这段代码工作，因为while循环工作，但当我删除UserThread类中的此注解时

/*  for(Entry<Integer,List<String>> m: server.lista.entrySet()) {
                        if(c==m.getKey()) {
                        m.getValue().add(name);
                        //toUser.println("");
                    }
                    }
                    for(Entry<Integer,List<String>> m: server.lista.entrySet()) {
                        System.out.println(m.getKey()+" "+m.getValue());
                    }*/

客户端没有收到下一个问题。循环在这里停止。我能知道为什么会这样吗？代码在下面。

package quiz;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
import java.util.List;

public class Server {
public static int test_port=12321;
private int port;
private int counter=0;
private int length;
BufferedReader fromDocument;
public int numberOfClients=0;
public static HashMap<Integer,List<String>> lista=new HashMap<Integer,List<String>>();

    public static void main(String[] args) {
        //int l=lengthHashMap();
        
        // TODO Auto-generated method stub
Server server=new Server(test_port);
int l=server.lengthHashMap();
for(int i=1;i<l;i++) {
    lista.put(i, null);
}
server.execute();
    }
private void execute() {
        // TODO Auto-generated method stub
        try(ServerSocket server=new ServerSocket(port)){
            
            while(true) {
                Socket client=server.accept();
                System.out.println("Client connected");
                numberOfClients++;
                UserThread user=new UserThread(client,this);
                user.start();
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
public Server(int port) {
    this.port=port;
}
private int lengthHashMap() {
    try {
        fromDocument=new BufferedReader(new InputStreamReader(new FileInputStream("Questions.txt")));
        String line=fromDocument.readLine();
        while(line!=null) {
            counter++;
            line=fromDocument.readLine();
        }
        length=counter/5;
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }finally {
        return length;
    }

}
}

package quiz;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.List;
import java.util.Map.Entry;

public class UserThread extends Thread{
    Socket client;
    Server server;
    BufferedReader fromDocument;
    private int counter=0;
    PrintWriter toUser;
    BufferedReader fromUser;
    String correctAnswer;
    String answer;
    String correctedLine;
    private int c=0;
    public UserThread(Socket client, Server server) {
        // TODO Auto-generated constructor stub
        this.client=client;
        this.server=server;
    }
public void run() {
    try {
        
        while(server.numberOfClients<2) {
            System.out.println();
        }
        
        fromDocument=new BufferedReader(new InputStreamReader(new FileInputStream("Questions.txt")));
        fromUser=new BufferedReader(new InputStreamReader(this.client.getInputStream()));
        toUser=new PrintWriter(this.client.getOutputStream(),true);
        String line=fromDocument.readLine();
        String name=fromUser.readLine();
        System.out.println(name);
                while(!line.equalsIgnoreCase("")) {
                    while(counter<5) {
                    counter++;
                    if(line.endsWith("*")){
                        correctAnswer=line.substring(0,1);
                        correctedLine=line.substring(0,line.length()-1);
                        toUser.println(correctedLine);
                    }
                    else {
                        toUser.println(line);   
                    }
                    line=fromDocument.readLine();

                }
                    c++;
                    counter=0;
                    answer=fromUser.readLine();
 
                        
                    
                    if(answer.equalsIgnoreCase(correctAnswer))
                        toUser.println("Correct!");
                    else
                        toUser.println("Incorrect!");
                    //line=fromUser.readLine();
                    //System.out.println(line);
                /*  for(Entry<Integer,List<String>> m: server.lista.entrySet()) {
                        if(c==m.getKey()) {
                        m.getValue().add(name);
                        //toUser.println("");
                    }
                    }
                    for(Entry<Integer,List<String>> m: server.lista.entrySet()) {
                        System.out.println(m.getKey()+" "+m.getValue());
                    }*/
                    
                    
    }
    } catch (Exception e) {
        // TODO: handle exception
    }
    
}
}

package quiz;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Client {
private String name;
private String hostname;
private int port;
String answer;
BufferedReader fromServer;
PrintWriter toServer;
    public static void main(String[] args) {
        // TODO Auto-generated method stub
Client client=new Client("localhost",Server.test_port);
client.execute();
    }
private void execute() {
    try {
        this.setName();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
        // TODO Auto-generated method stub
        try(Socket client=new Socket(this.hostname,this.port)){
            
            fromServer=new BufferedReader(new InputStreamReader(client.getInputStream()));
            toServer=new PrintWriter(client.getOutputStream(),true);
            System.out.println("Connected to server: "+this.hostname);
            toServer.println(this.name);
            String line;
            while(true) {
                for(int i=0;i<5;i++) {
                    line=fromServer.readLine();
                    System.out.println(line);
                }
                System.out.println("Your answer is: ");
                Scanner sc=new Scanner(System.in);
                answer=sc.nextLine();
                toServer.println(answer);
                line=fromServer.readLine();
                System.out.println(line);
                //toServer.println("Next");
                //for(int j=0;j<5;j++)
                //  line=fromServer.readLine();
            }
            
        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
public Client(String hostname,int port) {
    this.hostname=hostname;
    this.port=port;
}
private void setName() throws IOException {
    // TODO Auto-generated method stub
    System.out.println("Enter your name: ");
    BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
    this.name=stdin.readLine();
}
}

文件Questions.txt的内容：

1. Ko je režirao film Kad jaganjci utihnu?
A) Robert Zemekis
B) Frenk Darabont
C) Džonatan Dem *
D) Rob Rajner
2. U kojoj državi se nalazi jezero Retba? 
A) U Senegalu * 
B) U Ugandi
C) U Gani 
D) U Nigeriji 
3. Kako se zove drugi studijski album grupe Zabranjeno pušenje?
A) Dok čekaš sabah sa šejtanom * 
B) Male priče o veliko ljubavi 
C) Pozdrav iz zemlje Safari 
D) Fildžan viška 
4. Pod kojom zastavom nastupa teniser Alehandro Davidovič Fokina? 
A) Pod zastavom Argentine 
B) Pod zastavom Rusije 
C) Pod zastavom Velike Britanije 
D) Pod zastavom Španije *