is this final variable modified

[venu surampudi]

ranchers,

In the new for construct assuming that a is an integer array

for (final int v: a){
System.out.println(v);
}

why does java allow us to declare the iteration variable to be final and not complain? doesent it (v) change after every iteration?

Thanks
venu

[Stevi Deter]

This question has been addressed very recently in this very forum.

The short answer is: a new final variable is created on each pass through the for loop.

[Sunny Jain]

Venu, i want to ask you a very simple question :
when you declare a variable inside a "for loop", at which point it scope finishes.

Answer to this question is, answer to your question.

I hope it will work, if you still face any problem feel free to put your doubt on the forum.

[Ram Manoj]

I can understood the reason why the following will compile even though 'v' is final.

for (final int v: a){
System.out.println(v);
}

And the following cannot be used as a normal 'for' construct

for (final int v=0;v<a.size(); v++){
System.out.println(v);
}

But any ideas on why is that the new 'for' construct is designed so, that it creates a new variable on every iteration.

[Mamadou Touré]

Hi,

In the first example you are just printing the value of V (you don't modify it), so it's ok. But in the second example, you modify the value of V (by incrementing it V++), so that's why the compiler complains

--------------------------------------------------------------------------------

for (final int v: a){System.out.println(v);}

--------------------------------------------------------------------------------



And the following cannot be used as a normal 'for' construct

code:
--------------------------------------------------------------------------------

for (final int v=0;v<a.size(); v++){System.out.println(v);}

[Stevi Deter]

Ram,

It should be clearer if you realize that the foreach (enhanced for loop) is the equivalent of saying:

    
for (int index = 0; index < a.size; index++) {
   final int i = a.get(index); // or a[index] for an array
}