How to use a FontAwesomeIconView object as a Stage's icon?

I just figured it out. The goal is to get an InputStream. I was able to do that using SwingFXUtils.fromFXImage(icon, null); to get a bufferedImage. From there I used ImageIO.write(bImage, "png", s); to get a byte array. I used to byte array to get an InputStream.

import de.jensd.fx.glyphs.fontawesome.FontAwesomeIcon;
import de.jensd.fx.glyphs.fontawesome.FontAwesomeIconView;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.SnapshotParameters;
import javafx.scene.image.Image;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javax.imageio.ImageIO;

public class FontAwesomeIconExample extends Application {

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

    @Override
    public void start(Stage primaryStage) {

        try {
            // Simple Interface
            VBox root = new VBox(10);
            root.setAlignment(Pos.CENTER);
            root.setPadding(new Insets(10));

            // Convert the FontAwesomeIconView node to an Image
            FontAwesomeIconView iconView = new FontAwesomeIconView(FontAwesomeIcon.AMAZON);
            WritableImage icon = iconView.snapshot(new SnapshotParameters(), null);
            BufferedImage bImage = SwingFXUtils.fromFXImage(icon, null);
            ByteArrayOutputStream s = new ByteArrayOutputStream();
            ImageIO.write(bImage, "png", s);
            InputStream is = new ByteArrayInputStream(s.toByteArray());

            primaryStage.getIcons().add(new Image(is, 16, 16, false, false));

            // Show the stage
            primaryStage.setWidth(300);
            primaryStage.setHeight(100);
            primaryStage.setScene(new Scene(root));
            primaryStage.setTitle("Sample");
            primaryStage.show();
        } catch (IOException ex) {
            Logger.getLogger(FontAwesomeIconExample.class.getName()).log(Level.SEVERE, null, ex);
        }
    }    
}

This is worth noting from the javadoc.

The images should be different sizes of the same image and the best size will be chosen, eg. 16x16, 32x32.

In addition to Sedrick's answer, another (shorter) solution could be to just create an Image (javafx package) and add it stage icons :

FontAwesomeIconView iconView = new FontAwesomeIconView(FontAwesomeIcon.AMAZON);
WritableImage writableImg = iconView.snapshot(null, null);
Image img = SwingFXUtils.toFXImage(SwingFXUtils.fromFXImage(writableImg, null), null);
primaryStage.getIcons().add(img);

P.S A relative post could be found here : Snapshot Image can't be used as stage icon

Edit:

For some reason, the version 8.15 of the FontawesomeFx require the FontAwesomeIconView to be added on a Scene in order to initialize its content, something that is not necessary to do on the newest version of FontawesomeFx. So, in my opinion, you have to either upgrade your FontawesomeFx version or to add the FontAwesomeIconView on a Scene and after to take the snapshot. Like this :

FontAwesomeIconView iconView = new FontAwesomeIconView(FontAwesomeIcon.ID_CARD_ALT);
Scene scene = new Scene(new StackPane(iconView));
WritableImage writableImg = iconView.snapshot(null, null);
Image img = SwingFXUtils.toFXImage(SwingFXUtils.fromFXImage(writableImg, null), null);

Here is the result (using 8.5 version):