public class CommandTestItem extends SimplePlayerCommand implements Listener {

    private ItemStack itemStack;

    public CommandTestItem() {
        super("testitem", Rank.DEVELOPER);
        Bukkit.getPluginManager().registerEvents(this, SkyBlockSpawn.a());
        this.itemStack = createItem();
    }

    @Override
    public void onCommand(Player player, String[] strings) {
        Inventory inv = Bukkit.createInventory(player, 9, "Test Inv");
        inv.setItem(0, itemStack);

        player.openInventory(inv);
    }

    @EventHandler
    public void onInvClick(InventoryClickEvent e){
        if(e.getView().getTitle().equals("Test Inv")){
            if(e.getCurrentItem() != null){
                e.getWhoClicked().sendMessage("Similar: " + itemStack.isSimilar(e.getCurrentItem()));
            }
        }
    }

    private ItemStack createItem(){
        ItemStack itemStack = new ItemStack(Material.FILLED_MAP);
        MapMeta mapMeta = (MapMeta) itemStack.getItemMeta();
        mapMeta.setColor(DyeColor.GREEN.getColor());
        mapMeta.setLocationName("");
        mapMeta.addItemFlags(ItemFlag.HIDE_ATTRIBUTES);
        mapMeta.addItemFlags(ItemFlag.HIDE_PLACED_ON);
        mapMeta.addItemFlags(ItemFlag.HIDE_POTION_EFFECTS);
        mapMeta.addItemFlags(ItemFlag.HIDE_DESTROYS);
        mapMeta.addItemFlags(ItemFlag.HIDE_UNBREAKABLE);

        itemStack.setItemMeta(mapMeta);
        return itemStack;
    }
}