scope of local variable in enhanced for-loop

Question

I have a rather simple question about variable scope.

I am familiar with the Enhanced For-Loops but I do not get why I should declare a new variable to keep each element. One example might clarify my question:

        int[] ar = {1, 2, 3};
        int i = 0;
        for(i : ar) {  // this causes an error if I do not declare a new variable: int i
//        for(int i : ar) // this works fine
            System.out.println(i);
        }

So why I should declare this new variable? After all i is accessible inside the for loop. I did not want to use any previous value of i, just did not want to declare a new variable. (I guessed for other iterable items it might be faster using the same variable).

I guess that's how Enhanced For-Loops were built but does not this break the whole scope idea?

There is a question rising from the above behavior. Whether the compiler uses the same variable for the whole for loop and just updates its value or it creates a new variable for each iteration?

An interesting part is that if I keep both declaration of int i (before and inside the for loop) I even get a compiler error about

Duplicate local variable i

which makes (at least for me) things a bit more strange. So I cannot use the previous declared variable i inside the for loop but neither can I declare a new one inside it with the same name.

Answer 1

So why I should declare this new variable?

Because that's the way the syntax is defined.

After all i is accessible inside the for loop.

That's semantics. It's irrelevant to syntax.

I did not want to use any previous value of i, just did not want to declare a new variable. (I guessed for other iterable items it might be faster using the same variable).

Don 't guess about performance. Test and measure. But in this case there's nothing to measure, because any working code is faster than any non-working code.