Question

我正在尝试研究多客户端聊天服务器。由于我是Java的新手，我无法在Net Bean中运行这两个.java文件。我有两个java项目，并将这些文件放在它们下面。服务器项目成功运行，但客户端项目显示：

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at chatClient.main(chatClient.java:73)

客户项目

import java.net.*;
import java.io.*;
import java.util.*;
import java.awt.*;

class chatClient extends Frame implements Runnable {

    Socket soc;
    TextField tf;
    TextArea ta;
    Button btnSend, btnClose;
    String sendTo;
    String LoginName;
    Thread t = null;
    DataOutputStream dout;
    DataInputStream din;

    chatClient(String LoginName, String chatwith) throws Exception {
        super(LoginName);
        this.LoginName = LoginName;
        sendTo = chatwith;
        tf = new TextField(50);
        ta = new TextArea(50, 50);
        btnSend = new Button("Send");
        btnClose = new Button("Close");
        soc = new Socket("127.0.0.1", 5217);

        din = new DataInputStream(soc.getInputStream());
        dout = new DataOutputStream(soc.getOutputStream());
        dout.writeUTF(LoginName);

        t = new Thread(this);
        t.start();

    }

    void setup() {
        setSize(600, 400);
        setLayout(new GridLayout(2, 1));

        add(ta);
        Panel p = new Panel();

        p.add(tf);
        p.add(btnSend);
        p.add(btnClose);
        add(p);
        show();
    }

    public boolean action(Event e, Object o) {
        if (e.arg.equals("Send")) {
            try {
                dout.writeUTF(sendTo + " " + "DATA" + " " + tf.getText().toString());
                ta.append("\n" + LoginName + " Says:" + tf.getText().toString());
                tf.setText("");
            } catch (Exception ex) {
            }
        } else if (e.arg.equals("Close")) {
            try {
                dout.writeUTF(LoginName + " LOGOUT");
                System.exit(1);
            } catch (Exception ex) {
            }

        }

        return super.action(e, o);
    }

    public static void main(String args[]) throws Exception {
        chatClient Client1 = new chatClient(args[0],args[1]);
        Client1.setup();
    }

    public void run() {
        while (true) {
            try {
                ta.append("\n" + sendTo + " Says :" + din.readUTF());

            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
    }
}

服务器项目

import java.net.*;
import java.util.*;
import java.io.*;

class chatServer {

    static Vector ClientSockets;
    static Vector LoginNames;

    chatServer() throws Exception {
        ServerSocket soc = new ServerSocket(5217);
        ClientSockets = new Vector();
        LoginNames = new Vector();

        while (true) {
            Socket CSoc = soc.accept();
            AcceptClient obClient = new AcceptClient(CSoc);
        }
    }

    public static void main(String args[]) throws Exception {

        chatServer ob = new chatServer();
    }

    class AcceptClient extends Thread {

        Socket ClientSocket;
        DataInputStream din;
        DataOutputStream dout;

        AcceptClient(Socket CSoc) throws Exception {
            ClientSocket = CSoc;

            din = new DataInputStream(ClientSocket.getInputStream());
            dout = new DataOutputStream(ClientSocket.getOutputStream());

            String LoginName = din.readUTF();

            System.out.println("User Logged In :" + LoginName);
            LoginNames.add(LoginName);
            ClientSockets.add(ClientSocket);
            start();
        }

        public void run() {
            while (true) {

                try {
                    String msgFromClient = new String();
                    msgFromClient = din.readUTF();
                    StringTokenizer st = new StringTokenizer(msgFromClient);
                    String Sendto = st.nextToken();
                    String MsgType = st.nextToken();
                    int iCount = 0;

                    if (MsgType.equals("LOGOUT")) {
                        for (iCount = 0; iCount < LoginNames.size(); iCount++) {
                            if (LoginNames.elementAt(iCount).equals(Sendto)) {
                                LoginNames.removeElementAt(iCount);
                                ClientSockets.removeElementAt(iCount);
                                System.out.println("User " + Sendto + " Logged Out ...");
                                break;
                            }
                        }

                    } else {
                        String msg = "";
                        while (st.hasMoreTokens()) {
                            msg = msg + " " + st.nextToken();
                        }
                        for (iCount = 0; iCount < LoginNames.size(); iCount++) {
                            if (LoginNames.elementAt(iCount).equals(Sendto)) {
                                Socket tSoc = (Socket) ClientSockets.elementAt(iCount);
                                DataOutputStream tdout = new DataOutputStream(tSoc.getOutputStream());
                                tdout.writeUTF(msg);
                                break;
                            }
                        }
                        if (iCount == LoginNames.size()) {
                            dout.writeUTF("I am offline");
                        } else {

                        }
                    }
                    if (MsgType.equals("LOGOUT")) {
                        break;
                    }

                } catch (Exception ex) {
                    ex.printStackTrace();
                }

            }
        }
    }
}

提前致谢。

Answer 1

如果你看一下你客户的构造函数，你会发现它需要两个参数：

chatClient(String LoginName, String chatwith)

登录并与谁聊天。

我认为您没有指定它们，因此以下行会抛出异常，因为没有任何异常且args为空：

chatClient Client1 = new chatClient(args[0],args[1]);

Answer 2

从命令行传递的java参数实际上是String数组。如果你没有在命令行中键入任何内容（或者等效的NetBeans，你将得到一个ArrrayIndexOutOfBoundsException。因此你得到一个例外，因为你试图将一个字符串数组传递给chatClient方法，而实际上没有任何参数。

如何修复此数据索引超出边界异常？

2 个答案: