java解决多线程服务器网络编程问题

public class Client {
  public static void main(String[] args) throws Exception {
    Socket client = new Socket("localhost",8888);
    // 用户输入
    Scanner keyScan = new Scanner(System.in);
    // 接收服务器的信息
    Scanner netScan = new Scanner(client.getInputStream());
    netScan.useDelimiter("\n");
    PrintStream netOut = new PrintStream(client.getOutputStream());
    boolean flag = true;
    while(flag) {
      System.out.println("请输入要发送的信息：");
      String str= null;
      if(keyScan.hasNext()) {
        str = keyScan.next().trim();
        // 发送到服务器
        netOut.println(str);
        // 服务器端有回应
        if(netScan.hasNext()) {
          System.out.println(netScan.next());
        }
      }
      if("byebye".equals(str)) {
        flag = false;
        break;
      }
    }
    keyScan.close();
    netScan.close();
    client.close();
  }
}

public class SingleThreadServer {
  public static void main(String[] args) throws IOException {
    ServerSocket server = new ServerSocket(8888);
    // 等待连接
    Socket client = server.accept();
    // 接受客户端的输入
    Scanner scan = new Scanner(client.getInputStream());
    scan.useDelimiter("\n");
    // 对客户端的回应
    PrintStream out = new PrintStream(client.getOutputStream());
    boolean flag = true;
    while(flag) {
      // pandaUN客户达UN是否是有数据
      if(scan.hasNext()) {
        // 防止有空格出现
        String str = scan.next().trim();
        if("byebye".equals(str)) {
          out.println("byebye!!!");
          // 退出循环
          flag = false;
          break;
        }
        // 做出回应
        out.println("Server："+str);
      }
    }
    out.close();
    scan.close();
    server.close();
  }
}

public class MultiThreadServer {
  public static class MyThread implements Runnable{
    private Socket client;
    public MyThread(Socket client) {
      this.client = client;
    }
    @Override
    public void run() {
      try {
      // 接受客户端的输入
      Scanner scan = new Scanner(client.getInputStream());
      scan.useDelimiter("\n");
      // 对客户端的回应
      PrintStream out = new PrintStream(client.getOutputStream());
      boolean flag = true;
      while(flag) {
        // pandaUN客户达UN是否是有数据
        if(scan.hasNext()) {
          // 防止有空格出现
          String str = scan.next().trim();
          if("byebye".equals(str)) {
            out.println("byebye!!!");
            // 退出循环
            flag = false;
            break;
          }
          // 做出回应
          out.println("Server："+str);
        }
      }
      out.close();
      scan.close();
      }catch(Exception e) {
        e.printStackTrace();
      }
    }
  }
  public static void main(String[] args) throws IOException {
    ServerSocket server = new ServerSocket(8888);
    // 无限的接受客户端的请求
    boolean flag = true;
    while(flag) {
      // 等待连接
      Socket client = server.accept();
      // 开启线程  多线程服务器
      new Thread(new MyThread(client)).start();
    }
    server.close();
  }
}