From d88c61fc94ba55c5266fb376310c3dbd04461662 Mon Sep 17 00:00:00 2001
From: ceze88 <dev.ceze@gmail.com>
Date: Sat, 23 Mar 2024 19:17:01 +0100
Subject: [PATCH] Fix concurrent modification exception

---
 .../com.craftaro.ultimatestacker/tasks/StackingTask.java | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/UltimateStacker-Plugin/src/main/java/com.craftaro.ultimatestacker/tasks/StackingTask.java b/UltimateStacker-Plugin/src/main/java/com.craftaro.ultimatestacker/tasks/StackingTask.java
index 04270f2..3c42abe 100644
--- a/UltimateStacker-Plugin/src/main/java/com.craftaro.ultimatestacker/tasks/StackingTask.java
+++ b/UltimateStacker-Plugin/src/main/java/com.craftaro.ultimatestacker/tasks/StackingTask.java
@@ -89,12 +89,15 @@ public class StackingTask extends BukkitRunnable {
                 //Filter non-stackable entities to improve performance on main thread
                 entities.removeIf(this::isEntityNotStackable);
 
-                for (LivingEntity entity : entities) {
+                List<LivingEntity> remove = new ArrayList<>();
+                for (LivingEntity entity : entities) { //Q: What can cause current modification exception here?
                     // Check our WorldGuard flag.
                     Boolean flag = WorldGuardHook.isEnabled() ? WorldGuardHook.getBooleanFlag(entity.getLocation(), "mob-stacking") : null; //Does this work async?
-                    if (flag != null && !flag)
-                        entities.removeIf(entity1 -> entity1.getUniqueId().equals(entity.getUniqueId()));
+                    if (flag != null && !flag) {
+                        remove.add(entity);
+                    }
                 }
+                entities.removeAll(remove);
 
                 Bukkit.getScheduler().runTask(plugin, () -> {
                     // Loop through the entities.