Dialog Box in Java

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


class NewFrame implements ActionListener {
    JFrame frame;
    JButton b;
    JDialog dialog;
    NewFrame(){
        frame = new JFrame();
        b = new JButton("Show Dialog");
        dialog = new JDialog(frame, "My Dialog", false);
        JLabel label = new JLabel("Hello, world!");

        b.addActionListener(this);
        dialog.add(label);
        frame.add(b);

        frame.setSize(400,400);
        frame.setVisible(true);






    }


    public void actionPerformed(ActionEvent event){
        dialog.setVisible(true);
        dialog.setSize(600,600);
    }


}


public class GUI {
    public static void main(String[] args) {
        new NewFrame();




    }
}