stage.minHeightProperty().bind(stage.widthProperty().multiply(0.5));

stage.maxHeightProperty().bind(stage.widthProperty().multiply(0.5));

Stage stage = new Stage();

​

stage.widthProperty().addListener((obs, oldVal, newVal) -> {

  //on change width

});

​

stage.heightProperty().addListener((obs, oldVal, newVal) -> {

  //on change height

});

scene.widthProperty().addListener(new ChangeListener<Number>() {

    @Override public void changed(ObservableValue<? extends Number> observableValue, Number oldSceneWidth, Number newSceneWidth) {

        System.out.println("Width: " + newSceneWidth);

    }

});

scene.heightProperty().addListener(new ChangeListener<Number>() {

    @Override public void changed(ObservableValue<? extends Number> observableValue, Number oldSceneHeight, Number newSceneHeight) {

        System.out.println("Height: " + newSceneHeight);

    }

});

stage.widthProperty().addListener((obs, oldVal, newVal) -> {

     // Do whatever you want

});

​

stage.heightProperty().addListener((obs, oldVal, newVal) -> {

     // Do whatever you want

});

​

​

GraphicsDevice gd = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();

int width = gd.getDisplayMode().getWidth();

int height = gd.getDisplayMode().getHeight();

​

​

container.widthProperty().addListener(new ChangeListener<Number>() {

        @Override

        public void changed(ObservableValue<? extends Number> observable, Number oldValue, Number newValue) {

            if (newValue.floatValue()!=oldValue.floatValue()) resizeKids(newValue);

        }

    });