add(elements.next());
      }
      return this;
    }

    @CanIgnoreReturnValue
    @SuppressWarnings("unchecked") // ArrayBasedBuilder stores its elements as Object.
    Builder<E> combine(Builder<E> other) {
      if (hashTable != null) {
        for (int i = 0; i < other.size; ++i) {
          // requireNonNull is safe because the first `size` elements are non-null.

    @CanIgnoreReturnValue
    @Override
    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    @CanIgnoreReturnValue
    Builder<E> combine(Builder<E> other) {
      addAll(other.contents, other.size);
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableList} based on the contents of the {@code Builder}.
     */

      this.valueComparator = checkNotNull(valueComparator, "valueComparator");
      return this;
    }

    @CanIgnoreReturnValue
    Builder<K, V> combine(Builder<K, V> other) {
      checkNotNull(other);
      ensureCapacity(this.size + other.size);
      System.arraycopy(
          other.alternatingKeysAndValues,
          0,
          this.alternatingKeysAndValues,

      throw new UnsupportedOperationException("Not available on ImmutableSortedMap.Builder");
    }

    @CanIgnoreReturnValue
    Builder<K, V> combine(ImmutableSortedMap.Builder<K, V> other) {
      ensureCapacity(size + other.size);
      System.arraycopy(other.keys, 0, this.keys, this.size, other.size);

    /*
     * We keep an array of elements and counts.  Periodically -- when we need more room in the
     * array, or when we're building, or the like -- we sort, deduplicate, and combine the counts.
     * Negative counts indicate a setCount operation with ~counts[i].
     */

    private final Comparator<? super E> comparator;

    @VisibleForTesting E[] elements;
    private int[] counts;

         */
        I result = requireNonNull(elements[index]);
        elements[index] = null;
        index++;
        return result;
      }
    };
  }

  /**
   * Combines two iterators into a single iterator. The returned iterator iterates across the
   * elements in {@code a}, followed by the elements in {@code b}. The source iterators are not
   * polled until necessary.
   *

   * iterators that don't support remove, passing one to the FilteredEntryMultimap constructor would
   * lead to a multimap whose removal operations would fail. This method combines the predicates to
   * avoid that problem.
   */
  private static <K extends @Nullable Object, V extends @Nullable Object>
      Multimap<K, V> filterFiltered(