Paper/patches/server/0651-Use-a-CHM-for-StructureTemplate.Pallete-cache.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Shane Freeder <theboyetronic@gmail.com>
Date: Mon, 12 Jul 2021 12:28:29 +0100
Subject: [PATCH] Use a CHM for StructureTemplate.Pallete cache

fixes a CME due to this collection being shared across threads

diff --git a/src/main/java/net/minecraft/world/level/levelgen/structure/templatesystem/StructureTemplate.java b/src/main/java/net/minecraft/world/level/levelgen/structure/templatesystem/StructureTemplate.java
index e7900e7e8263cae131dad2427fb2bfdadf5b8d14..b120949667ae0169a667b329b3cabbd79a0a5bda 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/structure/templatesystem/StructureTemplate.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/structure/templatesystem/StructureTemplate.java
@@ -889,7 +889,7 @@ public class StructureTemplate {
     public static final class Palette {
 
         private final List<StructureTemplate.StructureBlockInfo> blocks;
-        private final Map<Block, List<StructureTemplate.StructureBlockInfo>> cache = Maps.newHashMap();
+        private final Map<Block, List<StructureTemplate.StructureBlockInfo>> cache = Maps.newConcurrentMap(); // Paper - Fix CME due to this collection being shared across threads
         @Nullable
         private List<StructureTemplate.JigsawBlockInfo> cachedJigsaws;