@Nonnull
	public Collection<Stage> getActiveWindows() {
		return activeWindows;
	}
Do not use this list to iterate over if within your loop you will be closing/creating windows.
This will cause a {@link ConcurrentModificationException}. Wrap this result in a new collection
if you want to do that.

@return Active windows.
recaf-ui/src/main/java/software/coley/recaf/services/window/WindowManager.java