Question

Which one of these two is more ‘efficient’:

for (int i = 0; i < 10; i++) {
    int x = i * 2;
}

or –

int x;
for (int i = 0; i < 10; i++) {
    x = i * 2;
}

(Just an example)

I understand they are different in essence – so please do not address the difference in their use.

In a case where both would prove to do the same thing – will creating the x variable multiple times be a less efficient method rather than just creating it once and simply reassigning its value?

Answer 1

No, in this case, with the way compilers are, there is no performance difference.

I prefer the first approach from a readability point of view, but that’s something to be discussed elsewhere.

However, as a bonus section to this answer:

for (int x = 0; x < calculateUserCountFromDatabaseOrSomething(); x++) {
   //Do stuff
} 

In the above case, this will be a performance issue since the calculateUserCountFromDatabaseOrSomething() method is going to be called on every iteration of the loop. This is something that definitely needs to be considered when writing software.