import javafx.application.Application; 
import javafx.event.ActionEvent; 
import javafx.event.EventHandler; 
import javafx.scene.Scene; 
import javafx.scene.control.Button; 
import javafx.scene.control.ContextMenu; 
import javafx.scene.control.MenuItem; 
import javafx.scene.control.Tab; 
import javafx.stage.Stage; 

public class ContextMenuTest extends Application { 

  public static void main(String[] args) { 
      launch(args); 
  } 

  @Override 
  public void start(Stage stage) { 
// for a button it is OK to set the context menu then nullify it 
    Button b1 = new Button("B1"); 
    b1.setContextMenu(createContextMenu("B1")); 
    b1.setContextMenu(null); 
     
// but for a tab it throws an exception 
    Tab t1 = new Tab("T1"); 
    t1.setContextMenu(createContextMenu("T1")); 
    t1.setContextMenu(null); 
     
    stage.setScene(new Scene(b1)); 
    stage.show(); 
  } 
   
  private static ContextMenu createContextMenu(String prefix) { 
final ContextMenu contextMenu = new ContextMenu(); 
MenuItem item1 = new MenuItem(prefix + ": About"); 
item1.setOnAction(new EventHandler<ActionEvent>() { 
public void handle(ActionEvent e) { 
System.out.println("About"); 
} 
}); 
MenuItem item2 = new MenuItem(prefix + ": Preferences"); 
item2.setOnAction(new EventHandler<ActionEvent>() { 
public void handle(ActionEvent e) { 
System.out.println("Preferences"); 
} 
}); 
contextMenu.getItems().addAll(item1, item2); 
return contextMenu; 
  } 
}