The FizzBuzz challenge in Java 8 written in a short, readable and interesting way
A guideline that I use for deciding on a StringBuilder or not is that it depends on whether I know beforehand how many times it will be used or not. I believe I've come across this recommendation on some MSDN page once but I'm not entirely sure.

In your case, you know that there are only two possible uses of your StringBuilder, and that there are no values added inside a loop, so I would use normal string concatenation:

Now you can also change your code a little to what I consider more easily interpretable:

private static String fizzBuzzify(final int value) {
   String result = "";

   if (value % 3 == 0) {
       result += "Fizz";
   }
   if (value % 5 == 0) {
       result += "Buzz";
   }
   return result.length() &gt; 0 ? result : Integer.toString(value);
}