Re: Is the finally block always executed ???

From:

Tom Hawtin <usenet@tackline.plus.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 04 Feb 2007 22:14:50 +0000

Message-ID:

<45c65acb$0$8736$ed2619ec@ptn-nntp-reader02.plus.net>

Neroku wrote:

Hi, I'm trying to know if the finally block in a try-catch-finally
construction is always executed. Throwing another exception inside the
catch block doesn't seem to skip the finally block execution. But I
don't understand why, consider the following code:

finally is supposed to be executed whichever way the block is executed.
For instance, usually you want to close a file stream whatever happened.

If you really don't want to execute the finally code after an exception
(and I suggest that is not the case), then add a flag:

     boolean disposeResource = true;
     Resource resource = acquire();
     try {
         ...
     } catch (SomeException exc) {
         // Must ensure flag is set at last possible moment.
         OtherException chainExc = new OtherException(exc, resource);
         disposeResource = false;
         throw chainExc;
     } finally {
         if (disposeResource) {
             resource.dispose();
         }
     }

It is more usual to use something similar where the resource is returned
in the normal response. Therefore the resource should not be disposed of
iff the try block completes successfully. No matter where or what the
other exception, even if it is an OutOfMemoryError, abnormal termination
should dispose of the resource.

Tom Hawtin