Re: On exceptions

From:
Daniel Pitts <googlegroupie@coloraura.com>
Newsgroups:
comp.lang.java.programmer
Date:
26 May 2007 16:45:02 -0700
Message-ID:
<1180223102.691319.26540@j4g2000prf.googlegroups.com>
On May 26, 1:56 pm, dvdsum <davide.sammart...@gmail.com> wrote:

On 25 Mag, 20:51, Twisted <twisted...@gmail.com> wrote:

On May 25, 8:39 am, dvdsum <davide.sammart...@gmail.com> wrote:

In java we have exceptions, which are too generic and are associated
with different errors. For example:

PipedInputStream read method throws an IOException if input is not
connected with an output stream, or pipe is closed or other IO errors.
Now, form the block catch(IOException e) how can I know the exact
error?


You can catch a specific subclass of IOException to trap on more
specific conditions and distinguish among them. Go to IOException in
the javadoc and then look at the "known subclasses" and their known
subclasses, etc. to get a picture of what you can trap. You should
still catch any remaining IOExceptions and deal with them somehow,
though:

FooStream something = null;
try {
something = somethingElse.openStream();
...} catch (FileNotFoundException e) {

// It's missing!
...} catch (SocketException e) {

// Network problem!
...} catch (IOException e) {

// Something else went wrong!
...} finally {

if (something != null) something.close();

}- Nascondi testo tra virgolette -

- Mostra testo tra virgolette -


Yes, it's right but if method read() threw only IOException, what
would you do? Also,
the IOException is thrown with the code:

throw new IOException(any_message);

and so no subclass of IOException is used (for exambple
SocketException, FileNotFoundException, ecc...).

I don't hava any chance to check the exact error.

Dvdsum


Well, in the case you cited, PipedInputStream.read(), generally you
only care that the pipe is broken anyway. What would be the good of
knowing exactly what caused the PipedInputStream to fail?

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