@Override
public void handle(Event event) {
    if (event.getSource() instanceof Tile) {
        Tile tile = (Tile) event.getSource();
        if (event.getEventType().equals(MouseEvent.MOUSE_CLICKED)) {
            if (((MouseEvent) event).getButton().equals(MouseButton.SECONDARY))
                tile.toggleFlag();
            else if (((MouseEvent) event).getClickCount() == 2)
                mineField.massClick(tile);
        }
        if (event.getEventType().equals(MouseEvent.DRAG_DETECTED))
            if (!((MouseEvent) event).getButton().equals(MouseButton.SECONDARY))
                tile.startFullDrag();
        if (event.getEventType().equals(MouseDragEvent.MOUSE_DRAG_ENTERED))
            tile.arm();
        if (event.getEventType().equals(MouseDragEvent.MOUSE_DRAG_EXITED))
            tile.disarm();
        if (event.getEventType().equals(MouseDragEvent.MOUSE_DRAG_RELEASED))
            mineField.clickedTile(tile);
        if (event.getEventType().equals(ActionEvent.ANY))
            mineField.clickedTile(tile);
    }
}

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        try {

            StackPane root = new StackPane();

            root.addEventFilter(MouseEvent.MOUSE_PRESSED, e -> {

                if( e.isPrimaryButtonDown() && e.isSecondaryButtonDown()) {
                    System.out.println( "Both down");
                } else if( e.isPrimaryButtonDown()) {
                    System.out.println( "Primary down");
                } else if( e.isSecondaryButtonDown()) {
                    System.out.println( "Secondary down");
                }

            });

            Scene scene = new Scene(root,400,400);
            primaryStage.setScene(scene);
            primaryStage.show();

        } catch(Exception e) {
            e.printStackTrace();
        }
    }

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

public class Main extends Application {

    BooleanProperty primaryMouseButtonDown = new SimpleBooleanProperty();
    BooleanProperty secondaryMouseButtonDown = new SimpleBooleanProperty();

    @Override
    public void start(Stage primaryStage) {
        try {

            StackPane root = new StackPane();

            root.addEventFilter(MouseEvent.MOUSE_PRESSED, e -> {
                primaryMouseButtonDown.setValue( e.isPrimaryButtonDown());
                secondaryMouseButtonDown.setValue( e.isSecondaryButtonDown());
            });

            root.addEventFilter(MouseEvent.MOUSE_RELEASED, e -> {
                primaryMouseButtonDown.setValue( e.isPrimaryButtonDown());
                secondaryMouseButtonDown.setValue( e.isSecondaryButtonDown());
            });

            BooleanBinding binding = Bindings.and(primaryMouseButtonDown, secondaryMouseButtonDown);
            binding.addListener( new ChangeListener<Boolean>() {

                @Override
                public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue) {
                    System.out.println( "Mouse Button Event: " + oldValue + " -> " + newValue);
                }
            });


            Scene scene = new Scene(root,400,400);
            primaryStage.setScene(scene);
            primaryStage.show();

        } catch(Exception e) {
            e.printStackTrace();
        }
    }

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

boolean mouse_1, mouse_2 = false;

public void mousePressed(MouseEvent e){
    //The numbers are just made up I don't remember the actual codes for the buttons but it's simple enough to figure out.
    if(e.getButton()==1){
        mouse_1  = true;
    }
    if(e.getButton()==2){
        mouse_2  = true;
    }

    if(mouse_1&&mouse_2){
    //Your code here
    }
}

public void mouseReleased(MouseEvent e){
    if(e.getButton() == 1){
        mouse_1 = false;
    }
    if(e.getButton() == 2){
        mouse_2 = false;
    }
}

//flag to track both buttons being pressed
private boolean wereBothButtonsPressed = false;

private void onMousePressed(MouseEvent e) {
    //single button press sets flag to false
    wereBothButtonsPressed = e.isPrimaryButtonDown() && e.isSecondaryButtonDown();
}

private void onMouseReleased(MouseEvent e) {
    if (e.isPrimaryButtonDown() || e.isSecondaryButtonDown()) {
        //do nothing if user is still holding the button
        return;
    }
    if (wereBothButtonsPressed) {
        System.out.prinln("Both buttons");
    } else if (e.getButton() == MouseButton.PRIMARY) {
        System.out.prinln("Only primary");
    } else if (e.getButton() == MouseButton.SECONDARY) {
        System.out.prinln("Only secondary");
    }
}

private boolean wereBothButtonsPressed = false;

@Override
public void handle(Event event) {
    ...

    if (event.getEventType().equals(MouseEvent.MOUSE_PRESSED)) {
        MouseEvent me = (MouseEvent) event;
        wereBothButtonsPressed = me.isPrimaryButtonDown() && me.isSecondaryButtonDown();
    } else if (event.getEventType().equals(MouseEvent.MOUSE_RELEASED)) {
        MouseEvent me = (MouseEvent) event;
        if (!me.isPrimaryButtonDown() && !me.isSecondaryButtonDown()) {
            if(wereBothButtonsPressed) {
                mineField.massClick(tile);
            } else if(me.getButton() == MouseButton.PRIMARY) {
                mineField.clickedTile(tile);
            } else if(me.getButton() == MouseButton.SECONDARY) {
                tile.toggleFlag();
            }
        }
    ...