first commit

src/ChatRoomGUI.java

+import javax.swing.*;
+import java.awt.*;
+
+public class ChatRoomGUI extends JFrame{
+    private final String WINDOWS_TITLE = "AUT Chat Room";
+    private final int WIDTH = 500, HEIGHT = 500;
+    private final int X = 100, Y = 100;
+
+    public ChatRoomGUI() {
+        super();
+        this.setTitle(WINDOWS_TITLE);
+        this.setLayout(new BorderLayout());
+        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        this.setSize(WIDTH, HEIGHT);
+        this.setLocation(X, Y);
+
+        chatArea chatbox = new chatArea();
+        chatbox.addMessage("amir","hello!");
+        chatbox.setVisible(true);
+        this.add(new JScrollPane(chatbox), BorderLayout.CENTER);
+
+        MessageArea messagebox = new MessageArea();
+        this.add(messagebox,BorderLayout.PAGE_END);
+
+        ParticipantsArea participantsArea = new ParticipantsArea();
+        this.add(participantsArea,BorderLayout.WEST);
+        this.setVisible(true);
+
+    }
+
+}
\ No newline at end of file

src/Main.java

+public class Main {
+
+    public static void main(String[] args){
+
+        ChatRoomGUI chat1 = new ChatRoomGUI();
+        UsernameFrame chat2 = new UsernameFrame();
+    }
+}

src/MessageArea.java

+import javax.swing.*;
+import java.awt.*;
+
+public class MessageArea extends JPanel {
+    JTextField textField;
+    JButton btn;
+
+
+    public MessageArea(){
+        super();
+        this.setLayout(new BorderLayout());
+        textField = new JTextField();
+        textField.setEditable(true);
+        add(textField, BorderLayout.CENTER);
+
+        btn = new JButton("send");
+        add(btn, BorderLayout.EAST);
+        this.setVisible(true);
+    }
+
+
+}

src/ParticipantsArea.java

+import javax.swing.*;
+import java.awt.*;
+import java.util.ArrayList;
+import javax.swing.JList;
+
+public class ParticipantsArea extends JPanel {
+
+
+    public ParticipantsArea(){
+
+        JLabel label = new JLabel("online users");
+        add(label, BorderLayout.NORTH);
+
+    }
+    DefaultListModel model = new DefaultListModel();
+    JList userslist = new JList(model);
+
+    public void addNewParticipant(String userName){
+        if(!model.contains(userName))
+        model.addElement(userName);
+
+    }
+    public void removeParticipant(String userName){
+        if(model.contains(userName))
+        model.removeElement(userName);
+    }
+}

src/UsernameFrame.java

+import javax.swing.*;
+import java.awt.*;
+
+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 = 400;
+    JTextField textField;
+    JButton btn;
+
+    public UsernameFrame() 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(BTN_TXT);
+        add(btn, BorderLayout.PAGE_END);
+        setSize(WIDTH, HEIGHT);
+        setVisible(true);
+    }
+}
\ No newline at end of file

src/chatArea.java

+import javax.swing.*;
+
+public class chatArea extends JTextArea {
+
+    private static final int ROWS = 10, COLUMNS = 30;
+
+    public chatArea(){
+        super(ROWS,COLUMNS);
+        this.setEditable(false);
+        this.setLineWrap(true);
+        setVisible(true);
+    }
+    public void addMessage(String name, String pm){
+        String str = name+ ":" + pm;
+        append(str);
+        setVisible(true);
+
+
+    }
+
+}