public int getFirstNotEmptySlot(ItemStackHandler inventory)
    {
        int slot = 0;
        int counter;
        for (counter = inventory.getSlots(); counter > 0; counter -= 1);
        {
            if (!inventory.getStackInSlot(counter).isEmpty())
            {
                return counter;
            }
        }
        return slot;
    }
    public int getFirstEmptySlot(ItemStackHandler inventory)
    {
        int slot = 0;
        int counter;
        for (counter = 0; counter < inventory.getSlots() - 1; counter += 1);
        {
            if (inventory.getStackInSlot(counter).isEmpty())
            {
                return counter;
            }
        }
        return slot;
    }