Assign final variable in a try block

Question

Very short question: Is there a more elegant way to do this:

Object tmp;
try {
 tmp = somethingThatCanFail();
} catch (Fail f) {
 tmp = null;
}
final Object myObject = tmp;
// now I have a final myObject, which can be used in anonymous classes

check out this similar SO thread: http://stackoverflow.com/questions/2773779/problems-initializing-a-final-variable-in-java — froadie, Jun 15 '10 at 13:54

score 12 · Accepted Answer · answered Jun 15 '10 at 12:43

12

You could extract the creation of the value in its own method:

final Object myObject = getObjectOrNull();

public Object getObjectOrNull() {
  try{
    return somethingThatCanFail();
  } catch (Fail f) {
    return null;
  }
}

It's longer, but depending on your definition of "elegant" it might be more elegant.

answered Jun 15 '10 at 12:43

Joachim Sauer

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+1 but anyway final is just a security but you can deal without it no? – Sebastien Lorber Jun 15 '10 at 13:16
`final` is a very useful tool to document and enforce invariants. Additionally it is sometimes required when interacting with anonymous inner classes. – Joachim Sauer Jun 15 '10 at 13:23
It also supposedly helps the compiler with optimization, but I guess it can do enough of that on its own. – Bart van Heukelom Jun 15 '10 at 14:42
AFAIK the finally flag on local variables is only checked by the compiler, it does not exist in the bytecode and so cannot be used by hotspot. Of course hotspot might still notice that variables are not modified and generate better code. – Jörn Horstmann Jun 15 '10 at 15:22

score 0 · Answer 2 · answered Jun 15 '10 at 12:43

0

Depends what you mean by "this" (and "more elegant")

I'm not sure why you think you need tmp AND myObject, but there's no way to avoid having one of those declarations outside the try block IF you want to access it in the catch block.

What's wrong with

Object myObject = null;
try {
  myObject = somethingThatCanFail();
} catch (Fail f) {
  // do nothing because we can deal with myObject being null just fine
}

answered Jun 15 '10 at 12:43

dty

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2

I think the question is explicitly about assigning a `final` variable. – Joachim Sauer Jun 15 '10 at 12:43
Yeah, the pre-edited version forgot to mention that really important requirement! – dty Jun 15 '10 at 15:35

score 0 · Answer 3 · answered Dec 21 '15 at 09:41

0

These days I tend to do it like this

final Thingy zeFing; {
    Thingy t = null;
    try {
        t = somethingThatCanFail();
    } catch (CurveBall f) {
        // log...
    }
    zeFing = t;
}

answered Dec 21 '15 at 09:41

Bart van Heukelom

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Assign final variable in a try block

3 Answers3