@SuppressWarnings("serial") // uses writeReplace(), not default serialization
@ElementTypesAreNonnullByDefault
class RegularImmutableBiMap<K, V> extends ImmutableBiMap<K, V> {
  @SuppressWarnings("unchecked") // TODO(cpovirk): Consider storing Entry<?, ?>[] instead.
  static final RegularImmutableBiMap<Object, Object> EMPTY =
      new RegularImmutableBiMap<>(
          null, null, (Entry<Object, Object>[]) ImmutableMap.EMPTY_ENTRY_ARRAY, 0, 0);

@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
@ElementTypesAreNonnullByDefault
final class RegularImmutableBiMap<K, V> extends ImmutableBiMap<K, V> {
  static final RegularImmutableBiMap<Object, Object> EMPTY = new RegularImmutableBiMap<>();

  @CheckForNull private final transient Object keyHashTable;
  @VisibleForTesting final transient @Nullable Object[] alternatingKeysAndValues;

    return (ImmutableBiMap<K, V>) RegularImmutableBiMap.EMPTY;
  }

  public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
    checkEntryNotNull(k1, v1);
    return new SingletonImmutableBiMap<K, V>(k1, v1);
  }

  public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
    return new RegularImmutableBiMap<K, V>(ImmutableMap.of(k1, v1, k2, v2));
  }

    return RegularImmutableBiMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2));
  }

  /**
   * Returns an immutable map containing the given entries, in order.
   *
   * @throws IllegalArgumentException if duplicate keys or values are added
   */
  public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {

  public static <K, V> ImmutableBiMap<K, V> of() {
    return (ImmutableBiMap<K, V>) RegularImmutableBiMap.EMPTY;
  }

  /** Returns an immutable bimap containing a single entry. */
  public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
    checkEntryNotNull(k1, v1);
    return new RegularImmutableBiMap<>(new Object[] {k1, v1}, 1);
  }

  /**

    for (int i = 0; i < 10; i++) {
      builder.put(i, i);
    }
    Entry<Integer, Integer>[] builderArrayAfterPuts = builder.entries;
    RegularImmutableBiMap<Integer, Integer> map =
        (RegularImmutableBiMap<Integer, Integer>) builder.build();
    Entry<Integer, Integer>[] mapInternalArray = map.entries;
    assertSame(builderArray, builderArrayAfterPuts);