How to create toolbar with left, center and right sections in javaFX?

Spring method for ToolBar section alignment works fine for me.

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.stage.Stage;

public class SectionalToolbar extends Application {
    @Override
    public void start(Stage stage) throws Exception {
        final Pane leftSpacer = new Pane();
        HBox.setHgrow(
                leftSpacer,
                Priority.SOMETIMES
        );

        final Pane rightSpacer = new Pane();
        HBox.setHgrow(
                rightSpacer,
                Priority.SOMETIMES
        );

        final ToolBar toolBar = new ToolBar(
                new Button("Good"),
                new Button("Boys"),
                leftSpacer,
                new Button("Deserve"),
                new Button("Fruit"),
                rightSpacer,
                new Button("Always")
        );
        toolBar.setPrefWidth(400);

        BorderPane layout = new BorderPane();
        layout.setTop(toolBar);

        stage.setScene(
                new Scene(
                        layout
                )
        );
        stage.show();
    }
    public static void main(String[] args) { launch(); }
}  

A ToolBar (at least in the standard modena.css stylesheet for Java 8), is already internally implemented as a HBox container, so you can just use the HBox.setHgrow method to adjust the internal layout constraints of items you place in a toolbar.

The left and right spacers in this example are implemented as blank panes which will just grow and shrink to fit available space.

If you wanted a spacer which was a fixed size, instead of HBox.setHgrow, you could use something like:

leftSpacer.setPrefSize(20); 
leftSpacer.setMinSize(HBox.USE_PREF_SIZE); 
leftSpacer.setMaxSize(HBox.USE_PREF_SIZE);