Unchecked exceptions

Question

From a book:
"When a class undergoes revision, it is not a violation of source or binary compatibility if an exported method is modified to throw additional unchecked exceptions.
Suppose a class invokes a method from another, independently written class. The authors of the former class may carefully document all of the unchecked exceptions that each method throws, but if the latter class is revised to throw additional unchecked exceptions, it is quite likely that the former class (which has not undergone revision) will propagate the new unchecked exceptions even though it does not declare them."
What does the last line about propagating mean? It sounded pretty simple up until then...what I got was that your code can call other code that can add unchecked exceptions at any time...correct? I just don't understand the ending.
Thanks.

Answer 1

But I thought one main differentiating factor of
unchecked exceptions is (more often than not -- if
not always) that you cannot recover from them.You generally either can't or shouldn't, because they're a sign of a programming error or of seros system trouble.
I'd think it'd be an irrelevant point that a callee
could add new unchecked exceptions because (forget
the new unchecked exceptions)It's worth making it clear that unchecked exceptions are not part of the method's contract.
what's a coder to do
with unchecked exceptions the callee already HAS
documented!?Usually nothing. Often it's just worth documenting them as a way laying out preconditions, assumptions, and limitations of the method being called.