客戶端 - 服務器（從服務器到客戶端的文件傳輸）

Question

這是一個文件傳輸程序。客戶端發送文件名，然後如果該文件存在，則服務器將文件發送給客戶端。當文件不存在時，我希望服務器發送「文件不存在」之類的消息。

public static void main(String[] args) { 

    Socket socket = null; 
String server = "localhost"; 
    DataInputStream in; 
BufferedReader input; 
    PrintWriter output; 
int port = 1500; 

    File file; 
    file = new File("G:\\o.txt"); 
    try{ 
    if(!file.exists()) 
     file.createNewFile(); 
    } 
    catch(Exception e){ 
     System.out.println("error1"); 
    } 


try { 
    socket = new Socket(server, port); 
    System.out.println("Connected To Server With This Ip" + socket.getInetAddress() + " On This Port :" + socket.getPort()); 
} 
catch (UnknownHostException e) { 
    System.out.println(e); 

} 
catch (IOException e) { 
    System.out.println(e); 

} 


try { 
    output = new PrintWriter(socket.getOutputStream(),true); 
    input = new BufferedReader(new InputStreamReader(socket.getInputStream())); 


    String filewanted="H:\\\\o.txt"; 
    output.println(filewanted); 

    in=new DataInputStream(socket.getInputStream()); 


     int flag=0; 
     FileWriter fw = new FileWriter(file); 
     BufferedWriter bw = new BufferedWriter(fw); 
     int b=in.readInt(); 
     for(int i=1;i<=b;i++) 
      { 
       String message= input.readLine(); 
       bw.write(message); 
       bw.newLine(); 

       flag++; 
      } 
       bw.close(); 
       if(flag!=0){ 
        System.out.println("File Was Transferd Successfuly!"); 


       } 


     } 

catch (IOException e) { 
    System.out.println(e); 
} 

try { 
    socket.close(); 
} 
catch (IOException e) { 
    System.out.println(e); 
} 
} 



//server 


public static void main(String[] args) { 

ServerSocket serversocket; 
    DataOutputStream out; 
PrintWriter output; 
    BufferedReader input; 
    String linesent; 
    int lines = 0; 
    int port=1500; 

try { 

    serversocket = new ServerSocket(port); 
    System.out.println("Server Waiting For Client On Port " + serversocket.getLocalPort()+"..."); 


    while(true) { 
    Socket socket= serversocket.accept(); 
    System.out.println("Connection Accepted With This Ip: " +socket.getInetAddress() +" On This Port :" + socket.getPort()); 
    input = new BufferedReader(new InputStreamReader(socket.getInputStream())); 
      output = new PrintWriter(socket.getOutputStream(),true); 



      String f=input.readLine(); 
      File file; 
      file = new File(f); 


      BufferedReader reader = new BufferedReader(new FileReader(f)); 
      if(file.exists()) 
      { 
       while (reader.readLine() != null) 
        lines++; 
       reader.close(); 
       out=new DataOutputStream(socket.getOutputStream()); 
       out.writeInt(lines); 
       Scanner scanner=new Scanner(file); 
       while(scanner.hasNext()) 
       { 
        linesent=scanner.nextLine(); 
        output.println(linesent); 
       }   


      } 
      else { 

       throw new FileNotFoundException(f); 


      } 

    try { 
     socket.close(); 
     System.out.println("Connection closed by client."); 
    } 
    catch (IOException e) { 
     System.out.println(e); 
    } 

    } 
    } 



catch (IOException e) { 
    System.out.println(e); 
} 


} 

Answer 1

那麼你爲什麼不只是更換：

throw new FileNotFoundException(f); 

通過

output.println("file not exist");