Reuse a runnable

src/main/java/org/syndicate_lang/actors/Actor.java

@@ -212,10 +212,12 @@ public class Actor {
         }
     }
 
+    private Runnable __runWorkItems = this::_runWorkItems;
+
     public void execute(WorkItem item) {
         tail.getAndSet(item).set(item);
         if (workItemCount.getAndIncrement() == 0) {
-            _executor.execute(this::_runWorkItems);
+            _executor.execute(__runWorkItems);
         }
     }