@ParametricNullness
    V rightValue();

    /**
     * Two instances are considered equal if their {@link #leftValue()} values are equal and their
     * {@link #rightValue()} values are also equal.
     */
    @Override
    boolean equals(@CheckForNull Object other);

    /**
     * The hash code equals the value {@code Arrays.asList(leftValue(), rightValue()).hashCode()}.
     */
    @Override

      assertTrue(item + " must not be Object#equals to null", !item.equals(null));
      assertTrue(
          item + " must not be Object#equals to an arbitrary object of another class",
          !item.equals(NotAnInstance.EQUAL_TO_NOTHING));
      assertTrue(item + " must be Object#equals to itself", item.equals(item));
      assertEquals(

      assertTrue(item + " must not be Object#equals to null", !item.equals(null));
      assertTrue(
          item + " must not be Object#equals to an arbitrary object of another class",
          !item.equals(NotAnInstance.EQUAL_TO_NOTHING));
      assertTrue(item + " must be Object#equals to itself", item.equals(item));
      assertEquals(

    assertFalse(
        "Two Sets should not be equal if exactly one of them contains null.",
        getSet().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_smallerSet() {
    Collection<E> fewerElements = getSampleElements(getNumElements() - 1);
    assertFalse(
        "Sets of different sizes should not be equal.",
        getSet().equals(MinimalSet.from(fewerElements)));
  }

        "Two Maps should not be equal if exactly one of them contains a null value.",
        getMap().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_smallerMap() {
    Collection<Entry<K, V>> fewerEntries = getSampleEntries(getNumEntries() - 1);
    assertFalse(
        "Maps of different sizes should not be equal.", getMap().equals(newHashMap(fewerEntries)));
  }

        "Two Maps should not be equal if exactly one of them contains a null value.",
        getMap().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_smallerMap() {
    Collection<Entry<K, V>> fewerEntries = getSampleEntries(getNumEntries() - 1);
    assertFalse(
        "Maps of different sizes should not be equal.", getMap().equals(newHashMap(fewerEntries)));
  }

    assertFalse(
        "Two Sets should not be equal if exactly one of them contains null.",
        getSet().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_smallerSet() {
    Collection<E> fewerElements = getSampleElements(getNumElements() - 1);
    assertFalse(
        "Sets of different sizes should not be equal.",
        getSet().equals(MinimalSet.from(fewerElements)));
  }

    Collection<E> moreElements = getSampleElements(getNumElements() + 1);
    assertFalse(
        "Lists of different sizes should not be equal.",
        getList().equals(new ArrayList<E>(moreElements)));
  }

  public void testEquals_set() {
    assertFalse("A List should never equal a Set.", getList().equals(MinimalSet.from(getList())));
  }

    Collection<E> moreElements = getSampleElements(getNumElements() + 1);
    assertFalse(
        "Lists of different sizes should not be equal.",
        getList().equals(new ArrayList<E>(moreElements)));
  }

  public void testEquals_set() {
    assertFalse("A List should never equal a Set.", getList().equals(MinimalSet.from(getList())));
  }

   * equals()} contract.
   *
   * <p><b>Java 7+ users:</b> This method should be treated as deprecated; use {@link
   * java.util.Objects#equals} instead.
   */
  public static boolean equal(@CheckForNull Object a, @CheckForNull Object b) {
    return a == b || (a != null && a.equals(b));
  }

  /**
   * Generates a hash code for multiple values. The hash code is generated by calling {@link