docs: @Override
      public boolean isEmpty() {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              JmfTr.entry(this, tc, "isEmpty");
          synchronized (getMessageLockArtefact()) {
              if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
                  JmfTr.exit(this, tc, "isEmpty");
              return super.isEmpty();
          }
      }