Item and ItemStack

Here, I want to talk about the distinction between Item and ItemStack. Let's start with ItemStack and think step by step about why they need to be distinguished.

As the name implies, ItemStack is an Item Stack. In fact, in the game, all the items in the item slots are individual ItemStacks.

For example, in this case, there are three ItemStacks.

But this begs the question, although one set of apples is different in number from the second set, that number doesn't actually affect their actual performance. They can also be eaten, and the effect of the reply is the same when eaten.

These are the same as Properties or Default Behavior, and the same logic should be extracted from them, which is called Item.

Again, there are only two kinds of Items here: apples and iron swords.

You can imagine that ItemStack is a wrapper for Item, which provides additional attributes such as quantity, NBT tags, etc.

It's worth noting here that just because ItemStack is zero, it doesn't mean it's null, so you have to use the isEmpty() method under ItemStack to determine if it's null.

ItemStack contains Item is actually the same instance, the reason is very simple, if it is not the same instance, it will pointlessly produce many of the same instance, for optimization purposes, of course, is appropriate to share an instance, which also means that you can useresult.getItem() == Items to detect which Item is stored in ItemStack.