PrintWriter在构造函数外部不起作用（聊天室程序）

Question

我对此代码有疑问：

public ServerClient(Socket s, int id, String name)throws IOException{
    this.name = name;
    this.id = id;
    this.mysocket = s;
    this.out = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
    this.in = new BufferedReader(new InputStreamReader(s.getInputStream()));
    IgnoreList = new ArrayList<ServerClient>();
}

private void print(String s){
    //System.out.println(s);
    this.out.print(s);
}

问题是，当我在构造函数中编写'this.out.print（“SomeString”）'并执行程序时，PrintWriter会完成它的工作并写入OutputStream。当我在下面的方法中完全相同时，它什么也没打印出来。我在print方法中检查过String，它不只是“”。 现在我不知道为什么会这样......

以下是该程序的完整代码，一个连接客户端的聊天室：

import java.net.*;
import java.io.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;

public class Server {

private String name;
private ConcurrentHashMap<Integer,ServerClient> chm;
private ServerSocket socket;
private int ClientID;

public Server(String name,int portnr) throws IOException{
    this.name = name;
    this.socket = new ServerSocket(portnr);
    this.ClientID =0;
    chm = new ConcurrentHashMap<Integer,ServerClient>();
}    

public static void main(String[] args){

    try{
        new Server("Chatroom", 6000).work();
    }catch(IOException e){
        System.out.println("IO Exception: "+e.getMessage());
    }
}

public void work()throws IOException{

    Runtime.getRuntime().addShutdownHook(new Thread(){

        @Override
        public void run() {
            try{
               if(socket != null){
                   socket.close();
               }
            }catch(IOException e){
                System.out.println("IO Exception: "+e.getMessage());
            }
        }    
    });

    while(true){
        Socket client = socket.accept();

        int ClientID = this.ClientID++;   
        ServerClient servant = new ServerClient(client,ClientID,"Client "+ClientID);

        this.chm.put(ClientID,servant);
        Thread t = new Thread(servant);
        t.start();
        servant.sendPersonalMessage("Beigetreten");
    }     
}

private void writeMessage(String s, ServerClient client){
    String message = String.format("[%s]: %s",client.name,s);

    for(ServerClient sc : this.chm.values()){
        if(!sc.IgnoreList.contains(client)){    
            sc.print(message); 
        }
    }
 }

class ServerClient implements Runnable{

private ArrayList<ServerClient> IgnoreList;
private String name;
private int id;
private Socket mysocket;
private PrintWriter out;
private BufferedReader in;

public ServerClient(Socket s, int id, String name)throws IOException{
    this.name = name;
    this.id = id;
    this.mysocket = s;
    this.out = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
    this.in = new BufferedReader(new InputStreamReader(s.getInputStream()));
    IgnoreList = new ArrayList<ServerClient>();
}

private void print(String s){
    //System.out.println(s);
    this.out.print(s);
}

@Override
public void run(){
    boolean exit = false;
    writeMessage("Entering Chatroom",this);

    try{

        String read;
        while(!exit && (read=in.readLine()) != null){

           String[] command = read.split(" ");   

           switch (command[0]){
               case "CNAME" : 
                   if(command.length != 2){
                       sendPersonalMessage("Korrekte Eingabe bitte: CNAME [neuer username]");
                   }else this.name = command[1];
               break;
               case "IGNORE" :     
                   if(command.length != 2){
                       sendPersonalMessage("Korrekte Eingabe bitte: IGNORE [zu ignorierender username]");
                   }else{
                       ServerClient ignore = null;
                       ServerClient actual = this;
                       Iterator<ServerClient> candidates = chm.values().iterator();

                       while(ignore == null && candidates.hasNext()){
                           actual = candidates.next();
                           if(actual.name.matches(command[1])){
                               ignore = actual;
                               IgnoreList.add(actual);
                           }
                       }  
                   } 
               break;
               case "LEAVE" : 
                   try{
                       closeConnection();

                   }catch(IOException e){
                       System.out.println("IO Exception: "+e.getMessage());
                       exit = true;
                   }
               break;
               default : {

                   writeMessage(read,this);

               }
               break;    
           }
        }

        }catch(IOException e){
           System.out.println("IO Exception: "+e.getMessage());
        }finally{
            exit = true;
            try{
                this.closeConnection();
           }catch(IOException e){
               System.out.println("IO Exception: "+e.getMessage());
           }
         }    
    }

public void sendPersonalMessage(String s){
    this.out.println(s);
    this.out.flush();
}

private void closeConnection() throws IOException{
    if(!mysocket.isClosed()){
        chm.remove(this.id);
        mysocket.close();
        in.close();
        out.close();
        writeMessage(name+" has left the Chatroom",this);
    }
}

@Override
  public boolean equals(Object obj) {
     if (this == obj)
        return true;
     if (obj == null)
        return false;
     if (getClass() != obj.getClass())
        return false;
     ServerClient other = (ServerClient) obj;
     if (!getOuterType().equals(other.getOuterType()))
        return false;
     if (id != other.id)
        return false;
     return true;
  }

private Server getOuterType(){
    return Server.this;
}

@Override
  public int hashCode() {
     final int prime = 31;
     int result = 1;
     result = prime * result + getOuterType().hashCode();
     result = prime * result + id;
     return result;
  }
}
}