removeInventoryItem

public void removeInventoryItem(Inventory inv,chestItem ch) {
        ItemStack[] ls = inv.getContents();
        for(ItemStack is : ls) {
            if (compareItem(is,ch)) {
                if (is.getAmount()<=1) {
                    is.setType(Material.AIR);
                    is.setAmount(0);
                }
                else {
                    is.setAmount(is.getAmount()-1);
                }
                break;
            }
        }
        inv.setContents(ls);
    }