#fixed code
                                @Override
    public void stop() {
        if (!started) {
            return;
        }
        try {
            // 关闭端口，不关闭线程池
            if (LOGGER.isInfoEnabled()) {
                LOGGER.info("Stop the http rest server at port {}", serverConfig.getPort());
            }
            httpServer.stop();
        } catch (Exception e) {
            LOGGER.error("Stop the http rest server at port " + serverConfig.getPort() + " error !", e);
        }
        started = false;
    }
#vulnerable code 
                                @Override
    public void stop() {
        if (!started) {
            return;
        }
        try {
            // 关闭端口，不关闭线程池
            if (LOGGER.isInfoEnabled()) {
                LOGGER.info("Stop the http rest server at port {}", serverConfig.getPort());
            }
            httpServer.stop();
            httpServer = null;
        } catch (Exception e) {
            LOGGER.error("Stop the http rest server at port " + serverConfig.getPort() + " error !", e);
        }
        started = false;
    } 
                            #location 11 
                            #vulnerability type THREAD_SAFETY_VIOLATION