I am doing a code review and out of the blue I see that he has replaced the StringBuffer variable with a StringBuilder.
I could ask why but I figured it would be better to read a bit before I ask the question.
The first advantage I find for StringBuilder is that it is faster because it is not synchronized. This means that the advantage of StringBuffer is that it is thread-safe.
After reading this post about never using StringBuffer you can question what thread-safety means with StringBuffer and probably always use StringBuilder.
There is also a bonus performance comment about never using a String in a loop to append values to it.
I have learned a something useful with this code review (as always if I take the time to do it right).