Exceptional Puzzlers - Java Puzzlers: Traps, Pitfalls, and Corner Cases - page 109

this happens when in.close is called, the exception prevents out.close from getting called, and
the output stream remains open.
Note that this program violates the advice of Puzzle 36 : The calls to close can cause the finally
block to complete abruptly. Unfortunately, the compiler doesn't help you find the problem, because
close throws the same exception type as read and write , and the enclosing method ( copy ) is
declared to propagate it.
The solution is to wrap each call to close in a nested try block. The following version of the
finally block is guaranteed to invoke close on both streams:
} finally {
if (in != null) {
try {
in.close();
} catch (IOException ex) {
// There is nothing we can do if close fails
}
}
if (out != null) {
try {
out.close();
} catch (IOException ex) {
// Again, there is nothing we can do if close fails
}
}
}
As of release 5.0, you can refactor the code to take advantage of the Closeable interface: