Question

当我的服务器连接到客户端时出现问题，发生此异常，然后我的程序在连接后没有响应。我使用netbeans gui designer为gui类生成代码。我也在我的代码中评论下面例外中显示的行号，供大家考虑。在插座接受之前，一切都能找到。请帮忙！

线程中的异常＆＃34;线程0＆＃34; java.lang.NullPointerException at serverui.ServerUi.StartServer（ServerUi.java:62）at serverui.ServerThread.run（ServerUi.java:19）at java.lang.Thread.run（Thread.java:745）

class ServerThread implements Runnable{

public void run(){
 try {
      ServerUi t = new ServerUi();
      t.StartServer(); //Line 19
     } catch (IOException ex) {
       //Logger.getLogger(ServerThread.class.getName()).log(Level.SEVERE, null, ex);
        } catch (InterruptedException ex) {
            //Logger.getLogger(ServerThread.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

}


public class ServerUi {
byte s = 0;
static ServerSocket serverSocket = null;
Socket clientSocket = null;
PrintWriter out = null;
BufferedReader in = null;
public static boolean checklisten = false;
static gui winframe = null;
public static void main(String[] args)throws IOException {

winframe = new gui();
serverSocket = new ServerSocket(10007);
Thread tserver = new Thread(new ServerThread());
tserver.start();

java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                winframe.setVisible(true);
            }
        });


    }

    public void StartServer()throws IOException, InterruptedException
    {

               winframe.displayMessage("Listening for Connection");
               clientSocket = serverSocket.accept();
               winframe.displayMessage("Connected");
               String inputLine;
               while(true){
                while((inputLine=in.readLine()) != null) // Line 62
                {

                    winframe.displayMessage("Server: "+ inputLine);
                    out.println(inputLine);

                    if(inputLine.equals("Bye."))
                    {
                        this.Closeconnection();
                        break;
                    }

                    if(winframe.checkdisconnectbtn == true)
                    {
                        this.Closeconnection();
                        break;
                    }

                }

               }
    }

Answer 1

您永远不会初始化BufferedReader。

BufferedReader in = null;

...因此这一行失败了NullPointerException：

while((inputLine=in.readLine()) != null) // Line 62

通常，每当看到NullPointerException时，您只需查看该行并检查调用null方法的所有对象。

Answer 2

你没有初始化。

in = new BufferedReader(arguments);

Java Gui线程编码？

2 个答案: