Preferences Problem

Preferences.java

package application.preferences;

import com.dlsc.preferencesfx.PreferencesFx;
import com.dlsc.preferencesfx.model.Category;
import com.dlsc.preferencesfx.model.Group;
import com.dlsc.preferencesfx.model.Setting;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;

class Preferences {

  private final PreferencesFx preferencesFx;

  // General
  private final StringProperty welcomeText = new SimpleStringProperty("Hello World");
  private final IntegerProperty brightness = new SimpleIntegerProperty(50);
  private final BooleanProperty nightMode = new SimpleBooleanProperty(false);

  Preferences() {
    this.welcomeText.addListener((observable, oldValue, newValue) -> System.out.println(newValue));
    this.preferencesFx = this.createPreferences();
    this.preferencesFx.show(true);
  }

  private PreferencesFx createPreferences() {
    return PreferencesFx.of(Preferences.class, Category
        .of("General", Group.of("Greeting", Setting.of("Welcome Text", this.welcomeText)), Group
            .of("Display", Setting.of("Brightness", this.brightness),
                Setting.of("Night mode", this.nightMode)))).persistWindowState(false)
        .saveSettings(true).debugHistoryMode(false).buttonsVisibility(true);
  }
}