I didn't touch much Java Code for ~ 10 years now. I remember reading about the string concatenation problem in the Effective Java book. Using a StringBuilder wa

I didn't touch much Java Code for ~ 10 years now. I remember reading about the string concatenation problem in the Effective Java book. Using a StringBuilder was the very first thing I usually tried when I needed to improve performance on some unfamiliar code. I didn't know the Java compiler converts this automatically now. Since which version is this? I suspect there might be still edge cases where it doesn't work.