chars.add(randomAlpha());
    }
    for (int i = 0; i < nonAlpha; i++) {
      chars.add(randomNonAlpha());
    }
    Collections.shuffle(chars, random);
    char[] array = Chars.toArray(chars);
    this.testString = new String(array);
  }

  private char randomAlpha() {
    return ALPHA.charAt(random.nextInt(ALPHA.length()));
  }

  private char randomNonAlpha() {

  }

  static CharMatcher from(BitSet chars, String description) {
    // Compute the filter.
    long filter = 0;
    int size = chars.cardinality();
    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)) {

      chars.add(randomAlpha());
    }
    for (int i = 0; i < nonAlpha; i++) {
      chars.add(randomNonAlpha());
    }
    Collections.shuffle(chars, random);
    char[] array = Chars.toArray(chars);
    this.testString = new String(array);
  }

  private char randomAlpha() {
    return ALPHA.charAt(random.nextInt(ALPHA.length()));
  }

  private char randomNonAlpha() {

    String allMatchingChars = allMatchingChars(bitSet);
    char[] result = new char[STRING_LENGTH];
    // Fill with matching chars.
    for (int i = 0; i < result.length; i++) {
      result[i] = allMatchingChars.charAt(random.nextInt(allMatchingChars.length()));
    }
    // Replace some of chars by non-matching.
    int remaining = (int) ((100 - percentMatching) * result.length / 100.0 + 0.5);
    while (remaining > 0) {

    public List<Character> create(Character[] elements) {
      char[] chars = Chars.toArray(asList(elements));
      return charactersOf(String.copyValueOf(chars));
    }
  }

  public static class CharactersOfCharSequenceGenerator extends TestCharacterListGenerator {
    @Override
    public List<Character> create(Character[] elements) {
      char[] chars = Chars.toArray(asList(elements));

    public List<Character> create(Character[] elements) {
      char[] chars = Chars.toArray(asList(elements));
      return charactersOf(String.copyValueOf(chars));
    }
  }

  public static class CharactersOfCharSequenceGenerator extends TestCharacterListGenerator {
    @Override
    public List<Character> create(Character[] elements) {
      char[] chars = Chars.toArray(asList(elements));

   *
   * @return the replacement characters, or {@code null} if no escaping was required
   */
  @Override
  protected final char @Nullable [] escape(int cp) {
    if (cp < replacementsLength) {
      char[] chars = replacements[cp];
      if (chars != null) {
        return chars;
      }
    }
    if (cp >= safeMin && cp <= safeMax) {
      return null;
    }
    return escapeUnsafe(cp);
  }

          private final char[] unknown = new char[] {'?'};

          @Override
          protected char[] escapeUnsafe(char c) {
            return unknown;
          }
        };
    EscaperAsserts.assertBasic(replacingEscaper);

    // Replacements are applied first regardless of whether the character is in
    // the safe range or not ('&' is a safe char while '\t' and '\n' are not).

   */
  @Override
  protected final char @Nullable [] escape(char c) {
    if (c < replacementsLength) {
      char[] chars = replacements[c];
      if (chars != null) {
        return chars;
      }
    }
    if (c >= safeMin && c <= safeMax) {
      return null;
    }
    return escapeUnsafe(c);
  }

  /**

   *
   * @return the replacement characters, or {@code null} if no escaping was required
   */
  @Override
  protected final char @Nullable [] escape(int cp) {
    if (cp < replacementsLength) {
      char[] chars = replacements[cp];
      if (chars != null) {
        return chars;
      }
    }
    if (cp >= safeMin && cp <= safeMax) {
      return null;
    }
    return escapeUnsafe(cp);
  }