如何修复Java数组索引超出范围错误

Question

client server chat system as server start the server and client connect to the server..when client tries to connect to server, it success but the array goes to lost connection condition. catch (Exception ex) { outputTextArea.append("Lost a connection. \\n"); ex.printStackTrace(); clientOutputStreams.remove(client);

anyway to fix it?

Server side code

        public ClientHandler(Socket clientSocket, PrintWriter user) {
    // new inputStreamReader and then add it to a BufferedReader
                    client = user;
        try {
            sock = clientSocket;
            InputStreamReader isReader = new InputStreamReader(sock.getInputStream());
            reader = new BufferedReader(isReader);
        } // end try
        catch (Exception ex) {
            outputTextArea.append("Error beginning StreamReader. \n");
        } // end catch

    } // end ClientHandler()

    public void run() {
                    String message, connect = "Connect", disconnect = "Disconnect", chat = "Chat" ;
        String[] data;

        try {
            while ((message = reader.readLine()) != null) {

                outputTextArea.append("Received: " + message + "\n");
                data = message.split(":");
                                    for (String token:data) {

                                    outputTextArea.append(token + "..\n");

                                    }

                                    if (data[2].equals(connect)) {

                                            tellEveryone((data[0] + ":" + data[1] + ":" + chat));
                                            userAdd(data[0]);

                } else if (data[2].equals(disconnect)) {

                                        tellEveryone((data[0] + ":has disconnected." + ":" + chat));
                                        userRemove(data[0]);

                } else if (data[2].equals(chat)) {

                                        tellEveryone(message);

                } else {
                                        outputTextArea.append("No Conditions were met. \n");
                                    }


             } // end while
        } // end try
        catch (Exception ex) {
            outputTextArea.append("Lost a connection. \n");
                            ex.printStackTrace();
                            clientOutputStreams.remove(client);
        } // end catch
    } // end run()
    public void userAdd (String data) {
        String message, add = ": :Connect", done = "Server: :Done", name = data;
        outputTextArea.append("Before " + name + " added. \n");
        userlist.add(name);
        outputTextArea.append("After " + name + " added. \n");
        String[] tempList = new String[(userlist.size())];
        userlist.toArray(tempList);

            for (String token:tempList) {

                message = (token + add);
                tellEveryone(message);
            }
            tellEveryone(done);
}

public void userRemove (String data) {
            String message, add = ": :Connect", done = "Server: :Done", name = data;
            userlist.remove(name);
            String[] tempList = new String[(userlist.size())];
    userlist.toArray(tempList);

            for (String token:tempList) {

                message = (token + add);
                tellEveryone(message);
            }
            tellEveryone(done);
}

    public void tellEveryone(String message) {
// sends message to everyone connected to server
    Iterator it = clientOutputStreams.iterator();

    while (it.hasNext()) {
        try {
            PrintWriter writer = (PrintWriter) it.next();
            writer.println(message);
            writer.flush();
                            outputTextArea.setCaretPosition(outputTextArea.getDocument().getLength());

        } // end try
        catch (Exception ex) {
            outputTextArea.append("Error telling everyone. \n");
        } // end catch
    } // end while
} // end tellEveryone()

errors

java.lang.ArrayIndexOutOfBoundsException: 2
at chatsystemserver.ServerSide$ClientHandler.run(ServerSide.java:55)
at java.lang.Thread.run(Thread.java:745)

any idea how to fix the data[2]?

Answer 1

Check if the array has at least 3 elements. That is, change

if (data[2].equals(connect)) {

to

if (data.length > 2 && data[2].equals(connect)) {