code: public static String wrapIfMissing(final String str, final String wrapWith) {
          if (isEmpty(str) || isEmpty(wrapWith)) {
              return str;
          }
          final StringBuilder builder = new StringBuilder(str.length() + wrapWith.length() + wrapWith.length());
          if (!str.startsWith(wrapWith)) {
              builder.append(wrapWith);
          }
          builder.append(str);
          if (!str.endsWith(wrapWith)) {
              builder.append(wrapWith);
          }
          return builder.toString();
      }
docs: <p>
  Wraps a string with a string if that string is missing from the start or end of the given string.
  </p>
  
  <pre>
  StringUtils.wrap(null, *)         = null
  StringUtils.wrap("", *)           = ""
  StringUtils.wrap("ab", null)      = "ab"
  StringUtils.wrap("ab", "x")       = "xabx"
  StringUtils.wrap("ab", "\"")      = "\"ab\""
  StringUtils.wrap("\"ab\"", "\"")  = "\"ab\""
  StringUtils.wrap("ab", "'")       = "'ab'"
  StringUtils.wrap("'abcd'", "'")   = "'abcd'"
  StringUtils.wrap("\"abcd\"", "'") = "'\"abcd\"'"
  StringUtils.wrap("'abcd'", "\"")  = "\"'abcd'\""
  StringUtils.wrap("/", "/")  = "/"
  StringUtils.wrap("a/b/c", "/")  = "/a/b/c/"
  StringUtils.wrap("/a/b/c", "/")  = "/a/b/c/"
  StringUtils.wrap("a/b/c/", "/")  = "/a/b/c/"
  </pre>
  
  @param str
  the string to be wrapped, may be {@code null}
  @param wrapWith
  the char that will wrap {@code str}
  @return the wrapped string, or {@code null} if {@code str==null}
  @since 3.5