Lifetime and scope of a variable

[Nancy Kan]

Can anyone explain this:

(a) for(int x=0;x<3;x++){int y=-1;} // it works


(b) for(int x=0;x<3;x++)
int y=-1;
case b does not work -- compile time error

(c) for(int x=0;x<3;x++);
int y=-1;

this also compiles

Why it does not allow a variable declaration without brackets?

[balajee annamalai]

This is beacuse in the (b) option you are declaring int y inside the loop which is not allowed. You can declare like the following,

int y=1;
for(int i=1;<=5;i++)
y=1;

[Nancy Kan]

Thanks a lot, I got it, it will try to declare same var again and again on the same stack , hence error!

[balajee annamalai]

Then i have a doubt why then option A is working.

[Sabber bhatia]

i agree with you balajee
but first one is working because you put ({)curly braces.
its like a variable inside loop

but i did not understand if this is the case then why not

for(int i=0;i<4;i++)
int y=-1;
not working
see it means you have a loop with one variable declaration then what's the problem.

Seriously its confusing

[horri khaled]

Hi
i think in (b) the declaration statement is not permitted.I search in the

Java specification, but nothing is specified to explain this error.

I have another doubt

 for(int x=0;x<3;x++);
int y=-1; 

this statement works fine, but if i make the infinite loop, i have a cmpile
time error

    for(; :wink: ;
int y=-1; 

So if anyone have an explanation,it be appreciated

[fred rosenberger]

this statement works fine, but if i make the infinite loop, i have a compile time error

as a general note, it is often quite helpful if you post the exact text of that compile time error.

[anuj bhatnagar]

int y=0; is declaration and its not considered as a statement according to the java language specification and since only statements are allowed after if or for construct, it gives a compiler error.
When you put {} it makes it as a block which is always allowed in these construct.