Create a simple java Application program that implements ActionListener using TextField

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Blt1 extends JFrame implements ActionListener{
    JTextField txt;
    public Blt1(){
        txt=new JTextField(" Write somthing & press enter");
        add(txt);
        txt.addActionListener(this);
        setSize(200,300);
        setVisible(true);
    }
    public static void main(String args[])
    {
        Blt1 bt = new Blt1();
         bt.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE );
    }
    public void actionPerformed(ActionEvent ae)
    {
        String st=" ";
        st=txt.getText()+"  ";
        JOptionPane.showMessageDialog(null,st);
    }

}