Get NBT Data Tag from Item Stack

main.java

// Do note this is for NMS ItemStacks, not Bukkit ItemStacks.
// You'll need to use CraftItemStack.asCraftCopy/CraftItemStack.asCraftCopy
// if you plan on using Bukkit ItemStacks.

// Imports at top of file
import net.minecraft.server.v1_10_R1.NBTTagCompound;
import net.minecraft.server.v1_10_R1.ItemStack;

// Add this is a method to whatever
private NBTTagCompound getTag(ItemStack stack) {
	NBTTagCompound tag = null;
	if (!stack.hasTag()) {
		tag = new NBTTagCompound();
		stack.setTag(tag);
	}
	if (tag == null) tag = stack.getTag();
	return tag;
}

// To get the NBT of a NMS ItemStack:
NBTTagCompound tag = getTag(stack);

// To update the NBT of a NMS ItemStack:
stack.setTag(tag);

// If you run into an issue with ItemStack already being defined or overwritten by the new import,
// YOU LOSE. http://stackoverflow.com/q/2447880/4633828

// My friend zro is all "pls terminology", so here you go:
// * NBT: Named Binary Tag, so kinda like JSON but for Minecraft. Does cool things.
//   For example: http://minecraft.gamepedia.com/Chunk_format
// * NMS: Node Minecraft Server. Spigot wants you to only use Spigot APIs but I (a bukkit
//   developer for three hours) don't think you should. After all Spigot doesn't let you
//   deal with NBT easily!
// * Bukkit: lol