Replace last instance of comma with 'and' in a string

Question

I have a string of comma separated words e.g. "a, b, c".
I need to replace the last comma instance with “and”, to make it look like "a, b and c".

I've tried using replaceFirst like this:

"a, b, c".replaceFirst("(,)[^,]+$", " and")

But it doesn't work. It replaces everything after the last comma with “and” rather than just the comma producing "a, b and".

How to make it work?
I'm on java8.

Ps. I thought that it's obvious, but it seems like I need to clarify, that I'm looking for a generic solution that works with any number of comma separated tokens, i.e. 'a, b, ...., c'

Answer 1

I think the replaceFirst is better than replaceAll for you because you want to replace only once not all, and it run faster than replaceAll.

1. using ${number} to capturing groups.

   "a, b, c".replaceFirst(",([^,]+)$", " and$1"); // return "a, b and c"
   

2. using positive lookahead:

   "a, b, c".replaceFirst(",(?=[^,]+$)", " and"); // return "a, b and c"