To change these slots, this event should be cancelled and all desired changes to the inventory applied. Alternatively, scheduling a task using BukkitScheduler. Returns a HashMap with all slots and ItemStacks in the inventory with the given Material. void, clear(). Clears out the whole Inventory. void, clear(int index). setSlot(slot_number, itemstack) you can iterate through slot numbers and set them to items with names/amounts to figure out Bukkit slot.