[JavaFX]Verbesserungsvorschläge für Code

package game;

import javafx.scene.control.Control;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.stage.Stage;

public class AllLightsOn extends Application {
    public Button[][] buttons = new Button[5][5];
    public Button btn_reset = new Button("reset");
    public boolean[] isButtonOn = new boolean[25];
    public Label lbl_On = new Label("On: ");
    public Label lbl_Off = new Label("Off: ");
    public HBox hBox = new HBox(30);
    public int counter = 0;
    public String pressedButtonId;
    public BorderPane root = new BorderPane();
    public GridPane gridPane = new GridPane();
    public Scene scene = new Scene(root, 350, 400);

    public void changeColor(String index) {
        for (int i = 0; i < 5; i++) {
            for (int j = 0; j < 5; j++) {
                if (buttons[i][j].getId() == index) {
                    if (isButtonOn[Integer.parseInt(index)] == true) {
                        buttons[i][j].setStyle("-fx-background-color: blue");
                        isButtonOn[Integer.parseInt(index)] = false;
                    } else {
                        buttons[i][j].setStyle("-fx-background-color: yellow");
                        isButtonOn[Integer.parseInt(index)] = true;
                    }
                }
            }
        }
    }

    public void startGame(String index) {
        for (int i = 0; i < 5; i++) {
            for (int j = 0; j < 5; j++) {
                if (buttons[i][j].getId() == index) {
                    changeColor(index);
                    if (i < 4) {
                        changeColor(buttons[i + 1][j].getId());
                    }
                    if (i > 0) {
                        changeColor(buttons[i - 1][j].getId());
                    }
                    if (j < 4) {
                        changeColor(buttons[i][j + 1].getId());
                    }
                    if (j > 0) {
                        changeColor(buttons[i][j - 1].getId());
                    }
                }
            }
        }
        refreshLabel();
    }

    public void refreshLabel() {
        int t = 0, f = 0;
        for (int i = 0; i < isButtonOn.length; i++) {
            if (isButtonOn[i] == true) {
                t++;
            } else {
                f++;
            }
        }
        lbl_On.setText("On: " + t);
        lbl_Off.setText("Off: " + f);
    }

       [MENTION=295804]Override[/MENTION]
    public void start(Stage primaryStage) throws Exception {
        for (int i = 0; i < 5; i++) {
            for (int j = 0; j < 5; j++) {
                buttons[i][j] = new Button();
                buttons[i][j].setId(String.valueOf(counter));
                buttons[i][j].setMaxWidth(Double.MAX_VALUE);
                buttons[i][j].setMaxHeight(Double.MAX_VALUE);
                buttons[i][j].setStyle("-fx-background-color: blue");
                isButtonOn[counter] = false;
                gridPane.add(buttons[i][j], i, j);
                gridPane.setHgrow(buttons[i][j], Priority.ALWAYS);
                gridPane.setVgrow(buttons[i][j], Priority.ALWAYS);
                GridPane.setFillWidth(buttons[i][j], true);
                GridPane.setFillHeight(buttons[i][j], true);
                lbl_On.setText("On: ");
                lbl_Off.setText("Off: 25");
                buttons[i][j].setOnAction(new EventHandler<ActionEvent>() {
                       [MENTION=295804]Override[/MENTION]
                    public void handle(ActionEvent event) {
                        pressedButtonId = ((Control) event.getSource()).getId();
                        startGame(pressedButtonId);
                    }
                });
                counter++;
            }
        }
        btn_reset.setOnAction(new EventHandler<ActionEvent>() {
               [MENTION=295804]Override[/MENTION]
            public void handle(ActionEvent event) {
                for (int k = 0; k < isButtonOn.length; k++) {
                    isButtonOn[k] = false;
                }
                for (int i = 0; i < 5; i++) {
                    for (int j = 0; j < 5; j++) {
                        buttons[i][j].setStyle("-fx-background-color: blue");
                    }
                }
                lbl_Off.setText("Off: 25");
                lbl_On.setText("On: ");
            }
        });
        gridPane.setGridLinesVisible(true);
        root.setCenter(gridPane);
        hBox.getChildren().addAll(btn_reset, lbl_On, lbl_Off);
        hBox.setAlignment(Pos.CENTER);
        root.setBottom(hBox);
        primaryStage.setTitle("JavaFX All Lights On");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
}