private HashSet<Block> opened = new HashSet<>();
    @EventHandler
    public void onOpen(InventoryOpenEvent e){
        if (GameStateManager.getGameState() != GameStates.INGAME) return;
        if (e.getInventory().getHolder() instanceof Chest){
            Block b = (Block) e.getInventory().getHolder();
            if (!opened.contains(b)){
                opened.add(b);

                addItems(e.getInventory(), 1);
            }
        } else if (e.getInventory().getHolder() instanceof EnderChest){
            Block b = (Block) e.getInventory().getHolder();
            if (!opened.contains(b)){
                opened.add(b);
                addItems(e.getInventory(), 2);

            }
        }
    }

    private void addItems(Inventory inventory, Integer tier){
        Random rand = new Random();
        int x = rand.nextInt(7) + 2;
        for (int i = 0; i < x; i++){
            int randomslot = rand.nextInt(inventory.getSize());
            int randomarray = rand.nextInt(randomItems(tier).size());
            inventory.setItem(randomslot, randomItems(tier).get(randomarray));
        }
    }

    private List<ItemStack> randomItems(Integer tier){
        Random r = new Random();
        ItemStack is;
        int x = r.nextInt(4) + 1;
        if (tier == 1) {
            is = new ItemStack(Material.ENDER_PEARL);
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.GOLDEN_APPLE);
            x = r.nextInt(5) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ARROW);
            x = r.nextInt(17) + 4;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.BOW);
            is.addEnchantment(Enchantment.ARROW_DAMAGE, 1);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            EnchantmentStorageMeta meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.DAMAGE_ALL, 1, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.PROTECTION_ENVIRONMENTAL, 1, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.ARROW_DAMAGE, 1, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.STICK);
            x = r.nextInt(6) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.FLINT);
            x = r.nextInt(6) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.FEATHER);
            x = r.nextInt(6) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.STRING);
            x = r.nextInt(3) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.APPLE);
            x = r.nextInt(3) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.GOLD_INGOT);
            x = r.nextInt(6) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.COBBLESTONE);
            x = r.nextInt(17) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.WATER);
            randomItems(tier).add(is);

            is = new ItemStack(Material.DIAMOND);
            randomItems(tier).add(is);

        } else {
            is = new ItemStack(Material.ENDER_PEARL);
            x = r.nextInt(6) + 1;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.GOLDEN_APPLE);
            x = r.nextInt(7) + 2;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ARROW);
            x = r.nextInt(17) + 4;
            is.setAmount(x);
            randomItems(tier).add(is);

            is = new ItemStack(Material.DIAMOND_SWORD);
            randomItems(tier).add(is);

            is = new ItemStack(Material.IRON_SWORD);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            EnchantmentStorageMeta meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.DAMAGE_ALL, 2, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.PROTECTION_ENVIRONMENTAL, 2, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.ARROW_DAMAGE, 2, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.DAMAGE_ALL, 3, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.PROTECTION_ENVIRONMENTAL, 3, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.ENCHANTED_BOOK);
            meta = (EnchantmentStorageMeta) is.getItemMeta();
            meta.addStoredEnchant(Enchantment.ARROW_DAMAGE, 3, true);
            is.setItemMeta(meta);
            randomItems(tier).add(is);

            is = new ItemStack(Material.DIAMOND_CHESTPLATE);
            randomItems(tier).add(is);

            is = new ItemStack(Material.DIAMOND_LEGGINGS);
            randomItems(tier).add(is);

            is = new ItemStack(Material.DIAMOND_HELMET);
            randomItems(tier).add(is);

            is = new ItemStack(Material.DIAMOND_BOOTS);
            randomItems(tier).add(is);

        }
        return new ArrayList<>(randomItems(tier));
    }