I can't over give my variable to the return in the get Method!

Question

Hello Java Cracks
At the moment I am working with JDOM. I am able to get access to the XML File with JDOM, but when I want to send, the value of a variable, which I get from the XML File it is not possible. When I try to send the variable to the get Method (getDtdVersion), the value I over give is always �null�. Please help me, and say what the problem is?
I also post you the second class, where I want to use the variable I over give.
Here is my code:
Class 1, I take the String from this class. See the arrow
package FahrplanXML;
import java.io.File;
import java.io.IOException;
import javax.swing.JFileChooser;
import javax.swing.filechooser.FileFilter;
import org.jdom.Attribute;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
import org.xml.sax.InputSource;
public class FileAuswahl {
private File filenames;
private String scheduledtdversion;
public void ablauf() throws JDOMException, IOException {
FileAuswaehlen();
saxwer();
grundoberflaeche xmloberflaeche = new grundoberflaeche();
xmloberflaeche.grundoberflaechen();
public void FileAuswaehlen() {
JFileChooser datei = new JFileChooser();
datei.setFileFilter(new FileFilter()
@Override public boolean accept (File f)
return f.isDirectory() ||
f.getName().toLowerCase().endsWith(".xml");
@Override public String getDescription()
return "XML-Files";
int state = datei.showOpenDialog(null);
if (state == JFileChooser.APPROVE_OPTION )
filenames = datei.getSelectedFile();
System.out.println (filenames);
if (filenames != null)
try {
System.out.print(filenames);
saxwer();
} catch (JDOMException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
else
System.out.println("Kein File ausgew�hlt");
else
System.out.println("Auswahl abgebrochen");
System.exit(0);
//Ausgew�hlter Dateiname an saxwer �bergeben
public File getNames() {
System.out.println (filenames);
return this.filenames;
public void saxwer() throws JDOMException, IOException {
//FileAuswahl filename = new FileAuswahl();
File files = getNames();
System.out.println (files);
SAXBuilder builder = new SAXBuilder();
Document doc = builder.build(files);
Element schedulemessage = doc.getRootElement();
//Root Element auslesen
String sch_msg_dtdversion = schedulemessage.getAttributeValue ("DtdVersion"); // <---
scheduledtdversion = sch_msg_dtdversion;
new grundoberflaeche().grundoberflaechen();
public String getDtdVersion() {
System.out.println (scheduledtdversion);
return this.scheduledtdversion;
Now, you will see the class in which I pass the String. See also arrow...
package FahrplanXML;
import java.awt.Component;
import java.awt.Container;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.text.Caret;
import org.jdom.Attribute;
import org.jdom.JDOMException;
public class grundoberflaeche {
// Layout f�r Laender vorbereiten
static void addComponent (Container cont,
GridBagLayout diversemoegl,
Component laenderdetails,
int x, int y,
int width, int height,
double weightx, double weighty )
GridBagConstraints grundoberflaechen = new GridBagConstraints();
grundoberflaechen.fill = GridBagConstraints.BOTH;
grundoberflaechen.gridx = x; grundoberflaechen.gridy = y;
grundoberflaechen.gridwidth = width; grundoberflaechen.gridheight = height;
grundoberflaechen.weightx = weightx; grundoberflaechen.weighty = weighty;
diversemoegl.setConstraints(laenderdetails, grundoberflaechen);
cont.add(laenderdetails);
//Ausw�hlen des XML Files
public void XMLAuswaehlen() {
JFrame xmlauswahl = new JFrame("Fahrplan ausw�hlen");
xmlauswahl.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container laenderdetails = xmlauswahl.getContentPane();
GridBagLayout diversemoegl = new GridBagLayout();
laenderdetails.setLayout(diversemoegl);
JButton dateiauswahl = new JButton ("Datei ausw�hlen");
addComponent(laenderdetails,diversemoegl,dateiauswahl,1,1,1,1,1,1);
ActionListener ersterdateiauswaehler = new ActionListener()
public void actionPerformed( ActionEvent e)
try {
new FileAuswahl().ablauf();
} catch (JDOMException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
dateiauswahl.addActionListener(ersterdateiauswaehler);
xmlauswahl.setSize(150,70);
xmlauswahl.setVisible(true);
//Layout machen
public void grundoberflaechen() {
JFrame fahrplan = new JFrame("Fahrplanauswahldetails");
fahrplan.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container laenderdetails = fahrplan.getContentPane();
GridBagLayout diversemoegl = new GridBagLayout();
laenderdetails.setLayout(diversemoegl);
//Klassenobjekt aufbauen
FileAuswahl fileauswahl = new FileAuswahl();
// Labelsbauen und einbauen in den Fahrpl�nen
String dtdversion = fileauswahl.getDtdVersion(); // <---
System.out.println(dtdversion);
JTextField DtdVersion = new JTextField(1);
DtdVersion.setText(dtdversion);
JTextField fahrplanzeit = new JTextField(1);
fahrplanzeit.setText("123");
JTextField fahrplanzeita = new JTextField(1);
fahrplanzeita.setText("piips");
//JButton oesterreich = new JButton("�sterreich");
//JButton italien = new JButton("Italien");
//JButton frankreich = new JButton("Frankreich");
//JButton spanien = new JButton("Spanien");
addComponent(laenderdetails,diversemoegl,new JLabel("Fahrplandetails"),0,0,1,1,0,0);
addComponent(laenderdetails,diversemoegl,DtdVersion,1,0,1,1,0,0);
addComponent(laenderdetails,diversemoegl,fahrplanzeit,2,0,1,1,0,0);
addComponent(laenderdetails,diversemoegl,fahrplanzeita,3,0,1,1,0,0);
// Action Listener f�r Dateiauswahl
// Action Listener f�r das Speichern der Datei
//addComponent(laenderdetails,diversemoegl,frankreich,2,1,1,1,0,0);
//addComponent(laenderdetails,diversemoegl,spanien,3,1,1,1,0,0);
fahrplan.setSize(600,750);
fahrplan.setVisible(true);
Thank you very much for your help....
Your Java Learner

Answer 1

I suspect you are setting the scheduledtdversion member in one instance of your FileAuswahl class, but are creating yet another instance of that class and printing the member of that instance, which is null. I notice you are creating a new FileAuswahl instance each time something happens, rather than reusing the same instance.
FileAuswahl fileauswahl = new FileAuswahl();Ok, new object here. Not the same one that you previously set the scheduledtdversion member in
String dtdversion = fileauswahl.getDtdVersion();It's null of course, for the reason above.