docs: @Override
  	public boolean containsKey(K key) {
  		readLock.lock();
  
  		try {
  			// 不存在或已移除
  			final CacheObj<K, V> co = cacheMap.get(key);
  			if (co == null) {
  				return false;
  			}
  
  			if (false == co.isExpired()) {
  				// 命中
  				return true;
  			}
  		} finally {
  			readLock.unlock();
  		}
  
  		// 过期
  		remove(key, true);
  		return false;
  	}