static <K, V> ImmutableMapEntry<K, V> makeImmutable(Entry<K, V> entry, K key, V value) {
    boolean reusable =
        entry instanceof ImmutableMapEntry && ((ImmutableMapEntry<K, V>) entry).isReusable();
    return reusable ? (ImmutableMapEntry<K, V>) entry : new ImmutableMapEntry<K, V>(key, value);
  }

  /** Makes an entry usable internally by a new ImmutableMap. */

  static final double MAX_LOAD_FACTOR = 1.2;

  @CheckForNull private final transient @Nullable ImmutableMapEntry<K, V>[] keyTable;
  @CheckForNull private final transient @Nullable ImmutableMapEntry<K, V>[] valueTable;
  @VisibleForTesting final transient Entry<K, V>[] entries;
  private final transient int mask;
  private final transient int hashCode;

   *
   * <p>A call to {@link Entry#setValue} on the returned entry will always throw {@link
   * UnsupportedOperationException}.
   */
  static <K, V> Entry<K, V> entryOf(K key, V value) {
    return new ImmutableMapEntry<>(key, value);
  }

  /**
   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
   * Builder} constructor.
   */