String vs. StringBuilder

Question

I understand the difference between String and StringBuilder (StringBuilder being mutable) but is there a large performance difference

Answer 1

Using strings for concatenation can lead to a runtime complexity on the order of O(n^2).

If you use a StringBuilder, there is a lot less copying of memory that has to be done. With the StringBuilder(int capacity) you can increase performance if you can estimate how large the final String is going to be. Even if you're not precise, you'll probably only have to grow the capacity of StringBuilder a couple of times which can help performance also.