From 1790c0ad4744d31ea3e30eb87822b4f506de449b Mon Sep 17 00:00:00 2001
From: OOP-778 <33358441+OOP-778@users.noreply.github.com>
Date: Mon, 5 Sep 2022 23:39:52 +0300
Subject: [PATCH] Fix concurrent errors in URLClassLoaderAccess (#3403)

---
 .../common/plugin/classpath/URLClassLoaderAccess.java       | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/common/src/main/java/me/lucko/luckperms/common/plugin/classpath/URLClassLoaderAccess.java b/common/src/main/java/me/lucko/luckperms/common/plugin/classpath/URLClassLoaderAccess.java
index 6cdc7a7d0..4e7f90af5 100644
--- a/common/src/main/java/me/lucko/luckperms/common/plugin/classpath/URLClassLoaderAccess.java
+++ b/common/src/main/java/me/lucko/luckperms/common/plugin/classpath/URLClassLoaderAccess.java
@@ -167,8 +167,10 @@ public abstract class URLClassLoaderAccess {
                 URLClassLoaderAccess.throwError(new NullPointerException("unopenedURLs or pathURLs"));
             }
 
-            this.unopenedURLs.add(url);
-            this.pathURLs.add(url);
+            synchronized (this.unopenedURLs)  {
+                this.unopenedURLs.add(url);
+                this.pathURLs.add(url);
+            }
         }
     }