*/
@ElementTypesAreNonnullByDefault
public abstract class ForwardingImmutableMap<K, V> extends ImmutableMap<K, V> {

  final transient Map<K, V> delegate;

  ForwardingImmutableMap(Map<? extends K, ? extends V> delegate) {
    this.delegate = Collections.unmodifiableMap(delegate);
  }

  @SuppressWarnings("unchecked")
  ForwardingImmutableMap(boolean throwIfDuplicateKeys, Entry<? extends K, ? extends V>... entries) {

/**
 * GWT emulation of {@link com.google.common.collect.ImmutableBiMap}.
 *
 * @author Hayward Chan
 */
@ElementTypesAreNonnullByDefault
public abstract class ImmutableBiMap<K, V> extends ForwardingImmutableMap<K, V>
    implements BiMap<K, V> {
  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
          Function<? super T, ? extends K> keyFunction,

 * around a {@link java.util.TreeMap}.
 *
 * @author Hayward Chan
 */
@ElementTypesAreNonnullByDefault
public final class ImmutableSortedMap<K, V> extends ForwardingImmutableMap<K, V>
    implements SortedMap<K, V> {

  @SuppressWarnings("unchecked")
  static final Comparator<?> NATURAL_ORDER = Ordering.natural();