String vs. StringBuilder

Question

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

Answer 1

String and StringBuilder are actually both immutable, the StringBuilder has built in buffers which allow its size to be managed more efficiently. When the StringBuilder needs to resize is when it is re-allocated on the heap. By default it is sized to 16 characters, you can set this in the constructor.

eg.

StringBuilder sb = new StringBuilder(50);