final List<String> list = newArrayList();
        list.add("aaa");
        list.add("bbb");
        list.add("ccc");

        final IndexedIterator<String> it = new IndexedIterator<String>(list.iterator());

        assertThat(it.hasNext(), is(true));

        final Indexed<String> indexed1 = it.next();
        assertThat(indexed1.getIndex(), is(0));
        assertThat(indexed1.getElement(), is("aaa"));

  ImmutableMapKeySet(ImmutableMap<K, V> map) {
    this.map = map;
  }

  @Override
  public int size() {
    return map.size();
  }

  @Override
  public UnmodifiableIterator<K> iterator() {
    return map.keyIterator();
  }

  @Override
  public Spliterator<K> spliterator() {
    return map.keySpliterator();
  }

  @Override
  public boolean contains(@Nullable Object object) {

      return ImmutableMap.this.isHashCodeFast();
    }

    @Override
    UnmodifiableIterator<Entry<K, ImmutableSet<V>>> entryIterator() {
      Iterator<Entry<K, V>> backingIterator = ImmutableMap.this.entrySet().iterator();
      return new UnmodifiableIterator<Entry<K, ImmutableSet<V>>>() {
        @Override
        public boolean hasNext() {
          return backingIterator.hasNext();
        }

  ImmutableMapKeySet(ImmutableMap<K, V> map) {
    this.map = map;
  }

  @Override
  public int size() {
    return map.size();
  }

  @Override
  public UnmodifiableIterator<K> iterator() {
    return map.keyIterator();
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return map.containsKey(object);
  }

  @Override
  K get(int index) {

        return true;
      }

      @Override
      public int hashCode() {
        return hashCode;
      }

      @Override
      public UnmodifiableIterator<Entry<V, K>> iterator() {
        return asList().iterator();
      }

      @Override
      public void forEach(Consumer<? super Entry<V, K>> action) {
        asList().forEach(action);
      }

      @Override

      this.alternatingKeysAndValues = alternatingKeysAndValues;
      this.keyOffset = keyOffset;
      this.size = size;
    }

    @Override
    public UnmodifiableIterator<Entry<K, V>> iterator() {
      return asList().iterator();
    }

    @Override
    int copyIntoArray(@Nullable Object[] dst, int offset) {
      return asList().copyIntoArray(dst, offset);
    }

    @Override

  static void checkPositive(int value, String name) {
    if (value <= 0) {
      throw new IllegalArgumentException(name + " must be positive but was: " + value);
    }
  }

  /**
   * Precondition tester for {@code Iterator.remove()} that throws an exception with a consistent
   * error message.
   */
  static void checkRemove(boolean canRemove) {
    checkState(canRemove, "no calls to next() since the last call to remove()");
  }

  // Refined Collection Methods

  /**
   * {@inheritDoc}
   *
   * <p>Elements that occur multiple times in the multiset will appear multiple times in this
   * iterator, though not necessarily sequentially.
   */
  @Override
  Iterator<E> iterator();

  /**
   * Determines whether this multiset contains the specified element.
   *

  Range<C> span();

  // Views

  /**
   * Returns a view of the {@linkplain Range#isConnected disconnected} ranges that make up this
   * range set. The returned set may be empty. The iterators returned by its {@link
   * Iterable#iterator} method return the ranges in increasing order of lower bound (equivalently,
   * of upper bound).
   */
  Set<Range<C>> asRanges();

  /**

        return value;
      }
    };
  }

  private static <K extends @Nullable Object, V extends @Nullable Object> Entry<K, V> control(
      K key, V value) {
    return singletonMap(key, value).entrySet().iterator().next();
  }

  public void testToString() {
    assertEquals("foo=1", entry("foo", 1).toString());
  }

  public void testToStringNull() {
    assertEquals("null=1", entry(NK, 1).toString());