我不知道為什么什么也沒發生。我正在嘗試編寫一個將json對象發送到碼頭服務器的java程序。該服務器已經被寫入（由其他人，它是一個項目），并且只有某些json對象除外。但是他沒有從我的程序中得到任何東西。public class client {    final static String HOST = "localhost";    final static int PORT = 3000;    public static void main(String[] args)    {           String URIString = "ws://" + HOST + ":" + PORT + "/servlets";        URI uri = URI.create(URIString);        WebSocketClient client = new WebSocketClient();        JSONObject js = new JSONObject();        js.put("toke","hallo");        Clientsocket clientsocket = new Clientsocket();        try {            client.start();            Future<Session> fut = client.connect(clientsocket, uri);            clientsocket.getSession().getRemote().sendString(js.toJSONString());;        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }public class Clientsocket extends WebSocketAdapter {    //private static final Logger LOG = Log.getLogger(Clientsocket.class);    @Override    public void onWebSocketClose(int statusCode,String reason)    {        super.onWebSocketClose(statusCode, reason);        //LOG.info("Websocket Close:{}  - {} ", statusCode,reason);    }    @Override    public void onWebSocketConnect(Session session)     {        super.onWebSocketConnect(session);        //LOG.info("Websocket Connect: {}", session);    }}啟動時出現錯誤信息：2018-06-22 14:26:43.789:INFO::main: Logging initialized @257ms to org.eclipse.jetty.util.log.StdErrLogjava.lang.NullPointerException[both classes: clientsocket, client][1]