Problem with username

Question

i doing a chat application and using vector for storing the usernames...but when i use the contains method in vector my client applet will hang...could anyone give me any example of chat server validating username and sending result back to client code....

Answer 1

below are my source code....pls help
ChatServer.java
import java.net.*;
import java.io.*;
import java.util.*;
public class ChatServer {
static LinkedList ClientList = new LinkedList();
public static void main (String args[]) throws IOException {
ServerSocket server = new ServerSocket (10000);
while (true) {
System.out.println( "Waiting for connection...");
Socket client = server.accept ();
ClientList.add( client );
System.out.println ("Accepted from " + client.getInetAddress ());
ChatHandler c = new ChatHandler (client);
c.start ();
ChatHandler.java
import java.net.*;
import java.io.*;
import java.util.*;
import javax.swing.JOptionPane;
public class ChatHandler extends Thread {
protected Socket s;
protected DataInputStream i;
protected DataOutputStream o;
String name;
public ChatHandler (Socket s) throws IOException {
this.s = s;
i = new DataInputStream (new BufferedInputStream (s.getInputStream ()));
o = new DataOutputStream (new BufferedOutputStream (s.getOutputStream ()));
protected static Vector clientlist = new Vector ();
protected static Vector handlers = new Vector ();
public void run () {
try {
name = i.readUTF();
if( name.startsWith( "NICKNAME:" ) )
name = name.substring( 9 );
     if ( clientlist.contains( name ) )
          o.writeUTF( "false" );
     else
     broadcast (name + " has joined.");
     handlers.addElement (this);
     clientlist.addElement(name);
Enumeration enum = clientlist.elements();
               while ( enum.hasMoreElements() )
                    broadcast ( "USERLIST:" + (String)enum.nextElement() );
while (true) {
String msg = i.readUTF ();
if(msg.equals("/who"))
     Enumeration enum = clientlist.elements();
               while ( enum.hasMoreElements() )
                    broadcast ( "USERLIST:" + (String)enum.nextElement() );
broadcast (name + " - " + msg);
} catch (IOException ex) {
ex.printStackTrace ();
} finally {
handlers.removeElement (this);
broadcast (name + " has left.");
try {
s.close ();
} catch (IOException ex) {
ex.printStackTrace();
protected static void broadcast (String message) {
synchronized (handlers) {
Enumeration e = handlers.elements ();
while (e.hasMoreElements ()) {
ChatHandler c = (ChatHandler) e.nextElement ();
try {
synchronized (c.o) {
c.o.writeUTF (message);
c.o.flush ();
} catch (IOException ex) {
c.stop ();
ChatClient.java
// The chat applet gui
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JOptionPane;
import java.io.*;
import java.net.*;
import java.util.*;
public class ChatClient extends JApplet implements ActionListener, Runnable {
     Container c;
     JPanel mainPanel, chatLoginPanel, chatPanel, chatPanel_bottom;
     JTextField nickNameText, chatText;
     JTextArea chatArea;
JList userList;
     JButton enterChatButton, exitChatButton;
     JLabel nickLabel;
     // socket for connecting to the server
     private Socket socket;
     private DataOutputStream dout;
     private DataInputStream din;
     public void init()
     c = getContentPane();
          // The JPanel with CardLayout
     mainPanel = new JPanel();
          mainPanel.setLayout( new CardLayout() );
          // chatLoginPanel for user login into chat
          chatLoginPanel = new JPanel();
          chatLoginPanel.setLayout( new FlowLayout() );
          nickLabel = new JLabel( "Nickname:" );
     nickNameText = new JTextField( 20 );
          enterChatButton = new JButton( "Enter" );
          enterChatButton.addActionListener( this );
          enterChatButton.setActionCommand( "Enter Chat" );
          chatLoginPanel.add( nickLabel );
          chatLoginPanel.add( nickNameText );
          chatLoginPanel.add( enterChatButton );
          chatLoginPanel.setBackground( Color.white );
          // chatPanel for user chatting
          chatPanel = new JPanel();
          chatPanel.setLayout( new BorderLayout() );
     chatArea = new JTextArea( 9, 31 );
          userList = new JList();
          userList.setSelectionMode( ListSelectionModel.SINGLE_SELECTION );
          userList.setVisibleRowCount( 0 );
          userList.setFixedCellWidth( 90 );
          chatPanel_bottom = new JPanel();
          chatPanel_bottom.setLayout( new BorderLayout() );
          chatText = new JTextField( 31 );
          chatText.addActionListener( this );
          chatText.setActionCommand( "Chat Text" );
          exitChatButton = new JButton( "Exit from chat" );
          exitChatButton.addActionListener( this );
          exitChatButton.setActionCommand( "Exit Chat" );
          chatPanel_bottom.add( BorderLayout.WEST, chatText );
          chatPanel_bottom.add( BorderLayout.EAST, exitChatButton );
          chatPanel.add( BorderLayout.WEST, new JScrollPane( chatArea ) );
          chatPanel.add( BorderLayout.EAST, new JScrollPane( userList ) );
          chatPanel.add( BorderLayout.SOUTH, chatPanel_bottom );
          chatPanel_bottom.setBackground( Color.white );
          chatPanel.setBackground( Color.white );
          c.add( chatLoginPanel );     
          // Connecting to the server
          try {
          // Initiate the connection
          socket = new Socket( "127.0.0.1", 10000 );
          // We got a connection!     Tell the world
          System.out.println( "connected to "+socket );
          // Let's grab the stream and create DataInput/Output stream
          // from them
          din = new DataInputStream( socket.getInputStream() );
          dout = new DataOutputStream( socket.getOutputStream() );
          // Start a background thread for receiving messages
          new Thread( this ).start();
          } catch( IOException ie ) { System.out.println( ie ); }
     private void processMessage( String message ) {
          try {
               // Send it to the server
               dout.writeUTF( message );
               // Clear out text input field
               chatText.setText( "" );
          } catch( IOException ie ) { System.out.println( ie ); }
     // Background thread runs this, show messages from other window
     public void run() {
          try {
               // Receive messages one-by-one, forever
               while (true) {
                    // Get the next message
                    String message = din.readUTF();
                    if( message.equals( "false" ) )
                    JOptionPane.showMessageDialog( null, "The nickname you entered is already choosed", "Cannot enter", JOptionPane.PLAIN_MESSAGE );
                    nickNameText.setEditable( true );
                    enterChatButton.setText( "Enter" );
                    enterChatButton.setEnabled( true );
                    else if ( message != null )
                    //userList.setListData( chatPro.userListed() );
                    mainPanel.add( chatLoginPanel, "chatLoginPanel" );
                    mainPanel.add( chatPanel, "chatPanel" );
               CardLayout cl = ( CardLayout )( mainPanel.getLayout() );
                    cl.show( mainPanel, ( String )"chatPanel" );
                    c.add( mainPanel );     
                    // Print it to our text window
                    chatArea.append( message+"\n" );
          }     catch( IOException ie ) { System.out.println( ie ); }
     public void actionPerformed( ActionEvent e )
          if ( e.getActionCommand() == "Enter Chat")
               nickNameText.setEditable( false );
               enterChatButton.setText( "Validating" );
               enterChatButton.setEnabled( false );
               if( nickNameText.getText().equals("") )
                    JOptionPane.showMessageDialog( null, "Please key in your nickname", "Cannot enter", JOptionPane.PLAIN_MESSAGE );
                    nickNameText.setEditable( true );
                    enterChatButton.setText( "Enter" );
                    enterChatButton.setEnabled( true );
               else
                    String userName = nickNameText.getText();
                    processMessage( "NICKNAME:" + userName );
          if ( e.getActionCommand() == "Exit Chat")
               mainPanel.add( chatLoginPanel, "chatLoginPanel" );
               mainPanel.add( chatPanel, "chatPanel" );
          CardLayout cl = ( CardLayout )( mainPanel.getLayout() );
     cl.show( mainPanel, ( String )"chatLoginPanel" );
               c.add( mainPanel );
               nickNameText.setEditable( true );
               enterChatButton.setText( "Enter" );
               enterChatButton.setEnabled( true );
          if ( e.getActionCommand() == "Chat Text" )
               processMessage( chatText.getText() );