java - 套接字 () - 错误 : variable client might not have been initialized

Question

我写了一个很简单的客户端程序

import java.net.*;
import java.io.*;

public class GreetingClient
{
   private Socket cSocket;

   public GreetingClient() throws IOException
   {
        String serverName = "127.0.0.1";
        int port = 5063;
        cSocket = new Socket(serverName,port);
   }


   public static void main(String [] args)
   {
      GreetingClient client;
      try
      {
          client = new GreetingClient();
      }
      catch(IOException e)
      {
          e.printStackTrace();
      }

      while (true)
      {
        try
        {
                InputStream inFromServer = client.cSocket.getInputStream();
                DataInputStream in = new DataInputStream(inFromServer);

                System.out.println("Server says " + in.readUTF());
        }
        catch(IOException e)
        {
                e.printStackTrace();
        }
      }
   }
}

当我编译这个程序时，我得到了这样的错误

GreetingClient.java:33: error: variable client might not have been initialized
            InputStream inFromServer = client.cSocket.getInputStream();
                                       ^
1 error

这个错误是什么意思？如果 new Socket() 调用失败(例如，如果打开了太多套接字)那么这是否意味着我不能在代码中使用它？我如何处理情况像这样。？

Answer 1

try
{
    client = new GreetingClient();  // Sets client OR throws an exception
}
catch(IOException e)
{
    e.printStackTrace();            // If exception print it
                                    // and continue happily with `client` unset 
}

稍后您正在使用；

// Use `client`, whether set or not.
InputStream inFromServer = client.cSocket.getInputStream();

要修复它，要么在声明它的地方将 client 设置为 null(这可能会在以后使用时导致 nullref 异常)，要么在打印异常后不要“盲目地”继续(例如, 打印并返回)。