Java: saved settings with Preferences not restored when a GUI application starts

Question

In my Java app, I have a number of saved values and settings that I would like to get as soon as the application starts. All these values are supposed to be stored in a singleton. For example, I have a JDialog, where I save a path to my file using this:

AppSingleton appSingleton = AppSingleton.getInstance( );
private Preferences prefs;

private void btnSetPanelSetNavdataActionPerformed(java.awt.event.ActionEvent evt) {                                                      

        appSingleton.setNavdataPath(txtNavdataPath.getText());

        prefs = Preferences.userRoot().node(this.getClass().getName());
        prefs.put("NAVDATA_PATH", txtNavdataPath.getText());

        dispose();
}

I am checking and the value is saved.

This is my singleton:

public class AppSingleton 
{

    private static AppSingleton instance = null;   
    private String navdataPath = "";

    private AppSingleton() 
    {

    }

    public static AppSingleton getInstance() 
    {
        if(instance == null) 
        {
            instance = new AppSingleton();
        }
      return instance;
    }

    public String getNavdataPath() {
        return navdataPath;
    }

    public void setNavdataPath(String navdataPath) {
        this.navdataPath = navdataPath;
    }


    public void initDefaultValues()
    {
        Preferences prefs = Preferences.userRoot().node(this.getClass().getName());
        this.navdataPath = prefs.get("NAVDATA_PATH","");

        System.out.printf("CHECK DEFAULT: %s",this.navdataPath);
    }
}

I am trying to get the saved values from the main() method in the class that initializes the JFrame:

public static void main(String args[]) {

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() 
        {
            public void run() {
                new IGAMainFrame().setVisible(true);

                /* HERE!!! */
                AppSingleton appSingleton = AppSingleton.getInstance();
                appSingleton.initDefaultValues();
            }
        });
}

But the values are not initialized from the Preference class. "CHECK DEFAULT" shows empty string. I do not understand why and whether there is a better practice of restoring all saved values when a GUI application starts.

Thanks!

Answer 1

Change the line prefs = Preferences.userRoot().node(this.getClass().getName()); inside btnSetPanelSetNavdataActionPerformed to prefs = Preferences.userRoot().node(Appsingleton.class.getName()); Inside button click method, this.getClass() is not AppSingleton