From 3cd83fe77b1f1c37592895e602d2c4588aa9cbdc Mon Sep 17 00:00:00 2001
From: Joseph Hirschfeld <joe@ibj.io>
Date: Sat, 20 Feb 2016 00:42:18 -0500
Subject: [PATCH] Change implementation of (tile)entity removal list

As it stood, the complexity of a ArrayList.removeAll(ArrayList) is
much greater as the argument array list grew than .removeAll(HashSet).

diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index a76d83c..f0cd810 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -3,6 +3,7 @@ package net.minecraft.server;
 import com.google.common.base.Predicate;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
 import org.bukkit.Bukkit;
 import org.bukkit.block.BlockState;
 import org.bukkit.craftbukkit.CraftServer;
@@ -58,11 +59,11 @@ public abstract class World implements IBlockAccess {
         }
     };
     // Spigot end
-    protected final List<Entity> g = Lists.newArrayList();
+    protected final Set<Entity> g = Sets.newHashSet(); // Paper
     //public final List<TileEntity> h = Lists.newArrayList(); // PaperSpigot - Remove unused list
     public final List<TileEntity> tileEntityList = Lists.newArrayList();
     private final List<TileEntity> b = Lists.newArrayList();
-    private final List<TileEntity> c = Lists.newArrayList();
+    private final Set<TileEntity> c = Sets.newHashSet(); // Paper
     public final List<EntityHuman> players = Lists.newArrayList();
     public final List<Entity> k = Lists.newArrayList();
     protected final IntHashMap<Entity> entitiesById = new IntHashMap();
@@ -1400,18 +1401,19 @@ public abstract class World implements IBlockAccess {
         int j;
         int k;
 
-        for (i = 0; i < this.g.size(); ++i) {
-            entity = (Entity) this.g.get(i);
-            j = entity.ae;
-            k = entity.ag;
-            if (entity.ad && this.isChunkLoaded(j, k, true)) {
-                this.getChunkAt(j, k).b(entity);
+        // Paper start - Set based removal lists
+        for (Entity e : this.g) {
+            j = e.ae;
+            k = e.ag;
+            if (e.ad && this.isChunkLoaded(j, k, true)) {
+                this.getChunkAt(j, k).b(e);
             }
         }
 
-        for (i = 0; i < this.g.size(); ++i) {
-            this.b((Entity) this.g.get(i));
+        for (Entity e : this.g) {
+            this.b(e);
         }
+        // Paper end
 
         this.g.clear();
         timings.entityRemoval.stopTiming(); // Spigot
-- 
2.7.1