final

src/ChatArea.java

+import javax.swing.*;
+import java.awt.*;
+
+public class ChatArea extends JTextArea {
+    private static final int ROWS = 20 , COLUMNS = 40;
+
+    public ChatArea()
+    {
+        super(ROWS, COLUMNS);
+        this.setEditable(false);
+        this.setLineWrap(true);
+        setVisible(true);
+        this.setBackground(Color.cyan);
+    }
+
+    public void addMessage(String username,String message)
+    {
+        this.append(username+": "+message+"\n");
+    }
+}
\ No newline at end of file

src/ChatRoomGUI.java

+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.util.ArrayList;
+
+public class ChatRoomGUI extends JFrame {
+    private final String WINDOWS_TITLE = "AUT Chat Room";
+    private final int WIDTH = 700 , HEIGHT = 700;
+    private final int X = 150 , Y = 150;
+    private ArrayList<String> users = new ArrayList<>();
+    ParticipantsArea participantsArea = new ParticipantsArea();
+    MessageArea messageArea = new MessageArea();
+    ChatArea chatBox = new ChatArea();
+
+
+    public ChatRoomGUI() {
+        super();
+        this.setFont(new Font("serif", Font.PLAIN, 40));
+        this.setTitle(WINDOWS_TITLE);
+        this.setLayout(new BorderLayout());
+        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        this.setSize(WIDTH, HEIGHT);
+        this.setLocation(X, Y);
+        this.add(new JScrollPane(chatBox), BorderLayout.CENTER);
+        this.add(participantsArea, BorderLayout.WEST);
+        this.add(messageArea, BorderLayout.SOUTH);
+        this.setVisible(true);
+        participantsArea.addPart("armin");
+        participantsArea.addPart("arta");
+        participantsArea.addPart("aava");
+        participantsArea.addPart("ali");
+        participantsArea.addPart("reza");
+        participantsArea.removePart("ali");
+    }
+
+    public ChatArea getChatBox() {
+        return chatBox;
+    }
+
+    public MessageArea getMessageArea() {
+        return messageArea;
+    }
+
+    public void showGUI() {
+        this.setVisible(true);
+    }
+
+    public void addNewPart(String user) {
+        users.add(user);
+        participantsArea.addPart(user);
+    }
+
+    public void removePart(String user) {
+        try
+        {
+            users.remove(user);
+        } catch (Exception e)
+        {
+
+        }
+    }
+
+
+}
\ No newline at end of file

src/Main.java

+public class Main {
+    public static void main(String[] args) {
+        UsernameFrame usernameFrame1 = new UsernameFrame(1);
+        usernameFrame1 = new UsernameFrame("a");
+
+    }
+}

src/MessageArea.java

+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+
+public class MessageArea extends JPanel
+{
+    private static final String BTN_TXT = " Send Message ";
+    JTextField textField;
+    JButton btn;
+
+    public MessageArea() throws HeadlessException {
+        super();
+        this.setLayout(new BorderLayout());
+        textField = new JTextField();
+        add(textField, BorderLayout.CENTER);
+        btn = new JButton(BTN_TXT);
+
+        add(btn, BorderLayout.EAST);
+        setVisible(true);
+        this.setBackground(Color.gray);
+
+    }
+
+    public void setTextField(String textField) {
+        this.textField.setText(textField);
+    }
+
+    public JButton getBtn() {
+        return btn;
+    }
+
+    public JTextField getTextField() {
+        return textField;
+    }
+}

src/ParticipantsArea.java

+import javax.swing.*;
+import java.awt.*;
+
+
+public class ParticipantsArea extends JPanel
+{
+    private static final String LABEL_TXT = "Online People:";
+    private static int count = 0;
+    DefaultListModel model = new DefaultListModel();
+    public ParticipantsArea() throws HeadlessException {
+        super();
+        this.setLayout(new BorderLayout());
+        JLabel label = new JLabel(LABEL_TXT);
+        JList list = new JList(model);
+        add(label, BorderLayout.NORTH);
+        add(list, BorderLayout.CENTER);
+        setVisible(true);
+    }
+
+    public void addPart(String user)
+    {
+        model.addElement(user) ;
+    }
+
+    public void removePart(String user)
+    {
+        model.removeElement(user) ;
+    }
+
+
+}

src/RemoveFrame.java

+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.KeyAdapter;
+import java.awt.event.KeyEvent;
+
+public class RemoveFrame extends JFrame {
+    private static final String BTN_TXT = " Start Chatting ...";
+    private static final String LABEL_TXT = " Choose Your UserName  ";
+    private static final int WIDTH = 300, HEIGHT = 200;
+
+    public static ChatRoomGUI mainChatRoom;
+
+    JTextField textField;
+    JButton btn;
+    public String userName;
+
+    public static ChatRoomGUI getMainChatRoom() {
+        return mainChatRoom;
+    }
+
+    public RemoveFrame() throws HeadlessException {
+        super();
+        this.setLayout(new BorderLayout());
+        JLabel label = new JLabel("Choose Your UserName");
+        add(label, BorderLayout.PAGE_START);
+        textField = new JTextField();
+        add(textField, BorderLayout.CENTER);
+        btn = new JButton("Enter Your UserName");
+        btn.addActionListener(new ActionListener(){
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                userName=textField.getText();
+                setVisible(false);
+                mainChatRoom = new ChatRoomGUI();
+                mainChatRoom.removePart(userName);
+                JTextField txtField = mainChatRoom.getMessageArea().getTextField();
+                txtField.addKeyListener(new KeyAdapter()
+                {
+                    public void keyPressed(KeyEvent evt)
+                    {
+                        if(evt.getKeyCode() == KeyEvent.VK_ENTER && !evt.isShiftDown())
+                        {
+                            String txt = mainChatRoom.getMessageArea().getTextField().getText();
+                            mainChatRoom.getChatBox().addMessage(userName,txt);
+                            mainChatRoom.getMessageArea().setTextField("");
+                        }
+                        else if(evt.getKeyCode() == KeyEvent.VK_ENTER)
+                            txtField.setText(txtField.getText()+'\n');
+                        else
+                            txtField.setText(txtField.getText()+evt.getKeyChar());
+                    }
+                });
+                JButton btn = mainChatRoom.getMessageArea().getBtn();
+                btn.addActionListener(new ActionListener() {
+                    @Override
+                    public void actionPerformed(ActionEvent e) {
+                        String txt = mainChatRoom.getMessageArea().getTextField().getText();
+                        mainChatRoom.getChatBox().addMessage(userName,txt);
+                        mainChatRoom.getMessageArea().setTextField("");
+                    }
+                });
+            }
+        });
+
+        add(btn, BorderLayout.PAGE_END);
+        setSize(WIDTH, HEIGHT);
+        setVisible(true);
+        this.setBackground(Color.green);
+    }
+
+    public String getUserName() {
+        return userName;
+    }
+}
+

src/UsernameFrame.java

+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.KeyAdapter;
+import java.awt.event.KeyEvent;
+
+public class UsernameFrame extends JFrame {
+    private static final String BTN_TXT = " Start Chatting ...";
+    private static final String LABEL_TXT = " Choose Your UserName  ";
+    private static final int WIDTH = 300, HEIGHT = 200;
+
+    public static ChatRoomGUI mainChatRoom;
+
+    JTextField textField;
+    JButton btn;
+    public String userName;
+
+    public static ChatRoomGUI getMainChatRoom() {
+        return mainChatRoom;
+    }
+
+    public UsernameFrame(String b) throws HeadlessException {
+        super();
+        this.setLayout(new BorderLayout());
+        JLabel label = new JLabel("Choose Your UserName");
+        add(label, BorderLayout.PAGE_START);
+        textField = new JTextField();
+        add(textField, BorderLayout.CENTER);
+        btn = new JButton("Enter Your UserName");
+        btn.addActionListener(new ActionListener(){
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                userName=textField.getText();
+                setVisible(false);
+                mainChatRoom = new ChatRoomGUI();
+                mainChatRoom.addNewPart(userName);
+                JTextField txtField = mainChatRoom.getMessageArea().getTextField();
+                txtField.addKeyListener(new KeyAdapter()
+                {
+                    public void keyPressed(KeyEvent evt)
+                    {
+                        if(evt.getKeyCode() == KeyEvent.VK_ENTER && !evt.isShiftDown())
+                        {
+                            String txt = mainChatRoom.getMessageArea().getTextField().getText();
+                            mainChatRoom.getChatBox().addMessage(userName,txt);
+                            mainChatRoom.getMessageArea().setTextField("");
+                        }
+                        else if(evt.getKeyCode() == KeyEvent.VK_ENTER)
+                            txtField.setText(txtField.getText()+'\n');
+                        else
+                            txtField.setText(txtField.getText()+evt.getKeyChar());
+                    }
+                });
+                JButton btn = mainChatRoom.getMessageArea().getBtn();
+                btn.addActionListener(new ActionListener() {
+                    @Override
+                    public void actionPerformed(ActionEvent e) {
+                        String txt = mainChatRoom.getMessageArea().getTextField().getText();
+                        mainChatRoom.getChatBox().addMessage(userName,txt);
+                        mainChatRoom.getMessageArea().setTextField("");
+                    }
+                });
+            }
+        });
+
+        add(btn, BorderLayout.PAGE_END);
+        setSize(WIDTH, HEIGHT);
+        setVisible(true);
+        this.setBackground(Color.green);
+    }
+
+    public UsernameFrame(int a) throws HeadlessException {
+        super();
+        this.setLayout(new BorderLayout());
+        JLabel label = new JLabel("Choose Your UserName");
+        add(label, BorderLayout.PAGE_START);
+        textField = new JTextField();
+        add(textField, BorderLayout.CENTER);
+        btn = new JButton("Enter Your UserName");
+        btn.addActionListener(new ActionListener(){
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                userName=textField.getText();
+                setVisible(false);
+                mainChatRoom = new ChatRoomGUI();
+                mainChatRoom.removePart(userName);
+                JTextField txtField = mainChatRoom.getMessageArea().getTextField();
+                txtField.addKeyListener(new KeyAdapter()
+                {
+                    public void keyPressed(KeyEvent evt)
+                    {
+                        if(evt.getKeyCode() == KeyEvent.VK_ENTER && !evt.isShiftDown())
+                        {
+                            String txt = mainChatRoom.getMessageArea().getTextField().getText();
+                            mainChatRoom.getChatBox().addMessage(userName,txt);
+                            mainChatRoom.getMessageArea().setTextField("");
+                        }
+                        else if(evt.getKeyCode() == KeyEvent.VK_ENTER)
+                            txtField.setText(txtField.getText()+'\n');
+                        else
+                            txtField.setText(txtField.getText()+evt.getKeyChar());
+                    }
+                });
+                JButton btn = mainChatRoom.getMessageArea().getBtn();
+                btn.addActionListener(new ActionListener() {
+                    @Override
+                    public void actionPerformed(ActionEvent e) {
+                        String txt = mainChatRoom.getMessageArea().getTextField().getText();
+                        mainChatRoom.getChatBox().addMessage(userName,txt);
+                        mainChatRoom.getMessageArea().setTextField("");
+                    }
+                });
+            }
+        });
+
+        add(btn, BorderLayout.PAGE_END);
+        setSize(WIDTH, HEIGHT);
+        setVisible(true);
+        this.setBackground(Color.green);
+    }
+    public String getUserName() {
+        return userName;
+    }
+}
+