/**
 * Implementation of the {@code equals}, {@code hashCode}, and {@code toString} methods of {@code
 * Entry}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractMapEntry<K extends @Nullable Object, V extends @Nullable Object>
    implements Entry<K, V> {

  @Override
  @ParametricNullness
  public abstract K getKey();

  @Override
  @ParametricNullness

/**
 * Implementation of the {@code equals}, {@code hashCode}, and {@code toString} methods of {@code
 * Entry}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractMapEntry<K extends @Nullable Object, V extends @Nullable Object>
    implements Entry<K, V> {

  @Override
  @ParametricNullness
  public abstract K getKey();

  @Override
  @ParametricNullness

import com.google.common.annotations.GwtCompatible;
import java.util.Map.Entry;
import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@code AbstractMapEntry}.
 *
 * @author Mike Bostock
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public class AbstractMapEntryTest extends TestCase {
  private static final @Nullable String NK = null;

 * common.collect} as a superclass.
 */
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault
class ImmutableEntry<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMapEntry<K, V> implements Serializable {
  @ParametricNullness final K key;
  @ParametricNullness final V value;

  ImmutableEntry(@ParametricNullness K key, @ParametricNullness V value) {
    this.key = key;

    ImmutableMultimap.Builder<String, Integer> builder = new Builder<>();
    final StringHolder holder = new StringHolder();
    holder.string = "one";
    Entry<String, Integer> entry =
        new AbstractMapEntry<String, Integer>() {
          @Override
          public String getKey() {
            return holder.string;
          }

          @Override
          public Integer getValue() {

    ImmutableMultimap.Builder<String, Integer> builder = new Builder<>();
    final StringHolder holder = new StringHolder();
    holder.string = "one";
    Entry<String, Integer> entry =
        new AbstractMapEntry<String, Integer>() {
          @Override
          public String getKey() {
            return holder.string;
          }

          @Override
          public Integer getValue() {

    return new Itr<Entry<K, V>>() {
      @Override
      Entry<K, V> output(BiEntry<K, V> entry) {
        return new MapEntry(entry);
      }

      class MapEntry extends AbstractMapEntry<K, V> {
        private BiEntry<K, V> delegate;

        MapEntry(BiEntry<K, V> entry) {
          this.delegate = entry;
        }

        @Override
        @ParametricNullness

    ImmutableMap.Builder<String, Integer> builder = new Builder<>();
    final StringHolder holder = new StringHolder();
    holder.string = "one";
    Entry<String, Integer> entry =
        new AbstractMapEntry<String, Integer>() {
          @Override
          public String getKey() {
            return holder.string;
          }

          @Override
          public Integer getValue() {

   * null} even for a map which supposedly does not contain null elements, if the key is not present
   * when {@code getValue()} is called.
   */
  final class EntryForKey extends AbstractMapEntry<K, V> {
    @ParametricNullness final K key;
    int index;

    EntryForKey(int index) {
      // The cast is safe because we call forEntry only for indexes that contain entries.

    ImmutableMap.Builder<String, Integer> builder = new Builder<>();
    final StringHolder holder = new StringHolder();
    holder.string = "one";
    Entry<String, Integer> entry =
        new AbstractMapEntry<String, Integer>() {
          @Override
          public String getKey() {
            return holder.string;
          }

          @Override
          public Integer getValue() {