* current array, create a new array.
     */
    private void ensureRoomFor(int newElements) {
      @Nullable Object[] contents = this.contents;
      int newCapacity = expandedCapacity(contents.length, size + newElements);
      // expandedCapacity handles the overflow case
      if (newCapacity > contents.length || forceCopy) {
        this.contents = Arrays.copyOf(this.contents, newCapacity);
        forceCopy = false;
      }

      if (newCount > array.length) {
        array = Arrays.copyOf(array, expandedCapacity(array.length, newCount));
      }
    }

    // Unfortunately this is pasted from ImmutableCollection.Builder.
    private static int expandedCapacity(int oldCapacity, int minCapacity) {
      if (minCapacity < 0) {

      if (newCount > array.length) {
        array = Arrays.copyOf(array, expandedCapacity(array.length, newCount));
      }
    }

    // Unfortunately this is pasted from ImmutableCollection.Builder.
    private static int expandedCapacity(int oldCapacity, int minCapacity) {
      if (minCapacity < 0) {

           * sync with one another). We accommodate that by resizing as necessary.
           */
          toJoin = Arrays.copyOf(toJoin, expandedCapacity(toJoin.length, toJoin.length + 1));
        }
        toJoin[i++] = toString(part);
      }
      // We might not have seen the expected number of elements, as discussed above.
      if (i != toJoin.length) {

   */
  private void ensureCapacity(int minCapacity) {
    if (nextInBucketKToV.length < minCapacity) {
      int oldCapacity = nextInBucketKToV.length;
      int newCapacity = ImmutableCollection.Builder.expandedCapacity(oldCapacity, minCapacity);

      keys = Arrays.copyOf(keys, newCapacity);
      values = Arrays.copyOf(values, newCapacity);
      nextInBucketKToV = expandAndFillWithAbsent(nextInBucketKToV, newCapacity);

          case 1:
            return second;
          default:
            return rest[index - 2];
        }
      }
    };
  }

  // cloned from ImmutableCollection
  private static int expandedCapacity(int oldCapacity, int minCapacity) {
    if (minCapacity < 0) {
      throw new IllegalArgumentException("cannot store more than Integer.MAX_VALUE elements");
    } else if (minCapacity <= oldCapacity) {

   *
   * @since 10.0
   */
  @DoNotMock
  public abstract static class Builder<E> {
    static final int DEFAULT_INITIAL_CAPACITY = 4;

    static int expandedCapacity(int oldCapacity, int minCapacity) {
      if (minCapacity < 0) {
        throw new IllegalArgumentException("cannot store more than Integer.MAX_VALUE elements");
      } else if (minCapacity <= oldCapacity) {

     * elements.
     */
    private void ensureCapacity(int minCapacity) {
      if (minCapacity > dedupedElements.length) {
        int newCapacity =
            ImmutableCollection.Builder.expandedCapacity(dedupedElements.length, minCapacity);
        dedupedElements = Arrays.copyOf(dedupedElements, newCapacity);
      }
    }

      if (minCapacity * 2 > alternatingKeysAndValues.length) {
        alternatingKeysAndValues =
            Arrays.copyOf(
                alternatingKeysAndValues,
                ImmutableCollection.Builder.expandedCapacity(
                    alternatingKeysAndValues.length, minCapacity * 2));
        entriesUsed = false;
      }
    }

    /**

    }

    private void ensureCapacity(int minCapacity) {
      if (minCapacity > entries.length) {
        entries =
            Arrays.copyOf(
                entries, ImmutableCollection.Builder.expandedCapacity(entries.length, minCapacity));
        entriesUsed = false;
      }
    }

    /**
     * Associates {@code key} with {@code value} in the built map. If the same key is put more than