From David L. from the user the mailing list:
I'm trying to read annotations from PDFs and am having trouble matching up
replies with the annotations they're in reply to.
PDPage.getAnnotations() returns a list of PDAnnotation. When I have
a PDAnnotationMarkup, I try to call getInReplyTo to get the previous
annotation in the thread. But I have two problems:
1) getInReplyTo() crashes if the annotation isn't a reply. It'd be nice if
it just returned null. I can work around this by getting the COSDictionary
and checking for an IRT entry first.
(... other problem already solved...)
it is an IOException, this isn't as bad as a nullpointerexception. But it is kindof weird indeed, usually we just return null when something doesn't exist.