private static final int ENDPOINT = -2;

  /**
   * Contains the link pointers corresponding with the entries, in the range of [0, size()). The
   * high 32 bits of each long is the "prev" pointer, whereas the low 32 bits is the "succ" pointer
   * (pointing to the next entry in the linked list). The pointers in [size(), entries.length) are
   * all "null" (UNSET).
   *

  // entry in a *single* long[], though that reduces the maximum size of the set by a factor of 2

  /**
   * Pointer to the predecessor of an entry in insertion order. ENDPOINT indicates a node is the
   * first node in insertion order; all values at indices ≥ {@link #size()} are UNSET.
   */
  @CheckForNull private transient int[] predecessor;

  /**

    ImmutableSet.Builder<String> builder = ImmutableSet.builderWithExpectedSize(4);
    builder.add("a");
    assertEquals(1, builder.size);
    builder.add("a");
    assertEquals(1, builder.size);
    builder.add("b", "c", "d");
    assertEquals(4, builder.size);
    Object[] table = builder.hashTable;
    assertNotNull(table);
    assertSame(table, ((RegularImmutableSet<String>) builder.build()).table);
  }

    }
  }

  public void testSize0() {
    Iterator<String> iterator = Iterators.emptyIterator();
    assertEquals(0, Iterators.size(iterator));
  }

  public void testSize1() {
    Iterator<Integer> iterator = Collections.singleton(0).iterator();
    assertEquals(1, Iterators.size(iterator));
  }

  public void testSize_partiallyConsumed() {
    Iterator<Integer> iterator = asList(1, 2, 3, 4, 5).iterator();

    return CollectSpliterators.indexed(size(), SPLITERATOR_CHARACTERISTICS, this::get);
  }

  @Override
  int copyIntoArray(@Nullable Object[] dst, int offset) {
    // this loop is faster for RandomAccess instances, which ImmutableLists are
    int size = size();
    for (int i = 0; i < size; i++) {
      dst[offset + i] = get(i);
    }
    return offset + size;
  }

  /**

    try {
      getList().listIterator(getNumElements() + 1);
      fail();
    } catch (IndexOutOfBoundsException expected) {
    }
  }

  public void testListIterator_atSize() {
    getList().listIterator(getNumElements());
    // TODO: run the iterator through ListIteratorTester
  }

  /**
   * Returns the {@link Method} instance for {@link #testListIterator_fullyModifiable()} so that

      builder.add(i % setSize);
    }
    ImmutableSet<Integer> set = builder.build();
    assertTrue(set instanceof RegularImmutableSet);
    assertEquals(
        "Input size " + inputSize + " and set size " + setSize,
        tableSize,
        ((RegularImmutableSet<Integer>) set).table.length);
  }

  public void testCopyOf_copiesImmutableSortedSet() {

  static final int MAX_TABLE_SIZE = Ints.MAX_POWER_OF_TWO;

  // Represents how tightly we can pack things, as a maximum.
  private static final double DESIRED_LOAD_FACTOR = 0.7;

  // If the set has this many elements, it will "max out" the table size
  private static final int CUTOFF = (int) (MAX_TABLE_SIZE * DESIRED_LOAD_FACTOR);

  /**

    Builder<K, V> combine(Builder<K, V> other) {
      checkNotNull(other);
      ensureCapacity(this.size + other.size);
      System.arraycopy(
          other.alternatingKeysAndValues,
          0,
          this.alternatingKeysAndValues,
          this.size * 2,
          other.size * 2);
      this.size += other.size;
      return this;
    }

    private ImmutableMap<K, V> build(boolean throwIfDuplicateKeys) {

      return forwardList;
    }

    private int reverseIndex(int index) {
      int size = size();
      checkElementIndex(index, size);
      return (size - 1) - index;
    }

    private int reversePosition(int index) {
      int size = size();
      checkPositionIndex(index, size);
      return size - index;
    }

    @Override
    public void add(int index, @ParametricNullness T element) {