If you run the code below on JDK 8 it renders a left arrow and a right arrow as expected. If you run on JDK 8 update 20 then square boxes are rendered.

I'm using Font Awesome but I expect it is the case with other fonts as well. When running the code you need the fontawesome-webfont.ttf in the root directory.

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.FlowPane;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class FontAwesomeTest extends Application {
    @Override
    public void start(Stage stage) throws Exception {
        String fontLocation = getClass().getResource("/fontawesome-webfont.ttf").toExternalForm();
        Font.loadFont(fontLocation, 12);

        FlowPane pane = new FlowPane();
        Scene scene = new Scene(pane, 500, 500);
        stage.setScene(scene);

        Text leftArrow = new Text("\uf060");
        leftArrow.setStyle("-fx-font-family: FontAwesome; -fx-font-size: 40px;");
        Text rightArrow = new Text("\uf061");
        rightArrow.setStyle("-fx-font-family: FontAwesome; -fx-font-size: 40px;");

        pane.getChildren().addAll(leftArrow, rightArrow);

        stage.show();
    }

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