code: private AbstractInvocation dequeue() {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "dequeue");
  
      AbstractInvocation invocation;
  
      synchronized (barrier) {
        invocation = queue.remove(0);
      }
  
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "dequeue", invocation);
      return invocation;
    }
docs: Dequeue an invocation by removing it from the front of the queue