java frage

[jopp]

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

class SimpleFrame extends JFrame implements ActionListener {
JTextField jtf;
JButton jb;

//Varibale mit dem Text
String text = "hi alex";

public SimpleFrame (String title) {

super(title);

//ein WindowListener um das Fenster wieder schließen zu können
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent event) {
System.exit(0);
}
});

setSize(160, 100);

//LayoutManager festlegen
this.getContentPane().setLayout(new FlowLayout());

Dimension d = new Dimension(100,20);
jtf = new JTextField("");
jtf.setPreferredSize(d);
getContentPane().add(jtf);

jb = new JButton("Text zeigen");
getContentPane().add(jb);
//ActionListener für Button hinzufügen
jb.addActionListener(this);

show();
}

public void actionPerformed (ActionEvent event) {
jtf.setText(text);
}

public static void main (String[] args) {
SimpleFrame w = new SimpleFrame("TEST");
}
}

damit sollte es funktionieren