Transfer Stack In Slot

@Override
	public ItemStack transferStackInSlot(EntityPlayer playerIn, int index)
	{
		ItemStack itemstack = ItemStack.EMPTY;
        Slot slot = this.inventorySlots.get(index);

        if (slot != null && slot.getHasStack())
        {
            ItemStack itemstack1 = slot.getStack();
            itemstack = itemstack1.copy();

            if (index < this.numRows * 9)
            {
                if (!this.mergeItemStack(itemstack1, this.numRows * 9, this.inventorySlots.size(), true))
                {
                    return ItemStack.EMPTY;
                }
            }
            else if (!this.mergeItemStack(itemstack1, 0, this.numRows * 9, false))
            {
                return ItemStack.EMPTY;
            }

            if (itemstack1.isEmpty())
            {
                slot.putStack(ItemStack.EMPTY);
            }
            else
            {
                slot.onSlotChanged();
            }
        }

        return itemstack;
	}