package com.sample.demos;

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class ComboBoxApp extends Application {
private static boolean isAdded = false;

@Override
public void start(Stage primaryStage) throws Exception {

  ObservableListString> hobbies = FXCollections.observableArrayList("Tennis", "Football", "Cricket");
  ComboBoxString> hobbiesComboBox = new ComboBox(hobbies);

  Button button = new Button("Add Some more hobbies");
  button.setOnAction(new EventHandlerActionEvent>() {
@Override
public void handle(ActionEvent event) {
if (!isAdded) {
     hobbiesComboBox.getItems().add("CoCo");
     hobbiesComboBox.getItems().addAll("Rugby", "kabaddy");
     isAdded = true;
}
}
});

  HBox hBox = new HBox(10, hobbiesComboBox, button);

  primaryStage.setScene(new Scene(hBox));
  primaryStage.setTitle("Combo Box Example");
  primaryStage.setWidth(900);
  primaryStage.setHeight(500);
  primaryStage.show();
}

}

package com.sample.demos;

import javafx.application.Application;

public class TestFX {
public static void main(String args[]) {
  Application.launch(ComboBoxApp.class, args);
}
}