JFrame Problem

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

public class dashboard extends JFrame {

    public static void main(String[] agrs)
    {
        new dashboard();
    }

    public dashboard()
    {
        this.setSize(500,500);
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setTitle("OEMGE APP");
        this.setLocationRelativeTo(null);
        this.setResizable(false);

        JPanel p = new JPanel(new FlowLayout());
        JTextField welcomeMSG = new JTextField("Hello There");
        JButton randomButton = new JButton("Click Me :D");
        p.add(welcomeMSG);
        p.add(randomButton);
        this.add(p);
    }

}