public static ItemStack<?, ?> AIR = of(new ItemStack(Material.AIR));

 public Inventory getPage(int page) {
        return page < 0 || page >= getPagesAmount() ? null : inventories.get(page);
    }


    public ItemStack<?, ?>[] getContents() {
        ItemStack<?, ?>[] contents = new ItemStack[0];
        int pagesAmount = getPagesAmount();

        if(pagesAmount == 0)
            return contents;

        for(int page = 0; page < pagesAmount; page++){
            CraftInventory inventory = inventories.get(page);
            int oldLength = contents.length;
            contents = Arrays.copyOf(contents, contents.length + inventory.getSize());
            System.arraycopy(inventory.getContents(), 0, contents, oldLength, inventory.getSize());
        }

        return contents;
    }


    public ItemStack<?, ?> getItem(int i) {
        Inventory firstPage = getPage(0);

        if(firstPage == null)
            return WildItemStack.AIR.cloneItemStack();

        int pageSize = firstPage.getSize();
        int page = i / pageSize;
        int slot = i % pageSize;

        CraftInventory actualPage = (CrafInventory) getPage(page);

        if(actualPage == null)
            return ItemStack.AIR.cloneItemStack();

        return actualPage.getItem(slot);
    }

 public void setItem(int i, ItemStack<?, ?> itemStack) {
        Inventory firstPage = getPage(0);

        if(firstPage == null)
            return;

        int pageSize = firstPage.getSize();
        int page = i / pageSize;
        int slot = i % pageSize;

        CraftWildInventory actualPage = (CraftWildInventory) getPage(page);

        if(actualPage == null)
            return;

        actualPage.setItem(slot, itemStack);
    }