Difference between declaring variables before or in loop?
initialization, java, loops, performance, variables
Solution
Which is better, a or b?
From a performance perspective, you'd have to measure it. (And in my opinion, if you can measure a difference, the compiler isn't very good).
From a maintenance perspective, b is better. Declare and initialize variables in the same place, in the narrowest scope possible. Don't leave a gaping hole between the declaration and the initialization, and don't pollute namespaces you don't need to.
Problem
I have always wondered if, in general, declaring a throw-away variable before a loop, as opposed to repeatedly inside the loop, makes any (performance) difference? A (quite pointless) example in Java: a) declaration before loop: ``` double intermediateResult; for(int i=0; i < 1000; i++){ intermediateResult = i; System.out.println(intermediateResult); } ``` b) declaration (repeatedly) inside loop: ``` for(int i=0; i < 1000; i++){ double intermediateResult = i; System.out.println(intermediateResult); } ``` Which one is better, a or b? I suspect that repeated variable declaration (example b) creates more overhead in theory, but that compilers are smart enough so that it doesn't matter. Example b has the advantage of being more compact and limiting the scope of the variable to where it is used. Still, I tend to code according example a. Edit: I am especially interested in the Java case.