Class Panel

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Panel extends JPanel implements ActionListener {

    private JLabel name, paswd;
    private JTextField nm, pw;
    private JButton ok;

    public Panel() {

        this.setLayout(new GridLayout(2, 1));

        JPanel p1 = new JPanel();
        p1.setLayout(new GridLayout(2, 2));

        name = new JLabel();
        name.setText("Input your User Name :");

        paswd = new JLabel();
        paswd.setText("Input your Password :");

        nm = new JTextField();
        nm.setColumns(22);
        nm.addActionListener(this);

        pw = new JTextField();
        pw.setColumns(22);
        pw.addActionListener(this);

        p1.add(name);
        p1.add(nm);
        p1.add(paswd);
        p1.add(pw);

        JPanel p2 = new JPanel();
        p2.setLayout(new FlowLayout());
        ok = new JButton("OK");
        ok.addActionListener(this);
        p2.add(ok);

        this.add(p1);
        this.add(p2);
    }

    public void actionPerformed(ActionEvent e) {
        String button;
        button = e.getActionCommand();

        if (button.equals("OK")) {
            if ((nm.getText().equals("root")) && (pw.getText().equals("123456"))) {
                JOptionPane.showMessageDialog(this, "ok");
            } else {
                JOptionPane.showMessageDialog(this, "Salah");
            }
        }
    }
}