Updating an inventory

I need a way to update an inventory.
Is there any way I can do this ? (this isn't a player inventory it will be either a workbench, furnace, or player craft table inventory)
e.g.

Code:

Inventory inv = ...;//I get the inventory here
...// This is where I change things
inv.something // Now I need it to update

 

Can't you just update the BlockState?

 

Why do you want to update block's inventory? It refreshes as soon as you add any item to it.

 

Tried that it didn't do anything.
I did fix this though I just sent a setslot packet.
@Acrobot : I was setting a slot to null for the result in a workbench but it still showed up as the item instead of nothing.

 

@Crash
That's not how it should be done, you should probably look into changing recepies.

 

Is it possible to remove recipes with the CraftingManager ?

 

updateInventory()

 

It's not a player inventory