Matcher matcher = linkPattern.matcher(line);
        while (matcher.find()) {
            MatchResult xrefMatcher = matcher.toMatchResult();
            String link = xrefMatcher.group(1);
            if (link.contains("#")) {
                Matcher linkMatcher = linkWithHashPattern.matcher(link);
                if (linkMatcher.matches()) {

  private static final class IsEither extends FastMatcher {

    private final char match1;
    private final char match2;

    IsEither(char match1, char match2) {
      this.match1 = match1;
      this.match2 = match2;
    }

    @Override
    public boolean matches(char c) {
      return c == match1 || c == match2;
    }

    @GwtIncompatible // used only from other GwtIncompatible code

            final Matcher matcher = pattern.matcher(v.trim());
            if (matcher.matches()) {
                final PrunedTag tag = new PrunedTag(matcher.group(1));
                if (matcher.group(2) != null) {
                    final String attrPair = matcher.group(2).substring(1, matcher.group(2).length() - 1);

            if (obj != null) {
                value = obj.toString();
            }
            final Matcher matcher = entry.getValue().matcher(value);
            if (allRequired) {
                if (!matcher.matches()) {
                    return false;
                }
            } else if (matcher.matches()) {
                return true;
            }
        }

        return allRequired;
    }

    protected String parseCharset(final String content) {
        final Pattern pattern = Pattern.compile("; *charset *= *([a-zA-Z0-9\\-_]+)", Pattern.CASE_INSENSITIVE);
        final Matcher matcher = pattern.matcher(content);
        if (matcher.find()) {
            return matcher.group(1);
        }
        return null;
    }

    protected RequestData getDuplicateUrl(final RequestData requestData) {

            throw new RobotsTxtException("Failed to parse robots.txt.", e);
        }
    }

    protected String getValue(final Pattern pattern, final String line) {
        final Matcher m = pattern.matcher(line);
        if (m.matches() && m.groupCount() > 0) {
            return m.group(1);
        }
        return null;
    }

    protected String stripComment(final String line) {

        final Matcher matcher = pattern.matcher(value);
        while (matcher.find()) {
            final String key = matcher.group(2);
            String replacement = System.getProperty(key);
            if (replacement == null) {
                replacement = matcher.group(1);
            }

        if (lastHyphen > 0) {
            int prevHyphen = version.lastIndexOf('-', lastHyphen - 1);
            if (prevHyphen > 0) {
                Matcher m = Artifact.VERSION_FILE_PATTERN.matcher(version);
                if (m.matches()) {
                    return m.group(1) + "-" + Artifact.SNAPSHOT_VERSION;
                }
            }
        }
        return version;
    }

   * in Android) requires a successful match in order to generate a {@code MatchResult}:
   * https://cs.android.com/android/platform/superproject/+/android-2.3.7_r1:libcore/luni/src/main/java/java/util/regex/Matcher.java;l=550;drc=5850271b4ab93ebc27c1d49169a348c6be3c7f04
   */
  private static MatchResult createMatchResult() {
    Matcher matcher = Pattern.compile(".").matcher("X");

                return null;
            }
            final Matcher matcher = Pattern.compile(pattern, Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE).matcher(value);
            final StringBuffer buf = new StringBuffer(value.length() + 100);
            while (matcher.find()) {
                matcher.appendReplacement(buf, Matcher.quoteReplacement(highlightTagPre + matcher.group(0) + highlightTagPost));
            }