Exceptions and Assertions - The Java Programming Language - page 427

TRy blocks can be further complicated if both pre and the other actions
can throw the same exceptionsquite common with I/O operationsand we
wish to propagate the exception after using it in some way; an excep-
tion thrown by the other actions would get caught twice and we would
have to code our catch blocks to watch for and deal with that situation.
A finally clause can also be used to clean up for break , continue , and
return , which is one reason you will sometimes see a try clause with no
catch clauses. When any control transfer statement is executed, all rel-
evant finally clauses are executed. There is no way to leave a try block
without executing its finally clause.
The preceding example relies on finally in this way to clean up even
with a normal return . One of the most common reasons goto is used in
other languages is to ensure that certain things are cleaned up when a
block of code is complete, whether or not it was successful. In our ex-
ample, the finally clause ensures that the file is closed when either the
return statement is executed or the stream throws an exception.
A finally clause is always entered with a reason. That reason may be
that the try code finished normally, that it executed a control flow state-
ment such as return , or that an exception was thrown in code executed
in the TRy block. The reason is remembered when the finally clause
exits by falling out the bottom. However, if the finally block creates
its own reason to leave by executing a control flow statement (such as
break or return ) or by throwing an exception, that reason supersedes the
original one, and the original reason is forgotten. For example, consider
the following code:
try {
// ... do something ...
return 1;
} finally {
return 2;
}