public static final CharMatcher OLD_WHITESPACE =
      new CharMatcher() {
        @Override
        public boolean matches(char c) {
          return OLD_WHITESPACE_TABLE.charAt(c % 79) == c;
        }
      };

  @Param private boolean useNew;

  @Param({"20", "50", "80"})
  private int percentMatching;

  private String teststring;
  private CharMatcher matcher;

    checkNotNull(a);
    checkNotNull(b);

    int maxPrefixLength = Math.min(a.length(), b.length());
    int p = 0;
    while (p < maxPrefixLength && a.charAt(p) == b.charAt(p)) {
      p++;
    }
    if (validSurrogatePairAt(a, p - 1) || validSurrogatePairAt(b, p - 1)) {
      p--;
    }
    return a.subSequence(0, p).toString();
  }

  /**

  public static CharMatcher anyOf(final CharSequence sequence) {
    switch (sequence.length()) {
      case 0:
        return none();
      case 1:
        return is(sequence.charAt(0));
      case 2:
        return isEither(sequence.charAt(0), sequence.charAt(1));
      default:
        // TODO(lowasser): is it potentially worth just going ahead and building a precomputed
        // matcher?
        return new AnyOf(sequence);
    }

        }
      }
    }
    if (ipString.charAt(0) == IPV6_DELIMITER && ipString.charAt(1) != IPV6_DELIMITER) {
      return null; // ^: requires ^::
    }
    if (ipString.charAt(ipString.length() - 1) == IPV6_DELIMITER
        && ipString.charAt(ipString.length() - 2) != IPV6_DELIMITER) {
      return null; // :$ requires ::$
    }

    if (s1 == s2) {
      return true;
    }
    if (length != s2.length()) {
      return false;
    }
    for (int i = 0; i < length; i++) {
      char c1 = s1.charAt(i);
      char c2 = s2.charAt(i);
      if (c1 == c2) {
        continue;
      }
      int alphaIndex = getAlphaIndex(c1);
      // This was also benchmarked using '&' to avoid branching (but always evaluate the rhs),

            return null;
        }
        if (trimText == null) {
            trimText = " ";
        }
        int pos = 0;
        for (; pos < text.length(); pos++) {
            if (trimText.indexOf(text.charAt(pos)) < 0) {
                break;
            }
        }
        return text.substring(pos);
    }

    /**
     * 右側の空白を削ります。
     *
     * @param text
     *            テキスト

        }

        private void concatPath(StringBuilder url, String path) {
            if (!path.isEmpty()) {
                boolean initialUrlEndsWithSlash = url.charAt(url.length() - 1) == '/';
                boolean pathStartsWithSlash = path.charAt(0) == '/';

                if (pathStartsWithSlash) {
                    if (initialUrlEndsWithSlash) {
                        // 1 extra '/' to remove

        while ( ( line = br.readLine() ) != null ) {
            line = line.toUpperCase().trim();
            if ( line.length() == 0 ) {
                continue;
            }
            else if ( line.charAt(0) == '#' ) {
                if ( line.startsWith("#INCLUDE ") ) {
                    line = line.substring(line.indexOf('\\'));
                    String url = "smb:" + line.replace('\\', '/');

        }
        String item = list.get(index).trim();
        if (StringUtil.isBlank(item)) {
            return StringUtil.EMPTY;
        }
        if (item.length() > 1 && item.charAt(0) == '"' && item.charAt(item.length() - 1) == '"') {
            item = item.substring(1, item.length() - 1);
        }
        return item;
    }

            final StringBuilder sb = new StringBuilder();
            for (int i = 0; i < s.length(); i++) {
                final char ch = s.charAt(i);
                if (ch == '\\' && i < s.length() - 1) {
                    i++;
                    sb.append(s.charAt(i));
                } else {
                    sb.append(ch);
                }
            }
            return sb.toString();
        }