code: protected String formatStr(int bits, HashMap m, Object key, String defVal) {
  
          String ret = getObjectOr(m, key, defVal).trim();
          return formatStr(bits, ret, key);
      }
docs: Format the output string with maximum length
  
  @param bits Maximum length of the output string
  @param m the experiment data holder
  @param key the key of field in the map
  @param defVal the default return value when error happens
  @return formated string of number