Java style: Variable declaration in a switch

Question

The following code does not compile because eater is defined twice:

switch (vegetable) {
    case TOMATO:
        Eater eater = new Eater(Tomato.class, many parameters);
        eater.eat(more parameters);
        return true;

    case POTATO:
        Eater eater = new Eater(Potato.class, many parameters);
        eater.eat(more parameters);
        return true;

    case CARROT:
        doSomethingElse();
        return true;
}

Should I:

Use separate variables `tomatoEater` and `potatoEater`, making the code less maintainable?
Define `eater` before the `switch`, making it accessible to more than it should?
Define `eater` the first time only, leading to potential confusion?
Add braces, making the code more verbose?
Any better idea?

I really don't want to know what the doSomethingElse() method does. — CurtainDog
– CurtainDog, Commented Sep 17, 2010 at 6:22
BTW, I am seeing { in a new line after a long time... Feels good when someone else codes the same way I do :-) — Nivas
– Nivas, Commented Sep 17, 2010 at 6:32
CurtainDog: LOL I swear it was totally random! Nivas: Fixed ;-) — Nicolas Raoul
– Nicolas Raoul, Commented Sep 17, 2010 at 6:38

Jon Skeet · Accepted Answer · 2010-09-17 06:17:04Z

6

I would personally either use braces, or just abandon the local variable completely:

new Eater(Potato.class, many parameters)
     .eat(more parameters);

The disadvantage of this is that it makes it a little harder to debug. Obviously this isn't your real code though... which makes it hard to say the right thing to do. It's quite possible that the right thing to do is actually to break out the bodies of the cases into separate methods.

answered Sep 17, 2010 at 6:17

Jon Skeet

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2 Comments

mjfgates Over a year ago

Extract Method IS your friend.

Jon Skeet Over a year ago

@mjfgates: Not always. Take each case as it comes. For a two-liner, I think I'd often rather go with extra braces. In many other cases though, I agree.

Nivas · Accepted Answer · 2010-09-17 06:17:29Z

2

Why not this:

switch (vegetable) 
{ 
    case TOMATO: 
        new Eater(Tomato.class, many parameters).eat(more parameters); 
        return true; 

    case POTATO: 
        new Eater(Potato.class, many parameters).eat(more parameters); 
        return true; 

    case CARROT: 
        doSomethingElse(); 
        return true; 
}

If you dont have any use of the Eater reference anywhere else later, I would do this.

answered Sep 17, 2010 at 6:17

Nivas

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Comments

CurtainDog · Accepted Answer · 2010-09-17 06:28:16Z

1

Not quite the same logic as your method (carrot is treated as default) but shows an alternative approach (with some more behind the scenes wiring that I haven't worried about here):

Eater eater = vegetable.getEater(many parameters);
if (eater != null) eater.eat(more parameters);
else doSomethingElse();
return true;

answered Sep 17, 2010 at 6:28

CurtainDog

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Comments

Joel · Accepted Answer · 2010-09-17 06:22:08Z

0

How would using separate variables make the code less maintainable? (first bullet point). If anything I would say it would do the opposite as the variable name better explains what it is. I would go with that if keeping it in that scope is important to you.

answered Sep 17, 2010 at 6:22

Joel

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1 Comment

Nicolas Raoul Over a year ago

The more each case is similar, the easiest it is to copy-paste to create a new case, or refactor. Let's say I want to add a eater.init() after each creation, it will be painful if I have to adapt the variable name for each case. I avoid creating many variable names if there is no good reason. And also, it takes a bit more memory if not used with braces.

Community · Accepted Answer · 2017-05-23 11:47:48Z

0

Maybe using a switch isn't such a good idea at all.

In what better example can represent a switch statement in Java ?

edited May 23, 2017 at 11:47

CommunityBot

11 silver badge

answered Sep 17, 2010 at 6:32

Colin Hebert

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