return new AbstractSet<Entry<K, V>>() {
      private Set<Entry<K, V>> delegate() {
        return delegate.entrySet();
      }

      @Override
      public boolean contains(Object object) {
        try {
          return delegate().contains(object);
        } catch (NullPointerException | ClassCastException e) {
          return false;
        }
      }

      @Override

    return new AbstractSet<Entry<K, V>>() {
      private Set<Entry<K, V>> delegate() {
        return delegate.entrySet();
      }

      @Override
      public boolean contains(Object object) {
        try {
          return delegate().contains(object);
        } catch (NullPointerException | ClassCastException e) {
          return false;
        }
      }

      @Override

  }

  public void test_contains_nonnull_yes() {
    Iterator<@Nullable String> set = Arrays.<@Nullable String>asList("a", null, "b").iterator();
    assertTrue(Iterators.contains(set, "b"));
  }

  public void test_contains_nonnull_no() {
    Iterator<String> set = asList("a", "b").iterator();
    assertFalse(Iterators.contains(set, "c"));
  }

  public void test_contains_null_yes() {

   * keys and values are the result of applying the provided mapping functions to the input
   * elements. The generated map is sorted by the specified comparator.
   *
   * <p>If the mapped keys contain duplicates (according to the specified comparator), an {@code
   * IllegalArgumentException} is thrown when the collection operation is performed. (This differs

      fail("putAll(containsNullKey) should throw");
    } catch (NullPointerException expected) {
    }
    expectUnchanged();
    expectNullKeyMissingWhenNullKeysUnsupported(
        "Should not contain null key after unsupported putAll(containsNullKey)");
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_VALUES})
  public void testPutAll_nullValueSupported() {
    putAll(containsNullValue);

  SingletonImmutableSet(E element) {
    this.element = Preconditions.checkNotNull(element);
  }

  @Override
  public int size() {
    return 1;
  }

  @Override
  public boolean contains(@CheckForNull Object target) {
    return element.equals(target);
  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    return Iterators.singletonIterator(element);
  }

  @Override

/**
 * Tester for {@code Spliterator} implementations.
 *
 * @since 21.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class SpliteratorTester<E extends @Nullable Object> {
  /** Return type from "contains the following elements" assertions. */
  public interface Ordered {
    /**
     * Attests that the expected values must not just be present but must be present in the order
     * they were given.
     */

    try {
      getQueue().offer(null);
      fail("offer(null) should throw");
    } catch (NullPointerException expected) {
    }
    expectUnchanged();
    expectNullMissingWhenNullUnsupported("Should not contain null after unsupported offer(null)");
  }

      fail("removeIf(x -> true) should throw " + "UnsupportedOperationException");
    } catch (UnsupportedOperationException expected) {
    }
    expectUnchanged();
    assertTrue(collection.contains(samples.e0()));
  }

   *
   * <p>The returned supplier is thread-safe. The delegate's {@code get()} method will be invoked at
   * most once unless the underlying {@code get()} throws an exception. The supplier's serialized
   * form does not contain the cached value, which will be recalculated when {@code get()} is called
   * on the deserialized instance.
   *
   * <p>When the underlying delegate throws an exception then this memoizing supplier will keep