code: private void initializePattern(ICUCache<String, Map<String, PatternInfo>> cache) { 
          String fullPattern = fDateFormat.toPattern();
          ULocale locale = fDateFormat.getLocale();
          String key = null;
          Map<String, PatternInfo> patterns = null;
          if (cache != null) {
              if ( fSkeleton != null ) {
                  key = locale.toString() + "+" + fullPattern + "+" + fSkeleton;
              } else {
                  key = locale.toString() + "+" + fullPattern;
              }
              patterns = cache.get(key);
          }
          if (patterns == null) {
              Map<String, PatternInfo> intervalPatterns = initializeIntervalPattern(fullPattern, locale);
              patterns = Collections.unmodifiableMap(intervalPatterns);
              if (cache != null) {
                  cache.put(key, patterns);
              }
          } 
          fIntervalPatterns = patterns;
      }
docs: /*
  Initialize interval patterns locale to this formatter.