From c949ff1e8360b6c7a27a4e31ed5e9c78a9b71b5d Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 21 Dec 2016 03:48:29 -0500
Subject: [PATCH] Optimize ItemStack.isEmpty()

Remove hashMap lookup every check, simplify code to remove ternary

diff --git a/src/main/java/net/minecraft/server/ItemStack.java b/src/main/java/net/minecraft/server/ItemStack.java
index a8f7ff98..9465f4c1 100644
--- a/src/main/java/net/minecraft/server/ItemStack.java
+++ b/src/main/java/net/minecraft/server/ItemStack.java
@@ -143,9 +143,15 @@ public final class ItemStack {
         this.F();
     }
 
+    // Paper start - optimize isEmpty
+    private static Item airItem;
     public boolean isEmpty() {
-        return this == ItemStack.a ? true : (this.item != null && this.item != Item.getItemOf(Blocks.AIR) ? (this.count <= 0 ? true : this.damage < -32768 || this.damage > '\uffff') : true);
+        if (airItem == null) {
+            airItem = Item.REGISTRY.get(new MinecraftKey("air"));
+        }
+        return this == ItemStack.a || this.item == null || this.item == airItem || (this.count <= 0 || (this.damage < -32768 || this.damage > '\uffff'));
     }
+    // Paper end
 
     public static void a(DataConverterManager dataconvertermanager) {
         dataconvertermanager.a(DataConverterTypes.ITEM_INSTANCE, (DataInspector) (new DataInspectorBlockEntity()));
-- 
2.14.3