Is it better practice to use String.format over string Concatenation in Java?

361

Is there a perceptible difference between using String.format and String concatenation in Java?

I tend to use String.format but occasionally will slip and use a concatenation. I was wondering if one was better than the other.

The way I see it, String.format gives you more power in "formatting" the string; and concatenation means you don't have to worry about accidentally putting in an extra %s or missing one out.

String.format is also shorter.

Which one is more readable depends on how your head works.

Edit Report

1 Answer

I haven't done any specific benchmarks, but I would think that concatenation may be faster. String.format() creates a new Formatter which, in turn, creates a new StringBuilder (with a size of only 16 chars). That's a fair amount of overhead especially if you are formatting a longer string and StringBuilder keeps having to resize.

However, concatenation is less useful and harder to read. As always, it's worth doing a benchmark on your code to see which is better. The differences may be negligible in server app after your resource bundles, locales, etc are loaded in memory and the code is JITted.

Maybe as a best practice, it would be a good idea to create your own Formatter with a properly sized StringBuilder (Appendable) and Locale and use that if you have a lot of formatting to do.

answered 2009-05-29T14:55:43.383

Is it better practice to use String.format over string Concatenation in Java?

1 Answer

Your Answer