* powerSet(ImmutableSet.of(1, 2))} returns the set {@code {{}, {1}, {2}, {1, 2}}}.
   *
   * <p>Elements appear in these subsets in the same iteration order as they appeared in the input
   * set. The order in which these subsets appear in the outer set is undefined. Note that the power
   * set of the empty set is not the empty set, but a one-element set containing the empty set.
   *

   * function on that value. The resulting multimap is created as an immutable snapshot. In the
   * returned multimap, keys appear in the order they are first encountered, and the values
   * corresponding to each key appear in the same order as they are encountered.
   *
   * <p>For example,
   *
   * {@snippet :
   * List<String> badGuys =

   * function on that value. The resulting multimap is created as an immutable snapshot. In the
   * returned multimap, keys appear in the order they are first encountered, and the values
   * corresponding to each key appear in the same order as they are encountered.
   *
   * <p>For example,
   *
   * {@snippet :
   * List<String> badGuys =

							<mapper>
								<type>perm</type>
								<user>${packaging.fess.user}</user>
								<group>${packaging.fess.group}</group>
							</mapper>
						</data>
						<data>
							<type>directory</type>
							<src>${project.build.directory}/fess/WEB-INF/classes/org/codelibs/fess/tomcat</src>
							<mapper>
								<type>perm</type>

            buf.append(',');
            buf.append("\"page_number\":");
            buf.append(currentPageNumber);
            buf.append(',');
            buf.append("\"record_count\":");
            buf.append(allRecordCount);
            buf.append(',');
            buf.append("\"record_count_relation\":");
            buf.append(escapeJson(allRecordCountRelation));
            buf.append(',');
            buf.append("\"page_count\":");

      return first;
    }

    StringBuilder sb = new StringBuilder().append("expected one element but was: <").append(first);
    for (int i = 0; i < 4 && iterator.hasNext(); i++) {
      sb.append(", ").append(iterator.next());
    }
    if (iterator.hasNext()) {
      sb.append(", ...");
    }
    sb.append('>');

    throw new IllegalArgumentException(sb.toString());
  }

  /**

    StringBuilder buf = new StringBuilder((len * 3 / 2) + 16);

    int oldpos = 0;
    do {
      buf.append(string, oldpos, pos);
      buf.append(replacement);
      oldpos = pos + 1;
      pos = indexIn(string, oldpos);
    } while (pos != -1);

    buf.append(string, oldpos, len);
    return buf.toString();
  }

  /**

      buildString {
        if (scheme != null) {
          append(scheme)
          append("://")
        } else {
          append("//")
        }

        if (encodedUsername.isNotEmpty() || encodedPassword.isNotEmpty()) {
          append(encodedUsername)
          if (encodedPassword.isNotEmpty()) {
            append(':')
            append(encodedPassword)
          }
          append('@')

        final StringBuilder buf = new StringBuilder(100);
        buf.append("/WEB-INF/view/").append(page);
        if (StringUtil.isNotBlank(lang)) {
            buf.append('_').append(lang);
            if (StringUtil.isNotBlank(country)) {
                buf.append('_').append(country);
            }
        }
        buf.append(".jsp");
        return buf.toString();
    }

    /**

    default String getLdapAdminUserSecurityPrincipal(final String name) {
        final StringBuilder buf = new StringBuilder(100);
        buf.append(String.format(getLdapAdminUserFilter(), name));
        if (StringUtil.isNotBlank(getLdapAdminUserBaseDn())) {
            buf.append(',').append(getLdapAdminUserBaseDn());
        }
        return buf.toString();
    }

    String getLdapAdminRoleObjectClasses();