Java TCP if語句

對於此應用程序，用戶發出一條命令並且服務器發送一個回覆。 if聲明由於某種原因而不起作用，並且對於其運行的每個輸入sentance = "Unknown Command" + '\n';。我想知道我做錯了什麼。Java TCP if語句

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

// SERVER 

class StartingPoint { 
    public static void main(String argv[]) throws Exception{ 

     double srvversion = 0.1; 
     double cliversion = 0.1; 

     String clientSentence; 
     String sentance = null; 
     String capitalizedSentence; 

     //Commands cmds = new Commands(); 

     ServerSocket welcomeSocket = new ServerSocket(6789); 
     System.out.println("Server Started"); 
     while (true) { 

      Socket connectionSocket = welcomeSocket.accept(); 
      BufferedReader inFromClient = new BufferedReader(
        new InputStreamReader(connectionSocket.getInputStream())); 
      DataOutputStream outToClient = new DataOutputStream(
        connectionSocket.getOutputStream()); 
      clientSentence = inFromClient.readLine(); 
      System.out.println("Received: " + clientSentence); 
      capitalizedSentence = clientSentence.toUpperCase(); 


      if(capitalizedSentence == "VERSION"){ 
       sentance = "Current Server Version: " + srvversion 
         + " | Current Client Version: " + cliversion + '\n'; 
      }else{ 
       sentance = "Unknown Command" + '\n'; 
      } 

      outToClient.writeBytes(sentance); 
      System.out.println("Sent: " + sentance); 
     } 
    } 
     }

來源

2011-12-29 Sock

你或許應該打印出什麼無效的命令_was_ - - 至少在試圖調試這個時候...... – sarnold 2011-12-29 05:43:12

您應該使用.equals（）方法比較字符串，而不是使用==。

變化

if(capitalizedSentence == "VERSION"){

到

if(capitalizedSentence.equals("VERSION")){

來源

2011-12-29 05:42:16 Manish

爲此而歡呼 – Sock 2011-12-29 05:59:37

比較字符串，你必須使用.equals()方法如下：

String str1; 
String str2; 

if (str1.equals(str2)) // do something 
else //do something else

來源

2011-12-29 05:42:53

Java TCP if語句

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