#vulnerable code 
                                @Override
    public void close() {
        this.connManager.shutdown();
        if (this.closeables != null) {
            for (final Closeable closeable: this.closeables) {
                try {
                    closeable.close();
                } catch (final IOException ex) {
                    this.log.error(ex.getMessage(), ex);
                }
            }
        }
    } 
                            #location 3 
                            #vulnerability type INTERFACE_NOT_THREAD_SAFE
#fixed code
                                @Override
    public void close() {
        if (this.closeables != null) {
            for (final Closeable closeable: this.closeables) {
                try {
                    closeable.close();
                } catch (final IOException ex) {
                    this.log.error(ex.getMessage(), ex);
                }
            }
        }
    }