* @since 12.0
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingNavigableMap<K extends @Nullable Object, V extends @Nullable Object>
    extends ForwardingSortedMap<K, V> implements NavigableMap<K, V> {

  /** Constructor for use by subclasses. */
  protected ForwardingNavigableMap() {}

  @Override
  protected abstract NavigableMap<K, V> delegate();

  @Override
  @CheckForNull

 * @since 12.0
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingNavigableMap<K extends @Nullable Object, V extends @Nullable Object>
    extends ForwardingSortedMap<K, V> implements NavigableMap<K, V> {

  /** Constructor for use by subclasses. */
  protected ForwardingNavigableMap() {}

  @Override
  protected abstract NavigableMap<K, V> delegate();

  @Override
  @CheckForNull

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@code ForwardingNavigableMap}.
 *
 * @author Robert Konigsberg
 * @author Louis Wasserman
 */
public class ForwardingNavigableMapTest extends TestCase {
  static class StandardImplForwardingNavigableMap<K, V> extends ForwardingNavigableMap<K, V> {
    private final NavigableMap<K, V> backingMap;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@code ForwardingNavigableMap}.
 *
 * @author Robert Konigsberg
 * @author Louis Wasserman
 */
public class ForwardingNavigableMapTest extends TestCase {
  static class StandardImplForwardingNavigableMap<K, V> extends ForwardingNavigableMap<K, V> {
    private final NavigableMap<K, V> backingMap;