public class ExampleStaticGUI extends StaticGUI {

    public final StaticGUI gui = new ExampleStaticGUI();

    private ExampleStaticGUI() {
        super(9, "Example GUI!");
        setItem(0, createButton(Material.DIAMOND, "I am a normal button",
                List.of("lore line 1!", "lore line 2!!"), (_player, clickType) -> {
            _player.sendMessage("You clicked this button with the click type: " + clickType.name());
        }));
        setItem(1, ench(createButton(Material.DIAMOND, "I am a normal button but I am enchanted!",
                List.of("lore line 1!", "lore line 2!!"), (_player, clickType) -> {
                    _player.sendMessage("You clicked this button with the click type: " + clickType.name());
                })));
        for (int i = 2; i < 9; i++) addItem(createGrayPlaceHolder("I am a placeholder"));
        setOnCloseRun((_player, clickType) -> {
            _player.sendMessage("You closed a menu, the click type, 'clickType' in this case, will always be null when an on close event is run");
        });
    }
}

public class ExampleGUICreator extends GUIUtils {

    public static void openMainMenu(Player player) {
        GUICreator c = new GUICreator(9, "This gui was created using the GUICreator class!");
        //c.setDestroyOnClose(true); you should avoid making this call (in most cases) as it will keep ths GUI in memory
        //forever. It is set to false by default. Whenever a menu is closed, it is destroyed (taken out of memory) by default.
        //If you want it to not be destroyed, maybe consider using StaticGUI (applicable in most cases)
        c.setItems(
                c.createButton(Material.EMERALD, "Your IGN is: " + player.getName(), List.of("I am lore!"), (_player, clickType) -> {
                    _player.sendMessage("You clicked a button!");
                }),
                ench(c.createButton(Material.EMERALD, "Your IGN is: " + player.getName(), List.of("I am an enchanted button!"), (_player, clickType) -> {
                    _player.sendMessage("You clicked a button!");
                }))
        );
        c.setOnCloseRun((_player, clickType) -> {
            _player.sendMessage("You closed the example menu, have fun making your own!");
        });
        c.open(player);
    }
}

  ExampleStaticGUI.open(player);
  ExampleGUICreator.openMainMenu(player);