Question

Given the following code snippets, is there any appreciable difference?

public boolean foo(int input) {
   if(input > 10) {
       doStuff();
       return true;
   }
   if(input == 0) {
       doOtherStuff();
       return true;
   }

   return false;
}

vs.

public boolean foo(int input) {
   if(input > 10) {
      doStuff();
      return true;
   } else if(input == 0) {
      doOtherStuff();
      return true;
   } else {
      return false;
   }
}

Or would the single exit principle be better here with this piece of code…

public boolean foo(int input) {
   boolean toBeReturned = false;
   if(input > 10) {
      doStuff();
      toBeReturned = true;
   } else if(input == 0) {
      doOtherStuff();
      toBeReturned = true;
   }

   return toBeReturned;
}

Is there any perceptible performance difference? Do you feel one is more or less maintainable/readable than the others?

Answer 1

With the second example you state very clearly that both conditions are mutually exclusive.
With the first one, it is not so clear, and in the (unlikely) event that an assignment to input is added between both ifs, the logic would change.
Suppose someone in the future adds input = 0 before the second if.
Of course this is unlikely to happen, but if we are talking about maintainability here, if-else says clearly that there are mutually exclusive conditions, while a bunch of ifs don’t, and they are not so dependent between each other as are if-else blocks.

edit:Now that I see, in this particular example, the return clause forces the mutual exclusivity, but again, we’re talking about maintainability and readability.

Anyway, about performance, if this is coded in Java you shouldn’t care for performance of a couple of if blocks, if it were embedded C in a really slow hardware, maybe, but certainly not with java.