写一段Java代码实现：修改 Knock Knock 游戏项目设计，为游戏增加计分机制。例如用 ConcurrentHashMap 实时保存所有客户机得分，并将最高得分的玩家姓名返 回给客户机

以下是一段Java代码实现，用于修改 Knock Knock 游戏项目设计，增加计分机制：

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.concurrent.ConcurrentHashMap;

public class KnockKnockServer {
    
    private static final int PORT = 4444;
    private static ConcurrentHashMap<String, Integer> scores = new ConcurrentHashMap<String, Integer>();

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(PORT);
        System.out.println("Server started");
        
        while (true) {
            Socket clientSocket = serverSocket.accept();
            System.out.println("Client connected");
            
            PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            
            String inputLine, outputLine;
            
            // Initialize the conversation
            KnockKnockProtocol kkp = new KnockKnockProtocol();
            outputLine = kkp.processInput(null);
            out.println(outputLine);
            
            while ((inputLine = in.readLine()) != null) {
                outputLine = kkp.processInput(inputLine);
                out.println(outputLine);
                
                // Add score to ConcurrentHashMap if guess is correct
                if (kkp.guessCorrect()) {
                    String playerName = kkp.getPlayerName();
                    if (scores.containsKey(playerName)) {
                        int score = scores.get(playerName) + 1;
                        scores.replace(playerName, score);
                    } else {
                        scores.put(playerName, 1);
                    }
                }
                
                // Get highest score and return to client
                if (inputLine.equals("getscore")) {
                    String highestScorer = "";
                    int highestScore = 0;
                    
                    for (String playerName : scores.keySet()) {
                        if (scores.get(playerName) > highestScore) {
                            highestScorer = playerName;
                            highestScore = scores.get(playerName);
                        }
                    }
                    
                    out.println("Highest scorer: " + highestScorer);
                }
                
                if (outputLine.equals("Bye.")) {
                    break;
                }
            }
            
            out.close();
            in.close();
            clientSocket.close();
        }
    }
}

在以上代码中，我们通过使用 ConcurrentHashMap 来实现对所有客户端得分的实时保存，并在客户端猜谜语正确时更新对应客户端的得分。在客户端发送获取最高得分的请求时，遍历 ConcurrentHashMap，获取最高得分的客户端名称，并将其返回给客户端。