Java：Simple If語句沒有執行

Question

好的，所以這已經讓我很煩了幾個小時。我不明白爲什麼不是這個if語句沒有執行。這是我的完整代碼。有兩類，'客戶'是主類，另一類是連接器類。

package com.app.client; 

import java.net.ServerSocket; 
import java.sql.SQLException; 

public class Client{ 

    private int IntervalForDatabase=60000; 
    private int IntervalForIPCheck=180000; 
    private boolean AppRunning=true; 
    public boolean ConnectionSuccess=false; 
    private Connector ConnectionTools = new Connector(); 

    public static void main(String args[]){ 
     Thread thread = new Thread(new Runnable(){ 
      public void run(){ 
       Client client = new Client(); 
      } 
     }); 
     thread.start(); 
    } 

    Client(){ 
     /* Check For Current Instance Of Program */ 
     try{ 
      ServerSocket ApplicationSocket = new ServerSocket(6251); 
     }catch(Exception e){ 
      System.exit(0); 
     } 

     Thread Network = new Thread(new Runnable(){ 
      public void run(){ 
       while(!ConnectionSuccess){ 
        try{ 
         ConnectionTools.ConnectToDatabaseServer(); 
         ConnectionSuccess=true; 
         System.out.println("bein a bit"); 
        }catch(Exception e){ 

        } 
       } 
      } 
     }); 
     Network.start(); 

     Thread LiveConnectionCheck = new Thread(new Runnable(){ 
      public void run(){ 
       while(AppRunning){ 
        if(ConnectionSuccess){ 
        /* THIS IF STATEMENT IS NOT EXECUTING */ 
         try { 
          System.out.println("tester"); 
          Thread.sleep(IntervalForIPCheck); 
         } catch (Exception e) { 
          e.printStackTrace(); 
         } 
        } 
       } 
      }   
     }); 

     LiveConnectionCheck.start(); 
    } 
} 

連接器類：

package com.app.client; 

import java.net.Socket; 
import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.PreparedStatement; 
import java.sql.ResultSet; 
import java.sql.SQLException; 

public class Connector { 
    public boolean DatabaseConnection=false; 
    Socket ClientSocket; 
    private String DatabaseHost="localhost"; 
    private String DatabaseUsername="root"; 
    private String DatabasePassword = ""; 
    private String DatabaseName = "spyware"; 
    private String TableName="activespywares"; 
    public String CurrentServerIP = ""; 
    private Connection MYSQLConnection = null; 
    public ResultSet result; 

    public void ConnectToDatabaseServer(){ 
     try{ 
      Class.forName("com.mysql.jdbc.Driver").newInstance(); 
      MYSQLConnection = DriverManager.getConnection("jdbc:mysql://"+DatabaseHost+"/"+DatabaseName,DatabaseUsername,DatabasePassword); 
      DatabaseConnection=true;    
      System.out.println("connected"); 
     }catch(Exception e){ 
      System.out.println(e); 
      DatabaseConnection=false; 
      return; 
     } 
    } 

    public String ObtainServerIP() throws SQLException{ 
     String text = "";   
     try{ 
      System.out.println("we've made it till here"); 
      PreparedStatement state = MYSQLConnection.prepareStatement("SELECT * FROM `activespywares`"); 
      result = state.executeQuery(); 
      System.out.println("we've made it till here"); 
      if(result.next()){ 
       result.next(); 
       text = result.getString("InternetProtocol"); 
      } 
      return text; 
     }catch(Exception e){ 
      System.out.println(e); 
      text=e+""; 
     } 
     return text; 
    } 
} 

我檢查的一切。我不知道這裏有什麼問題。 if語句位於「客戶」類中。連接器類只是讓你知道它不會導致問題。

Answer 1

使connectionSuccess或者volatile或更改爲AtomicBoolean（並標記爲final）。問題在於你正在將變量設置爲一個Thread，但是從另一個讀取它。

Answer 2

 if(result.next()){ 
      result.next(); 

沒道理。當你在這裏調用result.next（）兩次時，你會拋出第一個結果。

Answer 3

爲了您的例外，我會建議的

e.printStackTace() 

使用中的東西打破你的程序的情況。如果執行

//...your code 
    if(result.next()){ 
     result.next(); 
    //...your code 

現在

它扔掉你的第一個結果，並提出你與你的第二個結果。我會建議你使用

//...your code 
    while(result.next()){ 

    //...your code 

通過您的記錄滾動，請你