我正在尝试创建一个java聊天，我遇到了这个错误：当我使用name = scanner.nextLine（）时，我的程序工作得很好（但如果我使用System.out，它不会读取任何名称） .println（name）我得到了换行符），当我不使用它时，我的pg会自动连接到没有名字的服务器。任何人都可以告诉我为什么会发生这种情况吗？
import java.net.*;
import java.util.*;
import java.io.*;
class Cient
{
static String name;
public static void main(String[] args) throws Exception
{
Scanner scanner = new Scanner(System.in);
System.out.print("Adresa serverului si portul : ");//server adress and port
Socket cs = new Socket( scanner.next(), scanner.nextInt() );
DataOutputStream os = new DataOutputStream( cs.getOutputStream());
final DataInputStream is = new DataInputStream( cs.getInputStream());
String st = "";
System.out.println("Va rugam sa va introduceti numele");//get name
name = scanner.nextLine();
Thread T= new Thread(new Runnable()
{
public void run() {
while (true)
{
String s = "";
try
{
s = is.readUTF();
System.out.println(s);
if(s.equals("Intrerupem conexiunea .... Pa!"))//close connexion
{
return;
}
} catch (IOException ex)
{
}
}
}
});
T.start();
while (true)
{
st = scanner.nextLine();
os.writeUTF(st);
if(st.equals("QUIT") || st.equals("EXIT"))
{
return;//stop reading
}
}
}
}
这是服务器类，但我不相信这很重要：
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.Vector;
public class MyServer
{
Scanner scanner;
Vector<String> users = new Vector<String>();
Vector<HandleClient> clients = new Vector<HandleClient>();
String disconnectedUser = "InvalidUser";//String care imi spune daca un client s-a razgandit la conectare
int PORT;
public Vector<String> getUserList()
{
return users;
}
public void process() throws Exception
{
scanner = new Scanner(System.in);
System.out.println("PORT: ");
PORT = scanner.nextInt();
ServerSocket server = new ServerSocket(PORT);
System.out.println("Server Online...");
while(true)
{
Socket client = server.accept();
HandleClient c = new HandleClient(client);
if(!(c.userName().equals(disconnectedUser)))
{
clients.add(c);
users.add(c.userName());
}
}
}
public static void main(String ... args) throws Exception
{
new MyServer().process();
}
public void broadcast(String user, String message)throws Exception
{
for (HandleClient c : clients)
if (!(c.userName().equals(user)))
{
c.sendMessage(user,message);
}
}
public void twoUsersBroadcast(String fromUser,String toUser, String msg)throws Exception
{
for(HandleClient c : clients)
{
String a = (String) c.userName();
if(a.equals(toUser))
{
c.sendMessage(fromUser,msg);
return ;
}
}
}
public void changeUserName(String actualName,String newName)
{
int i = 0;
for(HandleClient c: clients)
{
if(c.userName().equals(actualName))
{
c.setUserName(newName);
users.set(i,newName);
}
i++;
}
}
boolean validUserName(String name)
{
for(String c : users)
{
if(c.equals(name))
{
return false;
}
}
return true;
}
class HandleClient extends Thread
{
String name = "";
DataInputStream input;
DataOutputStream output;
public String userName()
{
return name;
}
public void setUserName(String name)
{
this.name = name;
}
public void writeError(String message)
{
try
{
output.writeUTF("EROARE: " + message);
}
catch (IOException e)
{
System.out.print(e.getMessage());
}
}
public HandleClient(Socket client)throws Exception
{
input = new DataInputStream(client.getInputStream());
output= new DataOutputStream(client.getOutputStream());
boolean ok = true;
while(ok == true)
{
name = input.readUTF();
if(name.equals("EXIT"))
{
ok = false;
output.writeUTF("Intrerupem conexiunea .... Pa!");
name = "InvalidUser";//User-ul a renuntat la conexiune
}
else
{
if(validUserName(name) == true)
{
ok = false;
}
else
{
output.writeUTF("Numele este deja folosit. Va rugam sa introducet un alt nume sau EXIT in care doriti sa nu va mai conectati");
}
}
}
if("InvalidUser".equals(name))
{
return;
}
start();
}
public void sendMessage(String username,String msg)throws Exception
{
output.writeUTF( username + ": " + msg);
}
public void run()
{
String line;
try
{
boolean ok = true;
output.writeUTF("Introduceti:");
output.writeUTF("LIST pentru a vedea lista de utilizatori");
output.writeUTF("MSG pentru a transmite un mesaj unui anumit utilizator");
output.writeUTF("BCAST pentru a transmite un mesaj tuturor utilizatorilor");
output.writeUTF("NICK pentru a va schimba numele");
output.writeUTF("QUIT pentru a va deconecta de la server");
while(ok == true)
{
line = input.readUTF();
switch(line)
{
case "LIST":
{
Vector<String> users = getUserList();
output.writeUTF("Lista user-ilor este:");
for(String c : users)
{
output.writeUTF(c);
}
break;
}
case "MSG":
{
output.writeUTF("Introduceti numele persoanei careia doriti sa-i trimiteti mesajul");
line = input.readUTF();
if(validUserName(line) == true)
{
writeError("Numele persoanei nu exista");
break;
}
else
{
if(name.equals(line))
{
writeError("Selectati alt user");
break;
}
else
{
output.writeUTF("Introduceti mesajul pe care il aveti de transmis");
String message = input.readUTF();
if((validUserName(line) == false) && !(line.equals(name)))
{
twoUsersBroadcast(name,line,message);
}
break;
}
}
}
case "BCAST":
{
line = input.readUTF();
broadcast(name,line);
break;
}
case "NICK":
{
output.writeUTF("Va rugam sa va introduceti numele dorit");
line = input.readUTF();
if(validUserName(line))
{
changeUserName(name,line);
}
else
{
writeError("Invalid username");
}
break;
}
case "QUIT":
{
output.writeUTF("Intrerupem conexiunea .... Pa!");
clients.remove(this);
users.remove(name);
ok = true;
break;
}
default:
{
writeError("Comanda incorecta");
}
}
}
}
catch(Exception e)
{
System.err.println(e.getMessage());
clients.remove(this);
users.remove(name);
}
}
}
}
答案 0 :(得分：0)
这一行之后：
Socket cs = new Socket( scanner.next(), scanner.nextInt() );
添加：
scanner.nextLine();
所以在一起，它看起来像：
Socket cs = new Socket( scanner.next(), scanner.nextInt() );
scanner.nextLine();
这样做是为了吞下未由next()或nextInt()处理的悬空行尾（EOL）令牌，实际上只由nextLine()处理。