code: public boolean isEmpty(String group) {
  		group = StrUtil.nullToEmpty(group).trim();
  		readLock.lock();
  		try {
  			final LinkedHashMap<String, String> valueMap = this.get(group);
  			if (MapUtil.isNotEmpty(valueMap)) {
  				return valueMap.isEmpty();
  			}
  		} finally {
  			readLock.unlock();
  		}
  		return true;
  	}
docs: 某个分组对应的键值对是否为空
  
  @param group 分组
  @return 是否为空