code: private void initGMTPattern(String gmtPattern) {
          // This implementation not perfect, but sufficient practically.
          int idx = gmtPattern.indexOf("{0}");
          if (idx < 0) {
              throw new IllegalArgumentException("Bad localized GMT pattern: " + gmtPattern);
          }
          _gmtPattern = gmtPattern;
          _gmtPatternPrefix = unquote(gmtPattern.substring(0, idx));
          _gmtPatternSuffix = unquote(gmtPattern.substring(idx + 3));
      }
docs: Parses the localized GMT pattern string and initialize
  localized gmt pattern fields including {{@link #_gmtPatternTokens}.
  This method must be also called at deserialization time.
  
  @param gmtPattern the localized GMT pattern string such as "GMT {0}"
  @throws IllegalArgumentException when the pattern string does not contain "{0}"