private void shutdownClients() {
        synchronized (clientsLock) {
            for (HttpProxyCacheServerClients clients : clientsMap.values()) {
                clients.shutdown();
            }
            clientsMap.clear();
        }
    }
Checks is cache contains fully cached file for particular url.

@param url an url cache file will be checked for.
@return {@code true} if cache contains fully cached file for passed in parameters url.
VideoCache/src/main/java/com/yc/videocache/HttpProxyCacheServer.java