GridFinalizer.java

public class GridFinalizer implements Finalizer<InventoryButtonPage, GridTarget> {

    @Override
    public void display(Player player, GridTarget target, InventoryButtonPage page, PluginContainer owner) {
        CustomInventoryBuilder builder = new CustomInventoryBuilder();
        builder.of(InventoryArchetypes.CHEST).property(new InventoryDimension(9, target.height()))
                .property(new InventoryTitle(page.title()));
        int offset = (9 - target.length()) / 2;
        offset = offset < 0 ? 0 : offset;

        Inventory inventory = builder.build(owner.getInstance().get());
        for (int x = 0; x < target.length(); x++) {
            for (int y = 0; y < target.height(); y++) {
                Inventory slot = inventory.query(new SlotPos(x + offset, y)).query(Slot.class);
                if(slot instanceof Slot) {
                    target.get(x, y).ifPresent(stack -> ((Slot) slot).set(stack));
                }
            }
        }

        player.closeInventory(Cause.of(NamedCause.source(MenuPlugin.container()), NamedCause.of("reason", InventoryReason.NEW_MENU)));
        player.openInventory(inventory, Cause.of(NamedCause.source(MenuPlugin.container()), NamedCause.of("reason", InventoryReason.OPEN_MENU)));
    }

    @Override
    public Class<InventoryButtonPage> page() {
        return InventoryButtonPage.class;
    }

    @Override
    public Class<GridTarget> target() {
        return GridTarget.class;
    }

}