Добавить массив из кнопок

мне нужно добавить массив из кнопок, но у меня есть готовый шаблон fxml в который надо добавить кнопки, я не знаю как это сделать, так как у меня в приложение три окна, в последнее надо добавить кнопки, когда я пыталась добавить в main классе, то без метода stage.show(); кнопки не добавлялись, а если использовать этот метод, то первые два окна не открывались, а сразу третье, вот весь main, закомментировала код где пыталась добавить в 3 окно кнопки

    package sample;


import javafx.application.Application;
import javafx.fxml.FXMLLoader;

import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;

public class Main extends Application {

    public static void main(String[] args) {
        launch(args);
    }
    @Override
    public void start(Stage primaryStage) throws Exception{
        Pane root = FXMLLoader.load(getClass().getResource("Start/sample.fxml"));
      


        primaryStage.setScene(new Scene(root,600,400));
        primaryStage.show();

       /* Pane root1 = FXMLLoader.load(getClass().getResource("Map/MetroMap.fxml"));
        Button[] btn = new Button[10];
        for (
                int i = 0;
                i < 10; i++) {
            btn[i] = new Button();
            btn[i].setLayoutX(i * i*3);
             ;
            btn[i].setLayoutY(i * i*2);
            root1.getChildren().add(btn[i]);
            System.out.println(i);
        }

        Stage stage = new Stage();

        stage.setScene(new Scene(root1,1450,800));
        stage.show();

        */

    }


}

пыталась так же добавить в контроллере, но там вообще выходит ошибка на ошибке, понимаю что метод абсолютно неправильный

Controller

 Button [] buttons = new Button[10];
        Pane root = FXMLLoader.load(getClass().getResource("Map/MetroMap.fxml"));
        for (
                int i = 0;
                i < 10; i++) {
            buttons[i] = new Button();
            buttons[i].setLayoutX(i * i*3);
            ;
            buttons[i].setLayoutY(i * i*2);
            root.getChildren().add(buttons[i]);
            System.out.println(i);
        }

вот ошибки

at javafx.fxml/javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2625) at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2595) at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2466) at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:2435) at sample.Time.TimeWindow.lambda$initialize$1(TimeWindow.java:76) at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86) at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59) at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49) at javafx.base/javafx.event.Event.fireEvent(Event.java:198) at javafx.graphics/javafx.scene.Node.fireEvent(Node.java:8879) at javafx.controls/javafx.scene.control.Button.fire(Button.java:200) at javafx.controls/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:206) at javafx.controls/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274) at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218) at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80) at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59) at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54) at javafx.base/javafx.event.Event.fireEvent(Event.java:198) at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3851) at javafx.graphics/javafx.scene.Scene$MouseHandler.access$1200(Scene.java:3579) at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1849) at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2588) at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397) at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295) at java.base/java.security.AccessController.doPrivileged(AccessController.java:391) at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:434) at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:390) at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433) at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556) at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942) at javafx.graphics/com.sun.glass.ui.mac.MacView.notifyMouse(MacView.java:127) Caused by: java.lang.reflect.InvocationTargetException at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:564) at com.sun.javafx.reflect.Trampoline.invoke(MethodUtil.java:76) at jdk.internal.reflect.GeneratedMethodAccessor2.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:564) at javafx.base/com.sun.javafx.reflect.MethodUtil.invoke(MethodUtil.java:273) at javafx.fxml/com.sun.javafx.fxml.MethodHelper.invoke(MethodHelper.java:83) at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2591) ... 47 more Caused by: java.lang.NullPointerException: Location is required. at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3230) at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3194) at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3163) at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3136) at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3113) at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:3106) at sample.Map.MetroMap.addButtons(MetroMap.java:451) at sample.Map.MetroMap.initialize(MetroMap.java:445) ... 58 more