When a player right clicks the block with a key (tripwire hook) in hand, it creates an inventory that can be later accessed by right clicking that same block. I'm wondering what would be the best way to do this, to determine if the block already has an inventory, or if it needs to create a new one. I was thinking of something like this. Locations: 1: world,x,y,z 2: world,x,y,z 2: world,x,y,z Items: 1: - ItemStack list 2: - ItemStack list 3: - ItemStack list So it would be Locations.Key#, location value and Items.Key#, ItemStack list value. I could load the Locations section to a HashMap, and if the block location matches one of value, I get the key and load the ItemStack list of the same number. So if the block location matched #3, it would then get ItemStack list from Items.3 and load it in the inventory on open.