Use the setAlignment Method in JavaFX

import javafx.application.Application; // Package for the whole application
import javafx.geometry.Pos; // Geometric positioning Package for the variable "Pos"
import javafx.stage.Stage; // Package for the stage
import javafx.scene.Scene; // Package for the scene
import javafx.scene.layout.HBox; // The HBox Package
import javafx.scene.control.Button; // Package for the button

public class FxHBox extends Application  {  //Our main class extends to the Application class
    Button buttonOne, buttonTwo;  // Declared two buttons
    HBox _hbox; // Declared a HBox
    Scene scene; // Declared a scene

    public void start(Stage BasicStage) throws Exception {  // We have to use Exception Handling here as it can generate errors if anything goes wrong.
        BasicStage.setTitle("HBox Set Allignment"); // Set the  title of the application
        buttonOne = new Button("Button 1"); // Created button 1 with title
        buttonTwo = new Button("Button 2"); // Created button 2 with title

        _hbox = new HBox(buttonOne, buttonTwo); // Created an HBox element that holds the two buttons buttonOne & buttonTwo
        _hbox.setAlignment(Pos.CENTER); // Here we are customizing the default alignment and place our componet in center. Here 'Pos' provides the geometic allignment.

        scene = new Scene(_hbox, 400, 300); // Creates the scene with necessary heights and weights
        BasicStage.setScene(scene); // Set the scene
        BasicStage.show(); // Visualize the scene
    }

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

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.HBox;
import javafx.scene.control.Button;

public class FxHBox extends Application  {
    Button buttonOne, buttonTwo;
    HBox _hbox;
    Scene scene;

    public void start(Stage BasicStage) throws Exception {
        BasicStage.setTitle("HBox Set Allignment");
        buttonOne = new Button("Button 1");
        buttonTwo = new Button("Button 2");

        _hbox = new HBox(buttonOne, buttonTwo);
        _hbox.setAlignment(Pos.CENTER);

        scene = new Scene(_hbox, 400, 300);
        BasicStage.setScene(scene);
        BasicStage.show();
    }

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