java tricky one!

drak3 · 15 Nov 2007 at 21:29

Hey,

I wonder in what order the following is executed.

Assume there is a vector v passed an argument to a method which has the following:

Code:

try{ return v.remove(0); } finally { updateGui(gui); }

The question is, does the element FIRST get removed from the vector and THEN the gui will be updated?

thanks

voodooflux · 15 Nov 2007 at 21:37

drak3 said:
The question is, does the element FIRST get removed from the vector and THEN the gui will be updated?

Yes.

Pulseammo · 15 Nov 2007 at 21:53

Correct.

v.remove happens, finally block executes, method returns whatever was removed from v.

I'd be inclined not to use a try finally block to do that though. On one hand it's clean (although to be fair, I'd say that is a hacky use of a try block), but on the other hand it is tricky code, some one may not even realise that the finally block could be executed due to the return statement in the try block.

SiriusB · 15 Nov 2007 at 22:34

Code in the finally block should really only be code that will work no matter what.

Does your update gui code rely on v.remove at all? If it does, I suggest you move it into the try block.

Finally is meant more for things like closing file streams and cleaning up othe resources that could be left lingering if a function fails.

drak3 · 16 Nov 2007 at 02:53

Yes, the gui update relies on the element getting removed. The gui traverses the vector and draws the objects found, therefore it should ALWAYS happen after the removal.

I just like the "less code idea", but it can be done with

Code:

Object obj = v.remove(0); updateGui(gui); return obj;

I guess to avoid confusion and hackery

Just was not sure how exactly the finally clause works

Pulseammo · 16 Nov 2007 at 15:36

If you don't already know about it, you may wish to look up the Observer/Observable design pattern or Model-View-Controller architecture. Though the code that you have written may already appear within such a design pattern or arch (the passing of gui looks suspect though

), just thought you may find it interesting though if you've never encountered it.

Dj_Jestar · 16 Nov 2007 at 15:52

What's wrong with:

Code:

v.remove(0);
updateGui(gui);

?

drak3 · 17 Nov 2007 at 20:55

Must remove and return the element, and then update GUI to reflect the change.

Dj_Jestar · 18 Nov 2007 at 16:33

Code:

var = v.return(0);
updateGui(gui);
return var;

demon9k · 18 Nov 2007 at 17:29

Dj_Jestar said:
Code:

var = v.return(0); updateGui(gui); return var;

Agreed, try catch should not be used for process flow.

voodooflux · 18 Nov 2007 at 17:37

Slight correction:

Code:

var = v.[B][U]remove[/U][/B](0);
updateGui(gui);
return var;