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

  @Override
  @ParametricNullness
  public abstract K getKey();

  @Override
  @ParametricNullness

import java.util.Map.Entry;
import junit.framework.TestCase;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

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

    ImmutableMultimap.Builder<String, Integer> builder = new Builder<>();
    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() {