StringBuilder vs String concatenation in toString() in Java

Question

Given the 2 toString() implementations below, which one is preferred:

public String toString(){
    return \"{a:\"+ a + \", b:\" + b + \", c: \"         


        

Answer 1

There seems to be some debate whether using StringBuilder is still needed with current compilers. So I thought I'll give my 2 cents of experience.

I have a JDBC result set of 10k records (yes, I need all of them in one batch.) Using the + operator takes about 5 minutes on my machine with Java 1.8. Using stringBuilder.append("") takes less than a second for the same query.

So the difference is huge. Inside a loop StringBuilder is much faster.