first commit

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);
+        addMessage("abtin","safhudas");
+        setVisible(true);
+    }
+    public void addMessage(String userName,String message){
+        String sb_1=userName+ ":"+message;
+        append(sb_1);
+    }
+}

src/ChatRoomGUI.java

+
+
+import javax.swing.*;
+import java.awt.*;
+import java.util.ArrayList;
+
+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;
+    private ArrayList<String> users=new ArrayList<>();
+    public ChatRoomGUI(ParticipantsArea participantsArea){
+        super();
+        this.setTitle(WINDOWS_TITLE);
+        this.setLayout(new BorderLayout());
+        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        this.setSize(WIDTH, HEIGHT);
+        this.setLocation(X, Y);
+        participantsArea=new ParticipantsArea();
+        this.add(participantsArea,BorderLayout.WEST);
+        participantsArea.addPart("Abtin");
+        participantsArea.removePart("Abtin");
+        ChatArea chatBox = new ChatArea();
+        this.add(new JScrollPane(chatBox), BorderLayout.CENTER);
+        MessageArea messageArea=new MessageArea();
+        this.add(messageArea,BorderLayout.SOUTH);
+        this.setVisible(true);
+
+    }
+
+}

src/Main.java

+public class Main {
+    public static void main(String[] args) {
+        ParticipantsArea participantsArea=new ParticipantsArea();
+        ChatRoomGUI chatRoomGUI=new ChatRoomGUI(participantsArea);
+        UserNameFrame userNameFrame=new UserNameFrame();
+    }
+}

src/MessageArea.java

+import javax.swing.*;
+import java.awt.*;
+
+public class MessageArea<BTN_TXT> 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);
+    }
+    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="people:";
+    private static int count=0;
+    DefaultListModel model=new DefaultListModel();
+    public ParticipantsArea(){
+        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.add(count,user);
+        count++;
+    }
+    public void removePart(String user){
+        model.removeElement(user);
+    }
+}

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 = 100;
+    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(LABEL_TXT);
+        add(btn, BorderLayout.PAGE_END);
+        setSize(WIDTH, HEIGHT);
+        setVisible(true);
+    }
+}