); static ImmutableMap<K, V> filter(
            Map<K, V> baseMap,
            BiPredicate<K, V> filter); static ImmutableMap<K, V> filterByKeys(
            Map<K, V> baseMap,
            Predicate<K> keyFilter); static ImmutableMap<K, V> filterByValues(
            Map<K, V> baseMap,
            Predicate<V> valueFilter); static ImmutableMap<K, V> parse(
            String s,
            Function<String, K> keyParser,
            Function<String, V> valueParser); static ImmutableMap<K, V> parseAndFilter(
            String s,
            Function<String, K> keyParser,
            Function<String, V> valueParser,
            BiPredicate<K, V> filter);  }
@Test void testCreateFromKeysWithFunction() { ImmutableList<Integer> keys = ImmutableList.of(1, 2, 3, 4); ImmutableMap<Integer, Integer> expected = ImmutableMap.of( 1, 1, 2, 4, 3, 9, 4, 16); ImmutableMap<Integer, Integer> actual = ImmutableMapFactory.createFromKeys(keys, (key) -> key * key); Assertions.assertEquals(expected, actual); }
@Test void testCreateFromKeysWithDifferentType() { ImmutableList<String> keys = ImmutableList.of("1", "2", "3", "4"); ImmutableMap<String, Integer> expected = ImmutableMap.of( "1", 1, "2", 2, "3", 3, "4", 4); ImmutableMap<String, Integer> actual = ImmutableMapFactory.createFromKeys(keys, Integer::parseInt); Assertions.assertEquals(expected, actual); }
@Test void testCreateFromKeysWithValueSupplier() { ImmutableList<Integer> keys = ImmutableList.of(1, 2, 3, 4); ImmutableMap<Integer, Integer> expected = ImmutableMap.of( 1, 1, 2, 1, 3, 1, 4, 1); ImmutableMap<Integer, Integer> actual = ImmutableMapFactory.createFromKeys(keys, () -> 1); Assertions.assertEquals(expected, actual); }