[Java] tabulatortaste

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

public class Tabelle4 extends JFrame implements ActionListener
{
 JButton btn;
 TextField tfName,tfVname, tfFile;
 ButtonGroup bg_mw;
 JComboBox cKlasse;
 JTable jtable = new JTable(90, 5);
 JScrollPane jspane = new JScrollPane(jtable);
 int s=0, z=1;
 String str, st, klasse, mw;

 BufferedWriter f;
 
 Tabelle4()
 {
 super("Schüler-Tabelle");
 Image icon = this.getToolkit().getImage("logoPGS.jpg");
 this.setIconImage(icon);
 this.setSize(700, 500);
 this.setLocation(50, 50);
 this.setBackground(Color.orange);
 this.getContentPane().setLayout(null);

 JLabel l = new JLabel("Name");
 l.setBounds(20, 50, 90, 25);
 this.add(l);
 l = new JLabel("Vorname");
 l.setBounds(20, 90, 90, 25);
 this.add(l);
 l = new JLabel("Klasse");
 l.setBounds(20, 210, 90, 25);
 this.add(l);

 tfName = new TextField("");
 tfName.setBounds(140, 50, 100, 25);
 this.getContentPane().add(tfName);

 tfVname = new TextField("");
 tfVname.setBounds(140, 90, 100, 25);
 this.getContentPane().add(tfVname);

 tfFile = new TextField("");
 tfFile.setBounds(340, 390, 100, 25);
 this.getContentPane().add(tfFile);
 
 bg_mw = new ButtonGroup();
 JRadioButton rb1 = new JRadioButton ("Junge",true);
 JRadioButton rb2 = new JRadioButton ("Mädchen",false);
 bg_mw.add(rb1);
 bg_mw.add(rb2);
 rb1.setActionCommand(rb1.getText());
 rb2.setActionCommand(rb2.getText());
 rb1.setBounds(140, 130, 100, 30);
 rb2.setBounds(140, 160, 100, 30);
 this.add(rb1);
 this.add(rb2);
 
 String[] sKlasse = {"5a","5b","5c","5d"};
 cKlasse = new JComboBox(sKlasse);
 cKlasse.setBounds(140, 210, 60, 25);
 this.add(cKlasse);

 btn = new JButton("Übernehmen");
 btn.setBounds(100, 390, 140, 25);
 this.getContentPane().add(btn);
 btn.addActionListener(this);

 btn = new JButton("Speichern");
 btn.setBounds(480, 390, 100, 25);
 this.getContentPane().add(btn);
 btn.addActionListener(this);

 JScrollPane sPane1 = new JScrollPane(jtable);
 sPane1.setLocation(280,50);
 sPane1.setSize(350, 300);
 this.getContentPane().add(sPane1);

 jtable.setValueAt("Name", 0, 0);
 jtable.setValueAt("Vorname", 0, 1);
 jtable.setValueAt("Geschlecht", 0, 2);
 jtable.setValueAt("Klasse", 0, 3);

 this.addWindowListener(new WindowAdapter()
 {
 public void windowClosing(WindowEvent we)
 {
 System.exit(0);
 }
 });
 }

//////////////////////////////////////////////////////////////////////////////// 

 public static void main(String[] args)
 {
 Tabelle4 t = new Tabelle4();
 t.setVisible(true);
 }
//////////////////////////////////////////////////////////////////////////////// 

 public void actionPerformed(ActionEvent ae)
 {
 if(ae.getActionCommand().equals("Übernehmen"))
 {
 ButtonModel selected = bg_mw.getSelection();
 mw = selected.getActionCommand();

 klasse = (String) cKlasse.getSelectedItem();

 jtable.setValueAt(tfName.getText(), z, 0);
 jtable.setValueAt(tfVname.getText(), z, 1);
 jtable.setValueAt(mw, z, 2);
 jtable.setValueAt(klasse, z, 3);
 z++;
 }
 else if(ae.getActionCommand().equals("Speichern"))
 {
 int j =0;
 str = tfFile.getText();
 try {
 f = new BufferedWriter(new FileWriter("d:\\Temp\\"+str+".txt"));
 while (j<z) {
 st = (String)jtable.getValueAt(j,0) + '\t'+ (String)jtable.getValueAt(j,1) +
 '\t'+ (String)jtable.getValueAt(j,2) + '\t'+ (String)jtable.getValueAt(j,3);
 f.write(st);
 f.newLine();
 j++;
 }
 f.close();
 } catch (IOException e) {
 System.out.println("Fehler beim Erstellen der Datei");
 }
 }
 }

}