how to use gridpane in javafx code example

Example: gridpane javafx example

Button button1 = new Button("Button 1");
Button button2 = new Button("Button 2");
Button button3 = new Button("Button 3");
Button button4 = new Button("Button 4");
Button button5 = new Button("Button 5");
Button button6 = new Button("Button 6");

GridPane gridPane = new GridPane();

gridPane.add(button1, 0, 0, 1, 1);
gridPane.add(button2, 1, 0, 1, 1);
gridPane.add(button3, 2, 0, 1, 1);
gridPane.add(button4, 0, 1, 1, 1);
gridPane.add(button5, 1, 1, 1, 1);
gridPane.add(button6, 2, 1, 1, 1);