init

src/ChatArea.java

+import javax.swing.*;
+import java.awt.*;
+import java.util.ArrayList;
+
+public class ChatArea extends JTextArea{
+
+    private static final int COL = 30, ROW = 10;
+    private String text;
+
+    public ChatArea() {
+        super(ROW, COL);
+        text = "";
+        this.setEditable(false);
+        this.setLineWrap(true);
+    }
+
+    public void addText(String sender, String message){
+        text = text + (text.equals("") ? "" : "\n") + sender + ": " + message;
+        this.setText(text);
+    }
+
+    public static void main(String[] args) {
+        JFrame frame = new JFrame();
+        ChatArea chatArea = new ChatArea();
+        chatArea.addText("ali", "salam!!!!!");
+        chatArea.addText("amsen", "siloom!!!!!");
+        chatArea.addText("sadegh", "wooow!!!!!");
+        chatArea.addText("amsen","iln");
+
+        frame.add(chatArea);
+
+        frame.setSize(500, 500);
+        frame.setVisible(true);
+    }
+}

src/LoginPage.java

+import javax.swing.*;
+import java.awt.*;
+
+public class LoginPage extends JFrame{
+
+    private final String WINDOWS_TITLE = "Login page";
+    private final int WIDTH = 500, HEIGHT = 200;
+    private final int X = 100, Y = 100;
+
+    private JTextField usernamet;
+    private JButton loginb;
+    private JLabel usernamel;
+
+    public LoginPage(){
+        super();
+        this.setTitle(WINDOWS_TITLE);
+        this.setLayout(new GridLayout(3, 1));
+        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        this.setSize(WIDTH, HEIGHT);
+        this.setLocation(X, Y);
+
+        usernamel = new JLabel();
+        usernamel.setText("username");
+
+        usernamet = new JTextField();
+
+        usernamel = new JLabel();
+        usernamel.setText("username");
+
+        loginb = new JButton();
+        loginb.setText("login");
+
+        add(usernamel);
+        add(usernamet);
+        add(loginb);
+
+        this.setVisible(true);
+
+    }
+
+    public static void main(String[] args){
+        LoginPage tmp = new LoginPage();
+    }
+
+}
\ No newline at end of file

src/Main.java

+import javax.swing.*;
+import java.awt.*;
+
+public class Main {
+
+    public static void main(String[] args){
+        JFrame frame = new JFrame();
+
+        frame.setLayout(new BorderLayout());
+        OnlineList onlineList = new OnlineList();
+        ChatArea chatArea = new ChatArea();
+        TypeArea typeArea = new TypeArea();
+        frame.add(onlineList, BorderLayout.WEST);
+        frame.add(chatArea, BorderLayout.CENTER);
+        frame.add(typeArea, BorderLayout.SOUTH);
+        onlineList.addPerson("ali");
+        onlineList.addPerson("amsen");
+        chatArea.addText("amsen","salam!");
+        frame.setSize(500, 500);
+        frame.setVisible(true);
+    }
+}

src/OnlineList.java

+import javax.swing.*;
+import java.awt.*;
+import java.util.ArrayList;
+
+public class OnlineList extends JPanel{
+    private JLabel label;
+    private ArrayList<JLabel> onlinePersons;
+
+    public OnlineList(){
+        super();
+        onlinePersons = new ArrayList<>();
+        this.setLayout(new GridLayout(20, 1));
+        label = new JLabel("online persons");
+        label.setOpaque(true);
+        label.setBackground(Color.ORANGE);
+        label.setForeground(Color.WHITE);
+        add(label);
+    }
+
+    public void addPerson(String s){
+        onlinePersons.add(new JLabel(s));
+        add(onlinePersons.get(onlinePersons.size()-1));
+    }
+
+    public void removePerson(String s){
+        for(int i=0 ; i<onlinePersons.size() ; i++)
+            if(onlinePersons.get(i).getText().equals(s)){
+                onlinePersons.remove(i);
+                remove(i+1);
+                break;
+            }
+    }
+
+    public static void main(String[] args) {
+        JFrame frame = new JFrame();
+        OnlineList onlineList = new OnlineList();
+        onlineList.addPerson("hasan");
+        onlineList.addPerson("nilo");
+        onlineList.addPerson("salam");
+        onlineList.removePerson("nilo");
+        onlineList.removePerson("salam");
+        frame.add(onlineList);
+        frame.setSize(500, 500);
+        frame.setVisible(true);
+    }
+}

src/TypeArea.java

+import javax.swing.*;
+import java.awt.*;
+
+public class TypeArea extends JPanel{
+    private JTextField message;
+    private JButton send;
+
+    public TypeArea(){
+        super();
+        this.setLayout(new GridLayout(1, 2));
+        message = new JTextField("type your message here");
+        send = new JButton("send!");
+
+        add(message);
+        add(send);
+    }
+
+    public static void main(String[] args) {
+        JFrame frame = new JFrame();
+        TypeArea typeArea = new TypeArea();
+        frame.add(typeArea);
+        frame.setSize(500, 500);
+        frame.setVisible(true);
+    }
+}