Separate css file for JavaFX project

How can I apply a certain style for all lines objects in a separate css file for a javaFX project? This is the java code :

package com.example.demo;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Line;
import javafx.stage.Stage;

import java.io.IOException;

public class HelloApplication extends Application {
    @Override
    public void start(Stage stage) throws IOException {
        Pane root = new Pane();
        Scene scene = new Scene(root, 1200, 800);
        stage.setTitle("Simulink viewer");
        Label l1 = new Label("hdkhsd");
        l1.setLayoutX(100);
        l1.setLayoutY(100);
        Label l2 = new Label("helle");
        l2.setLayoutX(400);
        l2.setLayoutY(400);
        root.getChildren().addAll(l1,l2);
        Line l = new Line(10,10,90,90);
        root.getChildren().add(l);
        scene.getStylesheets().add(getClass().getResource("style.css").toExternalForm());
        stage.setScene(scene);
        stage.show();
    }

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

And this is the css file:

.root{
-fx-background-color : #ADD8E6;
}

.label {
-fx-border-color: red;
}

.line {
-fx-stroke = green;

}

The style works for both root and label, but it doesn't work for line. What is the problem?

I'm having this warning:

May 13, 2023 4:31:05 PM javafx.css.CssParser declaration WARNING: CSS Error parsing file:/E:/College/Now/Advanced/Projects/normal%20java%20projects/demo/target/classes/com/example/demo/style.css: Expected COLON at [10,11]

I actually read that style class for line is empty by default. What does that mean? Does it mean I can't style line in a separate css file?

Solution

First, note you have a syntax error in your CSS file:

-fx-stroke = green;

should be

-fx-stroke: green;

Additionally, note from the documentation that the style class of Line is empty by default. (Only Control and its subclasses, along with ImageView, WebView, and MediaView have default style classes.) Consequently, the selector will not select the line. You can either add the style class to the line explicitly:

    Line l = new Line(10,10,90,90);
    l.getStyleClass().add("line");

or us a Type Selector. From the documentation:

Node's getTypeSelector method returns a String which is analogous to a CSS Type Selector. By default, this method returns the simple name of the class.

So the following will work without adding the style class in the Java code:

Line {
-fx-stroke: green;

}