code: private synchronized String formatPattern(Pattern pat, String... args) {
          if (_patternFormatters == null) {
              _patternFormatters = new MessageFormat[Pattern.values().length];
          }
  
          int idx = pat.ordinal();
          if (_patternFormatters[idx] == null) {
              String patText;
              try {
                  ICUResourceBundle bundle = (ICUResourceBundle) ICUResourceBundle.getBundleInstance(
                      ICUData.ICU_ZONE_BASE_NAME, _locale);
                  patText = bundle.getStringWithFallback("zoneStrings/" + pat.key());
              } catch (MissingResourceException e) {
                  patText = pat.defaultValue();
              }
  
              _patternFormatters[idx] = new MessageFormat(patText);
          }
          return _patternFormatters[idx].format(args);
      }
docs: Private simple pattern formatter used for formatting generic location names
  and partial location names. We intentionally use JDK MessageFormat
  for performance reason.
  
  @param pat the message pattern enum
  @param args the format argument(s)
  @return the formatted string