@Override
	public synchronized String toString() {
		if (events.isEmpty()) {
			return "<no window events>";
		}
		return StringUtils.join(events, "\n");
	}
A spy that tracks window shown and hidden events from the {@link DropDownSelectionTextField}.

<P>Synchronization Policy: the event storage of this class is synchronized to prevent 
concurrent modification exceptions between reading and writing.
Ghidra/Framework/Docking/src/test/java/docking/widgets/SpyDropDownWindowVisibilityListener.java