code: private void setIntervalPattern(String skeleton,
                                      String lrgDiffCalUnit,
                                      PatternInfo ptnInfo) {
          Map<String, PatternInfo> patternsOfOneSkeleton = fIntervalPatterns.get(skeleton);
          patternsOfOneSkeleton.put(lrgDiffCalUnit, ptnInfo);
      }
docs: /* Set Interval pattern.
  
  @param skeleton         skeleton on which the interval pattern based
  @param lrgDiffCalUnit   the largest different calendar unit.
  @param ptnInfo          interval pattern infomration