From bfe2ce7ec6dc0598f06b91d0e380e6fe36e30e47 Mon Sep 17 00:00:00 2001
From: James Procter <j.procter@dundee.ac.uk>
Date: Wed, 25 Oct 2023 11:17:06 +0100
Subject: [PATCH] JAL-4312 defend against ConcurrentModificationException

---
 src/jalview/workers/AlignCalcManager.java |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/jalview/workers/AlignCalcManager.java b/src/jalview/workers/AlignCalcManager.java
index 435d40c..508a069 100644
--- a/src/jalview/workers/AlignCalcManager.java
+++ b/src/jalview/workers/AlignCalcManager.java
@@ -305,14 +305,16 @@ public class AlignCalcManager implements AlignCalcManagerI
           Class<? extends AlignCalcWorkerI> workerClass)
   {
     List<AlignCalcWorkerI> workingClass = new ArrayList<AlignCalcWorkerI>();
+    AlignCalcWorkerI[] workers;
     synchronized (canUpdate)
     {
-      for (AlignCalcWorkerI worker : canUpdate)
+      workers = canUpdate.toArray(new AlignCalcWorkerI[0]);
+    }
+    for (AlignCalcWorkerI worker : workers)
+    {
+      if (workerClass.equals(worker.getClass()))
       {
-        if (workerClass.equals(worker.getClass()))
-        {
-          workingClass.add(worker);
-        }
+        workingClass.add(worker);
       }
     }
     return (workingClass.size() == 0) ? null : workingClass;
-- 
1.7.10.2