Java Run Order

**collin389** · 11-24-2009, 03:47 AM

I might not be the best java programmer but I thought java waited until the expression ran until it went to the next one, unless you're useing threads.
In my program I run this code:

Java Code:

chatDoc.insertString(chatDoc.getLength(), "---Attemping to Connect...---\n", alertStyle);
System.out.println("---Attemping to Connect...---");
Thread.sleep(1000);

chatDoc is a Styled Document.

I thought java would first display the text in the Document, then println() and then sleep for 1 sec. However, first it runs println(), then sleeps for a sec, and then displays the text in the Doc. It is very important to my program that the code runs in order. Any ideas for why it doesn't run correctly?

**Fubarable** · 11-24-2009, 04:15 AM

Is this a Swing program?

**collin389** · 11-24-2009, 04:22 AM

Yes, swingworker required?

**Fubarable** · 11-24-2009, 04:40 AM

Yes. If you call sleep on a Swing program, you put the EDT to sleep and no component painting (including text updates to text components) gets done. As you've already guessed, use a SwingWorker, and never call Thread.sleep on the EDT.

**collin389** · 11-24-2009, 04:51 AM

Thanks, but that isnt the real problem, I just used Thread.sleep to find out the orderof output. My real program runs:

Java Code:

clientOS.write(username, 0, username.length());
clientOS.newLine();
clientOS.flush();

clientOS is the client's output stream to a socket. The server is running:

Java Code:

String clientUser;
            while ((clientUser = serverIS.readLine()) != null)
            {
               System.out.println("" + clientUser);
               System.out.println("" + clientSocket.getInetAddress().getHostAddress());
               break;
            }
            
            int accept = JOptionPane.showConfirmDialog( null, "Accept Connection Request from " + clientUser + " at: " + clientSocket.getInetAddress().getHostAddress() + "?", "Connection Request", JOptionPane.YES_NO_OPTION);

serverIS = server input stream
Please note that the server code is running on a seperate Thread.

In my test runs, I an connecting to myself (127.0.0.1) and I want the client to send the server it's username and the server will see this and be asked if they want to accept the connection. In the meantime, the client should see "attempting to connect...". Howver, when I test it, it doesnt display the attemtping to connect, and when the JDialog pops up there is nothing in the middle, just the frame, and then the program hangs. If you need I can post more code.

**Fubarable** · 11-24-2009, 05:08 AM

It still smells like a threading issue. Yeah, please post more code if you can.

**collin389** · 11-24-2009, 05:14 AM

Java Code:

Thread waitForConnection = 
          new Thread() {
             public void run() {
               try {
                  echoServer = new ServerSocket(7890);
                  clientSocket = echoServer.accept();
                  handleClient();
                                    
               } 
                   catch (IOException e) { handleException(e); waitForConnection.run(); }
                              
            } 
         };
         
        
                           
       public void handleClient()
      {
         try
         {
                     			 
            
            serverIS = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            serverOS = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
            String clientUser;
            while ((clientUser = serverIS.readLine()) != null)
            {
               System.out.println("" + clientUser);
               System.out.println("" + clientSocket.getInetAddress().getHostAddress());
               break;
            }
            
            int accept = JOptionPane.showConfirmDialog( null, "Accept Connection Request from " + clientUser + " at: " + clientSocket.getInetAddress().getHostAddress() + "?", "Connection Request", JOptionPane.YES_NO_OPTION);
            if (accept == 1){
               
               connected = false;
               serverOS.write("no", 0, 2);
               serverOS.newLine();
               serverOS.flush();
               serverIS.close();
               serverOS.close();
               clientSocket.close();
               
               return; }
            serverOS.write("yes", 0, 3);
            serverOS.newLine();
            serverOS.flush();
            
            while((input = serverIS.readLine()) != null)
            {
               chatDoc.insertString(chatDoc.getLength(), input + "\n", clientStyle);
               scrollPaneToBottom();
            }
         }
             catch (Exception e) {
               handleException(e);
            }
                     
      }
   
   
   
   
   
       public void connect()
      {
         connected = false;
         int i=0;
         String check;
         try
         {
            hostname = JOptionPane.showInputDialog(null, "Connect to Host IP Adress as " + username + " :");
            chatSocket = new Socket(hostname, 7890);
            clientIS = new BufferedReader(new InputStreamReader(chatSocket.getInputStream()));
            clientOS = new BufferedWriter(new OutputStreamWriter(chatSocket.getOutputStream()));
            chatDoc.insertString(chatDoc.getLength(), "---Attemping to Connect...---\n", alertStyle);
            System.out.println("---Attemping to Connect...---");
            clientOS.write(username, 0, username.length());
            clientOS.newLine();
            clientOS.flush();
            while(((check = clientIS.readLine()) != null) && !connected)
            {
               if (check == "yes")
               {
                  connected = true;
                  chatDoc.insertString(chatDoc.getLength(), "---Sucessfully Connected to " + hostname + "---\n", alertStyle);
               } 
               else {
                  chatDoc.insertString(chatDoc.getLength(), "---Failed to Connect to " + hostname + "---\n", alertStyle);
               }
               if ( i == 5000)
               {
                  chatDoc.insertString(chatDoc.getLength(), "---Failed to Connect to " + hostname + ", Server would not respond(timeout)---\n", alertStyle);
                  break;
               }
               i++;
            }
            while((input = serverIS.readLine()) != null)
            {
               chatDoc.insertString(chatDoc.getLength(), input + "\n", clientStyle);
               scrollPaneToBottom();
            }
         
            
             
         } 
             catch (Exception e) {
               handleException(e);
            }
      
      }

Note: thread waitForConnection is run in main(), and connect() is run from the Swing actionPreformed() with the hostIP as 127.0.0.1 (local)

**Fubarable** · 11-24-2009, 05:34 AM

connect() is run from the Swing actionPreformed()

Meaning that connect() will be run on the EDT including Thread.sleep.

And this code:

Java Code:

            while((input = serverIS.readLine()) != null)
            {
               chatDoc.insertString(chatDoc.getLength(), input + "\n", clientStyle);
               scrollPaneToBottom();
            }

suggests that you're trying to manipulate Swing directly from within a background thread.

Yeah you have some serious thread issues I believe. Also, you may want to fix these boys:

Java Code:

if (check == "yes")

If you need more help, you may wish to learn about, create and post a Short, Self Contained, Correct (Compilable), Example or SSCCE for short. The link will show you how to do this. You will need to substitute all your connections and whatnots with Thread.sleep to emulate server-client connections or anything else that takes a bit of time to perform.

**collin389** · 11-24-2009, 05:38 AM

Sorry, the Thread.sleep() shouldn't have been there, and whats wrong with if (check == "yes")

**collin389** · 11-24-2009, 05:43 AM

I think I know why, Because, when I call JDialog(), it uses EDT which is being used by connect, even though it is being called from it's own thread. Is there any way I could call connect() from the main Thread, or will i have to make a new one? Also, I still don't know why it wont display the text in chatDoc. Shouldn't it wait until the text is Displayed before it goes to the next line?

**Fubarable** · 11-24-2009, 06:00 AM

Originally Posted by collin389

Sorry, the Thread.sleep() shouldn't have been there

Doesn't matter. All that connection stuff will likely put your app to sleep and should probably be done from within a SwingWorker. You can update the text fields via publish / process.

and whats wrong with if (check == "yes")

When you use == you are checking to see if two variables refer to the same object, but that's not what you want to know here. You want to know if the two String objects hold the same character sequence. That's why you always compare Strings with the equals(...) or equalsIgnoreCase(...) methods.

**Fubarable** · 11-24-2009, 06:01 AM

Originally Posted by collin389

I think I know why, Because, when I call JDialog(), it uses EDT which is being used by connect, even though it is being called from it's own thread. Is there any way I could call connect() from the main Thread, or will i have to make a new one? Also, I still don't know why it wont display the text in chatDoc. Shouldn't it wait until the text is Displayed before it goes to the next line?

I have no idea. You'll need to create an SSCCE for us to use your code and see what works and what doesn't.

**collin389** · 11-24-2009, 06:15 AM

Its still pretty big, but it runs:

Java Code:

   import java.awt.*;
   import java.util.*;
   import javax.swing.*;
   import javax.swing.text.*;
   import java.awt.event.*;
   import java.io.*;
   import java.lang.*;
   import java.net.*;

    public class CMessage extends JFrame implements ActionListener
   {
      String username = "Username";
      JMenuBar menuBar;
      JMenu fileMenu;
      JMenuItem itmConnect;
      JMenuItem itmDisConnect;
      JMenuItem itmQuit;
      JTextPane chatText;
      StyledDocument chatDoc;
      JScrollPane chatScroll;
      JTextField inputText;
      JScrollPane inputScroll;
      Style userStyle, clientStyle, alertStyle;
      boolean connected = false;
      String line;
      BufferedReader serverIS = null;
      BufferedWriter serverOS = null;
      BufferedReader clientIS = null;
      BufferedWriter clientOS = null;
      Socket clientSocket = null, chatSocket = null;
      ServerSocket echoServer = null;
      String input;
      String hostname;
   
       public CMessage()
      {
      //Menubar and menus
         menuBar = new JMenuBar();
      //File menu
         fileMenu = new JMenu("File");
         menuBar.add(fileMenu);
      //Connect Button
         itmConnect = new JMenuItem("Connect", KeyEvent.VK_C);
         fileMenu.add(itmConnect);
         itmConnect.addActionListener(this);
      //Disconnect Button
         itmDisConnect = new JMenuItem("Disconnect", KeyEvent.VK_D);
         fileMenu.add(itmDisConnect);
         itmDisConnect.addActionListener(this);
      //Separator
         fileMenu.addSeparator();
      //Quit Button
         itmQuit = new JMenuItem("Quit", KeyEvent.VK_Q);
         fileMenu.add(itmQuit);
         itmQuit.addActionListener(this);
      //End Buttons
      //End Menus
      //End Menubar
      
      
      //Add Chat Textarea
         chatText = new JTextPane();
         chatText.setEditable(false);
         chatText.setAutoscrolls(true);    
      	
         chatDoc = chatText.getStyledDocument();
      
         userStyle = chatText.addStyle("User", null);
         StyleConstants.setForeground(userStyle, Color.red);
         
         clientStyle = chatText.addStyle("Client", null);
         StyleConstants.setForeground(clientStyle, Color.blue);
         
         alertStyle = chatText.addStyle("Alert", null);
         StyleConstants.setForeground(alertStyle, Color.black);
         StyleConstants.setAlignment(alertStyle, StyleConstants.ALIGN_CENTER);
         
      	
      //Add Chat Textarea ScrollPane
         chatScroll = new JScrollPane(chatText);
      	
      
         
      	
      //Add all JFrame
         setLayout(new BorderLayout());
      	
         setJMenuBar(menuBar);
         add(chatScroll, BorderLayout.CENTER);
      }
   
   
   		
       public void actionPerformed(ActionEvent e) {
         String event = e.getActionCommand();
         if (event == "Connect") { connect(); }  
         if (event == "Disconnect") { disconnect(); } 
         if (event == "Quit") { disconnect(); System.exit(0);}     	
      }
   	
    	
   
      Thread waitForConnection = 
          new Thread() {
             public void run() {
               try {
                  echoServer = new ServerSocket(7890);
                  clientSocket = echoServer.accept();
                  handleClient();
                                    
               } 
                   catch (IOException e) { handleException(e); waitForConnection.run(); }
                              
            } 
         };
         
        
                           
       public void handleClient()
      {
         //connected = true;
         try
         {
                     			 
            
            serverIS = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            serverOS = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
            String clientUser;
            while ((clientUser = serverIS.readLine()) != null)
            {
               System.out.println("" + clientUser);
               System.out.println("" + clientSocket.getInetAddress().getHostAddress());
               break;
            }
            
            int accept = JOptionPane.showConfirmDialog( null, "Accept Connection Request from " + clientUser + " at: " + clientSocket.getInetAddress().getHostAddress() + "?", "Connection Request", JOptionPane.YES_NO_OPTION);
            if (accept == 1){
               
               connected = false;
               serverOS.write("no", 0, 2);
               serverOS.newLine();
               serverOS.flush();
               serverIS.close();
               serverOS.close();
               clientSocket.close();
               
               return; }
            serverOS.write("yes", 0, 3);
            serverOS.newLine();
            serverOS.flush();
            
            while((input = serverIS.readLine()) != null)
            {
               chatDoc.insertString(chatDoc.getLength(), input + "\n", clientStyle);
            
            }
         }
             catch (Exception e) {
               handleException(e);
            }
                     
      }
   
   
   
   
   
       public void connect()
      {
         connected = false;
         int i=0;
         String check;
         try
         {
            hostname = JOptionPane.showInputDialog(null, "Connect to Host IP Adress as " + username + " :");
            chatSocket = new Socket(hostname, 7890);
            clientIS = new BufferedReader(new InputStreamReader(chatSocket.getInputStream()));
            clientOS = new BufferedWriter(new OutputStreamWriter(chatSocket.getOutputStream()));
            chatDoc.insertString(chatDoc.getLength(), "---Attemping to Connect...---\n", alertStyle);
            System.out.println("---Attemping to Connect...---");
            clientOS.write(username, 0, username.length());
            clientOS.newLine();
            clientOS.flush();
            while(((check = clientIS.readLine()) != null) && !connected)
            {
               if (check == "yes")
               {
                  connected = true;
                  chatDoc.insertString(chatDoc.getLength(), "---Sucessfully Connected to " + hostname + "---\n", alertStyle);
               } 
               else {
                  chatDoc.insertString(chatDoc.getLength(), "---Failed to Connect to " + hostname + "---\n", alertStyle);
               }
               if ( i == 5000)
               {
                  chatDoc.insertString(chatDoc.getLength(), "---Failed to Connect to " + hostname + ", Server would not respond(timeout)---\n", alertStyle);
                  break;
               }
               i++;
            }
            while((input = serverIS.readLine()) != null)
            {
               chatDoc.insertString(chatDoc.getLength(), input + "\n", clientStyle);
            
            }
         
            
             
         } 
             catch (Exception e) {
               handleException(e);
            }
      
      }
   
   
   
   
   
   
   
       public void disconnect()
      {
         if (!connected) { 
            return; }
         try {
            if (echoServer != null) { echoServer.close(); }
            if (chatSocket != null) { chatSocket.close(); }
            if (clientSocket != null) { clientSocket.close(); }
            if (serverIS != null) { serverIS.close(); }
            if (serverOS != null) { serverOS.close(); }
            if (clientIS != null) { clientIS.close(); }
            if (clientOS != null) { clientOS.close(); }
            
         }
             catch (Exception e) { handleException(e);  disconnect(); waitForConnection.run();}
             
         connected = false;
      }
   
   
   
   
   
   
       public void handleException(Exception e)
      {
         JOptionPane.showMessageDialog(null,
                  "Error: " + e.getMessage(),
                  "Error",
                  JOptionPane.ERROR_MESSAGE);
      }
   
   
   
   
   
       public static void main( String args[] )
      {
         final CMessage window = new CMessage();
         window.setSize( 300, 400 );
         window.setTitle("Collin's Instant Messager");
         window.setVisible( true );
         window.setLocation( (0 ), (0));
         window.setResizable(true);
         window.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
         window.addWindowListener(
                new WindowAdapter() {
                   public void windowClosing(WindowEvent we) {
                     window.disconnect(); System.exit(0);
                  }
               });
         window.disconnect();
         window.waitForConnection.run();
      }
   }

-you have to connect to 127.0.0.1

**Fubarable** · 11-24-2009, 06:36 AM

I don't do client server apps, so I don't know if that portion is correct, but if I place stuff into a SwingWorker, it works better. for instance

Java Code:

   public void connect() {
      connected = false;
         hostname = JOptionPane.showInputDialog(null,
                  "Connect to Host IP Adress as " + username + " :");
         //!! added
         if (hostname == null) { 
            return;
         }
         SwingWorker<String, String> worker = new SwingWorker<String, String>(){
            String check;
            int i = 0;
            
            @Override
            protected String doInBackground() throws Exception {
               try {
                  chatSocket = new Socket(hostname, 7890);
                  clientIS = new BufferedReader(new InputStreamReader(chatSocket
                           .getInputStream()));
                  clientOS = new BufferedWriter(new OutputStreamWriter(chatSocket
                           .getOutputStream()));
                  
                  publish("---Attemping to Connect...---\n");
                  
                  System.out.println("---Attemping to Connect...---");
                  clientOS.write(username, 0, username.length());
                  clientOS.newLine();
                  clientOS.flush();
                  while (((check = clientIS.readLine()) != null) && !connected) {
                     if (check.equalsIgnoreCase("yes")) {
                        connected = true;
                        
                        publish("---Sucessfully Connected to " + hostname + "---\n");
                        
                     }
                     else {
                        
                        publish("---Failed to Connect to " + hostname + "---\n");
                     }
                     if (i == 5000) {
                        publish("---Failed to Connect to " + hostname
                                          + ", Server would not respond(timeout)---\n");
                        break;
                     }
                     i++;
                  }
                  while ((input = serverIS.readLine()) != null) {
                     publish(input + "\n");

                  }                  
               }
               catch (Exception e) {
                  handleException(e);
               }
               
               return null;
            }
            
            protected void process(List<String> chunks) {
               for (String chunk : chunks) {
                  try {
                     chatDoc.insertString(chatDoc.getLength(),
                              chunk, alertStyle);
                  }
                  catch (BadLocationException e) {
                     e.printStackTrace();
                  }
               }
            }
            
         };
         worker.execute();
      }

**collin389** · 11-24-2009, 06:38 AM

String a = "b"
return (a == "b");
that will return true so I don't understand the reason why you have to say
return a.equals("b");
they accomplish the same task.
And thanks for taking the insult off, but I still saw it :)

OK, nevermind. When i tested it i set String one = "one" and said (one == "one") ok, you're right. Thanks very much for all the help.

**Fubarable** · 11-24-2009, 07:22 AM

Originally Posted by collin389

String a = "b"
return (a == "b");
that will return true so I don't understand the reason why you have to say
return a.equals("b");
they accomplish the same task.

Strings are held in a String pool so that Java often will reuse a String object if it can. Thus it is often true that String variable a will == String variable b, but there is no guarantee. For instance, to force the issue, check out this:

Java Code:

public class Fu3 {
   public static void main(String[] args) {
      String str1 = "Foo";
      String str2 = new String("Foo");
      
      System.out.println(str1);
      System.out.println(str2);
      System.out.println("str1 == str2: " + (str1 == str2));
      System.out.println("str1.equals(str2): " + (str1.equals(str2)));
   }
}

And thanks for taking the insult off, but I still saw it :)

Yeah, sorry for that. I spoke in haste and without thought.

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