testserver/patches/server/0804-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 9c45e49f480ccd72f6d6c94e5dec41c4becc76cf..4aac9be67a073e60272a68b52c2cda026d4ee28f 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
@@ -832,7 +832,7 @@ 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
 
         Palette(List<StructureTemplate.StructureBlockInfo> infos) {
             this.blocks = infos;