Re: Some same exceptions used in a given file

From:

Patricia Shanahan <pats@acm.org>

Newsgroups:

comp.lang.java.help

Date:

Sun, 24 Apr 2011 06:53:11 -0700

Message-ID:

<_q6dnZ2mCMrWtinQnZ2dnUVZ_vOdnZ2d@earthlink.com>

On 4/24/2011 12:34 AM, Merciadri Luca wrote:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Patricia Shanahan<pats@acm.org> writes:

On 4/23/2011 10:08 AM, Merciadri Luca wrote:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,

In some of my code files, I've got the following catch block

==
          catch (IOException cantOpenFile)
              {
                  System.err.println("Can't open " + inputFilename + ".");
                  System.exit(1);
              }
==
more than once, but at different places in the file. Is it possible to
define this somewhere so that I can directly catch the exception with
the two given commands? (Just as one would define his own exception.)

I can see two options for reducing the amount of duplicate code:

1. Put the try-catch for IOException at a high enough level in the call
hierarchy, and wide enough scope, that it will catch all instances of
IOException for which you want the same handling.

2. Extract the handling for IOException into a method that can be called
from multiple catch blocks.

And what is the difference between try and catch at a high enough
level and the same, but with a throw in the method that might generate
an exception?

If I understand the question correctly, the difference is which
exception the high level method sees.

I generally design and document the exceptions a method throws along
with designing and documenting its arguments and return. Sometimes it
may make sense to let something like IOException filter up. In other
cases it is better to throw an exception that adds information the
method has, and wraps the IOException as its cause.

Patricia