InventoryClickEvent isn't being cancled

Code:

public class Main extends JavaPlugin implements Listener {
 
    public static Inventory shopInventory;
 
    public void onEnable() {
        shopInventory = Bukkit.createInventory(null, 9, "Welcome To The Shop");
        System.out.print("ShopInventory has been enabled");
        getServer().getPluginManager().registerEvents(this, this);
    }
 
    public void onDisable() {
        System.out.print("ShopInventory has been disabled");
    }
 
    public boolean onCommand(CommandSender sender, Command command,
            String label, String[] args) {
        if (label.equalsIgnoreCase("shop")) {
            List<String> ls = new ArrayList<String>();
            ls.add(ChatColor.GREEN + "(Hero Item)");
            ls.add(ChatColor.GOLD + "200 Gold");
            List<String> villan = new ArrayList<String>();
            villan.add(ChatColor.DARK_RED + "(Villian Item)");
            villan.add(ChatColor.AQUA + "200 Diamonds");
            if (sender instanceof Player) {
                ((Player)sender).openInventory(shopInventory);
                shopInventory.clear();
                shopInventory.addItem(setName(
                        new ItemStack(Material.SLIME_BALL), ChatColor.DARK_RED
                                + "Slime Grenade", ls));
                shopInventory.addItem(setName(new ItemStack(
                        Material.GOLDEN_APPLE), ChatColor.DARK_PURPLE
                        + "Jester's Apple", villan));
            } else if (!(sender instanceof Player)) {
                sender.sendMessage(ChatColor.GRAY + "[" + ChatColor.GOLD + "GameName" + ChatColor.GRAY + "]" + ChatColor.DARK_RED + "You must be a player");
                return true;
            }
        }
        return false;
    }
 
    private ItemStack setName(ItemStack is, String name, List<String> lore) {
        ItemMeta im = is.getItemMeta();
        if (name != null)
            im.setDisplayName(name);
        if (lore != null)
            im.setLore(lore);
        is.setItemMeta(im);
        return is;
    }
 
    @EventHandler
    public void onInventoryClick(InventoryClickEvent event) {
        if (event.getInventory() == shopInventory) {
            if (event.getCurrentItem().getType() == Material.SLIME_BALL) {
                event.setCancelled(true);
                event.getWhoClicked().getInventory()
                        .addItem(new ItemStack(Material.SLIME_BALL));
            }
        }
    }
}
 
 

This is my code and when i click the slimeball the event isn't being canceled and i can take it out of the shopInventory. Does anyone know what i did wrong?

 

maybe try replacing
event.setCancelled(true);
with
event.setResult(DENY);

 

I tried event.setResult(Result.DENY); instead of event.setResult(DENY);

 

setCanceled() actually sets Result.DENY, see the source code.

The problem is in your inventory comparison, I doubt that works.
You should compare title and size instead.

 

How would i got about comparing title and size?

Edit: I Fixed it, that you digi. I compared it with the inventory size instead you are a great help