boolean containsZero = chars.get(0);
    // Compute the hash table.
    char[] table = new char[chooseTableSize(size)];
    int mask = table.length - 1;
    for (int c = chars.nextSetBit(0); c != -1; c = chars.nextSetBit(c + 1)) {
      // Compute the filter at the same time.
      filter |= 1L << c;
      int index = smear(c) & mask;
      while (true) {
        // Check for empty.
        if (table[index] == 0) {

    }
    return result;
  }

  private static String allMatchingChars(BitSet bitSet) {
    char[] result = new char[bitSet.cardinality()];
    for (int j = 0, c = bitSet.nextSetBit(0); j < result.length; ++j) {
      result[j] = (char) c;
      c = bitSet.nextSetBit(c + 1);
    }
    return new String(result);
  }

  private static String newTestString(Random random, BitSet bitSet, int percentMatching) {

   * Returns the index of the first appearance of the value {@code target} in {@code array}.
   *
   * <p><b>Note:</b> consider representing the array as a {@link java.util.BitSet} instead, and
   * using {@link java.util.BitSet#nextSetBit(int)} or {@link java.util.BitSet#nextClearBit(int)}.
   *
   * @param array an array of {@code boolean} values, possibly empty
   * @param target a primitive {@code boolean} value

   * Returns the index of the first appearance of the value {@code target} in {@code array}.
   *
   * <p><b>Note:</b> consider representing the array as a {@link java.util.BitSet} instead, and
   * using {@link java.util.BitSet#nextSetBit(int)} or {@link java.util.BitSet#nextClearBit(int)}.
   *
   * @param array an array of {@code boolean} values, possibly empty
   * @param target a primitive {@code boolean} value

    switch (totalCharacters) {
      case 0:
        return none();
      case 1:
        return is((char) table.nextSetBit(0));
      case 2:
        char c1 = (char) table.nextSetBit(0);
        char c2 = (char) table.nextSetBit(c1 + 1);
        return isEither(c1, c2);
      default:
        return isSmall(totalCharacters, table.length())

          @Override
          protected @Nullable Set<E> computeNext() {
            if (bits.isEmpty()) {
              bits.set(0, size);
            } else {
              int firstSetBit = bits.nextSetBit(0);
              int bitToFlip = bits.nextClearBit(firstSetBit);

              if (bitToFlip == index.size()) {
                return endOfData();
              }

              /*