code: public static String createEndSuffixFileName(String fileName, String endSuffix) {
          int    index       = fileName.lastIndexOf(".");
          String preFileName = fileName.substring(0, index);
          String suffix      = fileName.substring(index);
          return preFileName + endSuffix + suffix;
      }
docs: 在文件名后加上指定后缀，不包括后缀名
  
  @param fileName
  @param endSuffix
  @return