🚀 go-pugleaf

You can do it like this:

try {
    // throw an exception here
    ...
} catch (Throwable e) {
    // process the exception here
    ...
    // and re-throw it
    throw e;
}

Regards,
S�ren Bak

"edwin taitz" <taitz@bigpond.net.au> skrev i en meddelelse
news:puIna.11699$hF.92186@news-server.bigpond.net.au...
> is it possible to rethrow an exception.
> and if so how??
>
>

In comp.lang.java.help edwin taitz <taitz@bigpond.net.au> wrote:
> is it possible to rethrow an exception.
> and if so how??


try
    {
    istream = new FileInputStream("foo.txt");
    }
catch(IOException error)
    {
    System.out.println("Exception thrown: " + error);
    error.printStackTrace();

    // here's what's important to you
    throw error;
    }

-- 
/**
 * @author Darryl L. Pierce <mcpierce@myrealbox.com>
 * @see    The J2ME FAQ <http://bellsouthpwp.net/m/c/mcpierce/j2mefaq.html">
 * @quote  "What do you care what others think, Mr. Feynman?"
 * @geek   echo '$_ = "Jvtu bopuifs Pfsm ibdlfs."; y/a-z/za-y/; print' | perl
 */

>     throw e;

whats the point of rethrowing exceptions?

Mike Crenshaw wrote:
> 
> >     throw e;
> 
> whats the point of rethrowing exceptions?

    Cleaning up before giving up:

	hal.openPodBayDoors();
	try {
	    pod.enter();
	}
	catch (CannotEnterPodException e) {
	    hal.closePodBayDoors();
	    throw e;
	}
	...

-- 
Eric.Sosman@sun.com

>     Cleaning up before giving up:

> catch (CannotEnterPodException e) {
>     hal.closePodBayDoors();
>     throw e;
> }

hmm i still dont follow you.. you can execute the hal.closePodBayDoors()
without the throw e anyway cant you?

"Mike Crenshaw" <crenshaw@worldonline.dk> skrev i en meddelelse
news:Xxboa.22515$y3.1976088@news010.worldonline.dk...
> >     Cleaning up before giving up:
>
> > catch (CannotEnterPodException e) {
> >     hal.closePodBayDoors();
> >     throw e;
> > }
>
> hmm i still dont follow you.. you can execute the hal.closePodBayDoors()
> without the throw e anyway cant you?
>
>

You know that you should invoke hal.closePodBayDoors exactly because you
catch the exception. If you don't catch it, there is no-one who knows how to
clean up. But that is not the same as saying that the exception should not
be passed further on.

As well as closing the pod bay doors, you may also need to notify the object
that called the method that an exception has been thrown, otherwise it may
not realise that something went wrong.


"Mike Crenshaw" <crenshaw@worldonline.dk> wrote in message
news:Xxboa.22515$y3.1976088@news010.worldonline.dk...
> >     Cleaning up before giving up:
>
> > catch (CannotEnterPodException e) {
> >     hal.closePodBayDoors();
> >     throw e;
> > }
>
> hmm i still dont follow you.. you can execute the hal.closePodBayDoors()
> without the throw e anyway cant you?
>
>

> As well as closing the pod bay doors, you may also need to notify the
object
> that called the method that an exception has been thrown, otherwise it may
> not realise that something went wrong.

hmm
ok so where would it be recaught?

On Sun, 20 Apr 2003 11:14:58 +0200, Mike Crenshaw wrote:

>> As well as closing the pod bay doors, you may also need to notify the
> object
>> that called the method that an exception has been thrown, otherwise it may
>> not realise that something went wrong.
> 
> hmm
> ok so where would it be recaught?

In whoever called the method. A more complete example is below. This also
illustrates one example why you would actually want to do this. enterPod
is a low-level method that actually enters the pod, and cleans up if
something went wrong. It doesn't know what kind of user interface you
have, and therefore cannot report any errors. But it does know that the
pod door needs to be closed if something went wrong.

The higher level method getIntoPod() knows how to actually tell the user
that something went wrong, but shouldn't have to deal with the details of
opening or closing the doors.

(Side note: in real life applications, the exception would often not be
rethrown verbatim because it, too, is low-level information. Rather, it
would be wrapped into another exception. But that's immaterial here).

void enterPod() throws CannotEnterPodException
{
 hal.openPodBayDoors();
 try {
   pod.enter();
 }
 catch (CannotEnterPodException e) {
   hal.closePodBayDoors();
   throw e;
 }
}

void getIntoPod()
{
  try {
    enterPod();
  }
  catch (CannotEnterPodException e) {
    System.out.println( "Sorry, I cannot do that, Dave" );
  }
}

In comp.lang.java.help Mike Crenshaw <crenshaw@worldonline.dk> wrote:
> ok so where would it be recaught?

Any method that (re)throws an exception has to declare such explicitly.
It would be recaught wherever it's logical and appropriate in your
application, higher up the call stack.

-- 
/**
 * @author Darryl L. Pierce <mcpierce@myrealbox.com>
 * @see    The J2ME FAQ <http://bellsouthpwp.net/m/c/mcpierce/j2mefaq.html">
 * @quote  "What do you care what others think, Mr. Feynman?"
 * @geek   echo '$_ = "Jvtu bopuifs Pfsm ibdlfs."; y/a-z/za-y/; print' | perl
 */

Well doing an experiment i think i actually get it now:)

> hal.openPodBayDoors();
> try {
>     pod.enter();
> }
> catch (CannotEnterPodException e) {
>     hal.closePodBayDoors();
>     throw e;
> }


My question might sound basic but whats the point
with the 'finally' statement ? Shouldn't it be used
specifically for those cases ?

On Mon, 21 Apr 2003 21:05:59 +0200, .Saphyr <saphyr@infomaniak.ch> wrote:

>> hal.openPodBayDoors();
>> try {
>> pod.enter();
>> }
>> catch (CannotEnterPodException e) {
>> hal.closePodBayDoors();
>> throw e;
>> }
>
>
> My question might sound basic but whats the point
> with the 'finally' statement ? Shouldn't it be used
> specifically for those cases ?
>

Yes, assuming you want the doors closed regardless of whether pod.enter() 
succeeds, try...finally would be a better solution.  However if your logic 
is such that you require the doors to be closed only in an exceptional 
circumstance, you would need to catch the exception and re-throw it.

Dan.

In comp.lang.java.help .Saphyr <saphyr@infomaniak.ch> wrote:
>> hal.openPodBayDoors();
>> try {
>>     pod.enter();
>> }
>> catch (CannotEnterPodException e) {
>>     hal.closePodBayDoors();
>>     throw e;
>> }
> 
> 
> My question might sound basic but whats the point
> with the 'finally' statement ? Shouldn't it be used
> specifically for those cases ?

No. You may only want to close the pod bay doors if there's a problem
while trying to open them. Finally will _always_ execute; catch() will
only execute on an exception...

-- 
/**
 * @author Darryl L. Pierce <mcpierce@myrealbox.com>
 * @see    The J2ME FAQ <http://bellsouthpwp.net/m/c/mcpierce/j2mefaq.html">
 * @quote  "What do you care what others think, Mr. Feynman?"
 * @geek   echo '$_ = "Jvtu bopuifs Pfsm ibdlfs."; y/a-z/za-y/; print' | perl
 */