Question

我需要做IRC客户端，我遇到登录问题。我试图循环通过服务器输入找到按钮004或433，其中指出成功登录或登录使用。这是我的代码：`

import ecs100.*;
import java.io.*;
import java.net.Socket; 
import java.util.*; 



public class ChatClient {
private String server = "irc.ecs.vuw.ac.nz";  
private static final int IRC_PORT = 6667;     



private static String nick; 
private static String name;
private Socket socket;
private Scanner serverIn;
private PrintStream serverOut; 
private String line; 
private String channel; 
// Constructor
public ChatClient (){
    this.setupGUI();

}

public void setupGUI(){ 
    UI.addButton("Connect", this::connect);


}



public void connect(){

    try {

    socket = new Socket(server,IRC_PORT); 
    serverIn = new Scanner(socket.getInputStream());
    serverOut = new PrintStream(socket.getOutputStream());
    UI.println("login");
    this.login();
    UI.println("listening");
    this.listenToServer(); 
}catch(IOException e){UI.println("IO failure "+ e);}

}

private boolean login(){
    String username = UI.askToken("Enter your usercode: ");
    String realname = UI.askString("Enter your real name: ");

    this.nick = username;
    this.name = realname;
    send("NICK " + username);
    send("USER " + username + " 0 unused :" + realname);
    UI.println("listening to server");
   while(this.serverIn.hasNext()){
    this.line = serverIn.nextLine();
    UI.println("SERVER" + line);
    if (line.indexOf("004") >= 0){
        UI.println("true");
        return true;
    } else if(line.indexOf("433") >= 0){
        UI.println("failed to connect, username already in use");
        return false;
    } else {
        UI.println("else");
        return false;
    }
}

}

private void send(String msg){

      serverOut.print(msg + "\r\n");

    serverOut.flush();

}


private void listenToServer() {

    while(this.serverIn.hasNext()){
        String line = serverIn.nextLine();
        UI.println("SERVER" + line);
        if(line.equals("SQUIT")){
            this.closeConnection();
        }
        if(line.equals("PING")){
          String pingMsg = line.split(" ",2)[1];  
          this.send("PONG " + pingMsg);  
        }
    }
}


public void closeConnection(){

    try {
    this.socket.close();
    this.serverIn.close();
    this.serverOut.close();
    UI.println("Closed");
} catch(IOException e){UI.println("IO failure "+ e);}
}

public void joinChannel(){
    String channel = UI.askString("Enter channel name: ");
    send("JOIN " + channel);
}
public void leaveChannel(){
    send("PART " + channel);
}

public static void main(String[] args) {
    new ChatClient();
}

}

问题是它在登录方法中不断丢失返回语句。任何人都可以看看我的代码，看看这里可能有什么问题？

编辑：好的，所以当我将if语句更改为两个if并且在循环之外放置return false时，程序可以正常工作。有人可以解释为什么while循环中的if / else语句不起作用吗？

  private boolean login(){
    String username = UI.askToken("Enter your usercode: ");
    String realname = UI.askString("Enter your real name: ");
    this.nick = username;
    this.name = realname;
    send("NICK " + username);
    send("USER " + username + " 0 unused :" + realname);
    UI.println("listening to server");
   while(this.serverIn.hasNext()){
    this.line = serverIn.nextLine();
    UI.println("SERVER" + line);
    if (line.indexOf("004") >= 0){
        UI.println("true");
        return true;
    } 
    if(line.indexOf("433") >= 0){
        UI.println("failed to connect, username already in use");
        return false;
    } 
   }
   UI.println("else");
   return false;
}
enter code here

Answer 1

因为有一个代码路径会导致没有return被调用，并且编译器不能允许这种方法用于非void方法。

如果this.serverIn.hasNext()返回false，如果你最后没有返回语句，该方法会返回什么？毕竟它需要返回boolean。

可以编写程序逻辑，以便从不采用特定的代码路径，但理论上它是可能的，这就是编译器抱怨的原因。

IRC登录缺少退货声明

1 个答案: