Java Gui线程编码？

Question

当我的服务器连接到客户端时出现问题，出现此异常，然后我的程序在连接后没有响应。我使用 netbeans gui designer 为 gui class 生成代码。我还在我的代码中注释了下面异常显示的行号，供你们考虑。在套接字接受之前找到一切工作。请帮忙！

Exception in thread "Thread-0" 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

您从未初始化 BufferedReader。

BufferedReader in = null;

... 因此此行失败并显示 NullPointerException:

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

一般来说，只要看到 NullPointerException，您所要做的就是查看该行并检查所有正在调用 null 方法的对象。

Answer 2

你没有初始化。

in = new BufferedReader(arguments);

Java Gui线程编码？

Java Gui Thread Coding?

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netbeans

tcp