How to use

getFilterStack

method

in

cofh.core.util.filter.ItemFilterWrapper

public ItemStack getFilterStack() {
  return filterWrapper.getFilterStack();
}

public void onSlotChanged() {
  ItemStack item = player.inventory.mainInventory.get(containerIndex);
  if (valid && !item.isEmpty() && item.getItem() == filterWrapper.getFilterItem()) {
    player.inventory.mainInventory.set(containerIndex, filterWrapper.getFilterStack());
  }
}