HashMap of ItemStacks?

[Atijaf]

How would I put and obtain the values within hashmap.  It always returns null?

 

class 1

public static HashMap<ItemStack, Integer> Levels = new HashMap(200)
...//code
ItemStack stack = new ItemStack(Blocks.stone);
Levels.put(stack, 5)

 

class2

ItemStack stack = new ItemStack(Blocks.stone);
int requiredLevel = Levels.get(stack)//Is Null

 

 

[Choonster]

ItemStack

doesn't override the

hashCode

method, so two instances are treated as different keys even if they share the same contents.

 

To use an

ItemStack

as a key, you'll need a wrapper class that overrides

hashCode

to return the hash code of the

ItemStack

's contents;

com.google.common.base.Objects#hashCode

will combine the hash codes of multiple objects for you.

 

Exactly which parts of the

ItemStack

you use in the hash code depends on your requirements: Do you only care about the

Item

, stack size and metadata; or do you include the NBT as well?

NBTTagCompound

overrides

hashCode

to return the hash of its contents, so you don't need to calculate that yourself.

[kauan99]

also, if you'll only need to differentiate between item, stack size and metadata, and if you won't need to put or get things into the map too often then you could put/get ItemStack.toString. I think it would work, but it's probably slow.

[Atijaf]

Thank you for the replies.  I will probably create a wrapper class that holds the item, stack size(Maybe), and metadata and override hashcode.

[Draco18s]

If you don't want to use a wrapper class you can also use a TCustomHashMap from the trove library (Minecraft comes with it). This lets you specifiy how to calculate equals and hashCode instead of using the normal methods.

 

While I will probably just use wrapper objects, that's pretty neat.