/**
 * Skeletal implementation of {@link NavigableMap}.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractNavigableMap<K extends @Nullable Object, V extends @Nullable Object>
    extends IteratorBasedAbstractMap<K, V> implements NavigableMap<K, V> {

  @Override
  @CheckForNull
  public abstract V get(@CheckForNull Object key);

/**
 * Skeletal implementation of {@link NavigableMap}.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractNavigableMap<K extends @Nullable Object, V extends @Nullable Object>
    extends IteratorBasedAbstractMap<K, V> implements NavigableMap<K, V> {

  @Override
  @CheckForNull
  public abstract V get(@CheckForNull Object key);

  }

  @GwtIncompatible // NavigableMap
  private static final class NavigableAsMapView<
          K extends @Nullable Object, V extends @Nullable Object>
      extends AbstractNavigableMap<K, V> {
    /*
     * Using AbstractNavigableMap is simpler than extending SortedAsMapView and rewriting all the
     * NavigableMap methods.
     */

    private final NavigableSet<K> set;

  }

  @GwtIncompatible // NavigableMap
  private static final class NavigableAsMapView<
          K extends @Nullable Object, V extends @Nullable Object>
      extends AbstractNavigableMap<K, V> {
    /*
     * Using AbstractNavigableMap is simpler than extending SortedAsMapView and rewriting all the
     * NavigableMap methods.
     */

    private final NavigableSet<K> set;