Java ServerSocket - problem with Clients synchronization

Question

I am writing a multiplayer quiz application for two players (Clients) and I would like to have a mechanism which would allow only one player (the fastest to type the answer) to answer the question. So if for example: Player1 answers the question, Player2 immedietaly is moved to next question (just like Player1).

How can I make Server notify Client thread that the other Client answered the Question?

Client:

package com.company;

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

public class Client
{
    private static Scanner scanner;

    private static BufferedReader serverReader;

    private static PrintWriter serverWriter;

    public static void main(String[] args)
    {
        try
        {
            connect();
        }
        catch ( Exception e )
        {
            e.printStackTrace();
        }
    }

    public static void connect()
    {
        try( Socket clientSocket = new Socket( "localhost", 1236 ) )
        {
            scanner = new Scanner( System.in );
            serverReader = new BufferedReader( new InputStreamReader( clientSocket.getInputStream() ) );
            serverWriter = new PrintWriter( clientSocket.getOutputStream(), true );
            String serverResponse;
            while( ( serverResponse = serverReader.readLine() ) != null )
            {
                System.out.println( "[SERVER] - " + serverResponse );
                break;
            }
            for( int i = 0; i < 3; i++ )
            {
                System.out.println( "[SERVER] - " + serverReader.readLine() );
                System.out.print( "Your answer: " );
                String answer = scanner.nextLine();
                serverWriter.println( answer );
            }
        }
        catch ( IOException e )
        {
            e.printStackTrace();
        }
    }
}

Server:

package com.company;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class Server
{
    private static final ArrayList< PrintWriter > writers = new ArrayList<>();

    private static final ArrayList< BufferedReader > readers = new ArrayList<>();

    private static final HashMap< String, Socket > players = new HashMap<>();

    private static final ArrayList< Question > questions = new ArrayList<>();

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

    public static void startServer()
    {
        questions.addAll( List.of( new Question( "2 + 2 = 4", "YES" ),
                new Question( "2 + 2 = 6", "NO" ), new Question( "2 + 2 = 8", "NO" ) ) );
        int i = 0;
        try( ServerSocket serverSocket = new ServerSocket( 1236 ) )
        {
            while( i < 2 )
            {
                Socket socket = serverSocket.accept();
                players.put( "Player" + ( i +  1 ), socket );
                System.out.println( "[CLIENT] - " + "Player" + ( i + 1 ) + " has joined the server." );

                i++;
                BufferedReader clientReader = new BufferedReader( new InputStreamReader( socket.getInputStream() ) );
                PrintWriter clientWriter = new PrintWriter( socket.getOutputStream(), true );
                writers.add( clientWriter );
                readers.add( clientReader );
            }
            writers.forEach( writer -> writer.println( "Game will start in 5 seconds" ) );
            try
            {
                Thread.sleep( 5000 );
            }
            catch ( InterruptedException e )
            {
                e.printStackTrace();
            }
            for( Question question : questions )
            {
                writers.forEach( writer -> writer.println( question.getContent() ) );

                // what to do now???
                while( true )
                {
                    // so server doesnt stop
                }
            }
        }
        catch ( IOException e )
        {
            e.printStackTrace();
        }
    }
}

Question:

package com.company;

public class Question
{
    private final String content;

    private final String  correctAnswer;

    public Question( String aContent, String aCorrectAnswer )
    {
        content = aContent;
        correctAnswer = aCorrectAnswer;
    }

    public String getContent()
    {
        return content;
    }

    public String getCorrectAnswer()
    {
        return correctAnswer;
    }
}