I believe the very next paragraph of section 11.2.2 answers the question:
A throw statement whose thrown expression is a final or effectively final exception parameter of a catch clause C can throw an exception class E iff:
- E is an exception class that the
try block of the try statement which declares C can throw; and
- …
So, throw e; “can throw” only exceptions which the corresponding try-block “can throw,” where the latter is defined by the actual statements in the try-block.
Obviously an empty try-block does not qualify as a “can throw” section for any exception class. Your second example “can throw” NullPointerException, and since the catch-block “can throw” only the exception that the try-block “can throw,” the catch-block too can throw only the unchecked NullPointerException.
Your third example’s try-block “can throw” java.lang.Exception itself, therefore the catch-block “can throw” java.lang.Exception, so java.lang.Exception must be caught or declared to be thrown.
